JP2023101789A - Liquid discharge device and control method of liquid discharge device - Google Patents

Abstract

To shorten the FPOT (First Print Out Time) in a configuration of circulating ink in between a recording head and a tank.SOLUTION: An inkjet recording device includes: a tank for storing ink; a recording head for performing recording operation by discharging ink supplied from the tank; a supply passage for supplying ink from the tank to the recording head; a recovery passage for recovering ink from the recording head to the tank; and a pump provided in the supply passage or the recovery passage. The inkjet recording device circulates ink in a circulation passage including the tank, the supply passage and the recovery passage by driving the pump at a first speed, in between recording operations, and drives the pump at a second speed faster than the first speed, until a prescribed time has passed from starting the circulation of ink.SELECTED DRAWING: Figure 14

Description

The present invention relates to an inkjet recording apparatus and an inkjet recording apparatus control method.

2. Description of the Related Art There is an ink jet recording apparatus that employs an ink circulation system that circulates ink in pressure chambers communicating with ejection ports for ejecting ink. Japanese Patent Application Laid-Open No. 2002-200001 describes a head module having an ink circulation type pressure chamber, and describes an ink circulation supply system in which ink circulates in the order of a first main flow path, a head module, and a second main flow path. In Patent Document 1, a first liquid pump is provided in a first main flow path, and a second liquid pump is provided in a second main flow path.

JP 2011-79169 A

The time from the input of the print instruction to the start of ejection is called FPOT (First Print Out Time). 2. Description of the Related Art In an ink jet recording apparatus employing an ink circulation system, ink circulation is stopped when a recording operation is not performed. When ink circulation is started in response to a print instruction from a state in which ink circulation is stopped, the FPOT may become long.

In addition, in the configuration in which the ink in the pressure chamber is circulated as in Patent Document 1, the air in the flow path may contract according to the temperature change and draw air from the ejection port, or the air may expand and the ink may leak from the ejection port. Therefore, in some cases, a buffer chamber is provided in the circulation path to absorb the volume change of the air in the flow path. In order to generate an ink flow in the pressure chamber of the head module, it is necessary to adjust the inside of the circulation path to an appropriate pressure.

In view of the above problems, it is an object of the present invention to provide a liquid ejection device, a circulation device, a control method for the liquid ejection device, and a control method for the circulation device that can control the flow rate of liquid in a liquid circulation configuration.

An inkjet recording apparatus according to an aspect of the present invention is an inkjet recording apparatus comprising: a tank containing ink; a recording head that performs a recording operation by ejecting ink supplied from the tank; a supply channel that supplies ink from the tank to the recording head; a recovery channel that recovers ink from the recording head to the tank; and the pump is driven at a second speed higher than the first speed until a predetermined time elapses after the start of ink circulation.

ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to control the flow volume of a liquid in the structure which circulates a liquid.

FIG. 4 is a diagram when the recording device is in a standby state; 3 is a control configuration diagram of the recording apparatus; FIG. FIG. 4 is a diagram when the recording device is in a recording state; 4 is a transport path diagram of a recording medium fed from a first cassette; FIG. FIG. 4 is a transport path diagram of a recording medium fed from a second cassette; FIG. 10 is a conveying route diagram when a recording operation is performed on the back surface of a recording medium; FIG. 10 is a diagram when the recording device is in a maintenance state; 4 is a perspective view showing the configuration of the maintenance unit; FIG. FIG. 3 is a diagram for explaining a flow channel configuration of an ink circulation system; It is a figure which shows an example of a buffer chamber. It is a figure which shows the cross section of a buffer chamber. FIG. 4 is a diagram showing open/closed states of valves in a circulation flow path and driving states of a pump; FIG. 4 is a diagram showing open/closed states of valves in a circulation flow path and driving states of a pump; It is a figure which shows a flowchart. FIG. 3 is a diagram for explaining a flow channel configuration of an ink circulation system; FIG. 3 is a diagram for explaining a flow channel configuration of an ink circulation system; It is a figure explaining an ejection port and a pressure chamber. It is a figure explaining a negative pressure control unit.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings. It should be noted that the following embodiments do not limit the present invention, and not all combinations of features described in the embodiments are essential for the solution of the present invention. In addition, the same configuration will be described by attaching the same reference numerals. In addition, the relative arrangement, shape, etc. of the constituent elements described in the embodiments are merely examples, and are not meant to limit the scope of the present invention only to them.

<<Embodiment 1>>
FIG. 1 is an internal configuration diagram of an inkjet recording apparatus 1 (hereinafter referred to as recording apparatus 1) used in this embodiment. In the drawing, the x direction is the horizontal direction, the y direction (perpendicular to the paper surface) is the direction in which ejection ports are arranged in the recording head 8 described later, and the z direction is the vertical direction.

The recording apparatus 1 is a multi-function machine including a print unit 2 and a scanner unit 3, and various processes related to recording operation and reading operation can be executed by the print unit 2 and the scanner unit 3 individually or in conjunction with each other. The scanner unit 3 includes an ADF (automatic document feeder) and an FBS (flatbed scanner), and can read (scan) documents automatically fed by the ADF and documents placed on the document table of the FBS by the user. Although the present embodiment is a multifunction device having both the printing unit 2 and the scanner unit 3, a configuration without the scanner unit 3 is also possible. FIG. 1 shows the recording apparatus 1 in a standby state in which neither recording operation nor reading operation is performed.

In the printing unit 2, a first cassette 5A and a second cassette 5B for containing recording media (cut sheets) S are detachably installed at the bottom of the housing 4 in the vertical direction. The first cassette 5A accommodates relatively small recording media up to A4 size, and the second cassette 5B accommodates relatively large recording media up to A3 size in a flat stack. In the vicinity of the first cassette 5A, a first feeding unit 6A for separating and feeding the contained recording media one by one is provided. Similarly, a second feeding unit 6B is provided near the second cassette 5B. When the recording operation is performed, the recording medium S is selectively fed from one of the cassettes.

The transport roller 7, discharge roller 12, pinch roller 7a, spur 7b, guide 18, inner guide 19, and flapper 11 are a transport mechanism for guiding the recording medium S in a predetermined direction. The transport rollers 7 are driving rollers arranged upstream and downstream of the recording head 8 and driven by a transport motor (not shown). The pinch roller 7 a is a driven roller that rotates while nipping the recording medium S together with the transport roller 7 . The discharge roller 12 is a drive roller arranged downstream of the transport roller 7 and driven by a transport motor (not shown). The spur 7 b conveys the recording medium S while nipping it together with the conveying roller 7 and the discharging roller 12 arranged on the downstream side of the recording head 8 .

The guide 18 is provided on the transport path of the recording medium S and guides the recording medium S in a predetermined direction. The inner guide 19 is a member extending in the y direction and has a curved side surface, and guides the recording medium S along the side surface. The flapper 11 is a member for switching the direction in which the recording medium S is conveyed during the double-sided recording operation. The ejection tray 13 is a tray for stacking and holding the recording medium S ejected by the ejection roller 12 after the printing operation is completed.

The print head 8 of the present embodiment is a full-line type color inkjet print head, and a plurality of ejection openings for ejecting ink according to print data are arranged along the y direction in FIG. 1 by a width corresponding to the width of the print medium S. When the recording head 8 is at the standby position, the ejection port surface 8a of the recording head 8 faces vertically downward and is capped by the cap unit 10 as shown in FIG. When performing a printing operation, the direction of the printing head 8 is changed by the print controller 202 to be described later so that the ejection port surface 8 a faces the platen 9 . The platen 9 is composed of a flat plate extending in the y direction, and supports the recording medium S on which the recording operation is performed by the recording head 8 from the back. The movement of the recording head 8 from the standby position to the recording position will be described later in detail.

The ink tank unit 14 stores four color inks to be supplied to the recording head 8 . The ink supply unit 15 is provided in the middle of the flow path connecting the ink tank unit 14 and the recording head 8, and adjusts the pressure and flow rate of the ink inside the recording head 8 to appropriate ranges. This embodiment employs a circulating ink supply system, and the ink supply unit 15 adjusts the pressure of the ink supplied to the recording head 8 and the flow rate of the ink recovered from the recording head 8 within appropriate ranges.

The maintenance unit 16 includes the cap unit 10 and the wiping unit 17 and activates them at predetermined timings to perform maintenance operations on the recording head 8 . The maintenance operation will be explained later in detail.

FIG. 2 is a block diagram showing a control configuration in the printing apparatus 1. As shown in FIG. The control configuration is mainly composed of a print engine unit 200 that controls the print section 2, a scanner engine unit 300 that controls the scanner section 3, and a controller unit 100 that controls the entire printing apparatus 1. FIG. The print controller 202 controls various mechanisms of the print engine unit 200 according to instructions from the main controller 101 of the controller unit 100 . Various mechanisms of the scanner engine unit 300 are controlled by the main controller 101 of the controller unit 100 . Details of the control configuration will be described below.

In the controller unit 100 , a main controller 101 composed of a CPU controls the entire printing apparatus 1 using a RAM 106 as a work area according to programs and various parameters stored in a ROM 107 . For example, when a print job is input from the host device 400 via the host I/F 102 or wireless I/F 103 , the image processing unit 108 performs predetermined image processing on the received image data according to instructions from the main controller 101 . Then, the main controller 101 transmits the processed image data to the print engine unit 200 via the print engine I/F 105 .

Note that the printing apparatus 1 may acquire image data from the host device 400 via wireless communication or wired communication, or may acquire image data from an external storage device (such as a USB memory) connected to the printing apparatus 1 . A communication method used for wireless communication or wired communication is not limited. For example, Wi-Fi (Wireless Fidelity) (registered trademark) or Bluetooth (registered trademark) can be applied as a communication method used for wireless communication. As a communication method used for wired communication, USB (Universal Serial Bus) or the like can be applied. Also, for example, when a read command is input from the host device 400 , the main controller 101 transmits this command to the scanner section 3 via the scanner engine I/F 109 .

The operation panel 104 is a mechanism for the user to input/output to/from the printing apparatus 1 . A user can instruct operations such as copying and scanning, set a print mode, and recognize information of the printing apparatus 1 via the operation panel 104 .

In the print engine unit 200 , a print controller 202 configured by a CPU controls various mechanisms provided in the print section 2 while using a RAM 204 as a work area according to programs and various parameters stored in a ROM 203 . When various commands and image data are received via the controller I/F 201 , the print controller 202 temporarily stores them in the RAM 204 . The print controller 202 causes the image processing controller 205 to convert the stored image data into print data so that the print head 8 can be used for printing operations. When print data is generated, the print controller 202 causes the print head 8 to perform a print operation based on the print data via the head I/F 206 . At this time, the print controller 202 drives the feeding units 6A and 6B, the transport rollers 7, the ejection rollers 12, and the flapper 11 shown in FIG. In accordance with an instruction from the print controller 202, the recording operation by the recording head 8 is executed in conjunction with the conveying operation of the recording medium S, and printing processing is performed.

The head carriage control unit 208 changes the direction and position of the recording head 8 according to the operating state such as the maintenance state and recording state of the recording apparatus 1 . The ink supply control unit 209 controls the ink supply unit 15 so that the pressure of the ink supplied to the recording head 8 is within an appropriate range. The maintenance control unit 210 controls operations of the cap unit 10 and the wiping unit 17 in the maintenance unit 16 when performing maintenance operations on the recording head 8 .

In the scanner engine unit 300 , the main controller 101 controls hardware resources of the scanner controller 302 while using the RAM 106 as a work area according to programs and various parameters stored in the ROM 107 . As a result, various mechanisms provided in the scanner section 3 are controlled. For example, the main controller 101 controls the hardware resources in the scanner controller 302 via the controller I/F 301 to transport the document placed on the ADF by the user via the transport control unit 304 and read it by the sensor 305 . The scanner controller 302 stores the read image data in the RAM 303 . The print controller 202 converts the image data obtained as described above into print data, thereby making it possible for the print head 8 to execute a print operation based on the image data read by the scanner controller 302.

FIG. 3 shows the recording device 1 in the recording state. 1, the cap unit 10 is separated from the ejection port surface 8a of the recording head 8, and the ejection port surface 8a faces the platen 9. As shown in FIG. In this embodiment, the plane of the platen 9 is tilted about 45 degrees with respect to the horizontal direction, and the ejection port surface 8a of the recording head 8 at the recording position is also tilted about 45 degrees with respect to the horizontal direction so that the distance from the platen 9 is kept constant.

When moving the print head 8 from the standby position shown in FIG. 1 to the print position shown in FIG. 3, the print controller 202 uses the maintenance control section 210 to lower the cap unit 10 to the retracted position shown in FIG. As a result, the discharge port surface 8a of the recording head 8 is separated from the cap member 10a. Thereafter, the print controller 202 rotates the recording head 8 by 45 degrees while adjusting the vertical height of the recording head 8 using the head carriage control unit 208 , so that the ejection port surface 8 a faces the platen 9 . When the print operation is completed and the print head 8 is moved from the print position to the standby position, the print controller 202 performs the reverse steps.

Next, the transport path of the recording medium S in the printing section 2 will be described. When a print command is input, the print controller 202 first uses the maintenance control section 210 and the head carriage control section 208 to move the print head 8 to the print position shown in FIG. After that, the print controller 202 uses the transport control unit 207 to drive either the first feeding unit 6A or the second feeding unit 6B according to the recording command to feed the recording medium S. FIG.

FIGS. 4(a) to 4(c) are diagrams showing the transport path when the A4 size recording medium S housed in the first cassette 5A is transported. The recording medium S stacked at the top in the first cassette 5A is separated from the second and subsequent recording media by the first feeding unit 6A, and conveyed toward the recording area P between the platen 9 and the recording head 8 while being nipped between the conveying roller 7 and the pinch roller 7a. FIG. 4A shows the conveying state immediately before the leading edge of the recording medium S reaches the recording area P. FIG. While the recording medium S is fed to the first feeding unit 6A and reaches the recording area P, the direction of travel of the recording medium S is changed from the horizontal direction (x direction) to a direction inclined approximately 45 degrees with respect to the horizontal direction.

In the recording area P, ink is ejected toward the recording medium S from a plurality of ejection openings provided in the recording head 8 . The back surface of the recording medium S in the area to which ink is applied is supported by the platen 9, and the distance between the ejection port surface 8a and the recording medium S is kept constant. The recording medium S to which ink has been applied passes through the left side of the flapper 11 whose tip is inclined to the right while being guided by the transport roller 7 and the spur 7b, and is transported vertically upward of the recording apparatus 1 along the guide 18. FIG. 4B shows a state in which the leading edge of the recording medium S passes through the recording area P and is transported vertically upward. The traveling direction of the recording medium S is changed vertically upward by the conveying roller 7 and the spur 7b from the position of the recording area P which is inclined by about 45 degrees with respect to the horizontal direction.

After being transported vertically upward, the recording medium S is discharged to the discharge tray 13 by the discharge roller 12 and the spur 7b. FIG. 4C shows a state in which the leading edge of the recording medium S passes through the ejection roller 12 and is ejected to the ejection tray 13 . The discharged recording medium S is held on the discharge tray 13 with the surface on which the image is recorded by the recording head 8 facing downward.

FIGS. 5(a) to 5(c) are diagrams showing the transport path when the A3 size recording medium S housed in the second cassette 5B is fed. The recording medium S loaded at the top in the second cassette 5B is separated from the second and subsequent recording media by the second feeding unit 6B, and conveyed toward the recording area P between the platen 9 and the recording head 8 while being nipped between the conveying roller 7 and the pinch roller 7a.

FIG. 5A shows the conveying state immediately before the leading edge of the recording medium S reaches the recording area P. FIG. A plurality of conveying rollers 7, a pinch roller 7a and an inner guide 19 are arranged on the conveying path from the second feeding unit 6B to the recording area P, so that the recording medium S is curved in an S shape and conveyed to the platen 9.

The subsequent transport path is the same as in the case of the A4 size recording medium S shown in FIGS. 4(b) and 4(c). FIG. 5B shows a state in which the leading edge of the recording medium S passes through the recording area P and is transported vertically upward. FIG. 5C shows a state in which the leading edge of the recording medium S passes through the ejection roller 12 and is ejected to the ejection tray 13 .

FIGS. 6A to 6D show the transport path when performing a recording operation (double-sided recording) on the back side (second side) of the recording medium S of A4 size. When double-sided recording is performed, the recording operation is performed on the second side (back side) after recording on the first side (front side). The conveying process for recording the first side is the same as that shown in FIGS. Hereinafter, the transfer process after FIG. 4(c) will be described.

When the recording operation on the first side by the recording head 8 is completed and the trailing edge of the recording medium S passes the flapper 11 , the print controller 202 reversely rotates the conveying roller 7 to convey the recording medium S into the recording apparatus 1 . At this time, the flapper 11 is controlled by an actuator (not shown) so that its tip is tilted to the left, so that the tip of the recording medium S (the trailing edge in the recording operation of the first surface) passes the right side of the flapper 11 and is conveyed downward in the vertical direction. 6A shows a state in which the leading edge of the recording medium S (the trailing edge in the recording operation on the first surface) passes the right side of the flapper 11. FIG.

After that, the recording medium S is transported along the curved outer peripheral surface of the inner guide 19 and transported to the recording area P between the recording head 8 and the platen 9 again. At this time, the second surface of the recording medium S faces the ejection port surface 8 a of the recording head 8 . FIG. 6B shows the conveying state immediately before the leading edge of the recording medium S reaches the recording area P for the recording operation on the second surface.

The transport path after that is the same as in the first surface recording shown in FIGS. 4(b) and 4(c). FIG. 6C shows a state in which the leading edge of the recording medium S passes through the recording area P and is transported vertically upward. At this time, the flapper 11 is controlled by an actuator (not shown) so that the tip thereof is tilted to the right. FIG. 6D shows a state in which the leading edge of the recording medium S passes through the ejection roller 12 and is ejected to the ejection tray 13 .

<Maintenance operation>
Next, maintenance operations for the recording head 8 will be described. As explained in FIG. 1, the maintenance unit 16 of this embodiment includes the cap unit 10 and the wiping unit 17, and operates these at predetermined timings to perform maintenance operations.

FIG. 7 is a diagram when the recording apparatus 1 is in a maintenance state. When moving the recording head 8 from the standby position shown in FIG. 1 to the maintenance position shown in FIG. 7, the print controller 202 moves the recording head 8 upward in the vertical direction and moves the cap unit 10 downward in the vertical direction. Then, the print controller 202 moves the wiping unit 17 rightward in FIG. 7 from the retracted position. After that, the print controller 202 moves the recording head 8 downward in the vertical direction to the maintenance position where the maintenance operation can be performed.

On the other hand, when moving the recording head 8 from the recording position shown in FIG. 3 to the maintenance position shown in FIG. 7, the print controller 202 moves the recording head 8 vertically upward while rotating it by 45 degrees. The print controller 202 then moves the wiping unit 17 rightward from the retracted position. After that, the print controller 202 moves the recording head 8 downward in the vertical direction to the maintenance position where the maintenance operation by the maintenance unit 16 is possible.

FIG. 8A is a perspective view showing the maintenance unit 16 at the standby position, and FIG. 8B is a perspective view showing the maintenance unit 16 at the maintenance position. 8(a) corresponds to FIG. 1, and FIG. 8(b) corresponds to FIG. When the recording head 8 is at the standby position, the maintenance unit 16 is at the standby position shown in FIG. The cap unit 10 has a box-shaped cap member 10a extending in the y-direction, and is brought into close contact with the ejection port surface 8a of the recording head 8, thereby suppressing evaporation of ink from the ejection ports. The cap unit 10 also has a function of recovering the ink ejected to the cap member 10a by preliminary ejection or the like and causing the recovered ink to be sucked by a suction pump (not shown).

On the other hand, in the maintenance position shown in FIG. 8B, the cap unit 10 has moved downward in the vertical direction, and the wiping unit 17 has been pulled out from the maintenance unit 16 . The wiping unit 17 includes two wiper units (wiping members), a blade wiper unit 171 and a vacuum wiper unit 172 .

In the blade wiper unit 171, a blade wiper 171a for wiping the ejection port surface 8a along the x direction is arranged in the y direction by a length corresponding to the array region of the ejection ports. When performing a wiping operation using the blade wiper unit 171, the wiping unit 17 moves the blade wiper unit 171 in the x-direction while the recording head 8 is positioned at a height where it can contact the blade wiper 171a. Due to this movement, the blade wiper 171a wipes off ink adhering to the ejection port surface 8a.

At the entrance of the maintenance unit 16 when the blade wiper 171a is accommodated, a wet wiper cleaner 16a is arranged for removing ink adhering to the blade wiper 171a and applying a wet liquid to the blade wiper 171a. Every time the blade wiper 171a is housed in the maintenance unit 16, the wet wiper cleaner 16a removes deposits and coats the blade wiper 171a with a wet liquid. Then, when the ejection port surface 8a is wiped next time, the wet liquid is transferred to the ejection port surface 8a to improve the slipperiness between the ejection port surface 8a and the blade wiper 171a.

On the other hand, the vacuum wiper unit 172 has a flat plate 172a having an opening extending in the y direction, a carriage 172b movable in the opening in the y direction, and a vacuum wiper 172c mounted on the carriage 172b. The vacuum wiper 172c is arranged so as to be able to wipe the discharge port surface 8a in the y direction as the carriage 172b moves. A suction port connected to a suction pump (not shown) is formed at the tip of the vacuum wiper 172c. Therefore, when the carriage 172b is moved in the y direction while the suction pump is operated, the ink or the like adhering to the ejection port surface 8a of the recording head 8 is sucked into the suction port while being wiped by the vacuum wiper 172c. At this time, the flat plate 172a and the positioning pins 172d provided at both ends of the opening are used for positioning the discharge port surface 8a with respect to the vacuum wiper 172c.

In this embodiment, a first wiping process in which the blade wiper unit 171 performs the wiping operation and the vacuum wiper unit 172 does not perform the wiping operation, and a second wiping process in which both wiping processes are performed in order can be performed. When performing the first wiping process, the print controller 202 first pulls out the wiping unit 17 from the maintenance unit 16 while the recording head 8 is retracted vertically above the maintenance position in FIG. Then, the print controller 202 moves the wiping unit 17 into the maintenance unit 16 after moving the recording head 8 vertically downward to a position where it can contact the blade wiper 171a. Due to this movement, the blade wiper 171a wipes off ink or the like adhering to the ejection port surface 8a. That is, the blade wiper 171a wipes the discharge port surface 8a when moving into the maintenance unit 16 from the position pulled out from the maintenance unit 16. As shown in FIG.

After the blade wiper unit 171 is retracted, the print controller 202 next moves the cap unit 10 vertically upward to bring the cap member 10 a into close contact with the ejection port surface 8 a of the recording head 8 . In this state, the print controller 202 drives the recording head 8 to perform preliminary ejection, and the ink collected in the cap member 10a is sucked by the suction pump.

On the other hand, when performing the second wiping process, the print controller 202 first slides the wiping unit 17 out of the maintenance unit 16 while the recording head 8 is retracted vertically above the maintenance position in FIG. Then, the print controller 202 moves the wiping unit 17 into the maintenance unit 16 after moving the recording head 8 vertically downward to a position where it can contact the blade wiper 171a. As a result, the blade wiper 171a performs a wiping operation on the discharge port surface 8a. Next, the print controller 202 slides the wiping unit 17 out of the maintenance unit 16 to a predetermined position while the recording head 8 is retracted vertically above the maintenance position in FIG. Subsequently, the print controller 202 positions the discharge port surface 8a and the vacuum wiper unit 172 using the flat plate 172a and the positioning pin 172d while lowering the recording head 8 to the wiping position shown in FIG. After that, the print controller 202 performs the wiping operation by the vacuum wiper unit 172 described above. The print controller 202 retracts the recording head 8 vertically upward, retracts the wiping unit 17, and then performs preliminary discharge into the cap member by the cap unit 10 and sucking of the collected ink in the same manner as the first wiping process.

<Ink supply unit (ink circulation system)>
FIG. 9 is a diagram including the ink supply unit 15 employed in the inkjet recording apparatus 1 of this embodiment. The flow path configuration of the ink circulation system of this embodiment will be described with reference to FIG. The ink supply unit 15 is configured to supply ink from the ink tank unit 14 to the recording head 8 . Although the configuration for one color of ink is shown here, such a configuration is actually prepared for each ink color. The ink supply unit 15 is basically controlled by the ink supply controller 209 shown in FIG. Each configuration of the unit will be described below.

Ink circulates mainly between the sub-tank 151 and the recording head 8 (the head unit in FIG. 9). In the head unit 8, an ink ejection operation is performed based on the image data, and the ink that has not been ejected is recovered in the sub-tank 151 again.

A sub-tank 151 containing a predetermined amount of ink is connected to a supply channel C2 for supplying ink to the head unit 8 and a recovery channel C4 for recovering ink from the head unit 8 . In other words, the sub-tank 151, the supply channel C2, the head unit 8, and the recovery channel C4 constitute a circulation path through which the ink circulates.

The sub-tank 151 is provided with a liquid level detection means 151a composed of a plurality of pins, and the ink supply control unit 209 detects the presence or absence of conduction current between the plurality of pins, thereby ascertaining the height of the ink liquid level, that is, the amount of remaining ink in the sub-tank 151. The decompression pump P0 is a negative pressure generating source for decompressing the inside of the sub-tank 151 . The atmosphere release valve V0 is a valve for switching whether or not the inside of the sub-tank 151 is communicated with the atmosphere.

The main tank 141 is a tank that stores ink to be supplied to the sub-tank 151 . The main tank 141 is composed of a flexible member, and the sub-tank 151 is filled with ink by the volume change of the flexible member. The main tank 141 is detachable from the main body of the printing apparatus. A tank supply valve V1 for switching connection between the sub-tank 151 and the main tank 141 is arranged in the middle of the tank connection channel C1 that connects the sub-tank 151 and the main tank 141 .

With the above configuration, when the ink supply control unit 209 detects that the ink level in the sub-tank 151 is less than a predetermined amount by the liquid level detection means 151a, it closes the atmosphere release valve V0, the supply valve V2, the recovery valve V4, and the head replacement valve V5, and opens the tank supply valve V1. In this state, the ink supply control unit 209 operates the decompression pump P0. Then, the inside of the sub-tank 151 becomes negative pressure, and ink is supplied from the main tank 141 to the sub-tank 151 . When the liquid level detection means 151a detects that the ink in the sub-tank 151 has exceeded a predetermined amount, the ink supply control unit 209 closes the tank supply valve V1 and stops the decompression pump P0.

The supply channel C2 is a channel for supplying ink from the sub-tank 151 to the head unit 8, and a supply pump P1 and a supply valve V2 are arranged in the middle of the supply channel C2. During the recording operation, by driving the supply pump P1 with the supply valve V2 open, the ink can be supplied to the head unit 8 and circulated in the circulation path. The amount of ink ejected per unit time by the head unit 8 varies according to image data. The flow rate of the supply pump P1 is determined so as to be able to cope with the case where the head unit 8 performs an ejection operation that maximizes the amount of ink consumed per unit time.

The relief channel C3 is a channel that is upstream of the supply valve V2 and connects the upstream side and the downstream side of the supply pump P1. A relief valve V3, which is a differential pressure valve, is arranged in the middle of the relief passage C3. When the amount of ink supplied from the supply pump P1 per unit time is greater than the total value of the discharge amount per unit time of the head unit 8 and the flow rate (ink withdrawal amount) per unit time of the recovery pump P2, the relief valve V3 is opened according to the pressure acting on itself. As a result, a circular flow path is formed by a part of the supply flow path C2 and the relief flow path C3. By providing the configuration of the relief channel C3, the amount of ink supplied to the head unit 8 can be adjusted according to the amount of ink consumed in the head unit 8, and the pressure in the circulation path can be stabilized regardless of image data.

The recovery channel C4 is a channel for recovering ink from the head unit 8 to the sub-tank 151, and a recovery pump P2 and a recovery valve V4 are arranged in the middle of the channel. A buffer chamber 85 is arranged in the recovery channel C4. The buffer chamber 85 will be described later. The recovery pump P2 serves as a source of negative pressure and sucks ink from the head unit 8 when circulating the ink in the circulation path. By driving the recovery pump P2, an appropriate pressure difference is generated between the IN channel 80b and the OUT channel 80c in the head unit 8, and ink can be circulated between the IN channel 80b and the OUT channel 80c. The configuration of the flow paths within the head unit 8 will be described later in detail.

The recovery valve V4 is a valve for preventing backflow when the recording operation is not performed, that is, when the ink is not circulated in the circulation path. In the circulation path of this embodiment, the sub-tank 151 is arranged above the head unit 8 in the vertical direction (see FIG. 1). Therefore, when the supply pump P1 or the recovery pump P2 is not driven, ink may flow backward from the sub-tank 151 to the head unit 8 due to the difference in water head between the sub-tank 151 and the head unit 8 . In order to prevent such backflow, in this embodiment, a recovery valve V4 is provided in the recovery channel C4.

Similarly, the supply valve V2 also functions as a valve for preventing the supply of ink from the sub-tank 151 to the head unit 8 when the recording operation is not performed, that is, when the ink is not circulated in the circulation path.

The head replacement flow path C5 is a flow path that connects the supply flow path C2 and the air layer (the portion where ink is not stored) of the sub-tank 151, and the head replacement valve V5 is arranged in the middle of the flow path. One end of the head replacement channel C5 is connected upstream of the head unit 8 in the supply channel C2, and the other end is connected above the sub-tank 151 to communicate with the internal air layer. The head replacement channel C5 is used when recovering ink from the head unit 8 in use, such as when replacing the head unit 8 or when transporting the recording apparatus 1 . The head replacement valve V5 is controlled by the ink supply control unit 209 so as to be closed except when the recording apparatus 1 is initially filled with ink and when ink is recovered from the head unit 8. FIG. Further, the supply valve V2 described above is provided in the supply channel C2 between the connection portion with the head replacement channel C5 and the connection portion with the relief channel C3.

Next, the configuration of the flow paths within the head unit 8 will be described. Ink supplied to the head unit 8 from the supply channel C2 passes through a filter 83, and then is supplied to a first negative pressure control unit (first negative pressure control means) 81 and a second negative pressure control unit (second negative pressure control means) 82. The control pressure of the first negative pressure control unit 81 is set to a weak negative pressure. The control pressure of the second negative pressure control unit 82 is set to a strong negative pressure. The pressures in the first negative pressure control unit 81 and the second negative pressure control unit 82 are generated within an appropriate range by driving the recovery pump P2.

In the ink ejection section 80, a plurality of recording element substrates 80a each having a plurality of ejection openings are arranged to form a long ejection opening array. A common supply channel 80b (IN channel) for guiding ink supplied from the first negative pressure control unit 81 and a common recovery channel 80c (OUT channel) for guiding ink supplied from the second negative pressure control unit 82 also extend in the arrangement direction of the recording element substrates 80a. Further, individual supply channels connected to the common supply channel 80b and individual recovery channels connected to the common recovery channel 80c are formed in each recording element substrate 80a. Therefore, in each recording element substrate 80a, an ink flow is generated that flows in from the common supply channel 80b with relatively weak negative pressure and flows out to the common recovery channel 80c with relatively strong negative pressure. Pressure chambers that communicate with the ejection ports and are filled with ink are provided in the paths of the individual supply channels and the individual recovery channels, and the ink flows even in the ejection ports and pressure chambers that are not performing printing. When an ejection operation is performed in the recording element substrate 80a, part of the ink that moves from the common supply channel 80b to the common recovery channel 80c is consumed by being ejected from the ejection openings, but the ink that has not been ejected moves to the recovery channel C4 via the common recovery channel 80c.

FIG. 17(a) is a schematic plan view enlarging a portion of the recording element substrate 80a, and FIG. 17(b) is a schematic cross-sectional view taken along the cross-sectional line XVIIb-XVIIb of FIG. 17(a). The printing element substrate 80a is provided with pressure chambers 1005 filled with ink and ejection ports 1006 for ejecting ink. A printing element 1004 is provided at a position facing the ejection port 1006 in the pressure chamber 1005 . In the recording element substrate 80a, a plurality of individual supply flow paths 1008 connected to the common supply flow path 80b and a plurality of individual recovery flow paths 1009 connected to the common recovery flow path 80c are formed for each ejection port 1006. FIG.

With the above-described configuration, in the recording element substrate 80a, a flow of ink is generated that flows in from the common supply channel 80b with relatively weak negative pressure (high pressure) and flows out to the common recovery channel 80c with relatively strong negative pressure (low pressure). More specifically, the ink flows in the order of common supply channel 80b→individual supply channel 1008→pressure chamber 1005→individual recovery channel 1009→common recovery channel 80c. When ink is ejected by the recording elements 1004, part of the ink that moves from the common supply channel 80b to the common recovery channel 80c is ejected from the ejection port 1006 and discharged to the outside of the head unit 8. FIG. On the other hand, the ink not ejected from the ejection port 1006 is recovered to the recovery channel C4 through the common recovery channel 80c.

FIG. 18 shows a first negative pressure control unit 81 provided in the head unit 8. As shown in FIG. 18(a) and 18(b) are external perspective views, and in particular, FIG. 18(b) shows a state in which the flexible film 232 is not shown in order to show the inside of the first negative pressure control unit 81. FIG. FIG. 18(c) shows a cross section along line XVIIIc-XVIIIc in FIG. 18(a). The first negative pressure control unit 81 and the second negative pressure control unit 82 are differential pressure valves, and since they have the same configuration except for the difference in control pressure (initial load of the spring), description of the second negative pressure control unit 82 is omitted.

The first negative pressure control unit 81 has a pressure receiving plate 231 shown in FIG. 18(b) and a flexible film 232 sealing the surrounding space to form a first pressure chamber 233 inside. The flexible film 232 is welded to the circular edge and the pressure receiving plate 231 shown in FIG. 18(b). The flexible film 232 and the pressure-receiving plate 231 welded to the flexible film 232 are vertically displaced according to the increase or decrease of the ink in the first pressure chamber 233 .

A second pressure chamber 238 connected to the supply pump P1, a shaft 234 connected to the pressure receiving plate 231, a valve 235 connected to the shaft 234, and an orifice 236 contacting the valve 235 are provided upstream of the first pressure chamber 233 in the ink supply direction. The orifice 236 of this embodiment is provided at the boundary between the first pressure chamber 233 and the second pressure chamber 238 . The valve 235 , the shaft 234 and the pressure receiving plate 231 are further biased vertically upward by a biasing member (spring) 237 .

When the absolute value of the pressure in the first pressure chamber 233 is equal to or greater than the first threshold (when the negative pressure is weaker than the first threshold), the biasing force of the biasing member 237 causes the valve 235 to come into contact with the orifice 236, thereby blocking the connection between the first pressure chamber 233 and the second pressure chamber 238. On the other hand, when the absolute value of the pressure in the first pressure chamber 233 becomes less than the first threshold, that is, when a negative pressure higher than the first threshold is applied to the first pressure chamber 233, the flexible film 232 shrinks and displaces downward. As a result, the pressure receiving plate 231 and the valve 235 are displaced downward against the bias of the biasing member 237, the valve 235 and the orifice 236 are separated, and the first pressure chamber 233 and the second pressure chamber 238 are connected. This connection causes the ink supplied by the supply pump P1 to flow into the first pressure chamber 233 .

The first negative pressure control unit 81 has the structure of the differential pressure valve described above, thereby controlling the inflow pressure and the outflow pressure to be constant. In order to generate a stronger negative pressure than the first negative pressure control unit 82, the second negative pressure control unit 82 employs a biasing member 237 having a greater biasing force than the first negative pressure control unit. That is, the second negative pressure control unit 82 opens the valve when the absolute value of the pressure is less than the second threshold, which is smaller than the first threshold. Therefore, when the recovery pump P2 is driven, first the first negative pressure control unit 81 is opened and then the second negative pressure control unit 82 is opened.

Based on the above configuration, when performing a printing operation, the ink supply control unit 209 closes the tank supply valve V1 and the head replacement valve V5, opens the air release valve V0, the supply valve V2, and the recovery valve V4, and drives the supply pump P1 and the recovery pump P2. As a result, a circulation path of sub-tank 151→supply channel C2→head unit 8→recovery channel C4→sub-tank 151 is established. When the amount of ink supplied per unit time from the supply pump P1 is greater than the sum of the discharge amount per unit time of the head unit 8 and the flow rate per unit time of the recovery pump P2, ink flows from the supply channel C2 into the relief channel C3. As a result, the flow rate of ink flowing into the head unit 8 from the supply channel C2 is adjusted.

When the printing operation is not performed, the ink supply control unit 209 stops the supply pump P1 and the recovery pump P2, and closes the atmosphere open valve V0, the supply valve V2, and the recovery valve V4. As a result, the flow of ink in the head unit 8 is stopped, and backflow due to the difference in water head between the sub-tank 151 and the head unit 8 is also suppressed. In addition, by closing the air release valve V0, leakage of ink from the sub-tank 151 and evaporation of ink are suppressed.

When ink is recovered from the head unit 8, the ink supply control unit 209 closes the atmosphere release valve V0, the tank supply valve V1, the supply valve V2, and the recovery valve V4, opens the head replacement valve V5, and drives the decompression pump P0. As a result, the inside of the sub-tank 151 is brought into a negative pressure state, and the ink inside the head unit 8 is recovered to the sub-tank 151 via the head replacement channel C5. As described above, the head replacement valve V5 is closed during normal printing operation and standby, and is opened when ink is recovered from the head unit 8. FIG. However, the head replacement valve V5 is also opened when the head replacement flow path C5 is filled with ink in the initial filling of the head unit 8 .

<Buffer room>
Next, in the ink circulation system described with reference to FIG. 9, the buffer chamber 85 (indicated by "B" in FIG. 9) arranged in the recovery passage C4 will be described.

In the ink circulation system, it is ideal that the ink circulates in a state in which the air in the circulation path is completely exhausted. However, actually, a small amount of air bubbles remain in the head unit 8 and the flow path. Such bubbles may expand or contract due to environmental changes (for example, temperature changes). The expansion and contraction of the bubbles change the pressure applied to the ejection port, resulting in ink leakage and air entrainment. For example, when the air temperature drops, the air bubbles shrink, the negative pressure at the ejection port increases, and the meniscus of the ejection port is broken, which may cause air to be sucked into the head unit. When the temperature rises, the bubbles may expand and the ink may leak from the ejection port. The buffer chamber 85 absorbs expansion and contraction of such bubbles.

FIG. 10 is a diagram showing an example of the buffer chamber 85. As shown in FIG. FIG. 10(a) shows a perspective view of the buffer chamber 85, and FIG. 10(b) shows a perspective view including a cross section taken along line Xb--Xb. The buffer chamber 85 has a frame 851 , a film 852 , a pressure receiving plate 853 and a compression spring 854 . The frame 851 has an opening on the first surface, and a film 852 is stretched so as to cover the first surface. The film 852 is a flexible member and adhered to the pressure receiving plate 853 . The pressure receiving plate 853 is connected with the compression spring 854 . With such a configuration, the position of the pressure receiving plate 853 can be moved according to the expansion and contraction of the compression spring 854 . The film 852 expands or contracts according to the position of the pressure receiving plate 853 . Hereinafter, such expansion (or contraction) of the film 852 is referred to as expansion of the buffer chamber 85 (or contraction of the buffer chamber 85). That is, the volume of the buffer chamber 85 is variable. By providing such a buffer chamber 85, when bubbles expand or contract due to temperature change or the like in a state in which ink is not circulated, the buffer chamber 85 expands or contracts according to the volume change of the bubbles in the flow path. With the buffer chamber 85 acting in this manner, the expansion and contraction of the bubbles can be absorbed. Therefore, it is possible to prevent ink leakage and air suction as described above.

The first negative pressure control unit 81 and the second negative pressure control unit 82 each have a pressure regulating valve. When the ink is not circulating, that is, when no negative pressure is generated, the pressure regulating valves of the first negative pressure control unit 81 and the second negative pressure control unit 82 are closed and separated from the upstream supply flow path. Therefore, in the example of FIG. 9, the buffer chamber 85 is arranged in the flow path where the expansion and contraction of bubbles can affect the ejection openings of the head unit 8 when ink is not circulating, specifically in the recovery flow path C4.

The buffer chamber 85 is provided with an inlet through which ink flows in at one longitudinal end (front side in FIG. 10), and an outlet through which ink flows out at the other end (back side in FIG. 10). The height of the vertically upper ceiling portion of the buffer chamber 85 is configured to increase from the inflow port toward the outflow port.

<Cause of long FPOT>
The reason why the FPOT becomes long when the ink circulation system provided with the buffer chamber 85 as described above is employed will be described. As shown in FIG. 9, the buffer chamber 85 is arranged on the upstream side (head unit 8 side) of the recovery pump P2 in the recovery channel C4. When ink circulation is started, the recovery pump P2 serves as a source of negative pressure, and ink is sucked from the head unit 8, as described above. More specifically, when the negative pressure applied to the head unit 8 is stabilized, the pressure regulating valves of the first negative pressure control unit 81 and the second negative pressure control unit 82 are opened, and a predetermined differential pressure within the head unit 8 causes flow from the IN flow path to the OUT flow path, thereby starting ink circulation. Here, the buffer chamber 85 has the configuration of the spring bag as described above, and when negative pressure is generated by the collection pump P2, it starts to contract (the film portion is crushed). In the initial stage when negative pressure is generated, the pressure change acts on the buffer chamber 85 near the source of the negative pressure, so in order to stabilize the negative pressure of the head unit 8, the buffer chamber 85 needs to reach a predetermined pressure after the buffer chamber 85 has fully contracted (completely collapsed). As a result, the FPOT from when the recording instruction is output to when the recording is actually performed becomes long.

FIG. 11 is a diagram showing a cross section of the buffer chamber 85 of FIG. 10 taken along line Xb--Xb. FIG. 11(a) shows the first state of the buffer chamber 85. FIG. The first state is a state in which ink is circulating. When the ink is circulating, the buffer chamber 85 is fully contracted due to the negative pressure generated by the recovery pump P2.

FIGS. 11(b) to 11(d) show the state of the buffer chamber 85 when the circulation of ink is stopped. 11(b) to 11(d), the buffer chamber 85 is expanded more than the first state during circulation in FIG. FIG. 11(b) shows the second state of the buffer chamber 85. FIG. The second state is a state in which the air bubbles contract due to environmental changes during circulation stoppage. Even if the buffer chamber 85 contracts due to contraction of air bubbles, the buffer chamber 85 is in a swelled state compared to the first state during circulation. FIG. 11(c) shows the third state of the buffer chamber 85. FIG. The third state is a standby state in which the circulation is stopped and no environmental change occurs (no contraction or expansion of bubbles). The third state is a reference state during circulation stop, and if the bubbles contract in this state, the buffer chamber 85 changes to the second state shown in FIG. 11(b). FIG. 11(d) shows the fourth state of the buffer chamber 85. FIG. The fourth state is a state in which the bubbles expand due to environmental changes during circulation stop. In the fourth state, the buffer chamber 85 is expanded more than in the third state. As shown in FIG. 11, the first state of the buffer chamber 85 during ink circulation is a state in which the buffer chamber 85 is more contracted than any of the second to fourth states in which ink circulation is stopped. In other words, when ink circulation starts from a state in which ink circulation has stopped, the time it takes for the buffer chamber 85 to contract from any state between FIGS. 11B to 11D to the first state shown in FIG. 11A affects FPOT. A configuration for shortening the FPOT will be described below.

<Pump flow rate control>
12A and 12B are diagrams showing the opening/closing state of valves in the circulation flow path and the drive state of the pump when ink is circulated in the circulation system shown in FIG. When a recording operation is being performed, ink circulation is performed as shown in FIG. When the ink is circulating, the tank supply valve V1 and the head replacement valve V5 are closed. The decompression pump P0 is in a stopped state. On the other hand, the atmosphere release valve V0, the supply valve V2, and the recovery valve V4 are open. Feed pump P1 and recovery pump P2 are in operation. When the ink is circulated in this manner, the buffer chamber 85 is in the first state shown in FIG. 11(a). That is, the buffer chamber 85 is in a fully contracted state due to the negative pressure.

FIG. 13 is a diagram showing the opening/closing state of valves in the circulation flow path and the driving state of the pump when ink circulation is stopped in the circulation system shown in FIG. When the recording operation ends, the ink circulation stops as shown in FIG. Compared to FIG. 12, the atmosphere release valve V0, the supply valve V2, and the recovery valve V4 are closed. Also, the supply pump P1 and the recovery pump P2 are in a stopped state. In this case, the buffer chamber 85 is in the third standby state shown in FIG. 11(c). This is because when the recovery pump P2 stops operating, the portion that has contracted due to the pressure loss will swell due to the stopping of the ink flow, or the ink will flow into the buffer chamber 85 from the upstream side.

In the present embodiment, when ink circulation is started in response to a print instruction from the state in which the circulation is stopped as shown in FIG. 13, the flow rate of the recovery pump P2 is temporarily increased from the flow rate during the printing operation. As a result, the inflated buffer chamber 85 is quickly transferred to the contracted state (first state) as shown in FIG. 11(a).

In addition, in this embodiment, the recovery pump P2 is provided with restrictions on the flow rate. The lower limit of the flow rate is defined as a value required to secure a sufficient flow rate for ejection, that is, a value required to circulate the ink within the head unit 8 . On the other hand, if the flow rate is too high, the pressure loss with respect to the ejection port becomes too large, and the meniscus at the ejection port breaks, resulting in non-ejection. For this reason, the upper limit of the flow rate is also restricted. Thus, the lower limit and upper limit of the flow rate are set, and the recovery pump P2 is driven and controlled within this range. As an example, the recovery pump P2 is driven and controlled to achieve a flow rate of 10 ml/min.

Thus, the flow rate of the recovery pump P2 is restricted in consideration of discharge. However, the buffer chamber 85 before the printing operation is in the third state shown in FIG. 11(c), and the flow rate of the ink circulating in the head unit 8 is not stable until it reaches the fully contracted first state shown in FIG. 11(a). Therefore, in the present embodiment, the recovery pump P2 is controlled to increase the flow rate at the start of ink circulation. For example, the ink supply control unit 209 performs control to increase the drive amount (rotational speed) of the recovery pump P2 so that the flow rate (second flow rate) is 30 ml/min, which is three times as high as the flow rate (first flow rate) of 10 ml/min during ink circulation that enables the printing operation. That is, assuming that the rotation speed of the recovery pump P2 during the printing operation is the first speed, the recovery pump P2 is driven at the second speed, which is higher than the first speed, until a predetermined time elapses from the start of rotation. By increasing the flow rate, a high negative pressure can be applied to the upstream side of the recovery pump P2 including the head unit 8, so that the buffer chamber 85 quickly contracts. Therefore, FPOT can be shortened. The predetermined time for increasing the flow rate of the recovery pump P2 may be set by measuring the time required for the ink flow rate inside the head unit 8 and through the recovery channel C4 to stabilize, and setting the measured time. After the predetermined time has passed, the ink supply control unit 209 changes the drive amount of the recovery pump P2 so that the normal ink circulation flow rate is achieved.

In the above example, the recovery pump P2 is driven and controlled so as to generate a second flow rate that is three times as large as the first flow rate during ink circulation. However, the present invention is not limited to this. At the start of ink circulation, the recovery pump P2 may be driven and controlled so that a second flow rate, which is higher than the first flow rate during ink circulation, is generated. By making the flow rate higher than the first flow rate, the FPOT can be shortened compared to the case where the control as in the present embodiment is not performed. Also, the second flow rate may not be a fixed flow rate, and may be a variable flow rate within a range larger than the first flow rate.

Further, in the present embodiment, control may be performed to change the time during which the recovery pump P2 is driven at the second speed, which is faster than normal. For example, if the standby time from the end of a printing operation to the start of the next printing operation is long, the ink near the ink ejection port 1006 may adhere. In such a case, by lengthening the time period during which the recovery pump P2 is driven at the second speed, the fixed ink can be sufficiently circulated from the ink ejection port 1006, and the ink can be stably ejected. That is, the time for driving the recovery pump P2 at the second speed is changed according to the elapsed time from the end of the previous printing operation.

Further, the print head of this embodiment can eject black ink and color ink. In this embodiment, the ink circulation can be switched according to the print mode. That is, only black ink is circulated in monochrome mode, and both black ink and color ink are circulated in color mode. When the recording operation is continuously performed in the monochrome mode, the color ink is not circulated for a long period of time, so the color ink tends to adhere near the ink ejection port 1006 . Therefore, when the color mode printing operation is performed after the monochrome mode printing operation, the time for which the recovery pump P2 is driven at the second speed is lengthened.

In this manner, the recovery pump P2 is normally driven at the second speed from the start of rotation until the first time elapses. However, when the standby time is long, when the recording mode is switched from the monochrome mode to the color mode, or when the error is recovered, the recovery pump P2 is driven at the second speed until the second time longer than the first time elapses.

<Flowchart>
FIG. 14 is a diagram showing a flowchart when ink circulation is started according to the present embodiment. In step S1410, the print controller 202 inputs a print instruction. The print controller 202 instructs the ink supply control unit 209 to start circulation.

In step S1420, the ink supply control unit 209 performs control to open the valve so that the state shown in FIG. 12 is obtained. Specifically, the ink supply control unit 209 opens the supply valve V2 and the recovery valve V4. In step S1430, the ink supply control unit 209 starts driving the supply pump P1.

In step S1440, the ink supply control unit 209 starts driving the recovery pump P2 with a drive amount that realizes a second flow rate that is larger than the flow rate (first flow rate) of normal ink circulation. In step S1450, the process waits until a predetermined time elapses, and when the predetermined time elapses, the process proceeds to step S1460. In step S1460, the ink supply control unit 209 changes the driving amount of the recovery pump P2 to the first flow rate. In step S1470, the print controller 202 controls the head carriage control unit 208 to execute the recording operation.

As described above, in the present embodiment, at the start of ink circulation, control is performed to increase the flow rate of the recovery pump P2 for a predetermined period of time, compared to that during normal ink circulation. As a result, the contraction time of the buffer chamber 85 can be shortened, so that the FPOT can be shortened.

<<Embodiment 2>>
In the present embodiment, a form in which a buffer chamber cutoff valve is provided on the upstream side of the buffer chamber 85 in the recovery channel C4 will be described.

FIG. 15 is a diagram showing the channel configuration of this embodiment. FIG. 15 shows the flow path with ink circulation stopped. The buffer chamber cutoff valve V6 is a driven valve that can be driven to open and close under the control of the ink supply control unit 209. FIG. In this embodiment, the ink supply control unit 209 performs control to close the buffer chamber cutoff valve V6 when stopping the circulation of ink. As a result, the buffer chamber 85 is maintained under pressure (negative pressure) during circulation. Therefore, the buffer chamber 85 can be expected to be maintained in a state close to the fully contracted first state, as shown in FIG. 11(a). As a result, the FPOT can be shortened when the recording operation is repeated in a short period of time.

However, depending on the timing of closing the buffer chamber cutoff valve V6, the buffer chamber 85 may be maintained in a slightly inflated state. Further, when the buffer chamber 85 is not used for a long period of time, control is performed to open the buffer chamber shutoff valve V6 in order to exhibit the function of the buffer chamber 85 . In this case as well, the buffer chamber 85 is in a swollen state.

In this embodiment, as in the first embodiment, at the start of ink circulation, the flow rate of the recovery pump P2 is increased for a certain period of time from the flow rate during normal ink circulation (during printing operation). As a result, the buffer chamber 85 can be contracted in a short period of time even when the buffer chamber cutoff valve V6 is provided, so that the FPOT can be shortened.

<<other embodiments>>
Although the configuration in which the buffer chamber 85 is arranged in the recovery channel C4 has been described, the configuration is not limited to this. As shown in FIG. 16 , the buffer chamber 85 may be arranged in the flow path inside the head unit 8 . More specifically, it may be arranged downstream of the pressure control unit in the head unit 8 . That is, it may be arranged downstream of the first negative pressure control unit 81 and the second negative pressure control unit 82 .

Moreover, although the embodiment in which one buffer chamber 85 is disposed on the flow path has been described as an example, the present invention is not limited to this. Two buffer chambers 85 for absorbing contraction and for absorbing expansion having different spring pressures may be arranged, and the size of each buffer chamber may be reduced.

8 recording head (head unit)
85 buffer chamber 209 ink supply controller C4 recovery channel P1 supply pump P2 recovery pump

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide a liquid ejection apparatus capable of controlling the flow rate of liquid in a configuration in which liquid is circulated, and a method of controlling the liquid ejection apparatus.

A liquid ejecting apparatus according to an aspect of the present invention includes a reservoir that stores liquid to be supplied to a head that ejects liquid, a first flow path configured to flow liquid from the storage section to the head, a second flow path configured to flow the liquid from the head, a third flow path branching from the first flow path, a valve provided in the second flow path for regulating the flow of the liquid, and a liquid circulating from the first flow path to the head and from the head to the second flow path. and a pump capable of circulating the liquid at two flow rates, a first flow rate and a second flow rate different from the first flow rate, wherein the liquid flows from the first flow path to the third flow path when the liquid is circulated at the first flow rate.

Claims (14)

a tank containing ink;
a recording head that performs a recording operation by ejecting ink supplied from the tank;
a supply channel for supplying ink from the tank to the recording head;
a recovery channel for recovering ink from the recording head to the tank;
a pump provided in the supply channel or the recovery channel;
In an inkjet recording device comprising
during a printing operation, driving the pump at a first speed to circulate ink in a circulation channel including the tank, the supply channel, the print head and the recovery channel;
An inkjet recording apparatus, wherein the pump is driven at a second speed higher than the first speed until a predetermined time elapses after ink circulation is started. the pump includes a supply pump arranged in the supply channel and a recovery pump arranged in the recovery channel;
2. An ink jet recording apparatus according to claim 1, wherein said recovery pump is driven at said second speed until said predetermined time elapses. The recording head includes an ejection port for ejecting ink, and a pressure chamber communicating with the ejection port and filled with the ink to be ejected from the ejection port,
3. The ink jet recording apparatus according to claim 1, wherein during a recording operation, the pump is driven to circulate the ink from the supply channel through the inside of the pressure chamber to the recovery channel. The recording head has a common supply channel connected to the supply channel for supplying ink to the pressure chamber, a common recovery channel connected to the supply channel and the recovery channel for recovering ink from the pressure chamber, a first negative pressure control means provided between the supply channel and the common supply channel for controlling negative pressure, and a second negative pressure control means provided between the supply channel and the common recovery channel for controlling negative pressure,
4. An ink jet recording apparatus according to claim 3, wherein said predetermined time is a time until a predetermined differential pressure is generated between said first negative pressure control means and said second negative pressure control means. 5. The inkjet recording apparatus according to any one of claims 1 to 4, wherein the pump is driven at the first speed after the predetermined time has passed. 6. The inkjet recording apparatus according to claim 1, wherein when the instruction for the recording operation is input, circulation of the ink is started. 7. The inkjet printing apparatus according to claim 1, wherein the time for driving the pump at the second speed is changed according to the elapsed time from the end of the previous printing operation. The recording head is capable of ejecting black ink and color ink,
Only black ink is circulated when recording in monochrome mode, and black ink and color ink are circulated when recording in color mode.
8. The inkjet printing apparatus according to any one of claims 1 to 7, wherein when a color mode printing operation is performed after a monochrome mode printing operation, the time during which the pump is driven at the second speed is made longer than the predetermined time. a buffer chamber that is arranged inside the recording head or in the recovery channel and has a variable volume;
a valve provided upstream of the buffer chamber in the direction in which the ink circulates;
Further comprising control means for controlling opening and closing of the valve,
4. An ink jet recording apparatus according to claim 3, wherein said control means opens said valve when said recording operation is being performed, and closes said valve when said recording operation is finished. 10. The inkjet recording apparatus according to claim 9, wherein the volume of the buffer chamber when the ink is circulating is smaller than the volume when the ink is not circulating. The buffer chamber is
a frame having an open first surface;
a film covering the first surface of the frame;
a pressure plate adhered to the film;
11. An inkjet recording apparatus according to claim 9, further comprising a compression spring connected to said pressure receiving plate. 12. An inkjet recording apparatus according to claim 11, wherein a plurality of buffer chambers are provided inside said recording head or in said recovery channel, and spring pressures of said compression springs in respective buffer chambers are different. 13. The inkjet recording apparatus according to any one of claims 9 to 12, wherein the recording head includes a pressure control unit that controls downstream pressure to be constant, and the buffer chamber is provided in a flow path downstream of the pressure control unit. a tank containing ink;
a recording head that performs a recording operation by ejecting ink supplied from the tank;
a supply channel for supplying ink from the tank to the recording head;
a recovery channel for recovering ink from the recording head to the tank;
a pump provided in the supply channel or the recovery channel;
A control method for an inkjet recording apparatus comprising
circulating ink in a circulation channel including the tank, the supply channel, the print head and the recovery channel by driving the pump at a first speed during a printing operation;
and driving the pump at a second speed higher than the first speed until a predetermined time elapses after ink circulation is started.

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