JP2010012653A - Inkjet recorder and recovery processing method of recording head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recorder which can carry out optimum recovery processing by accurately grasping a state of a formation surface of ejection openings in a recording head, and to provide a recovery processing method of the recording head. <P>SOLUTION: A level of recovery processing is made higher as a recording speed becomes lower when a recording duty is in a high duty range. Consequently, the level of recovery processing is raised as the possibility of adhesion of ink on the formation surface of ejection openings in the recording head becomes higher. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an ink jet recording apparatus using a recording head capable of ejecting ink, and a recovery processing method for the recording head.

  In recent years, inkjet recording apparatuses (inkjet printers) that eject ink (ink droplets) from a plurality of ejection openings formed in a recording head and record an image on a recording medium have been widely used as various image output apparatuses. Yes. As a technique for ejecting ink from an ejection port, there is known a system in which an electrothermal converter (heater), a piezo element, or the like is provided in an ink flow path communicating with the ejection port, and these are driven. When an electrothermal converter is used, a drive pulse is applied to the electrothermal transducer to generate thermal energy, thereby foaming ink in the ink flow path and ejecting ink from the ejection port using the foaming energy. be able to. An image can be recorded on a recording medium by ejecting ink from the recording head based on the recording data. Hereinafter, the component including the discharge energy generating means such as the electrothermal converter and the piezo element, the ink flow path, and the discharge port is also referred to as “nozzle”.

  As such an ink jet recording apparatus, there are a so-called serial scan type and a full line type. The serial scan type recording apparatus repeats a recording operation in which the recording head moves in the main scanning direction and ejects ink and a conveying operation in which the recording medium is conveyed in the sub-scanning direction intersecting the main scanning direction. The images are sequentially recorded on the recording medium. A full-line type recording apparatus uses a long recording head extending over the entire width direction of the recording medium, and continuously conveys the recording medium in the length direction while discharging ink from the recording head. Thus, images are continuously recorded on the recording medium. As a recording head used in these types of recording apparatuses, there is a multi-nozzle head in which a plurality of nozzles are integrated and arranged. As a recording head for a full-line type recording apparatus, there is a line head in which a large number of multi-nozzle heads are arranged in a direction orthogonal to the conveyance direction of the recording medium.

  Such an ink jet recording apparatus can satisfy a generally required requirement, that is, a requirement to record a high-quality and high-resolution image at high speed. In addition, since the recording head and the recording medium do not come into contact with each other during image recording, very stable image recording can be performed.

  On the other hand, since the ink jet recording apparatus handles ink, which is a fluid, there is a possibility that various hydrodynamic problems may occur in the recording head. In addition, when the viscosity of the ink, which is a liquid, changes due to the environmental temperature, the standing time, or the like, there is a possibility that the image recording is greatly affected. In addition, it is known that one ink droplet ejected from a nozzle of a recording head is separated into a main droplet and a sub droplet (satellite). The main droplet is separated from the ejection port before the sub droplet, and the main droplet is separated from the main droplet. Sub-droplet leaves the discharge port following the drop.

  The driving frequency of the recording head increases as the recording speed increases. The recording speed corresponds to the conveyance speed of the recording medium in the full-line type ink jet recording apparatus. Further, the period of the ink actually ejected from the recording head is converted according to the recording duty. The recording duty corresponds to the ink ejection amount per unit recording area, and the higher the recording duty, the shorter the ink ejection cycle.

  Also, when ink adheres to the ejection port surface where the ejection port of the recording head is formed, there is a risk of causing non-ejection of the ink. Therefore, in order to maintain the ejection state of the ink of the recording head normally. Recovery processing is being performed. The recovery process includes a wiping process for wiping the ejection port surface, and preliminary ejection for ejecting ink that does not contribute to image recording from the ejection port.

  Conventionally, the degree of such recovery processing, for example, the number of ink ejections during preliminary ejection, is required for the recording duty corresponding to the amount of ink applied to the unit recording area, or for the recording operation up to the time when the recovery processing is performed. It is controlled according to the recording time.

  However, it is difficult to perform the optimal recovery process according to the print head status simply by controlling the recovery process according to the recording duty and the recording time. There is a risk of causing discharge. In addition, if the recovery process is performed more than necessary, there is a possibility that ink is wasted and throughput is reduced. For example, when the number of ink ejections in the preliminary ejection is excessive, ink is ejected more than necessary and is wasted. In general, a wiping operation with a high level of recovery processing requires a relatively long time. Therefore, if the wiping operation is performed more than necessary, the throughput may be greatly reduced and the wiper may be deteriorated. There is. In the case of a full-line type recording apparatus, a difference in use frequency is likely to occur among a large number of nozzles in a long recording head, and it is difficult to perform an optimal recording operation according to the state of those nozzles.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an ink jet recording apparatus and a recording head recovery processing method capable of performing an optimal recovery process by accurately grasping the state of the ejection port formation surface in the recording head. .

  The ink jet recording apparatus of the present invention maintains a good ink ejection state in the recording head in an ink jet recording apparatus that records an image on a recording medium using a recording head in which a plurality of nozzles capable of ejecting ink are formed. A recovery processing means for performing a recovery process for controlling, a control means for controlling the recovery processing means based on a recording duty corresponding to an ink discharge amount per unit recording area and a recording speed, The control means divides the recording duty into a low duty range, a middle duty range, and a high duty range, and when the recording duty is in the high duty range, the degree of the recovery process is increased as the recording speed decreases. The recovery processing means is controlled.

  According to another aspect of the present invention, there is provided a recording head recovery processing method in an ink jet recording apparatus that records an image on a recording medium using a recording head having a plurality of nozzles capable of ejecting ink. A recovery process method for a print head that performs a recovery process for maintaining good, and controls the recovery process based on a recording duty corresponding to an ink discharge amount per unit recording area and a recording speed. Including a control step, wherein the control step divides the recording duty into a low duty range, a middle duty range, and a high duty range, and when the recording duty is in the high duty range, the degree of the recovery process is reduced as the recording speed is reduced. It is characterized by being raised.

  According to the present invention, the optimal recovery process is performed by controlling the recovery process of the recording head based on at least the recording duty and the recording speed and accurately grasping the state of the ejection port formation surface in the recording head. be able to. That is, when the recording duty is in the high duty range, the degree of the recovery process increases as the recording speed decreases, and the degree of the recovery process increases as the possibility of ink adhesion on the ejection port formation surface of the recording head increases. Can be increased. By performing such an optimal recovery process, it is possible to maintain a good ink discharge state in the recording head and to record a high-quality image without causing waste of ink or a decrease in throughput.

  Further, by adding the recording time in addition to the recording duty and the recording speed as a control parameter for the recovery process, a more optimal recovery process can be performed.

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

(First embodiment)
FIG. 1 is a schematic front view of an ink jet recording apparatus to which the present invention is applicable. The recording apparatus 10 of this example is a so-called full line type ink jet recording apparatus.

  Connected to the recording device 10 is a host device (host PC) 12 for sending image information to the recording device. The recording apparatus 10 includes four recording heads 22K, 2C, 22M, and 22Y for ejecting black (K), cyan (C), magenta (M), and yellow (Y) inks. In this case, the roll paper is arranged so as to be aligned in the transport direction (in the direction of arrow A) of P. These recording heads 22K, 22C, 22M, and 22Y (hereinafter collectively referred to as “recording head 22”) are so-called long line heads. The recording head 22 extends in a direction crossing the arrow A direction (in the present example, a direction orthogonal), and its length is slightly larger than the maximum recording width of the recording medium that can be recorded by the recording apparatus 10. Long and fixed during image recording and does not move.

  The recording apparatus 10 incorporates a recovery unit 40 that performs a recovery process for maintaining a good ink discharge state in the recording head 22. The recovery unit 40 is provided with a capping mechanism 50 capable of capping the ejection port formation surface of the recording head 22. The capping mechanism 50 is provided independently for each of the recording heads 22. In the case of this example, in addition to the four recording heads 22, two additional recording heads can be provided. In order to cope with this, in addition to the four capping mechanisms 50, two preliminary heads are provided. A capping mechanism 50 is provided. The additional recording head is, for example, a recording head for ejecting light magenta and short cyan ink. As will be described later, the capping mechanism 50 includes a blade, an ink removing member, a blade holding member, a cap, and the like.

  The recording medium (roll paper) P is supplied from the roll paper supply unit 24 and is transported in the direction of arrow A by the transport mechanism 26 incorporated in the recording apparatus 10. The transport mechanism 26 includes a transport belt 26a for placing and transporting the roll paper P, a transport motor 26b for rotating the transport belt 26a, a roller 26c for applying tension to the transport belt 26a, and the like.

  When recording an image on the roll paper P, the roll paper P is continuously conveyed, and when the recording start position on the roll paper P reaches below the recording head 22K, the recording data (image information) is recorded. Based on this, the recording head 22K starts discharging black ink. When the recording start position on the roll paper P sequentially reaches below the recording heads 22C, 22M, and 22Y, these recording heads are cyan, magenta, and yellow based on the recording data (image information). Ink ejection starts. In this way, a color image is recorded on the roll paper P by ejecting ink of each color from the recording head 22.

  The recording apparatus 10 includes main tanks 28K, 28C, 28M, and 28Y (collectively referred to as “main tank 28”) that store ink to be supplied to the recording heads 22K, 22C, 22M, and 22Y, respectively. It has been. Further, the recording apparatus 10 is provided with a pump for supplying the ink in the main tank 28 to the recording head 22 through a sub tank (not shown) and for performing a recovery process described later. The ink supply device is configured by the ink tank 28 and the pump.

  FIG. 2 is a block diagram of the control system of the recording apparatus 10.

  Recording data and commands transmitted from the host PC 12 are received by the CPU 100 of the recording apparatus 10 via the interface controller 102. The CPU 100 is an arithmetic processing unit that controls the entire recording apparatus, such as reception of recording data, recording operation, and handling of the roll paper P. After analyzing the received command, the CPU 100 rasterizes the image data of the recording data component by rasterizing the image data into the image memory 106 and assigns the data to each of the recording heads. Before the recording operation, the capping motor 122 and the head up / down motor 118 are driven via the output port 114 and the motor driving unit 116, and the recording head 22 is moved away from the capping mechanism 50 to the recording position. As will be described later, the capping motor 122 is a motor for moving the capping mechanism 50 in the arrow A direction and the reverse direction. The head up / down motor 118 is a motor for moving the recording head 22 up and down in the direction of arrow C in FIG.

  Via the output port 114 and the motor drive unit 116, a roll motor (not shown) for feeding out the roll paper P, a transport motor 26b for transporting the roll paper P at a constant speed, and the like are driven. Roll paper P is conveyed to the recording position. A leading edge detection sensor (not shown) detects the leading edge position of the roll paper P in order to determine the timing (recording timing) at which ink starts to be ejected onto the roll paper P conveyed at a constant speed. . Thereafter, in synchronization with the conveyance of the roll paper P, the CPU 100 sequentially reads the recording data corresponding to each of the recording heads 22 from the image memory 106. The read recording data is transferred to the corresponding recording head 22 via the recording head control circuit 112.

  The operation of the CPU 100 is executed based on a processing program stored in the program ROM 104. The program ROM 104 stores a processing program corresponding to the control flow, a data table, and the like. The work RAM 108 is used as a working memory. The CPU 100 drives the pump motor 124 via the output port 114 and the motor driving unit 116 during the cleaning and recovery processing of each recording head 22 to control the pressurization and suction of ink, which will be described later.

  FIG. 3 is a cross-sectional view of the nozzle portion for explaining the configuration of the recording head and the ink ejection mechanism in this example. The recording head of this example uses an electrothermal transducer (heater) as ink ejection energy generating means. As the discharge energy generating means, a piezo element or the like can be used.

  The recording head 22 is configured so that a number of nozzles 21 are arranged in the front and back direction of the paper surface in FIG. The ink supplied into the common liquid chamber 21A is guided to the ejection port 21C through the ink flow path 21B, and a meniscus M is formed at the ejection port 21C. The ink flow path 21B is provided with an electrothermal converter (heater) 21D as ink discharge energy generating means. Ink is supplied from a sub tank (not shown) to the common liquid chamber 21A by a pressure adjusting pump. Therefore, the magnitude of the negative pressure of the ink supplied in the recording head 22, that is, the magnitude of the negative pressure acting on the ink in the nozzle 21 can be controlled by changing the rotation speed of the pressure adjusting pump. . Ink is supplied from the main tank 28 to the sub tank.

  By causing the electrothermal transducer 21D to generate heat, the ink in the ink flow path 21B foams to generate bubbles B, and the ink is ejected from the ejection port 21C. The electrothermal transducer 21D is formed on the silicon element substrate 156 by a known technique. The nozzle 21 is formed between the silicon element substrate 156 and the silicon top plate 158 in order to make the wettability of the ink near the meniscus M uniform. The electrothermal transducer 21D is formed by patterning an electric resistance layer and wiring. The electrothermal transducer 21D generates heat by applying a voltage to the electric resistance layer and passing a current through the wiring.

  3, (a) is a standby state of the nozzle 21, (b) is a heating state of the electrothermal transducer 21D, (c) is a film boiling state of ink, (d) is a maximum foaming state of ink, and (e). Is the ink ejection state, and (f) is the bubble B defoaming state. The ink is ejected as a main droplet D1 and a sub-droplet (satellite) D2. (G) is a state of refilling ink accompanying the defoaming of the bubbles B, and ink is supplied from the common liquid chamber 21A into the ink flow path 21B. (H) is an overshoot state, and the meniscus M becomes convex due to excessive supply of ink from the common liquid chamber 21A into the ink flow path 21B. In this state, ink may leak from the ejection port 21C.

  FIG. 4 is an explanatory diagram of changes in the position of the meniscus M accompanying the ink ejection operation as shown in FIG. 4, P0 is the opening position of the discharge port 21C, P1 is the position of the meniscus M in the standby state of FIG. 3A, P2 is the maximum retracted position of the meniscus M in the defoaming state of FIG. 3F, and P3 is This is the position of the meniscus M in the overshoot state of FIG.

  3B, 3C, and 3D, the position of the meniscus M is displaced outward from the ejection port 21C (hereinafter also referred to as “positive direction”). Then, due to the defoaming of the bubbles B before and after the ink is discharged, the position of the meniscus M is directed inward from the discharge port 21C as shown in FIGS. 3E and 3F (hereinafter referred to as “negative direction”). It is also displaced. t0 is the ink ejection timing. Thereafter, the position of the meniscus M returns to the positive direction by ink refilling as shown in FIG. At that time, when an overshoot as shown in FIG. 3H occurs, the position of the meniscus M exceeds the position P0 of the discharge port 21C. Curves L1 and L2 in FIG. 4 are detection results of the position of the meniscus M in two experiments in which overshoot occurred.

  When such an overshoot occurs, there is a possibility that ink leaks from the ejection port 21C and wets the ejection port forming surface (surface on which the ejection port 21C is formed). Such wetting of the ejection port forming surface may hinder normal ejection of ink from the ejection port 21C, and may lead to a non-ejection state in which ink cannot be ejected. Hereinafter, such non-ejection of ink due to wetting of the ejection port forming surface is also referred to as “non-ejection due to wetting”.

  FIG. 5 is an explanatory diagram of the relationship between the meniscus position and the drive interval (OCW) in the block drive system of the recording head. As a driving method of the recording head, there is a block driving method in which all nozzles are divided into a plurality of blocks and the nozzles are driven for each block. There is also an intra-block division driving method in which adjacent nozzles are divided and driven in the same block. Hereinafter, in such a block drive system, the drive interval between the blocks is referred to as OCW (One Heat Cycle Width).

  In FIG. 5, reference numerals 501 and 502 denote drive pulses for driving all nozzles divided into 8 blocks. The OCW in the drive pulse 501 is 17.2 μs, and the OCW in the drive pulse 502 is 42.7 μs. Reference numerals 503 and 503 are curves conceptually representing the vibration (displacement) of the meniscus in the nozzle for each block. When the driving pulse 501 is used, as shown by a curve 503, the meniscuses in the nozzles of each block vibrate so as to overlap in a short time. For this reason, there is a possibility that the meniscus vibration wave becomes large as shown by the curve 505 due to the crosstalk of the ink in each nozzle, leading to overshoot. On the other hand, when the driving pulse 502 is used, the meniscus at the nozzles of each block vibrates with a time shift as shown by a curve 504, so that the influence of ink crosstalk is suppressed and the meniscus is shown as a curve 506. The vibration wave of can be kept small.

  The driving frequency for each block differs depending on the recording speed. For example, when the recording speed is 100 mm / s, which is a high speed, the recording head driving frequency (driving frequency for each block) is 2.4 KHz, and one cycle is relatively short. Eight blocks can be driven in C1. Further, when the recording speed is 50 mm / s, which is a low speed, the driving frequency of the recording head is 1.2 KHz, and eight blocks can be driven within one relatively long cycle C2. Therefore, the settable range of the OCW is relatively narrow when the recording speed is 100 mm / s, which is a high speed, and is relatively wide when the recording speed is 50 mm / s, which is a low speed.

  The OCW can be changed according to the recording duty in addition to being changed according to the recording speed. For example, when the recording duty is high, the OCW can be lengthened in order to avoid the influence of ink crosstalk and to maintain the ink refill performance in the nozzle after ink ejection.

  When the recording speed is 50 mm / s and the driving frequency is 1.2 KHz, the OCW can be extended to 42.7 μs because there is a margin in the OCW setting range because the recording duty is low. When the OCW is set to 17.2 μs, there is no time until the vibration is attenuated, so the vibration is amplified and becomes a large vibration. However, if the OCW is 42.7 μm, the vibration can be damped by the next pulse, so that it does not become a large meniscus vibration wave like the curve 505 in FIG.

  The recording head may be formed by dividing a plurality of nozzles for each block on a plurality of nozzle rows. In that case, the vibration of the meniscus can be suppressed by driving the plurality of nozzles in each block while shifting each nozzle row in time. The nozzle rows may be, for example, two nozzle rows adjacent to each other, and the positions of the nozzles on each nozzle row may be shifted from each other by a half pitch of the nozzle pitch. In this case, odd numbered nozzles are arranged in one nozzle row, and even numbered nozzles are arranged in the other nozzle row.

  FIG. 6 is a diagram for explaining a capping operation and a wiping operation of the capping mechanism 50.

  The capping mechanism 50 of this example is provided with a cap 52 and a wiper blade (cleaning blade) 54 on a ridge 60, and constitutes a recovery unit for performing recovery processing of the recording head 22. The recovery process of the recording head 22 can include, for example, preliminary ejection, suction recovery, pressure recovery, circulation recovery, and wiping.

  The preliminary ejection is an operation of ejecting ink that does not contribute to image recording from the ejection port of the recording head 22 toward the inside of the cap 52 or the like. In the suction recovery, negative pressure is introduced into the cap 52 in the state where the ejection port forming surface 22A of the recording head 22 is capped, and ink that does not contribute to image recording is ejected from the ejection port of the recording head 22 into the cap 52. This is an operation of sucking and discharging. The pressure recovery is an operation of pressurizing ink in the recording head 22 and discharging ink that does not contribute to image recording from the ejection port toward the inside of the cap 52 or the like. Circulation recovery is an operation of circulating ink between the recording head 22 and a sub tank (not shown). Wiping is an operation of wiping the discharge port forming surface 22A with the wiper blade 54, as will be described later. This wiping operation usually takes longer time than other recovery processes such as preliminary ejection. Further, the cap 52 caps the ejection port forming surface 22A in a standby state or the like, thereby preventing the ejection port of the recording head 22 from being dried and protecting it.

  FIG. 6A shows a standby state of the recording head 22, and the cap 52 caps the ejection port forming surface 22A. At the time of wiping, first, as shown in FIG. 6B, the recording head 22 is lifted in the direction of the arrow C1, so that capping is released and the amount of penetration of the wiper blade 54 into the recording head 22 is relatively large. Set to amount h. Thereafter, as shown in FIG. 6C, the capping mechanism 50 moves in the direction of arrow B (the direction opposite to the direction of arrow A), so that the wiper blade 54 hits the corner 22B of the recording head 22 and is bent. I is ink adhering to the ejection port forming surface 22A. Thereafter, as shown in FIG. 6D, the recording head 22 is further raised in the direction of arrow C1, the amount of penetration of the wiper blade 54 into the recording head 22 is set to a relatively small amount i, and the capping mechanism 50 is moved to the arrow. Wiping starts by moving in the B direction. When the wiping is completed as shown in FIG. 6E, the ejection port forming surface 22B is cleaned, and the ink I is moved to the position of the absorber 23. Ink I is absorbed by the absorber 23. Thereafter, as shown in FIG. 6F, the recording head 22 is further raised in the direction of the arrow C1, and then the capping mechanism 50 is moved in the direction of the arrow A as shown in FIG. 6G. Then, as shown in FIG. 6 (h), the recording head 22 is lowered in the direction of the arrow C2, thereby returning to the standby state shown in FIG. 6 (a).

  FIG. 7 is a conceptual diagram of a method for controlling the recovery process of the recording head 22 and controls the recovery process based on three parameters: recording speed, recording time, and recording duty. Therefore, the three-dimensional space defined by these parameters is the control space area for the recovery process.

  The recording speed as a parameter corresponds to the driving frequency of the recording head as described above. The recording speed can include, for example, a low speed of 50 mm / s to 60 mm / s, a medium speed of 70 mm / s to 80 mm / s, and a high speed of 90 mm / s to 100 mm / s. The recording time as a parameter is an elapsed time from the start of the recording operation to the end of the recording operation, and a recovery process is performed after the end of the recording operation.

  The recording duty as a parameter corresponds to the ink discharge amount per unit recording area. In this example, the nozzles of the recording head 22 are divided into a plurality of blocks and driven as shown in FIG. 8, and the maximum dot count value (hereinafter referred to as “maximum dot count value”) for each block. ) To obtain the maximum recording duty. The maximum recording duty is set as a recording duty as a parameter. That is, the maximum one of the recording duty for each block (block unit recording duty) is the recording duty as a parameter.

  The dot count value for each block is the total number of ink ejected per unit recording area from the nozzles in each block, that is, the total number of ink dots formed in the unit recording area. Such a dot count value can be calculated based on the recording data for each block. When an image is recorded on one page of the recording medium as shown in FIG. 8, the dot count value of the third block from the left becomes the maximum dot count value, and the maximum recording duty is obtained based on this. A block with a large dot count value is more likely to cause “non-ejection due to wetting” than a block with a small dot count value.

  When one page of the recording medium is used as a unit recording area, the maximum recording duty can be obtained by the following equation.

  a is the maximum dot count value. “b” is a dot count value per block when an image with a recording duty of 100% is solid-recorded on one page of the recording medium, and can be calculated based on information on the size of the recording medium. c is the number of pages of the recording medium to be recorded, and can be obtained based on information related to the number of recording media or information related to the size and recording time of the recording medium.

  Alternatively, the maximum recording duty may be obtained after weighting the dot count value for each block or the recording duty calculated for each block.

  FIG. 9 is a flowchart for explaining control of recovery processing when the same image is recorded on a plurality of recording media. First, in a series of processing steps for recording the first recording medium, the maximum recording duty is calculated and the recording speed is acquired (steps S1 and S2). Thereafter, after the recording operation for a predetermined plurality of recording media is completed (step S3), the recording time is acquired (step S3). Thereafter, a table to be described later is referred to (step S5), and recovery processing is performed based on the three parameters of recording speed, recording time, and recording duty (in this example, maximum recording duty) (step S6). Before the recording operation for a predetermined number of recording media is completed, the recovery operation may be performed by interrupting the recording operation. In this case, the recording time as a parameter is the recording time at the time when the recording operation is interrupted.

  FIG. 10 is a flowchart in the case where the recovery process is controlled after the end of one job of a normal recording operation, that is, a recording operation in which various images are recorded on one or a plurality of recording media. First, the recording speed is acquired during a series of processing steps for executing the recording operation of one job (step S11). Thereafter, after the recording operation is completed (step S12), the recording time is acquired and the maximum recording duty is calculated (steps S13 and S14). Thereafter, a table to be described later is referred to (step S15), and recovery processing is performed based on the three parameters of recording speed, recording time, and recording duty (in this example, maximum recording duty) (step S16). Before one job of the recording operation is completed, the recording operation may be interrupted and the recovery process may be performed. In that case, the recording time and the maximum recording duty as parameters are the recording time and the maximum recording duty when the recording operation is interrupted.

  FIGS. 11 to 13 are explanatory diagrams of a control example of the recovery process based on three parameters of the recording speed, the recording time, and the recording duty (in this example, the maximum recording duty). In the case of this example, the recovery process is preliminary ejection and wiping, and the control mode of the recovery process includes a mode in which one of preliminary ejection and wiping is performed, and a mode in which neither is performed. In the preliminary ejection, ink that does not contribute to image recording is ejected from all the nozzles of the recording head, and the number of ejections is controlled in the range of 800 to 600. The greater the number of ejections, the higher the degree of recovery processing (strong recovery processing). As described above, the wiping is an operation of wiping the discharge port forming surface 22A with the wiper blade 54. In this example, the wiping is performed at least once for the specified number of times. This wiping is a recovery process having a higher degree of recovery process than the preliminary discharge and stronger than the preliminary discharge.

  When the maximum recording duty is 0 to 8%, 8 to 25%, and 25 to 100%, the recovery process is performed according to the relationship between the recording speed and the recording time using the tables of FIGS. 11, 12, and 13, respectively. Control. In the following, 0 to 8% of the maximum recording duty is also referred to as “low duty range”, 8 to 25% is also referred to as “medium duty range”, and 25 to 100% is also referred to as “high duty range”. The table of FIG. 11 for the low duty range, the table of FIG. 12 for the medium duty range, and the table of FIG. 13 for the high duty range are each characterized as follows.

(Low duty range control)
For example, in the low duty range (1 to 8%) for recording text, barcode, spot color, etc., the possibility of “non-ejection due to wetting” increases as the recording speed decreases.

  The recording apparatus can set the drive frequency according to the recording speed. For example, the recording speed is compared between 100 mm / s and 25 mm / s. In the case of 100 mm / s, the time allotted for recording one line in one second is 480 μs, and one line is divided into eight, so the OCW, which is the allocation of one dot ejection time, is 48 μs. . On the other hand, in the case of 20 mm / s, the time allotted for one line recording is 1.92 ms (1920 μs), so the OCW, which is the allocation of one dot ejection time, is 190 μs.

  However, since the OCW cannot be controlled by changing the recording duty with respect to these recording speeds, when the recording duty is low, the interval between the lines is wide and the interval of the OCW is wide. Can be attenuated. That is, a situation is generated in which satellites are continuously generated by the amount that can be stably discharged during low-speed recording.

  The main cause of non-ejection due to wetting when the recording duty is low is the adherence of satellite to the ejection port surface that occurs in accordance with the ejection of the main droplet. Furthermore, if the recording time is long, the satellites accumulate and there is a high possibility of non-ejection due to wetting.

  The table of FIG. 11 is set in consideration of the possibility of such “non-ejection due to wetting”. That is, the control tendency of the recovery process in the low duty range using the table tends to strengthen the recovery process as the recording speed decreases, and strengthen the recovery process as the recording time increases. Therefore, when the recording speed is high and the recording time is short, a weak recovery process is performed. When the recording speed is 90 mm / s and 100 mm / s and the recording time is 0 to 10 s, the recovery process is not performed. On the other hand, when the recording speed is low and the recording time is long, a strong recovery process is performed. As the number of ink ejections during preliminary ejection increases, the degree of preliminary ejection increases. When the recording speed is 50 mm / s and 60 mm / s and the recording time is 90 seconds or more, wiping, which is the strongest recovery process, is performed.

  Due to such control tendency, the occurrence of “non-ejection due to wetting” in the low duty range can be efficiently suppressed. If wiping, which is the strongest recovery process, is performed regardless of the recording speed and recording time, the wiping takes a long time, which may lead to a decrease in throughput.

(Medium duty range control)
For example, in the middle duty range (9 to 50%) for recording illustrations and photographs, the higher the recording speed, the higher the possibility of “non-ejection due to wetting”. This is because in the case of low duty, there was sufficient decay time even if overshooting, but in the case of these medium duty, the recording allocation time is shortened, the recording speed is increased and the drive frequency is increased. This is because the interval of OCW, which is the allocation of the ejection time for one dot, is reduced. That is, the OCW allocation interval is reduced, the meniscus after ink ejection cannot be attenuated, and the meniscus becomes a convex state due to the amplified vibration, and an overshoot that ejects ink in that state occurs. , Non-ejection due to wetting is likely to occur.

  The table in FIG. 12 is set in consideration of the possibility of such “non-ejection due to wetting”. That is, the control tendency of the recovery process in the low duty range using the table tends to strengthen the recovery process as the recording speed increases, and strengthen the recovery process as the recording time increases. Therefore, when the recording speed is low and the recording time is short, weak recovery processing is performed. When the recording speed is 50 mm / s and 60 mm / s and the recording time is 0 to 10 s, the recovery process is not performed. On the other hand, when the recording speed is high and the recording time is long, a strong recovery process is performed. When the recording speed is 90 mm / s and 100 mm / s and the recording time is 90 s or more, wiping, which is the strongest recovery process, is performed.

  Due to such a control tendency, occurrence of “non-ejection due to wetting” in the middle duty range can be efficiently suppressed. If wiping, which is the strongest recovery process, is performed regardless of the recording speed and recording time, the wiping takes a long time, which may lead to a decrease in throughput.

(High duty range control)
For example, in the case of a high duty range (51 to 100%) for recording a solid image or the like, the possibility of “non-ejection due to wetting” increases as the recording speed decreases. At high duty, the effect of overshoot due to the recording speed is almost unchanged at each recording speed. Within a high duty range, overshoot tends to be caused uniformly at any recording speed.

  However, since the ink ejection is relatively stable when the recording speed is slow, and the ink ejection is stable compared to the case where the recording speed is fast, the main droplets, as occurred at low duty, The influence of satellites generated with the discharge of water becomes dominant.

  The table in FIG. 13 is set in consideration of the possibility of such “non-ejection due to wetting”. That is, the control tendency of the recovery process of the high duty range using the table tends to strengthen the recovery process as the recording speed decreases, and strengthen the recovery process as the recording time increases. Therefore, when the recording speed is high and the recording time is short, a weak recovery process is performed. When the recording speed is 90 mm / s and 100 mm / s and the recording time is 0 to 10 s, the recovery process is not performed. On the other hand, when the recording speed is low and the recording time is long, a strong recovery process is performed. When the recording speed is 50 mm / s and 60 mm / s and the recording time is 90 seconds or more, wiping, which is the strongest recovery process, is performed.

  Due to such a control tendency, the occurrence of “non-ejection due to wetting” in the high duty range can be efficiently suppressed. If wiping, which is the strongest recovery process, is performed regardless of the recording speed and recording time, the wiping takes a long time, which may lead to a decrease in throughput.

  As described above, in this example, the recovery process is controlled based on the three parameters using the tables shown in FIGS. However, without using such a table, the recovery process can be similarly controlled using a mathematical formula relating three parameters.

(Other embodiments)
The three ranges (low, medium, and high duty ranges) that divide the recording duty are not limited to the ranges of 0% to 8%, 8% to 25%, and 25% to 100%, and are arbitrary and 4 You may divide into the above range. The high duty range may be a range including at least 100%, and the low duty may be a range including at least 0%.

  Further, the recovery process can include various processes such as suction recovery, pressurization recovery, and circulation recovery in addition to preliminary discharge and wiping. The degree of the recovery process is controlled according to, for example, the number of wiping in the case of wiping, the suction time in the case of suction recovery, the pressurization time in the case of pressure recovery, and the circulation time in the case of circulation recovery. be able to. Further, it is sufficient that at least two of the recording duty and the recording speed can be used as parameters for controlling the recovery process. Furthermore, the recovery process can be controlled more accurately by using three parameters obtained by adding the recording time required for image recording to the recording duty and recording speed. Further, the host device (host PC) 12 may be provided with at least a part of the recording operation control function and at least a part of the recovery process control function.

1 is a front view of an ink jet recording apparatus according to an embodiment of the present invention. FIG. 2 is a block configuration diagram of a control system of the inkjet recording apparatus of FIG. 1. (A) to (h) are cross-sectional views of a nozzle portion for explaining an ink discharge state. It is explanatory drawing of the displacement of the meniscus of the ink formed in a nozzle. FIG. 4 is an explanatory diagram of a relationship between block driving of a recording head and vibration of an ink meniscus. (A) to (h) are explanatory views of a wiping operation in the ink jet recording apparatus of FIG. It is a conceptual diagram of the control space area | region of the recovery process in embodiment of this invention. FIG. 2 is an explanatory diagram of a relationship between a recording head and a recorded image in the inkjet recording apparatus of FIG. 1. It is a flowchart for demonstrating the 1st control example of the recovery process by this invention. It is a flowchart for demonstrating the 2nd control example of the recovery process by this invention. It is explanatory drawing of the control table of a recovery process in case the maximum recording duty is 0%-8% by this invention. It is explanatory drawing of the control table of a recovery process in case the maximum recording duty is 8%-25% by this invention. It is explanatory drawing of the control table of a recovery process in case the maximum recording duty is 25%-100% by this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Inkjet recording device 21 Nozzle 21A Common liquid chamber 21B Ink flow path 21C Ejection port 21D Electrothermal converter (heater)
22 (22Y, 22M, 22C, 22K) Recording head 26 Conveying mechanism 40 Recovery unit 50 Capping mechanism

Claims (10)

In an inkjet recording apparatus that records an image on a recording medium using a recording head in which a plurality of nozzles capable of ejecting ink is formed.
Recovery processing means for performing recovery processing for maintaining a good discharge state of ink in the recording head;
Control means for controlling the recovery processing means based on the recording duty corresponding to the ink discharge amount per unit recording area and the recording speed;
With
The control means divides the recording duty into a low duty range, a middle duty range, and a high duty range, and when the recording duty is in the high duty range, the degree of the recovery process is increased as the recording speed decreases. An ink jet recording apparatus, wherein the recovery processing means is controlled. 2. The control unit according to claim 1, wherein when the recording duty is in the middle duty range, the control unit controls the recovery processing unit to increase the degree of the recovery processing as the recording speed increases. Inkjet recording apparatus. The recovery processing means includes, as the recovery processing, preliminary discharge for discharging ink that does not contribute to image recording from the nozzle,
The control means controls the recovery processing means to increase the number of ink ejected from the nozzles by the preliminary ejection in order to increase the degree of the recovery processing. Or the inkjet recording apparatus according to 2; The inkjet recording apparatus according to any one of claims 1 to 3, wherein the recovery processing unit includes a process of wiping an ejection port forming surface on which the nozzle is formed in the recording head as the recovery process. . The control means controls the recovery processing means based on a recording time required for image recording together with the recording duty and the recording speed, and the recovery processing is performed so that the degree of the recovery processing increases as the recording time increases. The inkjet recording apparatus according to any one of claims 1 to 4, wherein the processing unit is controlled. The recording head is block-driven by dividing the plurality of nozzles into a plurality of blocks,
The inkjet according to any one of claims 1 to 5, wherein the recording duty is a maximum one of block unit recording duties corresponding to an ink discharge amount per unit recording area in each block. Recording device.   The inkjet recording apparatus according to claim 6, further comprising a changing unit capable of changing a drive interval of the block according to at least one of the recording duty or the recording speed.   In the recording head, the plurality of nozzles for each block are formed separately on a plurality of nozzle rows, and the plurality of nozzles for each block are driven while being shifted in time for each nozzle row. The ink jet recording apparatus according to claim 6 or 7, characterized in that A transport means for transporting the recording medium in a predetermined transport direction;
The inkjet recording apparatus according to claim 1, wherein the recording head extends over the entire recording area in a direction intersecting the transport direction. In an ink jet recording apparatus that records an image on a recording medium using a recording head on which a plurality of nozzles capable of ejecting ink are formed, recording for performing a recovery process for maintaining a good ink ejection state of the recording head A head recovery method,
Including a control step of controlling the recovery processing based on a recording duty corresponding to an ink discharge amount per unit recording area and a recording speed,
The control step divides the recording duty into a low duty range, a middle duty range, and a high duty range, and when the recording duty is in the high duty range, the degree of the recovery process is increased as the recording speed is reduced. The recording head recovery processing method.

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