Inkjet recording device

Abstract

To provide an inkjet recording device which can maintain stable discharge performance regardless of an amount of an ink discharged from a full line recording head in a structure which circulates the ink.SOLUTION: An inkjet recording device includes: a full line type recording head; an ink tank which stores an ink to be supplied to the recording head; a supply passage which supplies the ink from the ink tank to the recording head; a supply pump which is disposed in the middle of the supply passage; a recovery passage which recovers the ink from the recording head to the ink tank; and a recovery pump which is disposed in the middle of the recovery passage. The ink is circulated between the recording head and the ink tank by the supply pump and the recovery pump. The inkjet recording device further includes: a detour path which is connected at one end to the supply passage at the upstream side of the supply pump in an ink supply direction and is connected at the other end to the supply passage at the downstream side of the supply pump in the supply direction; and a differential pressure regulating valve which is disposed in the middle of the detour path.SELECTED DRAWING: Figure 13

Description

[Technical field]

[0001] The present invention relates to an inkjet recording apparatus that records an image using a line head. [Background technology]

[0002] Patent Document 1 discloses an inkjet recording device that includes a full-line inkjet head that ejects ink and an ink tank that contains the ink to be supplied to the inkjet head. The ink tank and the inkjet head are connected by an ink supply path and an ink return path, and are configured so that ink circulates between the ink tank and the inkjet head. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2010-155449 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, when an ink circulation configuration like that of Patent Document 1 is adopted, if the amount of ink ejected from the print head is large, the supply pump that pressurizes and supplies the ink may not supply enough ink, resulting in ejection failure.On the other hand, if the amount of ink ejected from the print head is small, the supply pump may supply too much ink, resulting in destruction of the meniscus of the print head and leakage of ink.

[0005] The present invention has been made in consideration of the above problems, and has an object to provide an inkjet printing apparatus capable of maintaining the ejection performance of the print head in a configuration in which ink is circulated. [Means for solving the problem]

[0006] In order to achieve the above object, an inkjet recording apparatus according to the present invention is provided with a supply pump for flowing ink, a supply flow path through which ink is supplied from a tank that stores ink to a recording head, and a recovery flow path through which ink leaving the recording head passes, the circulation path having a first flow path for circulating ink so that the ink leaves the recording head and re-enters the recording head, and a second flow path that branches off from the first flow path downstream of the supply pump provided in the first flow path in the ink flow direction, and circulates ink so as to send ink upstream of the supply pump, and the recording head is provided with ejection ports for ejecting ink, and a second flow path for ejecting ink from the first flow path, the second flow path being provided corresponding to the ejection ports and configured to eject ink from the first flow path. the ink jet head has an energy generating element for generating energy used in the ink jet recording and a pressure chamber located opposite the energy generating element, a common supply flow path connected to the supply flow path for supplying ink to the pressure chamber, and a common recovery flow path connected to the supply flow path and the recovery flow path for recovering ink from the pressure chamber, and further comprises a first pressure control means for controlling the pressure, which is provided between the supply flow path and the common supply flow path, and a second pressure control means for controlling the pressure, which is provided between the supply flow path and the common recovery flow path, and which generates a negative pressure stronger than that of the first pressure control means, and the first pressure control means and the second pressure control means are provided within the printhead. Effect of the Invention

[0007] According to the present invention, it is possible to provide an inkjet printing apparatus capable of maintaining the ejection performance of the print head in a configuration in which ink is circulated. [Brief description of the drawings]

[0008] [Figure 1] FIG. 2 is a diagram illustrating the inkjet recording apparatus when in a standby state. [Diagram 2] FIG. 2 is a control configuration diagram of the inkjet recording apparatus. [Diagram 3] FIG. 2 is a diagram showing the inkjet recording apparatus in a recording state. [Figure 4]13(a) to 13(c) are diagrams showing the transport path of a recording medium fed from a first cassette. [Diagram 5] 13(a) to 13(c) are diagrams showing the transport path of the recording medium fed from the second cassette. [Figure 6] 13A to 13D are diagrams showing the transport path when a recording operation is performed on the back surface of the recording medium. [Figure 7] FIG. 2 is a diagram illustrating the inkjet recording apparatus in a maintenance state. [Figure 8] 1A and 1B are perspective views showing the configuration of a maintenance unit. [Figure 9] FIG. 2 is a diagram showing an ink supply unit. [Figure 10] FIG. 4 is a diagram showing a configuration of a relief valve. [Figure 11] FIG. 2 is a diagram showing a configuration of an ink ejection unit of a recording head. [Figure 12] FIG. 4 is a diagram showing a configuration of a first negative pressure control unit of the print head. [Figure 13] 5A and 5B are diagrams illustrating the flow of ink in an ink supply unit during a printing operation by a print head. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] 1 is a diagram showing the internal configuration of an inkjet recording apparatus (hereinafter, recording apparatus) 1 according to this embodiment. Hereinafter, in the figure, the x direction indicates the horizontal direction, the y direction (perpendicular to the paper surface) indicates the direction in which ejection ports are arranged in a recording head 8 (described later), and the z direction indicates the vertical direction.

[0010] The recording device 1 is a multifunction device equipped with a print unit 2 and a scanner unit 3, and various processes related to recording and reading operations can be executed by the print unit 2 and the scanner unit 3 individually or in conjunction with each other. The scanner unit 3 is equipped with an ADF (automatic document feeder) and an FBS (flatbed scanner), and can read documents automatically fed by the ADF and read (scan) documents placed on the platen of the FBS by a user. Note that although this embodiment is a multifunction device equipped with both the print unit 2 and the scanner unit 3, it may be configured not to include the scanner unit 3. FIG. 1 shows the recording device 1 in a standby state in which neither recording nor reading operations are being performed.

[0011] In the printing section 2, a first cassette 5A and a second cassette 5B for accommodating recording media (cut sheets) S are removably installed at the bottom vertically below the housing 4. The first cassette 5A accommodates relatively small recording media up to A4 size, while the second cassette 5B accommodates relatively large recording media up to A3 size, stacked flat. A first feeding unit 6A is provided near the first cassette 5A for separating and feeding the accommodated recording media one by one. Similarly, a second feeding unit 6B is provided near the second cassette 5B. When a recording operation is performed, the recording media S is selectively fed from one of the cassettes.

[0012] The conveying roller 7, the discharge roller 12, the pinch roller 7a, the spur 7b, the guide 18, the inner guide 19, and the flapper 11 constitute a conveying mechanism for guiding the recording medium S in a predetermined direction. The conveying roller 7 is disposed on the upstream side and downstream side of the recording head 8, and is a driving roller driven by a conveying motor (not shown). The pinch roller 7a is disposed on the upstream side of the recording head 8, and is a driven roller that nips the recording medium S together with the conveying roller 7 and rotates. The discharge roller 12 is disposed at the most downstream position in the conveying path, and is a driving roller driven by a conveying motor (not shown). The spur 7b is disposed on the downstream side of the recording head 8, and guides the recording medium S in a predetermined direction. Among the spurs 7b, those disposed at a position facing the conveying roller 7 or the discharge roller 12 convey the recording medium S by pinching it with the conveying roller 7 or the discharge roller 12.

[0013] 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, has a curved side, and guides the recording medium S along the side. The flapper 11 is a member for switching the direction in which the recording medium S is transported during double-sided recording operation. The discharge tray 13 is a tray for stacking and holding the recording medium S discharged by the discharge roller 12 after the recording operation is completed.

[0014] The recording head 8 of this embodiment is a full-line type color inkjet recording head, and has a plurality of ejection ports arranged in the y direction in FIG. 1, which eject ink according to recording data, corresponding to the width of the recording medium S. When the recording head 8 is in the standby position shown in FIG. 1, the ejection port surface 8a of the recording head 8 is capped by a cap unit 10. This position of the cap unit 10 is also called a capping position. When the recording head 8 performs a recording operation, the orientation of the recording head 8 is changed by a print controller 202, which will be described later, so that the ejection port surface 8a faces a platen 9. The platen 9 is made 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 rear. The movement of the recording head 8 from the standby position to the recording position will be described in detail later.

[0015] The ink tank unit 14 stores each of the four colors of ink to be supplied to the recording head 8. The ink supply unit 15 is provided in the middle of a flow path connecting the ink tank unit 14 and the recording head 8, and adjusts the pressure and flow rate of the ink in the recording head 8 to appropriate ranges. In this embodiment, a circulation type ink supply system is adopted, 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 collected from the recording head 8 to appropriate ranges.

[0016] The maintenance unit 16 includes a cap unit 10 and a wiping unit 17, and operates these at a predetermined timing to perform a maintenance operation on the recording head 8. The maintenance operation will be described in detail later.

[0017] 2 is a block diagram showing the control configuration of the recording apparatus 1. The control configuration mainly comprises 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 recording apparatus 1. A print controller 202 controls various mechanisms of the print engine unit 200 according to instructions from a 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. The control configuration will be described in detail below.

[0018] In the controller unit 100, a main controller 101 constituted by a CPU controls the entire recording device 1 using a RAM 106 as a work area in accordance with programs and various parameters stored in a ROM 107. For example, when a print job is input from a host device 400 via a host I / F 102 or a wireless I / F 103, an image processing unit 108 performs predetermined image processing on the received image data in accordance with instructions from the main controller 101. The main controller 101 then transmits the processed image data to a print engine unit 200 via a print engine I / F 105.

[0019] The recording device 1 may obtain image data from the host device 400 via wireless communication or wired communication, or may obtain image data from an external storage device (such as a USB memory) connected to the recording device 1. The 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 used as a communication method used for wireless communication. Also, USB (Universal Serial Bus) or the like can be used as a communication method used for wired communication. Also, for example, when a read command is input from the host device 400, the main controller 101 transmits the command to the scanner unit 3 via the scanner engine I / F 109.

[0020] The operation panel 104 is a mechanism for a user to perform input and output to the recording device 1. The user can instruct operations such as copying and scanning, set the print mode, and recognize information about the recording device 1 via the operation panel 104.

[0021] In the print engine unit 200, a print controller 202 constituted by a CPU controls various mechanisms of the print section 2 in accordance with programs and various parameters stored in a ROM 203, using a RAM 204 as a work area. When various commands and image data are received via a controller I / F 201, the print controller 202 temporarily stores them in the RAM 204. The print controller 202 causes an image processing controller 205 to convert the stored image data into print data, so that the print head 8 can use it for printing operations.

[0022] When the recording data is generated, the print controller 202 causes the recording head 8 to execute a recording operation based on the recording data via the head I / F 206. At this time, the print controller 202 drives the first feeding unit 6A, the second feeding unit 6B, the conveying rollers 7, the discharge rollers 12, and the flapper 11 shown in Fig. 1 via the conveying control unit 207 to convey the recording medium S. According to an instruction from the print controller 202, the recording head 8 executes a recording operation in conjunction with the conveying operation of the recording medium S, and printing processing is performed.

[0023] The head carriage control unit 208 changes the orientation and position of the recording head 8 depending on the operating state, such as the maintenance state and recording state, of the recording device 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 falls within an appropriate range. The maintenance control unit 210 controls the operations of the cap unit 10 and the wiping unit 17 in the maintenance unit 16 when performing a maintenance operation on the recording head 8.

[0024] In the scanner engine unit 300, the main controller 101 controls the hardware resources of the scanner controller 302 using the RAM 106 as a work area according to the program and various parameters stored in the ROM 107. This controls various mechanisms of the scanner unit 3. For example, the main controller 101 controls the hardware resources in the scanner controller 302 via the controller I / F 301, so that the document placed on the ADF by the user is conveyed via the conveyance control unit 304 and read by the sensor 305. The scanner controller 302 then stores the read image data in the RAM 303. The print controller 202 can convert the image data acquired as described above into print data, thereby causing the print head 8 to perform a print operation based on the image data read by the scanner controller 302.

[0025] Fig. 3 shows the recording apparatus 1 in a recording state. Compared to the standby state shown in Fig. 1, the cap unit 10 is spaced away from the ejection port surface 8a of the recording head 8, and the ejection port surface 8a faces the platen 9. In this embodiment, the plane of the platen 9 is inclined at about 45 degrees with respect to the horizontal direction, and the ejection port surface 8a of the recording head 8 in the recording position is also inclined at about 45 degrees with respect to the horizontal direction so that the distance from the platen 9 is maintained constant.

[0026] When the recording head 8 moves from the standby position shown in FIG. 1 to the recording position shown in FIG. 3, the print controller 202 uses the maintenance control unit 210 to lower the cap unit 10 to the retracted position shown in FIG. 3. This separates the ejection port surface 8a of the recording head 8 from the cap member 10a. Thereafter, the print controller 202 uses the head carriage control unit 208 to rotate the recording head 8 by 45 degrees while lowering the vertical height of the recording head 8, so that the ejection port surface 8a faces the platen 9. When the recording operation is completed and the recording head 8 moves from the recording position to the standby position, the print controller 202 performs the above steps in reverse.

[0027] Next, a description will be given of the transport path of the recording medium S in the printing section 2. When a recording command is input, the print controller 202 first uses the maintenance control section 210 and the head carriage control section 208 to move the recording head 8 to the recording position shown in Fig. 3. Then, the print controller 202 uses the transport control section 207 to drive either the first feeding unit 6A or the second feeding unit 6B in accordance with the recording command, and feeds the recording medium S.

[0028] 4(a) to 4(c) are diagrams showing the conveying path when the A4 size recording medium S housed in the first cassette 5A is fed. In FIG. 4 and subsequent figures, the conveyed recording medium S is indicated by a dotted line. The topmost recording medium S in the first cassette 5A is separated from the second and subsequent recording media by the first feeding unit 6A, and is 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. 4(a) shows the conveying state just before the leading edge of the recording medium S reaches the recording area P. The traveling direction of the recording medium S is changed from the horizontal direction (x direction) to a direction inclined at about 45 degrees from the horizontal direction while being fed by the first feeding unit 6A and reaching the recording area P.

[0029] In the recording area P, ink is ejected from a plurality of ejection ports provided in the recording head 8 toward the recording medium S. The recording medium S in the area where the ink is applied has its back surface supported by a platen 9, and the distance between the ejection port surface 8a and the recording medium S is kept constant. The recording medium S after the ink is applied passes the left side of the flapper 11, the leading edge of which is inclined to the right in FIG. 4, while being guided by the discharge roller 12 and the spur 7b, and is transported vertically upward in the recording device 1 along the guide 18. FIG. 4(b) shows a state in which the leading edge of the recording medium S passes through the recording area P and is transported vertically upward. After the recording medium S passes the recording area P, which is inclined at about 45 degrees to the horizontal direction, the traveling direction of the recording medium S is changed to the vertically upward by the transport roller 7 and the spur 7b.

[0030] The recording medium S is transported vertically upward, and then discharged onto the discharge tray 13 by the discharge rollers 12 and spurs 7b. Fig. 4(c) shows the state in which the leading edge of the recording medium S is discharged onto the discharge tray 13. The recording medium S is discharged with the side on which the image is recorded by the recording head 8 facing down, and is held on the discharge tray 13.

[0031] 5(a) to 5(c) are diagrams showing the conveying path when A3 size recording media S contained in the second cassette 5B are fed. The topmost recording medium S in the second cassette 5B is separated from the second and subsequent recording media by the second feeding unit 6B, and is 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.

[0032] 5(a) shows a conveying state immediately before the leading edge of the recording medium S reaches the recording area P. A plurality of conveying rollers 7, pinch rollers 7a, and an inner guide 19 are arranged on the conveying path from when the recording medium S is fed by the second feeding unit 6B to when it reaches the recording area P, so that the recording medium S is conveyed to the platen 9 while being curved in an S-shape.

[0033] The subsequent transport path is the same as that of the A4-sized recording medium S shown in Figures 4(b) and (c). Figure 5(b) shows the state in which the leading edge of the recording medium S passes through the recording area P and is transported vertically upward. Figure 5(c) shows the state in which the leading edge of the recording medium S is discharged onto the discharge tray 13.

[0034] 6(a) to (d) show the transport path when performing a recording operation (double-sided recording) on ​​the back side (second side) of an A4-sized recording medium S. When the recording device 1 performs double-sided recording, it performs a recording operation on the second side (back side) after recording on the first side (front side). The transport process when recording on the first side is the same as in Figs. 4(a) to (c), so a description thereof will be omitted here. Hereinafter, the transport process from Fig. 4(c) onwards will be described.

[0035] When the recording operation on the first side by the recording head 8 is completed and the rear end of the recording medium S passes the flapper 11, the print controller 202 rotates the transport roller 7 in the reverse direction to transport the recording medium S into the recording device 1. At this time, the flapper 11 is controlled by an actuator (not shown) so that its leading end is tilted to the left in Fig. 6, so that the leading end of the recording medium S (the rear end in the recording operation on the first side) passes the right side of the flapper 11 and is transported vertically downward. Fig. 6(a) shows the state in which the leading end of the recording medium S (the rear end in the recording operation on the first side) passes the right side of the flapper 11.

[0036] The recording medium S is then transported along the curved outer peripheral surface of the inner guide 19, and is transported again to the recording area P between the recording head 8 and the platen 9. At this time, the second surface of the recording medium S faces the ejection port surface 8a of the recording head 8. Fig. 6(b) shows the transport state immediately before the leading edge of the recording medium S reaches the recording area P for the recording operation on the second surface.

[0037] The transport path thereafter is the same as in the case of first-side recording shown in Figures 4(b) and (c). Figure 6(c) 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 leading edge moves to a position inclined to the right. Figure 6(d) shows a state in which the leading edge of the recording medium S passes through the discharge rollers 12 and is discharged to the discharge tray 13. Note that a similar transport is performed in double-sided recording of an A3-sized recording medium S.

[0038] Next, a description will be given of the maintenance operation for the recording head 8. As described in Fig. 1, the maintenance unit 16 includes a cap unit 10 and a wiping unit 17, and performs the maintenance operation by operating these at a predetermined timing.

[0039] Fig. 7 is a diagram showing the recording device 1 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 first moves the recording head 8 diagonally upward in the vertical direction and moves the cap unit 10 vertically downward. Then, the print controller 202 moves the wiping unit 17 from the retracted position to the right in Fig. 7. After that, the print controller 202 moves the recording head 8 vertically downward to a maintenance position where maintenance operation is possible.

[0040] On the other hand, when the recording head 8 moves from the recording position shown in Fig. 3 to the maintenance position shown in Fig. 7, the print controller 202 first moves the recording head 8 vertically upward while rotating it by about 45 degrees. Then, the print controller 202 moves the wiping unit 17 from the retracted position to the right. After that, the print controller 202 moves the recording head 8 vertically downward to the maintenance position where the maintenance operation by the maintenance unit 16 can be performed.

[0041] FIG. 8(a) is a perspective view showing a state in which the maintenance unit 16 is in a standby position, and FIG. 8(b) is a perspective view showing a state in which the maintenance unit 16 is in a maintenance position. FIG. 8(a) corresponds to the position of the maintenance unit 16 shown in FIG. 1, and FIG. 8(b) corresponds to the position of the maintenance unit 16 shown in FIG. 7. When the recording head 8 is in the standby position, the maintenance unit 16 is in the standby position shown in FIG. 8(a), the cap unit 10 is in the capping position, and the wiping unit 17 is stored inside the maintenance unit 16. The cap unit 10 has a box-shaped cap member 10a extending in the y direction, and by bringing this into close contact with the discharge port surface 8a of the recording head 8, it is possible to suppress evaporation of ink from the discharge port. The cap unit 10 also has a function of collecting ink discharged by preliminary discharge or the like into the cap member 10a, and sucking the collected ink into a suction pump (not shown).

[0042] 8(b), the cap unit 10 has moved to a retracted position vertically downward, and the wiping unit 17 has been pulled out from the maintenance unit 16. The wiping unit 17 includes two wiper units: a blade wiper unit 171 and a vacuum wiper unit 172.

[0043] 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 arrangement area 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 with the recording head 8 positioned at a height that allows it to abut against the blade wiper 171a. With this movement, ink and the like adhering to the ejection port surface 8a is wiped off by the blade wiper 171a.

[0044] A wet wiper cleaner 16a is disposed at the entrance of the maintenance unit 16 when the blade wiper 171a is stored, for removing ink adhering to the blade wiper 171a and applying wet liquid to the blade wiper 171a. As a result, every time the blade wiper 171a is stored in the maintenance unit 16, the wet wiper cleaner 16a removes adhering matter and applies wet liquid to the blade wiper 171a. Then, the next time the ejection port surface 8a is wiped, the wet liquid is transferred to the ejection port surface 8a, improving the slipperiness between the ejection port surface 8a and the blade wiper 171a.

[0045] 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 y direction within the opening, and a vacuum wiper 172c mounted on the carriage 172b. The vacuum wiper 172c is arranged so that it can wipe the ejection 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 and 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 positioning pins 172d provided on both ends of the flat plate 172a and the opening are used to align the ejection port surface 8a with respect to the vacuum wiper 172c.

[0046] FIG. 9 is a diagram showing the ink supply unit 15 employed in the recording apparatus 1. The ink supply unit 15 is configured to supply ink from the ink tank unit 14 to the recording head 8. Here, a configuration for one color of ink is shown, but in reality, such a configuration is prepared for each ink color. The ink supply unit 15 is basically controlled by the ink supply control unit 209 shown in FIG. 2. Each configuration of the unit will be described below.

[0047] Ink mainly circulates between a subtank (ink tank) 151 and a recording head 8 (head unit 8 in FIG. 9). In the head unit 8, an ink ejection operation is performed based on image data, and ink that is not ejected is collected back into the subtank 151.

[0048] The subtank 151, which contains a predetermined amount of ink, is connected to a supply flow path C2 for supplying ink to the head unit 8 and a recovery flow path C4 for recovering ink from the head unit 8. In other words, the subtank 151, the supply flow path C2, the head unit 8, and the recovery flow path C4 form a circulation path through which the ink circulates.

[0049] The subtank 151 is provided with a liquid level detection means 151a consisting of multiple pins, and the ink supply control unit 209 can detect the presence or absence of a conductive current between these multiple pins to grasp the height of the ink liquid level, i.e., the amount of ink remaining in the subtank 151. The pressure reduction pump P0 is a negative pressure generating source for reducing the pressure inside the subtank 151. The atmosphere release valve V0 is a valve for switching whether or not the inside of the subtank 151 is connected to the atmosphere.

[0050] The main tank 141 is a tank that contains ink to be supplied to the sub tank 151. The main tank 141 is made of a flexible member, and ink is filled into the sub tank 151 by changing the volume of the flexible member. The main tank 141 is configured to be detachable from the recording apparatus body. A tank supply valve V1 for opening and closing the connection between the sub tank 151 and the main tank 141 is provided in the middle of a tank connection flow path C1 that connects the sub tank 151 and the main tank 141.

[0051] With the above configuration, when the ink level detection means 151a detects that the ink in the subtank 151 is less than a predetermined amount, the ink supply control unit 209 closes the atmosphere release valve V0, supply valve V2, recovery valve V4, relief valve V3, and head replacement valve V5. In this state, the ink supply control unit 209 opens the tank supply valve V1 and operates the pressure reduction pump P0. This creates a negative pressure inside the subtank 151, and ink is supplied from the main tank 141 to the subtank 151. When the ink level detection means 151a detects that the ink in the subtank 151 has exceeded a predetermined amount, the ink supply control unit 209 closes the tank supply valve V1 and stops the pressure reduction pump P0.

[0052] The supply flow path C2 is a flow path for supplying ink from the subtank 151 to the head unit 8, and a supply pump P1 and a supply valve V2 are arranged along the way. During a recording operation, the supply pump P1 is driven with the supply valve V2 open, so that ink can be circulated in the circulation path while being supplied to the head unit 8. The amount of ink consumed per unit time by the head unit 8 varies according to image data. For this reason, the flow rate of the supply pump P1 is determined so as to be able to cope with a case where a discharge operation is performed in which the amount of ink consumed per unit time in the head unit 8 is at its maximum.

[0053] The relief flow path (bypass path) C3 is upstream of the supply valve V2 and is a flow path connecting the upstream and downstream sides of the supply pump P1, and a relief valve V3, which is a differential pressure valve, is disposed midway along the relief flow path C3. When the ink supply amount per unit time from the supply pump P1 is greater than the total value of the discharge amount per unit time of the head unit 8 and the flow rate per unit time of the recovery pump P2, the relief valve V3 opens according to the pressure acting on itself. As a result, a circulating flow path is formed that is composed of a part of the supply flow path C2 and the relief flow path C3. By providing the above-mentioned configuration of the relief flow path C3, the ink supply amount to the head unit 8 is adjusted according to the ink consumption amount in the head unit 8, and the flow pressure in the circulation path can be stabilized regardless of the image data.

[0054] Fig. 10 shows a detailed configuration of the relief valve V3. Fig. 10(a) is an external perspective view of the relief valve V3, and Figs. 10(b) and (c) are cross-sectional views of AA in Fig. 10(a). As shown in Fig. 10(b), a seal member 1001, a slider 1002, and a spring 1003 are provided inside the relief valve V3. Also provided are an inlet 1004 through which ink flows into the relief valve V3, and an outlet 1005 through which ink flows out of the relief valve V3.

[0055] Fig. 10(b) shows a state in which the slider 1002 is pressed against the seal member 1001 by the bias of the spring 1003, and the inlet 1004 is closed. When a pressure equal to or greater than a predetermined value is applied to the relief flow path C3, the slider 1002 is moved in a direction against the bias of the spring 1003, and the inlet 1004 that was blocked by the seal member 1001 and the slider 1002 is opened (Fig. 10(c)). As shown in Fig. 10(c), the opening of the inlet 1004 causes ink to flow in from the inlet 1004 and flow out from the outlet 1005, and the ink is returned to the supply flow path C2 upstream of the supply pump P1.

[0056] The recovery flow path C4 is a flow path for recovering ink from the head unit 8 to the subtank 151, and a recovery pump P2 and a recovery valve V4 are arranged along the way. When circulating ink in the circulation path, the recovery pump P2 serves as a negative pressure generating source to suck ink from the head unit 8. When the recovery pump P2 is driven, an appropriate pressure difference is generated between the IN flow path 80b and the OUT flow path 80c in the head unit 8, and ink moves from the IN flow path 80b to the OUT flow path 80c. The flow path configuration in the head unit 8 will be explained in detail later.

[0057] The recovery valve V4 is a valve for preventing ink from flowing from the subtank 151 to the head unit 8 via the recovery flow path C4 when a recording operation is not being performed, i.e., when ink is not circulating in the circulation path. In the circulation path of this embodiment, the subtank 151 is disposed vertically above the head unit 8 (see FIG. 1). For this reason, when the supply pump P1 and the recovery pump P2 are not driven, there is a risk that ink will flow back from the subtank 151 to the head unit 8 due to the head difference between the subtank 151 and the head unit 8. To prevent such backflow, in this embodiment, the recovery valve V4 is provided in the recovery flow path C4.

[0058] Similarly, the supply valve V2 also functions as a valve to prevent the supply of ink from the subtank 151 to the head unit 8 when no printing operation is being performed, i.e., when no ink is circulating in the circulation path.

[0059] The head replacement flow path C5 is a flow path that connects the supply flow path C2 and the air space (the portion that does not contain ink) of the subtank 151, and a head replacement valve V5 is disposed midway through the flow path. One end of the head replacement flow path C5 is connected to the supply flow path C2 upstream of the head unit 8, and the other end is connected above the subtank 151 and communicates with the air space inside. The head replacement flow path 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 device 1.

[0060] 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 collected from the head unit 8. The head replacement flow path C5 is connected to the supply flow path C2 downstream of the supply valve V2. That is, the above-mentioned supply valve V2 is provided in the supply flow path C2 between the connection portion with the head replacement flow path C5 and the connection portion with the relief flow path C3.

[0061] Next, the flow path configuration in the head unit 8 will be described. The ink supplied to the head unit 8 from the supply flow path C2 passes through a filter 83, and then is supplied to a first negative pressure control unit (first pressure control means) 81 that generates a weak negative pressure, and a second negative pressure control unit (second pressure control means) 82 that generates a strong negative pressure. The absolute value of the pressure generated by the second negative pressure control unit 82 is smaller than the absolute value of the pressure generated by the first negative pressure control unit 81. The pressures in the first negative pressure control unit 81 and the second negative pressure control unit 82 are generated by driving the recovery pump P2.

[0062] In the ink ejection section 80, a plurality of recording element substrates 80a, each having a plurality of ejection ports arranged thereon, are arranged to form a long ejection port array. In the recording element substrate 80a, a recording element 2323 (see FIG. 11(b)), which is a heating element for foaming the ink with thermal energy, is formed. A common supply flow path 80b (IN flow path) for guiding the ink supplied from the first negative pressure control unit 81 and a common recovery flow path 80c (OUT flow path) for guiding the ink supplied from the second negative pressure control unit 82 also extend in the arrangement direction of the recording element substrates 80a. The common supply flow path 80b is connected to the supply flow path C2. The common recovery flow path 80c is connected to both the supply flow path C2 and the recovery flow path C4.

[0063] Fig. 11(a) is a schematic plan view of an enlarged portion of the recording element substrate 80a, and Fig. 11(b) is a schematic cross-sectional view taken along the cross-sectional line XX in Fig. 11(a). The recording element substrate 80a is provided with pressure chambers 2402 filled with ink and ejection ports 2311 for ejecting ink. In the pressure chambers 2402, recording elements 2323 are provided at positions facing the ejection ports 2311. In addition, the recording element substrate 80a is provided with a plurality of individual supply flow paths 2321 connected to the common supply flow path 80b and individual recovery flow paths 2322 connected to the common recovery flow path 80c, each for each ejection port 2311.

[0064] With the above-mentioned configuration, in the recording element substrate 80a, a flow of ink is generated in which the ink flows in through the common supply flow path 80b, which has a relatively weak negative pressure (high pressure), and flows out to the common recovery flow path 80c, which has a relatively strong negative pressure (low pressure). More specifically, the ink flows in the order of the common supply flow path 80b → individual supply flow paths 2321 → pressure chamber 2402 → individual recovery flow path 2322 → common recovery flow path 80c. When ink is ejected by the recording element 2323, a part of the ink moving from the common supply flow path 80b to the common recovery flow path 80c is ejected from the ejection port 2311 and discharged to the outside of the head unit 8. On the other hand, the ink that is not ejected from the ejection port 2311 is recovered to the recovery flow path C4 via the common recovery flow path 80c.

[0065] Fig. 12 shows the first negative pressure control unit 81 provided in the head unit 8. Figs. 12(a) and (b) are external perspective views, and in particular Fig. 12(b) shows the first negative pressure control unit 81 without showing the flexible film 232 in order to show the inside of the first negative pressure control unit 81. Fig. 12(c) shows a cross section of XIVC-XIVC in Fig. 12(a). The first negative pressure control unit 81 and the second negative pressure control unit 82 are differential pressure valves, and have the same configuration except for the difference in control pressure (initial load of the spring), so a description of the second negative pressure control unit 82 will be omitted.

[0066] In the first negative pressure control unit 81, a first pressure chamber 233 is formed inside by a pressure-receiving plate 231 shown in Fig. 12(b) and a flexible film 232 that seals the space around it. The flexible film 232 is welded to the circular edge shown in Fig. 12(b) and the pressure-receiving plate 231. In response to an increase or decrease in the amount of ink in the first pressure chamber 233, the flexible film 232 and the pressure-receiving plate 231 welded to the flexible film 232 are displaced up and down.

[0067] Provided on the upstream side of the first pressure chamber 233 in the ink supply direction are 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 fitted into the valve 235. The orifice 236 in 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 urged vertically upward by an urging member (spring) 237.

[0068] 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 valve 235 engages with the orifice 236 by the biasing force of the biasing member 237, 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 is less than the first threshold, that is, when a negative pressure stronger than the first threshold is applied to the first pressure chamber 233, the flexible film 232 contracts and displaces downward. As a result, the pressure receiving plate 231 and the valve 235 displace downward against the biasing force 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 allows ink supplied by the supply pump P1 to flow toward the first pressure chamber 233.

[0069] The first negative pressure control unit 81 has the above-mentioned differential pressure valve configuration, which controls the inflow pressure and outflow pressure to be constant. The second negative pressure control unit 82 uses a biasing member 237 with a biasing force greater than that of the first negative pressure control unit in order to generate a stronger negative pressure than the first negative pressure control unit.

[0070] 13 is a diagram showing the ink supply unit 15 during a recording operation by the head unit 8. The valves provided in the flow paths shown by solid lines are open, forming a flow of ink, but the valves provided in the flow paths shown by dotted lines are closed, so that no ink or air flows. First, when performing a recording operation by the head unit 8, the ink supply control unit 209 closes the tank supply valve V1 and the head replacement valve V5, opens the atmosphere release valve V0, the supply valve V2, and the recovery valve V4, and drives the supply pump P1 and the recovery pump P2. This establishes a circulation path from the subtank 151 to the supply flow path C2 to the head unit 8 to the recovery flow path C4 to the subtank 151.

[0071] Here, the amount of ink supplied by the supply pump P1 per unit time is set so as to correspond to the maximum amount of ink that the head unit 8 can eject per unit time (hereinafter, a predetermined ejection amount). The maximum amount of ink that can be ejected is defined, for example, by the ejection amount of each ejection port x the ejection frequency per unit time x the number of ejection ports. In addition, in this embodiment, since ink is circulated from the supply flow path C2 to the recovery flow path C4 via the head unit 8, it is necessary to supply from the supply pump P1 an amount of ink (hereinafter, a circulation flow rate) that is recovered by the recovery pump P2 to the recovery flow path C4 for circulation. The circulation flow rate through the recovery flow path C4 is determined according to the amount of ink to be circulated, and in this embodiment, it is configured to maintain a constant circulation flow rate. Therefore, the recovery pump P2 is driven at a constant amount so as to be able to recover an almost constant flow rate.

[0072] For the above reasons, the amount of ink supplied per unit time by the supply pump P1 is set to correspond to the sum of the predetermined ejection amount and the circulation flow rate through the recovery passage C4, and the drive amount is set to be approximately constant. In other words, both the supply pump P1 and the recovery pump P2 are driven at an approximately constant drive amount to supply and recover ink, and circulate the ink in the circulation path.

[0073] FIG. 13(a) shows the flow of ink when a recording operation is performed in which a large amount of ink is discharged from the head unit 8. At this time, most of the predetermined amount of ink supplied from the supply pump P1 is discharged from the head unit 8 and discharged. Therefore, the negative pressure generated by the discharge operation and the negative pressure by the recovery pump P2 are applied to the negative pressure control unit, and the differential pressure valve is maintained in an open state. In other words, a state is maintained in which ink is supplied to the head unit 8 at a rate equal to or greater than the sum of the predetermined discharge amount and the circulation flow rate supplied by the supply pump P1. In such a case, pressure equal to or greater than the predetermined value is not applied to the relief valve V3, and the relief valve V3 is not opened. Therefore, the flow of ink is blocked in the relief flow path C3 before the relief valve V3, and no ink flows through the entire relief flow path C3.

[0074] FIG. 13(b) shows the flow of ink when a recording operation is being performed with a small amount of ink discharged from the head unit 8. At this time, most of the predetermined amount of ink supplied from the supply pump P1 is not discharged. Therefore, only a small negative pressure generated by the discharge operation and negative pressure from the recovery pump P2 are applied to the negative pressure control unit, making it difficult to maintain the differential pressure valve open. This creates a state in which excess ink is supplied from the supply pump P1, and pressure above a predetermined value is applied to the relief valve V3. Then, as shown in FIG. 10(c), the inlet 1004 of the relief valve V3 is opened, and the ink excessively supplied to the supply flow path C2 flows through the relief flow path C3, allowing the pressure to be released.

[0075] If the relief flow path C3 and the relief valve V3 were not provided, the ink pressure would increase between the negative pressure control unit and the supply pump P1, which could result in damage to the flow path or ink leakage. By providing the relief flow path C3 and the relief valve V3 as in this embodiment, the pressure inside the flow path in the ink circulation configuration can be kept appropriate regardless of the ejection volume in the head unit 8. Furthermore, the supply pump P1 and the recovery pump P2 can be kept almost constant in drive, eliminating the need for complex control according to the ejection volume, and stable ejection performance can be maintained with a simple configuration.

[0076] In this embodiment, a configuration is adopted in which the ink in the pressure chambers 2402 of the recording head 8 is also circulated, but the present invention is not limited to this, and can also be applied to a configuration in which only the ink in the common liquid chamber of the recording head 8 is circulated. [Explanation of symbols]

[0077] 1 Inkjet recording device 8 Recording head (head unit) 151 Subtank (ink tank) C2 Supply Channel C3 Relief channel (bypass route) C4 Recovery channel P1 Supply Pump P2 Recovery Pump V3 Relief valve (differential pressure valve)

Claims

1. A supply pump for supplying ink; a circulation path including a supply flow path through which ink is supplied from a tank that stores ink to a recording head and a recovery flow path through which ink discharged from the recording head passes, the circulation path having a first flow path for circulating the ink so that the ink discharges from the recording head and re-enters the recording head, and a second flow path that branches off from the first flow path downstream of the supply pump provided in the first flow path in the ink flow direction and for circulating the ink so as to send the ink upstream of the supply pump; Equipped with the recording head has ejection ports for ejecting ink, energy generating elements provided corresponding to the ejection ports and for generating energy used to eject ink, and pressure chambers located opposite the energy generating elements, a common supply flow path connected to the supply flow path for supplying ink to the pressure chambers, and a common recovery flow path connected to the supply flow path and the recovery flow path for recovering ink from the pressure chambers, a first pressure control means provided between the supply flow path and the common supply flow path and configured to control a pressure; a second pressure control means that is provided between the supply flow path and the common recovery flow path and controls pressure, and that generates a negative pressure stronger than that of the first pressure control means; 2. An ink jet recording apparatus, comprising: a recording head including a first pressure control means and a second pressure control means, the first pressure control means and the second pressure control means being provided within the recording head.

2. A supply pump for supplying ink; a circulation path including a supply flow path through which ink is supplied from a tank that stores ink to a recording head and a recovery flow path through which ink discharged from the recording head passes, the circulation path having a first flow path for circulating the ink so that the ink discharges from the recording head and re-enters the recording head, and a second flow path that branches off from the first flow path downstream of the supply pump provided in the first flow path in the ink flow direction and for circulating the ink so as to send the ink upstream of the supply pump; Equipped with the recording head has ejection ports for ejecting ink, energy generating elements provided corresponding to the ejection ports and for generating energy used to eject ink, and pressure chambers located opposite the energy generating elements, a common supply flow path connected to the supply flow path for supplying ink to the pressure chambers, and a common recovery flow path connected to the supply flow path and the recovery flow path for recovering ink from the pressure chambers, a first pressure control means provided between the supply flow path and the common supply flow path and configured to control a pressure; a second pressure control means that is provided between the supply flow path and the common recovery flow path and controls pressure, and that generates a negative pressure stronger than that of the first pressure control means; a differential pressure valve is provided in the second flow path; the differential pressure valve has an inlet through which ink flows in, an outlet through which ink flows out, a sealing member, a slider connected to the sealing member, and a biasing member that biases the slider and the sealing member against the inlet, and when the pressure generated by the supply pump reaches or exceeds a predetermined value, the slider moves against the bias of the biasing member, thereby opening the inlet.

3. 3. The inkjet recording apparatus according to claim 1, wherein the first flow path is provided with a supply pump that flows ink from a tank that stores ink to be supplied to the recording head to the recording head, and a recovery pump that flows ink discharged from the recording head.

4. the first flow path includes a supply flow path through which ink is supplied from the tank to the recording head, and a recovery flow path through which ink discharged from the recording head passes; 4. The inkjet recording apparatus according to claim 3, wherein the supply pump is driven so as to flow a substantially constant amount of ink in the supply flow path, regardless of the amount of ink ejected from the recording head, and the recovery pump is driven so as to flow a substantially constant amount of ink in the recovery flow path.

5. 5. The inkjet recording apparatus according to claim 4, wherein the recovery pump is driven so that a substantially constant circulation flow rate flows through the recovery flow path, and the supply pump is driven so that a flow rate equal to or greater than the sum of a predetermined discharge amount discharged from the recording head and the circulation flow rate flows.

6. 6. The inkjet recording apparatus according to claim 5, wherein the predetermined ejection amount is a maximum amount of ink that can be ejected from the recording head per unit time.

7. a differential pressure valve is provided in the second flow path; 7. The ink jet recording apparatus according to claim 5, wherein the differential pressure valve opens when the amount of ink ejected from the recording head is smaller than the predetermined ejection amount, allowing ink to flow into the second flow path.

8. 8. The ink jet recording apparatus according to claim 1, wherein the ink is circulated through the inside of the pressure chamber by driving the supply pump.

9. 3. The ink jet recording apparatus according to claim 2, wherein the first pressure control means and the second pressure control means are provided within the recording head.

10. 10. The inkjet recording device according to claim 1, wherein the recording head has, for each of the ejection ports, an individual supply flow path connected to the common supply flow path and an individual recovery flow path connected to the common recovery flow path, and the ink is supplied to the pressure chamber via the common supply flow path and the individual supply flow path by the supply pump, and the ink is recovered from the individual recovery flow path to the common recovery flow path.

11. a differential pressure valve is provided in the second flow path; 2. The inkjet recording device according to claim 1, wherein the differential pressure valve has an inlet through which ink flows in, an outlet through which ink flows out, a sealing member, a slider connected to the sealing member, and a biasing member that biases the slider and the sealing member against the inlet, and when the pressure generated by the supply pump reaches or exceeds a predetermined value, the slider moves against the bias of the biasing member, thereby opening the inlet.

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