JP2021155222A - Double-sided printing device - Google Patents

Abstract

To provide a double-sided printing device that calculates a double-sided conveyance speed that is higher than the printing speed without reducing the productivity of double-sided printing and that is within the range of the rated speed of a motor.SOLUTION: The double-sided printing device includes: a secondary paper feed unit 14, which feeds printing media P at regular intervals toward a printing unit 30; a reversing unit 50, which reverses and discharges the printed media that have been printed on one side by the printing unit 30; and a control unit 60, which controls conveyance speed of the print media P. The control unit 60 calculates a number of sheets of the printed media in a conveyance path of the printed media P and double-sided conveyance speed when the printed media are circulated and fed again to a resist unit on the basis of size of the print media P and printing speed. If the calculated double-sided conveyance speed is outside a preset range, the control unit 60 re-calculates the double-sided conveyance speed by changing the number of sheets of the print media in the conveyance path and control conditions of the reversing unit 50.SELECTED DRAWING: Figure 1

Description

The present invention relates to a double-sided printing apparatus that performs double-sided printing on a printing medium.

Conventionally, there is known a double-sided printing apparatus that circulates and conveys a printing medium having a printing process on one side, flips the front and back by switching back at a reversing portion, and performs a printing process on the other side. In recent years, there has been an increasing demand for high-speed printing for printing devices to improve productivity, and it is desired to realize high productivity by high-speed printing not only during single-sided printing but also during double-sided printing.

In the case of single-sided printing, the printing paper can be fed one after another, so that the printing medium can be output in the number of prints per unit time that the printing unit that performs the printing process can print. On the other hand, in the case of double-sided printing, the front-side printed printing medium is circulated and inverted to perform back-side printing, so that the double-sided transfer speed during the circulatory transfer affects the productivity of the printing apparatus. That is, if the double-sided transfer speed is not appropriate, a situation may occur in which the print medium is not transferred to the printing section even though the printing process can be performed by the printing section, and the same productivity as in single-sided printing is ensured. I can't.

By the way, in the case of double-sided printing, two printing processes are required in the case of single-sided printing. Therefore, if the number of output sheets for double-sided printing per unit time is 1/2 of the number of output sheets for single-sided printing, double-sided printing can be performed with the same productivity per single side as for single-sided printing.

In Patent Document 1, in order to ensure the same productivity as single-sided printing even during double-sided printing, the number of circulating sheets of the printing medium is determined based on the size of the printing medium, the paper spacing (paper spacing), and the printing speed. A method of determining a double-sided transfer speed capable of guaranteeing the above productivity has been proposed based on the number of sheets circulated. In the present specification, the printing speed is the transport speed of the printing medium when the printing process is performed by ejecting ink onto the printing medium.

Further, in Patent Document 1, in order to avoid collision of printing media in the circulation transport path, when the double-sided transport speed is lower than the printing speed, the number of circulating sheets is reduced and the double-sided transport speed is recalculated. Proposed. If the double-sided transport speed is less than the printing speed, the double-sided transport speed of the print medium that is cyclically transported is slower than the transport speed of the print medium that is ejected from the printing unit. The tips of subsequent printing media ejected from the printing unit will collide.

However, when the number of circulating sheets is reduced to increase the double-sided transfer speed as described above, the double-sided transfer speed may exceed the rated rotation speed of the motor of the transfer mechanism. Therefore, Patent Document 1 proposes to calculate a double-sided transfer speed that does not exceed the rated rotation speed of the motor by widening the paper spacing (paper spacing) of the print medium at this time.

JP-A-2009-46303

However, if the double-sided transfer speed is reduced by adjusting the paper spacing as in the method of Patent Document 1, there is a problem that the productivity of double-sided printing is lowered.

In view of the above circumstances, it is an object of the present invention to provide a double-sided printing apparatus capable of calculating a double-sided transport speed that does not cause transport defects and maintains productivity.

In the double-sided printing apparatus of the present invention, one side is subjected to printing processing by a printing unit that performs printing processing on the printing medium, a resist unit that feeds the printing medium toward the printing unit at regular intervals, and a printing unit. The printed print medium is fed, and the printed print medium is inverted and ejected, and a control unit for controlling the transport speed of the print medium is provided. Based on this, the number of print media in the transport path of the print medium and the double-sided transport speed when the printed print medium is circulated and fed back to the resist unit are calculated, and the calculated double-sided transport speed is preset. If it is out of the specified range, the double-sided transfer speed is recalculated by changing the number of print media in the transfer path and the control conditions of the reversing part.

According to the double-sided printing apparatus of the present invention, when the number of print media in the transport path of the print medium and the printed print medium are circulated and transported to the resist unit based on the size and print speed of the print medium. If the calculated double-sided transfer speed is out of the preset range, the number of print media in the transfer path and the control conditions of the reversing part are changed to change the double-sided transfer speed. Is recalculated, so that it is possible to calculate the double-sided transport speed so as not to cause transport defects and maintain productivity. The effects of changing the number of print media and the control conditions of the reversing portion in the transport path on the double-sided transport speed will be described in detail later.

The figure which shows the schematic structure of the 1st Embodiment of the inkjet printing apparatus of this invention. A block diagram showing a schematic configuration of a control system of the inkjet printing apparatus shown in FIG. A timing chart for explaining the transfer operation of the print medium of the inkjet printing apparatus shown in FIG. Diagram for explaining the printing schedule during double-sided printing The figure for demonstrating the collision of the print medium when the double-sided transport speed is slower than the print speed. A flowchart for explaining a method of adjusting the double-sided transfer speed in the inkjet printing apparatus shown in FIG. A flowchart for explaining a method of adjusting the double-sided transfer speed in consideration of the space between papers according to the time required for post-processing. The figure which shows the schematic structure of the 2nd Embodiment of the inkjet printing apparatus of this invention. A block diagram showing a schematic configuration of a control system of the inkjet printing apparatus shown in FIG. A timing chart for explaining the transfer operation of the print medium of the inkjet printing apparatus shown in FIG. A flowchart for explaining a method of adjusting the double-sided transfer speed in the inkjet printing apparatus shown in FIG.

Hereinafter, the first embodiment of the inkjet printing apparatus of the present invention will be described in detail with reference to the drawings. The inkjet printing apparatus of the present embodiment is characterized in controlling the transport speed of the printing medium during double-sided printing. First, the overall configuration thereof will be described. FIG. 1 is a diagram showing a schematic configuration of the inkjet printing apparatus 1 of the present embodiment. The vertical and horizontal directions shown in FIG. 1 are the vertical and horizontal directions of the inkjet printing apparatus 1 of the present embodiment. Further, the front side of the paper surface in FIG. 1 is the front direction, and the back side of the paper surface is the rear direction.

As shown in FIG. 1, the inkjet printing apparatus 1 of the present embodiment includes a side paper feeding unit 10, an internal paper feeding unit 20, a printing unit 30, a paper ejection unit 40, and an inversion unit 50. ..

The printing unit 30 and the internal paper feeding unit 20 are housed and installed in a housing made of metal, resin, or the like. Further, the side paper feed unit 10 and the paper discharge unit 40 are installed in a state in which a part of the side paper feed unit 10 and the paper discharge unit 40 are housed in the housing and a part of the side paper feed unit 10 and the paper discharge unit 40 project out of the housing.

The side paper feed unit 10 includes a paper feed base 11 on which the print medium P is placed, a primary paper feed unit 12 that feeds out and conveys only the print medium P at the uppermost position from the paper feed base 11, and a primary paper feed unit 10. It includes a secondary paper feeding unit 14 that sends the print medium P conveyed by the unit 12 to the printing unit 30 at a predetermined timing.

The primary paper feed unit 12 includes a paper feed roller, a paper feed motor for driving the paper feed roller, and the like.

The secondary paper feed unit 14 is slackened by temporarily stopping the print medium P when the tip of the print medium P conveyed from the primary paper feed unit 12 or the tip of the print medium P conveyed from the internal paper feed unit 20 comes into contact with each other. A resist roller 14a for performing skew correction and a resist motor for driving the resist roller 14a are provided. In the present embodiment, the secondary paper feed unit 14 corresponds to the resist unit of the present invention.

The internal paper feed unit 20 includes a paper feed base 21a on which the print medium P is placed, a primary paper feed unit 22a that feeds out and conveys only the print medium P at the uppermost position from the paper feed base 21a, and the print medium P. It includes a paper feed table 21b on which the paper is placed, a primary paper feed unit 22b that feeds out and conveys only the print medium P at the uppermost position from the paper feed table 21b, a transfer roller 23, and a vertical transfer roller 15.

The primary paper feed units 22a and 22b include a paper feed roller and a paper feed motor for driving the paper feed roller.

The print medium P fed from the paper feed tray 21a by the primary paper feed unit 22a and the print medium P fed out from the paper feed tray 21b by the primary paper feed unit 22b are directed toward the vertical transport roller 15 by the transport roller 23. Be transported.

The vertical transfer roller 15 is provided on a transfer path between the resist roller 14a and the transfer roller 23 and between the resist roller 14a and the second double-sided transfer roller 45 described later.

Therefore, the print medium P is conveyed to the vertical transfer roller 15 from the primary paper feeding units 22a and 22b, and the print medium P is also conveyed from the reversing unit 50, which will be described later. Therefore, in front of the vertical transfer roller 15 in the transfer direction, the transfer path of the print medium P fed from the internal paper feed section 20 and the transfer of the print medium P on which one side of the print medium P conveyed from the reversing section 50 is printed. There is a confluence point where the route merges.

In the present embodiment, the transfer path from the resist roller 14a to the reversing roller 52 described later via the printing unit 30 and the first double-sided transfer roller 44 described later is referred to as the first double-sided transfer path DS1 with the resist roller 14a as a reference. Call. Further, the transfer path from the reversing roller 52 to the resist roller 14a via the second double-sided transfer roller 45 and the vertical transfer roller 15, which will be described later, is referred to as a second double-sided transfer path DS2. Further, the transport path from the second belt platen roller 34 to the paper discharge section 40, which will be described later, is called a paper discharge transport path HS, and the transport path in which the print medium P switches back in the reversing section 50 is called a reverse transport path SR.

Further, a large number of paper detection sensors for detecting the print medium P are provided on the transfer path of the print medium P such as the first double-sided transfer path DS1, the second double-sided transfer path DS2, the paper discharge transfer path HS, and the reverse transfer path SR. Based on the detection signal detected by the paper detection sensor, the control unit 60, which will be described later, controls the transfer of the print medium P. In particular, the reversing transport sensor RS is provided on the first double-sided transport path DS1 between the most downstream first double-sided transport roller 44 and the reversing roller 52, and in the vicinity of the downstream side of the first double-sided transport roller 44. ing. The reverse transfer sensor RS is also a sensor that detects the print medium P.

The printing unit 30 includes four line heads 31, an annular conveyor belt 32 provided facing the line head 31, a first belt platen roller 33, and a second belt platen roller 34.

The transport belt 32 is formed of an annular endless belt and has a large number of suction holes. The print medium P fed from the secondary paper feed unit 14 is conveyed to the annular transfer belt 32. Then, the print medium P is attracted to the transfer belt 32 by suction of a suction fan (not shown) installed on the back surface side of the transfer path surface of the transfer belt 32, and is conveyed at a predetermined transfer speed. Then, while the print medium P is conveyed by the transfer belt 32, ink is ejected from the line head 31 to the print medium P, whereby the print process is applied to the print medium P.

A conveyor belt 32 is hung on the first belt platen roller 33 and the second belt platen roller 34, and the first belt platen roller 33 and the second belt platen roller 34 are driven by a conveyor motor (not shown). As a result, the transport belt 32 rotates clockwise in FIG. 1.

Each line head 31 is extended in a direction orthogonal to the conveying direction of the printing medium P, and ejects ink to the printing medium P conveyed by the conveying belt 32. As shown in FIG. 1, the four line heads 31 are arranged at predetermined intervals along the transport path of the print medium P. Each of the four line heads 31 ejects CMYK ink.

Each line head 31 has a head row in which three inkjet heads are arranged at equal intervals in a direction (front-back direction) orthogonal to the transport direction of the print medium P. Each line head 31 has two rows of head rows, and the two rows of head rows are arranged in a staggered manner so that the inkjet heads of each head row overlap by a predetermined number of nozzles. ..

Then, a one-line printed image is formed by printing with the inkjet heads of the two rows of head rows of each line head 31.

A switching mechanism 43 is provided at the confluence of the first double-sided transport path DS1 and the paper discharge transport path HS. The switching mechanism 43 switches whether to guide the print medium P, which has been printed by the printing unit 30, to the paper ejection unit 40 or to circulate the print medium P on the first double-sided transfer path DS1.

The paper ejection unit 40 has a tray-shaped paper ejection table 41 protruding from the housing of the inkjet printing apparatus 1, and three pairs of paper ejection rollers 42 for ejecting the print medium P on the paper ejection table 41. Then, the print medium P guided to the paper ejection transport path HS by the switching mechanism 43 is ejected to the paper ejection table 41 by the paper ejection roller 42.

The reversing unit 50 transports the print medium P from the first double-sided transport path DS1 to the reverse transport path SR, and the print medium P conveyed to the reverse transport path SR. It includes a reversing roller 52 that switches back and returns to the second double-sided transport path DS2, a reversing motor (not shown) that drives the reversing roller 52, and the like.

The print medium P guided to the first double-sided transfer path DS1 by the switching mechanism 43 is conveyed from the first double-sided transfer path DS1 to the reverse transfer path SR by the first double-sided transfer roller 44. Then, the print medium P is returned from the reverse transfer path SR to the second double-sided transfer path DS2 by the reversing roller 52, so that the print medium P is conveyed on the second double-sided transfer path DS2 with the front and back reversed. Then, the print medium P whose front and back sides are reversed is conveyed toward the vertical transfer roller 15 by the second double-sided transfer roller 45 provided on the second double-sided transfer path DS2.

The print medium P conveyed by the vertical transfer roller 15 is again conveyed to the resist roller 14a of the secondary paper feed unit 14, and is again sent out to the printing unit 30 at a predetermined timing by the resist roller 14a. Then, the printing unit 30 performs a printing process on the back surface of the printing medium P.

The print medium P whose back surface has been printed by the printing unit 30 is guided to the paper ejection transport path HS by the switching mechanism 43, and is ejected to the paper ejection table 41 by the paper ejection roller 42.

FIG. 2 is a block diagram showing a schematic configuration of a control system of the inkjet printing apparatus 1 of the present embodiment. As shown in FIG. 2, the inkjet printing apparatus 1 includes a control unit 60 and an operation panel 70.

The control unit 60 controls the entire inkjet printing device 1, and includes a CPU (Central Processing Unit), a semiconductor memory, and the like. The control unit 60 controls the operation of each unit of the inkjet printing device 1 by causing the CPU to execute a program stored in advance in the semiconductor memory.

Further, the control unit 60 acquires image data output from a computer or the like or image data read by a scanner or the like, and controls the printing unit 30 based on the image data to perform printing processing.

Further, the control unit 60 acquires printing conditions such as the size and printing speed of the printing medium P, calculates the double-sided conveying speed of the printing medium P, which will be described later, based on the printing conditions, and the number of sheets of the conveying path paper of the printing medium P. Performs processing such as calculation of.

The operation panel 70 is composed of a touch panel having a liquid crystal display, displays various setting input screens, and accepts various setting inputs such as a print start instruction input and a print condition setting input. The size of the print medium P acquired by the control unit 60 is set and input on the operation panel 70, for example. Further, the size of the print medium P may be detected by sensors installed on the paper feed trays of the side paper feed unit 10 and the internal paper feed unit 20.

Next, the transfer operation of the print medium P of the inkjet printing apparatus 1 of the present embodiment will be described with reference to the timing chart shown in FIG. The horizontal axis of FIG. 3 is time, and the vertical axis is the transport speed of the print medium P. Further, here, the transport operation during double-sided printing will be described.

First, the tip of the print medium P conveyed by the side paper feed unit 10 or the internal paper feed unit 20 comes into contact with the resist roller 14a, and temporarily stops in a state where slack is formed.

Then, the print medium P is conveyed toward the printing unit 30 by the resist roller 14a at the timing of time t1. At this time, secondary paper feeding section 14, after accelerated at the acceleration [alpha] 1, conveys the print medium P at a conveying speed V _1.

The secondary paper feeding section 14 is then decelerated in the deceleration [alpha] 2, transfers the print medium P to the conveying belt 32 at a time t2 which became the conveyance speed V _2. As shown in FIG. 3, the relationship between the transport speed V ₁ and the transport speed V _{2 is V 1} > V ₂ . This makes it possible to close the space between the papers.

Conveyance belt 32 is also driven at the conveying speed V _2, to a constant velocity transport the print medium P received from the secondary paper feeding unit 14 at the conveying speed V _2. Then, the surface of the print medium P transported at the transportation speed V _2, the print processing by the printing unit 30 is performed. The printing medium P fed from the conveyor belt 32 is then by the first duplex conveyance roller 44 and reversing roller 52 and is subsequently transported at a constant rate over the conveying speed V _2.

Then, the rear end of the printing medium P, and reaches the reverse conveyance sensor RS (time t3), the reverse roller 52 is accelerated by the acceleration .alpha.3, to a constant velocity transport the print medium P in the conveyance speed V _3. The print medium P is guided to the reverse transfer path SR by the transfer by the reverse roller 52.

After the print medium P is guided to the reverse transfer path SR, the reverse roller 52 decelerates at the deceleration α4 in order to stop the print medium P by switchback. Then, when the rear end of the print medium P reaches a position separated from the reversing roller 52 by a distance Ls (the amount of the rear end remaining at the time of reversing), the reversing roller 52 stops (time t4).

The amount Ls left at the rear end at the time of inversion is set in advance as a distance at which the print medium P can be sufficiently conveyed into the inversion transport path SR so that the print medium P can be inverted, and the print medium P can be conveyed in both directions without being disengaged from the inversion roller 52. It is set. Therefore, the deceleration start position of the reverse roller 52, when decelerated by the deceleration α4 from the conveyance speed V _3, the rear end of the printing medium P is a position that can be stopped at a distance Ls from the reversing roller 52.

Then, the reversing roller 52 resumes rotation in the reverse direction from the time t5 when the reversing portion wait time elapses from the time t4 when the transfer of the printing medium P by the reversing roller 52 is temporarily stopped, and the printing medium P switches back. Be transported. _{The inverted portion wait time SB wait} from the time t4 to the time t5 is initially set to an initial value, but is changed as necessary when calculating the double-sided transport speed described later.

Then, after the inversion of the print medium P is started, the print medium P is accelerated and conveyed by the inversion roller 52 and the second double-sided transfer roller 45 at an acceleration of α3. Print medium P and reaches the conveying speed V _4, it is a constant velocity transport by the second duplex conveyance roller 45 and the vertical conveying roller 15.

After that, in order to stop the print medium P on the resist roller 14a, the second double-sided transfer roller 45 and the vertical transfer roller 15 are decelerated at the deceleration α5. In the present embodiment, in the course of deceleration in the deceleration .alpha.5, it is moving at a constant speed conveyor at the conveying speed V ₅ a print medium P. In this way, before the tip of the print medium P comes into contact with the resist roller 14a of the secondary paper feed unit 14, the print medium P can be conveyed at a constant speed to slow down the speed at which the print medium P collides with the resist roller 14a. It can reduce the collision noise. However, it is not always necessary to provide this constant velocity transport period.

Further, the deceleration start position of the second duplex conveyance roller 45 and the vertical conveying rollers 15 described above, when decelerated by the deceleration α5 from the conveyance speed V _4, it stops the leading end of the printing medium P in the secondary feeder 14 It may be a position. However, in the secondary paper feed unit 14, as described above, the print medium P comes into contact with the print medium P once to correct the skew, so that the secondary paper feed unit 14 is stopped with a slack. The amount of slack formed during this skew correction is preset.

Then, the resist roller 14a rotates from the time t6 when the transfer of the print medium P by the second double-sided transfer roller 45 and the vertical transfer roller 15 is stopped to the time t7 when the preset resist start waiting time elapses, and the print medium P is rotated. It is sent out to the printing unit 30.

Then, it performed repeatedly operate from the time t1 shown in FIG. 3, the rear surface is printed by the line head 31 while being constant speed transported at the transportation speed V ₂ by the conveyor belt 32.

The print medium P on which the back surface is printed is guided to the paper discharge transport path HS on the paper discharge table 41 side by the switching mechanism 43, and is discharged by the paper discharge roller 42 at a transport speed suitable for paper discharge.

Next, the printing schedule for double-sided printing will be described.

The inkjet printing apparatus 1 of the present embodiment can feed the succeeding print medium P before the preceding print medium P is ejected. Therefore, for example, after printing the front surface of the first printing medium P, the second printing medium P is printed before the first printing medium P is inverted by circular transport and printed on the back surface thereof. The surface of the second sheet can be printed by feeding the paper. Therefore, when a plurality of printing media can be circulated, it is necessary to schedule the order in which each side of the printing medium P is printed in double-sided printing.

Regarding the printing order when a plurality of print media P can be circulated, the surface of the newly fed print medium P and the print medium circulated through the first double-sided transport path DS1 and the second double-sided transport path DS2. Productivity is improved by alternately printing the back side of P.

For example, when two printing media P are circulated, as shown in FIG. 4A, the surface of the first sheet is printed, and then the surface of the second sheet is printed with a printing time of one sheet. Printing is performed, and then the back side of the first sheet that has been circulated and transported is printed. In this figure, the front side printing of the Kth sheet is represented by the black character K on a white background, and the backside printing of the Kth sheet is represented by the white character K on a black background.

Then, after printing the back surface of the first sheet, the front surface of the third sheet is printed, and then the back surface of the second sheet that has been circulated and conveyed is printed. After that, the front surface of the newly fed print medium P and the back surface of the circularly conveyed print medium P are alternately printed in the same manner. However, when the feeding of the new printing medium P is completed at the end of printing, the back side printing of the circulated and conveyed printing medium is performed twice in succession with a printing time of one sheet, and the printing is completed. In the present embodiment, the number of print media P that is circulated and conveyed between the end of printing on the front surface of the predetermined print medium P and the printing of the back surface of the print medium P is the number of sheets N in the transport path. In the case of FIG. 4A, N = 2.

By the way, when the inkjet printing apparatus 1 performs single-sided printing, it is assumed that the time from the start of printing on the first sheet to the start of printing on the second sheet is dt, as shown in FIG. 4 (b). In the case of single-sided printing, since the print media P can be fed one after another, printing can be executed with the maximum productivity of the printing unit 30 of the inkjet printing apparatus 1. That is, the printing medium may be conveyed at a printing speed at which the printing unit 30 can print and between papers (paper spacing) within a range in which the required print quality and the like can be maintained.

On the other hand, when the inkjet printing device 1 performs double-sided printing, if double-sided printing can be performed with the same productivity as single-sided printing, that is, the double-sided printing can be performed with a printing time dt per single side, the maximum productivity of the inkjet printing device 1 is double-sided. Printing will be done.

In order to realize this productivity, when N = 2, for example, as shown in FIG. 4A, the first printing medium P, which started printing on the surface at time t11, circulates. Since printing on the back side is started at time t14, the print medium P may be circulated between 3 × dt.

However, since the dt is determined by the size of the print medium P (the length of the print medium P in the transport direction), the space between the papers, and the print speed, when the print speed is high, 3 × dt depends on the size of the print medium P. Becomes shorter. Then, in order to circulate and convey the first print medium P before the time of 3 × dt elapses, the motor or the like that drives the second double-sided transfer roller 45 exceeds the rated rotation speed. was there. In such a case, if the paper feed interval is widened as shown in FIG. 4C, the time of 3 × dt becomes long, so that double-sided printing can be performed, but there is a problem that the productivity is lowered.

Therefore, in the present embodiment, the productivity at the time of double-sided printing is ensured, and the motor or the like of the second double-sided transfer roller 45 is prevented from exceeding the rated rotation speed. Specifically, in the present embodiment, the double-sided transfer speed is adjusted by changing the control conditions of the number of sheets N for the transfer path and the reversing section 50 in the circulation transfer. The duplex conveying speed in the first embodiment, the conveyance velocity V ₄ shown in FIG. 3, that is, the conveying speed of the constant velocity transport at the time of reversing convey the print medium P by reversing roller 52.

Note that when increasing the conveyance path number of sheets N, it is possible to increase the number of print media P present in the first conveying path DS1 and the second conveying path DS2, slowing the double-sided transport speed V ₄ described above be able to. For example, the print schedule for double-sided printing when the number of sheets of transport path N = 2 is the print schedule as shown in FIG. 4A as described above, but double-sided printing when the number of sheets of transport path N = 3 The print schedule at the time is the print schedule as shown in FIG. 4 (d). That is, since the printing medium P between 5 × dt it suffices circulating conveyor, can slow the duplex conveying speed V _4.

Further, in the present embodiment, as the control condition of the inverting unit 50, the conveying speed V ₃ at the time of forward rotation convey the print medium P to the reverse transport path SR by reversing roller 52, and an inverting portion wait time SB _wait the above Adjust as needed.

Specifically, when the number of sheets N of the transport path is increased as described above, the double-sided transport speed V ₄ can be slowed down, but as a result, the recalculated double-sided transport speed V ₄ is the printing speed (convey speed). It may be slower than _{V 2).} If the double-sided transfer speed V ₄ is slower than the printing speed (transfer speed V ₂ ), an inconvenience occurs. Specifically, when performing feeding of the print medium P from the internal sheet feeding section 20, toward the interior sheet feeding section 20 from the resist roller 14a, the paper feed in printing speed (conveyance speed V ₂₎ and the same speed Will be done. Then, the print medium P is supplied from the second double-sided transfer path DS2 between the paper feeds of the print medium P from the internal paper feed unit 20, so that the print medium P always reaches the resist roller 14a at regular intervals. Is controlled by.

In such control, when the double-sided transfer speed V ₄ is slower than the printing speed (transfer speed V ₂ ), the transfer speed between the vertical transfer roller 15 and the resist roller 14a also becomes slow. On the other hand, since it is necessary to keep the time when the print medium P arrives at the resist roller 14a unchanged, the print medium P is conveyed toward the resist roller 14a at an earlier timing. When the transfer control of the print medium P is performed in this way, as shown in FIG. 5, the rear end of the print medium P1 fed from the internal paper feed unit 20 and the print supplied from the second double-sided transfer path DS2. The tip of the medium P2 may collide.

Therefore, in order to avoid such collision of the print medium P, when the double-sided transfer speed V ₄ becomes slower than the printing speed (convey speed V ₂ ), the transfer speed V ₃ is slowed down by that amount. to allow fast two-sided conveyance speed V _{4. If the double-sided transport speed V 4} does not exceed the printing speed (convey speed V ₂ ) even if the transport speed V ₃ is lowered, the double-sided transport speed V 4 can be increased by increasing the reverse portion wait time SB _wait. to be able to increase the transport speed V _4.

That is, in the present embodiment, the productivity at the time of double-sided printing is ensured, the motor of the second double-sided transfer roller 45 and the like do not exceed the rated rotation speed, and the double-sided transfer speed is equal to or higher than the printing speed. The control conditions of the number of sheets N and the reversing section 50 are changed to adjust the double-sided transfer speed.

Here, before the specific description of the method for adjusting the double-sided transport speed V _{4 described above, the method for calculating the double-sided transport speed V 4} will be described with reference to FIG. The numbers 1 to 5 shown in the upper part of FIG. 3 are numbers indicating each section in the range of the arrow, 1a to 1c indicate a section further dividing the section 1, and 3a to 3d further divide the section 3. 4a to 4e indicate a section in which the section 4 is further divided. Then, in the following description, when a section number is attached as a subscript of T, it means the transport time of the print medium P in the section of that number (excluding section 5), and is used as a subscript of L. When a section number is attached, it means the transport distance of the print medium P in the section with the number.

_{First, the double-sided transport time T INV} from the time t1 when the transfer of the print medium P by the secondary paper feed unit 14 is started until the print medium P is circulated and conveyed again by the secondary paper feed unit 14 is , Calculated by the following equation (1).
T _INV = T ₁ + T ₂ + T ₃ + T ₄ + T ₅ ... (1)

Next, the conveyance time T ₁ in a section 1 shown in FIG. 3 is calculated by the following equation (2). L ₁ is the distance from the resist roller 14a of the secondary paper feed unit 14 to the first belt platen roller 33.

The transport time T ₂ in the section 2 shown in FIG. 3 is calculated by the following equation (3). L ₂ is the distance from the first belt platen roller 33 to the reverse transfer sensor RS + the length of the print medium P.

The transport time T ₃ in the section 3 shown in FIG. 3 is calculated by the following equation (4). In addition, L ₃ is the distance from the reversing transfer sensor RS to the reversing roller 52-the amount of left end remaining at the rear end at the time of reversing Ls. Further, T _3d = SB _wait is a time for temporarily stopping the print medium P in the reverse transfer path SR, and an initial value is initially set.

The transport time T ₄ in the section 4 shown in Figure 3, is calculated by the following equation (5). Note that L ₄ is the distance from the reversing roller 52 to the resist roller-the amount of remaining rear end at the time of reversing Ls + the amount of slack.

The time T ₅ in the section 5 shown in FIG. 3, the registration roller is waiting to start.

_{Then, if T 4} represented by the above equation (5) is arranged, it can be expressed by the following equation (6).

Then, by substituting _{T 4} represented by the above equation (6) for the above equation (1) _{and moving the T INV} to the right side, it can be expressed by the following equation (7).

By multiplying V ₄ to both sides of the above equation (7), it is possible to obtain the second-order equation of V _4, such as the following equation (8). By solving the quadratic equation of the equation (8), the double-sided transfer speed V ₄ can be expressed by the following equation (9).

_{The T INV} in the above equation (9) needs to satisfy the double-sided transfer time of 3 × dt when N = 2 in FIG. 4 (a) in order to secure the same production rate as that of single-sided printing. As described above, it is necessary to satisfy the following equation (10).
T _INV = {(length of print medium P / print speed) + paper spacing} (2 x number of sheets in the path N-1)
... (10)

Next, the adjusting method of the double-sided transport speed V ₄ described above will be explained with reference to a flow chart shown in FIG.

First, the control unit 60 tentatively determines the number of sheets N of the transport path in the circulation transport based on the print conditions (size (length) and print speed of the print medium P, etc.) set by the user (S10). Specifically, the control unit 60 calculates the total transport path length La by adding _{the above-mentioned L 1} , L ₂ , L ₃ , and L ₄ as in the following equation (11).
La = L ₁ + L ₂ + L ₃ + L ₄ ... (11)

In the case of double-sided transfer, since the print medium P for front side printing and the print medium P for backside printing are alternately conveyed, the length apparently is the sum of the length of the print medium P and the paper spacing. Considering that two print media are circulating, the number of sheets N for the transport path is tentatively calculated by the following formula (12). The reason why the number of sheets N of the transfer path is tentatively calculated in this way is that the number of sheets N of the transfer path may be increased later. Physically, the maximum number of sheets for the transfer path is twice the number of sheets N for the transfer path calculated by the following formula (12).
Number of sheets of transport path N = Overall transport path length La / {2 x (length of print medium P + paper spacing)}
・ ・ (12)

Then, when the control unit 60 provisionally calculates the number of sheets N of the transfer path sheets, the temporarily calculated number of sheets of transfer path sheets N is substituted into the above equation (9) _{to calculate the double-sided transfer speed V 4} (S12).

Control unit 60, the double-sided transport speed _{V 4} calculated in S12, checks whether available calculated by the above equation (9) (S14). The double-sided transfer speed V ₄ is calculated by solving the quadratic equation shown in the above equation (8), but when the solution is an imaginary number, the control unit 60 cannot calculate the _{double-sided transfer speed V 4.} (S14, NO). When the double-sided transfer speed V ₄ cannot be calculated, the print medium P that has been circulated and conveyed has a timing set in advance for the resist roller 14a in the transfer path sheet number N provisionally calculated in S10. This is a case where arrival is not possible due to the size of the print medium P, the print speed, and the timing determined between the papers).

Therefore, when the control unit 60 determines that the double-sided transfer speed V ₄ cannot be calculated (S14, NO), the control unit 60 changes the number of sheets of the transfer path N to N + 1 (S16), and again, the number of sheets of the transfer path N + 1. Is substituted into the above equation (9) _{to calculate the double-sided transfer speed V 4} (S12). Control unit 60, to the duplex conveyance speed _{V 4} is can be calculated, and repeatedly performs the calculation of the two-sided conveyance velocity _{V 4,} an increase of the conveyance path number of sheets N (S16) (S12). Note that, in S16, increasing the conveyance path number of sheets N, as well in order to allow calculation of two-sided conveyance speed V _4, the determination at S18 in after a maximum two-sided than the conveying speed of the double-sided transport speed V ₄ It is also to make it.

Then, when the control unit 60 determines in S14 that the double-sided transport speed V ₄ can be calculated (S14, YES), _{the control unit 60 compares the calculated double-sided transport speed V 4} with the preset maximum double-sided transport speed. (S18). Up The duplex conveying speed is a value calculated from the upper limit value of the rated rotation speed of the motor for driving the rollers for conveying the printing medium P in both transport speed V ₄ such as a second duplex conveyance roller 45.

When the double-sided transfer speed V ₄ is equal to or less than the maximum double-sided transfer speed (S18, NO) in S18, the control unit 60 determines whether or not _{the double-sided transfer speed V 4} is equal to or higher than the printing speed (transfer speed V _2). Judgment (S20). Here, the reason for determining S20 is as described above.

Then, when the double-sided transfer speed V ₄ is equal to or higher than the printing speed (convey speed V ₂ ) (S20, YES), the control unit 60 calculates the reversing unit drive margin (S22). The reversing unit drive margin is set so that the printing medium P that is then conveyed toward the reversing unit 50 does not collide with the printing medium P while the printing medium P is inverted in the reversing unit 50. The method of calculating the inverting unit drive margin will be described later.

Next, the control unit 60 determines whether or not the inversion unit drive margin is 20 ms or less (S24). Then, the control unit 60, when the inverting portion driving margin exceeds 20 ms (S24, NO), the double-sided transport speed _{V 4} ends the adjustment process as appropriate.

On the other hand, in S20, when the double-sided transfer speed V ₄ is lower than the print speed (convey speed V ₂ ) (S20, NO), _{the control unit 60 sets the transfer speed V 3} shown in FIG. 3 to the print speed (convey). Check whether the speed is V ₂ ) + 100 mm / s or more (S26). The transport speed V3 is the transport speed when the printed print medium P is fed to the reversing section 50, and is the reverse rotation speed of the reversing section of the present invention. When the transport speed V ₃ is the initial value, the printing speed (convey speed V ₂ ) + 100 mm / s or more is set.

Then, the control unit 60, the conveyance speed _{V 3,} when it is printing speed (conveyance speed _V 2) + 100mm / s or more, to calculate the conveying speed _V 3 -100 mm / s, i.e. the conveying speed _{V 3} Decrease by 100 mm / s (S28), return to S12, _{substitute the decelerated transport speed V 3} into the above equation (9), and recalculate the double-sided transport speed V _4. Then, the control unit 60 performs the processing after S14 again.

Then, even when the control unit 60 recalculates the double-sided transfer speed V _{4 while lowering the transfer speed V 3} , the double-sided transfer speed V ₄ remains less than the printing speed in S20, and as a result, in S26. If the transport speed V ₃ is less than the printing speed (convey speed V ₂ ) + 100 mm / s (S26, NO), _{whether the transport speed V 3} and the printing speed (convey speed V ₂ ) are different. Is confirmed (S30). Control unit 60, when the printing speed conveyance speed _{V 3} of the (conveying speed _{V 2)} are different set to the same size as the (S30, YES), the printing speed conveyance speed _{V 3} (the conveying velocity _{V 2)} (S32). Then, the control unit 60 returns to S12 and substitutes the transfer speed V _{3 having the same magnitude as the printing speed (convey speed V 2} ) into the above equation (9) to recalculate the double-sided transfer speed V _4. Then, the control unit 60 performs the processing after S14 again.

Then, as a result, when the determination results of S18, S20 and S26 become NO again, or as a result of lowering the _{transport speed V 3 in S28, the transport speed V 3} and the printing speed (convey speed V ₂ ) are increased in S30. If they are the same, the control unit 60 determines in S30 that the transport speed V ₃ and the printing speed (convey speed V ₂ ) are the same (S30, NO). In this case, since it is impossible to adjust the double-sided transport speed V _{4 by decelerating the transport speed V 3 , T 3d} = SB _wait shown in FIG. 3, which is the wait time of the reversing portion 50, is lengthened by 1 ms (S34). Then, the control unit 60 returns to S12 _{and substitutes T 3 after adding T 3d} = SB _wait by 1 ms to the above equation (9) to recalculate the double-sided transfer speed V _4. Then, the control unit 60 performs the processing after S14 again.

Then, the control unit 60 repeats the above-described processing until the double-sided transfer speed V ₄ becomes equal to or higher than the printing speed (convey speed V ₂ ) in S20, but in S18, the double-sided transfer speed V ₄ is the maximum double-sided transfer speed. If it is determined that more than (S18, YES), or in S24, the inversion unit in a case where the driving margin is determined to be 20ms or less (S24, YES), the conveyance speed _{V 3} and the inverting unit wait time described above adjusted alone, can not be set the duplex conveying speed V ₄ properly, but would drop the productivity, adds the sheet interval only 1 ms (S36).

Then, the control unit 60 returns to S12 and recalculates the double-sided transfer speed V _{4 by substituting the T IN} V obtained by adding 1 ms between the papers to the above equation (9). Then, the control unit 60 performs the processing after S14 again. The control unit 60 repeats the addition between papers in S36 until it is determined in S20 that the double-sided transfer speed V ₄ is equal to or higher than the printing speed (convey speed V _{2) and the inversion unit drive margin exceeds 20 ms.} conduct.

Then, the control unit 60 ends the process when it is determined in S20 that the double-sided transfer speed V ₄ is equal to or higher than the printing speed (convey speed V ₂ ) and the inversion unit drive margin exceeds 20 ms. duplex conveying speed _{V 4} is in is calculated, performing duplex conveyance control using the conveying speed _{V 3,} the inversion unit wait time _T 3d _{= SB wait.}

According to the inkjet printing apparatus 1 of the above embodiment, the number of sheets N and the double-sided transfer speed V ₄ of the transfer path of the print medium P are calculated based on the size and the print speed of the print medium P, and the calculated double-sided transfer speed V _{When 4} exceeds the maximum double-sided transfer speed or becomes lower than the printing speed, the control conditions of the number of sheets N for the transfer path and the reversing section 50 are changed so that the double-sided transfer speed is recalculated. It is possible to calculate _{the double-sided transfer speed V 4} within a preset range (less than the maximum double-sided transfer speed and higher than the print speed) without lowering the printing productivity.

Also, the duplex conveying speed V _4, which is calculated based on the size and the printing speed of the printing medium P, in the case is less than the printing speed is lowered to (S20 in FIG. 6, NO), the inversion unit forward speed (FIG. 6 of S28), since so as to recalculate the duplex conveying speed, amount of lowering the inverted portion forward speed as described above, it is possible to increase the two-sided conveyance speed V _4, as shown in FIG. 5 It is possible to avoid a collision between the print medium P1 and the print medium P2.

Also, the duplex conveying speed V _4, which is calculated by reducing the reversing portion forward speed, if the same as the inversion unit forward speed (S30 in FIG. 6, NO), the inversion portion wait time of the printing medium P at the inverting portion 50 by increasing the T _{3d =} SB _wait (S34 in FIG. 6). Thus recalculating the duplex conveying speed V _4, even if it is not possible to lower the inversion unit forward speed and long inversion portion wait time min, it is possible to increase the two-sided conveyance speed V _4, it is possible to avoid collision of the printing medium P2 and the printing medium P1 as shown in FIG.

That is, in the inkjet printing apparatus 1 of the present embodiment, as described above, the number of sheets N of the transport path is added, the reverse rotation speed of the reverse rotation portion 50 is reduced, and the reverse rotation portion wait time is changed. Since the double-sided transfer speed V ₄ can be set to be less than the maximum double-sided transfer speed and higher than the print speed without increasing the speed, it is possible to avoid the collision between the print medium P1 and the print medium P2 as shown in FIG.

Further, in the present embodiment, since the inverting portion drive margin is also secured, the collision of the print medium P in the inverting portion 50 can be avoided.

Therefore, the inkjet printing apparatus 1 of the present embodiment can maintain productivity while not causing transport defects.

Regarding productivity, for example, when the paper spacing for single-sided printing is 100 ms, the paper spacing had to be widened to 200 ms during double-sided printing in the conventional method, but according to the inkjet printing apparatus of the present embodiment, the transport path The paper spacing can be maintained at 100 ms by changing the control conditions of the number of sheets N and the reversing section 50.

Further, in the inkjet printing apparatus 1 of the above embodiment, so as to adjust the reversing portion forward speed as described above and (conveyance speed V ₃₎ reversing unit wait time, reversing unit weight inversion unit forward speed I try to adjust before the time. By preferentially decelerating the forward rotation speed of the reversing portion in this way, the acceleration time can be shortened, so that the transport of the print medium P can be stabilized. Further, vibration and power consumption can be suppressed by reducing the normal rotation speed of the reversing part.

Further, in the inkjet printing apparatus 1 of the above embodiment, the double-sided transfer speed V ₄ is adjusted before the reverse rotation speed (convey speed V _{3) of the reversing portion.} This is because longer towards the conveying distance in the duplex conveying speed V ₄ than the transport distance in the reversing section forward speed can thereby increase the width of the adjustment.

Next, the method of calculating the reversing part drive margin described above will be described. The inverting unit drive margin is set so that the printing medium P, which is then conveyed toward the inverting unit 50, does not collide with the printing medium P while the printing medium P is inverted in the inverting unit 50 as described above.

First, the interval at which the print medium P conveyed from the printing unit 30 rushes into the reversing unit 50 (paper reversing rushing interval) is calculated. The time required for printing by the printing unit 30 can be calculated by dividing the length of the printing medium P by the printing speed, and the feeding interval of the printing unit 30 is calculated by adding the time required for printing and the space between papers. Can be done.

Since the printed print medium P is inserted into the reversing section 50 at an interval of one in two sheets, the paper reversing rushing interval into the reversing section 50 is twice as long as the feeding interval of the printing section 30. .. Therefore, the paper reversal plunge interval Tnp is calculated by the following equation (13).
Tnp = {(length of print medium P / printing speed) + paper spacing} x 2 ... (13)

_{On the other hand, the operating time T SB} of the reversing roller 52 of the reversing unit 50 is T _SB = T ₃ + T ₄ .

Then, while the printing medium P is inverted, in order to avoid hitting the next print medium _P, the relationship of _{T SB} and Tnp _must be _T SB _{<T np.} Therefore, the inversion unit drive margin can be calculated by _{T np} −T _SB. In S24 shown in FIG. 6, it is determined whether or not _{T np} −T _{SB is 20 ms or less.}

_{Next, in the first embodiment, when adjusting the double-sided transfer speed V 4} according to the flowchart of FIG. 6, _{the double-sided transfer speed V 4} is calculated based on the above equations (9) and (10). In this case, a preset paper spacing is used, but when the post-processing apparatus is connected to the inkjet printing apparatus 1, for example, the post-processing performed in the post-processing apparatus is required. You need to consider the time.

Specifically, for example, in the post-processing apparatus, when the matching process is performed as the post-processing for each print medium P ejected from the inkjet printing apparatus 1, the matching process of the previously ejected print medium P is completed. It is necessary to adjust the space between the papers so that the next print medium P is ejected later.

Therefore, in the following, taking into account the sheet interval corresponding to the time required for the above-mentioned post-treatment, a method of adjusting the duplex conveying speed V _4, will be described with reference to a flow chart shown in FIG. Here, the points different from the processing of the flowchart shown in FIG. 6 will be mainly described.

First, the control unit 60 temporarily sets the number of sheets N of the transport path in the circulation transport based on the print conditions (size (length) and print speed of the print medium P, etc.) set by the user, as in the above embodiment. Decide (S40).

Specifically, the number of sheets N of the transport path is tentatively calculated based on the above equation (12), and at this time, the shortest paper spacing according to the time required for post-processing is substituted as the paper spacing. The paper spacing according to the time required for post-processing may be set in advance in the inkjet printing device 1, or the time required for post-processing may be obtained from the post-processing device connected to the inkjet printing device 1 and the time required for post-processing may be obtained. It may be calculated based on the time required for the acquired post-processing, the size of the print medium P, and the print speed.

_{Then, the control unit 60 calculates the double-sided transport speed V 4} by substituting the provisionally calculated number of sheets of transport path sheets N into the above equations (9) and (10) in the same manner as in the above embodiment (S42). ), At this time, as the paper space to be substituted in the equation (10), the shortest paper space according to the time required for the above-mentioned post-treatment is used. Then, for the subsequent processing from S44 to S60, the same processing as the processing of S14 to S30 in the flowchart shown in FIG. 6 is performed.

Then, even when the control unit 60 _{recalculates the double-sided transfer speed V 4 while lowering the transfer speed V 3} (normal rotation speed of the reversing unit), the double-sided transfer speed V ₄ remains less than the printing speed in S50. There, when in relation to the printing speed can not be lowered conveying speed V ₃ any more, that is, in S60, if the printing speed conveyance speed V ₃ is determined to be the same (S60, nO) , The step proceeds to the step of adjusting the wait time of the reversing portion 50 as in the above embodiment.

Then, at this time, the control unit 60 _{confirms whether or not the wait time SB wait} of the reversing unit 50 is equal to or less than the shortest paper spacing according to the time required for the post-processing described above (S64). Hereinafter, the shortest paper spacing according to the time required for post-treatment is referred to as the shortest post-treatment required paper spacing. In this way, the comparison between the wait time SB wait and the shortest post-processing request paper is made to the print medium P temporarily stopped at the reversing section 50 if the wait time SB wait is longer than the shortest post-processing request paper. On the other hand, the next print medium P collides with each other.

Then, in S64, when _{it is determined that the wait} time SB wait is equal to or less than the shortest post-processing request paper spacing, the control unit 60 _{lengthens the wait} time SB wait by 1 ms (S66). Then, the control unit 60 returns to S42 _{and substitutes T 3 after adding T 3d} = SB _wait by 1 ms to the above equation (9) to recalculate the double-sided transfer speed V _4. Then, the control unit 60 performs the processing after S44 again.

Then, in S50, the control unit 60 _{repeats the above-described processing until the double-sided transfer speed V 4} becomes equal to or higher than the printing speed (convey speed V ₂ ), but in S64, the wait time SB _wait is the shortest post-processing request paper. If it is determined that the interval is longer than the interval, it is confirmed whether or not the shortest post-processing request interval is 200 ms or less (S68). Note that 200 ms is the longest paper spacing allowed in the inkjet printing apparatus 1, and is a preset value. This value varies depending on the configuration of the inkjet printing apparatus 1, and is not limited to 200 ms.

Then, the control unit 60, in S68, among the post-processing requests shortest paper, if it is determined that the 200ms or less (S68, YES), only the adjustment of the conveying speed _{V 3} and the inverting unit wait time described above Since the double-sided transfer speed V ₄ cannot be set appropriately, the productivity is reduced, but the space between papers is added by 1 ms (S72).

Then, the control unit 60 returns to S42, but to calculate the two-sided conveyance velocity _{V 4} according to equation (9) and the above equation (10) (S42), this time, as between the paper into equation (10) Is used for the shortest post-processing requirement. Next, the control unit 60 performs the processing after S44 again.

The control unit 60 repeats the addition between papers in S72 until it is determined in S50 that the double-sided transfer speed V ₄ is equal to or higher than the printing speed (convey speed V _{2) and the inversion unit drive margin exceeds 20 ms.} conduct.

On the other hand, as a result of repeating the addition between the papers in S72, the control unit 60 determines that the double-sided transfer speed V ₄ is equal to or higher than the printing speed (convey speed V ₂ ), and the inversion unit drive margin exceeds 20 ms. Previously, in S68, when the paper spacing after addition exceeds 200 ms (S68, NO), the number of sheets of the transfer path N is changed to N + 1 (S70), and the number of sheets of the transfer path N + 1 is increased again. into equation (10), calculates the two-sided conveyance velocity _{V 4} on the basis of the above equation (9) (S42). Then, the control unit 60 performs the processing after S44 again.

The control unit 60, in S48, if the two-sided conveyance velocity _{V 4} calculated in S44 is determined to exceed the maximum duplex conveying speed (S48, YES), or in S54, the inversion unit driving margin is 20ms or less If it is determined that (S54, YES) also, only the adjustment of the conveying speed V ₃ and the inverting unit wait time described above can not be set the duplex conveying speed V ₄ properly, repeated processing of subsequent S68 lines Be told.

Then, the control unit 60 ends the process when it is determined in S50 that the double-sided transfer speed V ₄ is equal to or higher than the printing speed (convey speed V ₂ ) and the inversion unit drive margin exceeds 20 ms. in the duplex conveying speed _{V 4} is calculated, the conveyance speed _{V 3,} the inversion unit wait time _T 3d _{= SB wait,} and performing duplex conveyance control using the sheet interval.

By adjusting the two-sided conveyance velocity V ₄ according to the flowchart shown in FIG. 7, as described above, it is possible to adjust the double-sided transport speed V ₄ in consideration of the sheet interval corresponding to the time required for post-processing. That is, it is possible to eject the paper from the inkjet printing device 1 to the post-processing device at a timing corresponding to the space between the papers, and it does not reduce the productivity of double-sided printing and is within a preset range (maximum double-sided printing). can be adjusted below the transport velocity, the two-sided conveyance velocity V ₄ of the printing or speed).

Also, the size of the print medium P, the duplex conveying speed V _4, which is calculated based on the between printing speed and post requests shortest paper, when less than the printing speed (S50 in FIG. 7, NO), the inverted portion forward speed (Transfer speed V ₃ ) was lowered (S58 in FIG. 7) _{to recalculate the double-sided transport speed V 4. Therefore, as described above, the double-sided transport speed V 4} was reduced by the amount of the reduction in the reverse rotation speed of the reversing part. Since the speed can be increased, the collision between the print medium P1 and the print medium P2 as shown in FIG. 5 can be avoided.

When the double-sided transfer speed V ₄ calculated by lowering the reverse rotation speed (convey speed V ₃ ) is less than the print speed, the print medium P in the reverse portion 50 is within the range between the shortest post-processing required papers. Since the double-sided transfer speed V4 is recalculated by changing the stop time of the above, it is possible to avoid the collision of the print medium P in the reversing unit 50.

Next, the inkjet printing apparatus 2 using the second embodiment of the double-sided printing apparatus of the present invention will be described. In the inkjet printing apparatus 1 of the first embodiment, as shown in FIG. 1, the reversing portion 50 is provided in the lower part of the inkjet printing apparatus 1, and the printing medium P inverted by the reversing portion 50 is a second double-sided transfer path. Although it is conveyed to the resist unit 1 via the DS2, in the inkjet printing apparatus 2 of the second embodiment, as shown in FIG. 8, the reversing unit 150 is arranged on the upper side, and the reversing unit 150 The inverted print medium P is directly conveyed to the resist unit 114. Hereinafter, the inkjet printing apparatus 2 of the second embodiment will be specifically described. The vertical and horizontal directions shown in FIG. 8 are the vertical and horizontal directions of the inkjet printing apparatus 2 of the second embodiment. Further, the front side of the paper surface in FIG. 8 is the front direction, and the back side of the paper surface is the rear direction.

As shown in FIG. 8, the inkjet printing apparatus 2 of the present embodiment includes a side paper feeding unit 110, an internal paper feeding unit 120, a printing unit 130, a paper ejection unit 140, and an inversion unit 150. ..

The printing unit 130 and the internal paper feeding unit 120 are housed and installed in a housing made of metal, resin, or the like. Further, the side paper feed unit 110 and the paper discharge unit 140 are installed in a state in which a part of the side paper feed unit 110 and the paper discharge unit 140 are housed in the housing and a part of the side paper feed unit 110 and the paper discharge unit 140 project out of the housing.

The side paper feed unit 110 includes a paper feed table 111 on which the print medium P is placed, a primary paper feed unit 112 that feeds out and conveys only the print medium P at the uppermost position from the paper feed table 111, and a primary paper feed unit 112. It includes a secondary paper feeding unit 114 that sends the print medium P conveyed by the unit 112 to the printing unit 130 at a predetermined timing.

The primary paper feed unit 112 includes a paper feed roller, a paper feed motor for driving the paper feed roller, and the like.

The secondary paper feed unit 114 is slackened by temporarily stopping the print medium P when the tip of the print medium P conveyed from the primary paper feed unit 112 or the print medium P conveyed from the internal paper feed unit 120 comes into contact with the secondary paper feed unit 114. A resist roller 114a for performing skew correction and a resist motor for driving the resist roller 114a are provided. In the present embodiment, the secondary paper feed unit 114 corresponds to the resist unit of the present invention.

The internal paper feed unit 120 is a primary paper feed unit that feeds out only the paper feed table 121a on which the print medium P is placed and the print medium P at the uppermost position from the paper feed table 121a and conveys them onto the paper feed transfer path FR. The 122a, the paper feed tray 121b on which the print medium P is placed, the primary paper feed unit 122b that feeds out only the print medium P at the uppermost position from the paper feed tray 121b and conveys it onto the paper feed transfer path FR, and printing. The paper feed tray 121c on which the medium P is placed, the primary paper feed unit 122c that feeds out only the print medium P at the uppermost position from the paper feed tray 121c and conveys it onto the paper feed transfer path FR, and the vertical transfer roller 115. It has.

The primary paper feed units 122a, 122b, 122c include a paper feed roller, a paper feed motor for driving the paper feed roller, and the like.

The print medium P fed from the paper feed tray 121a by the primary paper feed unit 122a and the print medium P fed out from the paper feed tray 121b by the primary paper feed unit 122b are conveyed toward the vertical transfer roller 115.

The vertical transfer roller 115 is provided on the transfer path between the resist roller 114a and the primary paper feed units 122a, 122b, 122c.

In this way, the print medium P is conveyed to the secondary paper feed unit 114 from the side paper feed unit 110 or the internal paper feed unit 120, and the print medium P is also conveyed from the reversing unit 150, which will be described later.

Therefore, in front of the secondary paper feed unit 114 in the transport direction, there is a transport path of the print medium P fed from the side paper feed section 110 or the internal paper feed section 120, and one surface conveyed from the reversing section 150. There is a confluence point where the transport path of the printed print medium P merges. With reference to this confluence, the path on the paper feed mechanism side is called the paper feed transfer path FR, and the other paths are called the circulation transfer path CR.

Further, a large number of paper detection sensors for detecting the print medium P are provided on the circulation transport path CR, and based on the detection signal detected by the paper detection sensor, the control unit 160 described later determines the print medium P. Transport control is performed.

Similar to the first embodiment, the printing unit 130 includes four line heads 131, an annular conveyor belt 132 provided facing the line head 131, a first belt platen roller 133, and a second belt platen. It is equipped with a roller 134.

The transport belt 132 is formed of an annular endless belt and has a large number of suction holes. The print medium P fed from the secondary paper feed unit 114 is conveyed to the annular transfer belt 132. Then, the print medium P is attracted to the transfer belt 132 by suction of a suction fan (not shown) installed on the back surface side of the transfer path surface of the transfer belt 132, and is conveyed at a predetermined transfer speed. Then, while the print medium P is conveyed by the transfer belt 132, ink is ejected from the line head 131 to the print medium P, whereby the print process is applied to the print medium P.

A conveyor belt 132 is hung on the first belt platen roller 133 and the second belt platen roller 134, and the first belt platen roller 133 and the second belt platen roller 134 are driven by a conveyor motor (not shown). As a result, the transport belt 132 rotates clockwise in FIG. 1.

The configuration of each line head 131 is the same as that of each line head 31 of the first embodiment.

The print medium P printed by the printing unit 130 is conveyed on the circulation transfer path CR by a transfer roller or the like arranged on the circulation transfer path CR. The circulation transport path CR is provided with a switching mechanism 143 for switching between guiding the print medium P conveyed on the circulation transfer path CR to the paper ejection unit 140 and recirculating the print medium P on the circulation transfer path CR. There is. Specifically, the switching mechanism 143 switches between the transport path on the paper ejection section 140 side and the transport path on the reversing section 150 side.

The paper ejection unit 140 has a tray-shaped paper ejection table 141 protruding from the housing of the inkjet printing apparatus 1, and a pair of paper ejection rollers 142 for ejecting the print medium P on the paper ejection table 141. Then, the print medium P guided toward the paper ejection unit 140 by the switching mechanism 143 is ejected to the paper ejection table 141 by the paper ejection roller 142.

The reversing unit 150 transports the print medium P from the reversing table 151 having the reversing transfer path SR for reversing the print medium P and the circulation transfer path CR to the reversing table 151, and the printing medium P conveyed to the reversing table 151. It is provided with a reversing roller 152 for returning the reversing roller 152 back onto the circulation transport path CR, a reversing motor (not shown) for driving the reversing roller 152, and the like.

The print medium P guided to the reversing section 150 by the switching mechanism 143 is conveyed from the circulation transport path CR to the reversing table 151 by the reversing roller 152, and is returned from the reversing table 151 to the circulation transport path CR again, so that the front and back sides are reversed. In this state, it is transported on the circulation transport path CR. Then, the print medium P whose front and back sides are reversed is conveyed again toward the printing unit 130 by a plurality of rollers such as a transfer roller 153 provided on the circulation transfer path CR.

The print medium P conveyed by the transfer roller 153 is again conveyed to the resist roller 114a of the secondary paper feed unit 114, and is sent out to the printing unit 130 again at a predetermined timing by the resist roller 114a. Then, the printing unit 130 performs a printing process on the back surface of the printing medium P.

FIG. 9 is a block diagram showing a schematic configuration of a control system of the inkjet printing apparatus 2 of the present embodiment. As shown in FIG. 9, the inkjet printing apparatus 2 of the second embodiment also includes a control unit 160 and an operation panel 170.

The control unit 160 controls the entire inkjet printing apparatus 2, and includes a CPU (Central Processing Unit), a semiconductor memory, and the like. The control unit 160 controls the operation of each unit of the inkjet printing device 2 by causing the CPU to execute a program stored in advance in the semiconductor memory.

Further, the control unit 160 acquires image data output from a computer or the like or image data read by a scanner or the like, and controls the printing unit 130 based on the image data to perform printing processing.

Further, the control unit 160 acquires printing conditions such as the size and printing speed of the printing medium P, calculates the double-sided conveying speed of the printing medium P, which will be described later, based on the printing conditions, and the number of sheets of the conveying path paper of the printing medium P. Performs processing such as calculation of.

Next, the transfer operation of the print medium P of the inkjet printing apparatus 2 of the present embodiment will be described with reference to the timing chart shown in FIG. The horizontal axis of FIG. 10 is time, and the vertical axis is the transport speed of the print medium P. Further, here, the transport operation during double-sided printing will be described.

First, the tip of the print medium P conveyed by the side paper feed unit 110 or the internal paper feed unit 120 comes into contact with the resist roller 114a, and temporarily stops in a state where slack is formed.

Then, the print medium P is conveyed toward the printing unit 130 by the resist roller 114a at the timing of time t1. At this time, secondary paper feeding section 114, after accelerated at the acceleration [alpha] 1, conveys the print medium P at a conveying speed V _1.

The secondary paper feeding unit 114, then decelerated at the deceleration [alpha] 2, transfers the print medium P to the conveying belt 132 at time t2 became conveying speed _{V 2.} As shown in FIG. 10, the relationship between the transport speed V ₁ and the transport speed V _{2 is V 1} > V ₂ . This makes it possible to close the space between the papers.

The conveyor belt 132 are also driven at a conveying speed V _2, to a constant velocity transport the print medium P received from the secondary sheet feed unit 114 at the conveying speed V _2. Then, the surface of the print medium P transported at the transportation speed V _2, the print processing by the printing unit 130 is performed. Then, the rear end of the printing medium P is accelerated by the acceleration α3 from the time t3 it comes out of the conveyor belt 132, to a constant velocity transport the print medium P in the conveyance speed V ₃ in the circulation path on the CR. Next, the print medium P is guided to the reverse transfer path SR by the transfer by the reverse roller 152.

After the print medium P is guided to the reverse transfer path SR, the reverse roller 152 decelerates at the deceleration α4 in order to stop the print medium P by switchback. Then, when the rear end of the print medium P reaches a position separated from the reversing roller 152 by a distance Ls (the amount of the rear end remaining at the time of reversing), the reversing roller 152 stops (time t4).

The amount Ls left at the rear end at the time of inversion is set in advance as a distance at which the print medium P can be sufficiently conveyed into the inversion transport path SR so that the print medium P can be inverted, and the print medium P can be conveyed in both directions without being disengaged from the inversion roller 152. It is set. Therefore, the deceleration start position of the reversing roller 152, when decelerated by the deceleration α4 from the conveyance speed V _3, the rear end of the printing medium P is a position that can be stopped at a distance Ls from the reversing roller 152.

Then, the reversing roller 152 resumes rotation in the reverse direction from the time t5 when the reversing portion wait time elapses from the time t4 when the transfer of the printing medium P by the reversing roller 152 is temporarily stopped, and the printing medium P switches back. Be transported. _{The inverted portion wait time SB wait} from the time t4 to the time t5 is initially set to an initial value, but is changed as necessary when calculating the double-sided transport speed described later.

Then, after the inversion of the print medium P is started, the print medium P is accelerated and conveyed by the inversion roller 152 at an acceleration of α5. Print medium P and reaches the conveying velocity V ₃ again, is it a constant velocity transport by reversing rollers 152 and the conveying roller 153.

After that, in order to stop the print medium P on the resist roller 114a, the reversing roller 152 and the conveying roller 153 are decelerated at the deceleration α6. In the present embodiment, in the course of deceleration in the deceleration alpha6, moving at a constant speed convey the printing medium P at a transport speed V _4. In this way, before the tip of the print medium P comes into contact with the resist roller 114a of the secondary paper feed unit 114, the print medium P can be conveyed at a constant speed to slow down the speed at which the print medium P collides with the resist roller 114a. It can reduce the collision noise. However, it is not always necessary to provide this constant velocity transport period.

Further, the deceleration start position of the reverse roller 152 and the conveying roller 153 described above, when decelerated by the deceleration α6 from the conveyance speed V _3, if the position can be stopped in the print medium P the tip of the secondary feeding unit 114 good. However, in the secondary paper feed unit 114, as described above, the print medium P comes into contact with the print medium P once to correct the skew, so that the secondary paper feed unit 114 is stopped with a slack. The amount of slack formed during this skew correction is preset.

Then, the resist roller 114a rotates from the time t6 when the transfer of the print medium P by the reversing roller 152 and the transfer roller 153 is stopped to the time t7 when the preset resist start waiting time elapses, and the print medium P is transferred to the printing unit 130. It is sent out toward.

Then, performed repeatedly operate from the time t1 shown in FIG. 10, the back side is printed by the line head 131 while being constant speed transported at the transportation speed V ₂ by the conveyor belt 132.

The print medium P on which the back surface is printed is guided to the paper ejection table 141 side by the switching mechanism 143, and is ejected by the paper ejection roller 142 at a transport speed suitable for paper ejection.

Next, the printing schedule at the time of double-sided printing in the inkjet printing apparatus 2 of the second embodiment will be described.

In the inkjet printing apparatus 1 of the first embodiment, the transfer in circulation transfer ensures productivity during double-sided printing and prevents the motor of the second double-sided transfer roller 45 and the like from exceeding the rated speed. The control conditions for the number of sheets N and the reversing section 50 were changed to adjust the double-sided transfer speed, but the basic idea is the same for the second embodiment, ensuring productivity during double-sided printing. In addition, the control conditions of the number of sheets N of the transfer path and the reversing section 150 are changed so that the motor of the transfer roller on the circulation transfer path RS does not exceed the rated rotation speed, and the double-sided transfer speed is adjusted. In the present embodiment, the conveyance speed V ₃ shown in FIG. 10, corresponding to the duplex conveying speed of the present invention.

Note that when increasing the conveyance path number of sheets N, it is possible to increase the number of print media P on the circular path RS, it is possible to slow down the transport speed V ₃ shown in FIG. 10.

Further, in the present embodiment, as the control condition of the reversing unit 150, the above-mentioned reversing unit wait time SB _wait is adjusted as necessary.

Specifically, when the number of sheets N of the transport path is increased as described above, the transport speed V ₃ can be slowed down, but as a result, the recalculated transport speed V ₃ is the printing speed (convey speed V _2). ) May be slower than. If the transport speed V ₃ is slower than the printing speed (convey speed V ₂ ), an inconvenience occurs. Specifically, when performing feeding of the print medium P from the internal paper feed unit 120, toward the interior feed unit 120 from the registration rollers 114a, fed at printing speed (conveyance speed V ₂₎ and the same speed Will be done. Then, during the paper feeding of the print medium P from the internal paper feed unit 120, the print medium P is supplied from the reversing unit 150 via the circulation transport path CR, and the print medium is always supplied to the resist roller 114a at regular intervals. It is controlled so that P arrives.

In such control, when the transfer speed V ₃ is slower than the printing speed (transfer speed V ₂ ), the transfer speed between the reversing portion 150 and the resist roller 114a also becomes slow. On the other hand, since it is necessary to keep the time when the print medium P arrives at the resist roller 114a unchanged, the print medium P is conveyed toward the resist roller 114a at an earlier timing. When the transfer control of the print medium P is performed in this way, the rear end of the print medium P fed from the internal paper feed section 120 may collide with the tip of the print medium P conveyed from the reversing section 150. be.

Therefore, in order to avoid such collision of the print medium P, when the transfer speed V ₃ becomes slower than the print speed (convey speed V ₂ ), the reverse portion wait time SB _wait is increased. min, to allow faster transport speed V _3.

That is, in this embodiment, to ensure the productivity at the time of duplex printing, and circulating a motor of the conveying roller on the conveying path CR is to avoid exceeding the rated speed, further conveyance speed V ₃ or greater printing speed by changing the control condition of the conveyance path number of sheets N and inverted portion 50 so as to adjust the conveying speed V _3.

The basic concept of the calculation method of the transport speed V ₃ is the same as the calculation method of the double-sided transport speed V ₄ of the first embodiment, and the calculation is performed based on the timing chart shown in FIG. Specifically, the transport speed V ₃ is calculated by the following equation (14).

The numbers 1 to 5 shown in the upper part of FIG. 10 are numbers indicating each section in the range of the arrow as in FIG. 3, and 1a to 1c indicate sections in which the section 1 is further divided, and 3a to 3a to 1c. 3d indicates a section in which the section 3 is further divided, and 4a to 4e indicate a section in which the section 4 is further divided. When a section number is added as a subscript of T, it means the transport time of the print medium P in the section of that number (excluding section 5), and the section number is added as a subscript of L. If it is, it means the transport distance of the print medium P in the section of the number.

_{The T INV} in the above formula (14) must satisfy the following formula (15) in order to secure a production rate equivalent to that of single-sided printing.
T _INV = {(length of print medium P / print speed) + paper spacing} (2 x number of sheets in the path N-1)
... (15)

Next, the method of adjusting the conveying speed V ₃ described above will be described with reference to the flowchart shown in FIG. 11. Here, in consideration of the sheet interval corresponding to the time required for post-processing described above, a method for adjusting a transport speed V _3.

First, the control unit 160 tentatively determines the number of sheets N of the transfer path in the circulation transfer path CR based on the print conditions (size (length) of the print medium P, print speed, etc.) set by the user (S80). .. Specifically, the control unit 160 tentatively calculates the number of sheets N for the transport path according to the above equation (12). In the case of the second embodiment, the total transport path length La is L1 + L2 + L3 + L4 shown in FIG.

Then, the control unit 160, when the temporary calculated conveyance path number of sheets N, the conveyance path number of sheets N provisionally calculated by substituting the above equation (14) and the above equation (15) calculating the two-sided conveyance speed V ₃ (S82).

Control unit 160, the two-sided conveyance speed _{V 3} calculated in S82, checks whether available calculated by the above equation (14) (S84). The double-sided transfer speed V ₃ is calculated by solving the quadratic equation shown in the above equation (14), but when the solution is an imaginary number, the control unit 160 cannot calculate the _{double-sided transfer speed V 3.} (S84, NO). When the double-sided transfer speed V ₃ cannot be calculated, the timing at which the print medium P that has been circulated and conveyed is preset with respect to the resist roller 114a in the transfer path sheet number N provisionally calculated in S80 ( This is a case where arrival is not possible due to the size of the print medium P, the print speed, and the timing determined between the papers).

Therefore, when the control unit 160 determines that the double-sided transfer speed V ₃ cannot be calculated (S84, NO), the control unit 160 changes the number of sheets of the transfer path N to N + 1 (S86), and again, the number of sheets of the transfer path N + 1. Is substituted into the above equation (14) _{to calculate the double-sided transfer speed V 3} (S82). Controller 160, until the duplex conveying speed _{V 3} enables calculation is performed by repeating the calculation of the two-sided conveyance speed _{V 3} and the increase of the conveyance path number of sheets N (S86) (S82). Note that, in S86, increasing the conveyance path number of sheets N, as well in order to allow calculation of two-sided conveyance speed V _3, the determination at S88 after the maximum two-sided than the conveying speed of the two-sided conveyance speed V ₃ It is also to make it.

Then, when the control unit 160 determines in S84 that the double-sided transport speed V ₃ can be calculated (S84, YES), _{the control unit 160 compares the calculated double-sided transport speed V 3} with the preset maximum double-sided transport speed. (S88). Up The duplex conveying speed is a value calculated from the upper limit value of the rated rotation speed of the motor for driving the rollers for conveying the printing medium P at a duplex conveying speed V _3.

When the double-sided transfer speed V ₃ is equal to or less than the maximum double-sided transfer speed (S88, NO) in S88, the control unit 160 determines whether or not _{the double-sided transfer speed V 3} is equal to or higher than the printing speed (transfer speed V _2). Judgment (S90). Here, the reason for determining S90 is as described above.

Then, when the double-sided transfer speed V ₃ is equal to or higher than the printing speed (convey speed V ₂ ) (S90, YES), the control unit 160 calculates the reversing unit drive margin (S92).

Next, the control unit 160 determines whether or not the inversion unit drive margin is 20 ms or less (S94). Then, the control unit 160, when the reversing section drive margin exceeds 20 ms (S94, NO), the double-sided conveyance speed _{V 3} ends the adjustment process as appropriate.

On the other hand, in S90, when the double-sided transfer speed V ₃ is lower than the printing speed (convey speed V ₂ ) (S90, NO), the control unit 160 proceeds to the step of adjusting the wait time of the reversing unit 150. _{At this time, it is confirmed whether or not the wait time SB wait} of the reversing unit 50 is equal to or less than the shortest post-processing request paper spacing (S96).

Then, in S96, when _{it is determined that the wait} time SB wait is equal to or less than the shortest post-processing request paper spacing (S96, YES), the wait time SB _wait is lengthened by 1 ms (S98). Then, the control unit 160 returns to S82, with respect to the above equation (14), the wait time _{SB wait} by substituting the time after 1ms sum recalculating duplex conveying speed _{V 3.} Then, the control unit 160 performs the processing after S84 again. By so long wait time SB _wait, it is possible to increase the two-sided conveyance speed V _3, and the rear end of the printing medium P fed from the inside paper feeding unit 120 is conveyed from the reversing unit 150 It is possible to avoid a collision with the tip of the print medium P. _{Further, as described above, by adding the wait} time SB wait within the range between the shortest post-processing required papers, it is possible to avoid the collision of the print medium P in the reversing unit 150.

Then, in S90, the control unit 160 performs a process of adding the _wait time SB wait by 1 ms as described above until _{the double-sided transfer speed V 3} becomes equal to or higher than the printing speed (convey speed V _2). When the wait time SB _wait after the addition becomes longer than the shortest post-processing request paper spacing (S96, NO), it is confirmed whether or not the shortest post-processing request paper spacing is 200 ms or less (S100). ). Note that 200 ms is the longest paper spacing allowed in the inkjet printing apparatus 2, and is a preset value. This value varies depending on the configuration of the inkjet printing apparatus 2, and is not limited to 200 ms.

Then, when the control unit 160 determines in S100 that the shortest post-processing request paper spacing is 200 ms or less (S100, YES), the double-sided transfer speed V can be _{achieved only by adjusting the wait time SB wait described above. Since 3} cannot be set appropriately, the productivity is reduced, but the space between papers is added by 1 ms (S104).

Then, the control unit 160 returns to S82, but to calculate the two-sided conveyance speed _{V 3} based formula (14) and the above equation in (15) (S82), this time, as between the paper into equation (15) Is used for the shortest post-treatment request paper spacing. Next, the control unit 160 performs the processing after S84 again.

The control unit 160 repeats the addition between papers in S104 until it is determined in S90 that the double-sided transfer speed V ₃ is equal to or higher than the printing speed (convey speed V _{2) and the inversion unit drive margin exceeds 20 ms.} conduct.

On the other hand, as a result of repeating the addition between the papers in S104, the control unit 160 determines that the double-sided transfer speed V ₃ is equal to or higher than the printing speed (convey speed V ₂ ), and that the reversing unit drive margin exceeds 20 ms. Previously, in S100, when the shortest post-processing request paper spacing exceeded 200 ms (S100, NO), the number of sheets of the transfer path sheet N was changed to N + 1 (S102), and the number of sheets of the transfer path sheet N + 1 was changed again. substituted in the above equation (15), it calculates the two-sided conveyance speed _{V 3} based on the equation (14) (S82). Then, the control unit 160 performs the processing after S84 again.

Note that, in S88, if the double-sided conveyance speed _{V 3} is determined to exceed the maximum duplex conveying speed (S88, YES), or in S94, when the reversing section drive margin is equal to or 20ms or less (S94, YES) also, only the adjustment of the reversing portion wait time SB _wait described above, can not be set the duplex conveying speed V ₃ proper is performed repeatedly processes after S100.

Then, the control unit 160 ends the process when it is determined in S90 that the double-sided transfer speed V ₃ is equal to or higher than the printing speed (convey speed V ₂ ) and the inversion unit drive margin exceeds 20 ms. in duplex conveying velocity V ₃ that it has been _calculated, inverted unit wait time SB _wait, and performing duplex conveyance control using the sheet interval.

Although the above embodiment is an example in which the double-sided printing apparatus of the present invention is applied to an inkjet printing apparatus, the printing method is not limited to the inkjet method, and the double-sided printing of the present invention can be applied to a laser type or stencil printing type printing apparatus. The device may be applied.

The following additional notes are further disclosed with respect to the double-sided printing apparatus of the present invention.
(Additional note)

In the double-sided printing apparatus of the present invention, when the double-sided transfer speed calculated based on the size of the printing medium and the printing speed is less than the printing speed, the control unit changes the control conditions of the reversing unit to reduce the double-sided transfer speed. It can be recalculated.

Further, in the double-sided printing apparatus of the present invention, when the double-sided transfer speed calculated based on the size and printing speed of the printing medium is less than the printing speed, the control unit feeds the printed print medium to the reversing unit. The double-sided transfer speed can be recalculated by lowering the normal rotation speed of the reversing part of.

Further, in the double-sided printing apparatus of the present invention, when the double-sided transfer speed calculated by lowering the normal rotation speed of the reversing part is less than the printing speed, the control unit changes the stop time of the printing medium in the reversing part to perform double-sided printing. The transport speed can be recalculated.

Further, in the double-sided printing apparatus of the present invention, the control unit changes the stop time of the printing medium in the reversing unit when the double-sided transfer speed calculated based on the size and printing speed of the printing medium is less than the printing speed. Therefore, the double-sided transfer speed can be recalculated.

Further, in the double-sided printing apparatus of the present invention, the control unit determines the size of the printing medium, the printing speed, and the space between the sheets according to the time required for the post-processing in the post-processing apparatus connected to the double-sided printing apparatus. It is possible to calculate the number of print media in the transport path and the double-sided transport speed when the printed print media is circulated and fed back to the resist unit.

Further, in the double-sided printing apparatus of the present invention, the control unit determines that the double-sided transfer speed calculated based on the paper spacing according to the size of the printing medium, the printing speed, and the time required for post-processing is less than the printing speed. The double-sided transfer speed can be recalculated by reducing the normal rotation speed of the reversing part when the printed print medium is fed to the reversing part.

Further, in the double-sided printing apparatus of the present invention, when the double-sided transfer speed calculated by lowering the normal rotation speed of the reversing part is less than the printing speed, the control unit is within the range between papers according to the time required for post-processing. , The double-sided transfer speed can be recalculated by changing the stop time of the print medium in the reversing part.

Further, in the double-sided printing apparatus of the present invention, the control unit determines that the double-sided transfer speed calculated based on the paper spacing according to the size of the printing medium, the printing speed, and the time required for post-processing is less than the printing speed. The double-sided transfer speed can be recalculated by changing the stop time of the print medium in the reversing portion within the range between the papers according to the time required for the post-processing.

1 Inkjet printing device 10,110 Side paper feed unit 11,111 Paper feed tray 12,112 Primary paper feed unit 14,114 Secondary paper feed unit 14a, 114a Resist roller 15,115 Vertical transport roller 20,120 Internal paper feed Sections 21a, 21b, 121a, 121b, 121c Paper feed trays 22a, 22b, 122a, 122b, 122c Primary paper feed section 23 Transport rollers 30, 130 Printing section 31, 131 Line head 32, 132 Transport belts 40, 140 Paper ejection Units 41, 141 Paper ejection base 42, 142 Paper ejection rollers 43, 143 Switching mechanism 50, 150 Reversing unit 52, 152 Reversing rollers 60, 160 Control unit 70, 170 Operation panel HS Paper ejection transport path P, P1, P2 Printing medium RS Reverse transfer sensor SR Reverse transfer path DS1 1st double-sided transfer path DS2 2nd double-sided transfer path CR Circulation transfer path FR Paper feed transfer path

Claims (9)

A printing unit that performs printing processing on the printing medium,
A resist unit that feeds the print medium toward the print unit at regular intervals,
A reversing section in which a printed print medium having been printed on one side of the printing section is fed by the printing section, and the printed printing medium is inverted and ejected.
A control unit for controlling the transport speed of the print medium is provided.
When the control unit circulates and conveys the number of print media in the transfer path of the print medium and the printed print medium based on the size and print speed of the print medium and re-feeds them to the resist unit. The double-sided transfer speed is calculated, and when the calculated double-sided transfer speed is out of the preset range, the number of print media in the transfer path and the control conditions of the reversing portion are changed to obtain the above. A double-sided printing device that recalculates double-sided transfer speed. When the double-sided transfer speed calculated by the control unit based on the size of the print medium and the print speed is less than the print speed, the control condition of the reversal unit is changed to recalculate the double-sided transfer speed. The double-sided printing apparatus according to claim 1. When the double-sided transfer speed calculated by the control unit based on the size and printing speed of the printing medium is less than the printing speed, the reversing unit corrects when the printed printing medium is fed to the reversing unit. The double-sided printing apparatus according to claim 2, wherein the rolling speed is reduced and the double-sided transfer speed is recalculated. When the double-sided transfer speed calculated by the control unit by lowering the normal rotation speed of the reversing unit is less than the printing speed, the stop time of the printing medium in the reversing unit is changed to reduce the double-sided transfer speed. The double-sided printing apparatus according to claim 3, which is recalculated. When the double-sided transfer speed calculated by the control unit based on the size and print speed of the print medium is less than the print speed, the stop time of the print medium in the reversal unit is changed to carry the double-sided transfer. The double-sided printing apparatus according to claim 2, wherein the speed is recalculated. The control unit prints in the transport path of the print medium based on the size of the print medium, the print speed, and the time required for post-processing in the post-processing device connected to the double-sided printing device. The double-sided printing apparatus according to claim 1, wherein the number of media and the double-sided transfer speed when the printed print medium is circulated and conveyed and re-fed to the resist unit are calculated. When the double-sided transfer speed calculated by the control unit based on the size of the printing medium, the printing speed, and the space between papers according to the time required for post-processing is less than the printing speed, the printing is performed on the reversing unit. The double-sided printing apparatus according to claim 6, wherein the double-sided transfer speed is recalculated by reducing the normal rotation speed of the reversing portion when the finished print medium is fed. When the double-sided transfer speed calculated by the control unit by lowering the normal rotation speed of the reversing unit is less than the printing speed, the reversing unit within a range between papers according to the time required for the post-processing. The double-sided printing apparatus according to claim 7, wherein the stop time of the printing medium is changed to recalculate the double-sided transfer speed. The time required for the post-processing when the double-sided transport speed calculated by the control unit based on the size of the printing medium, the printing speed, and the time required for the post-processing is less than the printing speed. The double-sided printing apparatus according to claim 6, wherein the stop time of the printing medium in the reversing portion is changed to recalculate the double-sided transfer speed within the range between papers according to the above.

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