Liquid discharge apparatus

Abstract

To solve the problem that foreign matter may adhere to a head.SOLUTION: A liquid ejecting apparatus includes a liquid ejecting unit that ejects a liquid onto a medium, a transporting belt that has an clinging surface that clings to the medium and transports the medium to a position facing the liquid ejecting unit, a charging unit that charges the clinging surface to a first polarity, and a control unit that controls the transporting belt and the charging unit. The control unit causes the charging unit to charge at least a part of the conveyance region of the clinging surface to the first polarity and not to charge the non-conveyance region of the clinging surface to the first polarity.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a liquid ejection device. [Background technology]

[0002] 2. Description of the Related Art Conventionally, as disclosed in Patent Document 1, an inkjet recording apparatus is known as a liquid ejection apparatus that alternately charges a conveyor belt with positive and negative charges to attract recording paper to the conveyor belt. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-103857 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the above-described liquid ejection device, there is a risk that foreign matter such as paper dust may adhere to the head, causing problems. [Means for solving the problem]

[0005] The liquid ejection device includes a liquid ejection unit that ejects liquid onto a medium, a conveying belt that has an adsorption surface that adsorbs the medium and transports the medium to a position opposite the liquid ejection unit, a charging means that charges the adsorption surface to a first polarity, and a control unit that controls the conveying belt and the charging means, wherein the adsorption surface has a conveying area that contacts the medium being transported and a non-conveying area provided between the conveying areas, and the control unit charges at least a portion of the conveying area of ​​the adsorption surface to the first polarity using the charging means, and does not charge the non-conveying area of ​​the adsorption surface to the first polarity. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 1 is a cross-sectional view showing a configuration of a liquid ejection device. [Figure 2] FIG. 4 is a schematic diagram showing the state of charging at the support portion. [Figure 3] FIG. 10 is a schematic diagram showing a state in which a portion of the charge is removed from the support portion. DETAILED DESCRIPTION OF THE INVENTION

[0007] The liquid ejection device 1 will be described with reference to the drawings. Directions in the drawings will be described using a three-dimensional coordinate system. For convenience of description, the positive direction of the Z axis will be referred to as the upward direction, upward, or simply upward; the negative direction will be referred to as the downward direction, downward, or simply downward; the positive direction of the X axis will be referred to as the rightward direction, rightward, or simply right; the negative direction will be referred to as the leftward direction, leftward, or simply left; the positive direction of the Y axis will be referred to as the forward direction, forward, or simply forward; and the negative direction will be referred to as the rearward direction, rearward, or simply rearward.

[0008] 1. Configuration of the liquid ejection device 1, the liquid ejection device 1 includes a head 2, which is a liquid ejection unit. The head 2 is, for example, a line-type inkjet head extending in the left-right direction. The head 2 performs recording by ejecting ink, which is a liquid, from an upper liquid ejection surface 2a onto a medium M supported from below by a support portion 10. Note that, hereinafter, the liquid ejection surface 2a will be simply referred to as the ejection surface 2a.

[0009] The liquid ejection device 1 has a plurality of paths for transporting the medium M. For convenience of illustration, the medium M transported in each path is omitted in FIG. The liquid ejection device 1 has one path for the medium M, which is along the transport direction F of the medium M. The liquid ejection device 1 has arranged, from upstream to downstream in the transport direction F of this path, a paper feed tray T1 which is a paper feed unit, a first path P1, a head 2, a support unit 10 facing the head 2, a second path P2, and a paper discharge tray T2 which is a paper discharge unit. The medium M is transported along the transport direction F, and when it reaches between the head 2 and the support part 10, the upper head 2 records on one of its surfaces, that is, the front surface.

[0010] The liquid discharge device 1 also has a third path P3, which is another path for the medium M, that supplies the medium M from the front of the case 5 in the manual insertion direction F1. The operator inserts the medium M into the third path P3 in the manual insertion direction F1. The third path P3 is connected to the first path P1, and once the medium M is transported from the third path P3 to the first path P1, it is transported along the transport direction F described above.

[0011] A branching section 4 is disposed midway along the second path P2. The branching section 4 is rotatable about a branching axis 4a. The branching section 4 has been rotated clockwise around the branching axis 4a in advance. The clockwise rotation of the branching section 4 allows the medium M, whose surface has been recorded, to pass smoothly, leading edge first, through the branching section 4 of the second path P2 in the transport direction F.

[0012] When the rear end of the medium M transported along the second path P2 passes through the branching unit 4, the transport of the medium M is temporarily stopped. The branching unit 4 rotates counterclockwise around the branching shaft 4a. In this state, when the medium M is transported in a reverse direction R, which is the opposite direction to the transport direction F, the medium M is guided from its rear end to the branching section 4 and transported along a fourth path P4 that branches upward from the second path P2. Note that the liquid ejection device 1 may be configured to transport the medium M in the reverse direction R by including a switchback path that is parallel to the second path P2.

[0013] The fourth path P4 is curved and communicates with the first path P1 below. The medium M transported from the fourth path P4 to the first path P1 is turned over. Thereafter, the medium M is transported along the transport direction F described above. The other side, the back side, of the medium M is recorded on by the head 2. In this way, the medium M can be recorded on both sides by first recording on the front side, then flipping the medium M over and recording on the back side. The first path P1, the second path P2, the third path P3, and the fourth path P4 are each provided with a plurality of transport rollers (not shown), and are capable of transporting the medium M.

[0014] The support unit 10 includes a belt 11 which is a conveyor belt, a first roller 12, and a second roller 13. The support unit 10 also has, for example, a roller motor (not shown) that rotates the first roller 12. In this case, the first roller 12 is a driven roller that is driven by the roller motor, and the second roller 13 is a driven roller that rotates in conjunction with the first roller 12.

[0015] The support unit 10 rotates the first roller 12 and the second roller 13 using a roller motor. The belt 11, which is an endless belt, is stretched over the first roller 12 and the second roller 13 and configured to rotate. As the first roller 12 and the second roller 13 rotate counterclockwise and the belt 11 rotates counterclockwise, the support unit 10 can transport the medium M on the belt 11 along the transport direction F from front to rear. The belt 11 transports the medium M to a position facing the head 2, and the head 2 can eject ink onto the medium M to perform recording.

[0016] Furthermore, the support unit 10 includes a charging means, a charge removal brush 9, and a blade 6. The charging means includes a charging roller 7 capable of charging the belt 11, and a laser 8, which is a light emitting unit capable of emitting laser light L. These components of the support unit 10 will be described in detail later.

[0017] The liquid ejection device 1 includes a control unit 14 mounted on a control board (not shown). The control unit 14 comprehensively controls each part of the liquid ejection device 1. The control unit 14 is configured to include a CPU (Central Processing Unit). The CPU is also called a processor. The control unit 14 includes memories such as a flash ROM (Read Only Memory), which is a rewritable nonvolatile memory, and a RAM (Random Access Memory), which is a volatile memory. The control unit 14 reads out the programs stored in the flash ROM and executes various processes using the RAM as a work area. Specifically, the control unit 14 can also control the ejection of ink from the head 2, and control actuators such as the motors and laser 8 of each part of the liquid ejection device 1.

[0018] 2. Charging at the support First, with reference to Fig. 2, we will explain the charging of the belt 11 by the charging roller 7, the polarization of the first medium M1, the second medium M2, and the third medium M3 at the support unit 10, and the transition of each charge, including the de-ionization by the de-ionization brush 9. Note that Fig. 2 shows a case where the laser 8 does not irradiate the outer peripheral surface 11a of the belt 11 with laser light L. 2 also shows the transition of charge, including polarization and neutralization, of the first foreign object D1, the second foreign object D2, and the third foreign object D3. Note that, hereinafter, the first medium M1, the second medium M2, and the third medium M3 will be collectively referred to simply as medium M.

[0019] 2, under the control of the control unit 14, the first roller 12 in the support unit 10 rotates counterclockwise and comes into contact with the inner peripheral surface 11b of the belt 11, causing the belt 11 to rotate counterclockwise. The charging roller 7 is driven by the first roller 12 and rotates clockwise with the belt 11 sandwiched between the first roller 12 and the charging roller 7. The medium M is placed on the outer peripheral surface 11a of the belt 11 by the support unit 10 and transported along the transport direction F.

[0020] 2, multiple media M including at least the leading edge of a first medium M1, a second medium M2, and a third medium M3 are placed on the outer peripheral surface 11a of the belt 11 and are transported in the transport direction F. Thus, FIG. 2 shows a state in which, when the leading edge of the first medium M1 is placed on the belt 11, a second medium M2 and a third medium M3, which are separate from the first medium M1, are being transported downstream. As will be described later, the outer peripheral surface 11a of the belt 11 also serves as an adsorption surface that adsorbs the media M. In the following, the outer peripheral surface 11a of the belt 11 will be simply referred to as the belt 11.

[0021] 2 can also be explained as showing a state in which the same first medium M1 changes position from the upstream side to the first medium M1, the second medium M2, and the third medium M3 as it is conveyed on the belt 11 along the conveying direction F. For convenience, the following explanation will be given assuming that the first medium M1 changes position in this way in FIG. 2. The same will be explained for the first to third foreign objects D1 to D3 described later. The same applies to FIG. 3 described later.

[0022] While being rotated by the first roller 12, the belt 11 comes into contact with the outer periphery of the charging roller 7, which rotates clockwise, below and in front of the support part 10. The charging means includes the charging roller 7, a DC power supply (not shown), and a laser 8. The charging roller 7 is made of conductive rubber. Under the control of the control unit 14, a positive voltage of a first polarity, for example, is applied from a DC power supply to the outer periphery of the charging roller 7, and a first charge Q1, which is a positive charge of the first polarity, is charged. The second polarity is negative.

[0023] The outer peripheral surface 11a of the belt 11 of the rotating support part 10 is sequentially charged with the first charge Q1 from the portion that comes into contact with the rotating charging roller 7, and is charged with the second charge Q2, which is a positive charge. In this way, the charging roller 7 included in the charging means can charge the outer peripheral surface 11a of the belt 11 with the second charge Q2 of the first polarity.

[0024] The inner peripheral surface 11b of the belt 11 is made of, for example, a conductive material such as conductive polyimide and is electrically grounded. The outer peripheral surface 11a of the belt 11 is made of, for example, a thermoplastic resin such as ETFE, which is an insulating material. In other words, the outer peripheral surface 11a of the belt 11, which is the attraction surface, is formed of an insulating layer. The belt 11 having such a configuration has a property that the outer peripheral surface 11a is easily charged with the second charge Q2. Specifically, the first charge Q1 of the charging roller 7 dielectrically charges the outer peripheral surface 11a of the belt 11 with the second charge Q2. In reality, the second charge Q2 is applied to the outer peripheral surface 11a of the belt 11, but for convenience of illustration, Fig. 2 shows the second charge Q2 applied to the inner peripheral surface 11b of the belt 11. The same applies to Fig. 3.

[0025] The first medium M1 is placed on the belt 11, with its leading edge in contact with the belt 11 along the conveyance direction F. The first medium M1 is induced by the second charge Q2 applied to the belt 11 and becomes polarized internally. Specifically, starting from the leading edge that contacts the belt 11, the first medium M1 generates a positive charge H on the first surface M1a side and a negative charge N on the first back surface M1b side. First foreign matter D1, such as paper dust, adhering to the first surface M1a of the first medium M1 is also induced in accordance with the polarization of the first medium M1 and becomes polarized internally. 2, the laser 8 does not irradiate the belt 11 with the laser light L, and therefore the second charge Q2 on the belt 11 is not removed, as will be described later in FIG. 2. In FIG. 2, the second charge Q2 charged on the outer peripheral surface 11a of the belt 11 is maintained along the conveyance direction F.

[0026] The static elimination brush 9 above the belt 11 is made of a conductive metal brush or conductive fibers, and is electrically grounded. The first medium M1 is transported downstream in the transport direction F and reaches a position facing the head 2. As shown in Fig. 2, the first medium M1 that has reached this position is referred to as the second medium M2. The second medium M2 is transported by the belt 11 while its second surface M2a is in contact with the static elimination brush 9 above. The grounded charge removal brush 9 removes the positive charge H polarized on the second surface M2a side of the second medium M2. The removal of charge is also called static elimination. The positive charge H to be removed is shown as the second charge to be removed H0. Meanwhile, the negative charge N polarized on the second back surface M2b side of the second medium M2, which is not in contact with the charge removal brush 9, remains.

[0027] The negative charge N remaining on the second back surface M2b of the second medium M2 is attracted to the second charge Q2, which is a positive charge on the belt 11. That is, the second back surface M2b of the second medium M2 is attracted to the outer peripheral surface 11a of the belt 11 by electrostatic force, which is a Coulomb force. As a result, the second medium M2 is attracted to the belt 11.

[0028] In this way, the charged belt 11 can attract the medium M by electrostatic force and can transport the second medium M2 with high precision. Such a belt 11 is also called an electrostatic attraction belt, and the outer peripheral surface 11a of the belt 11 is also called an attraction surface. Furthermore, the distance between the second medium M2 attracted to the belt 11 and the ejection surface 2a of the head 2 can be kept constant. In this state, ink is ejected from the ejection surface 2a of the head 2, so that it can land on the second medium M2 with high precision, thereby improving the recording quality.

[0029] The second medium M2 on which the recording has been performed by the head 2 is subsequently attracted to the second charge Q2 of the belt 11 by the negative charge N on the second rear surface M2b side, and is transported while being attracted to the belt 11. The second medium M2 is transported downstream in the transport direction F and reaches a position away from the head 2. As shown in FIG. 2, the second medium M2 that has reached this position is referred to as the third medium M3. Subsequently, the remaining negative charge N in the third medium M3 is also attracted to the second charge Q2 of the belt 11. The third medium M3 is also transported while being attracted to the belt 11.

[0030] The first foreign matter D1 adhering to the first medium M1 is also transported together with the first medium M1, and as shown in FIG. 2, reaches a position referred to as a second foreign matter D2 adhering to the second medium M2. As the second medium M2 is transported by the belt 11, the second foreign matter D2 adhering to the second medium M2 comes into contact with the static elimination brush 9 above. The static elimination brush 9 sweeps the second foreign matter D2 away. The swept-out second foreign matter D2 is referred to as a third foreign matter D3. The third foreign matter D3 attempts to fall into a position between the first medium M1 and the second medium M2 on the belt 11.

[0031] As described above, the second removal charge H0, which was the positive charge H on the second surface M2a of the second medium M2, is removed by the static elimination brush 9. At this time, the second removal charge H0, which was the positive charge on the second medium M2, is removed by the static elimination brush 9, and the negative charge on the polarized second foreign matter D2 is also removed. As a result, the third foreign matter D3 has only positive charges.

[0032] As described above, the third foreign object D3, which now has only positive charges, attempts to fall onto the belt 11. However, the belt 11 is charged with a second positive charge Q2 of the same first polarity as the third foreign object D3. An electrostatic force acts on the positively charged third foreign object D3, repelling it from the second positive charge Q2 of the same first polarity that is charged to the belt 11, causing it to float upward. Incidentally, an air current is generated around the third foreign matter D3 in the transport direction F due to the belt 11 and medium M being transported in the transport direction F. This air current may cause the third foreign matter D3 floating upward to float toward the head 2 in the transport direction F. As a result, the third foreign matter D3 may adhere to the ejection surface 2a of the head 2, which may cause problems such as poor ink ejection.

[0033] 2, a positive voltage of a first polarity (positive polarity) is applied to the charging roller 7 by a DC power supply, and the charging roller 7 is charged with a first positive charge Q1. By switching the polarity of the applied voltage of the DC power supply, a negative voltage of a second polarity (negative polarity) can also be applied to the charging roller 7. In this case, the charging roller 7 is charged with a negative charge equivalent to the first charge Q1, and the polarities of the components shown in Figure 2 are reversed. Although the polarities are different from those in Figure 2, the second medium M2 can be attracted to the belt 11 in the same way as in Figure 2.

[0034] 3. Removal of some charge from the support Next, referring to Fig. 3, a case where the laser 8 irradiates the outer peripheral surface 11a of the belt 11 with laser light L will be described. In contrast to Fig. 2, Fig. 3 shows the transition of charge when the laser 8 irradiates the charged belt 11 with laser light L to partially remove the charge. In the description of FIG. 3, the same components as those in FIG. 2 are denoted by the same reference numerals, and some of the parts overlapping with the description of FIG. 2 are omitted.

[0035] 3, similarly to the case of FIG. 2, a first positive charge Q1 is applied to the outer periphery of the charging roller 7. The first charge Q1 is transferred to the outer periphery 11a of the rotating belt 11, starting from the portion that comes into contact with the rotating charging roller 7, and the belt 11 is charged as a second positive charge Q2.

[0036] In the conveyance direction F of the belt 11, under the control of the control unit 14, a region on the belt 11 where the laser light L is not irradiated by the laser 8 is formed. This region is referred to as region A. Region A is a region on the belt 11 where the second charge Q2 is maintained. Area A is an area on belt 11 where media M, including first medium M1, second medium M2, and third medium M3, are placed. Area A can also be called a transport area on belt 11 that comes into contact with media M and transports the media M.

[0037] Meanwhile, under the control of the control unit 14, a region of the belt 11 is formed in the conveying direction F of the belt 11 where the laser 8 is irradiated with laser light L. This region is referred to as region B. Region B is a region of the belt 11 where the second charge Q2 that was present has been removed by the laser light L, and is an uncharged region. The second charge Q2 to be removed by the laser 8 is referred to as the first charge to be removed Q0. Area B is an area of ​​the belt 11 where no media M, including the first medium M1, the second medium M2, and the third medium M3, are placed. Area B can also be called a non-transport area of ​​the belt 11 that does not come into contact with the media M and is not used to transport the media M. The area B is also an area on the belt 11 between the media M. The area B is also a non-conveying area provided between the area A, which is a conveying area.

[0038] In this way, under the control of the control unit 14, the charging means including the charging roller 7 and the laser 8 can charge at least a part of the area A, which is the transport area of ​​the belt 11, with a positive charge of the first polarity. On the other hand, under the control of the control unit 14, the charging means including the charging roller 7 and the laser 8 can remove the positive charge from the non-transport area B of the belt 11, leaving it uncharged.

[0039] In addition, under the control of the control unit 14, the laser 8 may also irradiate the laser light L onto an area of ​​the belt 11 located closer to the edge than the center of the medium M in the conveying direction F, thereby removing the positive second charge Q2 of the first polarity. As a result, the belt 11 that comes into contact with the areas of the medium M located at the front-rear end portions can be prevented from being charged with the second charge Q2.

[0040] That is, the area B can be an area including the edge of the medium M. This can more effectively suppress the generation of electrostatic force due to the second charge Q2 of the belt 11 acting on the third foreign matter D3 (described later). In this case, region A is a region located in the center of medium M excluding the edges, and is a region charged with a positive second charge Q2 of the first polarity. In the center of each of second medium M2 and third medium M3, negative charge N is attracted to the second charge Q2 of belt 11, and each can be attracted to belt 11.

[0041] Due to the second charge Q2 applied to the belt 11, the first medium M1 is polarized internally, starting from the tip that contacts the belt 11, into a positive charge H on the first surface M1a side and a negative charge N on the first back surface M1b side. The first foreign matter D1 attached to the first surface M1a of the first medium M1 is also polarized in the same manner.

[0042] When the first medium M1 is transported and reaches the position of the second medium M2, the second surface M2a comes into contact with the charge removal brush 9, and the positive charge H on the second surface M2a side is removed. The positive charge H to be removed is shown as the second removal charge H0. Meanwhile, the negative charge N on the second back surface M2b side remains. The negative charge N of the second medium M2 is attracted to the second charge Q2 of the belt 11, and the second medium M2 is attracted to the belt 11.

[0043] The first foreign matter D1 is transported along with the first medium M1 and reaches the position of the second foreign matter D2 attached to the second medium M2. The discharging brush 9 sweeps out the second foreign matter D2 and it falls as a third foreign matter D3 into a position in area B between the first medium M1 and the second medium M2 on the belt 11. At this time, the negative charge of the polarized second foreign matter D2 has been removed by the charge removal brush 9, so that the third foreign matter D3, which is the second foreign matter D2 that has been swept out, has only a positive charge.

[0044] 2, in FIG. 3, the second charge Q2 has been removed from the area B of the belt 11 by the laser 8. The third foreign matter D3 falls into the uncharged area B of the belt 11. The third foreign matter D3 has only a positive charge, but there is no second charge Q2 in the area B of the belt 11 where the third foreign matter D3 falls. Therefore, no electrostatic force due to the second charge Q2 is generated on the third foreign matter D3. The third foreign matter D3 is prevented from floating upward due to the electrostatic force. As a result, the third foreign matter D3 is prevented from adhering to the ejection surface 2a of the head 2, and the occurrence of malfunctions is prevented.

[0045] The third foreign matter D3 is swept away by the charge removal brush 9 and falls onto the belt 11 between the first medium M1 and the second medium M2. The third foreign matter D3 is transported while being placed on the rotating belt 11. Then, as shown in FIG. 1, the third foreign matter D3 is scraped off by the blade 6 and removed from the belt 11 as a foreign matter D.

[0046] 4. Other Embodiments As described above with reference to Fig. 3, a positive voltage of a first polarity, i.e., a DC power supply is applied to the charging roller 7, and the charging roller 7 is charged with a first positive charge Q1. Below, several examples of other embodiments of Fig. 3 will be described.

[0047] In another embodiment, the polarity of the voltage applied by the DC power supply may be switched so that a negative voltage of the second polarity, i.e., a negative charge equivalent to the first charge Q1, is applied to the charging roller 7. In this case, as in the case of FIG. 3, although the polarity is different, the charge is removed from the region B of the belt 11 where the third foreign matter D3 falls, thereby preventing the third foreign matter D3 from floating. In this way, the polarity of the voltage applied by the DC power supply can be switched. The charging roller 7 can be charged either positively as shown in FIG. 3 or negatively.

[0048] In another embodiment, an AC power supply (not shown) may alternately apply a positive voltage of a first polarity and a negative voltage of a second polarity to the outer periphery of the charging roller 7. The polarity of the voltage applied to the charging roller 7 is switched by the AC power supply. The applied voltage may be a square wave. The charging roller 7 is alternately charged with a first positive charge Q1 and a negative charge of the same value as the first charge Q1. At this time, under the control of the control unit 14, the belt 11 of the support unit 10 can be charged with a second charge Q2 in region A and a negative charge of the same value as the second charge Q2 in region B. As in FIG. 3, the first medium M1 and the first foreign matter D1 are polarized.

[0049] In this case, in area A of belt 11, as in the case of Figure 3, second medium M2 comes into contact with discharge brush 9, the positive charge H is removed, and the negative charge N is attracted to and adsorbed by the second charge Q2 of belt 11. On the other hand, the area B of the belt 11 into which the third foreign object D3, which has only a positive charge, falls is negatively charged with the same value as the second charge Q2. The positively charged third foreign object D3 is attracted to the negatively charged area B of the belt 11 by electrostatic force. Even without using the laser 8, the third foreign matter D3 is prevented from floating upward, and therefore is prevented from adhering to the ejection surface 2a of the head 2 and causing problems.

[0050] In another embodiment, an AC power supply that switches the applied voltage may alternately apply a positive voltage of the first polarity and a ground voltage of non-polarity to the outer periphery of the charging roller 7. The polarity of the applied voltage, including non-polarity, is switched by the AC power supply. The applied voltage may be a square wave. On the charging roller 7, regions charged with a positive first charge Q1 and regions not charged with a polarity change alternately. Under the control of the control unit 14, region A of the belt 11 of the support unit 10 can be charged with a second charge Q2, and region B can be made a region not charged with a polarity change. In this case, each region can be charged in a state similar to that shown in FIG. 3 without using the laser 8. Alternatively, a negative voltage of the second polarity and a ground voltage of no polarity may be applied alternately to the outer periphery of the charging roller 7 by an AC power source. Alternatively, an AC power source may be used to alternately apply a positive voltage of a first polarity and a negative voltage of a second polarity to the outer periphery of the charging roller 7. In this case, the belt 11 in region B is negatively charged, and the positively charged third foreign matter D3 is attracted by electrostatic force.

[0051] As described above, the liquid ejection device 1 includes the head 2, which is a liquid ejection unit that ejects ink, which is a liquid, onto the medium M; the belt 11, which has an outer peripheral surface 11a that is an adsorption surface that adsorbs the medium M and transports the medium M to a position facing the head 2; charging means that charges the outer peripheral surface 11a to a first polarity, which is positive; and the control unit 14 that controls the belt 11 and the charging means. The charging means includes a charging roller 7 and a laser 8. The outer peripheral surface 11a of the belt 11 has an area A, which is a transport area that comes into contact with the medium M being transported, and an area B, which is a non-transport area provided between the areas A. The control unit 14 causes the charging means to charge at least a part of the area A on the outer circumferential surface 11a of the belt 11 to the first polarity, and does not charge the area B to the first polarity.

[0052] In the liquid ejection device 1 configured as above, as shown in FIG. 3, for example, the negative charge N of the second medium M2 is attracted to the second charge Q2 of the belt 11, and the second medium M2 is attracted to the belt 11 and can be transported. Further, the second foreign matter D2 adhering to the second medium M2 is swept away by the charge removal brush 9 and falls into the area B of the belt 11 as a third foreign matter D3 having only a positive charge. At this time, since the area B of the belt 11 is not charged, the third foreign matter D3 is prevented from floating upward due to electrostatic force and adhering to the head 2, thereby preventing the occurrence of problems.

[0053] The above describes the embodiments in detail with reference to the drawings, but the specific configuration is not limited to the embodiments, and may be changed, replaced, deleted, etc. as long as it does not deviate from the gist of the present invention.

[0054] In the above description, the second charge Q2 charged on the belt 11 is removed by the laser 8. An ultraviolet irradiator may be provided as the light irradiating unit, and the charge may be removed by irradiating ultraviolet light. The second charge Q2 may also be removed by an ionizer. In this case, the ionizer generates negative ions to neutralize and remove the second charge Q2, which is a positive charge.

[0055] In the above description, the head 2 is an example of a line-type inkjet head, but it may also be a serial-type inkjet head mounted on a carriage. [Explanation of symbols]

[0056] 1...liquid ejection device, 2...head, 2a...liquid ejection surface, 6...blade, 7...charging roller, 8...laser, 9...discharge brush, 10...support part, 11...belt, 11a...outer surface, 11b...inner surface, 12...first roller, 13...second roller, 14...control part, D1...first foreign matter, D2...second foreign matter, D3...third foreign matter, F...conveyance direction, H...positive charge, H0...second removed charge, L...laser light, M...medium, M1...first medium, M1a...first surface, M1b...first back surface, M2...second medium, M2a...second surface, M2b...second back surface, M3...third medium, N...negative charge, Q0...first removed charge, Q1...first charge, Q2...second charge.

Claims

1. a liquid ejection unit that ejects liquid onto a medium; a conveyor belt having an adsorption surface that adsorbs the medium and that conveys the medium to a position facing the liquid ejection unit; charging means for charging the attraction surface to a first polarity; a control unit that controls the conveyor belt and the charging means, the suction surface has a transport area that contacts the medium being transported and a non-transport area provided between the transport areas, The control unit controls the charging unit to: charging at least a portion of the transport area of ​​the attraction surface to the first polarity; the non-transport area of ​​the attraction surface is not charged to the first polarity; A liquid ejection device characterized by:

2. The liquid ejection device according to claim 1 , The control unit controls the charging unit to: charging the attraction surface that contacts the central region of the medium to the first polarity; the attraction surface that comes into contact with an area positioned from the center portion to the edge of the medium is not charged to the first polarity; A liquid ejection device characterized by:

3. 3. The liquid ejection device according to claim 1, The first polarity is a positive polarity, The control unit controls the charging unit to: The attraction surface can be positively charged, removing the charge from the non-transport area of ​​the attraction surface; A liquid ejection device characterized by:

4. The liquid ejection device according to claim 3, The adsorption surface is formed of an insulating layer. A liquid ejection device characterized by:

5. The liquid ejection device according to claim 1 , The charging means includes a charging roller, and the charging roller is charged positively or negatively by switching the applied voltage. A liquid ejection device characterized by:

6. The liquid ejection device according to claim 5 , The first polarity is a positive polarity, the control unit causes the charging unit to negatively charge the non-transport area of ​​the attraction surface. A liquid ejection device characterized by:

7. The liquid ejection device according to claim 1 , The charging means includes a charging roller. A liquid ejection device characterized by:

8. The liquid ejection device according to claim 1 , The charging unit includes a charging roller and a light irradiating unit capable of neutralizing the conveying belt. A liquid ejection device characterized by:

9. The liquid ejection device according to claim 1 , a static elimination brush in contact with the medium; A liquid ejection device characterized by:

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