Image forming apparatus, method, and computer program

Abstract

To provide an image forming apparatus in which decrease of deaeration of ink supplied to an inkjet head is suppressed and which therefore enables degradation of image quality to be prevented.SOLUTION: The image forming apparatus comprises: an inkjet head 241 ejecting liquid ink; a deaeration module 14 performing deaeration of the ink; a supply-side sub tank 12 storing ink which is supplied to the inkjet head 241; and a printer-side control circuit performing control in such a manner that ink deaerated by the deaeration module 14 is supplied to the supply-side sub tank 12 and further is supplied to the inkjet head 241. The printer control circuit performs control in such a manner that at least a part of ink stored in the supply-side sub tank 12 is supplied from the supply-side sub tank 12 to the deaeration module 14 and then is deaerated by the deaeration module 14, during stand-by for image formation by the inkjet head 241.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present disclosure relates to a technique for forming an image by discharging liquid ink.

Background Art

[0002] Conventionally, in an inkjet recording apparatus that discharges ink supplied from an ink tank storing ink by an inkjet head, when it detects a decrease in the amount of ink stored in the ink tank, it stops the printing operation, replenishes the ink tank with ink from a replenishment tank, and resumes the printing operation when the ink replenishment to the ink tank is completed. For this reason, printing cannot be performed during ink replenishment, and there is a risk that the productivity of printing by the inkjet recording apparatus will decrease.

[0003] According to Patent Document 1, when the pressure value of the inkjet nozzle is less than the lower limit value, if the height of the ink in the ink tank is higher than a predetermined value, outside air is introduced into the ink tank to increase the pressure value of the nozzle. On the other hand, when the pressure value of the nozzle is less than the lower limit value, if the height of the ink in the ink tank is less than or equal to the predetermined value, new ink is replenished to increase the pressure value of the nozzle. In this way, the inkjet recording apparatus can replenish the ink in the ink tank while adjusting the pressure of the nozzle without stopping the printing operation, preventing a decrease in the productivity of printing by the inkjet recording apparatus.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the inkjet recording apparatus of Patent Document 1, when the ink is exposed to air in the ink tank for a long time, the concentration of dissolved gas in the ink increases. In other words, the degree of degassing of the ink decreases. When the degree of degassing of the ink decreases, at the nozzles of the inkjet head, a normal pressure cannot be applied to the ink, and there is a problem that image quality deterioration such as image defects occurs due to the ink not being ejected normally.

[0006] An aspect of the present disclosure aims to provide an image forming apparatus, method, and computer program that can suppress a decrease in the degree of degassing of ink supplied to ejection means and prevent image quality deterioration.

Means for Solving the Problems

[0007] An aspect of the present disclosure is an image forming apparatus that forms an image with a discharged liquid, comprising: a degassing means for degassing the liquid; a supply-side tank for storing the liquid; A first pump for varying the air pressure of the air layer formed above the liquid in the supply-side tank; an ejection means for ejecting the liquid; A recovery-side tank for recovering and storing the remaining liquid discharged by the discharge means; a second pump for varying the air pressure of the air layer formed above the liquid in the recovery-side tank; control means for supplying the liquid degassed by the degassing means to the supply-side tank and controlling the supply of the liquid from the supply-side tank to the ejection means; Make the air layer of the supply-side tank have a positive pressure and the air layer of the recovery-side tank have a negative pressure, and the supply-side tank wherein the control means supplies at least a part of the liquid stored in the supply-side tank during standby for image formation by the ejection means from the supply-side tank to the degassing means in a direction opposite to the supply direction from the degassing means to the supply-side tank, and degasses the liquid by the degassing means. Via the recovery-side tank It is characterized by controlling as follows. , To Here, the control means may control to degas at least a part of the liquid stored in the supply-side tank during standby for image formation by the ejection means by the degassing means before the next image formation. During, the It may be controlled as follows. At the same time, maintain the air layer of the supply-side tank at positive pressure and the air layer of the recovery-side tank at negative pressure, and supply from the supply-side tank to the recovery-side tank through the discharge means It is characterized by controlling as follows.

[0008] Here, the control means supplies at least a part of the liquid stored in the supply-side tank during standby for image formation by the ejection means from the supply-side tank to the degassing means in a direction opposite to the supply direction from the degassing means to the supply-side tank, and degasses the liquid by the degassing means. At the same time, supply from the supply-side tank to the recovery-side tank through the discharge means It may be controlled as follows.

[0009] Here, during the standby for image formation by the ejection means, at least a part of the liquid stored in the supply-side tank is degassed by the degassing means when the next image formation is performed. At the same time, supply from the supply-side tank to the recovery-side tank through the discharge means It may be controlled in this way.

[0010] Here, during the standby for image formation by the ejection means, at least a part of the liquid stored in the supply-side tank is degassed by the degassing means when a predetermined time has elapsed since the last image formation. At the same time, supply from the supply-side tank to the recovery-side tank through the discharge means It may be controlled in this way.

[0011] Here, the control means Of The liquid is supplied to the ejection means Via the recovery-side tank and the liquid supplied While supplying to the recovery-side tank is supplied again to From the recovery-side tank the supply-side tank to perform a circulation operation, and it may be controlled. Do as such.

[0012] Here, during the stop of the circulation operation, at least a part of the liquid stored in the supply-side tank may be controlled to be degassed by the degassing means before the next circulation operation is performed.

[0013] Here, during the stop of the circulation operation, at least a part of the liquid stored in the supply-side tank may be controlled to be degassed by the degassing means when the next circulation operation is performed.

[0014] Here, during the stop of the circulation operation, at least a part of the liquid stored in the supply-side tank may be controlled to be degassed by the degassing means when a predetermined time has elapsed since the last stop of the circulation operation.

[0015] Here, when an error occurs during the image formation process or when a power-off operation is performed, Including the operation of supplying the liquid in the supply-side tank to the recovery-side tank through the discharge means the circulation operation may be stopped.

[0016] Here, further, a moving member including the discharging means and the supply-side tank, a guide member that supports the moving member so as to be reciprocally movable, a movement control means that controls the moving member to reciprocate along the guide member, and a support member that supports the degassing means at a fixed position may be provided.

[0017] Here, further, a main tank that stores liquid in advance is provided, and the control means controls the liquid stored in the main tank to be degassed by the degassing means and supplied to the supply-side tank, and waits for image formation by the discharging means. During, the At least a part of the liquid stored in the supply-side tank may be controlled to be returned to the main tank.

[0018] Here, the control means may control at least a part of the liquid stored in the supply-side tank to be returned to the main tank through a supply path connecting the main tank and the supply-side tank.

[0019] Here, the control means may control at least a part of the liquid stored in the supply-side tank to be returned to the main tank when a predetermined time has elapsed since the last image formation. In combination, the The main tank may be returned.

[0020] Here , The The control means may further control the liquid stored in the recovery-side tank to be returned to the main tank.

[0021] Here, further, a main tank that stores liquid in advance Clutch is provided, and the control means further supplies the liquid to the main tank for performing the next image formation When, the The main tank for the recording Stored in Liquid , Degas by the degassing means and send it to the supply-side tank is supplied, the liquid is supplied to the recovery-side tank through the discharging means, and after the liquid levels of the supply-side tank and the recovery-side tank reach predetermined heights, image formation may be controlled to be performed.

[0022] Also, one aspect of the present disclosure is a method used in an image forming apparatus that forms an image with a discharged liquid, wherein the image forming apparatus includes a degassing means for degassing the liquid, a supply-side tank for storing the liquid, and A first pump for varying the air pressure of the air layer formed above the liquid in the supply-side tank; a discharging means for discharging the liquid And a recovery-side tank for recovering and storing the remaining liquid discharged by the discharge means; a second pump for varying the air pressure of the air layer formed above the liquid in the recovery-side tank; and the method includes a first control step of supplying the liquid degassed by the degassing means to the supply-side tank and controlling to supply the liquid from the supply-side tank Make the air layer of the supply-side tank have a positive pressure and the air layer of the recovery-side tank have a negative pressure, and the supply-side tank to the discharging means Via the recovery-side tank , and a second control step of controlling to supply at least a part of the liquid stored in the supply-side tank during standby for image formation by the discharging means During, the in a direction opposite to the supply direction from the degassing means to the supply-side tank, from the supply-side tank to the degassing means, and degassing the liquid by the degassing means At the same time, maintain the air layer of the supply-side tank at positive pressure and the air layer of the recovery-side tank at negative pressure, and supply from the supply-side tank to the recovery-side tank through the discharge means . It is characterized by including the above.

[0023] Also, one aspect of the present disclosure is a computer program for control used in an image forming apparatus that forms an image with a discharged liquid and is recorded on a computer-readable recording medium. The image forming apparatus includes a degassing means for degassing the liquid, a supply-side tank for storing the liquid, and A first pump for varying the air pressure of the air layer formed above the liquid in the supply-side tank; a discharging means for discharging the liquid And a recovery-side tank for recovering and storing the remaining liquid discharged by the discharge means; a second pump for varying the air pressure of the air layer formed above the liquid in the recovery-side tank; and the computer program causes a computer, which is the image forming apparatus, to execute a first control step of supplying the liquid degassed by the degassing means to the supply-side tank and controlling to supply the liquid from the supply-side tank Make the air layer of the supply-side tank have a positive pressure and the air layer of the recovery-side tank have a negative pressure, and the supply-side tank to the discharging means Via the recovery-side tank , and a second control step of controlling to supply at least a part of the liquid stored in the supply-side tank during standby for image formation by the discharging means During, the in a direction opposite to the supply direction from the degassing means to the supply-side tank, from the supply-side tank to the degassing means, and degassing the liquid by the degassing means At the same time, maintain the air layer of the supply-side tank at positive pressure and the air layer of the recovery-side tank at negative pressure, and supply from the supply-side tank to the recovery-side tank through the discharge means . It is characterized by causing the above to be executed.

Advantages of the Invention

[0024] According to the above aspect, it is possible to suppress a decrease in the degree of degassing of the ink supplied to the ejection means and prevent image quality degradation.

Brief Description of the Drawings

[0025]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

Embodiments for Carrying Out the Invention

[0026] 1 Embodiment An image forming apparatus 1 as one embodiment according to the present disclosure will be described with reference to the drawings.

[0027] 1.1 Image Forming Apparatus 1 As shown in FIG. 1, the image forming apparatus 1 is configured by providing a paper feeding unit 17 at the bottom of the housing for accommodating and feeding sheets. Above the paper feeding unit 17, a printer 16 for forming an image by an inkjet method is provided. Further above the printer 16, an operation panel 15 for displaying an operation screen and receiving operations by a user is provided. The operation panel 15 is provided with a display unit composed of a liquid crystal display panel or the like, and displays the contents set by the user and various messages. The operation panel 15 notifies the control circuit 50 provided inside the housing of instructions and the like received by the operation of the user.

[0028] The image forming apparatus 1 is connected to an information processing apparatus such as a personal computer (not shown) via a network. The image forming apparatus 1 receives a print job including a print instruction, the number of print repetitions, and image data to be printed from the information processing apparatus. The image forming apparatus 1 generates print image data from the image data included in the received print job.

[0029] The paper feeding unit 17 includes a paper cassette 90 for accommodating a plurality of sheets, a pickup roller 91 for feeding out the sheet S from the paper cassette 90, and the like. The sheet S fed out from the paper feeding unit 17 is conveyed toward the printer 16 by a conveyance path 92 provided above the paper feeding unit 17.

[0030] The printer 16 is provided with an endless belt 20 stretched by a driving roller 22 and a driven roller 21. The driving roller 22 is rotated by a motor 51, and the motor 51 is rotationally controlled by a driving circuit 52. According to the rotation of the driving roller 22, the belt 20 travels in a circular motion in the X direction. The sheet S is conveyed by the belt 20 traveling in a circular motion.

[0031] In the space above the belt 20, a carriage 10 provided with a plurality of inkjet heads 241 (FIG. 3(b)) for discharging ink onto the sheet S conveyed on the belt 20 by an inkjet method is provided. Based on the generated print image data, the plurality of inkjet heads 241 discharge ink, and an image is formed on the sheet S.

[0032] The sheet S on which the image is formed is conveyed on the belt 20 and carried out toward the discharge tray 95 through the conveyance path 94.

[0033] 1.2 The carriage 10 and the guide rail 19 As shown in FIGS. 2(a) and 2(b), above the belt 20, a guide rail 19 (guide member) that is long in the width direction of the belt 20 and formed in a frame shape is supported by a support member provided in the housing and is provided. A carriage 10 (moving member) equipped with a plurality of inkjet heads 241 is attached to the guide rail 19 so as to be reciprocally movable. The carriage 10 reciprocally moves in the reciprocating movement direction C along the guide rail 19 by a drive mechanism (not shown).

[0034] When the sheet S is conveyed by the belt 20 to a position directly below the carriage 10, based on the print image data generated from the received print job, the carriage 10 moves along the guide rail 19 from the first end of the guide rail 19 toward the second end of the guide rail 19 while the inkjet head 241 ejects ink to form an image of a predetermined width in the main scanning direction on the sheet S. When the formation of the image of the predetermined width is completed, the belt 20 conveys the sheet S forward by a predetermined width. Next, the carriage 10 that has returned to the first end of the guide rail 19 moves along the guide rail 19 again from the first end of the guide rail 19 toward the second end of the guide rail 19 while the inkjet head 241 ejects ink.

[0035] In this way, by repeating the movement of the carriage 10 along the guide rail 19 and the conveyance of the sheet S by a predetermined width by the belt 20, an image corresponding to the print image data is formed on the sheet S.

[0036] 1.3 Head units 31a, 31b, 31c, and 31d As shown in FIGS. 2(a) and (b), four head units 31a, 31b, 31c, and 31d are provided on the carriage 10 so as to be arranged in a straight line along the reciprocating movement direction C of the carriage 10.

[0037] The head units 31a, 31b, 31c, and 31d respectively eject four colors of ink, namely black (K), yellow (Y), magenta (M), and cyan (C), individually. One color ink is filled in one head unit.

[0038] Note that the color inks used in the image forming apparatus 1 are not limited to this, and for example, other colors such as light yellow (LY), light magenta (LM), and light cyan (LC) can also be used. In this case, head units corresponding to each color are mounted on the carriage 10.

[0039] 1.4 Main tank 11 In the image forming apparatus 1, for each color, a main tank 11 (Fig. 1) for storing color ink is provided and supported by a support member provided in the housing. The main tank for each color is connected to a head unit corresponding to each color via an ink supply tube. The ink in the main tank 11 for each color is supplied to the head unit via the ink supply tube.

[0040] For the sake of simplicity of description, only one main tank 11 is shown in Fig. 1. Also, hereinafter, for the sake of simplicity of description, the main tank 11 storing the color ink of one color will be referred to, and the reference to the main tank 11 storing the color ink of other colors will be omitted.

[0041] As shown in Fig. 4, the main tank 11 is connected to the pump 71 by an ink supply tube 151, and the pump 71 is connected to the deaeration module 14 by an ink supply tube 152. Also, the main tank 11 is connected to the pump 72 by an ink supply tube 158, and the pump 72 is connected to a recovery side sub-tank 13 described later by an ink supply tube 157.

[0042] Under the control of a printer control circuit 109 described later, the drive circuit 61 operates the pump 71 to supply the ink stored in the main tank 11 to the deaeration module 14 (in the E direction).

[0043] Also, under the control of the printer control circuit 109, the drive circuit 62 operates the pump 72 to supply the ink stored in the recovery side sub-tank 13 to the main tank 11 (in the E direction).

[0044] Note that Fig. 4 schematically shows the connection relationship among the main tank 11, the deaeration module 14, the supply side sub-tank 12, the recovery side sub-tank 13, etc., and does not show the vertical arrangement relationship among the main tank 11, the deaeration module 14, the supply side sub-tank 12, the recovery side sub-tank 13, etc. Attention is required. The same applies to Figs. 7, 12 to 15 described later.

[0045] 1.5 Details of the head units 31a, 31b, 31c, and 31d Here, taking the head units 31a, 31b, 31c, and 31d as representatives, the details of the head unit 31a will be described. Note that since the head units 31b, 31c, and 31d have the same configuration as the head unit 31a, the description thereof will be omitted.

[0046] FIG. 3(a) is a schematic diagram of the internal configuration of the head unit 31a when viewed from the side. FIG. 3(b) is a schematic diagram of the head unit 31a when viewed from the side of the sheet S conveyed on the belt 20.

[0047] The head unit 31a is formed in a long shape in the conveyance direction (arrow Y direction) of the sheet S.

[0048] The head unit 31a includes a plurality of inkjet heads 241 (discharging means). In the example shown in FIG. 3(b), 16 inkjet heads 241 are provided in one head unit 31a, and the 16 inkjet heads 241 are grouped into 8 ink head modules 242 with 2 inkjet heads 241 in each group. Among the 8 ink head modules 242, 4 ink head modules 242 are arranged in a row in the arrow Y direction, and the remaining 4 ink head modules 242 are also arranged in a row in the arrow Y direction.

[0049] The inkjet head 241 is provided such that a plurality of nozzles 2411 arranged in the arrow Y direction face the sheet S conveyed on the belt 20 and are exposed on the lower surface side of the head unit 31a. Each nozzle 2411 is provided with an actuator composed of a piezoelectric element and a diaphragm (not shown). When a voltage is applied to the electrode provided in the piezoelectric element, the actuator deforms and ink is discharged from each nozzle 2411.

[0050] In this way, the inkjet head 241 discharges ink from a plurality of nozzles 2411 to form an image on the sheet S.

[0051] 1.6 Supply-side sub-tank 12 and recovery-side sub-tank 13 As shown in Fig. 3(a), the head unit 31a includes a supply-side sub-tank 12 (supply-side tank) for storing the ink supplied to the inkjet head 241 and a recovery-side sub-tank 13 (recovery-side tank) for storing the ink recovered from the inkjet head 241.

[0052] As shown in Fig. 4, the supply-side sub-tank 12 is connected to the degassing module 14 by an ink supply pipe 153. Also, the supply-side sub-tank 12 is connected to the recovery-side sub-tank 13 via the inkjet head 241 by an ink supply pipe 155. Further, the supply-side sub-tank 12 is connected to the pump 73 by an ink supply pipe 154.

[0053] When ink is supplied to the supply-side sub-tank 12, an ink layer composed of ink and an air layer composed of air are formed inside the supply-side sub-tank 12, with the air layer above the ink layer.

[0054] The supply-side sub-tank 12 is provided with a sensor 41 for detecting the height of the liquid level of the ink stored inside (Fig. 3(a)). The sensor 41 is, for example, a float sensor. The float sensor is provided inside the supply-side sub-tank 12 to detect the height of the liquid level of the ink.

[0055] When heating the ink stored in the supply-side sub-tank 12 so that the temperature of the ink falls within a predetermined temperature range, the sensor 41 may be an infrared sensor. The infrared sensor is provided in the space outside the supply-side sub-tank 12 so that it can measure the temperature of the outer wall surface of the supply-side sub-tank 12. The infrared sensor detects the height of the ink liquid level by measuring the temperature of the wall surface of the supply-side sub-tank 12. Since the ink stored in the supply-side sub-tank 12 is heated, the temperature of the ink layer and the temperature of the air layer above it are different inside the supply-side sub-tank 12. By knowing the position where the temperature difference occurs based on the measurement result of the infrared sensor, the height of the ink liquid level can be detected.

[0056] The sensor 41 outputs the detected liquid level height H0 (Fig. 6) to the printer control circuit 109.

[0057] Also, as shown in Fig. 4, the recovery-side sub-tank 13 is connected to the supply-side sub-tank 12 via the ink supply pipe 155 and the ink jet head 241. The recovery-side sub-tank 13 is connected to the pump 72 via the ink supply pipe 157, and the pump 72 is connected to the main tank 11 via the ink supply pipe 158. The recovery-side sub-tank 13 is also connected to the pump 74 via the ink supply pipe 156.

[0058] The recovery-side sub-tank 13 recovers and stores the remaining ink ejected by the ink jet head 241.

[0059] When ink is supplied to the recovery-side sub-tank 13, an ink layer composed of ink and an air layer composed of air are formed inside the recovery-side sub-tank 13, with the air layer above the ink layer.

[0060] In FIG. 4, for the sake of simplicity of explanation, only one inkjet head 241 is described, and the description of the other plurality of inkjet heads 241 is omitted. Actually, similar to the inkjet head 241 shown in FIG. 4, the other plurality of inkjet heads 241 are connected to the ink supply pipe 155.

[0061] 1.7 Degassing Module 14 In the image forming apparatus 1, a degassing module 14 (degassing means in FIG. 1) for each color is supported at a fixed position by a support member provided in the housing. Further, as shown in FIG. 4, the degassing module 14 for each color is connected to the pump 71 by an ink supply pipe 152. Also, the degassing module 14 for each color is connected to the supply-side sub-tank 12 for each color by an ink supply pipe 153.

[0062] For the sake of simplicity of description, FIGS. 1 and 4 show only one degassing module 14 for the color ink of one color. Since the degassing modules 14 for the color inks of other colors have the same configuration, the mention here is omitted.

[0063] Gas is dissolved in the ink or bubbles are present. The degassing module 14 has a function of removing (degassing) those dissolved gases and bubbles. The degassing module 14 has a hollow fiber filter composed of a gas permeable membrane that allows only gas to pass through among liquid and gas, and removes dissolved gas and bubbles from the ink by the gas permeable membrane.

[0064] The degassing module 14 removes dissolved gas and the like from the ink supplied from the main tank 11. The ink from which the dissolved gas and the like have been removed is supplied to the supply-side sub-tank 12 by the pump 71.

[0065] Also, the degassing module 14 removes dissolved gas and the like from at least a part of the ink supplied from the supply-side sub-tank 12. The ink from which the dissolved gas and the like have been removed is supplied to the main tank 11 by the pump 71.

[0066] 1.8 Ink Circulation The ink circulation from the main tank 11, through the degassing module 14, the supply-side sub-tank 12, the inkjet head 241, and the recovery-side sub-tank 13, and back to the main tank 11 will be described with reference to FIG. 4.

[0067] Under the control of the printer control circuit 109, the drive circuit 61 operates the pump 71 to supply the ink stored in the main tank 11 to the degassing module 14 (in the E direction).

[0068] The degassing module 14 removes the dissolved gas and the like in the ink.

[0069] The ink from which the dissolved gas and the like have been removed by the degassing module 14 is supplied to the supply-side sub-tank 12 (in the E direction).

[0070] Under the control of the printer control circuit 109, the drive circuit 63 operates the pump 73 to make the air pressure in the air layer in the supply-side sub-tank 12 a positive pressure, and under the control of the printer control circuit 109, the drive circuit 64 operates the pump 74 to make the air pressure in the air layer in the recovery-side sub-tank 13 a negative pressure.

[0071] As a result of making the air pressure in the air layer in the supply-side sub-tank 12 a positive pressure and the air pressure in the air layer in the recovery-side sub-tank 13 a negative pressure, the ink stored in the supply-side sub-tank 12 is supplied to each nozzle in the inkjet head 241 through the ink supply pipe 155 (in the E direction).

[0072] A part of the ink supplied to each nozzle in the inkjet head 241 is ejected from each nozzle using a piezoelectric element that converts voltage into force.

[0073] The remaining ink that has not been ejected by the inkjet head 241 is supplied to the recovery-side sub-tank 13 through the ink supply pipe 155 (in the E direction).

[0074] Under the control of the printer control circuit 109, the drive circuit 62 operates the pump 72 to supply the ink stored in the recovery-side sub-tank 13 to the main tank 11 (in the E direction).

[0075] In this way, the ink is supplied from the supply-side sub-tank 12, through the inkjet head 241, to the recovery-side sub-tank 13, and then returned to the supply-side sub-tank 12 again. Such a supply of circulating ink is called circulating liquid feeding (or circulating operation).

[0076] The circulating liquid feeding is performed from when the power of the image forming apparatus 1 is turned on until it is turned off, except when an error occurs in the image forming apparatus 1.

[0077] The circulating liquid feeding has the effect of preventing the nozzles from drying, and when the ink is a pigment with a high density, it has the effect of preventing its sedimentation.

[0078] Here, when an error occurs during the image formation process, or when the power off operation of the image forming apparatus 1 is performed, etc., the circulating liquid feeding is stopped.

[0079] 1.9 Control Circuit 50 As shown in FIG. 5, the control circuit 50 is composed of a CPU 101, a ROM 102, a RAM 103, an image memory 104, an image processing circuit 105, a network communication circuit 106, an input / output circuit 108, a printer control circuit 109 (control means), a storage circuit 110, etc.

[0080] The CPU 101, ROM 102, and RAM 103 constitute the main control unit 101a.

[0081] The RAM 103 temporarily stores various control variables and image formation conditions set by the operation panel 15, and provides a work area for program execution by the CPU 101.

[0082] The ROM 102 stores control programs and the like for executing various jobs such as image formation operations.

[0083] The CPU 101 operates according to a control program stored in the ROM 102.

[0084] By operating according to the control program, the main control unit 101a uniformly controls the image memory 104, the image processing circuit 105, the network communication circuit 106, the input / output circuit 108, the printer control circuit 109, the storage circuit 110, and the like.

[0085] As described above, the control circuit 50 is a computer system including a microprocessor and a memory. The memory stores a computer program (control program), and the microprocessor operates according to the computer program. Here, the computer program is configured by combining a plurality of instruction codes indicating instructions to the computer in order to achieve a predetermined function.

[0086] The network communication circuit 106 receives a print job from an information processing device such as a personal computer via a network such as a LAN.

[0087] When the network communication circuit 106 receives a print job, the main control unit 101a causes the printer control circuit 109 to execute image formation processing based on the received print job.

[0088] The image memory 104 temporarily stores image data such as a print job.

[0089] The image processing circuit 105 performs various data processes on the image data of each color component included in the print job, for example, and converts it into print image data of each reproduced color of Y, M, C, and K.

[0090] The input / output circuit 108 relays the transmission and reception of information between the operation panel 15 and the main control unit 101a.

[0091] The memory circuit 110 has an area for storing data.

[0092] The printer control circuit 109 will be described next.

[0093] 1.10 Printer Control Circuit 109 Similar to the control circuit 50, the printer control circuit 109 is also composed of a CPU, ROM, RAM, etc. not shown in the figure.

[0094] The RAM temporarily stores various control variables and provides a work area during program execution by the CPU. The ROM and RAM store control programs for executing various jobs such as printing operations. The CPU operates according to the control program stored in the ROM or RAM.

[0095] When the CPU operates according to the control program stored in the ROM or RAM, the printer control circuit 109 performs its functions.

[0096] The printer control circuit 109 controls the drive circuit 52 to make the belt 20 run in a circular motion.

[0097] Also, the printer control circuit 109 (movement control means) controls the drive mechanism to reciprocate the carriage 10 along the guide rail 19 in the reciprocating movement direction C.

[0098] Also, the printer control circuit 109 controls the drive circuits 61, 62, 63, 64 to operate the pumps 71, 72, 73, 74 respectively, and controls the ink to return from the main tank 11 to the main tank 11 again (in the E direction in FIG. 4) via the degassing module 14, supply-side sub-tank 12, inkjet head 241, and recovery-side sub-tank 13.

[0099] Also, during standby for image formation (i.e., waiting for reception of a print job or waiting for printing), or during stoppage of liquid supply from the supply-side sub-tank 12 to the inkjet head 241, the printer control circuit 109 controls the drive circuit 61 to operate the pump 71 to return the ink stored in the supply-side sub-tank 12 back to the main tank 11 (in the F direction in FIG. 7) via the deaeration module 14 from the supply-side sub-tank 12.

[0100] In this way, the pump 71 operates so that ink flows in both the E direction (FIG. 4) and the reverse F direction (FIG. 7).

[0101] Further, the printer control circuit 109 receives the height H0 (FIG. 6) of the ink liquid level in the supply-side sub-tank 12 from the sensor 41 provided in the supply-side sub-tank 12. The printer control circuit 109 compares the received height H0 with a predetermined height H1 (FIG. 6), and when the height H0 is lower than the predetermined height H1, it controls the drive circuit 61 to operate the pump 71 to supply ink from the main tank 11 to the supply-side sub-tank 12.

[0102] After the received height H0 reaches the predetermined height H1, the printer control circuit 109 controls to perform image formation.

[0103] Also, when an error occurs during the image formation process, when the power-off operation of the image forming apparatus 1 is performed, etc., the printer control circuit 109 controls to stop the circulating liquid supply.

[0104] 1.11 Ink flow for preventing image quality deterioration The ink flow for suppressing a decrease in the degree of deaeration of the ink and preventing image quality deterioration will be described with reference to FIG. 7.

[0105] For example, when a predetermined time T1 has elapsed since the previous printing stopped, before the next printing is executed, under the control of the printer control circuit 109, the drive circuit 61 operates the pump 71 to supply at least a part of the ink stored in the supply-side sub-tank 12 from the deaeration module 14 to the supply-side sub-tank 12 in a direction opposite to the supply direction (direction E in FIG. 4), that is, from the supply-side sub-tank 12 to the deaeration module 14 (direction F in FIG. 7).

[0106] Here, the predetermined time T1 is, for example, one day. When one day has elapsed since the previous printing stopped, the ink stored in the supply-side sub-tank 12 has been in contact with the air in the supply-side sub-tank 12 for a long time, so it is considered that the degree of deaeration of the ink decreases.

[0107] Also, the predetermined time T1 varies depending on the operating environment of the image forming apparatus 1.

[0108] The deaeration module 14 removes dissolved gases and the like in the ink supplied from the supply-side sub-tank 12.

[0109] The ink from which the dissolved gases and the like have been removed is supplied from the deaeration module 14 to the main tank 11 (in the F direction) and stored in the main tank 11.

[0110] Next, when printing is executed, as described with reference to FIG. 4, the ink from which the dissolved gases and the like have been removed and stored in the main tank 11 is supplied to the inkjet head 241 via the supply-side sub-tank 12 (in the E direction).

[0111] In this way, when a predetermined time T1 has elapsed since the previous printing stopped, the ink is supplied from the supply-side sub-tank 12 to the deaeration module 14. The deaeration module 14 removes the dissolved gases and the like in the ink, and the ink from which the dissolved gases and the like have been removed is supplied to and stored in the main tank 11. Next, when using the ink for printing, since the dissolved gases and the like in the ink have been removed, it is possible to suppress a decrease in the degree of deaeration of the ink and prevent image quality deterioration.

[0112] 1.12 Operations in the Image Forming Apparatus 1 The operations in the image forming apparatus 1 will be described.

[0113] (1) Overall Operations of the Image Forming Apparatus 1 The overall operations of the image forming apparatus 1 will be described using the flowcharts shown in FIGS. 8 to 9.

[0114] When the power of the image forming apparatus 1 is turned on (step S101), the printer control circuit 109 receives the height H0 of the ink liquid level in the supply-side sub-tank 12 from the sensor 41, compares the received height H0 with a predetermined height H1, and determines whether the height H0 has reached the predetermined height H1 (step S102).

[0115] If it is determined that the height H0 has not reached the predetermined height H1 (''NO'' in step S102), the printer control circuit 109 controls the drive circuit 61 to supply ink from the main tank 11 to the supply-side sub-tank 12 (step S103). Next, the printer control circuit 109 returns the control to step S102 and repeats the process.

[0116] If it is determined that the height H0 has reached the predetermined height H1 (''YES'' in step S102), the printer control circuit 109 instructs to perform circulation liquid feeding, and the circulation liquid feeding is repeatedly performed (step S120).

[0117] Next, the printer control circuit 109 determines whether or not a predetermined time T1 has elapsed since the last time printing was stopped (step S105). Note that the printer control circuit 109 may determine whether or not the predetermined time T1 has elapsed since the last time the circulation liquid supply was stopped. When it is determined that the predetermined time T1 has elapsed ( "YES" in step S105), the printer control circuit 109 supplies ink from the supply-side sub-tank 12 to the main tank 11 via the deaeration module 14 (in the direction F in FIG. 7), and supplies ink from the recovery-side sub-tank 13 to the main tank 11 (in the direction E in FIG. 7), and controls the pumps 71, 72, 73, 74 (step S106).

[0118] When it is determined that the predetermined time T1 has not elapsed ( "NO" in step S105), there is no processing by the printer control circuit 109.

[0119] The network communication circuit 106 receives a print job, or the operation panel 15 receives an input operation by the user (step S107).

[0120] When a print job is received ( "YES" in step S108), the printer control circuit 109 receives the height H0 of the ink liquid level in the supply-side sub-tank 12 from the sensor 41, compares the received height H0 with a predetermined height H1, and determines whether or not the height H0 has reached the predetermined height H1 (step S109).

[0121] When it is determined that the height H0 has not reached the predetermined height H1 ( "NO" in step S109), the printer control circuit 109 controls the drive circuit 61 to supply ink from the main tank 11 to the supply-side sub-tank 12 (step S114). Next, the printer control circuit 109 returns the control to step S109 and repeats the process.

[0122] When it is determined that the height H0 has reached a predetermined height H1 ( "YES" in step S109), the printer control circuit 109 executes printing according to the print job (step S111). Next, the printer control circuit 109 determines the printing state (step S112). When it is determined that the execution of printing has ended normally ( "normal end" in step S112), the printer control circuit 109 returns control to step S105 and repeats the process.

[0123] When it is determined that an error has occurred during the execution of printing ( "error occurred" in step S112), the printer control circuit 109 stops the circulating liquid supply (step S113) and waits until the occurred error is resolved.

[0124] If it is not the reception of a print job ( "NO" in step S108) and an operation to turn off the power is received ( "YES" in step S115), the image forming apparatus 1 enters the power-off state (step S118). When it enters the power-off state, of course, the circulating liquid supply stops.

[0125] If it is not the reception of a print job ( "NO" in step S108) and it is not an operation to turn off the power ( "NO" in step S115), the image forming apparatus 1 executes other processing corresponding to the input operation (step S117), and the printer control circuit 109 returns control to step S105 and repeats the process.

[0126] Thus, a series of processes ends.

[0127] (2) Operation of Circulating Liquid Supply The operation of the circulating liquid supply will be described using the flowchart shown in FIG. 10.

[0128] Note that the operation described here is the detail of step S120 in FIG. 8.

[0129] The printer control circuit 109 controls the pump 73 to be operated by the drive circuit 63 so that the air pressure in the air layer in the supply-side sub-tank 12 becomes a positive pressure (step S131).

[0130] Next, the printer control circuit 109 controls the pump 74 to be operated by the drive circuit 64 so that the air pressure in the air layer in the recovery-side sub-tank 13 becomes a negative pressure (step S132).

[0131] Note that steps S131 and S132 may be performed simultaneously.

[0132] Next, the printer control circuit 109 controls the pump 72 to be operated by the drive circuit 62 so as to supply the ink in the recovery-side sub-tank 13 to the main tank 11 (step S133).

[0133] By the operations of steps S131 and S132, the ink stored in the supply-side sub-tank 12 is supplied to the recovery-side sub-tank 13 via the inkjet head 241. Also, by the operation of step S133, the ink stored in the recovery-side sub-tank 13 is recovered to the main tank 11.

[0134] The printer control circuit 109 controls to repeatedly execute steps S131 to S133.

[0135] In this way, the circulation of the liquid is realized.

[0136] (3) Stopping the Circulation of the Liquid The operation of stopping the circulation of the liquid will be described using the flowchart shown in FIG. 11.

[0137] Note that the operation described here is the detail of step S113 in FIG. 9.

[0138] The printer control circuit 109 controls to operate the pump 73 by the drive circuit 63 and operate the pump 74 by the drive circuit 64 so that the air pressure in the air layer in the supply-side sub-tank 12 and the air pressure in the air layer in the recovery-side sub-tank 13 become the same (step S141).

[0139] When the air pressure in the air layer in the supply-side sub-tank 12 and the air pressure in the air layer in the recovery-side sub-tank 13 become the same, the supply of the ink stored in the supply-side sub-tank 12 to the recovery-side sub-tank 13 through the inkjet head 241 is stopped.

[0140] 1.13 Summary As described above, according to the above aspect, during standby for image formation or during the stop of the supply of liquid from the supply-side sub-tank 12 to the inkjet head 241, at least a part of the ink stored in the supply-side sub-tank 12 is supplied to the deaeration module 14 to remove the dissolved gas and the like of the ink. Further, the ink from which the dissolved gas and the like have been removed is supplied to the main tank 11 and stored. Next, when using the ink for printing, since the dissolved gas and the like of the ink have been removed, it is possible to suppress a decrease in the degree of deaeration of the ink supplied to the inkjet head 241 and prevent image quality deterioration.

[0141] (a) The above-described error may occur when detecting a sheet jam, a paper feed failure, a defective image formation, etc. Also, the stop of the circulating liquid supply of the ink may be performed when detecting a sheet jam, a paper feed failure, a defective image formation, etc.

[0142] Here, the detection of a defective image formation may be performed as follows. A sensor for photographing an image formed on the sheet S conveyed on the belt 20 is provided, an image of a predetermined pattern is formed on the sheet S, and a defective image formation can be detected by comparing the image of the predetermined pattern with the image obtained by the sensor.

[0143] (b) As described above, it is assumed that the supply-side sub-tank 12 is provided with a sensor 41 for detecting the height of the ink level stored inside. However, the recovery-side sub-tank 13 may also be provided with a sensor for detecting the height of the ink level stored inside, similar to the supply-side sub-tank 12.

[0144] Also, in steps S102 and S109 shown in FIG. 8, the printer control circuit 109 receives the height H0 of the ink level in the supply-side sub-tank 12 from the sensor 41, compares the received height H0 with a predetermined height H1, and determines whether the height H0 has reached the predetermined height H1. However, for the recovery-side sub-tank 13, it may also be determined whether the height of the ink level in the recovery-side sub-tank 13 detected by the sensor provided in the recovery-side sub-tank 13 has reached a predetermined height.

[0145] Further, the printer control circuit 109 may determine whether the ink level has reached a predetermined height for both the supply-side sub-tank 12 and the recovery-side sub-tank 13. The printer control circuit 109 may control to supply ink from the main tank 11 to the supply-side sub-tank 12 until the ink levels of both the supply-side sub-tank 12 and the recovery-side sub-tank 13 reach a predetermined height.

[0146] Furthermore, in step S109 of FIG. 8, the printer control circuit 109 may control to start printing execution when the ink levels of both the supply-side sub-tank 12 and the recovery-side sub-tank 13 reach a predetermined height.

[0147] (c) It can be said that step S117 in FIG. 8 is in a state of waiting for the reception of a print job. Also, in step S113 of FIG. 9, the circulating liquid supply (circulating operation) stops.

[0148] In this way, when in the printing standby state or when the circulating liquid supply is stopped, the printer control circuit 109 may control to supply ink from the supply-side sub-tank 12 to the main tank 11 via the deaeration module 14 and to supply ink from the recovery-side sub-tank 13 to the main tank 11.

[0149] Also, after a predetermined time has elapsed during the printing standby, the printer control circuit 109 may control to supply ink from the supply-side sub-tank 12 to the main tank 11 via the deaeration module 14 and to supply ink from the recovery-side sub-tank 13 to the main tank 11.

[0150] Here, the predetermined time is determined depending on the temperature of the ink.

[0151] Also, after a predetermined time has elapsed during the stop of the circulating liquid supply, the printer control circuit 109 may control to supply ink from the supply-side sub-tank 12 to the main tank 11 via the deaeration module 14 and to supply ink from the recovery-side sub-tank 13 to the main tank 11.

[0152] In this case, the printer control circuit 109 may control to empty the ink in the supply-side sub-tank 12 and to empty the ink in the recovery-side sub-tank 13.

[0153] (d) The printer control circuit 109 may control to deaerate at least a part of the liquid stored in the supply-side sub-tank 12 by the deaeration module 14 before the next image formation during the standby for image formation.

[0154] Also, the printer control circuit 109 may control to deaerate at least a part of the liquid stored in the supply-side sub-tank 12 by the deaeration module 14 when the next image formation is performed during the standby for image formation.

[0155] Further, when at least a part of the liquid stored in the supply-side sub-tank 12 has elapsed a predetermined time since the last image formation during the standby for image formation, the printer control circuit 109 may control to degas the liquid by the degassing module 14.

[0156] Further, when at least a part of the liquid stored in the supply-side sub-tank 12 during the stop of the circulation operation, the printer control circuit 109 may control to degas the liquid by the degassing module 14 before the next circulation operation.

[0157] Further, when at least a part of the liquid stored in the supply-side sub-tank 12 during the stop of the circulation operation, the printer control circuit 109 may control to degas the liquid by the degassing module 14 when the next circulation operation is performed.

[0158] Further, when at least a part of the liquid stored in the supply-side sub-tank 12 during the stop of the circulation operation has elapsed a predetermined time since the last stop of the circulation operation, the printer control circuit 109 may control to degas the liquid by the degassing module 14.

[0159] 2 Other Modification Examples The aspects of the present disclosure have been described based on the above embodiments, but are not limited to the above embodiments. The following may be adopted.

[0160] (1) Modification Example (1) In Modification Example (1) of the embodiment, instead of the head unit 31a of the embodiment, the head unit 31x shown in FIG. 12 may be provided. Also, for the head units 31b, 31c, and 31d, instead of these, the head unit 31x may be provided.

[0161] In addition to the configuration of the head unit 31a, the head unit 31x includes a pump 75 and a drive circuit 65, connects the recovery-side sub-tank 13 and the pump 75 by an ink supply pipe 161, and connects the supply-side sub-tank 12 and the pump 75 by an ink supply pipe 162.

[0162] Under the control of the printer control circuit 109, the drive circuit 65 operates the pump 75 to supply the ink stored in the recovery-side sub-tank 13 to the supply-side sub-tank 12 (in the G direction).

[0163] This realizes part of the circulating liquid supply. Similar to the embodiment, the circulating liquid supply has the effects of preventing the nozzles from drying and, when the ink is a pigment with a high density, preventing its sedimentation.

[0164] Also, similar to the head unit 31a of the embodiment, in the head unit 31x, as shown in FIG. 13, during the standby of image formation or during the stop of the liquid supply from the supply-side sub-tank 12 to the inkjet head 241, the ink stored in the supply-side sub-tank 12 is supplied to the deaeration module 14. The deaeration module 14 removes the dissolved gas and the like in the ink, and the ink from which the dissolved gas and the like have been removed is supplied to and stored in the main tank 11. Next, when using the ink for printing, since the dissolved gas and the like in the ink have been removed, it is possible to suppress a decrease in the degree of deaeration of the ink and prevent image quality degradation.

[0165] (2) Modification Example (2) In the modification example (2) of the embodiment, instead of the head unit 31a of the embodiment, it may be provided with the head unit 31y shown in FIG. 14. The head units 31b, 31c, and 31d may also be provided with the head unit 31y instead of these.

[0166] The head unit 31y may be such that, in addition to the configuration of the head unit 31a, an ink supply pipe 171 is connected to the supply-side sub-tank 12.

[0167] Also, in the image forming apparatus 1, a pump 76 and a drive circuit 66 are supported by a support member provided in the housing and provided. The supply-side sub-tank 12 and the pump 76 are connected by an ink supply pipe 171, and the main tank 11 and the pump 76 are connected by an ink supply pipe 172.

[0168] The printer control circuit 109 controls the drive circuit 66 to operate the pump 76 so as to supply the ink stored in the supply-side sub-tank 12 to the main tank 11 (in the H direction) via the ink supply pipes 171 and 172 (supply paths).

[0169] Thereby, a part of the circulating liquid supply is realized. Similar to the embodiment, the circulating liquid supply has the effects of preventing the nozzles from drying and, when the ink is a pigment with a high density, preventing its sedimentation.

[0170] Also, in the head unit 31y, during the standby of image formation or during the stop of the liquid supply from the supply-side sub-tank 12 to the inkjet head 241, the ink stored in the supply-side sub-tank 12 is supplied to the deaeration module 14. The deaeration module 14 removes the dissolved gas and the like in the ink, and the ink from which the dissolved gas and the like have been removed is supplied to and stored in the main tank 11. Next, when using the ink for printing, since the dissolved gas and the like in the ink have been removed, a decrease in the degree of deaeration of the ink can be suppressed, and image quality deterioration can be prevented.

[0171] (3) Modification Example (3) In the modification example (3) of the embodiment, instead of the head unit 31a of the embodiment, the head unit 31z shown in FIG. 15 may be provided. For the head units 31b, 31c, and 31d, instead of these, the head unit 31z may be provided.

[0172] Also, in addition to the configuration of the head unit 31a, the head unit 31z includes a pump 75 and a drive circuit 65. The recovery-side sub-tank 13 and the pump 75 are connected by an ink supply pipe 161, and the supply-side sub-tank 12 and the pump 75 are connected by an ink supply pipe 162.

[0173] Under the control of the printer control circuit 109, the drive circuit 65 operates the pump 75 to supply the ink stored in the recovery-side sub-tank 13 to the supply-side sub-tank 12 (in the G direction).

[0174] This realizes a part of the circulating liquid supply.

[0175] Also, the head unit 31z may be configured such that, in addition to the configuration of the head unit 31a, an ink supply pipe 171 is connected to the supply-side sub-tank 12.

[0176] In the image forming apparatus 1, a pump 76 and a drive circuit 66 are provided, supported by a support member provided in the housing, the supply-side sub-tank 12 and the pump 76 are connected by an ink supply pipe 171, and the main tank 11 and the pump 76 are connected by an ink supply pipe 172.

[0177] Under the control of the printer control circuit 109, the drive circuit 66 operates the pump 76 to supply the ink stored in the supply-side sub-tank 12 to the main tank 11 (in the H direction).

[0178] This realizes a part of the circulating liquid supply.

[0179] Similar to the embodiment, the circulating liquid supply has the effect of preventing nozzle drying and, when the ink is a pigment with a high density, the effect of preventing its sedimentation.

[0180] Also, in the head unit 31z, during standby for image formation or during stoppage of liquid supply from the supply-side sub-tank 12 to the inkjet head 241, the ink stored in the supply-side sub-tank 12 is supplied to the deaeration module 14. The deaeration module 14 removes dissolved gas and the like in the ink, and the ink from which the dissolved gas and the like have been removed is supplied to and stored in the main tank 11. Next, when using the ink for printing, since the dissolved gas and the like in the ink have been removed, a decrease in the degree of deaeration of the ink can be suppressed and image quality degradation can be prevented.

[0181] (4) The image forming apparatus 1 may further include an image reader that reads a document and generates image data.

[0182] (5) It is also possible to combine the above embodiments and the above modification examples respectively.

Industrial Applicability

[0183] The image forming apparatus according to the aspect of the present disclosure has an effect of suppressing a decrease in the degree of degassing of the ink supplied to the ejection means and preventing image quality deterioration, and is useful as a technique for forming an image by ejecting liquid ink.

Explanation of Signs

[0184] 1 Image forming apparatus 10 Carriage 11 Main tank 12 Supply side sub-tank 13 Recovery side sub-tank 14 Degassing module 15 Operation panel 16 Printer 17 Paper feeding unit 19 Guide rail 31a Head unit 31b Head unit 31x Head unit 31y Head unit 31z Head unit 41 Sensor 50 Control circuit 51 Motor 52 Drive circuit 61~66 Drive circuit 71~76 Pump 101 CPU 101a Main control unit 102 ROM 103 RAM 104 Image memory 105 Image processing circuit 106 Network communication circuit 108 Input / Output Circuit 109 Printer Control Circuit 110 Memory Circuit 241 Inkjet Head 242 Ink Head Module 2411 Nozzle

Claims

1. An image forming apparatus that forms an image by ejecting liquid, A degassing means for degassing the liquid; a supply tank for storing liquid; a first pump for varying an air pressure of an air layer formed above the liquid in the supply tank; A discharge means for discharging a liquid; a recovery tank for recovering and storing the remaining liquid of the liquid discharged by the discharge means; a second pump for varying the air pressure of an air layer formed above the liquid in the recovery tank; a control means for controlling the liquid degassed by the degassing means to be supplied to the supply-side tank, and for controlling the air space in the supply-side tank to be under positive pressure and the air space in the recovery-side tank to be under negative pressure, so that the liquid is supplied from the supply-side tank to the recovery-side tank via the discharge means; Equipped with The control means controls, during standby for image formation by the ejection means, to supply at least a portion of the liquid stored in the supply side tank from the supply side tank to the degassing means in a direction opposite to a supply direction from the degassing means to the supply side tank, to degas the liquid by the degassing means, and to supply the liquid from the supply side tank to the recovery side tank via the ejection means while maintaining the air layer in the supply side tank at a positive pressure and the air layer in the recovery side tank at a negative pressure.

1. An image forming apparatus comprising:

2. The control means controls so that, during standby for image formation by the ejection means, at least a part of the liquid stored in the supply-side tank is degassed by the degassing means and is supplied from the supply-side tank to the recovery-side tank via the ejection means before a next image is formed.

2. The image forming apparatus according to claim 1,

3. The control means controls so that at least a part of the liquid stored in the supply side tank during standby for image formation by the discharge means is degassed by the degassing means when a next image is to be formed, and is supplied from the supply side tank to the recovery side tank via the discharge means.

2. The image forming apparatus according to claim 1,

4. The control means controls so that, during standby for image formation by the discharge means, when a predetermined time has elapsed since the last image formation, at least a part of the liquid stored in the supply side tank is degassed by the degassing means and is supplied from the supply side tank to the recovery side tank via the discharge means.

2. The image forming apparatus according to claim 1,

5. The control means controls the liquid in the supply side tank to be supplied to the recovery side tank via the discharge means, while performing a circulation operation in which the liquid supplied to the recovery side tank is again supplied from the recovery side tank to the supply side tank.

2. The image forming apparatus according to claim 1,

6. The control means stops the circulation operation, which includes the operation of supplying the liquid in the supply tank to the recovery tank via the discharge means, when an error occurs during the image formation process or when a power-off operation is performed.

6. The image forming apparatus according to claim 5,

7. The control means controls the degassing means to degas at least a part of the liquid stored in the supply tank while the circulation operation is stopped, before the next circulation operation is performed.

7. The image forming apparatus according to claim 6,

8. The control means controls the degassing means to degas at least a part of the liquid stored in the supply tank while the circulation operation is stopped, when the next circulation operation is performed.

7. The image forming apparatus according to claim 6,

9. The control means controls the degassing means to degas at least a part of the liquid stored in the supply tank while the circulation operation is stopped, when a predetermined time has elapsed since the circulation operation was last stopped.

7. The image forming apparatus according to claim 6,

10. moreover, a moving member including the discharge means and the supply side tank; A guide member that supports the moving member so that the moving member can reciprocate; A movement control means for controlling the moving member to move back and forth along the guide member; a support member for supporting the degassing means at a fixed position; The image forming apparatus according to claim 1 , further comprising:

11. In addition, it is equipped with a main tank that stores liquid in advance, The control means controlling the liquid stored in the main tank to be degassed by the degassing means and to be supplied to the supply side tank; During standby for image formation by the ejection means, at least a part of the liquid stored in the supply tank is controlled to return to the main tank.

2. The image forming apparatus according to claim 1,

12. The control means controls the liquid stored in the supply tank to be returned to the main tank via a supply path connecting the main tank and the supply tank.

12. The image forming apparatus according to claim 11.

13. The control means controls so that at least a part of the liquid stored in the supply tank is returned to the main tank when a predetermined time has elapsed since the last image formation.

13. The image forming apparatus according to claim 12.

14. The control means further controls the liquid stored in the recovery side tank to be returned to the main tank.

12. The image forming apparatus according to claim 11.

15. moreover, Equipped with a main tank that stores liquid in advance, The control means Furthermore, when a next image is formed, the liquid stored in the main tank is degassed by the degassing means and supplied to the supply tank, and the liquid is supplied to the recovery tank via the discharge means. After the liquid levels in the supply tank and the recovery tank reach a predetermined height, image formation is performed.

2. The image forming apparatus according to claim 1,

16. A method for use in an image forming apparatus for forming an image by ejecting liquid, comprising the steps of: The image forming apparatus includes: A degassing means for degassing the liquid; a supply tank for storing liquid; a first pump for varying an air pressure of an air layer formed above the liquid in the supply tank; A discharge means for discharging a liquid; a recovery tank for recovering and storing the remaining liquid of the liquid discharged by the discharge means; a second pump for varying the air pressure of an air layer formed above the liquid in the recovery side tank, The method comprises: a first control step of supplying the liquid degassed by the degassing means to the supply side tank, and controlling an air space in the supply side tank to have a positive pressure and an air space in the recovery side tank to have a negative pressure, so that the liquid is supplied from the supply side tank to the recovery side tank via the discharge means; a second control step of controlling, during standby for image formation by the ejection means, to supply at least a part of the liquid stored in the supply side tank from the supply side tank to the degassing means in a direction opposite to a supply direction from the degassing means to the supply side tank, to degas the liquid by the degassing means, and to supply the liquid from the supply side tank to the recovery side tank via the ejection means while maintaining an air layer in the supply side tank at a positive pressure and an air layer in the recovery side tank at a negative pressure; The method according to claim 1, further comprising:

17. A computer program for control used in an image forming apparatus that forms an image by ejecting liquid, the computer program being recorded on a computer-readable recording medium, The image forming apparatus includes: A degassing means for degassing the liquid; A supply tank for storing liquid; a first pump for varying an air pressure of an air layer formed above the liquid in the supply tank; A discharge means for discharging a liquid; a recovery tank for recovering and storing the remaining liquid of the liquid discharged by the discharge means; a second pump for varying the air pressure of an air layer formed above the liquid in the recovery side tank, The computer program comprises: The image forming device is a computer. a first control step of supplying the liquid degassed by the degassing means to the supply side tank, and controlling an air space in the supply side tank to have a positive pressure and an air space in the recovery side tank to have a negative pressure, so that the liquid is supplied from the supply side tank to the recovery side tank via the discharge means; a second control step of controlling, during standby for image formation by the ejection means, to supply at least a part of the liquid stored in the supply side tank from the supply side tank to the degassing means in a direction opposite to a supply direction from the degassing means to the supply side tank, to degas the liquid by the degassing means, and to supply the liquid from the supply side tank to the recovery side tank via the ejection means while maintaining an air layer in the supply side tank at a positive pressure and an air layer in the recovery side tank at a negative pressure; A computer program characterized by:

Images