JP2009143087A - Liquid droplet delivering apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make both controlling a back pressure applied to ink fed into an inkjet recording head and controlling the flow rate for circulating the ink in the inkjet recording head compatible, and to enlarge alternatives of a pump to be used for the controlling. <P>SOLUTION: Circulation of the ink in the inkjet recording head 20Y is performed by the water head difference between a feeding side water head difference generating part 46 and a discharging side water head difference generating part 66. Therefore, a first pump 45 and a second pump 65 are not used for the circulation of the ink, but it is enough that only the flow rate for generating the back pressure applied to the ink fed into the inkjet recording head 20Y is controlled, so that the alternatives of the pump can be enlarged. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a droplet discharge device.

  As the droplet discharge device, an ink jet recording device disclosed in Patent Document 1 and an ink jet printer disclosed in Patent Document 2 are known. In the ink jet recording apparatus disclosed in Japanese Patent Application Laid-Open No. 2004-228620, ink is supplied and collected in the ink discharge section in the recording head by the height difference between the two ink chambers in the ink discharge section.

An ink jet printer disclosed in Patent Document 2 connects a print head and an ink tank via an ink supply pipe and an ink return pipe, and drives a feed pump interposed in the ink supply tube to drive the print head from the ink tank. The ink can be supplied to the ink and the return pump interposed in the ink return tube is driven so that the ink in the print head can be returned to the ink tank, and the feed pump is operated with the return pump stopped or driven at a low speed. The ink supply tube, the print head, the ink return tube, and the ink tank can be set to an empty state by being driven so that the ink in the ink tank can be discharged from each nozzle of the print head to the outside.
JP 2001-219580 A JP-A-11-91124

  The present invention achieves both control of the back pressure applied to the liquid supplied to the droplet discharge head and control of the flow rate for circulating the liquid in the droplet discharge head, and a pump used for the control The challenge is to expand the options.

  A droplet discharge device according to claim 1 of the present invention includes a droplet discharge head that discharges a droplet, and a supply channel that is connected to the droplet discharge head and supplies liquid to the droplet discharge head. , Connected to the droplet discharge head and connected to the discharge channel for discharging liquid from the droplet discharge head, the supply channel and the discharge channel, respectively, the supply channel side and the discharge channel side A liquid head difference is generated between the liquid supply head and the liquid supply to the droplet discharge head from the supply flow path to the discharge flow path to circulate the liquid in the liquid droplet discharge head. And a first pump for controlling the back pressure applied to the liquid supplied to the droplet discharge head.

  According to a second aspect of the present invention, in the configuration of the first aspect, the droplet discharge device has one end connected to the water head difference generating unit connected to the supply flow path and the other end joined to the supply flow path. A first flow path, the first pump provided in the first flow path, a one-way valve provided in the supply flow path and allowing only the liquid to flow to the droplet discharge head side. , Provided.

  According to a third aspect of the present invention, in the liquid droplet ejection device according to the first or second aspect, one end is connected to the water head difference generating portion connected to the discharge flow path, and the other end is the discharge. A second flow path that merges with the flow path, a second pump that is provided in the second flow path and that controls the back pressure applied to the liquid discharged from the droplet discharge head, and is provided in the discharge flow path And a one-way valve that allows only the liquid to flow from the droplet discharge head side.

  According to a fourth aspect of the present invention, in the configuration of the first aspect, the droplet discharge device is provided with the first pump provided in the supply flow path and the discharge flow path, and is discharged from the droplet discharge head. And a second pump for controlling the back pressure applied to the liquid to be applied.

  According to a fifth aspect of the present invention, there is provided the liquid droplet ejection apparatus according to any one of the first to fourth aspects, wherein the liquid storage section stores the liquid and the water head difference generation section connected to the discharge flow path. A return path for returning the liquid from the liquid storage section to the liquid storage section, a feed path for sending the liquid from the liquid storage section to a hydraulic head difference generation section connected to the supply flow path, and a hydraulic head difference between the pair of hydraulic head difference generation sections And a holding mechanism for holding at a constant.

  According to a sixth aspect of the present invention, in the configuration of any one of the first to fourth aspects, the droplet discharge device is connected to the supply flow path from the water head difference generation unit connected to the discharge flow path. A return path for returning the liquid to the hydraulic head difference generating section; a liquid storing section for storing the liquid; a feed path for sending liquid from the liquid storing section to the hydraulic head difference generating section connected to the supply flow path; And a holding mechanism for keeping the water head difference of the water head difference generating portion constant.

  According to the configuration of the first aspect of the present invention, it is possible to achieve both the control of the back pressure applied to the liquid supplied to the droplet discharge head and the control of the flow rate for circulating the liquid in the droplet discharge head. As compared with the configuration in which both controls are performed by the pump, the options of the pump can be expanded.

  According to the configuration of the second aspect of the present invention, even if the pump is provided in the first flow path provided separately from the supply flow path, the liquid does not flow backward from the liquid droplet ejection head side to the water head difference generating portion side.

  According to the configuration of the third aspect of the present invention, even if the pump is provided in the second flow path provided separately from the discharge path, the liquid does not flow backward from the head difference generating unit side to the liquid droplet ejection head side.

  According to the configuration of claim 4 of the present invention, the number of flow paths can be reduced and the apparatus configuration can be reduced in size as compared with a configuration in which flow paths for disposing the first pump and the second pump are separately provided. .

  According to the configuration of the fifth aspect of the present invention, since the water head difference between the pair of water head difference generating portions is kept constant, the flow rate for circulating the liquid in the droplet discharge head can be made constant.

  According to the configuration of the sixth aspect of the present invention, the liquid discharged from the discharge path to the head difference generator is directly returned to the head difference generator connected to the supply channel without returning to the liquid reservoir. The liquid in the liquid reservoir is not soiled.

  Below, an example of an embodiment concerning the present invention is described based on a drawing.

  In this embodiment, as an example of a droplet discharge device that discharges droplets, an ink jet recording device that discharges ink droplets and records an image on a recording medium will be described.

  The droplet discharge device is not limited to the ink jet recording device. As a droplet discharge device, for example, a color filter manufacturing device that manufactures a color filter by discharging ink or the like onto a film or glass, a device that forms a bump for mounting components by discharging molten solder onto a substrate Further, an apparatus for forming a wiring pattern by discharging a liquid containing a metal and various film forming apparatuses for forming a film by discharging a droplet may be used as long as the apparatus discharges a droplet.

(Overall configuration of inkjet recording apparatus according to this embodiment)
First, the overall configuration of the ink jet recording apparatus according to the present embodiment will be described. 1 and 2 schematically show the overall configuration of the ink jet recording apparatus according to the present embodiment.

  As shown in FIGS. 1 and 2, an inkjet recording apparatus 10 includes a recording medium storage unit 12 that stores a recording medium P such as paper, an image recording unit 14 that records an image on the recording medium P, and a recording medium storage. Conveying means 16 for transporting the recording medium P from the section 12 to the image recording section 14 and a recording medium discharging section 18 for discharging the recording medium P on which an image is recorded by the image recording section 14 are provided.

  The image recording unit 14 is an example of a droplet discharge head that discharges droplets, and inkjet recording heads 20Y, 20M, 20C, and 20K (hereinafter referred to as 20Y to 20K) that discharge ink droplets and record an image on a recording medium. ).

  The inkjet recording heads 20Y to 20K are arranged in parallel in the order of yellow (Y), magenta (M), cyan (C), and black (K) from the upstream side in the conveyance direction of the recording medium P. The ink droplets corresponding to the respective colors are ejected from a plurality of nozzles formed on the nozzle surface by a piezoelectric method, and an image is recorded. In the inkjet recording heads 20Y to 20K, the configuration for ejecting ink droplets may be a configuration for ejecting ink droplets by other methods such as a thermal method.

  Further, the ink jet recording heads 20Y to 20K are configured to be longer in the width direction (main scanning direction) of the recording medium P than the conveyance direction (sub scanning direction) of the recording medium P. The inkjet recording heads 20Y to 20K can form one line in the main scanning direction without moving relative to the recording medium P in the main scanning direction, and move relative to the recording medium P in the sub scanning direction. Thus, color images are recorded. The width direction of the recording medium P is a direction that intersects with the conveyance direction of the recording medium P.

  The ink jet recording apparatus 10 is provided with ink tanks 21Y, 21M, 21C, and 21K (hereinafter referred to as 21Y to 21K) that store ink as liquid storage units that store liquid. Ink is supplied from the ink tanks 21Y to 21K to the inkjet recording heads 20Y to 20K. As the ink supplied to the inkjet recording heads 20Y to 20K, various inks such as water-based ink, oil-based ink, and solvent-based ink can be used.

  Furthermore, the inkjet recording apparatus 10 is provided with maintenance units 22Y, 22M, 22C, and 22K (hereinafter referred to as 22Y to 22K) that perform maintenance of the inkjet recording heads 20Y to 20K. The maintenance units 22Y to 22K are respectively opposed to the nozzle surfaces of the ink jet recording heads 20Y to 20K (see FIG. 2) and retracted from the nozzle surfaces of the ink jet recording heads 20Y to 20K (see FIG. 1). It is configured to be movable between.

  Each of the maintenance units 22Y to 22K includes a cap that covers the nozzle surfaces of the ink jet recording heads 20Y to 20K, a receiving member that receives preliminarily ejected (empty ejected) liquid droplets, and a cleaning member that cleans the nozzle surfaces of the ink jet recording heads 20Y to 20K. When the ink jet recording heads 20Y to 20K are maintained, the ink jet recording heads 20Y to 20K are raised by a predetermined height and the maintenance unit 22Y is provided. ˜22K moves to the opposite position and performs various maintenance.

  The transport unit 16 includes a feed roll 24 that sends out the recording medium P accommodated in the recording medium storage unit 12, a transport roll pair 25 that sandwiches and transports the recording medium P sent out by the feed roll 24, and a transport roll pair 25. And an endless conveyance belt 30 that causes the recording surface of the recording medium P conveyed by the inkjet recording heads 20Y to 20K to face each other.

  The conveyance belt 30 is wound around a driving roll 26 disposed on the downstream side in the conveyance direction of the recording medium P and a driven roll 28 disposed on the upstream side in the conveyance direction of the recording medium P, and is wound in a predetermined direction (A in FIG. 1). Direction).

  The transport belt 30 may be a transport body that transports the recording medium P. For example, a transport drum as an example of a transport body that transports the recording medium P on the outer peripheral surface may be used.

  In addition, a pressing roll 27 that presses the recording medium P against the conveyance belt 30 is provided above the driven roll 28. The pressing roll 27 is driven by the conveying belt 30 and also serves as a charging roll. When the conveying belt 30 is charged by the pressing roll 27, the recording medium P is electrostatically attracted to the conveying belt 30 and conveyed. It is a configuration.

  When the conveyance belt 30 conveys the recording medium P, the inkjet recording heads 20Y to 20K and the recording medium P move relative to each other, and ink droplets are ejected onto the relatively moving recording medium P to form an image.

  Note that the inkjet recording heads 20Y to 20K may move with respect to the recording medium P, and the recording medium P and the inkjet recording heads 20Y to 20K may be configured to move relative to each other.

  Further, the conveyance belt 30 is not limited to a configuration that holds the recording medium P by electrostatic adsorption, but is a non-electrostatic means such as friction with the recording medium P or suction or adhesion of the recording medium P. It may be configured to be held by.

  A separation claw for separating the recording medium P from the conveyance belt 30 is disposed on the downstream side of the conveyance belt 30 so as to be able to approach and separate. The recording medium P on which an image is recorded by the ink jet recording heads 20Y to 20K is configured such that the recording medium P is peeled off from the transport belt 30 by the curvature of the transport belt 30 and the peeling claw. In addition, in FIG.1 and FIG.2, illustration of the peeling nail | claw is abbreviate | omitted.

  On the downstream side of the peeling claw, a plurality of transport roll pairs 29 in which the recording surface side of the recording medium P is a star wheel are provided. The recording medium P on which an image is recorded by the image recording unit 14 is conveyed to the recording medium discharge unit 18 by the conveyance roll pair 29.

  A reversing unit 37 that reverses the recording medium P is provided below the conveyance belt 30. After the conveyance roll pair 29 once conveys the recording medium P downstream, the conveyance roll pair 29 reverses and records. The medium P is sent to the reversing unit 37.

  The reversing unit 37 is provided with a plurality of conveying roll pairs 23 in which the recording surface side of the recording medium P is a star wheel, so that the recording medium P sent to the reversing unit 37 is sent to the conveying belt 30 again. It has become.

  In addition, although not shown, the inkjet recording apparatus 10 performs the overall operation of the inkjet recording apparatus 10 and the ejection timing of ink droplets, the head controller that determines the nozzles of the inkjet recording heads 20Y to 20K to be used, and the inkjet recording apparatus 10. System control means for controlling.

  Next, an image recording operation of the inkjet recording apparatus 10 will be described.

  First, the recording medium P is sent out from the recording medium container 12 by the sending roll 24, and sent to the transport belt 30 by the transport roll pair 25 on the upstream side of the transport belt 30.

  The recording medium P sent to the conveying belt 30 is attracted and held on the conveying surface of the conveying belt 30 and conveyed to the recording positions of the ink jet recording heads 20Y to 20K, and an image is recorded on the recording surface of the recording medium P. The Then, after the image recording is finished, the recording medium P is peeled off from the transport belt 30 by a peeling claw.

  When an image is recorded only on one side of the recording medium P, it is discharged to the recording medium discharge unit 18 by a pair of conveying rolls 29 on the downstream side of the conveying belt 30.

  When recording an image on both sides of the recording medium P, after the image is recorded on one side, the recording medium P is reversed by the reversing unit 37 and sent to the transport belt 30 again. Images are recorded on the opposite side of the recording medium P in the same manner as described above, images are recorded on both sides of the recording medium P, and are discharged to the recording medium discharge unit 18.

(Configuration in which ink in the inkjet recording heads 20Y to 20K according to the present embodiment is circulated)
Next, a configuration for circulating the ink in the inkjet recording heads 20Y to 20K according to the present embodiment will be described. Here, the configuration in which the ink in the ink jet recording head 20Y is circulated will be described as an example, but the ink jet recording heads 20M to 20K are similarly configured. 3 to 7 are diagrams schematically showing a configuration for circulating the ink in the ink jet recording heads 20Y to 20K.

  Further, in this specification, the circulation of ink in the ink jet recording heads 20Y to 20K means that ink that has not been ejected out of ink supplied to the ink jet recording heads 20Y to 20K is discharged from the ink jet recording heads 20Y to 20K. Is not necessarily limited to the case where the ink is recovered from the ink jet recording head 20Y and supplied again to the ink jet recording head 20Y. The old ink is discharged from the ink jet recording heads 20Y to 20K and the new ink is discharged from the ink jet recording heads 20Y to 20K. This includes the case where the old ink is not re-supplied but only supplied to the printer.

  As shown in FIG. 3, a supply-side back pressure generator 40 and a discharge-side back pressure generator 60 are connected to the inkjet recording head 20Y. The supply-side back pressure generator 40 generates a back pressure applied to the ink supplied to the inkjet recording head 20Y.

  The supply-side back pressure generating unit 40 is provided with a detection sensor 42 for detecting the pressure in the supply-side back pressure generating unit 40.

  On the other hand, the discharge side back pressure generator 60 generates a back pressure applied to the ink discharged from the inkjet recording head 20Y.

  Similarly to the supply-side back pressure generation unit 40, the discharge-side back pressure generation unit 60 is provided with a detection sensor 62 for detecting the pressure in the discharge-side back pressure generation unit 60.

  In addition, one end of a supply path 44 for supplying ink to the supply side back pressure generation unit 40 is connected to the supply side back pressure generation unit 40. A supply-side hydraulic head difference generation unit 46 is connected to the other end of the supply path 44.

  As a result, a supply channel for supplying ink from the supply-side hydraulic head difference generating unit 46 to the inkjet recording head 20Y is formed by the supply channel 44 and the supply-side back pressure generating unit 40.

  The supply path 44 is provided with a one-way valve 48 that allows only ink to flow to the ink jet recording head 20Y side.

  On the other hand, one end of a discharge path 64 for discharging ink from the discharge side back pressure generation unit 60 is connected to the discharge side back pressure generation unit 60. A discharge-side hydraulic head difference generating unit 66 is connected to the other end of the discharge path 64.

  As a result, a discharge channel for discharging ink from the inkjet recording head 20 </ b> Y to the discharge-side hydraulic head difference generating unit 66 is formed by the discharge channel 64 and the discharge-side back pressure generating unit 60.

  The discharge path 64 is provided with a one-way valve 68 that allows only ink to flow from the ink jet recording head 20Y side.

  The supply-side hydraulic head difference generating unit 46 and the discharge-side hydraulic head difference generating unit 66 generate a hydraulic head difference between the supply channel 44 side and the discharge channel 64 side, thereby providing a supply channel (the supply channel 44 and the supply side profile difference). The ink supplied from the pressure generating unit 40) to the inkjet recording head 20Y is discharged to the discharge channel (the discharge path 64 and the discharge side back pressure generating unit 60), and the ink of the inkjet recording head 20Y is circulated.

  Between the supply-side hydraulic head difference generation unit 46 and the discharge-side back pressure generation unit 60, there is a hydraulic head difference from the supply-side hydraulic head difference generation unit 46 to the discharge-side back pressure generation unit 60 so that a predetermined ink flow rate can be secured. Is set.

  The ink flow rate is set to, for example, about 230 [cc / min] in order to satisfactorily suppress the increase in the viscosity of the ink and discharge the bubbles in the ink, which are the purpose of the ink circulation.

  Further, one end of the first flow path 43 is connected to the supply-side hydraulic head difference generation unit 46, and the other end of the first flow path 43 is connected to the supply-side back pressure generation unit 40. The first flow path 43 is provided with a first pump 45 that controls the back pressure applied to the ink supplied to the inkjet recording head 20Y. As the first pump 45, for example, a tube pump that squeezes a tube forming the first flow path 43 and sends ink is used.

  The first pump 45 is configured so that the pressure in the supply-side back pressure generator 40 becomes a set value by a control device (not shown) based on a signal from the detection sensor 42 provided in the supply-side back pressure generator 40. Be controlled.

  On the other hand, one end of the second flow path 63 is connected to the discharge-side hydraulic head difference generation unit 66, and the other end of the second flow path 63 is connected to the discharge-side back pressure generation unit 60. The second flow path 63 is provided with a second pump 65 that controls the back pressure applied to the ink discharged from the ink jet recording head 20Y. As the second pump 65, for example, a tube pump that squeezes a tube forming the second flow path 63 and sends ink is used.

  The second pump 65 is configured so that the pressure in the discharge-side back pressure generation unit 60 becomes a set value by a control device (not shown) based on a signal from the detection sensor 62 provided in the discharge-side back pressure generation unit 60. Be controlled.

  Further, the discharge-side hydraulic head difference generating unit 66 is connected to the ink tank 21Y through a return path 67. The return path 67 is connected to a predetermined height of the discharge-side head difference generating unit 66, and when the ink in the discharge-side head difference generating unit 66 reaches a predetermined amount, the ink is returned to the ink tank 21Y. The position of the liquid level in the water head difference generating unit 66 is made constant.

  On the other hand, the supply-side hydraulic head difference generating unit 46 is a return path 47 and a feed path 49 that function as a holding mechanism that keeps the hydraulic head difference between the supply-side back pressure generating unit 40 and the discharge-side back pressure generating unit 60 constant. It is connected to the ink tank 21Y. The feed path 49 is provided with a supply pump 41 for supplying ink from the ink tank 21 </ b> Y to the supply-side head difference generator 46. The supply pump 41 is always driven, and ink is always sent from the ink tank 21Y to the supply-side head difference generating unit 46.

  The return path 47 is connected to a predetermined height of the supply-side hydraulic head difference generation unit 46, and when the ink in the supply-side hydraulic head difference generation unit 46 reaches a predetermined amount, returns the ink to the ink tank 21Y, The position of the liquid level in the water head difference generator 46 is made constant. Thereby, the water head difference between the supply-side back pressure generator 40 and the discharge-side back pressure generator 60 is kept constant.

(Operation of this embodiment)
Next, the operation of the above embodiment will be described.

  In the configuration of the present embodiment, when the ink droplets are not ejected from the ink jet recording head 20Y, the supply path 44 and the supply are caused by the water head difference between the supply side water head difference generation unit 46 and the discharge side water head difference generation unit 66. The ink flows from the supply-side hydraulic head difference generation unit 46 to the discharge-side back pressure generation unit 60 through the side back pressure generation unit 40, the inkjet recording head 20Y, the discharge side back pressure generation unit 60, and the discharge path 64, and the inkjet recording head 20Y. The ink inside circulates.

  The circulation of the ink is performed in order to suppress the increase in the viscosity of the ink and to discharge the bubbles in the ink. In order to realize these, the ink flow rate needs about 230 [cc / min], for example.

  In the present embodiment, the ink flow rate is maintained at, for example, about 230 [cc / min] due to the water head difference between the supply-side water head difference generating unit 46 and the discharge-side water head difference generating unit 66.

  At this time, since ink droplets are not ejected, ink is not consumed by the inkjet recording head 20Y, and the pressure in the supply-side back pressure generation unit 40 and the pressure in the discharge-side back pressure generation unit 60 are usually There is no change, and the first pump 45 and the second pump 65 do not operate.

  On the other hand, when ink droplets are ejected from the inkjet recording head 20Y, the ink is consumed by the inkjet recording head 20Y, and the supply-side back pressure generation unit 40 and the discharge-side back pressure are usually generated only by the circulation of the ink due to the water head difference. The pressure drop in the section 60 is detected by the detection sensor 42 and the detection sensor 62, and the lack of ink supply to the inkjet recording head 20Y is detected.

  In order to supply ink to the inkjet recording head 20Y without shortage, for example, about 6 [cc / min] is required as the ink flow rate.

  The ink flow rate is controlled to, for example, about 6 [cc / min] by the first pump 45 and the second pump 65 so as to compensate for the shortage to the ink jet recording head 20Y.

  That is, the first pump 45 supplies ink from the supply-side hydraulic head difference generation unit 46 to the supply-side back pressure generation unit 40, and the second pump 65 supplies ink from the discharge-side hydraulic head difference generation unit 66 to the discharge-side back pressure generation unit 60. Is supplied. Thereby, the fluctuation | variation of the back pressure of the supply side back pressure generation part 40 and the discharge | emission side back pressure generation part 60 is suppressed.

  In the present embodiment, ink circulation in the ink jet recording head 20 </ b> Y is performed by a water head difference between the supply side water head difference generation unit 46 and the discharge side water head difference generation unit 66. For this reason, the first pump 45 and the second pump 65 are not used for the circulation of the ink, but the flow rate for generating the back pressure applied to the ink supplied to the inkjet recording head 20Y (compared to the circulation of the ink). Therefore, it is only necessary to control a very small flow rate (for example, about 6 [cc / min]), and it is possible to expand pump options and reduce costs. Further, since the ink is circulated by the water head difference, the power consumption during non-ejection can be reduced.

  In the present embodiment, the one-way valve 48 and the one-way valve 68 are provided in the supply passage 44 and the discharge passage 64, respectively, so that the flow due to the water head difference is caused by the first pump 45 and the second pump 65. , Never flow backwards.

  In addition, as shown in FIG. 4, the structure which does not have the 2nd pump 65 provided in the 2nd flow path 63 and the 2nd flow path 63 may be sufficient. Thereby, the number of flow paths can be reduced, and the apparatus configuration can be reduced in size.

  Further, in a configuration in which old ink is discharged from the ink jet recording heads 20Y to 20K and new ink is supplied to the ink jet recording heads 20Y to 20K and old ink is not resupplied, as shown in FIG. The water head difference generating unit 66 may be connected to the waste ink tank 61 through the drainage channel 69. In this configuration, the ink is discharged to the waste ink tank 61 when the amount of ink in the discharge-side head difference generating unit 66 reaches a predetermined amount.

  Further, as shown in FIG. 6, the first flow path 43 and the second flow path are not provided, the first pump 45 is provided in the supply path 44, and the second pump 65 is provided in the discharge path 64. Also good.

  As the 1st pump 45 and the 2nd pump 65, the pump which does not interrupt | block the supply path 44 and the discharge path 64 at the time of non-operation, for example, an axial flow pump is used.

  In this configuration, when ink droplets are not ejected from the ink jet recording head 20Y, there is no flow path closure by the first pump 45 and the second pump 65, and the supply-side hydraulic head difference generation unit 46 and the discharge-side hydraulic head difference generation unit 66. The discharge-side back pressure from the supply-side head difference generation unit 46 through the supply path 44, the supply-side back pressure generation unit 40, the inkjet recording head 20Y, the discharge-side back pressure generation unit 60, and the discharge path 64. Ink flows to the generation unit 60, and the ink in the inkjet recording head 20Y circulates.

  On the other hand, when ink droplets are ejected from the inkjet recording head 20Y, the ink is consumed by the inkjet recording head 20Y, and the supply-side back pressure generation unit 40 and the discharge-side back pressure are usually generated only by the circulation of the ink due to the water head difference. The pressure drop in the section 60 is detected by the detection sensor 42 and the detection sensor 62, and the lack of ink supply to the inkjet recording head 20Y is detected.

  The ink flow rate is controlled to, for example, about 6 [cc / min] by the first pump 45 and the second pump 65 so as to compensate for the shortage to the ink jet recording head 20Y.

  That is, the first pump 45 supplies ink from the supply-side hydraulic head difference generation unit 46 to the supply-side back pressure generation unit 40, and the second pump 65 supplies ink from the discharge-side hydraulic head difference generation unit 66 to the discharge-side back pressure generation unit 60. Is supplied. Thereby, the fluctuation | variation of the back pressure of the supply side back pressure generation part 40 and the discharge | emission side back pressure generation part 60 is suppressed.

  Further, as shown in FIG. 7, the ink from the discharge-side head difference generating unit 66 may be directly returned to the supply-side head difference generating unit 46 instead of the ink tank 21Y.

  In this configuration, the discharge-side hydraulic head difference generating unit 66 is connected to the supply-side hydraulic head difference generating unit 46 by a return path 67. The return path 67 is connected to a predetermined height of the discharge-side head difference generator 66, and when the ink in the discharge-side head difference generator 66 reaches a predetermined amount, the return pump 52 provided in the return path 67. As a result, the ink is returned to the supply-side hydraulic head difference generating section 46, and the position of the liquid level in the discharge-side hydraulic head difference generating section 66 is made constant.

  In addition, a sensor 50 that detects the liquid level of the supply-side water head difference generating unit 46 is provided. The supply pump 41 is driven by a control device (not shown) when the sensor 50 detects that the liquid level of the supply-side water head difference generating unit 46 is lower than the set value, and the supply-side water head difference generating unit The position of the liquid level in 46 is made constant. Thereby, the water head difference between the supply-side back pressure generator 40 and the discharge-side back pressure generator 60 is kept constant.

  With this configuration, the ink that has circulated through the inkjet recording head 20Y is directly returned from the discharge-side head difference generating unit 66 to the supply-side head difference generating unit 46, so that the ink in the ink tank 21Y and the ink jet recording head 20Y The discharged ink is not mixed and the ink in the ink tank 21Y is not soiled.

  The present invention is not limited to the above-described embodiment, and various modifications, changes, and improvements can be made.

FIG. 1 is a schematic diagram showing the overall configuration of the ink jet recording apparatus according to the present embodiment. FIG. 2 is a schematic view showing a state in which the maintenance unit is in a facing position facing the nozzle surface of the ink jet recording head in the ink jet recording apparatus according to the present embodiment. FIG. 3 is a diagram schematically illustrating a configuration for circulating the ink in the ink jet recording head according to the present embodiment. FIG. 4 is a diagram schematically illustrating a configuration that circulates ink in the ink jet recording head according to the present embodiment and that does not include the second flow path and the second pump provided in the second flow path. It is. FIG. 5 is a diagram schematically showing a configuration in which the ink in the ink jet recording head according to the present embodiment is circulated and old ink is not re-supplied. FIG. 6 is a diagram schematically illustrating a configuration in which the ink in the ink jet recording head according to the present embodiment is circulated, and the first pump is provided in the supply path and the second pump is provided in the discharge path. . FIG. 7 schematically shows a configuration in which the ink in the inkjet recording head according to the present embodiment is circulated, and the ink from the discharge-side head difference generator is directly returned to the supply-side head difference generator. FIG.

Explanation of symbols

10 Inkjet Recording Devices 20Y-20K Inkjet Recording Heads 21Y-21K Ink Tank (Liquid Storage Unit)
40 Supply-side back pressure generator (supply channel)
43 1st flow path 44 Supply path (supply flow path)
45 1st pump 46 Supply side head difference generating part 47 Return path (holding mechanism)
48 one-way valve 49 feed path 60 discharge side back pressure generator (discharge channel)
63 Second channel 64 Discharge channel (discharge channel)
65 Second pump 66 Discharge-side hydraulic head difference generating portion 67 Return path 68 One-way valve

Claims (6)

A droplet discharge head for discharging droplets;
A supply flow path connected to the droplet discharge head for supplying liquid to the droplet discharge head;
A discharge passage connected to the droplet discharge head for discharging liquid from the droplet discharge head;
Connected to the supply flow path and the discharge flow path, respectively, and a water head difference is generated between the supply flow path side and the discharge flow path side, thereby being supplied from the supply flow path to the droplet discharge head A pair of water head difference generating portions for discharging the liquid to the discharge flow path and circulating the liquid in the droplet discharge head;
A first pump for controlling a back pressure applied to the liquid supplied to the droplet discharge head;
A droplet discharge apparatus comprising: A first flow path having one end connected to the water head difference generation section connected to the supply flow path and the other end joined to the supply flow path;
The first pump provided in the first flow path;
A one-way valve provided in the supply flow path and allowing only the liquid to flow to the liquid droplet ejection head;
The liquid droplet ejection apparatus according to claim 1, further comprising: A second flow path having one end connected to the hydraulic head difference generation section connected to the discharge flow path and the other end joined to the discharge flow path;
A second pump that is provided in the second flow path and controls a back pressure applied to the liquid discharged from the droplet discharge head;
A one-way valve provided in the discharge flow path and allowing only the liquid to flow from the droplet discharge head side;
The droplet discharge device according to claim 1, further comprising: The first pump provided in the supply flow path;
A second pump that is provided in the discharge channel and controls a back pressure applied to the liquid discharged from the droplet discharge head;
The liquid droplet ejection apparatus according to claim 1, further comprising: A liquid reservoir for storing the liquid;
A return path for returning the liquid from the water head difference generating section connected to the discharge flow path to the liquid storage section;
A feed path for sending the liquid from the liquid storage section to a water head difference generation section connected to the supply flow path;
A holding mechanism for holding the water head difference of the pair of water head difference generating parts constant;
The liquid droplet ejection apparatus according to claim 1, wherein the liquid droplet ejection apparatus is provided. A return path for returning the liquid from the head difference generating unit connected to the discharge channel to the head difference generating unit connected to the supply channel;
A liquid reservoir for storing the liquid;
A feed path for sending liquid from the liquid reservoir to the head difference generator connected to the supply flow path;
A holding mechanism for holding the water head difference of the pair of water head difference generating parts constant;
The liquid droplet ejection apparatus according to claim 1, wherein the liquid droplet ejection apparatus is provided.

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