JP2014019109A - Image forming apparatus, image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus having no risk of a discharge failure and a deterioration in printing quality due to attachment to a nozzle face and landing at an optional position on paper of mist in the case that a generation amount of mist is generated in a large amount.SOLUTION: The image forming apparatus includes an ink jet head 11, an electrode 3 provided so as to turn in the direction of paper P near a generation part of mist M of ink generated when grains of ink is discharged from the ink jet head 11, and an electrode control part for predicting a generating state of the mist from image data, making the electrode 3 to be the same polarity as the polarity of electricity charged in the mist M in the case of predicting that the generation of the mist M is equal to or greater than a predetermined amount, and making the electrode 3 to be polarity opposite to the polarity of the electricity charged in the mist M in the case of predicting that the generation of the mist M is less than the predetermined amount.

Description

  The present invention relates to an inkjet image forming apparatus and an image forming method.

  Ink jet image forming apparatuses generate ink mist when ink particles are ejected from an ink jet head. The mist reaches the recording material and adversely affects the print quality. Thus, for example, the following ink jet recording apparatus is known as a solution to the problem relating to the mist.

The ink jet recording apparatus is provided close to the ink jet recording head and holding means for holding and transporting the recording material by electrostatic force, and is separated from the ink droplets by discharging the ink droplets from the ink discharge port. An electrode for collecting satellite droplets floating in the space near the ink jet recording head, and means for applying a voltage having a polarity opposite to the surface potential of the recording material to collect the satellite droplets to the electrodes And a removing means for removing the satellite droplets collected on the electrode.
According to this ink jet recording apparatus, satellites charged to the same potential as the surface potential of the recording material and other foreign matters can be efficiently collected, and these satellites and other foreign matters are discharged from the ink jet recording head. It is said that there is an effect that it is possible to continuously prevent the surface from adhering to the vicinity of the discharge port and to prevent discharge failure (see Patent Document 1).

The satellite droplets described above are ink mist generated when ink particles are ejected from the inkjet head.
As described above, the conventional ink jet recording apparatus is configured to always capture mist with an electrode having a polarity opposite to that of the mist regardless of the amount of mist generated.

However, the conventional ink jet recording apparatus has the following problems.
For example, when a solid image region is printed, a large amount of mist is generated, but there may be a case where not all of the mist can be captured by the electrodes.
The mist that could not be captured by the electrode floats in the space, and then a certain mist adheres to the nozzle surface of the inkjet head, or a certain mist lands at an arbitrary position on the recording material.
If mist adheres and accumulates on the nozzle surface, ejection failure may occur, and if mist lands on an arbitrary position on the recording material, print quality may deteriorate.
As described above, the conventional ink jet recording apparatus has a problem in that there is a risk of ejection failure and deterioration in print quality due to mist.

  In order to solve the above problems, an image forming apparatus according to the present invention, based on image data, an ink jet head that ejects ink particles toward a recording material, and the ink particles eject from the ink jet head. An electrode provided so as to face the direction of the recording material in the vicinity of the ink mist generation portion generated at the time, and the generation state of the mist are predicted from the image data, and the generation of the mist is a predetermined amount or more. And an electrode control unit configured to make the electrode have the same polarity as the polarity of electricity in the mist when predicted.

  According to the present invention, the electrode control unit predicts the occurrence of mist from the image data, and when the occurrence of mist is predicted to be a predetermined amount or more, the electrode provided near the inkjet head is electrically connected to the mist. Use the same polarity as As a result, the mist repels in the direction of the recording material with respect to the electrode and lands on the recording material at or near the position where the ink particles land. Can eliminate the risk of causing Further, when the amount of mist generated is a predetermined amount or more, since the ejection of ink particles is also a predetermined amount or more, even if the mist is landed on the recording material at or near the position where the ink particles land, the mist Is not conspicuous, and there is no possibility that the print quality will deteriorate.

FIG. 3 is a schematic side view of the image forming apparatus in a state where the polarity of a pair of electrodes is the same as the polarity of mist. FIG. 2 is a schematic plan view of FIG. 1. It is explanatory drawing which showed the discharge process of the ink particle, and the production | generation process of mist. It is a hardware block diagram. It is a functional block diagram. It is the flowchart which showed the operation | movement to the setting of the polarity of an electrode. It is the typical side view which showed the state which made the polarity of the electrode the polarity opposite to the polarity of mist. It is explanatory drawing which showed typically the behavior of the mist according to the polarity of an electrode, (a) when the polarity of an electrode and a mist is made different, (b) is the case where the polarity of an electrode and a mist is matched. Each one is shown. FIG. 4 is a partial plan view of a document illustrating the ratio of an image portion to an arbitrary area of the document, where (a) illustrates a case where the document is divided into a plurality of belt-shaped regions, and (b) illustrates a document divided into a plurality of square shapes. Each case is shown. It is a top view of a manuscript (an example). 11 is a time chart showing a change in polarity of an electrode when the original shown in FIG. 10 is printed. FIG. 3 is a schematic side view of an image forming apparatus in a state where one electrode has a positive polarity and the other electrode has a negative polarity. It is the typical top view which showed the modification of the electrode (the electrode is subdivided in the longitudinal direction). It is the typical top view which showed the modification (one electrode) of the electrode.

Embodiments of an image forming apparatus according to the present invention will be described below.
<Embodiment 1>
<< Device configuration >>
FIG. 1 is a schematic side view showing a mechanical configuration of an inkjet image forming apparatus. FIG. 2 is a schematic plan view of FIG.
As shown in FIGS. 1 and 2, the image forming apparatus according to the first embodiment includes an inkjet head unit 1, a transport belt unit 2, an electrode 3, and a control unit (FIG. 4).

The inkjet head unit 1 includes an inkjet head 11 and a carriage unit.
The inkjet head 11 is a piezo-type or thermal-type inkjet head 11 and can eject ink particles D toward a sheet P as an example of a recording material based on image data obtained by converting a document into data. Composed.

  The piezoelectric inkjet head includes a piezoelectric element 14 (FIG. 4) that reduces the volume of the liquid chamber when energized. Then, pressure is applied to the ink filled in the liquid chamber by energizing the piezoelectric element 14 to reduce the volume of the liquid chamber. Thereby, the ink particles D are ejected onto the external paper P through the nozzles.

  On the other hand, the thermal inkjet head includes a heater 15 (FIG. 4) that generates heat when energized. When the heater 15 is energized with ink filled in the liquid chamber, bubbles are generated on the heater surface and pressure is applied to the ink. Thereby, the ink particles D are ejected onto the external paper P through the nozzles.

Here, an ink particle D ejection process and a mist M generation process will be described with reference to FIG.
The ink before ejection of the ink particles D forms a meniscus in the nozzle 11a (FIG. 3A).
When the ejection operation of the ink particle D is started, the ink is gradually pushed out from the nozzle 11a (FIG. 3B).
During ejection of the ink particles D, the ink pushed out from the nozzle 11a becomes elongated (FIG. 3C). The elongated ink at the stage of FIG. 3C is ejected mainly as ink particles D. At this time, the rear part of the elongated ink is separated and mist M is generated. The ink in the nozzle 11a immediately after the ejection of the ink particles D forms a meniscus again.

  The carriage unit is configured to be reciprocally movable in a direction (main scanning direction) perpendicular to the sheet conveyance direction by a carriage movement motor 12 and the carriage movement motor 12, and supports the inkjet head 11. A carriage 13.

The conveyor belt unit 2 includes a conveyor belt motor 21, a roller unit, a conveyor belt 24, and a charging roller 25.
The conveyance belt motor 21 is electrically connected to a conveyance belt motor drive unit 910 described later, and a motor shaft is rotated by a pulse signal from the conveyance belt motor drive unit 910.

The roller section includes a driving roller 22 that rotates in conjunction with the motor shaft of the conveyor belt motor 21, and a driven roller 23 that is provided to face the driving roller 22.
The conveyor belt 24 is configured such that the belt surface can be charged, and is rotatably stretched around a roller portion.

  The charging roller 25 is a conductive rubber roller, and is electrically connected to a charging roller control unit 911 described later, and is provided so as to rotate with the rotation of the conveyance belt 24. The charging roller 25 is charged with a DC voltage or a DC voltage superimposed with an AC voltage by the charging roller control unit 911, so that the surface of the conveyor belt 24 is charged to the positive electrode or the negative electrode, and the electrostatic adsorption force is increased. generate.

In the conveyor belt unit 2 configured as described above, the motor shaft intermittently rotates, whereby the conveyor belt 24 laid over the roller unit intermittently rotates, and the charging roller 25 makes the surface of the conveyor belt 24, for example, a negative electrode. By charging, a negative electrostatic attraction force is generated on the surface of the conveyor belt 24. As a result, the paper P moves intermittently while being attracted to the surface of the transport belt 24. At this time, the surface of the paper P and the mist M are negatively charged.
In this way, the transport belt unit 2 imparts the polarity of the negative electrode to the ink mist M generated when the ink particles D are ejected from the inkjet head 11.

  In the present embodiment, the electrostatic adsorption type conveyor belt unit 2 is exemplified as the one that causes the mist M to be negatively charged. However, the present invention is not limited to this. That is, it is possible to attract or repel the electrode 3 by using a negatively charged anionic ink or a positively charged cationic ink. Therefore, a component that causes the mist M to be charged from the outside, such as the conveyor belt unit 2, is not necessarily required.

The electrodes 3 are a pair of chargeable plate-like members that are electrically connected to the electrode charge control unit 913, extending in the main scanning direction along the inkjet head 11 with the inkjet head 11 interposed therebetween, and The ink particles D are stretched over the moving ballistic side. Thus, the electrode 3 is provided in the direction of the paper P near the mist M generating portion.
Note that the main scanning direction is a direction orthogonal to the sheet conveyance direction (sub-scanning direction) in FIG.

  Next, the hardware configuration of the control unit 9 will be described with reference to the hardware configuration diagram shown in FIG.

  The hardware configuration of the control unit 9 includes a CPU (Central Processing Unit) 901, a ROM (Read Only Memory) 902, and a RAM (Random Access Memory) 903 as shown in FIG. Furthermore, it has NVRAM (Non Volatile RAM) 904, ASIC (Application Specific Integrated Circuit) 905, I / O 906, and host I / F 907. Further, a head drive control unit 908, a head driver 909, a conveyance belt motor drive unit 910, a charging roller control unit 911, an electrode charge control unit 913, and a carriage movement motor drive unit 914 are provided.

  The CPU 901 processes / calculates data according to a program recorded in a ROM 902 to be described later, and controls each operation of the transport belt unit 2, the inkjet head 11, the electrodes, and the like.

The ROM 902 stores programs executed by the CPU 901 and fixed data.
The RAM 903 is used as a development memory for program development, data development, and memory printing.
The NVRAM 904 records data that needs to be retained even when the image forming apparatus is turned off, such as printer mode setting information.

The ASIC 905 processes various signal processing on image data, image processing for performing rearrangement, and other input / output signals for controlling the entire apparatus.
The I / O 906 receives detection signals from various sensors such as a temperature / humidity sensor S that detects temperature and humidity and a paper sensor that detects the paper P.

  The host I / F 907 is an interface for transmitting and receiving print data including image data from the host side such as an information processing apparatus such as a personal computer and an image reading apparatus such as an image scanner via a cable or a network.

The head drive control unit 908 includes a ROM that stores drive waveform (drive signal) pattern data, and a waveform generation circuit and amplifier that includes a D / A converter that performs D / A conversion on drive waveform data read from the ROM. And a drive waveform generation circuit including the above.
Upon receiving the print raster data, the head drive control unit 908 sends the raster data to the head driver 909 as serial data in synchronization with the clock signal, and sends a latch signal to the head driver 909 at a predetermined timing.

  The head driver 909 includes a shift register that inputs a clock signal from the head drive control unit 908 and serial data that is image data, and a latch circuit that latches a register value of the shift register using a latch signal from the head drive control unit 908. . Furthermore, a level shifter for changing the level of the output value of the latch circuit, an analog switch array whose on / off is controlled by the level shifter, and the like are provided.

  The head driver 909 selectively energizes the piezoelectric elements 14 and the heaters 15 of the inkjet head 11 by selectively turning on / off the analog switch array to control a required drive waveform included in the drive waveform. As a result, the ink particles D are discharged to the outside. An image based on the print raster data is printed on the paper P by continuous and intermittent ejection of the ink particles D.

The conveyor belt motor drive unit 910 outputs a pulse signal for driving the conveyor belt motor 21 based on a control command from the CPU 901.
Based on a control command from the CPU 901, the charging roller control unit 911 outputs to the charging roller 25 a DC voltage or a DC voltage superposed with an AC voltage. Note that the charging roller controller 911 in the present embodiment applies a negative voltage side to the charging roller 25 so that the surface of the transport belt 24 is charged to the negative electrode.

The electrode charging control unit 913 outputs a DC voltage or a voltage obtained by superimposing an AC voltage on the DC voltage to the electrode 3 based on a control command from the CPU 901. Note that the electrode charge control unit 913 in this embodiment appropriately applies the negative electrode side or the positive electrode side of the voltage to the electrode 3 so that the surface of the electrode 3 is charged to the negative electrode or the positive electrode. The switching of the polarity of the electrode 3 will be described later.
The carriage movement motor drive unit 914 outputs power or a pulse signal for driving the carriage movement motor 12 based on a control command from the CPU 901.

Next, the functional configuration of the image forming apparatus according to the first embodiment will be described with reference to the functional configuration diagram of FIG.
The image forming apparatus according to this embodiment further includes a transmission / reception unit 950, an input reception unit 951, a mechanism control unit 952, and an electrode control unit 953.
These configurations are based on hardware from the control unit 9 (conveyor belt motor drive unit 910, etc.) and a mechanism unit electrically connected to the hardware (in accordance with a command from the CPU 901 according to a program recorded in the ROM 902). This is realized by operating the conveyor belt motor 21 and the like.

The transmission / reception unit 950 uses the host I / F 907 to receive image data from an image reading apparatus such as an image scanner and an information processing apparatus such as a personal computer via a communication network, and transmit various types of information about the image forming apparatus. To do.
The input receiving unit 951 receives various information input by the user from the operation panel OP.
The mechanism control unit 952 performs operation control of each mechanism unit (inkjet head 11, transport belt unit 2, carriage unit, etc.).

  The electrode control unit 953 includes an image region selection unit 954 and a mist occurrence prediction unit 955.

  Based on the image data, the image area selection unit 954 calculates the ratio of the image portion that ejects the ink particles D for each arbitrary area of the document, and the ratio is a predetermined area or more and the ratio is less than the predetermined value. Sort into areas.

The above-mentioned arbitrary areas are for the same areas set arbitrarily.
For example, in FIG. 9A, a rectangular area in which the length of the original in the main scanning direction is a horizontal width and the arbitrary length of the original in the sub-scanning direction is a vertical width is used as the above-described selection criterion. The thing is illustrated.
In FIG. 9B, a square area having a width equal to one-eighth of the length of the document in the main scanning direction as a horizontal width and a vertical width equal to the horizontal width is used as the above-described selection criterion. This is an example.

  The mist occurrence prediction unit 955 predicts the region where the above-described ratio is greater than or equal to the predetermined value as the occurrence of mist M is greater than or equal to the predetermined amount, and predicts the region where the ratio is less than the predetermined value as the occurrence of mist M is less than the predetermined amount. .

  And when this electrode control part 953 estimates that generation | occurrence | production of mist M is more than predetermined amount, it makes the electrode 3 the same polarity as the polarity of the electricity tinged with mist M, and generation | occurrence | production of mist M is estimated to be less than predetermined amount. In this case, the polarity of the electrode 3 is opposite to the polarity of the electricity charged in the mist M.

  In the present embodiment, since the mist M is negatively charged, the electrode control unit 953 charges the electrode 3 to the negative electrode when the discharge amount per time of the ink particles D is equal to or greater than a predetermined value. . When the discharge amount per time of the ink particles D is less than a predetermined value, the electrode 3 is charged to the positive electrode.

<< Description of operation >>
Next, a series of operations of the image forming apparatus according to the first embodiment will be described based on the flowchart of FIG. 6 showing the operation up to the setting of the polarity of the electrode 3. Since the printing operation itself is known, the description of the operation is omitted.

First, the transmission / reception unit 950 reads image data from the host side such as an information processing apparatus such as a personal computer or an image reading apparatus such as an image scanner via the host I / F 907 (S1).
When the reading of the image data is completed, the image area selection unit 954 calculates the ratio of the image portion that ejects the ink particles D for each arbitrary area of the document based on the image data. For example, the ratio is 50% or more. Sort into areas and areas with a percentage of less than 50%. The mist occurrence prediction unit 955 predicts that the above-described ratio of 50% or more is an occurrence of mist M equal to or greater than a predetermined amount, and predicts an area of less than 50% that mist M is less than a predetermined amount. (S2).

  In the case of FIG. 9A in which the document is divided into a plurality of band-like areas, the ratio of the image portion is calculated for each of the divided band-like areas. And the area | region whose ratio is 50% or more is estimated that generation | occurrence | production of mist M is more than predetermined amount. An area of less than 50% is predicted to have less than a predetermined amount of mist M. Note that, in the band-shaped region illustrated in FIG. 9A, since the image portion is less than 50%, the occurrence of mist M is predicted to be less than a predetermined amount.

  The same applies to the case of FIG. 9B in which the document is divided into a plurality of squares. In addition, since the image area is less than 50% in the 1st to 5th square regions illustrated in FIG. 9B, the occurrence of mist M is predicted to be less than a predetermined amount. In the 6th to 8th square regions, the image portion is 50% or more, and therefore the occurrence of mist M is predicted to be a predetermined amount or more.

When the generation amount of mist M is predicted, the electrode control unit 953 determines whether or not the generation of mist M is greater than or equal to a predetermined amount with respect to the area to be printed from now on, that is, the image portion is in the area to be printed from now on. It is determined whether or not the ratio is 50% or more (S3).
When the ratio is 50% or more (S3Y), the electrode control unit 953 sets the polarity of the electrode 3 to the same polarity as the polarity of the mist M (S4).
When the ratio is less than 50% (S3N), the electrode control unit 953 sets the polarity of the electrode 3 to a polarity opposite to the polarity of the mist M (S5).

  Before or after the polarity of the electrode 3 is set, printing operations such as transport of the paper P by the transport belt 24 and movement of the carriage 13 supporting the inkjet head 11 are started. Then, after the polarity of the electrode 3 is set, the ink particle D ejection operation is started, and printing based on the image data is started (S6).

When the ejection operation of the ink particles D is started, mist M is generated along with the ejection of the ink particles D. The mist M is negatively charged via the conveying belt 24 charged on the negative electrode and the surface of the paper P.
The amount of mist M generated when the ratio is 50% or more is larger than the amount of mist M generated when the ratio is less than 50%. Therefore, even if it is intended to capture the floating mist M with the electrode 3 having the opposite polarity to that of the mist M, there may be a case where not all of the mist M can be captured.

  Therefore, when the ratio of the image portion in the area where printing is to be performed is 50% or more, the polarity of the electrode 3 is set to the same polarity as that of the mist M. As a result, as shown in FIGS. 1 and 8B, the mist M repels the electrode 3 in the paper direction and lands at or near the position where the ink particles D land on the paper.

  When the ratio is less than 50%, the polarity of the electrode 3 is set to the opposite polarity to that of the mist M. As a result, the mist M is attracted to the electrode 3 and landed on the electrode 3 as shown in FIGS.

  Next, the CPU 901 determines whether printing based on the image data has been completed (S7). If printing has not ended (S7N), the process returns to S3, and if printing has ended (S7Y), a series of operations ends.

As described above, in the case of FIG. 9A in which the document is divided into a plurality of band-like areas, the polarity of the electrode 3 is set for each of the divided band-like areas.
For example, in the case of the document illustrated in FIG. 10 (the black portion is the image portion and the white portion is the background of the paper P), the polarity change of the electrode 3 is as shown in the time chart of FIG.

That is, since the ratio of the image portion of each band-like area in the section a of the document and each band-shaped area in the section c of the document is 50% or more, the polarity of the electrode 3 is the same as the polarity of the mist M. A voltage is applied to the electrode 3 so as to have the same negative electrode.
In the individual band-like areas in the section b of the document, since the ratio of the image portion is less than 50%, a voltage is applied to the electrode 3 so that the polarity of the electrode 3 is a positive polarity opposite to the polarity of the mist M. .

<< Effect >>
As described above, in the image forming apparatus according to the first embodiment, when the electrode control unit 953 predicts the occurrence state of the mist M from the image data and predicts the occurrence of the mist M to be a predetermined amount or more, the electrode 3 The polarity is the same as the polarity of electricity on the mist M. As a result, a force toward the paper acts on the mist M, and the mist M lands on the paper at or near the position where the ink particles D land. Can eliminate the risk of causing

  Further, when the generation of the mist M is a predetermined amount or more, since the ejection of the ink particles D is also a predetermined amount or more, the mist M has landed on or near the position where the ink particles D land on the paper. However, the mist M does not stand out, and there is no possibility that the print quality is deteriorated.

In addition, when the generation of mist M is predicted to be less than a predetermined amount, the electrode control unit 953 sets the electrode 3 provided near the inkjet head 11 to a polarity opposite to the polarity of the electricity charged in the mist M. Thereby, since the mist M is attracted to the electrode 3 and landed on the electrode 3, the possibility that the mist M adheres to the nozzle surface and causes discharge failure can be eliminated.
Furthermore, since the mist M does not land on the paper P, there is no possibility that the print quality will deteriorate.
Further, the conventional ink jet recording apparatus is provided with a mist receiver and a mist collecting mechanism because a large amount of mist M collects at the electrode 3 and drains from the electrode 3 at a time. On the other hand, according to the image forming apparatus according to the present embodiment, a large amount of mist M is not collected at once on the electrode 3, so that the above-described mist receiving and mist collection mechanism, which is a countermeasure against dripping, is unnecessary. Can be expected to do.

<Embodiment 2>
The electrode control unit 953 according to the first embodiment described above predicts the occurrence state of the mist M for each arbitrary region of the document, and the electrode 3 is set for each arbitrary region of the document according to the generation state of the mist M. The polarity was set.
Instead, the electrode control unit according to the second embodiment predicts the discharge amount of the ink particles D per arbitrary time, and the electrode 3 every arbitrary time according to the generation state of the mist M. Set the polarity.

  That is, since the moving speed of the carriage 13 in the main scanning direction is a constant speed, the time required for each time that the inkjet head 11 scans the paper P in the main scanning direction is constant. The electrode control unit according to the second embodiment divides the required time for each desired time interval, and predicts the ejection amount of the ink particles D for each divided time from the image data.

  According to the second embodiment, the mist M is adsorbed to the electrode 3 or repelled by the electrode 3 (the landing of the mist M on the paper P) more efficiently than the first embodiment. ) Can be executed.

<Embodiment 3>
In addition, when the electrode control unit 953 according to the first embodiment described above determines that the generation of the mist M is less than the predetermined amount, the pair of electrodes 3 is set to have a polarity opposite to the polarity of the electricity charged in the mist M. .
Instead, when the electrode control unit according to the third embodiment determines that the generation of the mist M is less than the predetermined amount, the one electrode 3 is set to the same polarity as the polarity of the electricity charged in the mist M, The other electrode 3 is set to a polarity opposite to the polarity of electricity charged to the mist M. When it is determined that the amount of mist M generated is equal to or greater than a predetermined amount, the pair of electrodes 3 are set to have the same polarity as the polarity of electricity on the mist M, as in the first embodiment.

Here, FIG. 12 shows a schematic side view of the image forming apparatus in a state where the polarity of one electrode 3 is a negative electrode and the other electrode 3 is a positive electrode when the generation of mist M is less than a predetermined amount.
The electrode control unit controls the polarity of the electrode 3 in this manner, so that the mist M repels the one electrode 3 and is simultaneously attracted to the other electrode 3. Thereby, the mist M floating between the paper P and the inkjet head 11 is landed on the other electrode 3 charged to the positive electrode.

  According to the third embodiment, when the generation of mist M is less than a predetermined amount, the force toward the sheet and the force toward one electrode 3 are applied to the mist M floating between the sheet P and the inkjet head 11. By applying simultaneously, the improvement of the capture | acquisition of mist M can be anticipated.

<Embodiment 4>
The electrode control unit according to the fourth embodiment sets the electrode 3 to the same polarity as the polarity of electricity on the mist M only when printing the image portion of the same color or substantially the same color with respect to the color of the paper P. In this example, the mist M is landed on the paper P.
Therefore, even if the occurrence of mist M in the image portion is predicted to be less than a predetermined amount, the polarity is the same as the polarity of electricity charged in mist M. Except for this control, the control is the same as in the first to third embodiments.

For example, for paper P of the same color as white, yellow, or yellow, for the image area near yellow or yellow, the electrode 3 is electrically connected to the mist M regardless of the amount of mist M generated. Use the same polarity as
Note that the color of the paper P is set via the operation panel OP of the image forming apparatus or via an information processing apparatus such as a personal computer or an image reading apparatus such as an image scanner via the host I / F 907. Configure to set on the host side. Alternatively, a color sensor for detecting the color of the paper P may be provided in the image forming apparatus so that the obtained color (color information) of the paper P is automatically set.
In addition, whether or not the color of the paper P and the color of a certain image area are the same color or substantially the same color is determined based on a threshold (based on a required width) based on the color of the paper P. ) Is set, and the threshold value is compared with the color information of a certain image area.

  According to the fourth embodiment, the landing of the mist M on the electrode 3 is reduced, and the maintenance frequency of the electrode 3 can be reduced.

<Embodiment 5>
The electrode control unit according to the fifth embodiment is an example in which the control of the electrode 3 is executed in consideration of the temperature and humidity information detected by the temperature / humidity sensor S.
For example, (1) an environment with a temperature of 10 ° C. and a humidity of 15%, (2) an environment with a temperature of 23 ° C. and a humidity of 50%, (3) an environment with a temperature of 27 ° C. and a humidity of 80%, As a result of evaluating the generation amount, the present inventor has confirmed that the generation amount of mist M is large in the order of the environment (1), the environment (2), and the environment (3).

  Therefore, if the electrode control unit according to the fifth embodiment determines that the environment in which a large amount of mist M is generated, for example, the control exemplified in the above-described first to fourth embodiments is performed. If it is determined that there is not, control of the polarity of the electrode 3 is stopped. Or if it judges that it is the environment where much mist M generate | occur | produces, the electrode 3 will be controlled so that the electric charge amount of an electrode surface may increase. The determination as to whether or not the environment (temperature and humidity information) in which a large amount of mist M is generated is made by setting the environment in which a large amount of mist M is generated in advance as a threshold value and the temperature and humidity detected by the temperature and humidity sensor S. Judge by comparing with information.

According to the fifth embodiment, it is possible to efficiently perform the adsorption of the mist M to the electrode 3 or the repulsion of the mist M by the electrode 3 (landing of the mist M onto the paper P).
Moreover, it becomes possible to improve energy saving by making it possible to pause the control of the polarity of the electrode 3.
In particular, the viscosity of the ink increases at low temperatures, and the ligament length of the ink particles D (the tail portion that comes with the ink particles D) becomes longer, and the amount of mist generated tends to increase. Since the viscosity of the ink tends to increase as compared with the humidity, the environment in which much mist M is generated may be determined only by the temperature.

<Embodiment 6>
The sixth embodiment is a modification of the electrode 3 as shown in FIGS.
As described above, the electrode 3 exemplified in the first embodiment and the like is a pair of electrodes provided so as to extend in a direction (main scanning direction) perpendicular to the sheet conveyance direction with the inkjet head 11 interposed therebetween. It consists of a plate-shaped member. Therefore, the area where printing will be performed from now on, for example, when it is necessary to change the polarity of the electrode 3 from the positive electrode to the negative electrode, the entire electrode is changed from the positive electrode to the negative electrode, which is extremely suitable from the viewpoint of energy saving. It is hard to say that it is a simple structure.

Therefore, as shown in FIG. 13, a pair of electrode groups 32 in which a plurality of electrodes 3 are arranged linearly are provided so as to extend in the main scanning direction with the inkjet head 11 interposed therebetween. Each electrode 3 is electrically connected to an electrode charging controller 913.
The electrode control unit according to the sixth embodiment, for example, when the region where printing is to be performed needs to change the polarity of the electrode 3 from the positive electrode to the negative electrode, for the electrode 3 corresponding to the region, Control to change from positive electrode to negative electrode is executed.

According to the sixth embodiment, by using a plurality of electrodes 3 and applying individual control to each of the electrodes 3, it is possible to more efficiently mist the electrodes 3 as compared with the first embodiment. The adsorption of M or the repulsion of the mist M by the electrode 3 (landing of the mist M on the paper P) can be performed.
Further, when the width of the paper P is narrower than the electrode width, it is possible to improve energy saving by not applying a voltage to the electrode 3 through which the paper P does not pass.

  FIG. 14 shows an example in which the electrode 3 is installed only on the upstream side in the sub-scanning direction from the position of the inkjet head 11. If it is difficult to arrange the electrodes 3 with the recording head sandwiched due to the configuration of the image forming apparatus, or if it is desired to reduce the production cost of the image forming apparatus, the number of electrodes 3 to be installed can be reduced. is there. In this case, the polarity of the electrode 3 can be controlled by an electrode control unit other than the third embodiment.

  The image forming apparatus according to the present embodiment has been described above. However, the above-described embodiment shows an example of a preferred embodiment of the present invention, and the present invention is not limited thereto. Various modifications are possible.

  For example, the image forming apparatus according to the present embodiment exemplifies a so-called serial method in which the inkjet head 11 moves in the main scanning direction to perform printing. However, printing is performed with the inkjet head 11 fixed at a fixed position. The so-called line head method may be used.

  Further, in the present embodiment, the electrode 3 is illustrated as spanning in the main scanning direction, but the electrode 3 may be directly attached to the inkjet head 11 or the carriage 13.

In this embodiment, the image forming apparatus is exemplified. However, an image forming method in which ink mist generated when ink droplets are ejected from an inkjet head based on image data is processed by an electrode may be used. The processing process includes a prediction process for predicting the occurrence of mist from the image data, and when it is determined that the generation of mist by the prediction process is greater than or equal to a predetermined amount, the electrode is set to the same polarity as the polarity of electricity on the mist. And a second polarity control step of setting the electrode to a polarity opposite to the polarity of the electricity on the mist when it is determined that the occurrence of mist by the prediction step is less than a predetermined amount.
Furthermore, when a plurality of electrodes are provided and it is determined that the occurrence of mist in the prediction process is less than a predetermined amount, the second polarity control process replaces some of the electrodes with electric power charged with mist. The polarity may be opposite to the polarity, and the remaining electrodes may be in the third polarity control step in which the polarity of the electricity is the same as the polarity of the mist.

11 Inkjet head 2 Conveying belt section (charging section)
3 Electrode 953 Electrode control unit 954 Image area selection unit 955 Mist generation prediction unit D Ink grain M Mist S Temperature / humidity sensor P Paper (recording material)

Japanese Patent No. 2846082

Claims (7)

An ink jet head that ejects ink particles toward a recording material based on image data;
An electrode provided so as to face the direction of the recording material in the vicinity of the ink mist generating portion generated when the ink particles are ejected from the ink jet head;
An electrode control unit that predicts the occurrence state of the mist from the image data and sets the electrode to the same polarity as the polarity of electricity in the mist when the occurrence of the mist is predicted to be a predetermined amount or more. An image forming apparatus. The electrode control unit
Based on the image data, the ratio of the image portion that ejects the ink particles is calculated for each arbitrary area of the document that is the source of the image data, and the ratio is equal to or greater than a predetermined value. An image region sorting unit for sorting into regions less than the value;
The image forming apparatus according to claim 1, further comprising: a mist generation prediction unit that predicts that the mist generation is a predetermined amount or more in an area where the ratio is a predetermined value or more. The electrode control unit always sets the electrode to the same polarity as the polarity of the electricity on the mist when printing an image region of the same color or substantially the same color as the color of the recording material. The image forming apparatus according to claim 1, wherein: The electrode control unit predicts an ejection amount per arbitrary time of the ink particles from the image data, and when the ejection amount per arbitrary time of the ink particles is a predetermined value or more, the electrode control unit The image forming apparatus according to claim 1, wherein the occurrence is predicted to be a predetermined amount or more. It has a temperature and humidity sensor that detects temperature and humidity.
5. The image forming apparatus according to claim 1, wherein the electrode control unit executes control of the electrode in consideration of temperature and humidity information detected by the temperature and humidity sensor. 6. . A plurality of the electrodes are provided,
When it is predicted that the occurrence of the mist is less than a predetermined amount, the electrode control unit sets some of the electrodes to have a polarity opposite to the polarity of the electricity on the mist, and sets the remaining electrodes to the The image forming apparatus according to claim 1, wherein the polarity is the same as the polarity of electricity in the mist. An image forming method in which ink mist generated when ink particles are ejected from an inkjet head based on image data is processed by an electrode,
A prediction step of predicting the occurrence of the mist from the image data;
An image forming method comprising: a polarity control step for setting the electrode to have the same polarity as the polarity of electricity on the mist when the generation of the mist in the prediction step is predicted to be a predetermined amount or more. .

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