Image forming apparatus

Abstract

To provide an image forming apparatus which is reduced in power consumption and furthermore is constituted in such a manner that drying of the surface of liquid in a nozzle can be suppressed.SOLUTION: An image forming apparatus 1 comprises: a head unit 12 including a recording head 14 that ejects ink from a nozzle toward a paper sheet; a conveying part 15 that conveys the paper sheet, at a position opposing to the heat unit 12; and a moving part 20 that moves the head unit 12 in a reciprocated manner along a separating / approaching direction (a vertical direction) in which the unit separates from the conveying part 15 or approaches the conveying part 15. The moving part 20 executes vibration operation of vibrating the surface of ink in the nozzle, by moving the head unit 12 in a reciprocated manner in the separating / approaching direction repeatedly.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to an inkjet image forming apparatus. [Background technology]

[0002] An inkjet recording device is known that has a transport means for transporting a recording medium and a recording head that records an image by ejecting ink while moving back and forth (Patent Document 1). In this inkjet recording device, a control means positions the recording head outside the edge of the recording medium and applies a drive signal to the recording head that includes a pulse for vibrating the ink surface at the tip of the nozzle without ejecting ink. This vibrates the meniscus formed by the ink surface inside the nozzle, preventing the ink surface from drying out. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-170615 Summary of the Invention [Problem to be solved by the invention]

[0004] However, because the drive signal is a high voltage, the above-mentioned technique has the problem of consuming a large amount of power to vibrate the meniscus inside the nozzle.

[0005] In consideration of the above circumstances, the present invention provides an image forming apparatus that can suppress drying of the liquid surface inside the nozzles while reducing power consumption. [Means for solving the problem]

[0006] The image forming device comprises a head unit including a recording head that ejects liquid from a nozzle toward a medium, a transport unit that transports the medium at a position opposite the head unit, and a moving unit that moves the head unit back and forth along a separation direction away from or toward the transport unit, and the moving unit repeatedly moves the head unit back and forth along the separation direction, performing a vibration operation that vibrates the surface of the liquid in the nozzle.

[0007] In this case, the apparatus may further include a maintenance unit that performs maintenance operations to maintain the recording head, and the moving unit performs the vibration operation each time a first predetermined time elapses while the recording head is in a standby state in which it is stopped from operating, and when the recording head is operated after a second predetermined time longer than the first predetermined time has elapsed while in the standby state, the moving unit moves the head unit to a maintenance position separated from the transport unit, and the maintenance unit performs the maintenance operation on the recording head of the head unit placed at the maintenance position.

[0008] In this case, the transport unit may transport the medium in a vertical direction, and the recording head may eject the liquid toward the medium being transported in the vertical direction.

[0009] In this case, the head unit may include a plurality of the recording heads arranged to cover the width of the medium perpendicular to the transport direction. [Effects of the Invention]

[0010] According to the present invention, it is possible to suppress the surface of the liquid in the nozzle from drying out while reducing power consumption. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a schematic view (front view) showing the internal structure of an image forming apparatus according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a plan view showing a line head of the image forming apparatus according to the first embodiment of the present invention. [Figure 3] 1 is a block diagram showing a moving unit, a maintenance unit, etc. of an image forming apparatus according to a first embodiment of the present invention. [Figure 4] 1 is a front view showing a head unit, a conveying unit, and a maintenance unit of an image forming apparatus according to a first embodiment of the present invention. [Figure 5] 1 is an explanatory diagram illustrating how the surface (meniscus) of ink inside a nozzle vibrates as the head unit moves back and forth in the image forming apparatus according to the first embodiment of the present invention. FIG. [Figure 6] 6 is a flowchart showing the procedure for performing a maintenance operation and a vibration operation by a control unit of the image forming apparatus according to the first embodiment of the present invention. [Figure 7] FIG. 10 is a schematic view (front view) showing the internal structure of an image forming apparatus according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. Note that Fr, Rr, L, R, U, and D shown in the drawings indicate front, rear, left, right, top, and bottom. Terms indicating directions and positions are used in this specification, but these terms are used for convenience of explanation and do not limit the technical scope of the present invention.

[0013] [First embodiment: image forming apparatus] An image forming apparatus 1 according to a first embodiment will be described with reference to Figures 1 and 2. Figure 1 is a schematic diagram (front view) showing the internal structure of the image forming apparatus 1. Figure 2 is a plan view showing a line head 13.

[0014] The image forming apparatus 1 is an inkjet printer that ejects ink droplets to form an image on paper M (medium). As shown in FIG. 1, the image forming apparatus 1 has a box-shaped housing 3 that houses various devices. A paper feed cassette 4 in which paper M is set is housed in the lower part of the housing 3, and a paper output tray 5 on which printed paper M is stacked is provided on the upper left side of the housing 3. A first transport path 6 is formed on the right side inside the housing 3 for transporting paper M from the paper feed cassette 4 toward the head unit 12. A paper feed unit 10 is provided upstream of the first transport path 6, and a registration roller 11 is provided downstream of the first transport path 6.

[0015] The head unit 12 has four line heads 13 corresponding to four colors of ink: black, cyan, magenta, and yellow. Each line head 13 is equipped with multiple (e.g., three) recording heads 14 (see FIG. 2). The multiple recording heads 14 are arranged to cover the front-to-rear width of the paper M (the horizontal width perpendicular to the conveying direction). Each recording head 14 is connected to an ink pack (not shown) of the corresponding color via a tube (not shown), and receives a supply of ink (liquid) from the ink pack. Note that the four line heads 13 have the same structure, so the following explanation will mainly focus on one line head 13. Similarly, the multiple recording heads 14 also have the same structure, so the following explanation will mainly focus on one recording head 14.

[0016] As shown in FIGS. 1 and 2, the recording head 14 is supported by a head base 13A with its nozzle surface 14A (nozzles N) facing downward (toward a transport unit 15, described later). The recording head 14 has a plurality of ink chambers formed corresponding to the plurality of nozzles N, and a plurality of piezoelectric elements provided corresponding to the plurality of ink chambers (neither of which is shown). Each piezoelectric element is electrically connected to a high-voltage power supply (not shown), which applies a drive signal (high voltage) to each piezoelectric element under the control of a control unit 19. The recording head 14 is a so-called piezo-type inkjet head that applies a drive signal to the piezoelectric element to deform the ink chamber, thereby ejecting ink from the nozzles N.

[0017] As shown in Fig. 1, a transport section 15 for transporting paper M is provided below the head unit 12. The transport section 15 includes a transport belt 16 that is wound around a plurality of tension rollers 16A. A large number of through holes (not shown) are formed in the transport belt 16, and a suction section 16B is provided on the inside of the transport belt 16.

[0018] A decurling device 17 that corrects curls in the paper M is installed on the left side of the head unit 12. A second transport path 7 that transports the paper M from the decurling device 17 toward the paper output tray 5 is formed on the left side of the housing 3, and a paper output unit 18 is provided downstream of the second transport path 7. A third transport path 8 that transports the paper M from the middle of the second transport path 7 to the registration rollers 11 is formed in the upper part of the housing 3.

[0019] A control unit 19 for appropriately controlling various control target devices is provided inside the housing 3. The control unit 19 includes a processor or the like that executes various arithmetic processes in accordance with programs and parameters stored in memory. Note that the control unit 19 may be realized by a logic circuit (hardware) formed in an integrated circuit or the like, instead of a processor or the like that executes programs or the like.

[0020] [Printing Processing] Here, the printing process (image forming process) will be described. The control unit 19 controls various control target devices as appropriate, and executes the printing process as follows.

[0021] The paper feed unit 10 sends out the paper M taken out from the paper feed cassette 4 to the first transport path 6. The registration rollers 11 temporarily block the paper M to correct skew, and then send the paper M onto the transport belt 16 in accordance with the timing of the ejection of ink droplets (liquid droplets) from the recording head 14. The transport unit 15 transports the paper M at a position opposite the head unit 12 (recording head 14). The paper M is transported while being adsorbed onto the transport belt 16, and the head unit 12 (recording head 14) ejects ink (liquid) toward the paper M. As a result, a full-color image is formed (printed) on the paper M. After passing below the head unit 12, the paper M is sent to the decurling device 17, where the curl is corrected.

[0022] The paper M printed on one side passes through the second transport path 7 and is discharged to the paper output tray 5. When performing double-sided printing, the paper M printed on one side enters the third transport path 8, is turned over, and is transported again toward the registration rollers 11. An image is then formed on the back side of the paper M in the same order as in the single-sided printing described above, and the double-sided printed paper M is straightened and discharged to the paper output tray 5.

[0023] The image forming apparatus 1 is equipped with a maintenance unit 30 that performs maintenance operations to maintain the recording head 14 (see FIG. 1). The image forming apparatus 1 also has a moving unit 20 that moves the head unit 12 back and forth in the up and down direction (the direction in which the head unit 12 moves away from or toward the conveying unit 15) in order to perform the maintenance operations (see FIGS. 3 and 4). The moving unit 20 and the maintenance unit 30 will be described below with reference to FIGS. 3 and 4. FIG. 3 is a block diagram showing the moving unit 20, the maintenance unit 30, etc. FIG. 4 is a front view showing the head unit 12, the conveying unit 15, and the maintenance unit 30.

[0024] [Moving part] Prior to describing the maintenance unit 30, the movement unit 20 will be described. As shown in FIG. 3, the movement unit 20 has a movement motor 21 and a movement sensor 22. The movement motor 21 is, for example, a direct current (DC) motor or the like, and is electrically connected to the control unit 19. The movement motor 21 is connected to the head unit 12 via a transmission mechanism (not shown) composed of a gear train, pulleys, belts, etc., and raises and lowers the head unit 12 under the control of the control unit 19. As shown in FIG. 4, the head unit 12 moves (raises and lowers) between a printing position P1, where it is close to the conveyance unit 15 (conveyor belt 16) and allows printing processing to be performed, and a maintenance position P2, which is set above and spaced apart from the printing position P1. Placing the head unit 12 in the maintenance position P2 enables the maintenance unit 30 to perform maintenance on the recording head 14. The movement sensor 22 is, for example, a reflective optical sensor or the like, and detects the head unit 12 placed at each of the positions P1 and P2. Movement sensor 22 is electrically connected to control unit 19 and transmits the detection result to control unit 19. Control unit 19 controls the driving of movement motor 21 based on the detection result of movement sensor 22. Note that movement motor 21 may be a stepping motor or a servo motor, and the transmission mechanism may be a gear mechanism such as a rack and pinion. Furthermore, movement sensor 22 may be, for example, a transmissive optical sensor or a microswitch.

[0025] [Maintenance Department] The maintenance unit 30 is disposed inside the housing 3 to the left of the head unit 12 (see FIG. 1). The maintenance unit 30 performs maintenance operations to prevent or clear clogging of the nozzles N of the recording head 14. As shown in FIG. 4, the maintenance unit 30 includes a maintenance housing 31, a capping device 32, and a wiping device 33.

[0026] <Maintenance cabinet> The maintenance housing 31 is formed in a box shape with an opening on the right side, and houses a capping device 32 and a wiping device 33. The capping device 32 and the wiping device 33 are each provided so as to be movable in the left-right direction by a sliding device 34. The sliding device 34 is driven and controlled by the control unit 19 (see FIG. 3), and moves either the capping device 32 or the wiping device 33, as selected.

[0027] <Capping device> The capping device 32 includes multiple caps 32A corresponding to the multiple recording heads 14. The caps 32A are formed in the shape of a tray with edges protruding upward from the bottom surface. The capping device 32 is provided so as to be movable left and right between a storage position (see FIG. 4) in the maintenance housing 31 and a capping position (not shown) set directly below the head unit 12 disposed at the maintenance position P2. When performing capping, which is an example of a maintenance operation, the moving unit 20 moves the head unit 12 from the print position P1 to the maintenance position P2, and the sliding device 34 moves the capping device 32 from the storage position to the capping position. The moving unit 20 then lowers the head unit 12 at the maintenance position P2, causing the edges of the caps 32A to come into close contact with the nozzle surface 14A of the recording head 14 and seal the area where the multiple nozzles N are formed. This prevents ink from drying out in the nozzles N and prevents the nozzles N from clogging.

[0028] Furthermore, the cap 32A is connected to a suction pump 35 (see FIG. 3) via a tube (not shown). When purging (discharge of waste) is performed as an example of a maintenance operation, the suction pump 35 is driven and controlled by the control unit 19 with the edge of the cap 32A in close contact with the nozzle surface 14A, and a negative pressure is created in the space surrounded by the nozzle surface 14A and the cap 32A. This forcibly sucks out ink that has thickened inside the nozzles N, thereby preventing (or eliminating) clogging of the nozzles N. The sucked ink is stored in a waste tank (not shown).

[0029] When capping or purging is completed, the moving section 20 raises the head unit 12 to the maintenance position P2, and the slide device 34 returns the capping device 32 to the storage position.

[0030] <Wiping device> The wiping device 33 is provided so as to be movable in the left-right direction between a storage position (see FIG. 4) housed in the maintenance housing 31 and a wiping position (not shown) set directly below the head unit 12 disposed at the maintenance position P2. The wiping device 33 has four wiper carriages 33A, a plurality of wiper blades 33B, and a wiper moving device 33C (see FIG. 3). The four wiper carriages 33A are provided so as to correspond to the four line heads 13. The wiper carriages 33A are provided so as to be movable in the front-rear direction when disposed at the wiping position. Three wiper blades 33B corresponding to the three recording heads 14 are provided in an upright position on each wiper carriage 33A. The wiper blades 33B are formed in a plate shape using an elastic material such as synthetic rubber. The wiper moving device 33C reciprocates the wiper carriage 33A (wipe blades 33B) in the front-rear direction.

[0031] When wiping is performed as an example of a maintenance operation, the moving unit 20 moves the head unit 12 from the print position P1 to the maintenance position P2, and the sliding device 34 moves the wiping device 33 from the storage position to the wiping position. The moving unit 20 then lowers the head unit 12 from the maintenance position P2, causing the tip (upper end) of the wiper blade 33B to contact the nozzle surface 14A. The wiper moving device 33C is then driven and controlled by the control unit 19 to move the wiper carriage 33A from front to rear, causing the wiper blade 33B to wipe away ink adhering to the nozzle surface 14A. When wiping is completed, the moving unit 20 raises the head unit 12 to the maintenance position P2, the wiper moving device 33C returns the wiper carriage 33A to the wiping start position, and the sliding device 34 returns the wiping device 33 to the storage position. Wiping may be performed, for example, after purging ink.

[0032] As described above, the maintenance unit 30 can prevent (eliminate) clogging of the nozzles N of the recording head 14 by performing various maintenance operations. The maintenance operations by the maintenance unit 30 are performed, for example, when the recording head 14 is put into operation (made printable) after a preset time (a second predetermined time (T2) described below) has elapsed while the recording head 14 is in a standby state in which it is stopped from operating (printing is stopped). However, because the maintenance operations by the maintenance unit 30 require a long time, it takes a long time to return to a state in which printing can be performed, which can reduce user convenience (satisfaction). Therefore, to improve user convenience, it is preferable to extend the interval between maintenance operations (the second predetermined time (T2) described below).

[0033] To extend the interval between maintenance operations, there is a technique in which a drive signal is applied to the piezoelectric element at a level that does not cause ink to be ejected from the nozzle N of the recording head 14, thereby vibrating the meniscus formed by the surface of the ink in the nozzle N. This prevents the surface of the ink in the nozzle N from drying (hardening), making it possible to extend the interval between maintenance operations by the maintenance unit 30. However, the above-mentioned technique for vibrating the meniscus has the problem of consuming a large amount of power because a high-voltage drive signal is continuously applied to the piezoelectric element.

[0034] Therefore, the image forming apparatus 1 according to the first embodiment has a structure that suppresses drying of the surface of the ink inside the nozzles N while reducing power consumption. This structure will be described with reference to Fig. 5. Fig. 5 is an explanatory diagram that explains how the surface (meniscus) of the ink inside the nozzles N vibrates as the head unit 12 moves back and forth.

[0035] In a standby state in which the recording head 14 is stopped, the moving unit 20 repeatedly moves the head unit 12 back and forth in the vertical direction (contact direction) to vibrate the surface of the ink in the nozzles N. For example, with the head unit 12 positioned at the printing position P1, the moving unit 20 (movement motor 21) is controlled by the control unit 19 to alternately switch the forward and reverse rotation of the rotor (not shown) of the movement motor 21 in a short period of time. This causes the head unit 12 to move back and forth in short intervals in the vertical direction, vibrating the surface of the ink (meniscus) in the nozzles N (see the enlarged cross-sectional view of the nozzle N circled in FIG. 5). In the vibration operation, the vibration frequency is, for example, 1 to 9 kHz, and the amplitude is, for example, 1 to 10 mm, sufficiently smaller than the distance between the printing position P1 and the maintenance position P2. Note that the vibration operation may also be performed with the head unit 12 positioned at the maintenance position P2.

[0036] [Maintenance and vibration operation procedures] The procedure for performing the maintenance operation and vibration operation by the control unit 19 will be described below with reference to Fig. 6. Fig. 6 is a flowchart showing the procedure for performing the maintenance operation and vibration operation by the control unit 19.

[0037] After the printing process is completed (after the recording head 14 is stopped), the control unit 19 starts measuring the waiting time (T) and initializes the count value (N) (step S1). The count value (N) is a natural number, and its initial value is set to "1". Next, the control unit 19 determines whether the waiting time (T) has elapsed the first predetermined time (T1) (step S2). The first predetermined time (T1) is a value obtained by multiplying the preset reference time (T0) by the count value (N). In step S2, it is determined whether the waiting time (T) is equal to or greater than the first predetermined time (T1 = T0×N). When the waiting time (T) is equal to or greater than the first predetermined time (T1) (YES in step S2), the control unit 19 increases the count value (N) by 1 and controls the moving unit 20 (moving motor 21) to execute the above-described vibration operation (step S3). The control unit 19 causes the moving unit 20 to execute the vibration operation for a preset time and then ends the vibration operation. On the other hand, when the waiting time (T) is less than the first predetermined time (T1) (NO in step S2), the control unit 19 continues measuring the waiting time (T). And the control unit 19 causes the moving unit 20 to execute the vibration operation each time the first predetermined time (T1) elapses.

[0038] Next, when the control unit 19 receives an interrupt signal (step S4) instructing the start of the printing process (operation of the recording head 14), it determines whether the waiting time (T) has elapsed a second predetermined time (T2) that is longer than the first predetermined time (T1) (step S5). When the waiting time (T) has elapsed the second predetermined time (T2) (T≧T2) (YES in step S5), the control unit 19 controls the moving unit 20 to move the head unit 12 to the maintenance position P2 separated from the transport unit 15, and controls the maintenance unit 30 to execute a maintenance operation on the recording head 14 of the head unit 12 arranged at the maintenance position P2 (step S6). The control unit 19 causes the maintenance operation to be executed for a preset time and then ends the maintenance operation, putting the printing process into a state where it can be started. On the other hand, when the waiting time (T) has not elapsed the second predetermined time (T2) (T<T2) (NO in step S5), the control unit 19 does not execute the maintenance operation and puts the printing process into a state where it can be started.

[0039] The first predetermined time (T1) (reference time (T0)) and the second predetermined time (T2) are set experimentally and empirically, taking into consideration the properties of the ink (viscosity, quick-drying property, etc.) and the nozzle diameter, and are stored in the memory of the control unit 19. In addition, various other parameters required for executing the maintenance operation and vibration operation are also stored in the memory of the control unit 19.

[0040] In the image forming apparatus 1 according to the first embodiment described above, the moving unit 20 repeatedly moves the head unit 12 back and forth in small increments in the up and down direction (contact and separation direction), thereby performing a vibration operation that vibrates the surface of the ink in the nozzles N. With this configuration, it is possible to vibrate the surface of the ink (meniscus) in the nozzles N without applying a high-voltage drive signal to the recording head 14. This makes it possible to suppress drying of the surface of the ink in the nozzles N while reducing power consumption.

[0041] Furthermore, in the image forming apparatus 1 according to the first embodiment, the moving unit 20 is configured to perform a vibration operation each time a first predetermined time (T1) has elapsed in a standby state. Furthermore, when the recording head 14 is operated (printing processing is started) after a second predetermined time (T2) has elapsed in a standby state, the moving unit 20 moves the head unit 12 to the maintenance position P2, and the maintenance unit 30 performs a maintenance operation on the recording head 14 of the head unit 12 positioned at the maintenance position P2. This configuration prevents the ink surface in the nozzles N from drying out by the vibration operation, thereby lengthening the interval (the second predetermined time (T2)) between maintenance operations by the maintenance unit 30. This increases the number of situations in which maintenance operations can be omitted, thereby improving user convenience (satisfaction).

[0042] [Second embodiment] In the image forming apparatus 1 described above, the head unit 12 (transport unit 15) and the maintenance unit 30 are arranged side by side in the left-right direction, and a horizontal transport system is adopted in which the paper M is transported in the left-right direction. Because such an image forming apparatus 1 is wide in the left-right direction, a large installation area is required, and there is a risk that the image forming apparatus 1 cannot be installed in a small office, etc. Therefore, in the image forming apparatus 2 according to the second embodiment, as shown in FIG. 7 , the head unit 12 (transport unit 15) and the maintenance unit 30 are arranged side by side in the vertical direction. More precisely, the head unit 12 (transport unit 15) and the maintenance unit 30 are tilted obliquely from below toward the upper right. The transport unit 15 transports the paper M in the vertical direction, and the recording head 14 ejects ink toward the paper M transported in the vertical direction. The moving unit 20 reciprocates the head unit 12 in the left-right direction (contact / separation direction).

[0043] The image forming apparatus 2 according to the second embodiment described above employs a vertical conveying method in which the paper M is conveyed generally in an up-down direction, and therefore the width in the left-right direction can be narrower than that of the image forming apparatus 1 which employs a horizontal conveying method, thereby enabling the installation area of the image forming apparatus 2 to be reduced.

[0044] In the image forming apparatuses 1 and 2 according to the first and second embodiments, the moving unit 20, the maintenance unit 30, etc. are controlled by the control unit 19 that performs overall control, but the present invention is not limited to this. For example, a dedicated control unit (not shown) may be provided that controls the moving unit 20, the maintenance unit 30, etc.

[0045] Furthermore, in the image forming apparatuses 1 and 2 according to the first and second embodiments, the head unit 12 includes four line heads 13, but this is not a limitation and the head unit 12 may include one or more line heads 13. Furthermore, although three recording heads 14 are mounted on one line head 13, this is not a limitation and the head unit 12 may include one or more recording heads 14. Furthermore, although the recording heads 14 are arranged in a staggered pattern on the head base 13A, this is not a limitation and the arrangement may be freely changed, for example, to arrange them in a line.

[0046] Furthermore, in the image forming apparatus 1 according to the first embodiment, the maintenance unit 30 is provided downstream of the head unit 12, and in the image forming apparatus 2 according to the second embodiment, the maintenance unit 30 is provided upstream of the head unit 12, but the present invention is not limited to this. The maintenance unit 30 may be located near the head unit 12 regardless of whether it is upstream or downstream in the transport direction of the paper M.

[0047] Furthermore, the image forming apparatuses 1 and 2 according to the first and second embodiments are color printers, but are not limited to this and may be monochrome printers, copy machines, facsimiles, or the like.

[0048] The above-described embodiment shows one aspect of the image forming apparatus according to the present invention, and the technical scope of the present invention is not limited to the above-described embodiment. The present invention may be variously changed, substituted, or modified without departing from the spirit of the technical concept, and the claims include all embodiments that may fall within the scope of the technical concept. [Explanation of symbols]

[0049] 1. Image forming device 12 Head Unit 14 Recording head 15 Conveying section 20 Moving Section 30 Maintenance Department M Paper (medium) N nozzle P2 maintenance position

Claims

1. a head unit including a recording head that ejects liquid from nozzles toward a medium; a transport unit that transports the medium at a position facing the head unit; a moving unit that moves the head unit back and forth along a separation direction in which the head unit moves away from the transport unit or approaches the transport unit, The image forming apparatus is characterized in that the moving section repeatedly moves the head unit back and forth along the separation direction, and performs a vibration operation that vibrates the surface of the liquid inside the nozzle.

2. a maintenance unit that performs a maintenance operation to maintain the recording head; the moving unit executes the vibration operation every time a first predetermined time elapses in a standby state in which the operation of the recording head is stopped, The image forming apparatus of claim 1, characterized in that when the recording head is operated after a second predetermined time longer than the first predetermined time has elapsed in the standby state, the moving unit moves the head unit to a maintenance position separated from the transport unit, and the maintenance unit performs the maintenance operation on the recording head of the head unit positioned at the maintenance position.

3. the transport unit transports the medium in a vertical direction; 3. The image forming apparatus according to claim 1, wherein the recording head ejects the liquid toward the medium that is transported in a vertical direction.

4. 3. The image forming apparatus according to claim 1, wherein the head unit includes a plurality of the recording heads arranged to cover a width of the medium perpendicular to the transport direction.

Images