JP2014144536A - Droplet discharge head and droplet discharge device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To discharge air bubbles within a liquid channel of a droplet discharge device by a simple configuration.SOLUTION: A droplet discharge head includes a bypass 40 that is set as follows: a pump 42 is driven by control of a control device 44 when ink is supplied; the ink is circulated to a recovery passage 30 from a supply passage 26; pressure for circulating the ink is adjusted to make the ink flow backward to the recovery passage 30 from the bypass 40; and the ink is discharged from a nozzle so that air bubbles can be discharged from the nozzle.

Description

  The present invention relates to a droplet discharge head and a droplet discharge device.

  As a droplet discharge apparatus, an ink jet recording apparatus that transports a recording medium such as paper by a transport drum and discharges ink onto the recording medium to form an image is well known, and various techniques have been proposed.

  For example, in the technique disclosed in Patent Document 1, a plurality of supply-side common flow paths and circulation-side common flow paths are alternately arranged, and a plurality of pressure chambers communicating with the supply-side common flow paths via ink supply paths are provided. Is provided. Each of the plurality of pressure chambers communicates with the circulation-side common flow path through the ink circulation path, and the supply-side common flow path and the adjacent circulation-side common flow path are located at the most downstream end of the supply-side common flow path. , And a bypass channel is provided for flowing ink from the supply-side common channel to the circulation-side common channel. As a result, air bubbles remaining in the supply-side common channel are caused to flow together with the ink to the circulation-side common channel through the bypass channel.

In the technique described in Patent Document 2, the first and second ink chambers having the ink discharge ports are provided.
The first ink supply port communicates with the first reservoir, the second ink supply port communicates with the second reservoir, and the flow from the second ink supply port to the ink ejection port. The path resistance is configured to be smaller than the channel resistance from the first ink supply port to the ink discharge port. In the technique described in Patent Document 2, the circulation of ink and the discharge of bubbles are switched by forward / reverse rotation of the pump.

  In the technique described in Patent Document 3, a first communication path serving as a bubble discharge path that connects the downstream chamber and the discharge path is provided in the tank case of the head tank, and the upstream chamber and the discharge path are provided. A second communication path serving as a bubble discharge path that communicates with the first and second communication paths so that the fluid resistance of the second communication path is greater than the fluid resistance of the first communication path. Try to form.

  In the technique described in Patent Document 4, when the head module is replaced, etc., when the ink flow rate fluctuates before and after the replacement, the back pressure is maintained within a predetermined allowable range, A control program for controlling the differential pressure ΔP to make a transition to an appropriate flow rate is executed. That is, when the head module is replaced, the driving state (in practice, the rotational speed) of the supply side pump and the recovery side pump is detected, and the pressure on the supply side and the recovery side are determined in a stepwise manner in a direction opposite to each other. The flow rate is controlled to an appropriate value by monitoring the driving state of the supply side pump and the recovery side pump (monitoring the rotational speed) while changing the flow rate.

  Furthermore, in the technique described in Patent Document 5, in the process, the flow rate 1 and the flow rate 2 (flow rate 1> flow rate 2) are set, and the pressure is increased at a relatively rapid pressure change rate. The pressure is reduced at a moderate pressure change rate. Thereby, bubbles adhering to the inner wall of the storage chamber of the head module at the time of pressure increase can be peeled off to float in the ink, and then the bubbles can be discharged from the nozzle of the head module at the time of pressure decrease.

JP 2010-214847 A Japanese Patent Laid-Open No. 06-024000 JP 2012-056248 A JP 2012-016904 A JP 2012-056306 A

  An object of the present invention is to discharge bubbles in a liquid channel of a droplet discharge device with a simple configuration.

  The droplet discharge head according to claim 1, wherein a supply path for supplying liquid to the nozzle, a recovery path for recovering the liquid circulated from the supply path to the nozzle, the supply path bypassing the nozzle and the supply path And a bypass channel set to a channel resistance that switches the channel direction of the liquid flowing through the recovery channel according to the pressure of the liquid supplied to the supply channel.

  According to a second aspect of the present invention, in the first aspect of the present invention, the bypass flow path may be configured such that the pressure of the liquid supplied to the supply path is higher than the pressure at which the liquid flows out of the nozzle. The channel resistance is set so that the channel direction of the flowing liquid is switched.

  The invention according to claim 3 is the invention according to claim 1 or claim 2, wherein the entire supply path for supplying liquid to the supply path, and the entire recovery path for recovering liquid from the recovery path The supply path, the recovery path, and the bypass flow path are set to flow path resistances that satisfy the following conditions.

And when
cx = cA ⁻¹ b> 0
c = [0 0 -1 0 0 0 0 0 1]
| A | ≠ 0
Vi is supply side pressure, Vo is recovery side pressure, R1 is supply path overall flow resistance, i1 is supply side overall flow rate, Rdi is supply path flow resistance, idi is supply path flow rate, and Rdo is recovery path flow path. Resistance, ido is the recovery flow rate, R2 is the recovery flow rate, i2 is the recovery flow rate, Rna is the nozzle resistance, ina is the nozzle flow rate, Rb is the bypass flow rate resistance, iRb is the bypass flow rate, and V 'is supplied The side bypass pressure, V ″, indicates the recovery side bypass pressure.

  According to a fourth aspect of the present invention, the liquid droplet ejection apparatus according to any one of the first to third aspects and the liquid droplet ejection head according to any one of the first to third aspects can supply liquid to the supply path and the pressure for supplying the liquid can be changed. The supply means pressurizes from a predetermined first pressure for circulating the liquid to a third pressure equal to or higher than a second pressure at which the meniscus is destroyed and the liquid flows out from the nozzle, and the third time is determined for the predetermined time. Control means for controlling the supply means so as to reduce the pressure to the first pressure after maintaining the pressure.

  The invention according to claim 5 is the invention according to claim 4, further comprising driving means for discharging droplets from the nozzle, wherein the control means maintains the third pressure. The driving means is further controlled to discharge droplets from the nozzles over time.

  A liquid droplet ejection apparatus according to a sixth aspect of the present invention is a liquid droplet ejection head according to any one of the first to third aspects of the present invention, and supplies the liquid to the supply path and can change the pressure for supplying the liquid The supply means pressurizes from a predetermined first pressure for circulating the liquid to a third pressure equal to or higher than a second pressure at which the meniscus is destroyed and the liquid flows out from the nozzle, and the third time is determined for the predetermined time. After maintaining the pressure, the pressure is reduced to a fourth pressure larger than the first pressure and smaller than the second pressure, and after maintaining the fourth pressure for a predetermined time, the third pressure The supply means so as to repeat the pressurization, the maintenance of the third pressure for a predetermined time, the decompression to the fourth pressure, and the maintenance of the predetermined time for the fourth pressure a plurality of times. And a control means for controlling.

  The invention according to claim 7 is the invention according to claim 6, further comprising driving means for discharging droplets from the nozzle, wherein the control means maintains the third pressure. The driving means is further controlled to discharge droplets from the nozzles over time.

  According to the first aspect of the present invention, it is possible to discharge the bubbles in the ink flow path with a simple configuration as compared with the case where no bypass is provided in which the direction in which the ink flows changes according to the pressure. There is.

  According to the second aspect of the present invention, there is an effect that bubbles can be easily discharged compared to a case where there is no configuration in which the ink flows backward at a pressure equal to or higher than the pressure at which the ink flows out from the nozzle.

  According to the third aspect of the present invention, there is an effect that it is possible to set a bypass in which the direction of ink flow is switched according to the pressure according to the conditions of this configuration.

  According to invention of Claim 4, compared with the case where control of this structure is not performed, there exists an effect that it can make it easy to discharge | emit a bubble.

  According to the fifth aspect of the present invention, the bubbles are discharged compared to the case where the driving means is not controlled to discharge the ink from the nozzle while the pressure is higher than the pressure at which the ink flows out from the nozzle. There is an effect that it can be made easy.

  According to the sixth aspect of the present invention, there is an effect that the bubbles can be easily discharged as compared with the case where the control of this configuration is not performed.

  According to the seventh aspect of the present invention, air bubbles are discharged compared to the case where the driving means is not controlled so that the ink is ejected from the nozzle while the pressure is higher than the pressure at which the ink flows out from the nozzle. There is an effect that it can be made easy.

It is a figure which shows the inkjet recording head in the inkjet recording device concerning embodiment of this invention. (A) is a figure which shows the recording surface of each inkjet recording head in the inkjet recording device concerning embodiment of this invention, (B) is sectional drawing which shows an example of the head module mounted in each inkjet recording head. is there. FIG. 3 is an enlarged cross-sectional view of the vicinity of the recording surface of the head module in the inkjet recording apparatus according to the embodiment of the present invention. FIG. 3 is an enlarged cross-sectional view of the vicinity of a nozzle in the ink jet recording apparatus according to the embodiment of the present invention. (A) is a figure which shows the backflow of a bubble, (B) is a figure which shows the example which changes the flow direction of an ink, and shakes a bubble, (C) is the inkjet recording device concerning embodiment of this invention. It is a figure which shows the example which provided the bypass in the inkjet recording device. (A) is a figure which shows the example which switches the flow direction of an ink by switching the rotation direction of a pump, (B) is an example which provides the pressure control apparatus in each of a supply side and a collection | recovery side, and switches the flow direction of an ink. (C) is a diagram showing an example of switching the direction of ink flow using a plurality of valves. (A) is a figure which shows the state which circulated the ink from the supply path to the collection | recovery path with the inkjet recording head in the inkjet recording device concerning embodiment of this invention, (B) shows the state backflowed by the bypass. FIG. 2C is a block diagram showing a schematic configuration of a control system of the ink jet recording apparatus according to the embodiment of the present invention. It is a figure which shows the equivalent circuit which caught the flow path of the inkjet recording head in the inkjet recording device concerning this Embodiment. It is a figure which shows an example of the pressure adjustment of the inkjet recording device concerning this Embodiment. It is a figure which shows the modification of the pressure adjustment of the inkjet recording device concerning this Embodiment.

  Hereinafter, an example of an embodiment of the present invention will be described in detail with reference to the drawings. In this embodiment, an ink jet recording apparatus will be described as an example of a droplet discharge apparatus.

  FIG. 1 is a diagram showing an ink jet recording head in an ink jet recording apparatus according to an embodiment of the present invention.

  As shown in FIG. 1, the inkjet recording apparatus 10 includes a plurality of inkjet recording heads 12. In the present embodiment, four ink jet recording heads 12 are arranged on the drum 14.

  Each of the inkjet recording heads 12 has a long shape in the width direction of the drum 14 and is disposed in order along the circumferential direction of the drum 14. Each inkjet recording head 12 ejects ink of a different color, and ejects ink onto a recording medium conveyed between the drum 14 and the inkjet recording head 12 to form an image on the recording medium. In this embodiment, an inkjet recording head 12M that ejects magenta (M) ink, an inkjet recording head 12K that ejects black (K) ink, and an inkjet recording head 12C that ejects cyan (C) ink. , And yellow (Y) ink jet recording heads 12Y are sequentially arranged along the circumferential direction of the drum 14 (the conveyance direction of the recording medium). Note that the arrangement order is not limited to this.

  2A is a diagram showing a recording surface of each inkjet recording head 12 in the inkjet recording apparatus according to the embodiment of the present invention, and FIG. 2B is an example of a head module mounted on each inkjet recording head. FIG. 3 is an enlarged sectional view of a dotted line portion (near the recording surface) of FIG. 2B of the head module in the ink jet recording apparatus according to the embodiment of the present invention, and FIG. FIG. 3 is an enlarged cross-sectional view of the vicinity of a nozzle in the ink jet recording apparatus according to the embodiment of the present invention.

  As shown in FIG. 2A, the inkjet recording head 12 is configured by arranging a plurality of head modules 18 in which a plurality of nozzles 16 are arranged in a matrix.

  2 to 4, each head module 18 includes an ink supply port 20, an ink supply chamber 22, a common ink supply channel 24, a supply channel 26, a storage chamber 28, a recovery channel 30, and a common ink recovery flow. A path 32, an ink recovery chamber 34, and an ink recovery port 36 are provided.

  As shown in FIG. 2B, ink is supplied into the head module 18 from the ink supply port 20 that supplies ink, and the ink supplied from the ink supply port 20 is the ink supply chamber 22 in which the filter 38 is provided. Supplied to.

  As shown by an arrow A in FIG. 3, the ink supplied to the ink supply chamber 22 circulates to the ink supply common flow path 24, which is a flow path common to the plurality of nozzles 16, and is indicated by an arrow D in FIG. As shown, ink is supplied to the nozzle 16 through the supply path 26 after being stored in the storage chamber 28 via the supply path 26. Although not shown, a drive unit 46 (see FIG. 7) for ejecting ink such as a piezo element is provided on the upper side of the storage chamber 28 in FIG. 4 and drives the drive unit 46. Thus, pressure is applied from the storage chamber 28 to the nozzle 16, and ink is ejected from the nozzle 16. In FIG. 3, the ink supply common flow path 24 and the ink collection common flow path 32 are shown as the same part, but the ink supply flow path 24 and the ink collection common flow path 32 are indicated by arrows X in FIG. 3. They are arranged alternately in the direction.

  Further, as shown by a dotted arrow E in FIG. 4, the remaining ink supplied to the nozzles is circulated through the recovery path 30 on the side of the nozzles 16 to the ink recovery common path 32.

  The ink circulated through the ink collecting common flow path 32 circulates in the ink collecting chamber 34 and is discharged from the ink collecting port 36 to the outside of the head module 18 as indicated by an arrow B in FIG.

  By the way, in the circulation type ink jet recording head, such as the ink jet recording head 12 according to the present embodiment, bubbles that do not flow in the normal ink circulation remain in the recovery path, and the remaining bubbles are formed by the ink from the nozzles 16. As shown by the arrow in FIG. 5A, the reverse flow that occurs during discharge may be carried to the vicinity of the nozzle 16 and cause discharge failure.

  As a method of removing bubbles in the ink recovery path, for example, as shown in FIG. 5B, the direction of flow in the recovery path is switched a plurality of times and the bubbles are shaken to promote the movement of the bubbles. A direction that promotes the movement of bubbles by increasing the flow rate of the recovery path is effective.

  Here, as a method of changing the direction of ink flow, as shown in FIG. 6A, the rotation direction of the pump 80 of the pressure control device is switched, or as shown in FIG. Out side) is also provided with a pressure control device, and the ink flow method is switched by the pressure control devices on the supply side and the recovery side, or a plurality of valves and bypasses are provided as shown in FIG. It is conceivable to switch the direction of ink circulation by switching.

  However, when the rotation direction of the pump of the pressure control device is switched, there is a possibility that the load of the pump 80 is increased due to the switching of the rotation and the life is shortened. Further, when a pressure control device is provided also on the recovery side, or when a plurality of valves and bypasses are provided, there is a problem that the device becomes large.

  Therefore, in the present embodiment, as shown in FIG. 5C, a bypass 40 is provided to pressurize the supply side until the meniscus is destroyed, and ink is allowed to flow out from the nozzles 16 to discharge bubbles. ing. Specifically, as shown in FIG. 3, a bypass 40 is provided between the ink supply chamber 22 and the ink recovery chamber 34.

  By providing the pressure control device only on the supply side with the bypass 40, the direction of ink flow can be switched before and after the ink flows out from the nozzle 16.

  In the present embodiment, when supplying ink, the pump 42 (see FIG. 7C) is driven to drive the supply path 26 to the recovery path 30 as indicated by the dotted line in FIG. Circulate the ink. Then, by adjusting the pressure for circulating the ink, as indicated by the dotted line in FIG. 7B, the ink is caused to flow backward from the bypass 40 to the recovery path 30, and the ink is discharged from the nozzle 16, thereby removing bubbles and the like. The nozzle 16 is discharged.

  In this embodiment, as shown in FIG. 7C, a pump 42 that circulates ink is provided, and the control device 44 controls the driving of the pump 42 to adjust the pressure for circulating ink. It is supposed to be.

  Here, in order to increase the flow rate of the recovery path 30 for discharging bubbles, it is necessary to reduce the flow path resistance of the recovery path 30, but the flow rate of the recovery path 30 in circulation is equal to the flow path resistance of the supply path 26. Also depends. If the flow path resistance of the supply path 26 is also lowered, the discharge efficiency is lowered. Therefore, it is difficult to increase the flow rate of the recovery path 30 in the circulation state, and the ink circulation direction can be switched simply by providing the bypass 40. I can't.

  Considering an ink jet recording head having a bypass 40 as in the present embodiment, by lowering both the bypass flow path and the flow path resistance of the recovery path, the recovery path 30 is in reverse flow (supply side → bypass → recovery). The path → nozzle) can flow more ink than during circulation.

  In this embodiment, the position of the bypass 40 is shown inside the ink jet recording head 12, but may be provided outside, but as in this embodiment, the position of the ink jet recording head 12 may be provided. By providing inside, it can utilize for the temperature control in the inkjet recording head 12, and a deaeration effect improvement.

  Next, a method for setting each flow path of the ink jet recording head 12 in the ink jet recording apparatus according to the present embodiment will be described in detail.

  In the present embodiment, each part of the inkjet recording head 12 is considered as an equivalent circuit in order to set each flow path resistance.

  FIG. 8 is a diagram showing an equivalent circuit capturing the flow path of the ink jet recording head 12 in the ink jet recording apparatus 10 according to the present embodiment.

  In the present embodiment, the flow path resistance in the portion from the ink supply port 20 to the ink supply chamber 22 shown in FIG. 2B is the supply-side overall flow path resistance R1, and the ink recovery chamber 34 is connected to the ink recovery port 36. The flow path resistance of the portion at is the recovery-side overall flow path resistance R2.

  Further, the flow path resistance of the bypass 40 portion indicated by arrow C in FIG. 3 is defined as bypass flow resistance Rb, and the portion of the supply path 26 extending from the supply path 26 through the storage chamber 28 to the nozzle 16 is indicated by arrow D in FIG. Let the flow path resistance be a supply path flow path resistance Rdi.

  Further, the flow path resistance of the nozzle 16 is defined as the nozzle flow path resistance Rna, and the flow path resistance of the recovery path 30 connected from the nozzle 16 to the ink recovery common flow path 32 indicated by the arrow E in FIG. Let Rdo.

  As shown in FIG. 8, the inkjet recording head 12 has a supply-side overall flow path resistance R1, a supply-path flow path resistance Rdi, a recovery-path flow path resistance Rdo, and a recovery-side overall flow path resistance R2 connected in series. A bypass flow path resistance Rb is connected between the supply side overall flow path resistance R1 and the supply path flow path resistance Rdi and between the recovery path flow path resistance Rdo and the recovery side overall flow path resistance R2. Further, a nozzle flow path resistance Rna at the time of ink outflow is connected between the supply path flow path resistance Rdi and the recovery path flow path resistance Rdo.

  In the equivalent circuit of FIG. 8, the other end of the nozzle flow path resistance Rna is considered as 0. When there are a plurality of nozzles, the supply path channel resistance Rdi, the recovery path channel resistance Rdo, and the nozzle channel resistance Rna are approximated as parallel connections.

  In the above equivalent circuit, if the pressure at the connection point of the bypass flow path resistance Rb between the recovery path flow path resistance Rdo and the recovery side overall flow path resistance R2 is V ″ (recovery side bypass pressure), a bypass 40 is provided. Thus, each flow path resistance for generating the backflow satisfies the condition of V ″> Vna (backflow condition).

  Moreover, the relationship of each flow path is represented by the following formula | equation. The pressure at the connection point of the bypass flow path resistance Rb between the supply-side overall flow path resistance R1 and the supply path flow path resistance Rdi is V ′ (supply-side bypass pressure), and the controllable ink supply pressure is Vi (supply). Side pressure), the recovery pressure Vo (recovery side pressure) when recovering ink, the flow rate flowing through the supply side overall flow path resistance R1, i1 (supply side overall flow rate), and the flow rate flowing through the supply path flow path resistance Rdi as idi ( Supply channel flow rate), flow rate flowing through the recovery channel flow path resistance Rdo (recovery channel flow rate), flow rate flowing through the recovery side overall flow path resistance R2 (i2) (recovery side total flow rate), and flow rate flowing through the nozzle resistance Rna as ina ( Nozzle flow rate), the flow resistance of the bypass 40 is shown as Rb (bypass flow resistance), and the flow through the bypass 40 is shown as iRb (bypass flow).

Vi−V ′ = R1 × i1
V′−V ″ = Rb × ib
V′−Vna = Rdi × idi
V ″ −Vna = Rdo × ido
V ″ −Vo = R2 × i2
i1-ib-idi = 0
Ib-Ido-i2 = 0
idi + ido-ina = 0
Vna = Rna × ina
These simultaneous equations are arranged in matrix form as shown below.

  The above-described backflow condition (V ″ −Vna> 0) is expressed as follows using the above determinant.

cx = cA ⁻¹ b> 0
C = [0 0 -1 0 0 0 0 0 1]
In addition, the condition that the inverse matrix A- ^{1 of the} matrix A exists is as follows.

| A | ≠ 0
By setting the bypass flow path resistance Rb, the supply path flow path resistance Rdi, and the recovery path flow path resistance Rdo so that the above equation is satisfied, the pressure on the supply side is adjusted, so that the ink can be supplied using the bypass 40. It becomes possible to make it flow backward.

  Here, the pressure adjustment method of the inkjet recording apparatus 10 according to the present embodiment will be described. FIG. 9 is a diagram illustrating an example of pressure adjustment of the inkjet recording apparatus 10 according to the present embodiment.

  In the present embodiment, as shown in FIG. 9, the control device 44 controls the pump 42 using a plurality of pressure values, thereby controlling the bubble discharge and the like of the inkjet recording head 12.

  Specifically, as shown in FIG. 9, in a normal state in which the ink is circulated, by setting the normal circulation pressure P1, the ink is supplied from the supply path 26 toward the recovery path 30 as shown in FIG. 7A. Is circulated. In addition, the control device 44 controls the pump 42 to be driven at the normal circulation pressure P1, and controls the driving means 46 such as a piezo element, whereby ink is ejected from the nozzles 16.

  And when discharging | emitting air bubbles etc., the control apparatus 44 controls the pump 42, pressurizes to the pressure P3, and maintains it to become the pressure P3 during the predetermined time T1. That is, by applying a pressure equal to or higher than the pressure P <b> 2 at which the meniscus is destroyed and the ink starts to flow out of the nozzle 16, the ink flows backward from the collection path 30 side toward the nozzle 16 via the bypass 40. In addition, when the control device 44 controls the pump 42 to apply a pressure P3 that is equal to or higher than the pressure P2 at which the ink starts to flow out of the nozzles 16, the flow rate of the backflow increases during the period in which the pressure P3 is applied, and bubbles are reliably generated. Discharged.

  Further, in the vicinity of the pressure P2 at which ink outflow from the nozzle 16 is started, switching of the ink flow occurs, so that bubbles are shaken to promote movement.

  In this embodiment, the normal circulation pressure P1 is increased to the pressure P3, the ink is caused to flow backward from the bypass toward the recovery path 30 and the nozzle 16, and the pressure P3 is maintained for a predetermined time T1. Bubbles are discharged from the nozzle 16 by a cycle for returning to the circulation pressure P1, but the pressure cycle is not limited to this, and for example, as shown in FIG.

  That is, in the example shown in FIG. 10, first, similarly to the above (FIG. 9), the control device 44 controls the pump 42 to pressurize from the normal circulation pressure P1 to the pressure P3, and the predetermined time T2 (FIG. 9). Similarly, the pressure P3 may be maintained during T1). As a result, the ink flows backward and bubbles are discharged from the nozzle 16.

  Subsequently, the control device 44 controls the pump 42 to maintain the time T3 as the pressure P4 smaller than the pressure P2 at which the meniscus is destroyed and ink starts to flow out from the nozzle 16 at a pressure larger than the normal circulation pressure P1, Then, the ink is circulated in the positive direction and the pressure P3 is set again. Then, by repeating the cycles of pressure P3 and P4 a plurality of times and repeatedly performing the normal circulation and the reverse flow of the ink, the discharge of the bubbles is promoted and the bubbles are discharged from the nozzles 16.

  In the example of FIG. 10, the pressure change time when switching the circulation direction is shortened by changing the circulation direction to the pressure P4 larger than the normal circulation pressure P1 without returning from the pressure P3 for backflowing ink to the normal circulation pressure P1. Thus, the switching time of the circulation direction is shortened. Accordingly, the switching speed of the ink circulation direction becomes faster than the repetition of the pressure cycle shown in FIG. 9, and bubbles are easily discharged.

  In the above-described embodiment, the pressure of the supplied ink is increased from the normal circulation pressure to the pressure P3 that is equal to or higher than the pressure P2 at which the meniscus is destroyed and the ink starts to flow out of the nozzle 16. By flowing out, the ink flowing through the recovery path 30 is made to flow backward, but the control device 44 drives the driving means 46 such as a piezo element so that the ink is discharged from the storage chamber 28 without setting the pressure P2 or higher. Thus, the ink may be discharged from the nozzle 16 and the pressure of the supplied ink may be adjusted (pressurized) by controlling the pump 42, or the pressure may be increased to a pressure P3 that is equal to or higher than the pressure P2. And the controller 16 simultaneously drives the drive means 46 to assist the ink discharge. It may be so that. For example, the controller 44 may drive the driving means 46 such as a piezo element during the time T1 in FIG. 9 or during the time T2 in FIG. Thereby, the flow rate at the time of backflow of the ink increases, and bubbles are more easily discharged.

DESCRIPTION OF SYMBOLS 10 Inkjet recording device 12 Inkjet recording head 16 Nozzle 18 Head module 20 Ink supply port 22 Ink supply chamber 24 Ink supply common channel 26 Supply channel 28 Reservoir chamber 30 Collection channel 32 Ink collection channel 34 Ink collection chamber 36 Ink Recovery port 40 Bypass 42 Pump 44 Controller 46 Driving means Vi Supply side pressure Vo Recovery side pressure R1 Supply path overall flow resistance i1 Supply side overall flow Rdi Supply path flow resistance idi Supply path flow Rdo Recovery path flow resistance ido Recovery Channel flow rate R2 Recovery side overall flow resistance i2 Recovery side overall flow rate Rna Nozzle resistance ina Nozzle flow rate Rb Bypass flow resistance iRb Bypass flow rate V 'Supply side bypass pressure V''Recovery side bypass pressure

Claims (7)

A supply path for supplying liquid to the nozzle;
A recovery path for recovering the liquid circulated from the supply path to the nozzle;
The flow path resistance is set so that the flow path direction of the liquid flowing through the recovery path is switched according to the pressure of the liquid supplied to the supply path while connecting the supply path and the recovery path by bypassing the nozzle. A bypass channel;
A droplet discharge head comprising:   The bypass flow path is set to a flow path resistance that switches a flow path direction of the liquid flowing through the recovery path when the pressure of the liquid supplied to the supply path is equal to or higher than the pressure at which the liquid flows out from the nozzle. 2. A droplet discharge head according to 1. An overall supply path for supplying liquid to the supply path, and an overall recovery path for recovering liquid from the recovery path,
The liquid droplet ejection head according to claim 1, wherein the supply path, the recovery path, and the bypass flow path are set to flow path resistances that satisfy the following conditions.
And when
cx = cA ⁻¹ b> 0
c = [0 0 -1 0 0 0 0 0 1]
| A | ≠ 0
Vi is supply side pressure, Vo is recovery side pressure, R1 is supply path overall flow resistance, i1 is supply side overall flow rate, Rdi is supply path flow resistance, idi is supply path flow rate, and Rdo is recovery path flow path. Resistance, ido is the recovery flow rate, R2 is the recovery flow rate, i2 is the recovery flow rate, Rna is the nozzle resistance, ina is the nozzle flow rate, Rb is the bypass flow rate resistance, iRb is the bypass flow rate, and V 'is supplied The side bypass pressure, V ″, indicates the recovery side bypass pressure. The droplet discharge head according to any one of claims 1 to 3,
A supply means for supplying a liquid to the supply path and capable of changing a pressure for supplying the liquid;
The pressure is increased from a predetermined first pressure for circulating the liquid to a third pressure equal to or higher than a second pressure at which the meniscus is destroyed and the liquid flows out from the nozzle, and the third pressure is maintained for a predetermined time. And a control means for controlling the supply means so as to reduce the pressure to the first pressure;
A droplet discharge device comprising: A driving means for discharging droplets from the nozzle;
5. The droplet discharge device according to claim 4, wherein the control unit further controls the drive unit to discharge a droplet from a nozzle during the predetermined time during which the third pressure is maintained. The droplet discharge head according to any one of claims 1 to 3,
A supply means for supplying a liquid to the supply path and capable of changing a pressure for supplying the liquid;
The pressure is increased from a predetermined first pressure for circulating the liquid to a third pressure equal to or higher than a second pressure at which the meniscus is destroyed and the liquid flows out from the nozzle, and the third pressure is maintained for a predetermined time. Then, the pressure is reduced to a fourth pressure larger than the first pressure and smaller than the second pressure, and after maintaining the fourth pressure for a predetermined time, pressurization to the third pressure is performed. , A control for controlling the supply means to repeat the maintenance of the third pressure for a predetermined time, the depressurization to the fourth pressure, and the maintenance of the predetermined time for the fourth pressure a plurality of times. Means,
A droplet discharge device comprising: A driving means for discharging droplets from the nozzle;
The liquid droplet ejection apparatus according to claim 6, wherein the control unit further controls the driving unit so that the liquid droplets are ejected from a nozzle during the predetermined time during which the third pressure is maintained.