JP2012218302A - Inkjet recorder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a recorder including a sub tank arranged between a main tank and an inkjet head, while preventing an increase in size, and removing air bubbles produced in the inkjet head.SOLUTION: In the inkjet recorder including the sub tank arranged between the main tank and the inkjet head, a tube pump is used as a pressure adjusting means for adjusting air pressure in the sub tank, while a valve for opening/closing a channel is not used. Furthermore, the inside of the sub tank is divided into three spaces such as an ink inflow part, an ink outflow part and an outside air communication part by a porous member, and thereby, ink and gas necessarily move through the porous member.

Description

  The present invention relates to a recording apparatus, and more particularly to an inkjet recording apparatus.

  Conventionally, as shown in Japanese Patent Application Laid-Open No. 2003-182104, an ink jet head that discharges ink for drawing and a sub tank is provided at a position higher than the ink jet head, and the inside of the sub tank is forcibly decompressed by a decompression pump, There has been disclosed a system in which a speed controller is provided, the pressure of the sub tank is sensed by a pressure sensor, and when the pressure exceeds a predetermined pressure value, outside air is introduced by the speed controller to keep the sub tank at a predetermined pressure. In addition, since an ink jet printer has an ink jet head for each ink color, a sub tank is provided for each ink color.

JP 2003-182104 A

  However, with the conventional technology, the pressure adjustment pump can only be adjusted to the decompression side in order to maintain a state where drawing is possible, so it is necessary to arrange each sub-tank higher than the inkjet head, which is a design constraint of the device. As a result, the carriage holding the inkjet head is deviated, leading to an increase in the rigidity of the Y-axis rail that supports the carriage and makes the carriage movable in the main scanning direction. This leads to a situation that does not exist. In addition, since the conventional technology uses a positive pressure pump for filling work, in order to initially fill the head with ink accumulated in the sub tank, the sub tank is pressurized by the positive pressure pump and ink is ejected from the tip of the head. I was letting. However, since a viscous liquid such as ink passes through an ink discharge port having a diameter of several tens of μm, the ink flow rate from the sub tank to the ink jet head decreases. The filter at the ink discharge port, the bent flow path, and the air bubble trapped in the other flow path stay in the head without being discharged out of the ink jet head together with the ink. The ink accumulates in the ink pressure chamber that gives discharge energy to the ink, causing a problem that ink discharge failure occurs.

  In order to solve this problem, the present inventor makes it possible to perform long-time printing arranged in a printing machine main body outside a carriage that holds an inkjet head that discharges ink of a single color or a plurality of colors and moves it in the main scanning direction. A main tank corresponding to each color and a carriage, and the head back pressure supplied from the main tank is maintained within a range of +100 mmAq or less to −300 mmAq or more, preferably −50 mmAq or less to −100 mmAq or more. A sub-tank having a first communication port that holds the corresponding ink independently and communicates with the ink-jet head, and the sub-tank connects the main tank and the sub-tank and serves as a communication port for an ink supply tube that can supply ink. In the middle or end of the ink supply tube path An ink supply pump for supplying ink from the in-tank to the sub-tank, a valve mechanism that enables communication between the main tank and the sub-tank in the ink supply tube, and a plurality of positions at a position higher than the first communication port At least one of the pressure adjustment tubes provided with the third communication port and connected to each of the third communication ports and the other end communicating with the outside air is located in the middle or the end of the pressure adjustment tube and is in the sub tank. A pressure pump for adjusting the air pressure of the engine to the back pressure and an external air communication valve that enables communication and shutoff with the outside air, and at least one of the pressure adjustment tubes enables communication and shutoff with the decompression pump and the external air Detecting means for detecting the air pressure in the sub tank provided in the outside air communication valve, the sub tank, or a part of the pressure adjustment tube Provided, and so can also be adjusted to a positive pressure in the sub-tank.

  Furthermore, when the ink jet head is in a standby state or a maintenance state, it has a cap mechanism that can be sealed to prevent the ink discharge port of the ink jet head from drying and to prevent entry of foreign matter. A maintenance unit that has a suction function that can suck ink from the air and an air introduction valve mechanism that can be released from the sealed structure is provided, and when filling ink, the sub-tank from the inkjet head or the upstream communicating part is made negative pressure, An ink jet recording apparatus has been proposed in which ink filling can be started after the area from the ink jet head to the sub-tank or further upstream is evacuated or close to it (30 kPa or less).

  However, in the invention proposed by the inventor, it is possible to remove bubbles generated in the ink jet head which cannot be solved by Japanese Patent Laid-Open No. 2003-182104. However, the ink in the supply pump and the sub tank is disposed in the middle path of the ink supply tube. A valve mechanism that enables communication and disconnection is required. Further, a plurality of pressure adjusting tubes are provided to adjust the pressure in the sub tank, and an external air communication valve that enables communication with and disconnection from the pressurizing pump and the outside air, and at least one of the pressure adjusting tubes is connected to the pressure reducing pump and the outside air. This requires an outside air communication valve for enabling and shutting off the ink, and the ink supply mechanism and the pressure adjustment mechanism are complicated, leading to an increase in product cost. In addition, there is a problem that the recording apparatus itself is increased in size.

  In order to solve the above-described problems, the present invention enables long-time printing arranged in a recording apparatus main body outside a carriage that holds an inkjet head that discharges ink of a single color or a plurality of colors and moves it in the main scanning direction. A main tank corresponding to each color and a carriage are provided in the ink jet head by independently holding ink corresponding to each head while maintaining the head back pressure supplied from the main tank within the range of +100 mmAq or less to −300 mmAq or more. A sub-tank having a first communication port that communicates, and the sub-tank has a second communication port that serves as a communication port for an ink supply tube that connects the main tank and the sub-tank so that ink can be supplied. Ink supply for supplying ink from the main tank to the sub tank at the end The tube has a so-called tube pump that moves in the direction of ink flow while crushing a portion of the tube with a rigid body and performs the pump effect with the restoring force of the tube, and by always crushing a portion of the tube, it also has a valve effect By omitting the valve mechanism. Further, by providing a tube pump in the middle of the pressure adjusting tube in which the third communication port is provided at a position higher than the first communication port and the other communication port is connected to the third communication port, the rigid body is Pressure adjustment was realized by applying pressure by moving in the pressurizing direction and decreasing pressure by moving in the depressurizing direction. Therefore, in the above-described invention, a pressure pump and a pressure reducing pump are required, but they can be used together. In addition, the outside air communication valve that enables communication and blocking with the outside air is realized by crushing the tube of the tube pump, so that it can be omitted. In addition, a detection means for detecting the air pressure in the sub tank or in a part of the pressure adjustment tube is provided, and the rotation direction and the rotation time of the tube pump are controlled based on the detection result.

  Furthermore, when the ink jet head is in a standby state or a maintenance state, it has a cap mechanism that can be sealed to prevent the ink discharge port of the ink jet head from drying and prevent foreign matter from entering. A maintenance unit with a suction function that can suck ink from the outlet and an air introduction valve mechanism that can be released from the sealed structure is provided, and when ink is filled, the sub tank or the upstream communication part is made negative pressure from the inkjet head. Ink filling can be started after the area from the inkjet head to the sub-tank or further upstream is evacuated or close to it (30 kPa or less).

  The present invention can simplify the ink supply system by omitting the open / close valve by using a tube pump as the ink supply pump. In addition, by using a tube pump as a pressure adjustment pump, both the pressurization pump and the pressure reduction pump can be shared by a single pump, and the open / close valve can also be shared by a tube pump to simplify the pressure adjustment mechanism. It was.

  Further, the ink can be spread all over the path from the sub tank to the ink jet head, and bubbles can be prevented from staying.

  In addition, it is located between the pressure adjustment pump of the pressure adjustment tube and the sub tank, and is equipped with an air buffer that can store a certain amount of air at the same pressure as the air pressure of the sub tank. Thus, a rapid change in back pressure due to a change in ink height can be reduced, and stable printing can always be continued.

  Furthermore, in an ink jet recording apparatus that discharges a plurality of colors of ink, by connecting the air buffers of all colors or arbitrary colors, a decompression pump, a pressurization pump, and an outside air communication valve can be used in common. Simplify roads and reduce costs.

  The maintenance of the ink jet head can selectively perform either the ink suction operation by the suction mechanism or the discharge operation by the pressure pump, so that the reliability of the ink jet head can be improved.

  Further, a fourth communication port is provided at a height lower than the second communication port of the sub tank, and has an ink circulation tube that connects the main tank and the sub tank so that the main tank can be discharged. An ink circulation pump for supplying ink from the main tank to the sub-tank at the end, and a valve mechanism that enables the ink communication between the main tank and the sub-tank on the ink circulation tube are provided. By circulating, precipitation of dispersed pigments and the like can be prevented.

  Further, the sub-tank is interposed between the first communication port, the second communication port, and the third communication port, and includes a space having at least the first communication port and a space having the second and third communication ports. It has a porous wall that has a capillary effect, and the bubbles that are sent together with the ink supplied from the ink supply tube are retained in the porous wall to prevent inflow into the ink jet. I can do it.

  Furthermore, the sub-tank has a means for detecting the remaining amount of ink in a space that is separated from the porous wall by at least two locations, and at least one of the walls is a lower surface in the direction of gravity. By detecting the remaining amount of ink exceeding the porous height on the lower surface, it is possible to prevent fluctuations in the liquid level caused by vibration when moving in the main scanning direction together with the head, and accurately in the sub tank. The remaining amount of ink can be detected.

  Furthermore, the sub-tank has a heater function capable of heating and keeping the ink maintained at a constant temperature to the ink-jet head, and the temperature-dependent ink always injects the ink under the same conditions. Can be supplied to the head.

1 is a perspective view illustrating an entire inkjet recording apparatus according to an embodiment of the present invention. FIG. 3 is a block diagram of an ink and air flow path system of the recording apparatus according to the embodiment of the invention. It is a block diagram of the ink suction structure of the embodiment of the present invention. It is the schematic of the air buffer used for the recording device of embodiment of this invention. It is the schematic when the air buffer of embodiment of this invention is shared. It is the schematic of the sub tank of embodiment of this invention. It is the schematic in the case of having the circulation path of the sub tank of embodiment of this invention. It is a figure of the 1st example which shows the ink residual amount detection method in the sub tank of embodiment of this invention. It is a figure of the 2nd example which shows the ink residual amount detection method in the sub tank of embodiment of this invention. It is a figure of the 3rd example which shows the ink residual amount detection method in the sub tank of embodiment of this invention. It is an external view of the sub tank of the embodiment of the present invention. It is a block diagram of a channel system in the case of having a circulation path of an embodiment of the present invention. It is the schematic of the tube pump currently implemented by embodiment of this invention.

Embodiments of the present invention will be described with reference to the drawings.
First, the entire recording apparatus will be described with reference to FIG. FIG. 1 is a perspective view showing a configuration of a recording apparatus according to an embodiment of the present invention. As shown in FIG. 1, the ink jet recording apparatus 9 conveys a sheet-like or plate-like recording medium 8 indicated by a one-dot chain line, and an image or character corresponding to image data on the surface of the recording medium 8 by an ink jet method. Etc. are recorded. The recording medium 8 is a sheet made of paper, cloth, synthetic resin such as polyester or PVC.

  The ink jet recording apparatus 9 includes a conveyance roller that is rotated by a rotational drive of a motor, and a pressure roller unit 11 that is a roller that presses the conveyance roller. The recording medium 8 is sandwiched between the conveying roller and the pressure roller, and is conveyed by the rotation of these rollers.

  A platen 6 that supports the recording medium 8 is provided downstream of the pressure roller unit 11 in the conveying direction. The platen 6 is a place where printing is performed on the recording medium 8 by an ink jet head mounted on the carriage 1. In the ink box 3, an ink cartridge containing ink to be supplied to the inkjet head is accommodated so as to be inserted and removed. The carriage 1 reciprocates along a linear Y rail 4. A heater for heating the platen 6 is provided below the platen 6. With this heater, the platen 6 is heated, and the recording medium 8 is further heated, thereby facilitating the fixing of the ink ejected to the recording medium 8. Further, a paper guide 7 is provided downstream of the platen 6, and the recording medium 8 is conveyed along the paper guide 7 and output. The cable bear 2 includes an ink supply tube that supplies ink therein, a pressure adjustment tube, and the like, and can move while smoothly bending the above-described tube when the carriage moves in the main scanning direction. It is like that. The cap mechanism 5 is sealed to prevent the ink-jet head from drying during standby, suction of ink when the ink-jet head is filled with ink, and foreign matter and bubbles when ink or foreign matter enters the ink-jet head. Can suck. The cap mechanism 5 is disposed outside the conveyance path of the recording medium.

  Next, the ink supply system will be described with reference to FIGS. FIG. 2 is a block diagram showing an ink supply system and a pressure adjustment system using air, that is, a flow path system for ink and air, according to an embodiment of the present invention.

  The ink jet recording apparatus 9 includes a carriage 1 that houses an ink jet head 14 that performs recording by ejecting ink droplets with the ink ejection surface facing the recording medium 8, and a sub tank 20 that supplies ink to the ink jet head 14. A conveyor belt (not shown) connected to the carriage 1, a drive pulley (not shown) and a driven pulley (not shown) for moving the conveyor belt, and a drive motor (not shown) for driving the drive pulley to rotate. And a guide rail 15 that guides the scanning of the carriage 1 in a direction (main scanning direction) orthogonal to the conveyance direction (sub-scanning direction) of the recording medium 8, and the Y rail 4 that supports the guide rail 15 over its entire length. Is equipped. The Y rail 4 is generated by an extruded material of aluminum or a square member of sheet metal or the like, and depends on fluctuations in the distance between the recording medium 8 and the ink jet head 14 due to vibration when the carriage 1 travels in the main scanning direction, and on the weight of the carriage 1. Rigidity is secured so that fluctuations in the distance between the recording medium 8 and the inkjet head 14 can be suppressed as much as possible.

  Ink supplied to the inkjet head 14 is stored in the ink cartridge 30. The ink cartridge 30 is a replaceable cartridge type ink container that is stored in the ink box 3 shown in FIG.

  The sub tank 20 is connected to one end of the ink supply tube 16, and the other end of the ink supply tube 16 is connected to the ink cartridge 30. The ink supply tube 16 supplies ink from the ink cartridge 30 to the sub tank 20 by operating the ink supply pump 31. The sub tank 20 will be described later.

  An ink supply pump 31 for supplying ink from the ink cartridge 30 to the sub tank 20 is provided in the middle of the path of the ink supply tube 16, and when the ink in the sub tank 20 falls below a predetermined amount, the ink supply pump 31 is driven. To supply ink. The ink supply pump 31 may be disposed at the end of the ink supply tube 16. The sub tank 20 and the inkjet head 14 are connected by a head tube 21. The ink supply pump 31 uses a tube pump described later. Since the tube pump always crushes a part of the tube with a rigid body, the tube can be closed. Thereby, the backflow of ink can be prevented, and a check valve and a solenoid valve for preventing backflow can be eliminated.

  The sub tank 20 is provided with a third communication port 13 as a pressure adjustment port at a position higher in the direction of gravity than the first communication port 10 to which the head tube 21 is connected, and the pressure adjustment tube 18 is connected. The sub tank 20 is provided with a second communication port 12 to which the ink supply tube 16 is connected.

  Further, a pressure adjusting pump 33 is provided at the other end of the pressure adjusting tube 18. The position of the pressure adjusting pump 33 may be not the end of the pressure adjusting tube 18 but the middle. Further, at least one pressure adjusting pressure sensor 19 is provided between the pressure adjusting pump 33 on the pressure adjusting tube 18 and the sub tank 20, and when the atmospheric pressure in the sub tank 20 is higher than the set value. The pressure adjusting pump 33 is operated in the pressure reducing direction, and conversely, when the atmospheric pressure is lower than the set value, the pressure adjusting pump 33 is operated in the pressurizing direction, so that the back pressure necessary for stable ink ejection of the inkjet head 14 can always be maintained.

  Further, as the pressure adjusting pump 33, a tube pump is used in the same manner as the ink supply pump 31, but since a part of the tube is always crushed by a rigid body, it can be shut off from the outside air and no solenoid valve is required.

  The ink jet head 14, the sub tank 20, the ink cartridge 30, the ink supply tube 16, the pressure adjusting tube 18, the ink supply pump 31 connected to each tube, and the pressure sensor 19 are provided for each ink color.

  As shown in FIG. 4, an air buffer 37 may be provided between the sub tank 20 and the pressure adjustment pump 33. The air buffer 37 functions to alleviate sudden pressure fluctuations in the sub tank 20. The volume of the sub tank 20 placed on the carriage 1 is limited by the driving conditions of the carriage 1 and the external shape of the apparatus, and it is difficult to take a large volume. Further, the ink in the sub tank 20 is a factor that determines how much printing can be performed after the ink cartridge 30 runs out of ink, so that considering the ease of use of the printing apparatus, the sub tank 20 has as much ink as possible. Is advantageous. For these reasons, when the volume occupied by air is reduced, the volume fluctuation due to the increase / decrease in ink greatly affects the pressure fluctuation in the sub-tank 20, so that the pressure adjustment pump 33 frequently switches between pressurization and decompression and cannot follow up. Although the pressure fluctuation in the sub tank 20 may become large, if the air buffer 37 is provided as described above, the volume occupied by air is larger than the ink fluctuation volume, so that the pressure fluctuation can be suppressed small. . If the pressure in the air buffer 37 is detected by the pressure sensor 19, pressure fluctuation and vibration are reduced, so that the accuracy of the pressure value is improved.

  In FIG. 4, the air buffer 37 is connected by one air buffer 37 for one color, but the present invention is not limited to this. As shown in FIG. 5, a plurality of colors may be connected by a common air buffer 37.

  In FIG. 5, the sub-tanks 20a, 20b, 20c, and 20d that are paired with the four inkjet heads 14a, 14b, 14c, and 14d are connected to a common air buffer 37, thereby simplifying the pressure adjustment mechanism. Yes. That is, if at least one pressure adjusting pump 33 is provided in the common air buffer 37, the back pressures of the ink jet heads 14a, 14b, 14c, and 14d can be maintained equal, so that the pressure adjusting mechanism can be further simplified. Furthermore, if the pressure in the air buffer 37 is detected by the pressure sensor 19, the number of pressure sensors 19 can be reduced. The sub tanks 20a, 20b, 20c, and 20d are respectively corresponding ink cartridges 30a, 30b, 30c, and 30d, ink supply tubes 16a, 16b, 16c, and 16d, ink supply pumps 31a, 31b, 31c, and 31d, and pressure adjustment tubes 18a, 18b, 18c, and 18d are provided.

  Next, the sub tank 20 will be described. FIG. 6 is a cross-sectional view of the recording apparatus according to the embodiment of the present invention when divided in the vertical direction of the sub tank. The sub-tank 20 prevents the ink in the ink supply tube 16 from being transmitted to the inkjet head 14 when the ink in the ink supply tube 16 repeatedly expands and contracts in accordance with the movement of the carriage 1 in the main scanning direction. In order to provide the inkjet head 14 with a stable pressure generated inside, it is roughly composed of an outer frame 20a and a side plate 20b covering the cross-sectional direction in order to temporarily store ink. Various structures and processing methods can be considered for the component configurations of the outer frame 20a and the side plate 20b. For example, a method in which one of the outer frame 20a and the side plates 20b on both sides is formed by aluminum die casting or integral plastic molding, and the other one side plate 20b is formed by a later screwing or welding, etc., outer frame A method may be considered in which 20a is formed of aluminum or a plastic extruded material, and the side plates 20b on both sides are screwed or welded to form a sealed structure. The method is not limited to one. In this embodiment, as shown in FIGS. 6 and 11, the outer frame 20a is made of an extruded aluminum material, and both sides are sandwiched between aluminum side plates 20b. The frame 24 is fixed to the inner wall of the outer frame 20a. The frame 24 is provided with screw holes along the outer frame 20a. The side plate 20b is fixed to the frame 24 using screws 25, and the side plate 20b It can be tightened so as to sandwich both sides of the outer frame 20a. At this time, a seal such as rubber (not shown) is sandwiched between the outer frame 20a and the side plates 20b attached to both sides, so that the inside of the sub tank 20 is secured. In this embodiment, it is made so that a sealed space of about 120 ml can be obtained. The sub tank 20 is provided with a first communication port communicating with the inkjet head 14, and the first communication port is connected to one end of the head tube 21. The other end of the head tube 21 is connected to the ink supply port of the inkjet head 14. Further, a second communication port that communicates with the ink supply tube 16 and serves as an ink supply port is provided. This second communication port is preferably located near the bottom surface inside the sub tank 20 in order to prevent foaming at the time of supply. If a second communication port is provided at the top of the design, a pipe is extended into the sub tank 20. A structure in which ink is dropped near the bottom is desirable. Further, the sub tank 20 is provided with a third communication port. The third communication port is connected to the pressure adjusting tube 18. The third communication port is provided in the upper part of the sub tank 20 in the vertical direction.

  Next, members included in the sub tank will be described. A space 45 having at least a first communication port, a space having a second communication port, and a space interposed between the first communication port, the second communication port, and the third communication port in the sub tank 20; There is a porous member 26 having a capillary effect that partitions into a space having a third communication port. Each space is constituted by the porous member 26, the outer frame 20a, and the side plate 20b. This prevents bubbles and bubbles discharged from the ink supply tube 16 from flowing into the first communication port connected to the ink jet head 14, and the ink level in the sub tank 20 when the carriage moves in the main scanning direction. This prevents the fluctuation of the pressure in the sub-tank 20 from being transmitted to the first communication port. Further, it becomes an obstacle to the movement of ink in the sub-tank 20, can prevent sudden ink movement and accompanying pressure fluctuation, and can stably supply ink to the inkjet head 14.

  The sub tank 20 is provided with a mechanism for detecting the remaining amount of ink as shown in FIG. This remaining amount detection method is characterized in that the liquid level in a space surrounded by at least two sides including the lower part of at least the porous member 26 is observed. A microswitch 23 is used that operates when the float 22 that floats or sinks according to the height of the liquid level reaches a specific position. Here, it is preferable to look at the liquid level in the space surrounded by the lower and left and right three directions. The purpose is to detect the remaining amount of ink as accurately as possible while suppressing the fluctuation of the liquid level that occurs when the carriage 1 moves in the main scanning direction as much as possible. Further, by setting the remaining amount of ink in the sub tank 20 within a predetermined range, it is possible to suppress pressure fluctuation according to the remaining amount of ink. That is, by reducing the difference between the change speed of the air pressure when there is a lot of air and the change speed of the air pressure when there is little air, the influence on the ink ejection can be suppressed. Therefore, management of the remaining amount of ink is important, and it is necessary to perform control according to the exact remaining amount of ink.

  As a detection method, there is a method of detecting that the float 22 shown in FIG. 8A and FIG.

  Further, as shown in FIGS. 9A and 9B, there is a method of embedding a magnet 27 in the float 22 and detecting the fluctuation of the magnet by the magnetic sensor 28. FIG. Furthermore, as shown in FIGS. 10A and 10B, there is a method of directly reading the height of the liquid level with a photo interrupter 29 without using the float 22. The detection method for detecting the position of the liquid level by such detection means and detecting the remaining amount in the sub-tank 20 is not limited to this, but the ink level in the space surrounded by the porous member 26 is detected. Needless to say, any method that can be detected is applicable. However, in any method, for example, it is necessary to suppress fluctuations in the liquid level of the ink 100 such as fluctuations in the liquid level accompanying movement of the carriage 1 as much as possible. is there.

  Further, as shown in FIG. 7, the sub tank 20 may have a structure in which a fourth communication port is provided, the circulation tube 40 is connected, and the ink in the sub tank 20 is returned to the ink cartridge 30. In this case, the first communication port and the fourth communication port open into the space 45 and are separated from the other communication ports by the porous member 26. Ink is circulated from a position close to the inkjet head 14 so that the ink does not stay in the sub tank 20.

  As shown in FIG. 12, the circulation tube 40 is connected to the fourth communication port 17, and a circulation pump 38 is provided on the other end or path of the circulation tube 40, and the ink in the sub tank 20 is supplied to the ink cartridge 30. It is possible to return to. This mechanism is effective in the case of ink in which particles such as pigment dispersed in the ink are settled. For example, when the carriage 1 is stopped during standby, the circulation pump 38 is driven and the sub tank 20 is driven. The ink can be collected in the ink cartridge 30 and the supply pump 31 can be driven to circulate the ink between the ink cartridge 30 and the sub tank 20 to prevent the ink from settling. A diaphragm pump or a piston pump is used as the circulation pump 38, but an electromagnetic valve 39 for preventing a backflow is required depending on the structure of the pump. It is also possible to omit the solenoid valve using a tube pump.

  Further, in FIG. 11, a heater 43 is provided on the outer periphery of the sub tank 20 to adjust the ink temperature in the sub tank to a certain temperature range. This purpose is effective when using high-viscosity inks. By increasing and decreasing the temperature of the ink to a constant temperature, the viscosity of the ink supplied to the head can be kept within a certain range, and the ink ejection stability In this case, there is an effect that the driving method of the ink jet head 14 for ensuring the discharge and the ejection can be simplified, and the compatibility with the external environment in a wide temperature range is widened. Needless to say, when the heater 43 is provided outside, it is better to select a metal material such as aluminum or stainless steel having good thermal conductivity as the material of the outer walls 20a and 20b of the sub tank 20.

  Further, as shown in FIGS. 1, 3 and 4, the ink jet printer 9 is used to prevent the ink discharge port of the ink jet head 14 from drying and to prevent foreign matter from entering when the ink jet head 14 is in a standby state or a maintenance state. The cap mechanism 5 has a cap mechanism 5 that can be sealed. The cap mechanism 5 sucks ink from the ink discharge port through the cap 50 that seals the ink discharge port of the inkjet head 14 and the waste liquid tube 54. A maintenance unit having a suction pump 51 to be sent and an air introduction valve mechanism 53 that can be released from the sealed state via a valve tube 55 is provided. When filling the ink jet head 14 with ink, first, the suction pump 51 is also operated to make the inside of the ink jet head 14, the sub tank 20, and the ink supply tube 16 have a negative pressure. Further, the ink supply pump 31 is operated to supply ink to the sub tank 20 to accelerate the ink flow. The purpose is to accelerate the flow of ink and cause bubbles that tend to stay in the ink supply path to flow together and to be discharged from the inkjet head 14. Next, when a certain amount of ink is accumulated in the sub tank 20 by the ink remaining amount detection method provided in the sub tank 20, the ink supply pump 31 and the suction pump 51 are stopped to complete ink filling.

  In the case of the ink supply system shown in the conventional example, the ink is sent into the head by accumulating the ink in the sub tank and pressurizing the sub tank with air. However, in this case, the filter trapped in the ink discharge port of the inkjet head from the sub tank, the bent flow path, and the air bubble trapped in the other flow path stay in the head without being discharged out of the inkjet head together with the ink. Occasionally, the ink stays in the ink pressure chamber, which gives the ink ejection energy to cause the ink to be ejected, and causes the ejection failure of the ink, or causes the problem that the stagnant bubbles block the flow path and the ink does not flow. .

  In the present embodiment, when ink is discharged from the ink jet head 14 during maintenance of the ink jet head 14, it is possible to select whether to discharge ink by the ink supply pump 31 or to suck ink by the suction pump 51. That is, cleaning is completed by preventing the ink jet head 14 from being clogged with dust or pressurizing the ink by the supply pump 31 during the wiping operation (not shown), that is, during normal cleaning, and pushing out the ink. However, when the media 8 is jammed and the media 8 and the inkjet head 14 are brought into intense contact with each other, air may be mixed into the inkjet head 14 and an ejection failure may occur. In such a case, suction is performed from the nozzle side of the ink jet head 14 by the suction pump 51, the air pressure in the ink jet head 14 is lowered, the ink has a flow velocity, and the ink is discharged out of the ink jet head 14 while entraining air. Thus, the cleaning of the inkjet head 14 can be completed effectively by using the supply pump 31 and the suction pump 51 properly in accordance with the cleaning mode.

  The air introduction valve 53 is necessary for discharging the ink remaining in the cap 50 after sucking out the ink. Without this valve, the cap mechanism 5 continues to suck ink from the head and after the ink is sucked, the meniscus of the nozzle is sucked. It becomes impossible to form.

  Next, the tube pump will be described with reference to FIG. The tube pump is a general pump used in an ink jet recording apparatus and a medical device, and the pump used in the present invention is also the same.

  The pump case 60 is provided with a curved surface 60a on an arc concentric with the pump drive shaft 64, and holds the pump tube 65 together with the tube roller 62 along the curved surface 60a. The tube roller 62 is a rigid body that is rotatably supported by a pin 63 in the vicinity of the outer periphery of the disk 61 that is rotatably supported by the pump drive shaft 64. The tube roller 62 rotates with the rotation of the disk 61 while crushing the pump tube 65 on the outer periphery of the tube roller 62. A circular motion can be performed. At least two tube rollers 62 are provided in the disk 61, and at least one tube roller 62 can always crush the tube roller to block the fluid flowing in the pump tube 65. The material of the pump tube 65 is preferably an elastic tube such as a plastic tube or a rubber tube. The pump drive shaft 64 is connected to a drive motor (not shown) and can rotate forward and backward in accordance with the rotation direction of the drive motor. Accordingly, when used as the ink supply pump 31, the ink supply pump 31 may be incorporated so that the ink flows from the ink cartridge 30 to the sub tank 20 while being fixed in one direction in the driving direction. When the pressure adjusting pump 33 is used, it is installed in the middle or at the end of the pressure adjusting tube 18 to rotate the drive motor in the direction of feeding air, and to depressurize the drive motor in the direction of sucking air. Rotate. The pressure adjusting tube 18 connected to the outside air can block the outside air because a part of the pump tube 65 is always crushed. When the pressure adjusting tube 18 does not operate, the outside air can be shut off and the sub tank can be sealed.

  The present invention can be used in a recording apparatus such as an ink jet printer having a sub tank.

DESCRIPTION OF SYMBOLS 1 Carriage 5 Cap mechanism 14 Inkjet head 16 Supply tube 18 Pressure adjustment tube 19 Pressure sensor 20 Sub tank 22 Float 23 Micro switch 26 Porous member 27 Magnet 28 Magnetic sensor 29 Photo interrupter 30 Ink cartridge 31 Supply pump 33 Pressure adjustment pump 38 Circulation pump 50 Cap 51 Suction pump 53 Air introduction valve mechanism

Claims (6)

An ink jet head that discharges ink supplied from a main tank, a second communication port that is disposed in the middle of a path from the main tank to the ink jet and communicates with the ink jet head and a second tank that communicates with the main tank. A sub tank provided with a communication port and a third communication port that is provided at a position higher than the first communication port and communicates with a pressure adjusting means that varies the internal air pressure, and the inkjet head are mounted and moved in the main scanning direction. In the ink jet recording apparatus, wherein the air pressure is varied in order to maintain a back pressure in the ink jet head within a range of +100 mmAq or less to −300 mmAq or more by the pressure adjusting unit.
The pressure adjusting means is a tube pump for moving the air in the elastic tube and closing the elastic tube by moving the rigid body while crushing a part of the elastic tube disposed inside by the rigid body,
The sub-tank is interposed between the first communication port, the second communication port, and the third communication port, and has a space having the first communication port and a space having the second communication port. And a wall of a porous member that causes a capillary phenomenon to be partitioned into a space having the third communication port,
A liquid surface detecting means for detecting a position of a liquid surface of the ink in the recessed portion, having a recessed portion in a vertical direction in a part of the wall forming the space having the third communication port;
The ink jet recording apparatus further includes an air pressure detecting means for detecting the air pressure,
An ink jet which stores a predetermined amount of the ink in the sub-tank based on a detection result of the liquid level detection means and varies the air pressure of the sub-tank based on the air pressure detected by the atmospheric pressure detection means. Recording device.   An air buffer is further disposed between the sub tank and the pressure adjusting means to suppress pressure fluctuations in the sub tank, and the detecting means detects the pressure of the air buffer, and the detected pressure is used as the sub tank. The ink jet recording apparatus according to claim 1, wherein the pressure is an internal pressure.   The inkjet head and the sub tank are provided corresponding to each of a plurality of colors of ink, and the air buffer is connected to the plurality of sub tanks, and the air pressures of the connected sub tanks are the same. The ink jet recording apparatus according to claim 2. A cap for sealing the ink discharge port of the inkjet head;
A suction means for sucking the ink from the ink discharge port when the ink discharge port is sealed by the cap;
A pump that is disposed between the sub tank and the main tank and supplies ink from the main tank to the sub tank;
Have
When the ink jet head is filled with ink, the ink is sucked by the suction means when the ink discharge port is sealed with the cap, and the ink is supplied from the main tank to the sub tank by the pump. 4. The inkjet recording apparatus according to claim 1, wherein the ink is supplied from the sub tank to the inkjet head. 5. The sub tank has a fourth communication port at a position lower than the second communication port,
The ink jet printer further connects the main tank and the fourth communication port, allows an ink circulation tube to discharge the ink from the fourth communication port to the main tank, and the ink in the ink circulation tube. A pump for discharging the ink to the main tank, a valve for closing the ink circulation tube to stop the movement of the ink from the sub tank to the main tank, and a supply for moving the ink from the main tank to the sub tank The inkjet recording apparatus according to claim 1, further comprising a pump, wherein the ink circulates between the main tank and the sub tank.   6. The ink jet recording apparatus according to claim 1, wherein the sub tank includes a heater that maintains the ink supplied to the ink jet head at a constant temperature.

Images