Liquid ejection device

A control section controls an ejection operation to eject liquid in each of a first state in which the liquid flows from a supply tank to a liquid ejection head in a supply channel, the liquid flows from the liquid ejection head to a collection tank in a collection channel, and the liquid flows from the collection tank to the supply tank in a feedback channel, and a second state in which the liquid flows from the supply tank to the liquid ejection head in the supply channel and the liquid flows from the supply tank to the liquid ejection head and the liquid flows from the collection tank to the liquid ejection head in the collection channel.

The present application is based on, and claims priority from JP Application Serial Number 2019-190898, filed on Oct. 18, 2019, the disclosure of which is hereby incorporated by reference herein in its entirety.

BACKGROUND

1. Technical Field

The present disclosure relates to a liquid ejection device.

2. Related Art

As an example of liquid ejection devices, for example, an ink jet printer that performs printing by ejecting ink from an ink jet head to paper is disclosed in JP-A-2013-184336. Such an ink jet printer is configured to supply ink, for example, from a sub tank to an ink jet head and feed back the ink from the ink jet head to a collection tank through an exhaust channel to cause the ink to circulate. Furthermore, there are ink jet printers in which an ejection defect is suppressed by collecting bubbles or the like in a flow channel, adjusting temperature in the channel, or the like. Note that the collection tank is used only for collecting the ink during circulation, and therefore, only a supply tank supplies the ink to the ink jet head.

However, there is a problem that, in a case in which an ejection amount of the ink is large, when the ink is supplied only from the supply tank, an ink supply amount to the head is insufficient.

SUMMARY

According to an aspect of the present disclosure, a liquid ejection device includes a liquid ejection head configured to eject liquid, a first reservoir configured to store liquid that is supplied to the liquid ejection head, a second reservoir configured to store liquid collected from the liquid ejection head, a first flow channel configured to communicate the liquid ejection head and the first reservoir with each other, a second flow channel configured to communicate the liquid ejection head and the second reservoir with each other, a third flow channel configured to communicate the first reservoir and the second reservoir with each other, and an ejection control section configured to control an ejection operation of ejecting the liquid from the liquid ejection head, the ejection control section controls the ejection operation to eject the liquid in each of a first state in which the liquid flows from the first reservoir to the liquid ejection head in the first flow channel, the liquid flows from the liquid ejection head to the second reservoir in the second flow channel, and the liquid flows from the second reservoir to the first reservoir in the third flow channel and a second state in which the liquid flows from the first reservoir to the liquid ejection head in the first flow channel and the liquid flows from the second reservoir to the liquid ejection head in the second flow channel.

In the above described liquid ejection device, in the second state, the liquid may flow from the second reservoir to the first reservoir in the third flow channel.

In the above described liquid ejection device, a flow channel resistance of the second flow channel may be smaller than a flow channel resistance of the first flow channel.

The above described liquid ejection device may further include a temperature detection section configured to detect temperature of the liquid, and a temperature adjustment section configured to adjust the temperature of the liquid, based on a detection result of the temperature detection section.

In the above described liquid ejection device, the temperature detection section may include a first temperature detection section configured to detect the temperature of the liquid in the first flow channel and a second temperature detection section configured to detect the temperature of the liquid in the second flow channel, the temperature adjustment section may include a first temperature adjustment section arranged in the first reservoir and a second temperature adjustment section arranged in the second reservoir, the first temperature adjustment section may be configured to adjust the temperature of the liquid in the first reservoir, based on a detection result of the first temperature detection section, and the second temperature adjustment section may be configured to adjust the temperature of the liquid in the second reservoir, based on a detection result of the second temperature detection section.

In the above described liquid ejection device, the first temperature adjustment section and the second temperature adjustment section may be configured to adjust the temperature of the liquid such that the temperature of the liquid in the second reservoir is higher than the temperature of the liquid in the first reservoir.

In the above described liquid ejection device, a filter configured to catch a foreign matter in the liquid may be provided in the first reservoir and the second reservoir.

In the above described liquid ejection device, the second reservoir may be arranged higher in a gravity direction than the first reservoir.

In the above described liquid ejection device, the first reservoir and the second reservoir may be arranged higher in the gravity direction than the liquid ejection head.

In the above described liquid ejection device, the ejection control section may be configured to control the ejection operation such that, when an ejection amount per unit time is a first amount, the liquid is ejected in the first state and, when the ejection amount per unit time is a second amount that is larger than the first amount, the liquid is ejected in the second state.

In the above described liquid ejection device, the liquid ejection head may be configured to perform the ejection operation while performing scanning relatively on a unit region on a recording medium, the ejection control section may be configured to control the ejection operation such that, when the number of times the scanning is performed on the unit region is a first number of times, the liquid is ejected in the first state and, when the number of times the scanning is performed on the unit region is a second number of times that is less than the first number of times, the liquid is ejected in the second state.

In the above described liquid ejection device, the liquid ejection head may be configured to perform the ejection operation while performing scanning relatively on a unit region on a recording medium, and the ejection control section may be configured to control the ejection operation such that, when speed of the scanning performed on the unit region is first speed, the liquid is ejected in the first state and, when the speed of the scanning performed on the unit region is second speed that is higher than the first speed, the liquid is ejected in the second state.

In the above described liquid ejection device, the liquid ejection head may include a liquid ejection section configured to eject liquid, a fourth flow channel configured to communicate the liquid ejection section and the first flow channel with each other, and a fifth flow channel configured to communicate the liquid ejection section and the second flow channel with each other, and a flow channel resistance of the fifth flow channel may be smaller than a flow channel resistance of the fourth flow channel.

In the above described liquid ejection device, the second flow channel may further include a switching section configured to switch between an allowable state in which a flow of the liquid from the second reservoir to the liquid ejection head is allowed and an unallowable state in which a flow of the liquid from the second reservoir to the liquid ejection head is not allowed, and a switching control section configured to control an operation of the switching section such that a flow of the liquid is put in the second state by putting the switching section in the allowable state and a flow of the liquid is put in the first state by putting the switching section in the unallowable state.

In the above described liquid ejection device, the switching control section may be configured to control, when a signal from a flow amount detection section arranged in the first flow channel is detected and a flow amount that can be possibly in the allowable state is detected, switching to the allowable state regardless of the ejection operation.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Embodiments of the present disclosure will be described below with reference to the accompanying drawings. Note that, in each of the drawings below, each layer or each member is illustrated in a different scale from an actual scale thereof in order to make each layer or each member large enough such that each layer or each member is recognizable.

First Embodiment

FIG.1is a conceptual block diagram illustrating an entire configuration of a liquid ejection device1a. The entire configuration of the liquid ejection device1awill be described below with reference toFIG.1.

As illustrated inFIG.1, the liquid ejection device1aincludes a supply tank2as a first reservoir, a collection tank3as a second reservoir, a pump4, a supply channel5as a first flow channel, a collection channel6as a second flow channel, a sensor8as a temperature detection section and a first temperature detection section, and a liquid ejection head9.

Liquid is, for example, ink having a predetermined viscosity. The supply tank2includes a temperature control section10aas a first temperature adjustment section. The collection tank3includes a temperature control section10bas a second temperature adjustment section. Temperature of the liquid is detected by the sensor8provided in the supply channel5and is adjusted via the temperature control section10aand the temperature control section10b.

The supply tank2is a liquid reservoir member configured to store liquid that is ejected from the liquid ejection head9. The liquid in the supply tank2is supplied to the liquid ejection head9via the pump4and the supply channel5.

The collection tank3is a liquid reservoir member configured to store ink discharged from the liquid ejection head9. Specifically, when the liquid supplied from the supply tank2to the liquid ejection head9is not ejected but is discharged from the liquid ejection head9, the collection tank3stores the liquid via the collection channel6. The supply tank2and the collection tank3are connected to each other via a feedback channel7as a third flow channel.

The pump4is provided in the supply channel5between the supply tank2and the liquid ejection head9. Specifically, the pump4serving as a liquid sending function that sends the liquid to the liquid ejection head9via the supply channel5adjusts a pressure of liquid to be supplied to a predetermined pressure. The pump4is formed of, for example, a tube pump or a diaphragm pump. Note that the pump4may be configured so as not to be arranged in the supply channel5.

A control section11serving as an ejection control section includes a processing circuit, such as, for example, a central processing unit (CPU), a field programmable gate array (FPGA), or the like, and a memory circuit, such as a semiconductor memory or the like, and controls the liquid ejection head9. Note that a plurality of control sections11may be provided and, in that case, the plurality of control sections11may be configured such that one of the control sections11and the other ones of the control sections11execute different processing.

FIG.2is a conceptual diagram illustrating a configuration of the liquid ejection device1ain the first embodiment.FIG.3is a conceptual diagram illustrating a configuration of the liquid ejection head9that forms the liquid ejection device1a. The configurations of the liquid ejection device1aand the liquid ejection head9will be described below with reference toFIG.2.

As illustrated inFIG.2, the liquid ejection device1aincludes the supply tank2, the supply channel5that connects the supply tank2and the liquid ejection head9, the collection channel6that connects the liquid ejection head9and the collection tank3, and the feedback channel7that connects the collection tank3and the supply tank2.

Liquid circulates in each flow channel due to the pump4functioning as a liquid sending mechanism. Note that, inFIG.2, a liquid reservoir used for supplementing the liquid by an amount corresponding to liquid consumed by ejection from the liquid ejection head9is not illustrated. Although the configuration of the liquid ejection device1athat uses one type of liquid is illustrated inFIG.2, in a configuration in which a plurality of types of liquid are used, a liquid ejection device is provided for liquid of each type. Moreover, although one liquid ejection head9is illustrated inFIG.2, the number of the liquid ejection heads9may be one or more. Note that a configuration in which connection is made from the collection tank3to the supply tank2is common.

In this embodiment, a first state in which the liquid flows in an A direction in each flow channel and a second state in which the liquid flows in a B direction in each flow channel can be established.

The first state is a state in which the liquid flows from the supply tank2toward the liquid ejection head9in the supply channel5, the liquid flows from the liquid ejection head9to the collection tank3in the collection channel6, and the liquid flows from the collection tank3to the supply tank2in the feedback channel7. That is, in the first state, the liquid circulates between the supply tank2, the liquid ejection head9, and the collection tank3via the supply channel5, the collection channel6, and the feedback channel7. A flow of the liquid in the first state can be caused by driving of the pump4and pressure control of the collection tank3and the supply tank2.

The second state is a state in which the liquid flows from the supply tank2toward the liquid ejection head9in the supply channel5, the liquid flows from the collection tank3to the liquid ejection head9in the collection channel6, and the liquid flows from the collection tank3to the supply tank2in the feedback channel7. That is, in the second state, the liquid flows from both of the supply tank2and the collection tank3to the liquid ejection head9. Therefore, in the second state, a supply amount of the liquid to the liquid ejection head9per unit time is larger than that in the first state, and a shortage of liquid supply is less likely to occur.

The second state is used in a case in which the supply amount of the liquid to the liquid ejection head9is insufficient. For example, in a case in which the liquid is supplied to the liquid ejection head9only by driving of the pump4in the first state, when an ejection amount of the liquid from the liquid ejection head9per unit time is larger than the supply amount of the liquid to the liquid ejection head9by driving of the pump4, the first state is switched to the second state.

In this case, the collection tank3is arranged higher in a gravity direction than the supply tank2, and therefore, also in the second state, the liquid flows from the collection tank3to the supply tank2in the feedback channel7in a manner described above. However, in the second state, the liquid flows from the collection tank3to the liquid ejection head9, and therefore, the supply amount of the liquid from the collection tank3to the supply tank2in the feedback channel7is smaller in the second state than in the first state.

In this case, in the second state, it can be made easier to cause the liquid to flow in the B direction by causing a flow channel resistance of the collection channel6to be smaller than a flow channel resistance of the supply channel5.

As illustrated inFIG.3, the liquid ejection head9includes a liquid ejection section23, a fourth flow channel13that supplies liquid to the liquid ejection section23, and a fifth flow channel14that discharges liquid that has not been ejected by the liquid ejection section23.

The liquid ejection section23includes a plurality of nozzles22that discharge liquid and a plurality of common liquid chambers21in which liquid supplied from the fourth flow channel13is stored.

In the fourth flow channel13that supplies the liquid to each of the common liquid chambers21, as a flow channel cross-sectional area is increased, a flow channel resistance is reduced, and therefore, a flow velocity of the liquid in the fourth flow channel13is increased. Thus, there is a high probability that bubbles stay in the fourth flow channel13. This is because bubbles move from a lower side to an upper side due to buoyancy and, on the other hand, when the flow channel cross-sectional area is increased to increase a velocity of a flow of the liquid from the upper side to the lower side in the fourth flow channel13, the bubbles are prevented from escaping to the upper side. Therefore, considering a bubble discharging capability, it is not preferable to increase the flow channel cross-sectional area and reduce the flow channel resistance for the purpose of increasing the amount of liquid that is supplied.

On the other hand, in the fifth flow channel14, the liquid flows from the lower side to the upper side in the first state, and therefore, even when the flow channel cross-sectional area is increased, the bubble discharging capability is not inhibited. Therefore, in this embodiment, the flow channel resistance of the collection channel6is smaller than the flow channel resistance of the supply channel5. According to this configuration, when the supply amount of liquid to the liquid ejection head9is insufficient and the first state transitions to the second state, it can be made easier to cause the liquid to flow in the B direction.

As a temperature adjustment function that adjusts temperature of liquid in a circulation flow channel, for example, the sensor8configured to detect the temperature of the liquid is provided in the supply channel5, and the temperature control section10aand the temperature control section10bthat adjust the temperature of the liquid in the circulation flow channel, based on a detection result of the sensor8, are provided in the supply tank2and the collection tank3. According to this configuration, the temperature of the liquid in the circulation flow channel can be kept at a uniform level and circulation can be stably performed.

Note that, separate from the sensor8arranged in the supply channel5, a sensor (not illustrated) serving as a temperature detection section and a second temperature detection section that detect the temperature of the liquid may be arranged in the collection channel6. In this case, the temperature control section10acan adjust the temperature of the liquid in the supply tank2, based on the detection result of the sensor8arranged in the supply channel5, and the temperature control section10bcan adjust the temperature of the liquid in the collection tank3, based on a detection result of the sensor arranged in the collection channel6.

As for temperatures of the supply tank2in which the temperature control section10ais provided and the collection tank3in which the temperature control section10bis provided, a control temperature of the temperature control section10bis set higher than a control temperature of the temperature control section10a, and thus, a temperature gradient can be formed between the collection tank3and the supply tank2, so that circulation in the feedback channel7can be efficiently performed. Specifically, temperature of ink is adjusted such that the temperature of the ink in the collection tank3is higher than the temperature of the ink in the supply tank2.

Furthermore, a water head difference can be generated by setting a level at which the collection tank3is arranged higher in the gravity direction than a level at which the supply tank2is arranged, so that circulation can be efficiently performed by water pressure head control.

Moreover, the supply tank2and the collection tank3are arranged higher in the gravity direction than the liquid ejection head9, and thus, a liquid circulation system can be set near the liquid ejection head9. As a result, the entire liquid ejection device1acan be arranged in a space-saving manner, the device can be made compact, and deterioration of the temperature adjustment function due to heat radiation in the liquid circulation flow channel can be suppressed.

A filter12is provided in the supply tank2and the collection tank3in order to catch foreign matters and bubbles in the circulation flow channel. Thus, specially, bubbles existing in the circulation flow channel can be reliably caught and, even in a case in which the liquid flows in the B direction from the collection tank3in the second state, the bubbles can be prevented from mixing into the liquid ejection head9. Furthermore, the filter12is arranged in the tanks2and3, and thus, an area of the filter12that can be possibly a flow channel resistance can be made large, so that there is no longer a concern about a shortage of liquid supply due to increase of the flow channel resistance caused by disposing of the filter12.

There is a probability that an ejection state of the liquid ejection head9that can be possibly the second state occurs in a case in which an ejection operation is controlled by the control section11such that an ejection amount per unit time is a second amount that is larger than a first amount. The ejection amount can be calculated based on a setting ejection amount of one nozzle per unit time x the number of ejecting nozzles x the number of times an ejection is performed and, when the ejection amount exceeds a circulation flow amount, the second state is established. For example, in a case in which the liquid ejection head9performs an ejection operation while performing scanning relatively on a unit region on a recording medium and the number of times scanning is performed on the unit region is small, the number of times an ejection is performed per scanning is increased, and therefore, the ejection amount per unit time is increased. In a case in which the liquid ejection head9performs the ejection operation while performing scanning relatively on the unit region on the recording medium and scanning speed of scanning performed on the unit region is high, the ejection amount per unit time is large. Therefore, in a case in which the number of times scanning is performed is small or in a case in which the scanning speed is high, the second state is established.

As described above, according to the liquid ejection device1aaccording to the first embodiment, the following advantageous effects can be achieved.

According to the first embodiment, the first state and the second state can be controlled by the control section11and, in a case in which the ejection amount from the liquid ejection head9is increased to be larger than the circulation flow amount, the control section11performs control to establish the second state, and therefore, the ink supply amount can be supplemented from the collection tank3, so that a shortage of the supply amount of the liquid can be reduced.

Second Embodiment

FIG.4is a block diagram of a liquid ejection device1bin a second embodiment. An entire configuration of the liquid ejection device1bin the second embodiment will be described below with reference toFIG.4. Note that the same components as those in the first embodiment are denoted by the same reference symbols and overlapping description will be omitted. The description of similar parts as those in the first embodiment will be also omitted.

FIG.5is a schematic diagram illustrating a configuration of the liquid ejection device1bin the second embodiment. The configuration of the liquid ejection device1bwill be described below with reference toFIG.5.

The liquid ejection device1bof the second embodiment has a similar configuration as that of the liquid ejection device1aof the first embodiment and further includes a switching section15configured to switch between an unallowable state and an allowable state that correspond to the first state and the second state.

In this embodiment, a collection channel17and a collection channel18are connected to the collection channel6via the switching section15. The switching section15can switch between a state in which the collection channel6and the collection channel18do not communicate with each other and the collection channel6and the collection channel17communicate with each other and a state in which the collection channel6and the collection channel17do not communicate with each other and the collection channel6and the collection channel18communicate with each other. The switching section15is configured such that flow channel switching is performed by a control section16serving as a switching control section. The control section16performs a flow channel switching operation in the switching section15, based on information indicating the ejection amount per unit time, the number of times scanning is performed on the unit region, and the scanning speed at which scanning is performed on the unit region, or the like.

In this case, a one-way valve19used for preventing a backflow or the like is arranged in the collection channel17. On the other hand, no one-way valve is arranged in the collection channel18. Therefore, the state in which the collection channel6and the collection channel18do not communicate with each other and the collection channel6and the collection channel17communicate with each other corresponds to the unallowable state in which a flow of liquid from the collection tank3to the liquid ejection head9is not allowed. The state in which the collection channel6and the collection channel17do not communicate with each other and the collection channel6and the collection channel18communicate with each other corresponds to the allowable state in which a flow of the liquid from the collection tank3to the liquid ejection head9is allowed.

FIG.6is a flowchart illustrating a switching control method for controlling switching of the liquid ejection device1b. The switching control method will be described below with reference toFIG.6.

As illustrated inFIG.6, in the control section11, whether the allowable state or the unallowable state is established by the switching section15is determined. In Step S1, based on a printing condition sent to the liquid ejection head9by the control section11, the ejection amount per unit time is calculated, when it is determined that a calculated value exceeds the circulation flow amount, the switching section15operates so as to be in the allowable state in Step S2and, after a state in which the liquid in an amount corresponding to a shortage in the circulation flow amount can be supplied from the collection tank3is established, an ejection operation is executed in Step S4.

On the other hand, when it is determined that the calculated value is the circulation flow amount or less, the switching section15operates so as to be in the unallowable state in Step S3and, after a state in which the ejection amount is supplemented by the circulation flow amount is established, the ejection operation is executed in Step S4. When the ejection operation ends and a new printing condition is set, the printing condition sent from the control section11is detected again and, after the above described control operation is performed, the ejection operation is performed.

In the control method, for example, a rule in accordance with the number of times scanning is performed may be set.FIG.7is a flowchart illustrating a control method used in such a case. The number of times scanning is performed on the unit region is calculated based on the printing condition set by the control section11in Step S5, when it is determined that the number of times scanning is performed is smaller than a first number of times, the switching section15is put in the unallowable state in Step S7, and then, an ejection operation is executed in Step S8. On the other hand, when it is determined that the number of times scanning is performed is the first number of times or more, the switching section15is put in the allowable state in Step S6, and then, an ejection operation is performed in Step S8. Furthermore, this control can be performed to control the scanning speed in a similar manner.

As described above, according to the liquid ejection device1baccording to the second embodiment, the following advantageous effects can be achieved.

According to the second embodiment, in accordance with the ejection operation of the liquid ejection head9controlled by the control section11, the control section16is controlled and the allowable state and the unallowable state can be switched from one to another by the switching section15, so that a shortage of ink supply can be avoided and efficient circulation is enabled.

MODIFIED EXAMPLES

FIG.8is a block diagram illustrating an entire configuration of a liquid ejection device1cin a modified example.FIG.9is a schematic diagram illustrating the configuration of the liquid ejection device1cof the modified example. The entire configuration of the liquid ejection device1cin the modified example will be described below with reference toFIG.8andFIG.9. Note that the same components as those in the first embodiment and the second embodiment are denoted by the same reference symbols and overlapping description will be omitted.

As illustrated inFIG.8, the liquid ejection device1cincludes the supply tank2, the collection tank3, the pump4, the supply channel5, the collection channel6, a sensor20, and the liquid ejection head9, the switching section15is arranged in a flow channel from the liquid ejection head9to the collection tank3, and the switching section15is controlled by the control section16, so that flow channel switching is performed. Examples of a signal transmitted to the control section16include a signal detected by the sensor20serving as a flow amount detection section in the flow channel or the like. At this time, as the sensor20, a flow amount sensor, a pressure sensor, or the like is used and, in a case in which the flow amount sensor is used, in accordance with a detected flow amount, the switching section15is controlled by the control section16and a flow channel switching operation is performed.

The liquid ejection device1cof the modified example has a similar configuration to those of the liquid ejection devices1aand1bof the first embodiment and the second embodiment. The liquid ejection device1cfurther includes the sensor20used for measuring the flow amount in the flow channel.

FIG.10is a flowchart illustrating a control method for the liquid ejection device1cof the modified example. According to this control method, in the liquid ejection device1c, in a circulation state including an ejection state, for example, when it is determined in Step S9that the flow amount detected by the sensor20is less than the first flow amount, for example, due to clogging in the flow channel and increase of a liquid viscosity that are caused by bubbles or foreign matters, the switching section15is put in the allowable state in Step S10, and then, an ejection operation is executed in Step S12. On the other hand, when it is determined that the flow amount detected by the sensor20is the first flow amount or more, the switching section15is put in the unallowable state in Step S11, an ejection operation is executed in Step S12.

According to this modified example, regardless of the ejection operation of the liquid ejection head9, in accordance with a result of detection performed by the sensor20, the switching section15is controlled by the control section16, the allowable state and the unallowable state can be switched from one to another and, even under some other ejection condition than a certain ejection condition, a shortage of ink supply can be avoided.

Contents derived from embodiments will be described below.

A liquid ejection device includes a liquid ejection head configured to eject liquid, a first reservoir configured to store liquid that is supplied to the liquid ejection head, a second reservoir configured to store liquid collected from the liquid ejection head, a first flow channel configured to communicate the liquid ejection head and the first reservoir with each other, a second flow channel configured to communicate the liquid ejection head and the second reservoir with each other, a third flow channel configured to communicate the first reservoir and the second reservoir with each other, and an ejection control section configured to control an ejection operation of ejecting the liquid from the liquid ejection head, the ejection control section controls the ejection operation to eject the liquid in each of a first state in which the liquid flows from the first reservoir to the liquid ejection head in the first flow channel, the liquid flows from the liquid ejection head to the second reservoir in the second flow channel, and the liquid flows from the second reservoir to the first reservoir in the third flow channel and a second state in which the liquid flows from the first reservoir to the liquid ejection head in the first flow channel and the liquid flows from the second reservoir to the liquid ejection head in the second flow channel.

According to this configuration, the second flow channel can be controlled between the first state and the second state and, in a case in which an ejection amount from the liquid ejection head is increased to a larger amount than a circulation flow amount, the second flow channel is controlled to be in the second state. Therefore, the supply amount of the liquid from the second reservoir can be supplemented, so that insufficient supply amount of the liquid can be avoided.

In the above described liquid ejection device, in the second state, the liquid may flow from the second reservoir to the first reservoir in the third flow channel.

According to this configuration, even in the second state, the liquid in the third flow channel flows from the second reservoir to the first reservoir, and therefore, a liquid storage amount of the first reservoir can be kept at a uniform level, so that the circulation flow amount in a supply channel can be stabilized.

In the above described liquid ejection device, a flow channel resistance of the second flow channel may be lower than a flow channel resistance of the first flow channel.

According to this configuration, when the second flow channel is put in the second state, the flow channel resistance of the second flow channel can be made small and sufficient liquid supply from the second flow channel can be performed.

The above described liquid ejection device may further include a temperature detection section configured to detect temperature of the liquid and a temperature adjustment section configured to adjust the temperature of the liquid, based on a detection result of the temperature detection section.

According to this configuration, temperature in the flow channels is adjusted based on the detection result of the temperature detection section, and thus, the liquid can be caused to have proper temperature, so that stable circulation can be performed. Moreover, a temperature difference between the first flow channel and the second flow channel in the second state can be eliminated and stable circulation can be performed.

In the above described liquid ejection device, the temperature detection section may include a first temperature detection section configured to detect the temperature of the liquid in the first flow channel and a second temperature detection section configured to detect the temperature of the liquid in the second flow channel, the temperature adjustment section may include a first temperature adjustment section arranged in the first reservoir and a second temperature adjustment section arranged in the second reservoir, the first temperature adjustment section may be configured to adjust the temperature of the liquid in the first reservoir, based on a detection result of the first temperature detection section, and the second temperature adjustment section may be configured to adjust the temperature of the liquid in the second reservoir, based on a detection result of the second temperature detection section.

According to this configuration, the temperature of the liquid in the first reservoir and the temperature of the liquid in the second reservoir can be properly kept.

In the above described liquid ejection device, the first temperature adjustment section and the second temperature adjustment section may be configured to adjust the temperature of the liquid such that the temperature of the liquid in the second reservoir is higher than the temperature of the liquid in the first reservoir.

According to this configuration, a temperature gradient can be formed between the first reservoir and the second reservoir, a flow of the liquid due to the temperature gradient can be caused to occur, and circulation in a feedback channel can be stabilized.

In the above described liquid ejection device, a filter configured to catch a foreign matter in the liquid may be provided in the first reservoir and the second reservoir.

According to this configuration, the liquid that is supplied from the first reservoir and the second reservoir is filtered by the filter, so that bubbles or foreign matters can be prevented from being mixed in. Moreover, the filter is arranged in the first reservoir and the second reservoir, and thus, a filter area can be increased, so that a concern about reduction of the flow amount due to the flow channel resistance can be eliminated.

In the above described liquid ejection device, the second reservoir may be arranged higher in a gravity direction than the first reservoir.

According to this configuration, water head difference control of the feedback channel that extends from the first reservoir and connects to the second reservoir can be performed and the liquid can be caused to circulate by a water head pressure.

In the above described liquid ejection device, the first reservoir and the second reservoir may be arranged higher in the gravity direction than the liquid ejection head.

According to this configuration, the first reservoir and the second reservoir can be arranged near the liquid ejection head, so that space-saving of a circulation system can be achieved and reduction of a temperature adjustment function due to heat radiation between the flow channels can be suppressed.

In the above described liquid ejection device, the ejection control section may be configured to control the ejection operation such that, when an ejection amount per unit time is a first amount, the liquid is ejected in the first state and, when the ejection amount per unit time is a second amount that is larger than the first amount, the liquid is ejected in the second state.

When the ejection amount exceeds the first amount, it is likely that the supply amount of the liquid is insufficient in the first state. However, according to the above described configuration, the first state can be switched to the second state, so that a shortage of liquid supply can be avoided.

In the above described liquid ejection device, the liquid ejection head may be configured to perform the ejection operation while performing scanning relatively on a unit region on a recording medium, the ejection control section may be configured to control the ejection operation such that, when the number of times the scanning is performed on the unit region is a first number of times, the liquid is ejected in the first state and, when the number of times the scanning is performed on the unit region is a second number of times that is less than the first number of times, the liquid is ejected in the second state.

In a case in which printing is performed, it is likely that, when the number of times the scanning is performed on the unit region is less than the first number of times, the ejection amount during one scanning is increased and the supply amount of the liquid is insufficient. However, according to the above described configuration, the first state can be switched to the second state, so that a shortage of liquid supply can be avoided.

In the above described liquid ejection device, the liquid ejection head may be configured to perform the ejection operation while performing scanning relatively on a unit region on a recording medium, the ejection control section may be configured to control the ejection operation such that, when speed of the scanning performed on the unit region is first speed, the liquid is ejected in the first state and, when the speed of the scanning performed on the unit region is second speed that is higher than the first speed, the liquid is ejected in the second state.

In a case in which printing is performed, it is likely that, when the speed of the scanning performed on the unit region is the second speed that is higher than the first speed, the ejection amount per unit time is increased and the supply amount of the liquid is insufficient. However, according to the above described configuration, the first state can be switched to the second state, so that a shortage of liquid supply can be avoided.

In the above described liquid ejection device, the liquid ejection head may include a liquid ejection section configured to eject liquid, a fourth flow channel configured to communicate the liquid ejection section and the first flow channel with each other, and a fifth flow channel configured to communicate the liquid ejection section and the second flow channel with each other, and a flow channel resistance of the fifth flow channel may be smaller than a flow channel resistance of the fourth flow channel.

From a view point of the bubble discharging capability of the liquid ejection section, in the fourth flow channel, a liquid flow velocity needs to be increased, and the flow channel resistance has to be reduced, and therefore, in a case in which there is only the first state, it is likely that the liquid flow amount is insufficient accordingly. However, according to the above described configuration, in the fifth flow channel, the flow channel resistance can be made small, so that a shortage of liquid supply can be avoided in the second state.

In the above described liquid ejection device, the second flow channel may further include a switching section configured to switch between an allowable state in which a flow of the liquid from the second reservoir to the liquid ejection head is allowed and an unallowable state in which a flow of the liquid from the second reservoir to the liquid ejection head is not allowed, and a switching control section configured to control an operation of the switching section such that a flow of the liquid is put in the second state by putting the switching section in the allowable state and a flow of the liquid is put in the first state by putting the switching section in the unallowable state.

According to this configuration, the switching section is controlled in accordance with the ejection operation of the liquid ejection head to perform switching between the allowable state and the unallowable state, so that an unnecessary flow from the second reservoir can be suppressed, more efficient circulation can be performed, and a shortage of liquid supply can be avoided.

In the above described liquid ejection device, the switching control section may be configured to control, when a signal from a flow amount detection section arranged in the first flow channel is detected and a flow amount that can be possibly in the allowable state is detected, switching to the allowable state, regardless of the ejection operation.

According to this configuration, regardless of the ejection operation, a shortage of the flow amount in a case in which the viscosity of the liquid is increased by clogging, loss of the temperature adjustment function, sedimentation of components, or the like due to bubbles or foreign matters in the liquid flow channels can be detected and a shortage of liquid supply can be suppressed by switching between the allowable state and the unallowable state according to a result of the detection.