JP5338542B2 - Liquid ejection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To simplify a computing process, and to cause an observer to be not liable to recognize the fact that dots in no relation to a printed image are formed on a recording medium by preliminary ejection. <P>SOLUTION: In step S6, "m" is determined at random to be in a range from 0 or more to M or less set in step S4 and "m" is set to each of ejection holes in a one-to-one manner. In step S10, when it is determined that a counter value corresponding to a one-dot forming position on paper is equal to a value of "N+m" (S10: YES), the process is progressed to step S13, and then data is rewritten so as to perform the preliminary ejection from the ejection holes at a print cycle corresponding to the dot forming position. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a liquid ejection apparatus that performs preliminary ejection of a liquid onto a recording medium.

  The high-viscosity aqueous pigment ink used in the ink jet recording apparatus is liable to thicken the ink at the nozzles due to evaporation of the solvent. Therefore, conventionally, discharge flushing for discharging the thickened ink from the nozzles has been performed in order to prevent discharge failure due to the thickened ink.

  For example, Patent Document 1 discloses a technique in which ink droplets are ejected from a nozzle to a preliminary ejection region where no recording paper P is present on a recording paper transport belt, and then the ink droplets ejected on the belt are cleaned with a cleaner. Yes.

JP 2008-265057 A

  According to the above-described technique, the recording process on the recording medium is performed without considering the thickening of the ink that occurs during recording on one recording medium, and the preliminary ejection area is completed until the recording process on the recording medium is completed. The preliminary discharge is not performed. For this reason, there is a possibility that the ink is thickened during image recording on the recording medium and the image quality is deteriorated. Therefore, it is conceivable to perform preliminary ink ejection by applying the technique of Patent Document 1 during recording on the recording medium.

  However, in this case, in order to determine the number of preliminary ejections from each nozzle, it is necessary to calculate the total ejection amount from each nozzle in the recording area. Therefore, particularly in an inkjet recording apparatus having a large number of nozzles, a large amount of computation is required, and computation processing takes time. In addition, since the preliminary discharge start timing for each nozzle is based on the number of preliminary discharges, when the number of preliminary discharges for all nozzles is the same, the preliminary discharge is started at the same time, and the preliminary discharge is simultaneously performed thereafter. Therefore, a plurality of dots formed by preliminary ejection are formed on the recording medium as straight lines extending in a direction orthogonal to the transport direction, so dots that are not related to the recorded image are formed on the recording medium. This is easily recognized by the observer.

  SUMMARY OF THE INVENTION The main object of the present invention is to provide a liquid ejection apparatus that simplifies the arithmetic processing and makes it difficult for an observer to recognize that dots not related to a recorded image are formed on a recording medium by preliminary ejection. It is to be.

  The liquid ejection apparatus according to the present invention includes a transport mechanism that transports a recording medium, and a plurality of disposed at predetermined intervals corresponding to the print resolution in the orthogonal direction with respect to an orthogonal direction that is orthogonal to a recording medium transport direction by the transport mechanism. Recording is performed on a recording medium, including a discharge port, a plurality of individual liquid channels each having the discharge port at one end, a liquid discharge head having a plurality of actuators for applying discharge energy to the liquid in the individual liquid channel. Image data storage means for storing image data relating to a power image, and the image data storage means stored so that an image is recorded by ejecting liquid toward a recording medium transported by the transport mechanism. The image recording control means for controlling the plurality of actuators based on the image data, and the temperature of the environment in which the liquid discharge head is provided. Based on the environmental data detection means for detecting at least one value of humidity and the detection result by the environmental data detection means, a first value M is determined which decreases as the temperature increases or decreases as the humidity decreases. 1 determination means, second determination means for determining a second value m that is a random value between 0 and the first value M for each discharge port, and each discharge port stored in the image data storage means Preliminary ejection for ejecting the thickened liquid in the vicinity of the ejection port toward the recording medium on which an image is recorded by driving the actuator not based on the image data is from the start of recording on the recording medium or the nearest liquid ejection. So that the elapsed time from the time the preliminary discharge timing indicated by the second value m determined for the discharge port is reached is performed. And a flushing control means for controlling the Yueta.

  According to the above configuration, since the elapsed time from the start of recording on the recording medium or from the most recent liquid discharge reaches the preliminary discharge timing for each discharge port, the total liquid discharge amount from each discharge port is reduced. There is no need to calculate, and only a sequential calculation is required to calculate the elapsed time from the start of recording on the recording medium at each discharge port or from the latest liquid discharge. Therefore, simplification of arithmetic processing is realized. Further, since the preliminary ejection timing at which preliminary ejection is performed for each ejection port is indicated by the second value m, which is a random value, the liquid ejected by the preliminary ejection is positioned at random positions on the recording medium in the transport direction. Land. Therefore, a plurality of dots formed by preliminary ejection are not formed as a straight line extending in a direction orthogonal to the transport direction, and dots that are not related to the recorded image are formed on the recording medium by preliminary ejection. This is difficult for the observer to recognize. Further, the second value m is a random value of 0 or more and a first value M or less that decreases as the temperature of the environment in which the liquid ejection head is provided increases or decreases as the humidity decreases. It is a value based on temperature or humidity. Therefore, it is possible to appropriately eliminate the thickening of the liquid in consideration of the ease of thickening the liquid due to temperature or humidity. In addition, it is possible to reduce the situation such as wasteful discharge of liquid from the discharge port that does not require preliminary discharge. Accordingly, it is possible to prevent deterioration of image quality.

  The liquid ejection apparatus according to the present invention further includes third determination means for determining a third value N that decreases as the temperature increases or decreases as the humidity decreases, based on the detection result by the environmental data detection means. The flushing control means is configured so that the elapsed time from the start of recording on the recording medium or from the latest liquid ejection is earlier than the preliminary ejection timing, except when the image recording control means controls the plurality of actuators. It is preferable to control the plurality of actuators so that the plurality of actuators are not driven until the preliminary vibration permissible timing indicated by the previous third value N is reached.

  According to the above configuration, the plurality of actuators are not driven until the preliminary vibration allowable timing indicated by the third value N based on temperature or humidity is reached before the preliminary discharge timing. Therefore, considering the ease of thickening of the liquid due to temperature or humidity, it is possible to reduce situations such as wasteful discharge of liquid from the discharge port that does not require preliminary discharge. Accordingly, it is possible to prevent deterioration of image quality.

  In the present invention, the flushing control means may perform preliminary vibration for vibrating the actuator in a range in which liquid is not discharged from the discharge port for each discharge port whose second value m is other than zero from the preliminary vibration allowable timing. It is preferable to control the plurality of actuators so as to be performed at least once before the preliminary ejection timing.

  According to the above configuration, since the pre-vibration is performed at least once between the pre-vibration permissible timing and the pre-ejection timing for each discharge port whose second value m is not zero, the liquid thickening is more reliably eliminated. can do. Therefore, it is possible to more reliably prevent the image quality from deteriorating.

  Further, in the present invention, the flushing control means has a temperature higher than a first threshold value or a humidity of a first value for each ejection port whose second value m is other than zero, based on a detection result by the environmental data detection means. It is preferable to control the plurality of actuators so that the preliminary vibration is performed only when the threshold value is lower than 2.

  According to the above configuration, for each discharge port whose second value m is not zero, the preliminary vibration is performed only when the temperature is higher than the first threshold value or the humidity is lower than the second threshold value. More appropriate pre-vibration can be performed in consideration of the ease of thickening of the liquid due to temperature or humidity. Therefore, it is possible to reduce the situation such as wasteful pre-vibration for the discharge port that does not require pre-vibration.

  In the present invention, the image recording control unit and the flushing control unit may be configured to record the recording cycle, which is a time required for the recording medium to be conveyed by the conveying mechanism by a distance corresponding to the printing resolution in the conveying direction. The flushing control means controls the plurality of actuators, and the preliminary vibration is performed in each recording cycle from the preliminary vibration permissible timing to the preliminary ejection timing for each ejection port whose second value m is not zero. Thus, it is preferable to control the plurality of actuators.

  According to the above configuration, since the preliminary vibration is performed in each recording cycle from the preliminary vibration permissible timing to the preliminary discharge timing for each ejection port whose second value m is other than zero, it is possible to more reliably increase the viscosity of the liquid. Can be resolved. Therefore, it is possible to more reliably prevent the image quality from deteriorating.

  The liquid ejection device of the present invention increases based on the detection result by the environmental data detection unit as the temperature increases in a range where the amount of liquid ejected from the ejection port in the preliminary ejection does not exceed a predetermined upper limit value or It is preferable to further include preliminary discharge liquid amount adjusting means for adjusting the liquid amount so that the amount increases as the humidity decreases.

  According to the above configuration, the amount of liquid ejected from the ejection port in the preliminary ejection is adjusted in consideration of the ease of thickening of the liquid due to temperature or humidity. Can do. Therefore, it is possible to more reliably prevent the image quality from deteriorating.

  The liquid ejection apparatus of the present invention includes a waiting time detecting means for detecting a waiting time from the end of recording on a recording medium on which recording has been performed to the start of recording on a recording medium on which recording is performed next, and the waiting First elapsed time adjusting means for adjusting an initial value of elapsed time from the start of recording on the recording medium based on the waiting time detected by the time detecting means so as to increase as the waiting time becomes longer. Preferably it is.

  According to the above configuration, the initial value is adjusted in consideration of the waiting time from the end of recording on the recording medium on which recording has been performed most recently to the start of recording on the recording medium on which recording is performed next. When the waiting time is long, that is, when the liquid tends to thicken, the preliminary discharge timing is advanced. Therefore, the thickening of the liquid can be solved more appropriately. Therefore, it is possible to more reliably prevent the image quality from deteriorating.

  The liquid ejecting apparatus of the present invention is based on the detection result by the environmental data detecting means, and the liquid immediately after the start of recording on the recording medium is increased so that the temperature increases as the temperature increases or the humidity decreases. It is preferable to further include a second elapsed time adjusting unit that adjusts an initial value of the elapsed time from the discharge.

  According to the above configuration, the initial value is adjusted in consideration of the ease of thickening the liquid due to temperature or humidity.For example, when the temperature is high or the humidity is low, i.e., when the liquid tends to thicken easily. In this case, the preliminary ejection timing is advanced. Therefore, the thickening of the liquid can be solved more appropriately. Therefore, it is possible to more reliably prevent the image quality from deteriorating.

  The liquid ejection apparatus of the present invention starts recording on a recording medium in a range where the amount of liquid ejected from the ejection port does not exceed a predetermined upper limit in recording an image on a recording medium based on the control of the image recording control means. It is preferable to further include a recording liquid amount adjusting unit that adjusts the liquid amount so that the elapsed time from the last or most recent liquid discharge increases as the time elapses.

  According to the above configuration, the amount of liquid ejected from the ejection port in the recording of an image on a recording medium based on the control of the image recording control unit is adjusted in consideration of the ease of thickening of the liquid due to temperature or humidity. Therefore, it is possible to prevent a situation in which the amount of liquid landed on the recording medium is reduced due to the thickening of the liquid. Therefore, it is possible to more reliably prevent the image quality from deteriorating.

  For each discharge port, since the time elapsed from the start of recording on the recording medium or since the most recent liquid discharge reaches the preliminary discharge timing, there is no need to calculate the total liquid discharge amount from each discharge port, Only a sequential calculation for calculating the elapsed time from the start of recording on the recording medium at each ejection port or from the latest liquid ejection is required. Therefore, simplification of arithmetic processing is realized. Further, since the preliminary ejection timing at which preliminary ejection is performed for each ejection port is indicated by the second value m, which is a random value, the liquid ejected by the preliminary ejection is positioned at random positions on the recording medium in the transport direction. Land. Therefore, a plurality of dots formed by preliminary ejection are not formed as a straight line extending in a direction orthogonal to the transport direction, and dots that are not related to the recorded image are formed on the recording medium by preliminary ejection. This is difficult for the observer to recognize. Further, the second value m is a random value of 0 or more and a first value M or less that decreases as the temperature of the environment in which the liquid ejection head is provided increases or decreases as the humidity decreases. It is a value based on temperature or humidity. Therefore, it is possible to appropriately eliminate the thickening of the liquid in consideration of the ease of thickening the liquid due to temperature or humidity. In addition, it is possible to reduce the situation such as wasteful discharge of liquid from the discharge port that does not require preliminary discharge. Accordingly, it is possible to prevent deterioration of image quality.

1 is a schematic diagram schematically illustrating an internal configuration of an ink jet printer according to an embodiment of the present invention. FIG. 2 is a plan view of the head body of FIG. 1. FIG. 3 is an enlarged view of a portion straddling two adjacent actuator units in FIG. 2. It is sectional drawing of the flow-path unit along the IV-IV line shown in FIG. FIG. 5A is an enlarged cross-sectional view of a region indicated by a one-dot chain line in FIG. FIG. 5B is a plan view of the individual electrode. It is a functional block diagram of the inkjet printer shown in FIG. 2 is a flowchart showing a printing process of the ink jet printer shown in FIG. 1. 6 is a flowchart for explaining printing ink amount adjustment amount determination processing; This is a process that is performed on the ejection port 108 in a printing cycle corresponding to each dot formable position when performing the printing process. FIG. 10A shows the amount of ink to be ejected in the printing cycle corresponding to each dot formable position at the stage when the printing command related to the printing process is received. FIG. 10B shows the amount of ink actually ejected from each ejection port 108.

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

  FIG. 1 is a schematic diagram showing an internal configuration of an ink jet printer including an ink jet head according to an embodiment of the present invention. As shown in FIG. 1, the ink jet printer 101 has a rectangular parallelepiped casing 101a. In the casing 101a, four inkjet heads 1 (liquid ejection heads; hereinafter referred to as heads 1) that eject magenta, cyan, yellow, and black ink, and a transport mechanism 16 are arranged. A control unit 100 that controls the operation of the head 1, the transport mechanism 16, and the like is attached to the inner surface of the top plate of the housing 101 a. A paper discharge unit 15 is provided above the top plate, and the paper P on which an image is formed is discharged. Below the transport mechanism 16, a paper feed unit 101b that can be attached to and detached from the housing 101a is disposed. An ink tank unit 101c that can be attached to and detached from the housing 101a is disposed below the paper supply unit 101b.

  A paper transport path is formed along the thick arrow shown in FIG. 1 inside the ink jet printer 101, and the paper P is transported from the paper supply unit 101 b toward the paper discharge unit 15. The paper feed unit 101 b includes a paper feed tray 11 and a paper feed roller 12. The paper feed tray 11 has a box shape opened upward, and stores a plurality of paper sheets P in a stacked state. The paper feed roller 12 sends out the paper P at the uppermost position of the paper feed tray 11. The fed paper P is guided to the transport mechanism 16 while being guided by the guides 13 a and 13 b and sandwiched by the feed roller pair 14.

  The transport mechanism 16 includes two belt rollers 6 and 7, a transport belt 8, a tension roller 10, and a platen 18. The conveyor belt 8 is an endless belt wound around both rollers 6 and 7. The tension roller 10 is biased downward in contact with the inner peripheral surface of the lower loop of the conveyor belt 8 and applies tension to the conveyor belt 8. The platen 18 is disposed in the inner region of the conveyor belt 8 and supports the conveyor belt 8 at a position facing the head 1 so that the conveyor belt 8 does not bend downward. The belt roller 7 is a driving roller, and rotates in the clockwise direction in FIG. 1 when a driving force is applied to its shaft from the motor 19. The belt roller 6 is a driven roller, and rotates in the clockwise direction in FIG. 1 when the conveyor belt 8 travels as the belt roller 7 rotates. The driving force of the motor 19 is transmitted to the belt roller 7 via a plurality of gears.

  The outer peripheral surface 8a of the conveyance belt 8 has adhesiveness by being subjected to silicone treatment. A nip roller 4 is disposed at a position facing the belt roller 6. The nip roller 4 presses the paper P sent out from the paper supply unit 101 b against the outer peripheral surface 8 a of the transport belt 8. The paper P is transported in the paper transport direction (the right side in FIG. 1 and the sub-scanning direction) while being held on the outer peripheral surface 8a by the adhesive force.

  A peeling plate 5 is provided at a position facing the belt roller 7. The peeling plate 5 peels the paper P from the outer peripheral surface 8a. The peeled paper P is guided by the guides 29a and 29b and conveyed while being sandwiched between the two pairs of feed rollers 28. Then, the paper P is discharged from a discharge port 22 formed in the upper part of the housing 101a to a paper discharge recess (paper discharge unit) 15 provided on the top surface of the top of the housing 101a.

  The four heads 1 eject inks of different colors (magenta, yellow, cyan, black). These four heads 1 have a substantially rectangular parallelepiped shape elongated in the main scanning direction. Further, the four heads 1 are fixed side by side along the conveyance direction A of the paper P. That is, the printer 101 is a line type printer, and the conveyance direction A and the main scanning direction are orthogonal to each other.

  A head main body 33 having a plurality of ejection openings 108 (see FIG. 3) for ejecting ink is provided below the head 1. These discharge ports 108 are opened in the discharge surface 2 a that is the lower surface of the head body 33. When the transported paper P passes just below the four heads 1, the ink of each color is sequentially ejected from the ejection port 108 toward the top surface of the paper P, and thus the top surface (printing surface) of the paper P. A desired color image is formed. In addition, each ejection port 108 is formed in the ejection port 108 in a range where preliminary ink for ejecting the thickened ink near the ejection port 108 toward the paper P and a range in which no liquid is ejected from the ejection port 108 are formed. It is possible to perform a preliminary vibration for vibrating the meniscus.

  Each head 1 is connected to an ink tank 17 in the ink tank unit 101c. The four ink tanks 17 store different colors of ink. Ink is supplied from each ink tank 17 to the head 1 via a tube (not shown).

  A paper sensor 31 that is a reflection type optical sensor is disposed between the head 1 located at the most upstream of the four heads and the nip roller 4. The paper sensor 31 outputs a detection signal when the leading edge of the paper transported along the transport path reaches directly below the paper sensor 31.

  In addition, a temperature sensor 72 that can detect the temperature of the environment in which the four heads are provided and a humidity can be detected at a position slightly downstream of the head 1 that is located most downstream among the four heads. A humidity sensor 73 is disposed. The temperature sensor 72 and the humidity sensor 73 output the detected temperature and humidity to the control unit 100, respectively. In the present embodiment, only the temperature sensor 72 is used, but only the humidity sensor 73 or both may be used.

  Hereinafter, the head body 33 will be described. FIG. 2 is a plan view of the head main body 33. FIG. 3 is an enlarged view of a portion straddling two adjacent actuator units 21 in FIG. FIG. 4 is a partial cross-sectional view of the flow path unit 9 taken along the line IV-IV shown in FIG. 5 (a) and 5 (b) are an enlarged cross-sectional view of a region indicated by a one-dot chain line in FIG. 4 and a plan view of an individual electrode. In FIG. 3, the aperture 112 to be drawn with a broken line is drawn with a solid line for easy understanding of the drawing.

  As shown in FIG. 2, the head body 33 includes a flow path unit 9 and four actuator units 21 fixed to the upper surface 9 a of the flow path unit 9. As shown in FIG. 3, the flow path unit 9 has an ink flow path formed therein. The actuator unit 21 has a trapezoidal planar shape. The actuator unit 21 includes a plurality of actuators corresponding to the pressure chambers 110, and has a function of selectively giving ejection energy to the ink in the pressure chambers 110.

  A total of ten ink supply ports 105 b into which ink from the ink tank 17 flows are opened on the upper surface 9 a of the flow path unit 9. As shown in FIGS. 2 and 3, a manifold channel 105 communicating with the ink supply port 105 b and a sub manifold channel 105 a branched from the manifold channel 105 are formed inside the channel unit 9. The manifold channel 105 extends along the oblique side of the trapezoid of the actuator unit 21 in plan view. Below the actuator unit 21, four sub-manifold channels 105a extend along the main scanning direction. These four sub-manifold channels 105a branch from the manifold channel 105 on one oblique side of the actuator unit 21, extend along the main scanning direction, and merge with another manifold channel 105 on the other oblique side. ing. On the discharge surface 2a of the flow path unit 9, as shown in FIGS. 3 and 4, a large number of discharge ports 108 are arranged in a matrix.

  The pressure chamber 110 is open on the surface of the flow path unit 9. The pressure chambers 110 are arranged along the longitudinal direction (main scanning direction) of the flow path unit 9, thereby forming a plurality of pressure chamber rows. These pressure chamber rows are arranged in 16 rows at equal intervals in the sub-scanning direction. The number of pressure chambers 110 included in each of the pressure chamber rows corresponds to the outer shape (trapezoid) of the actuator unit 21 from its long side (lower base side) toward the short side (upper base side). It arrange | positions so that it may decrease gradually.

  The discharge ports 108 are also arranged so as to form a plurality of discharge port rows corresponding to the pressure chamber rows. These discharge port arrays are arranged in parallel to each other so as to avoid the sub-manifold channel 105a in plan view.

  As shown in FIG. 4, the flow path unit 9 includes nine metal plates 122 to 130 made of stainless steel. By laminating these plates 122 to 130 while being aligned with each other, the manifold channel 105 communicating with the ink supply port 105b, the manifold channel 105 to the sub-manifold channel 105a, and the outlet from the sub-manifold channel 105a to the pressure chamber A large number of individual ink flow paths 132 extending from 110 to the ejection port 108 are formed. In the individual ink flow path 132, the pressure chamber 110 is disposed substantially at the center of the path from the outlet to the sub-manifold flow path 105 a to the discharge port 108.

  The ink flow in the flow path unit 9 will be described. As shown in FIGS. 2 to 4, the ink supplied into the flow path unit 9 through the ink supply port 105b is branched from the manifold flow path 105 to the sub-manifold flow path 105a. The ink in the sub-manifold channel 105a flows into each individual ink channel 132 and reaches the ejection port 108 via the aperture 112 and the pressure chamber 110 functioning as a throttle.

  Next, the actuator unit 21 will be described. As shown in FIG. 2, the four actuator units 21 are arranged in a staggered manner so as to avoid the ink supply ports 105b. Furthermore, the parallel opposing sides of each actuator unit 21 are along the longitudinal direction of the flow path unit 9, and the oblique sides of the adjacent actuator units 21 overlap each other in the width direction (sub-scanning direction) of the flow path unit 9. Yes.

  As shown in FIG. 5A, the actuator unit 21 includes three piezoelectric sheets 141 to 143 made of a lead zirconate titanate (PZT) ceramic material having ferroelectricity. Each of the piezoelectric sheets 141 to 143 is formed of a single sheet having a shape and a size that straddle the plurality of pressure chambers 110. The lower surface of the lowermost piezoelectric sheet 143 is a fixed surface that is fixed to the flow path unit 9. Further, the upper surface of the uppermost piezoelectric sheet 141 is opposed to a COF (Chip On Film) 50 which is a flat flexible substrate. An individual electrode 135 is formed at a position facing the pressure chamber 110 on the upper surface of the piezoelectric sheet 141. The COF 50 is connected to the individual electrode 135 as described later. Between the piezoelectric sheet 141 and the piezoelectric sheet 142 below the piezoelectric sheet 141, a common electrode 134 that is integrally formed over the entire surface of these sheets is interposed.

  As shown in FIG. 5B, the individual electrode 135 has a substantially rhombic planar shape similar to the pressure chamber 110. In plan view, most of the individual electrodes 135 are in the region of the pressure chamber 110. One of the acute corners in the rhombus shape of the individual electrode 135 extends outside the pressure chamber 110. An individual bump 136 protruding upward is provided at the tip in the extending direction, and is electrically connected to the individual electrode 135. On the piezoelectric sheet 141, individual bumps for common electrodes are also formed. The common electrode 134 is electrically connected to the individual bumps via a conductor (not shown) in a through hole formed in the piezoelectric sheet 141.

  The common electrode 134 is equally applied with the ground potential in the region corresponding to all the pressure chambers 110 through the individual bumps. On the other hand, the individual electrode 135 is electrically connected to each output terminal of a driver IC 52, which will be described later, via the COF 50, and a drive signal from the driver IC 52 is selectively supplied.

  The piezoelectric sheet 141 is polarized in the thickness direction. When an electric field is applied in the polarization direction to the piezoelectric sheet 141 by setting the individual electrode 135 to a potential different from that of the common electrode 134, the electric field application portion corresponding to the individual electrode 135 works as an active portion distorted by the piezoelectric effect. In other words, a plurality of actuators corresponding to the number of pressure chambers 110 are built in the actuator unit 21, and each portion sandwiched between the individual electrodes 135 and the pressure chambers 110 functions as an individual actuator. For example, if the polarization direction and the electric field application direction are the same, the active portion contracts in a direction (plane direction) orthogonal to the polarization direction.

  As described above, the actuator unit 21 uses the upper one piezoelectric sheet 141 away from the pressure chamber 110 as a layer including the active portion, and deactivates the lower two piezoelectric sheets 142 and 143 close to the pressure chamber 110. It is a so-called unimorph type actuator made into a layer. In contrast to the active layer, the inactive layer does not spontaneously strain upon application of an electric field. As shown in FIG. 5A, since the piezoelectric sheets 141 to 143 are fixed to the upper surface of the plate 122 that partitions the pressure chamber 110, the electric field application portion of the piezoelectric sheet 141 and the piezoelectric sheets 142 and 143 below the electric field application portion. If there is a difference in the strain in the plane direction, the entire piezoelectric sheets 141 to 143 are deformed so as to be convex toward the pressure chamber 110 (unimorph deformation). As a result, pressure (discharge energy) is applied to the ink in the pressure chamber 110, and a pressure wave is generated in the pressure chamber 110. Then, the generated pressure wave propagates from the pressure chamber 110 to the ejection port 108, whereby ink droplets are ejected from the ejection port 108.

  By driving the actuator unit 21 in this way, ink is ejected from the ejection port 108. In the present embodiment, the ejection of ink from the ejection port 108 includes ejection for forming an image on the paper P and preliminary ejection performed for ejecting thickened ink near the ejection port 108. Further, in order to eliminate the increase in the viscosity of the ink near the ejection port 108, preliminary vibration that drives the actuator unit 21 can be performed on the ejection port 108 in a range where ink is not ejected from the ejection port 108. is there. The ink meniscus formed at the ejection port 108 vibrates due to the preliminary vibration.

  Returning to FIG. 1, the inkjet printer 101 includes a control unit 100. The control unit 100 controls the operation of each unit of the inkjet printer 101. The control unit 100 includes a plurality of hardware such as a CPU (Central Processing Unit), a RAM (Random Access Memory), and a ROM (Read Only Member). Various software for controlling the inkjet printer 101 is stored in the ROM. As the software and hardware in the control unit 100 cooperate, the control unit 100 includes an image data storage unit 44, a conveyance control unit 62, and an image print control unit 45 as shown in FIG. , Waiting time detection unit 46, first determination unit 41, second determination unit 42, third determination unit 43, flushing control unit 47, preliminary ejection ink amount adjustment unit 48, first elapsed time adjustment unit 49, second elapsed time An adjustment unit 60, a printing ink amount adjustment unit 61, and a counter 63 are constructed. Moreover, the control part 100 performs various processes other than the process which these perform in parts other than these. In the present embodiment, it is assumed that the control unit 100 includes a driver IC 52.

  Here, for the sake of convenience, the description will be made on the assumption that ejection is performed from only one of the inkjet heads 1, but the following processing is similarly applied to the other three inkjet heads 1.

  The image data storage unit 44 (image data storage means) stores image data sent from a host computer (not shown) for each color. The image data is configured based on, for example, bitmap format data, jpeg format data, and the like, and indicates the color, size, and position of the image dot on the paper P for the image to be printed on the paper P. . On the paper P, dots of i columns × j rows (i and j are natural numbers) can be formed. Correspondingly, the image data includes ink amount information indicating the amount of ink to be ejected in each printing cycle with respect to each of the i × j dot-formable positions. Here, the printing cycle means the time required for the paper P to be conveyed by a unit distance corresponding to the printing resolution in the sub-scanning direction (the direction parallel to the paper P conveyance direction). The amount of ink ejected from is “large” (21 pl), “medium” (14 pl), “small” (7 pl), and “none” (0 pl).

  The conveyance control unit 62 controls the motor 19 that is a drive source of the belt roller 7.

  The image printing control unit 45 controls the actuator unit 21 in units of printing cycles so that ink is ejected toward the paper P being conveyed by the conveyance mechanism 16 and an image is printed. This control is performed based on the detection signal of the leading edge of the paper P from the paper sensor 31 and the image data stored in the image data storage unit 44 while synchronizing with the control of the motor 19 by the conveyance control unit 62. .

  The waiting time detection unit 46 (waiting time detecting means) detects a waiting time from the end of printing on the paper P on which printing has been performed most recently to the start of printing on the paper P on which printing is performed next. Specifically, the waiting time detection unit 46 receives a print command indicating that the printer 101 performs printing on a plurality of sheets P, and after the printing of the most recently printed sheet P is finished, When printing is performed continuously, a value obtained by dividing a predetermined interval relating to these two sheets P by the conveyance speed is detected. In addition, the waiting time detection unit 46 determines that the latest printed sheet P is the last sheet P to be printed according to the print command, and the next sheet P is not printed continuously. The time obtained by adding the preparation time required for the print preparation started after receiving the print command to the time from the print end time of the paper P printed on to the time when the next print command is received is detected.

  The first determination unit 41 (first determination means) determines a value M that decreases as the temperature indicated by the output signal of the temperature sensor 72 increases. M is an index related to the determination of the timing for starting the preliminary discharge, and is an upper limit value for determining a random value m described later. In this embodiment, the 1st determination part 41 determines M with respect to the detected temperature with reference to the reference table A (not shown) predetermined so that M might be decided to one with temperature. The reference table A is determined such that M decreases as the temperature increases.

  Note that M may be a value that decreases as the humidity indicated by the output signal of the humidity sensor 73 decreases. In that case, the first determination unit 41 refers to a reference table A ′ (not shown) that is determined in advance so that M is determined to be one by the humidity, and determines M for the detected humidity. The reference table A ′ is defined such that M decreases as the humidity decreases.

  The second determination unit 42 (second determination means) determines a value m that is a random value between 0 and M for each ejection port 108. m is for instructing the timing (preliminary ejection timing) for starting the preliminary ejection described later for each ejection port 108. A different value m is set for each column formed by the dot formable positions.

  The third determination unit 43 (third determination means) determines a value N that decreases as the temperature indicated by the output signal of the temperature sensor 72 increases. N is for instructing preliminary vibration permissible timing. The preliminary vibration permissible timing is a timing at which preliminary vibration, which is a thickening suppressing operation, should be started, and is a timing following a limit time that can maintain the print quality without performing any thickening suppressing operation. In this embodiment, the 3rd determination part 43 determines N with respect to the detected temperature with reference to the reference table B (not shown) predetermined so that N might be decided to one with temperature. The reference table B is determined such that N decreases as the temperature increases.

  Note that N may be a value that decreases as the humidity indicated by the output signal of the humidity sensor 73 decreases. In that case, the third determination unit 43 refers to a reference table B ′ (not shown) that is determined in advance so that N is determined to be one by the humidity, and determines N for the detected humidity. The reference table B ′ is determined such that N decreases as the humidity decreases.

  The flushing control unit 47 (flushing control means) is configured so that the elapsed time from the start of printing on the paper P or the most recent ink discharge is the preliminary vibration allowable timing, except when the image print control unit 45 controls the actuator unit 21. The actuator unit 21 is controlled so that the actuator unit 21 is not driven until reaching. Note that the preliminary vibration permissible timing is a timing prior to the preliminary discharge timing. In the present embodiment, the flushing control unit 47 controls the actuator unit 21 in units of a printing cycle, and the preliminary vibration permissible timing is the ink from the start of printing on the paper P or the latest ink for each ejection port 108. This is a printing cycle in which the value of the counter 63 indicating the number of printing cycles that have elapsed since ejection is equal to N.

  In addition, the flushing control unit 47 performs preliminary vibration at each printing cycle from the preliminary vibration allowable timing to the later-described preliminary discharge timing for each ejection port 108 whose m determined by the second determination unit 42 is other than zero. The actuator unit 21 is controlled. However, the flushing control unit 47 controls the actuator unit 21 so that such preliminary vibration is performed only when the temperature indicated by the output signal of the temperature sensor 72 is higher than the first threshold value. In an environment where ink drying does not proceed, preliminary vibration is not performed, and power consumption can be reduced accordingly.

  Note that the flushing control unit 47 may control the actuator unit 21 so that such preliminary vibration is performed only when the detected humidity is lower than the second threshold value.

  In addition, the flushing control unit 47 performs preliminary ejection for each ejection port 108 as indicated by m determined for the ejection port 108 since the elapsed time from the start of printing on the paper P or from the most recent ink ejection. The actuator unit 21 is controlled so as to be performed every time the discharge timing is reached. In the present embodiment, the preliminary ejection timing is a printing cycle at which the value of the counter 63 is equal to the value of “N + m determined for the ejection port 108” for each ejection port 108.

  The preliminary ejection ink amount adjustment unit 48 (preliminary ejection liquid amount adjustment means) is based on the temperature indicated by the output signal of the temperature sensor 72, and the range in which the amount of ink ejected from the ejection port 108 in preliminary ejection does not exceed a predetermined upper limit value. The amount of ink is adjusted so as to increase as the temperature increases. In the present embodiment, the preliminary ejection ink amount adjustment unit 48 refers to a reference table C (not shown), and determines the ink amount as one of “large”, “medium”, and “small”. The reference table C is determined so that the ink amount increases from “small” → “medium” → “large” as the temperature increases.

  In the preliminary ejection, particularly the preliminary ejection onto the paper P, the ink ejection amount is reduced, and the visibility of the formed dots is lowered. In the reference table C, since the discharge amount reduction due to thickening at high temperature is taken into consideration, the temperature and the ink amount instruction value are associated with each other, so that the dot formed has low visibility in any combination. It becomes.

  Further, the preliminary ejection ink amount adjustment unit 48, based on the humidity indicated by the output signal of the humidity sensor 73, as the humidity decreases in a range where the ink amount ejected from the ejection port 108 in the preliminary ejection does not exceed a predetermined upper limit value. The amount of ink may be adjusted so as to increase. In this case, the preliminary ejection ink amount adjustment unit 48 refers to a reference table C ′ (not shown) and determines and adjusts the ink amount to one of “large”, “medium”, and “small”. The reference table C ′ is determined so that the ink amount increases from “small” → “medium” → “large” as the humidity decreases.

  The first elapsed time adjustment unit 49 (first elapsed time adjustment unit) starts from the start of printing on the paper P so as to increase as the waiting time increases based on the waiting time detected by the waiting time detection unit 46. Adjust the initial value of elapsed time. After receiving the print command, the cap is removed from the head 1 and the print preparation operation is performed in a state where the discharge port 108 is opened to the atmosphere. Even after the printing process based on the printing command is completed, the apparatus stands by for a predetermined time with the discharge port 108 open to the atmosphere. In either case, the thickening of the ink proceeds. The adjustment of the initial value by the first elapsed time adjustment unit 49 is an adjustment in consideration of these thickening factors, and the start of the discharge characteristic maintaining operation is advanced in accordance with the magnitude of the influence.

  In the present embodiment, the first elapsed time adjustment unit 49 refers to a reference table D (not shown) that is determined in advance so that the value W is determined to be one by the waiting time, and determines the value W for the detected waiting time. First decide. Then, the value of “the value W + a value E described later” is set as an initial value when the counter 63 indicates the number of print cycles that have elapsed since the start of printing on the paper P. The reference table D is determined such that W increases as the waiting time increases.

  The second elapsed time adjustment unit 60 (second elapsed time adjustment means) is based on the temperature indicated by the output signal of the temperature sensor 72, or increases from the start of printing on the paper P so as to increase as the temperature increases. The initial value of the elapsed time from the ink ejection is adjusted. In the present embodiment, the second elapsed time adjustment unit 60 refers to a predetermined reference table E (not shown) so that the value E is determined to be one by temperature, and first determines E for the detected temperature. . Then, the value of “W + the above-mentioned E” is set as an initial value when the counter 63 indicates the number of print cycles that have elapsed since the start of printing on the paper P, and the above-mentioned E is set from the most recent ink ejection. The initial value for indicating the number of elapsed printing cycles. The reference table E is determined such that E increases as the temperature increases.

  Further, the second elapsed time adjusting unit 60 has elapsed from the start of printing on the paper P or from the most recent ink discharge so as to increase as the humidity decreases based on the humidity indicated by the output signal of the humidity sensor 73. You may adjust the initial value of time. In that case, the second elapsed time adjustment unit 60 refers to a reference table E ′ (not shown) determined in advance so that E is determined to be one by the humidity, and calculates E for the humidity indicated by the output signal of the humidity sensor 73. decide. The reference table E ′ is defined such that E increases as the humidity decreases.

  The print ink amount adjustment unit 61 (recording liquid amount adjustment unit) adjusts the amount of ink discharged from the discharge port 108 in printing an image on the paper P based on the control of the image print control unit 45. At this time, the instructed ink amount increases as the elapsed time from the start of printing on the paper P or from the most recent ink discharge increases within a range not exceeding the predetermined upper limit value. In this embodiment, the value of the counter 63 and the corresponding ink amount change stage number are determined, and the relationship between the two is changed depending on the humidity. More specifically, first, reference is made to a reference table F (not shown) determined so that the value N1 and the value N2 (threshold value regarding the value of the counter 63) are each determined by the temperature, and the output of the temperature sensor 72 is determined. Determine N1 and N2 for the temperature indicated by the signal. When the value of the counter 63 related to the target ejection port 108 is smaller than N1, the ink amount to be ejected is kept as originally planned, and the value of the counter 63 is N1 or more and less than N2. Is an amount that is one step higher than the originally planned ink amount, and when the value of the counter 63 is N2 or more, it is an amount that is two steps higher than the originally planned ink amount. However, when the ink amount adjusted in this way exceeds a predetermined upper limit value, that is, the ink amount “large”, the ejected ink amount is set to “large”.

  Next, the printing process of the inkjet printer 1 according to the present embodiment will be described with reference to the flowcharts of FIGS. Here, for convenience, only the process for one inkjet head 1 is described, and the process for the other three inkjet heads 1 is omitted.

  Here, the image formed on the paper P is composed of i columns × j rows of dots. All the dots belonging to the same row are formed by ink ejected from the same ejection port 108. In one printing cycle, the amount of ink to be ejected to the dot-formable position in the i-th column and the j-th row is represented as X (i, j) (i and j are natural numbers). At the stage of receiving a print command from the host, X (i, j) includes an ink amount “large” (21 pl), “medium” (14 pl), “small” (7 pl), and “none” (0 pl). ) Is shown.

  First, when a print command is received from the host, image data included in the received print command is stored in the image data storage unit 44 in step S1. The image data includes X (i, j) indicating the amount of ink to be ejected to each dot formable position for each printing cycle. The print command includes the number of printed sheets and layout information.

  In step S <b> 2, the control unit 100 acquires the temperature detected by the temperature sensor 72. Next, in step S <b> 3, the control unit 100 acquires the waiting time detected by the waiting time detection unit 46.

In step S4, the following initial settings are made.
The first determination unit 41 refers to the reference table A and determines M for the temperature acquired in step S2.
The third determination unit 43 refers to the reference table B and determines N for the temperature acquired in step S2.
The printing ink amount adjustment unit 61 refers to the reference table F and determines N1 and N2 for the temperature acquired in step S2.
The first elapsed time adjustment unit 49 refers to the reference table D and determines W for the waiting time acquired in step S3.
The second elapsed time adjustment unit 60 refers to the reference table E and determines E for the temperature acquired in step S2.
The flushing control unit 47 determines whether or not the temperature acquired in step S2 is higher than the first threshold value. If the temperature is higher than the first threshold value, it is set to perform preliminary vibration in step S11 described later. Otherwise, it is set not to perform preliminary vibration.
The preliminary ejection ink amount adjustment unit 48 refers to the reference table C, determines the ink amount for the temperature acquired in step S2 to be one of “large”, “medium”, and “small”, which will be described later. This is set as the amount of ink ejected from the ejection port 108 in the preliminary ejection in step S13.

  In step S5, the counter 63 indicating the number of elapsed printing cycles from the start of printing on the paper P or from the most recent ink discharge is initialized. Specifically, the value of the counter 63 is set to “W + E” using W and E set in step S4.

  Next, in step S6, the second determination unit 42 randomly determines m within a range of 0 or more and M or less set in step S4. Note that step S6 is performed every time the value of i (a value indicating a row of dot formable positions) is incremented by 1 in step S22, so that m is one for each i, that is, each ejection port. One is determined for 108.

  Next, in step S7, the control unit 100 determines whether or not the ink amount: X (i, j) stored in step S1 is “none”. Note that the initial values of i and j are each “1”, and when the process of step S7 is performed for the first time, it is determined whether or not X (1,1) is “none”. And when it is judged that it is "none" (S7: YES), it progresses to step S8. When it is determined that it is not “none” (S7: NO), the process proceeds to step S15.

  In step S8, the flushing control unit 47 determines whether or not the value of the counter 63 is greater than or equal to N set in step S4. If it is determined that the value of the counter 63 is not equal to or greater than N (S8: NO), the process proceeds to step S9. In step S9, 1 is added to the value of the counter 63. Then, the process proceeds to step S18. If it is determined in step S8 that the value of the counter 63 is equal to or greater than N (S8: YES), the process proceeds to step S10. In the present embodiment, the printing cycle in which the value of the counter 63 becomes N or more for the first time in step S8 is the preliminary vibration permissible timing in this row created by the dot formable position.

  In step S10, the flushing control unit 47 determines whether or not the value of the counter 63 is equal to the value “N + m”. When it is determined that the value of the counter 63 is not equal to the value of “N + m” (S10: NO), the process proceeds to step S11. In step S11, if it is set in step S4 to perform preliminary vibration, the flushing control unit 47 indicates that the preliminary vibration is performed in the printing cycle corresponding to X (i, j). The data of (i, j) is rewritten. Then, the process proceeds to step S12. If it is set in step S4 not to perform preliminary vibration, the process proceeds to step S12 without rewriting such data. In step S12, 1 is added to the value of the counter 63. Then, the process proceeds to step S18.

  If it is determined in step S10 that the value of the counter 63 is equal to the value of “N + m” (S10: YES), the process proceeds to step S13. In step S13, the preliminary ejection ink amount adjustment unit 48 rewrites the data of X (i, j) so that preliminary ejection is performed from the ejection port 108 in the printing cycle corresponding to X (i, j). At this time, the ink amount: X (i, j) is set to the ink amount set by the preliminary ejection ink amount adjusting unit 48 in step S4. In the present embodiment, this printing cycle in which the value of the counter 63 becomes equal to the value of “N + m” in step S10 is the preliminary ejection timing at the dot formable position in the i-th column and j-th row. Thereafter, in step S14, the value of the counter 63 is set to E. Thereby, each process based on the value of the counter 63 is adapted to the change of the environment (temperature). Then, the process proceeds to step S18.

  In step S15, a printing ink amount adjustment amount determination process is performed when ejecting from the ejection port 108 in the printing cycle corresponding to X (i, j). Details of the printing ink amount adjustment amount determination process are shown in FIG.

  In the printing ink amount adjustment amount determination process, in step S101, the printing ink amount adjustment unit 61 determines whether or not the ejection ink amount X (i, j) indicated by the image data in the printing cycle is “large”. to decide. If it is determined to be “large”, the process proceeds to step S102. If it is determined that it is not “large”, the process proceeds to step S103.

  In step S103, the printing ink amount adjustment unit 61 determines whether or not the value of the counter 63 is equal to or greater than N1 set in step S4. If it is determined that it is N1 or more, the process proceeds to step S104. If it is determined that it is not N1 or more, the process proceeds to step S102. Here, the threshold value N1 corresponds to the maximum number of times that the printing cycle corresponding to X (i, j) = “none” can be repeated under the condition that the thickening of the ink hardly affects the printing quality.

  In step S102, a value L = 0 indicating the print ink amount adjustment amount is set. Then, the printing ink amount adjustment amount determination process ends. Here, the value L = 0 is set because there is no room for adjusting X (i, j) to other than “large” when step 102 is a step following step 101, and continues to step 103. This is because, in the case of the step, there is no influence of thickening and it is not necessary to adjust the ink amount: X (i, j).

  In step S104, the printing ink amount adjustment unit 61 determines whether or not the value of the counter 63 is equal to or greater than N2 set in step S4. When it is determined that it is N2 or more, the process proceeds to step S106, and when it is determined that it is not N2 or more, the process proceeds to step S105. Here, the threshold value N2 is an index for changing the print ink amount adjustment amount according to the degree of the influence under the condition that the ink thickening affects the print quality. If the value of the counter 63 is smaller than this, the adjustment amount for X (i, j) may be small, and if it is more than this, it is necessary to increase the adjustment amount.

  In step S106, the printing ink amount adjustment unit 61 determines whether or not the X (i, j) is “medium”. When it is determined that it is “medium”, the process proceeds to step S105, and when it is determined that it is not “medium”, the process proceeds to step S107.

  In step S105, L = 1 is set. Here, the value L = 1 is set when step S105 is a step following step S106 because there is no room for adjustment other than increasing X (i, j) by one step. This is because the influence of thickening is weak and the adjustment amount for X (i, j) may be small. Then, the printing ink amount adjustment amount determination process ends. In step S107, L = 2 is set. Here, L = 2 is set because the influence of thickening is strong, so it is necessary to increase the adjustment amount for X (i, j), and X (i, j) can be increased by two stages. Because. Then, the printing ink amount adjustment amount determination process ends.

  Then, it returns to step S16 of FIG. In step S16, the ink amount X (i, j) ejected from the ejection port 108 in the printing cycle corresponding to the value of the counter 63 is rewritten based on L determined by the printing ink amount adjustment unit 61 in step S15. . At this time, the ink amount: X (i, j) instructed by the image data is changed to an ink amount that is L steps higher than that. For example, when X (i, j) is “small” and L is determined to be 1 in step S15, the data of X (i, j) is an amount one step higher than “small”. Rewrite to “medium”. Thereafter, the process proceeds to step S17. In step S17, the value of the counter 63 is set to E. Then, the process proceeds to step S18.

  In step S18, it is determined whether or not there is a dot-formable position in the unprocessed j-th row in the i-th column. That is, it is determined whether or not processing has been performed for all j dot-formable positions in the i-th row. If it is determined that there is an unprocessed dot formable position (S18: YES), the process proceeds to step S19, and 1 is added to the value of j. Then, the process returns to step S7. If it is determined that there is no unprocessed dot formable position (S18: NO), the process proceeds to step S20.

  In step S20, it is determined whether there is a row of unprocessed dot formable positions. That is, it is determined whether or not all i columns have been processed. When it is determined that there is an unprocessed column (S20: YES), the process proceeds to step S21.

  In step S21, the value of the counter 63 is set to “W + E”, and the counter 63 is initialized. Subsequently, in step S22, 1 is added to the value of i. Then, the process returns to step S7.

  If it is determined in step S20 that there is no unprocessed column (S20: NO), the process proceeds to step S23. In step S23, image printing, preliminary vibration, and preliminary ejection are performed. Specifically, the image printing control unit 45 and the flushing control unit 47 synchronize with the control of the motor 19 by the conveyance control unit 62, and the detection signal of the leading edge of the paper P from the paper sensor 31, and step S11, The actuator unit 21 is controlled based on X (i, j) after the conversion is performed in S13 and S16. Then, the printing process ends.

  Next, an example of the printing process will be described with reference to FIG.

  In the present embodiment, the paper P can form 8 columns × 35 rows of dots. Each square shown in FIG. 9 is a dot-formable position where dots can be formed in each printing cycle. Here, the dot formable position of the i-th column and the j-th row on the paper P is represented as (i, j), and as described above, the amount of ink to be ejected in each printing cycle with respect to (i, j). X (i, j). For convenience, it is assumed that the 88 dots X (1, 1) to X (8, 11) all have the ink amount “none” at the stage of receiving the print command related to the print processing. Therefore, in FIG. 7, the process from step S7 through step S15 to step S18 is not performed. The head 1 used at this time is a line head having eight ejection ports 108.

  FIG. 9 shows a process performed for each ejection port 108 at a printing cycle corresponding to (1, 1) to (8, 11) in step S23 when a certain printing process is performed. is there. Preliminary vibration is performed on the ejection port 108 at a printing cycle corresponding to the square indicated as “vibration”, and at the ejection port 108 at a printing cycle corresponding to the square indicated as “discharge”. On the other hand, preliminary discharge is performed. Further, no preliminary vibration or preliminary ejection is performed on the ejection port 108 in the printing cycle corresponding to the squares where nothing is shown.

In the present embodiment, it is assumed that the following settings are made in step S4 of FIG.
M for the temperature acquired in step S2 is 5.
N with respect to the temperature acquired in step S2 is 10.
N1 and N2 for the temperature acquired in step S2 are 5, 10, respectively.
W for the waiting time acquired in step S3 is 2.
E for the temperature acquired in step S2 is 3.
The temperature acquired in step S2 is higher than the first threshold value, and therefore preliminary vibration is performed in step S11.
The ink amount with respect to the temperature acquired in step S2 is “medium”. Therefore, the amount of ink ejected from the ejection port 108 in the preliminary ejection in step S13 is “medium”.

  In a printing process, after the initial setting is performed in step S4 as described above, the counter 63 is initialized in step S5. At this time, since W = 2 and E = 3, the initial value of the counter 63 becomes 5. In step S6, m = 2 is determined for the first column.

  In step S7, it is first determined whether X (1,1) is “none”. Here, since X (1,1) to X (8,11) are all “none”, the determination is YES and the process proceeds to step S8. In step S8, it is determined whether or not the value of the counter 63 is N or more. Here, since the value of the counter 63 is 5 and N = 10, it is determined as NO, the process proceeds to step S9, and 1 is added to the value of the counter 63. Then, the process proceeds to step S18, where YES is determined because there is an unprocessed dot forming position in the first column, and 1 is added to j in step S19. Then, it returns to step S7. Such processing is performed until the value of the counter 63 = N = 10. That is, X (1,1) to X (1,5) remain the ink amount “none”. Therefore, as shown in FIG. 9, no preliminary vibration or preliminary ejection is performed on the ejection port 108 in the printing cycle corresponding to (1, 1) to (1, 5) in step S23.

  Thereafter, in the process for X (1,6), it is determined in step S8 that the value of the counter 63 = N = 10, and the process proceeds to step S10. In step S10, it is determined whether or not the value of the counter 63 is equal to the value “N + m”. Here, since the value of the counter 63 = 10 and N + m = 12, it is determined as NO and the process proceeds to step S11. In step S11, as set in step S4, the data of X (1,6) is rewritten so that the preliminary vibration is performed in the printing cycle corresponding to (1,6) in step S23. Thereafter, 1 is added to the value of the counter 63 in step S12. The same processing is performed until the value of the counter 63 = N + m = 12. That is, data rewriting is performed similarly for X (1, 7). Therefore, as shown in FIG. 9, preliminary vibration is performed on the ejection port 108 in the printing cycle corresponding to (1, 6) to (1, 7) in step S <b> 23.

  Thereafter, in the process for X (1, 8), since the value of the counter 63 = 12 ≧ N = 10 in step S8, it is determined YES and the process proceeds to step S10. In step S10, since the value of the counter 63 = N + m = 12, YES is determined and the process proceeds to step S13. In step S13, the data of X (1,8) is rewritten so that preliminary ejection is performed in the printing cycle corresponding to (1,8) in step S23. Specifically, X (1, 8) is rewritten to “medium” set in step S4. Therefore, as shown in FIG. 9, preliminary ejection is instructed to the ejection port 108 in the printing cycle corresponding to (1, 8) in step S23.

  The value of the counter 63 is set to E = 3, that is, 3. Thereafter, processing such as preliminary vibration or preliminary ejection is not performed until the value of the counter 63 becomes N = 10 again in step S8. Therefore, as shown in FIG. 9, no preliminary vibration or preliminary ejection is performed on the ejection port 108 in the printing cycle corresponding to at least (1, 9) to (1, 11) in step S23. .

  In the example of FIG. 9, m for the second to eighth columns is 4, 0, 3, 1, 3, 0, 5 respectively.

  Next, a specific example of the printing ink amount adjustment amount determination process will be described with reference to FIG. The number of dots that can be formed on the paper P and the values set in step S4 in FIG. 7 are the same as in the example in FIG.

  FIG. 10A shows ink amounts: X (1, 31) to X (8, 35) at the stage when a print command related to a certain print process is received. FIG. 10B shows the adjusted ink amounts in step S23: X (1, 31) to X (8, 35), that is, the ink amounts actually ejected from the ejection ports 108, respectively. It is. The amount of ink ejected from the ejection port 108 in the printing cycle corresponding to the squares where nothing is shown is “none”.

  Here, the (1,33) square is taken as an example. X (1, 33) at the stage of receiving the print command related to the print processing is “small” as shown in FIG. Therefore, in step S7 of FIG. 7, it is determined that X (1,33) is not “none”, and the process proceeds to the printing ink amount adjustment amount determination process in step S15.

  In the printing ink amount adjustment amount determination process, since X (1,33) is “small” in step S101, it is determined as NO and the process proceeds to step S103. In step S103, it is determined whether the value of the counter 63 is N1 or more. Assume that the value of the counter 63 at this time is 11, and N1 = 5. Therefore, YES is determined and the process proceeds to step S104. In step S104, it is determined whether the value of the counter 63 is N2 or more. Since the value of the counter 63 = 11 ≧ N2 = 10, YES is determined and the process proceeds to step S106. In step S106, since X (1, 33) is “small”, it is determined as NO and the process proceeds to step S107. In step S107, it is determined that L = 2, and the printing ink amount adjustment amount determination process ends.

  Returning to step S16, the data of X (1,33) is rewritten to “large”, which is an amount two steps higher than “small”. Therefore, as shown in FIG. 10B, the ink amount in step S23: X (1, 33), that is, the ink amount ejected from the ejection port 108 in the printing cycle corresponding to (1, 33). Becomes “large”.

  According to the embodiment described above, each ejection port 108 is preliminarily ejected each time the elapsed time from the start of printing on the paper P or the most recent ink ejection reaches the preliminary ejection timing. Therefore, it is not necessary to calculate the total ink discharge amount from the printer, and only a sequential calculation for calculating the elapsed time from the start of printing on the paper P at each discharge port 108 or from the latest ink discharge is required. Therefore, simplification of arithmetic processing is realized.

  In addition, since the preliminary ejection timing at which preliminary ejection is performed for each ejection port 108 is indicated by a random value m, the ink ejected by the preliminary ejection is landed at a random position on the paper P in the transport direction. Therefore, the plurality of dots formed by the preliminary ejection are not formed as a straight line extending in the direction orthogonal to the transport direction, and the dots not related to the printed image are formed on the paper P by the preliminary ejection. This is difficult for the observer to recognize.

  In addition, m is a random value of 0 or more and a value less than M that decreases as the temperature of the environment in which the head 1 is provided increases or decreases as the humidity decreases, and is a value based on the temperature or humidity. It is. Therefore, it is possible to appropriately eliminate the thickening of the ink in consideration of the ease of thickening the ink due to temperature or humidity. Further, it is possible to reduce a situation such as wasteful ejection of ink from the ejection port 108 that does not require preliminary ejection. Accordingly, it is possible to prevent deterioration of image quality.

  The actuator unit 21 is not driven until the preliminary vibration allowable timing indicated by N based on temperature or humidity is reached before the preliminary discharge timing. Therefore, considering the ease of thickening of the ink due to temperature or humidity, it is possible to reduce the situation such as wasteful ejection of ink from the ejection port 108 that does not require preliminary ejection. Accordingly, it is possible to prevent deterioration of image quality.

  For each ejection port 108 where m is not zero, the preliminary vibration is performed at least once from the preliminary vibration permissible timing to the preliminary ejection timing, so that it is possible to more reliably increase the viscosity of the ink while avoiding unnecessary ink consumption. Can be resolved. Therefore, it is possible to more reliably prevent the image quality from deteriorating.

  For each ejection port 108 where m is not zero, the preliminary vibration is performed only when the temperature is higher than the first threshold value or the humidity is lower than the second threshold value. More appropriate preliminary vibration can be performed in consideration of ease of operation. Therefore, it is possible to reduce the situation such as wasteful pre-vibration for the discharge port 108 that does not require pre-vibration. Thereby, unnecessary power consumption can be suppressed.

  For each ejection port 108 with m other than zero, preliminary vibration is performed in each printing cycle from the preliminary vibration permissible timing to the preliminary ejection timing, so that it is possible to more reliably eliminate ink thickening. Therefore, it is possible to more reliably prevent the image quality from deteriorating.

  Since the amount of ink ejected from the ejection port 108 in the preliminary ejection is adjusted in consideration of the ease of ink thickening due to temperature or humidity, ink thickening can be more appropriately eliminated. Therefore, it is possible to more reliably prevent the image quality from deteriorating.

  Since the initial value is adjusted in consideration of the waiting time from the end of printing on the paper P on which printing has been performed most recently to the start of printing on the paper P on which printing is performed next, the waiting time is long, for example. That is, when the ink viscosity is likely to increase, the preliminary ejection timing is advanced. Therefore, it is possible to more appropriately eliminate the thickening of the ink. Therefore, it is possible to more reliably prevent the image quality from deteriorating.

  Since the initial value is adjusted in consideration of the ease of ink thickening due to temperature or humidity, for example, when the temperature is high or humidity is low, i.e., ink thickening is likely to occur, the preliminary ejection timing is It will be faster. Therefore, it is possible to more appropriately eliminate the thickening of the ink. Therefore, it is possible to more reliably prevent the image quality from deteriorating.

  Since the amount of ink ejected from the ejection port 108 in printing an image on the paper P based on the control of the image print control unit 45 is adjusted in consideration of the ease of thickening of the ink due to temperature or humidity, the paper P It is possible to prevent a situation in which the amount of ink landed on the ink decreases due to the increase in the viscosity of the ink. Therefore, it is possible to more reliably prevent the image quality from deteriorating.

  The preferred embodiments of the present invention have been described above, but the present invention is not limited to the above-described embodiments, and various design changes can be made to the above-described embodiments as long as they are described in the claims. Is possible.

  In the above-described embodiment, the flushing control unit 47 operates the actuator unit so that the preliminary vibration is performed in each printing cycle from the preliminary vibration allowable timing to the preliminary discharge timing for each ejection port 108 where m is not zero. However, the actuator unit 21 may be controlled so that it is performed at least once between the preliminary vibration permissible timing and the preliminary discharge timing.

  Further, the amount of ink ejected from the ejection port 108 is not limited to four types of “small”, “medium”, “large”, and “none”. Therefore, the value of L in the printing ink amount adjustment amount determination process in step S15 is not limited to 0, 1, and 2.

  In the above-described embodiment, the liquid ejected from the ejection port 108 has been described as ink. However, the present invention can be applied to any liquid other than ink that thickens with time. Further, the liquid discharge head using PZT as an ink jet head has been described as an example, but the present invention can be applied to a liquid discharge head using an electrostatic method or bubbles generated by heating a liquid.

  Moreover, in the above-mentioned embodiment, the process repeated after step S7 in FIG. 7 is (1,1), (1,2), (1,3) ..., (2,1), (2,2) ... This is done for each dot-formable position in the order described above. That is, after the process for all the dot formable positions belonging to the i-th column is completed, the process is performed for the dot-formable positions belonging to the i + 1th line. However, the present invention is not limited to this, and belongs to the jth column in the order of (1,1), (2,1), (3,1)..., (1,2), (2,2). After the process for all the dot formable positions is completed, the process may be performed for the dot formable positions belonging to the j + 1th column. In that case, it is necessary to provide j counters corresponding to the number of columns.

  In the above-described embodiment, the second elapsed time adjustment unit 60 determines the value E with respect to the temperature when the print command is received. However, after receiving the print command, the second elapsed time adjustment unit 60 determines the temperature and the temperature at a predetermined time interval. The value E may be determined. As a result, the operation for maintaining the ejection characteristics as described above can be performed in response to changes in the environment (temperature) over time.

DESCRIPTION OF SYMBOLS 1 Inkjet head 9 Flow path unit 16 Conveyance mechanism 21 Actuator unit 41 1st determination part 42 2nd determination part 43 3rd determination part 44 Image data storage part 45 Image printing control part 46 Waiting time detection part 47 Flushing control part 48 Preliminary discharge Ink amount adjustment unit 49 First elapsed time adjustment unit 60 Second elapsed time adjustment unit 61 Print ink amount adjustment unit 72 Temperature sensor 73 Humidity sensor 108 Discharge port

Claims (9)

A transport mechanism for transporting the recording medium;
A plurality of individual liquid flow paths each having a plurality of discharge ports arranged at predetermined intervals corresponding to the print resolution in the orthogonal direction and the discharge ports at one end with respect to the orthogonal direction orthogonal to the conveyance direction of the recording medium by the conveyance mechanism And a liquid discharge head having a plurality of actuators for applying discharge energy to the liquid in the individual liquid flow path;
Image data storage means for storing image data relating to an image to be recorded on a recording medium;
Image recording for controlling the plurality of actuators based on the image data stored in the image data storage means so that an image is recorded by discharging liquid toward the recording medium conveyed by the conveyance mechanism. Control means;
Environmental data detection means for detecting at least one value of temperature and humidity of the environment in which the liquid ejection head is provided;
First determination means for determining a first value M that decreases as the temperature increases or decreases as the humidity decreases, based on a detection result by the environmental data detection means;
Second determination means for determining a second value m, which is a random value between 0 and the first value M, for each discharge port;
For each discharge port, preliminary discharge is performed to discharge a thickened liquid near the discharge port toward a recording medium on which an image is recorded by driving the actuator not based on the image data stored in the image data storage unit. The plurality of actuators so that an elapsed time from the start of recording on the recording medium or from the most recent liquid discharge reaches each preliminary discharge timing indicated by the second value m determined for the discharge port. And a flushing control means for controlling the liquid discharge device. Based on the detection result by the environmental data detection means, further comprising third determination means for determining a third value N that decreases as the temperature increases or decreases as the humidity decreases;
The flushing control unit is configured so that an elapsed time from the start of recording on the recording medium or from the latest liquid discharge is earlier than the preliminary discharge timing, except when the image recording control unit controls the plurality of actuators. 2. The liquid ejecting apparatus according to claim 1, wherein the plurality of actuators are controlled so that the plurality of actuators are not driven until a preliminary vibration permissible timing indicated by a certain third value N is reached.   The flushing control means, for each ejection port whose second value m is other than zero, pre-vibration that vibrates the actuator in a range in which liquid is not ejected from the ejection port, from the pre-vibration permissible timing to the pre-ejection timing. The liquid ejecting apparatus according to claim 2, wherein the plurality of actuators are controlled so as to be performed at least once in between.   The flushing control means has a temperature higher than the first threshold value or a humidity higher than the second threshold value for each ejection port whose second value m is other than zero, based on the detection result by the environmental data detection means. The liquid ejecting apparatus according to claim 3, wherein the plurality of actuators are controlled so that the preliminary vibration is performed only when the frequency is lower. The image recording control unit and the flushing control unit control the plurality of actuators in units of a recording cycle that is a time required for the recording medium to be conveyed by the conveying mechanism by a distance corresponding to the printing resolution in the conveying direction. And
The flushing control means includes the plurality of actuators so that the preliminary vibration is performed in each recording period from the preliminary vibration permissible timing to the preliminary discharge timing for each ejection port whose second value m is not zero. The liquid ejection apparatus according to claim 3, wherein the liquid ejection device is controlled.   Based on the detection result by the environmental data detection means, the amount of liquid discharged from the discharge port in the preliminary discharge increases as the temperature increases or the humidity decreases in a range not exceeding a predetermined upper limit value. The liquid discharge apparatus according to claim 1, further comprising preliminary discharge liquid amount adjustment means for adjusting a liquid amount. A waiting time detecting means for detecting a waiting time from the end of recording to a recording medium on which recording has been performed to the start of recording on a recording medium on which recording is performed next;
First elapsed time adjusting means for adjusting an initial value of elapsed time from the start of recording on the recording medium so as to increase as the waiting time becomes longer based on the waiting time detected by the waiting time detecting means; The liquid ejecting apparatus according to claim 1, wherein the liquid ejecting apparatus is provided.   Based on the detection result by the environmental data detection means, the initial value of the elapsed time from the start of recording on the recording medium or from the most recent liquid discharge so as to increase as the temperature increases or as the humidity decreases. The liquid ejecting apparatus according to claim 1, further comprising second elapsed time adjusting means for adjusting the time.   In the recording of an image on a recording medium based on the control of the image recording control means, the amount of liquid ejected from the ejection port does not exceed a predetermined upper limit value from the start of recording on the recording medium or from the latest liquid ejection. The liquid ejecting apparatus according to claim 1, further comprising a recording liquid amount adjusting unit that adjusts the liquid amount so as to increase as the elapsed time increases.

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