JP2010208146A - Inkjet recording apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recording apparatus capable of constituting the apparatus to be small-sized at a low cost by repeatedly feeding a fixed amount of ink from a first ink tank to a second ink tank, and surely suppressing overflowing of the ink from the second ink tank. <P>SOLUTION: The second ink tank 4 can be communicated with the first ink tanks 5 and 6 and a recording head 1 capable of discharging the ink. The inks in the first ink tanks 5 and 6 are repeatedly fed by a fixed amount to the second ink tank 4. The second ink tank 4 has a fixed amount or more of volume on the upper side in the vertical direction from a standard water head liquid face L3 which is a liquid face where the inks stored in the first ink tanks 5 and 6 are open to the atmosphere. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an ink jet recording apparatus that performs recording by discharging a liquid onto a recording medium.

  At present, as an ink jet recording apparatus that performs recording by discharging ink, a serial type ink jet recording apparatus in which a recording head and an ink tank are mounted on a carriage that moves in a direction crossing a recording sheet is known. In this type of ink jet recording apparatus, when the ink tank becomes large, a large amount of power is required for driving the carriage.

  Therefore, an ink jet recording that employs a so-called tube supply system in which the ink tank and the recording head are arranged at different positions, connected by a tube, and ink is supplied from the ink tank to the recording head via the tube. Devices are also known. However, even if the tube supply method is adopted, the amount of ink in the ink tank is finite, so that if the ink in the ink tank is used up, it is necessary to replace the ink tank.

  In the serial type ink jet recording apparatus, when the ink in the ink tank runs out during the recording operation for one recording medium, it is necessary to interrupt the recording operation and replace the ink tank. In this case, there may be a color difference between the recording portion formed immediately after resuming the recording operation and the other portions. That is, when the recording operation is continuously performed, inks of different hues ejected at the same position are mixed with each other on the recording medium, so that an appropriate mixed color can be obtained. However, when the recording operation is interrupted, liquid ink is ejected on the dried ink, so that both inks are not mixed sufficiently, and the ink ejected first and the ink ejected later A mixed color in which the hue of one of the inks is emphasized is obtained. In this case, a color difference (color unevenness) occurs between the recording portion where the recording is continuously performed and the portion where the recording is resumed after being interrupted by the in-tank replacement.

  In order to avoid running out of ink in the ink tank during such a recording operation, Patent Document 1 discloses an ink jet recording apparatus in which a sub tank is provided in addition to the main tank. In the ink jet recording apparatus shown here, ink is supplied from a replaceable large-capacity main tank to a sub-tank having a relatively small volume, and ink stored in the sub-tank is supplied to the recording head.

  Therefore, even if the main tank runs out of ink during recording on one recording medium, it is possible to continue recording by using the ink stored in the sub tank. If the replacement of the main tank is completed while recording is being performed with the ink supplied from the sub tank, the recording operation can be performed without interruption, and the quality of the recorded image can be maintained high. it can.

  Further, Patent Document 2 discloses a configuration in which when the surplus gas in the sub tank is exhausted by the pump and the ink liquid level rises, the float closes the exhaust port and the exhaust operation ends.

JP 2001-113716 A JP 2000-301737 A

By the way, in recent inkjet recording apparatuses, further performance improvement and cost reduction are required. As a measure for realizing the performance improvement, for example, increasing the number of inks used for expanding the color expression area is performed. However, in order to increase the number of inks to be used, it is necessary to increase the number of recording heads and the number of ink supply systems, which results in a contradiction to cost reduction. In particular, when the ink supply from the main tank to the sub tank is performed using a pump as in each of the above patent documents, a drive source, an ink flow path, a mechanism for preventing ink overflow from the sub tank, and the like are required for each color. These are major factors that increase the cost of the apparatus. For this reason, in order to realize an ink supply system from the main tank to the sub tank with a small and inexpensive configuration, a configuration is adopted in which the sub tank is filled with ink by repeatedly supplying a certain amount of ink from the main tank to the sub tank. It has been proposed. This eliminates the need for a large and expensive pump mechanism, thereby reducing the cost of the apparatus.
However, in the case of adopting a configuration in which the ink is supplied to the sub tank at regular intervals, even if the sub tank is full, the ink is continuously supplied until the quantitative supply is completed, and the ink may leak from the sub tank.

  The present invention can be configured in a small size and low cost by repeatedly supplying a certain amount of ink from the first tank to the second ink tank, and reliably prevents overflow of the ink from the second ink. An object of the present invention is to provide a possible ink jet recording apparatus.

  In order to achieve the above object, the present invention has the following configuration. That is, the first aspect of the present invention includes a second ink tank having a communication portion that communicates with a first ink tank that stores ink and a recording head that can eject ink and that can communicate with the atmosphere; Inkjet recording apparatus comprising: an ink filling unit that repeatedly supplies a certain amount of ink stored in a first ink tank to a second ink tank, the second ink tank comprising: The ink stored in the first ink tank has a volume equal to or greater than the predetermined amount above the reference head liquid surface, which is the liquid surface that is open to the atmosphere.

  According to the present invention, since a certain amount of ink is repeatedly flowed from the first ink tank to the second ink tank, the apparatus can be configured at low cost and in a small size. Furthermore, the ink can be reliably filled into the second ink tank without leaking ink without using the detection means for detecting the amount of ink in the second ink tank.

1 is a plan view schematically showing a schematic configuration of an ink jet recording apparatus in an embodiment of the present invention. 1 is a longitudinal side view illustrating an overall configuration of an ink supply system of an ink jet recording apparatus according to an embodiment of the present invention. It is a vertical side view which shows the state by which the diaphragm part was pressed from the state shown in FIG. It is a vertical side view which shows the state in which the ink tank in the main tank became empty. FIG. 5 is a longitudinal side view showing a state where ink in the sub tank is consumed and reduced in the state shown in FIG. 4. It is a vertical side view which shows the state by which the main tank was replaced | exchanged from the state shown in FIG. It is a bullet side view for explaining the operation of each part around the sub tank when ink is filled in the sub tank. 1 is a block diagram illustrating a schematic configuration of a control system of an ink jet recording apparatus according to an embodiment of the present invention. It is a flowchart which shows the filling operation | movement of the ink to the sub tank implemented in one Embodiment of this invention. It is an explanatory side view showing each standard head liquid level in one embodiment of the present invention.

Embodiments for carrying out the present invention will be described below with reference to the accompanying drawings.
(First embodiment)
FIG. 1 is a schematic plan view for explaining a schematic configuration of an ink jet recording apparatus to which the present invention is applied. Note that the ink jet recording apparatus shown here is a so-called serial type ink jet recording apparatus that performs recording by moving a recording head capable of ejecting ink droplets in a direction intersecting the conveyance direction of the recording medium.

  In FIG. 1, a recording head 1 is an ink jet recording head capable of ejecting supplied ink from a plurality of ejection ports. The recording head 1 is mounted on a carriage 102 in a replaceable manner. The carriage 102 is provided with a connector holder (electrical connection part) for transmitting a drive signal and the like to the recording head 1 via a connector (not shown). The carriage 102 is supported by a guide shaft 103 installed in the apparatus main body so as to be reciprocally movable in the main scanning direction indicated by an arrow A. A timing belt 107 connected to the carriage 102 is bridged between a motor pulley 105 and a driven pulley 106 that are rotationally driven by the main scanning motor 104. The carriage 102 is moved in the main scanning direction by a driving mechanism constituted by the motor 104, pulleys 105 and 106, timing belt 107, and the like.

  A recording medium 108 such as a print sheet or a plastic thin plate is separated and fed from an auto sheet feeder (ASF) 114 one by one when a pickup roller 113 is rotated by driving a sheet feeding motor 115. Further, the recording medium 108 is conveyed in the sub-scanning direction indicated by the arrow B by the rotation of the conveying roller 109, and passes through a position (recording unit) facing the ejection port formation surface (ejection port surface) in the recording head 1. The transport roller 109 is rotated by driving the LF motor 116. The determination as to whether or not the recording medium 108 has been fed and the determination of the leading position of the leading edge of the recording medium at the time of feeding are performed based on the detection signal of the paper end sensor 112 disposed upstream of the conveying roller 109. Is called. Further, the paper end sensor 112 is also used to determine the rear end position of the recording medium 108 and to determine the current recording position from the rear end position of the recording medium 108. Note that the back surface of the recording medium 108 is supported by a platen (not shown) so as to form a flat recording surface in the recording unit.

  In the ink jet recording apparatus having the above-described configuration, the recording head 1 repeats the recording scan in which ink is discharged while scanning in the direction of arrow A together with the carriage 102, and the recording medium conveyance operation performed between each scan of the recording head, An image is formed on a recording medium.

  FIG. 2 is a schematic diagram of an ink supply system of the inkjet recording apparatus 100 according to an embodiment of the present invention. Here, for simplicity of explanation, only the path for one color of ink as a liquid is shown. FIG. 2 is a diagram showing a state in which ink is sufficiently stored in the main tank 5 and recording is performed using the ink in the main tank 5.

  First, the configuration of the ink supply system of this embodiment will be described. The ink supply system according to the present embodiment includes a recording head 1, a sub tank 4 that can communicate with the recording head 1, a main tank 5 that can communicate with the sub tank 4, and a buffer chamber 6 that can communicate with the main tank 5. ing. The recording head 1 of the present embodiment includes an element substrate provided with a recording element for ejecting ink, and an orifice plate bonded to the element substrate. The orifice plate has a plurality of ejection openings for ejecting ink droplets, and is bonded to the element substrate to form a foaming chamber as an energy action chamber that communicates with the ejection openings and an ink flow path that communicates with the chamber. Has been. Then, the ink is formed to be ejected from the ejection port by driving the recording element. In the present embodiment, an electrothermal conversion element that converts electrical energy into thermal energy is used as the recording element. The ink can be ejected from the ejection port by causing film boiling in the ink by the heat energy generated from the heater as the electrothermal conversion element and utilizing the pressure of the bubbles in the ink generated at that time. . As the recording head, various ejection methods such as a method of ejecting ink using a piezoelectric element can be used.

  The main tank 5 is formed to be removable from the recording apparatus main body. In the present embodiment, the main tank 5 is formed so as to be able to store a relatively large volume of ink. The ink stored in the main tank 5 is supplied to a sub tank (second ink tank) 4 mounted on the recording apparatus main body, and the ink in the sub tank 4 is supplied to the recording head 1 mounted on the carriage. The recording head 1 discharges the supplied ink from the discharge port and records an image. As the recording operation proceeds, ink is supplied from the main tank to the sub tank, and the ink in the main tank 5 decreases. When the ink in the Maytank runs out, or when the amount becomes insufficient for recording on a single recording medium, the main tank 5 is filled with ink as shown in FIG. Replace with a new one.

  The sub tank 4 stores an amount of ink that can perform the recording operation during the replacement operation of the main tank 5 so that the recording operation is not interrupted while the main tank is empty and is replaced. Has been. For this reason, the volume of the sub tank 4 is formed to be relatively smaller than that of the main tank 5. The main tank 5 and the sub tank 4 are communicated with each other by a first hollow tube 11 protruding from the upper surface of the liquid chamber 4 of the sub tank 4. The first hollow tube 11 is formed of a conductive member such as metal, and is formed so that ink can be circulated therein.

  Here, the inner diameter of the first hollow tube 11 is sufficiently narrow so that the flow path through which the ink flows has a sufficient flow resistance. For this reason, even if the main tank 5 is arranged at a position higher than the sub tank 4, the ink stored in the main tank 5 is not supplied into the sub tank 4 only by gravity. Ink is discharged from the recording head 1 and the amount of ink in the sub-tank 4 decreases, so that when a negative pressure of a predetermined value or more is generated in the sub-tank 4, the ink is supplied from the main tank 5 to the sub-tank 4.

  Further, a supply tube 2 for connecting them is disposed between the recording head 1 and the sub tank 4. The supply tube 2 can circulate ink inside and supplies the ink inside the sub tank 4 to the recording head 1. The supply tube 2 is made of a flexible material, and can supply ink to the recording head 1 while scanning the recording head 1.

  Connected to the sub tank 4 is an air communication path 8 that allows the inside of the sub tank 4 to communicate with the atmosphere. The atmosphere communication path 8 includes an introduction portion 81 that rises upward from the highest position 41 in the sub tank 4, a space portion 82 that is connected to an outlet 81 b formed at the upper end of the introduction portion 81, and the space portion 82. And a discharge portion 83 that falls below the bottom surface of the sub tank 4. Therefore, the atmosphere communication path 8 is formed in an inverted U shape as a whole. The introduction port 81 a formed at the lower end portion of the introduction portion 81 is disposed at the same height position as the highest position in the sub tank 4. Further, the atmospheric communication passage 8 is provided with an atmospheric communication valve 9 slidably along the outer peripheral surface of the discharge portion 83, and the atmospheric communication valve 9 is moved to move the outlet of the atmospheric communication passage 8. A certain atmosphere communication port 8a can be opened and closed. Therefore, when the atmosphere communication port 8a is in an open state, the air inside the sub tank 4 can be discharged from the atmosphere communication port 9 to the atmosphere via the introduction portion 81, the space portion 82, and the discharge portion 83.

  A diaphragm portion 3 is provided on a part of the wall surface forming the sub tank 4 as a volume changing member operable to change the volume of the sub tank 4. In the present embodiment, the sub-tank 4 has an ink storage portion including a liquid chamber portion 4a and a flow passage portion 4b communicating with the liquid chamber portion 4a. The diaphragm portion 3 is provided in the flow passage portion 4b in the ink storage portion. ing. Moreover, the diaphragm part 3 is formed of rubber having flexibility. FIG. 2 shows an initial state in which the diaphragm portion 3 bulges outward from the wall surface of the flow path portion 4a, and the volume of the sub tank 4 is in an expanded state. On the other hand, FIG. 3 shows a state in which the central portion of the diaphragm portion 3 is pressed to a position where it comes into contact with the wall surface of the flow path portion 4a. In this embodiment, a communication port 4b1 that is opened and closed by the diaphragm unit 3 is formed in the flow path unit 4a, and downstream of the communication port 4b1 (downstream in the direction of ink flow from the sub tank to the recording head). Is connected to the lower end of the supply tube 2 described above. Accordingly, when the diaphragm portion 3 is pressed as shown in FIG. 3, the communication port 4b1 is closed by the diaphragm portion 3, and the communication between the liquid chamber portion 4a and the recording head 1 is blocked. Yes. As described above, the diaphragm section 3 also has a function as an on-off valve for communicating and blocking between the recording head and the liquid chamber section 4a.

  Moreover, the flow path part 4b in which the diaphragm part 3 is provided is arrange | positioned in the lower part in the liquid chamber part 4a of the sub tank 4, and the communicating port with the liquid chamber part 4a is formed in the comparatively low position. . As a result, the ink is consumed and the air does not flow into the flow path portion 4b and the diaphragm portion 3 until the amount of ink remaining in the sub tank 4 becomes a small amount.

  The buffer chamber 6 is formed to communicate with the main tank 5 as a container that can store ink therein. An atmosphere communication path 7 that is open to the atmosphere is disposed inside the buffer chamber 6, and the space inside the buffer chamber 6 communicates with the atmosphere via the atmosphere communication path 7. The main tank 5 and the buffer chamber 6 are connected by a second hollow tube 12. The second hollow tube 12 is also formed of a conductive member such as metal, and is formed so that ink can be circulated therein. Even if the main tank 5 and the buffer chamber 6 communicate with each other, the ink inside the main tank 5 expands due to the temperature rise, and the pressure inside the main tank 5 may increase. The ink inside can flow into the buffer chamber 6. For this reason, it can suppress that the pressure inside the main tank 5 rises excessively. The main tank 5 is formed so as to communicate with the atmosphere via the buffer chamber 6, and the buffer chamber 6 plays a role of balancing the pressure inside the main tank 5 with the atmospheric pressure. The main tank 2 and the buffer chamber 6 constitute a first ink tank.

  Here, a mechanism for pressing and releasing the diaphragm portion 3 and opening and closing the atmosphere communication port in the present embodiment will be described. In the present embodiment, the expansion / reduction operation of the volume of the sub tank 4 and the opening / closing operation of the atmospheric communication valve 9 by pressing and releasing the diaphragm portion 3 are performed by the drive mechanism 30 having the motor 14 as a single drive source. Is called. The drive mechanism 30 includes the motor 14 and a drive force transmission mechanism including a drive gear 14 a, an idle gear 15, and a planetary gear 16 fixed to the output shaft of the motor 14. The drive mechanism 30 includes a first gear 19 and a second gear 24 that are selectively rotated by a drive force transmission mechanism, a first cam 20 that rotates integrally with the first gear, and a second gear 24. It has the 2nd cam 25 which rotates integrally. Furthermore, the drive mechanism 30 has an atmospheric valve lever 21 that is operated by the first cam 20 and a diaphragm lever 27 that is operated by the second cam. In the present embodiment, the drive mechanism 30, the atmosphere communication valve 9, and the diaphragm section 3 constitute an ink supply mechanism.

  More specifically, the drive gear 14 a fixed to the output shaft of the motor 14 is arranged to mesh with the idle gear 15. Further, the idle gear 15 and the planetary gear 16 mesh with each other, and each gear transmits a driving force from the motor 14. The planetary gear 16 is connected to the idle gear 15 via the arm 17, and keeps a distance from the central axis of the idle gear 15, and either one of R 1 and R 2 depending on the rotation direction of the motor 14 shown in FIG. Can move in the direction. When the planetary gear 16 moves in the R1 direction, the planetary gear 16 can mesh with the gear 24, and when the planetary gear 16 moves in the R2 direction, it can mesh with the gear 19.

  The drive mechanism 30 further includes an atmospheric valve lever 21 that rotates about the fulcrum 22 as a central axis, and a diaphragm lever 27 that rotates about the fulcrum 26 as a central axis. One end of the atmospheric valve lever 21 is connected to the atmospheric communication valve 9 for opening and closing the atmospheric communication port 8a, and is always attached to a position where the atmospheric communication port 8a is opened by the urging force of the compression spring 23. It is energized. A pressing portion 20 a that protrudes outward is provided on a part of the outer periphery of the cam 20, and when the cam 20 rotates to a predetermined phase position, the pressing portion 20 a causes one end portion of the atmospheric valve lever 21 to move. It is pressed against the urging force of the compression spring 23. In addition, a pressing portion 20 a that protrudes outward is provided at a part of the outer peripheral portion of the cam 20, and the pressing portion 20 a resists the compression spring 23 when the cam 20 rotates to a predetermined phase position. Thus, the diaphragm lever 27 can be pressed. Sensors 42 and 43 for detecting the phases of the cam 20 and the cam 25 rotating together with the gear 24 and the gear 19 are disposed at positions close to the gear 24 and the gear 19, respectively. Among these, the diaphragm part sensor 42 detects the phase of the cam 25 that pushes the diaphragm lever 27 that operates the diaphragm part 3 with the pressing part 20a. The atmospheric valve sensor 43 detects the phase of the cam 20 that presses the atmospheric valve lever 21 that operates the atmospheric communication valve 9 with the pressing portion 25a. The phases of the gears 19 and 24 can be accurately detected by the sensors 42 and 43, and the opening / closing operation of the atmospheric communication valve 9 and the expansion / reduction operation of the volume of the sub tank 4 by the movement of the diaphragm portion 3 can be reliably performed. Has been. In this embodiment, the sensors 42 and 43 are optical photosensors having a light emitting element and a light receiving element. The sensors 42 and 43 detect the phases of the gears 19 and 24 by detecting the amount of light at the light receiving element. In the present embodiment, a flag is provided at a predetermined position of the gears 19 and 24. When the flag is positioned at a predetermined phase, light from the light emitting element is blocked and the amount of light received by the light receiving element is changed to change the gear. The phases 19 and 24 are detected. The form of the sensors 42 and 43 is not limited to this, and other forms may be used. For example, a magnetic sensor that detects a change in a magnetic field that is generated when a gear passes a nearby position may be used.

  FIG. 9 is a block diagram illustrating a schematic configuration of a control system of the ink jet recording apparatus according to the present embodiment. In FIG. 9, the operation of each unit of the ink jet recording apparatus is controlled by the CPU 120 serving as a control unit based on a control program stored in the ROM 121 and various data stored in the RAM 122. That is, the CPU 120 includes a head driving circuit 123 that drives an electrothermal transducer provided in the recording head 1, a main scanning motor driving circuit 124 that drives the main scanning motor 104, and an LF motor driving circuit 125 that drives the LF motor 116. Etc. are connected. Further, a motor 4 that is a driving source for opening and closing the atmospheric valve 9 and moving the diaphragm portion 3 is connected to the CPU 120. Further, the CPU 120 is connected to a display unit 52 that displays an operation state of the ink jet recording apparatus, an ASF 114 that supplies a recording medium, and the like. The CPU 120 is connected to the atmospheric valve sensor 43, the diaphragm sensor 42, the paper end sensor 112, and the like. Further, the CPU 120 is connected to a liquid detection circuit 50 that outputs a signal indicating whether or not the ink stored in the main tank 5 and the sub tank 4 has reached a predetermined amount or less. The liquid detection circuit 50 applies a predetermined voltage between the first hollow tube 11 and the second hollow tube 12 described above. Then, it is detected whether or not a current flows between the first hollow tube 11 and the second hollow tube 12, and when a current flows, a detection signal is output to the CPU 120. The liquid detection circuit 50, the first middle space 11 and the second hollow tube 12 constitute detection means for detecting whether or not the ink is substantially emptied in the main tank 5. Furthermore, an ink filling unit that repeatedly supplies ink from the main tank 5 to the sub tank 4 is configured by the above-described ink supply mechanism and the CPU 120 that controls driving of the ink supply mechanism.

  In the above control system, the CPU 120 performs various operations such as a recording operation and an ink filling operation to the sub tank according to a control program stored in the ROM 121 in accordance with signals output from the liquid detection circuit 50 and the sensors of the respective units. Operation is controlled. For example, in the ink filling operation to the sub tank executed after the replacement of the main tank 5, signals representing the phases of the cams 20 and 25 detected by the diaphragm sensor 42 and the atmospheric valve sensor 43 are input to the CPU 120. . The CPU 120 controls the rotation direction and the rotation amount of the motor 14 based on those phases and the signal from the liquid detection circuit 50. As described above, it is possible to repeatedly supply ink from the main tank 5 to the sub-tank 4 by the above-described ink supply mechanism and the CPU 120 that controls the drive of the ink supply mechanism based on the detection signal from each sensor. Ink filling means is configured.

  In the ink jet recording apparatus 100 having the above configuration, when the recording head 1 discharges ink and performs a recording operation, a negative pressure is generated in the recording head 1 accordingly. When the negative pressure in the recording head 1 exceeds a certain value, the ink in the sub tank 4 is supplied to the recording head 1 through the supply tube 2 by the negative pressure. Further, since the atmospheric communication valve 9 is closed during the recording operation, the sub tank 4 is in a sealed state. For this reason, as the ink in the sub tank 4 is supplied to the recording head 1, a negative pressure is generated in the sub tank 4. The ink in the main tank 5 is supplied to the sub tank via the first hollow tube 11 by this negative pressure. As described above, the buffer chamber 6 communicates with the main tank 5 via the second hollow tube 12 and also communicates with the atmosphere via the atmosphere communication path 7. For this reason, the pressure in the main tank 5 is always balanced with the atmosphere, and the pressure in the main tank 5 does not drop excessively even during the recording operation.

  In the present embodiment, the first hollow tube 11 has a sufficiently large flow path resistance so that ink does not flow from the main tank 5 to the sub tank 4 only by gravity. For this reason, the amount of ink supplied from the inside of the main tank 5 to the sub tank 4 during the recording operation corresponds to the amount consumed by the recording head, and excess ink is not supplied to the sub tank 4.

  When the printing operation is continued by the printing apparatus of the present embodiment and the ink in the main tank 5 is continuously consumed, finally all of the ink is consumed and the state becomes substantially empty. When the recording operation is continued in a state where all the ink in the main tank 5 is consumed, air flows from the main tank 5 to the sub tank 4. As shown in FIG. 4, the air flows into the supply path 10 in the sub tank 4 through the first hollow pipe 11 that connects the main tank 5 and the sub tank 4.

  In the present embodiment, a predetermined voltage is applied between the first hollow tube 11 and the second hollow tube 12, and the first middle space 11 and the second hollow tube are energized. Whether or not ink is present in the main tank 5 is determined based on whether or not the ink is present. That is, when ink is present in the main tank 5, the first hollow tube 11 and the second hollow tube 12 are energized through the ink, and the ink is present in the main tank 5. If not, the first hollow tube 11 and the second hollow tube 12 are not energized. By observing this conduction or non-conduction, the presence or absence of ink in the main tank 5 is detected. When the ink out of the main tank 5 is detected, the recording apparatus indicates this on the display or the display unit of the recording apparatus and notifies the user of the ink out. The user may replace the main tank 5 in response to this notification. As described above, when the recording device detects that the ink in the main tank 5 is out of ink, the main tank is exchanged accordingly.

  When the main tank 5 is replaced, a certain amount of ink is held in the sub tank 4. After ink out of the main tank 5 is detected by detecting the presence or absence of ink in the supply path 10 in the sub tank 4, the ink consumption by the recording head 1 is calculated by the number of ink ejections, and based on the ink consumption. The remaining amount of ink in the sub tank 4 is calculated. Thereafter, if the main tank 5 is not replaced, the recording is continued, and the recording is interrupted when the sub tank 4 becomes empty.

  When replacing the main tank 5, first, the main tank 5 is pulled upward, the main tank 5 is pulled out from the first hollow tube 11 and the second hollow tube 12, and removed from the sub tank 4 and the buffer chamber 6. . Next, when installing a new main tank 5, the first hollow tube 11 and the second hollow tube 12 are pierced into the bottom of the main tank 5, and the rod-shaped end portions of the hollow tubes 11 and 12 are inserted. Project into the ink tank.

  By the way, when the recording operation is interrupted by the replacement work of the main tank 5, as described above, there is a color change between the area recorded immediately after the interruption of the recording operation and the area where the recording operation is continuously performed. Differences may occur and image quality may be degraded. In order to suppress the color unevenness generated in such an image, it is necessary to perform the recording operation even while the main tank 5 is being replaced. Therefore, in this embodiment, the sub tank 4 is attached separately from the main tank 5, and the recording operation can be continued using the ink in the sub tank 4 even after the main tank 5 is removed. Thereby, it is possible to suppress a decrease in image quality due to the interruption of the recording operation when the main tank 5 is replaced.

  FIG. 5 is an explanatory diagram showing a state in which the ink in the sub tank 4 is consumed and reduced by further performing the recording operation from the state shown in FIG. In a state where the recording operation is being performed, the atmosphere communication valve 9 is closed and the diaphragm portion 3 is in an initial state in which it bulges outward, so that the volume in the sub tank 4 is maintained in an expanded state.

  Although the main tank 5 is disposed at a position higher than the sub tank 4, even if the main tank 5 storing ink is mounted, the ink is not immediately supplied into the sub tank 4. Normally, the main tank 5 is exchanged in an empty state. Therefore, when the main tank 5 is exchanged, as shown in FIG. Air is sucked from the tank 5 and air flows into the sub tank 4. Therefore, air is present in the supply path 10 of the sub tank 4 when the main tank 5 in which ink has run out is replaced with a new main tank.

  Further, when the main tank 5 is replaced, the air communication valve 9 is closed. Air is stored above the ink in the sub tank 4. For this reason, even if the main tank 5 containing the ink is attached to the apparatus by replacing the main tank 5 or the sub tank 4 communicates, the air in the sub tank 4 is not released to the outside of the sub tank 4. The ink hardly flows into the sub tank 4. For this reason, even if the main tank 5 is replaced, ink is not supplied from the main tank 5 unless a negative pressure is generated in the sub tank 4.

  Therefore, in order to supply ink to the sub tank 4, a negative pressure is generated in the sub tank 4, the ink in the main tank 5 exchanged with the air in the sub tank 4 is replaced, and the ink is put in the sub tank 4. It is required to be filled.

  Here, the outline of the ink filling operation to the sub tank will be described with reference to FIGS. 7A to 7C are explanatory views showing the operation of each part around the sub tank when the sub tank is filled with ink, and FIG. 9 is a diagram showing the operation during the ink filling operation to the sub tank shown in FIG. It is a flowchart which shows a control process.

  FIG. 7A shows a state in which the main tank 5 has been replaced and the ink in the sub tank is in a slight state. FIG. 7B shows a state in which the diaphragm portion 3 is moved inward to move the inside of the sub tank 4. The state where air is sent out to the outside of the sub tank 4 is shown. FIG. 7C shows a state in which ink is supplied from the main tank 5 into the sub tank 4 by moving the diaphragm portion 3 outward.

  As shown in FIG. 7A, immediately after the main tank 5 is replaced, the diaphragm portion 3 bulges outward and the volume of the sub tank 4 is expanded. At this time, the air communication valve 9 is closed. Next, as shown in FIG. 7B, after the atmospheric communication valve 9 is changed from the closed state to the open state (S201), the diaphragm 3 is positioned inward to reduce the volume of the sub tank 4 (S202). . As the diaphragm portion 3 moves, the volume in the sub tank 4 changes by about 0.5 cc. As described above, in the liquid filling method for the sub tank of the present embodiment, the volume changing member reducing step (S202) for reducing the volume of the diaphragm portion that can change the volume of the sub tank 4 after opening the atmosphere communication port 8a. )have. In addition, the liquid filling method for the sub-tank of the present embodiment includes a volume changing member enlarging step (S201) for enlarging the volume of the diaphragm section 3 after closing the atmosphere communication port 8a.

  By moving the diaphragm portion 3 inward, ink of a volume of about 0.5 cc is pushed from the diaphragm portion 3 to the main tank side in the sub tank 4. At this time, the flow path resistance from the diaphragm section 3 to the recording head 1 (flow path resistance of the supply tube 2) is overwhelmingly higher than the flow path resistance from the diaphragm section 3 to the sub tank 4 (main tank 5). Almost no ink is pushed out to the recording head 1 side.

  Therefore, when the diaphragm 3 moves inward and the volume of the sub tank 4 is reduced and the ink and air in the sub tank 4 are compressed, the air in the sub tank 4 is discharged to the atmosphere through the air communication valve 9. Will be. Accordingly, the pressure in the sub tank 4 does not increase and ink hardly flows into the main tank 5.

  Next, as shown in FIG. 7C, after the atmospheric communication valve 9 is changed from the open state to the closed state (S203), the initial state of bulging outward from the state in which the diaphragm portion 3 is pressed inward. (S204). The movement of the diaphragm 3 increases the volume of the sub tank 4. As a result, a negative pressure is generated in the sub tank 4, and about 0.5 cc of ink flows into the diaphragm portion 3, and ink is supplied from the main tank 5 to the sub tank. At this time, since the flow path resistance from the diaphragm section 3 to the recording head 1 is considerably higher than the flow path resistance from the diaphragm section 3 to the main tank 5, almost no ink flows into the diaphragm section 3 from the recording head 1 side. . In the present embodiment, the inner diameter of the supply path 10 is about 2 mm to 3 mm, the length is about 20 mm, the inner diameter of the first hollow tube 11 is φ1.6 mm, and the length is about 30 mm. At this time, since the atmosphere communication valve 9 is closed, air hardly enters the sub tank 4 from the outside of the recording apparatus via the atmosphere communication path 8. Although the main tank 5 has a negative pressure, air is introduced into the main tank 5 from the buffer chamber 6 via the atmosphere communication path 7, so the negative pressure in the main tank 5 is eliminated. As a result, a certain amount of ink is introduced from the main tank 5 to the sub tank 4.

Next, the operation of each part of the drive mechanism 30 when supplying ink from the main tank 5 to the inside of the sub tank 4 after replacement of the main tank 5 in the ink supply system of the present embodiment will be described.
As described above, in order to supply ink from the main tank 5 to the sub-tank 4 while discharging air from the sub-tank 4 after the replacement of the main tank 5, the expansion / reduction operation (movement of the diaphragm) of the diaphragm section 3 and the atmosphere The opening / closing operation of the communication valve 9 is repeated. As the states of the diaphragm section 3 and the atmosphere communication valve 9 in the recording apparatus at this time, two states can be considered. As one state, as shown in FIG. 2, the diaphragm portion 3 bulges outward from the sub-tank 4 and the volume of the diaphragm portion 3 is expanded (hereinafter, this state is referred to as an expanded state of the diaphragm portion). And the atmospheric communication valve 9 is closed. As the other state, as shown in FIG. 3, the diaphragm portion 3 is pressed and the internal volume thereof is reduced (hereinafter, this state is referred to as a reduced state of the diaphragm portion), and There is a state in which the air communication valve 9 is opened.

  First, as shown in FIG. 2, the diaphragm portion 3 is in an expanded state and the atmospheric communication valve 9 is closed, and then the diaphragm portion 3 is in a contracted state as shown in FIG. The operation of each part when closing is described.

  In the state shown in FIG. 2, the pressing portion 20a of the first cam 20 presses the end portion (right end portion in the figure) of the atmospheric valve lever 21 against the urging force of the compression spring 23, thereby the atmospheric valve lever. The atmospheric communication valve 9 provided at the other end portion (the left end portion in the figure) is closed at the atmospheric communication port 8a. The pressing portion 25a of the second cam 25 is in a state of being separated from the diaphragm lever 27, and the diaphragm lever 27 is in contact with the circular outer peripheral surface of the cam 25 by the biasing force of the spring. At this time, one end portion (left end portion in the figure) of the diaphragm lever 27 is in a state where the diaphragm 3 is not pressed (open state), and the diaphragm 3 is maintained in the expanded state.

  In this state, when the motor 14 is driven and the drive gear 14a is rotated in the S2 direction, the rotational force of the drive gear 14a is transmitted to the planetary gear 18 through the idle gear 15, and the planetary gear 18 rotates. Rotate around the central axis. The idle gear 15 rotates at a fixed position around a shaft (not shown) held at the fixed position. The rotation of the planetary gear 18 causes the first cam 20 to rotate together with the gear 19 engaged therewith, and the pressing portion 20a is separated from the end portion (right end portion) of the atmospheric valve lever 21. As a result, the atmospheric valve lever 21 rotates counterclockwise in FIG. 2 around the fulcrum 22 by the elastic force of the compression spring 23, and moves the atmospheric communication valve 9 from a position where the atmospheric communication port 8a is closed. Thereby, the atmosphere communication port 8a is opened to the atmosphere.

  Next, when the drive gear 14a is rotated in the S2 direction by the motor 14, the idle gear 15 meshed with the drive gear is rotated. Due to the rotation of the idle gear 15, the planetary gear 16 meshing with the idle gear 15 moves in the R1 direction and meshes with the gear 24 as shown in FIG. By continuing to drive the motor 14 after that, the gear 16 rotates around its rotation center, the pressing portion 25a moves to a position facing the diaphragm lever 27, and the end of the diaphragm lever 27 (see FIG. Middle, right end) is pressed against the compression spring 28. Thereby, the other end portion (left end portion in the figure) of the diaphragm lever 26 presses the diaphragm 3, and the diaphragm 3 is brought into a contracted state (see FIG. 3). By reducing the diaphragm 3 in this way, the ink in the diaphragm 3 is sent to the liquid chamber 4a side of the sub tank 4, and the liquid level of the ink in the liquid chamber 4 rises. At this time, since the atmosphere communication port 8a is opened by the atmosphere communication valve 9, the air accumulated in the upper part of the sub tank 4 as the ink level in the liquid chamber 4 rises from the atmosphere communication port 8a. Released into the atmosphere.

  As described above, the positional relationship of the diaphragm 3 and the atmospheric communication valve 9 can be changed from the state of FIG. 2 to the state of FIG. Next, as shown in FIG. 3, the diaphragm portion 3 is in a contracted state and the atmosphere communication valve 9 is opened, and then the diaphragm portion 3 is in an expanded state as shown in FIG. The operation of each part when 9 is closed will be described.

  When the motor 14 is driven to rotate the drive gear 14a in the S1 direction from the diaphragm contraction state shown in FIG. 3, the planetary gear 16 moves in the R2 direction as the idle gear 15 rotates, and the gear 19 Mesh. Thereafter, by continuously driving the motor 14, the planetary gear 16 rotates through the idle gear 15, and the gear 19 and the cam 20 rotate in conjunction with the rotation. By the rotation of the cam 20, the pressing portion 20 a presses the end of the atmospheric valve lever 21 against the compression spring 23 to rotate the atmospheric valve lever 21 around the fulcrum. The atmospheric communication valve 9 moves with the movement of the atmospheric valve lever 21 and closes the atmospheric communication port 8a that has been open until then. At this time, the rotation of the motor 14 is temporarily stopped. Moreover, the diaphragm part 3 maintains the contracted state shown in FIG.

  After the atmosphere communication port 8a is closed by the atmosphere communication valve 9 as described above, the motor 14 is driven and the drive gear 14a is rotated in the S2 direction. As the idle gear 15 rotates in conjunction with the rotation of the drive gear 14a, the planetary gear 16 moves in the R1 direction and meshes with the gear 24. Even after the planetary gear 16 and the gear 24 are engaged, the driving gear 14 continues to rotate by the driving force of the motor 14, whereby the planetary gear 16 rotates about its rotation center and rotates the gear 24. As a result, the pressing portion 25a of the cam 25 is separated from the diaphragm lever 27, and the die and the diaphragm lever 27 rotate around the fulcrum 26 in the clockwise direction in FIG. 3 by the urging force of the compression spring 28. As a result, the diaphragm lever 27 releases the pressing force against the diaphragm 3, and the diaphragm 3 returns to the expanded state shown in FIG. 2 by its own restoring force. At this time, since the air communication port 8a is closed, when the diaphragm 3 returns to the expanded state, a negative pressure is generated in the sub tank 4, and the ink in the main tank 5 passes through the hollow tube 11 into the sub tank. Inflow.

  As described above, by repeatedly reducing and expanding the diaphragm and opening and closing the atmosphere communication port 8a, the ink in the main tank 5 is supplied to the sub tank 4 by a fixed amount (0.5 cc in this embodiment). Go. In the above operation, when the gears 19 and 24 are rotated, the phases of the cams 20 and 25 are accurately detected by the diaphragm sensor 42 and the atmospheric valve sensor 43 attached to the gears 19 and 24, respectively. Has been. Therefore, it is possible to accurately grasp the open / close state of the atmosphere communication valve 9 and whether the diaphragm portion 3 is located relatively outside or inside the sub tank 4.

  As described above, in the present embodiment, the first step (S201, S202 in FIG. 9) and the second step (S203, S204 in FIG. 9) of opening the supply valve 3 after closing the atmosphere communication valve 9 are repeated. As a result, the sub tank 4 can be filled with ink. For this reason, filling the sub tank with ink does not require a large and expensive pump, and has a small and inexpensive configuration in which the diaphragm 3 and the air opening / closing valve 9 as described above are driven using a single drive source. The sub tank can be filled with ink.

  However, how much ink in the sub tank 4 is consumed until the main tank 5 is empty and the main tank 5 is replaced depends on when the user replaced the main tank 5 and what kind of image was recorded. It depends on It suffices if the sub tank 4 can be filled with ink by repeating the first step and the second step as much as the amount of ink consumed in the sub tank 4, but it is difficult to accurately grasp the ink consumption in the sub tank 4. . Furthermore, the error may increase as the number of replacements of the main tank 5 increases. Further, in an ink jet recording apparatus equipped with a plurality of colors, it is conceivable that the first step and the second step are repeated simultaneously using a single drive source to fill each sub tank 4 with ink. In this case, even if the ink consumption in each sub-tank 4 can be accurately grasped, the respective consumptions do not necessarily match, so it is difficult to properly supply ink to each sub-tank 4. That is, when ink is supplied to each sub-tank by a single drive source, there are cases where one sub-tank is full but other sub-tanks are not full. In this case, if the first and second steps are repeated in order to fill the other sub-tank 4, the ink may overflow from the sub-tank 4 that is already full.

  On the other hand, when a drive source is provided for each sub tank 4 without using a single drive source, ink corresponding to each consumption amount can be supplied to each sub tank 4. However, when a plurality of drive sources are used, there is a concern that the cost of the apparatus and the filling time for the sub tank increase.

  Further, in the ink filling method in which the ink is repeatedly supplied to the ink tank by a certain amount, the ink supply is continued until the ink supply operation of the certain amount is completed even if the ink amount in the tank reaches the full level. Ink may overflow from the sub tank.

  Therefore, in the present embodiment, by setting the volume of the sub tank 4 assuming the maximum ink consumption in the sub tank 4, regardless of the number of ink supply operations in the first and second steps described above, Ink overflow can be suppressed. Here, the maximum ink consumption amount of the sub tank is determined by the liquid level (reference head liquid level) where the ink in the main tank 5 communicates with the atmosphere.

FIG. 10 shows an example of the reference head liquid level. In this embodiment, the reference head liquid level of the main tank 5 varies depending on the ink storage state in the main tank 5 and the buffer chamber 6, as shown in FIGS. 11 (a), (b), and (c).
FIG. 10A shows the reference head liquid level L2 when there is ink in the main tank 5 and no ink in the buffer chamber 6 (= normal use). In this state, the reference head liquid level L <b> 2 of the main tank 5 becomes the lower surface of the second hollow tube 12.
FIG. 10B shows the case where ink is present in the main tank 5 and ink is present in the buffer chamber 6 (= the air in the main tank 5 expands due to temperature change, and the ink in the main tank 5 temporarily The reference head liquid level L2 in the case of being pushed out into the buffer chamber 6 is shown. As shown in the figure, the reference head liquid level L2 of the main tank 5 is the liquid level of the buffer chamber 6.

  FIG. 10C shows the reference head liquid level of the main tank 5 when the ink level is located below the supply path 10 in the main tank 5 and there is no ink in the buffer chamber 6.

  In the present embodiment, the reference head liquid level that is located at the uppermost vertical direction in the fluctuation range among the reference head liquid levels that change as described above is defined. That is, in FIG. 10, the position L3 shown in (c) is at the highest position, and this is defined as the reference head liquid level. The ink amount (ink volume) when the ink level stored in the sub tank 4 reaches the reference head liquid level is defined as the maximum ink filling amount of the sub tank.

  Further, the volume in the sub tank 4 is a volume obtained by adding the volume of the ink storage portion of the sub tank 4 and the volume of a part or all of the rising portion 81 of the atmosphere communication path 8. Here, the volume of the ink reservoir is the volume of the liquid chamber 4a and the volume of the portion upstream of the communication port 4b1 of the flow path 4b (upstream in the direction of ink flow from the sub tank 4 to the recording head). And the volume added. The sub-tank 4 has a volume equal to or larger than the maximum ink filling amount of the sub-tank determined as described above and a volume change amount (= a constant amount) of the supply valve 3 above the reference head liquid level of the main tank 5 in the vertical direction. The volume is added. By determining the volume of the sub tank 4 in this way, it is possible to reliably fill the sub tank 4 with ink while preventing overflow of the ink from the sub tank 4 in any case.

  In the present embodiment, the number of repetitions T of the first and second steps required for setting the ink amount equal to or larger than the maximum ink filling amount determined as described above and supplying the ink amount (FIG. 9). Is set. Then, when the recording operation for one sheet is completed, the ink filling operation in the first step and the second step shown in FIG. 9 is performed T times. According to this, regardless of the ink consumption in the sub tank 4, the sub tank 4 can be reliably filled with ink. At this time, even if an ink filling operation exceeding the actual ink consumption in the sub tank 4 is performed, the ink does not overflow from the sub tank 4.

  That is, by repeating the first and second steps, the liquid level in the sub tank 4 rises to the reference head liquid level. However, in the state where the sub tank 4 has reached the reference head liquid level, even if the first and second steps are repeated, the liquid level in the sub tank 4 temporarily becomes the reference head when the diaphragm portion 3 is pushed. By simply being pushed out above the liquid level, it immediately descends to the reference head liquid level due to the head difference. That is, the ink that is temporarily pushed above the reference head liquid level is lowered due to the head difference when the atmosphere communication port 8a is opened in the first and second steps.

  Even if the ink level temporarily rises above the reference head liquid level, the ink amount is a constant amount by the first and second steps, and the rising portion 81 of the atmosphere communication path 8 has a certain amount or more. The volume is defined above the reference head liquid level. For this reason, the ink does not reach the upper end position of the rising portion 81 of the atmosphere communication path 8, and the ink flows to the atmosphere communication port side of the atmosphere communication path 8 and does not leak to the outside.

  Accordingly, in a recording apparatus having a plurality of sub tanks 5, even if the ink supply operation to each sub tank is performed simultaneously and similarly using a single drive source, the ink will overflow from any sub tank 4. The ink can be reliably filled without any problem. For example, when a plurality of main tanks are provided corresponding to a plurality of sub-tanks, it is conceivable that ink runs out in one main tank, and only the ink in the corresponding sub-tank is reduced by the recording operation. Here, when the main tank is replaced, the first and second ink filling operations are performed on the corresponding sub tank. However, if the drive mechanism 30 provided for each sub-tank is driven by the same drive source (motor, etc.), ink filling is similarly performed for other sub-tanks already filled. The operation will be performed. However, even when the ink filling operation is performed on the other sub tank, the ink supplied to the other sub tank does not reach the upper side of the rising portion 81 of the atmosphere communication path 8 as described above. Ink does not leak.

  Thus, since it becomes possible to drive simultaneously and similarly the drive mechanism 30 corresponding to each sub tank using a single drive source, it is possible to realize a reduction in size and cost of the apparatus. Needless to say, the present invention is also effective for an ink jet recording apparatus equipped with a single sub tank.

(Other embodiments)
In the above embodiment, the case where the first ink tank is composed of the main tank 4 and the buffer chamber 6 communicating with the main ink tank 4 is exemplified. However, the first ink tank may be composed of only the main tank 4. Is possible. In this case, the main tank may be provided with an air communication part that opens the ink stored in the main tank to the atmosphere. As long as the atmosphere communication portion can avoid leakage of ink in the main tank, its shape, arrangement position, etc. are not particularly limited.

  In this embodiment, opening and closing of the diaphragm section 3 and opening and closing of the atmospheric communication valve 9 are performed by biasing the atmospheric valve lever 21 and the diaphragm lever 27 with springs, and changing the rotation direction of the motor 14 to engage with the planetary gear 16. It is operated by changing the gear to play. However, the present invention is not limited to this embodiment, and the diaphragm portion 3 may be driven and the air communication valve 9 may be opened and closed by other methods. For example, two motors for driving the gears 19 and 24 may be attached, and the gears 19 and 24 may be driven by the respective motors. Further, the movement of the diaphragm 3 and the movement of the air communication valve 9 can be selectively driven by a cam that rotates in conjunction with a single motor 14.

  Further, in the present embodiment, the diaphragm portion is provided in the flow path portion 4b in the sub tank, but the present invention is not limited to this, and a position where a negative pressure can be formed in the sub tank by operating the diaphragm portion. If so, it may be formed at another position. For example, you may provide so that the opening part formed in the wall part of the liquid chamber part 4a of the subtank 4, for example, the opening part formed in the bottom wall part or the side wall part, may be obstruct | occluded.

  In addition, the recording apparatus of the present embodiment is a tube supply type, and a so-called serial scan type recording apparatus that records an image with movement of the recording head in the main scanning direction and conveyance of the recording medium in the sub-scanning direction is used. However, the present invention is not limited to this form. The present invention can also be applied to a full-line recording apparatus that uses a recording head that extends over the entire width of the recording medium without scanning the recording head.

DESCRIPTION OF SYMBOLS 1 Recording head 3 Diaphragm part 4 Sub tank 4a Liquid chamber part 4b Flow path part 5 Main tank 8 Atmospheric communication path 8a Atmospheric communication port 81 Rising part 9 Atmospheric communication valve 30 Drive mechanism L3 Reference head liquid level

Claims (11)

A second ink tank having a communication portion communicating with the first ink tank for storing ink and a recording head capable of ejecting ink and capable of communicating with the atmosphere; and ink stored in the first ink tank An ink filling device comprising: an ink filling means for repeatedly supplying a predetermined amount to a second ink tank;
The second ink tank has a volume equal to or greater than the predetermined amount above a reference head liquid level, which is a liquid level at which ink stored in the first ink tank is released to the atmosphere. An ink jet recording apparatus.   The vertical position of the liquid level at which the ink stored in the first in-tank is released to the atmosphere varies depending on the ink storage state in the first ink tank, and the reference head liquid level is 2. The ink jet recording apparatus according to claim 1, wherein the liquid level is the highest level in a fluctuation range in the vertical direction of the liquid level.   3. The ink jet recording apparatus according to claim 1, wherein the constant amount is equal to a volume change amount of the second ink tank by the volume changing member.   The second ink tank includes an air communication passage in which the air communication port is formed, and the volume of the second ink tank provided above the reference head liquid level of the ink tank in the vertical direction includes 4. The ink jet recording apparatus according to claim 3, wherein the whole or a part of the atmosphere communication path is included.   The ink supply means includes a first ink tank so that a liquid level of ink stored in the second ink tank reaches a height equal to or higher than a reference head liquid level of the first ink tank. The ink jet recording apparatus according to claim 1, wherein a predetermined amount of ink is repeatedly supplied from the ink to the second ink tank.   The ink supply means has a maximum determined based on an ink amount such that a liquid level of ink stored in the second ink tank reaches a height equal to or higher than a reference head liquid level of the first ink tank. 6. The ink jet recording apparatus according to claim 5, wherein the number of ink filling operations is determined based on the ink filling amount and the constant amount, and the constant amount of ink supply operation is performed by the number of times.   The ink supply means includes an air communication valve capable of opening and closing an air communication port for opening the sub tank to the atmosphere, and a volume changing member capable of changing the volume of the sub tank. After the communication valve is opened and the volume of the second ink tank is reduced, the atmosphere communication valve is closed and the volume of the second ink tank is expanded, so that the second ink is discharged from the first ink tank. The ink jet recording apparatus according to claim 1, wherein a fixed amount of ink is supplied to the tank. A plurality of the second ink tanks are provided,
The ink supply means includes the atmospheric communication valve and the volume changing member provided corresponding to each of the plurality of ink tanks, and the atmospheric communication valve and the volume changing member.
8. The ink jet recording apparatus according to claim 7, wherein each of the ink supply units simultaneously performs the same operation of the atmospheric communication valve and the supply valve with respect to each of the second ink tanks.   The first ink tank includes a main tank that can communicate with the second ink tank, and a buffer chamber that communicates with the main tank and the atmosphere. The buffer chamber communicates with the atmosphere. An ink jet recording apparatus according to any one of claims 1 to 8.   The ink jet recording apparatus according to claim 1, further comprising a detecting unit that detects that ink has run out in the first ink tank.   11. The ink jet recording apparatus according to claim 1, wherein the volume changing member is a diaphragm provided on a part of a wall portion of the second ink tank.

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