Inkjet recording device

Abstract

This inkjet recording device (1) is provided with: a recording head (21) that discharges a liquid; a bubble countermeasure means that executes bubble countermeasure processing determined as countermeasures against bubbles in the liquid; a bubble generation amount calculation means that calculates a bubble generation amount from the liquid; and a control means that relaxes the bubble countermeasure processing when the bubble generation amount calculated by the bubble generation amount calculation means is not greater than a prescribed amount. The bubble generation amount calculation means calculates the bubble generation amount from the difference between a saturated dissolved gas amount at a first timing and a saturated dissolved gas amount at a second timing later than the first timing.

Description

Technical Field

[0001] The present invention relates to an inkjet recording apparatus.

Background Art

[0002] In an inkjet recording apparatus, if the amount of dissolved air in the ink increases, bubbles may be generated inside the recording head, which may cause ejection failure. Therefore, conventionally, techniques for reducing the amount of dissolved air in the ink have been studied. As an example, a configuration in which the ink is stirred while the ink tank is depressurized is known. For example, Patent Document 1 discloses a configuration in which the ink is stirred by rotating a stirrer provided in the ink tank with an external magnetic force.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, since the saturated dissolved gas amount of the ink depends on the temperature of the ink, the amount of bubbles generated from the ink is determined by the temperature change of the ink. For example, the larger the temperature rise range of the ink, the larger the decrease range of the saturated dissolved gas amount, and thus the amount of bubble generation increases. Therefore, in order to maintain the ejection performance of the recording head, it is important to take measures according to the amount of bubble generation.

[0005] An object of the present invention is to provide an inkjet recording apparatus capable of taking bubble countermeasures according to the amount of bubble generation in consideration of the above circumstances.

Means for Solving the Problems

[0006] To solve the above problems, the degassing device according to the present invention comprises a recording head for discharging liquid, a bubble control means for executing a bubble control process defined as a countermeasure against bubbles in the liquid, a bubble generation amount calculation means for calculating the amount of bubbles generated from the liquid, and a control means for mitigating the bubble control process when the amount of bubbles generated calculated by the bubble generation amount calculation means is less than or equal to a predetermined amount. [Effects of the Invention]

[0007] According to the present invention, it is possible to implement measures to control bubbles according to the amount of bubbles generated. [Brief explanation of the drawing]

[0008] [Figure 1] This is a schematic diagram showing an inkjet recording device according to one embodiment of the present invention. [Figure 2] This is a schematic diagram of an ink supply structure according to one embodiment of the present invention. [Figure 3] This is a schematic diagram of a circulation pump according to one embodiment of the present invention. [Figure 4] This is a flowchart showing the overall bubble control process for one embodiment of the present invention. [Figure 5] This is a flowchart showing the bubble generation amount calculation process related to one embodiment of the present invention. [Modes for carrying out the invention]

[0009] The inkjet recording device 1 of this embodiment will be described below with reference to the drawings. Figure 1 is a schematic diagram showing the inkjet recording device 1 according to this embodiment. For the sake of explanation, the front side of the paper in Figure 1 will be considered the front side of the inkjet recording device 1, and the left and right directions will be explained based on the direction in which the inkjet recording device 1 is viewed from the front. The arrows L, R, U, and Lo in each figure indicate the left, right, top, and bottom sides of the inkjet recording device 1, respectively.

[0010] As shown in Figure 1, the inkjet recording device 1 is configured to print by ejecting ink from each inkjet recording head 21 toward a sheet S, which serves as a recording medium. The inkjet recording device 1 includes a box-shaped housing 10 that houses various components. A paper feed cassette 11 into which the sheets S are set is housed in the lower part of the housing 10, and a manual feed tray 12 into which the sheets S are manually inserted is installed on the right side of the housing 10. An output tray 13 into which recorded sheets S are stacked is installed on the upper left side of the housing 10.

[0011] A first transport path 14 is formed on the right side of the housing 10 to transport sheets S from the paper feed cassette 11 to the recording head 21 in the center of the housing 10. Upstream of the first transport path 14 is a first paper feeding unit 15 that takes sheets S from the sheet bundle in the paper feed cassette 11, and downstream of the first transport path 14 is a pair of registration rollers 18 that adjust the timing of the sheet S being fed out. Further downstream of the first transport path 14 is a paper feeding path 16 for the manual feed tray 12, and the paper feeding path 16 is equipped with a second paper feeding unit 17 that takes sheets S from the sheet bundle in the manual feed tray 12.

[0012] Downstream of the pair of registration rollers 18 are a transport device 22 and recording heads 21 for each color (e.g., black, cyan, magenta, yellow). The pair of registration rollers 18 correct the skew of the sheet S and feed the sheet S to the transport device 22 in accordance with the ink ejection operation of each recording head 21. The housing 10 is provided with an ink container 31 and an ink tank 32 for each recording head 21. The ink from each ink container 31 is temporarily stored in the ink tank 32, and the ink is degassed as needed before being supplied from the ink tank 32 to the recording head 21.

[0013] The transport device 22 is configured by stretching a transport belt 24 over a plurality of tension rollers 23 installed below each recording head 21. Downstream of the transport device 22, a drying device 25 is provided for drying the ink on the sheet S. Downstream of the drying device 25, a decaling device 26 is provided for correcting the curl that occurs on the sheet S due to the drying of the ink. Downstream of the decaling device 26, a second transport path 27 is formed for transporting the sheet S toward the output tray 13. Downstream of the second transport path 27, a paper discharge section 28 is provided for discharging the recorded sheet S into the output tray 13.

[0014] Below the drying device 25 are a maintenance unit 35 for cleaning the recording head 21 and a cap unit 36 ​​for capping the recording head 21. The maintenance unit 35 is equipped with a squeegee-shaped wiping blade, which scrapes off any ink remaining on the nozzle surface of the recording head 21. The cap unit 36 ​​is equipped with a head cap, which is placed over the nozzle surface of the recording head 21. The head cap prevents the ink inside the nozzle from drying out. The drying of the ink inside the nozzle may be further suppressed by storing a liquid such as cleaning solution inside the head cap.

[0015] Furthermore, the inkjet recording device 1 is equipped with a control device 38 that provides overall control of the entire device. The control device 38 may be composed of a processor or of logic circuits (hardware) formed on an integrated circuit or the like. When composed of a processor, various processes are performed by the processor reading and executing a program stored in memory. For example, a CPU (Central Processing Unit) is used as the processor. Depending on the application, the memory is composed of one or more storage devices such as ROM (Read Only Memory) and RAM (Random Access Memory).

[0016] During image recording, the first paper feed unit 15 and the second paper feed unit 17 remove the sheet S from the paper cassette 11 or manual feed tray 12 and send it to the pair of registration rollers 18. In accordance with the ink ejection timing, the sheet S is sent from the pair of registration rollers 18 to the transport belt 24, and degassed ink is ejected from each recording head 21 to record a color image on the surface of the sheet S. The sheet S is dried by the drying device 25, and the curl of the sheet S is corrected by the decal device 26. The sheet S is transported to the paper discharge unit 28 via the second transport path 27, and the recorded sheet S is discharged into the paper discharge tray 13 by the paper discharge unit 28.

[0017] Incidentally, when the ink level in the ink tank 32 comes into contact with air, air dissolution progresses, and air bubbles in the ink can clog the nozzles of the recording head 21. For this reason, it is desirable to appropriately control the amount of dissolved air in the ink. For example, a method has been proposed in which ink is passed through a hollow fiber filter while the area around the filter is under reduced pressure, causing air to move from the walls of the hollow fiber to the reduced pressure side and thus degass the filter. However, this method requires expensive hollow fiber filters and necessitates periodic replacement, increasing costs.

[0018] Furthermore, to prevent nozzle clogging, a method has been proposed in which the ink in the ink tank 32 is degassed by stirring the ink with an agitator while the pressure inside the ink tank 32 is reduced to below atmospheric pressure (hereinafter referred to as the agitation degassing method). In the agitation degassing method, an external magnetic force is applied to the agitator inside the ink tank 32, and the agitator rotates due to the magnetic force, stirring the ink inside the ink tank 32. When the ink depth or tank diameter is large, the ink becomes difficult to stir, and the degassing efficiency decreases. Increasing the rotation speed of the agitator makes stirring easier, but if the rotation speed of the agitator becomes too high, a step-out phenomenon occurs and the rotation noise of the agitator also increases.

[0019] Therefore, in this embodiment, a method of circulating and degassing the ink in the ink tank 32 through the circulation channel 47 in a state where the inside of the ink tank 32 is depressurized to below atmospheric pressure (hereinafter referred to as the circulation degassing method) is adopted (see FIG. 2). In the circulation degassing method, as the ink circulates through the circulation channel 47 and inside the ink tank 32, the ink near the liquid surface with a small amount of dissolved air and the ink near the bottom surface with a large amount of dissolved air are exchanged, improving the degassing efficiency. Different from the stirring degassing method, it is not affected by the depth of the ink or the diameter of the tank, and the driving sound of the circulation pump 67 is suppressed more than the rotation sound of the stirring bar, enhancing the quietness.

[0020] [Degassing device] The degassing device 40 according to this embodiment will be described. FIG. 2 is a schematic diagram of the ink supply structure according to this embodiment. FIG. 3 is a schematic diagram of the circulation pump 67 according to this embodiment. The inkjet recording apparatus 1 according to this embodiment is provided with an ink supply structure for each color. Here, one ink supply structure will be described.

[0021] [Supply channel] As shown in FIG. 2, the ink tank 32 stores the ink supplied from the ink container 31 through the supply channel 41. The supply channel 41 is provided with a supply pump 61 and a supply valve 51, and the supply of ink to the ink tank 32 is controlled by the supply pump 61 and the supply valve 51.

[0022] [Vacuum channel] The upper space 34 of the ink tank 32 communicates with the vacuum channel 42. The vacuum channel 42 is provided with a vacuum pump 62.

[0023] [Atmospheric release channel] The upper space 34 of the ink tank 32 communicates with the atmospheric release channel 43. The atmospheric release channel 43 is provided with an atmospheric release valve 53, and the upper space 34 is opened to the atmosphere by the atmospheric release valve 53.

[0024] [Supply channel, recovery channel, bypass channel, head circulation means] Ink is supplied from the ink tank 32 to the recording head 21 via the supply channel 44, and ink is recovered from the recording head 21 to the ink tank 32 via the recovery channel 45. The supply channel 44 is equipped with a supply pump 64 and a supply valve 54, and the recovery channel 45 is equipped with a recovery valve 55. The supply pump 64, supply valve 54, and recovery valve 55 control the ink exchange operation and air bubble removal operation within the recording head 21. These constitute the head circulation means that circulates ink between the ink tank 32 and the recording head 21. A bypass channel 46 that bypasses the supply pump 64 is connected to the supply channel 44, and a bypass valve 56 is provided in the bypass channel 46. During printing, ink is passed through the bypass channel 46 by the bypass valve 56. In other words, head circulation does not occur during printing.

[0025] [Circulation channel] The ink level and bottom of the ink tank 32 are connected through a circulation channel 47. A circulation pump 67 is provided in the circulation channel 47, and the ink is circulated through the circulation channel 47 by the circulation pump 67. The inlet 72 from the circulation channel 47 to the ink tank 32 is higher than the outlet 71 from the ink tank 32 to the circulation channel 47. Specifically, the outlet 71 is opened in the bottom of the ink tank 32, and the inlet 72 is opened in the side of the ink tank 32 near the liquid level.

[0026] [Circulation pump] During the degassing operation, the inside of the ink tank 32 is under reduced pressure, making reciprocating pumps such as diaphragm pumps susceptible to the effects of reduced pressure. Therefore, it is preferable to use a pump that delivers ink by rotating a rotating body as the circulation pump 67. For example, the circulation pump 67 may be a non-positive displacement pump such as a centrifugal pump, a mixed-flow pump, or an axial-flow pump, or a positive displacement rotary pump such as a vane pump, a gear pump, or a screw pump. By using these pumps, unlike reciprocating pumps, the effects of reduced pressure inside the ink tank 32 can be suppressed and the ink can be circulated.

[0027] Generally, the recording head 21 may be included in the circulation channel 47 of the circulating degassing system, but in this embodiment, the recording head 21 is not included in the circulation channel 47. In other words, the circulation channel 47 is provided separately from the path that supplies ink to the recording head 21. By not including the recording head 21 in the circulation channel 47, the meniscus formed inside the nozzle of the recording head 21 is destroyed by the reduced pressure during degassing, and the possibility of outside air entering the recording head 21 is reduced.

[0028] As shown in Figure 3, the pump shaft 73 and motor shaft 75 of the circulation pump 67 are separated by a partition wall 77, allowing for non-contact power transmission. A pump casing 76 is formed in the middle of the circulation channel 47, and the pump shaft 73 with an impeller 74 attached is housed inside the pump casing 76. A motor (not shown) is installed outside the circulation channel 47. Disks 78 and 79 are provided at the ends of the pump shaft 73 and motor shaft 75, and the disks 78 and 79 face each other across the partition wall 77 of the pump casing 76. Magnets (not shown) with alternating south and north poles in the circumferential direction are installed on the opposing surfaces of the disks 78 and 79.

[0029] The pump shaft 73 and the motor shaft 75 are magnetically connected (magnetic coupling), and power is transmitted from the motor shaft 75 to the pump shaft 73 using magnetic force. The impeller 74 inside the pump casing 76 can be rotated without the motor shaft 75 passing through the pump casing 76, while the pump casing 76 remains liquid-tightly sealed. The space between the discs 78 and 79 of the pump shaft 73 and the motor shaft 75 is partitioned by the partition wall 77 of the pump casing 76, so that even if a pressure difference occurs inside and outside the pump casing 76 when the ink tank 32 is depressurized, ink leakage caused by this pressure difference is reliably prevented.

[0030] [Control device] The replenishment pump 61, pressure reducing pump 62, supply pump 64, circulation pump 67, replenishment valve 51, pressure reducing valve 52, atmospheric release valve 53, supply valve 54, recovery valve 55, and bypass valve 56 are controlled by the control device 38. The control device 38 is equipped with a determination unit 39 that determines whether or not a degassing operation is necessary depending on the ink's standing time. If the determination unit 39 determines that degassing of the ink is unnecessary, the degassing operation is restricted. Even if air has redissolved due to the ink being left standing, the ink can be used without degassing as long as it is within the allowable time. Details of the determination process performed by the determination unit 39 will be described later. In this ink supply structure of the inkjet recording device 1, the degassing device 40 is formed by the ink tank 32, pressure reducing channel 42, pressure reducing pump 62, pressure reducing valve 52, circulation channel 47, circulation pump 67, determination unit 39, etc.

[0031] Next, the operation of the degassing device 40 (an example of a degassing means) will be described. In the standby state of the inkjet recording device 1, the replenishment valve 51, the pressure reducing valve 52, and the supply valve 54 are closed, and the atmospheric release valve 53, the bypass valve 56, and the recovery valve 55 are open. Ink is stored in the ink tank 32, and as time passes, air dissolves into the ink as the liquid surface comes into contact with the air in the upper space 34 which is open to the atmosphere. During the pressure reduction operation, only the pressure reducing valve 52 is opened, and the other valves 51, 53-56 are closed. The pressure reducing pump 62 is driven to remove air from the upper space 34 inside the ink tank 32. When the inside of the ink tank 32 reaches the target pressure (for example, -50 [kPa]), the pressure reducing pump 62 is stopped.

[0032] During the degassing operation, all valves 51-56 are closed, and the circulation pump 67 is driven while the reduced pressure state inside the ink tank 32 is maintained, circulating the ink inside the ink tank 32 through the circulation channel 47. Ink near the bottom of the ink tank 32, where there is a large amount of dissolved air, flows out into the circulation channel 47 through the outlet 71, and ink in the circulation channel 47 flows towards the liquid surface inside the ink tank 32 through the inlet 72. The liquid surface of the ink is exposed to a reduced pressure atmosphere, and the air dissolved in the ink near the liquid surface is removed. The ink near the liquid surface, where there is a small amount of dissolved air, and the ink near the bottom, where there is a large amount of dissolved air, are smoothly exchanged, improving the degassing efficiency.

[0033] As shown in Figure 2, when the head circulation means is in operation, the replenishment valve 51, pressure reducing valve 52, and bypass valve 56 are closed, and the atmospheric release valve 53, supply valve 54, and recovery valve 55 are open. The supply pump 64 is driven to supply ink from the ink tank 32 to the recording head 21 through the supply channel 44, and the ink is recovered from the recording head 21 to the ink tank 32 through the recovery channel 45. As the ink circulates between the recording head 21 and the ink tank 32, the ink whose viscosity has increased in the recording head 21 is replaced, and air bubbles are removed from the recording head 21.

[0034] Furthermore, during printing operations by the recording head 21, the replenishment valve 51, pressure reducing valve 52, and supply valve 54 are closed, while the atmospheric release valve 53, bypass valve 56, and recovery valve 55 are open. In other words, during printing operations, the ink tank 32 is released to the atmosphere and is at atmospheric pressure. During printing operations, the ink tank 32 is not subjected to a pressure reduction that would cause substantial degassing. Each time ink is ejected from the recording head 21, ink is supplied from the ink tank 32 to the recording head 21 through the bypass channel 46 and the recovery channel 45. Ink may be replenished during ink replacement operations or during printing operations. During these ink replenishment operations, the replenishment valve 51 is opened and the replenishment pump 61 is driven. The replenishment pump 61 drives ink from the ink container 31 to the ink tank 32 through the replenishment channel 41.

[0035] Note that Figure 1 and other diagrams are schematic representations; in reality, the recording head 21 is positioned above the ink tank 32. A negative pressure is applied to the ink in the recording head 21 due to the difference in water head between it and the ink in the ink tank 32. This negative pressure creates a meniscus around the nozzle of the recording head 21. After ink is discharged from the recording head 21, the surface tension of the ink reduces the surface area of ​​the meniscus, and the resulting negative pressure draws the lost ink back from the ink tank 32 to the recording head 21. Alternatively, the recovery valve 55 may be closed to limit ink supply to the recording head 21 to only the bypass channel 46.

[0036] Furthermore, if the ink tank 32 is depressurized to the point of substantial degassing while the recording head 21 and the ink tank 32 are connected, the meniscus of the nozzle may be damaged. Even if the meniscus is not damaged, the shape of the meniscus inside the nozzle may change from when the ink tank 32 is open to the atmosphere, which may change the ink ejection characteristics. In this embodiment, during printing, the ink tank 32 is not depressurized to the point of substantial degassing, so the meniscus inside the nozzle of the recording head 21 is not damaged, nor does its shape change, and therefore the ejection characteristics do not change.

[0037] Next, the bubble control process will be described. The inkjet recording apparatus 1 according to this embodiment includes a recording head 21 that ejects liquid, bubble control means that executes a bubble control process defined as a countermeasure against bubbles in the liquid, bubble generation amount calculation means that calculates the amount of bubbles generated from the liquid, and control means that relaxes the bubble control process when the amount of bubbles generated calculated by the bubble generation amount calculation means is less than or equal to a predetermined amount. Specifically, it is as follows.

[0038] The bubble prevention treatment is a process defined as a countermeasure against bubbles in the ink. The bubble prevention treatment includes a non-discharge detection means, a purging means, the aforementioned head circulation means, and a degassing means. The non-discharge detection means discharges ink from the recording head 21 onto the sheet S according to pre-created image data, and optically reads the image formed on the sheet S to detect nozzles from which ink has not been discharged. The purging means forcibly discharges ink from the nozzles to the cap unit 36 ​​using a supply pump 64.

[0039] Figure 4 is a flowchart showing the overall bubble prevention process. The control device 38 (an example of a control means) performs the bubble prevention process when power is turned on to the inkjet recording device 1, and periodically thereafter. First, the control device 38 performs a bubble generation amount calculation process (step S01).

[0040] Figure 5 is a flowchart showing the bubble generation amount calculation process. First, the control device 38 calculates the saturated dissolved gas amount S1 at a first timing (step S11). Specifically, a temperature sensor 33 is provided below the liquid level inside the ink tank 32. The first timing is, for example, the timing when the degassing process is last performed, and the temperature of the ink in the ink tank 32 at that timing is stored in the determination unit 39. The determination unit 39 stores conversion information that shows the correspondence between the ink temperature and the saturated dissolved gas amount, and the saturated dissolved gas amount is estimated based on the temperature measured by the temperature sensor 33. Map data, lookup tables, and conversion formulas are used as conversion information. These map data, lookup tables, and conversion formulas are those that have been determined in advance experimentally, empirically, or theoretically.

[0041] Next, the control device 38 calculates the saturated dissolved gas amount S2 at a second timing (step S12). The second timing is, for example, the timing when step S12 is being performed, i.e., the current time. The control device 38 estimates the saturated dissolved gas amount based on the temperature measured by the temperature sensor 33.

[0042] Next, the control device 38 calculates the amount of bubbles generated B. The amount of bubbles generated B is the value obtained by subtracting the amount of saturated dissolved gas S2 at the second timing from the amount of saturated dissolved gas S1 at the first timing.

[0043] Next, the control device 38 determines whether the amount of bubbles generated is greater than a predetermined amount (Figure 4, step S02). Here, the predetermined amount is, for example, 0 (zero). If it is determined that the amount of bubbles generated is greater than the predetermined amount, that is, the amount of bubbles generated is a positive value (step S02: YES), the control device 38 determines whether the amount of non-discharge detected by the non-discharge detection means is greater than or equal to a standard value (step S03). If it is determined that the amount of non-discharge is greater than or equal to the standard value (step S03: YES), the control device 38 strengthens the bubble countermeasures treatment (step S04). On the other hand, if it is determined that the amount of bubbles generated is less than or equal to the predetermined amount, that is, the amount of bubbles generated is 0 (step S02: NO), and if it is determined that the amount of non-discharge is less than the standard value (step S03: NO), the control device 38 mitigates the bubble countermeasures treatment (step S05).

[0044] Here, specific examples of strengthening the bubble control treatment in step S04 will be described. For example, the control means may increase the discharge amount or discharge frequency of the purge means as strengthening the bubble control treatment (first form). Alternatively, the control means may increase the circulation time or circulation frequency of the head circulation means as strengthening the bubble control treatment (second form). That is, when operating the supply pump 64 that generates head circulation, the operating time per cycle may be increased or the operating frequency may be increased. The increase in operating time may be an increase in the operating time per unit time. Alternatively, the control means may increase the degassing time or degassing frequency of the degassing means as strengthening the bubble control treatment (third form). Note that the control means may implement two or more of the first to third forms as strengthening the bubble control treatment.

[0045] Next, specific examples of mitigating the bubble control treatment in step S05 will be described. For example, the control means may reduce the discharge amount or discharge frequency of the purge means as a mitigation of the bubble control treatment (fourth form). Alternatively, the control means may reduce the circulation time or circulation frequency of the head circulation means as a mitigation of the bubble control treatment (fifth form). That is, when operating the supply pump 64 that generates head circulation, the operating time per cycle may be reduced, or the operating frequency may be reduced. The reduction in operating time may be reduced by reducing the operating time per unit time. Alternatively, the control means may reduce the degassing time or degassing frequency of the degassing means as a mitigation of the bubble control treatment (sixth form). Note that the control means may implement two or more of the fourth to sixth forms as a mitigation of the bubble control treatment.

[0046] The inkjet recording apparatus 1 according to the embodiment described above includes a recording head 21 that ejects liquid, a bubble control means that performs a bubble control process defined as a countermeasure against bubbles in the liquid, a bubble generation amount calculation means that calculates the amount of bubbles generated from the liquid, and a control means that relaxes the bubble control process when the amount of bubbles generated calculated by the bubble generation amount calculation means is less than or equal to a predetermined amount. With this configuration, bubble control measures can be taken according to the amount of bubbles generated.

[0047] Furthermore, according to the inkjet recording apparatus 1 of this embodiment, the bubble generation amount calculation means calculates the bubble generation amount from the difference between the saturated dissolved gas amount at a first timing and the saturated dissolved gas amount at a second timing that occurs after the first timing. With this configuration, a highly reliable bubble generation amount can be calculated.

[0048] Furthermore, according to the inkjet recording apparatus 1 of this embodiment, the bubble countermeasure means includes a non-discharge detection means for detecting the non-discharge of the liquid from the recording head, and the control means causes the non-discharge detection means to perform detection when the amount of bubbles generated calculated by the bubble generation amount calculation means is greater than a predetermined amount, and when the non-discharge detected by the non-discharge detection means is less than a standard value, the bubble countermeasure treatment is relaxed. With this configuration, bubble countermeasures can be performed according to the degree of non-discharge.

[0049] Furthermore, according to the inkjet recording apparatus 1 of this embodiment, the bubble prevention means includes a purging means that forcibly ejects liquid from the recording head 21, and the control means reduces the ejection amount or ejection frequency of the purging means as a way to mitigate the bubble prevention process. With this configuration, the operation of the purging means can be suppressed when the amount of bubbles generated is small.

[0050] Furthermore, according to the inkjet recording apparatus 1 of this embodiment, the bubble prevention means includes a head circulation means that circulates liquid between the liquid tank and the recording head 21, and the control means reduces the circulation time or circulation frequency of the head circulation means as a relaxation of the bubble prevention process. With this configuration, the operation of the head circulation means can be suppressed when the amount of bubble generation is small.

[0051] Furthermore, according to the inkjet recording apparatus 1 of this embodiment, the bubble control means includes a degassing means for degassing the liquid in the liquid tank, and the control means reduces the degassing time or degassing frequency of the degassing means as a relaxation of the bubble control process. With this configuration, the operation of the degassing means can be suppressed when the amount of bubbles generated is small.

[0052] The above embodiment may be modified as follows.

[0053] The bubble generation amount calculation process (step S01) shown in Figure 4 may be performed periodically during image formation by the recording head 21. If the amount of bubbles generated is greater than a predetermined amount (step S02: YES) or if the non-discharge rate is above a standard value (step S03: YES), image formation may be interrupted and bubble countermeasures enhanced (step S04) may be performed.

[0054] In the above embodiment, an example was shown in which the present invention is applied to an inkjet recording device 1 equipped with a circulating degassing device 40. However, the present invention may also be applied to an inkjet recording device 1 equipped with a stirring degassing device that agitates the ink in the ink tank 32 using an impeller.

[0055] In the above embodiment, an example was shown in which the threshold amount for bubble generation was set to 0 (zero), but a positive value may be set as the threshold amount. Furthermore, multiple threshold amounts may be set, and the bubble control treatment may be strengthened in stages.

[0056] The control means may increase the detection frequency of the non-discharge detection means when the amount of bubbles generated calculated by the calculation means exceeds a predetermined amount. This configuration can reduce the chances of missed detection of non-discharge. Alternatively, the control means may decrease the detection frequency of the non-discharge detection means when the amount of bubbles generated calculated by the calculation means is less than or equal to a predetermined amount. This configuration can suppress non-discharge detection when there are few non-discharges.

Claims

1. A recording head that dispenses liquid, A bubble control means that performs a bubble control treatment specified as a countermeasure against bubbles in the liquid, A bubble generation amount calculation means for calculating the amount of bubbles generated from the liquid, The system includes a control means for mitigating the bubble countermeasures treatment when the amount of bubbles generated calculated by the bubble generation amount calculation means is less than or equal to a predetermined amount, The bubble generation amount calculation means is characterized by calculating the bubble generation amount from the difference between the saturated dissolved gas amount of the liquid at a first timing and the saturated dissolved gas amount of the liquid at a second timing that is later than the first timing.

2. A recording head that dispenses liquid, A bubble control means that performs a bubble control treatment specified as a countermeasure against bubbles in the liquid, A bubble generation amount calculation means for calculating the amount of bubbles generated from the liquid, The system includes a control means for mitigating the bubble countermeasures treatment when the amount of bubbles generated calculated by the bubble generation amount calculation means is less than or equal to a predetermined amount, The bubble prevention means includes a non-discharge detection means for detecting the non-discharge of the liquid from the recording head, The control means is characterized in that, when the amount of bubbles generated calculated by the bubble generation amount calculation means is greater than a predetermined amount, it causes the non-discharge detection means to perform detection, and when the non-discharge detected by the non-discharge detection means is less than a standard value, it mitigates the bubble countermeasures treatment.

3. The bubble prevention means includes a purging means for forcibly ejecting the liquid from the recording head, The inkjet recording apparatus according to claim 1, characterized in that the control means reduces the discharge amount or discharge frequency of the purging means as a way to mitigate the bubble countermeasures.

4. The bubble prevention means includes a head circulation means for circulating the liquid between the liquid tank and the recording head. The inkjet recording apparatus according to claim 1, characterized in that the control means reduces the circulation time or circulation frequency of the head circulation means as a relaxation of the bubble countermeasures treatment.

5. The bubble control means includes a degassing means for degassing the liquid in the liquid tank, The inkjet recording apparatus according to claim 1, characterized in that the control means reduces the degassing time or degassing frequency of the degassing means as a relaxation of the bubble countermeasures treatment.

6. The inkjet recording apparatus according to claim 2, characterized in that the control means reduces the detection frequency by the non-ejection detection means when the amount of bubbles generated calculated by the bubble generation amount calculation means is less than or equal to a predetermined amount.

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