JP2014080012A - Image formation device, image formation system, image formation method - Google Patents

Abstract

Provided is an image forming apparatus capable of preventing ink particles from being divided into a plurality of mists when ejected to a region having a high surface potential of a recording medium.
A surface potential measurement unit 653 that measures the surface potential of a sheet, a determination unit 654 that determines the size at which ink particles break up based on a measurement value by a surface potential measurement unit 653, and a determination unit 654 A data processing unit 655 that generates print data that avoids the use of the determined size of ink particles.
[Selection] Figure 4

Description

  The present invention relates to an inkjet image forming apparatus, an image forming system, and an image forming method for forming an image by landing ink particles on a recording medium while conveying the recording medium.

  In an inkjet image forming apparatus that forms an image by landing ink particles on a recording medium while the recording medium is being transported, examples of methods for transporting the recording medium include the following.

  Utilizing a method of conveying a recording medium using a conveying roller and a supporting part that supports the recording medium (hereinafter referred to as “conveying roller method”), and an electrostatic adsorption phenomenon caused by charging a conveying belt, There is a method in which a recording medium is conveyed while being in close contact with a conveying belt (hereinafter referred to as “conveying belt method”). In particular, the conveyor belt system is known as means for alternately changing electric charges using an AC bias (see, for example, Patent Document 1).

  However, in the former transport roller system, electric charges are generated on the surface of the recording medium due to friction between the recording medium and the support component. In the latter conveyance belt method, electric charges are generated on the surface of the recording medium due to the charging of the conveyance belt.

  The amount of charge generated on the surface of the recording medium (charge amount) varies depending on the type of recording medium, the environment during operation of the image forming apparatus, and the like.

  In addition, the amount of charge is often different depending on the location in the recording medium, and a region where the amount of charge is locally higher than other regions, that is, compared with other regions. A region having a high surface potential may occur locally.

  On the other hand, the ink jet type image forming apparatus ejects ink particles of different sizes, and varies the ratio of the area of the ink particles landed on the recording medium and the area of the background of the recording medium, A so-called area gradation method that represents a pseudo halftone is employed. Hereinafter, the size of the ink particles is referred to as “ink size”.

  From the above, it is possible that small ink particles are ejected to an area where the surface potential of the recording medium is high. Particularly in such a case, the ink particles may be divided into a plurality of mists.

  Here, with reference to FIG. 11, the process of ink particle splitting will be described in detail by taking an example of a conveyor belt system using an AC bias.

  The ink particles P (FIG. 11A) ejected from the nozzles N toward the recording medium S1 are recorded below the ink particles P as they approach the surface of the recording medium S1 having electric charges. Charges opposite to those on the surface of the medium S1 are attracted. Conversely, the same charge as that of the surface of the recording medium S1 is attracted to the upper part of the ink particle P (FIG. 11B).

  When the surface potential of the recording medium S1 is high, as the ink particles P approach the target landing position on the recording medium S1, the bias of the charge in the ink increases. When the deviation exceeds a certain value, the ink particle P1 having a charge opposite to that near the landing position of the recording medium S1 and the ink particle P2 having the same polarity charge are split into mist. (FIG. 11C).

  After the mist formation, the ink particle P1 having a charge opposite to the target position on the recording medium is landed on the target landing position on the recording medium, but the ink particle P2 having the same polarity charge is Depending on the size, the repulsive force generated by the electric charge causes the ball to be repelled from the target landing position. The ink particle P2 bounced from the target landing position is attracted and landed on a region having a reverse charge generated at a position slightly away on the recording medium S1 (FIG. 11D).

  In addition, when the discharge interval of small ink particles is short, that is, when the drive frequency of the recording head is high, mist is more likely to occur. The reason for this is that when the drive frequency of the recording head is high, the meniscus of the ink in the nozzle N becomes unstable. This is because if the ink particles are ejected from one to the next in the unstable state, the state of the ink particles becomes unstable and easily affected by disturbance.

  As described above, when the ink particles become mist, there is a problem that the image quality may be deteriorated or the recording medium may be soiled. As described above, this problem is likely to occur particularly when ejecting small ink particles in a region of the recording medium having a higher surface potential compared to other regions.

  In order to solve the above-described problem, an image forming apparatus according to the present invention includes a data processing unit that converts image data into print data based on an area gradation method, and the print processed by the data processing unit Based on the recording data, ink particles are ejected from the recording head toward the recording medium facing the recording head, and the recording medium is moved relative to the recording head. In an image forming apparatus that forms an image on a medium, a surface potential measurement unit that measures a surface potential of the recording medium, and a size at which the ink particles break up are determined based on a measurement value by the surface potential measurement unit And the data processing unit generates the printing data that avoids the use of the ink particles having the size determined by the determination unit.

  According to the present invention, since the small ink particles that may break up are not ejected in the region where the surface potential of the recording medium is high, the possibility of misting the ink particles is eliminated, the image quality is deteriorated, It can be expected to avoid the possibility of soiling the recording medium.

1 is a schematic diagram illustrating an example of an inkjet image forming apparatus according to an exemplary embodiment. 1 is a schematic longitudinal sectional view showing a configuration of a piezo-type recording head according to an embodiment. It is a hardware block diagram concerning this Embodiment. It is a functional block diagram concerning this Embodiment. FIG. 5 is a diagram illustrating an example of a relationship between a surface potential of a sheet and an ink size to be misted. 6 is a flowchart showing processing related to generation of print data according to the surface potential of the paper according to the exemplary embodiment. FIG. 5 is a schematic diagram showing the relationship between ink size change and area gradation processing in dots in Embodiment 1. FIG. 10 is a schematic diagram showing the relationship between ink size change and area gradation processing in dots in Embodiment 2. FIG. 10 is a schematic diagram showing the relationship between ink size change and area gradation processing in dots in Embodiment 3. FIG. 10 is a conceptual diagram of an image forming system in a fourth embodiment. It is explanatory drawing which showed the process in which the particle | grains of an ink are divided. FIG. 5 is a diagram showing a relationship between a drive frequency of a recording head and a surface potential of a sheet at the time of mist formation. FIG. 10 is a functional configuration diagram of an image forming apparatus according to a sixth embodiment. It is the schematic diagram which showed that the image formed with the particle | grains of the magnitude | size determined by the determination part was decomposed | disassembled into the frequency | count of scanning. It is the schematic diagram which showed that the image formed with the particle | grains of the magnitude | size determined by the determination part was decomposed | disassembled into the frequency | count of scanning. 14 is a flowchart illustrating a series of operations of the image forming apparatus according to the sixth embodiment. FIG. 10 is a functional configuration diagram according to a seventh embodiment; FIG. 5 is a schematic diagram showing dots before and after a change in a drive waveform of a voltage for driving a recording head. FIG. 6 is a diagram showing before and after a change of a drive waveform of a voltage for driving a recording head. FIG. 5 is a schematic diagram showing dots before and after a change in a drive waveform of a voltage for driving a recording head. FIG. 6 is a diagram showing before and after a change of a drive waveform of a voltage for driving a recording head.

An embodiment of an image forming apparatus according to the present invention will be described.
<Embodiment 1>
<< Device configuration >>
FIG. 1 is a schematic diagram illustrating an example of an inkjet image forming apparatus A. As illustrated in FIG. This image forming apparatus exemplifies a so-called serial head system in which the recording head is reciprocated in a direction orthogonal to the sheet feeding direction in plan view.

  As shown in FIG. 1, the image forming apparatus A according to the first embodiment includes a paper feed unit 1, a paper transport unit 2, a recording head unit 3, a surface potential sensor 4, a paper discharge unit 5, and a control. Unit 6 (FIGS. 3 and 4).

  The paper feed unit 1 includes a paper feed tray 11 on which paper S as an example of a recording medium is stacked, and a paper feed roller that rotates and feeds the paper S while pressing against the uppermost paper S stacked on the paper feed tray 11. 12, a separation pad 13 that is provided so as to face the sheet feeding roller 12 and separates the fed sheet S into one sheet, and a guide plate 14 that guides the sheet S separated into one sheet.

  The paper transport unit 2 is stretched between the first roller 21 and the second roller 22, electrostatically attracts the paper, and rotates counterclockwise to transport the paper, and a paper feed unit 1. A counter roller 24 that transports the paper S sent from 1 with the transport belt 23 interposed therebetween, and a transport guide 25 that converts the paper S sent upward to a horizontal direction so as to follow the transport belt 23. Prepare. Further, a pressure roller 26 that guides the sheet while pressing the sheet against the conveyance belt 23 and a rotation that is driven by the rotation of the conveyance belt 23 are provided, and an AC bias output from an AC bias supply unit 611 described below is applied. A charging roller 27 that charges the surface of the conveying belt 23 and a guide member 28 provided on the back side of the conveying belt 23 at a position corresponding to a printing area by a recording head described later.

  The recording head unit 3 is mounted on a left and right side plate (not shown) similarly to the guide rod 31 and a guide rod 31 spanning a left and right side plate (not shown) (depth (front and rear) direction in FIG. 1). A stay 32 is provided, and a carriage 33 is provided so as to be slidable by rotation of a carriage motor (not shown) using the guide rod 31 and the stay 32 as a guide.

  Further, the recording head unit 3 is attached to the carriage, and is attached to the carriage 33 and the carriage 33 provided with a nozzle group for each color for ejecting ink particles of each color of yellow, cyan, magenta, and black. And a sub tank 35 for supplying ink of a color corresponding to the nozzle group. The sub tank 35 is supplemented with ink from the main tank of each color via the ink supply tube 36.

  Next, the recording head 34 will be described with reference to FIG. FIG. 2 is a schematic longitudinal sectional view showing the configuration of the piezo recording head 34.

  The recording head 34 includes a nozzle container 341, a vibration plate 342, and a piezoelectric element (piezo element) 343.

  The nozzle container 341 is provided with a nozzle N on the bottom surface of the container, and an ink flow path is formed so that the nozzle N and the sub tank 35 are connected. Note that a plurality of the nozzles N described above are provided in a straight line at a predetermined interval in a direction orthogonal to the paper transport direction in a plan view, and a plurality of nozzles N are provided at a predetermined interval in the paper transport direction. Yes.

  The vibration plate 342 is a thin plate-like member that is elastically deformed with a slight force, and is provided so as to cover the opened upper portion of the nozzle container 341 facing the nozzle N.

  The piezoelectric element 343 converts voltage into force, and one surface is fixed to the diaphragm 342 and the other surface opposite to the one surface is fixed to a fixing member.

  The piezoelectric recording head 34 applies a voltage to the piezoelectric element 343, whereby the piezoelectric element 343 is distorted and the volume of the liquid chamber formed by the nozzle container 341 and the vibration plate 342 is reduced. As a result, pressure is applied to the ink filled in the liquid chamber, and ink particles P are ejected through the nozzle N to a predetermined position of the paper S immediately below the nozzle N.

  Further, since the deformation amount of the piezoelectric element 343 changes according to the voltage applied to the piezoelectric element 343, the piezo-type recording head 34 controls the voltage applied to the piezoelectric element 343 based on print data to be described later. In this way, it is possible to eject a desired ink size. In FIG. 2, the ink particle P indicated by the solid line corresponds to the amount of displacement of the diaphragm 342 indicated by the solid line, and the ink particle P indicated by the two-dot chain line indicates the diaphragm indicated by the two-dot chain line. This corresponds to the displacement amount 342.

  The surface potential sensor 4 detects the amount of charge charged on the surface of the paper in a non-contact manner and outputs an analog signal of a DC voltage proportional to the amount. The surface potential sensor 4 detects at least the entire width of the sheet (in the direction orthogonal to the sheet conveyance direction) between the nozzle N and the charging roller 27 upstream of the nozzle N in the sheet conveyance direction. It is provided as possible. Further, the surface potential sensor 4 is provided such that the position of the paper S that is longer than the length of the paper and away from the upstream side in the transport direction is the detection position with the position of the nozzle N as a base point. As a result, the front end of the paper S (the downstream side in the transport direction of the paper S) is not positioned directly below the nozzle N before the surface potential of the rear end portion (the upstream side of the paper S in the transport direction) of the paper S is measured. It is like that.

  As shown in FIG. 1, the paper discharge unit 5 has a separation claw 51 for separating the paper S from the conveyance belt 23 and a pair of discharges that feed the paper S separated from the conveyance belt 23 by the separation claw 51 and feed it away. Paper rollers 52 and 53 and a paper discharge tray 54 for receiving the paper S sent out by the pair of paper discharge rollers 52 and 53 are provided.

  Next, the hardware configuration of the control unit 6 will be described with reference to the hardware configuration diagram shown in FIG.

  The hardware configuration of the control unit 6 includes a CPU (Central Processing Unit) 601, a ROM (Read Only Memory) 602, and a RAM (Random Access Memory) 603. Furthermore, it has NVRAM (Non Volatile RAM) 604, ASIC (Application Specific Integrated Circuit) 605, and host I / F 606. Further, the recording head driving unit 607, a head driver 608, a carriage driving unit 609, a conveyance belt driving unit 610, an AC bias supply unit 611, a surface potential sensor I / O 612, and a paper supply / discharge driving unit 613 are provided. . A control unit including a recording head driving unit 607, a head driver 608, a carriage driving unit 609, a conveyance belt driving unit 610, an AC bias supply unit 611, a surface potential sensor I / O 612, and a paper supply / discharge driving unit 613. Each component 6 is an electronic circuit.

  The CPU 601 processes and calculates data according to a program recorded in a ROM 602 described later, and controls each operation in the paper transport unit 2, the recording head unit 3, the paper discharge unit 5, and the like. Further, the ASIC 605 is controlled to generate print data based on the surface potential of the paper.

  The ROM 602 stores programs executed by the CPU 601 and fixed data. The ROM 602 records data representing the relationship between the surface potential (measured value) of the paper and the ink size that is misted by that potential. Details of this data will be described later.

  The RAM 603 is used as a development memory for program development, data development, and memory printing. Further, the value of the surface potential on the sheet S measured by a surface potential measuring unit 653 described later is recorded.

  The NVRAM 604 stores data that needs to be retained even when the image forming apparatus is turned off, such as printer mode setting information. Note that the above-described data representing the relationship between the surface potential (measured value) of the paper and the ink size to be misted by the potential may be recorded in the NVRAM 604 instead of the ROM 602.

  The ASIC 605 performs processing for converting image data into printing data based on the area gradation method, image processing such as enlargement or reduction of an image to be printed, and other processing based on a control command from the CPU 601. is there. In this embodiment, an example in which image processing or the like is performed using the ASIC 605 is illustrated, but image processing may be performed by middleware.

  The host I / F 606 receives image data from an image reading device such as an image scanner or an image pickup device such as a digital camera, image data from an information processing device such as a personal computer, or printing data from a cable or network. It is an interface for transmitting and receiving via

  The recording head drive unit 607 includes a ROM that stores pattern data of a drive waveform (drive signal), and a waveform generation circuit and amplifier that include a D / A converter that performs D / A conversion of drive waveform data read from the ROM. And a drive waveform generation circuit including the above.

  When receiving the print data, the recording head driving unit 607 sends the print data to the head driver 608 as serial data in synchronization with the clock signal, and sends a latch signal to the head driver 608 at a predetermined timing. .

  The head driver 608 includes a shift register that inputs a clock signal from the recording head driving unit 607 and serial data that is image data, and a latch circuit that latches a resist value of the shift register with a latch signal from the recording head driving unit 607. . 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 608 selectively energizes the piezoelectric element 343 of the recording head 34 with a required drive waveform included in the drive waveform by controlling on / off of the analog switch array. As a result, ink particles are ejected to the outside.

  Based on a control command from the CPU 601, the carriage drive unit 609 outputs a pulse signal for driving the carriage drive motor so that the movement of the carriage 33 is synchronized with the ink particle ejection operation by the head driver 608. .

  The conveyor belt drive unit 610 outputs a pulse signal for driving the conveyor belt motor based on a control command from the CPU 601.

  The AC bias supply unit 611 outputs an AC bias applied to the charging roller 27 based on a control command from the CPU 601.

  The surface potential sensor controller 612 receives an analog signal from the surface potential sensor 4 and converts the analog signal into a measured value of a digital signal.

  The paper feed / discharge drive unit 613 drives a paper feed unit motor that rotates the paper feed roller 12 and the paper discharge unit motor that rotates the pair of paper discharge rollers 52 and 53 based on a control command from the CPU 601. Outputs a pulse signal.

  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 functional configuration of the image forming apparatus according to the present embodiment includes a transmission / reception unit 650, an input reception unit 651, an operation control unit 652, a surface potential measurement unit 653, a determination unit 654, and a data processing unit 655.

  These configurations are based on the control command from the CPU 601 according to the program recorded in the ROM 602, and the hardware of the control unit 6 (recording head drive unit 607, ASIC 605, I / O 612 for surface potential sensor) and the hardware thereof. This is realized by operating a mechanical part electrically connected to the wear.

  The transmission / reception unit 650 uses the host I / F 606 to receive image data, printing data, and the like from the information processing apparatus via the communication network, and transmits various types of information from the image forming apparatus.

  The input receiving unit 651 receives various types of information input by the user from the operation panel 7 (FIG. 3).

  The operation control unit 652 performs operation control of each mechanism unit (the paper feeding unit 1, the paper transport unit 2, the recording head unit 3, and the like).

  The surface potential measurement unit 653 includes a surface potential sensor 4 and a surface potential sensor controller 612. When the sheet S passes the surface potential sensor 4, the sheet potential S on the sheet corresponds to one pixel on the image data. The surface potential is measured over the entire area of the paper S with the print area as the basic unit of the measurement range.

  Next, before describing the determination unit 654, a relationship (an example) between the surface potential of the paper S and the ink size to be mist will be described with reference to FIG.

  FIG. 5 shows that when the measured value by the surface potential measuring unit 653 is 100 V or more, ink particles having an ink size of approximately 2 pl (picoliter) or less are split and misted, and the measured value increases by 25 V each time. It shows that the ink size to be mist increased by 1 pl. It should be noted that the potential at which ink particles of a certain ink size break up and become mist varies depending on the type of ink. Further, as shown in FIG. 5, the ink size to be mist is not necessarily proportional to the surface potential of the paper.

  Data indicating the relationship between the surface potential of the paper S and the ink size to be misted by the potential as shown in FIG. 5 is prepared for each color ink and recorded in the ROM 602 or the NVRAM 604.

  The determination unit 654 compares the measured value (surface potential) recorded in the RAM 603 with data indicating the relationship between the surface potential of the paper S and the ink size to be misted by the potential, and the ink ejected from the nozzle N The size at which the grains of the ink break up, that is, the ink size to be mist is determined and output as determination information. This determination information is output for each measurement range (for each pixel on the image data).

  The determination by the determination unit 654 is performed for each ink of each color of yellow, cyan, magenta, and black (for each ink type), and is output as determination information.

  The data processing unit 655 converts image data such as a raster image or a vector image into print data for each color image of yellow, cyan, magenta, and black based on the area gradation method. The printing data is data for obtaining a pseudo halftone image by changing the ink size and changing the ratio of the area of the ink particles landed on the paper and the area of the paper background. Note that the printing data immediately after the conversion process is provisional data.

  Further, the data processing unit 655 according to the first embodiment uses the determination information from the determination unit 654 to determine whether or not the ink particles may break up in the temporary print data.

  When it is determined that the ink particles may be split, the use of the ink particles having the size determined by the determination unit 654 is avoided, and print data is generated again. This series of processing is performed on the print data for each color image of yellow, cyan, magenta, and black.

  In this way, the data processing unit 655 according to the first embodiment generates print data that avoids the use of ink particles having a size determined by the determination unit 654.

<< Description of operation >>
Next, FIG. 6 is a flowchart showing processing related to generation of printing data in accordance with the surface potential of the paper, and FIG. 7 is an explanatory diagram showing the relationship between ink size change and area gradation processing. A series of operations of the image forming apparatus according to the first embodiment will be described based on FIG.

  First, the input receiving unit 651 receives a print mode input by the user via the operation panel 7 (FIG. 3). In addition, the transmission / reception unit 650 receives image data from the outside (S1). Note that the high-quality print mode has many ink particles with small ink size, and there is a high risk of mist formation. Conversely, the high-speed print mode has many ink particles with large ink size and mist formation. The fear is lower than the high-quality print mode.

  The data processing unit 655 converts the image data received by the transmission / reception unit 650 into print data for each color image of yellow, cyan, magenta, and black based on the area gradation method. This print data is provisional print data (S2).

  The operation control unit 652 outputs the AC bias via the rotation of the conveyance belt 23 and the AC bias supply unit 611 via the paper conveyance unit 2. As a result, the surface of the conveyor belt 23 is charged via the charging roller 27 driven by the rotation of the conveyor belt 23.

  At this time, a positive voltage and a negative output are alternately repeated from the AC bias supply unit 611 to the charging roller 27, that is, an AC bias of alternating voltage is applied, and the charging voltage pattern in which the conveying belt 23 alternates. In other words, plus and minus are alternately charged in a band shape with a predetermined width in the sub-scanning direction that is the circumferential direction.

  The operation control unit 652 sends out the paper S stacked on the paper feed tray 11 via the paper feed unit 1. The paper S sent out by the paper supply unit 1 is electrostatically attracted to the transport belt 23 and moves in the sub-scanning direction by the rotational movement of the transport belt 23. During this movement, the sheet S passes through the surface potential sensor 4.

  When the sheet S passes through the surface potential sensor 4, the surface potential measurement unit 653 covers the entire area of the sheet S with the print area on the sheet S corresponding to one pixel on the image data as a basic unit of the measurement range. The surface potential is measured and recorded in the RAM 603 (S4).

  The determination unit 654 compares the measured value (surface potential) recorded in the RAM 603 with data indicating the relationship between the surface potential of the paper S and the ink size to be misted by the potential, and the size of the ink particles is large. Is determined and output as determination information. The determination by the determination unit 654 is performed for each pixel of the image data and for each type of ink, and is output as determination information.

  The data processing unit 655 determines whether or not the ink particles may break up in the temporary printing data using the determination information from the determination unit 654 (S5).

  In the case where there is a possibility that the ink particles are disrupted in the temporary printing data (S5; Yes), the data processing unit 655 avoids the use of the ink particles of the size determined by the determination unit 654, The print data is generated again. This series of processing is performed on the print data for each color image.

  For example, as illustrated in FIG. 7, the ink size of the ink particles used for printing is set to 3 pl, 9 pl, and 27 pl, and the determination unit 654 displays “3 pl or less ink particles for a certain print area. In the case where 3 pl or less ink particles are used for the region in the provisional printing data, the data processing unit 655 according to the first embodiment outputs the 3 pl or less ink particles. Print data that avoids the use of is generated again.

  That is, the data processing unit 655 according to the first embodiment uses an ink particle having an ink size of 9 pl, and is equivalent to a halftone region (3 pl region in FIG. 7A) represented by an ink size of 3 pl. Print data is generated again so as to be a halftone area (a new 9 pl area in FIG. 7B) (S6). The new print data is set as formal print data (S7).

  In the case where there is no possibility that the ink particles break up in the temporary printing data (S5; No), the data processing unit 655 sets the temporary printing data as the formal printing data (S8, FIG. 7 ( a)).

  When the leading edge of the sheet S moves directly below the recording head 34, the operation control unit 652 switches the rotation of the transport belt 23 to intermittent rotation. Then, the operation of ejecting ink particles from the nozzle toward the paper facing the nozzle and the operation of moving the paper relative to the nozzle are started based on any of the above-described formal printing data. To do.

  That is, the operation control unit 652 drives the recording head 34 according to the printing data while moving the carriage 33, thereby ejecting ink particles onto the stopped paper S to print one line, After the sheet S is conveyed by a predetermined amount, the next line is printed. This printing operation is repeated until a printing end signal or a signal that the trailing edge of the paper S reaches the recording area is received.

  When the printing is finished, the operation control unit 652 cancels the intermittent rotation of the transport belt 23 and shifts to normal rotation. Then, the operation control unit 652 discharges the paper S to the paper discharge tray 54 via the paper discharge unit 5 (S9).

  The first embodiment exemplifies the case where the print data is generated again when there is a possibility that the ink particles may be split. However, the possibility that the ink particles may be split reaches a predetermined number. Then, the print data may be generated again. In this case, it is preferable that a predetermined number of print regions that are likely to break up the ink particles are adjacent.

<< Effect >>
According to the image forming apparatus according to the first embodiment, it is determined that the ink size is divided for a certain print area on the paper S, and there is a divided ink size in the area in the provisional print data. If it is determined, it is configured to generate print data anew while maintaining the halftone and avoiding the use of ink particles having a split ink size, and the print is executed using the new print data. Printing that can prevent mist generation and has little influence on image quality can be performed.

<Embodiment 2>
In the second embodiment, of the processing by the data processing unit 655 exemplified in the first embodiment, the processing (FIG. 6; S6) related to the generation of printing data that avoids the use of the ink particles of the split ink size is used. Another example is shown. Descriptions of other configurations common to the first embodiment are omitted.

<< Function of data processing section >>
A process related to generation of print data that avoids the use of ink particles having a split ink size by the data processing unit according to the second embodiment will be described with reference to FIG.

  As in the first embodiment, the data processing unit according to the second embodiment first processes the image data based on the area gradation method to generate provisional print data.

  Next, pattern matching is performed on the provisional print data using a matching pattern corresponding to the size determined by the determination unit.

  For example, the ink size of the ink particles used for printing is set to 3 pl, 9 pl, and 27 pl, and the determination unit 654 determines that “the ink particles of 3 pl or less are split” for a certain print area on the paper S. Is output to the provisional print data using the 3pl matching pattern (2 × 2 dots) shown in the left diagram of FIG. Pattern matching is performed on a).

  Since the 3 pl region in FIG. 8A is a region indicated by 6 × 6 dots, all of the regions match the 3 pl matching pattern.

  The data processing unit uses the conversion pattern associated with the matching pattern (the conversion pattern that avoids the use of ink particles of the size determined by the determination unit) to convert the matched area by pattern matching. Then, print data is generated.

  The conversion pattern is configured to obtain a halftone that is the same as or close to that of the matching pattern by the area gradation method.

  For example, in the case where the conversion pattern associated with the 3pl matching pattern has 9 pl dots at the two lower left and upper right positions of the 2 × 2 matrix as shown in the right figure of FIG. 8C. The 3 pl region in FIG. 8A is converted into FIG. 8B.

  The above-described collation pattern data and the conversion pattern data associated with the collation pattern are recorded in advance in the ROM 602 or the NVRAM 604 (FIG. 3).

<< Effect >>
The data processing unit according to the second embodiment performs pattern matching on the provisional print data using the ink size collation pattern determined by the determination unit, and converts the matching area by the pattern matching to the conversion pattern. Data for printing is generated by converting to. Therefore, similarly to the first embodiment, the image forming apparatus according to the second embodiment can prevent misting and can perform printing with less influence on image quality.

<Embodiment 3>
The third embodiment shows another example of the process (FIG. 6; S6) related to the generation of print data that avoids the use of ink particles having a split ink size, as in the second embodiment. Descriptions of other configurations common to the first embodiment are omitted.

<< Function of data processing section >>
With reference to FIG. 9, a description will be given of a process related to generation of print data that avoids the use of ink particles having a split ink size by the data processing unit according to the third embodiment.

  For example, the data processing unit according to the third embodiment sets the ink size of the ink particles used for printing to 3 pl, 9 pl, and 27 pl. When the determination information that “the ink particle of 3 pl or less is split” is output to the region having a high potential, and the ink particle of 3 pl or less is used for the region in the provisional print data (FIG. 9 ( a)) Printing data is generated by simply replacing ink particles of 3 pl or less with ink particles of a size that does not break, for example, 9 pl ink particles (FIG. 9B).

<< Effect >>
According to the data processing unit according to the third embodiment, compared with the first and second embodiments, the ink particle conversion process can be performed at a higher speed. Note that the processing by the data processing unit according to the third embodiment is highly effective particularly in a pattern with many lines and solids.

<Embodiment 4>
Although the above-described first to third embodiments exemplify an image forming apparatus, the fourth embodiment illustrates an image forming system.

  That is, as shown in FIG. 10, an image forming system A1 according to the fourth embodiment includes an information processing apparatus (for example, a personal computer) A2 and an image forming apparatus A3 connected to the information processing apparatus A2 so as to be capable of bidirectional communication. With.

  The information processing apparatus A2 side includes the above-described determination unit and data processing unit, and the image forming apparatus A3 side includes the above-described surface potential measurement unit.

  Since each of these configurations and effects are substantially the same as those described above, a detailed description thereof will be omitted.

<Embodiment 5>
The fifth embodiment exemplifies an image forming method.

  That is, in the image forming method according to the fifth embodiment, the image data is processed into printing data based on the area gradation method, and based on the printing data, the ink particles are directed toward the paper facing the nozzle. An image is formed on the paper by ejecting from the nozzle and moving the paper relative to the nozzle.

  Further, in the image forming method according to the fifth embodiment, the measurement step for measuring the surface potential of the paper and the size at which the ink particles ejected from the nozzles are divided are determined based on the measurement values acquired in the measurement step. A determination step and a generation step of generating printing data that avoids the use of ink particles having a size determined in the determination step.

  According to this image forming method, mist formation can be prevented and printing with less influence on image quality can be performed.

<Embodiment 6>
In Embodiment 6, a recording head that is driven at a required driving frequency is provided, and based on printing data, ink particles are ejected from the recording head toward a recording medium that faces the recording head, and In an image forming apparatus that forms an image on the recording medium by moving the recording medium relative to the recording head, a surface potential measuring unit that measures a surface potential of the recording medium, and the surface A determination unit that determines the size at which the ink particles are split based on a measurement value by the potential measurement unit, and converts the image data into the printing data based on an area gradation method, and the determination unit Using the determination information, a data processing unit that determines whether or not ink particles may break up in the printing data; and the data processing unit includes ink particles in the printing data. And a recording head drive control unit that executes image formation by reducing the drive frequency when it is determined that the image may be split.

  As described above, when ejecting small ink particles to a region where the surface potential of the paper S is high, the ink particles are divided into a plurality of mists, but when the ejection interval of the small ink particles is short, That is, when the driving frequency of the recording head (frequency at which the piezoelectric element 343 is driven) is high, it is more likely to be mist. The reason for this is that if the drive frequency of the recording head is high, the meniscus of the ink in the nozzle N becomes unstable. This is because if the ink particles are ejected from one to the next in the unstable state, the state of the ink particles becomes unstable and easily affected by disturbance.

  FIG. 12 shows the relationship between the drive frequency of the recording head and the surface potential of the paper when the 3 pl ink particles are misted.

  FIG. 12 shows an example of an ink having a proportional relationship between the recording head driving frequency and the sheet surface potential. For example, when the sheet surface potential is 100 V, the recording head driving frequency is about 20 KHz. It means that it has become a mist.

  The sixth embodiment is an example in which mist formation is avoided or reduced by lowering the drive frequency of the recording head when ejecting ink particles having the size determined by the determination unit 654.

  As shown in FIG. 13, the image forming apparatus according to the sixth embodiment includes a transmission / reception unit 650, an input reception unit 651, an operation control unit 652, a surface potential measurement unit 653, a determination unit 654, a data processing unit 655b, and a recording head drive. A control unit 656 is provided. Detailed descriptions of functional units that are substantially the same as the configurations exemplified in the other embodiments described above, such as the surface potential measurement unit 653 and the determination unit 654, are omitted.

  The data processing unit 655b converts the image data into the printing data based on the area gradation method and uses the determination information from the determination unit 654 to break up ink particles into the printing data. Determine whether or not.

  The recording head drive control unit 656 forms an image on the paper by reducing the drive frequency of the recording head when the data processing unit 655b determines that the ink particles may break up in the print data. The recording head drive control unit 656 is one function of the operation control of the recording head unit in the operation control of each mechanism unit by the operation control unit 652.

Specific examples of lowering the recording head drive frequency include the following.
(1) The carriage moving speed is decreased (the carriage motor is driven slower), and the recording head driving frequency is decreased in accordance with the carriage moving speed.
(2) An image formed by ink particles having a size determined by the determination unit 654 (an ink particle having a size to be mist) is increased by increasing the number of times the carriage is scanned. By disassembling the number of scans, the drive frequency of the recording head is substantially reduced.

  Here, a specific example of (2) will be described with reference to FIGS.

  FIG. 14A shows an example of an ejection pattern of ink particles ejected by one carriage scan. In this example, a plurality of ink particles having an ink size of 27 pl (picoliter), an ink particle having an ink size of 9 pl, and an ink particle having an ink size of 3 pl are ejected from the recording head in one carriage scan. Is assumed.

  When the ink particle having the size determined by the determination unit 654 is an ink particle having an ink size of 3 pl, the recording head drive control unit 656 scans an image portion formed by the ink particle having an ink size of 3 pl by the number of scans. Disassembled into In this example, the number of scans is two, and an image portion of 6 × 6 dots formed by ink particles having an ink size of 3 pl is decomposed into two, an odd number and an even number in the horizontal direction in FIG.

  In the first carriage scan, the recording head drive control unit 656 ejects 27 pl ink size ink particles, 9 pl ink size ink particles, and even-numbered 3 pl ink size ink particles. Control is performed (FIG. 14B).

  The recording head drive control unit 656 performs control so that ink particles having an odd size of 3 pl of ink size are ejected in the second carriage scan (FIG. 14C).

  Another example in which the image portion formed by the ink particles having the size determined by the determination unit 654 is decomposed into two is an example in which the image portion is decomposed into a checkered pattern. In this case, as shown in FIG. 15, the image portion of 6 × 6 dots formed by the ink particles of 3 pl ink size is decomposed into two checkered patterns with different pitches.

  The number of carriage scans is not limited to two. Further, the decomposition pattern of the image portion formed by the ink particles having the size determined by the determination unit 654 is not limited to the above-described pattern.

  A series of operations of the image forming apparatus according to the sixth embodiment will be described with reference to the flowchart of FIG.

  First, the input receiving unit 651 receives a print mode input by the user via the operation panel 7 (FIG. 3). In addition, the transmission / reception unit 650 receives image data from the outside (S11).

  The data processing unit 655b converts the image data received by the transmission / reception unit 650 into print data for each color image of yellow, cyan, magenta, and black based on the area gradation method (S12).

  The operation control unit 652 outputs the AC bias via the rotation of the conveyance belt 23 and the AC bias supply unit 611 via the paper conveyance unit 2. As a result, the surface of the conveyor belt 23 is charged via the charging roller 27 driven by the rotation of the conveyor belt 23.

  At this time, a positive voltage and a negative output are alternately repeated from the AC bias supply unit 611 to the charging roller 27, that is, an AC bias of alternating voltage is applied, and the charging voltage pattern in which the conveying belt 23 alternates. In other words, plus and minus are alternately charged in a band shape with a predetermined width in the sub-scanning direction that is the circumferential direction.

  The operation control unit 652 sends out the paper S stacked on the paper feed tray 11 via the paper feed unit 1. The paper S sent out by the paper supply unit 1 is electrostatically attracted to the transport belt 23 and moves in the sub-scanning direction by the rotational movement of the transport belt 23 (S13). During this movement, the sheet S passes through the surface potential sensor 4.

  When the sheet S passes through the surface potential sensor 4, the surface potential measurement unit 653 covers the entire area of the sheet S with the print area on the sheet S corresponding to one pixel on the image data as a basic unit of the measurement range. The surface potential is measured and recorded in the RAM 603 (S14).

  The determination unit 654 compares the measured value (surface potential) recorded in the RAM 603 with data indicating the relationship between the surface potential of the paper S and the ink size to be misted by the potential, and the size of the ink particles is large. Is determined and output as determination information. The determination by the determination unit 654 is performed for each pixel of the image data and for each type of ink, and is output as determination information.

  The data processing unit 655b uses the determination information from the determination unit 654 to determine whether or not ink particles may break up in the print data (S15).

  If there is a possibility that the ink particles may break up in the printing data (S15; Yes), as described above, the drive frequency of the recording head is lowered (S16), and printing is executed (S18).

  If there is no possibility that the ink particles will break up in the printing data (S15; No), the recording head drive frequency is set to normal (S17) and printing is executed (S18).

  According to the image forming apparatus according to the sixth embodiment, when it is determined that the ink size to be divided may be used for the print data, printing is executed with the drive frequency of the recording head lowered. As a result, the ink meniscus in the nozzle N is stabilized, and the ink particles that are not easily affected by the disturbance are ejected, so that it is possible to avoid or reduce the mist.

<Embodiment 7>
In the seventh embodiment, a recording head driven by a voltage having a required driving waveform is provided, and ink particles are ejected from the recording head toward a recording medium facing the recording head based on printing data. In addition, in an image forming apparatus that forms an image on the recording medium by moving the recording medium relative to the recording head, a surface potential measurement unit that measures the surface potential of the recording medium; A determination unit for determining a size at which the ink particles are split based on a measurement value by the surface potential measurement unit; and a process for converting the image data into the printing data based on an area gradation method, and the determination A data processing unit that determines whether ink particles may break up in the printing data using the determination information by the printing unit; and And a second recording head drive control unit configured to increase the height of the drive waveform and form an image on the recording medium when it is determined that there is a case where the grain of the cut is split. .

  The image forming apparatus according to the seventh embodiment is an example in which the wave height of the drive waveform of the voltage for driving the recording head is increased so that the size of the ink particles can be expected to avoid or reduce mist. .

  As shown in FIG. 17, the image forming apparatus according to the seventh embodiment includes a transmission / reception unit 650, an input reception unit 651, an operation control unit 652, a surface potential measurement unit 653, a determination unit 654, a data processing unit 655b, and a second processing unit. A recording head drive control unit 657 is provided. Detailed descriptions of functional units that are substantially the same as the configurations exemplified in the other embodiments described above, such as the surface potential measurement unit 653 and the determination unit 654, are omitted.

  When the data processing unit 655b determines that the ink particles may break up in the print data, the second recording head drive control unit 657 increases the peak of the driving waveform of the voltage for driving the recording head. An image is formed on a sheet. The second recording head drive control unit 657 is a function of the operation control of the recording head unit in the operation control of each mechanism unit by the operation control unit 652.

The following examples are given as specific examples of increasing the wave height of the drive waveform of the voltage for driving the recording head.
(1) Only the wave height of the drive waveform for ejecting the ink particles of the size determined by the determination unit 654 (ink particles of the size to be misted) is increased.

  Specific examples thereof will be described with reference to FIGS.

  FIG. 18A shows an example of an ejection pattern of ink particles ejected from the recording head. In this example, it is assumed that a plurality of ink particles having an ink size of 27 pl, ink particles having an ink size of 9 pl, and ink particles having an ink size of 3 pl are ejected from the recording head.

  FIG. 19A shows voltage drive waveforms when the respective ink sizes shown in FIG. 18A are ejected from the recording head. That is, FIG. 19A shows a voltage driving waveform for one ink particle of 27 pl ink size, a voltage driving waveform for one ink particle of 9 pl ink size, and a voltage driving waveform of ink of 3 pl ink size. Only the drive waveform of the voltage for one grain is shown.

  When the ink particle having the size determined by the determination unit 654 is an ink particle having an ink size of 3 pl, the voltage when the second recording head drive control unit 657 ejects an ink particle having an ink size of 3 pl is used. Only the height of the drive waveform is increased so that, for example, ink particles having an ink size of 4 pl are ejected (FIGS. 18B and 19B).

(2) Increase the wave height of the entire drive waveform.

  A specific example will be described with reference to FIG. 20 (same as FIG. 18A) and FIG.

  When the ink particle having the size determined by the determination unit 654 is an ink particle having an ink size of 3 pl, the second recording head drive control unit 657 has an ink particle having an ink size of 27 pl and an ink size having an ink size of 9 pl. Increasing the wave height of the voltage drive waveform when ejecting ink particles, 3 pl ink size ink particles, for example, 30 pl ink size ink particles, 11 pl ink size ink particles, 4 pl The ink particles of the ink size are discharged (FIGS. 20B and 21).

  Note that the series of operations of the image forming apparatus according to the seventh embodiment increases the wave height of the driving waveform of the voltage for driving the recording head in the flowchart of FIG. The description of the series of operations is omitted with the above description.

  According to the image forming apparatus according to the seventh embodiment, when it is determined that there is a case where a split ink size is used for the print data, printing is performed by increasing the height of the drive waveform of the voltage for driving the recording head. Run. Thereby, mist formation can be prevented.

  The image forming apparatus, the image forming system, and the image forming method according to the present embodiment have been described above. However, the above-described embodiment shows an example of a preferred embodiment of the present invention. However, the present invention is not limited to this, and various modifications can be made.

  For example, in the present embodiment, a serial head type image forming apparatus is illustrated, but the present invention may be applied to a line head type image forming apparatus.

  In the present embodiment, the surface potential measurement unit measures the surface potential over the entire area of the paper, with the print area on the paper corresponding to one pixel on the image data as the basic unit of the measurement range. Illustrated. The area where the measurement value is obtained, that is, the measurement range by the surface potential sensor is not limited to this. For example, it can be an arbitrary number of dots on the paper or image data, or can be arbitrarily set on the paper. Or a number of square millimeters (or square centimeters). Also in this case, as a matter of course, the determination unit 654 determines the ink size to be mist for each set measurement range and outputs it as determination information for each measurement range.

A Image forming apparatus N Nozzle S Paper (recording medium)
P Ink particle 653 Surface potential measuring unit 654 Determination unit 655 Data processing unit 656 Recording head drive control unit 657 Second recording head drive control unit

Japanese Patent No. 3804929

Claims (7)

A data processing unit for converting image data into printing data based on the area gradation method is provided, and based on the printing data processed by the data processing unit, toward the recording medium facing the recording head In an image forming apparatus for forming an image on the recording medium by ejecting ink particles from the recording head and moving the recording medium relative to the recording head,
A surface potential measuring unit for measuring the surface potential of the recording medium;
A determination unit for determining the size at which the ink particles break up based on the measurement value by the surface potential measurement unit;
The image forming apparatus, wherein the data processing unit generates the printing data that avoids the use of the ink particles having a size determined by the determination unit. The image forming apparatus is configured to be capable of forming an image on the recording medium using the inks of a plurality of colors.
The determination unit determines the size at which the ink particles break up for each color of the ink,
2. The image according to claim 1, wherein the data processing unit generates, for each color of the ink, the printing data that avoids the use of the ink particles having a size determined by the determination unit. Forming equipment. The data processing unit
The image data is processed based on the area gradation method to generate provisional print data,
Using the determination information by the determination unit, it is determined whether or not the ink particles may break up in the provisional printing data,
The printing data that avoids the use of the ink particles having the size determined by the determination unit is generated anew when it is determined that the ink particles may break up. Or the image forming apparatus according to 2; The data processing unit
The image data is processed based on the area gradation method to generate provisional print data,
For the temporary printing data, pattern matching is performed using a matching pattern corresponding to the size determined by the determination unit,
A conversion pattern that avoids the use of the ink particles having the size determined by the determination unit is provided corresponding to the pattern matching, and a portion matched by the pattern matching is converted using the conversion pattern. The image forming apparatus according to claim 1, wherein the printing data is generated. The data processing unit
The image data is processed based on the area gradation method to generate provisional print data,
Using the determination information by the determination unit, it is determined whether or not the ink particles may break up in the provisional printing data,
When it is determined that there is a case where the ink particles may be divided, a process of replacing the divided ink particles with non-split ink particles while maintaining the arrangement of the divided ink particles. The image forming apparatus according to claim 1, wherein the printing data is generated by execution. An information processing apparatus including a data processing unit that converts image data into printing data based on the area gradation method, and recording based on the printing data processed by the data processing unit of the information processing apparatus An image for forming an image on the recording medium by ejecting ink particles from the recording head toward the recording medium facing the head and moving the recording medium relative to the recording head. In an image forming system comprising a forming device,
The image forming apparatus includes a surface potential measuring unit that measures a surface potential of the recording medium,
The information processing apparatus includes a determination unit that determines a size at which the ink particles are split based on a measurement value by the surface potential measurement unit,
The image processing system, wherein the data processing unit generates the printing data while avoiding use of the ink particles having a size determined by the determination unit. The image data is processed into printing data based on the area gradation method, and based on the printing data, ink particles are ejected from the recording head toward the recording medium facing the recording head, and the recording is performed. In an image forming method of forming an image on the recording medium by moving the recording medium relative to a head,
A measuring step of measuring the surface potential of the recording medium;
A determination step of determining the size at which the particles of the ink ejected from the recording head are split based on the measurement value acquired in the measurement step;
And a generation step of generating the printing data avoiding the use of the ink particles having the size determined in the determination step.

Images