JP2014024249A - Inkjet recording apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inkjet recording apparatus in which preliminary discharge is performed by discharging an appropriate amount of ink according to positions of discharge ports.SOLUTION: An inkjet recording apparatus changes discharge amounts of ink when preliminary discharge for recovering discharged states of the ink by a recording head by discharging ink unrelated to recording is performed depending on positions where discharge ports are formed in the recording head. The discharge amounts of the ink in the preliminary discharge are controlled so that the lower a humidity at the position where the discharge port is formed is, the more the ink is discharged from the discharge port to perform the preliminary discharge.

Description

  The present invention relates to an ink jet recording apparatus that performs preliminary discharge for discharging ink that is not involved in recording in order to maintain a discharge state from an discharge port.

  In an ink jet recording apparatus that performs recording by discharging ink from a recording head, when there are discharge ports that are not used for a long period of time, volatile components contained in the ink inside the recording head are discharged from the discharge port. May evaporate through and the ink may thicken. When the viscosity of the ink is increased, the ink may not be ejected normally due to this, and ejection failure such as a deviation in ejection direction, insufficient ejection amount, or non-ejection may occur. In order to suppress the occurrence of such a discharge failure, an ink jet recording apparatus may perform so-called preliminary discharge for discharging ink that is not involved in recording. Thereby, the thickened ink around the discharge port can be discharged from the discharge port, and the ink stored in the recording head can be kept in a good state. Patent Document 1 discloses an ink jet recording apparatus in which preliminary ejection is performed in this way. Patent Document 1 discloses that humidified air is supplied around a discharge port in a recording head.

JP 2007-326322 A

  However, in the ink jet recording apparatus disclosed in Patent Document 1, a recording medium on which recording is performed passes through a recording area where recording is performed after passing through an area where humidified air is blown out. Therefore, when a recording medium that already contains a large amount of moisture contained in the humidified air passes through the recording area, the humidity may increase only in the area of the recording area through which the recording medium passes. Conversely, when the humidified air is supplied directly to the recording head without being blown toward the recording medium, the recording medium absorbs the moisture contained in the humidified air, so that the recording area is recorded. There is a possibility that the humidity decreases only in the area through which the medium passes. In this way, when the recording medium passes through the area where humidified air is supplied, a difference in humidity occurs between the area where the recording medium passes and the area where the recording medium does not pass, and in a direction crossing the conveyance direction of the recording medium. Along the way, the humidity may not be uniform. The ink ejection amount required for the preliminary ejection varies depending on the humidity around the ejection port where the preliminary ejection is performed. For this reason, there is a possibility that the ejection amount of ink required for the preliminary ejection differs for each ejection port along the direction intersecting the recording medium conveyance direction. Therefore, even if preliminary ejection is performed at a constant ejection amount for all ejection ports, the amount of ink ejected during preliminary ejection is partially insufficient or partially more ink than necessary. It may be discharged.

  In view of the above circumstances, an object of the present invention is to provide an ink jet recording apparatus in which preliminary ejection is performed by ejecting an appropriate amount of ink according to the position of the ejection port.

  The inkjet recording apparatus of the present invention includes a transport unit that transports a recording medium, a recording head in which a plurality of ejection ports that eject ink are arranged along a direction that intersects a direction in which the recording medium is transported by the transport unit, In an ink jet recording apparatus comprising: a preliminary ejection unit that ejects ink that is not involved in recording to the recording head; the amount of ink discharged when preliminary ejection is performed by the preliminary ejection unit is conveyed by the conveyance unit by the conveyance unit. The ink is changed in accordance with the position where the discharge port is formed along the direction intersecting the direction in which the discharge port is formed. The lower the humidity at the position where the discharge port is formed, the more ink is discharged from the discharge port and preliminary discharge is performed. In this case, a preliminary discharge amount control unit that controls the discharge amount of ink when performing the preliminary discharge is provided.

  According to the present invention, preliminary ejection can be performed with an appropriate ink ejection amount at each ejection port position, and a large amount of ink is consumed unnecessarily by ejecting ink excessively during preliminary ejection. That can be suppressed. In addition, it is possible to prevent the ink in the recording head from being thickened due to a shortage of ink discharge during preliminary ejection, thereby preventing ink ejection failure, and the quality of the recorded image obtained by recording can be reduced. Can be kept high.

1 is a schematic cross-sectional view illustrating an ink jet recording apparatus according to a first embodiment of the present invention. FIG. 2 is a schematic plan view showing the ink jet recording apparatus of FIG. 1. FIG. 2 is a schematic plan view illustrating a surface on which a discharge port is formed in a recording head mounted on the ink jet recording apparatus of FIG. 1. FIG. 2 is a plan view showing a recording medium on which recording is performed by the ink jet recording apparatus of FIG. 1. The relationship between the area through which the recording medium passes, the ejection ports used, the humidity distribution, and the ejection amount of ink ejected during preliminary ejection when recording is performed by the ink jet recording apparatus of FIG. 1 is shown. It is explanatory drawing. 3 is a flowchart illustrating a control flow when a recording operation is performed by the ink jet recording apparatus of FIG. 1. When the recording is performed by the ink jet recording apparatus according to the second embodiment of the present invention, the area through which the recording medium passes, the ejection ports used, the humidity distribution, and the ejection amount of the ink ejected during the preliminary ejection It is explanatory drawing shown about the relationship between. It is the typical sectional view shown about the ink-jet recording device concerning a 3rd embodiment of the present invention. 8 shows the relationship among the area through which the recording medium passes, the ejection ports used, the humidity distribution, and the ejection amount of ink ejected during preliminary ejection when recording is performed by the ink jet recording apparatus of FIG. It is explanatory drawing.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

(First embodiment)
FIG. 1 is a schematic cross-sectional view of an inkjet recording apparatus 1 according to the first embodiment of the present invention. FIG. 2 is a schematic plan view of the ink jet recording apparatus 1.

  The ink jet recording apparatus 1 of this embodiment has a recording head 2. In the present embodiment, the recording head 2 includes recording heads 2K, 2C, 2M, and 2Y that eject inks of four colors of black (K), cyan (C), magenta (M), and yellow (Y). ing. Each of the recording heads 2K, 2C, 2M, and 2Y has a length that is equal to or greater than the width of the recording medium in the width direction of the recording medium that is orthogonal to the conveyance direction X of the recording medium. This is a full line type recording head.

  In the recording head 2, the ink is stably held by forming a meniscus at the ejection port. Each of the flow paths in the recording head is provided with a heater (not shown). By energizing the heater and generating thermal energy from the heater, the ink in the flow path is heated and foamed by film boiling, and ink droplets are ejected from the ejection port by the foaming energy at that time. The recording head according to the present embodiment employs a system in which film boiling is generated by a heating element and foamed to eject ink droplets, but the present invention is not limited to this. A recording head that deforms the piezoelectric element and thereby discharges liquid inside the recording head may be applied to the ink jet recording apparatus, and other types of recording heads may be applied to the ink jet recording apparatus of the present invention. Also good.

  FIG. 3 is a schematic plan view showing the surface on which the discharge ports are formed in the recording head 2 of the present embodiment. As shown in FIG. 3, each recording head 2 is formed with a plurality of ejection openings 14 for ejecting ink, and the ejection opening arrays are formed in a line at a predetermined interval on the same surface. Each heater is driven and ink is ejected in accordance with ejection data sent from a control unit 9 to be described later. Ink is supplied from a common ink chamber (not shown) in the recording head 2 to the ejection port 14 after ejection, and the ink can be ejected when the ejection signal is applied to the heater again. .

  As shown in FIGS. 1 and 2, the inkjet recording apparatus 1 includes a paper feed unit 4 and a transport roller 5. Inside the paper feed unit 4, a recording medium 3 is stored as continuous paper. The recording medium 3 is wound in a roll and disposed inside the paper feeding unit 4, and one end of the recording medium 3 is drawn out from the recording medium 3, and the one end is driven by the rotation of the transport roller 5 to form the recording head 2 </ b> K, It is conveyed in the direction toward 2C, 2M, 2Y. The transport roller 5 is paired with the driven roller 18 to form a plurality of roller pairs.

  The ink jet recording apparatus 1 also includes an image data input unit 6, an image data processing unit 7, a preliminary ejection data storage unit 8, and a control unit 9. The image data input unit 6 is a component for inputting image data to be recorded on the recording medium 3 from the outside. The image data processing unit 7 converts the image data input to the image data input unit 6 into discharge data of each discharge port provided in each head. The preliminary ejection data storage unit 8 is a component that stores the number of inks ejected to each ejection port when performing preliminary ejection. The control unit 9 controls the image data processing unit 7, the image data storage unit 8 formed by preliminary ejection, the ejection operation of the recording head 2 </ b> K, and the driving of the transport roller 5.

  The ink jet recording apparatus 1 according to the present embodiment includes a humidification unit (first humidified air supply unit) 10 for humidifying and humidifying the recording medium 3. The humidifying unit 10 in the ink jet recording apparatus 1 includes a humidifying tank 11 and a duct 12. Inside the humidifying tank 11, a filter (not shown) and a heater (not shown) that can heat the air are arranged. Further, water is stored inside the humidifying tank 11. When the heater provided in the humidification tank 11 generates heat, the air in the humidification tank 11 is heated to a preset temperature by the heater. The air heated by the heater passes through a filter containing water stored in the tank, and at this time, moisture held in the filter is supplied to the heated air. As a result, humidified air is generated in the humidifying tank 11. At this time, humidified air with high humidity can be generated by increasing the energization amount to the heater when heating the air and increasing the temperature of the air. The humidified air generated in the humidifying tank 11 is supplied through the duct 12 to the humidified air blowing section 13 disposed in the recording medium conveyance path. When the humidified air is supplied to the humidified air blowing section 13, the humidified air is blown from the humidified air to the recording medium.

  A humidity sensor (not shown) is arranged in the humidified air blowing section, and the controller 9 controls the amount of current supplied to the heater in the humidified tank so that the humidity becomes a desired value or more while measuring the humidity of the humidified air to be blown. Feedback control.

  When the recording medium 3 is fed and transported, first, one end of the recording medium 3 housed in the paper feeding unit 4 is pulled out, and the recording medium 3 is fed. When paper feeding is performed, the recording medium 3 is transported by the transport roller 5 from there. When the recording medium 3 is conveyed, the fed recording medium 3 is sandwiched between the conveying roller 5 and the driven roller 18. Therefore, the recording medium 3 is transported in the transport direction (X direction) by rotating the transport roller 5.

  When the recording medium 3 reaches a position corresponding to the humidified air blowing section 13, the humidifying process is performed on the recording medium 3 by the humidifying section 10. In the humidification process of the recording medium 3, first, the recording medium 3 passes through a region where the humidified air is blown out through the humidified air blowing portion 13. As a result, the recording medium 3 absorbs moisture contained in the humidified air.

  The recording medium 3 wetted by the humidification process diffuses moisture from the recording medium 3 to the recording head 2 when passing the position corresponding to the recording head 2 for recording. For this reason, the air around the recording head 2 is humidified, and accordingly, the air near the discharge port 14 is humidified, and the humidity increases. Since the air around the ejection port 14 is humidified, evaporation of the volatile components of the ink from the ejection port 14 can be suppressed to a small level, and the viscosity of the ink stored in the recording head 2 can be suppressed. Accordingly, it is possible to suppress the ejection failure when the recording head 2 ejects ink, and the ejection reliability of the recording head 2 can be improved. In the present embodiment, the ink jet recording apparatus 1 has an absolute humidity LH = 0.02 [kg / kgDA] or higher obtained in advance by a test in order to maintain a good discharge performance during a recording operation. The humidity around the discharge port is maintained by controlling the temperature of the humidifying heater. The humidity set at this time may be appropriately changed according to the type of ink, the configuration of the recording head, and the recording conditions.

  Further, in the present embodiment, preliminary ejection for recovering the ejection state in the ink ejection from the ejection ports 14 is performed on the recording medium at a predetermined interval so that ejection failure does not occur at each ejection port of the recording head 2. Do. In the preliminary ejection, ink that is not involved in recording is ejected separately from the ejection of ink for recording, and the ink around the ejection port 14 with increased viscosity is ejected and discharged from the recording head 2. Thereby, the thickened component of the ink stored in the recording head 2 is discharged to the outside of the recording head 2, and the ink ejection state by the recording head 2 is recovered. By regularly performing preliminary ejection, a good ink ejection state by the recording head 2 is maintained.

  FIG. 4 shows a position between a desired recorded image (hereinafter referred to as a target image) 16 obtained by recording performed based on image data and an image 15 formed on the paper as a result of preliminary ejection in the present embodiment. It is a typical top view which shows a relationship. In FIG. 4, an image 15 formed by ink ejected by preliminary ejection is recorded between a plurality of target images 16 that are continuously recorded. As described above, in the present embodiment, every time one target image 16 is recorded, preliminary ejection of the ejection ports used for recording is performed on the area between the target images 16.

  The image 15 formed by the preliminary ejection ejects ink to all ejection ports located in the image recording area in the width direction orthogonal to the recording medium conveyance direction X, that is, all ejection ports used for recording the target image 16. As a result, a solid image formed on the paper surface is obtained. As described above, in this embodiment, the preliminary discharge is periodically performed by recording the image 15 formed by the preliminary discharge between the target images 16, and the ink around the discharge port is recovered each time. Has been done. Here, the mode in which the preliminary discharge is performed every time the target image 16 is recorded has been described, but the preliminary discharge is set to be performed once every time the target image 16 is recorded a plurality of times. May be.

  In the present embodiment, the portion of the image 15 formed by the preliminary ejection is unnecessary, and therefore, after the recording of the predetermined number of target images 16 is finished, the portion is disposed in the portion downstream of the recording head 2 in the transport direction. A portion of the image 15 is cut and discarded by a cutter (not shown).

  Here, in the above-described embodiment, the form in which roll paper is used as the recording medium 3 has been described, but the present invention is not limited to this. The recording medium may be cut paper that has been cut to a desired size in advance, and in that case, the cut paper conveyance timing is adjusted so that a gap is formed between the front and rear cut paper, and the cut paper is Preliminary discharge may be performed in the gap.

  In addition, the inkjet recording apparatus 1 of the present embodiment can perform borderless recording in which an image is recorded up to both ends in the width direction of the recording medium 3. In general, when borderless recording is performed, it is assumed that the recording medium 3 is slightly displaced, and recording is performed up to a portion protruding from the size of the recording medium 3. In this way, by recording to the area that protrudes outward from the recording medium 3, an area as a margin is formed outside the recording medium 3, and even if the position of the recording medium 3 is deviated, the deviation is absorbed. Thus, borderless recording can be performed so that no blank portion is generated in the recorded image.

  Even when borderless printing is performed, it is preferable to periodically perform preliminary ejection for ejection ports used for image recording (hereinafter, used ejection ports). In addition, when performing borderless recording, it is preferable to perform preliminary discharge for the discharge ports used for recording to a position protruding from the recording medium. In the preliminary ejection, the thickened ink is discharged from the ejection port, and the characteristics of the ink stored in the recording head are restored to a state suitable for ejection. At this time, the amount of ink ejected from the recording head 2 required to restore the thickened ink to normal ink viscosity varies depending on the humidity of the air near the ejection port.

  When the inventor of the present invention transports the position corresponding to the recording head 2 after humidifying the recording medium, a difference occurs in the humidity distribution for each position along the ejection port array direction (Y direction in FIG. 5). This was clarified by experiments.

  FIG. 5 is a graph showing the relationship between the humidity distribution along the Y direction in which the ejection port array is formed in the recording head 2 and the ink ejection amount at the time of preliminary ejection set according to the humidity distribution. . Here, a case where borderless recording is performed will be described. As shown in FIG. 5, the position facing the recording medium 3 with the position corresponding to the end of the recording medium 3 as a boundary has higher humidity than the position not facing the recording medium 3. This is because the moisture diffused from the recording medium 3 increases the humidity around the recording medium 3 by convection and diffusion around the recording medium 3. At this time, the humidity distribution is higher as the location is closer to the recording medium 3.

  For this reason, when the recording medium 3 humidified and wetted by the humidifying unit 10 is transported to an area recorded by the recording head 2, the ejection port 14 passes through each position where the ejection port is formed. The ease of thickening the ink inside is different. That is, it is difficult for the ink to thicken at the ejection port formed at a position corresponding to the region through which the recording medium 3 passes, and the ink is thickened at the ejection port formed at a position corresponding to the region through which the recording medium 3 does not pass. easy. Accordingly, the amount of ink ejected for the preliminary ejection is set to be larger in the region not facing the recording medium 3 than in the region facing the recording medium 3. In the present embodiment, the discharge ports formed in the recording head 2 are divided into a use discharge port P used for recording and a non-use discharge port Q not used for recording. Of the used ejection ports P, the ejection port group P1 used for ejecting ink droplets onto the recording medium 3 and the ejection port group P2 used for ejecting ink ejected outside the recording medium 3 are divided. It has been. The amount of ink ejected during preliminary ejection is varied between these ejection ports. In other words, the amount of ink ejected by the preliminary ejection is such that the amount ejected from the ejection port group P2 formed in the region not facing the recording medium 3 is the used ejection port formed in the region facing the recording medium 3. It is set to be larger than the amount discharged from the group P1. As described above, the ejection of the ink when the preliminary ejection is performed according to the position where the ejection port is formed along the direction intersecting the direction in which the recording medium 3 is transported by the transport unit (orthogonal in the present embodiment). The amount is changing.

  In the present embodiment, the ejection amount of ink ejected during preliminary ejection is set in units of a plurality of ejection ports. In this case, when performing preliminary ejection, in order to sufficiently recover all the ejection ports of the ejection port group for which the ejection amount is collectively set, the ink amount set in each ejection port group is the ejection amount. It is preferable that the necessary ink amount is set in accordance with the discharge port having the lowest humidity in the outlet group.

  As shown in FIG. 5, in the ejection port group P1, the ink ejection amount A1 for the preliminary ejection required at that time is set under the condition of the humidity HH1. Further, in the ejection port group P2, the ink ejection amount C at the time of preliminary ejection required at that time is set under the condition of the humidity LH. Therefore, the ejection amount of ink is set to be relatively small for the ejection port P1 formed at a position corresponding to the region through which the recording medium 3 passes. In this way, preliminary ejection with a relatively small ink ejection amount is performed on ejection ports formed in regions where the humidity around the ejection ports is relatively high and the amount of ink ejection during preliminary ejection is small. The ink discharge amount is set to be performed. For this reason, it is possible to suppress the wasteful discharge of a large amount of ink due to the excessive discharge of the ink by the preliminary discharge with respect to the discharge port P1 formed at the position corresponding to the region through which the recording medium passes. In addition, a relatively large ink discharge amount is set for the discharge port P2 formed at a position corresponding to a region through which the recording medium does not pass. In this way, a relatively large amount of ink is discharged from the discharge port formed in a region where the humidity around the discharge port is relatively low and a large amount of ink is required for preliminary discharge. The ink discharge amount is set so that the preliminary discharge is performed. Therefore, a sufficiently large amount of ink is ejected by preliminary ejection to the ejection port P2 formed at a position corresponding to a region through which the humidified recording medium does not pass. Accordingly, it is possible to suppress a partial shortage of the ink discharge amount at the time of preliminary discharge, and it is possible to suppress deterioration in the quality of the recorded image due to thickening of the ink from the discharge port.

  In FIG. 5, for the purpose of explanation, the used discharge ports P used in the preliminary discharge are divided into two discharge port groups P1 and P2, and the ink amount is set for each discharge port group. Is not limited to this. The use discharge port P may be divided into three or more and set the ink discharge amount at the time of preliminary discharge, or the ink discharge amount at the time of preliminary discharge may be set for each discharge port. In order to set the ink discharge amount in the preliminary discharge more appropriately, the ink discharge amount of each discharge port group can be set more finely as the number of divisions is increased. Ultimately, it is most preferable to set an ink discharge amount corresponding to each humidity for each discharge port.

  In the present embodiment, the unused ejection port Q that is not used for recording the target image is set to 0 for the ink ejection amount when the preliminary ejection is performed, but the present invention is not limited to this. . In preparation for a case where a recording medium having a larger width is conveyed, preliminary ejection is also periodically performed on the unused ejection port Q, and ink may be ejected there.

  Further, in the inkjet recording apparatus 1 of the present embodiment, the value of the ink ejection amount at the time of preliminary ejection is set by adjusting the number of ejections of ink. At this time, the amount of ink discharged per discharge varies depending on the type of ink and recording conditions. Accordingly, when setting the number of ink ejections during preliminary ejection, the ink ejection amount per time is first detected in advance. Then, by dividing the total ink amount required for the recovery operation by the preliminary ejection by the detected ink ejection amount per one time, the number of ejections at the time of ejecting ink is obtained. Settings are made.

  FIG. 6 shows a flowchart of the control flow in the present embodiment. In S 1, the recorded image data is input to the image data processing unit 7. In S2, the size of the recording medium 3 is set. In S3, the ejection port P used for recording is determined based on the recording image data obtained in the steps S1 and S2 and the size of the recording medium 3. In S4, preset preliminary discharge data is selected based on the humidity distribution generated by the combination of the size of the recording medium 3 and the discharge ports used. The preliminary ejection data selected here is stored in the preliminary ejection data storage unit 8 in advance, and the control unit 9 performs selection based on the size of the recording medium 3 and information on the ejection ports used. As described above, in this embodiment, the control unit 9 as the preliminary discharge amount control unit controls the ink discharge amount in the preliminary discharge. Next, in S5, the image data input to the image data processing unit 7 is distributed to multi-value image data for each color of each recording head, and the image data is converted into binary discharge data for each discharge port. Is done. If the preliminary ejection data and the ejection data of the recording image are ready, recording can be started there. Thereafter, the humidifying unit is operated in S6, and humidified air is supplied onto the conveyance path of the recording medium. Next, the recording medium is conveyed to an area corresponding to the recording head 2 in S7, and recording is started in S8. The humidifying and conveying operations are continued until all the images are recorded (S9).

  As described above, according to the ink jet recording apparatus 1 of the present embodiment, it is possible to perform preliminary ejection with an appropriate ink ejection amount for each region. Accordingly, it is possible to suppress wasteful consumption of ink by ejecting an excessive amount of ink during preliminary ejection. Since the amount of ink consumed by the preliminary ejection can be reduced, the cost when using the inkjet recording apparatus 1 can be kept low. In addition, since a sufficient amount of preliminary ejection can be performed according to each region, the ink in the recording head 2 is thickened due to insufficient ink discharge amount due to preliminary ejection, resulting in ink ejection failure. Can be suppressed. Therefore, it is possible to reliably perform the amount of preliminary ejection required for each region, and to ensure the quality of a recorded image obtained by recording.

(Second Embodiment)
Next, a second embodiment for carrying out the present invention will be described. The description of the same configuration as in the first embodiment will be omitted, and only different parts will be described.

  In the first embodiment, a case has been described in which the humidity distribution changes sharply between the area where the recording medium passes and the area where the recording medium does not pass, with the edge of the recording medium as a boundary. On the other hand, in the second embodiment, a case will be described in which the humidity distribution gradually changes in a region near the edge of the recording medium.

  FIG. 7 is a graph showing the relationship between the humidity distribution at the position corresponding to the recording head 2 and the amount of ink ejected by preliminary ejection when recording is performed by the ink jet recording apparatus according to the second embodiment. . As shown in FIG. 7, in the present embodiment, the humidity near the edge of the recording medium changes gently, so that the used discharge ports P are divided into three groups P1, P2, and P3, respectively. A discharge amount of ink at the time of preliminary discharge is set for each discharge port group. The ink amount set in each discharge port group is set to the discharge port with the lowest humidity in each discharge port group, and the ink discharge amount at the time of preliminary discharge suitable for the discharge port is set. That is, the ejection amount A2 required for the humidity HH2 is set for the ejection port group P1, and the ink ejection amount C required for the humidity LH is set for the ejection port group P2. In the group P3, the ink discharge amount B2 required under the condition of the humidity MH2 is set.

  As described above, in this embodiment, the area through which the recording medium passes is divided into P1 and P3, and the amount of ink ejected during preliminary ejection is set for each area. Accordingly, in the region P3 in which the recording medium passes, the amount of ink ejected during preliminary ejection is set to A2 which is smaller than C in the region P3, and the amount of ink ejected during preliminary ejection is small. It is suppressed. As described above, in the present embodiment, an appropriate ink ejection amount for preliminary ejection is set for each finer region, and preliminary ejection is performed based on the set ink ejection amount. Therefore, the amount of ink consumed when preliminary ejection is performed can be further reduced.

  When the humidity distribution changes gently as in the present embodiment, increasing the number of ejection port divisions is effective for reducing ink consumption during preliminary ejection. In the present embodiment, the case where the number of divisions is three has been described, but the number of divisions may be more than this. By setting the number of divisions more finely, the ink discharge amount can be set more finely. As a result, it is possible to perform preliminary discharge with an appropriate amount of discharge for each region. Thereby, for example, in an area where ink is excessively consumed by preliminary ejection, the amount of ink consumed by preliminary ejection can be further reduced, and the cost for using the ink jet recording apparatus can be further suppressed. .

(Third embodiment)
Next, a third embodiment for carrying out the present invention will be described. The description of the same configuration as in the first and second embodiments will be omitted, and only different parts will be described.

  In the first embodiment and the second embodiment, humidified air is supplied to the recording medium before being conveyed to the area corresponding to the recording head, and the humidified recording medium is conveyed to the recording head 2. The area around the discharge port is humidified. On the other hand, the third embodiment is that the inkjet recording apparatus includes a humidifying unit (second humidified air supply means) 17 that directly humidifies the recording head 2. Different from form.

  FIG. 8 is a schematic cross-sectional view of the ink jet recording apparatus according to the third embodiment.

  As shown in FIG. 8, the humidifying unit 17 supplies humidified air generated in the humidifying tank 11 to the vicinity of the recording head 2 through the duct 12 in order to humidify the air around the recording head 2. It is configured. The configuration in the humidification tank 11 is the same as that described in the first embodiment. The heater in the humidification tank is controlled in the same manner as described in the first embodiment so that the humidity of the air in the vicinity of the recording head 2 is equal to or higher than the desired humidity.

  When the recording medium passes through the region corresponding to the recording head 2 when the air around the recording head 2 is directly humidified and in a high humidity state, the recording medium 3 passes through the region corresponding to the recording head 2. At this time, moisture in the air is adsorbed to the recording medium 3. Accordingly, in the area through which the recording medium 3 passes, the moisture contained in the air is adsorbed by the recording medium 3, the moisture in the air in the area decreases, and the humidity of the humidified air in the area decreases. Further, in the area where the recording medium 3 does not pass, the moisture contained in the humidified air is not adsorbed and remains in that area. Therefore, the humidity of the humidified air is maintained high without decreasing the humidity in that region. This causes a difference in humidity distribution between the area through which the recording medium 3 passes and the area through which the recording medium 3 does not pass.

  FIG. 9 shows the relationship between the humidity distribution in the region corresponding to the recording head 2 in the present embodiment and the ejection amount of ink ejected during preliminary ejection set based on the humidity distribution.

  In the humidifying unit 17, in consideration of a decrease in humidity due to the passage of the recording medium 3, humidity LH = 0 that can maintain good ejection performance even when the humidity at the position corresponding to the recording head 2 decreases. The temperature of the heater is controlled so that it can be maintained at 0.02 [kg / kgDA] or more. However, the humidity set at this time may be appropriately changed according to the ink used and the recording conditions.

  In the present embodiment, the humidity of the humidified air around the ejection port is lowered in the region through which the recording medium 3 passes. In this region, the volatile component of the ink easily evaporates through the ejection port, and is contained in the recording head 2. The thickened ink tends to be thickened. Further, in the area where the recording medium 3 does not pass, the humidity of the humidified air is relatively high, and it is difficult for the ink to thicken. Accordingly, in the area through which the recording medium 3 passes, a relatively larger amount of ink ejection is set in the preliminary ejection than in the area through which the recording medium 3 does not pass.

  As shown in FIG. 9, in the used outlet group P, in the outlet group P1, the ink ejection amount A3 at the time of preliminary ejection required under the condition of the humidity HH2 is set, and in the outlet group P2, the humidity LH is set. An ink discharge amount C at the time of preliminary discharge that is required under conditions is set. As described above, in the present embodiment, a relatively large ink discharge amount is set for the preliminary discharge with respect to a region where moisture in the air is adsorbed by passing the recording medium 3 and the humidity is lowered. Accordingly, preliminary ejection with a sufficient amount of ink ejection can be performed in a region where ink thickening is likely to occur, and therefore it is possible to suppress ejection failure due to ink thickening. Further, in the area where the recording medium 3 does not pass, the humidity of the air is high and the ink does not thicken easily, so the ink discharge amount at the time of preliminary discharge is set to be relatively small. Accordingly, since preliminary ejection with a small amount of ink consumption can be performed in an area where ink thickening is unlikely to occur, excessive ink is ejected during preliminary ejection, and ink is consumed wastefully. Can be suppressed.

  Also in the present embodiment, as in the second embodiment, the larger the number of divisions for dividing a plurality of discharge ports into discharge port groups when setting the ink discharge amount in the preliminary discharge, the more each discharge port This is more preferable because preliminary ejection can be performed with an appropriate ink ejection amount for each group.

  In the present specification, “recording” is used not only for forming significant information such as characters and graphics but also for any case. It also represents the case where images, patterns, patterns, etc. are widely formed on a recording medium, or the recording medium is processed, regardless of whether it is manifested so that it can be perceived by human eyes. And

  The “recording device” includes a device having a printing function such as a printer, a printer multifunction device, a copying machine, and a facsimile device, and a manufacturing device that manufactures an article using an ink jet technique.

  “Recording medium” means not only paper used in general recording apparatuses but also a wide range of materials that can accept ink, such as cloth, plastic film, metal plate, glass, ceramics, wood, leather, etc. Shall.

  Furthermore, “ink” (sometimes referred to as “liquid”) should be interpreted widely as in the definition of “recording”. By being applied on the recording medium, it can be used for formation of images, patterns, patterns, etc., processing of the recording medium, or ink processing (for example, solidification or insolubilization of the colorant in the ink applied to the recording medium). It shall represent a liquid.

2 Recording head 5 Conveyance roller 9 Control unit 10, 17 Humidification unit

Claims (5)

Conveying means for conveying the recording medium;
A plurality of recording heads arranged along a direction intersecting with a direction in which a recording medium is conveyed by the conveying means;
In an inkjet recording apparatus comprising: a preliminary ejection unit that ejects ink that is not involved in recording to the recording head;
The amount of ink discharged when preliminary ejection is performed by the preliminary ejection unit is changed according to the position where the ejection port is formed along the direction intersecting the direction in which the recording medium is conveyed by the conveyance unit, Preliminary discharge amount control means for controlling the discharge amount of ink when performing preliminary discharge so that the lower the humidity at the position where the discharge port is formed, the more ink is discharged from the discharge port and the preliminary discharge is performed. An ink jet recording apparatus comprising: A humidifying air is supplied to the recording medium before being conveyed to a position corresponding to the recording head by the conveying means, and the first humidifying air supply means humidifies the recording medium;
The transport means transports the humidified recording medium to a position corresponding to the recording head;
The preliminary ejection amount control unit is configured to reduce the amount of ink ejected from an ejection port formed at a position corresponding to a region through which the recording medium humidified by the first humidified air supply unit passes. The ink discharge amount when the preliminary discharge is performed by the preliminary discharge unit is controlled so as to be smaller than the discharge amount of the ink from the discharge port formed at a position corresponding to the non-passing region. Item 10. The ink jet recording apparatus according to Item 1. When performing borderless recording in which images are recorded to both ends in the width direction of the recording medium, recording is performed by ejecting ink from the recording head to an area protruding outward from the recording medium,
The preliminary ejection amount control means is formed at a position corresponding to an area where the ejection amount of ink from an ejection port formed at a position corresponding to an area through which the recording medium passes protrudes outward from the recording medium. 3. The ink jet recording apparatus according to claim 2, wherein an ink discharge amount when the preliminary discharge is performed by the preliminary discharge unit is controlled so as to be smaller than an ink discharge amount from the discharge port. Second humidified air supply means for supplying humidified air to a position corresponding to the recording head;
The transport unit transports the recording medium to a position corresponding to the recording head humidified by the second humidified air supply unit;
The preliminary ejection amount control means is configured so that the ejection amount of ink from an ejection port formed at a position corresponding to a region through which the recording medium passes is from an ejection port formed at a position corresponding to a region through which the recording medium does not pass 2. The ink jet recording apparatus according to claim 1, wherein an ink discharge amount when the preliminary discharge is performed by the preliminary discharge unit is controlled so as to be larger than an ink discharge amount. When performing borderless recording in which images are recorded to both ends in the width direction of the recording medium, recording is performed by ejecting ink from the recording head to an area protruding outward from the recording medium,
The preliminary ejection amount control means is formed at a position corresponding to an area where the ejection amount of ink from an ejection port formed at a position corresponding to an area through which the recording medium passes protrudes outward from the recording medium. 5. The ink jet recording apparatus according to claim 4, wherein an ink discharge amount when the preliminary discharge is performed by the preliminary discharge unit is controlled so as to be larger than an ink discharge amount from the discharge port.