JP2018138331A - Inkjet printing device - Google Patents

Abstract

An inkjet printing apparatus capable of reducing a decrease in print image quality is provided. An ink jet printing apparatus 1 is disposed at intervals along a transport direction of a paper P, and transport roller pairs 11A to 11C that transport the paper P while niping between the transport roller pairs 11A and 11B and The ink jet heads 21A and 21B are disposed between the transport roller pairs 11B and 11C, respectively, and eject ink onto the paper P. It is movable downstream. [Selection] Figure 1

Description

  The present invention relates to an inkjet printing apparatus that prints by ejecting ink from an inkjet head.

  A line-type inkjet printing apparatus that prints an image by discharging ink from an inkjet head onto a sheet while conveying the sheet is known (for example, see Patent Document 1).

  Some line-type inkjet printing apparatuses convey a sheet under an inkjet head by a pair of conveyance rollers that convey the sheet while nipping the sheet. In such an ink jet printing apparatus, a pair of transport rollers is disposed on the upstream side and the downstream side of the ink jet head in the paper transport direction, and the paper transport is performed under the ink jet head by a plurality of transport roller pairs.

JP 2008-188935 A

  When a sheet is conveyed by a plurality of conveyance roller pairs, tension may be generated on the sheet due to a difference in conveyance speed between the conveyance roller pairs. For example, in a configuration in which the conveyance speed of the sheet is increased as the pair of conveyance rollers on the downstream side in order to suppress the sagging of the sheet, a tension is generated on the sheet due to a difference in conveyance speed between adjacent conveyance roller pairs. Even in a configuration in which the conveyance speed of the sheet by each conveyance roller pair is set to the same speed, a conveyance speed difference between the conveyance roller pair may occur due to a dimensional tolerance of the roller, and tension may be generated on the sheet.

  When tension is generated in the sheet as described above, the trailing edge of the sheet passes through the pair of conveying rollers and the tension is released, so that vibration of the sheet occurs. When the vibration of the paper occurs, the conveyance speed of the paper under the ink jet head becomes unstable, and the print image quality may be deteriorated.

  The present invention has been made in view of the above, and an object of the present invention is to provide an ink jet printing apparatus that can reduce a decrease in print image quality.

  In order to achieve the above object, a first feature of the ink jet printing apparatus according to the present invention is a plurality of pairs of transport rollers that are arranged at intervals from each other along the transport direction of the paper and transport the paper while nipping the paper. And at least one inkjet head that is disposed between each pair of transport rollers and that discharges ink onto a sheet, and the pair of transport rollers other than the most downstream pair of transport rollers in the transport direction is on the downstream side due to the tension of the sheet. It is to be movable.

  The second feature of the ink jet printing apparatus according to the present invention is that the paper is transported at a higher speed as the pair of transport rollers on the downstream side.

  According to the first feature of the ink jet printing apparatus according to the present invention, the conveyance roller pair other than the most downstream conveyance roller pair is movable to the downstream side by the tension of the paper. As a result, when tension is generated in the sheet due to the difference in the conveyance speed between the pair of conveyance rollers, the tension of the sheet is reduced by moving the pair of conveyance rollers pulled by the tension of the sheet to the downstream side. Thereby, the vibration of the sheet when the trailing edge of the sheet where the tension has occurred passes through the pair of conveying rollers can be suppressed, and the deterioration of the print image quality can be reduced.

  According to the second feature of the ink jet printing apparatus according to the present invention, since the sheet is conveyed at a higher speed as the pair of conveying rollers on the downstream side, occurrence of sagging of the sheet is suppressed. Thereby, since the fluctuation | variation of a head gap is suppressed, the fall of printing image quality can be reduced more.

1 is a schematic configuration diagram of an inkjet printing apparatus according to an embodiment. It is a control block diagram of the inkjet printing apparatus shown in FIG. 6 is a flowchart for explaining an operation of reducing the tension of a sheet in a transport unit. FIG. 10 is an operation explanatory diagram of an operation of reducing paper tension in a transport unit. FIG. 10 is an operation explanatory diagram of an operation of reducing paper tension in a transport unit. FIG. 10 is an operation explanatory diagram of an operation of reducing paper tension in a transport unit. FIG. 10 is an operation explanatory diagram of an operation of reducing paper tension in a transport unit. FIG. 10 is an operation explanatory diagram of an operation of reducing paper tension in a transport unit. FIG. 10 is an operation explanatory diagram of an operation of reducing paper tension in a transport unit.

  Embodiments of the present invention will be described below with reference to the drawings. Throughout the drawings, the same or equivalent parts and components are denoted by the same or equivalent reference numerals.

  The following embodiments exemplify devices for embodying the technical idea of the present invention, and the technical idea of the present invention is the material, shape, structure, arrangement, etc. of each component. Is not specified as follows. The technical idea of the present invention can be variously modified within the scope of the claims.

  FIG. 1 is a schematic configuration diagram of an inkjet printing apparatus according to an embodiment of the present invention. FIG. 2 is a control block diagram of the ink jet printing apparatus shown in FIG. In addition, let the direction orthogonal to the paper surface of FIG. Also, the top, bottom, left, and right of the paper surface in FIG.

  As shown in FIGS. 1 and 2, the ink jet printing apparatus 1 according to the present embodiment includes a transport unit 2, a printing unit 3, and a control unit 4.

  The transport unit 2 transports the paper P fed from a paper feed unit (not shown). The transport unit 2 includes transport roller pairs 11A to 11C, a transport motor 12, paper sensors 13A to 13C, and solenoids 14A and 14B. Note that alphabetical suffixes in the reference numerals of the transport roller pairs 11A to 11C and the like may be omitted and collectively described.

  The conveyance roller pairs 11 </ b> A to 11 </ b> C convey the paper P in the direction from left to right while nipping the paper P. In the following description, upstream and downstream mean upstream and downstream in the conveyance direction of the paper P.

  The conveyance roller pair 11 includes a pair of a driving roller 16 and a driven roller 17, and conveys a sheet while nipping the driving roller 16 and the driven roller 17. The driving roller 16 is rotationally driven by the driving force of the transport motor 12. The driven roller 17 rotates following the driving roller 16.

  The conveyance roller pairs 11 </ b> A to 11 </ b> C are arranged at intervals in the conveyance direction (sub-scanning direction) of the paper P. The transport roller pair 11A is disposed on the upstream side of the inkjet head 21A of the printing unit 3 to be described later. The conveyance roller pair 11B is disposed on the downstream side of the conveyance roller pair 11A and between the inkjet head 21A and the inkjet head 21B. The transport roller pair 11C is disposed downstream of the inkjet head 21B on the downstream side of the transport roller pair 11B. The distance between the most upstream conveying roller pair 11A and the most downstream conveying roller pair 11C is the sub-scanning direction length in the sub-scanning direction among the paper sizes used in the inkjet printing apparatus 1. Shorter than length.

  Among the transport roller pairs 11A to 11C, the transport roller pairs 11A and 11B other than the most downstream transport roller pair 11C are configured to be movable downstream by the tension of the paper P.

  The driving roller 16 of the conveying roller pair 11B has a larger diameter than the driving roller 16 of the conveying roller pair 11A. Further, the drive roller 16 of the transport roller pair 11C has a larger diameter than the drive roller 16 of the transport roller pair 11B. That is, the diameter of the driving roller 16 is larger in the downstream conveying roller pair 11. Accordingly, the paper P is transported at a higher speed as the transport roller pair 11 on the downstream side. Thereby, sagging of the paper P is prevented.

  The drive roller 16 is a one-way roller. As a result, the paper P is transported at the paper transport speed by the transport roller pair 11B until the paper P reaches the transport roller pair 11C after the paper P starts to be nipped by the transport roller pair 11B, and the transport roller pair 11A rotates with the paper P. To do. Further, in a state where the paper P is nipped by the transport roller pair 11C, the paper P is transported at the paper transport speed by the transport roller pair 11C, and the transport roller pairs 11A and 11B are rotated around the paper P.

  The conveyance motor 12 rotates and drives the drive rollers 16 of the conveyance roller pairs 11A to 11C. The rotational driving force of the conveyance motor 12 is transmitted to each driving roller 16 by a driving force transmission mechanism (not shown), and each driving roller 16 is configured to rotate.

  The paper sensors 13A to 13C detect the paper P that is transported by the transport roller pairs 11A to 11C. The paper sensors 13A to 13C are disposed in the vicinity of the upstream side of the transport roller pairs 11A to 11C, respectively. The paper sensor 13 is composed of, for example, an optical sensor having a light emitting unit and a light receiving unit.

  The solenoids 14A and 14B are for returning the transport roller pair 11A and 11B moved to the downstream side to their standard positions. The solenoids 14A and 14B are connected to support portions 18A and 18B that support the conveying roller pairs 11A and 11B, respectively. Thus, the solenoids 14A and 14B can be moved upstream in order to return the conveying roller pairs 11A and 11B to the standard positions, respectively.

  The printing unit 3 prints an image on the paper P. The printing unit 3 includes inkjet heads 21A and 21B.

  The inkjet head 21 prints an image by ejecting ink onto the conveyed paper P. The inkjet head 21 has a plurality of nozzles (not shown) arranged along the main scanning direction (front-rear direction), and ejects ink from the nozzles.

  The inkjet heads 21A and 21B are arranged with a space therebetween in the sub-scanning direction (left-right direction), and the inkjet head 21A is arranged on the upstream side and the inkjet head 21B is arranged on the downstream side. The ink jet head 21A is disposed between the transport roller pairs 11A and 11B, and the ink jet head 21B is disposed between the transport roller pairs 11B and 11C. The ink jet heads 21A and 21B are arranged so as to be displaced from each other in the main scanning direction (front-rear direction). That is, the ink jet heads 21A and 21B are arranged in a staggered manner in a plan view. As a result, the inkjet head 21A prints on one side of the main scanning direction on the paper P, and the inkjet head 21B prints on the other side of the main scanning direction.

  The control unit 4 controls the operation of each unit of the inkjet printing apparatus 1. The control unit 4 includes a CPU, a RAM, a ROM, a hard disk, and the like.

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

  When printing is performed by the inkjet printing apparatus 1, first, the control unit 4 starts driving the transport roller pairs 11 </ b> A to 11 </ b> C by the transport motor 12. Next, the control unit 4 feeds the paper P to the transport unit 2 by a paper feeding unit (not shown).

  The fed paper P is transported in the transport unit 2 while being nipped by the transport roller pairs 11A to 11C. The control unit 4 controls the ink jet heads 21A and 21B based on the image data to be printed, and ejects ink onto the conveyed paper P. As a result, an image is printed on the paper P.

  When performing the printing operation as described above, the inkjet printing apparatus 1 performs an operation of reducing the tension of the paper P in the transport unit 2. An operation for reducing the tension of the paper P will be described.

  FIG. 3 is a flowchart for explaining the operation of reducing the tension of the paper P in the transport unit 2. The process of the flowchart of FIG. 3 is started when the driving of the transport roller pairs 11A to 11C is started.

  In step S1 of FIG. 3, the control unit 4 determines whether or not the leading edge of the paper P has reached the pair of conveyance rollers 11B.

  Here, until the leading edge of the sheet P reaches the pair of conveying rollers 11B, the solenoids 14A and 14B are both on as shown in FIG. As a result, the transport roller pairs 11A and 11B are fixed at their standard positions and are incapable of moving. The sheet P is conveyed at a conveyance speed by the conveyance roller pair 11A from the time when the leading edge reaches the conveyance roller pair 11A to the time when it reaches the conveyance roller pair 11B.

  Based on the timing at which the paper sensor 13B detects the leading edge of the paper P, the control unit 4 determines whether or not the leading edge of the paper P has reached the transport roller pair 11B. When it is determined that the leading edge of the sheet P has not reached the transport roller pair 11B (step S1: NO), the control unit 4 repeats step S1.

  When it is determined that the leading edge of the sheet P has reached the transport roller pair 11B (step S1: YES), in step S2, the control unit 4 turns off the solenoid 14A as shown in FIG. As a result, the transport roller pair 11A is movable to the downstream side.

  Next, in step S3 of FIG. 3, the control unit 4 determines whether or not the leading edge of the paper P has reached the transport roller pair 11C. Here, the control unit 4 determines whether or not the leading edge of the paper P has reached the transport roller pair 11C based on the timing at which the paper sensor 13C detects the leading edge of the paper P. When it is determined that the leading edge of the sheet P has not reached the pair of conveyance rollers 11C (step S3: NO), the control unit 4 repeats step S3.

  When it is determined that the leading edge of the sheet P has reached the conveyance roller pair 11C (step S3: YES), in step S4, the control unit 4 turns off the solenoid 14B as shown in FIG. As a result, the transport roller pair 11B is movable downstream.

  Here, the paper P is transported at the transport speed by the transport roller pair 11B until the leading edge of the paper P reaches the transport roller pair 11B until it reaches the transport roller pair 11C. When the leading edge of the paper P reaches the transport roller pair 11B, the paper P is accelerated from the transport speed by the transport roller pair 11A, and tension is generated between the transport roller pair 11A and 11B. Due to the tension of the paper P, the transport roller pair 11A moves downstream as shown in FIG. Due to the downstream movement of the transport roller pair 11A, the tension of the paper P between the transport roller pair 11A and 11B is reduced.

  Further, after the leading edge of the paper P reaches the transport roller pair 11C, the paper P is transported at a transport speed by the transport roller pair 11C. When the leading edge of the paper P reaches the transport roller pair 11C, the paper P is accelerated from the transport speed by the transport roller pair 11B, and tension is generated between the transport roller pairs 11B and 11C. Due to the tension of the paper P, the transport roller pair 11B moves downstream. Due to the downstream movement of the transport roller pair 11B, the tension of the paper P between the transport roller pairs 11B and 11C is reduced.

  Next, in step S5 of FIG. 3, the control unit 4 determines whether or not the trailing edge of the paper P has passed through the transport roller pair 11A. Here, the control unit 4 determines whether or not the rear end of the paper P has passed through the transport roller pair 11A based on the timing at which the paper sensor 13A detects the rear end of the paper P. When it is determined that the trailing edge of the sheet P has not passed through the transport roller pair 11A (step S5: NO), the control unit 4 repeats step S5.

  If it is determined that the trailing edge of the sheet P has passed through the transport roller pair 11A (step S5: YES), in step S6, the control unit 4 turns on the solenoid 14A as shown in FIG. As a result, the solenoid 14A returns and fixes the transport roller pair 11A to the standard position (see FIG. 8).

  Here, when the rear end of the paper P passes through the transport roller pair 11A, the transport roller pair 11A moves downstream, while the rear end of the paper P passes through the transport roller pair 11A. For this reason, since the relative speed of the paper P with respect to the transport roller pair 11A is suppressed as compared with the case where the transport roller pair 11A is fixed, the tension of the paper P when passing through the transport roller pair 11A is reduced. Thereby, the vibration of the paper P when the trailing edge of the paper P passes through the pair of conveying rollers 11A is suppressed, so that the deterioration of the print image quality due to the vibration of the paper P is reduced.

  Next, in step S7 in FIG. 3, the control unit 4 determines whether or not the trailing edge of the sheet P has passed through the conveyance roller pair 11B. Here, the control unit 4 determines whether or not the rear end of the paper P has passed through the transport roller pair 11B based on the timing at which the paper sensor 13B detects the rear end of the paper P. When it is determined that the trailing edge of the sheet P has not passed through the conveying roller pair 11B (step S7: NO), the control unit 4 repeats step S7.

  When it is determined that the trailing edge of the sheet P has passed through the conveying roller pair 11B (step S7: YES), in step S8, the control unit 4 turns on the solenoid 14B as shown in FIG. As a result, as shown in FIG. 9, the solenoid 14B returns and fixes the conveying roller pair 11B to the standard position. As a result, the transport roller pair 11A, 11B returns to the fixed state at the respective standard positions, and the series of operations ends.

  Here, when the trailing edge of the paper P passes through the transport roller pair 11B, the transport roller pair 11B moves to the downstream side as in the case of passing through the transport roller pair 11A, while the trailing edge of the paper P moves to the transport roller pair 11B. Exit. For this reason, the vibration of the paper P when the rear end of the paper P passes through the transport roller pair 11B can be suppressed in the same manner as when the rear edge of the paper P passes through the transport roller pair 11A. Is reduced.

  As described above, in the inkjet printing apparatus 1, among the transport roller pairs 11 </ b> A to 11 </ b> C, the transport roller pairs 11 </ b> A and 11 </ b> B other than the most downstream transport roller pair 11 </ b> C are movable downstream by the tension of the paper P. This reduces the tension of the paper P when the trailing edge of the paper P passes through the transport roller pairs 11A and 11B, so that the vibration of the paper P when the trailing edge of the paper P passes through the transport roller pairs 11A and 11B is reduced. It can be suppressed. As a result, according to the ink jet printing apparatus 1, it is possible to reduce a decrease in print image quality.

  Further, the inkjet printing apparatus 1 is configured to transport the paper P at a higher speed as the transport roller pair 11 on the downstream side. As a result, the occurrence of sagging of the paper P can be suppressed, so that fluctuations in the head gap, which is the distance between the paper P and the inkjet head 21, can be suppressed. As a result, it is possible to further reduce the decrease in print image quality.

  In the above-described embodiment, in the configuration in which the conveyance roller pairs 11A to 11C are driven by the common conveyance motor 12, the downstream conveyance roller pair 11 is made larger in diameter so that the downstream conveyance is performed. The paper P is transported as fast as the roller pair 11. However, each conveyance roller pair 11 may be driven and controlled independently by a motor corresponding to each conveyance roller pair 11 so that the sheet P is conveyed at a higher speed as the conveyance roller pair 11 on the downstream side.

  Further, in the above-described embodiment, the example in which the paper P is transported at a higher speed as the transport roller pair 11 on the downstream side is shown. However, each transport roller pair 11 is designed to transport at the same speed. It may be a thing. Even in this case, for example, when tension is generated in the paper P due to a difference in transport speed between the transport roller pair 11 due to the dimensional tolerance of the transport roller pair 11, the transport roller pair 11 pulled by the tension of the paper P moves downstream. As a result, the tension of the paper P is reduced. Thereby, since the vibration of the paper P when the trailing edge of the paper P in which the tension has occurred passes through the conveyance roller pair 11 is suppressed, it is possible to reduce the deterioration of the print image quality.

  In the above-described embodiment, the configuration in which the number of the conveyance roller pairs 11 is three and the number of the inkjet heads 21 is two, but the number of the conveyance roller pairs 11 and the inkjet heads 21 is not limited thereto. What is necessary is just a structure provided with the some conveyance roller pair and the at least 1 inkjet head arrange | positioned between conveyance roller pairs.

  Further, each conveyance roller pair 11 other than the most downstream conveyance roller pair 11 may be configured to be movable downstream by a drive source such as a motor. For example, in the configuration in which the sheet P is conveyed at a higher speed as the conveyance roller pair 11 on the downstream side, the leading edge of the sheet P is downstream of the conveyance roller pair 11 for each conveyance roller pair 11 other than the most downstream conveyance roller pair 11. The tension of the paper P is reduced by moving the transport roller pair 11 to the downstream side by the drive source until the trailing edge of the paper P passes through the transport roller pair 11 after reaching the adjacent transport roller pair 11. It may be.

  In the above-described embodiment, the configuration in which the transport roller pair 11 that has moved downstream is returned to the standard position by the solenoid 14 is shown, but the mechanism for returning the transport roller pair 11 to the standard position is not limited thereto. For example, a mechanism that returns the conveying roller pair 11 to a standard position using a spring may be used.

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

DESCRIPTION OF SYMBOLS 1 Inkjet printing apparatus 2 Conveyance part 3 Printing part 4 Control part 11,11A-11C Conveyance roller pair 12 Conveyance motor 13,13A-13C Paper sensor 14,14A, 14B Solenoid 21,21A, 21B Inkjet head

Claims (2)

A plurality of pairs of transport rollers that are spaced apart from each other along the transport direction of the paper and transport the paper while nip it;
And at least one inkjet head that is disposed between each pair of transport rollers and that ejects ink onto a sheet,
The inkjet printing apparatus, wherein the pair of conveyance rollers other than the most downstream conveyance roller pair in the conveyance direction is movable to the downstream side by a tension of a sheet.   The inkjet printing apparatus according to claim 1, wherein the sheet is conveyed at a higher speed as the pair of conveying rollers on the downstream side.