JP7459518B2 - Recording liquid supply device and image forming device - Google Patents

Description

The present invention relates to a recording liquid supply device and an image forming apparatus.

Conventionally, there is known an inkjet image forming device that forms (records) an image on a recording medium by ejecting recording liquid (ink) from multiple nozzles provided in an inkjet head onto the recording medium transported by a transport device.

As a recording liquid used in such an inkjet image forming apparatus, a pigment-based aqueous ink containing an insoluble or slightly soluble pigment is generally used. Furthermore, in recent years, white ink containing titanium dioxide or the like as a pigment has been used for the purpose of recording on transparent recording media. Also used is a gel ink that contains a gelling agent, changes its phase to a gel or sol depending on the temperature, and has the property of being cured by irradiation with energy rays such as ultraviolet rays.

However, these recording liquids have the problem that the pigments contained in the recording liquid settle over time when left for long periods without flow. Settling of the pigments can lead to reduced image quality, such as uneven density in the image formed on the recording medium, and can also cause problems with the inkjet image forming device due to clogging of the recording liquid flow passages, which are the supply paths for the recording liquid, and the nozzle ejection openings. Settling of the pigments in the recording liquid flow passages, which are in the form of tubes or capillaries, can be particularly problematic because it is difficult to take measures to prevent this spatially.

To solve the above problem, the flow velocity of the plug-shaped air introduced into the recording liquid flow path (liquid supply path) can be instantaneously increased by opening and closing the head supply valve at a predetermined timing while operating the liquid pump. A technique has been proposed in which sediment is removed from a recording liquid flow path by generating turbulence in the flow of recording liquid (for example, see Patent Document 1).

JP 2017-52099 Publication

However, in the technique described in Patent Document 1, although turbulence is generated in the flow of the recording liquid in the recording liquid flow path, there is a possibility that the sediment in the recording liquid flow path cannot be sufficiently removed. be. Therefore, there is a need for a technique that prevents sediment from being generated in the recording liquid flow path in the first place.

An object of the present invention is to provide a recording liquid supply device and an image forming apparatus that can prevent sediment from being generated in a recording liquid flow path.

The recording liquid supplying device according to the present invention comprises:
A main tank for storing recording liquid;
an inkjet head that ejects the recording liquid supplied from the main tank onto a recording medium;
a recording liquid flow passage through which the recording liquid flows between the main tank and the inkjet head;
a recording liquid draining unit for controlling drainage of the recording liquid in the recording liquid flow passage;
a sub-tank for storing the recording liquid supplied from the main tank,
the inkjet head ejects the recording liquid supplied from the subtank onto the recording medium;
A height difference is provided between the main tank and the sub-tank so that the recording liquid in the recording liquid flow path between the main tank and the sub-tank flows to the main tank side by gravity.
Another recording liquid supplying device according to the present invention is
A main tank for storing recording liquid;
an inkjet head that ejects the recording liquid supplied from the main tank onto a recording medium;
a recording liquid flow passage through which the recording liquid flows between the main tank and the inkjet head;
a recording liquid draining section for controlling drainage of the recording liquid in the recording liquid flow passage;
a sub-tank for storing the recording liquid supplied from the main tank,
the inkjet head ejects the recording liquid supplied from the subtank onto the recording medium;
a supply pump that pumps out the recording liquid stored in the main tank under the control of the recording liquid draining unit so that the recording liquid in the recording liquid flow path between the main tank and the sub tank flows to the sub tank side;
a branch flow passage that branches off from the recording liquid flow passage between the supply pump and the sub-tank and is connected to the main tank;
The recording liquid ejection section further includes an adjustment section that adjusts the flow rate of the recording liquid flowing through the branch flow passage under the control of the recording liquid draining section.

An image forming apparatus according to the present invention includes the recording liquid supply device described above.

The present invention makes it possible to prevent sediment from occurring within the recording liquid flow path.

FIG. 1 is a diagram illustrating a schematic configuration of an inkjet image forming apparatus. FIG. 3 is a schematic diagram showing the configuration of a head unit. FIG. 3 is a diagram showing the configuration of an ink supply mechanism that supplies ink to an inkjet head. 1 is a block diagram showing a main functional configuration of an inkjet image forming apparatus; FIG. 7 is a diagram showing a modification of the configuration of an ink supply mechanism that supplies ink to an inkjet head.

The present embodiment will be described below with reference to the drawings.

Figure 1 is a diagram showing the schematic configuration of an inkjet image forming apparatus 1. The inkjet image forming apparatus 1 includes a paper feed section 10, an image forming section 20, a paper discharge section 30, and a control section 40 (see Figure 4). The control section 40 functions as the "recording liquid removal section" of the present invention.

The inkjet image forming device 1 (functioning as the "image forming device" of the present invention) conveys the recording medium P stored in the paper feed section 10 to the image forming section 20 under the control of the control section 40, forms an image on the recording medium P in the image forming section 20, and conveys the recording medium P on which the image has been formed to the paper discharge section 30. As the recording medium P, various media capable of fixing the ink that has landed on the surface, such as paper such as plain paper or coated paper, fabric or sheet-like resin, can be used.

The paper feed unit 10 has a paper feed tray 11 that stores the recording medium P, and a media supply unit 12 that transports and supplies the recording medium P from the paper feed tray 11 to the image forming unit 20. The media supply unit 12 has a ring-shaped belt supported by two rollers on the inside, and transports the recording medium P from the paper feed tray 11 to the image forming unit 20 by rotating the rollers with the recording medium P placed on this belt.

The image forming unit 20 includes a conveying unit 21, a transfer unit 22, a heating unit 23, a head unit 24, a fixing unit 25, and a delivery unit 28.

The transport unit 21 holds the recording medium P placed on the transport surface 211a (mounting surface) of the cylindrical transport drum 211, and performs a transport operation to transport the recording medium P on the transport drum 211 in the transport direction (Y direction) by rotating and moving the transport drum 211 around a rotation axis (cylindrical axis) that extends in the X direction (perpendicular to the paper surface of Figure 1).

The transport drum 211 includes a claw portion (not shown) and a suction portion (not shown) for holding the recording medium P on its transport surface 211a. The recording medium P is held on the conveyance surface 211a by having its ends pressed by the claws and being attracted to the conveyance surface 211a by the suction section. The conveyance unit 21 is connected to a conveyance drum motor (not shown) for rotating the conveyance drum 211. The conveyance drum 211 rotates by an angle proportional to the amount of rotation of the conveyance drum motor.

The delivery unit 22 delivers the recording medium P transported by the medium supply section 12 of the paper feed section 10 to the transport section 21 . The delivery unit 22 is provided at a position between the medium supply section 12 and the conveyance section 21 of the paper supply section 10, and picks up one end of the recording medium P conveyed from the medium supply section 12 by holding it with a swing arm section 221. , and delivered to the transport section 21 via the delivery drum 222.

The heating section 23 is provided between the arrangement position of the delivery drum 222 and the arrangement position of the head unit 24, and heats the recording medium P transported by the transport section 21 so that the temperature falls within a predetermined temperature range. Heat P. The heating unit 23 includes, for example, an infrared heater, and generates heat by applying current to the infrared heater based on a control signal supplied from the control unit 40 (see FIG. 4).

The head unit 24 ejects ink (corresponding to the "recording liquid" of the present invention) onto the recording medium P from nozzle openings provided on the ink ejection surface facing the transport surface 211a of the transport drum 211 at appropriate timing according to the rotation of the transport drum 211 holding the recording medium P, thereby forming an image. The head unit 24 is positioned so that the ink ejection surface and the transport surface 211a are separated by a predetermined distance.

In the inkjet image forming device 1 of this embodiment, four head units 24 corresponding to the four colors of ink, yellow (Y), magenta (M), cyan (C), and black (K), are arranged at predetermined intervals from the upstream side in the transport direction of the recording medium P in the order of Y, M, C, and K.

FIG. 2 is a schematic diagram showing the configuration of the head unit 24. As shown in FIG. Here, the surface of the head unit 24 that faces the transport surface 211a of the transport drum 211 is shown.

The head unit 24 has four inkjet heads 242 attached to a mounting member 244. Each inkjet head 242 is provided with a plurality of image forming elements (recording elements), each of which has a pressure chamber for storing ink, a piezoelectric element provided on the wall of the pressure chamber, and a nozzle 243. When a drive signal is input to deform the piezoelectric element, the image forming element deforms the pressure chamber due to the deformation of the piezoelectric element, changing the pressure within the pressure chamber, and ejects ink from a nozzle communicating with the pressure chamber.

The inkjet head 242 has two nozzle rows formed of nozzles 243 arranged at equal intervals in a direction intersecting the conveying direction of the recording medium P (in this embodiment, a direction perpendicular to the conveying direction, that is, the X direction). has been done. These two nozzle rows are provided such that the positions of the nozzles 243 are shifted from each other in the X direction by one half of the arrangement interval of the nozzles 243 in each nozzle row.

The four inkjet heads 242 are arranged in a houndstooth pattern so that the arrangement range of the nozzle rows in the X direction is seamlessly connected. The arrangement range in the X direction of the nozzles 243 included in the head unit 24 covers the width in the X direction of the area on which an image is formed of the recording medium P transported by the transport section 21. The position is fixed with respect to the rotation axis of the transport drum 211 during image formation. That is, the head unit 24 has a line head capable of ejecting ink over a width in which an image can be formed in the X direction on the recording medium P, and the inkjet image forming apparatus 1 is a single-pass type inkjet image forming apparatus. It is.

Note that the number of nozzle rows that the inkjet head 242 has may be one or three or more instead of two. Further, the number of inkjet heads 242 that the head unit 24 has may not be four, but may be three or less or five or more.

The ink ejected from the nozzle 243 of the image forming element is an ink containing a pigment, for example, a white ink containing titanium dioxide or the like as a pigment. The ink ejected from the nozzle 243 of the image forming element is a gel ink that contains a gelling agent, changes phase to a gel or sol state depending on the temperature, and hardens when exposed to energy rays such as ultraviolet light. In this embodiment, gel ink is used as the ink ejected from the nozzle 243 of the image forming element.

The head unit 24 includes an ink heating section (not shown) that heats ink stored within the head unit 24. The ink heating section operates under the control of the control section 40 and heats the ink to a temperature at which it becomes a sol.

The inkjet head 242 ejects ink that is heated and becomes a sol. When this sol-like ink is ejected onto the recording medium P, the ink droplets land on the recording medium P and are naturally cooled, so that the ink quickly becomes a gel and solidifies on the recording medium P.

The fixing unit 25 has a light emitting unit arranged across the width of the transport unit 21 in the X direction, and irradiates the recording medium P placed on the transport unit 21 with energy rays such as ultraviolet rays from the light emitting unit. The ink (gel ink) discharged onto the recording medium P is cured and fixed. The light emitting section of the fixing section 25 is arranged to face the transport surface 211a between the position of the head unit 24 and the position of the transfer drum 281 of the delivery section 28 in the transport direction.

The delivery unit 28 has a cylindrical transfer drum 281 that transfers the recording medium P from the transport unit 21 to the belt loop 282, and a belt loop 282 with a circular belt supported on the inside by two rollers. The recording medium P transferred from the transport unit 21 onto the belt loop 282 by the transfer drum 281 is transported by the belt loop 282 and sent to the paper discharge unit 30.

The paper discharge section 30 has a plate-shaped paper discharge tray 31 on which the recording medium P sent from the image forming section 20 by the delivery section 28 is placed.

Next, with reference to FIG. 3, the configuration of the ink supply mechanism 60 (functioning as the "recording liquid supply device" of the present invention) that supplies ink to the inkjet head 242 in the inkjet image forming apparatus 1 will be described.

As shown in FIG. 3, the ink supply mechanism 60 includes a main tank 62, a sub tank 64, a main tank side flow path 66, an inkjet head side flow path 70, a supply pump 72, an air release valve 76, an agitation unit 78, an air release valve 82, and solenoid valves 84 and 86.

The main tank 62 is provided outside the head unit 24 and stores ink L1 of a color (yellow (Y), magenta (M), cyan (C), or black (K)) corresponding to the head unit 24. The ink L1 stored in the main tank 62 is pumped out by a supply pump 72 that operates based on a control signal supplied from the control unit 40 (see FIG. 4), and is pumped out to the sub tank 64 via the main tank side flow path 66. is supplied to Note that as the supply pump 72, a pump having a backflow prevention function is used.

The sub tank 64 is connected to a flow path between the main tank 62 and the inkjet head 242 (main tank side flow path 66 and inkjet head side flow path 70), and receives the ink L2 pumped and supplied from the main tank 62. Store. In this embodiment, a metal container having a capacity of approximately 40 liters is used as the sub-tank 64.

When an image is formed on the recording medium P, the ink L2 stored in the sub-tank 64 is supplied to the inkjet head 242 via the inkjet head side flow path 70. The inkjet head 242 then ejects the ink supplied from the sub-tank 64. The main tank side flow path 66 and the inkjet head side flow path 70 function as the "recording liquid flow path" of the present invention.

The atmosphere release valve 76 opens the inside of the main tank 62 to the atmosphere based on a control signal supplied from the control unit 40, and brings the pressure inside the main tank 62 to atmospheric pressure.

The stirring unit 78 stirs the ink L1 stored in the main tank 62. Specifically, in the stirring section 78, a stirring member that is rotatable based on a control signal supplied from the control section 40 is accommodated in the main tank 62. The stirring member is made of, for example, a magnetic material coated with resin, and is formed into a triangular prism shape. With this configuration, when the stirring member is rotated to stir the ink L1 stored in the main tank 62, the ink L1 in the lower layer can be efficiently convected toward the upper layer.

The atmosphere release valve 82 opens the inside of the sub-tank 64 to the atmosphere based on a control signal supplied from the control unit 40, and brings the pressure inside the sub-tank 64 to atmospheric pressure. When the ink L1 stored in the main tank 62 is supplied to the sub-tank 64, the atmosphere release valve 82 opens the sub-tank 64 to the atmosphere and prevents the pressure in the sub-tank 64 from increasing more than necessary.

The electromagnetic valve 84 is provided near the sub-tank 64 and switches the open/close state of the main tank side flow path 66 based on a control signal supplied from the control unit 40.

The electromagnetic valve 86 is provided near the sub-tank 64 and switches the open/close state of the inkjet head side channel 70 based on a control signal supplied from the control unit 40.

Figure 4 is a block diagram showing the main functional configuration of the inkjet image forming device 1. The inkjet image forming device 1 includes a heating unit 23, a head driving unit 241, an inkjet head 242, a fixing unit 25, a control unit 40, a transport driving unit 51, an operation display unit 52, an input/output interface 53, etc.

The head driver 241 supplies a drive signal to the image forming element of the inkjet head 242 at an appropriate timing to deform the piezoelectric element in accordance with the image data, thereby causing the nozzle 243 of the inkjet head 242 to eject an amount of ink in accordance with the pixel value of the image data.

The control unit 40 includes a CPU 41 (Central Processing Unit), a RAM 42 (Random Access Memory), a ROM 43 (Read Only Memory), and a storage unit 44.

The CPU 41 reads various control programs and setting data stored in the ROM 43, stores them in the RAM 42, and executes the programs to perform various calculation processes. Further, the CPU 41 centrally controls the overall operation of the inkjet image forming apparatus 1 .

RAM 42 provides working memory space for CPU 41 and stores temporary data. RAM 42 may include non-volatile memory.

The ROM 43 stores various control programs and setting data executed by the CPU 41. Note that a rewritable non-volatile memory such as an EEPROM (Electrically Erasable Programmable Read Only Memory) or a flash memory may be used instead of the ROM 43.

The storage unit 44 stores print jobs (image formation commands) input from the external device 2 via the input/output interface 53, image data related to the print jobs, and the like. The print job includes information specifying the image data related to the image to be formed, as well as information related to the type of recording medium P on which the image is to be formed (e.g., the size and thickness of the recording medium P). For example, a hard disk drive (HDD) is used as the storage unit 44, and a dynamic random access memory (DRAM) or the like may also be used in combination.

The conveyance drive section 51 supplies a drive signal to the conveyance drum motor of the conveyance drum 211 based on the control signal supplied from the control section 40, and rotates the conveyance drum 211 at a predetermined speed and timing.

The transport drive unit 51 also supplies drive signals to motors for operating the medium supply unit 12, the transfer unit 22, and the delivery unit 28 based on control signals supplied from the control unit 40, thereby supplying the recording medium P to the transport unit 21 and discharging it from the transport unit 21.

The operation display unit 52 includes a display device such as a liquid crystal display or an organic EL display, and an input device such as operation keys and a touch panel placed over the screen of the display device. The operation display section 52 displays various information on the display device, and also converts a user's input operation on the input device into an operation signal and outputs it to the control section 40.

The input/output interface 53 mediates the transmission and reception of data between the external device 2 and the control unit 40. The input/output interface 53 is, for example, composed of any one of various serial interfaces, various parallel interfaces, or a combination of these.

The external device 2 is, for example, a personal computer, and supplies print jobs, image data, etc. to the control unit 40 via the input/output interface 53.

By the way, when the ink (white ink, gel ink, etc.) used in the inkjet image forming apparatus 1 is left for a long period without flowing, the pigment contained in the ink settles over time. have Pigment sedimentation can cause deterioration of image quality such as density unevenness in the image formed on the recording medium P, as well as damage to the recording liquid flow path (main tank side flow path 66 and inkjet head side flow path 70) which is the ink supply path. This causes failure of the inkjet image forming apparatus 1 due to clogging of the nozzle ejection ports. In particular, sedimentation of pigment within the recording liquid flow path, which is shaped like a tube or a thin tube, can be a big problem because it is difficult to take measures spatially.

Therefore, in this embodiment, in order to prevent sediment from occurring in the first place in the recording liquid flow path, the control unit 40 performs control to drain ink from the main tank side flow path 66 and the inkjet head side flow path 70, which serve as the recording liquid flow path, at a specified timing when the operation of ejecting ink onto the recording medium P to form an image is not performed.

Here, the predetermined timing is the timing when the power of the inkjet image forming apparatus 1 and the ink supply mechanism 60 is turned off, the timing when the recording medium P is not being conveyed toward the inkjet head 242, and the timing when ink is ejected onto the recording medium P. Examples include timing between print jobs (paper intervals) between print jobs, and timing when a predetermined standby time has elapsed after execution of a print job in which ink is ejected onto the recording medium P is completed.

The control unit 40 performs control to drain the ink in the main tank side flow path 66 and the inkjet head side flow path 70 by flowing the ink to the inkjet head 242 side.

For example, the control unit 40 controls the atmospheric release valves 76, 82 to open the main tank 62 and the sub tank 64 to the atmosphere, and controls the solenoid valve 84 to switch the state of the main tank side flow path 66 to "open". The control unit 40 then controls the supply pump 72 to pump out the ink L1 stored in the main tank 62. This causes the ink in the main tank side flow path 66 to be supplied (flowed) to the sub tank 64 shortly before sediment forms, preventing ink from being left in a stagnant state in the main tank side flow path 66 for a long period of time and preventing sediment from forming.

Further, the control unit 40 controls the atmosphere release valve 82 to open the sub-tank 64 to the atmosphere, and controls the solenoid valve 86 to switch the state of the inkjet head side flow path 70 to "open". In this embodiment, the inkjet head side flow path 70 is connected to the bottom of the sub tank 64. Further, a height difference is provided between the sub-tank 64 and the ink-jet head 242 so that the ink in the ink-jet head-side flow path 70 between the sub-tank 64 and the ink-jet head 242 flows toward the ink-jet head 242 due to gravity. .

As a result, the ink in the inkjet head side flow path 70 is supplied (flowed) to the inkjet head 242 immediately before sediment is generated, preventing the ink from being left in a state of no flow in the inkjet head side flow path 70 for a long period of time and preventing the generation of sediment. Note that the ink supplied to the inkjet head 242 is discharged from the nozzle 243 of the inkjet head 242, in the same way as head cleaning, which is performed to maintain good ink ejection conditions.

Note that the control unit 40 may perform control to drain the ink in the main tank side flow path 66 by causing the ink to flow toward the main tank 62 side. FIG. 5 shows the configuration of an ink supply mechanism 60 that has been improved to flow ink in the main tank side flow path 66 to the main tank 62 side.

As shown in FIG. 5, in addition to the configuration shown in FIG. The flow path 68 (functions as the "branch flow path" of the present invention) and the solenoid valve 74 (functions as the "adjustment section" of the present invention) that adjusts the flow rate of ink flowing through the branch flow path 68 under the control of the control section 40. ).

The control unit 40 controls the atmosphere release valves 76 and 82 to open the main tank 62 and the sub-tank 64 to the atmosphere, and also controls the electromagnetic valve 74 to switch the state of the main tank side flow path 66 to "open". The main tank side flow path 66 is connected to the bottom of the sub tank 64. Further, a height difference is provided between the main tank 62 and the sub-tank 64 so that the ink in the main tank-side channel 66 between the main tank 62 and the sub-tank 64 flows toward the main tank 62 by gravity. .

As a result, the ink in the main tank side flow path 66 (more precisely, the main tank side flow path 66 between the supply pump 72 and the sub tank 64) is supplied (flowed) to the main tank 62 via the branch flow path 68 shortly before sediment occurs, so that ink is prevented from being left for a long period of time in the main tank side flow path 66 without flow, and sediment does not occur. As described above, a pump with a backflow prevention function is used as the supply pump 72, so the ink in the main tank side flow path 66 cannot pass through the supply pump 72 and is supplied to the main tank 62 via the branch flow path 68. By stirring the ink supplied to the main tank 62 with the stirring unit 78, it is possible to prevent ink from being left for a long period of time in the main tank 62 without flow, and to prevent sediment from occurring.

As described above in detail, the ink supply mechanism 60 (recording liquid supply device) in this embodiment includes a main tank 62 that stores ink (recording liquid), an inkjet head 242 that ejects the ink supplied from the main tank 62 onto the recording medium P, a main tank side flow path 66 and an inkjet head side flow path 70 (recording liquid flow path) through which ink flows between the main tank 62 and the inkjet head 242, and a control unit 40 (recording liquid drainage unit) that controls the drainage of ink from the main tank side flow path 66 and the inkjet head side flow path 70.

In this embodiment, which is configured in this manner, the ink in the main tank side flow path 66 and the inkjet head side flow path 70 is supplied (flowed) to the main tank 62, sub tank 64, or inkjet head 242 shortly before sediment forms. This prevents ink from being left in a state of no flow for long periods of time in the main tank side flow path 66 and the inkjet head side flow path 70, and prevents sediment from forming.

Although the technique described in Patent Document 1 generates turbulence in the flow of ink (recording liquid) in the recording liquid flow path, there is a possibility that the sediment in the recording liquid flow path may not be sufficiently removed. There is. In contrast, in the present embodiment, sediment is generated in the main tank side flow path 66 and the inkjet head side flow path 70 by removing ink from the main tank side flow path 66 and the inkjet head side flow path 70. Therefore, a completely different technology from the technology described in Patent Document 1 is applied.

In the above embodiment, the single-pass type inkjet image forming apparatus 1 has been described as an example, but the present invention may be applied to an inkjet image forming apparatus that records an image while scanning the head unit. . Further, the present invention may be applied to an inkjet image forming apparatus in which a head unit is provided with a single nozzle.

Further, the above embodiments are merely examples of implementation of the present invention, and the technical scope of the present invention should not be construed as limited by these embodiments. That is, the present invention can be implemented in various forms without departing from its gist or main features.

REFERENCE SIGNS LIST 1 Inkjet image forming apparatus 2 External device 10 Paper feed section 11 Paper feed tray 12 Medium supply section 20 Image forming section 21 Transport section 211 Transport drum 211a Transport surface 22 Delivery unit 23 Heating section 24 Head unit 241 Head driving section 242 Inkjet head 243 Nozzle 244 Mounting member 25 Fixing section 28 Delivery section 30 Paper discharge section 31 Paper discharge tray 40 Control section 41 CPU
42 RAM
43 ROM
44 Memory unit 51 Transport drive unit 52 Operation display unit 53 Input/output interface 60 Ink supply mechanism 62 Main tank 64 Sub tank 66 Main tank side flow path 68 Branch flow path 70 Inkjet head side flow path 72 Supply pump 74, 84, 86 Solenoid valve 76, 82 Atmospheric release valve 78 Stirring unit L1, L2 Ink P Recording medium

Claims (15)

A main tank that stores recording liquid,
an inkjet head that discharges recording liquid supplied from the main tank onto a recording medium;
a recording liquid flow path through which recording liquid flows between the main tank and the inkjet head;
a recording liquid draining section that controls draining the recording liquid in the recording liquid flow path;
A sub-tank for storing recording liquid supplied from the main tank,
The inkjet head discharges the recording liquid supplied from the sub-tank onto the recording medium,
A height difference is provided between the main tank and the sub-tank so that the recording liquid in the recording liquid flow path between the main tank and the sub-tank flows toward the main tank by gravity.
Recording liquid supply device. A main tank for storing recording liquid;
an inkjet head that discharges recording liquid supplied from the main tank onto a recording medium;
a recording liquid flow passage through which the recording liquid flows between the main tank and the inkjet head;
a recording liquid draining section that controls draining the recording liquid in the recording liquid flow path;
A sub-tank for storing recording liquid supplied from the main tank,
the inkjet head ejects the recording liquid supplied from the subtank onto the recording medium;
The recording liquid stored in the main tank is drained under the control of the recording liquid draining section so that the recording liquid in the recording liquid flow path between the main tank and the sub tank flows toward the sub tank. a supply pump for pumping;
a branch flow path branching from the recording liquid flow path between the supply pump and the sub-tank and connected to the main tank;
further comprising an adjusting section that adjusts the flow rate of the recording liquid flowing through the branch flow path under control of the recording liquid draining section;
Recording liquid supply device. the recording liquid draining unit controls draining of the recording liquid by causing the recording liquid in the recording liquid flow passage to flow toward the main tank.
3. The recording liquid supplying device according to claim 1 . the recording liquid draining unit controls draining of the recording liquid by causing the recording liquid in the recording liquid flow channel to flow toward the inkjet head.
3. The recording liquid supplying device according to claim 1 . a height difference is provided between the sub-tank and the inkjet head so that the recording liquid in the recording liquid flow path between the sub-tank and the inkjet head flows toward the inkjet head by gravity;
The recording liquid supplying device according to any one of claims 1 to 4 . the recording liquid flow passage is connected to the bottom of the sub-tank;
The recording liquid supplying device according to any one of claims 1 to 5 . the recording liquid draining unit controls draining of the recording liquid in the recording liquid flow path at a timing when the power supply device is turned off.
The recording liquid supplying device according to any one of claims 1 to 6 . The recording liquid draining section performs control to drain the recording liquid from the recording liquid flow path at a timing when the recording medium is not being conveyed toward the inkjet head.
The recording liquid supply device according to any one of claims 1 to 6 . the recording liquid draining unit controls draining of the recording liquid inside the recording liquid flow path at a timing between print jobs in which the recording liquid is discharged onto the recording medium.
The recording liquid supplying device according to any one of claims 1 to 6 . The recording liquid draining unit performs control to drain the recording liquid from the recording liquid flow path at a timing when a predetermined standby time has elapsed after execution of a print job in which recording liquid is discharged onto the recording medium is completed.
The recording liquid supply device according to any one of claims 1 to 6 . The recording liquid contains a pigment.
The recording liquid supply device according to any one of claims 1 to 10 . the recording liquid is white ink;
The recording liquid supply device according to claim 11 . the recording liquid is gel ink;
The recording liquid supply device according to claim 11 . comprising a stirring section that stirs the recording liquid stored in the main tank;
The recording liquid supply device according to any one of claims 1 to 13 . An image forming apparatus comprising the recording liquid supply device according to claim 1 .

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