JP2010149337A - Device and method for ink jet recording - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device for ink jet recording capable of supplying ink while stably carrying out a recording operation in the case of a consecutive recording operation. <P>SOLUTION: An ink supply tank 30 is connected to an ink supply container 32 via an ink supply pipe 31. The ink supply container 32 is connected to an ink storage section 20 via an ink supply pipe 34 and a connection pipe 35. Ink is supplied to the ink supply container 32 from the ink supply tank 30 by a feed pump P1. The pressurized air is supplied in the ink supply container 32 from a pressurizing pump P2, and ink is pressurized by pressurized air. Also, since negative pressure in the ink storage section 20 is maintained, by opening a two-way valve 35a provided in the connection pipe 35, ink is supplied into the ink storage section 20 from the ink supply container 32 by a difference in air pressure between them. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an ink jet recording apparatus and method for performing recording by ejecting ink from nozzles communicating with an ink reservoir.

  The ink jet recording method is a method for performing printing or image recording by ejecting minute ink droplets from an ink ejection port of an ink recording head to a recording medium, and can perform a recording operation while being separated from the recording medium. It can be recorded on recording media and articles of various materials and has been used for a wide range of purposes.

  Various types of ink-jet heads used for ink-jet recording have been developed. For example, a pressure chamber filled with ink is expanded and deformed by applying a voltage to a piezoelectric element and deforming it. On-demand type heads have been developed, such as a piezo system that causes pressure fluctuations by contraction, and a thermal system that uses the pressure generated by energizing and heating the heating resistor to foam the ink.

In such an on-demand type head, ink droplets are ejected as required to record an image. However, since the amount of ink consumed varies from head to head or from color to color, it is necessary to supply ink appropriately. Various improvements have been made. For example, Patent Document 1 describes a liquid ejecting apparatus that pressurizes an ink pack in an ink cartridge with a pressure pump to replenish ink in a sub tank and supplies ink in the sub tank to a recording head. Japanese Patent Application Laid-Open No. 2004-228561 discloses a droplet discharge device that supplies ink from an ink tank to a common liquid chamber of a recording head through a supply path by a pump and circulates ink by providing a return path from the common liquid chamber to the ink tank. Are listed. Patent Document 3 describes a droplet discharge device that replenishes ink from a main tank to a second reservoir tank via a first reservoir tank and supplies ink from the second reservoir tank to a recording head. In Patent Document 4, a first liquid chamber for supplying ink to the ink jet head and a second liquid chamber for replenishing ink to the first liquid chamber are provided, and the two liquid chambers communicate with each other. An ink jet printing apparatus is described in which an air communication pipe is provided to cancel pressure fluctuations that occur when ink is replenished.
JP 2004-90432 A JP 2006-68904 A JP 2007-216568 A Japanese Patent Laid-Open No. 10-146888

  In Patent Document 1 described above, when continuous recording is performed for a long time, it is necessary to increase the capacity of the pressurized ink pack, and the size of the apparatus cannot be increased, and the cost burden increases. Further, when the ink cartridge is replaced, the recording operation must be stopped once, which hinders continuous recording operation.

  In Patent Document 2, if ink is constantly supplied to the recording head by a pump during continuous recording operation, the possibility of pump failure increases, which is not preferable from the viewpoint of pump life. Further, the pulsation is transmitted to the recording head along with the liquid feeding operation by the pump, and the recording operation may become unstable. Further, when a filter or the like is installed in the liquid supply path, if the pulsation due to the pump operation is large, the filter may be damaged.

  In Patent Document 3, since ink is replenished from the first reservoir tank to the second reservoir tank by a differential pressure using a height difference, the ink water level in the second reservoir tank fluctuates and the water head difference with the recording head is constant. In addition, the ink is circulated from the second reservoir tank to the recording head using an ink circulation pump, and the ink pressure in the recording head is affected by the pulsation of the pump, resulting in unstable recording operation. It is easy to become.

  In Patent Document 4, ink is replenished from the second liquid chamber to the first liquid chamber by a pump. However, the ink water level in the first liquid chamber needs to be kept constant. It is necessary to operate the pump frequently in accordance with the fluctuation of the pump, which is not preferable from the viewpoint of pump life.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an ink jet recording apparatus and method capable of supplying ink while performing a stable recording operation when performing a continuous recording operation.

  An ink jet recording apparatus according to the present invention is connected to a recording head section having an ink storage section and a nozzle communicating with the ink storage section, and is supplied to the ink storage section through a supply pipe and to the ink storage section. An ink supply unit for storing ink, a pressure adjusting unit for setting the inside of the ink supply unit to a higher air pressure than the air pressure in the ink storage unit, and the ink supply due to a difference in air pressure between the ink storage unit and the ink supply unit A supply valve means for controlling ink supply from the ink supply section to the ink storage section, an ink supply section connected to the ink supply section via a supply line and storing ink to be supplied to the ink supply section, An ink supply unit that is provided in the supply line and supplies ink in the ink supply unit to the ink supply unit. The features. And a circulation line connected to the downstream side of the supply line to the ink storage part and connected to the ink supply part to circulate ink from the supply line to the ink supply part. And a circulation valve means for controlling the circulation of the ink and provided in the circulation pipe. Further, the supply pipe line is provided with a housing portion containing a filter for collecting impurities in the ink. A branch pipe connected to the storage section and the ink supply section to return the ink in the storage section to the ink supply section; and a reflux valve means provided in the branch pipe and controlling the return of the ink. Is provided.

  An ink jet recording method according to the present invention is an ink jet recording method in which ink is ejected from a nozzle communicating with an ink reservoir, and is recorded at a pressure higher than an air pressure state in an ink supply unit from an ink replenishment unit. Ink is replenished, the inside of the ink supply unit is set to a higher air pressure than the inside of the ink storage unit, and ink is supplied from the ink supply unit to the ink storage unit due to the difference in air pressure between the two. Ink is circulated through the nozzles for recording.

  Since the present invention has the above-described configuration, ink is supplied from the ink supply unit that is set to a higher air pressure than the air pressure in the ink storage unit. Can be performed smoothly without using a pump or the like, and the ink supply operation to the recording head unit can be performed without affecting the recording operation. Then, if ink supply is controlled by opening / closing operation of the supply valve means and is performed at a supply speed at which the air pressure state of the ink storage unit can be maintained, ink supply is performed while maintaining the pressure in the ink storage unit constant. The ink supply operation can be performed even during the recording operation.

  Further, since the ink supply unit can be appropriately supplied with ink from the ink supply unit by the feeding unit, the ink supply unit may be supplied when the remaining amount of ink in the ink supply unit decreases even during the recording operation. Since ink can be supplied from the ink supply unit to the ink storage unit even during the recording operation, it is possible to sequentially supply ink to the recording head unit while performing a stable continuous recording operation, which greatly increases production efficiency. be able to.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The embodiments described below are preferable specific examples for carrying out the present invention, and thus various technical limitations are made. However, the present invention is particularly limited in the following description. Unless otherwise specified, the present invention is not limited to these forms.

  FIG. 1 is a schematic configuration diagram relating to an embodiment of the present invention. A recording medium T such as fabric is placed on an endless conveyance belt 3 driven by a conveyance roller 4 and conveyed in the conveyance direction Y. The recording unit 1 is configured by arranging recording head units over the entire width of the image forming area intersecting the conveyance direction Y, and color recording units 10Y, 10M, 10C, and 10K are arranged in the conveyance direction Y. . The color recording units 10Y, 10M, 10C, and 10K are supplied with color inks to perform full color recording.

  Each color recording unit is configured by arranging a plurality of recording head units 10a to 10f in a direction orthogonal to the transport direction Y, and each recording head unit performs recording by discharging ink from nozzles provided below. Operation is performed.

  FIG. 2 is a side view of the color recording unit viewed from the conveyance direction Y. FIG. An ink supply pipe L1 and an air pipe L2 are connected to the upper portions of the recording head portions 10a to 10f. The ink supply pipe L1 and the air pipe L2 are connected to each recording head unit so that pressure control and ink supply can be individually performed.

  FIG. 3 is a schematic cross-sectional view relating to the recording head unit. The recording head unit is made of a metal casing, and an ink storage unit 20 is formed inside. The lower part in the ink storage part 20 is demarcated in the ink area | region B in which the ink was stored to predetermined height, and the upper part is demarcated in the gas area | region A into which air was introduce | transduced. An ink supply pipe L1 communicates with the ink area B, and an air pipe L2 communicates with the gas area A.

  A connecting portion 23 is provided at the tip of the ink supply tube L1, and is detachably attached to the connecting portion 22 of the recording head portion. Inside the connecting portions 22 and 23, valve bodies 22a and 23a are slidable in the connecting direction, and when connected, the valve bodies 22a and 23a are always pressed against each other by an elastic member such as a spring. Is set. For this reason, the valve bodies 22a and 23a are pressed against each other and moved so as to be pulled in and held in an open state, and the ink supply pipe L1 and the recording head unit are connected to each other.

  Similarly, the air pipe L2 is provided with a connecting portion 25, which is detachably attached to the connecting portion 24 of the recording head portion. And the valve bodies 24a and 25a of the connection parts 24 and 25 are set so that it may mutually press with an elastic member, it moves, and is hold | maintained in the open state. Therefore, the air pipe L2 and the recording head unit are connected to each other.

  When the recording head part is removed, the connection parts are disconnected so that the valve bodies 22a and 23a are pushed out by the biasing force of an elastic member such as a spring as shown in FIG. And each valve body is hold | maintained in the state which closed the opening part. Therefore, even if the recording head part is removed, ink does not leak out from the ink supply pipe L1, and air flows into the ink storage part 20 from the ink supply pipe L1 and affects the negative pressure state of the gas region A. Nothing will happen. Similarly, in the case of the air pipe L2, it is possible to prevent the air from flowing in due to the opening being closed by the valve body.

  A plate-like nozzle portion 21 is disposed on the bottom surface of each recording head portion, and a plurality of nozzles 21a are formed in the nozzle portion 21 so as to open downward. These nozzles may be arranged in a line in a straight line, or a plurality of nozzles, for example, 32, 64, 128 nozzle holes are made into one block, and each block has a linear shape, a staggered shape, a staircase shape, etc. Or may be arranged in a combination of these.

  A communication passage 20a communicating with the nozzle portion 21 is formed on the bottom surface of the ink storage portion 20, and ink in the ink storage portion 20 is supplied into the nozzle portion 21 via the communication passage 20a. . A pressure control device, which will be described later, communicates with the gas region A in the ink storage unit 20 via the air pipe L2, and the pressure in the gas region A is maintained in a predetermined air pressure state by the pressure control device. ing. In this example, the predetermined air pressure state is controlled to a negative pressure state or a pressurized state.

  In the case where the gas region A is in a negative pressure state, ink is supplied into the nozzle portion 21, but ink does not leak from the nozzle 21a formed on the bottom surface. The ink is ejected from the nozzle 21a by applying pressure to the ink in the flow path communicating with the nozzle 21a using a pressure means such as a piezoelectric element provided for each nozzle 21a.

  When the gas region A is in a pressurized state, the ink in the ink reservoir 20 is pressurized and the ink flows out from the nozzles 21a, and a maintenance operation such as prevention of nozzle clogging can be performed.

  In this example, the nozzle unit is integrally attached to the bottom surface of the recording head unit. However, the nozzle unit may be separated and connected to the ink storage unit by a communication pipe.

  FIG. 5 is a block configuration diagram relating to ink supply control to the recording unit 1 and pressure control in the ink storage unit 20. Ink supply control and pressure control are performed by the control unit 100 transmitting a control signal to each component.

  An ink supply container 32 is connected to the ink supply tank 30 via an ink supply pipe 31. The ink supply pipe 31 is provided with a strainer 33 and a feed pump P1, and ink from which dust or the like has been filtered by the strainer 33 is supplied to the ink supply container 32 by the operation of the feed pump P1. The ink supply pipe 31 is provided with a check valve 31a to prevent the ink from flowing back through the ink supply pipe 31 when the ink in the ink supply container 32 is pressurized.

  The ink replenishing tank 30 has an opening 30a communicating with the atmosphere at the top, and the internal space is always set to atmospheric pressure. When ink having sedimentation properties is stored, the ink can be stirred by inserting a stirring rod or the like through the opening 30a. An ink remaining amount detection sensor 30b is attached to the side wall of the ink replenishing tank 30, and when the ink remaining amount decreases and the ink level decreases, the ink remaining amount detection sensor 30b. Detects the liquid level that has decreased, and outputs a detection signal. When the ink remaining amount in the ink supply tank 30 is reduced, ink is supplied from a supply pipe (not shown).

  Each ink storage unit 20 is connected to the ink supply container 32 via an ink supply pipe 34. A connection pipe 35 branched from the ink supply pipe 34 is connected to the ink reservoir 20 and communicates with the ink supply pipe 34. Each of the connecting pipes 35 is provided with a two-way valve 35a as a supply valve means. When the two-way valve 35a is opened, ink is supplied to the ink reservoir 20, and the ink reservoir is closed by closing the two-way valve 35a. The ink supply to 20 is stopped.

  The ink supply container 32 is a sealed container, and pressurized air is supplied to the internal space from the pressure pump P2 as will be described later, so that the ink in the ink supply container 32 is higher than the air pressure state in the ink reservoir 20. The air pressure state (in this example, a pressure state higher than the atmospheric pressure) is set. By setting the inside of the ink supply container 32 to a higher air pressure state than the air pressure state in the ink storage unit 20, the ink in the ink supply container 32 is supplied to the ink storage unit 20 due to the difference in air pressure between the two.

  In this example, the air pressure state in the ink storage unit 20 is a negative pressure state. However, even when the air pressure state is maintained at a pressure state other than the negative pressure state, the ink supply container has a higher air pressure state than the pressure state. If the inside of 32 is set, ink can be supplied.

  Liquid level detection sensors 32a and 32b for detecting the liquid level of the ink in the container are attached to the side wall of the ink supply container 32. The liquid level detection sensor 32a is installed at a low position so that the lower limit ink liquid level is set. The liquid level detection sensor 32b is installed at a high position to detect the upper limit ink liquid level.

  The ink supply pipe 34 is provided with a storage container 36 containing a filter 37, and the ink that has flowed into the ink supply pipe 34 from the ink supply container 32 is collected by the filter 37 in the storage container 36. It is supplied to the storage unit 20.

  The storage container 36 is connected to the ink supply tank 30 via a branch pipe 38, and opens a two-way valve 38 a that is a reflux valve means provided in the branch pipe 38, thereby returning the return pipe line (ink supply tank 30). → Ink supply pipe 31 → Ink supply container 32 → Container container 36 → Branch pipe 38 → Ink supply tank 30) can be formed. Further, the ink recirculation can be stopped by closing the two-way valve 38a.

  By returning the ink to such a reflux line, the ink can be prevented from settling in the ink supply container 32 or the like when the ink having settling properties is supplied.

  The ink supply pipe 34 is further extended from a portion to which the connection pipe 35 is connected, and is connected to the ink supply tank 30 through a return pipe 39. By opening a two-way valve 39a which is a circulation valve means provided in the return pipe 39, a circulation pipe line (ink supply tank 30 → ink supply pipe 31 → ink supply container 32 → storage container 36 → ink supply pipe 34 → return) Tube 39 → ink replenishment tank 30) can be formed. Further, the circulation of the ink can be stopped by closing the two-way valve 39a.

  By circulating the ink in such a circulation line, the ink settling can be suppressed in the ink supply container 32 or the like when the ink having the sedimentation property is supplied. In addition, when changing the color of the ink, the ink staying in the circulation line can be circulated, recovered, and reused.

  The ink supply operation is controlled by pressurized air supplied from the pressure pump P2. Pressurized air is supplied to the ink supply container 32 via the regulator R 1 and the three-way valve 70. The regulator R1 acts so that the pressure in the ink supply container 32 is maintained at a constant supply pressure state, and when the internal pressure rises from a predetermined air pressure state, the pressurized air is discharged to the outside air and the pressure is increased. Is reduced to a predetermined air pressure state. When the internal pressure falls below a predetermined air pressure state, pressurized air is supplied to increase the air pressure to a predetermined air pressure state. The three-way valve 70 is set so as to switch and connect the ink supply container 32 to the side communicating with the regulator R1 or the side communicating with the outside air. In a state where the regulator R 1 and the ink supply container 32 are connected, the pressurized air from the regulator R 1 is sent to the ink supply container 32. In a state where the ink supply container 32 communicates with the outside air, it functions as an air release valve that quickly discharges the pressurized air in the ink supply container 32 to the outside air and releases the pressure in the pneumatic state. In this example, the pressurizing pump P2 and the regulator R1 correspond to the pressure adjusting unit.

  The feed pump P1 is a positive displacement pump (diaphragm pump) and is driven by pressurized air supplied via a regulator R2 and a three-way valve 71. The regulator R2 and the three-way valve 71 function in the same manner as the regulator R1 and the three-way valve 70, respectively. Pressurized air having a predetermined pressure is supplied to the feed pump P1 by the regulator R2, and the feed pump P1 is fed by the three-way valve 71. Are switched so as to be connected to the regulator R2 side or the outside air side.

  The two-way valves 38a and 39a are also operated by being supplied with pressurized air from the pressure pump P2 via the three-way valves 72 and 73, respectively.

  The ink supply operation from the ink supply tank 30 to the ink supply container 32 is performed by operating the feed pump P1 when the liquid level detection sensor 32a outputs a detection signal. If the ink pressure fed by the feed pump P1 is made higher than the air pressure state in the ink supply container 32, the ink can be supplied into the container.

  As ink is replenished into the ink supply container 32, the ink liquid level rises and the internal air pressure rises. However, since the internal air pressure is maintained at a predetermined air pressure by the regulator R1, ink replenishment is performed. Can continue. When the ink level rises and is detected by the level sensor 32b, the operation of the feed pump P1 is stopped.

  Although the ink pressure is reduced by stopping the operation of the feed pump P1, the check valve 31a is provided, so that the ink does not flow backward from the ink supply container 32. Further, when the pressurized air in the ink supply container 32 is released, the ink supply container 32 is positioned higher than the ink supply tank 30 so that ink does not flow into the ink supply container 32 from the ink supply tank 30 due to the siphon phenomenon. It is good to set to.

  By performing the ink replenishment operation as described above, it is sufficient to replenish ink as necessary so that the ink supply container 32 stores a predetermined amount of ink, and this is used for intermittently operating the feed pump P1. Less frequently and can extend the life of the pump.

  The ink supply operation from the ink supply container 32 to the ink storage unit 20 is such that the ink in the ink supply container 32 is always maintained at a higher air pressure than the atmospheric pressure, and the interior of the ink storage unit 20 is higher than the atmospheric pressure as will be described later. Since the low air pressure state (negative pressure state) is maintained, the ink can be supplied into the ink storing portion 20 by opening the two-way valve 35a of the connecting pipe 35 due to the difference in air pressure between the two. Since the ink can be supplied into the ink reservoir 20 by opening and closing the valve, the ink can be frequently supplied little by little, and the liquid level of the ink reservoir can be maintained with high accuracy. it can. Further, by using an ink supply control component such as a valve, the control response regarding supply and supply stop can be accelerated, so that the ink supply amount can be controlled with high accuracy.

  Further, since the filter 37 is installed on the downstream side of the ink supply container 32, the filter 37 is not subjected to the pulsation of the pump during the ink supply, and the filter is not damaged due to the pulsation of the feed pump P1. Can do. In addition, although the pressure loss of the ink is caused by the filter 37, the air pressure in the ink supply container 32 may be increased correspondingly, and an excessive load is not applied to the pump as in the case where the pump is used for ink supply. . Therefore, even when a filter that removes fine foreign matters is used as the filter 37, there is no problem in ink supply.

  In addition, when ink having settling properties is supplied, the ink can be prevented from settling in the ink supply container 32 by periodically refluxing or circulating the ink to the branch pipe 38 or the return pipe 39.

  The ink supply operation described above is performed by the control unit 100 controlling the feed pump P1, the pressure pump P2, the regulators R1 and R2, and the two-way valves and the three-way valves. Further, an ink supply tank 30 and an ink supply container 32 may be provided for each of the color recording units 10Y, 10M, 10C, and 10K so as to supply ink to each color recording unit.

  The pressure control in the air pressure state in the ink storage unit 20 is performed by controlling the negative pressure adjustment mechanism 40, the pressure adjustment mechanism 50, and the switching unit 60. The negative pressure adjusting mechanism 40 includes a vacuum pump P3 as a negative pressure source, and a vacuum holding container 41 is connected to the vacuum pump P3. The vacuum holding container 41 has a structure capable of holding a pressure close to a vacuum, and periodically drives the vacuum pump P3 to lower the pressure in the vacuum holding container 41 to a level close to vacuum.

  A pressure buffer container 43 is connected to the vacuum holding container 41 via a two-way valve 42. The two-way valve 42 sets the communication state or the cutoff state between the vacuum holding container 41 and the pressure buffer container 43. The pressure buffer container 43 is connected so as to communicate with the ink storage unit 20 of each inkjet head via the switching unit 60, and the air pressure in the pressure buffer container 43 is changed to the ink storage unit in a communication state with the ink storage unit 20. 20 is the same as the air pressure in the gas region A.

  The pressure buffer container 43 is provided with a pressure gauge 44 that detects the air pressure in the container and a two-way valve 45 that communicates or blocks the inside of the container with outside air. The air pressure in the pressure buffer container 43 is always detected by the pressure gauge 44, and when the internal air pressure falls below a predetermined negative pressure state, the two-way valve 45 is opened to communicate with the outside air to increase the internal air pressure. When the internal air pressure rises from a predetermined negative pressure state, the two-way valve 42 is opened to allow the vacuum holding container 41 and the pressure buffer container 43 to communicate with each other, thereby reducing the internal air pressure.

  Therefore, it is not necessary to operate the vacuum pump P3 when adjusting the air pressure inside the pressure buffer container 43, and the operating frequency of the movable parts that operate when the vacuum pump P3 and the pump are driven is reduced. The life of parts can be extended.

  Also, by providing the pressure gauge 44 and the two-way valve 45 in independent pipes, the influence of pressure fluctuation due to the opening of the two-way valve 45 on the pressure gauge 44 can be reduced, and the diameter of the pipe of the two-way valve 45 can be reduced. Can be adjusted so that the inflow of air from the piping is restricted and a sudden pressure fluctuation in the pressure buffer container 43 does not occur.

  When the two-way valves 42 and 45 are shut off, the pressure buffer container 43 is completely shut off from the outside air, and can maintain a stable negative pressure state without performing pressure control. Further, the capacity of the pressure buffer container 43 is set to be larger than, for example, the total capacity of the ink storage part 20 of the recording head part of the color recording part, and the air pressure in the ink storage part 20 fluctuates rapidly. Even in this case, the pressure fluctuation is relaxed in the pressure buffer container 43. For example, if the capacity of the pressure buffer container 43 is set to 200 times or more of the capacity of the ink reservoir 20, the pressure fluctuation in the ink reservoir 20 can be sufficiently relaxed to the extent that it does not affect others.

  The pressurizing adjustment mechanism 50 controls the supply of pressurized air from the pressurizing pump P4 that is a pressurizing source. The pressurizing pump P4 is connected to the switching unit 60 through the two-way valve 51 and the three-way valve 52, and is connected to the ink storage unit 20 through the switching unit 60. The two-way valve 51 opens and closes so that the pressurizing pump P4 communicates with or shuts off the ink reservoir 20. The three-way valve 52 is connected to the pressurizing pump P4 side, the switching unit 60 side, and the side communicating with the outside air, and is connected or switched between the pressurizing pump P4 side and the switching unit 60 side. The unit 60 side and the side communicating with the outside air can be switched to a connected state. In the former state, the pressurized air from the pressure pump P4 is sent from the switching unit 60 to the ink storage unit 20. In the latter state, it functions as an air release valve that quickly discharges the pressurized air in the ink reservoir 20 to the outside air and releases the pressurized state. Note that the two-way valve 51 can be omitted if the pressurized air can be controlled only by the three-way valve 52.

  The switching unit 60 includes a negative pressure side manifold 61 connected to the negative pressure adjustment mechanism 40 and a pressure side manifold 63 connected to the pressure adjustment mechanism 50. The negative pressure side manifold 61 includes a collecting pipe connected to the negative pressure adjusting mechanism 40 and a branch pipe branched from the collecting pipe corresponding to each inkjet head. Each branch pipe is connected to an air pipe L2 of each inkjet head via a two-way valve 62. Since the two-way valve 62 is provided for each branch pipe, it is possible to set a communication state or a cutoff state with the negative pressure adjustment mechanism 40 for each inkjet head.

  The ink storage unit 20 of each recording head unit is set in a state of communicating with the pressure buffer container 43 of the negative pressure adjusting mechanism 40 via the negative pressure side manifold 61, and in the state of communicating with the pressure buffer container 43 in the ink storage unit 20. Is in the same negative pressure state as in the container.

  The pressure side manifold 63 includes a collecting pipe connected to the pressure adjusting mechanism 50 and a branch pipe branched from the collecting pipe corresponding to each recording head unit. Each branch pipe is connected to an air pipe L2 of each recording head portion via a two-way valve 64. Since the two-way valve 64 is provided for each branch pipe, similarly to the negative pressure adjustment mechanism 40, the communication state or the cutoff state with the pressure adjustment mechanism 50 can be set for each recording head unit.

  At the time of normal recording operation or standby, the two-way valve 62 corresponding to each recording head portion is opened, the two-way valve 64 is closed, and the air pipe L2 is connected to the negative pressure adjusting mechanism 40. Then, the ink storage unit 20 is set in a state of communicating with the pressure buffer container 43. Since the pressure buffer container 43 is maintained in a predetermined negative pressure state as described above, the ink reservoir 20 is also set to the same negative pressure state.

  In this case, since the ink reservoirs 20 of the recording heads of the color recording units communicate with the same pressure buffer container 43, all the ink reservoirs 20 can be set to the same negative pressure state. Since the space that communicates the pressure buffer container 43 and each ink reservoir 20 is a closed space that is blocked from outside air, the negative pressure state can be maintained in a stable state. Further, when the negative pressure state fluctuates in some of the ink storage units 20, the pressure buffer container 43 has a much larger capacity than the ink storage unit 20. Thus, it is possible to suppress the influence on the other ink storage unit 20.

  The air pressure inside the pressure buffer container 43 is constantly monitored by the pressure gauge 44 so that a predetermined negative pressure state is maintained, and the ink storage portion of each recording head portion is also in a stable negative pressure state. Retained.

  During a maintenance operation for discharging pressurized ink from the nozzles, first, the two-way valve 62 corresponding to the recording head unit that performs the maintenance operation is closed to block the communication state with the negative pressure adjustment mechanism 40. Next, the two-way valve 51 is opened, the three-way valve 52 is set to a state where the pressure pump P4 side and the switching unit 60 side are connected, and the pressure pump P4 is operated. Then, the two-way valve 64 corresponding to the recording head unit that performs the maintenance operation is opened, and pressurized air is introduced into the ink storage unit 20 via the pressure side manifold 63. By pressurizing the inside of the ink reservoir 20, ink is continuously ejected from the nozzles, and clogging of the nozzles is removed.

  In this example, a two-way valve is used as the on-off valve. However, instead of the two-way valve, one of the three-way valves may be always closed to be used as the on-off valve.

  In this case, since the two-way valve 62 on the negative pressure side is closed, the pressurized air does not flow into the negative pressure adjusting mechanism 40. Further, since the two-way valve 64 is opened only in the target recording head portion, the other recording head portions are not affected by the pressurized air.

  Note that the two-way valve 62 may be closed for the parts other than the target recording head part to block the communication state with the negative pressure adjusting mechanism 40. Even if the communication state is cut off, the ink reservoir 20 of the recording head unit is maintained in a negative pressure state, so that no ink leakage occurs.

  When the maintenance operation is stopped, the three-way valve 52 is set to a state where the switching unit 60 side and the side communicating with the outside air are connected, the communication state with the pressurizing pump P4 is shut off, and the pressurized air is exhausted. The pressure state in the ink storage unit 20 is released. After reducing the pressure inside the ink reservoir 20 to a pressure equal to the atmospheric pressure, the two-way valve 64 is closed and the two-way valve 62 is opened. By opening the two-way valve 62, the state of communication with the negative pressure adjusting mechanism 40 is recovered, and the inside of the ink reservoir 20 can be set to the negative pressure state again.

  In addition, instead of the three-way valve used in this example, a four-way valve in which one side is normally closed may be used, or a four-way valve or more may be used.

  Thus, by providing two-way valves on the negative pressure side and the pressure side corresponding to each recording head portion, it is possible to reliably prevent the influence of pressurized air and perform a maintenance operation. Further, by using an open valve for releasing the pressurization state, it is possible to shorten the time required for pressure reduction, and it is possible to shorten the maintenance operation time. In addition, by controlling the pressure with two two-way valves, the ink reservoir 20 can be set in a closed state with both closed, and the ink is changed during a period in which pressure fluctuation is likely to occur when switching from the negative pressure side to the pressure side. It becomes possible to make the inside of the storage unit 20 completely shut off.

  In the negative pressure adjusting mechanism 40 described above, a pressure buffer container 43 may be provided for each of the color recording units 10Y, 10M, 10C, and 10K so as to communicate with each color recording unit. By providing the pressure buffer container 43 corresponding to each color ink, the negative pressure state can be finely set according to the characteristics such as the viscosity of the ink.

  As described above, by supplying pressurized air into the ink supply container 32 and setting the air pressure state in the internal space to be higher than the air pressure state in the ink reservoir 20, ink is supplied due to the difference in air pressure between the two. Thus, even during the continuous recording operation, it is possible to supply the ink as necessary and continue the recording operation in a stable state. Ink supply can be performed while maintaining the ink in the ink supply container 32 at the supply pressure state, so that the ink supply is continued while supplying ink as necessary even if the volume of the ink supply container 32 is small. And the recording operation can be continued for a long time.

It is a schematic block diagram regarding embodiment which concerns on this invention. FIG. 6 is a side view of the color recording unit when viewed from a conveyance direction Y. It is a schematic sectional drawing regarding a recording head part. It is a schematic sectional drawing regarding a connection part. It is a block block diagram regarding ink supply control and pressure control.

Explanation of symbols

L1 ink supply pipe
L2 Air tube 1 Recording unit 3 Conveyor belt
10 Color recording section
20 Ink reservoir
21 Nozzle
24 Connecting part
25 Connecting part
30 Ink supply tank
31 Ink supply tube
32 Ink supply container
33 Strainer
34 Ink supply tube
35 Connection pipe
36 Container
37 Filter
38 branch pipe
39 Return pipe
40 Negative pressure adjustment mechanism
41 Vacuum holding container
42 2-way valve
43 Pressure buffer container
44 Pressure gauge
45 2-way valve
50 Pressure adjustment mechanism
51 Two-way valve
52 3-way valve
60 selector
61 Vacuum side manifold
62 2-way valve
63 Pressure side manifold
64 2-way valve
100 Control unit

Claims (5)

  A recording head unit having an ink storage unit and a nozzle communicating with the ink storage unit, an ink supply unit connected to the ink storage unit via a supply pipe and storing ink supplied to the ink storage unit; Ink from the ink supply unit to the ink storage unit due to a difference in air pressure in the ink storage unit and in the ink supply unit, and a pressure adjustment unit that sets the inside of the ink supply unit to a higher air pressure than the air pressure in the ink storage unit Supply valve means for controlling supply, an ink supply unit connected to the ink supply unit via a supply line and storing ink supplied to the ink supply unit, and provided in the supply line and the ink An ink jet recording apparatus comprising: an ink supply unit that supplies ink in a replenishment unit to the ink supply unit.   A circulation line connected to the downstream side of the supply line to the ink reservoir and connected to the ink replenishment part to circulate ink from the supply line to the ink replenishment part; 2. The ink jet recording apparatus according to claim 1, further comprising a circulation valve means which is provided in the circulation pipe and controls the circulation of the ink.   3. The ink jet recording apparatus according to claim 1, wherein the supply pipe is provided with a housing portion containing a filter for collecting impurities in the ink.   A branch pipe connected to the storage section and the ink supply section to return the ink in the storage section to the ink supply section, and a reflux valve means provided in the branch pipe and controlling the return of the ink are provided. The inkjet recording apparatus according to claim 3, wherein the inkjet recording apparatus is provided.   An ink jet recording method for recording by ejecting ink from a nozzle communicating with an ink storage unit, wherein the ink supply unit supplies ink to the ink supply unit at a pressure higher than a pneumatic state in the ink supply unit, and supplies the ink The inside of the ink storage unit is set to a higher air pressure than the inside of the ink storage unit, the ink is supplied from the ink supply unit to the ink storage unit due to the difference between the two air pressures, and the ink in the ink storage unit is circulated to the nozzles for recording. An ink jet recording method comprising:

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