Inkjet recording device and inkjet recording method

Abstract

To provide an inkjet recording device and an inkjet recording method which can sufficiently suppress occurrence of a failure in discharging ink from an ink nozzle.SOLUTION: The inkjet recording device is provided with: an inkjet head 2 that discharges ink (k) from an ink nozzle 11; a circulating device that circulates the ink (k) between the inkjet head 2 and the outside thereof; an air spray device 21 that sprays air towards an ink nozzle surface 11a of the inkjet head 2 to remove a foreign matter and mist generated from the discharged ink (k); and a control device that controls the circulating device, so that the device drives the inkjet head 2 when the air spray device 21 is spraying air, so as to make circulation differential pressure at the time of circulating the ink (k) lower than when forming an image.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an inkjet recording apparatus and an inkjet recording method. [Background technology]

[0002] Inkjet heads used in inkjet recording devices form images by ejecting ink from ink nozzles. When ink is ejected from the ink nozzles, a mist containing fine ink particles derived from the ink floats in the air. The ink particles in this mist adhere to the ink nozzle surface of the inkjet head. Furthermore, the ink that has adhered also causes foreign matter such as dust to adhere to the ink nozzle surface. If the mist or foreign matter that has adhered to the ink nozzle surface is left as it is, it can impede the ejection of ink from the nozzles or cause the ink to be ejected in a distorted direction.

[0003] In response to this, the technology disclosed in Patent Document 1 blows away the mist suspended in the air as described above with a jet of air, thereby preventing the mist and foreign matter from adhering to the ink nozzle surface. Patent Document 1 also mentions circulating the ink in the inkjet head. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 4-16356 Summary of the Invention [Problem to be solved by the invention]

[0005] The technology of Patent Document 1 can reduce the problems of mist and foreign matter adhering to the ink nozzle surface. However, blowing air onto the ink nozzle surface as in the technology of Patent Document 1 promotes drying of the ink nozzle surface and also traps air inside the ink nozzles, which can easily cause problems with ink ejection from the ink nozzles. In response to this, if the ink near the nozzles in the inkjet head is circulated between inside and outside the inkjet head, it is possible to prevent the ink nozzle surface from drying out and to prevent air from being drawn into the ink nozzles, which is expected to prevent problems with ink ejection from the nozzles.

[0006] However, when the air is blown as described above, the air is blown onto almost all the nozzles of the inkjet head. Therefore, if the circulation pressure difference when circulating the ink is large as described above, the flow of ink inside the inkjet head is promoted, and more air is drawn into the inkjet head from the ink nozzle side. This causes a problem that it is not possible to sufficiently prevent the occurrence of defective ink ejection from the ink nozzles. SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to provide an inkjet recording apparatus and an inkjet recording method that can sufficiently prevent defects in ink ejection from the ink nozzles. [Means for solving the problem]

[0007] (1) The present invention provides an inkjet recording apparatus comprising an inkjet head which ejects ink from ink nozzles, a circulation device which circulates the ink between the inkjet head and an outside thereof, an air blowing device which blows air onto an ink nozzle surface of the inkjet head, and a control unit which controls the circulation device to reduce a circulation differential pressure which circulates the ink while the air blowing device is blowing air, compared to when the inkjet head is driven to form an image. It is.

[0008] (2) The inkjet recording apparatus may be such that the circulation device circulates the ink by a pressure difference between an inlet side and an outlet side of the inkjet head.

[0009] (3) The inkjet recording apparatus according to (1) may be of a scan type, and the air blowing device blows the air when the inkjet head is in a position other than the position where the image is formed.

[0010] (4) The inkjet recording apparatus may be such that the air blowing device blows air after a carriage that moves the inkjet head is moved to a maintenance section.

[0011] (5) The inkjet recording device may be of a single-pass type, and a plurality of air nozzles from which the air blowing device blows out air may be arranged in a row along the row of the inkjet heads.

[0012] (6) The inkjet recording device according to (1) may further include a moving device that moves an air nozzle of the air blowing device, which blows out air, in a sub-scanning direction along the arrangement of the inkjet heads.

[0013] (7) The inkjet recording apparatus may be configured as described in (1) above, wherein the air blowing device is capable of varying a wind speed of the air blown out, and the control unit increases the circulating differential pressure as the wind speed increases.

[0014] (8) The inkjet recording device may be the one described in (1), further comprising a shielding member that prevents the foreign matter and the mist removed by the air blowing device from adhering to an image forming medium, which is an object on which an image is formed by ejecting the ink.

[0015] (9) The ink jet recording apparatus according to (1) may be configured such that the control unit sets the circulation differential pressure to a break pressure or less.

[0016] (10) The inkjet recording device may be configured as described in (1), wherein the control unit controls the air blowing device to blow air only to inkjet heads among the plurality of inkjet heads that are used more frequently than a predetermined level, based on image data for forming an image with the inkjet heads.

[0017] (11) The inkjet recording apparatus may be of a scan type, and the air blowing device may blow away the foreign matter and the mist with the air in the scan direction when the inkjet head moves in a scan direction.

[0018] (12) The inkjet recording apparatus according to (1) may be of a scan type, and the air blowing device blows air for each scan.

[0019] (13) The inkjet recording device according to (1) may be of a scanning type, in which a nozzle of the air blowing device that blows out air faces a direction different from a direction toward an image forming medium that is an object on which an image is formed by ejecting the ink, and the air blowing device blows the air when a carriage that moves the inkjet head moves toward the image forming medium.

[0020] (14) Another aspect of the present invention is an inkjet recording method that uses an inkjet recording apparatus including an inkjet head that ejects ink from ink nozzles, a circulation device that circulates the ink between the inkjet head and an outside thereof, and an air blowing device that blows air toward an ink nozzle face of the inkjet head, and that reduces a circulation differential pressure when circulating the ink by the circulation device while the air blowing device is blowing air compared to when the inkjet head is driven to form an image. Effect of the Invention

[0021] According to the present invention, it is possible to provide an inkjet recording apparatus and an inkjet recording method that can sufficiently prevent defects in ink ejection from ink nozzles. [Brief description of the drawings]

[0022] [Figure 1] 1 is a conceptual diagram of an inkjet head and its peripheral structure used in an inkjet recording apparatus according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a system diagram illustrating the configuration of a circulation device used in the inkjet recording apparatus according to the first embodiment of the present invention. [Diagram 3] 1 is a vertical sectional view of a main part of an inkjet recording apparatus according to a first embodiment of the present invention. [Figure 4] FIG. 2 is a block diagram showing a schematic diagram of electrical connections in a control system of the inkjet recording apparatus according to the first embodiment of the present invention. [Diagram 5] 5 is a flowchart illustrating control executed by the inkjet recording apparatus according to the first embodiment of the present invention. [Figure 6] FIG. 11 is a vertical sectional view of an inkjet recording apparatus according to a second embodiment of the present invention. [Figure 7] FIG. 11 is a plan view of an air blowing device of an inkjet recording apparatus according to a second embodiment of the present invention. [Figure 8] FIG. 11 is a side view of an air blowing device of an inkjet recording apparatus according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] Several embodiments of the present invention will now be described. <Embodiment 1> The inkjet recording apparatus according to the first embodiment of the present invention is an example of a scan-type inkjet recording apparatus, that is, an inkjet recording apparatus in which an inkjet head moves to form an image.

[0024] FIG. 1 is a conceptual diagram of an inkjet head and its surrounding structure used in an inkjet recording device according to the first embodiment. The inkjet head 2 of this inkjet recording device 1 (FIG. 3) is provided with a nozzle plate 12 in which ink nozzles 11 for ejecting ink are formed. In the inkjet recording device 1, a plurality of ink nozzles 11 are generally provided corresponding to a plurality of colors of ink, respectively, but in FIG. 1, only a single ink nozzle 11 is illustrated for convenience. The inner circumferential surface of the ink nozzle 11 and the surface of the nozzle plate 12 in the vicinity thereof are referred to as an ink nozzle surface 11a here. A channel 14 for guiding ink k to the ink nozzle 11 and an actuator 28 such as a piezoelectric element for applying a volume change to the channel 14 to eject the ink k from the ink nozzle 11 are provided within a housing 13 of the inkjet head 2.

[0025] The ink k is supplied to the channel 14 from the first sub-tank 55 via a flow path 302. The flow of the ink k in each part is indicated by an outlined arrow in FIG. 1. The ink k is circulated between the inkjet head 2 and its outside by a circulation device 29 (details of which will be described later with reference to FIG. 2). In order to circulate the ink k, a manifold circulation flow path 15 is provided as a flow path for discharging the ink k from the upper part of the channel 14 in the housing 13 to the outside of the inkjet head 2. In addition, a nozzle circulation flow path 16 is also provided as a flow path for discharging the ink k from the ink nozzle 11 side (near the ink nozzle 11) to the outside of the inkjet head 2 at the lower part of the channel 14. The manifold circulation flow path 15 and the nozzle circulation flow path 16 join at their downstream sides and connect to a flow path 303, and the ink k in the inkjet head 2 is discharged to the second sub-tank 56 via the flow path 303.

[0026] The air blowing device 21 is a device that blows air from the air nozzles 22 onto the ink nozzle surface 11a in synchronization with the operation of the inkjet head 2. The air blowing device 21 blows air using an actuator 42 (FIG. 4), such as a pump, as a drive source. The air blowing device 21 blows air onto the ink nozzle surface 11a, blowing away mist containing fine ink particles that is generated from the ink k ejected from the ink nozzles 11 and floats in the air. This prevents the mist and foreign matter such as dust resulting from the mist from adhering to the ink nozzle surface 11a. The configuration of the air blowing device 21 will be described in more detail later.

[0027] 2 is a system diagram illustrating the configuration of a circulation device used in the inkjet recording apparatus according to the present embodiment 1. The circulation device 29 includes a main tank 54, a first sub-tank 55, a second sub-tank 56, a degassing module 61, a filter 62, an air pressure control unit 66, and the like. The main tank 54 and the first sub-tank 55 are connected by a flow path 301, the first sub-tank 55 and the inkjet head 2 are connected by a flow path 302, the inkjet head 2 and the second sub-tank 56 are connected by a flow path 303, and the second sub-tank 56 and the main tank 54 are connected by a flow path 304. Each of the flow paths 301 to 304 is, for example, a tube-shaped member through which the ink k passes.

[0028] The inkjet head 2 ejects a portion of the ink k supplied from the first sub-tank 55 from the ink nozzle 11, and discharges the remaining ink k into the second sub-tank 56. The main tank 54 stores the ink k circulated to each part of the circulation device 29. The first sub-tank 55 stores the ink k supplied from the main tank 54, and the stored ink k is supplied to the inkjet head 2. The first sub-tank 55 is a tank-like container sealed except for various connection points, and an ink layer 55a and an air layer 55b are formed therein. The second sub-tank 56 stores the ink collected from the inkjet head 51. The second sub-tank 56 is a tank-like container sealed except for various connection points, and an ink layer 56a and an air layer 56b are formed therein.

[0029] A degassing module 61 is provided in the flow path 301, and degassing is performed on the ink k passing through the flow path 301. The degassing module 61 is configured, for example, to cause the ink k to flow down one side through a gas-permeable membrane and reduce the air pressure on the opposite side by a vacuum pump or the like, so that only the dissolved gas in the ink k in contact with the gas-permeable membrane is removed by passing through the gas-permeable membrane. A filter 62 is provided in the flow path 302 to remove foreign matter such as dust contained in the ink k passing through the flow path 302. The pore diameter of the filter 62 is preferably large enough to remove foreign matter having a particle size equal to or larger than the nozzle diameter of the inkjet head 2.

[0030] A pump 63 is provided in the flow path 301. The pump 63 supplies the ink k from the main tank 54 to the first sub-tank 55. As the pump 63, for example, a positive displacement pump such as a diaphragm pump, a tube pump, or the like is used. A pump 64 is provided in the flow path 304. The pump 64 supplies the ink k from the second sub-tank 56 to the main tank 54. As the pump 64, for example, a positive displacement pump such as a diaphragm pump, a tube pump, or the like is used.

[0031] The air pressure control unit 65 is an actuator connected to the first subtank 55 and adjusts the pressure of the air layer 55b in the first subtank 55. The air pressure control unit 66 is an actuator connected to the second subtank 56 and adjusts the pressure of the air layer 56b in the second subtank 56. By controlling the air pressure control unit 65 and the air pressure control unit 66, it is possible to adjust the circulation pressure difference of the ink k flowing from the first subtank 55 to the inkjet head 2 and from the inkjet head 2 to the second subtank 56. That is, the ink k can be circulated by the pressure difference between the inlet side and the outlet side of the inkjet head 2, and the flow speed of the ink k in the inkjet head 2 can be adjusted. In addition, by controlling the air pressure control unit 65 and the air pressure control unit 66, the pressure of the ink nozzle 11 of the inkjet head 2 is made negative, which makes it possible to prevent ink from leaking from the ink nozzle 11 when image formation or various maintenance is not performed.

[0032] With this configuration, in the circulation device 29, the ink k circulates in the following order: main tank 54 - first sub-tank 55 - inkjet head 2 - second sub-tank 56 - main tank 54. Such circulation of the ink k by the circulation device 29 basically continues while the inkjet recording apparatus 1 is on standby, regardless of whether an image forming operation by the inkjet head 2 is in progress or the image forming operation is suspended.

[0033] 3 is a vertical cross-sectional view of the main part of the inkjet recording device according to the first embodiment. The inkjet recording device 1 includes a conveyor belt 31 that carries an image forming medium c, such as cloth or paper, on which an image is to be formed, in a sub-scanning direction (perpendicular to the paper surface of FIG. 3). A carriage rail 32 is provided above the image forming medium c and the conveyor belt 31, with the scanning direction (main scanning direction, left-right direction in FIG. 3) as its longitudinal direction, and a carriage 33 is also provided that is supported by the carriage rail 32 and moves in the longitudinal direction of the carriage rail 32. An inkjet head 2 is provided on the carriage 33, and the inkjet head 2 is moved in the scanning direction by the carriage 33. In general, the carriage 33 has a plurality of inkjet heads 2 that correspond to ink k of each color aligned in the scanning direction.

[0034] An area 34 on the conveyor belt 31 is a position where the inkjet head 2 moves and forms an image. The maintenance section 35 is located outside the area 34, and is an area where predetermined maintenance is performed on the inkjet head 2. The air blowing device 21 is disposed below the maintenance section 35 (for example, on the side of the conveyor belt 31), and blows air onto the ink nozzle surface 11a of the inkjet head 2 located in the maintenance section 35. The air nozzle 22 faces in a direction different from the image forming medium c side on the conveyor belt 31. In this example, the air nozzle 22 faces in a direction inclined from the area 34 side toward the maintenance section 35 side. In this way, the air blowing device 21 blows off the mist and foreign matter in the scanning direction.

[0035] A shield member 36, which is a defensive wall-like member, is provided in a predetermined area between the area 34 and the maintenance section 35. The shield member 36 serves as a shield that prevents foreign matter and mist removed by the air blowing device 21 from adhering to the image forming medium c.

[0036] Next, the contents of the control executed by the inkjet recording apparatus 1 of the present embodiment 1 will be described. Fig. 4 is a block diagram showing a schematic diagram of the electrical connections of a control system that executes this control. This control system is mainly composed of a control device 41 (control unit) that is composed of a microcomputer, an ASIC (Application Specific Integrated Circuit), etc. To the control device 41, various actuators such as an actuator 42 of the air blowing device 21, air pressure control units 65, 66, and a motor 43 that serves as a drive source for the carriage 33, as well as various sensors, are connected via predetermined interfaces.

[0037] Fig. 5 is a flow chart showing the contents of the control executed by the inkjet recording apparatus 1 of the present embodiment 1. The inkjet recording method of the present invention is carried out by this process. As described above, the circulation device 29 circulates the ink k through the route described above with reference to Fig. 2. At that time, the control device 41 controls the air pressure control parts 65, 66 so that the circulation differential pressure of the ink k is equal to or lower than the break pressure. The break pressure is the maximum pressure at which the meniscus of the ink k is correctly formed.

[0038] The flowchart in Fig. 5 relates to control over the blowing of air by the air blowing device 21. This process starts when the carriage 33 (inkjet head 2) finishes one scanning operation and starts moving from the maintenance unit 35 toward the area 34 for the next scanning operation. That is, the process in Fig. 5 is performed for each scan.

[0039] First, as described above, the carriage 33 is generally provided with inkjet heads 2 of each color k aligned in the scanning direction. The control device 41 then performs a selection process for selecting an inkjet head 2 to be the target of air blowing by the air blowing device 21 (step S1). In this process, a process for selecting an inkjet head 2 that is used more frequently than a predetermined level among the multiple inkjet heads 2 is performed based on image data for forming an image with the inkjet heads 2. Before this process, the carriage 33 performs one scanning operation. How many ink droplets are ejected from each inkjet head 2 for an image formed in this one scanning operation, that is, how frequently each inkjet head 2 is used in this one scanning operation, can be determined by referring to the image data that is the target of image formation. Therefore, by referring to the image data, an inkjet head 2 that is used more frequently than a predetermined level is selected as the inkjet head 2 to be the target of air blowing. Step S1 may be completed before the carriage 33 starts to be driven for the next scan.

[0040] Next, the control device 41 judges whether the inkjet head 2 selected in step S1 is in a predetermined position (step S2). The control device 41 can judge the current position of each inkjet head 2 from the rotation speed of the motor 43 and the like. The predetermined position is a position where the air blown from the air nozzle 22 is appropriately blown to each ink nozzle 11 of one inkjet head 2. When the inkjet head 2 selected in step S1 is in a predetermined position (Yes in step S2), the control device 41 controls the actuator 42 to blow air to the inkjet head 2 that has reached the predetermined position (step S3). At the same time, when blowing air, the control device 41 controls the air pressure control units 65, 66 to reduce the circulation differential pressure when circulating the ink k compared to when the inkjet head 2 is driven to form an image (ejection of the ink k) (step S3). By the process of step S3, the air nozzle 22 is disposed as described above, and thus the foreign matter and mist are blown away by air in the scanning direction when the inkjet head 2 moves in a scanning direction.

[0041] If the inkjet head 2 selected in step S1 is not at the predetermined position (No in step S2), the control device 41 proceeds to step S4. The control device 41 also proceeds to step S4 when the processing of step S3 is completed. In step S4, the control device 41 determines whether all the inkjet heads 2 have passed the predetermined position. If there are any inkjet heads 2 that have not passed the predetermined position (No in step S4), the control device 41 returns to the processing of step S2. If the control device 41 determines that all the inkjet heads 2 have passed the predetermined position (Yes in step S4), it returns the circulating differential pressure to its original value (step S5) and ends the processing of FIG. 5.

[0042] Furthermore, the control device 41 may control the actuator 42 to vary the wind speed of the air blown out from the air nozzle 22. For example, when there is an inkjet head 2 that is determined to have been used particularly frequently in the previous scan in the process of step S1, the wind speed of the air blown out from the air nozzle 22 may be made faster than normal when blowing air to the inkjet head 2. When making the wind speed of the air blown out from the air nozzle 22 faster in this manner, the control device 41 may increase the circulation differential pressure above normal.

[0043] Next, the effects of the first embodiment will be described. First, the problem of mist and foreign matter adhering to the ink nozzle surface 11a can be reduced by blowing air using the air blowing device 21. However, this accelerates the drying of the ink nozzle surface 11a and also traps air inside the nozzles, which can easily cause problems with the ejection of ink k from the ink nozzles 11. In contrast, by circulating the ink k as described above, it is possible to prevent the ink nozzle surface 11a from drying out and to prevent air from being drawn into the ink nozzle 11, which is expected to prevent defects in the ink ejection from the ink nozzle 11.

[0044] However, when the air is blown as described above, the air is blown onto almost all of the ink nozzles 11 of the inkjet head 2. Therefore, if the circulation differential pressure when circulating the ink is large as described above, the flow of the ink k inside the inkjet head 2 is promoted, and more air is entrained from the ink nozzles 11 side into the inkjet head 2. Therefore, there is a problem in that it is not possible to sufficiently prevent the occurrence of defective ejection of the ink k from the ink nozzles 11.

[0045] Therefore, in the inkjet recording device 1, when the air blowing device 21 is blowing air, the circulation differential pressure when circulating the ink k is reduced (step S3) compared to when the inkjet head 2 is driven to form an image (ejection of the ink k). This makes it possible to suppress air from being sucked into the inkjet head 2 due to the circulation of the ink k, and therefore makes it possible to sufficiently suppress the occurrence of defects in the ejection of ink from the ink nozzles 11.

[0046] In addition, the air blowing device 21 blows air when the inkjet head 2 is in a position (maintenance section 35) other than the position (area 34) where image formation is performed. Therefore, it is possible to prevent mist and foreign matter blown away by air from adhering to the image formation medium c. When the air blowing device 21 blows out air at a speed faster than normal, the circulation differential pressure is also increased above normal, thereby preventing the ink nozzle surface 11a from becoming excessively dry due to an increase in the air speed.

[0047] Furthermore, the presence of the shield member 36 can prevent the mist and foreign matter blown away by the air blow from adhering to the image forming medium c. Furthermore, since the circulation differential pressure is set to be equal to or lower than the break pressure, the meniscus of the ink k can be formed correctly. The inkjet recording device 1 performs a selection process (step S1) and blows air only to the inkjet heads 2 that are used frequently (step S3). Therefore, for the inkjet heads 2 that are considered to have little mist or foreign matter attached thereto, drying of the ink nozzles 11a can be suppressed.

[0048] The air blowing device 21 blows foreign matter and mist in the scanning direction with air when the inkjet head 2 moves in a scan direction. This makes it possible to reduce the possibility that foreign matter, etc. will be blown away in the sub-scanning direction or the like and soil the image forming medium c. Furthermore, by blowing air after every scan, mist and foreign matter can be carefully removed from the ink nozzle surface 11a. The ink nozzles 11 face in a direction different from the image forming medium c, and the air blowing device 21 blows air when the carriage 33 that moves the inkjet head 2 moves toward the image forming medium c. This makes it possible to prevent the image forming medium c from being soiled by mist or foreign matter blown away by the air.

[0049] <Embodiment 2> The inkjet recording apparatus according to the second embodiment of the present invention is an example of a single-pass type inkjet recording apparatus, that is, an inkjet recording apparatus that forms an image while the inkjet head remains fixed in a predetermined position. In the description of the second embodiment, the same reference numerals as in the first embodiment are used for the same members as in the first embodiment, and detailed description thereof will be omitted. However, the second embodiment also includes all of the configurations of the first embodiment that can be applied to the second embodiment.

[0050] 6 is a vertical cross-sectional view of an inkjet recording apparatus according to the present embodiment 2. The inkjet recording apparatus 401 includes a supply section 410, an image forming section 420, and a discharge section 430. The supply unit 410 supplies the image formation medium c on which an image is formed to the image forming unit 420. The supply unit 410 includes a paper feed tray 411 that holds the image formation medium c, and a conveying unit 412 that supplies the image formation medium c to the image forming unit 420.

[0051] The paper feed tray 411 is a plate-like member on which one or more image forming media c can be placed. The paper feed tray 411 is provided so as to move up and down according to the amount of image forming media c placed thereon, and the topmost image forming medium c is held at a position where it can be transported by the transport unit 412. The conveying section 412 feeds the top image forming medium c out of the image forming media c placed on the paper feed tray 411 onto the belt 123, and rotates the belt 123 with the rollers 121 and 122 to convey the image forming medium c on the belt 123.

[0052] The image forming section 420 forms an image by ejecting ink k onto the image forming medium c supplied from the supply section 410. The image forming section 420 includes an image forming drum 421, a delivery unit 422, a paper heating section 423, a head unit 424, an irradiation section 425, and a delivery section 426. The image forming drum 421 carries the image forming medium c along its cylindrical outer peripheral surface and transports the image forming medium c as the image forming drum 421 rotates counterclockwise. The outer peripheral surface of the image forming drum 421 faces a paper heating section 423, a head unit 424, and an irradiation section 425.

[0053] The delivery unit 422 delivers the image forming medium c transported by the transport section 412 to the image forming drum 421. The delivery unit 422 includes a swing arm section 221 that supports one end of the image forming medium c, a cylindrical delivery drum 222, and the like, and picks up the image forming medium c on the transport section 412 with the swing arm section 221, and guides the image forming medium c in a direction along the outer circumferential surface of the image forming drum 421 with the delivery drum 222 to deliver it to the image forming drum 421.

[0054] The paper heating section 423 heats the image forming medium c carried by the image forming drum 421. The paper heating section 423 has, for example, an infrared heater that generates heat in response to energization. The paper heating section 423 is provided near the outer circumferential surface of the image forming drum 421 and upstream of the head unit 424 in the transport direction of the image forming medium c. The paper heating section 423 is controlled so that the image forming medium c carried by the image forming drum 421 and passing near the paper heating section 423 is heated to a predetermined temperature.

[0055] The head unit 424 ejects ink k onto the image forming medium c carried by the image forming drum 421 to form an image. The multiple head units 424 (four in this example) eject different colors of ink k. Each head unit 424 ejects different colors of ink k, and each head unit 424 has multiple inkjet heads 2 arranged in the barrel length direction of the image forming drum 421 (the direction perpendicular to the paper surface of FIG. 6).

[0056] After the ink k is discharged onto the image forming medium c, the irradiation unit 425 irradiates the image forming medium c with energy rays for curing the ink k. The irradiation unit 425 includes, for example, a fluorescent tube such as a low-pressure mercury lamp. The irradiation unit 425 is provided near the outer circumferential surface of the image forming drum 421 and downstream of the head unit 424 in the transport direction of the image forming medium c.

[0057] The delivery unit 426 transports the image forming medium c from the image forming drum 421 to the discharge unit 430. The delivery unit 426 delivers the image forming medium c supported on the image forming drum 421 by the delivery drum 264 to the belt 263, and drives the belt 263 to rotate by the rollers 261 and 262 to transport the image forming medium c on the belt 263. The discharge section 430 includes a plate-shaped discharge tray 431 and stores the image formation medium c conveyed from the image forming section 420 .

[0058] FIG. 7 is a plan view of the air blowing device used in the second embodiment, and FIG. 8 is a side view of the same. The air blowing device 451 is provided with a pair of rails 452 (moving device). The rails 452 are curved in an arc shape so as to follow the arc shape of the outer periphery of the image forming drum 421 as shown in FIG. 8 (for convenience, the rails are illustrated linearly in FIG. 7). A shaft-shaped nozzle support portion 453 is supported on the pair of rails 452. The nozzle support portion 453 can move on the rails 452 along the length direction of the pair of rails 452 by driving a motor 454. A plurality of air nozzles 22 are provided on the nozzle support portion 453 lined up in the length direction, and each air nozzle 22 blows out air in the same manner as in the first embodiment.

[0059] With this mechanism, the plurality of air nozzles 22 (nozzle support section 453) can move in the space between the head unit 424 and the image forming drum 421 in the circumferential direction (sub-scanning direction) of the image forming drum 421. As shown by the arrows in Figs. 7 and 8, the nozzle support section 453 can move in both forward and reverse directions along the longitudinal direction of the rail 452. Therefore, the longitudinal direction of the nozzle support section 453, and thus the arrangement direction of the plurality of air nozzles 22, intersects (is perpendicular to) the sub-scanning direction. When the nozzle support section 453 is positioned directly below each head unit 424, each of the air nozzles 22 faces the plurality of inkjet heads 2 of the corresponding head unit 424 in a one-to-one relationship, and it is possible for each air nozzle 22 to blow air onto each ink nozzle surface 11a of each inkjet head 2. Also, the second embodiment includes a circulation device 29 similar to that described above. When the space between the head unit 424 and the image forming drum 421 is too narrow for the nozzle support portion 453 to pass through, a mechanism may be provided that retracts each head unit 424 from the image forming drum 421 side only when the nozzle support portion 453 is to pass through the space. FIG. 6 illustrates a state in which the space between the head unit 424 and the image forming drum 421 is narrow when forming an image. Each rail 452 is provided at a position on both sides of the image forming drum 421 where it does not interfere with image formation. When forming an image, the nozzle support portion 453 retracts to an area where it does not interfere with image formation.

[0060] In this configuration, in order to blow air onto the ink nozzle surface 11a of each inkjet head 2, the nozzle support portion 453 is driven so that air is blown from each air nozzle 22 onto the ink nozzle surface 11a of each inkjet head 2 of each head unit 424. When blowing air from the air nozzle 22 in this manner, the circulation device 29 is controlled to adjust the circulation differential pressure in the same manner as in the first embodiment.

[0061] In this embodiment 2, a plurality of air nozzles 22 are provided on the nozzle support portion 453 in correspondence with the arrangement of the inkjet heads 2 of each head unit 424, so that air can be blown to all of the multiple inkjet heads 2 arranged in each head unit 424.

[0062] Furthermore, since the nozzle support portion 453 passes under all of the head units 424, air can be blown to all of the inkjet heads 2 of all of the head units 424 aligned in the sub-scanning direction. It should be noted that each of the above-described embodiments is merely one embodiment of the present invention and does not limit the present invention. [Explanation of symbols]

[0063] 1,401 Inkjet recording device 2 Inkjet head 11 Ink nozzle 11a Ink nozzle surface 21,451 Air blowing device 22 Air nozzle 29 Circulation device 34 position (area) 35 Maintenance Department 36 Shielding material 41 Control device (control unit) 452 Rail (movement device) c Imaging media k ink

Claims

1. an inkjet head that ejects ink from ink nozzles; a circulation device that circulates the ink between the inkjet head and an outside thereof; an air blowing device directed toward an ink nozzle surface of the inkjet head; a control unit that controls the circulation device to reduce a circulation differential pressure that circulates the ink when the air blowing device is blowing air, compared to when the inkjet head is driven to form an image; and An inkjet recording apparatus comprising:

2. 2. The inkjet recording apparatus according to claim 1, wherein the circulating device circulates the ink by a pressure difference between an inlet side and an outlet side of the inkjet head.

3. It is a scan type, The inkjet recording apparatus according to claim 1 , wherein the air blowing device blows the air when the inkjet head is in a position other than the position where the image is formed.

4. 4. The inkjet recording apparatus according to claim 3, wherein the air blowing device blows the air after a carriage that moves the inkjet head has been moved to a maintenance section.

5. It is a single-path type, The inkjet recording apparatus according to claim 1 , wherein a plurality of air nozzles of the air blowing device for blowing out the air are arranged in line along an arrangement of the inkjet heads.

6. It is a single-path type, 2. The inkjet recording apparatus according to claim 1, further comprising a moving device that moves an air nozzle of said air blowing device that blows out air along an arrangement of said inkjet heads in a sub-scanning direction.

7. The air blowing device can vary the wind speed of the air it blows out, The inkjet recording apparatus according to claim 1 , wherein the control unit increases the circulation differential pressure in accordance with an increase in the wind speed.

8. 2. The inkjet recording apparatus according to claim 1, further comprising a shield member that prevents the foreign matter and the mist removed by the air blowing device from adhering to an image forming medium, which is an object on which an image is formed by ejecting the ink.

9. The inkjet recording apparatus according to claim 1 , wherein the control unit sets the circulation differential pressure to be equal to or lower than a break pressure.

10. 2. The inkjet recording apparatus according to claim 1, wherein the control unit controls the air blowing device to blow air only to one of the plurality of inkjet heads that is used more frequently than a predetermined level, based on image data for forming an image with the inkjet head.

11. It is a scan type, The inkjet recording apparatus according to claim 1 , wherein the air blowing device blows off the foreign matter and the mist in a scanning direction with the air when the inkjet head moves in a scanning direction.

12. It is a scan type, The inkjet recording apparatus according to claim 1 , wherein the air blowing device blows the air for each scan.

13. It is a scan type, a nozzle of the air blowing device for blowing out air faces a direction different from a side of an image forming medium which is an object on which an image is formed by discharging the ink; 2. The inkjet recording apparatus according to claim 1, wherein the air blowing device blows the air when a carriage that moves the inkjet head moves toward the image forming medium.

14. an inkjet head that ejects ink from ink nozzles; a circulation device that circulates the ink between the inkjet head and an outside thereof; an air blowing device that blows air toward the ink nozzle surface of the inkjet head, the inkjet recording method, wherein the circulation device reduces a circulation differential pressure when circulating the ink while the air blowing device is blowing air, compared to when the inkjet head is driven to form an image.

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