JP5131231B2 - Inkjet recording device - Google Patents

Description

  The present invention relates to an ink jet recording apparatus that performs recording on a recording medium.

  The ink jet recording apparatus includes a transport mechanism that transports a recording medium such as paper, and an ink jet head that discharges ink onto the recording medium transported by the transport mechanism. Then, when the recording medium is transported between the transport mechanism and the ink jet head, the recording medium is attracted to the transport surface of the transport mechanism so that the recording medium does not cause a transport failure due to contact with the ink jet head. Has been done.

  Patent Document 1 includes an endless belt having an electrode for applying a high voltage, and an adsorption roller that adsorbs the recording medium to the endless belt, and the voltage applied to the area where the adsorption roller adsorbs the recording medium is By making the voltage higher than the voltage applied to the area where printing is performed on the recording medium, the recording medium does not cause a conveyance failure due to contact with the inkjet head or the like, and the printing on the recording medium is deteriorated due to the influence of the electric field. It is disclosed not to do so. Further, Patent Document 1 discloses that the voltage is changed according to the temperature and humidity conditions.

JP 2007-119223 A

  However, if the voltage is increased too much according to the temperature and humidity conditions, the product may be damaged by a leakage current, which may cause problems in product safety. Therefore, it is desired to improve the attractive force with respect to the recording medium without increasing the voltage.

  An object of the present invention is to provide an ink jet recording apparatus capable of improving the attractive force to a recording medium without increasing the voltage.

The ink jet recording apparatus of the present invention has an ink jet head on which a discharge surface for discharging ink is formed, and a transport surface facing the discharge surface, and transports a recording medium along the transport direction at least on the transport surface. A transport mechanism is provided so as to face the discharge surface across the transport surface and partly located at a predetermined position on the upstream side of the discharge surface, and orthogonal to the direction facing the discharge surface Each having a plurality of electrodes arranged in an orthogonal direction, and a pair of comb electrodes in which one electrode and another electrode are alternately arranged in the orthogonal direction, and between the pair of comb electrodes An application means for applying a voltage to the recording medium, and a front end of the recording medium transported by the transport mechanism is located at the predetermined position and facing each of the pair of comb-tooth electrodes with the transport surface interposed therebetween. , As serial voltage between the pair of comb electrodes is changed, and a control means for controlling said applying means.

  According to the above configuration, the voltage between the pair of comb electrodes changes when the front end of the recording medium is positioned at a predetermined position upstream of the ejection surface. At this time, it is known that a strong current instantaneously flows through the pair of comb electrodes. Here, the adjacent electrodes constitute a capacitor that passes through the recording medium. When a minute current that charges the capacitor flows to the adjacent electrode, an electric field is generated, and the John Sens between the recording medium and the electrode.・ Adsorption force called Rabeck force is generated. Since this Johnsen-Rahbek force is proportional to the square of the electric field, when a strong current flows momentarily through a pair of comb electrodes, a strong attracting force is instantaneously generated, and the front edge of the recording medium is placed on the transport surface. Strongly adsorbed. Thereby, it is possible to improve the attracting force to the recording medium without increasing the voltage.

  In the inkjet recording apparatus of the present invention, each of the plurality of electrodes may be provided along the transport direction. According to the above configuration, each of the plurality of electrodes included in each of the pair of comb electrodes is provided along the transport direction. Thus, fluctuations in the adsorption force acting on the recording medium can be reduced.

  Further, in the ink jet recording apparatus of the present invention, the control means may control the application means so as to apply a voltage of the same level with different polarities between one and the other between the pair of comb electrodes. . According to said structure, the attractive force by electrostatic adsorption | suction can be suitably generate | occur | produced by applying the voltage of the same level from which polarity differs between one and the other between a pair of comb-tooth electrodes.

In the ink jet recording apparatus of the present invention, the pressing member that is disposed at a position that is the predetermined position and that faces each of the pair of comb-tooth electrodes across the transport surface, presses the recording medium against the transport surface. A roller may be further included. According to said structure, the resistance value of a recording medium and a conveyance surface falls by pressing a recording medium on a conveyance surface with the pressing roller arrange | positioned in the predetermined position. Thereby, the front end of the recording medium can be strongly adsorbed to the transport surface.

  In the ink jet recording apparatus of the present invention, the ink jet recording apparatus may further include a fixing unit that fixes the pair of comb electrodes at positions facing the transport surface, and each of the plurality of electrodes is a portion facing the ejection surface. The width may be narrower than the width of the portion not facing the discharge surface. According to the above configuration, each of the plurality of electrodes included in each of the pair of comb-tooth electrodes has a width at a portion facing the discharge surface that is narrower than a width at a portion not facing the discharge surface. An interval between adjacent electrodes at a location facing the surface is wider than an interval between adjacent electrodes at a location not facing the ejection surface. As a result, it is difficult for a current to charge a capacitor formed by adjacent electrodes to flow at a location facing the ejection surface, and therefore the position at which the ink ejected from the inkjet head lands on the recording medium is disturbed by the electric field between the electrodes. Can be suppressed.

  In the ink jet recording apparatus of the present invention, another pair of comb electrodes provided on the downstream side in the transport direction with respect to the pair of comb electrodes, the pair of comb electrodes, and the other pair Fixing means for fixing each of the comb-tooth electrodes to a position facing the transport surface, and the application means may apply a voltage between the other pair of comb-tooth electrodes. According to the above configuration, since the other pair of comb-teeth electrodes that generate the suction force is provided on the downstream side of the pair of comb-teeth electrodes, the front end of the recording medium faces the pair of comb-teeth electrodes on the transport surface. After passing through the location, the voltage between the pair of comb electrodes is changed without waiting for the rear end of the recording medium to pass through the location facing the pair of comb electrodes on the transport surface, and the next recording medium Can strongly adsorb the front end. Thereby, a plurality of recording media can be continuously conveyed at short intervals.

  According to the ink jet recording apparatus of the present invention, when the voltage between the pair of comb electrodes changes, a strong current instantaneously flows through the pair of comb electrodes. As a result, a strong suction force is instantaneously generated, and the front end of the recording medium is strongly suctioned to the transport surface, so that the suction force to the recording medium can be improved without increasing the voltage.

1 is a schematic side view showing an internal structure of an ink jet printer according to a first embodiment of the present invention. It is a top view which shows a comb-tooth electrode. It is a figure which shows a timing chart. It is a figure which shows the electrical constitution of an inkjet printer. It is a figure which shows an adsorption | suction process routine. It is a top view which shows the comb electrode by 2nd Embodiment of this invention. It is a figure which shows a timing chart. It is a figure which shows an adsorption | suction process routine.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

[First Embodiment]
(Mechanical configuration of inkjet printer)
As shown in FIG. 1, an ink jet printer (ink jet recording apparatus) 1 according to the first embodiment of the present invention has a rectangular parallelepiped housing 1a, and magenta, cyan, yellow, and black inks are respectively contained therein. This is a color ink jet printer having four ink jet heads 2 for discharging. The ink jet printer 1 is provided with a paper feeding device 10 at the lower side in FIG. 1 and a paper discharge unit 15 at the upper side in FIG. 1, and a paper (recording medium) P along the conveying direction A therebetween. A transport mechanism 50 is provided for transporting. Furthermore, the inkjet printer 1 includes a control unit 100 that controls these operations.

  The four inkjet heads 2 have a substantially rectangular parallelepiped shape elongated in the main scanning direction, and are fixed to a frame-like frame 7 in a state of being adjacent to each other along the sub-scanning direction. That is, the ink jet printer 1 is a line printer. In this embodiment, the sub-scanning direction is a direction parallel to the conveyance direction A of the paper P, and the main scanning direction is a direction orthogonal to the sub-scanning direction and along a horizontal plane (the paper surface in FIG. 1). Vertical direction).

  The inkjet head 2 has a laminated body (both not shown) in which a flow path unit in which an ink flow path including a pressure chamber is formed and an actuator that applies pressure to ink in the pressure chamber are bonded together. Is an ejection surface 2a for ejecting ink. A plurality of ejection openings for ejecting ink are formed on the ejection surface 2a.

  The sheet feeding device 10 includes a sheet feeding cassette 11 that can store a plurality of stacked sheets P, a sheet feeding roller 12 that feeds the sheet P from the sheet feeding cassette 11, and a sheet feeding motor (not shown) that rotates the sheet feeding roller 12. And have. The paper feed cassette 11 is detachably disposed in the direction perpendicular to the paper surface of FIG. 1, and is disposed at a position overlapping the transport mechanism 50 in the vertical direction in FIG. 1 when mounted on the housing 1a. The paper feed roller 12 feeds the paper P from the paper feed cassette 11 by rotating and contacting the paper P positioned at the uppermost position. The paper feed motor that rotates the paper feed roller 12 is controlled by the control unit 100.

  On the left end side in FIG. 1, between the paper feed cassette 11 and the transport mechanism 50 along the transport path, a supply guide 17 extending while curving from the paper feed cassette 11 toward the transport mechanism 50, and a supply guide Two feed rollers 23 a and 23 b provided on the downstream side of 17 are arranged. The feed roller 23b is rotationally driven by a feed motor (not shown) controlled by the control unit 100. The feed roller 23a is a driven roller and rotates as the paper is conveyed.

  In this configuration, when the paper feed roller 12 rotates clockwise in FIG. 1 under the control of the control unit 100, the paper P in contact with the paper feed roller 12 passes through the supply guide 17 and is sent upward in FIG. 1. . Then, the paper P is supplied to the transport mechanism 50 while being held between the feed rollers 23a and 23b.

  The transport mechanism 50 includes two belt rollers 51 and 52, an endless transport belt 53 wound around the belt rollers 51 and 52, and a tension roller 55 that applies tension to the transport belt 53. A conveyance motor (not shown) that rotates the belt roller 52 and a substantially rectangular parallelepiped platen (fixing means) 61 are provided. The two belt rollers 51 and 52 are juxtaposed along the transport direction A. The transport belt 53 has a transport surface (outer peripheral surface) 54 that supports the paper P.

  The belt roller 52 is a driving roller, and is rotated clockwise in FIG. 1 by a conveyance motor (not shown). The belt roller 51 is a driven roller, and rotates in the clockwise direction in FIG. 1 as the conveyor belt 53 travels as the belt roller 52 rotates. The tension roller 55 is rotatably supported by the housing 1a in a state where a tension is applied to the conveyor belt 53 while contacting the inner peripheral surface of the lower loop of the conveyor belt 53, and the conveyor belt 53 travels. As this occurs, it rotates in the clockwise direction in FIG. The platen 61 is formed slightly longer than the lengths of the paper P and the conveyor belt 53 in the main scanning direction.

  Further, the upper surface of the platen 61 is in contact with the inner peripheral surface of the upper loop of the transport belt 53 and supports it from the inner peripheral side of the transport belt 53. Thereby, the conveyance surface 54 of the upper loop of the conveyance belt 53 and the ejection surface 2a of the inkjet head 2 are parallel to each other, and a slight gap is formed between the ejection surface 2a and the conveyance surface 54 of the conveyance belt 53. Is formed. This gap constitutes a part of the paper transport path.

  A pressing roller 48 is disposed upstream of the inkjet head 2 disposed upstream in the transport direction A and at a position facing the belt roller 51. The pressing roller 48 is urged against the transport surface 54 by an elastic member (not shown) such as a spring, and presses the paper P sent out from the paper feeding device 10 against the transport surface 54. The pressing roller 48 is a driven roller, and rotates with the rotation of the conveyance belt 53.

  In addition, a resin-made pressing roller 49 is disposed at a predetermined position upstream of the inkjet head 2 disposed on the most upstream side in the transport direction A and downstream of the pressing roller 48 and facing the platen 61. ing. The pressing roller 49 is urged against the transport surface 54 by an elastic member (not shown) such as a spring, and presses the paper P against a predetermined position on the transport surface 54, thereby pressing the paper P. It is pressed against the platen 61 indirectly. Thus, the sheet P is easily electrostatically attracted by a pair of comb electrodes 62a and 62b described later. The pressing roller 49 is a driven roller and rotates with the rotation of the conveyance belt 53.

  A pair of comb electrodes 62 a and 62 b are provided on the upper surface of the platen 61, and the upper surface is coated with a protective layer that protects against wear due to contact with the conveyor belt 53. As shown in FIG. 2, each of the pair of comb electrodes 62 a and 62 b is provided such that a part thereof is located at a predetermined position facing the pressing roller 49. Each of the pair of comb electrodes 62a and 62b includes a plurality of electrodes (parallel electrode portions) provided along the transport direction A and continuously provided in the main scanning direction. The electrodes of the other are alternately arranged in the main scanning direction. When a voltage is applied between the pair of comb electrodes 62 a and 62 b by the power source (applying means) 63, the adjacent electrodes are the gap between the electrode and the conveyor belt 53, the conveyor belt 53, the conveyor belt 53 and the paper P. And a capacitor passing through the paper P, and a minute current that charges the capacitor flows to adjacent electrodes, thereby generating an electric field. As a result, a Johnsen-Rahbek force (adsorption force) is generated between the paper P and the electrode. With this attracting force, the paper P on the transport belt 53 is electrostatically attracted to the transport surface 54. The power source 63 that applies a voltage between the pair of comb electrodes 62 a and 62 b is controlled by the control unit 100.

  In this configuration, the conveyor belt 53 is rotated by rotating the belt roller 52 clockwise in FIG. At this time, the belt roller 51, the tension roller 55, the pressing roller 48, and the pressing roller 49 also rotate with the rotation of the conveyance belt 53. At this time, under the control of the control unit 100, when a voltage is applied between the pair of comb electrodes 62a and 62b, a minute current for charging a capacitor formed by the adjacent electrodes flows to the adjacent electrodes.・ Rabeck force is generated. As a result, the paper P sent out from the paper feeding device 10 is transported in the transport direction A while being electrostatically attracted to the transport surface 54. Thereby, it is possible to suppress the occurrence of a jam due to the front end of the paper P hitting the inkjet head 2. Further, at this time, when the paper P that is conveyed while being held on the conveyance surface 54 of the conveyance belt 53 sequentially passes immediately below the four inkjet heads 2, the control unit 100 controls each inkjet head 2. Ink of each color is ejected toward the paper P. Thus, a desired color image is formed on the paper P.

  Further, the two sensors 71 and 72 are disposed between the pressing roller 48 and the inkjet head 2 and downstream of the inkjet head 2 that is most downstream in the conveyance direction A so that the detection surface faces the conveyance surface 54. Is provided. These sensors 71 and 72 are reflection-type optical sensors that detect the paper P by reflecting light on the surface of the paper P, and are arranged at positions facing the center of the transport surface 54 in the main scanning direction. Yes. These sensors 71 and 72 detect the front end of the paper P that has been transported by the transport belt 53. The sensors 71 and 72 are not limited to reflective optical sensors, and may be transmissive optical sensors or the like.

  Further, as shown in FIG. 3, the voltage applied between the pair of comb electrodes 62a and 62b is changed at timings A and B when a predetermined time has elapsed after the sensor 71 detects the front edge of the paper P. . Here, the predetermined time is the distance along the conveyance path from the front edge of the paper P when the sensor 71 detects the front edge of the paper P to the predetermined position facing the pressing roller 49, as the conveyance speed of the paper P. Divided time. Timing A is a timing when the front end of the first sheet P is positioned at a predetermined position, and timing B is a timing when the front end of the second sheet P is positioned at a predetermined position. At this time, a transient current for charging a capacitor formed by the adjacent electrodes flows in adjacent electrodes. This transient current is larger than the direct current flowing through the adjacent electrodes thereafter. Here, the attracting force (Johnsen-Rahbek force) by electrostatic attraction is proportional to the square of the electric field, so that a stronger attracting force than usual is generated when a transient current flows to adjacent electrodes. As a result, the front end of the paper P is strongly adsorbed to the transport surface 54. Thereafter, a substantially constant direct current that increases with an increase in the adsorption area of the paper P and decreases with a decrease in the adsorption area of the paper P flows to adjacent electrodes, thereby stabilizing the adsorption force by electrostatic adsorption. To do.

  Specifically, at the timing A when the front edge of the first sheet P is positioned at a predetermined position, the voltage of the comb electrode 62a is changed from 0V to + 1000V, and the voltage of the comb electrode 62b is changed from 0V to -1000V. Change. At timing B when the front edge of the second sheet P is positioned at a predetermined position, the voltage of the comb electrode 62a is changed from + 1000V to -1000V, and the voltage of the comb electrode 62b is changed from -1000V to + 1000V. As a result, the polarity of the voltage applied between the pair of comb electrodes 62a and 62b is switched. After that, at the timing when the front end of the next sheet P is positioned at a predetermined position, the voltage is changed so that the polarity of the voltage of the same level applied between the pair of comb electrodes 62a and 62b is switched.

  As described above, when the front end of the sheet P is located at a predetermined position upstream of the ejection surface 2a, the voltage between the pair of comb electrodes 62a and 62b is rapidly changed. At this time, a strong current instantaneously flows between the pair of comb-tooth electrodes 62a and 62b, a strong suction force is instantaneously generated, and the front end of the paper P is strongly attracted to the transport surface 54. The suction force with respect to the paper P can be improved without increasing it.

  In addition, since each of the plurality of electrodes included in each of the pair of comb-tooth electrodes 62a and 62b is provided along the transport direction A, after the attraction force due to electrostatic adsorption is stabilized, the electrodes are aligned along the transport direction A. Thus, fluctuations in the attractive force acting on the paper P can be reduced.

  Further, by applying a voltage of the same level with different polarities between one and the other between the pair of comb-tooth electrodes 62a and 62b, an attractive force due to electrostatic adsorption can be suitably generated.

  Further, as described above, the pressing roller 49 is disposed at a predetermined position. When the front end of the sheet P is pressed against the conveyance surface 54 by the pressing roller 49, the gap between the sheet P and the conveyance surface 54 is narrowed, and the gap between the conveyance surface 54 and the electrode is narrowed. As a result, the electrical resistance value between the paper P and the transport surface 54 decreases, and the electrical resistance value between the transport surface 54 and the electrode decreases. For this reason, the adjacent electrode charges the gap between the electrode and the conveyance belt 53, the conveyance belt 53, the gap between the conveyance belt 53 and the paper P, and the current value for charging the capacitor formed via the paper P. growing. Thereby, the front end of the paper P can be strongly adsorbed by the transport surface 54.

  Further, as shown in FIG. 2, each of the plurality of electrodes has a width at a portion facing the discharge surface 2 a of the inkjet head 2 smaller than a width at a portion not facing the discharge surface 2 a. An interval a between adjacent electrodes at a position facing 2a is wider than an interval b between adjacent electrodes at a position not facing the discharge surface 2a. As a result, it is difficult for a current to charge the capacitor formed by the adjacent electrodes to flow at a location facing the ejection surface 2a. Therefore, the position where the ink ejected from the inkjet head 2 lands on the paper P is the electric field between the electrodes. Disturbance can be suppressed.

  As shown in FIG. 1, a peeling plate 9 is provided immediately downstream in the transport direction A of the transport mechanism 50. The peeling plate 9 peels the paper P from the transport surface 54 by the leading end of the peeling plate 9 entering between the paper P and the transport belt 53.

  Between the transport mechanism 50 and the paper discharge unit 15, the discharge rollers disposed between the four feed rollers 21a, 21b, 22a, 22b and the feed rollers 21a, 21b and the feed rollers 22a, 22b. A guide 18 is arranged. The feed rollers 21b and 22b are rotationally driven by a feed motor (not shown) controlled by the control unit 100. The feed rollers 21a and 22a are driven rollers and rotate as the paper is conveyed.

  In this configuration, under the control of the control unit 100, the feed motor is driven so that the feed rollers 21b and 22b rotate, and the sheet P discharged from the transport mechanism 50 is held in the discharge guide 18 while being held between the feed rollers 21a and 21b. And sent upward in FIG. Then, the paper P is discharged to the paper discharge unit 15 while being held between the feed rollers 22a and 22b.

(Electrical configuration of inkjet printer)
As shown in FIG. 4, the operation of the inkjet printer 1 is controlled by the control unit 100. The control unit 100 includes a microcomputer 101 disposed on a circuit board as a main component, and is configured by adding various circuits thereto. The microcomputer 101 includes a CPU (Central Processing Unit) 102 that performs control operations in accordance with preset programs, a ROM (Read Only Memory) 103 that stores various programs, and a RAM (Random Access Memory) 104 that serves as a temporary storage unit. And have.

  The CPU 102 includes a head control circuit 106 that controls the inkjet head 2, a transport mechanism 50 and feed rollers 21b, 22b, and 23b, a transport mechanism control circuit 107 that controls the paper feed roller 12, and a pair of comb electrodes 62a and 62b. Communication between the suction control circuit 110 that controls the power supply 63 that applies the voltage, the interface circuit 111 that receives the paper detection signals from the sensors 71 and 72, and a general-purpose personal computer (not shown) via the communication unit 20 The communication circuit 112 for performing the above is connected, and the CPU 102 controls them. The CPU 102 and the suction control circuit 110 constitute a control unit.

  The head control circuit 106 controls each inkjet head 2 so as to eject ink onto the paper P based on print data transferred via a communication unit 20 from a general-purpose personal computer or the like (not shown). At this time, the head control circuit 106 sets each inkjet head so that ink discharge to the paper P is started after a predetermined time has elapsed since the sensor 71 detects the front end of the paper P conveyed by the conveyance mechanism 50. 2 is controlled. The predetermined time here refers to the distance along the transport path from the front end of the paper P when the sensor 71 detects the front edge of the paper P to the most upstream discharge port of the inkjet head 2 upstream. The time divided by the conveyance speed of P.

  Further, the transport mechanism control circuit 107 controls the transport mechanism 50, the feed rollers 21b, 22b, and 23b, and the paper feed roller 12 so as to transport the paper P from the paper feeder 10 to the paper discharge unit 15.

  Further, the adsorption control circuit 110 controls the power supply 63 so as to apply a voltage between the pair of comb-tooth electrodes 62a and 62b. In particular, the suction control circuit 110 controls the power supply 63 so that the voltage applied between the pair of comb electrodes 62a and 62b is changed at the timing when the front end of the sheet P being conveyed is positioned at a predetermined position.

(Inkjet printer operation)
In the above configuration, the operation of the inkjet printer 1 will be described with reference to the suction processing routine shown in FIG.

(Adsorption processing routine)
When the adsorption processing routine is executed, as shown in FIG. 5, the voltage between the pair of comb electrodes 62a and 62b is set to “0” (S1). Then, it is determined whether printing has started (S2). If it is determined that printing is not started, the process returns to step S1. On the other hand, if it is determined that printing has started, it is determined whether the upstream sensor 71 has detected the front edge of the paper P (S3).

  If it is determined that the front edge of the paper P has not been detected, the process waits for detection of the front edge of the paper P by repeating step S3. On the other hand, if it is determined that the front edge of the paper P has been detected, it is determined whether or not a predetermined time has elapsed (S4). Here, the predetermined time is a time required for the front end of the paper P to be positioned at a predetermined position facing the pressing roller 49. If it is determined that the predetermined time has not elapsed, step S4 is repeated to wait for the predetermined time to elapse. On the other hand, if it is determined that the predetermined time has elapsed, the front end of the paper P is located at a predetermined position, and thus a voltage is applied between the pair of comb electrodes 62a and 62b (S5) (timing in FIG. 3). A).

  Thereafter, it is determined whether or not to end printing (S6). If it is determined that printing is to end, the process returns to step S1. On the other hand, if it is determined not to end printing, the other paper P is continuously printed, so it is determined whether or not the upstream sensor 71 has detected the front edge of the paper P (S7).

  If it is determined that the front edge of the paper P is not detected, the process waits for detection of the front edge of the paper P by repeating step S7. On the other hand, if it is determined that the front edge of the paper P has been detected, it is determined whether or not a predetermined time has elapsed (S8). If it is determined that the predetermined time has not elapsed, step S8 is repeated to wait for the elapse of the predetermined time. On the other hand, if it is determined that the predetermined time has elapsed, the polarity of the voltage applied between the pair of comb electrodes 62a and 62b is switched because the front end of the paper P is located at the predetermined position (S9). (See timing B in FIG. 3). Then, it returns to step S6.

  As described above, when the front end of the sheet P is located at a predetermined position upstream of the ejection surface 2a, the voltage between the pair of comb electrodes 62a and 62b is rapidly changed. At this time, a strong current instantaneously flows between the pair of comb-tooth electrodes 62a and 62b, a strong suction force is instantaneously generated, and the front end of the paper P is strongly attracted to the transport surface 54. The suction force with respect to the paper P can be improved without increasing it.

  In addition, since each of the plurality of electrodes included in each of the pair of comb-tooth electrodes 62a and 62b is provided along the transport direction A, after the attraction force due to electrostatic adsorption is stabilized, the electrodes are aligned along the transport direction A. Thus, fluctuations in the attractive force acting on the paper P can be reduced.

  Further, by applying a voltage of the same level with different polarities between one and the other between the pair of comb-tooth electrodes 62a and 62b, an attractive force due to electrostatic adsorption can be suitably generated.

  Further, since the pressing roller 49 is disposed at a predetermined position and the front end of the paper P is pressed against the transport surface 54 by the pressing roller 49, the front end of the paper P can be strongly adsorbed by the transport surface 54.

  Further, as shown in FIG. 2, each of the plurality of electrodes has a width at a portion facing the discharge surface 2 a of the inkjet head 2 smaller than a width at a portion not facing the discharge surface 2 a. An interval a between adjacent electrodes at a position facing 2a is wider than an interval b between adjacent electrodes at a position not facing the discharge surface 2a. As a result, it is difficult for a current to charge the capacitor formed by the adjacent electrodes to flow at a location facing the ejection surface 2a. Therefore, the position where the ink ejected from the inkjet head 2 lands on the paper P is the electric field between the electrodes. Disturbance can be suppressed.

[Second Embodiment]
(Mechanical configuration of inkjet printer)
Next, an inkjet printer 201 according to a second embodiment of the present invention will be described. The difference between the inkjet printer 201 according to the second embodiment and the inkjet printer 1 according to the first embodiment is that, as shown in FIG. 6, two sets of comb-shaped electrodes 64a, 64b, 65a, and 65b are provided on the platen 61, respectively. It is a point provided. The upper surfaces of the two sets of comb electrodes 64 a, 64 b, 65 a, 65 b are coated with a protective layer that protects against wear due to contact with the conveyor belt 53.

  The pair of comb electrodes 64 a and 64 b are provided on the upstream side in the transport direction A so as to face the two inkjet heads 2 on the upstream side. Further, the other pair of comb-tooth electrodes 65 a and 65 b are provided on the downstream side in the transport direction A so as to face the two inkjet heads 2 on the downstream side. The power source 63 is configured to apply a voltage between the pair of comb electrodes 64a and 64b and between the other pair of comb electrodes 65a and 65b. In other words, the pair of comb electrodes 62a and 62b in the first embodiment is divided into two sets of comb electrodes in the second embodiment.

  Then, as shown in FIG. 7, the voltage applied between the pair of comb electrodes 64a and 64b at the timings A, B, and C when a predetermined time has elapsed after the sensor 71 detects the front edge of the paper P. Change. Here, the predetermined time is the distance along the conveyance path from the front edge of the paper P when the sensor 71 detects the front edge of the paper P to the predetermined position facing the pressing roller 49, as the conveyance speed of the paper P. Divided time. Timing A is a timing at which the front edge of the first sheet P is positioned at a predetermined position, and timing B is a timing at which the front edge of the second sheet P is positioned at a predetermined position. Is the timing at which the front edge of the third sheet P is positioned at a predetermined position. At this time, in the pair of comb-tooth electrodes 64a and 64b, a transient current that charges a capacitor formed by the adjacent electrodes flows. As a result, the front end of the paper P is strongly adsorbed to the transport surface 54. Thereafter, a substantially constant direct current that increases with an increase in the adsorption area of the paper P and decreases with a decrease in the adsorption area of the paper P flows to adjacent electrodes, thereby stabilizing the adsorption force by electrostatic adsorption. To do.

  Specifically, at the timing A when the front edge of the first sheet P is positioned at a predetermined position, the voltage of the comb electrode 64a is changed from 0V to + 1000V, and the voltage of the comb electrode 64b is changed from 0V to -1000V. Change. Further, at the timing B when the front edge of the second sheet P is positioned at a predetermined position, the voltage of the comb electrode 64a is changed from + 1000V to -1000V, and the voltage of the comb electrode 64b is changed from -1000V to + 1000V. As a result, the polarity of the voltage applied between the pair of comb electrodes 64a and 64b is switched. After that, at the timing when the front end of the next sheet P is positioned at a predetermined position, the voltage is changed so that the polarity of the voltage of the same level applied between the pair of comb-tooth electrodes 64a and 64b is switched.

  On the other hand, the voltage applied between the other pair of comb-shaped electrodes 65a and 65b is changed at predetermined timings A 'and B' when a predetermined time has elapsed from the timings A and B. Here, the fixed time is a distance along the conveyance path from a predetermined position to the intermediate position B that faces the pair of comb electrodes 64a and 64b and does not face the other pair of comb electrodes 65a and 65b. The time divided by the conveyance speed of P. Further, the predetermined timing A ′ is a timing when the front end of the first sheet P is positioned at the intermediate position B, and the predetermined timing B ′ is a timing when the front end of the second sheet P is at the intermediate position B. It is the timing when it is located. The predetermined timing A ′ is earlier than the timing B, and the predetermined timing B ′ is earlier than the timing C.

  Then, by changing the voltage between the other pair of comb electrodes 65a and 65b at a predetermined timing A 'and B', a transient current instantaneously flows between the other pair of comb electrodes 65a and 65b. After that, after a substantially constant DC current flows, the intermediate position B is set so that the front end of the paper P is located at a position facing the other pair of comb electrodes 65a and 65b on the transport surface 54. Has been. As a result, the sheet P is conveyed while being adsorbed by an adsorbing force by a substantially constant DC current at a position facing the pair of comb electrodes 64 a and 64 b on the conveying surface 54, and then another pair of paper on the conveying surface 54. In the place facing the comb-shaped electrodes 65a and 65b, it is transported while being adsorbed with an equivalent adsorbing force by a substantially constant DC current without being affected by a strong adsorbing force due to an instantaneous transient current. .

  Specifically, at a predetermined timing A ′ when the front end of the first sheet P is located at the intermediate position B, the voltage of the comb electrode 65a is changed from 0V to + 1000V, and the voltage of the comb electrode 65b is set to 0V. To -1000V. At a predetermined timing B ′ when the front end of the second sheet P is located at the intermediate position B, the voltage of the comb electrode 65a is changed from + 1000V to −1000V, and the voltage of the comb electrode 65b is changed from −1000V. By changing to +1000 V, the polarity of the voltage applied between the other pair of comb-tooth electrodes 65a and 65b is switched. Thereafter, at a predetermined timing when the front end of the next sheet P is positioned at the intermediate position B, the voltage is applied so that the polarity of the voltage of the same level applied between the other pair of comb electrodes 65a and 65b is switched. Change.

  Further, when a plurality of sheets P are continuously conveyed, the front end of the next sheet P is passed after the front end of the previous sheet P passes through the portion of the transport surface 54 facing the pair of comb electrodes 64a and 64b. Is positioned at a predetermined position. That is, if the front end of the preceding paper P is positioned at a position facing the other pair of comb electrodes 65 a and 65 b on the transport surface 54, the rear end of the previous paper P is a pair of comb teeth on the transport surface 54. Even if it is located at a position facing the electrodes 64a and 64b, the front end of the next sheet P is positioned at a predetermined position. Then, the front end of the next sheet P is strongly adsorbed by abruptly changing the voltage between the pair of comb electrodes 64a and 64b. That is, when the plurality of sheets P are continuously conveyed, the next end of the previous sheet P does not wait for passing through the portion facing the pair of comb electrodes 64a and 64b on the conveyance surface 54, and the next By positioning the front end of the paper P at a predetermined position, the interval of continuous conveyance is shortened.

  As described above, after the front end of the paper P passes through the portion facing the pair of comb electrodes 64 a and 64 b on the transport surface 54, the rear end of the paper P faces the pair of comb electrodes 64 a and 64 b on the transport surface 54. Without waiting for the passage of the position, the voltage between the pair of comb electrodes 64a and 64b is changed abruptly to strongly adsorb the front end of the next sheet P, thereby separating the plurality of sheets P at short intervals. Can be continuously conveyed.

  Since other configurations are the same as those of the first embodiment, the description thereof is omitted.

(Inkjet printer operation)
In the above configuration, the operation of the inkjet printer 201 will be described with reference to the second suction processing routine shown in FIG. Note that a first suction processing routine similar to the suction processing routine described above with reference to FIG. 5 is executed for the pair of comb electrodes 64a and 64b. Therefore, the second adsorption processing routine is a routine for the other pair of comb electrodes 65a and 65b.

(Second adsorption processing routine)
When the second adsorption processing routine is executed, the voltage between the other pair of comb electrodes 65a and 65b is set to “0” as shown in FIG. 8 (S101). Then, it is determined whether printing has started (S102). If it is determined that printing is not started, the process returns to step S101. On the other hand, if it is determined that printing has started, it is determined whether or not it is a predetermined timing (S103). Here, the predetermined timing is a timing at which the front end of the paper P is located at the intermediate position B.

  If it is determined that the predetermined timing is not reached, the predetermined timing is waited by repeating step S103. On the other hand, when it is determined that the predetermined timing is reached, a voltage is applied between the other pair of comb electrodes 65a and 65b (S104) (see the predetermined timing A 'in FIG. 7).

  Thereafter, it is determined whether or not to end printing (S105). If it is determined to end printing, the process returns to step S101. On the other hand, if it is determined that the printing is not finished, the printing of another sheet P is performed continuously, and therefore it is determined whether or not it is a predetermined timing (S106).

  If it is determined that it is not the predetermined timing, step S106 is repeated to wait for the predetermined timing. On the other hand, when it is determined that the predetermined timing is reached, the polarity of the voltage applied between the other pair of comb electrodes 65a and 65b is switched (S107) (see the predetermined timing B ′ in FIG. 7). ). Thereafter, the process returns to step S105.

  As described above, since the other pair of comb electrodes 65 a and 65 b is provided on the downstream side of the pair of comb electrodes 64 a and 64 b, the sheet P faces the pair of comb electrodes 64 a and 64 b on the transport surface 54. After passing through the location, the voltage between the pair of comb electrodes 64a and 64b is rapidly increased without waiting for the trailing edge of the paper P to pass through the location facing the pair of comb electrodes 64a and 64b on the transport surface 54. Thus, the front edge of the next paper P can be strongly adsorbed. As a result, a plurality of sheets P can be continuously conveyed at short intervals.

(Modification of this embodiment)
The embodiment of the present invention has been described above, but only specific examples are illustrated, and the present invention is not particularly limited, and the specific configuration and the like can be appropriately changed in design. Further, the actions and effects described in the embodiments of the invention only list the most preferable actions and effects resulting from the present invention, and the actions and effects according to the present invention are described in the embodiments of the present invention. It is not limited to what was done.

  For example, in the above-described embodiment, the comb electrode is provided on the platen 61, but may be embedded in the conveyance belt 53. In this case, each of the plurality of electrodes included in each comb electrode may have a uniform width.

  In the above-described embodiment, each of the plurality of electrodes included in each of the comb electrodes is provided along the transport direction A, but may be provided along the main scanning direction.

  Moreover, in the above-mentioned embodiment, it is configured to apply a voltage of the same level that is different in polarity between one and the other between a pair of comb electrodes. For example, the voltage of one comb electrode is + 2000V. A configuration may be employed in which the voltage is alternately switched between +1000 V and the voltage of the other comb electrode is alternately switched between +1000 V and +2000 V.

  Further, in the above-described embodiment, the pressing roller 49 that presses the paper P against the transport surface 54 is made of resin, but by forming it with a conductive material, the current flowing through the paper P can be reduced. It may be configured to increase. Further, by applying a voltage to the pressing roller 49, a larger current may be caused to flow between the paper P and the transport belt 53. Further, the pressing roller 49 may not be provided.

  In the second embodiment, the voltage applied between the other pair of comb electrodes 65a and 65b may not be changed.

  The ink jet recording apparatus according to the present invention is not limited to the ink jet type, but can be applied to a thermal type, and is not limited to a line type, and can also be applied to a serial type in which a head reciprocates. Further, the present invention is not limited to a printer, and can be applied to a facsimile, a copier, and the like. Further, the transport mechanism 50 in the present embodiment transports the paper P in the horizontal direction, but the paper P can be transported in a direction other than the horizontal direction (for example, an oblique direction and a vertical direction). The conveyance surface 54 parallel to the discharge surface 2a may be disposed inclined with respect to the horizontal direction.

1 Inkjet printer (inkjet recording device)
2 Inkjet head 2a Discharge surface 49 Pressing roller 50 Conveying mechanism 54 Conveying surface 61 Platen 62a, 62b Comb electrode 63 Power supply (applying means)
100 control unit 102 CPU
110 Adsorption control circuit P Paper (recording medium)

Claims (7)

An inkjet head having an ejection surface for ejecting ink;
A transport mechanism having a transport surface facing the ejection surface, and transporting the recording medium along the transport direction on at least the transport surface;
Opposite to the ejection surface across the transport surface, a part is provided to be located at a predetermined position upstream of the ejection surface, and in an orthogonal direction orthogonal to the facing direction of the ejection surface A pair of comb-like electrodes each having a plurality of electrodes arranged continuously, one having electrodes and the other having electrodes arranged alternately in the orthogonal direction;
Applying means for applying a voltage between the pair of comb electrodes;
When the front end of the recording medium transported by the transport mechanism is located at the predetermined position and facing each of the pair of comb electrodes across the transport surface, between the pair of comb electrodes Control means for controlling the application means such that the voltage changes;
An ink jet recording apparatus comprising:   The inkjet recording apparatus according to claim 1, wherein each of the plurality of electrodes is provided along the transport direction.   The said control means controls the said application means so that the voltage of the same level from which polarity differs between one side and the other between said pair of comb-tooth electrodes is characterized by the above-mentioned. Inkjet recording apparatus. And characterized in that the sides of the predetermined position and a in the conveying surface is disposed at a position opposed to each of the pair of comb electrodes, further comprising a pressing roller for pressing the recording medium to the conveying surface The inkjet recording apparatus according to any one of claims 1 to 3. A fixing means for fixing the pair of comb electrodes at a position facing the conveying surface;
5. The width of a portion of each of the plurality of electrodes that faces the discharge surface is narrower than a width of a portion that does not face the discharge surface. 6. The ink jet recording apparatus described. Another pair of comb electrodes provided on the downstream side in the transport direction with respect to the pair of comb electrodes;
Fixing means for fixing the pair of comb-tooth electrodes and the other pair of comb-tooth electrodes at positions facing the transport surface, respectively;
Further comprising
The ink jet recording apparatus according to claim 1, wherein the applying unit applies a voltage between the other pair of comb electrodes. Wherein, when the front end of the recording medium in which the conveying mechanism conveys is located at each position opposed to the pair of comb electrodes across said conveying surface a predetermined position, the pair The polarity and voltage level of one electrode of the comb-teeth electrode become the polarity and voltage level of the other electrode of the pair of comb-teeth electrodes, and the polarity and voltage level of the other electrode become the polarity and voltage level of the one electrode. so as to, ink jet recording apparatus according to any one of claims 1 to 6, wherein the controller controls the applying means.

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