JP2015083366A - Inkjet recording device and inkjet recording method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inkjet recording device and an inkjet recording method capable of stably discharging ink until the ink in a closed type ink tank and a recording head is used up sufficiently while achieving downsizing of a device body.SOLUTION: When a negative pressure in a recording head 22 is a predetermined negative pressure or greater, a pressure greater than the predetermined negative pressure is introduced from a buffer chamber 16 into the recording head 22 to relieve the negative pressure in the recording head 22.

Description

  The present invention relates to an ink jet recording apparatus that records an image using an ink tank that stores ink in a sealed space so as to apply a negative pressure, and a recording head that can eject ink supplied from the ink tank, and The present invention relates to an ink jet recording method.

  In an inkjet recording apparatus, negative pressure-applied ink is supplied from an ink tank to a recording head, and the recording head uses an ejection energy generating element such as an electrothermal conversion element (heater) or a piezo element from an ejection port. Ink is ejected. Since such a recording apparatus is also used in a small place such as a cash register counter or shelf in a store or on an office desk, it is required to reduce its size.

  In order to reduce the size of the recording apparatus, it is ideal to directly connect the recording head and the ink tank. In order to accommodate a large amount of ink while reducing the size of the ink tank and the recording apparatus, it is advantageous to use a sealed ink tank as the ink tank. As described in Patent Document 1, this sealed ink tank is provided with a flexible bag containing ink, and the bag is energized by a spring or the like in the direction of increasing the internal volume. Some inks supply negative pressure to the ink supplied to the recording head.

  In a sealed ink tank, a flexible bag that contains ink forms a sealed space that communicates only with the recording head. So, for example, when the ink tank runs out of ink and the flexible bag is crushed, and the ink is still left in the recording head, the recording head discharges the ink remaining in the inside, The negative pressure in the recording head will increase. As a result, the ink cannot be discharged satisfactorily, which may cause image recording failure.

  Japanese Patent Application Laid-Open No. 2004-228561 describes a recording apparatus that includes a sub tank and a pressure adjusting mechanism between an ink tank and a recording head, and adjusts the negative pressure of ink supplied to the recording head in the sub tank.

JP 2007-313711 A

  An object of the present invention is to provide an ink jet recording apparatus and an ink jet recording method capable of stably ejecting ink in a sealed ink tank and a recording head.

  The inkjet recording apparatus of the present invention includes a recording head capable of ejecting ink supplied from an ink tank that accommodates ink in a sealed space so as to apply a negative pressure, an outside of a liquid chamber of the recording head, and the liquid chamber A communication path for communicating with the recording head, an opening / closing means for opening / closing the communication path, and opening / closing the communication path by the opening / closing means according to the pressure in the recording head to communicate the outside with the liquid chamber. And a control means.

  According to the present invention, in accordance with the pressure in the recording head, the communication path is opened by the opening / closing means so that the outside communicates with the recording head, and the negative pressure in the recording head is relieved. The pressure fluctuation can be reduced. As a result, the ink in the sealed ink tank and the recording head can be stably discharged.

1 is a schematic front view of an ink jet recording apparatus according to an embodiment of the present invention. FIG. 2 is a block diagram of a control system of the ink jet recording apparatus of FIG. 1. FIG. 2 is a schematic configuration diagram of an ink supply system in the ink jet recording apparatus of FIG. 1. FIG. 4 is an enlarged sectional view of an ink tank and a recording head in FIG. 3. FIG. 4 is an enlarged view of an ink holding member in FIG. 3. FIG. 4 is a flowchart for explaining negative pressure relaxation processing by the ink supply system of FIG. 3. FIG. It is explanatory drawing of operation | movement of the ink supply system in the negative pressure relaxation process of FIG. It is a schematic block diagram of the principal part in the 2nd Embodiment of this invention. It is a flowchart for demonstrating the negative pressure relaxation process in the 3rd Embodiment of this invention. It is explanatory drawing of operation | movement of the ink supply system in the negative pressure relaxation process of FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The recording apparatus of this embodiment is an application example as a full-line type inkjet recording apparatus.

(First embodiment)
FIG. 1 is an explanatory diagram of a conceptual configuration example of a full-line type ink jet recording apparatus (hereinafter also referred to as “printer”) 110.

  The printer 110 is connected to a host device 120 such as a personal computer, and image information and the like are sent from the host device 120 to the printer 110. In the printer 110, four recording heads 22 (22K, 22C, 22M, 22Y) capable of ejecting ink are arranged so as to be aligned in the conveyance direction (arrow A direction) of the roll paper P as a recording medium. The recording heads 22K, 22C, 22M, and 22Y are recording heads for ejecting black, cyan, magenta, and yellow ink, respectively. Each recording head 22 includes a nozzle that ejects corresponding ink from a plurality of ejection ports using ejection energy generating elements such as an electrothermal conversion element (heater) and a piezo element. In the case of using an electrothermal conversion element, the ink can be foamed by the generated heat, and the ink can be ejected from the ejection port at the tip of the nozzle using the foaming energy. These discharge ports are arranged in a direction intersecting (in the present example, orthogonal) with the conveyance direction of the arrow A. These recording heads 22 are so-called long line heads, and the recording heads 22K, 22C, 22M and 22Y are arranged side by side in the direction of the arrow A in the conveying direction. The lengths of these recording heads 22 are slightly longer than the maximum width of recording media that can be recorded by the printer 110 (the length in the direction perpendicular to the paper surface of FIG. 1). The recording heads 22 are positioned at predetermined recording positions during the image recording operation.

  A recovery unit 400 is incorporated in the printer 110 for the recovery operation of the recording head 22K (operation for maintaining a good ink discharge state). The recovery unit 400 includes a recovery mechanism 50 for removing ink from the discharge port formation surfaces (discharge port formation surfaces) of the respective recording heads 22K, 22C, 22M, and 22Y. The recovery mechanism 50 is provided independently for each of the recording heads 22K, 22C, 22M, and 22Y. The recovery mechanism 50 includes a wiper for wiping the discharge port forming surface, a wiper holding member for holding the wiper, an ink removing member for removing ink adhering to the wiper, and a cap that is in close contact with the discharge port surface. Is provided.

  The roll paper P is supplied from the supply unit 25 and is conveyed in the direction of arrow A by the conveyance mechanism 26 incorporated in the printer 110. The transport mechanism 26 includes a transport belt 26a for placing and transporting the roll paper P, a transport motor 26b for rotating the transport belt 26a, and a roller 26c for applying tension to the transport belt 26a. The conveyance mechanism 26 may be configured to convey the roll paper P using a conveyance roller, or may constitute a unitized conveyance unit.

  When an image is recorded on the roll paper P, after the recording start position on the roll paper P being conveyed reaches below the recording head 22K, a plurality of discharges in the recording head 22K is performed based on the recording data (image information). Black ink is selectively ejected from the outlet. Similarly, each color ink is ejected in the order of the recording head 22C, the recording head 22M, and the recording head 22Y to record a color image on the roll paper P. The printer 110 includes an ink tank 28 (28K, 28C, 28M, 28Y) that supplies ink to each recording head 22 (22K, 22C, 22M, 22Y). Further, the printer 110 is provided with various pumps for performing ink supply operation and recovery operation to the respective recording heads 22K, 22C, 22M, and 22Y.

  FIG. 2 is a block configuration diagram of the control system of the printer 110.

  Information such as recording data and commands transmitted from the host device 120 is received by the CPU 100 via the interface controller 102. The CPU 100 is an arithmetic processing unit that performs overall control of the printer 110 such as reception of recording data of the printer 110, recording operation, handling of the roll paper P, and the like. After analyzing the received command, the CPU 100 renders image data of each color component of the recording data by developing a bitmap on the image memory 106.

  When recording an image, first, the capping motor 122 and the head lifting / lowering motor 118 are driven and controlled via the output port 114 and the motor drive unit 116, and the respective recording heads 22 are separated from the corresponding capping mechanism 50 for recording. Move to position. The capping motor 122 is a motor for moving the capping mechanism 50 in the directions of arrows B1 and B2 in FIG. 1, and the head elevating motor 118 is for elevating the recording head 22 in the directions of arrows C1 and C2 in FIG. Motor. Thereafter, a drive motor (not shown) for feeding the roll paper P, a transport motor 26b for transporting the roll paper P at a constant speed, and the like are driven and controlled via the output port 114 and the motor drive unit 116. The roll paper P is conveyed in the direction of arrow A. The timing (recording timing) at which ink starts to be ejected onto the roll paper P conveyed at a constant speed is determined based on the detection timing of the leading edge of the roll paper P by a leading edge detection sensor (not shown). . In synchronism with the conveyance of the roll paper P, the CPU 100 sequentially reads out the recording data corresponding to each ink color from the image memory 106, and the corresponding recording heads 22 </ b> K and 22 </ b> C via the recording head control circuit 112. , 22M, 22Y. The valve 17, the valve 20, and the valve 33 are connected to the CPU 100, and the CPU 100 performs an opening / closing operation. The ink detection sensor 24 is connected to the CPU 100, and based on the output from the ink detection sensor 24, the CPU 100 determines whether or not there is a predetermined amount of ink in a liquid chamber to be described later.

  The CPU 100 executes various processes including a negative pressure relaxation process (see FIG. 6), which will be described later, based on a processing program stored in the program ROM 104. The program ROM 104 stores processing programs and tables corresponding to the control flow. The work RAM 108 is used as a working memory. The CPU 100 drives and controls the pump motor 124 via the output port 114 and the motor driving unit 116 during the cleaning operation and the recovery operation of the respective recording heads 22 so as to pressurize and suck ink.

  FIG. 3 is an explanatory diagram of an ink supply system between the ink tank 28 and the recording head 22, and FIG. 4 is an enlarged sectional view of the ink tank 28 and the recording head 22.

  The ink tank 28 is a sealed ink tank that forms a substantially sealed space in which the liquid chamber 6 inside communicates with the outside only through the joint portion 5, and the liquid chamber 6 that forms the sealed space has at least one. The part is formed of a flexible member. The liquid chamber 6 is provided with a spring 7A that urges the liquid chamber 6 in an expanding direction. A predetermined negative pressure is generated in the liquid chamber 6 by the spring 7A. Therefore, the ink tank 28 stores the ink in the sealed space so as to apply a negative pressure. The spring 7A of this example urges the liquid chamber 6 from the inside toward the outside via the pressure plate 7B so as to expand the internal space of the liquid chamber 6. A negative pressure generating portion is formed by the spring 7A and the pressure plate 7B. A non-woven filter 8 is attached to the joint portion 5.

  The filter 13 and the ink holding member 14 are attached to the joint portion 31 of the recording head 22. The filter 13 is formed of a SUS mesh. The mesh has a structure in which metal fibers are woven, and the average width of the eyes (ink conduction part) of the filter 13 is about 10 μm. The filter 13 has such fine eyes to prevent foreign dust from entering the recording head 22. As shown in FIG. 5, the ink holding member 14 has a plurality of cylindrical flow paths 14A formed therein, and the inner diameter of the flow paths 14A is about 1.0 mm. When the filter 8 on the ink tank 28 side is in pressure contact with the filter 13 on the recording head 22 side, the recording head 22 and the ink tank 28 are connected, and the liquid chamber 6 of the ink tank 28 is connected to the liquid chamber of the recording head 22. 10 communicates.

  The recording head 22 includes a discharge energy generating element (not shown) for discharging the ink in the liquid chamber 10 from the discharge port 9. As the discharge energy generating element, an electrothermal conversion element (heater), a piezoelectric element, or the like can be used. When the electrothermal converter is used, the ink can be foamed by the generated heat, and the ink can be ejected from the ejection port 9 using the foaming energy. In the liquid chamber 10, there are a space where the ink layer 11 is formed and a space where the air layer 12 is formed.

  The ink introduced from the ink tank 28 into the recording head 22 is held in the flow path 14A of the ink holding member 14, and forms a meniscus of ink at the lower end of the flow path 14A. When ink is ejected from the ejection port 9 of the recording head 22 and the ink in the liquid chamber 10 is consumed, the pressure in the liquid chamber 10 decreases due to the decrease in the ink layer 11 and the increase in the air layer 12. When the inside of the liquid chamber 10 falls below a predetermined pressure, the ink meniscus formed at the lower end of the flow path 14 </ b> A is broken and ink is supplied from the ink tank 28 into the recording head 22. When the inside of the liquid chamber 10 returns to the original predetermined pressure by such supply of ink, the supply of ink from the ink tank 28 into the recording head 22 stops, and an ink meniscus is formed again at the lower end of the flow path 14A. . In this way, ink is supplied from the ink tank 28 into the recording head 22 through the flow path 14A of the holding member 14 so as to eliminate the pressure drop in the liquid chamber 10 due to ink consumption. The flow path 14 </ b> A allows ink supply from the ink tank 28 to the recording head 22 due to a differential pressure between the recording chamber 22 and the liquid chamber 10 in the sealed space of the ink tank 28.

  An ink detection sensor 24 for detecting the height of the ink layer 11 is provided in the liquid chamber 10. The ink detection sensor 24 is provided with two metal electrode plates 24A and 24B in parallel. When the liquid surface of the ink layer 11 is at a position higher than the height of the lower ends of the electrode plates 24A and 24B, the electrode plates 24A and 24B are electrically connected to each other, and the liquid surface of the ink layer 11 is the electrode plates 24A and 24B. When positioned below the lower end of the electrode plate 24A, the electrode plates 24A and 24B are electrically insulated. Based on the electrical change between the electrode plates 24A and 24B, the CPU 100 determines whether the liquid level of the ink layer 11 is equal to or lower than a predetermined height (the lower end positions of the electrode plates 24A and 24B). Whether or not can be detected.

  In addition to the joint portion 31, the recording head 22 is formed with a communication path 15 for communicating with the outside, and a filter 27 is provided at an opening of the communication path 15. The communication path 15 communicates with a buffer chamber (negative pressure chamber) 16 via a first valve 17 that can be opened and closed. The buffer chamber 16 has a space of about 30 ml and communicates with the pump 18. The pump 18 of this example is a tube pump that can rotate forward and backward. A flow path 19 communicating with the atmosphere is connected to the buffer chamber 16, and the flow path 19 is provided with a second valve 20 that can be opened and closed. A waste ink tank 32 is connected to the pump 18.

  A cap 34 is connected to the buffer chamber 16 via a third valve 33 that can be opened and closed. The cap 34 can be in close contact with the formation surface (ejection port formation surface) of the ejection port 9 in the recording head 22. In a state where the cap 34 is in close contact with the discharge port forming surface and the discharge port 9 is capped, the inside of the cap 34 is sucked by the pump 18 to suck and discharge ink from the discharge port 9 into the cap 34 (suction recovery operation). ). In addition, a preliminary ejection operation for ejecting ink that does not contribute to image recording into the cap 34 from the ejection port 9, and pressurizing the ink in the recording head 22, forcing it into the cap 34 from the ejection port 9. A pressure recovery operation for discharging ink can also be performed. In the pressure recovery operation, the pressurizing force generated by the pump 18 can be applied to the recording head 22 through the buffer chamber 16 and the first valve 17. The ink received in the cap 34 by such a recovery process can be discharged to the waste ink tank 32 through the buffer chamber 16 by the suction force generated by the pump 18.

  Each color ink tank 28 is provided with a storage element 41 (storage unit) capable of storing various information for each color. When the ink tank 28 is attached to the main body of the recording apparatus (apparatus main body) so that the ink tank 28 is connected to the recording head 22, the storage information of the storage element 41 of the ink tank 28 is read from the apparatus main body side. Read by the unit 40. The CPU 100 can perform control based on the read information, and can also store information in the storage element 41 of the ink tank 28.

  The negative pressure in the sealed ink tank 28 tends to increase with the negative pressure in the recording head 22 as the ink remaining amount in the ink tank 28 decreases. In particular, after ink runs out in the ink tank 28, the negative pressure in the ink tank 28 tends to increase rapidly together with the negative pressure in the recording head 22. For this reason, when the ink remaining in the ink tank 28 becomes small and the ink is further consumed, the negative pressure in the liquid chamber 10 of the recording head 22 may increase to such an extent that defective ink ejection occurs. There is.

  In the case of this example, by performing the negative pressure relaxation process, the increase in the negative pressure in the liquid chamber 10 of the recording head 22 is suppressed even in the recording operation after the remaining amount of ink in the ink tank 28 is reduced. It is possible to record a high quality image while maintaining a good ink discharge state.

  FIG. 6 is a flowchart for explaining the negative pressure relaxation process, and FIG. 7 is an explanatory view of the adjustment state of the negative pressure in the recording head 22 in the negative pressure relaxation process.

  The recording apparatus counts the number of ink ejections from the recording head 22 during the recording operation based on the recording data, thereby sequentially measuring and accumulating the ink consumption after starting to use the ink tank 28. Furthermore, by adding the ink consumption by the recovery operation (including suction recovery operation, preliminary ejection operation, and pressure recovery operation) to the ink consumption by such a recording operation, more accurate ink consumption can be obtained. Consumption can be measured. The ink consumption calculated in this way is stored in a storage element provided in the ink tank 28. Therefore, the storage element stores the cumulative consumption of ink in the ink tank 28 provided with the storage element. When the cumulative consumption amount of ink stored in the storage element becomes equal to or greater than a predetermined amount, it is determined that the ink is almost exhausted in the ink tank 28, and the process proceeds to the negative pressure relaxation mode in FIG.

  When the mode is shifted to the negative pressure relaxation mode, first, the value V related to the upper pressure increase of the negative pressure in the liquid chamber 10 of the recording head 22 after the transition to the negative pressure relaxation mode is reset (step S1), and then the recording is performed. An image is recorded based on the data (step S2). After that, information on the negative pressure increase (increase negative pressure in the recording head) V1 in the liquid chamber 10 of the recording head 22 resulting from the recording operation in step S2 is acquired (step S3).

  In the case of this example, this increased negative pressure V1 is predicted from the ink consumption during the recording operation in step S2. That is, first, the number of ink ejections during the recording operation in step S2 is counted based on the recording data, and the ink consumption is predicted based on the count value and the ink amount per ejection of ink. To do. Since the negative pressure in the recording head 22 tends to increase in accordance with the ink consumption, the negative pressure V1 in the recording head 22 during the recording operation in step S2 is predicted based on the ink consumption. be able to. The increased negative pressure V1 can also be obtained by directly detecting the pressure in the recording head 22 or the ink tank 28.

  Next, it is determined whether or not the total negative pressure (V + V1) of the rising negative pressure V1 and the negative pressure V described above is equal to or higher than a predetermined negative pressure VA (step S4). The predetermined negative pressure VA is a negative that can maintain a good ink discharge state even if the negative pressure (V + V1) in the recording head 22 rises to the extent that the negative pressure is not reached after the transition to the negative pressure relaxation mode. Pressure. When the negative pressure (V + V1) exceeds the predetermined negative pressure VA to some extent, there is a possibility that a good ink ejection state cannot be maintained.

  When the negative pressure (V + V1) is less than the predetermined negative pressure VA, the process proceeds to step S5 described later. On the other hand, when the negative pressure (V + V1) is equal to or higher than the predetermined negative pressure VA, a series of processes (steps S11, S12, S13, S14, S15, and S16) for relaxing the pressure in the recording head 22 are performed, which will be described later. The process proceeds to step S5.

  In step S11, as shown in FIG. 7A, the second valve 20 is opened while the first and third valves 17 and 33 are closed, and the buffer chamber 16 is brought to atmospheric pressure. Then, after closing the second valve 20 as shown in FIG. 7B (step S12), the pump 18 is rotated in the direction of discharging the air in the buffer chamber 16 as shown in FIG. 7C. (Step S13), the inside of the buffer chamber 16 is set to a negative pressure. Then, after making the inside of the buffer chamber 16 a negative pressure at least smaller than the predetermined negative pressure VA, the first valve 17 is opened as shown in FIG. 7D (step S14). Thereby, the negative pressure in the recording head 22 is relieved. Thereafter, the first valve 17 is closed as shown in FIG. 7E (step S15), and the negative pressure V is reset (step S16).

  It is desirable that the negative pressure in the liquid chamber 10 of the recording head 22 is reduced to an ideal appropriate negative pressure range that can ensure a good ink discharge state. Further, by reducing the pressure in the buffer chamber 16 before the buffer chamber 16 and the recording head 22 communicate with each other, the meniscus of ink formed at the ejection port when the buffer chamber 16 and the recording head 22 communicate with each other. Can be prevented. Thereby, it is possible to prevent the ink from bleeding from the ejection port.

  In step S5, it is determined whether or not the ink detection sensor 24 detects ink, that is, whether or not the amount of ink in the recording head 22 exceeds a predetermined amount. If the ink detection sensor 24 detects ink, it is determined whether or not recording of all images has been completed (step S6). If the image recording has not ended, the negative pressure (V + V1) is updated as the negative pressure V (step S7), and then the process returns to the previous step S2 to repeat the above-described processing. If the image recording is completed, the negative pressure relaxation process in FIG. 6 is terminated.

  In step S5, if the ink detection sensor 24 does not detect ink, that is, if the amount of ink in the recording head 22 is equal to or less than a predetermined amount, the pressure in the liquid chamber 10 of the recording head 22 is reduced by a suction operation (step S5). S8). As a result, the ink in the ink tank 28 is sucked into the liquid chamber 10 of the recording head 22 as much as possible. Specifically, the first valve 17 is opened, and the pump 18 is rotated in a direction to reduce the pressure in the liquid chamber 10 of the recording head 22. Thereafter, it is determined again whether or not the ink detection sensor 24 detects ink (step S9). If ink is detected, the process proceeds to step S6, and if it is not detected, the user is informed of the ink tank 28. Exchange is urged (step S10).

  As described above, in this example, the ink consumption corresponding to the negative pressure in the recording head is acquired as information on the negative pressure in the recording head. When the consumption amount exceeds a predetermined amount, that is, when the negative pressure in the recording head exceeds a predetermined negative pressure, the reduced pressure buffer and the recording head are temporarily connected. Then, the negative pressure in the recording head is relieved, and then the recording operation is resumed. Thereby, at the time of recording after the ink remaining in the ink tank is almost exhausted, an increase in the negative pressure in the recording head can be suppressed and a good ink ejection state can be maintained. As a result, the ink in the ink tank and the recording head can be used to the maximum without causing image recording failure.

(Second Embodiment)
As shown in FIG. 8, a plurality of recording heads may be commonly connected to one buffer chamber. The other parts are the same as those in the above-described embodiment, and thus the description thereof is omitted. In this example, four recording heads 22 (22Y, 22M, 22C, 22K) are connected to one buffer chamber 16 through corresponding first valves 17 (17Y, 17M, 17C, 17K). Has been. When the negative pressure in the recording head 22Y becomes equal to or higher than the predetermined negative pressure, the CPU 100 depressurizes the inside of the buffer chamber 16 in advance, and then temporarily opens the first valve 17Y, whereby the recording head 22Y. The negative pressure inside can be relieved. The same applies to the other recording heads 22M, 22C, and 22K.

  In the embodiment described above, based on the comparison result between the negative pressure (V + V1) obtained by accumulating the negative pressure increase V1 in the recording head 22 after shifting to the negative pressure relaxation mode, and the predetermined negative pressure VA. The valves 17 and 20 and the pump 18 are controlled. Since the negative pressure in the recording head 22 corresponds to the negative pressure in the ink tank 28 corresponding to the cumulative consumption of ink accumulated from the start of use of the ink tank 28, the cumulative consumption of ink is calculated in the recording head 22. It can also be used as information regarding negative pressure. For example, it is determined whether or not the negative pressure in the recording head 22 is equal to or higher than a predetermined negative pressure by comparing the cumulative consumption of the ink with a predetermined threshold. When the negative pressure in the recording head 22 is equal to or higher than the predetermined negative pressure, the negative pressure in the recording head 22 can be relieved by connecting the buffer chamber 16 to the recording head 22.

  In the above-described embodiment, when the negative pressure in the recording head is equal to or higher than the predetermined negative pressure between the preceding recording operation and the subsequent recording operation for recording an image, the recording head is interposed between those recording operations. By making the buffer chamber communicate with each other, the negative pressure in the recording head is relieved. When the negative pressure in the recording head 22 becomes equal to or higher than a predetermined negative pressure during image recording, the negative pressure in the recording head 22 can be relaxed before recording the image. For example, the ink consumption when the image is recorded is predicted from the number of ink ejections counted based on the recording data for recording the image, and the image is recorded based on the ink consumption. In this case, the negative pressure in the recording head 22 is predicted. When the predicted negative pressure in the recording head 22 is equal to or higher than the predetermined negative pressure, the negative pressure in the recording head 22 is relieved before the image is recorded.

  Since the liquid chamber 10 of the recording head 22 forms a relatively small space, it reacts sensitively to the pressure drop in the liquid chamber 10 and, as described above, from the ink tank 28 through the ink holding member 14 to the recording head 22. Ink can be reliably supplied into the liquid chamber 10. When the liquid chamber 10 of the recording head 22 is temporarily in communication with the buffer chamber 16, the volume of the liquid chamber 10 is substantially enlarged. However, since the expansion of the volume of the liquid chamber 10 is temporary, and since the recording operation for ejecting ink from the recording head 22 is not in progress, there is no problem in the ink supply.

(Third embodiment)
In the recording apparatus of this embodiment, the inside of the recording head 22 can be pressurized through the communication path 15 in consideration of the case where the filter 27 provided in the communication path 15 of the recording head 22 is wetted by ink.

  The filter 27 is provided in the communication path 15 in order to prevent foreign matters such as dust from entering the recording head 22 from the communication path 15. If foreign matter enters the recording head 22 and moves into the nozzle, ink ejection failure may occur. For example, like the filter 13, the filter 27 may have an average width of about 10 μm and a structure in which metal fibers are woven from SUS.

  When the ink in the recording head 22 comes into contact with such a filter 27 or the ink passes through the filter 27 and the filter 27 is once wetted by the ink, an ink film is formed on the mesh of the filter 27. And there is a risk that the membrane will obstruct the passage of gas. Since such a film is strongly maintained by the surface tension of the ink, the pressure in the space before and after the filter 27 in the communication path 15 is blocked. The force for blocking such pressure becomes stronger as the mesh of the filter 27 becomes finer. When the negative pressure in the recording head 22 is to be adjusted through the communication path 15 after the ink film for blocking the pressure is formed on the filter 27 as in the above-described embodiment, the adjustment is performed. It becomes difficult. That is, a meniscus force is generated in the ink film due to the surface tension of the ink, and the negative pressure introduced into the liquid chamber 10 of the recording head 22 from the communication path 15 may be blocked by the meniscus force. In this case, the negative pressure in the liquid chamber 10 cannot be reduced, and the negative pressure may increase to cause ink ejection failure.

  In the present embodiment, the ink film formed on the filter 27 is broken by the pressure difference so that the adjustment of the negative pressure in the recording head 22 is not impaired. The ink film formed on the filter 27 has a pressure difference in the space before and after the filter 27 in the communication path 15, that is, a pressure difference in the space before and after the ink film formed on the filter 27 is greater than the meniscus force of the ink. You can break it. Thereby, gas can pass through the filter 27 and the pressure in the space before and after the filter 27 in the communication path 15 is balanced.

Specifically, in the negative pressure relaxation process for adjusting the negative pressure in the recording head 22, the communication path 15 is connected from the buffer chamber 16 side so as to generate a pressure difference in the space before and after the filter 27 in the communication path 15. Adjust the pressure inside. In the case of this example, the pressure in the communication path 15 is adjusted by introducing a positive pressure into the communication path 15 from the buffer chamber 16 side so as to pressurize the space on the buffer chamber 16 side in the communication path 15. . By setting the pressure Pb in the buffer chamber 16, the meniscus force of the ink film formed on the filter 27 to Pm, and the pressure (negative pressure) Ph in the recording head 22 by the relationship of the following expression (1), the filter 27 The ink film formed can be broken.
Pb-Ph> Pm (1)

Further, the pressure Ph in the recording head 22 is made larger than the predetermined pressure Pf as shown in the following equation (2).
Ph> Pf (2)

  The predetermined pressure Pf is a pressure (negative pressure) at which there is a possibility that a good ink ejection state cannot be maintained when the pressure Ph in the recording head 22 becomes smaller than that. If the pressure Ph in the recording head 22 is greater than the predetermined pressure Pf, a good ink discharge state can be maintained.

In order to perform the negative pressure relaxation processing for adjusting the negative pressure in the recording head 22 so as to establish the relationship of the above equation (1) while maintaining the relationship of the above equation (2), the following equation (3) It is necessary to establish the relationship.
Pb-Pm>Ph> Pf (3)
Therefore, the pressure Pb in the buffer chamber 16 may be set so as to satisfy the following expression (4).
Pb> Pm + Pf (4)

  In the present embodiment, as in the first embodiment described above, when it is determined that the ink in the ink tank 28 is almost exhausted, the mode shifts to the negative pressure relaxation mode. In the negative pressure relaxation mode, a negative pressure relaxation process as shown in FIG. 9 is executed. Steps S1 to S10 are the same as the processing of FIG. 6 in the above-described embodiment.

  In step S11, as shown in FIG. 10A, the second valve 20 is opened while the first and third valves 17 and 33 are closed, and the buffer chamber 16 is brought to atmospheric pressure. Then, after the second valve 20 is closed as shown in FIG. 10B (step S12), the pump 18 is rotated in the direction in which air is introduced into the buffer chamber 16 as shown in FIG. 10C. (Step S13A), the inside of the buffer chamber 16 is set to a positive pressure. At that time, the buffer chamber 16 is used as a pressurized pressure chamber. The pressure Pb in the buffer chamber 16 at this time is set to a magnitude of Pb> Pm + Pf as described in (4) above. Next, as shown in FIG. 10D, the first valve 17 is opened (step S14). Thereafter, the first valve 17 is closed as shown in FIG. 10E (step S15), and the negative pressure V is reset (step S16).

  As shown in FIG. 10D, after the pressure (positive pressure) Pb in the buffer chamber 16 is introduced into the communication path 15, the pressure in the recording head 22 decreases (the negative pressure increases) with the recording operation. . When the pressure Ph in the recording head 22 decreases to become Ph1, a differential pressure larger than the meniscus force Pm is generated. As a result, when an ink film is formed on the filter 27, the film is broken. The pressure Ph1 can be set larger than the predetermined pressure Pf. Accordingly, it is possible to break the ink film formed on the filter 27 while maintaining a good ink discharge state by setting the pressure Ph1 in the recording head 22 to be larger than the predetermined pressure Pf. Thus, by breaking the ink film on which the filter 27 is formed, the pressure is propagated through the filter 27 and the negative pressure in the recording head 22 is relieved. If the atmospheric pressure PA is introduced from the buffer chamber 16 into the communication path 15, the inside of the recording head 22 must be set to a pressure Ph2 smaller than the pressure Ph1 in order to generate a differential pressure larger than the meniscus force Pm. . In this case, the pressure Ph2 becomes smaller than the predetermined pressure Pf, and there is a possibility that a good ink ejection state cannot be maintained.

(Fourth embodiment)
For example, there is a possibility that the ink in the recording head 22 passes through the filter 27 and enters the communication path 15 due to the falling of the recording apparatus, and the ink remains on the filter 27. If the filter 27 is blocked by the residual ink on the filter 27, the pressure in the space before and after the filter 27 in the communication path 15 may be strongly blocked. When the ink remains on the filter 27 and the inside of the communication path 15 is pressurized from the buffer chamber 16 as in the third embodiment, the ink film is not broken. Residual ink on the filter 27 moves to the recording head 22 side. For this reason, the pressure in the recording head 22 is increased, and the ink in the recording head 22 may ooze out from the discharge port at the tip of the nozzle.

  In this embodiment, when the mode is shifted to the negative pressure relaxation mode, the inside of the communication path 15 is pressurized from the inside of the buffer chamber 16 and the residual ink on the filter 27 is moved into the recording head 22, whereby the negative pressure thereafter. Stabilizes the pressure relief operation. At that time, since the ink may ooze out from the ejection port of the recording head 22, the cap 34 and the recording head 22 are opposed to receive the ink by the cap 34. In addition, by wiping the discharge port forming surface of the recording head 22 where the discharge port is formed, the ink exuding from the discharge port is wiped off and the discharge port forming surface is cleaned. As a result, it is possible to stabilize the negative pressure relaxation operation and to avoid the influence of the ink oozing out from the ejection port on the recording operation.

16 Buffer chamber (negative pressure chamber)
17 1st valve (opening and closing means)
22 Recording Head 28 Ink Tank 110 Printer (Inkjet Recording Device)

Claims (16)

A recording head capable of ejecting ink supplied from an ink tank that houses the ink in a sealed space so as to apply a negative pressure;
A communication path for communicating the outside of the liquid chamber of the recording head with the liquid chamber;
Opening and closing means for opening and closing the communication path;
Control means for opening the communication path by the opening and closing means to communicate the outside and the liquid chamber in accordance with the pressure in the recording head;
An ink jet recording apparatus comprising:   2. The ink jet recording apparatus according to claim 1, wherein the control means opens the communication path by the opening / closing means when a negative pressure in the recording head becomes equal to or higher than a predetermined negative pressure.   3. The ink jet recording apparatus according to claim 2, wherein the negative pressure in the recording head is equal to or higher than the predetermined negative pressure, and the ink consumption in the ink tank is equal to or higher than a predetermined amount.   4. The ink jet recording apparatus according to claim 3, wherein the ink consumption is obtained based on the number of ink ejections from the recording head.   When the negative pressure in the recording head is equal to or higher than the predetermined negative pressure between the preceding recording operation and the subsequent recording operation for recording an image by discharging ink from the recording head, 5. The ink jet recording apparatus according to claim 2, wherein the communication path is temporarily opened by the opening / closing means between the preceding recording operation and the subsequent recording operation. 6.   When the negative pressure in the recording head is equal to or higher than the predetermined pressure during a recording operation for discharging an ink from the recording head and recording an image, the control unit is configured to open the opening / closing unit before the recording operation. The inkjet recording apparatus according to claim 2, wherein the communication path is temporarily opened. Detecting means for detecting the amount of ink in the recording head;
Pressure reducing means for reducing the pressure in the recording head so as to suck ink from the ink tank into the recording head when the amount of ink detected by the detecting means is equal to or less than a predetermined amount;
The inkjet recording apparatus according to claim 1, comprising:   The ink jet recording apparatus according to claim 7, wherein the decompression unit decompresses the inside of the recording head through a negative pressure chamber.   A flow path is provided between the ink tank and the recording head to allow ink to be supplied from the sealed space to the recording head due to a differential pressure between the sealed space and the recording head. The ink jet recording apparatus according to claim 1, wherein:   10. The ink jet recording apparatus according to claim 8, wherein a plurality of the recording heads communicate with one negative pressure chamber via the corresponding communication passages. 10.   The inkjet recording apparatus according to claim 1, wherein a filter is provided in the communication path.   The ink jet recording apparatus according to claim 1, further comprising a pressure adjusting unit capable of pressurizing the inside of the recording head through the communication path.   The pressure adjusting means includes a pressure chamber communicated with the liquid chamber of the recording head through the communication path opened and closed by the opening and closing means, and the pressure chamber is added with the communication path closed by the opening and closing means. 13. The ink jet recording apparatus according to claim 12, wherein after the pressure is applied, the inside of the recording head can be pressurized by opening the communication path by the opening / closing means.   When the negative pressure in the recording head is equal to or higher than a predetermined negative pressure between the preceding recording operation and the subsequent recording operation for recording an image by discharging ink from the recording head, 14. The ink jet recording apparatus according to claim 12, wherein the inside of the recording head is pressurized through the communication path between the preceding recording operation and the subsequent recording operation. The recording head is capable of ejecting ink from an ejection port formed on the ejection port forming surface,
15. The cleaning apparatus according to claim 12, further comprising a cleaning unit that cleans the ejection port forming surface of the recording head when the pressure adjusting unit pressurizes the inside of the recording head. Inkjet recording apparatus. An ink jet recording method for recording an image by discharging ink supplied from within a sealed space of an ink tank to which a negative pressure is applied, from a recording head,
An ink jet recording method, wherein when the negative pressure in the recording head becomes equal to or higher than a predetermined negative pressure, a pressure equal to or higher than the predetermined negative pressure is introduced into the recording head.

Images