Inkjet recording device

Abstract

To provide an inkjet recording device that can prevent a defective image from occurring.SOLUTION: An inkjet recording device is provided with a recording part, a conveying belt in an endless shape, a charging part, an inversion-conveying part and a control part. The charging part applies charging voltages to the conveying belt to charge the conveying belt, so as to electrostatically adsorb a recording medium on a recording medium-conveying surface of the conveying belt. The inverse-conveying part turns back the recording medium conveyed, with a first surface thereof set as a front surface, by the conveying belt, and supplies the recording medium with a second surface thereof set as a front surface. The control part partitions a printing region on the first surface of the recording medium, calculates printing rates of the partitioned regions, and determines charging voltages at which the printing medium is supplied to the conveying belt again, with the second surface thereof set as the front surface, on the basis of the printing rate that is highest among the printing rates calculated in the partitioned regions.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an inkjet recording apparatus. [Background technology]

[0002] A conventional inkjet recording device is an inkjet recording device that includes a recording unit, an endless conveying belt, a charging unit, a reverse conveying unit, and a control unit. The recording unit has a recording head that ejects ink. The conveying belt conveys the recording medium to a position facing the recording head. The charging unit applies a charging voltage to the conveying belt to charge the conveying belt, thereby electrostatically adsorbing the recording medium to the recording medium conveying surface of the conveying belt. The reverse conveying unit turns over the recording medium that has been conveyed by the conveying belt with its first side facing up, and supplies the recording medium to the conveying belt again with its second side facing up. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-343636 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the inkjet recording device disclosed in Patent Document 1 mentioned above had the possibility of the recording medium curling after printing on the first side of the recording medium in the recording unit. In this case, when the recording medium was fed back onto the conveyor belt with the second side facing up, a portion of the recording medium could float above the recording medium conveying surface of the conveyor belt and come into contact with the recording head. This could result in the recording medium becoming contaminated with ink, causing image defects. There was also the possibility of ink not being ejected from the recording head, causing image defects.

[0005] SUMMARY OF THE INVENTION An object of the present invention is to provide an inkjet recording apparatus that can prevent the occurrence of image defects. [Means for solving the problem]

[0006] In order to achieve the above object, a first configuration of the present invention is an inkjet recording device including a recording unit, an endless conveying belt, a charging unit, a reverse conveying unit, and a control unit. The recording unit has a recording head that ejects ink. The conveying belt conveys the recording medium to a position facing the recording head. The charging unit applies a charging voltage to the conveying belt to charge the conveying belt, thereby electrostatically adsorbing the recording medium to the recording medium conveying surface of the conveying belt. The reverse conveying unit turns over the recording medium conveyed by the conveying belt with its first side facing up, and supplies the recording medium to the conveying belt again with its second side facing up. The control unit controls the recording unit and the charging unit. The control unit divides the printing area on the first side of the recording medium, calculates a printing rate for each division, and determines the charging voltage to be used when supplying the recording medium to the conveying belt again with its second side facing up, based on the highest printing rate among the printing rates calculated for each division. [Effects of the Invention]

[0007] According to the first aspect of the present invention, it is possible to provide an inkjet recording apparatus that can prevent the occurrence of image defects. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a schematic cross-sectional view showing the overall configuration of a printer 100 as an inkjet recording apparatus according to an embodiment of the present invention. [Figure 2] 1 is a partially enlarged view of the periphery of a recording unit 9 of a printer 100 as an inkjet recording apparatus according to an embodiment of the present invention. [Figure 3] FIG. 1 is a block diagram showing an example of a control path of a printer 100 as an inkjet recording apparatus according to an embodiment of the present invention. [Figure 4] FIG. 1 is an explanatory diagram illustrating paper P on a conveyor belt 51 of a printer 100 as an inkjet recording apparatus according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0009] 1. Configuration of Inkjet Recording Apparatus A printer 100 (inkjet recording device, hereinafter referred to as printer 100) according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is an explanatory diagram showing the general configuration of the printer 100 according to an embodiment of the present invention, and FIG. 2 is a partially enlarged view of the periphery of the recording unit 9 of the printer 100. Also, FIG. 3 is a block diagram showing an example of a control path for the printer 100.

[0010] For ease of explanation, the vertical direction in the installed state (shown in FIG. 1) when the printer 100 is usable is defined as the up-down direction (Z1-Z2 direction). The front-to-back direction (Y1-Y2 direction) is defined with the face of the printer 100 on the page shown in FIG. 1 as the front (front face). The left-to-right direction (X1-X2 direction) is defined with the front of the printer 100 in the installed state as the reference point. In this embodiment, the left-to-right direction (X1-X2 direction) is perpendicular to the up-to-down direction (Z1-Z2 direction) and the front-to-back direction (Y1-Y2 direction).

[0011] The printer 100 includes a recording unit 9, a first transport unit 5, a second transport unit 12, a control unit 70, and a paper feed cassette 2. The paper feed cassette 2 is located at the bottom inside the printer main body 1. Paper P, which is an example of a recording medium, is stored inside the paper feed cassette 2. A paper feed device 3 is located downstream of the paper feed cassette 2 in the paper transport direction, that is, above the right side of the paper feed cassette 2 in FIG. 1. The paper feed device 3 separates and sends out the paper P one sheet at a time toward the upper right of the paper feed cassette 2 in FIG. 1.

[0012] The printer 100 also has a first paper transport path 4a inside it. The first paper transport path 4a is located in the upper right corner, which is the paper feed direction of the paper feed cassette 2. Paper P sent out from the paper feed cassette 2 is transported vertically upward along the side of the printer body 1 by the first paper transport path 4a.

[0013] A pair of registration rollers 13 is provided at the downstream end of the first paper transport path 4a in the paper transport direction. Furthermore, a first transport unit 5 and a recording unit 9 are arranged immediately downstream in the paper transport direction of the pair of registration rollers 13. The paper P sent out from the paper feed cassette 2 passes through the first paper transport path 4a and reaches the pair of registration rollers 13. The pair of registration rollers 13 temporarily stops the paper P to correct any skew, timing it with the ink ejection operation performed by the recording unit 9, and then transports the paper P again toward the first transport unit 5.

[0014] The first conveying unit 5 has a conveying belt 51, a driving roller 52, a driven roller 53, a charging roller (charging section) 54, and an attraction roller 55 (see FIG. 2).

[0015] The conveyor belt 51 is endless and is supported by a drive roller 52 and a driven roller 53. A motor (not shown) is connected to the drive roller 52, and when the motor rotates, the drive roller 52 rotates, driving the conveyor belt 51. As a result, the conveyor belt 51 conveys paper (recording medium) P to a position facing a recording head (not shown) of the recording unit 9.

[0016] The charging roller (charging unit) 54 applies a charging voltage to the conveyor belt 51. This charges the conveyor belt 51, and the paper P is conveyed while being electrostatically attracted to the conveyor belt 51. That is, the charging roller 54 applies a charging voltage to the conveyor belt 51 to charge the conveyor belt 51, thereby electrostatically attracting the paper (recording medium) to the conveying surface (recording medium conveying surface) 51a of the conveyor belt 51.

[0017] In this embodiment, the charging roller (charging section) 54 is disposed opposite the driven roller 53 across the conveyor belt 51. The application of the charging voltage is started when the leading edge of the paper P reaches the conveyor belt 51, and is stopped when the trailing edge of the paper P reaches the conveyor belt 51. The charging voltage is applied to the paper P having a basis weight of 64 g / m when the paper P is fed to the conveyor belt 51 with the first side facing up. 2In the case of plain paper, a voltage of +2.0 kV is applied.

[0018] The adsorption roller 55 is disposed at the upstream end of the conveying surface 51a of the conveyor belt 51 and is grounded (earthed). The adsorption roller 55 presses the leading edge of the paper P supplied by the conveyor belt 51 against the conveying surface 51a, thereby ensuring electrostatic adsorption.

[0019] The recording unit 9 is supported at a height that forms a predetermined gap (for example, 1 mm) with respect to the conveying surface 51a of the conveyor belt 51. The recording unit 9 has a recording head (not shown) that ejects ink. The recording head is disposed on the lower surface of the recording unit 9, and ejects water-based ink onto the paper P that is conveyed by the conveyor belt 51. As the paper P passes under the recording unit 9, it is printed with the ink ejected from the recording unit 9.

[0020] A second transport unit 12 is disposed downstream (on the left side X2 in FIG. 1) of the first transport unit (transport section) 5 in the paper transport direction. The paper P on which an ink image has been recorded in the recording section 9 is sent to the second transport unit 12, and the ink ejected onto the surface of the paper P is dried while passing through the second transport unit 12.

[0021] A decurler unit 14 is provided downstream of the second transport unit 12 in the paper transport direction and near the left side of the printer body 1. The paper P from which the ink has dried in the second transport unit 12 is sent to the decurler unit 14, where any curl that has occurred in the paper P is straightened using multiple rollers lined up in the paper width direction.

[0022] A second paper transport path 4b is provided downstream of the decurler unit 14 in the paper transport direction (upper in Figure 1). If double-sided recording is not performed on the paper P that has passed through the decurler unit 14, it is discharged from the second paper transport path 4b via a pair of discharge rollers to a paper discharge tray 15 provided outside the left side of the printer 100.

[0023] A reverse transport path 16 for double-sided recording is provided at the top of the printer main body 1, above the recording unit 9 and second transport unit 12. When double-sided recording is performed, after recording on one side (first side) of the paper P is completed and the paper P passes through the second transport unit 12 and the decurler unit 14, it is sent to the reverse transport path 16 via the second paper transport path 4b.

[0024] The paper P sent to the reverse conveyance path 16 has its conveyance direction switched so that recording can be performed on the other side (second side) of the paper P. The paper P then passes over the top of the printer main body 1 and is conveyed to the right side, passes through the pair of registration rollers 13, and is sent again to the first conveyance unit 5 with the second side facing up.

[0025] The reverse conveying section 60 includes a reverse conveying path 16, and turns over the paper (recording medium) P conveyed by the conveying belt 51 with its first side facing up, and supplies the paper (recording medium) P to the conveying belt 51 again with its second side facing up.

[0026] In the first transport unit 5, the paper P is transported to a position facing the recording unit 9, and an image is recorded on the second side by ink ejection from the recording unit 9. After double-sided recording, the paper P passes through the second transport unit 12, the decurler unit 14, and the second paper transport path 4b in this order, and is discharged to the paper discharge tray 15.

[0027] In addition, a maintenance unit 19 and a cap unit 30 are disposed below the second transport unit 12. The maintenance unit 19 moves below the recording unit 9 when performing purging, wipes off ink extruded from nozzles (not shown) of a recording head (not shown) disposed on the underside of the recording unit 9, and collects the wiped ink. The cap unit 30 moves below the recording unit 9 when capping the ink ejection surface (not shown) of the recording unit 9, and then moves further upward to be attached to the underside of the recording head.

[0028] The control unit 70 includes a CPU and other electronic circuits and electronic components (none of which are shown). The CPU controls the operation of each component provided in the printer 100 based on control programs and data stored in the memory unit 71, and performs processing related to the functions of the printer 100. The paper feeder 3, the pair of registration rollers 13, the drive roller 52, the charging roller 54, the recording unit 9, the decurler unit 14, the maintenance unit 19, the cap unit 30, etc. individually receive commands from the control unit 70 and work together to record on the paper P.

[0029] The storage unit 71 is configured by combining a non-volatile storage device such as a program ROM and a data ROM, and a volatile storage device such as a RAM.

[0030] The ROM stores the control program for the printer 100, numerical values necessary for control, and other data that will not change while the printer 100 is in use. The RAM stores necessary data that arises during the control of the printer 100, and data that is temporarily required for controlling the printer 100. The RAM (or ROM) also stores the printing rate for each division of the paper P.

[0031] The CPU classifies the output image based on the image data of the first side temporarily stored in the storage unit 71, and calculates the printing rate for each section. Furthermore, based on the highest printing rate among the calculated printing rates for each section, it predicts the magnitude of the charging voltage when the second side is turned over and supplied to the conveyor belt 51 again.

[0032] 4 is an explanatory diagram showing paper P on conveyor belt 51, with print area 80 of paper P indicated by a dashed line. Paper P is conveyed to the front side X2 in the conveyance direction while in contact with conveyor belt 51. When paper P is conveyed directly below recording unit 9, the outer periphery of paper P is divided into a first area P1, a second area P2, a third area P3, a fourth area P4, a fifth area P5, a sixth area P6, a seventh area P7, and an eighth area P8. That is, control unit 70 divides print area 80 on the first side of paper P into first area P1 to eighth area P8.

[0033] The first area P1, the second area P2, the third area P3, and the fourth area P4 are arranged at the corners of the paper P, and are divided into rectangular areas with the same area.

[0034] The fifth region P5 and the sixth region P6 are disposed on either side of the transport direction (X1-X2 direction) of the paper P, and are divided into rectangular shapes extending in the front-to-rear direction (Y1-Y2 direction) of the paper P. The fifth region P5 is disposed between the first region P1 and the second region P2. The sixth region P6 is disposed between the third region P3 and the fourth region P4. The fifth region P5 and the sixth region P6 are divided into rectangular shapes with the same area.

[0035] The seventh region P7 and the eighth region P8 are disposed on either side of the front-to-rear direction (Y1-Y2 direction) of the paper P, and are divided into rectangular sections extending in the transport direction (X1-X2 direction) of the paper P. The seventh region P7 is disposed between the first region P1 and the third region P3. The eighth region P6 is disposed between the second region P2 and the fourth region P4. The seventh region P7 and the eighth region P8 are divided into sections with the same area.

[0036] The control unit 70 divides the print area 80 on the first side of the paper P (recording medium) into sections and calculates the print rate for each section. Based on the highest print rate among the print rates calculated for each section, the control unit 70 determines the charging voltage when the paper P is turned over to face up on the second side and fed back onto the conveyor belt 51.

[0037] Specifically, the control unit 70 calculates the printing rates for each of the first region P1, second region P2, third region P3, fourth region P4, fifth region P5, sixth region P6, seventh region P7, and eighth region P8 on the first side of the paper P (recording medium) based on the image data for printing on the first side stored in the storage unit 71. As a result, the curl position of the paper P is predicted from the distribution of the amount of ink ejected on the first side of the paper P.

[0038] Furthermore, the control unit 70 determines the charging voltage when the paper P is supplied again to the conveyor belt 51 with the second side facing up, based on the highest printing rate among the printing rates calculated for each of the first region P1 to eighth region P8. In this way, by determining the charging voltage according to the predicted curl position of the paper P, it is possible to set the charging voltage low when the curl of the paper P is small. This makes it possible to reduce power consumption. Furthermore, when the charging voltage is set low, it is possible to prevent paper dust and the like from being charged on the paper P. This makes it possible to prevent paper dust from adhering to the recording head and the like. It is also possible to prevent resistance changes of the conveyor belt 51 and the charging roller 54 over long-term use.

[0039] Furthermore, when the paper P has a large curl, the charging voltage can be set high to ensure that the second side of the paper (recording medium) P is adhered to the conveying surface 51a with confidence. This prevents the paper P from being soiled with ink, resulting in poor image quality, and also prevents ink from not being ejected from the recording head, resulting in poor image quality. It also prevents the paper P from jamming on the conveying belt 51. Note that the printing rate in this embodiment is the printing rate (image density).

[0040] Furthermore, in this embodiment, the outer periphery of the print area 80 of the paper P is divided into the first area P1 to the eighth area P8, but the number of areas is not limited to eight. Furthermore, the shapes of the areas of the first area P1 to the eighth area P8 are not limited to those of this embodiment. By increasing the number of areas and calculating the printing rate for each area, the curl position of the paper P can be determined more accurately from the distribution of the amount of ink ejected onto the first side of the paper P. Furthermore, in this embodiment, the outer periphery of the paper P is divided into areas and the printing rate is calculated for each area, but it is also possible to divide the center of the paper P and calculate the printing rate for each area.

[0041] Furthermore, it is more preferable that the control unit 70 weights the printing rate calculated for each of the sections from the first region P1 to the eighth region P8 according to the position of the section to determine the charging voltage. For example, a weighting coefficient by which the printing rate is multiplied for each of the sections from the first region P1 to the eighth region P8 is set in advance and stored in the storage unit 71.

[0042] It is preferable to set a larger weighting coefficient to be multiplied by the printing rate as curling becomes more likely to occur. Specifically, the first region P1, second region P2, third region P3, and fourth region P4, which are located at the corners of the print area 80, are more likely to curl than the other regions, and so the weighting coefficients are set larger than those of the other regions. Also, the weighting coefficients are set larger for the first region P1 and second region P2, which are located on the rear side X1 of the transport direction of the paper P, than for the third region P3 and fourth region P4, which are located on the front side X2 of the transport direction of the paper P.

[0043] For example, it is preferable to set the weighting coefficients to increase in the order of the first region P1, second region P2 > the third region P3, fourth region P4 > the fifth region P5 > the sixth region P6 > the seventh region P7, eighth region P8.

[0044] The control unit 70 determines the charging voltage based on the highest value among the values obtained by multiplying the printing rates calculated for each of the first to eighth regions P1 to P8 by the weighting coefficients. This makes it possible to more accurately predict the curl position of the paper P from the distribution of the ink amount ejected onto the first surface of the paper P.

[0045] The present invention is not limited to the above embodiment, and various modifications are possible without departing from the spirit of the present invention. For example, the division of the print area 80 on the first side of the paper P (recording medium) is not limited to this embodiment. Specifically, the first area P1, the second area P2, the third area P3, and the fourth area P4 do not have to be the same shape or rectangular. They also do not have to have the same area. The fifth area P5 and the sixth area P6 do not have to be the same shape or rectangular. They also do not have to have the same area. The seventh area P7 and the eighth area P8 do not have to be the same shape or rectangular. They also do not have to have the same area. [Industrial Applicability]

[0046] The present invention can be used in an inkjet recording apparatus having nozzles that eject water-based ink onto a recording medium. [Explanation of symbols]

[0047] 1 Printer body (inkjet recording device) 2 Paper cassette 3 Paper feeder 4a First paper transport path 4b Second paper transport path 5 First transport unit 9 Recording section 12 Second transport unit 13 Registration roller pair 14 Decaler section 15 Paper output tray 16 Reversing conveyance path 19 Maintenance Unit 30 Cap Units 51 Conveyor belt 51a Conveying surface (recording medium conveying surface) 52 Drive roller 53 Driven roller 54 Charging roller 55 Adsorption roller 60 Reversing conveying section 70 Control Unit 71 Storage section 80 printing area 100 printers P paper P1~P8 1st area~8th area X1 Rear side of conveying direction X2 Front side of conveying direction

Claims

1. a recording unit having a recording head that ejects ink; an endless conveyor belt that conveys a recording medium to a position facing the recording head; a charging unit that applies a charging voltage to the conveying belt to charge the conveying belt, thereby electrostatically attracting the recording medium to the recording medium conveying surface of the conveying belt; a reversing conveying unit that turns over the recording medium conveyed by the conveying belt with the first side facing up, and supplies the recording medium to the conveying belt again with the second side facing up; a control unit that controls the recording unit and the charging unit; Equipped with The control unit divides the printing area on the first side of the recording medium into sections, calculates a printing rate for each section, and determines the charging voltage when the second side of the recording medium is turned over and supplied to the conveyor belt again based on the highest printing rate among the printing rates calculated for each section.

2. The inkjet recording apparatus according to claim 1 , wherein the control unit determines the charging voltage by weighting the printing rate calculated for each section according to the position of the section.

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