JP6277965B2 - Inkjet recording device - Google Patents

Description

  The present invention relates to an ink jet recording apparatus.

  An ink jet recording apparatus, which is a type of image forming apparatus, forms an image by ejecting ink onto a recording sheet such as paper. The ink jet recording apparatus includes a recording head in which nozzles for ejecting ink are formed. In an ink jet recording apparatus, when foreign matter such as paper dust adheres to a nozzle, nozzle clogging may occur and image quality may deteriorate. In order to solve this problem, a technique for suppressing the adhesion of foreign matter to the nozzle has been proposed.

  For example, Patent Document 1 discloses an ink jet recording apparatus including a paper dust removing device on the upstream side in the conveyance direction of a recording sheet with respect to the recording head. Specifically, the paper dust removing device includes a static elimination brush and an air blower. The neutralizing brush neutralizes the recording sheet. Thereby, paper dust becomes easy to peel from a recording sheet. The air blower blows air onto the discharged recording sheet to remove paper dust from the recording sheet.

JP 2011-183746 A

  However, the ink jet recording apparatus described in Patent Document 1 requires a static eliminating brush and an air blower in order to remove paper dust from the recording sheet. This complicates the configuration of the ink jet recording apparatus.

  The present invention has been made in view of the above problems, and an object thereof is to provide an ink jet recording apparatus capable of suppressing adhesion of paper dust to nozzles with a simple configuration.

  The ink jet recording apparatus of the present invention includes a recording head, a transport unit, and a voltage application unit. The recording head ejects ink onto a recording sheet. The conveyance unit conveys the recording sheet to a position facing the recording head. The voltage application unit is arranged upstream of the recording head in the conveyance direction of the recording sheet. The recording head has an opposing surface on which a plurality of nozzles that eject the ink are formed. The voltage application unit applies a voltage to the recording sheet to charge the recording sheet with the same polarity as the charging polarity of the facing surface.

  According to the ink jet recording apparatus of the present invention, it is possible to suppress the adhesion of paper dust to the nozzles with a simple configuration.

It is a figure which shows the structure of the inkjet recording device which concerns on Embodiment 1 of this invention. FIG. 2 is a diagram illustrating a configuration of an image forming unit illustrated in FIG. 1. FIG. 3 is a cut perspective view illustrating configurations of a conveyance belt, an air circulation chamber, and a guide member illustrated in FIG. 2. (A) is a top view which shows the structure of the groove | channel and through-hole which were formed in the guide member shown in FIG. 3, (b) is sectional drawing along the AA of FIG. 4 (a). . It is a figure which shows the structure for setting the voltage which the needle electrode shown in FIG. 2 applies to a paper. It is a figure which shows the housing shown in FIG. It is a figure which shows the state which decomposed | disassembled the housing shown in FIG. It is an enlarged view of the needle electrode shown in FIG. It is a figure which shows the effect | action of the needle electrode shown in FIG. It is a figure which shows the relationship between the DC component contained in the voltage applied to the needle electrode which concerns on Embodiment 1 of this invention, and the surface potential of a paper. It is a figure which shows the relationship between the surface potential of the paper which concerns on Embodiment 1 of this invention, and the number of non-ejection nozzles. It is a figure which shows the structure of the image formation part which concerns on Embodiment 2 of this invention. It is a figure which shows the structure of the image formation part which concerns on Embodiment 3 of this invention. It is a top view of the guide member shown in FIG. It is a figure which shows the effect | action of the airflow which flows in into the foreign material collection | recovery space shown in FIG.

  Embodiments of the present invention will be described below with reference to the drawings (FIGS. 1 to 15). In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof is not repeated.

[Embodiment 1]
First, an ink jet recording apparatus 1 according to the present embodiment will be described with reference to FIG. FIG. 1 is a diagram illustrating a configuration of an inkjet recording apparatus 1 according to the present embodiment. The ink jet recording apparatus 1 includes an apparatus casing 100, a sheet feeding unit 2 disposed below the inside of the apparatus casing 100, an image forming unit 3 disposed above the sheet feeding unit 2, and one side of the image forming unit 3. A sheet conveying unit 4 disposed on the right side in FIG. 1, a sheet discharging unit 5 disposed on the other side of the image forming unit 3 (left side in FIG. 1), and a control unit 6 are provided.

  The paper feed unit 2 includes a paper feed cassette 21, a paper feed roller 22, and a first guide plate 23. The paper feed cassette 21 is detachably attached to the apparatus housing 100. The paper feed cassette 21 accommodates a plurality of recording papers P. Hereinafter, “recording paper” is simply referred to as “paper” for convenience. The paper feed roller (pickup roller) 22 is disposed above one side end (right side end in FIG. 1) of the paper feed cassette 21. The paper feed roller 22 takes out the paper P stored in the paper feed cassette 21 one by one from the top. The first guide plate 23 is disposed between the paper feed roller 22 and the paper transport unit 4 and guides the paper P taken out by the paper feed roller 22 to the paper transport unit 4. The paper P corresponds to an example of “recording sheet”.

  The paper transport unit 4 includes a second guide plate 41. The second guide plate 41 constitutes a substantially C-shaped paper conveyance path L. The paper transport unit 4 includes a first transport roller pair 42 provided on the entrance side of the paper transport path L, a second transport roller pair 43 provided in the middle of the paper transport path L, and an exit side of the paper transport path L. A registration roller pair 44 provided in

  The first transport roller pair 42 and the second transport roller pair 43 are feed roller pairs that feed the paper P along the paper transport path L. The first transport roller pair 42 feeds the paper P guided by the first guide plate 23 into the paper transport path L. The second transport roller pair 43 feeds the paper P sent by the first transport roller pair 42 toward the registration roller pair 44 across the paper P.

  The registration roller pair 44 corrects the skew of the paper P sent out by the second transport roller pair 43. In addition, the registration roller pair 44 temporarily stops the paper P in order to synchronize the timing of image formation on the paper P and the conveyance timing of the paper P, and then sets the paper P to the image formation timing. Send to forming unit 3.

  The image forming unit 3 includes a conveyance belt 32, four types of recording heads 34a, 34b, 34c, and 34d, and a third guide plate 36. Since the four types of recording heads 34a, 34b, 34c, and 34d have substantially the same configuration, they may be referred to as recording heads 34. The conveyance belt 32 is driven to convey the paper P sent from the registration roller pair 44 in a predetermined direction. In FIG. 1, the conveyor belt 32 is driven counterclockwise. As a result, the paper P is conveyed leftward in FIG. The transport belt 32 corresponds to an example of an “endless belt”. Hereinafter, the direction in which the paper P is transported by the transport belt 32 may be referred to as a transport direction D. The paper P is transported by the transport belt 32 and passes through a position facing the recording head 34. The recording head 34 discharges ink onto the paper P passing through a position facing the recording head 34, and forms an image on the paper P. The paper P on which an image is formed by the recording head 34 is conveyed toward the third guide plate 36 by the conveyance belt 32.

  The third guide plate 36 guides the paper P transported from the transport belt 32 to the paper discharge unit 5. The paper discharge unit 5 includes a discharge roller pair 51 and a discharge tray 52. The discharge tray 52 is fixed to the apparatus housing 100 so as to protrude from a discharge port 101 formed in the apparatus housing 100 to the outside.

  The discharge roller pair 51 sends the paper P guided by the third guide plate 36 toward the discharge port 101. The paper P sent out by the discharge roller pair 51 is discharged to the outside of the apparatus housing 100 through the discharge port 101. The sheet P discharged from the discharge port 101 is placed on the discharge tray 52.

  The control unit 6 has a storage area. In the storage area, programs and setting information are stored. The storage area is composed of a magnetic disk, a random access memory (RAM), and a read only memory (ROM), which are provided in an HDD (Hard Disk Drive). The control unit 6 controls the operation of each unit of the inkjet recording apparatus 1 by executing a control program stored in advance in the storage area.

  Next, the image forming unit 3 will be described with reference to FIG. FIG. 2 is a diagram showing the configuration of the image forming unit 3 shown in FIG.

  As shown in FIG. 2, in addition to the recording head 34, the image forming unit 3 includes a conveyance unit 31, a negative pressure application unit 33, a head base 37, a needle electrode 11 that is an example of a voltage application unit, and a needle electrode 11. A housing 110 is provided. The transport unit 31 includes a transport belt 32.

  The transport unit 31 is disposed to face the recording head 34. In addition to the conveyance belt 32, the conveyance unit 31 includes a belt speed detection roller 311, an adsorption roller 312, a drive roller 313, a tension roller 314, and a pair of guide rollers 315.

  The belt speed detection roller 311, the driving roller 313, the tension roller 314, and the pair of guide rollers 315 stretch the conveyance belt 32.

  The belt speed detection roller 311 is arranged on the upstream side (right side in FIG. 2) in the transport direction D with respect to the negative pressure application unit 33, and rotates due to the frictional force between the belt and the transport belt 32. The belt speed detection roller 311 includes a pulse plate (not shown), and the pulse plate rotates integrally with the belt speed detection roller 311. By measuring the rotational speed of the pulse plate, the rotational speed of the conveyor belt 32 is detected.

  The suction roller 312 is a driven roller. The suction roller 312 faces the guide member 332 included in the negative pressure application unit 33 via the transport belt 32. The suction roller 312 guides the paper P sent from the registration roller pair 44 onto the transport belt 32. The paper P is preferably guided to the transport belt 32 so that the center of the paper P in the direction orthogonal to the transport direction D coincides with the center of the transport belt 32 in the direction orthogonal to the transport direction D. Hereinafter, the direction orthogonal to the conveyance direction D in the paper P may be referred to as the width direction of the paper P. In addition, the direction perpendicular to the conveyance direction D in the conveyance belt 32 may be described as the width direction of the conveyance belt 32.

  The drive roller 313 is disposed on the downstream side (left side in FIG. 2) in the transport direction D with respect to the negative pressure application unit 33. Preferably, the driving roller 313 is arranged so as to maintain the flatness of the conveyance belt 32 at a position facing the recording head 34 together with the belt speed detection roller 311.

  The driving roller 313 is rotationally driven by a motor (not shown), and rotates the conveying belt 32 in the counterclockwise direction of FIG.

  The tension roller 314 applies tension to the conveyance belt 32 so that the conveyance belt 32 does not bend.

  The pair of guide rollers 315 are disposed below the negative pressure application unit 33 and form a space below the negative pressure application unit 33. By arranging in this way, contact between the conveyance belt 32 and the negative pressure application unit 33 below the negative pressure application unit 33 can be prevented.

  The negative pressure application unit 33 is disposed on the back side of the conveyance belt 32 so as to face the recording head 34 with the conveyance belt 32 interposed therebetween. The negative pressure application unit 33 applies the negative pressure to the paper P via the transport belt 32, thereby causing the paper P to be attracted to the transport belt 32. The negative pressure application unit 33 includes an air flow chamber 331, a negative pressure generation unit 336, and a duct 337 in addition to the guide member 332. The guide member 332, the air circulation chamber 331, the negative pressure generator 336, and the duct 337 are arranged in this order from the upper side to the lower side.

  The guide member 332 covers the upper surface opening of the air circulation chamber 331 and supports the paper P via the transport belt 32. Hereinafter, the portion of the rotating conveyor belt 32 that is supported by the guide member 332 may be referred to as the upper surface of the conveyor belt 32. In the present embodiment, the guide member 332 is made of a metal material. Specifically, as the material of the guide member 332, an aluminum die cast, a pressed plate, or the like can be used. Alternatively, as the material of the guide member 332, a resin excellent in slidability with the transport belt 32 can be selected. The guide member 332 corresponds to an example of a “conveyance plate”.

  In the present embodiment, for the sake of convenience, the form in which the negative pressure application unit 33 includes the guide member 332 has been described, but the transport unit 31 may include the guide member 332.

  The air circulation chamber 331 is formed by a bottomed cylindrical box-shaped member whose upper surface is open. The upper surface of the side wall constituting the air circulation chamber 331 is fixed to the guide member 332. The negative pressure generator 336 is disposed below the air circulation chamber 331. By driving the negative pressure generating unit 336, a negative pressure is generated in the air circulation chamber 331. As a result, the paper P is sucked toward the transport belt 32. The air sucked through the conveyance belt 32 and the guide member 332 is discharged from the duct 337 to the outside. In the present embodiment, the air circulation chamber 331 is in a negative pressure state that is lower by about 0.005 atm (≈about 500 Pa) than the atmospheric pressure by the negative pressure generator 336.

  The negative pressure generator 336 generates a negative pressure in the air circulation chamber 331, and is a fan in this embodiment. However, the negative pressure generator 336 is not limited to a fan, and may be a vacuum pump, for example.

  The four types of recording heads 34a, 34b, 34c, and 34d are arranged in parallel on the head base 37 from the upstream side to the downstream side in the transport direction D. In the present embodiment, the recording head 34 is a line type. That is, the ink jet recording apparatus 1 is a line head type ink jet recording apparatus.

  Each of the four types of recording heads 34a, 34b, 34c, and 34d has a plurality of nozzles (not shown).

  Ink of each color is ejected from the nozzles of the recording heads 34a, 34b, 34c, and 34d onto the paper P that is passing through the positions facing the recording heads 34a, 34b, 34c, and 34d. As a result, images such as characters and figures are formed on the paper P. Each recording head 34 a, 34 b, 34 c, 34 d has a facing surface 341 that faces the guide member 332. The facing surface 341 has a plurality of nozzles. The facing surface 341 is configured by a coating layer that covers the lower surfaces of the recording heads 34a, 34b, 34c, and 34d. In this embodiment, a fluororesin is used as a material for the coating layer in order to improve water repellency.

  The image forming unit 3 further includes a surface potential measuring unit 342. Of the recording heads 34a, 34b, 34c, and 34d, a surface potential measuring unit 342 is provided on the facing surface 341 of the recording head 34a. The surface potential measurement unit 342 measures the surface potential of the facing surface 341 of the recording head 34a. The opposing surface 341 of each recording head 34 is charged with a negative polarity when ink is ejected from the nozzle.

  The housing 110 is provided at the upstream end in the transport direction D in the head base 37. A needle electrode 11 is accommodated in the housing 110. That is, the needle electrode 11 is provided on the upstream side in the transport direction D with respect to the recording head 34. The needle electrode 11 charges the paper P by applying a predetermined voltage to the paper P passing through the position facing the needle electrode 11. Specifically, the needle electrode 11 applies a predetermined voltage to the paper P so that the paper P is charged with the same polarity as the charging polarity of the facing surface 341 of each recording head 34. Thereby, the potential difference between the sheet P and the facing surface 341 of each recording head 34 is reduced. In the present embodiment, the distance H1 between the needle electrode 11 and the upper surface of the conveyor belt 32 is 3.0 mm.

  Next, with reference to FIGS. 3 and 4, the configuration of the conveyance belt 32, the air circulation chamber 331, and the guide member 332 will be described. 3 is a cut perspective view showing the configuration of the conveyor belt 32, the air circulation chamber 331, and the guide member 332 shown in FIG. 4A is a plan view showing the configuration of the groove 334 and the through hole 335 formed in the guide member 332 shown in FIG. 3, and FIG. 4B is the AA line in FIG. 4A. FIG.

  As shown in FIG. 3, a plurality of suction holes 321 are formed in the conveyor belt 32 at substantially equal intervals. Specifically, a plurality of rows made of a large number of suction holes 321 arranged in the transport direction D are formed in the width direction of the transport belt 32. The plurality of rows are arranged so that the suction holes 321 are arranged in a staggered manner. In the present embodiment, the diameter of the suction holes 321 is 2 mm, and the interval between the adjacent suction holes 321 is 8 mm. The paper P transported from the paper transport unit 4 onto the transport belt 32 covers a part of the many suction holes 321.

  A plurality of grooves 334 are formed on the upper surface of the guide member 332 (the surface on the conveying belt 32 side). Specifically, a plurality of rows made of a plurality of grooves 334 arranged along the transport direction D are formed in a direction orthogonal to the transport direction D in the guide member 332. Hereinafter, the direction orthogonal to the conveyance direction D in the guide member 332 may be referred to as the width direction of the guide member 332. The rows of the plurality of grooves 334 are respectively arranged corresponding to the rows of the plurality of suction holes 321 in the transport belt 32. Each of the plurality of grooves 334 faces at least two suction holes 321. As the transport belt 32 moves, the suction holes 321 facing each of the plurality of grooves 334 are replaced one by one. Thereby, the air circulation chamber 331 communicates with the suction hole 321 of the conveyance belt 32 through the through hole 335 and the groove 334 of the guide member 332.

  As shown in FIG. 4A, the shape of the groove 334 is an ellipse extending in the transport direction D. A through hole 335 is formed at a substantially central position in the conveyance direction D in the groove 334. As shown in FIG. 4B, the through hole 335 penetrates the guide member 332 in the thickness direction of the guide member 332.

  Subsequently, the voltage applied to the paper P by the needle electrode 11 will be described with reference to FIG. FIG. 5 is a diagram showing a configuration for setting a voltage applied to the paper P by the needle electrode 11 shown in FIG.

  As shown in FIG. 5, the ink jet recording apparatus 1 described with reference to FIG. 1 further includes a power supply device 391 connected to the needle electrode 11. A predetermined voltage is applied to the needle electrode 11 from the power supply device 391. In the present embodiment, a voltage obtained by superimposing a direct current component on an alternating current component is applied to the needle electrode 11. As a result, a potential difference is generated between the needle electrode 11 and the paper P passing under the needle electrode 11, and discharge is generated. As a result, the paper P is charged.

  When the potential difference between the facing surface 341 of the recording head 34 and the paper P passing under the recording head 34 increases, an electric field is generated between the facing surface 341 and the paper P passing under the recording head 34. , And the paper dust PD adhering to the paper P may fly toward the facing surface 341 of the recording head 34. However, according to the present embodiment, as described above, when the needle electrode 11 applies a voltage to the paper P, the potential difference between the paper P and the facing surface 341 of the recording head 34 is reduced. As a result, the paper dust PD is suppressed from adhering to the facing surface 341 of the recording head 34. Note that the surface potential of the facing surface 341 of the recording head 34 varies depending on the number of times ink is continuously ejected from the nozzles and the type of ink ejected from the nozzles.

  As shown in FIG. 5, the control unit 6 includes a surface potential acquisition unit 61 and a voltage setting unit 62. The surface potential acquisition unit 61 acquires the surface potential of the facing surface 341 of the recording head 34 a measured by the surface potential measurement unit 342. The voltage setting unit 62 sets the voltage applied to the paper P by the needle electrode 11 according to the surface potential acquired by the surface potential acquisition unit 61. Specifically, in the voltage setting unit 62, the power supply device 391 has the needle electrode 11 so that the difference between the surface potential of the facing surface 341 of the recording head 34 and the surface potential of the paper P passing under the recording head 34 becomes small. Set the voltage to be applied to. Thereby, the potential difference between the facing surface 341 of the recording head 34 and the paper P can be stably reduced.

  Next, a configuration for fixing the needle electrode 11 will be described with reference to FIGS. 6 and 7. FIG. 6 is a view showing the housing 110 shown in FIG. FIG. 7 is a diagram illustrating a state in which the housing 110 illustrated in FIG. 6 is disassembled.

  As shown in FIG. 7, the housing 110 includes a base portion 111 and a cover portion 112. The base part 111 and the cover part 112 are each made of an insulating resin. The base part 111 is attached to the head base 37. A convex portion 111 a is formed on the base portion 111. The needle electrode 11 is formed with a hole portion 11a through which the convex portion 111a of the base portion 111 penetrates. Further, the cover 112 is also formed with a hole 112a through which the convex portion 111a of the base 111 is inserted. When attaching the cover part 112 to the base part 111, first, the convex part 111 a of the base part 111 is inserted into the hole part 11 a of the needle electrode 11. Next, the convex portion 111 a protruding from the hole portion 11 a of the needle electrode 11 is inserted into the hole portion 112 a of the cover portion 112. As a result, the cover part 112 is attached to the base part 111 as shown in FIG. Thereby, the housing 110 is formed. A needle electrode 11 is accommodated in the housing 110.

  Next, the configuration of the needle electrode 11 will be described in detail with reference to FIG. FIG. 8 is an enlarged view of the needle electrode 11 shown in FIG. As shown in FIG. 8, the needle electrode 11 is a long plate-like member. The needle electrode 11 is accommodated in the housing 110 so that the longitudinal direction thereof is orthogonal to the transport direction D. On the lower end side (conveying belt 32 side) of the needle electrode 11, a plurality of protrusions 11b whose tip is pointed like a needle are formed. The plurality of protrusions 11 b are formed at substantially equal intervals along the longitudinal direction of the needle electrode 11. The length LA of the portion of the needle electrode 11 where the plurality of protrusions 11b are formed is longer than the width of the image formable region and shorter than the length of the conveyance belt 32 in the width direction. The image formable area is an area where the recording head 34 can form an image. The width of the image formable area is the length in the direction orthogonal to the transport direction D in the image formable area. In the present embodiment, the length LA is 300 mm. Moreover, the thickness of the needle electrode 11 is 0.1 mm. An interval LN between adjacent protrusions 11b is 4.0 mm. The material of the needle electrode 11 is a metal such as stainless steel.

  Next, the operation of the needle electrode 11 will be described with reference to FIG. FIG. 9 is a diagram showing the action of the needle electrode 11 shown in FIG.

  As shown in FIG. 9, when a voltage is applied from the power supply device 391 to the needle electrode 11, a discharge is generated and the paper P passing below the needle electrode 11 is charged. In the present embodiment, the voltage applied from the power supply device 391 to the needle electrode 11 is a voltage obtained by superimposing a DC component (200 V) on an AC component (maximum amplitude 5500 V). As shown in FIG. 9, when discharge occurs, the paper P is charged with a negative polarity. That is, the paper P is charged with the same polarity as the facing surface 341 of the recording head 34. This makes it difficult for an electric field to be formed between the paper P and the opposing surface 341 of the recording head 34, and the paper dust PD is prevented from adhering to the opposing surface 341 of the recording head 34. Moreover, the paper dust PD adhering to the paper P may be charged to a negative polarity due to the discharge. That is, the paper powder PD may be charged with the same polarity as the facing surface 341 of the recording head 34. When the paper dust PD is charged with the same polarity as the facing surface 341 of the recording head 34, the paper dust PD is electrically repelled from the facing surface 341 of the recording head 34. As a result, the paper dust PD is less likely to adhere to the facing surface 341 of the recording head 34.

  Next, the relationship between the voltage applied from the power supply device 391 to the needle electrode 11 and the surface potential PV of the paper P will be described with reference to FIG. FIG. 10 is a diagram showing the relationship between the DC component DC included in the voltage applied to the needle electrode 11 and the surface potential PV of the paper P. Specifically, FIG. 10 shows the relationship between the DC component DC superimposed on the AC component (maximum amplitude 5500 V) and the surface potential PV of the paper P. In FIG. 10, the vertical axis indicates the surface potential PV (V) of the paper P, and the horizontal axis indicates the direct current component DC (V). Note that the frequency of the AC component is 5 kHz.

  As shown in FIG. 10, for example, when the surface potential PV of the paper P is set to −100 V or more and less than 0 V, the DC component DC is set to about 0 V to 300 V. In the present embodiment, the direct current component DC is 200V. Therefore, according to the present embodiment, the surface potential PV of the paper P is about −50V.

  Next, the relationship between the surface potential PV of the paper P and the number M of non-ejection nozzles will be described with reference to FIG. A non-ejection nozzle refers to a nozzle that cannot eject ink. FIG. 11 is a diagram illustrating the relationship between the surface potential PV of the paper P and the number M of non-ejection nozzles. In FIG. 11, the vertical axis represents the number M of non-ejection nozzles (number), and the horizontal axis represents the surface potential PV (V) of the paper P. Further, PA (black circles) shown in FIG. 11 indicates the relationship between the surface potential PV of the paper P and the number M of non-ejection nozzles when the printing rate is 20%. Specifically, the number M of non-ejection nozzles is plotted against the surface potential PV of the paper P. A curve L1 shows a graph created based on PA (black circle). PB (black square mark) shown in FIG. 11 indicates the relationship between the surface potential PV of the paper P and the number M of non-ejection nozzles when the printing rate is 5%. Specifically, the number M of non-ejection nozzles is plotted against the surface potential PV of the paper P. A curve L2 indicates a graph created based on PB (black square mark). PC (black triangle mark) indicates the relationship between the surface potential PV of the paper P and the number M of non-ejection nozzles when the printing rate is 0.1%. Specifically, the number M of non-ejection nozzles is plotted against the surface potential PV of the paper P. A curve L3 indicates a graph created based on PC (black triangle mark).

  As shown in FIG. 11, the number M of non-ejection nozzles (curve L1) when the printing rate is 20% decreases in the range where the surface potential PV of the paper P is −100V or more and less than 0V. Similarly, the number M of non-ejection nozzles (curve L2) when the printing rate is 5% also decreases in the range where the surface potential PV of the paper P is -100V or more and less than 0V. Further, the number M of non-ejection nozzles (curve L3) when the printing rate is 0.1% also decreases in the range where the surface potential PV of the paper P is −100V or more and less than 0V. That is, in the range where the surface potential PV of the paper P is −100 V or more and less than 0 V, the number M of non-ejection nozzles decreases regardless of the printing rate. That is, the adhesion of the paper dust PD to the facing surface 341 of the recording head 34 is suppressed when the surface potential PV of the paper P is in the range of −100V to less than 0V. In the present embodiment, the surface potential PV of the paper P is about −50V. Accordingly, the adhesion of the paper dust PD to the facing surface 341 of the recording head 34 is suppressed.

  In the present embodiment, the case where one surface potential measuring unit 342 is used has been described as an example, but the number of surface potential measuring units 342 is not limited to one. For example, the surface potential measurement unit 342 may be provided on the facing surface 341 of each recording head 34. In this case, the voltage setting unit 62 calculates the average value of the surface potential of the facing surface 341 of each recording head 34, and sets the voltage that the power supply device 391 applies to the needle electrode 11 according to the calculated average value. obtain.

  In this embodiment, a voltage in which a direct current component DC (200 V) is superimposed on an alternating current component (maximum amplitude 5500 V) is used as a voltage applied to the needle electrode 11, but the direct current component DC superimposed on the alternating current component is 200 V. It is not limited. For example, as the direct current component DC, a voltage larger than 0V and smaller than 300V can be superimposed on the alternating current component (maximum amplitude 5500V).

  Moreover, although this embodiment demonstrated to the case where the voltage which superimposed the direct current | flow component DC on the alternating current component was used as a voltage applied to the needle electrode 11, the present invention is not limited to this. For example, only the DC voltage may be applied to the needle electrode 11, or only the AC voltage may be applied. When only a DC voltage is applied, the voltage value to be applied is desirably −2300V or more and less than −2000V. Thereby, the surface potential PV of the paper P becomes −100V or more and less than 0V. As a result, it is possible to suppress the paper dust PD from adhering to the facing surface 341 of the recording head 34. Moreover, when using only an alternating voltage, it is desirable that the maximum amplitude value of the alternating voltage to apply is 5500V or more and less than 6000V. Thereby, the surface potential PV of the paper P becomes −100V or more and less than 0V. As a result, it is possible to suppress the paper dust PD from adhering to the facing surface 341 of the recording head 34.

  In this embodiment, the case where a fluororesin is used as the material for the coating layer has been described as an example, but the material for the coating layer is not limited to the fluororesin. For example, a silicone resin can be used as a material for the coating layer.

[Embodiment 2]
Next, with reference to FIG. 12, the inkjet recording apparatus 1 which concerns on Embodiment 2 of this invention is demonstrated. The second embodiment is different from the first embodiment in that the image forming unit 3 includes a charging roller 12 as a voltage application unit instead of the needle electrode 11. Hereinafter, matters different from the first embodiment will be described with respect to the second embodiment, and descriptions of matters overlapping with the first embodiment will be omitted.

  FIG. 12 is a diagram illustrating a configuration of the image forming unit 3 according to the present embodiment. As shown in FIG. 12, the charging roller 12 is disposed on the upstream side in the transport direction D with respect to the recording head 34. The charging roller 12 is in contact with the conveyance belt 32. The charging roller 12 includes a cored bar and a coating layer that covers the cored bar. In the present embodiment, the coating layer is made of a fluororesin. A voltage is applied to the charging roller 12 from the power supply device 391. The charging roller 12 contacts the paper P being conveyed by the conveying belt 32 and applies a voltage to the paper P. As a result, the paper P is charged. As described above, in the present embodiment, the charging roller 12 can contact the paper P to charge the paper P. Therefore, the paper P can be charged more efficiently.

  In the present embodiment, the charging roller 12 applies a voltage to the paper P. Alternatively, the suction roller 312 may apply a voltage to the paper P. Thereby, the number of parts to be used can be suppressed.

[Embodiment 3]
Next, the inkjet recording apparatus 1 according to the third embodiment will be described with reference to FIGS. The third embodiment is different from the first embodiment in that the image forming unit 3 further includes a plate-like member 35. Hereinafter, matters different from the first embodiment will be described with respect to the third embodiment, and descriptions of matters overlapping with the first embodiment will be omitted.

  First, the configuration of the image forming unit 3 according to the present embodiment will be described with reference to FIG. FIG. 13 is a diagram illustrating a configuration of the image forming unit 3 according to the present embodiment.

  The plate-like member 35 is disposed on the upstream side in the transport direction D with respect to the recording head 34 and above the transport belt 32. The plate member 35 is fixed to a fixing member extending from the apparatus housing 100. Specifically, each end of the plate member 35 in a direction orthogonal to the transport direction D is fixed to the fixing member. The plate-like member 35 corresponds to a part of the “space forming part”. By arranging the plate-like member 35 above the transport belt 32, a foreign matter collection space 35 a is formed between the plate-like member 35 and the upper surface of the transport belt 32. The distance H2 is the vertical length of the foreign substance collection space 35a, and is set to a predetermined threshold distance HS (3 mm in this embodiment) or less. The threshold distance HS is set so that the velocity of the airflow flowing into the foreign matter collection space 35a from the space around the foreign matter collection space 35a is larger than that before flowing into the foreign matter collection space 35a and before entering the foreign matter collection space 35a. Is done. The threshold distance HS is preferably set so that the velocity (wind velocity) of the air flow flowing into the foreign substance collection space 35a is 6.0 m / second or more. In the present embodiment, the distance H2 is 2 mm.

  Next, the relationship between the plate-like member 35 and the guide member 332 will be described with reference to FIG. FIG. 14 is a top view of the guide member 332 shown in FIG. A two-dot chain line shown in FIG. 14 indicates the position of the plate-like member 35 projected onto the guide member 332. As described with reference to FIG. 3, on the upper surface of the guide member 332, a plurality of rows including a plurality of grooves 334 arranged along the transport direction D are formed in the width direction of the guide member 332. . As shown in FIG. 14, for each row of grooves 334, two grooves 334 are formed at positions facing the plate-like member 35. Of the two grooves 334, the groove 334 formed on the upstream side in the transport direction D is further upstream in the transport direction D than the position of the upstream end in the transport direction D within the range of the projection image of the plate-like member 35. Extends to the side. Further, the through hole 335 communicating with the groove 334 is formed within the range of the projection image of the plate-like member 35. Similarly, of the two grooves 334, the groove 334 formed on the downstream side in the conveyance direction D is further in the conveyance direction than the position of the downstream end in the conveyance direction D within the range of the projection image of the plate-like member 35. It extends downstream of D. A through hole 335 communicating with the groove 334 is also formed within the range of the projection image of the plate member 35. That is, the groove 334 and the through hole 335 are formed at a position facing the plate-like member 35.

  Next, with reference to FIG. 15, the effect | action of the airflow which flows in into the foreign material collection | recovery space 35a is demonstrated. FIG. 15 is a diagram illustrating the action of the airflow flowing into the foreign substance recovery space 35a shown in FIG.

  As shown in FIG. 15, when the air circulation chamber 331 is in a negative pressure state, air flows into the foreign substance collection space 35a along the arrows FD1 and FD2. The air that has flowed into the foreign matter collection space 35 a passes through the plurality of suction holes 321 (see FIG. 3) formed in the transport belt 32 and the plurality of through holes 335 formed in the guide member 332, and then the air circulation chamber 331. Flow into.

  When the leading end portion of the paper P being transported by the transport belt 32 enters the foreign matter collection space 35a, an air flow flows along the arrow FD1 above the leading end portion of the paper P. Similarly, when the rear end portion of the paper P moves away from the foreign matter collection space 35a, an air flow flows along the arrow FD2 above the rear end portion of the paper P. As described above, the velocity (wind speed) of the airflow flowing into the foreign material collection space 35a along the arrows FD1 and FD2 increases in the foreign material collection space 35a. For this reason, the paper dust PD adhering to the front end portion and the rear end portion of the paper P is peeled off from the paper P and removed.

  As described above, according to the present embodiment, the paper powder PD adhering to the paper P can be separated from the paper P by the air flow. Thereby, the adhesion of the paper dust PD to the facing surface 341 of the recording head 34 can be further suppressed.

  In the third embodiment, the configuration in which the plate-like member 35 is provided in the inkjet recording apparatus 1 described in the first embodiment has been described. However, the plate-like member 35 is provided in the inkjet recording apparatus 1 described in the second embodiment. Also good.

  The embodiments of the present invention have been described above with reference to the drawings. However, the present invention is not limited to the above-described embodiment, and can be implemented in various modes without departing from the gist thereof. For ease of understanding, the drawings schematically show each component as a main component, and the thickness, length, number, etc. of each component shown in the drawings are different from the actual for convenience of drawing. There is a case. Moreover, the shape, dimension, etc. of each component shown by said embodiment are an example, Comprising: It does not specifically limit, A various change is possible in the range which does not deviate substantially from the structure of this invention.

  For example, in the embodiment according to the present invention, the case where the transport belt 32 transports the paper P in the image forming unit 3 has been described. However, the image forming unit 3 may transport the paper P by other methods. For example, the paper P may be transported by a plurality of transport rollers. In this case, it is preferable to apply a negative pressure from between adjacent conveyance rollers.

  Moreover, although the case where the guide member 332 and the air circulation chamber 331 are separate members has been described in the present embodiment, the guide member 332 and the air circulation chamber 331 may be integrally formed. In this case, a negative pressure leak from the air circulation chamber 331 can be prevented. Specifically, air can be prevented from flowing into the air circulation chamber 331 from the gap between the guide member 332 and the air circulation chamber 331.

  Moreover, although this embodiment demonstrated the case where one negative pressure generation part 336 was used, the number of the negative pressure generation parts 336 is not limited to one. For example, two or more negative pressure generators 336 may be used.

  The present invention is applicable to an ink jet recording apparatus.

DESCRIPTION OF SYMBOLS 1 Inkjet recording device 3 Image formation part 11 Needle electrode 12 Charging roller 31 Conveyance part 33 Negative pressure application part 34 Recording head 341 Opposite surface 342 Surface potential measurement part 35 Plate-shaped member 391 Power supply device 6 Control part 61 Surface potential acquisition part 62 Voltage Setting section

Claims (3)

It has opposing surfaces in which a plurality of nozzles are formed for ejecting ink, a recording head for ejecting the ink onto a recording sheet,
A transport unit that transports the recording sheet to a position facing the recording head;
A needle electrode that is disposed upstream of the recording head in the conveyance direction of the recording sheet and charges the sheet by discharge ;
A power supply for applying a voltage to the needle electrode;
A surface potential measuring unit for measuring the surface potential of the facing surface;
Voltage setting for setting the voltage applied to the needle electrode by the power supply device so that the difference between the surface potential of the facing surface and the surface potential of the recording sheet is reduced according to the measurement result of the surface potential measuring unit. With
When the recording head ejects the ink, the opposing surface is charged with a negative polarity,
The power supply device applies a superimposed voltage in which a DC component is superimposed on an AC component to the needle electrode,
The said voltage setting part is an inkjet recording device which sets the voltage value of the said DC component so that the said recording sheet may be charged to a negative polarity .
The facing surface is made of fluororesin
2. The ink jet recording apparatus according to claim 1, wherein the needle electrode charges the recording sheet such that a surface potential of the recording sheet is −100 V or more and less than 0 V. 3. A space forming unit that forms a foreign substance recovery space through which the recording sheet passes between the conveying unit, and
A negative pressure application unit that applies a negative pressure to the foreign substance recovery space,
The inkjet recording apparatus according to claim 1, wherein the space forming unit is provided upstream of the needle electrode in the conveyance direction of the recording sheet.

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