Liquid ejecting apparatus

A liquid ejecting apparatus includes a plurality of nozzles which eject liquid; a common liquid chamber which supplies liquid to the plurality of nozzles; a liquid flow path for supplying liquid which is accommodated in a liquid accommodation unit to the common liquid chamber; a deaeration unit which deaerates liquid in the liquid flow path; a liquid flow unit which causes liquid in the liquid flow path to flow; a return flow path which connects the common liquid chamber and the liquid accommodation unit; and an on-off valve which closes the return flow path by being in a closed state.

CROSS REFERENCE TO RELATED APPLICATION(S)

This application claims priority under 35 U.S.C. §119 to Japanese Application No. 2014-022005, filed Feb. 7, 2014, the content of which is hereby incorporated by reference in its entirety.

BACKGROUND

1. Technical Field

The present invention relates to a liquid ejecting apparatus such as a printer.

2. Related Art

As an example of a liquid ejecting apparatus, there is an ink jet printer which performs printing by ejecting ink from nozzles which are provided in a recording head. Among such printers, there is a printer which suppresses dot omission which occurs when air bubbles are mixed in nozzles by performing deaeration of ink in a liquid storage chamber which stores ink which will be supplied to a recording head (for example, JP-A-2013-75371).

Meanwhile, in the above described printer, sedimentation of a pigment component which is included in ink is suppressed by circulating ink between a liquid storage chamber and a recording head when printing is not performed. When ink is circulated in this manner, it is also possible to expect an effect that air bubbles which are mixed into a flow path is collected in the liquid storage chamber. However, since a degree of deaeration of ink in the liquid storage chamber is decreased when ink containing air bubbles is collected, there is a problem in that deaeration of ink should be performed every time circulation is performed, and efficiency of deaeration deteriorates.

In addition, such a problem is not limited to a printer which performs printing by ejecting pigment ink, and is generally common to liquid ejecting apparatuses in which there is a concern that air bubbles which grow in liquid or air bubbles which are mixed into liquid may cause an ejection failure of liquid.

SUMMARY

An advantage of some aspects of the invention is to provide a liquid ejecting apparatus in which mixing of air bubbles into liquid or a growth of air bubbles in liquid which is accompanied with ejection is reduced.

Hereinafter, units for solving the above described problem and operation effects thereof will be described.

A liquid ejecting apparatus includes a plurality of nozzles which eject liquid; a common liquid chamber which supplies liquid to the plurality of nozzles; a liquid flow path for supplying liquid which is accommodated in a liquid accommodation unit to the common liquid chamber; a deaeration unit which deaerates liquid in the liquid flow path; a liquid flow unit which causes liquid in the liquid flow path to flow; a pressure adjusting unit which is provided between the deaeration unit and the common liquid chamber in the liquid flow path, and adjusts a pressure of liquid which is supplied to the common liquid chamber; a return flow path which connects the common liquid chamber and the liquid accommodation unit; and an on-off valve which closes the return flow path by being in a closed state.

According to the configuration, it is possible to collect air bubbles which are mixed in the common liquid chamber or a liquid flow path in the liquid accommodation unit by causing liquid in the common liquid chamber to flow to the liquid accommodation unit through the return flow path. In addition, it is possible to eject deaerated liquid from nozzles, since deaeration of liquid is performed using a deaeration unit in the liquid flow path through which liquid is supplied to the common liquid chamber. That is, by performing deaeration in the liquid flow path, it is possible to reduce mixing of air bubbles into liquid which is accompanied with ejection, or a growth of air bubbles in liquid compared to a case in which deaeration of liquid is performed in the liquid accommodation unit.

In the liquid ejecting apparatus, liquid in the common liquid chamber may be collected in the liquid accommodation unit when liquid in the return flow path is caused to flow toward the liquid accommodation unit by opening the on-off valve.

According to the configuration, it is possible to collect liquid in the common liquid chamber into the liquid accommodation unit without passing through the deaeration unit by causing liquid on the return flow path to flow toward the liquid accommodation unit by opening the on-off valve. In this manner, it is possible to efficiently perform deaeration of liquid which is accompanied with ejection by suppressing intermixing of liquid which is subjected to deaeration and liquid including air bubbles.

The liquid ejecting apparatus may further include a bypass flow path of which an upstream end is connected between the deaeration unit and the pressure adjusting unit in the liquid flow path, and of which a downstream end is connected between the on-off valve and the common liquid chamber on the return flow path; and a switching valve which is provided at a connection portion between the bypass flow path and the liquid flow path, and switches a flow path of liquid which flows toward the common liquid chamber from the deaeration unit between the liquid flow path and the bypass flow path, in which liquid may be supplied to the pressure adjusting unit through the liquid flow path in a state in which the on-off valve is closed, and the switching valve may switch the flow path of liquid to the liquid flow path, when liquid is ejected from the nozzle, and in which liquid may be supplied to the common liquid chamber through the bypass flow path in a state in which the on-off valve is closed, and the switching valve may switch the flow path of the liquid to the bypass flow path, when maintenance of causing liquid to flow out from the nozzle is performed.

According to the configuration, it is possible to supply liquid of which a pressure is appropriately adjusted in the pressure adjusting unit to the nozzle by supplying the liquid to the pressure adjusting unit through the liquid flow path, when the liquid is ejected from the nozzle. Meanwhile, when maintenance is performed, it is possible to cause liquid of which the pressure is not adjusted to flow out from the nozzle powerfully, by supplying the liquid to the common liquid chamber through the bypass flow path without passing through the pressure adjusting unit.

In the liquid ejecting apparatus, the pressure adjusting unit may include a pressure chamber of which a volume is changed when a flexible unit which configures a wall portion performs deflection displacement; a supply chamber which communicates with the pressure chamber through a communication flow path; an urging member which urges the flexible unit in a direction in which the volume of the pressure chamber increases; and a valve which is displaced in a direction which causes communication between the pressure chamber and the supply chamber according to a displacement of the flexible unit, when a pressure in the pressure chamber is lower than a pressure on an outer side of the flexible unit, in which the supply chamber may communicate with the deaeration unit through the liquid flow path, and the pressure chamber may communicate with the common liquid chamber through the liquid flow path, and in which a pressure in the pressure chamber decreases due to supplying of liquid in the pressurizing chamber to the common liquid chamber when the liquid flow unit supplies liquid which is in a pressurized state from the deaeration unit to the supply chamber, and liquid flows out from the nozzle.

According to the configuration, when liquid is flown out from the nozzle, the flexible unit performs deflection displacement in a direction in which a volume of the pressure chamber decreases due to a decrease in pressure of the pressure chamber when liquid in the pressure chamber is supplied to the common liquid chamber. In addition, the valve causes the pressure chamber and the supply chamber to communicate with each other according to a displacement of the flexible unit. In addition, since deaerated liquid is supplied to the supply chamber in a state of being pressurized using the liquid flow unit, when the pressure chamber and the supply chamber communicate with each other, liquid rapidly flows into the pressure chamber from the supply chamber. In addition, when a pressure of the pressure chamber returns to the original state due to flowing in of liquid, flowing in of liquid to the pressure chamber from the supply chamber is stopped due to an urging force of the urging member. On the other hand, when liquid is not flown out from the nozzle, since the pressure in the pressure chamber does not decrease, and pressurized liquid does not flow into the common liquid chamber through the pressure chamber, a meniscus in liquid which is formed in the nozzle is not destroyed due to the pressure. That is, it is possible to appropriately adjust a pressure in the common liquid chamber according to flowing out of liquid from the nozzle using the pressure adjusting unit.

In the liquid ejecting apparatus, a foreign substance capturing unit may be further included between the liquid accommodation unit and the deaeration unit in the liquid flow path.

According to the configuration, it is possible to suppress mixing in of foreign substances in the deaeration unit by capturing foreign substances which are mixed into liquid using the foreign substance capturing unit in the middle of the liquid flow path which goes toward the deaeration unit from the liquid accommodation unit.

In the liquid ejecting apparatus, the deaeration unit may include a depressurizing mechanism which depressurized liquid in the liquid flow path for deaeration, and the liquid flow unit may supply liquid which is in a pressurized state from the deaeration unit to the common liquid chamber.

According to the configuration, it is possible to perform deaeration by eliminating a gas in liquid when the depressurizing mechanism performs depressurizing of liquid. In addition, it is possible to cause liquid to flow from the deaeration unit to the common liquid chamber by pressurizing liquid which is depressurized using the liquid flow unit.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, embodiments of a liquid ejecting apparatus will be described with reference to drawings. The liquid ejecting apparatus is, for example, an ink jet printer which performs recording (printing) by ejecting pigment ink which is an example of liquid on a medium such as a sheet.

As illustrated inFIG. 1, a liquid ejecting apparatus11includes a liquid accommodation unit12which accommodates liquid, a plurality of liquid ejecting units13which eject liquid, a liquid flow path14for supplying liquid which is accommodated in the liquid accommodation unit12to the liquid ejecting unit13, and a maintenance unit15which performs maintenance of the liquid ejecting unit13. The liquid accommodation unit12is also be configured so as to pour liquid through a pouring hole (not illustrated) in a state of being mounted on the liquid ejecting apparatus11, and it is also possible to adopt a configuration in which a carriage-shaped liquid accommodation unit12is detachably mounted on the liquid ejecting apparatus11.

The liquid ejecting unit13includes a plurality of nozzles16which ejects liquid, and a common liquid chamber17for supplying liquid which is supplied from the liquid accommodation unit12to the plurality of nozzles16through a liquid flow path14. The number of liquid ejecting units13and nozzles16is arbitrarily changed. As a mechanism for ejecting liquid from the nozzle16, it is possible to adopt an actuator which includes a piezoelectric element which contracts when being electrically connected, for example. In this case, liquid is ejected (discharged) as liquid droplets from the nozzle16when a volume of a liquid chamber16awhich is provided between the common liquid chamber17and the nozzle16is changed due to contraction of the piezoelectric element.

The liquid ejecting apparatus11includes a return flow path18which connects the common liquid chamber17and the liquid accommodation unit12, an on-off valve19which closes the return flow path18by being in a closed state, and a circulation pump20for causing liquid to flow from the common liquid chamber17to the liquid accommodation unit12. When a plurality of the liquid ejecting units13are provided, a downstream side of the liquid flow path14and an upstream side of the return flow path18which are connected to the common liquid chamber17branch into a plurality of paths according to the number of common liquid chambers17.

A deaeration unit21which deaerates liquid in the liquid flow path14is provided in the liquid flow path14. The deaeration unit21includes a cylindrical hollow fiber membrane22which forms a part of the liquid flow path14, and a depressurizing mechanism25which depressurizes liquid in the liquid flow path14for deaeration, for example. In this case, the depressurizing mechanism25includes a depressurizing chamber23which accommodates the hollow fiber membrane22, and a vacuum pump24which depressurizes the depressurizing chamber23. In addition, liquid on the inside of the hollow fiber membrane22is deaerated when the vacuum pump24depressurizes the depressurizing chamber23, a space on the outer side of the hollow fiber membrane22is depressurized, and a gas dissolved in liquid on the inside of the hollow fiber membrane22is suctioned outward from the hollow fiber membrane22.

A pressure adjusting unit31which adjusts a pressure of liquid which is supplied to the liquid ejecting unit13is provided between the deaeration unit21and the liquid ejecting unit13in the liquid flow path14. The pressure adjusting unit31includes, for example, a pressure chamber33of which a volume is changed when a flexible unit32which configures a wall portion performs deflection displacement, a supply chamber35which communicates with the pressure chamber through a communication flow path34, an urging member36which urges the flexible unit in a direction in which the volume of the pressure chamber33increases, and a valve37which closes the communication flow path34. The supply chamber35communicates with the deaeration unit21through the liquid flow path14, and the pressure chamber33communicates with the common liquid chamber17through the liquid flow path14.

In addition, foreign substances such as air bubbles are easily accumulated at a portion in which a cross-sectional area of flow path increases such as the supply chamber35or the pressure chamber33, a portion in a complicated shape such as the urging member36, or the like. For this reason, according to the embodiment, in order to capture the foreign substances such as air bubbles, filters38and39are provided at an entrance of the pressure adjusting unit31and in the pressure adjusting unit31, respectively. It is possible to arbitrarily change the number and arrangements of filters38and39, and it is also possible to omit the filters38and39.

It is preferable for the liquid ejecting apparatus11to be provided with a bypass flow path41of which an upstream end is connected between the deaeration unit21and the pressure adjusting unit31in the liquid flow path14, and of which a downstream end is connected between the on-off valve19and the common liquid chamber17on the return flow path18. In addition, it is preferable to include a switching valve42which switches a flow path of liquid which flows from the deaeration unit21to the common liquid chamber17between the liquid flow path14and the bypass flow path41at a connection portion of the bypass flow path41and the liquid flow path14.

The switching valve42is set to a three-way valve which includes three valves which individually closes three flow paths of the bypass flow path41, an upstream side of a connection portion with the bypass flow path41in the liquid flow path14, and a downstream side of the connection portion with the bypass flow path41in the liquid flow path14.

It is preferable to provide a storage unit43which temporarily stores liquid which is deaerated using the deaeration unit21between the deaeration unit21and the switching valve42in the liquid flow path14. In addition, it is preferable to provide a pressurizing pump45which supplies liquid in a pressurized state from the deaeration unit21to the liquid ejecting unit13between the deaeration unit21and the liquid accommodation unit12in the liquid flow path14.

The pressurizing pump45functions as a liquid flow unit which causes liquid in the liquid flow path14to flow. That is, since liquid in the liquid flow path14is depressurized in the deaeration unit21, it is possible to efficiently supply liquid toward the liquid ejecting unit13by storing the deaerated liquid in the storage unit43in a state of being pressurized using the pressurizing pump45.

In addition, it is preferable to provide a one-way valve46which allows flowing of liquid from the deaeration unit21to the storage unit43, and regulates flowing of liquid from the storage unit43to the deaeration unit21, on the other hand, between the deaeration unit21and the storage unit43in the liquid flow path14. The reason for this is that it is possible to suppress a backflow of liquid from the storage unit43which is in a positive pressure state due to pressurizing to the deaeration unit21which is in a negative pressure state due to depressurizing, in this manner.

In addition, a configuration may be adopted in which an accommodation bag which is flexible is adopted as the storage unit43, the storage unit43which is formed of such an accommodation bag is accommodated in the pressurizing chamber47, and a gas which is suctioned in order to perform depressurizing using the vacuum pump24is introduced to the pressurizing chamber47through a gas flow path61. In this case, it is possible to pressurize liquid in the pressurizing chamber through the accommodation bag by introducing a gas to the pressurizing chamber47by driving the vacuum pump24.

In addition, when adopting such a configuration, if three-way valves62and63are respectively arranged on the upstream side and the downstream side of the vacuum pump24on the gas flow path61, it is possible to arbitrarily set a timing for depressurizing the depressurizing chamber23, and a timing for pressurizing the pressurizing chamber47.

That is, when depressurizing of the depressurizing chamber23and pressurizing of the pressurizing chamber47are performed at the same time, a gas in the depressurizing chamber23may be introduced to the pressurizing chamber47by driving the vacuum pump24by closing valves62aand63awhich communicate with the outside of the three-way valves62and63. In addition, when the depressurizing of the depressurizing chamber23is independently performed, the gas which is suctioned from the depressurizing chamber23may be discharged to the outside by driving the vacuum pump24by closing the valve62aand opening the valve63a. In addition, when pressurizing of the pressurizing chamber47is independently performed, a gas on the outside may be taken into the gas flow path61, and may be introduced to the pressurizing chamber47by driving the vacuum pump24by opening the valve62aand closing the valve63a.

It is preferable to provide a foreign substance capturing unit which captures foreign substances such as air bubbles or dust which are mixed into liquid, solidified substance from solute components which are dissolved in liquid, or the like, between the deaeration unit21and the liquid accommodation unit12in the liquid flow path14. The foreign substance capturing unit may be a filter48for filtering liquid, an air trap49for capturing air bubbles which are mixed into liquid, or a filter and an air trap may be used in combination according to there being a high probability of foreign substances being mixed in.

In addition, when the air trap49separates a gas from liquid by including a liquid storage unit49aand a gas storage unit49bwhich communicate with each other, it is preferable to include a discharging pump50which causes liquid to flow from the liquid accommodation unit12to the liquid storage unit49a.

The maintenance unit15includes a cap51which forms a closed space to which the nozzle16which is provided in the liquid ejecting unit13is open, a suction mechanism52, and a wiper unit53. The suction mechanism52includes a waste liquid tank54, a discharge flow path55which connects the waste liquid tank54and the cap51, and a depressurizing pump56which is arranged at a position in the middle of the discharge flow path55. In addition, an atmosphere opening valve57for opening a closed space to atmosphere is provided in the cap51.

The cap51performs capping in which a closed space is formed by covering a region including an opening face13a, by being in contact with the opening face13ato which the nozzle16is open in the liquid ejecting unit13, for example. In addition, the capping is performed by causing the liquid ejecting unit13to move in a direction which is close to the cap51, or by causing the cap51to move in a direction which is close to the liquid ejecting unit13. In addition, at the time of capping, a target with which the cap51comes into contact is not limited to the opening face13a, and for example, it is also possible to form a closed space to which the nozzle16opens by covering the region including the opening face13a, by causing the cap51to come into contact with a side face portion of the liquid ejecting unit13, a holding member which holds the liquid ejecting unit13, or the like, for example.

In addition, when the depressurizing pump56is driven in a state in which capping is performed, suction cleaning in which the closed space is in a negative pressure state, and liquid is suctioned and discharged from the common liquid chamber17, or the like, through the nozzle16is executed.

That is, when the depressurizing pump56is driven, and the closed space is in the negative pressure state, the inside of the pressure chamber33is depressurized, when liquid is discharged from the nozzle16, and the liquid in the pressure chamber33flows into the common liquid chamber17. As a result, the flexible unit32which configures a wall portion of the pressure chamber33performs deflection displacement in a direction in which the volume of the pressure chamber33is decreased. In addition, the valve37is displaced in a direction in which the pressure chamber33and the supply chamber35communicate with each other (left direction inFIG. 1) according to the displacement of the flexible unit32.

When there is a state in which the pressure chamber33and the supply chamber35communicate with each other (state of pressure adjusting unit31on right side inFIG. 1) due to the displacement of the valve37, liquid flows into the pressure chamber33from the supply chamber35in the pressurized state. Thereafter, since liquid does not flow out from the nozzle16when driving of the depressurizing pump56is stopped, the flexible unit32is displaced in a direction in which the volume of the pressure chamber33increases, and the valve37closes the communication flow path34by returning to the original position along with an increase in pressure in the pressure chamber33. In this manner, in the pressure adjusting unit31, liquid is supplied to the common liquid chamber17through the liquid flow path14while suction is performed on the nozzle16side.

When capping is released after the execution of such suction cleaning, it is preferable to separate the cap51from the liquid ejecting unit13after opening the closed space to the atmosphere, by causing the atmosphere opening valve57to be in an open state.

The wiper unit53includes a wiper58which wipes the opening face13a, and a moving body59which moves by holding the wiper58. In addition, a wiping operation in which the opening face13ais wiped using the wiper58is executed when the moving body59moves along the opening face13ain a state in which a tip end of the wiper58comes into contact with the opening face13a. In addition, the wiping is also performed when the liquid ejecting unit13moves in a state of being in contact with the wiper58.

In addition to this, as maintenance of the liquid ejecting unit13, a flushing operation in which liquid in the nozzle16is discharged by ejecting liquid from the liquid ejecting unit13to the cap51is executed. The flushing is performed in order to prevent or resolve clogging of the nozzle16between printing operations, or is performed so as to adjust the meniscus of liquid which is formed in the nozzle16, after the wiping, or the like, for example.

In addition, as illustrated inFIG. 2, a control unit100which performs control of constituent elements which configure the liquid ejecting apparatus11such as the liquid ejecting unit13, the discharging pump50, the pressurizing pump45, the vacuum pump24, a circulation pump20, the on-off valve19, the switching valve42, the moving body59, the atmosphere opening valve57, the depressurizing pump56, and the like, is provided. As the control unit100, a plurality of control units which individually control the constituent elements is provided, and it is also possible to provide a control unit which performs an overall control of the plurality of constituent elements.

In the liquid ejecting apparatus11, a state in which the on-off valve19and the atmosphere opening valve57are closed, and a flow path of liquid is switched to the liquid flow path14using the switching valve42due to a control of the control unit100is set to a normal state. In addition, in the normal state, drying of the nozzle16is suppressed when the control unit100performs capping of the liquid ejecting unit13using the cap51.

When the liquid ejecting apparatus11is started up, driving of the discharging pump50and the pressurizing pump45is controlled by the control unit100so that the inside of the storage unit43is maintained so as to have a predetermined positive pressure (pressurized state). In this manner, in the normal state, the storage unit43, the supply chamber35, and the liquid flow path14between the storage unit43and the supply chamber35are maintained in a predetermined pressurized state. In addition, the control unit100performs depressurizing of the depressurizing chamber23by controlling the vacuum pump24and the three-way valves62and63according to driving of the pressurizing pump45, and sends deaerated liquid to the storage unit43.

In addition, even when liquid in the supply chamber35is in a pressurized state, the liquid does not flow from the supply chamber35to the pressure chamber33while a state in which the valve37closes the communication flow path34(state of pressure adjusting unit31on left side inFIG. 1) using an urging force of the urging member36is maintained in the pressure adjusting unit31.

Subsequently, operations of the liquid ejecting apparatus11, and various processes which are executed by the control unit100will be described.

First, a first pouring process which is executed in order to pour liquid in the liquid flow path14into the common liquid chamber17, and a second pouring process which is executed in order to pour liquid in the common liquid chamber17into the nozzle16, subsequently to the first pouring process which are performed when starting use of the liquid ejecting apparatus11, or the like, will be described. In addition, the first pouring process and the second pouring process are started in the above described normal state. In the normal state, the atmosphere opening valve57of the cap51is in a closed state.

The first pouring process is performed when the control unit100executes the process which is illustrated inFIG. 3.

As illustrated inFIG. 3, as step S11, the control unit100changes the on-off valve19from a closed state which is the normal sate to an open state.

Subsequently, in step S12, the control unit100starts driving of the circulation pump20. Then, liquid in the common liquid chamber17flows to the liquid accommodation unit12through the return flow path18, and as a result, liquid in the pressure chamber33is supplied to the common liquid chamber17, and the inside of the pressure chamber33is depressurized. Then, the flexible unit32which configures the wall portion of the pressure chamber33performs deflection displacement in a direction in which the volume of the pressure chamber33is decreased. In addition, the valve37is displaced in a direction (left direction inFIG. 1) in which the pressure chamber33and the supply chamber35communicate with each other according to the displacement of the flexible unit32.

When the pressure chamber33and the supply chamber35are in a communicating state (state of pressure adjusting unit31on right side inFIG. 1) due to the displacement of the valve37, liquid flows into the pressure chamber33from the supply chamber35in the pressurized state. In addition, liquid flows in order of the pressure chamber33, the common liquid chamber17, and the return flow path18along with driving of the circulation pump20. At this time, in the supply chamber35, liquid is supplied from the storage unit43in a pressurized state through the liquid flow path14, and liquid in the storage unit43is replenished from the liquid accommodation unit12due to driving of the pressurizing pump45and the discharging pump50as denoted by the solid line arrow inFIG. 1.

Subsequently, as step S13, the control unit100stops driving of the circulation pump20. Then, since liquid does not flow out from the common liquid chamber17to the return flow path18, the flexible unit32is displaced in a direction in which the volume of the pressure chamber33increases along with an increase in pressure of the pressure chamber33, and the valve37closes the communication flow path34by returning to the original position.

In addition, as step S14, when the control unit100puts the on-off valve19back to the normal state which is the closed state from the open state, the first pouring process is finished. In this manner, pouring of liquid with respect to the common liquid chamber17is completed.

In addition, when the filters38and39are provided in the liquid flow path14, or the like, since a pressure loss on the flow path increases, it is difficult to cause liquid to flow to the pressure chamber33even when the liquid is supplied by being pressurized. For this reason, a configuration may be adopted in which the switching valve42is set to a three-way valve which includes the valve42awhich is arranged in the liquid flow path14on the downstream side of the connection portion with the bypass flow path41, and the valve42bwhich is arranged on the bypass flow path41, the valve42ais open for a fixed time between step S12and step S13, and then the valve42ais opened. By doing so, it is possible to efficiently perform pouring of liquid by causing liquid pressurized in a region which is in a negative pressure state along with opening of the valve42ato flow at once, since the negative pressure in the pressure chamber33influences the valve42awhile the valve42ais open.

Subsequently, the second pouring process will be described with reference toFIG. 4.

The second pouring process is executed as a preparation operation in which liquid is poured up to the common liquid chamber17using the first pouring process, and then the liquid in the common liquid chamber17is set to a state in which printing is performed by being poured into the nozzle16.

As illustrated inFIG. 4, as step S21, the control unit100causes driving of the depressurizing pump56to be started. Then, the closed space which is formed using capping is depressurized, liquid is suctioned through the nozzle16, and is flown out into the cap51.

Subsequently, as step S22, the control unit100stops driving of the depressurizing pump56.

In addition, as step S23, the control unit100changes the atmosphere opening valve57from a closed state to an open state. In this manner, the closed space is open to atmosphere, and flowing out of liquid from the nozzle16is stopped. At this time, liquid is poured into the nozzle16.

Subsequently, as step S24, the control unit100causes the driving of the depressurizing pump56to be restarted. In this manner, the liquid accumulated in the cap51is discharged to the waste liquid tank54through the discharge flow path55. When discharging of the liquid in the cap51is completed, as step S25, the control unit100stops driving of the depressurizing pump56.

Subsequently, as step S26, the control unit100releases capping. In addition, it is also possible to perform releasing of capping in step S26between steps S23and S24. In this case, discharging of liquid which is accumulated in the cap51is performed in a state in which capping is released.

In addition, as step S27, the control unit100executes wiping by moving the moving body59. In this manner, liquid droplets, and the like, which are discharged from the nozzle16due to suction, and are attached to the opening face13aare eliminated.

In addition, the second pouring process is finished when the control unit100fixes a meniscus of the nozzle16by executing flushing as step S28, and the control unit100executes capping as step S29. In addition, when printing is started immediately after the execution of the second pouring process, or the like, the capping in step S29may not be performed.

In this manner, when liquid is poured up to the nozzle16by performing the first and second pouring processes, the liquid ejecting apparatus11enters a state in which printing is executed. In addition, a series of operations which is executed in the second pouring process is the same as the operation in suction cleaning which is a maintenance operation in which foreign substances such as air bubbles are discharged through the nozzle16.

However, in the suction cleaning, a driving time of the depressurizing pump56is set so that liquid of an amount which is necessary for discharging of foreign substances is discharged from the nozzle16; however, in contrast to this, in the second pouring process, liquid of an amount which is necessary for pouring in the nozzle16may flow. For this reason, normally the driving time of the depressurizing pump56in the second pouring process is shorter than a time for suction cleaning.

In addition, when the liquid ejecting apparatus11performs printing, the control unit100releases capping, and ejects liquid to a medium from the liquid ejecting unit13.

In addition, when liquid flows out from the nozzle16along with ejection of liquid, and liquid in the common liquid chamber17decreases, a pressure in the pressure chamber33decreases due to flowing in of liquid in the common liquid chamber17from the pressure chamber33. That is, a pressure in the pressure chamber33decreases due to supplying of liquid in the pressure chamber33to the common liquid chamber17when liquid flows out from the nozzle16. Then, the flexible unit32performs deflection displacement in a direction in which the volume of the pressure chamber33is decreased. In addition, when the pressure in the pressure chamber33becomes lower than a pressure on the outer side of the flexible unit32, the valve37is displaced in a direction in which the pressure chamber33and the supply chamber35communicate with each other according to the displacement of the flexible unit32.

When the pressure chamber33and the supply chamber35are in a communicating state due to the displacement of the valve37, liquid flows in from the supply chamber35which is in the pressurized state to the pressure chamber33. At this time, as denoted by the solid line arrow inFIG. 1, the pressurizing pump45supplies liquid in a pressurized state from the deaeration unit21to the supply chamber35of the pressure adjusting unit31, and the discharging pump50supplies liquid from the liquid accommodation unit12to the liquid storage unit49a.

In addition, when the flexible unit32is displaced in a direction in which the volume of the pressure chamber33increases along with flowing in of liquid, the valve37returns to the original position, and closes the communication flow path34. In this manner, liquid is rapidly supplied from the supply chamber35in a pressurized state when liquid in the pressure chamber33is consumed, and meanwhile, when liquid is not consumed, the valve37closes the communication flow path34, and an increase in pressure of the liquid from the pressure chamber33to the nozzle16is suppressed.

In addition, when pressurizing and depressurizing of liquid is repeated in the liquid chamber16ain order to eject liquid from the nozzle16, a gas which is dissolved in liquid appears as air bubbles, and a change in pressure which occurs along with driving of the piezoelectric element is not sufficiently transmitted to the nozzle16, and this causes an ejection failure of liquid droplets. In addition, since liquid does not flow in the liquid ejecting apparatus11at a time of not performing ejection of liquid, when liquid is a solution including an ingredient with a sedimentation property such as a pigment, there is a case in which the pigment, or the like, sediments, and causes a difference in concentration of liquid.

Therefore, when the liquid ejecting unit13does not eject liquid, a circulation process in which liquid is circulated between the common liquid chamber17and the liquid accommodation unit12is performed by returning the liquid in the common liquid chamber17to the liquid accommodation unit12through the return flow path18.

Similarly to the first pouring process, the circulation process is performed by driving the circulation pump20after the control unit100sets the on-off valve19to an open state. That is, when the circulation pump20is driven, as denoted by the dotted arrow inFIG. 1, liquid in the common liquid chamber17flows to the liquid accommodation unit12through the return flow path18, and the valve37causes the supply chamber35and the pressure chamber33to communicate with each other due to depressurizing in the common liquid chamber17and the pressure chamber33.

Then, liquid is supplied to the supply chamber35through the liquid flow path14from the storage unit43, and liquid in the liquid accommodation unit12is supplied to the storage unit43using the discharging pump50and the pressurizing pump45. In this manner, liquid circulates between the liquid accommodation unit12and the common liquid chamber17. Then, agitating of a pigment, or the like, is performed due to a flow of liquid, and foreign substances such as air bubbles which are present in the common liquid chamber17, or the like, are collected in the liquid accommodation unit12. In this manner, when air bubbles are collected in the liquid accommodation unit12by circulating liquid, the collected air bubbles may be stimulated so as to be defoamed when floating on the liquid surface by opening the liquid accommodation unit12to atmosphere.

In addition, when the circulation process is performed in the liquid ejecting apparatus11, there is a case in which a pressure in the common liquid chamber17fluctuates along with flowing of liquid. When such a pressure fluctuation influences the nozzle16, there is a case in which a meniscus of liquid which is formed in the nozzle16is destroyed, and liquid leaks from the nozzle16. For this reason, it is preferable to perform capping of the liquid ejecting unit13using the cap51when performing the circulation process. In this case, it is preferable to open the atmosphere opening valve57of the cap51.

In addition, when liquid is caused to flow by driving the circulation pump20in the circulation process, there is a case in which a pressure in the common liquid chamber17is a negative pressure which is lower than an atmospheric pressure. When such a negative pressure influences the nozzle16, there is a case in which a meniscus of liquid which is formed in the nozzle16is destroyed, and air is drawn from the nozzle16. For this reason, it is preferable to drive the circulation pump20to an extent of not drawing air from the nozzle16when performing the circulation process. For example, it is preferable to drive the circulation pump20so that a pressure which acts on the meniscus which is formed in the nozzle16due to flowing of liquid becomes lower than a withstand pressure of the meniscus.

Subsequently, a pressurizing cleaning process which is one of maintenance operations in which liquid is discharged from the liquid ejecting unit13will be described with reference toFIG. 5.

As illustrated inFIG. 5, as step S31, the control unit100releases capping of the liquid ejecting unit13. In addition, when releasing the capping, as illustrated inFIG. 1, the cap51is arranged at a position which faces an opening of the nozzle16(for example, position which becomes lower part of opening face13ain vertical direction).

Subsequently, as step S32, the control unit100closes the valve42aof the switching valve42and opens the valve42b, and switches a flow path with which the storage unit43communicates from the liquid flow path14which is connected to the pressure adjusting unit31to the bypass flow path41.

Subsequently, as step S33, the control unit100starts additional pressurizing of the storage unit43by driving the vacuum pump24, or the like. In addition, it is also possible to perform pressurizing of the storage unit43by driving the pressurizing pump45instead of driving the vacuum pump24, or by driving the pressurizing pump45, in addition to driving of the vacuum pump24.

In this manner, liquid which is stored in the storage unit43is supplied to the common liquid chamber17by being pressurized through the bypass flow path41as denoted by the two dot chain line inFIG. 1. Then, the liquid in the common liquid chamber17flows out from the nozzle16, and is accommodated using the cap51. In this manner, foreign substances such as air bubbles which are present in the common liquid chamber17or the liquid chamber16a, liquid which is thickened due to evaporation of a solvent ingredient, or the like, which causes an ejection failure is discharged through the nozzle16along with liquid.

When an amount of liquid which is sufficient for discharging foreign substances is discharged from the nozzle16, as step S34, the control unit100stops additional pressurizing of the storage unit43by stopping driving of the vacuum pump24, or the like.

In addition, as step S35, the control unit100switches the flow path with which the storage unit43communicates from the bypass flow path41to the liquid flow path14to which the pressure adjusting unit31is connected by opening the valve42aof the switching valve42, and closing the valve42b, and returns the switching valve to the normal state.

Subsequently, as step S36, the control unit100starts driving of the depressurizing pump56. In this manner, the liquid accumulated in the cap51is discharged to the waste liquid tank54through the discharge flow path55. When discharging of liquid in the cap51is finished, as step S37, the control unit100stops driving of the depressurizing pump56.

Thereafter, as step S38, the control unit100moves the moving body59, and executes wiping. In this manner, liquid droplets, and the like, which are attached to the opening face13aare eliminated along with discharging of liquid from the nozzle16.

In addition, the pressurizing cleaning process is finished when the control unit100fixes a meniscus of the nozzle16by executing flushing as step S39, and executes capping as step S40. In addition, when printing is performed immediately after executing the pressurizing cleaning, or the like, capping in step S40may not be performed.

Subsequently, operations of the liquid ejecting apparatus11will be described.

When liquid is ejected from the nozzle16in the liquid ejecting apparatus11, flowing of liquid from the common liquid chamber17to the return flow path18is suppressed by opening the on-off valve19, and liquid is supplied to the pressure adjusting unit31through the liquid flow path14in a state in which the switching valve42switches the flow path of the liquid to the liquid flow path14. For this reason, it is possible to rapidly supply liquid from the pressure adjusting unit31to the common liquid chamber17along with a consumption of liquid while maintaining a back pressure of the nozzle16at a pressure which is appropriate for ejection of liquid using the pressure adjusting unit31.

In contrast to this, when performing pressurizing cleaning which is maintenance in which liquid is caused to flow out from the nozzle16, liquid is supplied to the common liquid chamber17through the bypass flow path41in a state in which the on-off valve19is closed, and the switching valve42switches a flow path of the liquid to the bypass flow path41. That is, it is possible to discharge foreign substances from the liquid ejecting unit13by causing pressurized liquid to flow out from the nozzle16powerfully by sending the liquid from the storage unit43to the common liquid chamber17without passing through the pressure adjusting unit31.

In addition, when performing pressurizing cleaning, liquid flows into the common liquid chamber17through a part of the return flow path18which is located between the bypass flow path41and the common liquid chamber17. For this reason, it is preferable to suppress flowing of foreign substances into the common liquid chamber17along with the pressurizing cleaning operation by providing a foreign substance capturing unit such as a filter60, or the like, in the return flow path18which is located between the bypass flow path41and the common liquid chamber17.

In addition, since the liquid ejecting apparatus11includes the return flow path18, liquid in the common liquid chamber17is collected in the liquid accommodation unit12by causing liquid on the return flow path18to flow toward the liquid accommodation unit12by opening the on-off valve19. In this manner, it is possible to suppress mixing in of air bubbles in the liquid chamber16aor the nozzle16by collecting foreign substances such as air bubbles which are accumulated in the common liquid chamber17, or the like, in the liquid accommodation unit12.

In addition, when circulating liquid in order of the common liquid chamber17, the return flow path18, the liquid accommodation unit12, and the liquid flow path14by driving the circulation pump20, the discharging pump50and the pressurizing pump45by opening the on-off valve19, the liquid on the flow path is agitated. In this manner, it is possible to suppress a change in concentration of liquid even when the liquid includes an ingredient with a sedimentation property such as a pigment. That is, since it is possible to suppress an occurrence of ejection failure of the nozzle16or deterioration in printing quality without discarding liquid including foreign substances or liquid of which concentration is changed, by causing the liquid to flow out from the nozzle16, it is possible to reduce an amount of liquid which is consumed for maintenance.

In addition, even when liquid including air bubbles is collected in the liquid accommodation unit12, liquid which is supplied to the common liquid chamber17from the liquid accommodation unit12is deaerated in the deaeration unit21whether the flow path is the liquid flow path14or the bypass flow path41. In this manner, occurrence of air bubbles in the flow path from the deaeration unit21to the nozzle16, or in the pressure adjusting unit31is suppressed.

According to the embodiment, it is possible to obtain the following effects.

(1) It is possible to collect air bubbles which are mixed in the common liquid chamber17or the liquid flow path14in the liquid accommodation unit12by causing liquid in the common liquid chamber17to flow in the liquid accommodation unit12through the return flow path18. In addition, it is possible to eject deaerated liquid from the nozzle16since deaeration of liquid is performed using the deaeration unit21in the liquid flow path14through which liquid is supplied to the common liquid chamber17. That is, by performing deaeration in the liquid flow path14, it is possible to reduce mixing of air bubbles into liquid which is accompanied with ejection, or a growth of air bubbles in liquid compared to a case in which deaeration of liquid is performed in the liquid accommodation unit12.

(2) It is possible to collect liquid in the common liquid chamber17into the liquid accommodation unit12without passing through the deaeration unit21, by causing liquid on the return flow path18to flow toward the liquid accommodation unit12by opening the on-off valve19. In this manner, it is possible to efficiently perform deaeration of liquid which is accompanied with ejection by suppressing intermixing of liquid which is subjected to deaeration and liquid including air bubbles.

(3) It is possible to supply liquid of which a pressure is appropriately adjusted in the pressure adjusting unit31to the nozzle16by supplying liquid to the pressure adjusting unit31through the liquid flow path14, when the liquid is ejected from the nozzle16. Meanwhile, when maintenance is performed, it is possible to cause liquid of which the pressure is not adjusted to flow out from the nozzle16powerfully, by supplying the liquid to the common liquid chamber17through the bypass flow path41without passing through the pressure adjusting unit.

(4) When liquid is flown out from the nozzle16, the flexible unit32performs deflection displacement in a direction in which a volume of the pressure chamber33decreases due to a decrease in pressure of the pressure chamber33when liquid in the pressure chamber33is supplied to the common liquid chamber17. In addition, the valve37causes the pressure chamber33and the supply chamber35to communicate with each other according to the displacement of the flexible unit32. In addition, since deaerated liquid is supplied to the supply chamber35in a state of being pressurized using the liquid flow unit, when the pressure chamber33and the supply chamber35communicate with each other, liquid rapidly flows into the pressure chamber33from the supply chamber35. In addition, when a pressure of the pressure chamber33returns to the original state due to flowing in of liquid, flowing in of liquid to the pressure chamber33from the supply chamber35is stopped due to an urging force of the urging member36. On the other hand, when liquid is not flown out from the nozzle16, since the pressure in the pressure chamber33does not decrease, and pressurized liquid does not flow into the common liquid chamber17through the pressure chamber33, a meniscus in liquid which is formed in the nozzle16is not destroyed due to the pressure. That is, it is possible to appropriately adjust a pressure in the common liquid chamber17according to flowing out of liquid from the nozzle16using the pressure adjusting unit31.

(5) It is possible to suppress mixing in of foreign substances in the deaeration unit21by capturing foreign substances which are mixed into liquid using the filter48which is the foreign substance capturing unit or the air trap49in the middle of the liquid flow path14which goes toward the deaeration unit21from the liquid accommodation unit12. It is possible to suppress deterioration in a deaeration property in the deaeration unit21, since clogging of the hollow fiber membrane22is suppressed in this manner.

(6) It is possible to perform deaeration by eliminating a gas in liquid when the depressurizing mechanism25performs depressurizing of liquid. In addition, it is possible to cause liquid to flow from the deaeration unit21to the common liquid chamber17by pressurizing liquid which is depressurized using the pressurizing pump45which functions as the liquid flow unit.

In addition, the embodiment may be modified as the following modification examples.

Deaeration of liquid is not limited to depressurizing using the hollow fiber membrane22, and it is possible to adopt an arbitrary method such as ultrasonic deaeration or centrifugal deaeration.

In the pressurizing cleaning process, the atmosphere opening valve57may be opened instead of releasing capping in step S31. According to the configuration, it is possible to suppress disperal of liquid which flows out from the nozzle16, since it is possible to execute pressurizing cleaning while performing capping.

At least one of pouring of liquid into the common liquid chamber17and pouring of liquid into the nozzle16may be performed by executing steps S31to S34of the above described pressurizing cleaning process.

In the liquid flow path14, a cross-sectional area of a flow path of a common liquid flow path which is on the upstream side of branching liquid flow paths which branch off according to the number of common liquid chambers17, and is on the downstream side of the switching valve42may be set to be larger than cross-sectional areas of flow paths on the front and rear sides thereof as illustrated inFIG. 1.

In the return flow path18, a cross-sectional area of a common return flow path which is on the downstream side of branching return flow paths which branch off according to the number of common liquid chambers17, and is on the upstream side of the on-off valve19may be set to be larger than cross-sectional areas of flow paths on the front and rear sides thereof as illustrated inFIG. 1.

Liquid which is ejected from the liquid ejecting unit may be liquid or a substance in a liquid-like state other than ink. For example, a configuration may be adopted in which recording is performed by ejecting a liquid body including a material such as an electrode material, or a coloring material (material of pixel) which is used when manufacturing, for example, a liquid crystal display, an electroluminescence (EL) display, a surface emission display, or the like, in a form of dispersion, mixing, or dissolution.

A medium is not limited to a sheet, and may be a plastic film, a panel, or the like, or, may be cloth which is used in a fabric printing apparatus, or the like.