Patent Description:
In an ink jet recording device, it is important to stabilize jetting of an ink from a recording head. In order to stabilize the jetting of the ink, an ink jet recording device that circulates the ink through a circulation flow passage provided between an ink tank and the recording head and that prevents removal of foreign substances and sedimentation of pigments is known.

Further, a technique of performing maintenance by changing a flowing direction of an ink in a circulation flow passage to a reverse direction is known. For example, <CIT> and <CIT> describe techniques of changing the flowing direction of the ink by changing a rotation direction of a pump to the reverse direction.

<CIT> discloses an inkjet printer ink delivery system. The ink delivery system includes a supply of ink and an inkjet printhead having a first port, second port and an ink ejection nozzle. The inkjet printhead is connected to the ink supply tank by a first fluid supply path. The first fluid supply path includes first and second check valves which permit ink to flow from the ink supply tank to the inkjet printhead, but prevent fluid flow in the opposite direction. The ink delivery system includes a second fluid supply path which is connected at one end to the first fluid supply path between the respective first and second check valves. The second fluid supply path is connected at its opposite end to the inkjet printhead's second port. The second fluid supply path further includes a bidirectional pump so as to direct fluid flow in either direction through the second fluid supply path. The delivery system operates in various modes including a re-circulate mode, pressure purge mode, maintenance mode and normal print mode. <CIT> discloses an ink jet recording device with ink circulating unit. <CIT> discloses a printing apparatus. <CIT> discloses a flow rate control device, liquid-droplet ejecting device, and computer readable medium. <CIT> discloses a liquid droplet circulation control apparatus, liquid droplet ejection apparatus, and computer readable storage medium. <CIT> discloses a liquid discharging apparatus and control method thereof. <CIT> discloses a liquid discharge apparatus.

However, <CIT> and <CIT> are techniques of removing air bubbles in the circulation flow passage and cannot prevent sedimentation of pigments in an ink. In addition, in a case where the ink flows in the reverse direction without consideration, there is a problem of a possibility in which the contaminated ink adversely affects jetting.

In view of such circumstances, an object of the present invention is to provide a liquid supply device, a control method of a liquid supply device, and a printing apparatus that effectively prevent sedimentation without a contaminated liquid adversely affecting jetting.

According to an aspect for achieving the object, there is provided a liquid supply device according to claim <NUM> of the appended claims.

According to the present aspect, the sequence including the first processing of generating the positive flow in the liquid in the first flow passage and the second processing of generating the negative flow is executed, in the first flow passage, the filter that removes the foreign substance in the liquid is disposed between the liquid tank and the liquid jetting head in the positive flow, the flow rate of the liquid of the positive flow is higher than the flow rate of the liquid of the negative flow, and the negative flow has the steady flow state. Thus, sedimentation can be effectively prevented without the contaminated liquid adversely affecting jetting.

It is preferable that in the first flow passage, the filter that removes the foreign substance in the liquid is not disposed between the liquid tank and the liquid jetting head in the negative flow. Even in a case where the filter is not disposed between the liquid tank and the liquid jetting head in the negative flow, the present aspect is suitable.

It is preferable that the processor is configured to execute the sequence a plurality of times. By generating a negative flow a plurality of times, a total flow rate of negative flows can be acquired while suppressing further return of the contaminated liquid, and thereby sedimentation in the liquid can be more effectively prevented.

It is preferable that the first flow passage includes a second flow passage different from the circulation flow passage. By executing the sequence also on a flow passage in which the liquid does not circulate, sedimentation can be effectively prevented.

It is preferable that the flow rate of the liquid of the negative flow is lower than a volume of the second flow passage. Accordingly, the contaminated liquid in the second flow passage can be prevented from being diffused in the first flow passage by the negative flow.

It is preferable that the processor is configured to replace the liquid in the second flow passage with the liquid from which the foreign substance is removed by the filter by controlling the pump before executing the sequence. Accordingly, the contaminated liquid can be prevented from being diffused in the first flow passage by the negative flow.

It is preferable that the processor is configured to replace the liquid in all flow passages of the first flow passage, in which the liquid of the negative flow has flowed, with the liquid from which the foreign substance is removed by the filter by controlling the pump after executing the sequence. Accordingly, a normal operation can be started in an appropriate state.

According to another aspect for achieving the object, there is provided a printing apparatus comprising a liquid tank that stores a liquid, a liquid jetting head that jets the liquid from an outlet, a moving mechanism that relatively moves the liquid jetting head and a printing substrate, and the liquid supply device, in which the processor is configured to print an image on the printing substrate by jetting the liquid from the outlet of the liquid jetting head while relatively moving the liquid jetting head and the printing substrate, circulate the liquid in the circulation flow passage during the printing, and execute the sequence during non-printing other than during the printing.

According to the present aspect, the liquid can be supplied during printing, and sedimentation in the first flow passage can be prevented during non-printing.

It is preferable that a volume speed of the positive flow is at least temporarily higher than a volume speed during the printing. Accordingly, sedimentation in the first flow passage can be prevented by the positive flow.

It is preferable that a volume speed of the negative flow is at least temporarily higher than a volume speed during the printing. Accordingly, sedimentation in the first flow passage can be prevented by the negative flow.

It is preferable that a diameter of a particle dispersed in the liquid exceeds <NUM>. In a case of supplying the liquid in which sedimentation of the particle is easy, the present aspect is suitable.

It is preferable that the liquid is a white ink that contains a titanium oxide material. In a case of supplying the white ink containing the titanium oxide material, in which sedimentation of pigments is a problem, the present aspect is suitable.

It is preferable that the circulation flow passage comprises a valve that opens and closes some of flow passages of the circulation flow passage, and the processor is configured to control the valve to determine the first flow passage. Accordingly, a desired flow passage can be the first flow passage.

According to still another aspect for achieving the object, there is provided a control method according to claim <NUM> of the appended claims.

With the present invention, sedimentation can be effectively prevented without the contaminated liquid adversely affecting jetting.

Hereinafter, a preferable embodiment of the present invention will be described in detail with reference to the accompanying drawings.

<FIG> is a diagram showing an overall configuration of an ink supply device <NUM> (an example of a liquid supply device). The ink supply device <NUM> is a device that supplies an ink from a buffer tank <NUM> to an ink jet bar <NUM> and, as shown in <FIG>, comprises a supply flow passage <NUM> and a collection flow passage <NUM>.

The buffer tank <NUM> (an example of a liquid tank) is an ink storage unit that stores an ink (an example of a liquid) for being supplied to the ink jet bar <NUM>.

The ink jet bar <NUM> (an example of a liquid jetting head) comprises n head modules <NUM> (<NUM>-<NUM>, <NUM>-<NUM>,. , and <NUM>-n) in which a plurality of nozzles <NUM> (see <FIG>) for discharging inks respectively are provided. The n head modules <NUM> are connected to each other in one direction. Each of the head modules <NUM> has an ink supply port 15A and an ink discharge port 15B respectively.

The supply flow passage <NUM> makes the buffer tank <NUM> and the ink jet bar <NUM> communicate with each other. The collection flow passage <NUM> makes the ink jet bar <NUM> and the buffer tank <NUM> communicate with each other. An ink stored in the buffer tank <NUM> is supplied to the ink jet bar <NUM> via the supply flow passage <NUM>. In addition, an ink not used in the ink jet bar <NUM> is collected in the buffer tank <NUM> via the collection flow passage <NUM>.

The supply flow passage <NUM> and the collection flow passage <NUM> are composed of, for example, tubes. The supply flow passage <NUM> and the collection flow passage <NUM> are connected to each component as appropriate by a splice F.

A degassing module <NUM>, a supply pump <NUM>, a supply-side filter <NUM>, and a heat exchanger <NUM> are provided at the supply flow passage <NUM>. Inside the ink jet bar <NUM>, a supply-side back pressure tank <NUM>, a supply-side head manifold <NUM>, a supply-side pressure sensor <NUM>, supply valves <NUM> (<NUM>-<NUM>, <NUM>-<NUM>,. , and <NUM>-n), and supply dampers <NUM> (<NUM>-<NUM>, <NUM>-<NUM>,. , and <NUM>-n) are further provided at the supply flow passage <NUM>.

In addition, a collection pump <NUM> and a collection flow passage valve <NUM> are provided at the collection flow passage <NUM>. Inside the ink jet bar <NUM>, collection dampers <NUM> (<NUM>-<NUM>, <NUM>-<NUM>,. , and <NUM>-n), collection valves <NUM> (<NUM>-<NUM>, <NUM>-<NUM>,. , and <NUM>-n), a collection-side head manifold <NUM>, a collection-side pressure sensor <NUM>, and a collection-side back pressure tank <NUM> are further provided at the collection flow passage <NUM>.

The degassing module <NUM> performs ink degassing processing. The supply pump <NUM> applies a pressure to an ink inside the supply flow passage <NUM> and generates a flow in the ink inside the supply flow passage <NUM>. The supply pump <NUM> is, for example, a tube pump. The supply-side filter <NUM> removes air bubbles and foreign substances in the ink. The heat exchanger <NUM> adjusts the temperature of the ink.

The supply-side back pressure tank <NUM> is a pressure buffering device that adjusts a pressure such that fluctuations in an internal pressure of the supply flow passage <NUM> are suppressed. The supply-side back pressure tank <NUM> has a liquid chamber 30C that communicates with the supply flow passage <NUM> via an ink inflow port 30A and an ink outflow port 30B, a gas chamber 30D that stores a gas, an elastic film 30E that separates the liquid chamber 30C and the gas chamber 30D from each other, an air bubble discharge port 30F that is provided in the liquid chamber 30C, and an air flow passage communication port <NUM> that is provided in the gas chamber 30D.

The ink inflow port 30A communicates with the heat exchanger <NUM>. The ink outflow port 30B communicates with the supply-side head manifold <NUM>. In a case where an ink flows from the ink inflow port 30A into the liquid chamber 30C, the elastic film 30E deforms to a gas chamber 30D side depending on the volume of the ink flowed in. Accordingly, the volume of the ink flowing out from the ink outflow port 30B does not fluctuate. Therefore, pressure fluctuations of the supply flow passage <NUM> can be suppressed. That is, the supply-side back pressure tank <NUM> has a pressure buffering function of suppressing internal pressure fluctuations of the ink jet bar <NUM> and fluctuations in the internal pressure of the supply flow passage <NUM> caused by a pulsating flow from an operation of the supply pump <NUM>.

The air bubble discharge port 30F communicates with a drain flow passage <NUM>. The drain flow passage <NUM> communicates with the air bubble discharge port 30F and the buffer tank <NUM>. The drain flow passage <NUM> is a flow passage for forcibly discharging an ink in the liquid chamber 30C. The drain flow passage <NUM> is provided with a drain valve <NUM> that switches between communication (open state) and shutoff (closed state) between the air bubble discharge port 30F and the buffer tank <NUM>. In a case where the drain valve <NUM> is in an open state, the ink in the liquid chamber 30C is fed to the buffer tank <NUM>.

In addition, the supply-side back pressure tank <NUM> comprises, as gas elastic adjusting units for determining a pressure buffering performance of the supply-side back pressure tank <NUM>, an air flow passage <NUM>, an air connect valve <NUM>, an air tank <NUM>, an atmospheric communication path <NUM>, and an air valve <NUM>. The air flow passage communication port <NUM> communicates with the air flow passage <NUM>. The air connect valve <NUM> is an air flow passage opening and closing unit that switches between communication and shutoff of the air flow passage <NUM>, and the gas chamber 30D communicates with the air tank <NUM> via the air connect valve <NUM>.

In addition, the atmospheric communication path <NUM> is provided with the air valve <NUM> that switches between communication and shutoff of the atmospheric communication path <NUM>, and the air tank <NUM> communicates with the atmosphere via the atmospheric communication path <NUM>.

A normally open type electromagnetic valve is used as the air connect valve <NUM>. In addition, by applying a normally closed type electromagnetic valve to the air valve <NUM>, a configuration where an ink does not leak from the ink jet bar <NUM> even in a case where a power supply is shut off in a state where an emergency stop function is activated or the like is adopted.

The gas chamber 30D communicates with the air tank <NUM> by opening the air connect valve <NUM>, and the volume of the gas chamber 30D can be increased in response to pressure control of ink feeding. Further, by opening the air valve <NUM>, the air tank <NUM> and the gas chamber 30D can communicate with the atmosphere. The air tank <NUM> functions as a buffer tank of the gas chamber 30D.

The supply-side head manifold <NUM> and the collection-side head manifold <NUM> are temporary storage units for an ink. A first bypass flow passage <NUM> and a second bypass flow passage <NUM> make the supply-side head manifold <NUM> and the collection-side head manifold <NUM> communicate with each other. The first bypass flow passage <NUM> is provided with a first bypass flow passage valve <NUM>, and a second bypass flow passage valve <NUM> is provided with a second bypass flow passage <NUM>.

The supply-side pressure sensor <NUM> is a pressure measuring unit that measures and outputs the internal pressure of the supply flow passage <NUM>. In addition, the collection-side pressure sensor <NUM> is a pressure measuring unit that measures and outputs the internal pressure of the collection flow passage <NUM>. Sensors such as a semiconductor piezo-resistance type sensor, a capacitance type sensor, and a silicon resonant type sensor can be applied to the supply-side pressure sensor <NUM> and the collection-side pressure sensor <NUM>.

The head module <NUM> comprises the ink supply port 15A and the ink discharge port 15B. Each of the ink supply ports 15A of the head modules <NUM>-<NUM>, <NUM>-<NUM>,. , and <NUM>-n communicates with the supply-side head manifold <NUM> via each of the supply valves <NUM>-<NUM>, <NUM>-<NUM>,. , and <NUM>-n. In addition, each of the ink discharge ports 15B of the head modules <NUM>-<NUM>, <NUM>-<NUM>,. , and <NUM>-n communicates with the collection-side head manifold <NUM> via each of the collection valves <NUM>-<NUM>, <NUM>-<NUM>,. , and <NUM>-n.

The supply valves <NUM> (<NUM>-<NUM>, <NUM>-<NUM>,. , and <NUM>-n) are flow passage opening and closing units that switch between communication and shutoff of the supply flow passage <NUM>. The collection valves <NUM> (<NUM>-<NUM>, <NUM>-<NUM>,. , and <NUM>-n) are flow passage opening and closing units that switch between communication and shutoff of the collection flow passage <NUM>. By applying a normally closed type (or a latch type) electromagnetic valve of which opening and closing are controlled by a control signal to the supply valves <NUM> and the collection valves <NUM>, a configuration where an ink does not leak from the head modules <NUM> even in a case where the power supply is shut off in a state where the emergency stop function is activated or the like is adopted.

The supply dampers <NUM>-<NUM>, <NUM>-<NUM>,. , and <NUM>-n are provided respectively between the supply valves <NUM>-<NUM>, <NUM>-<NUM>,. , and <NUM>-n and the respective ink supply ports 15A. In addition, the collection dampers <NUM>-<NUM>, <NUM>-<NUM>,. , and <NUM>-n are provided respectively between the collection valves <NUM>-<NUM>, <NUM>-<NUM>,. , and <NUM>-n and the respective ink discharge ports 15B. Each of the supply dampers <NUM> and the collection dampers <NUM> is a pressure buffering unit for suppressing pulsation of an ink, which is caused by a jetting operation of the ink jet bar <NUM>.

The collection-side back pressure tank <NUM> is a pressure buffering device that performs pressure adjustment such that fluctuations in the internal pressure of the collection flow passage <NUM> are suppressed and is configured the same as the supply-side back pressure tank <NUM>.

That is, the collection-side back pressure tank <NUM> has a liquid chamber 48C that communicates the collection flow passage <NUM> via an ink inflow port 48A and an ink outflow port 48B, a gas chamber 48D that stores a gas, an elastic film 48E that separates the liquid chamber 48C and the gas chamber 48D from each other, an air bubble discharge port 48F that is provided in the liquid chamber 48C, and an air flow passage communication port <NUM> that is provided in the gas chamber 48D. The air bubble discharge port 48F communicates with the buffer tank <NUM> via the drain flow passage <NUM> provided with a drain valve <NUM>. The air flow passage communication port <NUM> communicates with an atmospheric communication path <NUM> via an air flow passage <NUM>, an air connect valve <NUM>, an air tank <NUM>, and an air valve <NUM>.

The collection pump <NUM> applies a pressure to an ink inside the collection flow passage <NUM> and generates a flow in the ink inside the collection flow passage <NUM>. The collection pump <NUM> is, for example, a tube pump. The collection flow passage valve <NUM> is a flow passage opening and closing unit that switches between communication and shutoff between the collection pump <NUM> and the buffer tank <NUM>.

In addition, the ink supply device <NUM> comprises an ink main tank <NUM>, a replenishment flow passage <NUM>, an overflow flow passage <NUM>, and a replenishment pump <NUM>.

The ink main tank <NUM> is an ink storage unit that stores an ink for being supplied to the buffer tank <NUM>. The replenishment flow passage <NUM> makes the ink main tank <NUM> and the buffer tank <NUM> communicate with each other. The overflow flow passage <NUM> makes the buffer tank <NUM> and the ink main tank <NUM> communicate with each other.

The replenishment pump <NUM> applies a pressure to an ink inside the replenishment flow passage <NUM> and generates a flow in the ink inside the replenishment flow passage <NUM>. The replenishment pump <NUM> is, for example, a tube pump. By driving the replenishment pump <NUM>, an ink is replenished from the ink main tank <NUM> to the buffer tank <NUM>. The main tank filter 76A is provided at an end of the replenishment flow passage <NUM> on an ink main tank <NUM> side, and the buffer tank <NUM> is replenished with an ink from which foreign substances are removed by the main tank filter 76A. In addition, in a case of excessive replenishment, the ink returns from the buffer tank <NUM> to the ink main tank <NUM>.

The ink supply device <NUM> further comprises a first safety valve <NUM>, a second safety valve <NUM>, a third safety valve <NUM>, a collection-side filter <NUM>, and a collection-side filter valve <NUM>.

In a case where the internal pressure of the supply flow passage <NUM> rises above a predetermined value, the ink supply device <NUM> operates the first safety valve <NUM> and the second safety valve <NUM> to lower the internal pressure of the supply flow passage <NUM>. In addition, in a case where the internal pressure of the collection flow passage <NUM> rises above a predetermined value, the ink supply device <NUM> operates the third safety valve <NUM> to lower the internal pressure of the collection flow passage <NUM>.

The collection-side filter valve <NUM> is a flow passage opening and closing unit that switches between communication and shutoff between the collection pump <NUM> and the degassing module <NUM>. By bringing the collection-side filter valve <NUM> into an open state, the ink supply device <NUM> can pass an ink, which has passed through the degassing module <NUM>, through the collection-side filter <NUM>.

<FIG> is a block diagram showing a configuration of a control system of the ink supply device <NUM>. As shown in <FIG>, the ink supply device <NUM> comprises a general control unit <NUM>, a valve control unit <NUM>, and a pump control unit <NUM>.

The general control unit <NUM> performs general control of an operation of the ink supply device <NUM> by controlling each of the valve control unit <NUM> and the pump control unit <NUM>. The general control unit <NUM> comprises a processor <NUM> and a memory <NUM>.

The processor <NUM> executes a command stored in the memory <NUM>. A hardware structure of the processor <NUM> includes various types of processors described below. The various types of processors include a central processing unit (CPU) that is a general-purpose processor which executes software (program) and acts as various types of functional units, a graphics processing unit (GPU) that is a processor specialized in image processing, and a dedicated electric circuit or the like that is a processor having a dedicated circuit configuration designed to execute certain processing, such as a programmable logic device (PLD) and an application specific integrated circuit (ASIC) which are processors of which a circuit configuration can be changed after manufacturing a field programmable gate array (FPGA) or the like.

One processing unit may be configured by one of the various types of processors or may be configured by the same type or different types of two or more processors (for example, a plurality of FPGAs, a combination of a CPU and an FPGA, or a combination of a CPU and a GPU). In addition, one processor may configure a plurality of functional units. As an example of configuring a plurality of functional units by one processor, first, there is a form in which one processor is configured by a combination of one or more CPUs and software and the processor acts as the plurality of functional units, as represented by a computer such as a client and a server. Second, there is a form in which a processor that realizes functions of the entire system including a plurality of functional units with one integrated circuit (IC) chip is used, as represented by a system on chip (SoC) or the like. As described above, the various types of functional units are composed of one or more of the various types of processors used as a hardware structure.

Further, the hardware structure of the various types of processors is, more specifically, an electric circuit (circuitry) in which circuit elements such as semiconductor elements are combined.

The memory <NUM> stores a command to be executed by the processor <NUM>. The memory <NUM> includes a random access memory (RAM) (not shown) and a read only memory (ROM) (not shown). The processor <NUM> uses the RAM as a work region, uses various types of programs including a control program of the ink supply device <NUM> stored in the ROM and parameters to execute software, and executes various types of processing of the ink supply device <NUM> by using the parameters stored in the ROM or the like.

The valve control unit <NUM> controls an open state and a closed state of each of the supply valves <NUM>, the collection valves <NUM>, the collection flow passage valve <NUM>, the drain valve <NUM>, the first bypass flow passage valve <NUM>, the second bypass flow passage valve <NUM>, the drain valve <NUM>, and the collection-side filter valve <NUM>. The valve control unit <NUM> may control an open state and an closed state of each of the air connect valve <NUM>, the air valve <NUM>, the air connect valve <NUM>, and the air valve <NUM>.

The pump control unit <NUM> controls an operation of each of the supply pump <NUM>, the collection pump <NUM>, and the replenishment pump <NUM>.

<FIG> is a diagram showing a flow of an ink in a case of a normal operation of the ink supply device <NUM>. As shown in <FIG>, a circulation flow passage <NUM> in which an ink circulates in a case of the normal operation is composed of the supply flow passage <NUM> and the collection flow passage <NUM>. That is, the circulation flow passage <NUM> is a flow passage that connects the buffer tank <NUM>, the degassing module <NUM>, the supply pump <NUM>, the supply-side filter <NUM>, the heat exchanger <NUM>, the supply-side back pressure tank <NUM>, the supply-side head manifold <NUM>, the first bypass flow passage valve <NUM>, the second bypass flow passage valve <NUM>, the supply valves <NUM>, the supply dampers <NUM>, the head modules <NUM>, the collection valves <NUM>, the collection-side head manifold <NUM>, the collection-side back pressure tank <NUM>, the collection pump <NUM>, the collection flow passage valve <NUM>, and the buffer tank <NUM> to each other.

In <FIG>, filled valves are shown to be in a closed state. That is, in a normal operation, the valve control unit <NUM> brings the drain valve <NUM>, the drain valve <NUM>, and the collection-side filter valve <NUM> into a closed state and brings the supply valves <NUM>, the collection valves <NUM>, the collection flow passage valve <NUM>, the first bypass flow passage valve <NUM>, and the second bypass flow passage valve <NUM> into an open state. In addition, in the normal operation, the pump control unit <NUM> rotates the supply pump <NUM> and the collection pump <NUM> in a positive direction. Accordingly, the ink supply device <NUM> circulates an ink between the buffer tank <NUM> and the ink jet bar <NUM> in the circulation flow passage <NUM> as shown by arrows of <FIG>.

That is, an ink that has exited the buffer tank <NUM> first passes through the degassing module <NUM>, and dissolved air in the ink is removed. The ink from which the dissolved air is removed and which has passed through the supply pump <NUM> passes through the supply-side filter <NUM>, and foreign substances in the ink are removed. The ink from which the foreign substances are removed passes through the heat exchanger <NUM>, and a temperature thereof is adjusted. As the ink of which the temperature is adjusted passes through the supply-side back pressure tank <NUM>, fluctuations in the internal pressure of the supply flow passage <NUM> are suppressed. The ink which has passed through the supply-side back pressure tank <NUM> is supplied to the head modules <NUM> via the supply-side head manifold <NUM>.

The ink supplied to the head modules <NUM> may be jetted from the nozzles <NUM> (see <FIG>) as necessary. The ink which has not been jetted from the nozzles <NUM> is collected from the head modules <NUM> to the collection-side head manifold <NUM>.

In addition, a part of the ink which has passed through the supply-side back pressure tank <NUM> is collected from the supply-side head manifold <NUM> to the collection-side head manifold <NUM> via the first bypass flow passage <NUM> and the second bypass flow passage <NUM>.

As the ink collected in the collection-side head manifold <NUM> passes through the collection-side back pressure tank <NUM>, fluctuations in the internal pressure of the collection flow passage <NUM> are suppressed. The ink which has passed through the collection-side back pressure tank <NUM> passes through the collection pump <NUM> and the collection flow passage valve <NUM> and returns to the buffer tank <NUM>.

The ink stored in the buffer tank <NUM> of the ink supply device <NUM> is usually contaminated. This is because foreign substances can join an ink supplied from the ink main tank <NUM>, and sedimentation of pigments occurs while being left inside the buffer tank <NUM> for a long period of time. As shown in <FIG>, as the ink supply device <NUM> passes the ink through the supply-side filter <NUM> in a case of a normal operation, the contaminated ink can be prevented from spreading inside the circulation flow passage <NUM>.

Although the tube pumps are applied as the supply pump <NUM> and the collection pump <NUM> in the present embodiment, other forms of pumps such as diaphragm pumps may be applied. The supply pump <NUM> and the collection pump <NUM> read measurement values of the supply-side pressure sensor <NUM> and the collection-side pressure sensor <NUM> respectively and control rotational speeds through PID control or the like such that the pressures become appropriate.

In addition, although an ink circulates to the inside of the head modules <NUM> in the flow passage in a case of a normal operation in the present embodiment, at least one of the supply valves <NUM> or the collection valves <NUM> may be brought into a closed state, and the ink may circulate through only the supply-side head manifold <NUM> and the collection-side head manifold <NUM>. In addition, the ink may be intermittently circulated instead of being circulated at all times in a case of the normal operation.

<FIG> and <FIG> are diagrams showing a flow of an ink in a maintenance operation according to a first embodiment of the ink supply device <NUM>.

At least in the maintenance operation, the ink supply device <NUM> executes agitating sequences including first processing of generating a positive flow in a first direction in an ink in an agitating flow passage 99A (an example of a first flow passage) including at least a part of the circulation flow passage <NUM> and second processing of generating a negative flow in an opposite direction to the first direction in the ink in the agitating flow passage 99A.

As shown in <FIG> and <FIG>, the agitating flow passage 99A is a flow passage that connects the buffer tank <NUM>, the degassing module <NUM>, the supply pump <NUM>, the supply-side filter <NUM>, the heat exchanger <NUM>, the supply-side back pressure tank <NUM>, the supply-side head manifold <NUM>, the first bypass flow passage <NUM>, the second bypass flow passage <NUM>, the collection-side head manifold <NUM>, the collection-side back pressure tank <NUM>, the collection pump <NUM>, the collection flow passage valve <NUM>, and the buffer tank <NUM> to each other.

In <FIG> and <FIG>, filled valves are shown to be in a closed state. That is, in the maintenance operation, the valve control unit <NUM> brings the supply valves <NUM>, the collection valves <NUM>, the drain valve <NUM>, the drain valve <NUM>, and the collection-side filter valve <NUM> into a closed state and brings the collection flow passage valve <NUM>, the first bypass flow passage valve <NUM>, and the second bypass flow passage valve <NUM> into an open state.

As shown by arrows in <FIG>, a positive flow of first processing is a flow in the first direction in which an ink in the buffer tank <NUM> returns to the buffer tank <NUM> via the degassing module <NUM>, the supply pump <NUM>, the supply-side filter <NUM>, the heat exchanger <NUM>, the supply-side back pressure tank <NUM>, the supply-side head manifold <NUM>, the first bypass flow passage <NUM>, the second bypass flow passage <NUM>, the collection-side head manifold <NUM>, the collection-side back pressure tank <NUM>, the collection pump <NUM>, and the collection flow passage valve <NUM>. In the agitating flow passage 99A, the supply-side filter <NUM> is disposed between the buffer tank <NUM> and the ink jet bar <NUM> in the positive flow. The pump control unit <NUM> rotates the supply pump <NUM> and the collection pump <NUM> in the positive direction in the first processing.

In a case where an ink volume speed of a positive flow is U1 and a flow time is T1, an ink volume (a flow rate of an ink of the positive flow) V1 flowing in a case of the positive flow can be expressed as V1 = U1 × T1. It is desirable that the positive flow is limited to circulation in the supply-side head manifold <NUM> and the collection-side head manifold <NUM> by bringing the supply valves <NUM> and the collection valves <NUM> into a closed state. Accordingly, a probability in which foreign substances generated by a flow of an ink that is different in a case of a normal operation flow into the head modules <NUM> can be reduced. In addition, even in a case where a positive flow is generated at a flow speed that is different in the case of the normal operation, it is easy to control nozzle menisci of the head modules <NUM> so that an appropriate pressure is maintained.

In addition, as shown by arrows in <FIG>, a negative flow of second processing is a flow in the opposite direction to the first direction, in which an ink in the buffer tank <NUM> returns to the buffer tank <NUM> via the collection flow passage valve <NUM>, the collection pump <NUM>, the collection-side back pressure tank <NUM>, the collection-side head manifold <NUM>, the first bypass flow passage <NUM>, the second bypass flow passage <NUM>, the supply-side head manifold <NUM>, the supply-side back pressure tank <NUM>, the heat exchanger <NUM>, the supply-side filter <NUM>, the supply pump <NUM>, and the degassing module <NUM>. In the agitating flow passage 99A, a filter is not disposed between the buffer tank <NUM> and the ink jet bar <NUM> in the negative flow, that is, a filter is not disposed. The pump control unit <NUM> rotates the supply pump <NUM> and the collection pump <NUM> in a negative direction in the second processing.

In a case where an ink volume speed of a negative flow is U2 and a flow time is T2, an ink volume (a flow rate of an ink of the negative flow) V2 flowing in a case of the negative flow can be expressed as V2 = U2 × T2. It is desirable that even the negative flow is limited to circulation in the supply-side head manifold <NUM> and the collection-side head manifold <NUM> by bringing the supply valves <NUM> and the collection valves <NUM> into a closed state.

In a case where a negative flow of an ink is generated as shown in <FIG>, an ink which has not passed through the supply-side filter <NUM> can flow into the inside of the ink jet bar <NUM>. Accordingly, it is preferable that the ink volume V1 flowing in a case of a positive flow and the ink volume V2 flowing in a negative flow satisfy V1 > V2 by the start of the next normal operation. That is, it is preferable that the flow rate of an ink of the positive flow of first processing is higher than the flow rate of an ink of the negative flow of second processing.

A positive flow and a negative flow can be realized by alternately switching between rotation directions of the tube pumps applied to the supply pump <NUM> and the collection pump <NUM>. Since loads on the tube pumps are reduced and an ink flow has inertia, it is desirable to allow a waiting time of approximately one second before changing the direction of the ink flow. However, the waiting time depends on a flow passage design and a pump capacity. Thus, the waiting time cannot be generalized and thereby depends on design.

It is necessary for a negative flow to have a steady flow state for at least a certain period of time. Therefore, it is necessary to reliably secure the time T2 for generating the negative flow, that is equal to or longer than a time during which the negative flow becomes a steady flow. <FIG> are graphs showing time changes of an ink flow speed of the negative flow of a certain flow passage after driving the supply pump <NUM> and the collection pump <NUM> in the negative direction. In <FIG>, the horizontal axis represents time, and the vertical axis represents the ink flow speed.

In the case shown in <FIG>, the ink flow speed gradually increases from a timing T<NUM> when the driving of the supply pump <NUM> and the collection pump <NUM> has started and is the flow speed of a steady flow at the timing TS. In this case, a time until the ink flow becomes a steady flow is TS-T<NUM>, and the time T2 for generating a negative flow is set to satisfy T2 > TS-T<NUM>.

In the case shown in <FIG>, the ink flow speed gradually increases from the timing T<NUM> when the driving of the supply pump <NUM> and the collection pump <NUM> has started, decreases thereafter, and becomes the flow speed of a steady flow at the timing TS. In this case, a time until the ink flow becomes a steady flow is also TS-T<NUM>, and the time T2 for generating a negative flow is set to satisfy T2 > TS-T<NUM>.

Depending on flow passage design, it takes several seconds or more for an ink to become a steady flow after pump driving in some cases. This is because an ink flow path system has a pressure loss component, an inertance component, and an acoustic capacitance component. In particular, only by driving the pump for a short period of time, an ink flow or a pressure attributable to a negative flow is not generated unlike expected in the tube separated from the pump, and moving foreign substances including pigment sediment, which is expected as an effect of the negative flow, is impossible. In the present embodiment, since the negative flow has a steady flow state for at least a certain period of time, pigment sediment and foreign substances can be effectively removed.

<FIG> is a flowchart showing processing of a control method in a case of a maintenance operation of the ink supply device <NUM>. The processor <NUM> reads out the control program of the ink supply device <NUM> from the memory <NUM> and executes the control program. The control program may be provided by being stored in a non-transitory storage medium or may be provided via a network (not shown).

In Step S1, the valve control unit <NUM> controls the supply valves <NUM>, the collection valves <NUM>, the collection flow passage valve <NUM>, the drain valve <NUM>, the first bypass flow passage valve <NUM>, the second bypass flow passage valve <NUM>, the drain valve <NUM>, and the collection-side filter valve <NUM> and determines an ink flow passage.

Herein, as the valve control unit <NUM> brings the supply valves <NUM>, the collection valves <NUM>, the drain valve <NUM>, the drain valve <NUM>, and the collection-side filter valve <NUM> into a closed state and brings the collection flow passage valve <NUM>, the first bypass flow passage valve <NUM>, and the second bypass flow passage valve <NUM> into an open state, the agitating flow passage 99A shown in <FIG> and <FIG> is generated.

Step S2 is processing of generating a positive flow in an ink inside the agitating flow passage 99A before performing agitating sequences. In Step S2, the pump control unit <NUM> controls the supply pump <NUM> and the collection pump <NUM> and generates a positive flow in the ink inside the agitating flow passage 99A. Herein, the pump control unit <NUM> rotates the supply pump <NUM> and the collection pump <NUM> in the positive direction and flows an ink having a volume larger than the volume of the circulation flow passage <NUM>. As described above, it is preferable that the positive flow is generated before starting from a negative flow, which is second processing, and the ink inside the agitating flow passage 99A is replaced with an ink in a fresh state, which has passed through the supply-side filter <NUM>.

In Step S3, the processor <NUM> executes second processing of the agitating sequences. That is, the pump control unit <NUM> controls the supply pump <NUM> and the collection pump <NUM> and generates a negative flow having a steady flow state in the ink inside the agitating flow passage 99A at least for a certain period of time. Herein, the pump control unit <NUM> rotates the supply pump <NUM> and the collection pump <NUM> in the negative direction and flows an ink having the ink volume V2 at the ink volume speed U2.

The ink volume speed U2 is faster than an ink volume speed U0 in a case of a normal operation. Accordingly, pigment sediment and foreign substances in the ink, which are difficult to be removed, can be effectively removed.

In Step S4, the processor <NUM> executes first processing of the agitating sequences. That is, the pump control unit <NUM> controls the supply pump <NUM> and the collection pump <NUM> and generates a positive flow in the ink inside the agitating flow passage 99A. Herein, the pump control unit <NUM> rotates the supply pump <NUM> and the collection pump <NUM> in the positive direction and flows an ink having the ink volume V1 at the ink volume speed U1. Herein, V1 is larger than V2. Accordingly, an ink in the ink jet bar <NUM> can be replaced with an ink in a fresh state, which has passed through the supply-side filter <NUM>.

In addition, the ink volume speed U1 is faster than the ink volume speed U0 in a case of a normal operation. Accordingly, pigment sediment and foreign substances in the ink, which are difficult to be removed, can be effectively removed.

As described above, it is preferable that the processor <NUM> first executes agitating sequences by starting from a negative flow, which is second processing, and then executes a positive flow, which is first processing.

Although the processor <NUM> may perform agitating sequences only once, the processor <NUM> repeatedly executes second processing of Step S3 and first processing of Step S4 a plurality of times in the present embodiment.

As described above, by repeatedly generating a negative flow a plurality of times, a total flow rate of negative flows can be acquired while suppressing the return of a contaminated ink, and a measure against sedimentation of pigments in an ink becomes more effective. In addition, in a case where i and n are natural numbers and agitating sequences are repeated n times, it is preferable that V1(i) > V2(i) is satisfied for each of i = <NUM> to n, assuming that an ink volume of an ink flowing in a case of an ith positive flow is V1(i) and an ink volume of an ink flowing in a case of an ith negative flow is V2(i). The agitating sequences may include processing other than first processing and second processing, such as processing of switching between communication and shutoff of any valve and processing of stopping any pump. That is, the agitating sequences may include at least the first processing and the second processing.

After the agitating sequences end, by flowing, with a positive flow, an ink having a volume larger than the volume of the circulation flow passage <NUM>, it is better to replace the ink inside the agitating flow passage 99A with an ink in a fresh state, which has passed through the supply-side filter <NUM>.

Finally, in Step S5, the valve control unit <NUM> controls the supply valves <NUM>, the collection valves <NUM>, the collection flow passage valve <NUM>, the drain valve <NUM>, the first bypass flow passage valve <NUM>, the second bypass flow passage valve <NUM>, the drain valve <NUM>, and the collection-side filter valve <NUM> and ends the processing of the present flowchart. Herein, the valve control unit <NUM> generates the circulation flow passage <NUM> in a case of the normal operation shown in <FIG> by bringing the drain valve <NUM>, the drain valve <NUM>, and the collection-side filter valve <NUM> into a closed state and bringing the supply valves <NUM>, the collection valves <NUM>, the collection flow passage valve <NUM>, the first bypass flow passage valve <NUM>, and the second bypass flow passage valve <NUM> into an open state. The pump control unit <NUM> may control the supply pump <NUM> and the collection pump <NUM> as necessary.

Sedimentation of pigments included in an ink in a flow passage can be prevented by executing agitating sequences as described above.

<FIG> and <FIG> are diagrams showing a flow of an ink in a maintenance operation according to a second embodiment of the ink supply device <NUM>. At least in the maintenance operation, the ink supply device <NUM> executes agitating sequences including first processing of generating a positive flow in an ink in an agitating flow passage 99B (an example of the first flow passage) including at least a part of the circulation flow passage <NUM> and second processing of generating a negative flow in the ink in the agitating flow passage 99B.

As shown in <FIG> and <FIG>, the agitating flow passage 99B is a flow passage that connects the buffer tank <NUM>, the degassing module <NUM>, the supply pump <NUM>, the supply-side filter <NUM>, the heat exchanger <NUM>, the supply-side back pressure tank <NUM>, the drain valve <NUM>, and the buffer tank <NUM> to each other. As described above, the agitating flow passage 99B does not include the supply-side head manifold <NUM> and the collection-side head manifold <NUM>. In addition, in the agitating flow passage 99B, the drain flow passage <NUM> (an example of a second flow passage) that is shown by a thick line in <FIG> and that connects the supply-side back pressure tank <NUM>, the drain valve <NUM>, and the buffer tank <NUM> to each other is a flow passage that is not used in a case of a normal operation.

In <FIG> and <FIG>, filled valves are shown to be in a closed state. That is, in a maintenance operation, the valve control unit <NUM> brings the supply valves <NUM>, the collection valves <NUM>, the collection flow passage valve <NUM>, the first bypass flow passage valve <NUM>, the second bypass flow passage valve <NUM>, the drain valve <NUM>, and the collection-side filter valve <NUM> into a closed state and brings the drain valve <NUM> into an open state.

As shown by arrows in <FIG>, a positive flow of first processing is a flow in which an ink in the buffer tank <NUM> returns to the buffer tank <NUM> via the degassing module <NUM>, the supply pump <NUM>, the supply-side filter <NUM>, the heat exchanger <NUM>, the supply-side back pressure tank <NUM>, and the drain valve <NUM>. In the agitating flow passage 99B, the supply-side filter <NUM> is disposed between the buffer tank <NUM> and the ink jet bar <NUM> in the positive flow. In the first processing, the pump control unit <NUM> rotates the supply pump <NUM> in the positive direction and flows an ink having the ink volume V1 at the ink volume speed U1.

As shown by arrows in <FIG>, a negative flow of second processing is a flow in which an ink in the buffer tank <NUM> returns to the buffer tank <NUM> via the drain valve <NUM>, the supply-side back pressure tank <NUM>, the heat exchanger <NUM>, the supply-side filter <NUM>, the supply pump <NUM>, and the degassing module <NUM>. In the agitating flow passage 99B, a filter is not disposed between the buffer tank <NUM> and the ink jet bar <NUM> in the negative flow. In the second processing, the pump control unit <NUM> rotates the supply pump <NUM> in the negative direction and flows an ink having the ink volume V2 at the ink volume speed U2. The negative flow has a steady flow state for at least a certain period of time.

As described above, in a negative flow, an ink which has not passed through the filter can be flowed into the inside of the ink jet bar <NUM>. Therefore, as in the first embodiment, it is preferable that the ink volume V1 and the ink volume V2 satisfy a relationship of V1 > V2. In addition, it is desirable that agitating sequences are executed not only once but a plurality of times. Further, it is preferable that the ink volume speed U1 and the ink volume speed U2 satisfy relationships of U1 > U0 and U2 > U0 with respect to the ink volume speed U0 in a case of a normal operation.

In addition, in agitating sequences, an ink flows in the drain flow passage <NUM> where the ink does not flow in a case of a normal operation. Since there is little opportunity in which the ink flows in the case of the normal operation, the drain flow passage <NUM> is in a state where sedimentation of pigments is easy, and the sedimentation of the pigments can be prevented by the agitating sequences.

Herein, it is desirable to replace the ink in the drain flow passage <NUM> that connects the supply-side back pressure tank <NUM> and the buffer tank <NUM> to each other with a fresh ink which has passed through the supply-side filter <NUM>, before executing agitating sequences. For this reason, it is desirable that the positive flow shown in <FIG> is executed for a predetermined time.

In addition, in a case where the volume of the drain flow passage <NUM> that connects the supply-side back pressure tank <NUM> and the buffer tank <NUM> to each other is V3, it is desirable that the ink volume V2 of a negative flow is smaller than the volume V3 of the drain flow passage <NUM>. Accordingly, a probability in which an ink which has not passed through the supply-side filter <NUM> flows in an inappropriate region, such as the inside of the ink jet bar <NUM>, can be lowered.

<FIG> and <FIG> are diagrams showing a flow of an ink in a maintenance operation according to a third embodiment of the ink supply device <NUM>. At least in the maintenance operation, the ink supply device <NUM> executes agitating sequences including first processing of generating a positive flow in an ink in an agitating flow passage 99C (an example of the first flow passage) including at least a part of the circulation flow passage <NUM> and second processing of generating a negative flow in the ink in the agitating flow passage 99C.

As shown in <FIG> and <FIG>, the agitating flow passage 99C is a flow passage that connects the buffer tank <NUM>, the degassing module <NUM>, the collection-side filter valve <NUM>, the collection-side filter <NUM>, the collection pump <NUM>, the collection-side back pressure tank <NUM>, the drain valve <NUM>, and the buffer tank <NUM> to each other. As described above, the agitating flow passage 99C does not include the supply-side head manifold <NUM> and the collection-side head manifold <NUM>. In addition, in the agitating flow passage 99C, the drain flow passage <NUM> (an example of the second flow passage) that is shown by a thick line in <FIG> and that connects the collection-side back pressure tank <NUM>, the drain valve <NUM>, and the buffer tank <NUM> to each other is a flow passage that is not used in a case of a normal operation.

In <FIG> and <FIG>, filled valves are shown to be in a closed state. That is, the valve control unit <NUM> brings the supply valves <NUM>, the collection valves <NUM>, the collection flow passage valve <NUM>, the drain valve <NUM>, the first bypass flow passage valve <NUM>, and the second bypass flow passage valve <NUM> into a closed state and brings the drain valve <NUM> and the collection-side filter valve <NUM> into an open state.

As shown by arrows in <FIG>, a positive flow of first processing is a flow in which an ink in the buffer tank <NUM> returns to the buffer tank <NUM> via the degassing module <NUM>, the collection-side filter valve <NUM>, the collection-side filter <NUM>, the collection pump <NUM>, the collection-side back pressure tank <NUM>, and the drain valve <NUM>. In the agitating flow passage 99C, the collection-side filter <NUM> is disposed between the buffer tank <NUM> and the ink jet bar <NUM> in the positive flow. In the first processing, the pump control unit <NUM> rotates the collection pump <NUM> in the negative direction and flows an ink having the ink volume V1 at the ink volume speed U1.

As shown by arrows in <FIG>, a negative flow of second processing is a flow in which an ink in the buffer tank <NUM> returns to the buffer tank <NUM> via the drain valve <NUM>, the collection-side back pressure tank <NUM>, the collection pump <NUM>, the collection-side filter <NUM>, the collection-side filter valve <NUM>, and the degassing module <NUM>. In the agitating flow passage 99C, a filter is not disposed between the buffer tank <NUM> and the ink jet bar <NUM> in the negative flow. In the second processing, the pump control unit <NUM> rotates the collection pump <NUM> in the positive direction and flows an ink having the ink volume V2 at the ink volume speed U2. The negative flow has a steady flow state for at least a certain period of time.

As described above, in a negative flow, an ink which has not passed through the filter can be flowed into the ink jet bar <NUM>. Therefore, as in the above, it is preferable that the ink volume V1 and the ink volume V2 satisfy the relationship of V1 > V2. In addition, it is desirable that agitating sequences are executed not only once but a plurality of times. Further, it is preferable that the ink volume speed U1 and the ink volume speed U2 satisfy the relationships of U1 > U0 and U2 > U0 with respect to the ink volume speed U0 in a case of a normal operation.

Herein, it is desirable to replace the ink in the drain flow passage <NUM> that connects the collection-side back pressure tank <NUM> and the buffer tank <NUM> to each other with a fresh ink which has passed through the supply-side filter <NUM> before executing agitating sequences. For this reason, it is desirable that the positive flow shown in <FIG> is executed for a predetermined time.

In addition, in a case where the volume of the drain flow passage <NUM> that connects the collection-side back pressure tank <NUM> and the buffer tank <NUM> to each other is V4, it is desirable that the ink volume V2 of a negative flow is smaller than the volume V4 of the drain flow passage <NUM>. Accordingly, a probability in which an ink which has not passed through the collection-side filter <NUM> flows in an inappropriate region can be lowered.

It is desirable to execute the sequences for all tubes configuring a flow passage except for a tube for discarding an ink (not shown), other than a flow passage near the ink jet bar <NUM>. Alternatively, it is desirable to execute the sequences for all tubes configuring a flow passage other than a flow passage near the ink jet bar <NUM> on an upstream side from the buffer tank <NUM>. By doing so, the ink supply device <NUM> can be stably operated without sedimentation of pigments and foreign substances in an ink even in a tube that is not being used.

Although an example in which a filter between the buffer tank <NUM> and the ink jet bar <NUM> in a negative flow of each of the agitating flow passages 99A, 99B, and 99C is not disposed has been described hereinbefore, the filter may be disposed. In this case, foreign substances accumulate on an ink jet bar <NUM> side of the filter in a case of a normal operation. Then, in a case where a negative flow is generated in the filter in a case of a maintenance operation, foreign substances are peeled off from the filter and flow to the ink jet bar <NUM> side. Therefore, there is the same problem in that the contaminated ink flows to the ink jet bar <NUM> side in the negative flow regardless of the presence or absence of disposition of the filter between the buffer tank <NUM> and the ink jet bar <NUM> in the negative flow.

<FIG> and <FIG> are diagrams showing an overall configuration and a flow of an ink in a maintenance operation of an ink supply device <NUM> (an example of a liquid supply device). Portions common to the ink supply device <NUM> shown in <FIG> will be assigned with the same reference numerals, and detailed thereof will be omitted.

An ink jet bar <NUM> has an ink flow passage configuration where an ink does not circulate to the head modules <NUM>. That is, the head module <NUM> comprises the ink supply port 15A and does not comprise the ink discharge port 15B. An ink supplied to the supply-side head manifold <NUM> is supplied to the head modules <NUM> via the supply valves <NUM> and the supply dampers <NUM>.

At least in a maintenance operation, the ink supply device <NUM> executes agitating sequences including first processing of generating a positive flow in an ink in an agitating flow passage 99D (an example of the first flow passage) and second processing of generating a negative flow in the ink in the agitating flow passage 99D.

As shown in <FIG> and <FIG>, the agitating flow passage 99D is a flow passage that connects the buffer tank <NUM>, the degassing module <NUM>, the supply pump <NUM>, the supply-side filter <NUM>, the heat exchanger <NUM>, the supply-side back pressure tank <NUM>, the drain valve <NUM>, and the buffer tank <NUM> to each other. That is, the valve control unit <NUM> brings the drain valve <NUM> into an open state in a case of a maintenance operation.

As shown by arrows in <FIG>, a positive flow of first processing is a flow in which an ink in the buffer tank <NUM> returns to the buffer tank <NUM> via the degassing module <NUM>, the supply pump <NUM>, the supply-side filter <NUM>, the heat exchanger <NUM>, the supply-side back pressure tank <NUM>, and the drain valve <NUM>.

In the agitating flow passage 99D, the supply-side filter <NUM> is disposed between the buffer tank <NUM> and the ink jet bar <NUM> in a positive flow. In the first processing, the pump control unit <NUM> rotates the supply pump <NUM> in the positive direction and flows an ink having the ink volume V1 at the ink volume speed U1.

As shown by arrows in <FIG>, a negative flow of second processing is a flow in which an ink in the buffer tank <NUM> returns to the buffer tank <NUM> via the drain valve <NUM>, the supply-side back pressure tank <NUM>, the heat exchanger <NUM>, the supply-side filter <NUM>, the supply pump <NUM>, and the degassing module <NUM>. In the agitating flow passage 99D, a filter is not disposed between the buffer tank <NUM> and the ink jet bar <NUM> in the negative flow. In the second processing, the pump control unit <NUM> rotates the supply pump <NUM> in the negative direction and flows an ink having the ink volume V2 at the ink volume speed U2. The negative flow has a steady flow state for at least a certain period of time.

As described above, in a negative flow, an ink flows in a steady flow in an opposite direction to a direction in a case of a normal operation, from the supply-side back pressure tank <NUM> to the buffer tank <NUM> via the heat exchanger <NUM>, the supply-side filter <NUM>, the supply pump <NUM>, and the degassing module <NUM>, and an ink which has not passed through the supply-side filter <NUM> can flow into the inside of the ink jet bar <NUM>. Therefore, as in the above, it is preferable that the ink volume V1 and the ink volume V2 satisfy the relationship of V1 > V2. In addition, it is desirable that agitating sequences are executed not only once but a plurality of times. Further, it is preferable that the ink volume speed U1 and the ink volume speed U2 satisfy relationships of U1 > U0 and U2 > U0 with respect to the ink volume speed U0 in a case of the normal operation.

In addition, in agitating sequences, an ink flows in the drain flow passage <NUM> where the ink does not flow in a case of a normal operation. Since there is little opportunity in which the ink flows in the case of the normal operation, the drain flow passage <NUM> is in a state where sedimentation of pigments is easy, and the sedimentation of the pigments can be prevented by the agitating sequences. Also in the case of the normal operation, the ink may circulate as shown in <FIG>.

Herein, it is desirable to replace an ink in the drain flow passage <NUM> that connects the supply-side back pressure tank <NUM> and the buffer tank <NUM> to each other with a fresh ink which has passed through the supply-side filter <NUM>, before executing agitating sequences. For this reason, it is desirable that the positive flow shown in <FIG> is executed for a predetermined time.

<FIG> is an overall configuration diagram of an ink jet printing apparatus <NUM> to which the ink supply device <NUM> is applied. The ink jet printing apparatus <NUM> is a printer that prints an image on web-like paper <NUM> (an example of a printing substrate) in a single-pass method. General-purpose printing paper is used as the paper <NUM>. The general-purpose printing paper is not a so-called ink jet dedicated paper and refers to paper mainly made of cellulose, such as coated paper used in general offset printing or the like.

As shown in <FIG>, the ink jet printing apparatus <NUM> is composed of a transporting unit <NUM>, a feeding unit <NUM>, a pretreatment liquid coating unit <NUM>, a printing unit <NUM>, a drying unit <NUM>, and a winding unit <NUM>.

The transporting unit <NUM> transports the paper <NUM> along a transport path from the feeding unit <NUM> to the winding unit <NUM>. The transporting unit <NUM> comprises a plurality of pass rollers <NUM> that function as guide rollers.

The feeding unit <NUM> comprises a feeding roll <NUM>. The feeding roll <NUM> comprises a reel (not shown) that is rotatably supported. The paper <NUM> on which an image is yet to be printed is wound around the reel in a roll shape.

On the other hand, the winding unit <NUM> comprises a winding roll <NUM>. The winding roll <NUM> comprises a reel (not shown) rotatably supported. One end of the paper <NUM> is connected to the reel. The winding roll <NUM> comprises a winding motor (not shown) that rotationally-drives the reel.

The transporting unit <NUM> transports the paper <NUM> on the transport path from the feeding roll <NUM> to the winding roll <NUM> in a roll-to-roll method. As described above, the transporting unit <NUM> functions as a moving mechanism that relatively moves the printing unit <NUM> and the paper <NUM>.

The pretreatment liquid coating unit <NUM> is disposed on an upstream side of the printing unit <NUM> in the transport path. The pretreatment liquid coating unit <NUM> coats a printing surface of the paper <NUM> with a pretreatment liquid. The pretreatment liquid is a liquid that contains a component, which coagulates, insolubilizes, or thickens a coloring material component in an aqueous ink, and thickens by reacting with the aqueous ink.

The pretreatment liquid coating unit <NUM> comprises a coating roller <NUM>, an opposing roller <NUM>, and a pretreatment liquid drying unit <NUM>. The paper <NUM> transported from the feeding unit <NUM> is guided by the pass rollers <NUM> and is transported to a position opposing the coating roller <NUM>.

The coating roller <NUM> is rotated by a motor (not shown). A pretreatment liquid is supplied from a coater (not shown) to the surface of the coating roller <NUM>, and after then, an excess pretreatment liquid is scraped off by a blade (not shown). The paper <NUM> is nipped between the coating roller <NUM> and the opposing roller <NUM>, the surface of the coating roller <NUM>, to which the pretreatment liquid is supplied, touches the printing surface of the paper <NUM>, and the pretreatment liquid supplied to the surface is coated with the printing surface of the paper <NUM>.

A method of coating the printing surface of the paper <NUM> with a pretreatment liquid is not limited to a method using the coating roller <NUM> and may be, for example, a method of using a liquid jetting head.

The paper <NUM> coated with a pretreatment liquid is transported to the pretreatment liquid drying unit <NUM>. The pretreatment liquid drying unit <NUM> comprises a hot air heater (not shown). The pretreatment liquid drying unit <NUM> blows hot air from the hot air heater toward the printing surface of the paper <NUM> and dries the pretreatment liquid.

The paper <NUM> on which the pretreatment liquid is dried is guided by the pass rollers <NUM> and is transported to the printing unit <NUM>.

The printing unit <NUM> prints an image on the printing surface of the paper <NUM>. The printing unit <NUM> comprises a printing drum <NUM>, ink jet bars <NUM>, 14C, <NUM>, 14Y, and 14W, ink supply devices <NUM>, 10C, <NUM>, 10Y, and 10W, and a scanner <NUM>.

The paper <NUM> transported from the pretreatment liquid coating unit <NUM> is guided by the plurality of pass rollers <NUM> and is transported to the printing drum <NUM>.

The printing drum <NUM> is rotated by a motor (not shown) and holds and transports, on an outer peripheral surface thereof, the paper <NUM>. The printing drum <NUM> has a plurality of adsorption holes (not shown) in the outer peripheral surface. The printing drum <NUM> adsorbs the paper <NUM> with the outer peripheral surface by sucking through the adsorption holes with a pump (not shown).

The paper <NUM> transported by the printing drum <NUM> is transported to a position opposing the ink jet bars <NUM>, 14C, <NUM>, 14Y, and 14W.

The ink jet bar <NUM> shown in <FIG> can be applied to each of the ink jet bars <NUM>, 14C, <NUM>, 14Y, and 14W. The ink jet bars <NUM>, 14C, <NUM>, 14Y, and 14W jet black (K), cyan (C), magenta (M), yellow (Y), and white (W) aqueous inks, respectively. The aqueous ink refers to an ink obtained by dissolving or dispersing a coloring material such as a dye and a pigment in water and a solvent soluble in water. An aqueous white ink contains a titanium oxide material as a pigment, and an average particle diameter (an example of a diameter of a dispersed particle) of the titanium oxide material exceeds <NUM>. The average particle diameter is a particle diameter at an integrated value of <NUM>% in a particle size distribution acquired through a laser diffraction/scattering method.

Each of the ink jet bars <NUM>, 14C, <NUM>, 14Y, and 14W is composed of a line type recording head that can perform printing on the paper <NUM> transported by the printing drum <NUM> with one time of scanning. The ink jet bars <NUM>, 14C, <NUM>, 14Y, and 14W are configured by connecting the plurality of head modules <NUM> to each other in an X-direction. A nozzle surface of each of the ink jet bars <NUM>, 14C, <NUM>, 14Y, and 14W is disposed to oppose the printing drum <NUM>. The ink jet bars <NUM>, 14C, <NUM>, 14Y, and 14W are disposed at regular intervals along the transport path.

The ink supply device <NUM> shown in <FIG> can be applied to each of the ink supply devices <NUM>, 10C, <NUM>, 10Y, and 10W. The ink supply devices <NUM>, 10C, <NUM>, 10Y, and 10W supply aqueous inks of corresponding colors to the ink jet bars <NUM>, 14C, <NUM>, 14Y, and 14W, respectively.

The scanner <NUM> includes an image pick-up device that picks up an image printed on the printing surface of the paper <NUM> and that converts into an electrical signal. A color charge coupled device (CCD) linear image sensor can be used as the image pick-up device. Instead of the color CCD linear image sensor, a color complementary metal oxide semiconductor (CMOS) linear image sensor can be used.

In the printing unit <NUM>, aqueous ink droplets are jetted from at least one of the ink jet bars <NUM>, 14C, <NUM>, 14Y, and 14W toward the printing surface of the paper <NUM> transported by the printing drum <NUM>. As the jetted aqueous ink droplets adhere to the paper <NUM>, an image is printed on the printing surface of the paper <NUM>.

In addition, as the printing surface of the paper <NUM> transported by the printing drum <NUM> is read by the scanner <NUM>, a reading result is acquired.

The drying unit <NUM> dries an ink on the printing surface of the paper <NUM>. The drying unit <NUM> comprises a drying drum <NUM>.

The paper <NUM> transported from the printing unit <NUM> is transported to the drying drum <NUM>. The drying drum <NUM> is rotated by a motor (not shown) and holds and transports, on an outer peripheral surface thereof, the paper <NUM>. The drying drum <NUM> has a plurality of adsorption holes (not shown) in the outer peripheral surface. The drying drum <NUM> adsorbs the paper <NUM> with the outer peripheral surface by sucking through the adsorption holes with a pump (not shown).

The drying unit <NUM> comprises a hot air heater (not shown) around the drying drum <NUM>. The drying unit <NUM> blows hot air from the hot air heater toward the printing surface of the paper <NUM> and dries an ink.

Each of the ink jet bars <NUM>, 14C, <NUM>, 14Y, and 14W has a structure where the head module <NUM> are connected to each other in the X-direction. <FIG> is a perspective plan view showing a structural example of the head module <NUM>, and <FIG> is a cross-sectional view taken along line <NUM>-<NUM> of <FIG>.

The head module <NUM> includes a nozzle plate <NUM> in which the nozzle <NUM>, which is an outlet of ink droplets, is formed and a flow passage plate <NUM> in which an ink flow passage is formed. The nozzle plate <NUM> and the flow passage plate <NUM> are laminated and joined. The flow passage plate <NUM> has a structure where one or a plurality of plates of substrates are laminated. The nozzle plate <NUM> and the flow passage plate <NUM> can be processed into a required shape through a semiconductor manufacturing process with silicon as a material.

The head module <NUM> comprises the plurality of nozzles <NUM> in a nozzle surface <NUM>, which is a bottom surface. In addition, each of a plurality of ink chamber units <NUM>, which consists of a pressure chamber <NUM> or the like provided to correspond to each nozzle <NUM>, is two-dimensionally disposed in a regular arrangement pattern. Accordingly, a substantially high density of nozzle intervals that are projected to be aligned along the X-direction is achieved.

The pressure chamber <NUM> communicates with a supply tributary <NUM> via a supply throttle <NUM>, and each supply tributary <NUM> communicates with a common flow passage <NUM>. In addition, a descender <NUM> that communicates with each pressure chamber <NUM> communicates with a circulation common flow passage <NUM> via an ink circulation path <NUM> and a collection tributary <NUM>. The head module <NUM> is provided with the ink supply port 15A and the ink discharge port 15B, the ink supply port 15A communicates with the common flow passage <NUM>, and the ink discharge port 15B communicates with the circulation common flow passage <NUM>.

As described above, the ink supply port 15A and the ink discharge port 15B of the head module <NUM> are configured to communicate with each other via the common flow passage <NUM>, the supply tributary <NUM>, the supply throttle <NUM>, the pressure chamber <NUM>, the descender <NUM>, the ink circulation path <NUM>, the collection tributary <NUM>, and the circulation common flow passage <NUM>.

Therefore, an ink supplied to the ink supply port 15A flows in the common flow passage <NUM>, the supply tributary <NUM>, the supply throttle <NUM>, the pressure chamber <NUM>, and the descender <NUM>, some of the ink is jetted from each of the nozzles <NUM>, the remaining ink is discharged from the ink discharge port 15B via the ink circulation path <NUM>, the collection tributary <NUM>, and the circulation common flow passage <NUM>.

It is preferable that the ink circulation path <NUM> is configured to be provided near the nozzle <NUM>. Herein, the ink circulation path <NUM> is provided in a region communicating with the descender <NUM>, that is, the region of the flow passage plate <NUM>, which is in contact with the nozzle plate <NUM>. Accordingly, since an ink circulates in the vicinity of the nozzle <NUM>, the ink in the nozzle <NUM> is prevented from being thickened, and stable jetting becomes possible.

In addition, an actuator <NUM> that comprises an individual electrode (not shown) is joined to a vibration plate <NUM> that configures a top surface of the pressure chamber <NUM> and that serves as a common electrode. In a case where a predetermined voltage is applied to the individual electrode, the actuator <NUM> deforms in a direction in which the pressure chamber <NUM> is contracted. Accordingly, an ink is jetted from the nozzle <NUM>. After then, the actuator <NUM> deforms in a direction in which the pressure chamber <NUM> is expanded. Accordingly, a new ink is supplied from the common flow passage <NUM> to the pressure chamber <NUM> through the supply tributary <NUM> and the supply throttle <NUM>.

Herein, although the actuator <NUM> is applied as a jetting force generating unit that jets an ink from the nozzle <NUM>, it is also possible to apply a thermal method in which a heater is included in the pressure chamber <NUM> and the ink is jetted using a film boiling pressure caused by heating of the heater.

A disposition structure of the nozzle <NUM> is not limited to the shown example, and various nozzle disposition structures, such as a disposition structure having one nozzle row in the X-direction, can be applied.

<FIG> is a block diagram showing a configuration of a control system of the ink jet printing apparatus <NUM>. The ink jet printing apparatus <NUM> comprises a transport control unit <NUM>, a pretreatment liquid coating control unit <NUM>, a printing control unit <NUM>, a drying control unit <NUM>, a general control unit <NUM>, and a user interface <NUM>.

As the transport control unit <NUM> rotationally-drives the winding roll <NUM> with a motor (not shown), the paper <NUM> is unwound from the feeding roll <NUM>. The transporting unit <NUM> guides the paper <NUM> with the plurality of pass rollers <NUM>, and the winding unit <NUM> winds the printed paper <NUM> around the winding roll <NUM>. Accordingly, the paper <NUM> is transported through the feeding unit <NUM>, the pretreatment liquid coating unit <NUM>, the printing unit <NUM>, the drying unit <NUM>, and the winding unit <NUM>.

The transport control unit <NUM> controls a pump (not shown) so that the paper <NUM> is adsorbed to the outer peripheral surface of the printing drum <NUM>. The transport control unit <NUM> rotates the printing drum <NUM> with a motor (not shown). In addition, the transport control unit <NUM> acquires a rotary encoder value from a rotary encoder (not shown) disposed at the printing drum <NUM>.

The transport control unit <NUM> controls the pump (not shown) so that the paper <NUM> is adsorbed to the outer peripheral surface of the drying drum <NUM>. The transport control unit <NUM> rotates the drying drum <NUM> with a motor (not shown).

The pretreatment liquid coating control unit <NUM> causes the coating roller <NUM> to coat the printing surface of the paper <NUM> with a pretreatment liquid. In addition, the pretreatment liquid coating control unit <NUM> causes the hot air heater (not shown) of the pretreatment liquid drying unit <NUM> to dry the pretreatment liquid which coats the printing surface of the paper <NUM>.

The printing control unit <NUM> includes the valve control unit <NUM> and the pump control unit <NUM> and performs general control of an operation of the ink supply device <NUM>.

The printing control unit <NUM> controls jetting of inks by the ink jet bars <NUM>, 14C, <NUM>, 14Y, and 14W based on printing data. The printing control unit <NUM> synchronizes a rotary encoder value acquired via the transport control unit <NUM> and causes the ink jet bars <NUM>, 14C, <NUM>, 14Y, and 14W to jet black, cyan, magenta, yellow, and white ink droplets, respectively, toward the paper <NUM>. Accordingly, a color image is printed on the printing surface of the paper <NUM>, and the paper <NUM> becomes a "printed material".

The general control unit <NUM> causes the ink supply device <NUM> to perform a normal operation during printing in which an image is printed on the paper <NUM> by the ink jet bars <NUM>, 14C, <NUM>, 14Y, and 14W and causes the ink supply device <NUM> to perform a maintenance operation during non-printing other than during printing.

In addition, it is desirable that the general control unit <NUM> executes agitating sequences of the ink supply devices <NUM>, 10C, <NUM>, 10Y, and 10W in a start-up process in a case of starting of the ink jet printing apparatus <NUM>. In addition, it is desirable that the general control unit <NUM> executes the agitating sequences of the ink supply devices <NUM>, 10C, <NUM>, 10Y, and 10W periodically, for example, every three hours, after power supply shutoff of the ink jet printing apparatus <NUM>.

Herein, although the ink supply device <NUM> is applied for each of black, cyan, magenta, yellow, and white aqueous inks, in particular, it is important to apply the ink supply device <NUM> for an aqueous white ink. The aqueous white ink contains a titanium oxide material having an average particle diameter of larger than <NUM>, and sedimentation of the titanium oxide material is likely to occur. Therefore, by applying the ink supply device <NUM> for the aqueous white ink, sedimentation of the contaminated aqueous white ink can be effectively prevented without adversely affecting jetting.

In addition, the printing control unit <NUM> synchronizes a rotary encoder value acquired via the transport control unit <NUM>, reads an image printed on the paper <NUM> with the scanner <NUM>, and acquires a reading result.

The ink jet printing apparatus <NUM> may acquire information of a location of the nozzle <NUM> having a jetting defect by forming a detection pattern with the printing control unit <NUM> and analyzing a reading result read with the scanner <NUM>. The printing control unit <NUM> may output the information of the location of the nozzle <NUM> having a jetting defect to the general control unit <NUM>.

In addition, the printing control unit <NUM> may have a compensation function of correcting printing data to compensate for a print region of the nozzle <NUM> having a jetting defect. For example, there is a compensation function of compensating for the nozzle <NUM> having a jetting defect by increasing the volume of ink droplets of the plurality of adjacent nozzles <NUM>. The printing control unit <NUM> outputs information of a location of the printed material, which is compensated through the compensation function, to the general control unit <NUM>.

The drying control unit <NUM> controls heating by the hot air heater (not shown) to dry the paper <NUM> with the drying unit <NUM>.

The general control unit <NUM> controls each of the transport control unit <NUM>, the pretreatment liquid coating control unit <NUM>, the printing control unit <NUM>, and the drying control unit <NUM> to perform general control of an operation of the ink jet printing apparatus <NUM>. The general control unit <NUM> comprises a processor <NUM> and a memory <NUM>. The general control unit <NUM> includes the general control unit <NUM> (see <FIG>). The processor <NUM> may be the processor <NUM>. The memory <NUM> may be the memory <NUM>.

The user interface <NUM> comprises an input unit (not shown) for a user to operate the ink jet printing apparatus <NUM> and a display unit (not shown) for the user to present information. The input unit is, for example, an operation panel that receives an input from the user. The display unit is, for example, a display that displays image data and various types of information. The user can cause the ink jet printing apparatus <NUM> to print a desired image by using the user interface <NUM>.

Claim 1:
A liquid supply device comprising:
a circulation flow passage (<NUM>) through which a liquid is supplied from a liquid tank (<NUM>) storing the liquid to a liquid jetting head (<NUM>) via a supply flow passage (<NUM>) and the liquid is collected from the liquid jetting head (<NUM>) to the liquid tank (<NUM>);
a pump (<NUM>,<NUM>,<NUM>) that is provided at the circulation flow passage (<NUM>) and that generates a flow in the liquid in the circulation flow passage (<NUM>);
a memory (<NUM>) that stores a command which is executed by a processor; and
the processor (<NUM>) that executes the command stored in the memory (<NUM>),
wherein the processor (<NUM>) is configured, in a maintenance operation, to execute, by controlling the pump (<NUM>,<NUM>,<NUM>), a sequence that includes first processing of generating (s2) a positive flow in a first direction in the liquid in a first flow passage (99A-99D) including at least a part of the supply flow passage (<NUM>) and a further flow passage to the liquid tank (<NUM>), and second processing of generating (s3) a negative flow in an opposite direction to the first direction in the liquid in the first flow passage (99A-99D),
in the first flow passage (99A-99D), a filter that removes a foreign substance in the liquid is disposed in the supply flow passage (<NUM>) between the liquid tank (<NUM>) and the liquid jetting head (<NUM>) in the positive flow,
a flow rate of the liquid of the positive flow is higher than a flow rate of the liquid of the negative flow, and
the negative flow has a steady flow state.