JP2018140520A - Liquid discharge device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid discharge device in which a sub-tank is disposed upward in a gravity direction than a liquid discharge head having a discharge port for discharging liquid and which can prevent leakage of liquid from the discharge port even when sudden electricity failure occurs while the device is operating.SOLUTION: A liquid discharge device includes: a discharge flow channel which is disposed apart from a supply flow channel communicating a sub-tank with a liquid discharge head and can discharge liquid inside the sub-tank; a liquid storage part for storing the liquid discharged from the discharge flow channel; and liquid feeding means for supplying the liquid inside the liquid storage part to the sub-tank.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a liquid ejection apparatus.

  Inkjet recording devices are representative of liquid discharge devices that perform recording by discharging liquid onto the recording medium from the discharge ports provided in the liquid discharge head, and support multiple recording colors for recording color images. Those equipped with a liquid discharge head are widely used. An apparatus including a plurality of liquid discharge heads for each recording color is also known so that higher-definition recording can be performed at a high speed.

  The liquid ejection apparatus has a sub tank for storing the liquid supplied from the main tank and supplying it to the liquid ejection head, in addition to the main tank for the user to supply the ejection liquid (for example, recording liquid). There is something. Since the pressure applied to the liquid in the sub tank and the flow state of the liquid in the flow path from the sub tank to the liquid discharge head greatly affect the liquid in the liquid discharge head, the sub tank is disposed near the liquid discharge head. Is desirable. Further, in order to prevent liquid from accidentally leaking from the discharge port of the liquid discharge head, the pressure at the discharge port is controlled to be negative. In the conventional liquid discharge device, the sub tank is arranged at a position lower than the liquid discharge head in the direction of gravity so that the pressure at the discharge port is maintained at a negative pressure due to the water head difference between the liquid in the sub tank and the discharge port. What has been used is widely used. However, in the liquid ejection apparatus, generally, since the recording medium and the transport apparatus are disposed below the liquid ejection head, the distance between the sub tank and the liquid ejection head tends to increase, and the apparatus becomes larger. The piping becomes complicated. In addition, the long pipe increases the resistance of the flow path, which makes it unsuitable for high-speed recording. This problem is more serious as the liquid ejecting apparatus has more liquid ejecting heads.

  A supply unit that supplies a liquid for discharge to the liquid discharge head; and a recovery unit that recovers the liquid that has not been used for recording in the liquid discharge head. There is known a technique for circulating and circulating the water. By circulating the liquid, bubbles, dust and the like in the liquid discharge head can be removed. In addition, when pigment ink is used as the liquid for ejection, sedimentation of the pigment can be prevented. In the liquid ejecting apparatus in which such a technique is introduced, since the piping on the collection unit side is required in addition to the supply unit side, the above problem becomes more serious.

  Patent Document 1 discloses a liquid ejection device in which a reservoir, which is a sub-tank, is disposed above a liquid ejection head, and the pressure in the reservoir is reduced by pressure adjusting means attached to the reservoir and the pressure at the ejection port is controlled to a negative pressure. It is disclosed. Patent Document 2 discloses a technique in which a discharge liquid supply unit and a recovery unit are provided in a sub-tank disposed above a liquid discharge head, and the liquid is circulated in the liquid discharge head. In patent document 2, the supply part and the collection | recovery part are divided by providing a partition in a subtank. Also in Patent Document 2, the pressure within the sub-rank is reduced by the pressure adjusting means, and the pressure at the discharge port is controlled to a negative pressure.

Japanese Patent No. 5040039 JP 2011-201176 A

  In the liquid ejection devices described in Patent Document 1 and Patent Document 2, the inside of the sub tank is controlled to a negative pressure by a pressure adjusting unit configured by a pump or the like. However, if the power supply is suddenly interrupted due to a power failure or the like during operation of the liquid ejection device, the operation of the pressure adjustment means stops, and as a result, the sub tank The pressure inside gradually increases and approaches atmospheric pressure. If the pressure in the sub-tank, which is above the liquid discharge head in the direction of gravity, increases, the liquid in the sub-tank flows toward the liquid discharge head and leaks from the discharge port, which may contaminate the liquid discharge device or the recording medium. is there.

  An object of the present invention is to dispose the subtank above the liquid discharge head in the gravity direction, and even when the sudden power supply is cut off during operation, the liquid in the subtank is discharged from the discharge port of the liquid discharge head. An object of the present invention is to provide a liquid ejection device that does not leak from the liquid.

  A liquid discharge apparatus according to the present invention includes a liquid discharge head having a discharge port for discharging a liquid, and a liquid supply means for supplying a liquid to the liquid discharge head. A sub-tank that is disposed above the formed discharge port surface in the gravitational direction and stores liquid supplied to the liquid discharge head, a supply channel that connects the sub-tank and the liquid discharge head, and a liquid pressure at the discharge port. A pressure adjusting means for adjusting, a discharge channel that can discharge the liquid inside the sub-tank, different from the supply channel, a liquid storage unit that stores the liquid discharged from the discharge channel, and a liquid storage unit inside the liquid storage unit Liquid feeding means for supplying liquid to the sub-tank.

  According to the present invention, in the liquid ejection device in which the subtank is disposed above the liquid ejection head in the gravity direction, the liquid in the subtank is transferred to the liquid ejection head even when sudden power supply is interrupted during operation. It is possible to prevent leakage from the discharge port.

It is a figure which shows schematic structure of the liquid discharge apparatus of the 1st Embodiment of this invention. FIG. 2 is a schematic cross-sectional view illustrating a configuration of a liquid ejection head in the first embodiment. It is a figure explaining the liquid supply means in 1st Embodiment. It is a figure explaining the operation | movement at the time of normal completion | finish in the apparatus of 1st Embodiment. It is a figure explaining the liquid supply means in 2nd Embodiment. It is a figure explaining the liquid supply means in 3rd Embodiment. It is a figure which shows schematic structure of the liquid discharge apparatus of 4th Embodiment. It is a schematic sectional drawing which shows the structure of the liquid discharge head in 4th Embodiment. It is a figure explaining the liquid supply means in 4th Embodiment.

(First embodiment)
Next, the form for implementing this invention is demonstrated. FIG. 1 shows a schematic configuration of a liquid ejection apparatus 1 according to the first embodiment. In this embodiment, recording paper is used as the recording medium 40, but it is obvious that the recording medium 40 may be other than recording paper. The recording medium 40 is supplied to the liquid ejecting apparatus 1 as roll paper, is fed in the direction of the arrow by the paper feed roller 42, passes through the upper surface of the platen 41, and is discharged from the left end in the figure. The position where the platen 41 is provided is a position where recording with a recording liquid which is a liquid for ejection is performed on the recording medium 40. Conveying means 4 for the recording medium 40 is configured by the platen 41 and the paper feed roller 42. Opposite to the upper surface of the platen 41, four sets of liquid ejection heads 2 are provided along the conveyance direction of the recording medium 40. The four sets of liquid discharge heads 2 discharge cyan, magenta, yellow, and black liquids from the discharge ports downward in the direction of gravity, respectively, thereby recording on the recording medium 40 located on the platen 41. Is what you do. Each of these liquid ejection heads 2 is connected to a supply-side subtank 50 that stores liquid of the corresponding color via a supply channel 51. The sub tank 50 on the supply side is also called a first sub tank. The sub tank 50 and the supply flow path 51 form part of a liquid supply unit that supplies liquid to the liquid discharge head 2. Details of the liquid supply means will be described later. Each liquid discharge head 2 is connected to a drive circuit 31 that generates a drive signal for electrically driving a recording element to be described later and drives the liquid discharge head 2. The drive circuit 31 connected to each liquid ejection head 2 generates a drive signal based on an image signal or the like sent from the control unit 30. The drive circuit 31 for each liquid discharge head 2 and the control unit 30 provided in common for each drive circuit 31 constitute drive means for driving the liquid discharge head 2. In the attached drawings, hatching by a line from the upper right to the lower left conceptually indicates the presence of the ejection liquid or the location of the ejection liquid.

  FIG. 2 shows the configuration of the liquid ejection head 2 in the present embodiment. The liquid discharge head 2 is provided with a common liquid chamber 20 for storing the liquid supplied from the sub tank 50 on the supply side, and the liquid in the common liquid chamber 20 is a plurality of pressure chambers 21 provided in the liquid discharge head 2. Supplied to. A discharge port 25 for discharging a liquid is formed in the discharge port forming member 24, and each pressure chamber 21 communicates with the discharge port 25 formed in the discharge port forming member 24. In the pressure chamber 21, the surface that faces the discharge port forming member 24 is formed by the diaphragm 23. In the diaphragm 23, a piezoelectric element 22 is formed on the side opposite to the pressure chamber 21 as a recording element that generates energy for ejecting liquid. By driving the piezoelectric element 22 with a drive signal generated by the drive circuit 31 and deforming the diaphragm 23, the liquid in the pressure chamber 21 can be discharged from the discharge port 25 to the outside. Note that the surface of the liquid discharge head 2 on which the discharge port 25 is formed is referred to as a discharge port surface 26.

  Here, a so-called piezo-type liquid discharge head using a piezoelectric element as a recording element is shown as an example. However, the liquid discharge head used in the present invention is not limited to a piezo-type, and the present invention is not limited to the liquid discharge head. It does not depend on the type of discharge head. For example, a thermal type liquid discharge head that discharges liquid by foaming pressure due to the heat of the liquid, and an electrostatic type liquid discharge head that generates discharge pressure by deforming the electrode plate by electrostatic force between the electrode plates The present invention is applicable. The present invention can also be applied to an electrostatic attraction type liquid discharge apparatus that discharges liquid by applying an electrostatic force to the liquid due to a potential difference between the liquid discharge head and a counter electrode facing the liquid discharge head.

  FIG. 3 shows the liquid supply means 5 in the liquid ejection apparatus 1 of the present embodiment. The sub tank 50 on the supply side is provided inside the airtight casing 68. In the figure, the sub-tank 50 is shown as being provided inside the housing 68. However, the housing 68 itself can be configured as the sub-tank 50, which can simplify the configuration and reduce the member cost. Can be reduced. The liquid stored in the sub tank 50 is supplied to the liquid discharge head 2 through a supply flow channel 51 connected to the bottom of the sub tank 50. Here, the sub tank 50 is positioned above the liquid discharge head 2 in the direction of gravity. Further, the sub tank 50 is provided with a discharge channel 53 different from the supply channel 51. The discharge channel 53 is connected to the bottom of the sub tank 50, communicates with the liquid storage unit 55, and the end of the discharge channel 53 on the liquid storage unit 55 side is more than the liquid level position in the liquid storage unit 55. Located below the gravitational direction. The discharge flow path 53 is provided with a self-holding valve 54 that is inserted into the flow path. The self-holding valve is a kind of electromagnetic valve, but is a type of valve that maintains the final open / close state of the valve when the power is cut off. In the present embodiment, the self-holding valve 54 is configured to be opened when electric power is supplied and the liquid discharge apparatus 1 is operating. As a result, during operation of the liquid ejection device 1, the liquid in the sub tank 50 constantly flows to the liquid storage portion 55 via the self-holding valve 54.

  In addition to the sub tank 50, the liquid supply means 5 is provided with a main tank 60 for supplying or replenishing a discharge liquid by the user. In addition to the liquid from the sub tank 50, the liquid in the main tank 60 is supplied to the liquid storage unit 55 by the pump 61. The liquid level sensor (LS) 62 monitors the liquid level of the liquid in the liquid storage unit 55, and the amount of liquid fed by the pump 61 so that the liquid level in the liquid storage unit 55 falls within a predetermined range. Is controlled. Accordingly, a substantially constant amount of liquid is always stored in the liquid storage portion 55. In the present embodiment, a liquid storage unit 55 is provided separately from the main tank 60 so that a substantially constant amount of liquid is stored in the liquid storage unit 55. Therefore, if the main tank 60 is a disposable tank, the liquid can be replenished by replacing the main tank 60 itself while the liquid ejection apparatus 1 is in operation. Further, by adopting a configuration in which the liquid storage unit 55 also serves as the main tank 60, the number of members can be reduced, the liquid ejection apparatus 1 can be simplified, and the cost can be reduced.

  A flow path 56 for supplying the liquid stored in the liquid storage portion 55 to the sub tank 50 is provided, and a pump 57 and a filter 59 are provided in the flow path 56. The flow path 56 and the pump 57 constitute liquid feeding means for supplying the liquid inside the liquid storage portion 55 to the sub tank 50. The liquid in the liquid storage unit 55 is supplied by the pump 57 to the sub tank 50 on the supply side through the filter 59 for removing dust and bubbles in the liquid. A liquid level sensor 58 is provided to control the pump 57, and the liquid level sensor 58 monitors the liquid level of the liquid in the sub tank 50. The amount of liquid fed by the pump 57 is controlled so that the liquid level in the sub tank 50 falls within a predetermined range. As a result, the water head difference h1 between the discharge port surface 26 in which the discharge port 25 of the liquid discharge head 2 is formed and the liquid level in the sub tank 50 is kept substantially constant.

  An air pump (A) 81 for reducing the pressure of the gas inside the housing 68 is connected to the housing 68 in which the sub tank 50 is accommodated. The air pump 81 operates so as to continuously discharge the air in the housing 68 while the liquid discharge apparatus 1 is in operation. In order to control the inside of the casing 68 to a predetermined pressure, a regulator (R) 80 is provided in parallel with the air pump 81. The regulator 80 opens when the pressure on the casing 68 side becomes lower than a predetermined value, and operates to keep the pressure in the casing 68 constant by allowing outside air to flow in. The air pump 81 and the regulator 80 constitute a pressure adjusting mechanism that adjusts the pressure of the gas in the housing 68. A filter 82 is provided between the regulator 80 and the outside air in order to prevent dust and the like from entering with the outside air. In the liquid ejection apparatus 1 of the present embodiment, the sub tank 50 is located above the liquid ejection head 2 in the direction of gravity, so that when the inside of the housing 68 is not decompressed, the liquid ejection head 2 and The liquid in the sub tank 50 leaks out. Therefore, in this liquid discharge apparatus 1, the inside of the housing 68 is depressurized by the air pump 81 and the regulator 80, and the pressure of the liquid at the discharge port 25 is controlled to be a negative pressure. In the present embodiment, the pressure of the liquid at the discharge port 25 is kept at a stable negative pressure by pressure control by the water head difference h1 and the air pump 81 and the regulator 80. Further, this pressure control suppresses the pressure fluctuation other than the sub tank 50 from affecting the liquid pressure at the discharge port 25, that is, the discharge performance. As the air pump 81 used here, it is desirable to use a normally closed type air pump that closes when power supply is stopped. As described above, the head difference h1 is kept constant by controlling the liquid level height to be constant according to the detection value of the liquid level sensor 58, and the gas pressure in the housing 68 is made constant by the pressure adjustment mechanism. Kept. Therefore, in this embodiment, the liquid level sensor 58 and the pressure adjustment mechanism (the air pump 81 and the regulator 80) constitute a pressure adjustment unit that adjusts the pressure of the liquid at the discharge port 25.

  Next, an operation at the normal end time of ending the recording operation by the liquid ejection apparatus 1 of the present embodiment at the normal time (that is, when there is no power failure) will be described using FIG. FIG. 4 shows the same liquid supply means 5 as shown in FIG. 3, but for the sake of simplicity, the main tank 60 and related items are not drawn. When ending the recording operation, first, the pump 57 is stopped, and the supply of the liquid from the liquid storage portion 55 to the sub tank 50 is stopped. Next, after the self-holding valve 54 is closed, the operation of the self-holding valve 54 is stopped. Next, the air pump 81 is stopped, and a valve provided in the air pump 81 is closed. When the normally closed air pump as described above is used, the valve is automatically closed by stopping the air pump 81. By stopping the air pump 81 and closing the valve, the inside of the housing 68 is shut off from the outside air. Thereafter, the capping member 63 is attached to the ejection port surface 26 of the liquid ejection head 2 after the liquid ejection head 2 is moved upward in the direction of gravity to widen the gap with the recording medium 40. The capping member 63 can prevent drying at the discharge port 25 due to evaporation of the solvent component from the liquid, and can prevent the recording medium 40 and the conveying unit 4 from being soiled due to leakage of the liquid. Further, since the self-holding valve 54 is closed, the liquid is held in the sub tank 50 even when the liquid discharge apparatus 1 is stopped, so that bubbles are prevented from being mixed into the liquid discharge head 2 from the sub tank 50 side. And can start recording promptly at the next operation.

  Next, an operation when power supply to the liquid ejection apparatus 1 is suddenly interrupted due to a power failure or the like during operation will be described. When the power supply to the liquid discharge device 1 is interrupted, the operation of the pump 57 and the pump 61 is stopped, the air pump 81 is stopped, the valve provided in the air pump 81 is closed, and the inside of the housing 68 is closed. Blocked from outside air. At this time, since the self-holding valve 54 remains open, the liquid in the sub tank 50 is discharged to the liquid storage portion 55 through the discharge flow path 53. A state in which almost no liquid remains in the sub tank 50 is avoided, and a situation in which the liquid in the supply sub tank 50 leaks from the discharge port 25 of the liquid discharge head 2 is avoided. Since the sub tank 50 becomes empty, it is desirable to perform a recovery operation for removing bubbles from the liquid ejection head 2 at the start of the next operation after the power failure is restored. In addition, since the sub tank 50 is housed in an airtight casing 68 and is shielded from the outside air, the liquid level in the liquid container 55 is increased to ensure the discharge of the liquid into the liquid container 55. It is preferable that the liquid discharge head 2 be positioned below the discharge port surface 26 in the direction of gravity.

  In the present embodiment, the self-holding valve 54 is not provided, and the liquid can always flow from the sub tank 50 toward the liquid storage portion 55 via the discharge flow path 53. In that case, most of the liquid in the sub tank 50 is discharged to the liquid storage portion 55 even when the liquid discharge device 1 that stops the pump 57 is normally terminated. Therefore, it is desirable to perform a recovery operation for removing bubbles from the liquid ejection head 2 every time the operation of the liquid ejection apparatus 1 is resumed. According to the present embodiment, in the liquid ejection apparatus 1 having the supply-side subtank 50 above the liquid ejection head 2 in the direction of gravity, the liquid in the subtank 50 is not supplied even when power supply is suddenly interrupted due to a power failure or the like. It is possible to prevent leakage from the discharge port.

(Second Embodiment)
Next, a liquid ejection apparatus according to a second embodiment will be described. The liquid ejection apparatus according to the second embodiment is the same as the liquid ejection apparatus according to the first embodiment except for the configuration of the liquid supply means 5. In the following, description of matters common to the liquid ejection apparatus of the first embodiment will be omitted, and the configuration of the liquid supply means 5 in the liquid ejection apparatus of the second embodiment will be described with reference to FIG.

  In the liquid supply means 5 in the second embodiment, a liquid level sensor for controlling the pump 57 by monitoring the liquid level in the sub tank 50 is not provided. Instead, a partition member 64 for defining the liquid level height in the sub tank 50 is provided in the housing 68, and a part of the side wall of the sub tank 50 is formed by the partition member 64. There is a gap between the lower end of the partition member 64 and the bottom surface of the housing 68, and a discharge port 65 is formed. The discharge port 65 forms a part of the discharge channel 53. Here, when a sufficient amount of liquid is supplied from the liquid storage unit 55 to the sub tank 50 by the pump 57, liquids other than the amount supplied from the sub tank 50 to the liquid discharge head 2 are disposed on the upper side of the discharge port 65 or the partition member 64. As a result, it always flows to the liquid storage portion 55. As a result, the liquid surface height of the liquid in the sub tank 50 is kept substantially constant by the upper end of the partition member 64, and the water head difference h2 between the discharge port surface 26 of the liquid discharge head 2 and the liquid in the sub tank 50 is approximately. Kept constant. According to the present embodiment, in the liquid ejection apparatus 1 having the supply sub-tank 50 above the liquid ejection head 2 in the gravity direction, the liquid pressure at the ejection port 25 can be maintained at a stable negative pressure with a simple configuration. it can. Further, even when the supply of electric power is suddenly interrupted due to a power failure or the like, the liquid in the sub tank 50 can be prevented from leaking from the discharge port 25 as in the first embodiment. Also in this embodiment, the casing 68 itself may be used as the sub tank 50.

(Third embodiment)
Next, a liquid ejection apparatus according to a third embodiment will be described. The liquid ejection apparatus according to the third embodiment is the same as the liquid ejection apparatus according to the first embodiment except for the configuration of the liquid supply means 5. In the following, description of items common to the liquid ejection apparatus of the first embodiment is omitted, and the configuration of the liquid supply means 5 in the liquid ejection apparatus of the third embodiment will be described with reference to FIG.

  In the liquid supply means 5 in the third embodiment, the airtight casing 68 for housing the supply-side subtank 50 is not provided, and the subtank 50 is communicated with or opened to the atmosphere. Therefore, neither an air pump nor a regulator for keeping the inside of the housing 68 at a constant pressure is provided. Instead, a valve 66 is provided in the supply flow path 51 for supplying the liquid from the sub tank 50 to the liquid discharge head 2, and the pressure of the supply flow path 51 at a position downstream of the valve 66 (the liquid discharge head 2 side). A pressure sensor (PS) 67 for measuring the pressure is provided. The valve 66 and the pressure sensor 67 constitute pressure adjusting means for adjusting the pressure of the liquid at the discharge port 25. As the valve 66, a normally closed type valve that closes when power supply is stopped is used. The valve 66 is normally closed, but is configured to open when the measurement value of the pressure sensor 67 falls below a predetermined value due to the discharge of the liquid in the liquid discharge head 2. Liquid is supplied to the liquid discharge head 2 when the valve is opened. With such a configuration, the pressure of the liquid at the discharge port 25 of the liquid discharge head 2 is maintained within a predetermined range.

  In the liquid ejecting apparatus 1 of the present embodiment, a normally closed type valve 66 is used. Therefore, even when power supply is suddenly interrupted due to a power failure or the like, the valve 66 is closed, and the liquid ejecting head 2 is supplied with liquid. Supply is cut off. However, it is considered that it is difficult to completely shut off the flow of fluid even in the valve-closed state. When the power supply continues to be cut off, the liquid in the sub tank 50 gradually moves toward the liquid discharge head 2. It is possible for the flow and leakage from the discharge port 25 to occur. In the present embodiment, as in the first embodiment, the liquid in the sub tank 50 is discharged to the liquid storage portion 55 through the discharge flow path 53, so that almost no liquid remains in the sub tank 50. Become. Therefore, a situation in which the liquid in the sub tank 50 leaks from the discharge port 25 of the liquid discharge 2 is avoided. In addition, since the sub tank 50 communicates or opens to the atmosphere and the valve 66 closes in the event of a power failure, in this embodiment, the liquid level in the liquid container 55 is discharged to discharge the liquid to the liquid container 55. It does not necessarily have to be lower than the exit surface 26 in the direction of gravity.

(Fourth embodiment)
Next, a liquid ejection apparatus according to a fourth embodiment will be described. The liquid ejection apparatus according to the fourth embodiment uses a liquid ejection head 2 that circulates liquid from the supply unit side to the recovery unit side in the liquid ejection head as described in Patent Document 2. ing. FIG. 7 shows the configuration of the liquid ejection apparatus 1 in this embodiment. The configuration of the recording medium 40 and the transport unit 4 is the same as that of the first embodiment, and four sets of liquid ejection heads 2 are provided along the transport direction of the recording medium 40 so as to face the upper surface of the platen 41. Yes. The configuration of the driving means for driving each liquid ejection head 2 is the same as that of the first embodiment.

  In the liquid ejection apparatus 1 of the present embodiment, for each liquid ejection head 2, a recovery subtank 70 is provided in addition to the supply subtank 50 (first subtank) above the liquid ejection head 2 in the gravity direction. Yes. The recovery sub-tank 70 is also called a second sub-tank, and is for recovering liquid that has not been used in the liquid discharge head 2. The liquid discharge head 2 and the collection sub tank 50 are connected by a collection flow path 71. Although details will be described later, with such a configuration, it is possible to cause the liquid to flow in the liquid discharge head 2 from the sub tank 50 side to the recovery sub tank 70 side.

  FIG. 8 shows the configuration of the liquid ejection head 2 used in this embodiment. Similar to the liquid discharge head shown in FIG. 2, a plurality of pressure chambers 21 are provided, and each pressure chamber 21 communicates with the discharge port 25 formed in the discharge port forming member 24. A vibration plate 23 is formed on the pressure chamber 21 on the side facing the discharge port 25, and a piezoelectric element 22 that is a recording element is formed on the vibration plate 23. Further, the liquid discharge head 2 is provided with a common liquid chamber 27 on the supply side for storing the liquid supplied from the sub tank 50 through the supply flow path 51, and the liquid in the common liquid chamber 27 is supplied with each pressure. It is supplied to the chamber 21. Liquid other than the amount used by the liquid discharge head 2 due to discharge or the like is sent from the pressure chamber 21 to the common liquid chamber 28 side on the recovery side, and recovered to the sub tank 70 through the recovery flow path 71. In other words, as indicated by the arrows in the figure, a liquid flow is formed that is supplied from the common liquid chamber 27 to the pressure chamber 21 and passes through the vicinity of the discharge port 25 in the pressure chamber 21 toward the common liquid chamber 28. It is like that. As described above, the liquid is allowed to flow in the liquid discharge head 2 and the liquid is circulated through the liquid discharge head 2, whereby dust and bubbles in the liquid in the liquid discharge head 2 can be removed. It is known that the viscosity of the liquid in the vicinity of the discharge port 25 increases due to evaporation of the solvent component from the discharge port 25 and causes serious damage to the discharge. This phenomenon can be prevented by always supplying. Further, since the liquid constantly flows in the vicinity of the ejection port 25, an effect of cooling the recording element represented by the piezoelectric element 22 can be obtained.

  FIG. 9 shows the liquid supply means 5 in the liquid ejection apparatus 1 of the present embodiment. In the present embodiment, the first partition member 72 and the second partition member 75 for defining the liquid surface height are disposed in the airtight casing 68, thereby providing the sub tank 50 on the supply side in the casing 68. And the sub tank 70 on the collection side are partitioned and formed. The sub tank 50 and the sub tank 70 are partitioned by a first partition member 72. A part of the side wall of the sub tank 70 is formed by the second partition member 75. The supply channel 51 is connected to the bottom of the sub tank 50, and the recovery channel 71 is connected to the bottom of the sub tank 70. In this configuration, since the two sub tanks 50 and 70 are formed in one housing 68 and the first partition member 72 separates them, the cost of the sub tank can be reduced. In addition, combined with the arrangement of both the supply-side subtank 50 and the collection-side subtank 70 above the liquid ejection head 2 in the direction of gravity, the degree of freedom in arrangement becomes very high. A first discharge port 73 is formed with a gap between the lower end of the first partition member 72 and the bottom surface of the casing 68. The first discharge port 73 corresponds to a first discharge channel that is capable of discharging the liquid in the supply-side subtank 50 and is different from the supply channel 51. A second discharge port 76 is formed with a gap between the lower end of the second partition member 75 and the bottom surface of the casing 68. The housing 68 is provided with a second discharge channel 77 which is a channel different from the supply channel 51 and communicates with the liquid storage portion 55. The second discharge port 76 has a second discharge channel 76. A part of the passage 77 is formed. In the second discharge channel 77, the same self-holding valve 54 as that used in the first embodiment is provided.

  Similar to the first embodiment, a flow path 56 is provided for supplying the liquid stored in the liquid storage portion 55 to the sub tank 50 on the supply side, and a pump 57 and a filter 59 are provided in the flow path 56. However, a liquid level sensor for controlling the pump 57 is not provided. It is assumed that a sufficient amount of liquid is supplied from the liquid storage unit 55 to the sub tank 50 on the supply side by the pump 57. The liquid other than that supplied from the sub tank 50 to the liquid discharge head 2 via the supply flow path 51 always flows to the sub tank 70 through the upper side of the first discharge port 73 or the first partition member 72. Become. By the upper end of the first partition member 72, the liquid level of the ink in the sub tank 50 is kept substantially constant.

  The liquid flows into the recovery-side sub tank 70 from the liquid discharge head 2 through the recovery flow path 71, and also flows from the sub tank 50 through the upper side of the first partition member 72 or the first discharge port 73. As a result, a sufficient amount of liquid is supplied to the sub tank 70. Thus, the liquid collected in the sub-tank 70 always passes through the second discharge port 76 or the second partition member 75, passes through the second discharge channel 77, and always flows to the liquid storage unit 55. Due to the upper end of the second partition member 75, the liquid level of the liquid in the sub tank 70 on the collection side is kept substantially constant.

  In the present embodiment, the upper end of the second partition member 75 is lower than the upper end of the first partition member 72. Accordingly, a water head difference h3 corresponding to the height difference between the upper end of the first partition member 72 and the upper end of the second partition member 75 is provided between the supply-side subtank 50 and the recovery-side subtank 70. Will occur. Further, as in the first embodiment, an air pump 81 and a regulator 80 are connected to the housing 68, and a filter 82 is provided between the regulator 80 and the outside air. The pressure of the liquid at the discharge port 25 is controlled to be a negative pressure by a pressure adjustment mechanism using the air pump 81 and the regulator 80. By the water head difference between the sub tank 50 and the discharge port surface 26 and the pressure control by this pressure adjusting mechanism, the liquid pressure at the discharge port 25 is kept at a stable negative pressure, and the discharge port 25 of pressure fluctuations other than the sub tanks 50 and 70 is maintained. The effect on the liquid pressure is reduced. Due to the water head difference h3 between the supply-side subtank 50 and the collection-side subtank 70, the liquid is supplied from the subtank 50 to the liquid discharge head 2, and the liquid not used in the liquid discharge head 2 is discharged to the subtank 70. The In this manner, in the present embodiment, the liquid can be circulated and circulated from the supply-side subtank 50 to the recovery-side subtank 70 in the liquid discharge head 2. Here, the water head difference h3 is used as a pressure difference for allowing the liquid to flow from the sub tank 50 to the sub tank 70 via the supply flow path 51, the liquid discharge head 2 and the recovery flow path 71. Not limited to. For example, a pressure difference may be generated by providing an independent pressure adjusting mechanism for each of the sub tanks 50 and 70.

  Also in this embodiment, the self-holding valve 54 is open during operation. When the supply of electric power is suddenly interrupted due to a power failure or the like during operation, the liquid in the sub tanks 50 and 70 is discharged from the first discharge port 73 and the second discharge channel 77 which are the first discharge channels. Then, the liquid is discharged into the liquid storage portion 55. Therefore, there is almost no liquid remaining in the sub tanks 50 and 70, and a situation in which the liquid in the sub tanks 50 and 70 leaks from the discharge port 25 of the liquid discharge head 2 is avoided. According to this embodiment, in the liquid ejection apparatus 1 having the supply-side subtank 50 and the recovery-side subtank 70 above the liquid ejection head 2 in the direction of gravity, the liquid pressure at the ejection port 25 is stabilized with a simple configuration. Negative pressure can be maintained. In addition, in the liquid ejection apparatus 1 having such a configuration, it is possible to introduce a technique for causing the liquid to flow from the supply-side subtank 50 to the collection-side subtank 70 in the liquid ejection head 2 and to circulate between them. it can. Furthermore, even when the supply of electric power is suddenly interrupted due to a power failure or the like, it is possible to prevent the liquid in the supply-side subtank 50 and the recovery-side subtank 70 from leaking from the discharge port 25.

  In the above description, the supply-side subtank 50 and the collection-side subtank 70 are formed in one casing 68, but these subtanks 50, 70 may be formed separately. In that case, the first discharge channel and the second discharge channel 77 may be configured to be connected to the liquid container 55, respectively, or the first discharge channel may be recovered as described above. You may comprise so that it may connect to the subtank 70 of the side. The liquid storage unit 55 only needs to store the liquid discharged from at least one of the first discharge channel and the second discharge channel 77. When the first discharge channel and the second discharge channel 77 are configured to be connected to the liquid container 55, a self-holding valve may be provided in each discharge channel. Further, in each of the supply-side subtank 50 and the recovery-side subtank 70, control using a liquid level sensor can be introduced to adjust the liquid level. For example, the amount of liquid supplied from the liquid container 55 to the sub tank 50 on the supply side can be controlled by monitoring the liquid level of the sub tank 50. Similarly, the amount of liquid discharged from the collection-side sub tank 70 to the liquid storage portion 55 can be controlled by monitoring the liquid level of the sub tank 70.

DESCRIPTION OF SYMBOLS 1 Liquid discharge apparatus 2 Liquid discharge head 5 Liquid supply means 25 Discharge port 50 Sub tank 51 Supply flow path 53 Discharge flow path 55 Liquid storage part 57 Pump

Claims (16)

A liquid discharge head having a discharge port for discharging liquid;
Liquid supply means for supplying the liquid to the liquid discharge head;
Have
The liquid supply means includes
A sub-tank that stores liquid to be supplied to the liquid discharge head, disposed above the discharge port surface in which the discharge port is formed in the liquid discharge head, in the gravity direction;
A supply flow path connecting the sub-tank and the liquid discharge head;
Pressure adjusting means for adjusting the pressure of the liquid at the discharge port;
A discharge flow path different from the supply flow path capable of discharging the liquid inside the sub tank;
A liquid storage portion for storing the liquid discharged from the discharge flow path;
A liquid feeding means for supplying the liquid inside the liquid container to the sub tank;
A liquid ejecting apparatus comprising:   The liquid ejection apparatus according to claim 1, wherein the sub-tank is accommodated in an airtight casing, and the pressure adjusting unit includes a pressure adjusting mechanism that adjusts the pressure of gas inside the casing.   The pressure adjusting means includes a valve provided in the supply flow path and a pressure sensor that detects a pressure of the supply flow path at a position downstream of the valve, and the pressure sensor detects the pressure according to a detection value of the pressure sensor. The liquid ejection apparatus according to claim 1, wherein the valve is controlled.   4. The pressure adjusting device according to claim 1, wherein the pressure adjusting unit further includes a liquid level sensor that measures a liquid level height of the sub-tank, and performs control to maintain a constant liquid level height of the sub-tank. 5. The liquid discharge apparatus as described.   The pressure adjusting means has a partition member that defines a liquid level height in the sub tank, and the discharge flow path has a discharge port formed between a lower end of the partition member and a bottom surface of the housing, The liquid ejection device according to claim 1.   The liquid discharge according to any one of claims 1 to 5, wherein a self-holding valve that is opened when the liquid discharge device is in operation and is closed when the liquid discharge device is stopped is provided in the discharge flow path. apparatus. A liquid discharge head having a discharge port for discharging liquid;
Liquid supply means for supplying the liquid to the liquid discharge head;
Have
The liquid supply means includes
A first sub-tank that is disposed above the discharge port surface in which the discharge port is formed in the liquid discharge head and that stores liquid to be supplied to the liquid discharge head;
A supply flow path connecting the first sub tank and the liquid ejection head;
A second sub-tank that is disposed above the discharge port surface in the direction of gravity and stores the liquid recovered from the liquid discharge head;
A recovery flow path connecting the second sub-tank and the liquid ejection head;
The liquid pressure at the discharge port is adjusted, and the liquid flows from the first sub-tank to the second sub-tank through the supply flow path, the liquid discharge head, and the recovery flow path and circulates. Pressure adjusting means for forming a pressure difference;
A first discharge channel that is capable of discharging the liquid in the first sub-tank and is different from the supply channel;
A second discharge flow path different from the supply flow path capable of discharging the liquid in the second sub-tank;
A liquid storage section for storing liquid discharged from at least one of the first discharge flow path and the second discharge flow path;
A liquid feeding means for supplying the liquid inside the liquid container to the sub tank;
A liquid ejecting apparatus comprising:   The liquid ejection apparatus according to claim 7, wherein the first sub tank and the second sub tank are accommodated in a housing, and the pressure adjusting unit includes a pressure adjusting mechanism that adjusts the pressure of gas inside the housing.   The liquid ejection device according to claim 8, wherein the pressure difference is formed by a water head difference between a liquid level height of the first sub tank and a liquid level height of the second sub tank.   The pressure adjusting means defines a first partition member that defines a liquid level height of the first sub-tank and a liquid level height of the second sub-tank that is lower than a liquid level height of the first sub-tank. The liquid ejection device according to claim 9, further comprising: a second partition member that performs the operation.   The liquid ejection apparatus according to claim 10, wherein the first partition member partitions the first sub tank and the second sub tank.   The first discharge channel has a first discharge port formed between a lower end of the first partition member and a bottom surface of the housing, and the second discharge channel is the second discharge channel. A second discharge port formed between the lower end of the partition member and the bottom surface of the housing, and the first sub-tank and the second sub-tank communicate with each other via the first discharge port. The liquid ejection device according to claim 11.   The pressure adjusting means further includes a first liquid level sensor that measures the liquid level height of the first sub tank and a second liquid level sensor that measures the liquid level height of the second sub tank, The liquid ejection apparatus according to claim 9, wherein control is performed to maintain the liquid level height of the first sub-tank constant and to maintain the liquid level height of the second sub-tank constant.   The first self-holding valve provided in the second discharge flow path is opened during operation of the liquid discharge device and is closed when the liquid discharge device is stopped. The liquid ejection device according to item.   A first self-holding valve that is opened during operation of the liquid ejection device and is closed when the liquid ejection device is stopped is provided in the second discharge flow path, and is opened during operation of the liquid ejection device. The liquid discharge apparatus according to claim 7, wherein a second self-holding valve that is closed when the liquid discharge apparatus is stopped is provided in the first discharge flow path.   The liquid ejection apparatus according to claim 1, further comprising a main tank that supplies a liquid to the liquid storage unit.

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