JP6897186B2 - Inkjet recording device - Google Patents

Description

The present invention relates to an inkjet recording device.

Conventionally, there is an inkjet recording device that records an image on a recording medium by ejecting ink from the nozzle onto a recording medium by an ink ejection unit provided with a nozzle for ejecting ink. In this inkjet recording device, ink used for image recording is supplied into the ink ejection unit by sending ink from an ink storage portion provided outside the ink ejection unit to the ink ejection unit by a liquid feeding unit such as a pump. Will be done. In addition, ink is sent at high pressure by the liquid feeding unit, and the ink supplied to the ink ejection unit is forcibly ejected from the nozzle, thereby flushing out contaminants such as foreign matter and solidified ink that have flowed into the nozzle. A technique for performing maintenance is known (for example, Patent Document 1).

In recent years, in inkjet recording devices, the number of nozzles tends to increase in order to meet the demands such as improvement of recording speed and high definition of recorded images. One of the methods for increasing the number of nozzles is a method of forming a head unit by using a plurality of ink ejection portions. In such a head unit, the liquid feeding destination from a single liquid feeding unit can be divided into a plurality of individual flow paths, and the ink ejection unit can be connected to each individual flow path. In this case, the ink ejection unit for supplying ink can be selected by providing an opening / closing unit such as a solenoid valve in each individual flow path.

International Publication No. 2014/188955

However, in the ejection maintenance of the inkjet recording apparatus having the above configuration, the amount of liquid to be fed in order to make the pressure of the ink in the ink ejection unit a predetermined value suitable for ejection maintenance depends on the number of ink ejection portions to be maintained. It depends on each. Since the pressure of this ink is directly linked to the amount of liquid sent from the liquid feeding part, in order to stabilize the ink pressure in ejection maintenance at a predetermined value, the amount of liquid sent should be adjusted according to the number of ink ejection parts to be maintained. There is a problem that it is necessary to adjust with high precision and it takes time and effort. If the ink pressure deviates from a predetermined value in ejection maintenance, the removal of impurities becomes insufficient, or the amount of ink leaking from the nozzle increases, resulting in a large amount of waste.

An object of the present invention is to provide an inkjet recording apparatus capable of easily and stably removing impurities from an ink ejection portion while suppressing waste of ink.

In order to achieve the above object, the invention of the inkjet recording apparatus according to claim 1 is
Two or more predetermined number of ink ejection parts each having nozzles for ejecting ink, and
An ink storage unit that stores ink supplied to the predetermined number of ink ejection units, and an ink storage unit.
A common flow path that communicates with the ink storage section, a predetermined number of individual flow paths that connect the common flow path and the predetermined number of ink ejection sections, and a common flow path that branches from the common flow path and the ink. An ink flow path having a return flow path that connects the storage unit without passing through the individual flow path, and an ink flow path.
A liquid feeding unit that performs a liquid feeding operation to supply the ink stored in the ink storage unit to the ink ejection unit via the common flow path and the individual flow path, and a liquid feeding unit.
A first opening / closing unit provided in each of the predetermined number of individual flow paths and switching between a communication state and a non-communication state between the common flow path and the ink ejection section.
When the pressure of the ink in the common flow path provided in the return flow path is equal to or lower than a predetermined reference pressure, the return flow path is closed and the pressure of the ink in the common flow path is larger than the reference pressure. In some cases, the pressure adjusting unit that opens the feedback flow path and
Control unit and
With
The reference pressure is equal to or higher than the lower limit of the pressure range in which ink is ejected from the nozzle of the ink ejection portion communicating with the common flow path due to the pressure of the ink in the common flow path, and the ink flow path and the ink flow path The size is within the pressure resistance range of the ink ejection part.
The pressure adjusting unit has a reference pressure changing unit that changes the reference pressure.
In the control unit, at least a part of the predetermined number of ink ejection units communicates with the common flow path via the individual flow paths, and the ink pressure in the common flow path reaches the reference pressure. By causing the liquid feeding unit to perform the liquid feeding operation according to the amount of liquid, it is characterized in that the ejection maintenance control for ejecting ink from the nozzle of the ink ejection unit communicating with the common flow path is performed.

The invention according to claim 2 is the inkjet recording apparatus according to claim 1.
The control unit is characterized in that the amount of liquid supplied in the liquid feeding operation is determined so as to increase as the number of the ink ejection units communicating with the common flow path increases.

The invention according to claim 3 is the inkjet recording apparatus according to claim 1 or 2.
A recirculation flow path for refluxing the ink supplied to the predetermined number of ink ejection portions to the ink storage portion, and
A second opening / closing portion provided in the reflux flow path to open or close the reflux flow path,
With
The control unit
The pressure of the ink in the common flow path is the reference in a state where the return flow path is closed and at least a part of the predetermined number of ink ejection portions communicates with the common flow path via the individual flow path. The discharge maintenance control is performed by causing the liquid feeding unit to perform the liquid feeding operation with the liquid feeding amount reaching the pressure.
The ink communicating with the common flow path in a state where the reflux flow path is open and at least a part of the predetermined number of ink ejection portions communicates with the common flow path via the individual flow path. By causing the liquid feeding unit to perform the liquid feeding operation with a liquid feeding amount corresponding to the number of the discharging parts, the ink of the ink discharging part communicating with the common flow path is transmitted through the reflux flow path. It is characterized by performing reflux maintenance control to return the ink to the ink storage section.

The invention according to claim 4 is the inkjet recording apparatus according to any one of claims 1 to 3.
An ink temperature detection unit for detecting the temperature of the ink supplied to the ink ejection unit by the liquid feeding unit is provided.
The control unit is characterized in that the reference pressure changing unit changes the reference pressure to a preset value corresponding to the temperature detected by the ink temperature detecting unit.

Invention of Lee inkjet recording apparatus according to claim 5,
Two or more predetermined number of ink ejection parts each having nozzles for ejecting ink, and
An ink storage unit that stores ink supplied to the predetermined number of ink ejection units, and an ink storage unit.
A common flow path that communicates with the ink storage section, a predetermined number of individual flow paths that connect the common flow path and the predetermined number of ink ejection sections, and a common flow path that branches from the common flow path and the ink. An ink flow path having a return flow path that connects the storage unit without passing through the individual flow path, and an ink flow path.
A liquid feeding unit that performs a liquid feeding operation to supply the ink stored in the ink storage unit to the ink ejection unit via the common flow path and the individual flow path, and a liquid feeding unit.
A first opening / closing unit provided in each of the predetermined number of individual flow paths and switching between a communication state and a non-communication state between the common flow path and the ink ejection section.
When the pressure of the ink in the common flow path provided in the return flow path is equal to or lower than a predetermined reference pressure, the return flow path is closed and the pressure of the ink in the common flow path is larger than the reference pressure. In some cases, the pressure adjusting unit that opens the feedback flow path and
A recirculation flow path for refluxing the ink supplied to the predetermined number of ink ejection portions to the ink storage portion, and
A second opening / closing portion provided in the reflux flow path to open or close the reflux flow path,
Control unit and
With
The reference pressure is equal to or higher than the lower limit of the pressure range in which ink is ejected from the nozzle of the ink ejection portion communicating with the common flow path due to the pressure of the ink in the common flow path, and the ink flow path and the ink flow path The size is within the pressure resistance range of the ink ejection part.
The pressure adjusting unit has a reference pressure changing unit that changes the reference pressure.
The control unit
In a state where at least a part of the predetermined number of ink ejection portions communicates with the common flow path via the individual flow path, the ink feed in the common flow path reaches the reference pressure. By causing the liquid unit to perform the liquid feeding operation, ejection maintenance control for ejecting ink from the nozzle of the ink ejection unit communicating with the common flow path is performed.
The pressure of the ink in the common flow path is the reference in a state where the return flow path is closed and at least a part of the predetermined number of ink ejection portions communicates with the common flow path via the individual flow path. The discharge maintenance control is performed by causing the liquid feeding unit to perform the liquid feeding operation with the liquid feeding amount reaching the pressure.
The ink communicating with the common flow path in a state where the reflux flow path is open and at least a part of the predetermined number of ink ejection portions communicates with the common flow path via the individual flow path. By causing the liquid feeding unit to perform the liquid feeding operation with a liquid feeding amount corresponding to the number of the discharging parts, the ink of the ink discharging part communicating with the common flow path is transmitted through the reflux flow path. Performs reflux maintenance control to return the ink to the ink reservoir,
When the reflux maintenance control is started, the reference pressure changing unit is operated to adjust the reference pressure to a second reference pressure smaller than the first reference pressure when the discharge maintenance control is performed. ,
The reflux maintenance control is characterized in that the liquid feeding operation is performed by the liquid feeding unit at a liquid feeding amount at which the pressure of the ink in the common flow path reaches the second reference pressure.

According to the present invention, there is an effect that impurities can be easily and stably removed from the ink ejection portion while suppressing waste of ink.

It is a figure which shows the schematic structure of the inkjet recording apparatus. It is a figure which shows the internal structure of a head unit. It is sectional drawing which looked at the ink flow path in a recording head from the front. It is a schematic diagram which shows the structure of the ink supply mechanism. It is a schematic cross-sectional view which shows the structure of a pressure control valve. It is a block diagram which shows the main functional structure of an inkjet recording apparatus. It is a figure which shows the time change of the ink pressure in the ejection maintenance operation. It is a flowchart which shows the control procedure of a discharge maintenance process. It is a flowchart which shows the control procedure of a reflux maintenance process.

Hereinafter, embodiments relating to the image forming apparatus and the image forming method of the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing a schematic configuration of an inkjet recording device 1 according to an embodiment of the present invention.
The inkjet recording device 1 includes a transport unit 10, a head unit 20, and the like.

The transport unit 10 includes a ring-shaped transport belt 103 whose inside is supported by two transport rollers 101 and 102 that rotate around a rotation axis extending in the X direction of FIG. The transport unit 10 records by rotating the transport roller 101 in accordance with the operation of the transport motor (not shown) in a state where the recording medium M is placed on the transport surface of the transport belt 103, and the transport belt 103 orbits. The medium M is conveyed in the moving direction of the conveying belt 103 (conveying direction; Y direction in FIG. 1).
The recording medium M can be a sheet of paper cut to a certain size. The recording medium M is supplied onto the transport belt 103 by a paper feeding device (not shown), ink is ejected from the head unit 20, an image is recorded, and then the recording medium M is ejected from the transport belt 103 to a predetermined paper ejection unit. As the recording medium M, roll paper may be used. In this case, the recording medium M is pulled out from the roll on which the recording medium M is wound, supplied onto the transport belt 103, and is wound by another roll after the image is recorded. As the recording medium M, in addition to paper such as plain paper and coated paper, various media such as cloth or sheet-shaped resin capable of fixing the ink landed on the surface can be used.
The transport unit 10 of the present embodiment is configured to be capable of transporting a large recording medium M having a width of about 2 m in the X direction.

The head unit 20 ejects ink to the recording medium M conveyed by the conveying unit 10 at an appropriate timing based on the image data to record an image. In the inkjet recording apparatus 1 of the present embodiment, four head units 20 corresponding to four colors of ink of yellow (Y), magenta (M), cyan (C), and black (K) are in the transport direction of the recording medium M. They are arranged so as to be arranged at predetermined intervals in the order of Y, M, C, and K colors from the upstream side. The number of head units 20 may be 3 or less or 5 or more.

FIG. 2 is a diagram showing an internal configuration of the head unit 20. FIG. 2A is a schematic view of the internal configuration of the head unit 20 when viewed from the front. FIG. 2B is a schematic view of the internal configuration of the head unit 20 when viewed from the transport belt 103 side. The case where the head unit 20 is viewed from the front means a case where the head unit 20 is viewed from a direction parallel to the transport direction of the recording medium M at a position facing the head unit 20 on the transport surface of the transport belt 103. ..

The head unit 20 has a plurality of recording heads 22 provided with a plurality of recording elements for ejecting ink. The recording elements communicate with the pressure chamber (channel) for storing ink, the piezoelectric element provided on the wall surface of the pressure chamber, the electrode for applying a voltage to the piezoelectric element to generate an electric field, and the pressure chamber. It has a nozzle 221 for ejecting ink in the pressure chamber. When a voltage signal with a drive waveform that deforms the piezoelectric element is applied to the electrodes of the recording element, the pressure chamber is deformed in response to this voltage signal and the pressure in the pressure chamber changes, and in response to the change in pressure. Ink is ejected from the nozzle 221 communicating with the pressure chamber. In the recording head 22, a plurality of nozzles 221 are arranged in two rows along the X direction to form two nozzle rows, and these two nozzle rows form two minutes of the arrangement interval of the nozzles 221 in the X direction. Only 1 is arranged so as to be offset from each other.

In the head unit 20, two recording heads 22 are combined to form a head module 22M (ink ejection unit), and the head modules 22M are arranged in a houndstooth pattern. In each head module 22M, the recording heads 22 are arranged in such a positional relationship that the nozzles 221 of the two recording heads 22 are alternately arranged in the X direction. The number of head modules 22M provided in the head unit 20 is not particularly limited, but is 24 in the present embodiment. Due to such an arrangement of the recording head 22, the arrangement range of the nozzle 221 included in the head unit 20 in the X direction is the width of the area of the recording medium M conveyed by the transfer belt 103 in the X direction in which an image can be formed. It is designed to cover (recordable width). The head unit 20 is used with a fixed position when recording an image, and ink is sequentially ejected at predetermined intervals (transportation direction intervals) to positions having different transport directions according to the transport of the recording medium M. Record images using the single-pass method.

As shown in FIG. 2A, the recording head 22 has an inlet 223 into which the ink supplied into the recording head 22 flows in, an outlet 224 in which the ink discharged from the recording head 22 flows out, and the like.

FIG. 3 is a cross-sectional view of the ink flow path in the recording head 22 as viewed from the front.
The ink flow path in the recording head 22 has a common ink chamber 222 to which the inlet 223 and the outlet 224 are connected, and a head tip 225 for ejecting ink from each nozzle 221.
The ink flowing in from the inlet 223 is sent to the common ink chamber 222. The common ink chamber 222 is provided with a filter 226 that prevents the passage of impurities in the ink, and the inlet 223 communicates with one side of the filter 226 (upstream ink chamber 2221). The outlet 224 is provided on the same side as the inlet 223 (upstream ink chamber 2221) with respect to the filter 226 and on the side opposite to the inlet 223 (downstream ink chamber 2222) with the filter 226 interposed therebetween. It consists of a second outlet 2242.

The head chip 225 includes a plurality of element-corresponding flow paths 2251 (pressure chambers) provided corresponding to each of the plurality of recording elements, a nozzle 221 communicating with the plurality of element-corresponding flow paths 2251, and the like. Ink is ejected from the opening of 221. The position of the element-corresponding flow path 2251 is attached so as to coincide with the position of the through hole 2222a of the downstream ink chamber 2222, so that the ink of the common ink chamber 222 is distributed to each nozzle 221.

As the ink discharged from the nozzle 221 of the recording head 22, a liquid ink at room temperature is used. The amount and speed of the ink ejected from the nozzle 221 changes according to the viscosity of the ink. Also, the viscosity of the ink depends on the temperature. In this embodiment, an ink whose viscosity increases as the temperature decreases is used.

Further, the head unit 20 is provided so as to be movable in the X direction between a position facing the transport belt 103 and a position facing the cleaning portion (not shown). The head unit 20 is arranged at a position facing the transport belt 103 when performing an image recording operation of ejecting ink to the recording medium M, and faces the cleaning unit when performing ejection maintenance or reflux maintenance described later. Moved to the desired position. The movement of the head unit 20 may be performed by a human hand, or may be performed by a driving operation of a head unit moving mechanism (not shown) under the control of the control unit 40.

Next, an ink supply mechanism for supplying ink to the recording head 22 in the inkjet recording apparatus 1 will be described.
FIG. 4 is a schematic view showing the configuration of the ink supply mechanism 30.
In FIG. 4, the ink supply mechanism 30 related to the head unit 20 of one of the inkjet recording devices 1 is extracted and shown, but in the other head units 20, the same ink supply mechanism 30 inks the recording head 22. Is supplied. Further, in FIG. 4, the liquid feeding direction of the ink is indicated by an arrow.

In the ink supply mechanism 30, the ink in the external tank 61 that stores ink outside the head unit 20 is supplied to the main tank 311 provided in the head unit 20 by the supply pump 62. In the head unit 20, the main tank 311 is provided with an ink circulation path that returns to the main tank 311 via the common flow path 301, the individual flow path 302, the sub tank 312, the recording head 22 (head module 22M), and the return flow path 303. Ink can be circulated in this ink circulation path by the liquid feeding operation of the liquid feeding pump 32. Further, the ink circulation path is provided with a return flow path 304 that branches from the common flow path 301 and connects the common flow path 301 and the main tank 311. The ink flow path is composed of the common flow path 301, the individual flow path 302, the return flow path 303, and the return flow path 304 in the ink supply mechanism 30.

The external tank 61 is provided outside the head unit 20 and stores ink of a color corresponding to the head unit 20. The ink stored in the external tank 61 is pumped out by the supply pump 62 and supplied to the main tank 311 in the head unit 20. The supply pump 62 is not particularly limited, and for example, a volume transfer type pump such as a diaphragm pump, a tube pump that squeezes a tube with a roller to feed liquid, and the like can be used.

The main tank 311 stores ink supplied from the external tank 61 and supplied to the recording head 22. The main tank 311 communicates with the common flow path 301 and the return flow path 303. The main tank 311 is a container open to the outside, and is maintained at substantially atmospheric pressure regardless of an increase or decrease in the amount of ink.

In the main tank 311, an ink temperature detecting unit 34 for detecting the temperature of the ink stored in the main tank 311 is provided. The ink temperature detection unit 34 has a temperature detection element such as a thermistor, and outputs data related to the ink temperature to the control unit 40 based on a control signal supplied from the control unit 40. The installation position of the ink temperature detection unit 34 is not limited to the inside of the main tank 311 and may be provided at any position from the main tank 311 to the head module 22M in the ink flow path.

The liquid feeding pump 32 is provided in the common flow path 301, and performs a liquid feeding operation of flowing ink in the liquid feeding direction from the main tank 311 toward the sub tank 312 and the recording head 22 via the common flow path 301. The configuration of the liquid feed pump 32 is not particularly limited, but for example, a diaphragm pump or a tube pump can be used. The liquid feed pump 32 operates under the control of the control unit 40.

The common flow path 301 is branched into a predetermined number of individual flow paths 302 on the downstream side of the liquid feed pump 32. Here, the predetermined number is the same as the number of the head modules 22M, and is 24 in this embodiment. In each individual flow path 302, the sub tank 312 and the head module 22M communicate in series in this order. The sub tank 312 is a small ink chamber that temporarily stores the ink supplied to the recording head 22, and is sealed except for the connection points with the individual flow paths 302 and the ventilation passage 305. The ink that has entered the individual flow paths 302 from the common flow path 301 is temporarily stored in the sub tank 312, and is supplied from the sub tank 312 to the head module 22M by the liquid feeding operation by the liquid feeding pump 32. More specifically, ink is supplied from each sub-tank 312 in parallel to the inlets 223 of the two recording heads 22 constituting the head module 22M.

Further, each individual flow path 302 is provided with an ink supply valve 331 (first opening / closing portion) that switches between a communication state and a non-communication state between the common flow path 301 and the head module 22M. As the ink supply valve 331, for example, an electromagnetic valve is used, and the ink supply valve 331 opens and closes under the control of the control unit 40. By providing the ink supply valve 331 in each individual flow path 302 in this way, the head module 22M to which ink is supplied from the common flow path 301 can be selected.

From the common flow path 301, a return flow path 304 that connects the common flow path 301 and the main tank 311 without passing through the individual flow path 302 is branched. The branching position from the common flow path 301 to the return flow path 304 is on the downstream side of the liquid feed pump 32 in the ink feeding direction and on the upstream side of the branching position from the common flow path 301 to the individual flow path 302.

The return flow path 304 closes the return flow path 304 when the pressure of the ink in the common flow path 301 is equal to or lower than a predetermined reference pressure, and when the pressure of the ink in the common flow path 301 is higher than the reference pressure. A pressure adjusting valve 333 (pressure adjusting unit) that opens the return flow path 304 is provided.

FIG. 5 is a schematic cross-sectional view showing the configuration of the pressure regulating valve 333.
As shown in FIG. 5A, the pressure regulating valve 333 communicates with the primary side flow path 3331 in which ink flows from the return flow path 304 on the common flow path 301 side and the primary side flow path 3331, and the main tank 311. It has a secondary side flow path 3332 that allows ink to flow out to the side return flow path 304, and the joint portion between the primary side flow path 3331 and the secondary side flow path 3332 is located on the downstream side in the ink feeding direction. A funnel-shaped converging portion 3333 that widens is provided. The plug portion 3334 is pressed against the converging portion 3333 by the restoring force of the elastic member 3335a and is in contact with the converging portion 3333, and in the state of FIG. 5A, the converging portion 3333 is sealed by the plug portion 3334. The fixed position of the elastic member 3335a on the side opposite to the plug portion 3334 side can be adjusted in the vertical direction of FIG. 5A by rotating the adjusting screw 3335b.

In the state of FIG. 5A, the pressure of the ink supplied from the return flow path 304 to the primary side flow path 3331 becomes higher than the above reference pressure, and the liquid feeding direction (upward in FIG. 5) received by the plug portion 3334 from the ink. ) Is greater than the restoring force received from the elastic member 3335a in the direction opposite to the liquid feeding direction, the plug portion 3334 separates from the wall surface of the converging portion 3333, as shown in FIG. 5 (b). It moves upward by a distance according to the magnitude of the ink pressure. As a result, the primary side flow path 3331 and the secondary side flow path 3332 communicate with each other, and the return flow path 304 is opened. When the primary side flow path 3331 and the secondary side flow path 3332 communicate with each other, ink is supplied from the primary side flow path 3331 to the secondary side flow path 3332, so that the pressure of the ink in the primary side flow path 3331 (that is, feedback). Of the flow path 304, the pressure on the upstream side of the pressure regulating valve 333 and the common flow path 301) decreases. After that, the plug portion 3334 moves in the vertical direction to a position where the downward force received by the plug portion 3334 from the elastic member 3335a and the upward force received from the ink are balanced, so that the plug portion 3334 and the converging portion 3333 are combined. The amount of opening and closing between them is automatically adjusted, and the ink pressure of the primary side flow path 3331 is kept constant near the reference pressure.

The above-mentioned reference pressure (ink pressure when the pressure adjusting valve 333 is opened) moves the fixed position on one side of the elastic member 3335a by the rotation of the adjusting screw 3335b, and the elastic member 3335a gives the plug portion 3334 a restoration. It can be adjusted by changing the magnitude of the force. For example, in the discharge maintenance operation described later, the reference pressure is adjusted to be about 40 kPa. In the present embodiment, a drive motor (not shown) for rotationally driving the adjusting screw 3335b is provided, and the reference pressure can be changed by operating the motor under the control of the control unit 40. Of the above, the elastic member 3335a, the adjusting screw 3335b, and the drive motor constitute the reference pressure changing portion 3335, and the rotation of the adjusting screw 3335b corresponds to the operation of changing the reference pressure. The reference pressure may be changed by manually rotating the adjusting screw 3335b without providing the drive motor.

In the pressure adjusting valve 333 having the above configuration, the pressure in the common flow path 301 rises when the liquid is fed by the liquid feeding pump 32 in a state where all the ink supply valves 331 are closed due to a malfunction or failure. It functions as a fail-safe to prevent the members constituting the flow path from being damaged. Further, the pressure adjusting valve 333 stabilizes the pressure of the ink to be fed in the vicinity of the reference pressure when the liquid is fed by the liquid feed pump 32 at a liquid feeding amount such that the pressure of the ink becomes equal to or higher than the reference pressure. Functions as an ink pressure stabilizing means.

In the ink supply mechanism 30 of FIG. 4, the plurality of sub tanks 312 are connected to the exhaust pump 72 via the ventilation passage 305 and the air buffer tank 71. The exhaust pump 72 draws the ink in the recording head 22 toward the sub tank 312 by exhausting the air in the air buffer tank 71 and generating a negative pressure in the sub tank 312. This prevents ink from leaking from the nozzle 221 of the recording head 22 when various types of maintenance are not performed or when images are recorded. Further, the ventilation passage 305 is provided with an air valve 334 that switches between a communication state and a non-communication state between the sub tank 312 and the air buffer tank 71.

The outlet 224 of each head module 22M communicates with the reflux channel 303. Further, the recirculation flow path 303 is provided with an ink recirculation valve 332 (second opening / closing portion) that opens or closes the recirculation flow path 303. The ink recirculation valve 332 can be configured by a solenoid valve like the ink supply valve 331.

FIG. 6 is a block diagram showing a main functional configuration of the inkjet recording device 1.
The inkjet recording device 1 includes the liquid feed pump 32, the ink supply valve 331, the ink recirculation valve 332, the pressure adjusting valve 333, the reference pressure changing unit 3335, the air valve 334, the ink temperature detecting unit 34, the supply pump 62, and the exhaust pump 72. In addition, the control unit 40, the recording head control unit 21, the transfer drive unit 51, the operation display unit 52, the input / output interface 53, the bus 54, and the like are provided.

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, executes the programs, and performs various arithmetic processes. In addition, the CPU 41 controls the overall operation of the inkjet recording device 1.

The RAM 42 provides the CPU 41 with a working memory space and stores temporary data. The RAM 42 may include a non-volatile memory.

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

The storage unit 44 stores a print job (image recording command) input from the external device 2 via the input / output interface 53, image data related to the print job, various setting data, and the like. The set data includes table data described later in which the temperature of the ink and the reference pressure of the pressure regulating valve 333 are associated with each other. As the storage unit 44, for example, an HDD (Hard Disk Drive) may be used, or a DRAM (Dynamic Random Access Memory) or the like may be used in combination.

The recording head control unit 21 outputs various control signals and image data to the head drive unit provided in the recording head 22 at an appropriate timing according to the control signal from the control unit 40. Here, the control signal includes a signal that specifies a drive waveform related to the drive signal supplied from the head drive unit to the recording element. The head drive unit supplies a drive signal of the drive waveform to the electrodes in the recording element of the recording head 22 according to the control signal and image data input from the recording head control unit 21, from the nozzle 221 of the recording element. Discharge ink.

The transport drive unit 51 supplies a drive signal to the transport motor of the transport roller 101 based on the control signal supplied from the control unit 40 to orbit the transport belt 103 at a predetermined speed and timing.

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 an operation key and a touch panel arranged on the screen of the display device. The operation display unit 52 displays various information on the display device, converts the user's input operation to the input device into an operation signal, and outputs the operation signal to the control unit 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 composed of, for example, various serial interfaces, various parallel interfaces, or a combination thereof.

The bus 54 is a path for transmitting and receiving signals between the control unit 40 and other configurations.

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

Next, the maintenance operation of the head unit 20 in the inkjet recording device 1 will be described. The maintenance operation performed by the inkjet recording device 1 of the present embodiment includes a discharge maintenance operation (pressurized purge) and a reflux maintenance operation. Each of these maintenance operations is performed in a state where the head unit 20 is moved to a position facing the cleaning unit.

In the ejection maintenance operation, the pressure of the ink in the recording head 22 is increased by supplying ink from the main tank 311 to the head module 22M (recording head 22), and the nozzle 221 is forcibly ejected to clog the nozzle 221. It is done for the purpose of eliminating. That is, in the ejection maintenance operation, by supplying ink to the recording head 22 at high pressure by the liquid feeding pump 32, the ink pressure in the common ink chamber 222 in FIG. 3 increases, and the ink in the common ink chamber 222 increases due to the ink pressure. Is pushed out into the element-corresponding flow path 2251 and discharged from the nozzle 221. At this time, the clogging of the nozzle 221 is suppressed and eliminated by discharging the foreign matter and the solidified ink accumulated in the element-corresponding flow path 2251 and the nozzle 221 to the outside together with the discharged ink. To.

In the discharge maintenance operation, the ink recirculation valve 332 and the air valve 334 are closed, and the liquid feed operation by the liquid feed pump 32 is started with the ink supply valve 331 open, so that the common flow path 301 and the individual flow paths 301 are individually operated from the main tank 311. Ink is supplied to the recording head 22 of the head module 22M via the flow path 302 and the sub tank 312. Here, by opening only a part of the plurality of ink supply valves 331, the head module 22M communicating with the common flow path 301 via the individual flow path 302 provided with the opened ink supply valve 331. Ink can be supplied only to the head module 22M, and ejection maintenance can be performed only on the head module 22M.

The above-mentioned reference pressure of the pressure adjusting valve 333 when the discharge maintenance operation is performed is equal to or more than the lower limit value of the pressure range in which the ink is discharged from the nozzle 221 of the head module 22M due to the pressure of the ink in the common flow path 301. Within the pressure resistance range of the ink flow path and the head module 22M (that is, less than the lower limit of the pressure range in which the ink flow path and the head module 22M are damaged by the ink pressure), and is determined from the nozzle 221 by the ink pressure. The size is set so that the ink is ejected with the amount of ink within a predetermined range per hour. Here, the above-mentioned predetermined range related to the amount of ink to be ejected is equal to or more than the lower limit value at which contaminants can be effectively removed from the nozzle 221 by ejection maintenance, and ink is ejected only during the ejection maintenance time during which impurities can be sufficiently removed. Can be less than or equal to the upper limit that can be continued. In the discharge maintenance operation, the liquid feed pump has a liquid feed amount (volume of ink delivered per unit time) so that the pressure of the ink to be fed reaches the reference pressure while the reference pressure is set within this range. The liquid is sent according to 32. As a result, the pressure of the ink supplied to the head module 22M is stabilized near the reference pressure by the pressure adjusting valve 333, so that the liquid is stably fed at a pressure that allows the ink to be forcibly discharged from the nozzle 221. It can be performed.

Further, it is desirable that the reference pressure of the pressure adjusting valve 333 is further adjusted within the above range according to the temperature (viscosity) of the ink. That is, when the temperature of the ink becomes low and the viscosity increases in the vicinity of the liquid feeding pump 32, the pressure loss in the ink flow path becomes large and the pressure of the ink in the recording head 22 decreases, so that the liquid feeding pump 32 It is preferable to make adjustments to increase the reference pressure so as to compensate for the increase in pressure loss due to the increase in the viscosity of the ink in the vicinity of. On the other hand, when the temperature of the ink rises in the vicinity of the recording head 22 and the viscosity decreases, the drag force of the ink on the impurities of the nozzle 221 becomes small, and it becomes difficult to obtain the effect of flushing the impurities. Therefore, it is preferable to make adjustments to increase the reference pressure so as to compensate for the decrease in drag due to the decrease in ink viscosity in the vicinity of the recording head 22. In the present embodiment, the reference pressure of the pressure regulating valve 333 at each temperature is set to a value that maximizes the maintenance efficiency by integrating the pressure loss of the ink and the drag force exerted on the object in the ink. To. Specifically, the optimum reference pressure corresponding to each temperature of the ink is stored in the storage unit 44 as table data, and the reference pressure is a reference corresponding to the temperature detected by the ink temperature detection unit 34 based on the table data. Adjusted to pressure.

The pressure of the ink in the ink flow path (for example, the common flow path 301) is measured while changing the liquid feed amount to determine the liquid feed amount (target liquid feed amount) such that the pressure of the ink to be fed reaches the reference pressure. It can be obtained in advance. Further, the target liquid feed amount increases as the number of open ink supply valves 331 (that is, the number of head modules 22M that feed the liquid) increases. Therefore, by performing the above measurements by changing the number of ink supply valves 331 to be opened, an appropriate target liquid feed amount corresponding to the number of head modules 22M to be subject to ejection maintenance can be obtained in advance.

When the ejection of ink from the nozzle 221 is started and a predetermined time elapses, the liquid feeding by the liquid feeding pump 32 is stopped, and the ink stored in the sub tank 312 is prevented from flowing back to the main tank 311. The supply valve 331 is closed. In this state, the ink recirculation valve 332 is opened, the recirculation flow path 303 is opened, and the pressure of the ink in the recording head 22 decreases, so that the ink discharge is stopped. In the ejection maintenance operation, the time during which the ink is ejected from the nozzle 221 is set within a range equal to or more than the lower limit time during which impurities can be effectively ejected from the nozzle 221, and is set to, for example, about 3 seconds.

FIG. 7 is a diagram showing the time change of the ink pressure in the ejection maintenance operation. FIG. 7A shows the time change of the ink pressure in the ejection maintenance operation of the present embodiment, and FIG. 7B shows the ejection maintenance operation in a conventional inkjet recording device that does not use the pressure adjusting valve 333. The time change of the ink pressure when done is shown.

As shown in FIG. 7B, when the pressure regulating valve 333 is not used, if the liquid feed amount is increased too much for the purpose of reaching the target pressure pa earlier, the ink pressure becomes the target pressure. After reaching pa, the target pressure pa will be exceeded, so it is necessary to limit the amount of liquid to be sent. Therefore, in FIG. 7B, the rate of increase in the ink pressure is small, and the time from the start of liquid feeding at the timing t0 to the timing t2 when the ink pressure reaches the target pressure pa becomes long. There is. Further, even after the ink pressure reaches the target pressure pa, it is difficult to suppress fluctuations in the ink pressure due to various factors such as pulsation of the pump.

On the other hand, as shown in FIG. 7A, in the inkjet recording apparatus 1 of the present embodiment using the pressure adjusting valve 333, the reference pressure of the pressure adjusting valve 333 is adjusted so as to match the target pressure pa. By setting the pressure, the pressure adjusting valve 333 is opened after the timing t1 when the ink pressure reaches the target pressure pa even if the liquid feeding is started with a large amount of liquid to reach the target pressure pa at an early stage. The ink pressure stabilizes within the vicinity of the target pressure pa. Further, by such liquid feeding, the time (t1-t0) until the ink pressure reaches the target pressure pa can be significantly shortened as compared with the conventional example (t2-t0) of FIG. 7 (b).

Next, the reflux maintenance operation will be described.
Among the maintenance operations of the present embodiment, the recirculation maintenance operation is to recirculate the ink in the recording head 22 to the main tank 311 to flush out air bubbles contained in the ink in the recording head 22 and remove them from the recording head 22. With the goal. The ink bubbles removed from the recording head 22 are released under atmospheric pressure by being washed away by the main tank 311 and disappear.

In the recirculation maintenance operation, the ink supply valve 331 and the ink recirculation valve 332 are opened, and the liquid is fed by the liquid feed pump 32 with the air valve 334 closed. As a result, the ink stored in the main tank 311 circulates through the common flow path 301, the individual flow path 302, the sub tank 312, the upstream ink chamber 2221 of the recording head 22, the downstream ink chamber 2222, and the reflux flow path 303.

Here, the pressure of the liquid sent by the liquid feeding pump 32 is set to the pressure at which the ink supplied to the recording head 22 is not ejected (leaked) from the nozzle 221 due to the ink pressure. In order to stably supply ink at such a pressure, in the present embodiment, when the reflux maintenance operation is performed, the reference pressure of the pressure adjusting valve 333 is the first reference pressure in the discharge maintenance operation described above. It is set to a second reference pressure that is smaller than. This second reference pressure is set to a magnitude equal to or less than the upper limit value of the pressure range in which the ink does not leak from the nozzle 221 due to the pressure of the ink. In the recirculation maintenance operation, the liquid is fed by the liquid feeding pump 32 in a liquid feeding amount so that the pressure of the ink to be fed reaches the second reference pressure in a state where the reference pressure is set in this way. As a result, stable liquid feeding can be performed at a pressure at which ink does not leak from the nozzle 221.
Regarding the recirculation maintenance operation, the optimum reference pressure according to the ink temperature is acquired in advance and stored in the storage unit 44 as table data, and is based on the table data according to the temperature detected by the ink temperature detection unit 34. The reference pressure is adjusted.

In addition, the discharge maintenance operation and the reflux maintenance operation may be performed at a reference pressure fixed to a value corresponding to the characteristics of the elastic member 3355a by using the pressure adjusting valve 333 in which the position of the elastic member 3335a is fixed. In this case, the ink pressure may be adjusted by adjusting the liquid feed amount by the liquid feed pump 32. That is, if the amount of liquid sent by the liquid feeding pump 32 is adjusted according to the number of head modules 22M subject to recirculation maintenance so that the ink pressure in the recording head 22 becomes a pressure at which ink does not leak from the nozzle 221. Good.

The time during which the liquid is fed by the liquid feed pump 32 in the reflux maintenance operation is set within a range equal to or more than the lower limit time required for the ink bubbles to be sufficiently removed by refluxing the ink to the main tank 311. It is said to be about 20 seconds.

Next, the operation of the inkjet recording device 1 at the time of image recording will be described.
In the image recording operation, the ink supply valve 331 and the ink recirculation valve 332 are closed, and the air in the air buffer tank 71 is exhausted by the exhaust pump 72 with the air valve 334 open, and the inside of the sub tank 312 is set to negative pressure. .. As a result, the ink in the recording head 22 is drawn in the direction of the sub tank 312, and the pressure in the nozzle 221 is slightly negative. By such an operation, unintended leakage of ink from the nozzle 221 at the time of image recording is prevented. In this state, the transfer of the recording medium M by the transfer belt 103 is started, and the drive signal is supplied to the recording element of the recording head 22 at an appropriate timing according to the transfer, so that ink is ejected from the nozzle 221. The image is recorded on the recording medium M.

Next, the control procedure by the control unit 40 for the discharge maintenance process and the reflux maintenance process will be described with reference to the flowchart.
The discharge maintenance process and the reflux maintenance process are started when a predetermined input operation is performed by the user on the operation display unit 52 or when a predetermined condition related to the operation of the inkjet recording device 1 is satisfied. Examples of cases where a predetermined condition is satisfied include a case where an image is formed on a recording medium M of a predetermined amount or more, a case where a predetermined time has elapsed since the last image recording operation was performed, and the like.
When the discharge maintenance process and the reflux maintenance process are started, the head unit 20 is moved to a position facing the cleaning unit in advance under the control of the control unit 40 or by human hands.

FIG. 8 is a flowchart showing a control procedure of the discharge maintenance process.

When the ejection maintenance process is started, the control unit 40 detects the ink temperature by the ink temperature detecting unit 34 and acquires the information related to the ink temperature (step S101).

The control unit 40 refers to the table data stored in the storage unit 44, and acquires a reference pressure (first reference pressure) corresponding to the acquired ink temperature. Then, the control unit 40 operates the reference pressure changing unit 3335 of the pressure adjusting valve 333 to adjust the reference pressure of the pressure adjusting valve 333 to the acquired first reference pressure (step S102).

The control unit 40 closes the ink recirculation valve 332 and the air valve 334, and opens the head module 22M and the ink supply valve 331 corresponding to the target of discharge maintenance (step S103).

The control unit 40 transfers the amount of liquid to be fed by the liquid feed pump 32 based on the first reference pressure set in step S102 and the number of ink supply valves 331 opened in step S103. The pressure of the liquid is set to reach the first reference pressure (step S104).

The control unit 40 starts the ink feeding by the liquid feeding pump 32 at the set liquid feeding amount, and forcibly discharges the ink from the nozzle 221 of the recording head 22 (step S105).

When a predetermined time has elapsed from the start of ink feeding, the control unit 40 ends the liquid feeding by the liquid feeding pump 32 (step S106) and closes the ink supply valve 331 (step S107).

The control unit 40 opens the ink recirculation valve 332 for a predetermined time to reduce the pressure of the ink in the recording head 22 (step S108), then opens the air valve 334 (step S109), and ends the ejection maintenance process. ..

FIG. 9 is a flowchart showing a control procedure of the reflux maintenance process.

When the reflux maintenance process is started, the control unit 40 detects the ink temperature by the ink temperature detecting unit 34 and acquires the information related to the ink temperature (step S201).

The control unit 40 refers to the table data stored in the storage unit 44, and acquires a reference pressure (second reference pressure) corresponding to the acquired ink temperature. Then, the control unit 40 operates the reference pressure changing unit 3335 of the pressure adjusting valve 333 to adjust the reference pressure of the pressure adjusting valve 333 to the acquired second reference pressure (step S202).

The control unit 40 opens the ink supply valve 331 and the ink recirculation valve 332 corresponding to the head module 22M subject to recirculation maintenance, and closes the air valve 334 (step S203).

The control unit 40 transfers the amount of liquid supplied by the liquid feed pump 32 based on the second reference pressure set in step S202 and the number of ink supply valves 331 opened in step S203. The pressure of the liquid is set to reach the second reference pressure (step S204).

The control unit 40 starts the ink feeding by the liquid feeding pump 32 at the set liquid feeding amount, and returns the ink in the recording head 22 to the main tank 311 (step S205).

The control unit 40 ends the liquid feeding by the liquid feeding pump 32 when a predetermined time elapses from the start of the ink feeding (step S206). Then, the control unit 40 closes the ink supply valve 331 and the ink recirculation valve 332, opens the air valve 334 (step S207), and ends the recirculation maintenance process.

As described above, the inkjet recording apparatus 1 according to the present embodiment stores two or more predetermined number of head modules 22M each having a nozzle 221 for ejecting ink and ink supplied to the predetermined number of head modules 22M. A common flow path 301 communicating with the main tank 311 and the main tank 311, a predetermined number of individual flow paths 302 connecting the common flow path 301 and a predetermined number of head modules 22M, and a common flow path branched from the common flow path 301. An ink flow path having a return flow path 304 connecting the 301 and the main tank 311 without passing through the individual flow path 302, and an ink stored in the main tank 311 via the common flow path 301 and the individual flow path 302. The liquid feeding pump 32 that supplies the liquid to the head module 22M and the predetermined number of individual flow paths 302 are each provided to check the communication state and the non-communication state between the common flow path 301 and the head module 22M. When the pressure of the ink in the common flow path 301 is equal to or lower than the predetermined reference pressure, the return flow path 304 is closed and the ink in the common flow path 301 is provided with the switching ink supply valve 331 and the return flow path 304. A pressure adjusting valve 333 that opens the return flow path 304 when the pressure is higher than the reference pressure and a control unit 40 are provided, and the reference pressure communicates with the common flow path 301 by the pressure of the ink in the common flow path 301. The size is equal to or greater than the lower limit of the pressure range in which ink is ejected from the nozzle 221 of the head module 22M, and is within the pressure resistance range of the ink flow path and the head module 22M. In a state where at least a part of the ink is communicated with the common flow path 301 via the individual flow path 302, the liquid transfer operation is performed by the liquid transfer pump 32 with the amount of the ink to reach the reference pressure in the common flow path 301. By doing so, the ejection maintenance control for ejecting ink from the nozzle 221 of the head module 22M communicating with the common flow path 301 is performed.

According to such a configuration, in the discharge maintenance control, the liquid feeding operation is performed by the liquid feeding pump 32 at a liquid feeding amount at which the pressure of the ink in the common flow path 301 reaches the reference pressure, so that the pressure adjusting valve 333 operates. Therefore, the ink pressure in the common flow path 301 and the recording head 22 can be stabilized near the reference pressure. As a result, the amount of ink ejected from the nozzle 221 can be easily controlled to the minimum necessary amount, the amount of ink ejected can be reduced, and the sustainable time of the ejection maintenance operation can be lengthened. .. In addition, at the start of ejection maintenance, it is not necessary to control the amount of liquid to be sent in advance so that the ink pressure does not exceed the reference pressure, so the ink pressure can be raised to the target pressure in a shorter time. it can. As described above, according to the inkjet recording apparatus 1 of the present embodiment, impurities can be easily and stably removed from the head module 22M while suppressing waste of ink.
In addition, the moment when all the ink supply valves 331 that should be opened are closed due to a malfunction or failure, or when all the ink supply valves 331 are opened and closed during liquid feeding, all the ink supply valves 331 are closed. Even if the ink pressure in the common flow path 301 is unintentionally increased due to the occurrence, the ink pressure in the common flow path 301 is lowered by opening the pressure adjusting valve 333, so that the ink pressure in the common flow path 301 is reduced. It is possible to suppress the occurrence of a problem that the ink flow path such as the return flow path 304 and the liquid feed pump 32 are damaged. Further, when a part of the ink supply valve 331 that should be opened for ejection maintenance is closed due to a malfunction or failure, and the number of head modules 22M communicating with the common flow path 301 becomes less than the set number. In addition, it is possible to suppress the occurrence of a problem that the ink pressure in the recording head 22 in the head module 22M increases and the recording head 22 is damaged.
Further, the number of liquid feeding pumps can be reduced as compared with a configuration in which a liquid feeding pump is provided for each individual flow path 302 and ink is individually fed to the head module 22M by each liquid feeding pump. In general, an opening / closing part such as a solenoid valve is cheaper than a liquid feed pump, so that the above configuration can suppress an increase in the manufacturing cost of the inkjet recording device 1.

Further, the control unit 40 determines that the amount of liquid to be fed in the liquid feeding operation increases as the number of head modules 22M communicating with the common flow path 301 increases. As a result, in ejection maintenance, it is possible to suppress the occurrence of a problem that the pressure of the ink increases to a range in which the pressure adjusting action of the pressure adjusting valve 333 does not sufficiently function.

Further, a recirculation flow path 303 for recirculating the ink supplied to a predetermined number of head modules 22M to the main tank 311 and an ink recirculation valve 332 provided in the recirculation flow path 303 for opening or closing the recirculation flow path 303. The control unit 40 is provided with the ink in the common flow path 301 in a state where the return flow path 303 is closed and at least a part of the head module 22M communicates with the common flow path 301 via the individual flow path 302. Discharge maintenance control is performed by causing the liquid feed pump 32 to perform a liquid feed operation when the pressure reaches the reference pressure, the return flow path 303 is opened, and at least a part of the head module 22M is an individual flow path. In a state of being communicated with the common flow path 301 via 302, the liquid feeding operation is performed by the liquid feeding pump 32 with a liquid feeding amount corresponding to the number of head modules 22M communicating with the common flow path 301. The recirculation maintenance control is performed so that the ink of the head module 22M communicating with the flow path 301 is recirculated to the main tank 311 via the recirculation flow path 303. As a result, the inkjet recording device 1 can switch between ejection maintenance and reflux maintenance.

Further, the pressure adjusting valve 333 has a reference pressure changing portion 3335 for changing the reference pressure. Thereby, the reference pressure can be adjusted according to the temperature of the ink to be sent, and the reference pressure can be adjusted so as to be a pressure suitable for each of discharge maintenance and reflux maintenance.

Further, the inkjet recording device 1 includes an ink temperature detecting unit 34 that detects the temperature of the ink supplied to the head module 22M by the liquid feeding pump 32, and the control unit 40 detects the reference pressure by the ink temperature detecting unit 34. The reference pressure changing unit 3335 changes the value to a preset value corresponding to the temperature. As a result, ejection maintenance and reflux maintenance can be performed at an appropriate pressure according to the temperature of the ink to be sent.

Further, the pressure adjusting valve 333 has a reference pressure changing unit 3335 for changing the reference pressure, and the control unit 40 adjusts the reference pressure by operating the reference pressure changing unit 3335 when starting the recirculation maintenance control. Adjust to a second reference pressure that is smaller than the first reference pressure when discharge maintenance control is performed, and in recirculation maintenance control, the amount of liquid sent when the pressure of the ink in the common flow path 301 reaches the second reference pressure. The liquid feeding operation is performed by the liquid feeding pump 32. As a result, even in the reflux maintenance, the ink pressure in the common flow path 301 and the recording head 22 can be stabilized to the reference pressure by the action of the pressure adjusting valve 333. Therefore, it is possible to suppress the occurrence of a problem that the ink pressure in the recording head 22 increases and unintended ink leakage from the nozzle 221 occurs.

The present invention is not limited to the above embodiment and each modification, and various modifications can be made.
For example, when it is not necessary to perform recirculation maintenance, the recirculation flow path 303 and the ink recirculation valve 332 may not be provided in the ink supply mechanism 30.

Further, in the above embodiment, the head module 22M composed of a pair of recording heads 22 has been described as an example of the ink ejection unit connected to one individual flow path 302, but the present invention is not limited to this. For example, two or more head modules 22M may be communicated in series with one individual flow path 302, or a single recording head 22 may be communicated with one individual flow path 302.

Further, in the above embodiment, the example in which the reference pressure of the pressure regulating valve 333 is variable has been described, but a pressure regulating valve in which the reference pressure is fixed may be used.

Further, in the above embodiment, the negative pressure in the recording head 22 is generated by the exhaust pump 72 in the image recording operation, but the method of generating the negative pressure is not limited to this. For example, the position of the recording head 22 may be set higher than the position of the liquid level of the ink in the sub tank 312 to generate a negative pressure due to the head difference.

Further, in the ink flow path of the ink supply mechanism 30, a filter for capturing impurities contained in the ink, a degassing device for removing air bubbles in the ink, a heating device for adjusting the temperature of the ink, and cooling are provided. Various members and devices such as devices may be provided.

Further, in the above embodiment, an example in which an electromagnetic valve is used as the ink supply valve 331 and the ink recirculation valve 332 has been described, but the present invention is not limited to this, and other opening / closing units that open / close in response to a control signal from the control unit 40 are not limited to this. For example, an electric valve that opens and closes the valve by the operation of a motor may be used.

Further, in each of the above-described embodiments and modifications, the inkjet recording apparatus 1 for recording an image by a line head in which nozzles 221 are arranged over a recording range of an image in the X direction on the recording medium M has been described as an example. The present invention may be applied to an inkjet recording apparatus that records an image while scanning a recording head.

Although some embodiments of the present invention have been described, the scope of the present invention is not limited to the above-described embodiments, but includes the scope of the invention described in the claims and the equivalent scope thereof. ..

1 Ink inkjet recording device 10 Conveying unit 101, 102 Conveying roller 103 Conveying belt 20 Head unit 21 Recording head control unit 22 Recording head 221 Nozzle 222 Common ink chamber 223 Inlet 224 Outlet 22M Head module 30 Ink supply mechanism 301 Common flow path 302 Individual flow Path 303 Circulation flow path 304 Return flow path 305 Ventilation path 311 Main tank 312 Sub tank 32 Liquid feed pump 331 Ink supply valve 332 Ink recirculation valve 333 Pressure adjustment valve 3331 Primary side flow path 3332 Secondary side flow path 3333 Convergence part 3334 Plug part 3335 Reference pressure change unit 3335a Elastic member 3335b Adjusting screw 334 Air valve 34 Ink temperature detection unit 40 Control unit 61 External tank 62 Supply pump 71 Air buffer tank 72 Exhaust pump M Recording medium

Claims (5)

Two or more predetermined number of ink ejection parts each having nozzles for ejecting ink, and
An ink storage unit that stores ink supplied to the predetermined number of ink ejection units, and an ink storage unit.
A common flow path that communicates with the ink storage section, a predetermined number of individual flow paths that connect the common flow path and the predetermined number of ink ejection sections, and a common flow path that branches from the common flow path and the ink. An ink flow path having a return flow path that connects the storage unit without passing through the individual flow path, and an ink flow path.
A liquid feeding unit that performs a liquid feeding operation to supply the ink stored in the ink storage unit to the ink ejection unit via the common flow path and the individual flow path, and a liquid feeding unit.
A first opening / closing unit provided in each of the predetermined number of individual flow paths and switching between a communication state and a non-communication state between the common flow path and the ink ejection section.
When the pressure of the ink in the common flow path provided in the return flow path is equal to or lower than a predetermined reference pressure, the return flow path is closed and the pressure of the ink in the common flow path is larger than the reference pressure. In some cases, the pressure adjusting unit that opens the feedback flow path and
Control unit and
With
The reference pressure is equal to or higher than the lower limit of the pressure range in which ink is ejected from the nozzle of the ink ejection portion communicating with the common flow path due to the pressure of the ink in the common flow path, and the ink flow path and the ink flow path The size is within the pressure resistance range of the ink ejection part.
The pressure adjusting unit has a reference pressure changing unit that changes the reference pressure.
In the control unit, at least a part of the predetermined number of ink ejection units communicates with the common flow path via the individual flow paths, and the ink pressure in the common flow path reaches the reference pressure. An inkjet characterized by performing ejection maintenance control for ejecting ink from the nozzle of the ink ejection unit communicating with the common flow path by causing the liquid feeding unit to perform the liquid feeding operation according to the amount of liquid. Recording device. The inkjet according to claim 1, wherein the control unit determines the amount of liquid to be fed in the liquid feeding operation so as to increase as the number of the ink ejection units communicating with the common flow path increases. Recording device. A recirculation flow path for refluxing the ink supplied to the predetermined number of ink ejection portions to the ink storage portion, and
A second opening / closing portion provided in the reflux flow path to open or close the reflux flow path,
With
The control unit
The pressure of the ink in the common flow path is the reference in a state where the return flow path is closed and at least a part of the predetermined number of ink ejection portions communicates with the common flow path via the individual flow path. The discharge maintenance control is performed by causing the liquid feeding unit to perform the liquid feeding operation with the liquid feeding amount reaching the pressure.
The ink communicating with the common flow path in a state where the return flow path is open and at least a part of the predetermined number of ink ejection portions communicates with the common flow path via the individual flow path. By causing the liquid feeding unit to perform the liquid feeding operation with a liquid feeding amount corresponding to the number of the discharging parts, the ink of the ink discharging part communicating with the common flow path is transmitted through the recirculation flow path. The inkjet recording apparatus according to claim 1 or 2, wherein the recirculation maintenance control for recirculating the ink to the ink storage unit is performed. An ink temperature detection unit for detecting the temperature of the ink supplied to the ink ejection unit by the liquid feeding unit is provided.
Any of claims 1 to 3, wherein the control unit causes the reference pressure changing unit to change the reference pressure to a preset value corresponding to the temperature detected by the ink temperature detecting unit. The inkjet recording apparatus according to one item. Two or more predetermined number of ink ejection parts each having nozzles for ejecting ink, and
An ink storage unit that stores ink supplied to the predetermined number of ink ejection units, and an ink storage unit.
A common flow path that communicates with the ink storage section, a predetermined number of individual flow paths that connect the common flow path and the predetermined number of ink ejection sections, and a common flow path that branches from the common flow path and the ink. An ink flow path having a return flow path that connects the storage unit without passing through the individual flow path, and an ink flow path.
A liquid feeding unit that performs a liquid feeding operation to supply the ink stored in the ink storage unit to the ink ejection unit via the common flow path and the individual flow path, and a liquid feeding unit.
A first opening / closing unit provided in each of the predetermined number of individual flow paths and switching between a communication state and a non-communication state between the common flow path and the ink ejection section.
When the pressure of the ink in the common flow path provided in the return flow path is equal to or lower than a predetermined reference pressure, the return flow path is closed and the pressure of the ink in the common flow path is larger than the reference pressure. In some cases, the pressure adjusting unit that opens the feedback flow path and
A recirculation flow path for refluxing the ink supplied to the predetermined number of ink ejection portions to the ink storage portion, and
A second opening / closing portion provided in the reflux flow path to open or close the reflux flow path,
Control unit and
With
The reference pressure is equal to or higher than the lower limit of the pressure range in which ink is ejected from the nozzle of the ink ejection portion communicating with the common flow path due to the pressure of the ink in the common flow path, and the ink flow path and the ink flow path The size is within the pressure resistance range of the ink ejection part.
The pressure adjusting unit has a reference pressure changing unit that changes the reference pressure.
The control unit
In a state where at least a part of the predetermined number of ink ejection portions communicates with the common flow path via the individual flow path, the ink feed in the common flow path reaches the reference pressure. By causing the liquid unit to perform the liquid feeding operation, ejection maintenance control for ejecting ink from the nozzle of the ink ejection unit communicating with the common flow path is performed.
The pressure of the ink in the common flow path is the reference in a state where the return flow path is closed and at least a part of the predetermined number of ink ejection portions communicates with the common flow path via the individual flow path. The discharge maintenance control is performed by causing the liquid feeding unit to perform the liquid feeding operation with the liquid feeding amount reaching the pressure.
The ink communicating with the common flow path in a state where the reflux flow path is open and at least a part of the predetermined number of ink ejection portions communicates with the common flow path via the individual flow path. By causing the liquid feeding unit to perform the liquid feeding operation with a liquid feeding amount corresponding to the number of the discharging parts, the ink of the ink discharging part communicating with the common flow path is transmitted through the reflux flow path. Performs reflux maintenance control to return the ink to the ink reservoir,
When the reflux maintenance control is started, the reference pressure changing unit is operated to adjust the reference pressure to a second reference pressure smaller than the first reference pressure when the discharge maintenance control is performed. ,
The reflux maintenance control, the common flow the liquid feed operation characteristics and to Louis inkjet recording apparatus be performed by the liquid supply unit with feed volume the pressure reaches the second reference pressure of the ink in the passage ..

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