JP6318641B2 - Droplet discharge device, degassing method, nozzle cleaning method, and image forming apparatus - Google Patents

Description

  The present invention relates to a droplet discharge device that discharges ink and other liquids, a degassing method from a liquid, a nozzle cleaning method, and an image forming apparatus.

In an image forming apparatus such as a printer that performs recording using an ink jet type droplet discharge device, if the discharge head (ink jet head) is clogged, ink is not discharged from the nozzles in the discharge head and the image is recorded correctly. Can not do.
As a cause of clogging of the discharge head, it is known that bubbles are mixed in the ink and that the solid component of the ink is fixed to the nozzle portion.
When bubbles are mixed in the ink, the nozzles are clogged and the ejection of ink is hindered.

In addition, when ink that easily separates the solid component is used, if the ink in the flow path for supplying ink to the discharge head does not flow continuously, the solid component in the ink precipitates and closes the nozzle, and the ink is discharged. Be disturbed.
Furthermore, when the ink in the nozzles is dried, solid components in the ink block the nozzles, thereby preventing ink ejection.
As a means for removing bubbles in the ink, a deaeration device using a gas permeable member disclosed in an ink jet device disclosed in Patent Document 1 (Patent No. 5209431) is used.
This deaeration device has a structure in which an ink chamber and a gas chamber are separated by a member that transmits gas disposed in the deaeration chamber. When ink is flowed into the ink chamber and the gas chamber is depressurized, the gas dissolved in the ink in the ink chamber moves to the gas chamber via a member that allows the gas to pass through, and the inside of the ink is deaerated.

By the way, when ink is deaerated using a deaeration device using a gas-permeable member, if the gas chamber is decompressed in a state where ink does not sufficiently flow into the deaeration device, the ink in the ink chamber is excessive. Will be decompressed. In this case, the solvent constituting the ink moves to the gas chamber, and the ink concentration in the ink chamber increases. As a result, the viscosity of the ink rises and discharge failure occurs at the discharge head. For this reason, when deaeration is performed using a deaeration device, it is necessary to keep ink flowing at a certain flow rate through the deaeration device. As one of the methods, Patent Document 1 discloses a method of continuously supplying a constant flow of ink to a deaeration device using a pump.
According to this, since the ink always circulates in the ink flow path around the ejection head, it is possible to prevent the solid component in the ink from being precipitated at the same time.

Next, a technique of Patent Document 2 is known as a technique of flowing a cleaning liquid through an ejection head in order to remove a solid component of ink that has adhered and remained on a nozzle portion.
The ink jet device disclosed in Patent Document 2 is configured to allow the cleaning liquid to flow through the flow path in the head at a high pressure, so that the ink component solidified at the nozzle portion can be washed away.
A configuration in which a deaeration device is attached in the middle of a flow path for returning ink from the sub tank to the main tank by a pump by improving the configuration of the ink jet device disclosed in Patent Document 2 is also conceivable. However, since the ink tank disposed between the deaeration device and the head is in contact with the air, the air dissolves in the ink in the ink tank. For this reason, it is difficult to prevent the occurrence of clogging of the head due to air bubbles by the ink jet apparatus of Patent Document 2.

Further, in the configuration in which the liquid is moved by a pump as in the ink jet apparatus disclosed in Patent Document 1, the cleaning liquid is pushed out with sufficient pressure as compared with the case where the liquid is pressurized and moved by air pressure as in Patent Document 2. The solid component of the ink fixed to the nozzle cannot be sufficiently removed.
Moreover, many pumps for moving liquid have a mechanism for clogging the liquid. Therefore, when trying to pass the pressurized liquid through the pump, it interferes with a mechanism for blocking the liquid in the pump, and the pump may be damaged.
As described above, in the conventional technology, it is difficult to achieve both a configuration in which ink is circulated and degassed using a pump and a configuration in which the inside of the head is cleaned by pressurizing and ejecting the cleaning liquid with air pressure. .

  The present invention has been made in view of the above problems, and a mechanism for preventing clogging of nozzles due to bubbles in liquid such as ink and precipitation of solid components, and a mechanism for eliminating nozzle clogging due to drying of liquids A droplet discharge device, a deaeration method, a nozzle cleaning method, and an image forming apparatus.

  In order to achieve the above object, a droplet discharge device of the present invention includes a droplet discharge unit having a nozzle for discharging a droplet, a first path for supplying liquid to the droplet discharge unit, and a second channel. And a first liquid supply unit that supplies the first liquid to the droplet discharge unit via the first path, and a first switching valve connected to the first path. And a third path that is connected to the second path via a second switching valve and bypasses the droplet discharge section, and a liquid circulation means disposed on the third path, A second liquid is supplied to the droplet discharge section via the first path or the second path, a fourth path connected via a third switching valve, and the fourth path. A second liquid supply section, and the liquid in the first path or the second path is discharged into the droplet discharge section. It said first path to flow, or characterized in that it and a path switching means disposed on said second path.

According to the present invention, the foreign matter removing means such as a filter is disposed in the circulation path for circulating the liquid in the droplet discharge section and the flow path around the droplet discharge section, so that the precipitate generated in the liquid during the circulation. It is possible to prevent clogging of the nozzle due to objects. In addition, since the droplet discharge portion can be cleaned with the cleaning liquid, the solid component of the liquid fixed to the nozzle portion can be removed, and clogging of the nozzle can be eliminated.
That is, it is possible to provide a droplet discharge device that has both a mechanism for preventing clogging of nozzles due to bubbles in liquid and precipitation of solid components, and a mechanism for eliminating nozzle clogging due to drying of liquids.

1 is a schematic diagram illustrating a configuration of a droplet discharge device according to a first embodiment of the present invention. It is a flowchart which shows the procedure of the ink discharge in a printing process, circulation, and deaeration. It is a flowchart which shows a washing | cleaning process. It is the figure which showed the deformation | transformation embodiment about the path | route which sends a washing | cleaning liquid to a head. It is a schematic block diagram which shows 2nd Embodiment of the droplet discharge apparatus of this invention. It is a schematic block diagram which shows 3rd Embodiment of the droplet discharge apparatus of this invention. It is a perspective explanatory view of an ink jet recording apparatus using the droplet discharge device of the present invention. It is side explanatory drawing of the mechanism part of the inkjet recording device using the droplet discharge apparatus of this invention.

Hereinafter, the present invention will be described in detail with reference to embodiments shown in the drawings.
First Embodiment
FIG. 1 is a schematic diagram showing a configuration of a droplet discharge device (inkjet device) according to a first embodiment of the present invention.
The droplet discharge device 1 supplies nozzles 3 for discharging droplets of ink and the like, a head (droplet discharge unit) 2 having a discharge mechanism, and liquids (first liquid and second liquid) to the head 2. A first ink supply path (first path) 100 for supplying the liquid, and a second ink supply path (second path) for supplying the liquid (first liquid, second liquid) to the head 2 110, a first liquid supply unit 20 including an ink tank (first liquid storage unit) 21 that supplies ink (first liquid) 22 to the head 2 via the first ink supply path 100, The head 2 is connected to the first ink supply path 100 and the second ink supply path 110 via a valve A (first switching valve 101) and a valve B (second switching valve 111), respectively. Detour circulation path (third path) 120 and circulation path Degassing device 121 (degassing means 121a + vacuum generating device (pump) 121b) and liquid circulating means (pump) 122 arranged on 20 and first ink supply path 100 or second ink supply path 110 A cleaning liquid supply path (fourth path) 130 connected to the head via the valve C (third switching valve 102) and a cleaning liquid for supplying the cleaning liquid 42 (second liquid) to the head via the cleaning liquid supply path 130 In order to flow the liquid in the second liquid supply unit 40 provided with the tank 41 and the first ink supply path 100 or the second ink supply path 110 to the head, the first ink supply path 100 or the second ink supply path 100 is used. And a valve D (path opening / closing means 112) installed on the ink supply path 110.
The head (droplet discharge unit) 2 includes a plurality of fine nozzles 3 that discharge ink (first liquid) 22 on the tip surface, and a liquid chamber (not shown) that communicates with the nozzles and holds ink therein. It has. In addition, a first supply port 5 and a second supply port 6 for taking ink and cleaning liquid into and out of the liquid chamber are respectively arranged at different portions of the head 2. The first supply port 5 is connected to one end of the first ink supply path 100, and the second supply port 6 is connected to one end of the second ink supply path 110.

As a method for ejecting ink as droplets from the nozzle 3 (droplet ejection mechanism), there are a method in which ink is heated and pushed out, a method in which ink is pushed out by applying a voltage to a piezo element arranged inside the head, and the like. Can be mentioned.
Printing can be performed on a print target by relatively moving the head and the print target using a moving unit (not shown) while ejecting ink to the print target (not shown). Examples of the print target include sheet-like materials such as paper.
The liquid protruding from the droplet discharge device 1 is not limited to ink but includes liquid used for various purposes other than printing and image formation.
Examples of the moving means (not shown) include a moving stage that moves the printing object in the front-rear and left-right directions by motor control.

One end of the first ink supply path (first path) 100 is connected to the first supply port 5 of the head, and the other end communicates with the ink 22 in the ink tank 21, and the three flow paths r1 and r2 are connected. , R3.
The cleaning liquid supply path (fourth path) 130 includes a flow path r4 having one end connected to the valve C and the other end communicating with the cleaning liquid 42 in the cleaning liquid tank 41.
The valve A (first switching valve 101), the valve B (second switching valve 111), and the valve C (third switching valve 102) are connected in communication with three paths, respectively. It has a function of conducting (communication) any two of them simultaneously. That is, the valve A is disposed in the middle of the first ink supply path 100 and is connected to one end of the circulation path 120. The valve B is disposed in the middle of the second ink supply path 110 and is connected to the other end of the circulation path 120. The valve C is disposed in the middle of the first ink supply path 100 closer to the ink tank 21 than the valve A, and is connected to one end (downstream end) of the cleaning liquid supply path 130.
The valve D (path opening / closing means 112) is disposed in the middle of the second ink supply path 110 closer to the waste liquid tank 50 than the valve B, and opens and closes the second ink supply path 110 to communicate with the atmosphere. Has a function of connecting and disconnecting (blocking, connecting).
As a method of switching the connection pattern (opening / closing pattern) between paths by the valve A, the valve B, the valve C, and the valve D, there are a manual method, a pneumatic method, and an electromagnetic method. However, when these are controlled by a control circuit (not shown), an electromagnetic type is desirable.

Next, the ink tank 21 and its peripheral part (first liquid supply part 20) will be described.
The ink tank 21 is a container that stores ink discharged from the nozzles of the head 2.
A first pressurization device (first pressurization means) 23 and a decompression device (decompression means) 24 communicate with the gas phase at the upper part in the ink tank.
Also, one end (opening) of the first ink supply path 100 enters the ink tank and reaches the lower part thereof, and is arranged to communicate with the ink 22 inside the ink tank.
The first ink supply path 100 is connected from the ink tank 21 to the first supply port 5 through the valve C and the valve A.

The first pressurizing device 23 is a pneumatic pressurizing device that sends out compressed air, and is arbitrarily controlled to be driven and stopped in response to a control signal from a control circuit (not shown).
An example of the first pressurizing device 23 is a configuration in which a compressor and a solenoid valve that opens and closes a path for sending out compressed air generated by the compressor are combined.
When the first pressure device 23 is driven, the gas phase in the sealed ink tank is pressurized, and the ink is pushed out in the direction of the first ink supply path 100.

The decompression device 24 is a device that decompresses air, and is driven, stopped, and the amount of decompression is controlled by a control circuit (not shown). The decompression device 24 generates a pressure difference between the first liquid supply unit and the second ink supply path 110 to recover the ink (first liquid) from the head to the first liquid supply unit 20. 1 liquid recovery mechanism.
The decompression device 24 may be configured by combining a vacuum pump and an adjustment device that regulates the amount of decompression by limiting the flow rate of air flowing through a path connected to the vacuum pump.
When the decompression device 24 is driven to decompress the gas phase in the ink tank, the ink in the first ink supply path 100 is drawn back to the ink tank 21 side.

In the droplet discharge device 1, when the ink pressure in the head 2 is greater than atmospheric pressure, ink leaks unintentionally from the nozzle 3. In order to prevent this, it is effective to drive the decompression device 24. By depressurizing the gas phase in the sealed ink tank, the ink in the ink tank is depressurized. Thereby, a negative pressure is supplied into the liquid chamber of the head through the first ink supply path 100, and the ink in the head can be decompressed. For this reason, the pressure of the ink in the head can be maintained at an appropriate negative pressure.
Further, by increasing the amount of pressure generated by the pressure reducing device, the ink in the head can be collected in the ink tank through the first ink supply path 100.

Next, the configuration of the cleaning liquid tank 41 and its peripheral part (second liquid supply part 40) will be described.
The cleaning liquid tank 41 is a sealed container that stores the cleaning liquid 42 for cleaning the head 2 and its peripheral paths 100 and 110. A second pressurizing device (second pressurizing means) 43 communicates with the gas phase at the upper part in the cleaning liquid tank 41.
Further, the end (opening) of the cleaning liquid supply path 130 enters the cleaning liquid tank and extends to the lower part thereof, and is arranged to communicate with the cleaning liquid inside the cleaning liquid tank.
The cleaning liquid supply path 130 is connected to the valve C from the cleaning liquid tank 41.
The internal configuration of the second pressure device 43 is the same as that of the first pressure device 23.
When the second pressurizing device 43 is driven, the gas phase in the cleaning liquid tank is pressurized, and the cleaning liquid is pushed out toward the cleaning liquid supply path 130.

Next, the configuration of the waste liquid tank 50 and its periphery will be described.
The waste liquid tank 50 is a container for discharging a part of the cleaning liquid 42 that has cleaned the liquid chamber of the head. The liquid discharged from the head to the second ink supply path 110 is received by the waste liquid tank 50.
The waste liquid in the waste liquid tank is not in contact with the end of the second ink supply path 110, and the end of the second ink supply path 110 on the waste liquid tank side is in contact with the atmosphere.
Thereby, when the pressure reducing device 24 on the ink tank side is driven, the air can be sucked into the head 2 from the second ink supply path 110.
The waste liquid tank 50 is used for cleaning the head peripheral path in a cleaning process described later. However, as will be described later, the operation of cleaning the head peripheral path is not an essential operation for removing the solid component of the ink fixed to the nozzle. Therefore, the waste liquid tank is not an essential component in the present invention.

Next, the circulation path 120 that circulates the liquid through the path avoiding the head will be described.
The circulation path 120 has one end connected to the valve A and the other end connected to the valve B. A deaerator 121a, a pump 122, and a filter 123 are disposed on the circulation channel.
The deaeration device 121a is a device that removes dissolved gas in the ink. The inside of the deaeration device is divided into an ink chamber 121a-1 and a gas chamber 121a-2. The ink chamber and the gas chamber are partitioned by a member 121a-3 that allows the gas to pass through without passing the liquid. When ink is flowed into the ink chamber 121a-1 and the gas chamber 121a-2 is depressurized, the gas dissolved in the ink in the ink chamber moves to the gas chamber via the gas-permeable member 121a-3, and passes through the ink. I can degas. A hollow fiber membrane is mentioned as a member which permeate | transmits gas without letting a liquid pass.

In addition, as a deaeration device, a material having a property of allowing ink to pass, for example, a hollow fiber bundle made of a Teflon (registered trademark) tube or a silicon tube is arranged in a deaeration chamber, and the periphery thereof is degassed by a vacuum pump. What removes the gas dissolved in the ink by separating it can also be used. Furthermore, various other methods such as an ultrasonic vibration method and a centrifugal separation method can be adopted as the ink degassing method in the degassing device.
The filter 123 allows the ink flowing through the circulation path 120 to pass therethrough and removes dust, foreign matter, solid matter, and the like mixed in the ink. Examples of the filter material include fibrous materials such as glass fiber.
The pump 122 is means for circulating the ink in the circulation path 120 and the head 2 at a constant flow rate. Using a control circuit (not shown), the driving and stopping of the pump can be arbitrarily controlled.

The gas chamber 121a-2 of the deaerator is connected to the vacuum generator 121b through a tube 121c.
By depressurizing the gas chamber 121a-2 in the degassing device 121a by driving the vacuum generator 121b, degassing from the ink can be performed.
A vacuum pump etc. are mentioned as the vacuum generator 121b.
The vacuum generator can be arbitrarily controlled to be driven and stopped by a control circuit. Thereby, the deaeration and stop by a deaeration apparatus can be controlled arbitrarily.
The order in which the pump 122, the deaerator 121a, and the filter 123 are arranged in the circulation path may be in any order.

Next, a procedure for filling the circulation path 120 with ink will be described.
First, the valve A is operated and set so that the flow paths (r1, r2, r8) from the ink tank 21 to the deaeration device 121a are communicated. On the other hand, the flow path r3 is blocked by the valve A, and the flow path r4 is also blocked by the valve C. Further, the valve B is operated and set so that the pump 122 in the circulation path can communicate with the waste liquid tank 50 (atmosphere). The pump 122 is driven to move the ink from the ink tank 21 toward the waste liquid tank 50. In other words, the flow path r5 is blocked by the valve B to connect the flow paths r11 (flow paths r10, r9, r8) and the flow path r6, and the valve D is opened to connect the flow paths r6 and r7. The pump is driven until the circulation path 120 (r8, r9, r10, r11) from the valve A to the deaerator 121a, the pump 122, and the valve B is filled with ink. When the circulation path is filled with ink, the pump is stopped.
As a result, ink is filled in the circulation path of the valve A to the deaerator 121 to the pump 122 to the filter 123 to the valve B.

Next, a method for filling the head with ink will be described.
By operating the valves A and C, the flow paths (r1, r2, r3) from the ink tank 21 to the first supply port 5 are set in a communicating state. The valve r is operated to keep the flow path r8 open. Further, the valve C is operated to block the flow path r4. Further, the valve B is operated so that the flow paths r5, r6, r11 are communicated, and the flow path is set from the second supply port 6 to the waste liquid tank. At this time, the valve D is operated to open the flow path r7.
As a result, the flow paths r1, r2, r3, the liquid chamber in the head, and the flow paths r5, r6, r7 are in communication. The circulation path 120 is also in communication with the first ink supply path 100 and the valve B.

Next, the inside of the ink tank 21 is pressurized using the first pressurizing device 23, and the ink 22 is moved into the head 2 through the first ink supply path 100. When the first ink supply path 100, the liquid chamber in the head, and the flow paths r1 to r3, r5, r6 from the second supply port 6 to the valve D are filled with ink, pressurization of the ink tank is stopped. To do. Next, the valve D is closed.
As a result, ink is filled in the ink tank 21 to the deaerator 121a to the pump 122 to the filter 123 to the valve B circulation path and the head.
By driving the head in this state, it is possible to eject ink droplets from the nozzles.

In addition, by driving the vacuum generator 121b while circulating the ink in the circulation path by the pump 122, deaeration from the ink using the deaerator 121a can be performed.
Since the ink is circulated and degassed in the circulation path using the pump as described above, the ink can be degassed. Further, as will be described later, the inside of the head can be cleaned by pressurizing the cleaning liquid with air pressure and pushing it out from the nozzle, so that it is possible to simultaneously satisfy two requirements that have been difficult to achieve at the same time. It was.

Next, a method for ejecting ink (droplets) from the nozzles of the head will be described.
The valve A and the valve C are operated so that the first ink supply path 100 from the ink tank 21 to the first supply port 5 is communicated. Operate the valve B to connect the flow paths r5 and r6, set the flow path from the second supply port 6 to the waste liquid tank (atmosphere), and operate the valve D to open the flow path r7. set.
At this time, the liquid chamber in the head is filled with ink, and the first ink supply path 100 from the ink tank to the head is opened.

Next, the head is driven using a head drive circuit (not shown), and ink is ejected from the nozzles.
When ink is ejected and the ink in the liquid chamber in the head is consumed, the ink is supplied from the ink tank to the head by osmotic pressure.
Further, by driving the pressure reducing device 24 to adjust the amount of pressure reduction in the ink tank, the ink pressure in the head is maintained at an appropriate negative pressure through the gas phase in the ink tank and the first ink supply path 100. .

Here, a negative pressure amount for properly maintaining the ink pressure in the head will be described.
When the ink tank is installed at a position relatively higher than the head and the head is filled with ink, pressure is applied to the ink in the head according to Bernoulli's theorem.
Here, the pressure of the gas phase in the ink tank is P1. Further, the ink pressure of the nozzle portion in the head is set to P2. Further, the height of the bottom surface of the ink tank as viewed from the nozzle portion is h0.
At this time, the ink pressure P2 of the nozzle portion is given by the following equation.
P2 = P1 + ρ * h0 * g (Formula 1)
Here, ρ is the density of the ink, and g is the acceleration of gravity.

If the gas-phase pressure P1 in the ink tank is equal to the atmospheric pressure, the ink pressure P2 in the nozzle portion is higher than the atmospheric pressure according to Equation 1. At this time, since the pressure of the air outside the nozzle is atmospheric pressure, the pressure P2 in the nozzle portion becomes higher than the air outside the nozzle, and a phenomenon occurs in which ink dripping from the nozzle portion to the outside occurs.
In order to prevent ink from dripping from the nozzle portion to the outside, the ink pressure P2 of the nozzle portion needs to be approximately the same as the atmospheric pressure.
In order to prevent ink from dripping out of the nozzle portion, it is effective to make the gas phase pressure P1 in the ink tank smaller than the atmospheric pressure from the relationship of Equation 1.

Assuming that the pressure of the gas in the gas phase in the ink tank when the ink pressure P2 of the nozzle portion is equal to the atmospheric pressure is P1 ′, P1 ′ is given by the following equation from Equation 1.
P1 ′ = P0−ρ * h0 * g (Formula 2)
Here, P0 is atmospheric pressure.
When the ink is ejected from the head, the decompression device is driven so that the pressure in the gas phase of the ink tank is approximately the same as P1 ′ given by Equation 2.
Printing can be performed by relatively moving the print target and the head while discharging ink from the head.

Next, a method for circulating and degassing the ink in the circulation path 120 (circulation and degassing timing, ink flow direction and flow channel) will be described.
In the present embodiment, a degassing method is provided in the droplet discharge device 1 for degassing while circulating ink ( first liquid) in the circulation path 120 (third path).
In this deaeration method, a closed path (flow path) passing through the valve A (first switching valve 101), the circulation path 120, the valve B (second switching valve 111), and the head 2 (droplet discharge section). (r3, r8, r9, r10, r11, r5, head)), the ink is circulated by the pump 122 (liquid circulation means) and the deaeration device 121a (deaeration means) is used. The constitution that deaerates from the ink is characteristic.
In other words, in this example, circulation and deaeration are performed in a state where ink is filled in the valve A to the first supply port 5 to the head 2 to the second supply port 6 to the valve B and the circulation path 120. .

First, the valve A, the deaerator 121a, the pump 122, the filter 123, the valve B, the second supply port 6, the head 2, the first supply port 5, and the ink in the closed path of the valve A are circulated by a pump. To do.
At this time, the valve A is set so that the flow paths r3 and r8 from the first supply port 5 to the deaeration device communicate with each other (the flow path r2 is shut off). The valve B is set so that the flow paths r10, r11, r5 from the pump to the second supply port 6 communicate with each other (the flow path r6 is blocked).
Next, while the pump 122 is driven to circulate the ink in the path, the ink is deaerated using a deaeration device. That is, the vacuum generator 121b is driven to depressurize the gas chamber 121a-2 inside the deaerator. Thus, the dissolved air in the ink flowing inside the liquid chamber 121a-1 of the deaerator is sucked to the vacuum generator through the deaerator and the ink is deaerated.
At this time, since the ink passes through the filter 123 in the circulation path, fine particles such as dust mixed in the ink can be removed.

Ink circulation and deaeration are performed for a predetermined time. After a predetermined time has elapsed since the start of circulation and deaeration, the vacuum generator 121b is stopped to stop the deaeration operation. Next, the pump is stopped to stop the ink circulation.
The direction in which the ink is circulated in the closed path by the pump 122 can be circulated and deaerated by either clockwise or counterclockwise in FIG. However, when ink is allowed to flow bidirectionally with respect to the filter, dust once captured by the filter may be mixed into the ink again.

Further, when ink is ejected from the nozzle 3 of the head, undeaerated ink in the flow path r3 is supplied from the valve A to the first supply port 5 side. When the undeaerated ink is circulated by driving the pump, if the ink is circulated in the clockwise direction in FIG. 1, the undeaerated ink is directed from the first supply port 5 into the head. become. If bubbles are generated in the undeaerated ink, the bubbles may adhere to the nozzles in the head.
In order to cope with such a problem, it is desirable that the ink in the valve A to the first supply port 5 (flow path r3) is circulated in one direction in a direction toward the deaeration device 121a instead of the head 2. . Therefore, it is desirable that the direction in which the ink is circulated by the pump is only one of the counterclockwise directions in FIG.
Thus, in this example, the ink (first liquid) between the head 2 (droplet discharge unit) and the valve A (first switching valve) moves in one direction through the valve A to the deaerator 121a. In this way, the ink in the closed path (flow paths r3, r8 to r11, r5, head) is circulated. For this reason, it is possible to eliminate the possibility that undegassed ink in the flow path r3 enters the head from the first supply port 5 and bubbles are attached to the nozzle.

Next, the timing for circulating and degassing ink in the printing process will be described.
The operations of circulating and degassing the ink are performed in a printing step of printing using a droplet discharge device (inkjet device), before the operation of discharging ink and during the discharge operation. After filling the head with ink, circulation and deaeration are performed to remove bubbles in the ink. Then, an operation of ejecting ink from the head is performed.

Next, FIG. 2 shows a flowchart of ink discharge, circulation, and deaeration in the printing process.
In step 1, ink is filled into the liquid chamber of the head. In this filling step, the flow paths r1, r2, r8 to r11, r5, the head, and the flow path r3 are communicated by valves C, A, and B.
In step 2, the pump and the vacuum generator are driven to circulate and deaerate ink.
Thereafter, a printing process is performed, and ink is ejected until a certain amount of ink is consumed (step 3).
When ink is discharged from the head 2 and consumed, undeaerated ink is supplied from the valve A toward the first supply port 5 side. Further, when ink is ejected from the nozzle, undeaerated ink enters the head from the first supply port 5. Since there is a possibility that air bubbles are mixed in the undeaerated ink, the undeaerated ink flows into the circulation path 120 before entering the head from the first supply port 5 to be circulated and deaerated. It is desirable to do the work.
Therefore, when performing printing, it is desirable to repeat a cycle in which a certain amount of ink is consumed and then undeaerated ink is allowed to flow into the circulation path 120 for circulation and deaeration (step 4 → Step 2 → Step 3).
Circulation and deaeration are carried out until the printing of the predetermined area is completed, and the printing process is completed when the printing on the predetermined printing area is completed (step 4 Yes).

Next, a method for collecting ink remaining in the ink supply path will be described.
After finishing the work of ejecting ink from the head, the inside of the head is washed. As a preparatory work, it is necessary to collect the ink in the head into the ink tank 21. The method will be described next.
First, the valves A and C are operated so that only the flow paths r3, r2, and r1 from the first supply port 5 to the ink tank communicate with each other. Further, the valve B is operated so that the flow path r6 from the valve D to the second supply port 6 is opened. The valve D is set so that the flow path r7 is opened. At this time, the circulation path 120 is not communicated with the first ink supply path 100 and the second ink supply path 110. That is, during maintenance such as ink recovery work, ink supply path cleaning work, and cleaning liquid discharge work, the circulation path is closed by operating the valves A and B. In the ink collecting operation, the ink in the circulation path is not collected. Even in the cleaning operation, the inside of the circulation path is not cleaned. That is, the circulation path remains filled with ink.
In this state, the decompression device 24 is driven to adjust the decompression amount, and the inside of the ink tank 21 is decompressed. At this time, the decompression amount is adjusted so that the decompression amount of the decompression device is larger than when ejecting ink.

By performing the above operation, the ink in the second ink supply path 110 to the head to the first ink supply path 100 is sucked and collected in the ink tank. At this time, the atmosphere is sucked from the end of the second ink supply path 110 on the waste liquid tank 50 side, and the air in the second ink supply path 110 to the head to first ink supply path 100 is replaced with air.
When the ink in the second ink supply path 110 to the head to the first ink supply path 100 has been collected in the ink tank, the decompression device is stopped and the ink collection is finished.

Here, the amount of reduced pressure when collecting ink will be described.
In the second ink supply path 110 to the head to the first ink supply path 100, the height of the ink existing at the lowest position is h1, and the height of the ink existing at the highest position is h2. The pressure amount P3 for depressurizing the ink, which is required when the high-side ink is depressurized and the height of the low-side ink is moved from h1 to h2, is expressed by the following equation from Bernoulli's theorem.
P3 = ρ * (h2−h1) * g (Formula 3)
According to Equation 3, the ink can be collected by driving the pressure reducing device so that the pressure reduction amount generated in the ink tank is larger than the pressure amount P3.

In order to collect ink, the second ink supply path is applied by applying pressure by attaching a pressure means (not shown) to the end of the second ink supply path 110 on the waste liquid tank 50 side without using a decompression device. A method of pushing ink from 110 to the ink tank may be used.
Depending on the configuration of the decompression device 24, the amount of decompression that can be generated is small, and even if the ink in the head can be maintained at an appropriate negative pressure, the amount of decompression cannot be increased to the extent that the ink in the head is recovered. There can be.
In this case, in the cleaning process described later, the first ink supply path 100, the second ink supply path 110, and the ink in the head are moved together with the cleaning liquid to the nozzles and the second ink supply path 110 (flow). It is discharged from the end of the path r7). Even in this case, the function of cleaning the nozzle can be sufficiently exhibited.

Next, a method for cleaning the peripheral path of the head and the nozzle 3 will be described.
After the ink 22 is collected in the ink tank 21, the peripheral path of the head and the nozzle 3 are cleaned using the cleaning liquid 42.
Here, since only the operation of cleaning the nozzles may be performed in order to wash away the solid component of the ink fixed to the nozzles 3, the operation of cleaning the peripheral path of the head is not essential. However, the cleaning liquid and the ink are mixed in the vicinity of the second supply port 6, and as a result, the nozzle is cleaned with the mixed liquid. In this case, there is a possibility that the ability to clean the nozzle is inferior to the case of cleaning only with the cleaning liquid. In order to cope with such a problem, a method of cleaning the nozzle after cleaning the liquid chamber in the head will be described.

A flowchart of the cleaning process is shown in FIG.
In step 11, after the ink is collected from the inside of the head 2, a cleaning process is performed.
Hereinafter, a procedure for cleaning the peripheral path of the head will be described.
In step 12, the second pressurizing device 43 is operated to pressurize the cleaning liquid tank 41 and send out the cleaning liquid.
In the subsequent step 13, the first ink supply path 100, the liquid chamber in the head, and the second ink supply path 110 are cleaned by the cleaning liquid that has been sent out.
Prior to the delivery of the cleaning liquid in Step 12, first, the valve C and the valve A are operated, so that the cleaning liquid supply path 130 (flow path r4) and the first supply port 5 communicate with each other through the flow paths r2 and r3. Set as follows. Next, the valve B is operated so that the second supply port 6 and the valve D communicate with each other (the flow paths r5 and r6 are communicated). Further, the valve D is operated so that the channel r7 communicates with the channel r6. As described above, the circulation path 120 is not in communication with other paths.

Next, the second pressurizing device 43 is driven to pressurize the gas phase in the cleaning liquid tank. Thereby, the cleaning liquid in the cleaning liquid tank is pushed out to the cleaning liquid supply path. The pushed cleaning liquid passes through the liquid chamber in the head through the valve C to the valve A to the first supply port 5. As a result, the path from the valve C to the valve A to the first supply port 5 and the liquid chamber in the head are washed (step 13).
Next, the cleaning liquid that has passed through the head is discharged to the waste liquid tank 50 via the second supply port 6 to the valve B to the valve D. Thereby, the path | route of the 2nd supply port 6-valve | bulb B-valve | bulb D is also wash | cleaned (step 13).
Next, the nozzle cleaning operation in step 14 is performed. That is, the valve D is closed after the work for cleaning the path around the head is performed for a predetermined time. Accordingly, the cleaning liquid pushed out from the cleaning liquid tank is discharged from the nozzle 3 via the valve C to the valve A to the first supply port 5 to the head, and the nozzle can be cleaned.
After a certain time has elapsed from the start of cleaning, pressurization of the cleaning liquid tank 41 by the second pressurizing device 43 is stopped, pushing out of the cleaning liquid is stopped, and the cleaning process is terminated (step 15).

In the method of cleaning the nozzles in this way, the recovery step of recovering ink from the inside of the head, the step of communicating the cleaning liquid supply path 130 and the inside of the head, and the valve D (path opening / closing means) are opened to open the second. A step of communicating the inside of the head with the atmosphere via the ink supply path 110, and a cleaning liquid is sent out by the second pressurizing device 43 (second liquid supply unit 40), and the first ink supply path, the head, A cleaning process for cleaning the second ink supply path, a nozzle cleaning process for discharging the cleaning liquid from the nozzle by sending the cleaning liquid from the second pressurizing device 43 after closing the valve D, and a second And a step of stopping the delivery of the cleaning liquid from the pressurizing device.
According to this cleaning method, it is possible to prevent a problem that the cleaning liquid and the ink are mixed in the vicinity of the second supply port 6 and the nozzle is cleaned using the mixed liquid, thereby causing a cleaning failure. it can.

FIG. 4 shows a modified embodiment of the route for sending the cleaning liquid to the head. The same parts as those in the first embodiment are denoted by the same reference numerals.
In the modified embodiment of FIG. 4, a valve H (103) is arranged in the middle of the first ink supply path 100 instead of the valve C of FIG. 1, and the second liquid supply unit 40 is not connected to the valve H. . Instead, a valve G (104) is arranged in the middle of the second ink supply path 110 (between the valve B and the valve D), and one end of the cleaning liquid supply path 130 (flow path r4) is connected to the valve G. Connect.
The configuration of the second liquid supply unit 40 in FIG. 4 is the same as that of FIG.
Like the valves A and B, the valve G is connected to three paths (in the middle of the flow path r6), and has a function of electrically conducting any one of the two paths. The valve G, like the valve D, has a function of opening and closing a connected path.
The cleaning process in this embodiment is the same cleaning procedure as in FIG. 1 except that an operation of opening the valve G is added.

A method of cleaning the nozzle with the configuration of FIG. 4 will be described.
First, the valve H and the valve D are operated so that the first and second ink supply paths 100 and 110 are closed.
Next, the valve G and the valve B are operated so that the cleaning liquid supply path 130 and the second supply port 6 communicate with each other.
Next, the second pressurizing device 43 is driven to pressurize the inside of the cleaning liquid tank 41 and push out the cleaning liquid 42 to the cleaning liquid supply path 130. The cleaning liquid is discharged from the nozzle 3 through the valve G to the valve B to the second supply port 6 to the inside of the head 2 so that the nozzle can be cleaned.
After a certain time has elapsed from the start of the cleaning process, pressurization of the cleaning liquid tank by the second pressurizing device 43 is stopped to stop the extrusion of the cleaning liquid, and the cleaning process is terminated.

Next, a method for discharging the cleaning liquid after the cleaning is completed in the embodiment of FIG. 1 (also in FIG. 4) will be described.
First, the valve C and the valve A in FIG. 1 are operated to set the ink tank 21 and the first supply port 5 (flow paths r1, r2, r3) to communicate with each other. The valve B is operated and set so that the second supply port 6 and the valve D (flow paths r5, r6) communicate with each other. The valve D is operated so that the second ink supply path 110 (flow path r7) is opened. As described above, the circulation path 120 is not in communication with other paths.
Next, the head 2 is driven and the cleaning liquid is discharged from the nozzle 3. As a result, the cleaning liquid in the head is consumed, the air is sucked from the end of the second ink supply path 110 on the waste liquid tank 50 side, and the cleaning liquid in the second ink supply path 110 is discharged from the nozzle.

Further, during the ink recovery operation performed in advance, the air between the valve C and the ink tank (the flow path r1) of the first ink supply path 100 is replaced with air, so the air between the valve C and the ink tank is also the head. When the cleaning liquid is consumed, the head goes to the head. Accordingly, the cleaning liquid in the valve C to the first supply port 5 to the head is also discharged from the nozzle.
At this time, the ink in the ink tank 21 is sucked out to the first ink supply path 100, and the ink and the cleaning liquid may be mixed in the head 2. Therefore, the head is driven, and the liquid in which the ink and the cleaning liquid are mixed is discharged from the nozzle.
This completes the process of discharging the cleaning liquid.
When printing is performed again, printing and circulation can be performed by performing the printing process shown in the flowchart of FIG.

An ink jet apparatus equipped with a liquid droplet ejection apparatus having the above-mentioned features can deaerate while circulating the ink in the head and the ink flow path around the head, so the nozzle is clogged with bubbles or precipitates. Can be prevented. Further, since the head (nozzle) can be cleaned by pressurizing and feeding the cleaning liquid, the solid component of the ink fixed to the nozzle portion can be removed and the clogging of the nozzle can be eliminated.
In the above embodiment, two pressurizing devices are provided. However, pressurization to the ink tank and pressurization to the cleaning liquid tank may be performed by one pressurizing device.
Further, the configuration of the vacuum generator 121b may be simplified by realizing the role of the vacuum generator 121b by the decompressor 24. That is, the negative pressure from the decompression device 24 may be supplied into the gas chamber of the deaeration device to degas the ink in the circulation path.

<< Second Embodiment >>
FIG. 5 is a schematic configuration diagram showing a second embodiment of the droplet discharge device of the present invention. In addition, the same code | symbol is attached | subjected to FIG. 1 and an identical part, and description of the overlapping structure and effect | action is abbreviate | omitted.
A feature of the droplet discharge device 1 according to the present embodiment is a configuration in which a valve E (atmospheric communication valve) 131 is disposed in the middle of the cleaning liquid supply path 130 (flow path r4) in FIG. An atmospheric communication path (flow path r20) extends from the valve E. The valve E is connected to three paths (flow paths r4-1, r4-2, r20) and has a function of communicating any one of the two paths. One end of the valve E is in communication with the atmosphere (air flow path r20), and the other two are connected to the cleaning liquid supply path (flow paths r4-1 and r4-2). May be applied to the embodiment of FIG.
In this configuration, an operation for discharging the cleaning liquid in the head 2 will be described.

After performing the cleaning operation of the head 2 described in the first embodiment, the path of the cleaning liquid tank 41 to the valve E to the valve C to the valve A to the first supply port 5, the inside of the head, the second The cleaning liquid 42 remains in the ink supply path 110. As described above, the circulation path 120 is not in communication with other paths.
In the operation of discharging the cleaning liquid, first, the valve E is set so that the atmosphere and the path on the valve C side communicate with each other. That is, by operating the valve E, the flow path r20 and the flow path r4-2 are communicated.
Further, the valves A and C are operated so that the flow paths r4-2, r2, and r3 from the valve E to the first supply port 5 are communicated. The valve B is operated and set so that the passage from the valve D to the second supply port 6 (the flow paths r6 and r5) is communicated. Then, by opening the valve D, the flow path r7 on the atmosphere side is communicated with the flow path r6.

Next, the head is driven and the cleaning liquid is discharged from the nozzle.
As a result, the cleaning liquid in the liquid chamber in the head is consumed, and the air flows from the air flow path r20 connected to the valve E to the valves C to A to the first supply port 5 to the head. In addition, air flows into the valve D to the valve B to the second supply port 6 to the head through the second ink supply path 110.
Thereby, the first ink supply path 100, the second ink supply path 110, and the cleaning liquid in the head are all discharged and replaced with the air introduced from the air flow path r20. As described above, since the cleaning liquid and the ink are separated by air, the cleaning liquid and the ink are not mixed when the cleaning liquid is discharged, and wasteful consumption of the ink due to discharging the ink mixed with the cleaning liquid from the nozzle is eliminated.

<< Third Embodiment >>
Next, FIG. 6 is a schematic configuration diagram showing a third embodiment of the droplet discharge device of the present invention. The same parts as those in FIGS. 1 and 5 are denoted by the same reference numerals, and the description of the overlapping configuration and operation is omitted.
A feature of the droplet discharge device 1 according to the present embodiment is that a valve F (132) is disposed in the cleaning liquid supply path 130 (channel r4), and a third pressurizing device is provided at the end of the channel r20 extending from the valve F. (133) is arranged. The valve F is connected to three paths (flow paths r4-1, r4-2, r20) and has a function of communicating any one of the two paths. One end of the valve F communicates with a pressurizing device (pressurizing means) C, and the other two are connected to the cleaning liquid supply path (flow paths r4-1 and r4-2).
The third pressurizing device 133 has a function of sending out compressed air.
In the above configuration, the operation procedure for discharging the cleaning liquid in the head 2 will be described.

After the cleaning process of the head 2 described in the first embodiment, the paths of the cleaning liquid tank 41 to the valve F to the valve C to the valve A to the first supply port 5, the inside of the head, and the second ink supply path The cleaning liquid remains at 110.
In the discharge operation of the cleaning liquid, first, the valve F is operated so that a path (flow path r20 and flow path r4-2) connecting the third pressurizer 133 and the valve C is communicated (flow path r4). -1 is cut off). The valves A and C are operated so that the flow paths r20, r4-2, r2, and r3 from the valve F to the first supply port 5 communicate with each other. The valve B is operated so that the flow paths r6 and r5 from the valve D to the second supply port 6 are communicated. Then, the valve D is closed.
As described above, the circulation path 120 is not in communication with other paths.

Next, the third pressurizer is driven to send compressed air to the valve F.
Thereby, the path | route of the valve | bulb F-the valve | bulb C-the valve | bulb A-the 1st supply port 5, and the washing | cleaning liquid in a head are extruded from a nozzle by compressed air. At this time, the nozzle can be cleaned again with the cleaning liquid extruded with compressed air.
Also, the cleaning liquid in the path from the valve F to the valve C to the valve A to the first supply port 5 and in the head is discharged from the nozzle and replaced with air.
Next, by opening the valve D, the cleaning liquid in the second ink supply path 110 is discharged to the waste liquid tank 50 by the compressed air that has come from the third pressurizing device 133 to the head via the valve F. The
In addition, the nozzle can be pressure-washed when the cleaning liquid is discharged. Since the nozzle can be cleaned even when the cleaning liquid is discharged from the discharge end side of the second ink supply path to the outside, the efficiency of cleaning the nozzle with respect to the consumption of the cleaning liquid is improved.
By the above operation, all of the first ink supply path 100, the second ink supply path 110, and the cleaning liquid in the head can be discharged.

<< Printer using the droplet discharge device of the present invention >>
Next, the droplet discharge device according to the present invention can be applied to an image forming apparatus (inkjet recording apparatus).
FIG. 7 is a perspective explanatory view of an ink jet recording apparatus using the droplet discharge apparatus of the present invention, and FIG. 8 is a side explanatory view of a mechanism portion of the recording apparatus.
The ink jet recording apparatus shown in FIGS. 7 and 8 includes a carriage that can move in the main scanning direction inside the recording apparatus main body 201, a recording head that includes the ink jet head that implements the present invention mounted on the carriage, and supplies ink to the recording head. The printing mechanism 202 including an ink cartridge or the like is housed. A sheet feeding cassette (or a sheet feeding tray) 204 on which a large number of sheets P can be stacked from the front side can be detachably attached to the lower part of the apparatus main body 201. Further, the manual feed tray 205 for manually feeding the paper P can be opened, the paper P fed from the paper feed cassette 204 or the manual feed tray 205 is taken in, and a required image is displayed by the printing mechanism unit 202. After recording, the paper is discharged to a paper discharge tray 206 mounted on the rear side.

The printing mechanism unit 202 holds the carriage 209 slidably in the main scanning direction with a main guide rod 207 and a sub guide rod 208 which are guide members horizontally mounted on left and right side plates (not shown). The carriage 209 is provided with a head 210 comprising an ink jet head according to the present invention for ejecting ink droplets of each color of yellow (Y), cyan (C), magenta (M), and black (Bk). Holes) are arranged in a direction crossing the main scanning direction, and the ink droplet ejection direction is directed downward. Also, each ink cartridge 211 for supplying ink of each color to the head 210 is mounted on the carriage 209 in a replaceable manner.
The ink cartridge 211 has an air port that communicates with the atmosphere upward, a supply port that supplies ink to the inkjet head below, and a porous body filled with ink inside, and the capillary force of the porous body Thus, the ink supplied to the inkjet head is maintained at a slight negative pressure. Further, although the heads 210 of the respective colors are used here as the recording heads, a single head having nozzle holes for ejecting ink droplets of the respective colors may be used.

  Here, the carriage 209 is slidably fitted on the main guide rod 207 on the rear side (downstream side in the paper conveyance direction), and is slidably mounted on the sub guide rod 208 on the front side (upstream side in the paper conveyance direction). doing. In order to move and scan the carriage 209 in the main scanning direction, a timing belt 215 is stretched between a driving pulley 213 and a driven pulley 214 that are rotationally driven by a main scanning motor 212. The timing belt 215 is fixed to the carriage 209, and the carriage 209 is driven to reciprocate by forward and reverse rotation of the main scanning motor 212.

On the other hand, in order to convey the paper P set in the paper cassette 204 to the lower side of the head 210, the paper P is guided to the paper feed roller 216 and the friction pad 217 for separating and feeding the paper P from the paper cassette 204. A guide member 218, a transport roller 219 that reverses and transports the fed paper P, a transport roller 220 that is pressed against the peripheral surface of the transport roller 219, and a leading edge that defines the feed angle of the paper P from the transport roller 219 A roller 221 is provided. The transport roller 219 is rotationally driven by a sub-scanning motor 222 through a gear train.
A printing receiving member 223 is provided as a paper guide member for guiding the paper P sent from the transport roller 219 on the lower side of the recording head 210 corresponding to the movement range of the carriage 209 in the main scanning direction. A conveyance roller 224 and a spur 225 that are rotationally driven to send the paper P in the paper discharge direction are provided on the downstream side of the printing receiving member 223 in the paper conveyance direction, and the paper P is further delivered to the paper discharge tray 206. A roller 226 and a spur 227 and guide members 228 and 229 that form a paper discharge path are disposed.
At the time of recording, the recording head 210 is driven according to the image signal while moving the carriage 209, thereby ejecting ink onto the stopped paper P to record one line. Record the line. Upon receiving a recording end signal or a signal that the trailing edge of the paper P reaches the recording area, the recording operation is terminated and the paper P is discharged.

Further, a recovery device 230 for recovering the ejection failure of the head 210 is disposed at a position outside the recording area on the right end side in the moving direction of the carriage 209. The recovery device 230 includes a cap unit, a suction unit, and a cleaning unit. The carriage 209 is moved to the recovery device 230 side during printing standby, and the head 210 is capped by the capping unit, and the ejection port portion is kept in a wet state to prevent ejection failure due to ink drying. Further, by ejecting ink that is not related to recording during recording or the like, the ink viscosity of all the ejection ports is made constant and stable ejection performance is maintained.
When ejection failure occurs, etc., the ejection port (nozzle hole) of the head 210 is sealed by the capping unit, and bubbles and the like are sucked out from the ejection port by the suction unit through the tube. Etc. are removed by the cleaning means, and the ejection failure is recovered. Further, the sucked ink is discharged to a waste ink reservoir (not shown) installed at the lower part of the main body and absorbed and held by an ink absorber inside the waste ink reservoir.
The droplet discharge device of the present invention can be applied to other image forming apparatuses that discharge liquids other than ink. For example, the present invention can be applied to an apparatus (image forming apparatus) that ejects liquid resist formed on a substrate in a semiconductor process, a pattern material, or the like as droplets.

<< Summary of Configuration, Action, and Effect of the Present Invention >>
The droplet discharge device according to the first aspect of the present invention includes a head 2 (droplet discharge portion) having a nozzle 3 for discharging droplets, and a first ink supply path 100 for supplying liquid to the droplet discharge portion. (First path), a second ink supply path 110 (second path), and a first that supplies ink 22 (first liquid) to the liquid droplet ejection section via the first ink supply path. The liquid supply unit 20 is connected to the first ink supply path via a valve A (first switching valve 101), and the valve B (second switching valve 111) is connected to the second ink supply path. ) And a circulation path 120 (third path) that bypasses the droplet discharge section. Furthermore, the liquid circulation means 122 arranged on the circulation path and the first ink supply path or the cleaning liquid supply path 130 (the first liquid supply path 130) connected to the second ink supply path via the valve C (third switching valve 102). 4), a second liquid supply unit 40 that supplies the cleaning liquid 42 (second liquid) to the head 2 via the cleaning liquid supply path, and the first ink supply path or the second ink supply path. And a valve D (path opening / closing means 112) installed on the first ink supply path or the second ink supply path in order to flow the liquid to the head.

According to this, in order to circulate the ink in the head and the flow path around it, if a foreign matter removing means such as a filter is arranged in the circulation path, the clogging of the nozzle due to the precipitate generated in the ink during the circulation. Can be prevented. In addition, since the head can be cleaned with the cleaning liquid, the clogging of the nozzle can be eliminated by removing the solid component of the ink fixed to the nozzle portion.
That is, to provide a droplet discharge device that has a mechanism for preventing clogging of nozzles due to bubbles in liquid such as ink and precipitation of solid components, and a mechanism for eliminating nozzle clogging due to drying of liquids. Can do.

The liquid droplet ejection apparatus according to the second aspect of the present invention is characterized in that a deaeration device 121a (a deaeration unit) is disposed on the third ink supply path.
According to this, since the ink in the head and the flow path around the head is degassed, clogging of the nozzle due to bubbles can be prevented.

In the droplet discharge device according to the third aspect of the present invention, the second liquid supply unit 40 includes a pressurizing device 43 (pressurizing means) for extruding the liquid by air pressure.
Since the cleaning liquid is pushed out from the cleaning liquid tank to the head by air pressure, the cleaning liquid can be pushed out more strongly than when the cleaning liquid is pushed out by a pump, and the ability to clean the nozzle can be enhanced.

In the droplet discharge device according to the fourth aspect of the present invention, the first liquid supply unit 20 includes a decompression device 24 (decompression unit).
Since the ink in the head portion is reduced to an appropriate pressure, it is possible to prevent the ink from leaking from the nozzle.

In the liquid droplet ejection apparatus according to the fifth aspect of the present invention, a pressure difference is generated between the first liquid supply unit 20 and the second ink supply path 110 to generate ink (from the head 2 to the first liquid supply unit). A first liquid recovery mechanism for recovering the first liquid) is provided.
Before washing the head, the ink in the head and the flow path around it can be collected in the ink tank. For this reason, when the cleaning liquid is supplied to the head, the ink is not discharged wastefully together with the cleaning liquid. Thereby, ink consumption can be reduced.

The liquid droplet ejection apparatus according to the sixth aspect of the present invention is characterized in that a valve E (atmospheric communication valve 131) is provided on the cleaning liquid supply path 130 (fourth path).
According to this, the first ink supply path 100, the second ink supply path 110, and the cleaning liquid in the head can be completely discharged and replaced with air. Since the cleaning liquid and the ink are separated by air, the cleaning liquid and the ink are not mixed when the cleaning liquid is discharged, and the wasteful consumption of the ink due to the discharge of the ink mixed with the cleaning liquid from the nozzle is eliminated.

The droplet discharge device according to the seventh aspect of the present invention is characterized by including a pressurizing device 133 (pressurizing means) connected to the cleaning liquid supply path 130 (fourth path) via a valve F (132). To do.
By disposing the pressurizing device 133 in the cleaning liquid supply path via the valve F, the path from the valve F to the valve C to the valve A to the first supply port 5 and the cleaning liquid in the head are pushed out from the nozzle. Can be washed under pressure. Further, the cleaning liquid in the path and in the head is discharged from the nozzle and replaced with air. The cleaning liquid inside the second ink supply path 110 is discharged to the waste liquid tank 50 by the compressed air that has come from the pressure device 133 to the head via the valve F. Accordingly, the first ink supply path 100, the second ink supply path 110, and the cleaning liquid in the head can be completely discharged.
Since the nozzle can be cleaned even when the cleaning liquid is discharged from the discharge end side of the second ink supply path to the outside, the efficiency of cleaning the nozzle with respect to the consumption of the cleaning liquid is improved.

The droplet discharge device according to the eighth aspect of the present invention is characterized in that a filter 123 for removing fine particles from the liquid is disposed on the circulation path 120 (third path).
Since the filter removes foreign matters such as dust from the ink in the head and the flow path around the head, it is possible to prevent clogging of the nozzles due to dust and the like in the ink.

In the droplet discharge device according to the ninth aspect of the present invention, the deaeration device 121a is divided into a liquid chamber and a gas chamber through a member that passes gas without passing liquid, and a negative pressure is introduced into the gas chamber. The liquid in the liquid chamber is degassed.
Since the deaeration is performed using the vacuum generator, the deaeration can be performed while circulating the ink, unlike the deaeration method in which the ink is stirred in the liquid container.

The degassing method using the droplet discharge device according to the present invention is a degassing method for degassing while circulating a cleaning liquid (second liquid) in a circulation path 120 (third path). In a state where the second liquid 42 is filled in a closed path that passes through the switching valve 101, the third path 120, the second switching valve 111, and the droplet discharge unit 2, the liquid circulating means 122 The second liquid is circulated and the second liquid is degassed using the deaeration means 121.
Complicated configuration of a droplet discharge device that combines a mechanism for preventing clogging of nozzles due to precipitation of air bubbles and solid components such as ink and a mechanism for eliminating nozzle clogging due to liquid drying It becomes possible to perform deaeration effectively without doing.

In the deaeration method including the droplet discharge device according to the present invention, the second liquid between the droplet discharge unit and the first switching valve is provided with the filter in the third path, and the first switching is performed. The second liquid in the closed path is circulated so as to move in one direction through the valve to the deaeration means.
When ink is ejected from the nozzle 3 of the head, undeaerated ink in the flow path r3 is supplied from the valve A (first switching valve) to the first supply port 5 side. If bubbles are generated in the undeaerated ink, the bubbles may adhere to the nozzles in the head. Therefore, the above problem can be solved by circulating the valve A so as to move in one direction to the deaeration means.

In the droplet discharge device according to the present invention, in the cleaning method for cleaning the nozzle after cleaning the liquid chamber in the droplet discharge unit, a recovery step of recovering the second liquid from the inside of the droplet discharge unit; A step of communicating the fourth path with the inside of the droplet discharge unit, a step of opening the path opening / closing means to communicate the inside of the droplet discharge unit with the atmosphere via the second path, and a second liquid supply unit The second liquid is sent out to wash the first path, the droplet discharge section, and the second path, and the second opening from the second liquid supply section after closing the path opening / closing means. A nozzle cleaning step of discharging the second liquid from the nozzle by delivering the liquid and a step of stopping the delivery of the second liquid from the second liquid supply unit are provided. .
According to this cleaning method, it is possible to prevent a cleaning failure in which the cleaning liquid and the ink are mixed in the vicinity of the second supply port 6 and, as a result, the nozzle is cleaned using the mixed liquid.
An image forming apparatus according to the present invention includes the above-described droplet discharge device.

  DESCRIPTION OF SYMBOLS 1 ... Droplet discharge apparatus, 2 ... Head (droplet discharge part), 3 ... Nozzle, 5 ... Supply port, 6 ... Supply port, 20 ... 1st liquid supply part, 21 ... Ink tank, 22 ... Ink (first) 1), 23 ... pressurizing device (pressurizing means), 24 ... decompressing device (depressurizing means), 40 ... second liquid supply unit, 41 ... cleaning liquid tank, 42 ... cleaning liquid (second liquid), 43 ... pressurizing device (pressurizing means), 50 ... waste liquid tank, 100 ... first ink supply path (first path), 101 ... first switching valve, 102 ... third switching valve, 110 ... second Ink supply path (second path), 111 ... second switching valve, 112 ... path opening / closing means, 120 ... circulation path, 121 ... degassing means, 121a ... degassing device, 121a-1 ... liquid chamber, 121a -2 ... Gas chamber, 121a-3 ... Member, 121b ... Vacuum generator, 121c Tube, 122 ... Pump, 122 ... Liquid circulation means, 130 ... Cleaning liquid supply path, 131 ... Air communication valve, 133 ... Pressure device (pressurization means), 201 ... Recording apparatus body, 202 ... Print mechanism, 204 ... Feed Paper cassette, 205 ... Tray, 206 ... Discharge tray, 207 ... Main guide rod, 208 ... Sub guide rod, 209 ... Carriage, 210 ... Recording head, 211 ... Ink cartridge, 212 ... Main scanning motor, 214 ... Subordinate pulley, 215 ... Timing belt, 216 ... Feeding roller, 217 ... Friction pad, 218 ... Guide member, 219 ... Conveying roller, 220 ... Conveying roller, 221 ... Tip roller, 222 ... Sub-scanning motor, 223 ... Filter, 224 ... Pressure reducing device 224 ... conveying roller, 225 ... spur, 226 ... paper discharge roller, 227 ... spur, 228 ... gas De member, 213 ... driving pulley, 230 ... recovery device

Japanese Patent No. 5209431 Patent No. 5169120

Claims (13)

A droplet discharge section having a nozzle for discharging droplets;
A first path and a second path for supplying liquid to the droplet discharge section;
A first liquid supply section for supplying a first liquid to the droplet discharge section via the first path;
A third path connected to the first path via a first switching valve, connected to the second path via a second switching valve, and bypassing the droplet discharge section When,
Liquid circulation means disposed on the third path;
A fourth path connected to the first path or the second path via a third switching valve;
A second liquid supply section for supplying a second liquid to the droplet discharge section via the fourth path;
A path opening / closing means installed on the first path or the second path to flow the liquid in the first path or the second path to the droplet discharge section;
A droplet discharge device comprising: The droplet discharge device according to claim 1,
A liquid droplet ejection apparatus, wherein a deaeration unit is disposed on the third path. The droplet discharge device according to claim 2 ,
The deaeration means is divided into a liquid chamber and a gas chamber through a member that allows gas to pass therethrough, and degass the liquid in the liquid chamber by introducing a negative pressure into the gas chamber. A droplet discharge apparatus characterized by the above. The liquid droplet ejection apparatus according to any one of claims 1 to 3 ,
The liquid droplet ejection apparatus, wherein the second liquid supply unit includes a pressurizing unit for extruding the liquid by air pressure. The droplet discharge device according to any one of claims 1 to 4 ,
The liquid droplet ejection apparatus, wherein the first liquid supply unit includes a decompression unit. In the droplet discharge device according to any one of claims 1 to 5 ,
A first liquid recovery mechanism that generates a pressure difference between the first liquid supply unit and the second path to recover the first liquid from the droplet discharge unit to the first liquid supply unit. A droplet discharge device comprising: In the droplet discharge device according to any one of claims 1 to 6 ,
A droplet discharge device comprising an atmosphere communication valve on the fourth path. In the droplet discharge device according to any one of claims 1 to 7 ,
A droplet discharge apparatus comprising a pressurizing unit connected to the fourth path via a fourth switching valve. The droplet discharge device according to any one of claims 1 to 8 ,
A droplet discharge device, wherein a filter for removing fine particles from the liquid is disposed on the third path. The liquid droplet ejection apparatus according to any one of claims 1 to 9, wherein the degassing method is for degassing while circulating the first liquid in the third path,
In a state where the first liquid is filled in a closed path passing through the first switching valve, the third path, the second switching valve, and the droplet discharge section, the liquid circulation means The degassing method is characterized in that the first liquid is circulated by the degassing and the degassing means according to claim 2 is used to degas the first liquid. The deaeration method according to claim 10, comprising the filter according to claim 9 in the third path.
The first liquid between the droplet discharge unit and the first switching valve moves in one direction to the deaeration means via the first switching valve, and is in the closed path. A degassing method comprising circulating the first liquid. The droplet discharge device according to any one of claims 1 to 9, wherein the nozzle is cleaned after cleaning the liquid chamber in the droplet discharge unit.
A recovery step of recovering the first liquid from the inside of the droplet discharge section;
Communicating the fourth path with the inside of the droplet discharge section;
Opening the path opening / closing means and communicating the inside of the droplet discharge unit with the atmosphere via the second path;
A washing step of sending the second liquid from the second liquid supply unit to wash the first path, the droplet discharge unit, and the second path;
A nozzle cleaning step of discharging the second liquid from the nozzle by delivering the second liquid from the second liquid supply section after closing the path opening / closing means;
Stopping the delivery of the second liquid from the second liquid supply unit;
A method for cleaning a nozzle, comprising:   An image forming apparatus comprising the droplet discharge device according to claim 1.

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