Liquid dispensing device

Abstract

To provide a liquid dispensing device that can efficiently suppress dispensing failures in a configuration that includes a circulation channel. [Solution] A liquid dispensing device comprising: a dispensing head for dispensing liquid from the outlet of a pressure chamber; a storage section for storing liquid; a circulation path for circulating liquid, including an inflow path for introducing liquid into the pressure chamber and an outflow path for releasing liquid from the pressure chamber; a supply path for introducing liquid from the storage section into the circulation path; a discharge means for discharging the liquid from the pressure chamber; a first temperature detection means for detecting the temperature of the dispensing head; a second temperature detection means for detecting the ambient temperature; and a control means. The control means controls the discharge means based on the amount of liquid supplied per unit time to the supply path, the amount of liquid circulated per unit time in the circulation path, a first temperature detected by the first temperature detection means, and a second temperature detected by the second temperature detection means.

Description

Technical Field

[0001] The present invention relates to a liquid ejection device.

Background Art

[0002] Conventionally, as a liquid ejection device, there is known a configuration in which a liquid ejection element such as an electrothermal conversion element or an electromechanical conversion element provided in a pressure chamber having a liquid ejection port is driven to eject the liquid in the pressure chamber. When such a configuration is applied to an inkjet printer, it is common to provide a plurality of pressure chambers and ejection elements to improve the recording speed. However, with the driving of a plurality of ejection elements, the temperature in the pressure chamber may rise. As a result, a temperature difference from the ejected liquid (ink) occurs, and gas melted in the liquid may generate bubbles. These bubbles may inhibit the inflow of the liquid from the liquid storage portion, and there is a possibility that the liquid cannot be ejected from the ejection port. Therefore, a configuration for discharging the bubbles from the ejection port to the outside is known (see Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problem to be Solved by the Invention

[0004] In the configuration described in Patent Document 1, since it has a form with a flow path for circulating ink, as the temperature in the ejection pressure chamber rises, in addition to the ink flowing in from the ink tank (storage portion), bubbles also generate from the circulating ink. Therefore, with the control described in Patent Document 1, the bubbles cannot be sufficiently discharged, and ejection failure of the ink cannot be suppressed.

[0005] Therefore, an object of the present invention is to provide a liquid ejection device that can efficiently suppress ejection failure in a configuration provided with a circulation flow path. [Means for solving the problem]

[0006] The above objective is achieved by the present invention as described below. That is, the liquid dispensing device according to the present invention comprises: a dispensing head for dispensing liquid from a discharge port of a pressure chamber; a storage section for storing the liquid; a circulation section for circulating the liquid, including an inflow passage for introducing the liquid into the pressure chamber and an outflow passage for discharging the liquid from the pressure chamber; a supply passage for introducing the liquid from the storage section into the circulation section; a discharge means for discharging the liquid from the pressure chamber; a first temperature detection means for detecting the temperature of the dispensing head; a second temperature detection means for detecting the ambient temperature; and a control means, wherein the control means controls the discharge means based on the amount of liquid supplied per unit time to the supply passage, the amount of liquid circulated per unit time in the circulation section, a first temperature detected by the first temperature detection means, and a second temperature detected by the second temperature detection means. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a liquid dispensing device that can efficiently suppress dispensing defects in a configuration that includes a circulation channel. [Brief explanation of the drawing]

[0008] [Figure 1] A cross-sectional view of the main part of an inkjet printer to which the liquid ejection device of the present invention is applied. [Figure 2] A plan view of the main part of the recording head in the first embodiment. [Figure 3] A key part of the recording head around the pressure chamber in the first embodiment. [Figure 4] A schematic diagram of the main components of the ink supply system in the first embodiment. [Figure 5] Block diagram of the control system of an inkjet printer to which the liquid ejection device of the present invention is applied. [Figure 6] A flowchart illustrating the cumulative sequence of bubble volume in the first embodiment. [Figure 7] A table showing the temperature coefficients used in the cumulative sequence of bubble volume in the first embodiment. [Figure 8] A flowchart illustrating the suction recovery sequence during recording in the first embodiment. [Figure 9] Schematic diagrams of the main parts of the ink supply system in the second and third embodiments. [Figure 10] Diagram illustrating the flow of ink in the ink supply system in the second and third embodiments. [Figure 11] Diagram illustrating the bubble volume accumulation sequence in the second embodiment. [Figure 12] Diagram illustrating the bubble volume accumulation sequence in the third embodiment. [Modes for carrying out the invention]

[0009] The present invention will be described in more detail below with reference to preferred embodiments.

[0010] <First Embodiment> Figure 1 is a cross-sectional view of the main part of the inkjet printer in this embodiment. Figure 2 is a plan view of the main part of the recording head in this embodiment. In this embodiment, an example of applying the liquid ejection device of the present invention to an inkjet printer is shown, but it can be applied to other applications as appropriate.

[0011] The recording head 100, which corresponds to the ejection head, is provided with rows of ejection ports 101, 101M, 101Y, and 101K, on ​​its ejection port surface 102. Here, ejection ports 101C, 101M, 101Y, and 101K are rows of ejection ports for cyan ink, magenta ink, yellow ink, and black ink, respectively. Each row of ejection ports has 600 ejection ports 101, arranged in the direction indicated by the arrow Y in Figure 2 (Y direction), with a spacing of 600 dpi (dots / inch) between each port.

[0012] The recording head 100 is mounted on the carriage 111 and is reciprocally scanned in the directions indicated by arrows X1 and X2 (X1 direction, X2 direction) in FIG. 2, which are opposite to each other, by the rotation of a carriage motor (not shown) during recording. Further, the carriage 111 is reciprocally scanned in the X1 and X2 directions while the recording medium, which is intermittently conveyed in the direction indicated by Y1 (Y1 direction) in FIG. 2 on the platen 120 as the carriage motor (not shown) rotates, is stopped. Here, the X1 (X2) direction and the Y1 direction are substantially orthogonal. During this reciprocal scanning, ink is ejected from the ejection port 101 of the recording head 100 toward the recording medium, and an image is recorded. Note that components surrounded by the dotted line in FIG. 4 described later are mounted on the carriage 111 shown in FIG. 1. Also, in the present embodiment, the recording head 100 reciprocally scans in the X1 and X2 directions and the recording medium scans in the Y1 direction, but it is not limited to the above as long as the recording head 100 and the recording medium scan relatively. For example, the recording medium may reciprocally scan in the X1 and X2 directions and the recording head may scan in the Y1 direction.

[0013] As shown in FIG. 1, the cap 130 is a cap for suppressing the evaporation of the liquid component of the ink from the ejection port 101 by contacting the ejection port surface of the recording head. The cap 130 has a contact position (capping position) where it contacts the ejection port surface of the recording head and a separation position where it is separated from the recording head by a detaching and attaching mechanism (not shown). Note that FIG. 1 shows the state where the cap 130 is in the separation position. The cap 130 is connected to a suction pump 135 via a pump tube 131, and by driving the suction pump 135, ink and air can be sucked and discharged from the ejection port 101.

[0014] In addition, the pump tube 131 is provided with an on-off valve 132 and a charge buffer 133, enabling charge suction. Charge suction is a suction method capable of vigorously sucking ink from the ejection port array. Specifically, by driving the suction pump 135 with the on-off valve 132 closed, the large negative pressure stored in the charge buffer 133 is instantaneously applied to the ejection port array when the on-off valve 132 is opened, allowing the ink to be sucked vigorously. Charge suction makes it possible to efficiently suck and discharge the air bubbles in the recording head 100 while keeping the suction and discharge amount of the ink small.

[0015] Furthermore, an atmosphere release tube 136 equipped with an atmosphere release valve 137 is connected to the cap 130. By driving the suction pump 135 with the atmosphere release valve 137 open (and the on-off valve 132 also open), the ink remaining in the cap 130 can be sucked and discharged. An ink absorber A is provided in the cap 130. The ink sucked and discharged by driving the suction pump 135 is sent to a maintenance cartridge (not shown) via the waste ink tube 139 and held within the maintenance cartridge.

[0016] FIG. 3 shows the main part around the pressure chamber of the recording head in this embodiment. FIG. 3(a) is a cross-sectional view taken along the line A-A' of FIGS. 2 and FIG. (b), and FIG. 3(b) is a plan view thereof. As described above, the pressure chamber 301 includes an ejection port 101. An electrothermal conversion element 302 is provided opposite the ejection port 101. By applying an electrical signal based on a drive signal to this electrothermal conversion element 302, the ink is foamed, and the ink is ejected from the ejection port 101 by the pressure of the foaming.

[0017] An ink inlet 310 is formed in the pressure chamber 301, and through this ink inlet 310, it communicates with an individual inlet channel 311. Furthermore, the individual inlet channel 311 communicates with a common inlet channel 312. The common inlet channel 312 extends in the Y direction for approximately the length of the discharge port row, that is, about 25.4 mm. Also, the common inlet channel 312 is located around the connection point between the recording head and the inlet channel, and the accumulation of bubbles in this area may cause discharge problems. Similarly, an ink outlet 320 is formed in the pressure chamber 301, and through this ink outlet 320, it communicates with an individual outlet channel 321. Furthermore, the individual outlet channel 321 communicates with a common outlet channel 322. The common outlet channel 322 also extends in the Y direction for approximately the length of the discharge port row, that is, about 25.4 mm.

[0018] In Figure 3, there are multiple diode sensors 303 and 304, 13 of each, in the Y direction, for a total of 26. Diode sensors 303 and 304 correspond to the first temperature detection means, as they detect the temperature near the pressure chamber 301 (temperature of the recording head) for each row of discharge ports.

[0019] Figure 4 is a schematic diagram of the main parts of the ink supply system communicating with the connection inflow channel 313 and the connection outflow channel 323 in this embodiment. Here, Figure 4 shows only one ink supply system communicating with a row of discharge ports 101C (discharge port row) that discharges one color, for example, cyan ink, but similar ink supply systems are provided for other colors as well.

[0020] The inflow channel 315 is connected to the connecting inflow channel 313. In other words, the connection point between the inflow channel and the recording head is the point where the inflow channel 315 and the connecting inflow channel 313 connect. Similarly, the outflow channel 325 is connected to the connecting outflow channel 323. Here, there are a total of four connecting inflow channels 313 and connecting outflow channels 323, arranged along the Y direction, one for each color.

[0021] The circulation pump 330 is in communication with the inflow channel 315 and the outflow channel 325. The circulation pump 330, together with the inflow channel 315, the recording head 100, and the outflow channel 325, forms a circulation channel. The circulation channel may have a configuration other than the one described above. The ink circulates in the direction indicated by arrow J in Figure 4 when the circulation pump 330 is driven. The ink ejected or discharged from the recording head 100 is supplied from the ink tank 351, which corresponds to the ink storage section, through the inflow channel 315 and the circulation channel, in order to replace the amount consumed.

[0022] Near the ink tank 351, a thermistor (not shown) is provided, which corresponds to a second temperature detection means for detecting the ambient temperature, which is the temperature of the location where the inkjet printer is installed. In this embodiment, there is only one thermistor, and not one for each color. However, a configuration may be used in which multiple thermistors are provided at different locations to improve the accuracy of ambient temperature detection.

[0023] Figure 5 is a block diagram of the control system in this embodiment. The host computer 590 is connected to the inkjet printer, for example, by a USB interface. The printer driver 591 is stored in software form within the host computer 590. In response to a recording command from the user, the printer driver 591 generates print data from image data such as documents and photographs requested by the user and sends it to the inkjet printer.

[0024] The receive buffer 551 holds print data and other information transmitted from the host computer 590. The print data and other information held in the receive buffer 551 are transferred to the RAM 502 under the management of the CPU 501 and temporarily stored there. The ROM 503 stores programs and fixed data necessary for various controls of the inkjet printer. The NVRAM 504 is a non-volatile memory that retains information that should be stored even when the inkjet printer is powered off.

[0025] The actuator driver 510 drives various actuators 511, such as a motor for driving the suction pump 135 and a solenoid for opening and closing the on / off valve 132. The sensor controller 520 controls various sensors 521. The display / operation unit controller 530 controls the display unit and operation unit 531 of the inkjet printer. The head driver 540 drives the recording head 100. Here, the CPU 501 controls RAM 502, ROM 503, NVRAM 504, etc., and also performs various processing operations such as calculations, judgments, and settings.

[0026] Next, the bubble accumulation sequence in this embodiment will be described with reference to Figures 6 and 7. Here, the bubble accumulation sequence is a sequence for determining the cumulative amount of bubbles that accumulate mainly in the common inflow channel 312, which may obstruct the inflow of ink into the pressure chamber 301.

[0027] In Figure 6, the bubble accumulation sequence is started when the ink circulation begins (S600). More specifically, it is started when the CPU 501 sends a start command to the actuator driver 510. When the CPU 501 sends the above command, the process proceeds to S601.

[0028] In S601, CPU 501 retrieves the current cumulative bubble amount BT stored in NVRAM 504 for each color. Note that this BT is "0" for each color in the initial state and immediately after the charge suction described later.

[0029] Next, the process proceeds to S602, where the CPU 501 obtains the circulation rate J (liquid circulation rate) of the ink in the circulation channel per unit time from the RAM 502. In this embodiment, this rate is 0.5 mL / min for each color. Then, the process proceeds to S603, where the CPU 501 obtains the ambient temperature detected by the thermistor. After that, the CPU 501 determines whether a predetermined time ST has elapsed since the execution of the processes from S611 to S631 (hereinafter also referred to as cumulative processing) (S610). If the CPU 501 determines that the predetermined time ST has elapsed, the process proceeds to cumulative processing. After the processes up to S631, and in S610, if the CPU 501 determines that the predetermined time ST has not elapsed, the process proceeds to S699 to determine whether the circulation operation has ended. Specifically, the CPU 501 determines whether it has issued a command to the actuator driver 510 to stop the operation of the circulation pump 330. In S699, if the CPU 501 determines that the cyclic operation has ended, it terminates the bubble quantity accumulation sequence. On the other hand, if the CPU 501 determines that the cyclic operation has not ended, it returns to S610. In other words, the bubble quantity accumulation sequence repeats the accumulation process at predetermined time intervals ST until the cyclic operation ends. Here, the predetermined time ST can be set as appropriate, and in this embodiment it is 1 second.

[0030] The details of the cumulative processing are explained below. In S611, the CPU 501 obtains the amount of ink supplied to the inflow channel 315 per unit time (liquid supply amount S). Specifically, for each color, the CPU 501 obtains from the RAM 502 the number of times the electrothermal conversion elements of each discharge port row were driven (dot count value) during a predetermined time ST, and calculates the supply amount S by multiplying this by the amount of ink discharged per drive of the electrothermal conversion element. In this embodiment, the amount of ink discharged per drive of the electrothermal conversion element is stored in the ROM 503 and is 5 ng.

[0031] After S611, CPU 501 acquires the head temperature T1 for each color (S612). Specifically, it acquires the average value of the 26 diode sensors over a predetermined time ST.

[0032] After S612, the CPU 501 calculates the amount of bubbles B (S613). Specifically, the CPU 501 calculates a value R by adding the value obtained by multiplying the circulation amount J obtained in S602 by the coefficient α and the value obtained by multiplying the supply amount S obtained in S611 by the coefficient β. Then, the amount of bubbles B is calculated by multiplying R by the coefficient TT. In this embodiment, the coefficient α is 0.6 and the coefficient β is 0.8. Through the inventors' investigation, it was found that there are more bubbles generated from the ink supplied from the ink tank 351 to the inflow channel 315 than from the ink circulating in the circulation channel. The coefficients α and β represent the ratio and are stored in the ROM 503. The coefficient TT is a value determined by the ambient temperature T2 obtained in step S603 and the head temperature T1 obtained in step S612, and the corresponding table is shown in Figure 7.

[0033] After S613, the CPU 501 adds the amount of bubbles B to the cumulative amount of bubbles BT (S614). After S614, the CPU 501 determines whether the cumulative amount of bubbles BT exceeds the first threshold TBT1, which corresponds to a first predetermined amount (S620). The first threshold TBT1 will be described in detail later, but in this embodiment it is stored in the ROM 503 and is "5.0 × 10 4 In S620, if CPU501 determines that the first threshold TBT1 has been exceeded, the TBT1 flag is turned ON in NVRAM504 (S621). After S621, and in S620, if CPU501 determines that the first threshold TBT1 has not been exceeded, the process proceeds to S630.

[0034] In S630, the CPU 501 determines whether the cumulative bubble amount BT exceeds a second threshold TBT2, which corresponds to a second predetermined amount. The second threshold TBT2 will be described in detail later, but in this embodiment it is stored in ROM 503 and is "1.1 × 10 5In S630, if CPU501 determines that the second threshold TBT2 has been exceeded, the TBT2 flag is turned ON in NVRAM504 (S631). After S631, and in S630, if CPU501 determines that the first threshold TBT1 has not been exceeded, the process proceeds to S699.

[0035] The bubble accumulation sequence described above allows us to determine the cumulative amount of bubbles that accumulate mainly in the common inflow channel 312, which obstruct the flow of ink into the pressure chamber 301 and cause ejection failures.

[0036] Next, the suction recovery sequence during recording will be explained with reference to Figure 8. The suction recovery sequence during recording is executed in parallel with the bubble volume accumulation sequence shown in Figure 6. In S800, the CPU 501 determines whether recording has started. S800 is performed continuously until it determines that recording has started, at which point the process proceeds to S810. In S810, the CPU 501 determines whether the recording is "between scans". "Between scans" refers to the time between the end and start of each scan of the carriage 111 during recording. In S810, if the CPU 501 determines that it is "between scans", the process proceeds to S820. In S810, if the CPU 501 determines that it is not "between scans", the process proceeds to S899.

[0037] In S820, the CPU 501 determines whether the TBT2 flag is on. The TBT2 flag, stored in the NVRAM 504, is loaded into the RAM 502 when the recording of the suction recovery sequence begins. If S820 determines that the TBT2 flag is on, the process proceeds to S821, where the CPU 501 instructs the actuator driver 510 to perform charge suction. Specifically, the cap 130 is moved to the capping position and capping is performed. Next, with the atmospheric release valve 137 and the on / off valve 132 closed, the suction pump 135 is driven to accumulate a large negative pressure (for example, about -80kPa) in the charge buffer 133. Then, the on / off valve 132 is opened, and the negative pressure is suddenly applied to the discharge port row to suction and discharge ink and air bubbles. After that, the atmospheric release valve 137 is opened, and with that state, the suction pump 135 is driven to suction and discharge any ink remaining in the cap 130, etc., performing what is known as dry suction. After emptying the cylinder, it is preferable to perform a well-known wiping process using a wiper (not shown) or to perform a so-called pre-discharge, which involves discharging ink towards the cap 130 or other locations.

[0038] Thus, when the TBT2 flag is on, meaning the cumulative bubble amount BT exceeds the second threshold TBT2, charge suction is performed even in situations where there is little time to spare, such as between scans. Charge suction then sucks out and discharges bubbles accumulated in the common inflow channel 312 and other locations. By performing this process, the inflow of ink into the pressure chamber 301 is obstructed mainly by bubbles accumulated in the common inflow channel 312, thereby suppressing ejection failures. In other words, the TBT2 flag is an indicator for determining whether charge suction needs to be performed even in situations where there is little time to spare, such as "between scans".

[0039] After S821, CPU501 resets the cumulative bubble amount BT to "0" (S822). At this time, the cumulative bubble amount BT of RAM502 and NVRAM504 is reset. The TBT2 flag is also turned off. After S822, and if CPU501 determines in S820 that the TBT2 flag is off, the process proceeds to S830.

[0040] In S830, the CPU 501 determines whether the recording operation is in a state between the end of recording a term and the start of recording the next term (hereinafter also referred to as "between terms"). If the CPU 501 determines that it is between terms, the process proceeds to S840; if the CPU 501 determines that it is not between terms, the process returns to S810.

[0041] In S840, the CPU 501 determines whether the TBT1 flag is on. The TBT1 flag stored in the NVRAM 504 is also loaded into the RAM 502 when the suction recovery sequence being recorded is started. If the CPU 501 determines that the TBT1 flag is on, the process proceeds to S841, where the charge suction is executed. The specific flow of the charge suction is the same as in S821.

[0042] If the TBT1 flag is on, meaning the cumulative bubble amount BT exceeds the first threshold TBT1, charge suction should be performed immediately, even if the likelihood of discharge failure is low. Performing an operation such as charge suction, which takes a relatively long time, at a timing like the aforementioned "between scans" may cause image unevenness. Therefore, by suctioning and discharging bubbles accumulated in the common inflow channel 312 or other locations at a time when there is relatively ample time, such as between pages, it is possible to suppress the execution of charge suction at a time when there is no time leeway, such as "between scans".

[0043] After S841, similar to S822, the CPU 501 resets the cumulative bubble amount BT to "0" (S842). Then, the process proceeds to S899. In S899, the CPU 501 determines whether the recording operation has finished. If it determines that the recording operation has not finished, it returns to S810; if it determines that it has finished, it terminates the suction recovery sequence that was being recorded.

[0044] By executing the aforementioned bubble accumulation sequence and the recording-in-progress suction recovery sequence in parallel, bubbles that could lead to dispensing failures can be aspirated and discharged at the appropriate timing. Therefore, the occurrence of dispensing failures can be suppressed without wasting time or waste liquid required for bubble discharge. Furthermore, even when not recording, if the power is on, it is preferable to perform charge suction when the TBT1 flag is on.

[0045] <Second Embodiment> Figure 9 is a schematic diagram of the main components of the ink supply system of the inkjet printer in this embodiment. Components numbered the same as those in Figure 4 are similar and therefore their explanations are omitted. The other components are the same as in the first embodiment, so the differences from the first embodiment will be explained in detail.

[0046] In Figure 9, the bypass passage 910 is a passage for connecting the inlet passage 315 and the outlet passage 325, and is equipped with a well-known negative pressure regulator 911. Inside the negative pressure regulator 911 is a valve (not shown, hereinafter also referred to as the bypass valve) that opens only when the absolute value of the negative pressure in the passage on the outlet passage 325 side of the negative pressure regulator 911 (hereinafter also referred to as the downstream negative pressure) exceeds a predetermined value. In other words, the bypass valve is a valve that can automatically open and close the bypass passage using the negative pressure in the outlet passage. That is, the inlet passage 315 and the outlet passage 325 communicate via the bypass passage 910 when the downstream negative pressure falls below the predetermined value and the bypass valve opens. When the bypass valve opens, the inlet passage 315 and the outlet passage 325 communicate, and ink flows, causing the downstream negative pressure to rise above the predetermined value again. As a result, the bypass valve closes, and the bypass passage becomes blocked. The predetermined value may be set as appropriate, and in this embodiment, it is approximately -2kPa.

[0047] By using this ink supply system, the amount of ink ejected per unit time from the recording head 100 (ejected ink amount) can be increased compared to the first embodiment. Increasing the ejected ink amount delays the supply of ink from the ink tank 351 to the inflow channel 315, causing a temporary decrease in the downstream negative pressure. However, with the configuration shown in Figure 9, the bypass valve opens, and ink is supplied to the recording head 100 from the outflow channel 325 side as well, thereby restoring the downstream negative pressure to normal. Increasing the ejected ink amount leads to an increase in the drive frequency of the ejection element in the recording head 100, which can improve the recording speed.

[0048] Next, with reference to Figure 10, the change in ink flow due to the amount of ink discharged will be explained. Figure 10(a) shows the ink flow when the amount of ink discharged is large, that is, when ink is supplied from the outflow channel 325 side as well, and Figure 10(b) shows the ink flow when the amount of ink discharged is small, that is, when ink is supplied only from the inflow channel 315 side.

[0049] In Figure 10(a), the ink S supplied from the ink tank 351 is divided into two parts: ink S1 that passes through the inflow channel 315 and ink S2 that passes through the bypass channel 910 and the outflow channel 325. That is, the ink S supplied from the ink tank 351 is supplied to the recording head 100 through two paths. The ink S circulates through a circulation path consisting of the circulation pump 330, the inflow channel 315, the bypass channel 910, and the outflow channel 325, driven by the circulation pump 330. The amount of ink S1 can be considered as the amount of liquid moved per unit time from the inflow channel side to the pressure chamber. The amount of ink S2 can be considered as the amount of liquid moved per unit time in the channel on the pressure chamber side of the circulation path, which is driven by the circulation pump.

[0050] In such cases, the ink that generates bubbles in the common inflow channel 312, leading to ejection failure, is primarily ink S1, which is supplied to the recording head 100 via the inflow channel 315. Ink S2 also generates bubbles, but the amount of ink S2 is less than that of ink S1. The reason for this will be explained in detail later. Therefore, by taking into account the bubbles generated from ink S1, the occurrence of ejection failure can be suppressed.

[0051] In Figure 10, the bypass valve in the negative pressure regulator 911 repeatedly opens and closes instantaneously. The moment the downstream negative pressure falls below a predetermined value and the bypass valve opens, ink flows from the upstream flow path to the downstream flow path. This action immediately causes the downstream negative pressure to exceed the predetermined value, and the bypass valve closes again. The interval between opening and closing operations varies depending on the amount of ink discharged, and becomes shorter as the amount of ink discharged increases. This is because the more ink discharged, the more opportunities there are for the downstream negative pressure to fall below a predetermined value. Therefore, in Figure 10(a), the bypass valve is not always open, so the amount of ink S2 is less than the amount of ink S1.

[0052] Next, in Figure 10(b), the ink S flows in two directions, indicated by arrows D and H, due to the drive of the circulation pump 330. Hereafter, the ink passing through the bypass channel 910 indicated by arrow D will be referred to as ink D, and the ink passing through the recording head 100 indicated by arrow H will be referred to as ink H. Here, the ratio of the amounts of ink D and ink H differs depending on the interval between the opening and closing operations of the bypass valve. Specifically, as the interval between opening and closing operations decreases, the ratio of ink D increases. This is because the flow resistance of the recording head 100 is greater than the flow resistance of the bypass channel 910, which includes the negative pressure regulator 911, so when the bypass valve is open, more ink passes through the bypass channel 910.

[0053] Therefore, as shown in Figure 10(b), when the amount of ejected ink is relatively small, the inks that cause bubbles in the common inflow channel 312, leading to ejection failure, are ink S and ink H. However, as mentioned above, the amounts of ink S and H also increase or decrease with the increase or decrease in the amount of ejected ink.

[0054] Next, the bubble volume accumulation sequence in this embodiment will be explained, with particular emphasis on the differences from the first embodiment. Figure 11 is a graph showing the relationship between the discharge rate S (g / min) per unit time and the value R used to calculate the bubble volume B. In Figure 11, the horizontal axis represents the ink discharge rate per unit time, i.e., the discharged ink volume S, and the vertical axis represents the value R. The discharged ink volume S can be rephrased as the ink supply volume S supplied from the ink tank 351 to the supply channel 350.

[0055] As shown in Figure 11, even when the amount of ejected ink is 0, that is, when no ink is ejected from the recording head 100, ink H flows into the common inflow channel 312, so R does not become 0. As the amount of ejected ink S increases, R also increases, but as the amount of ink H gradually decreases, the rate of increase of R decreases. Furthermore, when the amount of ejected ink S increases to the state shown in Figure 10(a), the rate of increase becomes 0. As described above, in this embodiment, R is corrected according to the amount of ejected ink S, and the amount of bubbles B is calculated appropriately.

[0056] Thus, even with an ink supply system like that of this embodiment, by appropriately calculating the amount of bubbles B and performing the bubble accumulation sequence and the suction recovery sequence during recording in parallel, the same effects as in the first embodiment can be obtained.

[0057] <Third Embodiment> In this embodiment, in order to further suppress the increase in viscosity of the ink near the discharge port due to the evaporation of the liquid component of the ink from the discharge port, an example is described in which the driving force of the circulation pump 330 is improved compared to the ink supply system in the second embodiment. Specifically, the driving force of the circulation pump 330 is improved so that the amount of ink circulating per unit time in the portion indicated by arrow J in Figures 9 and 10 is 1 mL / min, which is twice that of the first and second embodiments. Note that, apart from the improved driving force of the circulation pump 330, the configuration is the same as in the second embodiment, so a detailed explanation of other points is omitted.

[0058] Figure 12 is a graph showing the relationship between the discharge rate S (g / min) per unit time and the value R used to calculate the amount of bubbles B in this embodiment. Compared to Figure 11, the value R is different even for the same amount of ink discharged S, as a result of improving the driving force of the circulation pump 330.

[0059] As described above, even when the driving force of the circulation pump 330 is increased, the same effects as in the first and second embodiments can be obtained by appropriately calculating the amount of bubbles B and performing the bubble accumulation sequence and the suction recovery sequence during recording in parallel.

[0060] <Other Embodiments> In the first to third embodiments, one ink inlet 310 and one ink outlet 320 were formed for each pressure chamber 301, but they may be formed, for example, one for each of two pressure chambers. Also, in the first to third embodiments, the pressure chamber 301 was equipped with an electrothermal conversion element 302, but other components such as an electromechanical conversion element may be provided.

[0061] In the first to third embodiments, the number of thermistors is not limited to one. For example, multiple thermistors may be provided for each ink tank 351. Also, the ambient temperature may be acquired at predetermined time intervals ST. Furthermore, although the driving force of the circulation pump 330 was constant, it may be varied for each color. In addition, in the method of removing air bubbles, in the first to third embodiments, this is done by performing charge suction, but any method that can remove air bubbles is acceptable.

[0062] In addition, the first to third embodiments illustrate an example of applying the present invention to a so-called serial scan type inkjet printer, which repeatedly performs a main scan of the recording head 100 and a sub-scan of the media. However, the present invention is not limited to such examples, and is also applicable to so-called full multi-type inkjet printers, which are equipped with ejection means across the full width of the media and drive the ejection means while the media is being transported. In that case, it is preferable to drive the ejection means between pages.

[0063] Furthermore, the liquid applicable to this invention may be not only ink, but also other liquids such as reaction solutions. Moreover, the liquid ejection device applicable to this invention may be not only an inkjet recording device, but any device that ejects liquid.

[0064] This embodiment includes the following configuration.

[0065] (Composition 1) A discharge head that discharges liquid from the discharge port of the pressure chamber, A storage section for storing the aforementioned liquid, A circulation channel for circulating liquid, including an inflow channel for introducing liquid into the pressure chamber and an outflow channel for discharging liquid from the pressure chamber, A supply channel for flowing the liquid from the storage section into the circulation channel, Discharge means for discharging the liquid from the pressure chamber, A first temperature detection means for detecting the temperature of the discharge head, A second temperature detection means for detecting ambient temperature, A liquid dispensing device comprising control means, The control means, The amount of liquid supplied per unit time to the supply channel, The amount of liquid circulated per unit time in the aforementioned circulation channel, The first temperature detected by the first temperature detection means, The second temperature detected by the second temperature detection means and A liquid dispensing device characterized by controlling the discharge means based on this.

[0066] (Configuration 2) The liquid discharge device according to Configuration 1, wherein the control means controls the discharge means to discharge liquid when the amount of bubbles around the connection between the inflow channel and the discharge head, which is determined based on the liquid supply amount, the liquid circulation amount, the first temperature, and the second temperature, exceeds a predetermined value.

[0067] (Composition 3) A bypass channel for connecting the inflow channel and the outflow channel, A liquid dispensing device according to configuration 1 or 2, comprising an on / off valve capable of opening and closing the bypass channel.

[0068] (Composition 4) The liquid discharge device according to configuration 3, wherein the on / off valve closes when the pressure in the outflow passage is above a predetermined value, thereby blocking the bypass passage, and opens when the pressure in the outflow passage is below a predetermined value, thereby opening the bypass passage.

[0069] (Composition 5) The control means, The amount of liquid transferred per unit time supplied from the inflow channel side to the pressure chamber, The amount of liquid moved per unit time in the circulation channel that is on the pressure chamber side of the bypass channel, driven by the circulation pump, 1. Temperature and AF2 temperature and, A liquid discharge device according to configuration 3 or 4, wherein the amount of bubbles around the joint between the inflow channel and the pressure chamber, based on the above, is driven when the amount of bubbles exceeds a predetermined value.

[0070] (Composition 6) A main scanning means for moving the ejection head and recording medium relative to each other in a first direction and in a direction opposite to the first direction, The system comprises a sub-scanning means that moves the ejection head and the recording medium relative to each other in a second direction substantially perpendicular to the first direction, The control means, If the amount of bubbles exceeds a first predetermined amount, the discharge means is driven between the end of recording to the recording medium and the start of recording to the next recording medium. A liquid discharge device according to configuration 2, wherein the discharge means is driven when the amount of bubbles exceeds a second predetermined amount different from the first predetermined amount.

Claims

1. A discharge head that discharges liquid from the discharge port of the pressure chamber, A storage section for storing the aforementioned liquid, A circulation channel for circulating liquid, including an inflow channel for introducing liquid into the pressure chamber and an outflow channel for discharging liquid from the pressure chamber, A supply channel for flowing the liquid from the storage section into the circulation channel, Discharge means for discharging the liquid from the pressure chamber, A first temperature detection means for detecting the temperature of the discharge head, A second temperature detection means for detecting ambient temperature, A liquid dispensing device comprising control means, The control means, The amount of liquid supplied per unit time to the supply channel, The amount of liquid circulated per unit time in the aforementioned circulation channel, The first temperature detected by the first temperature detection means, The second temperature detected by the second temperature detection means and A liquid dispensing device characterized by controlling the discharge means based on this.

2. The liquid discharge device according to claim 1, wherein the control means controls the discharge means to discharge liquid when the amount of bubbles around the connection between the inflow channel and the discharge head, which is determined based on the liquid supply amount, the liquid circulation amount, the first temperature, and the second temperature, exceeds a predetermined value.

3. A bypass channel for connecting the inflow channel and the outflow channel, The liquid dispensing device according to claim 1, further comprising an on / off valve capable of opening and closing the bypass channel.

4. The liquid discharge device according to claim 3, wherein the on / off valve closes when the pressure in the outflow passage is above a predetermined value, thereby blocking the bypass passage, and opens when the pressure in the outflow passage is below a predetermined value, thereby opening the bypass passage.

5. The control means, The amount of liquid transferred per unit time supplied from the inflow channel side to the pressure chamber, The amount of liquid moved per unit time in the circulation channel that is on the pressure chamber side of the bypass channel, driven by the circulation pump, The first temperature and, The above second temperature and, The liquid discharge device according to claim 4, wherein the amount of bubbles around the joint between the inflow channel and the pressure chamber, based on the above, is driven when the amount of bubbles exceeds a predetermined value.

6. A main scanning means that moves the ejection head and recording medium relative to each other in a first direction and in a direction opposite to the first direction, The system comprises a sub-scanning means that moves the ejection head and the recording medium relative to each other in a second direction substantially perpendicular to the first direction, The control means, If the amount of bubbles exceeds a first predetermined amount, the discharge means is driven between the end of recording to the recording medium and the start of recording to the next recording medium. The liquid dispensing device according to claim 2, wherein the discharge means is driven when the amount of bubbles exceeds a second predetermined amount different from the first predetermined amount.

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