Image forming apparatus and control method

Abstract

To provide a technology capable of reducing bubbles while suppressing cost increases. [Solution] The ink ejection device includes a recording head that ejects supplied ink from nozzles to perform recording; a circulation path that includes an internal flow path of the recording head that communicates with the nozzles, supplies recording material to the recording head, collects recording material that was not ejected from the recording head, and circulates the recording material; a removal means that removes dissolved gas from the recording material; and a control means that controls the removal means while controlling the circulation of the recording material in the circulation path.When the control means fills the internal flow path with recording material, it performs first circulation control in which the recording material is circulated continuously in the circulation path for a first time while the dissolved gas is removed by the removal means, and then performs second circulation control in which the recording material is circulated intermittently for a second time that is shorter than the first time.

Description

[Technical Field]

[0001] The present disclosure relates to an image forming apparatus that forms an image on a recording medium by ejecting a recording material and recording on the recording medium, and a control method for the image forming apparatus. [Background technology]

[0002] Patent Document 1 discloses a recording device that supplies ink as a recording material to a recording head and has a degassing device that removes dissolved gas from the ink in a circulation path that recovers the ink from the recording head.

[0003] In the recording device disclosed in Patent Document 1, the ink is circulated in the circulation path while a degassing device is driven, thereby reducing the amount of dissolved gas in the ink and dissolving the air bubbles generated in the circulation path into the ink, thereby reducing the amount of gas generated in the circulation path. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-083021 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the recording device disclosed in Patent Document 1 is designed to circulate ink continuously through the circulation path, which increases the frequency of replacing the pump that circulates ink through the circulation path, resulting in higher costs.

[0006] The present disclosure has been made in consideration of the above-mentioned problems, and aims to provide a technology that can reduce bubbles while suppressing cost increases. [Means for solving the problem]

[0007] In order to achieve the above-mentioned object, one embodiment of an image forming apparatus according to the present disclosure comprises a recording head that performs recording by ejecting supplied ink from nozzles, a circulation path that includes an internal flow path formed inside the recording head and connected to the nozzles, and that supplies recording material to the recording head and collects recording material that was not ejected from the recording head to circulate the recording material, a removal means that removes dissolved gas from the recording material circulating through the circulation path, and a control means that controls the removal means and controls the circulation of the recording material in the circulation path, wherein the control means, when filling the internal flow path of the recording head with recording material, performs first circulation control in which the recording material is circulated continuously in the circulation path for a first time while the dissolved gas is removed by the removal means, and then performs second circulation control in which the recording material is circulated intermittently for a second time that is shorter than the first time. [Effects of the Invention]

[0008] According to the present disclosure, it is possible to reduce bubbles while suppressing cost increases. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram illustrating the configuration of an image forming apparatus. [Figure 2] FIG. [Figure 3] FIG. 2 is a diagram showing a flow path (internal flow path of the head) formed in the recording head. [Figure 4] FIG. 3 is a diagram showing a flow path formed in an ink ejection unit. [Figure 5] FIG. 2 is a block diagram showing the configuration of a control system of the image forming apparatus. [Figure 6] 5A and 5B are diagrams illustrating ink circulation control in a circulation path. [Figure 7] FIG. 10 is a diagram showing an example of execution of circulation control. [Figure 8] FIG. 10 is a diagram showing a modified example of the circulation path. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an example of an embodiment of an image forming apparatus and a control method will be described in detail with reference to the accompanying drawings. The following embodiment does not limit the present disclosure, and not all of the combinations of features described in the embodiment are necessarily essential to the illustrative means of the present disclosure. Furthermore, the positions, shapes, etc. of components described in the embodiment are merely examples, and are not intended to limit the scope of the present disclosure to only those.

[0011] (Schematic configuration of image forming apparatus) 1 is a schematic diagram of an image forming apparatus. An image forming apparatus 10 according to this embodiment includes a conveying unit 12 that conveys a sheet-like recording medium M, and a recording head 14 that ejects a recording material onto the recording medium M conveyed by the conveying unit 12 to record. In this embodiment, the recording material is not limited to ink containing coloring material, but also includes a treatment liquid that performs a predetermined treatment on the ink ejected onto the recording medium M.

[0012] The recording head 14 has a plurality of nozzles that eject ink as droplets, and these nozzles are arranged in a range corresponding to the width of the recording medium M that can be recorded on, along a direction that intersects (orthogonal in this embodiment) the direction in which the recording medium M is transported by the transport unit 12. When the recording medium M passes below the recording head 14, ejection energy generating elements provided corresponding to each nozzle of the recording head 14 are driven under the control of a head control unit 524 (described later), and ink is ejected from the nozzles onto the recording medium M, thereby performing recording. As described above, in this embodiment, the image forming apparatus 10 is a full-line type recording apparatus that performs recording by ejecting ink from each nozzle arranged along the width direction of the recording medium M while continuously transporting the recording medium M.

[0013] The recording head 14 has a surface 14a (see FIG. 2) facing the recording medium M transported by the transport unit 12 (hereinafter referred to as the "nozzle surface"), on which a plurality of ink ejection units 310 (see FIG. 4) with a plurality of nozzles 400 (see FIG. 4) are arranged in the width direction. In this embodiment, the ink ejection units 310 are provided with known ejection energy generating elements such as heat elements, piezoelectric elements, and electrostatic elements corresponding to each nozzle 400. Each nozzle ejects ink using energy generated by the corresponding ejection energy generating element.

[0014] The image forming apparatus 10 includes a main tank 202 (see FIG. 2) that stores ink to be supplied to the recording head 14. In the image forming apparatus 10, the ink stored in the main tank 202 is supplied to the recording head 14 via a circulation path 200 (see FIG. 2), which will be described later. The image forming apparatus 10 also includes a drying unit 16 that dries the ink ejected onto the recording medium M downstream of the recording head 14 in the transport direction, thereby promoting the fixation of the ink onto the recording medium M.

[0015] The image forming apparatus 10 is equipped with a maintenance unit 220 (see FIG. 2) for maintaining and restoring the ink ejection performance of the recording head 14. In this embodiment, the maintenance unit 220 is provided so as to be able to move back and forth in the transport direction from the upstream side to the downstream side and from the downstream side to the upstream side. When the maintenance unit 220 performs a maintenance process on the recording head 14, first, the recording head 14 is raised by the elevator unit 522 (see FIG. 5). Next, the maintenance unit 220 is moved from the standby position to a maintenance position where the maintenance process on the recording head 14 can be performed. Thereafter, the recording head 14 is lowered so that the maintenance unit 220 and the recording head 14 come into contact with each other, and the maintenance process is performed.

[0016] The maintenance unit 220 is configured to be able to perform various known maintenance processes. In this embodiment, the maintenance unit 220 includes a cap 222 (see FIG. 2) that caps and protects the nozzle surface 14a on which the nozzles of the recording head 14 are formed, and a suction pump 224 (see FIG. 2) that generates negative pressure inside the cap 222.

[0017] (Circulation route) Next, the circulation path 200 will be described. Fig. 2 is a schematic diagram of the circulation path 200. The circulation path 200 includes a buffer tank 204 that stores ink supplied from a main tank 202, and a supply flow path 206 that supplies the ink stored in the buffer tank 204 to the print head 14. The circulation path 200 also includes the print head 14 that ejects the ink supplied by the supply flow path 206 and causes the ink that is not ejected to flow into a recovery flow path 208 (described later). The circulation path 200 also includes the recovery flow path 208 that recovers the ink that has flowed out of the print head 14 into the buffer tank 204.

[0018] As a result, the circulation path 200 is configured so that ink is transported in the order of buffer tank 204, supply flow path 206, print head 14, and recovery flow path 208, and then circulated so that it is recovered in the buffer tank 204. In this way, the circulation path 200 is configured to be able to circulate ink between the print head 14 and the buffer tank 204.

[0019] The supply flow path 206 is provided with a liquid feed pump 210 for transferring the ink stored in the buffer tank 204 to the recording head 14. The recovery flow path 208 is provided with a liquid feed pump 212 for transferring the ink flowing out from the recording head 14 to the buffer tank 204.

[0020] A degassing section (also referred to as a "removal section") 214 for removing dissolved gas from the ink is provided in the supply flow path 206 between the buffer tank 204 and the liquid feed pump 210. The degassing section 214 is configured to perform degassing under reduced pressure using a gas-permeable hollow fiber membrane, and a degassing pump 216 is connected to the degassing section 214. Note that the degassing method used by the degassing section 214 is not limited to the method described above, and various known methods capable of reducing dissolved gas from the ink in the flow path can be used.

[0021] The supply flow path 206 is provided with an on-off valve 218 between the liquid feed pump 210 and the recording head 14, which is used when filling the recording head 14 with ink after replacement, etc. When circulating ink in the circulation path 200, the on-off valve 218 is in an open state to allow the transfer of ink in the circulation path 200. When depressurizing the inside of the recording head 14, etc., the on-off valve 218 is in a closed state to restrict the transfer of ink from the supply flow path 206 to the recording head 14.

[0022] Although not shown, the supply flow path 206 and the recovery flow path 208 are provided with a filter for removing unnecessary solid matter, a damper for suppressing pulsation in the ink flow rate when the liquid feed pumps 210 and 212 are operating, a check valve for preventing backflow of ink, and the like. Also, the circulation path 200 is provided with various sensors for measuring the ink circulation flow rate, ink flow rate, pressure, and the like, such as a pressure sensor 526 (see FIG. 5) for detecting the pressure in the flow path within the recording head 14 (a flow path inside the head, described later). Since various known technologies can be used for the above-mentioned filter, damper, check valve, and pressure sensor 526, detailed description thereof will be omitted.

[0023] (Flow path configuration inside the recording head) Next, we will explain the flow path configuration inside the recording head 14. Figure 3 is a diagram showing the flow path configuration inside the recording head 14. Figure 4 is a diagram showing the flow path inside the ink ejection unit.

[0024] The recording head 14 is equipped with an inflow channel 302 to which ink is supplied from the supply channel 206, and an outflow channel 304 through which ink flows out to the recovery channel 208 (see FIG. 3). The ink that flows into the inflow channel 302 is supplied to a first negative pressure control unit 306 and a second negative pressure control unit 308. The first negative pressure control unit 306 has a control pressure set to a relatively weak negative pressure, while the second negative pressure control unit 308 has a control pressure set to a relatively strong negative pressure. The first negative pressure control unit 306 and the second negative pressure control unit 308 are connected to an ink ejection section 310 in which nozzles 400 are provided, and are configured to be able to supply ink to the nozzles 400.

[0025] The first negative pressure control unit 306 and the second negative pressure control unit 308 operate on the same operating principle as what is generally called a pressure reducing valve in order to control the negative pressure within a predetermined range, and at least a portion of their outer walls is formed of a soft material such as a flexible film. The first negative pressure control unit 306 and the second negative pressure control unit 308 are configured to press the outer walls in a direction that expands the volume of the flow path using a pressing member such as a spring. The first negative pressure control unit 306 and the second negative pressure control unit 308 adjust the negative pressure by changing the volume of the flow path as the outer wall portion, such as a flexible film, deforms.

[0026] A plurality of ink ejection units 310 are connected to the first negative pressure control unit 306 and the second negative pressure control unit 308. Specifically, the first negative pressure control unit 306 is connected to the plurality of ink ejection units 310 via an ink branching channel 312. The second negative pressure control unit 308 is connected to the plurality of ink ejection units 310 via an ink merging channel 314.

[0027] The pressure difference between the first negative pressure control unit 306 and the second negative pressure control unit 308 causes ink to flow from the first negative pressure control unit 306 toward the second negative pressure control unit 308 via the ink discharge unit 310. Therefore, ink supplied to the first negative pressure control unit 306 is sent to the ink branching channel 312, and then sent to the ink discharge unit 310 via a plurality of individual supply channels 316 connected to each ink discharge unit 310 in the ink branching channel 312. In addition, ink not discharged from the ink discharge unit 310 is sent to the ink junction channel 314 via individual recovery channels 318 connected to each ink discharge unit 310, and then sent to the outflow channel 304 connected to the ink junction channel 314.

[0028] In this embodiment, the recording head 14 has a configuration in which a plurality of ink ejection units are connected to two negative pressure control units, but this is not limiting. For example, the recording head 14 may have a configuration in which one ink ejection unit is connected to two negative pressure control units.

[0029] The ink ejection section 310 is provided with a plurality of nozzles 400 (see FIG. 4). Each nozzle 400 is provided at a position corresponding to a pressure chamber 402 that stores supplied ink, and an ejection energy generating element (not shown) is disposed in each pressure chamber 402. Each pressure chamber 402 is connected to an inlet 404 through which ink supplied from the individual supply flow path 316 flows in, and an outlet 406 through which ink from the pressure chamber 402 flows out to an individual recovery flow path 318.

[0030] Therefore, the recording head 14 is provided therein with an inlet channel 302, a first negative pressure control unit 306, a second negative pressure control unit 308, an ink branch channel 312, an ink merging channel 314, and an outlet channel 304. The recording head 14 is further provided therein with an individual supply channel 316, an inlet 404, a pressure chamber 402, an outlet 406, and an individual recovery channel 318. In the following description, these channels will be collectively referred to as the "head internal channel" where appropriate.

[0031] In this embodiment, for ease of understanding, the image forming apparatus 10 will be described as having one recording head 14 that ejects one type of ink. Note that the image forming apparatus 10 is not limited to having one recording head 14, but may be configured to have multiple recording heads 14. In this case, the image forming apparatus 10 will be provided with circulation paths 200 in numbers corresponding to the recording heads 14. Furthermore, the image forming apparatus 10 is not limited to having one type of ink ejected from the recording head 14, but may be configured to eject multiple types of ink from the recording head 14. In this case, circulation paths 200 corresponding to each ink will be formed, and internal head flow paths corresponding to each ink will be formed inside the recording head 14.

[0032] (Configuration of the control system of the image forming apparatus) Next, a description will be given of the configuration of the control system of the image forming apparatus 10. Fig. 5 is a block diagram showing the configuration of the control system of the image forming apparatus 10.

[0033] The image forming apparatus 10 includes a device control unit 500 that controls the overall operation of the image forming apparatus 10, and an operation unit 502 that displays information to the user and receives instructions input from the user. The device control unit 500 is connected to a host device 504 that is provided separately from the image forming apparatus 10, and various information such as jobs can be input from the host device 504.

[0034] The image forming apparatus 10 includes a recording control unit 506 that controls the recording head 14, and an ink supply control unit 508 that controls the supply of ink to the recording head 14 via the circulation path 200. The image forming apparatus 10 also includes a transport control unit 510 that controls the transport unit 12, a drying control unit 512 that controls the drying unit 16, and a maintenance control unit 514 that controls the maintenance unit 220.

[0035] The device control unit 500 includes a microprocessor-type CPU 516, a ROM-type program memory 518, and a RAM-type data memory 520. The device control unit 500 receives instructions from the host device 504 or the operation unit 502 and controls the components of the image forming apparatus 10. The control programs and control parameters for each component are stored in the program memory 518 or the data memory 520, and the CPU 516 reads these to control each component.

[0036] The recording control unit 506 controls the elevator unit 522 to raise and lower the recording head 14. The recording control unit 506 also controls the ejection of ink from the recording head 14 via the head control unit 524. The transport control unit 510 controls the transport unit 12 to control the transport of the recording medium M. The drying control unit 512 controls the drying unit 16 to promote the fixation of the ink applied to the recording medium M. The maintenance control unit 514 controls the maintenance unit 220 to perform various maintenance processes on the recording head 14.

[0037] The ink supply control unit 508 detects that the head internal flow path has been filled with ink based on the detection result of a pressure sensor 526 that detects the pressure in the head internal flow path. The ink supply control unit 508 also controls the liquid feed pumps 210 and 212 to control the circulation of ink in the circulation path 200. The ink supply control unit 508 also controls the ink supply pump 528 to control the supply of ink stored in the main tank 202 to the buffer tank 204. The ink supply control unit 508 also controls the degassing pump 216 to control the removal of dissolved gas from the ink circulating in the circulation path 200 by the degassing unit 214. The ink supply control unit 508 also controls the on-off valve to control the supply of ink to the head internal flow path of the recording head 14.

[0038] (Recording Processing) In the above configuration, when the image forming apparatus 10 receives a job including a recording instruction, the apparatus control unit 500 executes a preparation process for executing the recording process, and then executes the recording process based on the job.

[0039] As a preparation process, the device control unit 500 controls the conveyance control unit 510 to convey the recording medium M at a specified conveyance speed. The device control unit 500 also controls the maintenance control unit 514 to uncapping the recording head 14 with the cap 222, that is, to separate the cap 222 from the recording head 14. The device control unit 500 also controls the drying unit 16 to dry the recording medium M under the conditions set in the drying unit 16 via the drying control unit 512. The device control unit 500 also controls the ink supply control unit 508 to start circulating the ink in the circulation path 200 by the liquid feed pumps 210 and 212, and drives the degassing pump 216 to operate the degassing unit 214.

[0040] Once these preparation processes are complete, the recording process begins, and the device control unit 500 converts the recording data generated by the device control unit 500 via the recording control unit 506 into a drive signal in the head control unit 524, which drives the ejection energy generating elements of the recording head 14. At this time, the device control unit 500 controls the conveyance of the recording medium M via the conveyance control unit 510, and controls so that ink is ejected from the recording head 14 to a predetermined position on the recording medium for recording.

[0041] (Filling ink into the flow passages inside the head) Incidentally, the recording head 14 requires that the internal flow passages of the head be filled with ink in order to perform a recording process. In the image forming apparatus 10, the internal flow passages of the head are filled with ink at a predetermined timing, for example, when the recording head 14 is replaced. To fill the internal flow passages of the head with ink, ink is allowed to flow into the internal flow passages of the head from the supply flow passage 206 and the recovery flow passage 208 connected to the recording head 14.

[0042] Methods for causing ink to flow into the head internal flow channels include depressurizing the head internal flow channels or pressurizing the supply flow channels 206 and recovery flow channels 208. In the depressurizing method, the on-off valve 218 in the supply flow channel 206 is closed, and air in the head internal flow channels is sucked through the nozzles 400, creating a depressurized state in the head internal flow channels. The on-off valve 218 is then opened, allowing ink to flow into the head internal flow channels from the supply flow channels 206 and recovery flow channels 208. In the depressurizing method, the air expanded by the depressurization of the head internal flow channels contracts, thereby filling the head internal flow channels evenly with ink. For example, one method for sucking air from the head internal flow channels through the nozzles 400 involves capping the nozzle surface 14a of the recording head 14 with the cap 222, driving the suction pump 224, generating negative pressure inside the cap 222, and sucking the air.

[0043] In the image forming apparatus 10, for example, the ink is filled by depressurizing or pressurizing the head internal flow passage to cause the ink to flow into the head internal flow passage, and filling of the head internal flow passage with ink is considered to be complete when the pressure in the head internal flow passage returns to atmospheric pressure. The pressure in the head internal flow passage is detected by a pressure sensor 526, and the device control unit 500 determines whether atmospheric pressure has been reached based on the detection result of the pressure sensor 526.

[0044] (Concerns that arise when filling ink) In the recording head 14, the internal flow paths of the head have portions where the cross-sectional area of ​​the flow path is relatively wide and portions where the flow path bends in a substantially vertical direction. Therefore, when the internal flow paths of the head are depressurized and filled with ink, air tends to remain in these portions after contraction, making it difficult to fill with ink. Furthermore, remaining air bubbles tend to accumulate in relatively higher locations. For example, the negative pressure control units 306 and 308, the ink branch paths 312, and the ink junction path 314 have complex shapes, and contracted air may be trapped and accumulate as air bubbles near the top surfaces of these locations.

[0045] The generated bubbles can obstruct the flow of ink in the flow path and cause the ink to stick or thicken at the interface with the air. The stuck or thickened ink can then obstruct the circulating flow of ink, disrupting the ink ejection state from the nozzles 400 or causing ink not to be ejected from the nozzles 400.

[0046] In particular, if air bubbles remain in areas where the flow path volume changes, such as the negative pressure control units 306 and 308, the ink level will fluctuate up and down as the flow path volume changes. When the ink level drops, some of the ink may separate into small droplets and adhere to the wall surface. These small droplets isolated within the air bubbles have a large surface area relative to their volume, and the liquid components evaporate quickly, making them prone to becoming solidified.

[0047] Furthermore, if the temperature around the remaining bubbles rises, the temperature inside the remaining bubbles also rises, resulting in a decrease in relative humidity, which promotes evaporation of the liquid components from the ink at the interface. Generally, when the print head 14 performs an ejection operation from the nozzles 400, the temperature around the print head 14 tends to rise due to heat radiation from the electric board and heat transfer from the drying unit 16.

[0048] (Circulation control) Therefore, in this embodiment, after filling the print head 14 with ink, which has not been filled with ink, the ink circulation in the circulation path 200 is started before other processes or operations are performed. During this circulation, the degassing pump 216 is driven to activate the degassing unit 214. The circulation in the circulation path 200 is performed for a predetermined time to reduce remaining air bubbles in the head internal flow path to a level that does not degrade the ink ejection characteristics from each nozzle 400. Furthermore, after the predetermined time has elapsed, the ink is intermittently circulated in the circulation path 200. That is, in this embodiment, after filling the head internal flow path with ink, a first circulation control is performed in the circulation path 200 to continuously circulate the ink for a predetermined time, and then a second circulation control is performed to intermittently circulate the ink (see FIG. 6). FIG. 6 is a diagram showing the timing of the ink circulation in the circulation path 200 after filling the head internal flow path with ink.

[0049] The timing for starting the circulation of ink under the first circulation control is immediately after filling the flow path inside the head with ink, or at least before executing other processes or operations. Other processes or operations are, for example, ejection operations by the recording head 14. Note that the ejection operations by the recording head 14 include a recording operation on the recording medium M (i.e., a recording process), an ejection operation on the cap 222 to check the ejection state, an ejection operation for aging the ejection energy generating elements, and the like.

[0050] In the first circulation control, the ink is circulated while the degassing unit 214 is functioning, thereby reducing the amount of dissolved gas in the circulating ink, and by continuing this circulation for a predetermined period of time, air bubbles remaining in the head internal flow path are dissolved into the ink with the reduced amount of dissolved gas. This makes it possible to reduce the amount of air bubbles remaining in the head internal flow path. Furthermore, following the first circulation control, the degassing unit 214 is functioned in the second circulation control to intermittently circulate the ink, thereby making it possible to suppress thickening of the ink in the nozzles and suppress sedimentation of components contained in the ink.

[0051] Specifically, in the image forming apparatus 10, when the device control unit 500 detects via the ink supply control unit 508 that the pressure in the flow path inside the head has reached atmospheric pressure based on the detection result of the pressure sensor 526, the device control unit 500 drives the liquid feed pumps 210 and 212 to execute the first circulation control. In order to prevent ink from adhering due to residual air bubbles, it is desirable to execute the first circulation control promptly after ink filling. Thus, in this embodiment, the device control unit 500 and the ink supply control unit 508 function as a control unit that controls the circulation of ink in the circulation path 200 while removing dissolved air bubbles from the ink using the degassing unit 214.

[0052] In the first circulation control, ink is circulated in the circulation path 200 while the degassing unit 214 is functioning for a predetermined time T1. The predetermined time T1 is, for example, the time required to reduce the volume of residual air bubbles generated in the internal flow path of the head to a level that does not degrade the ink ejection characteristics from each nozzle 400. The lower limit of the predetermined time T1 is preferably, for example, 100 hours or more, and more preferably, 200 hours or more. The upper limit of the predetermined time T1 is, for example, the time at which residual air bubbles in the internal flow path of the head can no longer be reduced even when circulating ink with a reduced amount of dissolved gas. Specifically, the predetermined time T1 is, for example, 1000 hours or less. The predetermined time T1 is experimentally determined depending on, for example, the type of ink used, the shape of the circulation path 200 and the components that make up the circulation path 200, the operating environment of the image forming apparatus 10, and the like.

[0053] When the first circulation control ends, that is, when the circulation of ink in the circulation path 200, which has continued for a predetermined time T1 (or a time corresponding to the predetermined time T1), ends, the second circulation control is executed. In the second circulation control, the circulation of ink is executed intermittently. In other words, in the second circulation control, the circulation of ink in the circulation path 200 is executed and stopped alternately in a repeated manner. Note that the second circulation control also includes a case where the circulation is executed only once after the circulation is stopped. In the second circulation control, the circulation of ink in the circulation path 200 is stopped for a first time Tb, and the circulation of ink in the circulation path 200 is executed for a second time T2, and the stopping of the circulation for the first time Tb and the execution of the circulation for the second time T2 are repeatedly executed. In other words, in the second circulation control, the pattern of stopping the circulation of ink for the first time Tb and then circulating the ink for the second time T2 is continuously executed.

[0054] The first time Tb is the lower limit of the stoppage time during which the ink ejection characteristics may be degraded due to, for example, stoppage of circulation causing the ink to thicken in the nozzles due to evaporation of liquid components, the ink components to settle in the circulation path 200, and uneven ink temperature in the circulation path 200. The second time T2 is the lower limit of the time during which the circulation can eliminate, for example, the ink thickening in the nozzles caused by evaporation of liquid components, the ink components to settle in the circulation path 200, and uneven ink temperature in the circulation path 200.

[0055] In this way, the first circulation control is performed with the objective of reducing the amount of air bubbles remaining in the flow paths inside the head, whereas the second circulation control is performed with the objective of suppressing thickening of the ink from the nozzles, preventing the sedimentation of ink components, leveling the ink temperature, etc. The second circulation control is performed, for example, until the next time the recording head 14 is replaced.

[0056] In the first circulation control and the second circulation control, ink is circulated in the circulation path 200 by driving the liquid feed pumps 210, 212. For this reason, from the viewpoint of the durability of the liquid feed pumps 210, 212, it is preferable that the second time T2 is short. In this embodiment, the relationship between the predetermined time T1 during which the liquid feed pumps 210, 212 are driven and the second time T2 is set to T1>T2. As a result, in the image forming apparatus 10 according to this embodiment, it is possible to extend the life of the liquid feed pumps 210, 212 while maintaining the ability to remove residual air bubbles, compared to known techniques that constantly circulate ink in the circulation path.

[0057] Furthermore, from the viewpoint of the durability of the liquid feed pumps 210 and 212, it is preferable that the first time Tb be as long as possible without departing from the purpose of the second circulation control. Specifically, the total time of the first time Tb and the second time T2 is, for example, 11 minutes or more and 28 hours or less, and the second time T2 is, for example, 5 minutes. In other words, if the second time T2 is set to about 5 minutes and the total time of the first time Tb and the second time T2 is set to 11 minutes or more and 28 hours or less, the purpose of the second circulation control can be achieved and the lifespan of the liquid feed pumps 210 and 212 can be extended. In particular, by setting the relationship between the predetermined time T1, the first time Tb, and the second time T2 to T1>Tb>T2, the lifespan of the liquid feed pumps 210 and 212 can be more reliably extended while maintaining the performance of removing remaining bubbles.

[0058] (Specific circulation control) Next, specific examples of the execution of circulation control will be described. Figure 7 is a diagram showing specific examples of the execution of circulation control. Figure 7(a) is an example of the execution of reference circulation control. Figure 7(b) is an example of the execution of circulation control when a discharge operation is performed during first circulation control. Figure 7(c) is an example of the execution of circulation control when a discharge operation is performed during second circulation control.

[0059] In the image forming apparatus 10, even during circulation control, it is possible to perform a discharge operation involving the circulation of ink in the circulation path 200 for recording or other purposes. Specifically, it is possible to perform the discharge operation during the first circulation control, or to perform the discharge operation during the second circulation control.

[0060] First, a case where a discharge operation is performed during the first circulation control will be described. In the first circulation control, after the circulation of ink in the circulation path 200 starts, the circulation continues until a predetermined time T1 has elapsed. In this embodiment, even if a discharge operation involving the circulation of ink in the circulation path 200 is performed at any timing after the start of the circulation, the first circulation control ends when the predetermined time T1 is reached, regardless of the time required for the discharge operation (see FIG. 7(b)).

[0061] That is, even if a discharge operation is performed during the first circulation control, the first circulation control ends at the same timing as when no discharge operation is performed during the first circulation control (see FIG. 7(a)). Note that if a discharge operation is performed for a period exceeding the predetermined time T1, the first circulation control ends at the timing when the discharge operation ends.

[0062] Next, a case where a discharge operation is performed during the second circulation control will be described. In the second circulation control, after the first circulation control ends, the circulation of ink in the circulation path 200 is stopped for a first time Tb, and then the circulation of ink in the circulation path 200 is performed for a second time T2, thereby circulating the ink intermittently.

[0063] In this embodiment, when a discharge operation is performed during the second circulation control, the circulation of ink in the circulation path 200 accompanying the discharge operation is considered to be the circulation performed during the second circulation control, regardless of the timing of the discharge operation. Specifically, if a discharge operation is performed for a first time Tb, the circulation of ink in the circulation path 200 accompanying the discharge operation is considered to be the circulation of ink for a second time T2, regardless of the length of that time (see FIG. 7(c)). In this case, the time for stopping the circulation of ink is a time Tb' that is shorter than the first time Tb, and the time for performing the circulation of ink is a time T2' required for the discharge operation, which is different from the second time T2. Then, the circulation of ink is stopped for the first time Tb from the point when the discharge operation ends, and then the circulation of ink is performed for the second time T2. In other words, when an ejection operation is performed during the second circulation control, regardless of the length of time required for the ejection operation, after the ejection operation is completed, intermittent ink circulation is performed in a predetermined pattern that repeats stopping circulation for the first time Tb and executing circulation for the second time T2.

[0064] (Circulation time in the first circulation control) Next, the predetermined time T1, which is the circulation time for circulating ink in the circulation path 200 in the first circulation control, will be described.

[0065] When the head internal flow path is depressurized to fill the circulation path 200 with ink, the predetermined time T1, which is the circulation time of the ink in the first circulation control, can be determined based on the negative pressure value reached when the head internal flow path is depressurized. A method for determining the predetermined time T1 will be described below. However, the predetermined time T1 may be determined, for example, by obtaining the negative pressure value reached in the head internal flow path when the pressure is depressurized each time the head internal flow path is filled with ink, and determining the predetermined time T1 based on that negative pressure value. Alternatively, the negative pressure value in the head internal flow path when the head internal flow path is depressurized, such as at the time of shipping from the factory, may be obtained, and the predetermined time T1 may be determined based on that negative pressure value, and the determined predetermined time T1 may be set as the circulation time of the ink in the first circulation control.

[0066] The higher the negative pressure value reached in the internal ink flow path when the pressure is reduced, the greater the contraction rate of the gas in the internal head flow path when ink subsequently flows in and the internal ink flow path returns to normal pressure, and therefore the smaller the amount of air bubbles remaining in the internal head flow path after ink is filled.

[0067] If the volume of the flow path inside the head is D1, the atmospheric pressure is P1, and the ultimate negative pressure is P2, the volume D2 of the remaining air bubbles after filling with ink is expressed by the following formula (1). D2=(P1+P2)×D1 / P1 (1) For example, if D1 is 200 ml, P1 is 100 kPa, and P2 is -80 kPa, then according to the above formula (1), D2 will be 40 ml.

[0068] The predetermined time T1, which is the ink circulation time required to remove remaining air bubbles after ink filling, varies mainly depending on the ink flow rate during ink circulation and the ink degassing degree. The ink flow rate is controlled by the liquid feed rate of the liquid feed pumps 210 and 212, and the ink degassing degree is controlled by the performance of the degassing unit 214, and these are values ​​specific to each image forming apparatus 10.

[0069] If a constant specific to the machine, which is determined by the ink flow rate and the degree of degassing of the ink, is k, the predetermined time T1 is expressed by the following equation (2). T1=k×D2 (2) The pressure sensor 526 for measuring P2 may be disposed, for example, in one of the flow paths inside the head, or may be disposed in the cap 222. Alternatively, it may be disposed in the flow path from the on-off valve 218 to the inlet path 302.

[0070] (Inks suitable for use with circulation control according to the present disclosure) Next, we will explain inks that are suitable for use in the image forming apparatus 10 that performs circulation control according to this embodiment. Note that there are no particular limitations on the inks that can be used in the image forming apparatus 10 that performs circulation control according to this embodiment.

[0071] <Ink containing thermoplastic resin particles> An example of an ink suitable for use in the image forming apparatus 10 that performs circulation control according to this embodiment is an ink containing thermoplastic resin particles, which can ensure quality such as image robustness of the recorded material.

[0072] When an image formed by ejecting ink is heated to a temperature above its glass transition temperature, at least a portion of the thermoplastic resin particles soften or melt, thereby imparting scratch resistance and water resistance to the image. Specific materials for the thermoplastic resin particles include polystyrene, polyvinyl chloride, polyethylene, polypropylene, and polymethacrylate. The thermoplastic resin particles can be dispersed in the ink by, for example, dispersing them using a resin dispersant or by bonding hydrophilic groups such as anionic groups to the particle surface directly or via other atomic groups.

[0073] The weight-average molecular weight (Mw) of the thermoplastic resin microparticles is preferably 1,000 to 2,000,000. The volume-average particle diameter of the thermoplastic resin microparticles measured by dynamic light scattering is preferably 10 to 1,000 nm, more preferably 100 to 500 nm. The content (mass %) of the thermoplastic resin microparticles in the ink is preferably 1.0 to 50.0 mass %, more preferably 2.0 to 40.0 mass %, based on the total mass of the ink.

[0074] Ink containing thermoplastic resin particles is prone to forming solidified deposits because evaporation of the liquid components destroys the dispersion state at the interfaces of air bubbles remaining in the flow paths inside the head, causing the thermoplastic resin particles to aggregate or fuse together. Therefore, in an image forming apparatus 10 using ink containing such thermoplastic resin particles, the occurrence of solidified deposits can be suppressed by performing the ink circulation control described above, thereby achieving both stable ejection characteristics and robust images.

[0075] <Ink containing non-volatile solvent> Furthermore, examples of inks suitable for use in the image forming apparatus 10 that executes circulation control according to this embodiment include inks with a non-volatile solvent content of 1% by weight or less. Note that inks with a non-volatile solvent content of 1% by weight or less include inks with a non-volatile solvent content of 0% by weight, i.e., inks that do not contain a non-volatile solvent.

[0076] Nonvolatile solvents are used to prevent ink from drying, and even if air bubbles remain in the flow path inside the head, they suppress the occurrence of ink sticking near the interface. In this embodiment, nonvolatile solvents refer to solvents with a boiling point of 250°C or higher, and examples include polyhydric alcohols, polyhydric alcohol ethers, acetates, and amines. On the other hand, nonvolatile solvents may remain in images formed by ejecting the ink containing them, thereby reducing the abrasion resistance and water resistance.

[0077] Even in inks containing a small amount of nonvolatile solvent or substantially no nonvolatile solvent, i.e., inks containing 1% by weight or less of nonvolatile solvent, the occurrence of adhesion at the interface of bubbles remaining in the internal flow path of the head can be suppressed by controlling the circulation of the ink as described above. The content of nonvolatile tablets in the ink is preferably 1% by weight or less, and more preferably 0.1% by weight or less.

[0078] If the ink contains a large amount of non-volatile solvent, it takes a long time to dry, which can result in, for example, a longer conveyance distance in the drying section, making the device larger, or a longer drying time in the drying section, lengthening the time required for recording. However, by performing the circulation control described above and using ink with a non-volatile solvent content of 1% by weight or less, it is possible to prevent the device from becoming larger and the recording time from increasing, while also suppressing the occurrence of ink sticking due to air bubbles.

[0079] (Action and effect) As described above, in the image forming apparatus according to this embodiment, after filling the head internal flow passages that constitute the ink circulation path with ink, the first circulation control is performed to continuously circulate the ink, and then the second circulation control is performed to intermittently circulate the ink. As a result, in the image forming apparatus according to this embodiment, it is possible to reduce the amount of residual air bubbles generated in the head internal flow passages and reduce the frequency of replacing pumps in the circulation path, thereby suppressing costs.

[0080] Furthermore, the time required for one circulation in the second circulation control (second time T2) is shorter than the time required to stop one circulation in the second circulation control (first time Tb), and the stop time is shorter than the time required for circulation in the first circulation control (predetermined time T1), thereby more reliably extending the life of the liquid feed pump.

[0081] (Other embodiments) The above-described embodiment may be modified as shown in the following (1) to (6).

[0082] (1) Although not specifically mentioned in the above embodiment, when the image forming apparatus 10 includes multiple recording heads 14, for example, ink containing thermoplastic resin microparticles and ink not containing thermoplastic resin microparticles may be ejected from different recording heads 14. An example of an ink not containing thermoplastic resin microparticles is a treatment liquid that reduces the fluidity of ink containing thermoplastic resin microparticles. Such a treatment liquid prevents a decrease in image quality due to the ink dots being attracted to or mixed with each other on the recording medium when ejected.

[0083] Ink that does not contain thermoplastic resin particles is less likely to dry and solidify even if air bubbles remain in the flow path inside the head. Therefore, it is not necessary to circulate the ink for the predetermined time T1 after filling the print head 14 with the ink. Therefore, in a circulation path 200 including a print head 14 that ejects ink that does not contain thermoplastic resin microparticles, the first circulation control may be omitted and the second circulation control, i.e., intermittent circulation, may be immediately performed. In this case, different circulation controls are performed for the circulation path 200 including the print head 14 filled with ink that contains thermoplastic resin microparticles and the circulation path 200 including the print head 14 filled with ink that does not contain thermoplastic resin microparticles. Specifically, the circulation path 200 including the print head 14 filled with ink that contains thermoplastic resin microparticles performs both the first circulation control and the second circulation control. On the other hand, the circulation path 200 including the print head 14 filled with ink that does not contain thermoplastic resin microparticles performs only the second circulation control.

[0084] (2) In the above embodiment, the predetermined time T1, which is the time for circulating ink through the first circulation control, is not changed regardless of whether or not a discharge operation is performed during the first circulation control. However, this is not limited to this. The predetermined time T1 may be changed depending on the discharge operation performed during the first circulation control. Below, we will explain how to change the predetermined time T1 depending on the discharge operation performed during the first circulation control.

[0085] For example, when a recording operation is performed as a discharge operation during the first circulation control, the flow rate of the ink circulated during the recording operation is set to be different from the flow rate of the ink circulated during the first circulation control. Generally, the flow rate during ink circulation affects the state of ink discharge from the nozzles, so it is necessary to keep the flow rate within a predetermined range that does not affect the state of ink discharge during the recording operation. On the other hand, during circulation control to reduce residual air bubbles in the head internal flow path, it is desirable to increase the contact between the air bubbles and the degassed ink to remove the air bubbles from the flow path, and therefore it is preferable to set the flow rate as fast as possible. In this embodiment, the ink flow rate during the recording operation is set to, for example, 400 ml / min, and the flow rate during the first circulation control is set to, for example, 800 ml / min.

[0086] Therefore, when performing a recording operation during the first circulation control, the length of the predetermined time T1 is changed depending on the ink flow rate during the recording operation, thereby more reliably reducing residual bubbles in the internal flow path of the head. Here, when performing a recording operation during the first circulation control, the ink flow rate during the recording operation is slower than the ink flow rate during the first circulation control, and the bubble removal performance in the internal flow path of the head is reduced during the recording operation. Therefore, by extending the predetermined time T1, which is the total ink circulation time during the first circulation control, depending on the time required for the recording operation and the ink flow rate during the recording operation, residual bubbles in the internal flow path of the head are more reliably reduced.

[0087] For example, the ink flow rate during the first circulation control is Va (ml / min), the predetermined time T1 is Ta (min), the ink flow rate during circulation during a printing operation is Vb (ml / min), and the time required to circulate the ink at the flow rate Vb is Tb (min). In this case, the changed predetermined time T1' is determined by the following equation (3). T1´={(Va×Ta)-(Vb×Tb)} / Va+Tb ··· (3) For example, if the ink flow rate during the first circulation control is 800 ml / min and the predetermined time T1 is 200 hours, and a recording operation is performed for 10 hours with an ink flow rate of 400 ml / min during the first circulation control, then, using equation (3) above, the changed predetermined time T' becomes 205 hours, which means that the predetermined time T1 is extended by 5 hours.

[0088] (3) In the above embodiment, the degassing unit 214, the degassing pump 216, the liquid supply pumps 210 and 212, and the buffer tank 204 in the circulation path 200 are provided outside the print head 14, but this is not limited to this. For example, as shown in FIG. 8 , the degassing unit 214, the degassing pump 216, the liquid supply pumps 210 and 212, and the buffer tank 204 may be provided inside the print head 14, and the circulation path may be provided inside the print head 14. In this case, ink is supplied to the buffer tank 204 via a flow path 802 connected to the main tank 202. Even when the circulation path is formed inside the print head 14 in this way, the same effects as those of the above embodiment can be obtained by performing ink circulation control as in the above embodiment. Note that when the circulation path is formed inside the print head 14, the first circulation control is started when the circulation path is filled with ink, that is, immediately after the filling.

[0089] (4) Although not specifically described in the above embodiment, the print head 14 may be provided with a heater capable of maintaining the print head 14 at a set temperature, and the print head 14 may be maintained at the set temperature by the heater during circulation. In addition, in the above embodiment, the image forming apparatus 10 is provided with a so-called full-line type print head in which a nozzle array extends in the width direction of the recording medium M to a length corresponding to the width of the recording medium M that can be printed thereon, but this is not limited to this. The image forming apparatus 10 may also be provided with a so-called serial scan type print head in which a nozzle array extends in a direction intersecting the width direction of the recording medium and ejects ink while moving in the width direction.

[0090] (5) The present disclosure can also be realized by supplying a program that realizes one or more functions of the above-described embodiments to a system or device via a network or a recording medium, and having one or more processors in the computer of the system or device read and execute the program. It can also be realized by a circuit (e.g., ASIC) that realizes one or more functions.

[0091] (6) The above embodiment and the various configurations shown in (1) to (5) above may be combined as appropriate.

[0092] The disclosure of the above embodiment includes the following configurations and methods. (Configuration 1) a print head that prints by ejecting the supplied ink from nozzles; a circulation path including an internal flow path formed inside the recording head and communicating with the nozzles, which supplies a recording material to the recording head and collects the recording material that has not been ejected from the recording head, and circulates the recording material; a removal unit for removing dissolved gas from the recording material circulating through the circulation path; a control unit that controls the removing unit and controls the circulation of the recording material in the circulation path, The image forming apparatus is characterized in that, when the control means fills the internal flow path of the recording head with recording material, it performs first circulation control in which the recording material is circulated continuously in the circulation path for a first time while the dissolved gas is removed by the removal means, and then performs second circulation control in which the recording material is circulated intermittently for a second time that is shorter than the first time. (Configuration 2) a print head that supplies the supplied printing material to the nozzles and includes a circulation path that collects the printing material that has not been ejected from the nozzles and circulates the printing material, and that ejects ink from the nozzles to perform printing; a removal unit for removing dissolved gas from the recording material circulating through the circulation path; a control unit that controls the removing unit and controls the circulation of the recording material in the circulation path, The image forming apparatus is characterized in that, when the control means fills the circulation path of the recording head with recording material, it performs first circulation control in which the recording material is circulated continuously in the circulation path for a first time while the dissolved gas is removed by the removal means, and then performs second circulation control in which the recording material is circulated intermittently for a second time that is shorter than the first time. (Configuration 3) 3. The image forming apparatus according to claim 1, wherein the timing at which the first circulation control is started is before the ink ejection operation from the recording head is started. (Configuration 4) 3. The image forming apparatus according to claim 1, wherein the timing at which the first circulation control is started is immediately after the recording material is filled inside the recording head. (Configuration 5) The ink supply device further includes a detection means for detecting when the pressure in the flow path through which the ink circulates reaches atmospheric pressure, 3. The image forming apparatus according to claim 1, wherein the control unit starts the first circulation control based on the detection result of the detection unit. (Configuration 6) The image forming apparatus according to any one of configurations 1 to 5, characterized in that in the second circulation control, the time for which the circulation of the recording material is stopped is a third time that is shorter than the first time and longer than the second time. (Configuration 7) a suction means for applying a negative pressure to the internal flow path through a nozzle of the recording head; a valve that regulates and allows the supply of recording material to the internal flow path, The image forming apparatus according to configuration 1, characterized in that the control means, while restricting the supply of recording material to the internal flow path by the valve, applies negative pressure to the internal flow path via the ink by the suction means, and then allows the supply of recording material to the internal flow path by the valve, thereby filling the internal flow path with recording material. (Configuration 8) 8. The image forming apparatus according to any one of configurations 1 to 7, wherein the recording material is ink containing thermoplastic resin particles. (Configuration 9) 8. The image forming apparatus according to any one of configurations 1 to 7, wherein the recording material is ink containing 1% by weight or less of a nonvolatile solvent having a boiling point of 250° C. or higher. (Configuration 10) the recording head includes a first recording head that ejects ink containing thermoplastic resin microparticles as a recording material, and a second recording head that ejects ink that does not contain thermoplastic resin microparticles as a recording material; The control means In the circulation path including the first print head, the second circulation control is executed after the first circulation control is executed; 8. The image forming apparatus according to any one of configurations 1 to 7, wherein the second circulation control is executed in the circulation path including the second recording head. (Configuration 11) 11. The image forming apparatus according to any one of configurations 1 to 10, wherein the flow path through which ink circulates in the recording head has a portion where the cross-sectional area of ​​the flow path becomes relatively wide and a portion where the flow path bends in a substantially vertical direction. (Configuration 12) 12. The image forming apparatus according to any one of configurations 1 to 11, wherein the flow path through which ink circulates in the recording head has a portion where the flow path volume changes. (Configuration 13) The image forming apparatus according to any one of configurations 1 to 12, characterized in that when an ejection operation is performed during the first circulation control, the control means circulates the recording material in the circulation path while removing the dissolved gas using the removal means in accordance with the ejection operation. (Configuration 14) The image forming apparatus according to any one of configurations 1 to 13, characterized in that when an ejection operation is performed during the second circulation control, the control means circulates the recording material in the circulation path while removing the dissolved gas using the removal means in accordance with the ejection operation. (Configuration 15) The control means When a discharge operation is performed during the first circulation control, the recording material is circulated in the circulation path while the dissolved gas is removed by the removing means in response to the discharge operation, 15. The image forming apparatus according to any one of configurations 1 to 14, wherein the first time period is changed depending on the flow speed of the recording material in circulation accompanying the ejection operation and the time period for which the circulation is performed. (Configuration 16) The control means In the second circulation control, the circulation is stopped for a third time period that is shorter than the first time period and longer than the second time period, and then the circulation is performed for the second time period, and this is repeated to perform intermittent circulation of the ink in a predetermined pattern; When a discharge operation is performed during the second circulation control, the recording material is circulated in the circulation path while the dissolved gas is removed by the removing means in response to the discharge operation, The image forming apparatus according to any one of configurations 1 to 15, characterized in that when the ejection operation is performed during the second circulation control, the ink is circulated intermittently in the predetermined pattern from the timing when the ejection operation is completed. (Configuration 17) 17. The image forming apparatus of any one of configurations 1 to 16, wherein the first time period is 100 hours or more. (Configuration 18) the second circulation control includes continuously executing a pattern of stopping the circulation of ink for a third time period that is shorter than the first time period and longer than the second time period, and then circulating the ink for the second time period; 18. The image forming apparatus according to any one of configurations 1 to 17, wherein the sum of the second time period and the third time period is 28 hours or less. (Configuration 19) a print head that prints by ejecting the supplied ink from nozzles; a circulation path including an internal flow path formed inside the recording head and communicating with the nozzles, which supplies a recording material to the recording head and collects the recording material that has not been ejected from the recording head, and circulates the recording material; a removal unit that removes dissolved gas from the recording material circulating through the circulation path, A control method characterized by: when the internal flow path of the recording head is filled with recording material, a first circulation control is performed in which the recording material is circulated continuously for a first time while the dissolved gas is removed by the removal means in the circulation path; and then a second circulation control is performed in which the recording material is circulated intermittently for a second time that is shorter than the first time. (Configuration 20) a print head that supplies the supplied printing material to the nozzles and includes a circulation path that collects the printing material that has not been ejected from the nozzles and circulates the printing material, and that ejects ink from the nozzles to perform printing; a removal unit that removes dissolved gas from the recording material circulating through the circulation path, When the circulation path of the recording head is filled with recording material, a first circulation control is performed in which the recording material is continuously circulated for a first time while the dissolved gas is removed in the circulation path by the removal means, and then a second circulation control is performed in which the recording material is intermittently circulated for a second time that is shorter than the first time. [Explanation of symbols]

[0093] 10 Image forming device 14 Recording head 200 Circulation Route 214 Degassing section (removal means) 500 Device control section 508 Ink supply control unit

Claims

1. a print head that prints by ejecting the supplied ink from nozzles; a circulation path including an internal flow path formed inside the recording head and communicating with the nozzles, which supplies a recording material to the recording head and collects the recording material that has not been ejected from the recording head, and circulates the recording material; a removal unit for removing dissolved gas from the recording material circulating through the circulation path; a control unit that controls the removing unit and controls the circulation of the recording material in the circulation path, The image forming apparatus is characterized in that, when the control means fills the internal flow path of the recording head with recording material, it performs first circulation control in which the recording material is circulated continuously in the circulation path for a first time while the dissolved gas is removed by the removal means, and then performs second circulation control in which the recording material is circulated intermittently for a second time that is shorter than the first time.

2. a print head that supplies the supplied printing material to the nozzles and includes a circulation path that collects the printing material that has not been ejected from the nozzles and circulates the printing material, and that ejects ink from the nozzles to perform printing; a removal unit for removing dissolved gas from the recording material circulating through the circulation path; a control unit that controls the removing unit and controls the circulation of the recording material in the circulation path, The image forming apparatus is characterized in that, when the control means fills the circulation path of the recording head with recording material, it performs first circulation control in which the recording material is circulated continuously in the circulation path for a first time while the dissolved gas is removed by the removal means, and then performs second circulation control in which the recording material is circulated intermittently for a second time that is shorter than the first time.

3. 3. The image forming apparatus according to claim 1, wherein the timing at which the first circulation control is started is before the ink ejection operation from the recording head is started.

4. 3. The image forming apparatus according to claim 1, wherein the timing at which the first circulation control is started is immediately after the recording material is filled inside the recording head.

5. The ink supply device further includes a detection means for detecting when the pressure in the flow path through which the ink circulates reaches atmospheric pressure, 3. The image forming apparatus according to claim 1, wherein the control unit starts the first circulation control based on the detection result of the detection unit.

6. 3. The image forming apparatus according to claim 1, wherein in the second circulation control, the time for which circulation of the recording material is stopped is a third time that is shorter than the first time and longer than the second time.

7. a suction means for applying a negative pressure to the internal flow path through a nozzle of the recording head; a valve that regulates and allows the supply of recording material to the internal flow path, The image forming apparatus according to claim 1, characterized in that the control means, while restricting the supply of recording material to the internal flow path by the valve, applies negative pressure to the internal flow path via the ink by the suction means, and then allows the supply of recording material to the internal flow path by the valve, thereby filling the internal flow path with recording material.

8. 3. The image forming apparatus according to claim 1, wherein the recording material is ink containing thermoplastic resin particles.

9. 3. The image forming apparatus according to claim 1, wherein the recording material is ink containing 1% by weight or less of a non-volatile solvent having a boiling point of 250[deg.] C. or higher.

10. the recording head includes a first recording head that ejects ink containing thermoplastic resin particles as a recording material, and a second recording head that ejects ink that does not contain thermoplastic resin particles as a recording material; The control means In the circulation path including the first print head, the second circulation control is executed after the first circulation control is executed; 3. The image forming apparatus according to claim 1, wherein the second circulation control is executed in the circulation path including the second recording head.

11. 3. The image forming apparatus according to claim 1, wherein the flow path in the recording head through which the ink circulates has a portion where the cross-sectional area of ​​the flow path becomes relatively large and a portion where the flow path is bent in a substantially vertical direction.

12. 3. The image forming apparatus according to claim 1, wherein the flow path through which the ink circulates in the recording head has a portion where the flow path volume changes.

13. The image forming apparatus according to claim 1 or 2, characterized in that when an ejection operation is performed during the first circulation control, the control means circulates the recording material in the circulation path while removing the dissolved gas using the removal means in accordance with the ejection operation.

14. The image forming apparatus according to claim 1 or 2, characterized in that when an ejection operation is performed during the second circulation control, the control means circulates the recording material in the circulation path while removing the dissolved gas using the removal means in accordance with the ejection operation.

15. The control means When a discharge operation is performed during the first circulation control, the recording material is circulated in the circulation path while the dissolved gas is removed by the removing means in response to the discharge operation, 3. The image forming apparatus according to claim 1, wherein the first time period is changed in accordance with a flow speed of the recording material in circulation accompanying the ejection operation and a time period for which the circulation is performed.

16. The control means In the second circulation control, the circulation is stopped for a third time period that is shorter than the first time period and longer than the second time period, and then the circulation is performed for the second time period, and this is repeated to perform intermittent circulation of the ink in a predetermined pattern; When a discharge operation is performed during the second circulation control, the recording material is circulated in the circulation path while the dissolved gas is removed by the removing means in response to the discharge operation, 3. The image forming apparatus according to claim 1, wherein when the ejection operation is performed during the second circulation control, the ink is circulated intermittently in the predetermined pattern from the timing when the ejection operation is completed.

17. 3. The image forming apparatus according to claim 1, wherein the first time period is 100 hours or more.

18. the second circulation control includes continuously executing a pattern in which the circulation of ink is stopped for a third time period that is shorter than the first time period and longer than the second time period, and then the circulation of ink is started for the second time period; 3. The image forming apparatus according to claim 1, wherein the sum of the second time period and the third time period is 28 hours or less.

19. a print head that prints by ejecting the supplied ink from nozzles; a circulation path including an internal flow path formed inside the recording head and communicating with the nozzles, which supplies a recording material to the recording head and collects the recording material that has not been ejected from the recording head, and circulates the recording material; a removal unit that removes dissolved gas from the recording material circulating through the circulation path, A control method characterized by the fact that, when recording material is filled into the internal flow path of the recording head, a first circulation control is performed in which the recording material is circulated continuously for a first time while the dissolved gas is removed by the removal means in the circulation path, and then a second circulation control is performed in which the recording material is circulated intermittently for a second time that is shorter than the first time.

20. a print head that supplies the supplied printing material to the nozzles and includes a circulation path that collects the printing material that has not been ejected from the nozzles and circulates the printing material, and that ejects ink from the nozzles to perform printing; a removal unit that removes dissolved gas from the recording material circulating through the circulation path, An image forming apparatus characterized in that, when recording material is filled into the circulation path of the recording head, a first circulation control is performed in which the recording material is circulated continuously for a first time while the dissolved gas is removed in the circulation path by the removal means, and then a second circulation control is performed in which the recording material is circulated intermittently for a second time that is shorter than the first time.

Images