JP2016155686A - Printing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a printing apparatus capable of suppressing reduction in the elimination efficiency in an electric charge from a printing medium by a charge eliminating unit.SOLUTION: A printing apparatus includes a transport belt 53 that transports a sheet P, a charging roller 56 that supplies an electric charge to the transport belt 53, a print head 141 that causes ink to be attached to a printing surface of the sheet P electrostatically adsorbed on the transport belt 53, a charge eliminating unit 581 that is displaceable between a charge elimination position and a retreated position and that eliminates the electric charge from the printing surface by coming in contact with the printing surface of the sheet P, and a charge elimination control device that controls the position of the charge eliminating unit 581.SELECTED DRAWING: Figure 2A

Description

  The present invention relates to a printing apparatus that performs printing on a print medium that is electrostatically attracted to a conveyance belt.

  Patent Document 1 describes an example of a printing apparatus that includes a conveyance belt and a print head that discharges a printing material such as ink toward a print medium. In such a printing apparatus, when the conveyance belt is charged by the charging unit, the print medium fed onto the conveyance belt is electrostatically attracted to the conveyance belt. When the printing medium is conveyed by the operation of the conveying belt, the printing material from the printing head is attached to the printing surface that is not in contact with the conveying belt among both surfaces of the printing medium.

JP 2004-149280 A

  By the way, in order to increase the efficiency of electrostatic adsorption of the print medium by the transport belt, it is desirable to remove electric charges from the print surface of the print medium. Therefore, such a printing apparatus may be provided with a charge eliminating unit that removes electric charges from the printing surface by contacting the printing surface of the printing medium.

  However, in this case, in order to remove the electric charge from the printing surface of the print medium, the charge removal unit is brought into contact with the print medium, so that the charge removal unit gradually deteriorates. Then, when the deterioration of the charge removal unit proceeds as described above, the charge removal efficiency from the print medium by the charge removal unit is reduced.

  The objective of this invention is providing the printing apparatus which can suppress the fall of the removal efficiency of the electric charge from the printing medium by a static elimination part.

  A printing apparatus for achieving the above object includes a conveyance belt that conveys a print medium, a charging unit that supplies electric charges to the conveyance belt, and a surface that is in contact with the conveyance belt among both surfaces of the print medium. When the surface opposite to the contact surface is a print surface, the print head is attached to the print surface of the print medium electrostatically attracted to the transport belt, and is transported by the transport belt. The print surface is displaceable between a charge removal position that is a position where the print medium can be contacted and a retracted position that is a position where the print medium cannot be contacted, and the print surface by contacting the print surface of the print medium And a charge removal control device that controls the position of the charge removal portion. The charge removal control device is configured to remove the charge from the print medium that is electrostatically adsorbed to the conveyance belt. When in contactable position with, arranging the static eliminator unit to the charge eliminating position.

  According to the above configuration, when printing on the print medium, it is possible to select that the static elimination unit is brought into contact with the print medium conveyed by the conveyance belt and that the static elimination unit is not brought into contact with the print medium. Therefore, compared with the case where the static elimination unit is always arranged at the static elimination position, the chance of the static elimination unit coming into contact with the print medium or the conveyance belt can be reduced, so that the degradation of the static elimination unit is delayed. In addition, by delaying the deterioration of the charge removal unit in this way, it is possible to suppress a reduction in the charge removal efficiency from the print medium by the charge removal unit.

  In the printing apparatus, the charge removal control device determines whether or not the charge removal unit is brought into contact with the print medium conveyed by the conveyance belt according to the type of print medium to be printed, and the determination result is It is preferable to control the position of the static elimination unit based on the above.

  By specifying the type of the printing medium, it is possible to determine whether the printing medium is likely to be curled due to adhesion of the printing material, whether the printing medium has a high resistance value, or the like. When the print medium is likely to curl or has a high resistance value, the charge removal unit removes the charge from the print surface of the print medium, thereby electrostatically adsorbing the print medium by the conveyor belt. It is desirable to increase the force. On the other hand, when the print medium is less likely to curl, or when the print medium has a low resistance value, the electrostatic adsorption force of the print medium by the conveyance belt need not be so high. Therefore, in the above configuration, it is determined whether the static eliminator is arranged at the static eliminator position or the retracted position according to the type of print medium to be printed, and the position of the static eliminator is controlled based on the determination result. I made it. Thereby, when it can be judged that it is not necessary to increase the electrostatic attraction force of the print medium by the transport belt, the contact between the print medium and the charge eliminating portion can be avoided. For this reason, depending on the type of print medium to be printed, the static eliminator can be placed in the retracted position during printing, so the static eliminator is less likely to deteriorate than when the static eliminator is always placed in the static eliminator. . As a result, it is possible to suppress a reduction in charge removal efficiency from the print medium by the charge removal unit.

  In the printing apparatus, the static elimination control device determines whether or not the static elimination unit is brought into contact with the print medium conveyed by the conveyance belt based on humidity of an installation environment of the printing device, and the determination result is It is preferable to control the position of the static elimination unit based on the above.

  The higher the humidity of the installation environment of the printing apparatus, the lower the resistance value of the print medium. When the resistance value of the print medium is low, the charge on the print surface is easily neutralized without removing the charge from the print surface of the print medium by the static eliminator. That is, even if the charge removal unit does not remove the charge from the printing surface of the printing medium, the electrostatic adsorption force of the printing medium by the conveyance belt increases. Therefore, in the above configuration, the position of the static eliminator is controlled in consideration of the humidity of the installation environment of the printing apparatus. Therefore, depending on the humidity of the installation environment of the printing apparatus, the static eliminator can be placed at the retracted position during printing. As a result, compared with the case where the static elimination unit is always disposed at the static elimination position, the static elimination unit is less likely to be deteriorated, and it is possible to suppress a reduction in the charge removal efficiency from the print medium by the static elimination unit.

  The printing apparatus includes a determination device that determines whether or not a resistance value of a print medium to be printed is high based on a temperature and humidity of an installation environment of the printing device, When it is determined by the determination device that the resistance value of the print medium is high, the charge removal unit is disposed at the charge removal position, while the determination device determines that the resistance value of the print medium is low. In some cases, it is preferable to dispose the charge eliminating portion at the retracted position.

  The resistance value of the printing medium changes depending on the temperature and humidity of the installation environment of the printing apparatus. The relationship between the temperature and humidity of the installation environment and the resistance value of the print medium can be grasped to some extent by experiments and simulations. That is, the resistance value of the print medium can be estimated based on the temperature and humidity of the installation environment. Therefore, in the above configuration, it is determined whether or not the resistance value of the printing medium is high based on the temperature and humidity of the installation environment of the printing apparatus. The neutralization unit is brought into contact with the transported print medium. On the contrary, when it can be determined that the resistance value of the print medium is low, the static eliminator is not brought into contact with the print medium conveyed by the conveyance belt. That is, when it can be predicted that the charge on the printing surface is naturally neutralized without removing the charge from the printing surface of the printing medium by the charge eliminating unit, the electrostatic adsorption force of the printing medium by the conveyance belt is relatively large. Do not let the static eliminator touch the print medium. Therefore, the charge removal unit is less likely to deteriorate compared to the case where the charge removal unit is always placed at the charge removal position regardless of the temperature and humidity of the installation environment of the printing device. A decrease in efficiency can be suppressed.

  In the printing apparatus, after printing on the first surface of both sides of the print medium is finished, the first surface becomes the contact surface and the second surface is the surface opposite to the first surface. A reversing mechanism for reversing the front and back of the print medium and guiding the print medium onto the transport belt so that the surface becomes the print surface, and the print head is disposed downstream of the neutralization position in the transport direction. The neutralization control device preferably arranges the neutralization unit at the neutralization position when printing is performed on the second surface of the print medium guided from the reversing mechanism onto the conveyance belt.

  When performing double-sided printing on a printing medium, the printing medium is likely to curl on the conveyor belt when printing on the second side in a situation where the printing material is attached by printing on the first side. . Therefore, in the above configuration, when printing is performed on the second surface of the print medium guided from the reversing mechanism onto the conveyance belt, the charge removal unit is disposed at the charge removal position, and the charge removal unit charges the second surface of the print medium. To be removed. Thus, by removing the electric charge from the second surface, the electrostatic adsorption force of the print medium by the conveyance belt can be increased, so that the print medium is hardly curled on the conveyance belt. As a result, the occurrence of a printing defect can be suppressed as much as an event that the print medium comes into contact with the print head or the like is less likely to occur.

  In the printing apparatus, after printing on the first surface of both sides of the print medium is finished, the first surface becomes the contact surface and the second surface is the surface opposite to the first surface. A reversing mechanism for reversing the front and back of the print medium so that the surface becomes the print surface and guiding the print medium onto the transport belt, and the charge removal control device applies the print medium to the first surface. It is determined whether the print medium is curled by printing, and when it is determined that the print medium is curled by printing on the first surface of the print medium, When the neutralization unit is disposed at the neutralization position during printing and when it is determined that the print medium is not curled by printing on the first surface of the print medium, the neutralization portion is disposed on the second surface of the print medium. The discharging unit is removed when printing. It is preferably arranged in a position.

  According to the above configuration, when it is determined that the print medium does not curl even when printing is performed on the first surface, the static eliminator is not in contact with the print medium when printing on the second surface. Therefore, regardless of the printing mode on the first surface, the neutralization unit is less likely to deteriorate compared to the case where the neutralization unit is always placed at the neutralization position when printing on the second surface, so printing by the neutralization unit A decrease in the efficiency of removing charges from the medium can be suppressed.

  In the printing apparatus, after printing on the first surface of both sides of the print medium is finished, the first surface becomes the contact surface and the second surface is the surface opposite to the first surface. A reversing mechanism for reversing the front and back of the print medium so that the surface becomes the print surface and guiding the print medium onto the transport belt; the print medium has four sides and the two sides Having a corner which is a connecting portion of a side, dividing the first surface of the print medium into a plurality of areas, and among the areas, the area including the corner of the print medium is a determination area, The static elimination control device calculates a maximum discharge amount that is a maximum amount of the printing material that can be attached to the determination region by discharging the printing material from the print head to the determination region, and the first surface of the print medium. Based on the print data employed for printing A discharge amount that is the amount of the printing material discharged from the print head to the determination area, a discharge ratio that is a ratio of the discharge amount to the maximum discharge amount is calculated, and the discharge ratio is a determination ratio in the determination area When the print medium is less than the discharge medium, when the print medium is printed on the second surface, the static eliminator is disposed at the retracted position, and when the discharge ratio is equal to or higher than the determination ratio in the determination area, It is preferable that the static eliminating unit is disposed at the static elimination position when printing on the second surface.

  The more the amount of printing material that adheres to the area including the corners of the print medium due to printing on the first surface, the more the print medium is curled. Therefore, in the above configuration, when the area including the corner of the print medium is set as the determination area among the plurality of areas obtained by dividing the first surface, and the discharge ratio of the determination area is equal to or higher than the determination ratio, the first surface Since it can be determined that there is a possibility that the print medium may curl due to printing on the print, the electrostatic adsorption force of the print medium by the conveyance belt is increased by bringing the static elimination unit into contact with the print medium, and then printing on the second surface It is carried out. For this reason, it is possible to suppress the occurrence of printing defects because the phenomenon that the print medium comes into contact with the print head or the like is less likely to occur during printing on the second surface. On the other hand, when the ejection ratio in the determination area is less than the determination ratio, it can be determined that the print medium does not curl by printing on the first surface. Printing is in progress. Thus, the amount of opportunity for the charge eliminating unit to contact the print medium can be reduced, so that the deterioration of the charge eliminating unit is suppressed, and the reduction in the efficiency of removing charges from the print medium by the charge eliminating unit can be suppressed.

  In the printing apparatus, after printing on the first surface of both sides of the print medium is finished, the first surface becomes the contact surface and the second surface is the surface opposite to the first surface. A reversing mechanism for reversing the front and back of the print medium so that the surface becomes the print surface and guiding the print medium onto the transport belt; the print medium has four sides and the two sides An edge region having a corner which is a connecting portion of a side, dividing the first surface of the print medium into a plurality of regions, and an end region which is a region including the corner of the print medium among the regions and the edge When the area composed of the area adjacent to the partial area is set as the determination area, the static elimination control device can attach the printing material to the determination area by discharging the printing material from the print head to the determination area. The maximum discharge amount that is the maximum amount of Based on the print data employed for printing on the first surface, a discharge amount, which is the amount of printing material discharged from the print head to the determination area, is calculated, and the ratio of the discharge amount to the maximum discharge amount When the discharge ratio is less than the determination ratio in the determination region, the charge removal unit is disposed at the retracted position when printing on the second surface of the print medium. When the discharge ratio is equal to or higher than the determination ratio in a region, it is preferable to dispose the charge removal unit at the charge removal position when printing the second surface of the print medium.

  The more the amount of printing material that adheres to the area including the corners of the print medium due to printing on the first surface, the more the print medium is curled. Therefore, in the above configuration, the determination area is an area formed by the end area including the corners of the print medium and the area adjacent to the end area among the plurality of areas obtained by dividing the first surface. When the discharge ratio in the determination area is equal to or higher than the determination ratio, it can be determined that the print medium may be curled by printing on the first surface. The second surface is printed after increasing the electrostatic attraction force of the print medium. For this reason, it is possible to suppress the occurrence of printing defects because the phenomenon that the print medium comes into contact with the print head or the like is less likely to occur during printing on the second surface. On the other hand, when the ejection ratio in the determination area is less than the determination ratio, it can be determined that the print medium does not curl by printing on the first surface. Printing is in progress. Thus, the amount of opportunity for the charge eliminating unit to contact the print medium can be reduced, so that the deterioration of the charge eliminating unit is suppressed, and the reduction in the efficiency of removing charges from the print medium by the charge eliminating unit can be suppressed.

  In the printing apparatus, a plurality of the determination areas including one of the corners are set on the first surface of the print medium, and the static elimination control device performs the ejection in all the determination areas. When the ratio is less than the determination ratio, the static eliminator is arranged at the retracted position when printing on the second surface of the print medium, while at least one of the determination areas includes the determination area. When the discharge ratio is equal to or higher than the determination ratio, it is preferable that the charge removal unit is disposed at the charge removal position when printing on the second surface of the print medium.

  According to the above configuration, it is determined whether or not the discharge ratio is greater than or equal to the determination ratio for each determination area, and when there is at least one determination area in which the discharge ratio is equal to or greater than the determination ratio, It can be determined that the print medium may be curled by printing. For this reason, the neutralization unit is brought into contact with the print medium to increase the electrostatic adsorption force of the print medium by the conveyance belt, and then printing on the second surface is performed. On the other hand, when there is no determination area where the discharge ratio is equal to or higher than the determination ratio, it can be determined that the print medium does not curl by printing on the first surface. Printing on the side. Thus, the amount of opportunity for the charge eliminating unit to contact the print medium can be reduced, so that the deterioration of the charge eliminating unit is suppressed, and the reduction in the efficiency of removing charges from the print medium by the charge eliminating unit can be suppressed.

  In the printing apparatus, the static elimination unit includes the static pressure control unit that is in the static elimination position and can change the pressing force of the static elimination unit with respect to the print medium electrostatically attracted to the conveyance belt, and the static elimination control. It is preferable that the apparatus changes the pressing force of the charge removal unit according to the discharge rate by using the pressing force variable mechanism unit.

  If the discharge ratio is high, the degree of curl of the print medium, that is, the curvature of the print medium is likely to increase. Therefore, according to the above configuration, if the discharge rate is high, the pressing force of the static elimination unit can be increased, so that the resistance force when the static elimination unit contacts the print medium is suppressed, and the curled print medium is It is possible to increase the contact area of the printing medium with the conveyor belt.

In the printing apparatus, it is preferable that the static elimination control device arranges the static elimination unit at the retracted position when printing on the first surface of the print medium.
Unlike when printing on the second surface, when printing on the first surface, the printing material has not yet adhered to the print medium, so the possibility that the print medium is curled is low. Therefore, in the above configuration, when printing on the first surface, the static eliminator is disposed at the retracted position so that the static eliminator is not in contact with the print medium. As a result, compared with the case where the static eliminator is disposed at the static eliminator position even when printing on the first surface, the charge eliminator is less likely to deteriorate, and thus the reduction in the charge removal efficiency from the print medium by the static eliminator is suppressed. be able to.

  It is preferable that the printing apparatus includes a support roller that is disposed upstream in the transport direction from the static elimination position and presses a print medium against the transport belt, and the support roller is driven to rotate by operation of the transport belt.

  According to the above configuration, since the print medium is pressed against the conveyance belt by the support roller, the print medium can be appropriately polarized as much as the degree of adhesion between the print medium and the conveyance belt can be increased. As a result, the print medium can be easily electrostatically attracted to the transport belt.

In the printing apparatus, it is preferable that the support roller is grounded.
According to the above configuration, since the support roller is grounded, the charge can be removed from the printing surface to some extent by the support roller coming into contact with the printing surface of the printing medium.

1 is a side view illustrating a schematic configuration of a printing apparatus according to a first embodiment. The schematic diagram which shows the structure of the electrostatic conveyance part of a printing apparatus, and its peripheral member. The schematic diagram which shows the structure of the electrostatic conveyance part of a printing apparatus, and its peripheral member. FIG. 5 is an operation diagram illustrating a state in which a sheet is electrostatically attracted to a conveyance belt. FIG. 5 is an operation diagram illustrating a state in which a sheet is electrostatically attracted to a conveyance belt. A map for determining whether or not the resistance value of the sheet is high based on the temperature and humidity of the installation environment of the printing apparatus. 2 is a block diagram illustrating a functional configuration of the printing apparatus. FIG. 6 is a flowchart for explaining a processing procedure when printing on paper in the printing apparatus. 9 is a flowchart for explaining a processing procedure when printing on a sheet in the printing apparatus according to the second embodiment. 6 is a flowchart for explaining a processing procedure for determining whether or not there is a possibility that the paper is curled by printing on the first surface in the printing apparatus. FIG. 3 is a schematic diagram for explaining a state in which a determination area is set on a first surface of a sheet in the printing apparatus. The schematic diagram for demonstrating a mode that a determination area | region is set with the 1st surface of a paper in the printing apparatus in another embodiment.

(First embodiment)
Hereinafter, a first embodiment in which a printing apparatus is embodied as an ink jet printer will be described with reference to FIGS.

  As shown in FIG. 1, in the casing 12 of the printing apparatus 11 of the present embodiment, a conveyance device 29 that conveys a sheet P, which is an example of a print medium, along the medium conveyance path 20, and a sheet that is being conveyed A printing unit 14 for printing on P is provided. When the direction orthogonal to the paper surface in FIG. 1 is the paper width direction, the medium transport path 20 is formed so as to transport the paper P in a direction intersecting the paper width direction, preferably in a direction orthogonal to the width direction. ing.

  The printing unit 14 includes a line head type print head 141 that can simultaneously eject ink, which is an example of a printing material, over substantially the entire area in the width direction of the paper. The ink ejected from the print head 141 adheres to the paper P, whereby an image is formed on the paper P.

The transport device 29 includes a discharge mechanism unit 25 that discharges the printed paper P to the outside of the housing 12, and a feeding mechanism unit 30 that feeds the paper P before printing along the medium transport path 20. ing.
The discharge mechanism unit 25 has a plurality of discharge roller pairs 19 arranged along the medium conveyance path 20. The paper P conveyed by the discharge mechanism unit 25 is discharged out of the housing 12 through the medium discharge port 26 formed in the housing 12. That is, the medium discharge port 26 is the downstream end of the medium transport path 20, that is, the most downstream of the medium transport path. Then, the paper P discharged from the medium discharge port 26 is placed in a stacked state on the placement table 60 as indicated by a two-dot chain line in FIG.

  The feeding mechanism unit 30 includes a first medium supply unit 21, a second medium supply unit 22, a third medium supply unit 23, and an electrostatic transport unit 50. The electrostatic transport unit 50 is disposed immediately below the printing unit 14 in the drawing. That is, ink is ejected from the print head 141 onto the paper P being transported by the electrostatic transport unit 50.

  An openable / closable cover 12F is provided on one side surface (right side surface in FIG. 1) of the housing 12, and the insertion port 12a is exposed by opening the cover 12F. The first medium supply unit 21 includes a first feed roller pair 41 that sandwiches the paper P inserted into the housing 12 from the thus-exposed insertion opening 12a. Then, the sheet P is fed toward the electrostatic conveyance unit 50 by the rotation of the two rollers constituting the first feeding roller pair 41.

  In addition, a media cassette 12c in which sheets P before printing are set in a stacked state is provided at the lower portion of the housing 12 in FIG. The second medium supply unit 22 is a supply unit for feeding the paper P from the medium cassette 12c. That is, the second medium supply unit 22 includes a pickup roller 16a that feeds the uppermost sheet P in the medium cassette 12c to the outside of the medium cassette 12c, and a separation roller that suppresses the conveyance of the plurality of sheets P in an overlapping manner. A pair 16b and a second feeding roller pair 42 that sandwiches one sheet P that has passed through the separation roller pair 16b are provided. Then, the sheet P is fed toward the electrostatic transport unit 50 by the rotation of the two rollers constituting the second feeding roller pair 42.

  When the third medium supply unit 23 performs double-sided printing for printing on the sheet surfaces on both sides of the sheet P, the third medium supply unit 23 again statically removes the sheet P on which one side sheet surface (first surface) has been printed. It is a supply unit for guiding to the electric transport unit 50. That is, a branch conveyance path 24 branched from the medium conveyance path 20 is formed downstream of the electrostatic conveyance unit 50 in the sheet conveyance direction. The third medium supply unit 23 is disposed downstream of the electrostatic conveyance unit 50 in the sheet conveyance direction, and switches the conveyance path of the sheet P to the medium conveyance path 20 or the branch conveyance path 24. A branch conveyance path roller pair 44 arranged in the branch conveyance path 24 and capable of rotating in both forward and reverse directions is provided.

  When performing double-sided printing, the paper P on which one side of the sheet surface has been printed is guided from the electrostatic transport unit 50 to the branch transport path 24 by the branch mechanism 27. At this time, the paper P is transported downstream in the transport direction by the rotation of each roller constituting the branch transport path roller pair 44 in the forward direction. When the trailing edge of the paper P is guided to the branch conveyance path 24, each roller constituting the branch conveyance path roller pair 44 rotates in the reverse direction, and the paper P is conveyed in the reverse direction. . Then, the paper P is guided to the reverse supply path 31 located above the printing unit 14 in FIG. Then, the sheet P is fed along the reverse supply path 31 by the rotation of the plurality of reverse conveyance roller pairs 45 arranged on the reverse supply path 31. As a result, the paper P is joined to the medium transport path 20 upstream of the electrostatic transport unit 50 in the paper transport direction. Thereafter, the paper P is guided again to the electrostatic transport unit 50.

  When the sheet P is guided again to the electrostatic conveyance unit 50 in this way, the printed sheet surface (first surface) comes into contact with the electrostatic conveyance unit 50 and the unprinted sheet surface (second surface). Surface) faces the print head 141. Note that, among both surfaces of the paper P, a sheet surface that contacts the electrostatic conveyance unit 50 is referred to as a “contact surface”, and a surface opposite to the contact surface may be referred to as a “printing surface”. That is, in the printing apparatus 11 according to the present embodiment, after the third medium supply unit 23 finishes printing on the first surface of both sides of the paper P, the first surface becomes the contact surface and the first surface becomes the contact surface. An example of the “reversing mechanism” is configured to reverse the front and back of the paper P and guide the paper P to the electrostatic transport unit 50 so that the second surface becomes the printing surface.

  Next, with reference to FIG. 2A and FIG. 2B, the structure of the electrostatic conveyance part 50 and its peripheral member is demonstrated. As shown in FIGS. 2A and 2B, the electrostatic transport unit 50 includes a transport driving roller 51 disposed upstream of the print head 141 in the paper transport direction (that is, the right side in the drawing), and the print head 141. Is also provided with a driven roller 52 for conveyance disposed downstream in the sheet conveyance direction (that is, on the left side in the drawing). Further, an endless conveyance belt 53 is wound around these rollers 51 and 52. The transport driven roller 52 is urged in a direction away from the transport drive roller 51 (left side in the figure) as indicated by an arrow in FIG. 2A. Then, the driving of the transport motor 54 is transmitted to the transport drive roller 51, whereby the transport belt 53 is operated and the paper P is transported downstream in the transport direction. That is, the outer surface of the conveyance belt 53 functions as a support surface that contacts the contact surface of the paper P.

  Further, a metal backup plate 55 that supports the paper P through the transport belt 53 is provided immediately below the print head 141. The backup plate 55 is grounded. The backup plate 55 is in contact with the inner surface of the conveyor belt 53 that is the surface opposite to the support surface of the conveyor belt 53 and urges the conveyor belt 53 toward the print head 141.

  In addition, a charging roller 56 that is an example of a charging unit is provided upstream of the transport driving roller 51 in the transport direction (right side in the drawing). The charging roller 56 is in contact with the outer surface of the conveyance belt 53. Then, the rotation of the transport driving roller 51 is transmitted to the charging roller 56 through the transport belt 53, so that the charging roller 56 is driven to rotate with respect to the transport driving roller 51. At this time, the charging roller 56 applies a voltage to the contact portion on the outer surface of the conveyance belt 53, whereby the contact portion on the conveyance belt 53 is charged. That is, the transport belt 53 is charged by contact with the charging roller 56. In the printing apparatus 11 of the present embodiment, the charging roller 56 alternately supplies positive charges and negative charges to the conveying belt 53 that is in contact.

  A support roller 57 that presses the paper P fed to the electrostatic transport unit 50 against the transport belt 53 is provided upstream of the print head 141 in the paper transport direction (right side in the figure). The support roller 57 is made of, for example, a conductive material such as metal and is grounded. Then, the rotation of the transport drive roller 51 is transmitted to the support roller 57 through the transport belt 53, so that the support roller 57 is driven to rotate with respect to the transport drive roller 51.

  Further, a static eliminating device 58 is provided between the support roller 57 and the print head 141 in the paper transport direction. The static eliminator 58 includes a static eliminator 581 configured by a brush 583 and the like, and an actuator 582 that displaces the static eliminator 581. The static eliminating portion 581 extends in the extending direction whose main component is the width direction of the paper, and can contact the entire area in the width direction of the paper. And if the static elimination part 581 contacts the printing surface of the paper P currently conveyed by the conveyance belt 53, the static elimination part 581 will remove an electric charge from the printing surface.

  Further, the charge removal unit 581 can be displaced between a charge removal position, which is a position where the sheet P can be contacted, and a retreat position, which is a position where the sheet P cannot be contacted, by driving the actuator 582. That is, as shown by the arrow, the static elimination unit 581 can be displaced in a direction orthogonal to the printing surface of the paper P, and the location of the static elimination unit 581 shown in FIG. 2A is the static elimination position, which is shown in FIG. 2B. The position of the static eliminating unit 581 is the retracted position.

  In the present embodiment, the distance L1 between the print head 141 and the conveyor belt 53 is 0.9 mm in the direction in which ink is ejected from the print head 141 (the direction orthogonal to the print surface of the paper P).

  2A is in the neutralization position and the brush 583 presses the paper P attracted to the transport belt 53, the support surface 584 to the paper P in the direction orthogonal to the printing surface of the paper P. The distance L2 of the brush 583 is 5.5 mm, and the distance L3 in the range where the brush 583 contacts the conveyance belt 53 in the conveyance direction (left-right direction in the figure) is 8 mm.

  2B is in the retracted position and the brush 583 is separated from the conveying belt 53, the length L4 of the brush 583 standing from the support surface 584 in the direction orthogonal to the printing surface of the paper P is obtained. Is 6.5 mm.

Next, with reference to FIG. 3A and FIG. 3B, an operation when the paper P is electrostatically attracted to the transport belt 53 will be described.
As shown in FIG. 3A, when the conveyance belt 53 is operated by the rotation of the conveyance drive roller 51, the charging roller 56 is driven to rotate, so that a positive charge is a portion where a positive charge is charged on the outer surface of the conveyance belt 53. The portions 71 and the negative portions 72 that are charged with negative charges are alternately formed. When the paper P is pressed against the outer surface of the transport belt 53 by the support roller 57, the paper P comes into close contact with the transport belt 53 and polarization occurs in the paper P. In other words, the portion of the contact surface Pa (lower surface in the drawing) of the paper P that faces the positive portion 71 of the transport belt 53 is a negative portion 73 that is charged with negative charges, while the transport belt 53 is on the contact surface Pa of the paper P. The portion opposite to the negative portion 72 becomes a positive portion 74 charged with a positive charge. Accordingly, the positive portions 74 and the negative portions 73 are alternately formed on the contact surface Pa of the paper P.

  Note that the negative portions 75 charged with negative charges and the positive portions 76 charged with positive charges are alternately formed on the printing surface Pb of the paper P opposite to the contact surface Pa. When the resistance value of the paper P is small, the charges are naturally neutralized by the positive portion 76 and the negative portion 75 that are adjacent to each other on the printing surface Pb without bringing the neutralizing portion 581 into contact with the printing surface Pb. . Therefore, as shown in FIG. 3B, most of the charge on the printing surface Pb is removed before the paper P reaches just below the print head 141.

  However, when the resistance value of the paper P is high, the charges are not easily neutralized by the positive portion 76 and the negative portion 75 adjacent to each other on the printing surface Pb. In this case, the charge on the printed surface Pb side and the charge on the contact surface Pa side attract each other. The attracting force, which is a force generated by attracting the charge on the printing surface Pb side and the charge on the contact surface Pa side, is a force that draws the contact surface Pa toward the printing surface Pb. That is, the attracting force is a repulsive force with respect to the force that attracts the contact surface Pa of the paper P to the transport belt 53. Therefore, the force that attracts the paper P to the transport belt 53, that is, the electrostatic adsorption force is not easily increased. Therefore, when it is predicted that the resistance value of the paper P is large as described above, most of the electric charges can be removed from the printing surface Pb by bringing the neutralization unit 581 into contact with the printing surface Pb. As a result, the attraction force is reduced, and the electrostatic adsorption force of the paper P by the transport belt 53 is increased.

  By the way, when the static elimination part 581 is arrange | positioned in the static elimination position, unlike the support roller 57 and the charging roller 56, the static elimination part 581 is not driven to rotate with respect to operation of the conveyance belt 53. Therefore, the deterioration of the charge removal portion 581 due to contact with the conveyance belt 53 and the paper P is more likely to proceed than the support roller 57 and the charging roller 56. As the charge removal unit 581 is further deteriorated, the charge removal efficiency from the paper P by the charge removal unit 581 is reduced.

  Here, whether or not the resistance value of the paper P to be printed is high can be determined from the type of the paper P, that is, the composition of the paper, the weight of the paper, the thickness of the paper, and the like. For example, the user interface of the printing device 11 or an external device (personal computer or mobile terminal) that can communicate with the printing device 11 is used to select the type of paper P to be printed and control information according to the selection result. By analyzing with the apparatus, it is possible to determine whether or not the resistance value of the paper P to be printed is high.

  Therefore, in the printing apparatus 11 of the present embodiment, when it can be determined that the resistance value of the paper P to be printed is low, the static eliminator 581 is placed at the retracted position when printing on the paper P, while the paper P of the print target P is printed. When it can be determined that the resistance value is high, the neutralization unit 581 is arranged at the neutralization position when printing on the paper P.

  Note that, even with the same type of paper P, the resistance value of the paper P may change depending on the installation environment of the printing apparatus 11 or the like. That is, when the temperature TMP of the installation environment of the printing apparatus 11 is constant, the resistance value of the paper P decreases as the humidity HMD of the installation environment increases. In addition, when the humidity HMD of the installation environment of the printing apparatus 11 is constant, the resistance value of the paper P decreases as the installation environment temperature TMP increases.

  FIG. 4 shows an example of a map for determining whether or not the resistance value of the paper P is high based on the relationship between the temperature TMP and the humidity HMD of the installation environment. As shown in FIG. 4, when the point indicating the temperature TMP and the humidity HMD of the installation environment is included in the high resistance region A1 that is the lower left region from the boundary line L1, the resistance value of the paper P is high. It can be judged. On the other hand, when the point indicating the temperature TMP and the humidity HMD of the installation environment is included in the low resistance region A2, which is the upper right region from the boundary line L1, it may be determined that the resistance value of the paper P is low. it can.

  Therefore, in the printing apparatus 11 of the present embodiment, when it can be determined that the resistance value of the paper P to be printed is low based on the temperature TMP and the humidity HMD of the installation environment, the static elimination unit 581 when printing on the paper P. Was placed in the retracted position. On the other hand, when it can be determined that the resistance value of the paper P to be printed is high based on the temperature TMP and the humidity HMD of the installation environment, the static eliminator 581 is arranged at the static elimination position when printing on the paper P. .

  By the way, when the paper P is curled due to the adhesion of the ink, the paper P comes into contact with the print head 141 or the like, and the paper P becomes dirty or the paper P is damaged. As a result, a printing defect may occur. . Therefore, at the time of printing on the paper P where curling is likely to occur, it is not desirable that the electrostatic adsorption force of the paper P by the transport belt 53 is small from the viewpoint of suppressing the occurrence of printing defects. On the other hand, at the time of printing on the paper P where the curling is unlikely to occur, even if the electrostatic attraction force of the paper P by the transport belt 53 is small, the above-described printing defect is unlikely to occur.

  Note that depending on the type of paper P to be printed, the likelihood of curling varies depending on the adhesion of ink to the paper P. In other words, by specifying the type of the paper P, it is possible to predict the likelihood of curling of the paper P to be printed. Therefore, for example, by causing the user to select the type of the paper P to be printed as described above and analyzing the information according to the selection result by the control device, the printing device 11 uses the paper P to be printed this time. Therefore, it is possible to determine whether or not curling is likely to occur.

  Therefore, in the printing apparatus 11 according to the present embodiment, when it is determined that the paper P to be printed is likely to curl due to ink adhesion, the static eliminator 581 is arranged at the static elimination position when printing on the paper P. did. On the other hand, when it can be determined that the paper P to be printed is less likely to be curled due to ink adhesion, the neutralization unit 581 is disposed at the retracted position when printing on the paper P.

Next, the control device 80 of the printing apparatus 11 will be described with reference to FIG.
As shown in FIG. 5, the control device 80 includes a temperature sensor SE1 that detects the temperature TMP of the installation environment of the printing apparatus 11, a humidity sensor SE2 that detects the humidity HMD of the installation environment of the printing apparatus 11, and a user operation. The user interface 81 is electrically connected. The control device 80 can communicate with an external device 100 such as a personal computer or a mobile terminal.

  Such a control device 80 includes a microcomputer including a CPU, a ROM, a RAM, and the like, an ASIC (Application Specific IC), and various driver circuits. The control device 80 includes, as a functional unit configured by at least one of software and hardware, an input information processing unit 91, a temperature / humidity determination unit 92, a paper determination unit 93, a charge removal control unit 94, a conveyance control unit 95, and the like. A print control unit 96 is included.

  The input information processing unit 91 analyzes the information input from the user interface 81 and the information received from the external device 100, and outputs the analysis results to the paper determination unit 93, the conveyance control unit 95, and the print control unit 96 as appropriate. To do. For example, the input information processing unit 91 outputs information related to the type of paper P to be printed to the paper determination unit 93 and outputs information related to the transport mode of the paper P to the transport control unit 95. In addition, the input information processing unit 91 outputs information related to printing accuracy to the print control unit 96.

  Examples of information relating to the conveyance mode of the paper P include information relating to the conveyance speed of the paper P, information indicating that either single-sided printing or double-sided printing has been selected. Examples of the information related to printing accuracy include print data that is data related to an image formed on the paper P and information related to the resolution of the image formed on the print surface of the paper P.

  Based on the temperature TMP detected by the temperature sensor SE1 and the humidity HMD detected by the humidity sensor SE2, the temperature / humidity determination unit 92 determines whether the resistance value of the paper P is likely to increase. To do. At this time, the temperature / humidity determination unit 92 refers to the map shown in FIG. 4 to determine whether the current installation environment is included in the high resistance region A1 or the low resistance region A2, and information on the determination result is displayed. Output to the static elimination control unit 94. At this point, the temperature / humidity determination unit 92 determines whether or not the resistance value of the paper P to be printed is high based on the temperature TMP and the humidity HMD of the installation environment of the printing apparatus 11. An example is configured.

  Based on the information input from the input information processing unit 91, the sheet determination unit 93 determines whether the sheet P to be printed is a sheet having a high resistance value or whether the sheet is likely to be curled due to ink adhesion. Determine whether or not. Then, the sheet determination unit 93 outputs information regarding the determination result to the charge removal control unit 94.

  The charge removal control unit 94 determines whether the charge removal unit 581 is disposed at the charge removal position or the retreat position based on information input from the paper determination unit 93 and the temperature / humidity determination unit 92. That is, the neutralization control unit 94 determines whether or not the neutralization unit 581 is brought into contact with the paper P being conveyed by the conveyance belt 53 when printing on the paper P.

For example, the static elimination control unit 94 determines that the static elimination unit 581 is disposed at the static elimination position when at least one of the following three conditions is satisfied. On the other hand, the static elimination control unit 94 determines that the static elimination unit 581 is disposed at the retracted position when all of the following conditions are not satisfied.
When it is determined that the resistance value of the paper P to be printed is high based on the input information from the paper determination unit 93.
A case where it is determined based on the input information from the paper determination unit 93 that the paper P to be printed is easily curled.
A case where the current installation environment of the printing apparatus 11 is included in the high resistance region A1 based on input information from the temperature / humidity determination unit 92.

  When the static elimination control unit 94 determines to dispose the static elimination unit 581 at the static elimination position, when the paper P that is electrostatically attracted and conveyed by the conveyance belt 53 is in a position where it can come into contact with the static elimination unit 581, By driving the actuator 582, the static elimination unit 581 is disposed at the static elimination position. On the other hand, when the charge removal control unit 94 determines to place the charge removal unit 581 in the retracted position, the charge removal control unit 94 drives the actuator 582 to place the charge removal unit 581 in the retracted position. In this respect, in the printing apparatus 11 of the present embodiment, the static elimination control unit 94 configures an example of a “static elimination control device” that controls the position of the static elimination unit 581. When the position control of the static eliminator 581 is completed in this way, the static eliminator controller 94 outputs to the transport controller 95 and the print controller 96 that the printing start of the paper P is permitted.

  The conveyance control unit 95 controls the conveyance device 29 so that the sheet P is conveyed in a manner based on the input information from the input information processing unit 91 when the fact that printing start is permitted is input from the static elimination control unit 94. To do.

  The print control unit 96 controls the mode of ink ejection from the print head 141 based on the print data. At this time, the printing control unit 96 can form an image at an appropriate position on the printing surface Pb of the paper P in cooperation with the conveyance control unit 95.

Next, with reference to the flowchart shown in FIG. 6, a processing procedure when printing on the paper P will be described.
As shown in FIG. 6, first, in step S11, the temperature TMP and the humidity HMD of the installation environment of the printing apparatus 11 are acquired. In the next step S12, temperature / humidity determination processing is executed. This temperature / humidity determination processing is executed by the temperature / humidity determination unit 92. That is, it is determined whether the current installation environment indicated by the acquired temperature TMP and humidity HMD is included in the high resistance region A1 or the low resistance region A2. When the temperature / humidity determination process is completed, the process proceeds to the next step S13.

  In step S13, a paper type determination process is executed. This paper type determination process is executed by the paper determination unit 93. That is, based on the information regarding the type of the paper P input to the paper determination unit 93, it is determined whether or not the paper P to be printed is a paper having a high resistance value. Further, based on the information, it is determined whether or not the paper P to be printed is a paper that is likely to curl due to ink adhesion. When the paper type determination process is completed, the process proceeds to the next step S14.

  In step S <b> 14, it is determined whether or not it is necessary to execute a charge removal process for removing charges from the printing surface Pb of the paper P in the current printing. This determination is performed by the static elimination control unit 94. When it is determined that the charge removal process needs to be performed, it is determined that the charge removal unit 581 is disposed at the charge removal position. On the other hand, when it is determined that it is not necessary to perform the charge removal process, it is determined that the charge removal unit 581 is disposed at the retracted position.

And when it determines with execution of a static elimination process being required (step S14: YES),
The neutralization unit 581 is disposed at the neutralization position (step S15), and the process proceeds to step S17 described later. On the other hand, if it is determined that it is not necessary to perform the charge removal process (step S14: NO), the charge removal unit 581 is placed at the retracted position (step S16), and the process proceeds to the next step S17.

  In step S17, when the position control of the static eliminating unit 581 is completed, the conveyance control unit 95 and the print control unit 96 are instructed to start printing. Then, the transport device 29 and the printing unit 14 are driven so that the paper P is transported, and ink is ejected from the print head 141 onto the printing surface Pb of the paper P that is electrostatically attracted to the transport belt 53. Become.

In step S18, it is determined whether or not printing on the paper P has been completed. If printing has not yet been completed (step S18: NO), printing on the paper P is continued.
On the other hand, when the printing is completed (step S18: YES), the paper P is discharged toward the mounting table 60 by the transport device 29, and this process ends.

As described above, according to the printing apparatus 11 of the present embodiment, the following effects can be obtained.
(1) In the printing apparatus 11 of the present embodiment, the charge removal unit 581 can be disposed at the charge removal position or the retracted position. For this reason, it is possible to make the static eliminator 581 come into contact with the paper P that is electrostatically attracted to the transport belt 53, or not to make the static eliminator 581 come into contact with the paper P. Therefore, as compared with the case where the static elimination unit 581 is always disposed at the static elimination position, the chance of bringing the static elimination unit 581 into contact with the paper P or the conveyance belt 53 during printing can be reduced. As a result, the deterioration of the charge removal unit 581 is delayed, and the reduction of the charge removal efficiency from the paper P by the charge removal unit 581 can be suppressed.

  (2) For example, according to the type of paper P to be printed, it is determined whether the static eliminator 581 is arranged at the static eliminator position or the retracted position, and the position of the static eliminator 581 is controlled based on the determination result. I am doing so. Thereby, when it can be determined that the electrostatic attraction force of the paper P by the transport belt 53 does not need to be increased, the contact between the paper P and the charge removal portion 581 can be avoided. Therefore, depending on the type of paper P to be printed, the charge removal unit 581 can be disposed at the retracted position during printing, and the charge removal unit 581 is deteriorated compared to the case where the charge removal unit 581 is always disposed at the charge removal position. It becomes difficult to do. As a result, it is possible to suppress a reduction in the charge removal efficiency from the paper P by the static eliminating unit 581.

  (3) Further, it is determined whether or not the resistance value of the paper P is high based on the temperature TMP and the humidity HMD of the installation environment of the printing apparatus 11, and when it can be determined that the resistance value is high, the conveyance is performed. The static elimination unit 581 is brought into contact with the paper P conveyed by the belt 53. On the other hand, when it can be determined that the resistance value of the paper P is low, the static eliminator 581 is not brought into contact with the paper P being transported by the transport belt 53. That is, when it can be predicted that the charge on the printing surface Pb is likely to be neutralized naturally without removing the charge from the printing surface Pb of the paper P by the static elimination unit 581, the electrostatic attraction force of the paper P by the transport belt 53 is increased. Since it is relatively large, the static eliminating unit 581 is not brought into contact with the paper P. Therefore, compared with the case where the static elimination part 581 is always arrange | positioned in the static elimination position irrespective of the temperature and humidity of the installation environment of the printing apparatus 11, the opportunity which makes the static elimination part 581 contact the paper P and the conveyance belt 53 is reduced. Can do. Therefore, the deterioration of the charge removal unit 581 can be delayed, and the reduction of the charge removal efficiency from the paper P by the charge removal unit 581 can be suppressed.

(4) Since the reduction in the efficiency of removing charges from the paper P by the static eliminating unit 581 is suppressed in this manner, the replacement frequency of the static eliminating unit 581 can be reduced.
(5) The paper P fed to the electrostatic transport unit 50 is pressed against the transport belt 53 by the support roller 57. As a result, the adhesion between the paper P and the transport belt 53 can be improved, and the paper P is easily polarized. As a result, the electrostatic attraction force of the paper P by the transport belt 53 can be increased.

  (6) Further, a metal backup plate 55 is in contact with the inner surface of the conveyor belt 53 that is the surface opposite to the outer surface with which the paper P contacts. Since the backup plate 55 is grounded, the charge charged on the inner surface side of the conveyor belt 53 can be removed by the backup plate 55. Therefore, the electrostatic attraction force of the paper P by the transport belt 53 can be increased by the amount that can suppress the decrease in the amount of charge charged on the outer surface side of the transport belt 53.

(Second Embodiment)
Next, a second embodiment in which the printing apparatus 11 is embodied will be described with reference to FIGS. In the second embodiment, the point of determining whether to dispose the charge removal unit 581 at the charge removal position or the retreat position when printing on the second surface during duplex printing is the first implementation. It is different from the form. Therefore, in the following description, parts different from those of the first embodiment will be mainly described, and the same member configuration as that of the first embodiment will be denoted by the same reference numerals and redundant description will be omitted. To do.

When performing duplex printing, the ink has not yet adhered to the paper P when printing on the first surface of the paper P. On the other hand, at the time of printing on the second surface of the paper P, the ink has already adhered to the first surface, and the paper P may be curled depending on how the ink is adhered to the first surface.
When the paper P is curled in this way and conveyed immediately below the print head 141, the curled portion of the paper P may come into contact with the print head 141 or the like.

  Therefore, in the printing apparatus 11 of the present embodiment, based on the printing mode on the first surface, it is determined whether or not the paper P is likely to curl. When performing printing on the second surface, the neutralization unit 581 is arranged at the neutralization position. Thus, when the paper P is transported by the transport belt 53 to perform printing on the second surface, the charge removal unit 581 contacts the second surface of the paper P, and the charge is removed from the second surface. Is done. As a result, the electrostatic attraction force of the paper P by the transport belt 53 is increased, so that curling of the paper P on the transport belt 53 can be suppressed.

  On the other hand, when it is determined that the paper P does not curl even if printing is performed on the first surface, the charge removal unit 581 is disposed at the retracted position when performing printing on the second surface. Thereby, when performing duplex printing, compared with the case where the static elimination part 581 is always arrange | positioned in the static elimination position, deterioration of the static elimination part 581 becomes difficult to advance.

  In the printing apparatus 11 according to the present embodiment, the neutralization unit 581 is arranged at the retracted position when printing on the first surface when performing duplex printing and when printing only on one surface. Also in this respect, the progress of the deterioration of the static elimination unit 581 can be delayed.

Next, a processing procedure for executing double-sided printing will be described with reference to a flowchart shown in FIG.
As shown in FIG. 7, first, in step S31, a curl determination process for determining whether or not there is a possibility that the paper P is curled by printing on the first surface of the paper P is executed. This curl determination process is executed by the charge removal control unit 94. The curl determination process will be described in detail later with reference to FIGS.

  In the next step S32, prior to the start of printing on the first side of the paper P, the static eliminating unit 581 is disposed at the retracted position. In this state, the printing process for the first surface is started (step S33). For this reason, the neutralization unit 581 does not come into contact with the paper P conveyed by the conveyance belt 53 when printing on the first surface.

  Subsequently, in step S34, it is determined whether or not the printing process for the first surface has been completed. If the printing process for the first surface has not been completed yet (step S34: NO), the printing process is continued. On the other hand, when the printing process for the first surface is completed (step S34: YES), the process proceeds to the next step S35.

  In step S <b> 35, a reversing process is performed in which the third medium supply unit 23 is operated to reverse the front and back and guide the paper P onto the transport belt 53 again. By executing this reversal process, when the paper P is guided again to the transport belt 53, the second surface becomes the printing surface Pb and the first surface becomes the contact surface Pa. Thereby, printing on the second surface becomes possible.

  In the next step S36, when printing on the second surface, it is determined whether or not it is necessary for the neutralization unit 581 to execute a neutralization process for removing charges from the second surface. That is, based on the execution result of the curl determination process in step S31, when it can be determined that the paper P may curl due to the adhesion of ink to the first surface, it is determined that the charge removal process needs to be performed. The On the other hand, if it can be determined that the paper P does not curl even if ink adheres to the first surface, it is determined that it is not necessary to perform the charge removal process. When it is determined that the neutralization process needs to be performed, it is determined that the neutralization unit 581 is disposed at the neutralization position, while when it is determined that the neutralization process is not necessary, the neutralization unit 581 is moved to the retreat position. Is determined to be placed in

Therefore, when it is determined that the neutralization process is not necessary (step S36: NO), the state of the neutralization unit 581 is maintained without moving the neutralization unit 581, that is, the process is performed. The process proceeds to step S38 to be described later. On the other hand, when it is determined that it is necessary to execute the charge removal process (step S36: YES), the charge removal unit 581 is moved to the charge removal position (step S37). Then, the process proceeds to the next step S38. Note that such displacement of the static elimination unit 581 is performed while the third medium supply unit 23 feeds the paper P toward the transport belt 53.

In step S38, the printing process for the second surface is started. In step S39, it is determined whether the printing process for the second surface is completed. If the printing process for the second surface has not been completed yet (step S39: NO), the printing process is continued. On the other hand, when the printing process for the second surface is completed (step S39: YES), the paper P is discharged toward the mounting table 60 by the transport device 29 (step S40). Thereafter, this process is terminated.

  Next, an example of the curl determination process (step S31) in FIG. 7 will be described with reference to the flowchart shown in FIG. 8 and the schematic diagram shown in FIG. The curl determination process is a process executed by the charge removal control unit 94.

  As shown in FIG. 8, print data for forming an image on the first surface is acquired (step S61). In the next step S62, the first surface of the paper P is divided into a plurality of areas, and a plurality of divided areas R1, R2, R3, R4, R5, R6, R7, R8, and R9 are set.

  Here, an example of a method for setting the divided regions R1 to R9 will be described with reference to FIG. As shown in FIG. 9, the paper P has a substantially rectangular shape, and has four side edges PE1, PE2, PE3, and PE4. For this reason, the paper P has four corners PK1, PK2, PK3, and PK4, which are connecting portions of the two side edges, and these corners PK1 to PK4 are substantially perpendicular. Then, nine divided areas R1 to R9 are set on the first surface of the sheet P. For example, by dividing the first surface into three along the sheet conveyance direction Y and dividing the first surface into three along the sheet width direction Z, a total of nine divided regions R1 to R1 are divided. R9 is set.

  In the example illustrated in FIG. 9, the nine divided regions R <b> 1 to R <b> 9 include a large area and a small area. However, the present invention is not limited to this, and the areas of all the divided regions R1 to R9 may be equal.

  Returning to FIG. 8, in the next step S63, four determination areas HR1, HR2, HR3, and HR4 are set from among the set divided areas R1 to R9. That is, among the nine divided regions R1 to R9 shown in FIG. 9, the divided region including the corners PK1 to PK4 is set as the determination region. In this case, the divided region R1 is the determination region HR1, the divided region R3 is the determination region HR2, the divided region R7 is the determination region HR3, and the divided region R9 is the determination region HR4.

  Subsequently, in step S64, the maximum ink discharge amount Xmax is calculated for each of the determination regions HR1 to HR4. This maximum ejection amount Xmax is a value corresponding to the amount of ink ejected from the print head 141 when it is assumed that so-called solid printing is performed, in which ink is ejected uniformly over the entire determination region. At this time, if the areas of all the determination regions HR1 to HR4 are the same, all the four maximum discharge amounts Xmax have the same value. However, when a large area and a small area are mixed in each of the determination areas HR1 to HR4, the maximum discharge amount Xmax for the determination area with a large area is the maximum discharge for the determination area with a small area. It becomes larger than the amount Xmax.

  In step S65, an actual ink ejection amount Xr, which is the amount of ink actually ejected to the determination area, is calculated for each of the determination areas HR1 to HR4. For example, when forming an image on the first surface based on the print data acquired in step S61, the shape and size of the image formed in the determination area are grasped for each of the determination areas HR1 to HR4. Then, the amount of ink necessary for forming the image in the determination area is calculated for each of the determination areas HR1 to HR4. The value calculated in this way is set as the actual ink discharge amount Xr in the determination regions HR1 to HR4.

Subsequently, in step S66, the ejection ratio JR of each of the determination areas HR1 to HR4 is calculated. That is, the quotient (= Xr / Xm) obtained by dividing the actual ink discharge amount Xr by the maximum discharge amount Xmax.
ax) is the discharge rate JR. In the next step S67, it is determined whether or not there is a determination area in which the discharge ratio JR is equal to or higher than the determination ratio JRTh in each of the determination areas HR1 to HR4.

  Here, the paper P is more likely to curl when more ink is deposited around the corners PK1 to PK4. Therefore, by predicting the amount of ink adhering to the determination areas HR1 to HR4, which are the divided areas including the corners PK1 to PK4, whether or not there is a possibility that the paper P may be curled by printing on the first surface. Can be predicted. That is, the determination ratio JRTh is a determination value for determining from the discharge ratio whether or not the paper P may be curled.

  If the discharge ratio JR is less than the determination ratio JRTh in all the determination areas HR1 to HR4 (step S67: NO), it is determined that the paper P does not curl even if printing is performed on the first surface (step S68). Then, the curl determination process (step S31) in FIG. 7 ends.

  On the other hand, when the ejection ratio JR is equal to or greater than the determination ratio JRTh in at least one of the determination areas HR1 to HR4 (step S67: YES), the paper P may be curled by printing on the first surface. Is determined (step S69), and the curl determination process (step S31) in FIG. 7 is terminated.

As described above, according to the printing apparatus 11 of the present embodiment, in addition to the effects (1) and (4) to (6) in the first embodiment, the following effects can be further obtained.
(7) When performing double-sided printing on the paper P, curling is likely to occur on the paper P when printing on the second surface in a situation where ink is attached by printing on the first surface. Therefore, in the present embodiment, when printing is performed on the second surface of the paper P, it is determined whether the neutralization unit 581 is disposed at the neutralization position or the retreat position. When it is determined that the static elimination unit 581 is disposed at the static elimination position, the static elimination unit 581 is brought into contact with the second surface of the paper P being conveyed by the conveyance belt 53 so as to remove charges from the second surface. Yes. Accordingly, the electrostatic adsorption force of the paper P by the transport belt 53 is increased, and the paper P is not easily curled on the transport belt 53. As a result, the occurrence of a printing defect can be suppressed as much as an event that the paper P contacts the print head 141 or the like is less likely to occur.

  (8) In this embodiment, when it is determined that there is a possibility that the paper P may curl when printing is performed on the first side, the neutralization unit 581 is disposed at the neutralization position when printing on the second side. . For this reason, when printing on the second surface, the charge removal unit 581 comes into contact with the second surface, so that charges are removed from the second surface. Can be bigger. As a result, the paper P is less likely to curl on the transport belt 53. Therefore, the occurrence of printing defects can be suppressed by the amount that the event that the paper P contacts the print head 141 or the like is less likely to occur. On the other hand, if it is determined that the paper P does not curl even when printing on the first side, the neutralization unit 581 is disposed at the retracted position when printing on the second side. Therefore, the neutralization unit 581 is not brought into contact with the paper P when printing on the second surface. Therefore, regardless of the printing mode on the first surface, the neutralization unit 581 is less likely to deteriorate compared to the case where the neutralization unit 581 is always disposed at the neutralization position during printing on the second surface. Can be delayed.

  (9) As described above, the paper P is more easily curled as the amount of ink attached to the corners PK1 to PK4 of the paper P increases. Therefore, in the present embodiment, when the determination areas HR1 to HR4 including the corners PK1 to PK4 of the paper P are set and it can be determined that the amount of ink adhering to the determination areas HR1 to HR4 is large, the process proceeds to the first surface. It is determined that there is a possibility that the paper P will be curled by the printing. If it is predicted that the paper P will not curl by determining the position of the static elimination unit 581 based on the determination result, the static elimination unit 581 is not brought into contact with the paper P when printing on the second surface. Therefore, compared with the case where the static elimination part 581 is always arrange | positioned in the static elimination position at the time of printing on a 2nd surface, since the static elimination part 581 becomes difficult to deteriorate, degradation of the static elimination part 581 can be delayed.

  (10) On the other hand, at the time of printing on the first side, unlike the case of printing on the second side, since the ink has not adhered to the paper P, there is a possibility that the paper P is curled. Low. Therefore, in the present embodiment, the neutralization unit 581 is disposed at the retracted position so that the neutralization unit 581 is not brought into contact with the paper P during printing on the first surface. As a result, compared with the case where the neutralization unit 581 is arranged at the neutralization position even when printing on the first surface, the charge removal unit 581 is less likely to deteriorate, and the charge removal efficiency from the paper P by the neutralization unit 581 is reduced. Can be suppressed.

(Third embodiment)
Next, a third embodiment in which the printing apparatus 11 is embodied will be described. In the third embodiment, the first pressing point is that the pressing force of the charge removal unit 581 against the paper P is changed based on the ejection ratio on the first surface during printing on the second surface during duplex printing. It is different from the embodiment. Therefore, in the following description, parts different from those of the first embodiment will be mainly described, and the same member configuration as that of the first embodiment will be denoted by the same reference numerals and redundant description will be omitted. To do.

  In the present embodiment, the actuator 582 in FIG. 2A can change the pressing force that the static eliminating unit 581 presses against the paper P that is electrostatically attracted to the transport belt 53 and transported. That is, the actuator 582 is configured as a pressing force variable mechanism.

  In the present embodiment, when the static eliminator 581 is disposed at the static eliminator position in step S37 in FIG. 7, the static eliminator controller 94 in FIG. 5 performs the actuator operation based on the discharge ratio JR calculated in step S66 in FIG. By performing the drive control of 582, the pressing force against the paper P of the static eliminating unit 581 is set.

  Specifically, in step S69 of FIG. 8, when it is determined that there is a possibility that the paper curls, the static elimination control unit 94 increases the pressing force of the static elimination unit 581 against the paper P as the ejection ratio JR increases. Thus, the drive control of the actuator 582 is performed.

  Other processing procedures when executing double-sided printing in the present embodiment are the same as those described in the second embodiment with reference to the flowcharts of FIGS.

In addition, you may change each said embodiment as follows.
In each embodiment, the support roller 57 may be a roller made of a material other than a metal material (for example, synthetic resin) as long as the support roller 57 is driven and rotated by the operation of the transport belt 53.

In each embodiment, the support roller 57 may not be grounded.
In each embodiment, the support roller 57 does not need to be provided as long as the paper P can be electrostatically attracted to the transport belt 53 without pressing the paper P against the transport belt 53 by the support roller 57.

  -In 2nd Embodiment, you may change the setting method of determination area | region HR1-HR4 as shown below, for example. That is, the first surface of the paper P is divided into a plurality of areas, and a plurality of divided areas are set. Then, among each divided area, an area formed by an edge area that is a divided area including the corner of the paper P and an area adjacent to the edge area may be set as the determination area.

  FIG. 10 shows an example of such a determination area setting method. That is, as shown in FIG. 10, for example, an area configured by a divided area R1 (edge area) including the corner PK1 and a divided area R4 adjacent to the divided area R1 in the paper transport direction Y is determined. An area composed of a divided area R3 (edge area) including the corner PK2 and a divided area R2 adjacent to the divided area R3 in the paper width direction Z may be used as the determination area HR2. Similarly, an area composed of a divided area R9 (edge area) including the corner PK3 and a divided area R6 adjacent to the divided area R9 in the paper transport direction Y is set as a determination area HR3, and includes the corner PK4. An area formed by the area R7 (edge area) and the divided area R8 adjacent to the divided area R7 in the paper width direction Z may be set as the determination area HR4.

  Then, the ejection ratio JR is calculated for each of the determination areas HR1 to HR4 set as described above. If there is a determination area where the ejection ratio JR is equal to or greater than the determination ratio JRTh, the sheet P is printed by printing on the first surface. It may be determined that there is a possibility of curling.

In the second embodiment, the number of divided regions formed by dividing the first surface may be any number other than nine as long as the number is two or more.
A method other than the curl determination method described in the second embodiment may be used to determine whether or not the paper P is curled by printing on the first surface.

  -In 2nd Embodiment, when performing double-sided printing, you may make it arrange | position the static elimination part 581 in a static elimination position as needed also at the time of the printing to a 1st surface. For example, when printing on the high-resistance paper P, the static eliminator 581 may be brought into contact with the paper P even when printing on the first surface.

  In addition, if the neutralization unit 581 is arranged at the neutralization position when printing on the first surface in this way, regardless of the determination result of the curl determination process when printing on the second surface, or It may be determined that the charge removal unit 581 is disposed at the charge removal position without performing the curl determination process.

  In the first embodiment, when duplex printing is performed on the paper P, the neutralization unit 581 is set to the neutralization position when performing printing on the second surface regardless of the type of the paper P or the installation environment of the printing apparatus 11. It may be arranged.

  In the first embodiment, the temperature TMP of the installation environment of the printing apparatus 11 and the discharge environment 581 are determined according to the type of the paper P as long as the charge removal unit 581 is arranged at the charge removal position or the retreat position. The position of the static eliminating unit 581 based on the humidity HMD may not be determined.

  In the first embodiment, if the configuration determines whether the static eliminating unit 581 is arranged at the static elimination position or the retreat position based on the temperature TMP and the humidity HMD of the installation environment of the printing apparatus 11, the paper P The position of the static elimination unit 581 according to the type may not be determined.

  In the first embodiment, if it is possible to determine whether or not the resistance value of the paper P is high only by the humidity HMD of the installation environment of the printing apparatus 11, the position of the static elimination unit 581 is determined. It is not necessary to include the temperature TMP of the installation environment in the parameters at the time.

  In the first embodiment, when it can be determined that the sheet P to be printed is a sheet having a high resistance value based on the information regarding the type of the sheet selected by the user, regardless of the installation environment of the printing apparatus 11, You may make it arrange | position the static elimination part 581 in a static elimination position.

  In the first embodiment, when it can be determined that the sheet P to be printed is a sheet having a low resistance value based on the information regarding the type of the sheet selected by the user, regardless of the installation environment of the printing apparatus 11, You may make it arrange | position the static elimination part 581 in a retracted position.

  In the first embodiment, even if it is possible to determine that the paper P to be printed is a paper having a high resistance value based on the information on the paper type selected by the user, the installation environment of the printing apparatus 11 If it can be determined that the resistance value of the paper P is low based on the above, the static eliminator 581 may be disposed at the retracted position.

  In the first embodiment, even if it is possible to determine that the paper P to be printed is a paper having a low resistance value based on the information regarding the paper type selected by the user, the installation environment of the printing apparatus 11 If it can be determined that the resistance value of the paper P is high based on the above, the static eliminator 581 may be disposed at the static eliminator position.

  In each embodiment, the static eliminator 581 is displaced in a direction orthogonal to the print surface Pb of the paper P. However, the present invention is not limited to this, and the static eliminator 581 is brought into contact with the print surface Pb or the static eliminator 581. As long as it can be separated from the paper P, the static eliminator 581 may be displaced in any direction.

  The printing unit 14 may be a unit that ejects ink from the printing head onto the printing surface of the paper while moving the printing head in a predetermined scanning direction. The printing unit 14 may be a lateral scan type unit that ejects ink from the printing head 141 onto the paper P while moving the printing head 141 in the paper conveyance direction.

  In each embodiment, the printing apparatus can employ any ink as a printing material as long as an image can be formed on the paper P. In other words, the printing material may have a granular shape, a tear shape, or a thread shape. For example, the printing material may be in a state in which the substance is in a liquid phase, such as a liquid material having high or low viscosity, sol, gel water, other inorganic solvents, organic solvents, solutions, liquid resins, liquid metals. A fluid such as (metal melt) shall be included. In addition, the printing material includes not only a liquid as one state of a substance but also a material in which functional material particles made of solid materials such as pigments and metal particles are dissolved, dispersed, or mixed in a solvent. Typical examples of the printing material include ink and liquid crystal as described in the above embodiments. Here, the ink includes general water-based inks and oil-based inks, and various liquid compositions such as gel inks and hot melt inks.

  The printing medium on which printing is performed by the printing apparatus may be a medium other than paper as long as it can be electrostatically attracted to the conveyance belt 53.

  DESCRIPTION OF SYMBOLS 11 ... Printing apparatus, 141 ... Print head, 23 ... 3rd medium supply part which is an example of reversing mechanism, 53 ... Conveyance belt, 56 ... Charging roller which is an example of charging part, 57 ... Support roller, 581 ... Static elimination part , 92... Temperature / humidity determination unit as an example of a determination device, 94... Static elimination control unit as an example of a static elimination control device, HR1 to HR4... Judgment region, JR. Paper, Pa ... contact surface, Pb ... printing surface, PE1-PE4 ... side, PK1-PK4 ... corner, R1-R9 ... divided region, HMD ... humidity, TMP ... temperature, Xmax ... maximum discharge amount.

Claims (13)

A transport belt for transporting print media;
A charging unit for supplying a charge to the conveyor belt;
The printing of the print medium that is electrostatically adsorbed to the conveyance belt when the surface that is in contact with the conveyance belt is the contact surface and the surface opposite to the contact surface is the printing surface of both sides of the print medium A print head for attaching a printing material to the surface;
It is displaceable between a charge removal position, which is a position where the print medium conveyed by the conveyance belt can be contacted, and a retracted position, which is a position where the print medium cannot be contacted, and on the print surface of the print medium. A charge eliminating portion that removes electric charges from the printed surface by contact; and
A static elimination control device for controlling the position of the static elimination unit,
The neutralization control device arranges the neutralization unit at the neutralization position when the print medium electrostatically attracted to the conveyance belt is in a position where it can contact the neutralization unit. apparatus.   The charge removal control device determines whether or not the charge removal unit is brought into contact with the print medium conveyed by the conveyance belt according to the type of print medium to be printed, and the charge removal unit based on the determination result The printing apparatus according to claim 1, wherein the position of the printing apparatus is controlled.   The static elimination control device determines whether or not the static elimination unit is brought into contact with a print medium conveyed by the conveyance belt based on humidity of an installation environment of the printing device, and the static elimination unit is determined based on the determination result. The printing apparatus according to claim 1, wherein the position of the printing apparatus is controlled. Based on the temperature and humidity of the installation environment of the printing device, a determination device that determines whether or not the resistance value of the print medium to be printed is high,
The static elimination control device
When it is determined by the determination device that the resistance value of the print medium is high, the charge removal unit is disposed at the charge removal position,
2. The printing apparatus according to claim 1, wherein when the determination apparatus determines that the resistance value of the print medium is low, the neutralization unit is disposed at the retracted position. After the printing on the first surface of both sides of the print medium is completed, the first surface becomes the contact surface and the second surface opposite to the first surface is the printing surface. A reversing mechanism for reversing the front and back of the print medium and guiding the print medium onto the transport belt,
The print head is arranged downstream in the transport direction from the static elimination position,
The neutralization control device arranges the neutralization unit at the neutralization position when printing is performed on the second surface of the printing medium guided from the reversing mechanism onto the conveyance belt. The printing apparatus according to 1. After the printing on the first surface of both sides of the print medium is completed, the first surface becomes the contact surface and the second surface opposite to the first surface is the printing surface. A reversing mechanism for reversing the front and back of the print medium and guiding the print medium onto the transport belt,
The static elimination control device
Determining whether the print medium is curled by printing on the first side of the print medium;
When it is determined that the print medium is curled by printing on the first surface of the print medium, the neutralization unit is disposed at the neutralization position when printing on the second surface of the print medium,
When it is determined that the print medium is not curled by printing on the first surface of the print medium, the neutralization unit is disposed at the retracted position when printing the second surface of the print medium. The printing apparatus according to claim 1, wherein: After the printing on the first surface of both sides of the print medium is completed, the first surface becomes the contact surface and the second surface opposite to the first surface is the printing surface. A reversing mechanism for reversing the front and back of the print medium and guiding the print medium onto the transport belt,
The print medium has four sides and a corner that is a connecting portion of the two sides.
When the first surface of the print medium is divided into a plurality of areas, and the area including the corners of the print medium among the areas is a determination area,
The static elimination control device
Calculating a maximum discharge amount that is the maximum amount of printing material that can be adhered to the determination region by discharging the printing material from the print head to the determination region;
Based on print data employed for printing on the first surface of the print medium, a discharge amount that is an amount of a printing material discharged from the print head to the determination region is calculated,
Calculating a discharge ratio which is a ratio of the discharge amount to the maximum discharge amount;
When the discharge ratio is less than the determination ratio in the determination region, the neutralization unit is disposed at the retracted position when printing on the second surface of the print medium,
2. The discharge unit according to claim 1, wherein when the discharge ratio is equal to or higher than the determination ratio in the determination region, the charge removal unit is disposed at the charge removal position when printing on the second surface of the print medium. Printing device. After the printing on the first surface of both sides of the print medium is completed, the first surface becomes the contact surface and the second surface opposite to the first surface is the printing surface. A reversing mechanism for reversing the front and back of the print medium and guiding the print medium onto the transport belt,
The print medium has four sides and a corner that is a connecting portion of the two sides.
The first surface of the print medium is divided into a plurality of areas, and an area constituted by an end area that is an area including a corner of the print medium and an area adjacent to the end area among the areas. If it is a judgment area,
The static elimination control device
Calculating a maximum discharge amount that is the maximum amount of printing material that can be adhered to the determination region by discharging the printing material from the print head to the determination region;
Based on print data employed for printing on the first surface of the print medium, a discharge amount that is an amount of a printing material discharged from the print head to the determination region is calculated,
Calculating a discharge ratio which is a ratio of the discharge amount to the maximum discharge amount;
When the discharge ratio is less than the determination ratio in the determination region, the neutralization unit is disposed at the retracted position when printing on the second surface of the print medium,
2. The discharge unit according to claim 1, wherein when the discharge ratio is equal to or higher than the determination ratio in the determination region, the charge removal unit is disposed at the charge removal position when printing on the second surface of the print medium. Printing device. A plurality of the determination areas including one corner are set on the first surface of the print medium,
The static elimination control device
When the ejection ratio is less than the determination ratio in all the determination areas, the neutralization unit is disposed at the retracted position when printing on the second surface of the print medium,
When the discharge ratio is equal to or higher than the determination ratio in at least one determination area among the determination areas, the charge removal unit is disposed at the charge removal position when printing on the second surface of the print medium. The printing apparatus according to claim 7 or 8, characterized in that: A static pressure variable mechanism that is capable of changing the pressure of the static elimination unit against the print medium electrostatically adsorbed to the conveyance belt when the static elimination unit is in the static elimination position;
The said static elimination control apparatus changes the said pressing force of the said static elimination part according to the said discharge ratio using the said pressing force variable mechanism part, The any one of Claims 7-9 characterized by the above-mentioned. The printing apparatus as described in.   The said static elimination control apparatus arrange | positions the said static elimination part in the said retracted position, when printing on the said 1st surface of a printing medium, The any one of Claims 5-10 characterized by the above-mentioned. Printing device. It is arranged upstream of the static elimination position in the transport direction, and includes a support roller that presses the print medium against the transport belt,
The printing apparatus according to claim 1, wherein the support roller is driven and rotated by operation of the transport belt.   The printing apparatus according to claim 12, wherein the support roller is grounded.

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