Inkjet recording apparatus

Abstract

To improve ink removing performance while suppressing the consumption of a cleaning liquid.SOLUTION: An inkjet recording apparatus includes: an inkjet head 12; a cap 72 accommodating a part on a nozzle surface 14F side of the inkjet head 12; a cleaning liquid tank 13T that stores a cleaning liquid; a cleaning liquid pump 13P that supplies the cleaning liquid of an amount large enough for a nozzle surface 14 to be immersed, from the cleaning liquid tank 13T to the cap 72; a cleaning liquid discharge path 74 that discharges the cleaning liquid from the cap 72; a waste liquid tank 69 connected to the cleaning liquid discharge path 74; a three-way value 75 provided between the cap 72 and the waste liquid tank 69; and a branch path 76 that guides the cleaning liquid from the three-way value 75 to an intake port of the cleaning liquid pump 13P.SELECTED DRAWING: Figure 15

Description

Technical Field

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

Background Art

[0002] In an inkjet recording apparatus, it is conceivable that moisture evaporates from the ink in the nozzles of the inkjet head during a period when an image forming job is not being executed, and the nozzles become clogged due to an increase in the viscosity of the ink. Therefore, a purge process is performed to discharge the ink in the nozzles for the purpose of preventing clogging. However, if the ink remaining on the nozzle surface is left unattended, there are problems such as ink dropping onto the sheet during the execution of an image forming job or the ink sticking to the nozzle surface. Therefore, techniques for removing the ink remaining on the nozzle surface have been studied. For example, the configuration disclosed in Patent Document 1 immerses the nozzle surface in a cleaning liquid injected into a cleaning tank, drains the cleaning liquid, and sucks the inside of the cleaning tank. The configuration disclosed in Patent Document 2 forms a sealed space by covering the nozzle surface with a capping mechanism, introduces an atmosphere in which the humidity and temperature are adjusted into the sealed space to cause condensation on the nozzle surface, and wipes the nozzle surface with a wiping mechanism in a state where the deposits are swollen due to the condensation.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, the configuration disclosed in Patent Document 1 has a problem that the consumption amount of the cleaning liquid increases. The configuration disclosed in Patent Document 2 is considered to have inferior ink removal performance compared to the configuration in which the nozzle surface is immersed in the cleaning liquid.

[0005] In view of the above circumstances, an object of the present invention is to improve the ink removal performance while suppressing the consumption amount of the cleaning liquid.

Means for Solving the Problems

[0006] To solve the above problems, an inkjet recording apparatus according to the present invention includes an inkjet head, a cap that houses a portion on the nozzle surface side of the inkjet head, a cleaning liquid tank that stores a cleaning liquid, a cleaning liquid pump that supplies an amount of the cleaning liquid in which the nozzle surface is immersed from the cleaning liquid tank to the cap, a cleaning liquid discharge path that discharges the cleaning liquid from the cap, a waste liquid tank connected to the cleaning liquid discharge path, a three-way valve provided between the cap and the waste liquid tank, and a branch path that guides the cleaning liquid from the three-way valve to an inlet of the cleaning liquid pump.

[0007] The inkjet recording apparatus may include a sensor provided between the cap and the three-way valve that measures the degree of turbidity of the cleaning liquid discharged from the cap, and a control unit that switches the three-way valve according to the degree of turbidity measured by the sensor.

[0008] When the degree of turbidity measured by the sensor is equal to or greater than a reference value, the control unit may switch the three-way valve from the cleaning liquid pump side to the waste liquid tank side, and when the degree of turbidity measured by the sensor is less than the reference value, the control unit may switch the three-way valve from the waste liquid tank side to the cleaning liquid pump side.

[0009] The inkjet recording apparatus may include a cleaning liquid heating device that heats the cleaning liquid.

[0010] The cleaning liquid heating device may be provided in the cleaning liquid tank.

[0011] The inkjet recording apparatus includes a cleaning liquid supply path that guides the cleaning liquid from the cleaning liquid pump to the cap, and the cleaning liquid heating device may be provided in the cleaning liquid supply path.

[0012] The cleaning liquid heating device may be provided on the cap.

Advantages of the Invention

[0013] According to the present invention, it is possible to improve the ink removal performance while suppressing the consumption amount of the cleaning liquid.

Brief Description of the Drawings

[0014]

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

Figure 16

Figure 17

Figure 18

Mode for Carrying Out the Invention

[0015] Hereinafter, an inkjet recording apparatus 1 according to an embodiment of the present invention will be described with reference to the drawings.

[0016] First, the overall configuration of the inkjet recording apparatus 1 will be described. FIG. 1 is a front view schematically showing the internal configuration of the inkjet recording apparatus 1. FIG. 2 is a perspective view showing the arrangement of the inkjet head 12. FIG. 3 is a cross-sectional view showing the inkjet head 12. FIG. 4 is a diagram schematically showing the configuration of the ink supply unit 60. Hereinafter, the front side (front side) of the inkjet recording apparatus 1 is defined as the front side of the paper surface in FIG. 1, and the left and right directions will be described with reference to the direction when the inkjet recording apparatus 1 is viewed from the front. In each figure, U, Lo, L, R, Fr, and Rr indicate up, down, left, right, front, and rear, respectively.

[0017] The inkjet recording apparatus 1 (see FIG. 1) includes a rectangular parallelepiped main body housing 3. At the lower part inside the main body housing 3, there are provided a paper feed cassette 4 for accommodating single-sheet sheets S such as plain paper and coated paper, and a paper feed roller 5 for feeding the sheet S out to the right from the paper feed cassette 4. Above the paper feed cassette 4, there is provided a transport unit 7 for adsorbing the sheet S and transporting it in the Y direction. Above the transport unit 7, there is provided an image forming unit 6 for discharging ink to form an image. At the upper right part of the main body housing 3, there are provided a discharge roller 8 for discharging the sheet S on which an image is formed, and a discharge tray 9 on which the discharged sheet S is stacked.

[0018] Inside the main body housing 3, there is provided a transport path 10 that reaches the discharge roller 8 from the paper feed roller 5 through the gap between the transport unit 7 and the image forming unit 6. The transport path 10 is mainly formed by plate-like members facing each other with a gap for the sheet S to pass through, and transport rollers 17 for sandwiching and transporting the sheet S are provided at a plurality of locations in the transport direction Y. A registration roller 18 is provided on the upstream side in the transport direction Y from the image forming unit 6.

[0019] The transport unit 7 includes an endless transport belt 21, a support plate 23, and a suction unit 24. The transport belt 21 has a number of ventilation holes (not shown) and is wound around a drive roller 25 and a driven roller 22. The support plate 23 has a number of ventilation holes, and the upper surface is in contact with the inner surface of the transport belt 21. The suction unit 24 sucks air through the ventilation holes of the support plate 23 and the ventilation holes of the transport belt 21 to adsorb the sheet S to the transport belt 21. The drive roller 25 is driven in the counterclockwise direction by a drive unit (not shown) including a motor and a reduction gear, so that the transport belt 21 rotates in the counterclockwise direction, and the sheet S adsorbed to the transport belt 21 is transported in the Y direction.

[0020] The image forming unit 6 includes head units 11Y, 11Bk, 11C, and 11M (collectively referred to as the head unit 11). The head unit 11 includes one or more inkjet heads 12, for example, three inkjet heads 12 arranged in a staggered pattern (see FIG. 2). Ink containers 20Y, 20Bk, 20C, and 20M (collectively referred to as the ink container 20) filled with yellow, black, cyan, and magenta inks are connected to the head units 11Y, 11Bk, 11C, and 11M, respectively.

[0021] The inkjet head 12 (see FIG. 3) includes a rectangular parallelepiped housing 12H having a longitudinal direction in the front-rear direction, a nozzle plate 14 provided at the bottom of the housing 12H, and a socket 12S to which a pipe for supplying ink is connected. The nozzle plate 14 includes a large number of nozzles 14N arranged in the front-rear direction. The nozzle 14N includes a branch flow path 14B branched from the downstream side of the socket 12S and a discharge port 14A provided on the nozzle surface 14F which is the lower surface of the nozzle plate 14. The diaphragm 14V also serves as a part of the inner wall of the branch flow path 14B. A pressurizing element 14Z is provided on the diaphragm 14V. As the pressurizing element 14Z, a piezoelectric element, an electrostatic actuator, a heater, or the like is used. A drive circuit 12D for driving the pressurizing element 14Z is connected to the pressurizing element 14Z.

[0022] The inkjet recording apparatus 1 includes an ink supply unit 60 (see FIG. 4). In the figure, an ink supply unit 60 corresponding to one color of ink is shown, but in the present embodiment, since four colors of ink are used, four similar ink supply units 60 are provided. The ink supply unit 60 includes a container mounting portion 61 on which the ink container 20 is mounted, a filter 62 for filtering the ink, a pump 63 for sucking the ink from the ink container 20 through the filter 62, and a sub-tank 64 for storing the ink sent out from the pump 63.

[0023] The liquid level in the sub-tank 64 is adjusted to be slightly lower than the nozzle surface 14F. Due to the head difference between the liquid level and the nozzle surface 14F, a negative pressure acts on the ink in the nozzle 14N, and a meniscus is formed in the nozzle 14N. After the ink is ejected from the inkjet head 12, the surface tension of the ink acts to reduce the surface area of the meniscus, and due to the resulting negative pressure, the reduced amount of ink is drawn from the sub-tank 64 into the inkjet head 12.

[0024] The control unit 2 (see FIG. 1) includes an arithmetic unit and a storage unit (not shown). The arithmetic unit is, for example, a CPU (Central Processing Unit). The storage unit includes storage media such as a ROM (Read Only Memory), a RAM (Random Access Memory), and an EEPROM (Electrically Erasable Programmable Read Only Memory). The arithmetic unit performs various processes by reading and executing the control programs stored in the storage unit. Note that the control unit 2 may be realized by an integrated circuit that does not use software.

[0025] On the upper part of the main body housing 3, a display operation unit 19 is provided (see FIG. 1). The display operation unit 19 includes a display panel, a touch panel laminated on the display panel, and a keypad (not shown). The control unit 2 causes the display panel to display a screen representing the operation menu, status, etc. of the inkjet recording apparatus 1, and controls each part of the inkjet recording apparatus 1 according to the operations detected by the touch panel and the keypad.

[0026] The basic image forming operation of the inkjet recording apparatus 1 is as follows. When an image forming job is input to the inkjet recording apparatus 1 from the display operation unit 19 or an external computer or the like, the paper feed roller 5 feeds the sheet S from the paper feed cassette 4 to the conveyance path 10, and the registration roller 18 whose rotation has been stopped corrects the skew of the sheet S. When the registration roller 18 feeds the sheet S to the conveyance unit 7 at a predetermined timing, the conveyance unit 7 sucks the sheet S onto the conveyance belt 21 and conveys it in the Y direction. The drive circuit 12D supplies a discharge signal corresponding to the image data to the pressure element 14Z in synchronization with the conveyance of the sheet S. Thus, ink is discharged from the nozzles 14N, and an image is formed on the sheet S. The discharge roller 8 discharges the sheet S on which the image has been formed to the discharge tray 9.

[0027] [Maintenance Device] FIG. 5 is a block diagram showing the electrical configuration of the maintenance device 30. FIGS. 6 to 11 are perspective views showing the maintenance device 30. FIG. 12 is a perspective view showing the cap device 31. FIG. 13 is a perspective view showing the removal device 32. FIG. 14 is a perspective view showing the cap 72. The maintenance device 30 includes a cap device 31, a removal device 32, a frame 33, a carriage 34, a lifting device 35, and a slide device 36.

[0028] [Frame, Carriage] The frame 33 (see FIG. 8) is fixed to the main body housing 3 and supports the carriage 34 and the conveyance unit 7. The carriage 34 supports the cap device 31 and the removal device 32. The cap device 31 includes a cap 72. The removal device 32 includes a blade 82.

[0029] [Removal Device] The removal device 32 (see FIG. 13) includes a waste liquid tray 81 and a blade unit 84 that slides with respect to the waste liquid tray 81.

[0030] [Waste Liquid Tray] The waste liquid tray 81 is supported by the carriage 34. The waste liquid tray 81 includes a rectangular bottom 81B as viewed from above, and a pair of rails 81R provided in parallel to the left and right edges of the bottom 81B. The upper surface of the bottom 81B is inclined so as to be lower from both front and rear ends toward the center. A discharge port (not shown) for discharging waste liquid containing ink and cleaning liquid is provided at the center of the bottom 81B. A suction pump 68 and a waste liquid tank 69 are connected to the discharge port via a pipe (see FIG. 4).

[0031] [Blade Unit] The blade unit 84 includes a blade 82 and a support plate 83 that supports the blade 82. The blade 82 is a flexible plate-like member formed of rubber or the like. A plurality (12 in this embodiment) of blades 82 are arranged in the same positional relationship as the inkjet head 12. The support plate 83 includes a bottom 83B and upright side wall portions 83S provided at both left and right ends of the bottom 83B. Wheels 83W supported by an axis with the left-right direction as the axial direction are provided near both front and rear ends of the left and right side wall portions 83S. The wheels 83W are placed on the rails 81R and roll along the rails 81R. The removing device 32 is provided with a driving device 85 (see FIG. 5) for sliding the blade unit 84 in the front-rear direction. The driving device 85 is composed of, for example, a ball screw, a belt driving device, a rack and pinion, or the like.

[0032] [Cap Device] The cap device 31 (see FIG. 12) includes a cap 72 and a support plate 71 that supports the cap 72. Caps 72 corresponding to each of the inkjet heads 12 are arranged in a staggered manner on the upper surface of the support plate 71. The cap device 31 is arranged above the removing device 32. The support plate 71 is supported by the carriage 34.

[0033] [Cap] The cap 72 (see FIGS. 14 and 15) has a concave shape with an opening on the inkjet head 12 side. The cap 72 is formed of resin. The cap 72 includes a bottom portion 72B and an annular side wall portion 72S provided on the upper surface of the bottom portion 72B. The side wall portion 72S includes a pair of linear portions that face each other in the left-right direction with the front-rear direction as the longitudinal direction, and a pair of arcuate portions that connect the front end portions and the rear end portions of the pair of linear portions, respectively. The cap 72 is attached to the support plate 71 via a compression spring (not shown).

[0034] [Lifting device] The conveyance unit 7 is supported by the frame 33 via a lifting device 35 (see FIG. 5). The lifting device 35 is composed of, for example, a ball screw, a belt drive device, etc. The lifting device 35 raises and lowers the conveyance unit 7 between an image forming position (see FIG. 6) when performing image formation and a lower retracted position (see FIG. 7) below the image forming position. When moving the conveyance unit 7 to the image forming position, the conveyance unit 7 is positioned so that the distance between the conveyance belt 21 and the nozzle surface 14F becomes a distance suitable for image formation. When moving the conveyance unit 7 to the lower retracted position, a space is formed that allows the cap device 31 and the removal device 32 to move between the upper surface of the conveyance belt 21 and the nozzle surface 14F.

[0035] [Slide device] The carriage 34 is supported by the frame 33 via a slide device 36 (see FIG. 5). The slide device 36 is composed of, for example, a ball screw, a belt drive device, a rack and pinion, etc. The slide device 36 slides the carriage 34 between a lateral retracted position (a position not facing the image forming unit 6 and the conveyance unit 7) and a facing position (a position facing the image forming unit 6 and the conveyance unit 7).

[0036] The removing device 32 is supported by the carriage 34 and is slidable in the left - right direction together with the carriage 34. The cap device 31 is also supported by the carriage 34, but the cap device 31 is slidable in the left - right direction with respect to the carriage 34. With this configuration, there are two movement forms: a movement form (see Fig. 8) in which the cap device 31 and the removing device 32 are moved to the opposing positions by the carriage 34, and a movement form (see Fig. 10) in which only the removing device 32 is moved to the opposing position by the carriage 34 while the cap device 31 remains at the side - retracted position.

[0037] In the opposing position, the cap device 31 and the removing device 32 can be moved up and down using the conveyance unit 7. When the cap device 31 and the removing device 32 are in the opposing position (see Fig. 8), the elevating device 35 moves the cap device 31 up and down between the opposing position and the cap position (see Fig. 9). The cap position is the position where the cap 72 contacts the nozzle surface 14F. On the other hand, when only the removing device 32 is in the opposing position (see Fig. 10), the elevating device 35 moves the removing device 32 up and down between the opposing position and the wipe position (see Fig. 11). The wipe position is the position where the upper end of the blade 82 contacts the nozzle surface 14F.

[0038] Figs. 15 and 16 are cross - sectional views schematically showing the configuration for supplying the cleaning liquid to the cap 72. The inkjet recording apparatus 1 includes an inkjet head 12, a cap 72 that houses a portion on the nozzle surface 14F side of the inkjet head 12, a cleaning liquid tank 13T that stores the cleaning liquid, a cleaning liquid pump 13P that supplies an amount of cleaning liquid in which the nozzle surface 14F is immersed from the cleaning liquid tank 13T to the cap 72, a cleaning liquid discharge path 74 that discharges the cleaning liquid from the cap 72, a waste liquid tank 69 connected to the cleaning liquid discharge path 74, a three - way valve 75 provided between the cap 72 and the waste liquid tank 69, and a branch path 76 that guides the cleaning liquid from the three - way valve 75 to the inlet of the cleaning liquid pump 13P. Specifically, it is as follows.

[0039] [Inkjet head] The nozzle plate 14 (see FIGS. 3, 7, and 14) provided in the inkjet head 12 is formed in an overall elongated rectangular parallelepiped shape in the front-rear direction. However, at the front end portion and the rear end portion of the nozzle plate 14, protruding portions 14P protruding forward and rearward are provided, respectively. The lower surface of the protruding portion 14P is at a position higher than the nozzle surface 14F.

[0040] [Cap] The cap 72 houses the portion on the nozzle surface 14F side of the inkjet head 12. Specifically, the portion on the nozzle surface 14F side of the inkjet head 12 is, among the nozzle plate 14, the portion below the protruding portion 14P including the nozzle surface 14F. Hereinafter, this portion is referred to as the lower part 14G of the nozzle plate.

[0041] The length of the internal space of the cap 72 in the front-rear direction is longer than the length of the lower part 14G of the nozzle plate in the front-rear direction. The width of the internal space of the cap 72 in the left-right direction is wider than the width of the lower part 14G of the nozzle plate in the left-right direction. When the lower part 14G of the nozzle plate is housed in the cap 72, the upper edge portion of the side wall portion 72S of the cap 72 contacts the lower surface of the protruding portion 14P. Further, when the lower part 14G of the nozzle plate is housed in the cap 72, a gap through which the cleaning liquid can penetrate is formed between the nozzle surface 14F and the bottom portion 72B of the cap 72.

[0042] A cleaning liquid supply port 72N penetrating in the front-rear direction is provided at the rear portion of the side wall portion 72S of the cap 72. The cleaning liquid supply port 72N is provided on the bottom portion 72B side of the side wall portion 72S in the up-down direction. A cleaning liquid discharge port 72E penetrating in the front-rear direction is provided at the front portion of the side wall portion 72S of the cap 72. The cleaning liquid discharge port 72E is provided at a position higher than the cleaning liquid supply port 72N in the up-down direction.

[0043] [Cleaning Liquid Supply Device] The cleaning liquid supply device 13 includes a cleaning liquid tank 13T that stores the cleaning liquid and a cleaning liquid pump 13P that sends out the cleaning liquid from the cleaning liquid tank 13T. The cleaning liquid pump 13P is connected to the cleaning liquid supply port 72N of the cap 72 via a cleaning liquid supply path 13C.

[0044] [Cleaning liquid discharge path] One end of the cleaning liquid discharge path 74 is connected to the cleaning liquid discharge port 72E of the cap 72, and the other end of the cleaning liquid discharge path 74 is connected to the waste liquid tank 69.

[0045] [Three-way valve, branch path] A three-way valve 75 is provided in the cleaning liquid discharge path 74 between the cap 72 and the waste liquid tank 69. One end of a branch path 76 is connected to the three-way valve 75. The other end of the branch path 76 is connected to the intake port (not shown) of the cleaning liquid pump 13P. The three-way valve 75 is switchable between a discharge mode and a circulation mode. In the discharge mode (see FIG. 15), the three-way valve 75 communicates the cap 72 and the waste liquid tank 69 and closes the branch path 76. In the circulation mode (see FIG. 16), the three-way valve 75 communicates the cap 72 and the cleaning liquid pump 13P via the branch path 76 and closes the cleaning liquid discharge path 74 on the waste liquid tank 69 side. The three-way valve 75 is provided with a drive source (not shown) for driving the valve body. By driving the drive source by the control unit 2, the three-way valve 75 is switched between the discharge mode and the circulation mode.

[0046] [Sensor] A sensor 77 is provided in the cleaning liquid discharge path 74 between the cap 72 and the three-way valve 75. The sensor 77 measures the degree of turbidity of the cleaning liquid discharged from the cap 72. The sensor 77 includes, for example, a light emitting element, a light receiving element, and an RGB (Red, Green, Blue) color filter, and measures the degree of turbidity of the cleaning liquid from the intensity of the light transmitted through the cleaning liquid passing through the cleaning liquid discharge path 74. The control unit 2 switches the three-way valve 75 according to the degree of turbidity measured by the sensor 77. For example, when the degree of turbidity is equal to or higher than a reference value, the control unit 2 switches the three-way valve 75 from the cleaning liquid pump 13P side to the waste liquid tank 69 side (see FIG. 15), and when the degree of turbidity is less than the reference value, the control unit 2 switches the three-way valve 75 from the waste liquid tank 69 side to the cleaning liquid pump 13P side (see FIG. 16).

[0047] [Cleaning liquid heating device] The cleaning liquid heating device 13A is provided in the cleaning liquid tank 13T. The cleaning liquid heating device 13A heats the cleaning liquid to a temperature equal to or higher than the temperature of the inkjet head 12 and equal to or lower than 60 degrees Celsius. For example, a sensor (not shown) for detecting the temperature of the cleaning liquid tank 13T is provided. The control unit 2 controls the power of the cleaning liquid heating device 13A so that the temperature of the cleaning liquid tank 13T is equal to or higher than the temperature of the inkjet head 12 and equal to or lower than 60 degrees Celsius.

[0048] Next, the operation of the maintenance device 30 will be described. The following operations are executed by the control unit 2 controlling each part of the maintenance device 30.

[0049] When executing an image forming job (see FIG. 6), the removing device 32 is arranged at the side retracted position, and the conveying unit 7 is arranged at the image forming position.

[0050] The penetration process, the purge process, and the wipe process are executed at a predetermined timing. The predetermined timing is, for example, when a predetermined time has elapsed after the image forming job is completed. When the predetermined timing arrives, the control unit 2 moves the conveying unit 7 from the image forming position to the lower retracted position by the lifting device 35 (see FIG. 7), and moves the carriage 34 from the side retracted position to the opposing position by the slide device 36 (see FIG. 8).

[0051] Next, the control unit 2 raises the cap device 31 to the cap position by raising the conveying unit 7 by the lifting device 35, and houses the lower part 14G of the nozzle plate in the cap 72 (see FIGS. 9 and 15). Subsequently, the control unit 2 supplies the cleaning liquid to the cap 72 by the cleaning liquid supply device 13 and waits for a predetermined time (penetration process).

[0052] In the penetration treatment, first, the control unit 2 switches the three-way valve 75 to the circulation mode and drives the cleaning liquid pump 13P for a predetermined time. Then, the cleaning liquid is supplied from the cleaning liquid tank 13T to the cap 72, and the liquid level rises. When the liquid level reaches the cleaning liquid discharge port 72E, the cleaning liquid flows into the branch path 76 through the cleaning liquid discharge path 74 and the three-way valve 75. When the predetermined time has elapsed, the branch path 76 is filled with the cleaning liquid, and the cleaning liquid circulates along the circulation flow path from the cleaning liquid pump 13P through the cap 72, the cleaning liquid discharge path 74, the three-way valve 75, and the branch path 76 back to the cleaning liquid pump 13P. Since the cleaning liquid penetrates into the highly viscous ink remaining on the nozzle surface 14F by the circulation of the cleaning liquid, the ink removal performance is improved. Also, since the cleaning liquid is circulated and used, the consumption of the cleaning liquid is suppressed.

[0053] However, in this configuration, since a part of the ink dissolves in the cleaning liquid, turbidity occurs in the cleaning liquid. As the time for continuing the circulation of the cleaning liquid becomes longer, the turbidity of the cleaning liquid becomes stronger, and it becomes difficult for the cleaning liquid to penetrate into the ink remaining on the nozzle surface 14F.

[0054] Therefore, in this embodiment, during the execution of the penetration treatment, the control unit 2 measures the degree of turbidity of the cleaning liquid using the sensor 77. When the degree of turbidity is equal to or higher than the reference value, the control unit 2 switches the three-way valve 75 to the waste liquid tank 69 side (discharge mode). Then, since the cleaning liquid flows along the one-way flow path from the cleaning liquid tank 13T through the cleaning liquid pump 13P, the cap 72, the cleaning liquid discharge path 74, and the three-way valve 75 to the waste liquid tank 69, the turbid cleaning liquid in the cap 72 is discharged to the waste liquid tank 69, and at the same time, unused cleaning liquid is supplied from the cleaning liquid tank 13T to the cap 72.

[0055] After that, when the degree of turbidity becomes less than the reference value, the control unit 2 switches the three-way valve 75 to the cleaning liquid pump 13P side (circulation mode). Then, the cleaning liquid circulates again along the circulation flow path.

[0056] By the above penetration treatment, the cleaning liquid penetrates into the ink remaining on the nozzle surface 14F and the ink in the nozzle 14N, and the ink with increased viscosity softens.

[0057] When the impregnation process is completed, the control unit 2 increases the pressure in the nozzles 14N of the inkjet head 12 to eject the ink (purge process). Next, the control unit 2 lowers the cap device 31 from the cap position to the opposing position (see FIG. 8), slides only the cap device 31 to the side retracted position (see FIG. 10), and then raises the removal device 32 to the wipe position (see FIG. 11).

[0058] Next, the control unit 2 slides the blade unit 84 forward by the drive device 85 (wipe process). Then, the blade 82 is pressed against the nozzle surface 14F and advances while flexing, scraping off the ink and cleaning liquid adhering to the nozzle surface 14F. The scraped ink is diluted by the cleaning liquid and drops into the waste liquid tray 81.

[0059] Next, the control unit 2 lowers the removal device 32 from the wipe position to the opposing position (see FIG. 10), slides the cap device 31 from the side retracted position to the opposing position (see FIG. 8), raises the cap device 31 from the opposing position to the cap position (see FIG. 9), and waits until an image forming job is input. By this procedure, the lower part 14G of the nozzle plate is accommodated in the cap 72, so that an increase in the viscosity of the ink in the nozzles 14N is suppressed.

[0060] When an image forming job is input, the control unit 2 lowers the cap device 31 from the cap position to the opposing position by the elevating device 35 (see FIG. 8), then slides the carriage 34 to the side standby position by the slide device 36 (see FIG. 7), and then raises the transport unit 7 to the image forming position by the elevating device 35 (see FIG. 6), and then executes the image forming job.

[0061] According to the inkjet recording apparatus 1 according to the present embodiment described above, an inkjet head 12, a cap 72 that houses a portion on the nozzle surface 14F side of the inkjet head 12, a cleaning liquid tank 13T that stores a cleaning liquid, a cleaning liquid pump 13P that supplies the amount of the cleaning liquid in which the nozzle surface 14F is immersed from the cleaning liquid tank 13T to the cap 72, a cleaning liquid discharge path 74 that discharges the cleaning liquid from the cap 72, a waste liquid tank 69 connected to the cleaning liquid discharge path 74, a three-way valve 75 provided between the cap 72 and the waste liquid tank 69, and a branch path 76 that guides the cleaning liquid from the three-way valve 75 to the inlet of the cleaning liquid pump 13P are provided. According to this configuration, since the cleaning liquid penetrates into the highly viscous ink remaining on the nozzle surface 14F by the circulation of the cleaning liquid, it is possible to improve the ink removal performance while suppressing the consumption amount of the cleaning liquid.

[0062] Further, according to the inkjet recording apparatus 1 according to the present embodiment, a sensor 77 that is provided between the cap 72 and the three-way valve 75 and measures the degree of turbidity of the cleaning liquid discharged from the cap 72, and a control unit 2 that switches the three-way valve 75 according to the degree of turbidity measured by the sensor 77 are provided. According to this configuration, the switching of the three-way valve 75 can be automated.

[0063] Further, according to the inkjet recording apparatus 1 according to the present embodiment, when the degree of turbidity measured by the sensor 77 is equal to or higher than a reference value, the control unit 2 switches the three-way valve 75 from the cleaning liquid pump 13P side to the waste liquid tank 69 side, and when the degree of turbidity measured by the sensor 77 is less than the reference value, the control unit 2 switches the three-way valve 75 from the waste liquid tank 69 side to the cleaning liquid pump 13P side. According to this configuration, the three-way valve 75 can be switched with a simple control procedure.

[0064] Further, according to the inkjet recording apparatus 1 according to the present embodiment, a cleaning liquid heating device 13A that heats the cleaning liquid is provided. According to this configuration, since the ink is more likely to soften by heating the cleaning liquid, the ink removal performance can be improved.

[0065] Further, according to the inkjet recording apparatus 1 according to the present embodiment, the cleaning liquid heating device 13A is provided in the cleaning liquid tank 13T. According to this configuration, the configuration of the cap 72 can be simplified as compared with the case where the cleaning liquid heating device 13A is provided in the cap 72.

[0066] The above embodiment may be modified as follows.

[0067] [First Modification Example] FIG. 17 is a cross-sectional view schematically showing a configuration for supplying a cleaning liquid to the cap 72 (discharge mode). The inkjet recording apparatus 1 includes a cleaning liquid supply path 13C that guides the cleaning liquid from the cleaning liquid pump 13P to the cap 72, and the cleaning liquid heating device 13A is provided in the cleaning liquid supply path 13C. According to this configuration, the configuration of the cap 72 can be simplified as compared with the case where the cleaning liquid heating device 13A is provided in the cap 72.

[0068] [Second Modification Example] FIG. 18 is a cross-sectional view schematically showing a configuration for supplying a cleaning liquid to the cap 72 (discharge mode). The cleaning liquid heating device 13A is provided in the cap 72. According to this configuration, a decrease in the temperature of the cleaning liquid can be suppressed as compared with the case where the cleaning liquid heating device 13A is provided on the upstream side of the cap 72 (for example, the cleaning liquid supply path 13C and the cleaning liquid tank 13T).

[0069] In the above embodiment and modification examples, an example is shown in which the cap device 31 and the removing device 32 are slid in a space formed by lowering the transport unit 7, but the cap device 31 and the removing device 32 may be configured to be slid in a space formed by raising the image forming unit 6.

Explanation of Reference Numerals

[0070] 1 Inkjet recording apparatus 2 Control unit 12 Inkjet head 13A Cleaning liquid heating device 13C Cleaning liquid supply path 13P Cleaning liquid pump 13T cleaning liquid tank 14F nozzle surface 69 waste liquid tank 72 cap 74 cleaning liquid discharge path 75 three-way valve 76 branch path 77 sensor

Claims

1. An inkjet head, A cap that houses a portion on the nozzle surface side of the inkjet head, A cleaning liquid tank for storing a cleaning liquid, A cleaning liquid pump that supplies a cleaning liquid in an amount that the nozzle surface is immersed in from the cleaning liquid tank to the cap, A cleaning liquid discharge path for discharging the cleaning liquid from the cap, A waste liquid tank connected to the cleaning liquid discharge path, A three-way valve provided between the cap and the waste liquid tank, And a branch path that guides the cleaning liquid from the three-way valve to the inlet of the cleaning liquid pump, and an inkjet recording apparatus characterized by comprising the same.

2. A sensor provided between the cap and the three-way valve and measuring the degree of turbidity of the cleaning liquid discharged from the cap, And a control unit that switches the three-way valve according to the degree of turbidity measured by the sensor, and an inkjet recording apparatus according to claim 1, characterized by comprising the same.

3. When the degree of turbidity measured by the sensor is equal to or higher than a reference value, the control unit switches the three-way valve from the cleaning liquid pump side to the waste liquid tank side, When the degree of turbidity measured by the sensor is less than the reference value, the inkjet recording apparatus according to claim 2, characterized in that the three-way valve is switched from the waste liquid tank side to the cleaning liquid pump side.

4. An inkjet recording apparatus according to any one of claims 1 to 3, characterized by comprising a cleaning liquid heating device that heats the cleaning liquid.

5. The inkjet recording apparatus according to claim 4, characterized in that the cleaning liquid heating device is provided in the cleaning liquid tank.

6. A cleaning liquid supply path that guides the cleaning liquid from the cleaning liquid pump to the cap, The inkjet recording apparatus according to claim 4, wherein the cleaning liquid heating device is provided in the cleaning liquid supply path.

7. The inkjet recording apparatus according to claim 4, wherein the cleaning liquid heating device is provided in the cap.

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