JP2010208168A - Liquid jetting apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid jetting apparatus which can prevent an image formation surface side of a medium from curling in a concave shape on the downstream side of a head after an image is formed on the medium by the head. <P>SOLUTION: In the inkjet printing apparatus which forms the image on paper 12 being conveyed by jetting a water-based ink from the head 25, conveyance devices 28-30 are prepared on the downstream side of the head 25 to convey the paper 12 after formed with the image to the downstream side holding the paper 12 from both of front and rear sides. The conveyance devices 28-30 have pairs of upper and lower conveyance rollers 28c-30c and 28d-30d. Moreover, at least two sets or more of the devices are arranged in a conveyance direction A of the paper 12. Peripheral velocities V1-V3 of the conveyance rollers 28c-30c and 28d-30d are set to increase more as the conveyance rollers are of the more downstream side. An increase rate of the peripheral velocities V1-V3 of the conveyance rollers 28c-30c and 28d-30d varies in accordance with the width of the paper 12. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a liquid ejecting apparatus that includes, for example, an ink jet type liquid ejecting head and forms an image on a medium while conveying a sheet-like medium having flexibility such as paper to the liquid ejecting head.

  Conventionally, as this type of liquid ejecting apparatus, for example, as shown in FIG. 10, printing paper 61 is fed from a paper feeding section 62 to a printing apparatus main body 63 while being conveyed, and printing is performed in the printing apparatus main body 63. There is an ink jet printing apparatus 60 that prints on a sheet 61 and discharges the sheet from a printing apparatus main body 63 to a discharge unit 64.

  The printing apparatus main body 63 includes inkjet recording heads 65 and 66, conveyance roller apparatuses 67 to 69 that convey the printing paper 61 from both sides to the downstream side, and the conveyed printing paper 61 from below. And a support conveyance surface 70 to be supported. A plurality of recording heads 65 and 66 and conveying roller devices 67 to 69 are arranged in the conveying direction A of the printing paper 61.

  Each of the conveying roller devices 67 to 69 includes a lower conveying roller 67a to 69a that is forcibly driven to rotate by a rotation driving device 71 including a motor, and an upper conveying roller 67b that is driven to rotate by the rotation of the lower conveying rollers 67a to 69a. ~ 69b. The rotation driving device 71 is provided in common to the lower transport rollers 67a to 69a, and the peripheral speeds V of the lower transport rollers 67a to 69a are the same.

  According to this, the printing paper 61 fed from the paper feeding section 62 to the printing apparatus main body section 63 is conveyed below the recording heads 65 and 66 by the conveying roller devices 67 to 69. Water-based ink 72 is ejected from the printing paper 61 to the printing paper 61, and characters, graphics, and the like are printed on the printing paper 61. Thereafter, the printing paper 61 is discharged from the printing apparatus main body 63 to the paper discharge unit 64.

  The lower transport rollers 67a to 69a of each of the transport roller devices 67 to 69 are forcibly driven to rotate at the same peripheral speed V by the rotation driving device 71, so that the upper transport rollers 67b to 69b are driven at the peripheral speed V. The printing paper 61 rotates and is sandwiched between the lower conveyance rollers 67a to 69a and the upper conveyance rollers 67b to 69b of the respective conveyance roller devices 67 to 69 and conveyed downstream at a conveyance speed V.

  Patent Document 1 below describes a printing apparatus having a plurality of ink jet recording heads and a plurality of transport roller devices that transport roll paper. Further, Patent Document 1 described below also describes that the conveyance roller device is provided between a plurality of recording heads, and the conveyance speed of each conveyance roller device is increased as the conveyance roller device on the downstream side increases.

JP 2008-62432 A

  However, in the case shown in FIG. 10, when printing is performed on the printing paper 61 (plain paper) with the recording heads 65 and 66 using the water-based ink 72, the water of the water-based ink 72 is dried over time after printing. As shown in FIG. 11A, the water-based ink 72 contracts on the surface of the printing paper 61 as shown in FIG. 11A, and the printing surface side (image forming surface side) of the printing paper 61 becomes concave as shown in FIG. There is a problem that a curl that is curved into a shape occurs.

  Further, in the above-mentioned Patent Document 1, the printing paper is for preventing the printing paper from floating in a reverse concave shape with respect to the recording head. Therefore, similarly to the above, the printing paper is printed with the recording head using the water-based ink. After water is printed, the water-based ink is dried on the downstream side of the recording head, so that the water-based ink contracts on the paper surface and the printing surface side of the printing paper curls in a concave shape. Can not do it.

  An object of the present invention is to provide a liquid ejecting apparatus capable of preventing an image forming surface side of a medium from curling into a concave shape on the downstream side of the head after an image is formed on the medium by the head. .

In order to achieve the above object, a first aspect of the present invention is a liquid ejecting apparatus that ejects liquid from a liquid ejecting head to form an image on a medium on a flexible sheet-like medium being conveyed. There,
On the downstream side of the liquid ejecting head, a conveying device that conveys the medium after image formation from both the front and back sides to the downstream side is provided,
At least two or more sets of conveying devices are arranged in the conveying direction of the medium,
The transport speed of the transport device is set to increase as the transport device on the downstream side increases,
The rate of increase in the conveyance speed of the conveyance device is variable according to the width of the medium.

According to this, an image is formed on the medium by the liquid ejected from the liquid ejecting head while the medium is sandwiched from both the front and back sides by the transport device and transported to the downstream side.
At this time, since the transport speed of the transport device provided on the downstream side of the liquid ejecting head is set to increase as the transport device on the downstream side increases, the medium after image formation is located on the downstream side of the liquid ejecting head. It is pulled slightly in the transport direction between the transport device and another transport device downstream from the transport device. Along with this, the water-based ink adhering to the medium is pulled in the transport direction and finely divided (cut) so that it is not connected. Therefore, even if the moisture of the ink progresses, the ink contracts significantly. Can be reduced. This can prevent the image forming surface side of the medium from curling into a concave shape.

  In addition, since the speed increase rate of the transport device varies according to the width of the medium, the medium is pulled and damaged in the transport direction with an excessive force by decreasing the speed increase rate as the width of the medium decreases. Can be prevented.

In the liquid ejecting apparatus according to the second aspect of the present invention, the ratio of the area of the image portion formed on the image forming surface to the area of the image forming surface of the medium is an image forming rate.
The rate of increase in the conveyance speed of the conveyance device varies according to the image formation rate.

According to this, by changing the acceleration rate according to the image forming rate, the medium is pulled in the transport direction with the optimum force according to the image forming rate.
The liquid ejecting apparatus according to the third aspect of the invention divides the image forming surface of the medium into a plurality of image forming regions,
The ratio of the area of the image portion formed in the image forming area to the area of the image forming area is defined as an image forming rate.
The rate of increase in the conveyance speed of the conveyance device is variable according to the image formation rate obtained for each image forming area.

  According to this, the medium is pulled in the transport direction with an optimum force according to the image forming rate of each image forming area by changing the acceleration rate according to the difference in the image forming rate of each image forming area of the medium.

In the liquid ejecting apparatus according to the fourth aspect of the present invention, a transport device is provided on the upstream side of the liquid ejecting head.
The transport speed of the upstream upstream transport device and the transport speed of the downstream transport device closest to the liquid ejecting head are set to be the same.

  According to this, it is possible to prevent the medium from being pulled or loosened in the transport direction between the upstream transport device and the downstream transport device below the liquid ejecting head, which adversely affects the image. Can be prevented.

Further, in the liquid ejecting apparatus according to the fifth aspect of the invention, the transport device has a pair of transport rollers that transport the medium sandwiched from both the front and back sides,
The peripheral speed of the conveying roller of the conveying device provided on the downstream side of the liquid ejecting head is set so as to increase as the conveying roller of the conveying device on the downstream side increases.

  According to this, the medium is sandwiched from the front and back sides by the pair of transport rollers, and an image is formed on the medium by the liquid ejected from the liquid ejecting head while being transported downstream by the rotation of the transport roller.

  At this time, since the peripheral speed of the transport roller of the transport device provided on the downstream side of the liquid ejecting head is set to increase as the transport roller of the downstream transport device increases, on the downstream side of the liquid ejecting head, The medium after image formation is slightly stretched by being pulled in the transport direction between the transport roller of the transport device and the transport roller of another transport device downstream of the transport device.

  As described above, according to the present invention, it is possible to prevent the image forming surface of the medium from curling into a concave shape on the downstream side of the liquid ejecting head after an image is formed on the medium by the liquid ejecting head.

1 is a schematic side view showing a main configuration of a printing apparatus according to a first embodiment of the present invention. FIG. 3 is a perspective view of the printing apparatus main body of the printing apparatus. FIG. 2 is a plan view of a printing apparatus main body of the printing apparatus. 2 is a schematic side view of the printing apparatus main body of the printing apparatus. FIG. 2 is a block diagram of a control system of the printing apparatus main body of the printing apparatus. FIG. FIG. 6 is a schematic side view of the first to third transport devices on the middle portion and the paper discharge side of the printing device main body of the printing device. FIG. 4 is an enlarged view of printing paper and ink after printing by the printing apparatus. It is a top view of the printing paper printed with the printing apparatus in the 2nd Embodiment of this invention. It is a top view of the printing paper printed with the printing apparatus in the 3rd Embodiment of this invention. It is a schematic side view of the printing apparatus main-body part of the conventional printing apparatus. It is an enlarged view of the printing paper printed with the conventional printing apparatus, (a) shows the state in which the printing paper is not curled, (b) shows the state in which the printing paper is curled.

Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.
As shown in FIG. 1, reference numeral 11 denotes an ink jet printing apparatus which is an example of a liquid ejecting apparatus. The ink jet printing apparatus 11 conveys printing paper 12 (an example of a flexible sheet-like medium). However, there is a paper that is fed from the paper feeding unit 13 to the printing apparatus main body 14, printed on the printing paper 12 in the printing apparatus main body 14, and discharged from the printing apparatus main body 14 to the paper discharge unit 15.

  The paper feed unit 13 prints the paper feed stand 18 on which the print paper 12 is stacked, the paper feed roller 19 and the paper feed stand 20 for feeding the print paper 12 from the paper feed stand 18 one by one, and the fed print paper 12. A supply roller 21 that forms a pair on the upper and lower sides of the apparatus main body 14 is provided.

  The paper feed table 18 is provided with a pair of paper width guides 43 that guide both side edges of the printing paper 12. The two paper width guides 43 can be moved toward and away from each other in the width W direction of the printing paper 12, and the distance between the two paper width guides 43 can be adjusted according to the width W of the printing paper 12. Further, the paper feed unit 13 is provided with a paper width detection device 44 (see FIG. 5) that detects the width W of the print paper 12 based on the position of the both paper width guides 43.

In addition, the paper discharge unit 15 includes a paper receiving tray 22 that receives the printed paper 12 that has been printed and discharged.
As shown in FIGS. 1 to 4, the printing apparatus main body 14 includes first and second line-type recording heads 24 and 25 (an example of a liquid ejecting head) of an ink jet method and printing paper 12 on both front and back sides ( A feeding device 26-30 on the paper feeding side, the intermediate portion, and the paper discharging side that feeds downstream from both sides (upper and lower sides), and a support conveyance surface 31 that supports the printing paper 12 to be conveyed from the lower side are provided. Yes.

  Each of the line-type recording heads 24 and 25 has an image forming range having a predetermined width in the width direction B orthogonal to the transport direction A of the printing paper 12, and is formed in a line shape as schematically shown in FIG. A plurality of ink ejection portions 32 are arranged in a plurality of stages along the transport direction A. A water-based ink 41 (an example of a liquid) is ejected from these ink ejection portions 32 and an image is printed on the printing paper 12.

  A plurality of line-type recording heads 24 and 25 are provided and arranged in a staggered manner, and a plurality of line-type recording heads 24 and 25 arranged in parallel in the width direction B at a predetermined interval form a recording head row. The rows are arranged in multiple stages along the transport direction A.

  The support conveyance surface 31 is provided below the line type recording heads 24, 25, and the support conveyance surface 31 is formed with an opening 33 at a position facing each line type recording head 24, 25.

  The first line type recording head 24 is arranged in the preceding recording head row, and the second line type recording head 25 is arranged in the following recording head row. In this embodiment, the two recording head arrays are arranged before and after the conveyance direction A. However, the number of recording head arrays is not limited to the configuration exemplified in this embodiment, and the recording head arrays are arranged as follows. A plurality of three or more or a single number may be provided.

  The feeding device 26 on the sheet feeding side is disposed on the upstream side (feeding side) of the first line type recording head 24, and the conveying device 27 on the intermediate part includes the first line type recording head 24 and the second line type recording head 24. The first to third transport devices 28 to 30 on the paper discharge side are arranged between the recording head 25 and three sets (at least two sets) on the downstream side (paper discharge side) of the second line type recording head 25. The above example) is provided.

  Each of the conveying devices 26 to 30 includes lower and upper rotating shafts 26a to 30a and 26b to 30b provided over the width direction B, and lower conveying rollers 26c to 26c provided to the lower rotating shafts 26a to 30a. 30c and upper conveyance rollers 26d to 30d provided on the upper rotation shafts 26b to 30b.

  Among them, the sheet feeding side conveying device 26, the intermediate conveying device 27 (an example of the conveying device immediately upstream of the recording head 25) and the first conveying device 28 on the paper discharging side (immediately adjacent to the recording head 25). The lower transport rollers 26c to 28c with the downstream transport device) are forcibly rotated by the common first driving device 36, and the upper transport rollers 26d to 28d are driven to the lower transport rollers 26c to 26d. It is driven and rotated by 28c. The first driving device 36 includes a common first motor (not shown) and a first driving force transmission device (not shown) that transmits the rotational driving force of the first motor to the lower rotation shafts 26a to 28a. (Not shown). Further, the first driving force transmission device includes a driving pulley (not shown) provided in the first motor, a shaft pulley (not shown) provided in each of the lower rotating shafts 26a to 28a, and these And a timing belt (not shown) spanned between the drive side and shaft side pulleys.

  Further, the lower transport roller 29c of the second transport device 29 on the paper discharge side is forcibly rotated by the second drive device 37, and the upper transport roller 29d is driven to rotate by the lower transport roller 29c.

  Further, the lower conveying roller 30c of the third conveying device 30 on the paper discharge side is forcibly rotated by the third driving device 38, and the upper conveying roller 30d is driven and rotated by the lower conveying roller 30c.

  The second drive device 37 includes a second motor (not shown) that can adjust the rotation speed, and a second drive force transmission device (not shown) that transmits the rotational drive force of the second motor to the lower rotary shaft 29a. (Omitted). The second driving force transmission device includes a driving side gear (not shown) provided in the second motor, and a shaft side gear (not shown) provided on the lower rotating shaft 29a and meshed with the driving side gear. ).

  Similarly, the third driving device 38 includes a third motor (not shown) that can adjust the rotation speed, and a third driving force transmission that transmits the rotational driving force of the third motor to the lower rotating shaft 30a. And a device (not shown). The third driving force transmission device includes a driving gear (not shown) provided in the third motor, and a shaft gear (not shown) provided on the lower rotating shaft 30a and meshed with the driving gear. ).

  In addition, each lower conveyance roller 26c-30c and each upper conveyance roller 26d-30d have the same diameter. Each of the upper transport rollers 26d to 30d can be moved up and down in the vertical direction with respect to each of the lower transport rollers 26c to 30c, and is biased downward by a biasing means such as a spring (not shown). ing. Further, the front-rear intervals of the transport devices 26 to 30 in the transport direction A are set to be shorter than the length of the minimum size printing paper 12 that can be used.

  As shown in FIGS. 5 and 6, the printing apparatus main body 14 is provided with a control unit 39, which controls the sheet feeding side conveyance device 26, the intermediate portion conveyance device 27, and the paper discharge side first device. The peripheral speed V1 (an example of the transport speed) of each of the lower transport rollers 26c to 28c with the transport apparatus 28 is the same, and the peripheral speed V2 of the lower transport roller 29c of the second transport apparatus 29 on the paper discharge side ( An example of the conveyance speed) is higher than the peripheral speed V1, and a peripheral speed V3 (an example of the conveyance speed) of the lower conveyance roller 30c of the third conveyance device 30 on the paper discharge side is higher than the peripheral speed V2. The rotational speeds of the motors of the first to third driving devices 36 to 38 are controlled so that

  Further, as shown in Table 1 below, the control unit 39 sets the first peripheral speed V2 of the lower transport roller 29c of the second transport apparatus 29 to the peripheral speed V1 of the lower transport roller 28c of the first transport apparatus 28. The second stage speed increase rate R1 and the second stage speed increase rate of the peripheral speed V3 of the lower transport roller 30c of the third transport apparatus 30 relative to the peripheral speed V1 of the lower transport roller 28c of the first transport apparatus 28. The rotational speed of the motors of the first to third driving devices 36 to 38 is controlled so that R2 is changed according to the width W of the printing paper 12.

The speed increasing rates R1 and R2 (%) of the first stage and the second stage are obtained by the following equations, respectively.
R1 = (V2-V1) × 100 / V1
R2 = (V3-V1) × 100 / V1
For example, in Table 1 below, the acceleration rates R1 and R2 when the width W of the printing paper 12 is 210 mm or less are set to be smaller than the acceleration rates R1 and R2 when the width W exceeds 210 mm. The 210 mm corresponds to the width W of the A4 size printing paper 12.

  As shown in FIG. 1, the inkjet printing apparatus 11 is provided with an operation panel 45 for inputting the size of the printing paper 12 and the like.

以下、上記構成における作用を説明する。

Hereinafter, the operation of the above configuration will be described.

As shown in FIG. 1, the printing paper 12 is fed from a paper feed tray 18 by a paper feed roller 19 and supplied to a printing apparatus main body 14 by a supply roller 21.
In the printing apparatus main body 14, the lower transport rollers 26c to 28c are forcibly rotated by the common first driving device 36, and the upper transport rollers 26d to 28d are in contact with the lower transport rollers 26c to 28c. The lower conveying roller 29c is forcibly rotated by the second driving device 37, the upper conveying roller 29d is driven and rotated by the lower conveying roller 29c, and the lower conveying roller 30c is third driven. The upper conveying roller 30d is driven to rotate by the lower conveying roller 30c by being forcibly rotated by the driving device 38.

  The printing paper 12 supplied to the printing apparatus main body 14 is conveyed by being sandwiched between the lower conveying rollers 26c to 30c and the upper conveying rollers 26d to 30d from both the upper and lower sides, and is printed from the recording heads 24 and 25. The water-based ink 41 is ejected to print images such as characters and graphics on the printing paper 12.

  At this time, as shown in FIG. 6, each of the lower conveyance rollers 26c to 28c and each of the upper conveyance rollers 26d to 28d rotates at a peripheral speed V1, and each of the lower conveyance roller 29c and the upper conveyance roller 29d rotates in the circumferential direction. The lower conveyance roller 30c and the upper conveyance roller 30d rotate at a peripheral speed V3.

  As described above, the peripheral speeds V1 of the conveying rollers 28c to 30c and 28d to 30d of the first to third conveying devices 28 to 30 on the discharge side provided on the downstream side of the second line type recording head 25 are as follows. Since V3 is set so as to increase the speed of the transport device on the downstream side, the printing paper 12 after printing is connected to the first transport device 28 and the second transport device on the downstream side of the second line type recording head 25. Pulled slightly in the transport direction A with the transport device 29 and slightly stretched, and similarly pulled slightly in the transport direction A between the second transport device 29 and the third transport device 30. .

  When the printing paper 12 is stretched as described above, as shown in FIG. 7, the water-based ink 41 adhering on the surface of the printing paper 12 is pulled in the transport direction A to be finely divided (cut) and connected. Therefore, even if the moisture of the ink 41 is dried, the shrinkage of the ink 41 can be greatly reduced. Thereby, it is possible to prevent the printing surface side of the printing paper 12 from curling into a concave shape.

  As shown in Table 1, the control unit 39 determines that the first width W of the printing paper 12 detected by the paper width detection device 44 is 210 mm or less (that is, the size of the printing paper 12 is A4 or less). Control is performed so that the speed increase rate R1 of the stage is 0.1% and the speed increase rate R2 of the second stage is 0.2%, and the detected width W of the printing paper 12 exceeds 210 mm (ie, When the size of the printing paper 12 is larger than A4), control is performed so that the first stage speed increase rate R1 is 0.15% and the second stage speed increase rate R2 is 0.25%.

  In this way, the printing paper 12 is pulled in the transport direction A with an excessive force by decreasing the first stage and second stage acceleration rates R1 and R2 as the width W of the printing paper 12 is smaller. Damage can be prevented.

  Further, as shown in FIG. 6, the lower conveyance rollers 27c and 28c and the upper conveyance rollers 27d and 28d of the intermediate conveyance device 27 and the first conveyance device 28 on the paper discharge side have the same circumference. Since the printing paper 12 rotates at the speed V1, the printing paper 12 is moved in the transport direction A between the upstream intermediate transport device 27 and the downstream first transport device 28 below the second line type recording head 25. Pulling or slackening can be prevented.

  Similarly, the lower conveyance rollers 26c and 27c and the upper conveyance rollers 26d and 27d of the conveyance device 26 on the paper feeding side and the conveyance device 27 on the intermediate portion rotate at the same peripheral speed V1, respectively. The printing paper 12 is prevented from being pulled or loosened in the transport direction A between the upstream transport device 26 and the downstream intermediate transport device 27 below the line type recording head 24. Can do. Thereby, an adverse effect on the image can be prevented.

  In the first embodiment, the width W of the printing paper 12 is detected by the paper width detection device 44. However, as shown in FIG. 5, the inkjet printing device 11 is connected to a personal computer 48 (hereinafter referred to as a personal computer 48). When printing from a PC, the width W corresponding to the size of the printing paper 12 may be detected by setting the printer driver. Further, by operating the operation panel 45 of the inkjet printing apparatus 11, the width W corresponding to the size of the printing paper 12 input from the operation panel 45 may be detected.

Next, a second embodiment of the present invention will be described with reference to the drawings.
As shown in FIG. 8, the ratio of the area S2 of the printed portion 49 (an example of the image portion) printed on the printing surface 46 to the area S1 of the printing surface 46 (image forming surface) of the printing paper 12 is expressed as an image forming rate C ( (Printing duty), the image forming rate C can be obtained by the following equation.
C = (S2 / S1) × 100
The ink jet printing apparatus 11 is connected to a personal computer 48. When printing from the personal computer 48, when the printer driver develops various application data and converts it into printing data, the image forming rate C is detected. .

  As shown in Table 2 below, the control unit 39 changes the first stage and second stage acceleration rates R1 and R2 in accordance with the width W of the printing paper 12 and the image formation rate C. The rotational speeds of the motors of the first to third driving devices 36 to 38 are controlled.

以下、上記構成における作用を説明する。

Hereinafter, the operation of the above configuration will be described.

  For example, when the detected width W of the printing paper 12 is 210 mm or less and the image formation rate C is 55%, the control unit 39 sets the first stage acceleration rate R1 to 0.3% and the second stage. When the eye acceleration rate R2 is controlled to be 0.6%, and the detected width W of the printing paper 12 exceeds 210 mm and the image formation rate C is 55%, the first stage The speed increase rate R1 is controlled to be 0.35%, and the second stage speed increase rate R2 is controlled to be 0.65%.

  In this way, by changing the first stage and second stage acceleration rates R1 and R2 according to the image formation rate C, the printing paper 12 can be moved in the transport direction A with an optimum force according to the image formation rate C. Be pulled.

  In the second embodiment, the image formation rate C can be detected when the printer driver expands data of various applications and converts the data into print data. The image formation rate C can also be detected by scanning a data buffer for one page provided in the data storage 11 (including reading by a scanner).

Next, a third embodiment of the present invention will be described with reference to the drawings.
As shown in FIG. 9, the printing surface 46 (image forming surface) of the printing paper 12 is divided into a front printing region 46a (image forming region) and a rear printing region 46b (image forming region). .

The ratio of the area S2a of the print portion 49a (an example of the image portion) printed in the front print area 46a to the area S1a of the front print area 46a is defined as the front image formation rate Ca (%), Assuming that the ratio of the area S2b of the printed portion 49b (an example of the image portion) printed in the rear print region 46b to the area S1b of the print region 46b is the rear image formation rate Cb (%), each image formation rate Ca, Cb is calculated | required by the following formula, respectively.
Ca = (S2a / S1a) × 100
Cb = (S2b / S1b) × 100
The ink jet printing apparatus 11 is connected to a personal computer 48. When printing from the personal computer 48, when the printer driver develops various application data and converts it into printing data, the image forming rates Ca and Cb are determined as follows. Detected.

  As shown in Table 2 above, the control unit 39 controls the first and second stages according to the width W of the printing paper 12 and the image formation rates Ca and Cb obtained for the respective printing areas 46a and 46b. The rotational speeds of the motors of the first to third driving devices 36 to 38 are controlled so as to change the eye acceleration rates R1 and R2.

Hereinafter, the operation of the above configuration will be described.
For example, the control unit 39 has the detected width W of the printing paper 12 of 210 mm or less, the image forming rate Ca of the front printing area 46a of the printing paper 12 is 35%, and the image of the rear printing area 46b. When the formation rate Cb is 55%, the following control is performed.

  (1) First, when the front printing area 46a is being transported between the first transport device 28 and the third transport device 30, the first stage speed increase rate R1 is 0.2%, The second stage speed increase rate R2 is controlled to be 0.4%.

  (2) Next, when the rear printing area 46b is being transported between the first transport device 28 and the third transport device 30, the first stage speed increase rate R1 is 0.3%, The second stage speed increase rate R2 is controlled to be 0.6%.

  In this manner, the printing paper is obtained by changing the first stage and second stage acceleration rates R1 and R2 in accordance with the difference in the image formation rates Ca and Cb of the printing areas 46a and 46b of the common printing paper 12. 12 is pulled in the transport direction A with an optimum force according to the image formation rates Ca and Cb of the print areas 46a and 46b.

  In each of the above embodiments, the values of the acceleration rates R1 and R2 are changed based on the width W (= 210 mm) of the A4 size printing paper 12, but are limited to the width W of the A4 size printing paper 12. The width W of the printing paper 12 having a size other than A4 (for example, B5) may be used as a reference. Further, instead of the width W of the standard printing paper 12 as described above, an arbitrary numerical value width W may be used as a reference. Further, in each of the above-described embodiments, the values of the respective acceleration rates R1 and R2 are changed based on the width W (= 210 mm) of one type of printing paper 12, but on the basis of a plurality of types of width W. Good.

  In each of the above-described embodiments, as shown in FIG. 6, three sets of the first to third transport devices 28 to 30 on the paper discharge side are arranged on the downstream side of the second line type recording head 25, and two steps are performed. However, two sets of conveying devices may be arranged to set a one-stage acceleration rate. Further, four or more sets of conveying devices may be arranged, and a three-step or more speed increase rate may be set.

  In each of the above embodiments, the speed increasing rates R1 and R2 are set to the numerical values shown in Tables 1 and 2, but are not limited to the numerical values in Tables 1 and 2. Further, numerical values other than the respective acceleration rates R1 and R2 shown in Tables 1 and 2 are not limited.

In each of the above embodiments, the printing paper 12 has been described as an example of a flexible sheet-like medium, but a film or the like may be used.
In the second and third embodiments, as shown in Table 2, the image formation rate is divided every 20%, but is not limited to every 20%, and is divided every other numerical value. Also good.

11 Inkjet printing device (liquid ejecting device)
12 Printing paper (medium)
25 Recording head (liquid ejecting head)
27 Intermediate transport device (upstream transport device closest to the liquid jet head)
28 First transport device on the paper discharge side (transport device on the downstream side closest to the liquid jet head)
29 Second transport device 30 on the paper discharge side Third transport devices 27c to 30c, 27d to 30d on the paper discharge side Transport roller 46 Printing surface (image forming surface)
46a, 46b Print area (image formation area)
49, 49a, 49b Print part (image part)
A Transport direction W Print paper width (medium width)
C, Ca, Cb Image formation rate S1 Area of printing surface (area of image forming surface)
S2 Print area (image area)
R1, R2 Speed increase rate V1-V3 Peripheral speed (transport speed)

Claims (5)

A liquid ejecting apparatus that forms an image on a medium by ejecting a liquid from a liquid ejecting head to a flexible sheet-like medium being conveyed,
On the downstream side of the liquid ejecting head, a conveying device that conveys the medium after image formation from both the front and back sides to the downstream side is provided,
At least two or more sets of conveying devices are arranged in the conveying direction of the medium,
The transport speed of the transport device is set to increase as the transport device on the downstream side increases,
A liquid ejecting apparatus, wherein an increase rate of a conveying speed of a conveying device is variable according to a width of a medium. The ratio of the area of the image portion formed on the image forming surface to the area of the image forming surface of the medium is defined as an image forming rate.
The liquid ejecting apparatus according to claim 1, wherein the rate of increase in the conveyance speed of the conveyance device varies according to the image formation rate. Dividing the image forming surface of the medium into a plurality of image forming areas;
The ratio of the area of the image portion formed in the image forming area to the area of the image forming area is defined as an image forming rate.
The liquid ejecting apparatus according to claim 2, wherein the rate of increase in the conveying speed of the conveying device varies according to the image forming rate obtained for each image forming area. A transport device is provided upstream of the liquid jet head;
The conveying speed of the upstream conveying device immediately adjacent to the liquid ejecting head and the conveying speed of the downstream conveying device closest to the liquid ejecting head are set to be the same. The liquid ejecting apparatus according to any one of the above. The conveyance device has a pair of conveyance rollers that convey the medium from both the front and back sides,
5. The peripheral speed of the transport roller of the transport device provided on the downstream side of the liquid ejecting head is set so as to increase as the transport roller of the transport device on the downstream side increases. The liquid ejecting apparatus according to any one of the above.

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