Recording device

Abstract

It provides advantageous technology for maintaining proper ink density. [Solution] The recording device according to the present invention comprises a recording head that ejects ink to perform recording, a tank for storing ink to be supplied to the recording head, and a pump disposed in an ink circulation channel that passes through the tank and the recording head, further comprising measuring means for measuring the flow rate of ink circulating in the circulation channel by the pump as the circulating flow rate, and identifying means for identifying the quality of the ink in the circulating channel based on the circulating flow rate measured by the measuring means.

Description

Technical Field

[0001] The present invention mainly relates to a recording apparatus such as an inkjet printer.

Background Art

[0002] Among recording apparatuses typified by an inkjet printer, there is one configured to circulate ink supplied to a recording head (see Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In such a recording apparatus, it is conceivable that the ink concentration increases due to evaporation of the circulated ink at the ink ejection portion of the recording head. Therefore, a technique for appropriately maintaining the ink concentration is generally required.

[0005] An exemplary object of the present invention is to provide an advantageous technique for appropriately maintaining the ink concentration.

Means for Solving the Problems

[0006] One aspect of the present invention relates to a recording apparatus, the recording apparatus comprising: a recording head that ejects ink to perform recording; a tank that stores ink for supplying to the recording head; and a pump disposed in a circulation flow path of the ink passing through the tank and the recording head, measurement means for measuring an ink flow rate circulating through the circulation flow path by the pump as a circulation flow rate; The system further comprises a determination means for determining the quality of ink in the circulation channel based on the circulation flow rate measured by the measurement means. It is characterized by the following: [Effects of the Invention]

[0007] According to the present invention, it is possible to maintain the ink concentration appropriately. [Brief explanation of the drawing]

[0008] [Figure 1] A perspective view of the main part of the recording device according to this embodiment. [Figure 2] Block diagram of the control system for the recording device. [Figure 3] A schematic diagram showing the ink circulation system in a recording device. [Figure 4] A schematic diagram illustrating the amount of ink flowing into the recording head. [Figure 5] Perspective view of the recording head. [Figure 6] Disassembled perspective view of the recording head. [Figure 7] Schematic diagram of a flow channel component. [Figure 8] Partially enlarged schematic diagram of a flow channel component. [Figure 9] Schematic cross-sectional view of a flow channel member. [Figure 10] Perspective view of the discharge module. [Figure 11] Schematic diagram of a recording element substrate. [Figure 12] Cross-sectional perspective view of the recording element substrate. [Figure 13] Enlarged schematic diagram of the boundary between discharge modules. [Figure 14] A diagram showing the configuration of the recording element substrate. [Figure 15] A schematic diagram showing an example configuration for detecting the amount of ink in a buffer tank. [Figure 16] A schematic diagram showing an example configuration for detecting the amount of ink in a buffer tank. [Figure 17] A schematic diagram showing an example configuration for detecting the amount of ink in a buffer tank. [Figure 18]A diagram showing the relationship between the circulation flow rate and the ink viscosity. [Figure 19] A diagram showing the relationship between the liquid level height in the buffer tank and the circulation flow rate. [Figure 20] A diagram showing the relationship between the ink evaporation degree and the ink viscosity. [Figure 21] A diagram showing the relationship between the ink evaporation degree and the circulation flow rate. [Figure 22] A diagram showing the time change of the absorbance of white ink (corresponding to the ink concentration). [Figure 23] A diagram showing the time change of the circulation flow rate. [Figure 24] A flowchart showing the control content based on the quality of the ink in the circulation path. [Figure 25] A diagram showing the relationship between the ink viscosity and the ink temperature. [Figure 26] A diagram showing the relationship between the drive DUTY and the circulation flow rate. [Figure 27] A diagram showing the relationship between the drive DUTY and the ink viscosity at a certain circulation flow rate. [Figure 28] A diagram showing the relationship between the ratio of the drive DUTY to a certain circulation flow rate and the ink viscosity. [Figure 29] A flowchart showing the content of the arithmetic processing when a print job is received. [Figure 30] A flowchart showing the content of the arithmetic processing for calculating the evaporation amount. [Figure 31] A flowchart showing the content of the arithmetic processing for calculating the evaporation amount. [Figure 32] A flowchart showing the content of the arithmetic processing for calculating the consumed ink amount. [Figure 33] A flowchart showing the content of the arithmetic processing for calculating the ink concentration. [Figure 34] A schematic diagram showing a specific example of the ink circulation system in the recording device.

Modes for Carrying Out the Invention

[0009] The embodiments will be described in detail below with reference to the attached drawings. Note that the following embodiments do not limit the invention as defined in the claims. While the embodiments describe multiple features, not all of these features are essential to the invention, and the features may be combined in any way. Furthermore, in the attached drawings, identical or similar configurations are given the same reference numerals, and redundant descriptions are omitted.

[0010] ≪First Embodiment≫ (Overall configuration of the recording device) Figure 1 is a perspective view showing the main parts of the recording device 1000 according to the first embodiment. In this embodiment, the recording device 1000 is an inkjet printer that performs recording by ejecting ink, and includes a transport unit 1 and a recording head 3. The transport unit 1 is configured to transport a recording medium 2 such as paper material (e.g., cut sheets or roll sheets) in one direction, and includes, for example, rollers, a motor, etc. In this embodiment, the recording head 3 is a line head that extends across the entire width of the recording medium 2 (in a direction that intersects / is substantially perpendicular to the direction in which the recording medium 2 is transported by the transport unit 1), and performs recording on the recording medium 2 transported by the transport unit 1. In another embodiment, the recording head 3 may be a serial head that performs recording while reciprocating in the width direction of the recording medium 2.

[0011] In this context, "recording" refers to the formation of an image by ejecting ink onto the recording medium 2. The concept of an image includes characters, numbers, symbols, figures, photographs, etc., regardless of whether they are legible or not. The ink is typically a liquid containing dyes or pigments, but it may also be a colorless, transparent reaction or processing solution, and these may be collectively referred to as a liquid. In this regard, the recording device 1000 may be referred to as a liquid ejection device, and similarly, the recording head 3 may be referred to as a liquid ejection head. Furthermore, the recording device 1000 may be a copier that, in addition to having the above-described recording function as its main function, also has incidental functions such as a copy function, a scanner function, a facsimile function, etc., as secondary functions.

[0012] The recording head 3 comprises a pressure control unit 230, a supply unit 220, a connection part 111, and a housing 80 in which these are housed or mounted. The pressure control unit 230 is configured to control the pressure in the ink channel, which is the flow path for ink, to a negative pressure. The supply unit 220 is connected to and communicates (fluid communication) with the pressure control unit 230. The connection part 111 is configured to enable the inflow of ink into the supply unit 220 and the outflow of ink from the supply unit 220. The recording head 3 is capable of full-color printing using multiple inks (in this example, four colors: cyan C, magenta M, yellow Y, and black K), and is connected to the main tank 1006 (see Figure 3) via a predetermined ink flow path. The recording head 3 is also connected to an electrical control unit that provides signals and power supply voltage for ejecting ink.

[0013] Although the structural details will be described later, the recording device 1000 is configured to allow the ink supplied to such a recording head 3 to be circulated within the device (and, in detail later, between it and a predetermined tank).

[0014] Figure 2 is a block diagram showing an example configuration of the control system for the recording device 1000. The recording device 1000 includes, for example, a print engine unit 417 that manages the recording function, a scanner engine unit 411 that manages the scanner function, and a controller unit 410 that manages the drive control of the entire recording device 1000.

[0015] The print engine unit 417 includes a print controller 419, a ROM (Read-Only Memory) 420, a RAM (Random Access Memory) 421, a controller interface 418, an image processing controller 422, a head interface 427, a transport control unit 426, a head carriage control unit 425, an ink supply control unit 424, and a maintenance control unit 423.

[0016] The scanner engine unit 411 includes a scanner controller 415, a controller interface 414, a transport control unit 413, a sensor 416, and a RAM 412.

[0017] The controller unit 410 includes a main controller 401, ROM 407, RAM 406, host I / F 402, wireless I / F 403, image processing unit 408, print engine I / F 405, operation panel 404, and scanner engine I / F 409.

[0018] The print controller 419 incorporates an MPU (microprocessing unit) and non-volatile memory (such as EEPROM), and controls various mechanisms of the print engine unit 417 according to instructions from the main controller 401 of the controller unit 410. The various mechanisms of the scanner engine unit 411 are controlled by the main controller 401 of the controller unit 410.

[0019] In the controller unit 410, the main controller 401, which is composed of a CPU, controls the entire recording device 1000 using the RAM 406 as a working area, according to the program and various parameters stored in the ROM 407. For example, a print job is input from the host device 400 via the host I / F 402 or wireless I / F 403. In response, the image processing unit 408 performs predetermined image processing on the image data included in or input with the print job, according to the instructions of the main controller 401. Then, the main controller 401 transmits the processed image data to the print engine unit 417 via the print engine I / F 405.

[0020] The recording device 1000 may acquire image data from the host device 400 via wireless or wired communication, or it may acquire image data from an external storage device (such as a USB memory stick) connected to the recording device 1000. The communication method used for wireless or wired communication is not limited. For example, Wi-Fi (Wireless Fidelity) (registered trademark) and Bluetooth (registered trademark) can be used as communication methods for wireless communication. For example, USB (Universal Serial Bus) can be used as a communication method for wired communication. Also, for example, when a read command is input from the host device 400, the main controller 401 transmits this command to the scanner engine unit 411 via the scanner engine I / F 409.

[0021] The control panel 404 can receive user input for the recording device 1000 and display information to the user. This allows the user to instruct operations such as copying and scanning, set recording modes, and recognize information on the recording device 1000 via the control panel 404.

[0022] In the print engine unit 417, the print controller 419, which is composed of a CPU, controls the various mechanisms of the print engine unit 417 using the RAM 421 as a working area, according to the program and various parameters stored in the ROM 420.

[0023] When various commands and image data are received via the controller I / F 418, the print controller 419 temporarily stores them in the RAM 421. To make the recording head 3 available for recording, the print controller 419 uses the image processing controller 422 to convert the stored image data into recording data. Once the recording data is generated, the print controller 419 instructs the recording head 3 to perform a recording operation based on the recording data via the head I / F 427. At this time, the print controller 419 drives each transport unit (described later) via the transport control unit 426 to transport the recording medium 2. In accordance with the instructions of the print controller 419, the recording operation by the recording head 3 is performed in conjunction with this transport operation, thereby performing the recording process on the recording medium 2.

[0024] The head carriage control unit 425 changes the orientation and position of the recording head 3 according to the operating status of the recording device 1000, such as the maintenance status and recording status. The ink supply control unit 424 controls the supply unit 220 so that the pressure of the ink supplied to the recording head 3 is within an appropriate range. The maintenance control unit 423 controls the operation of the cap unit and wiping unit in the maintenance unit (not shown) when performing maintenance operations on the recording head 3.

[0025] In the scanner engine unit 411, the main controller 401 controls the hardware resources of the scanner controller 415, using the RAM 406 as a working area, according to the program and various parameters stored in the ROM 407. This controls the various mechanisms of the scanner engine unit 411. For example, via the controller I / F 414, the main controller 401 controls the hardware resources within the scanner controller 415 to transport the document loaded into the ADF (Auto Document Feeder (not shown)) by the user using the transport control unit 413, and read it using the sensor 416. The scanner controller 415 then stores the scanned image data in the RAM 412.

[0026] Furthermore, the print controller 419 converts the acquired image data into recording data as described above, thereby enabling the recording head 3 to perform a recording operation based on the image data read by the scanner controller 415.

[0027] (Regarding the ink circulation system) As shown in Figure 3, the recording device 1000 is configured to circulate the ink supplied to the recording head 3 within the device. For the sake of simplicity, the ink flow path for one of the multiple colors is shown here, but a similar configuration is assumed to be adopted for the other colors as well. In this embodiment, the recording device 1000 further comprises pumps 1001, 1002 and 1004, tanks 1003 and 1006, and sensors 1009a, 1009b and 1009c.

[0028] Tank 1006 is mounted on the main body of the device to store unused ink and is referred to as the main tank 1006 to distinguish it from tank 1003. Tank 1003 is built into the device to store circulating ink and is referred to as the buffer tank 1003 to distinguish it from tank 1006. Liquid level sensor 1009a is configured to detect the amount of ink in buffer tank 1003, and for example, a liquid level sensor that detects the height of the liquid level in buffer tank 1003 may be used.

[0029] Pump 1001 is configured to supply ink from the main tank 1006 to the buffer tank 1003. Pump 1001 may also be referred to as the liquid supply pump 1001 to distinguish it from pumps 1002 and 1004. Pumps 1002 and 1004 are positioned in the ink circulation path through the recording head 3 and the buffer tank 1003, so that the ink in the buffer tank 1003 is supplied to the recording head 3 and then returns to the buffer tank 1003, i.e., is circulating. In this embodiment, pump 1004 sends the ink in the buffer tank 1003 to the recording head 3, and pump 1002 returns the ink supplied to the recording head 3 to the buffer tank 1003, thereby making the ink circulating. Pump 1002 is positioned downstream of the recording head 3 in the direction of ink circulation, and may be referred to as the downstream circulation pump 1002 to distinguish it from pump 1004. Pump 1004 is positioned upstream of the recording head 3 in the direction of ink circulation, and may be referred to as the upstream circulation pump 1004 to distinguish it from pump 1002.

[0030] The ink supplied to the recording head 3 in this manner flows into the supply unit 220 via the connection part 111 on one side, passes through the filter 221, and is then adjusted to two different pressures (both negative pressures) by the pressure control unit 230. The ink is then branched into two ink flow paths, a high-pressure side and a low-pressure side, and supplied to the ejection unit 300. As will be described in more detail later, the discharge unit 300 includes a common supply channel 211 and a common recovery channel 212. High-pressure ink is supplied to the common supply channel 211, and low-pressure ink is supplied to the common recovery channel 212. Between the common supply channel 211 and the common recovery channel 212, multiple individual channels 215 corresponding to multiple recording element substrates 10 are formed. In each individual channel 215, the upstream side with respect to the corresponding recording element substrate 10 is designated as the individual supply channel 213, and the downstream side is designated as the individual recovery channel 214. With this configuration, ink can be supplied to each individual recording element substrate 10 by flowing from the common supply channel 211 through the individual channels 215 toward the common recovery channel 212. Ink that passes through the ejection unit 300 without being ejected is then discharged from the recording head 3 via the other connection part 111 by the pump 1002 and returned to the buffer tank 1003. Ink circulation is achieved in this way.

[0031] Pump 1002 can be any positive displacement pump capable of pumping ink at a desired flow rate. In this embodiment, a diaphragm pump is used, but other known pumps such as tube pumps, gear pumps, and syringe pumps may also be used. The amount of ink pumped by pump 1002 corresponds to the flow rate of ink circulating in the circulation channel (circulation flow rate) and can be adjusted based on the driving force of pump 1002. For example, in this embodiment, where a diaphragm pump is used as pump 1002, the circulation flow rate is determined by adjusting the duty cycle of the drive signal of pump 1002. Furthermore, a flow sensor 1009b is provided in the ink flow path from the recording head 3 to the buffer tank 1003, enabling measurement of the circulating flow rate. The circulating flow rate is defined as the amount of ink that passes through the ink flow path per unit time, and can be measured in units such as [milliliters / minute (ml / min)].

[0032] The recording device 1000 is preferably installed and managed in an environment with a constant temperature. Alternatively, a temperature sensor 1009c may be placed in the ink flow path from the buffer tank 1003 to the recording head 3, as well as a chiller 341 and a heat exchanger 342 (see Figure 34). This allows ink at a desired temperature (e.g., 25°C) to be supplied to the recording head 3, that is, the recording head 3 can be maintained at a desired temperature during recording (driving the recording head 3). The ink flow rate during recording should be set within the strength range of the components forming the ink flow path, and so that the temperature difference between the multiple recording element substrates 10 is within an acceptable range (for example, so that the image quality is above a certain standard).

[0033] Furthermore, the pressure control unit 230 is positioned in the ink flow path from the pump 1004 to the discharge unit 300, and suppresses or prevents pressure fluctuations associated with ink discharge during recording on the downstream side (i.e., the discharge unit 300 side), thereby maintaining a constant pressure. The pressure control unit 230 includes two known pressure adjustment mechanisms that generate two negative pressures, respectively (indicated as "H" on the high-pressure side and "L" on the low-pressure side in Figure 3), and may employ, for example, a pressure reducing regulator or an equivalent configuration. In this embodiment, the pump 1004 pressurizes the ink flow path upstream of the pressure control unit 230 via the supply unit 220. This suppresses the effect of the buffer tank 1003's hydrostatic pressure on the recording head 3, which is advantageous for simplifying the design of the buffer tank 1003, such as its layout in the recording device 1000. Pump 1004 should have a head pressure equal to or greater than the standard. In this embodiment, a diaphragm pump is used, but other positive displacement pumps or turbo pumps may also be used.

[0034] With this configuration, ink is supplied to the ejection unit 300 so as to pass through the common supply channel 211 and the common recovery channel 212, respectively, and a portion of it passes through the individual recording element substrates 10. At this time, the heat generated in the individual recording element substrates 10 is released to the outside of the recording element substrates 10 by the ink passing through the common supply channel 211 and the common recovery channel 212. Furthermore, with this configuration, during recording, ink flow can be generated not only in the areas where ink is ejected (the ejection port 13 and pressure chamber 23 described later (see Figure 12, etc.)), but also in areas where ink is not ejected. This suppresses the increase in viscosity of the ink in the circulation channel, or suppresses the accumulation of ink with increased viscosity (thickened ink), thereby enabling high-quality recording by the recording head 3.

[0035] Figures 4(a) and 4(b) are schematic diagrams illustrating the amount of ink flowing into the recording head 3. Figure 4(a) shows the ink flow rate in the case of non-discharge (when no ink is discharged from any of the discharge ports 13) during ink circulation, and Figure 4(b) shows the ink flow rate in the case of full discharge (when ink is discharged from all of the discharge ports 13). Here, the ink flow rate A in the common supply channel 211 and common recovery channel 212 in the non-discharge case can be set, as described above, so that the temperature difference between the multiple recording element substrates 10 is within an acceptable range. In the case of full discharge, the discharge amount F is determined by multiplying the amount of ink discharged from each discharge port 13, the number of discharge ports 13 that discharge ink, and the number of discharges per unit time (frequency). Therefore, the ink flow rate A flowing out from the recording head 3 is maintained at a predetermined value (value A) regardless of whether no ink is being ejected or all ink is being ejected. On the other hand, the amount of ink flowing into the recording head 3 varies depending on the number of ejection ports 13 that eject ink (it will be a value greater than or equal to A and less than or equal to A+F), for example, it will be A in the case of no ejection, and A+F in the case of all ejection.

[0036] (Regarding the configuration of the recording head) Figure 5 is a perspective view of the recording head 3 from another viewpoint. As mentioned above, in this embodiment, the recording head 3 is a line head. The recording head 3 includes a recording element substrate 10, as well as a flexible wiring board 40 and a wiring board 90, and signal input terminals 91 and power supply terminals 92 electrically connected via them. The signal input terminals 91 and power supply terminals 92 are electrically connected to each control unit of the recording device 1 and supply the ejection drive signal and the power required for ejection to the recording element substrate 10, respectively. By consolidating the wiring with electrical circuits in the wiring board 90, the number of signal output terminals 91 and power supply terminals 92 can be reduced compared to the number of recording element substrates 10. This reduces the number of electrical connections that need to be removed when mounting the recording head 3 to the recording device 1 or when replacing the recording head 3.

[0037] On the recording element substrate 10, an electrothermal conversion element or heater element is provided as a recording element 15 (see Figure 11(b)) corresponding to each ejection port 13. Each electrothermal conversion element is driven by an electric current to heat the ink and cause it to foam, and the foaming energy is used to eject the ink from the ejection port 13.

[0038] Figure 6 is an exploded perspective view of the recording head 3. The ejection unit 300, the supply unit 220, and the wiring board 90 are mounted on the housing 80. A filter 221 (see Figure 3) built into the supply unit 220 removes foreign matter from the ink that flows into the supply unit 220 via the connection part 111. The ink that has passed through the filter 221 is supplied to the pressure control unit 230 described above. The pressure control unit 230 mitigates or attenuates pressure loss changes in the supply system of the recording device 1000 (the supply system upstream of the recording head 3) that occur due to fluctuations in ink flow rate for each color, and stabilizes negative pressure changes downstream (on the ejection unit 300 side). As described above (see Figure 3), the pressure control unit 230 includes two known pressure adjustment mechanisms (high pressure side "H" and low pressure side "L") that generate two negative pressures, respectively.

[0039] The housing 80 includes an ejection unit support section 81 and a wiring board support section 82, which support the ejection unit 300 and the wiring board 90 respectively, and ensure the rigidity of the recording head 3. The wiring board support section 82, which supports the wiring board 90, is fixed to the ejection unit support section 81 by screws.

[0040] The ejection unit support section 81, which supports the ejection unit 300, ensures accuracy in the relative position of the individual recording element substrates 10 by correcting any warping or deformation of the ejection unit 300, thereby improving the quality of recording. The ejection unit support section 81 is also provided with openings 83 and 84 into which the joint rubber 100 is inserted, and the ink supplied by the supply unit 220 is guided to the flow path member 210, which will be described later, via the joint rubber 100. Metal materials such as SUS (Steel Use Stainless), aluminum, or ceramics such as alumina can be used for the ejection unit support section 81.

[0041] The ejection unit 300 includes a plurality of ejection modules 200 and a flow path member 210, and a cover member 130 is attached to the lower surface of the ejection unit 300 (the surface facing the recording medium 2). The cover member 130 is a frame-shaped member with a long opening 131, as shown in Figure 6, and exposes a part of the ejection module 200 (the aforementioned recording element substrate 10 and the sealing member 110 described later (see Figure 10(a))) through the opening 131. Furthermore, the frame surrounding the opening 131 functions as a cap member for capping the recording head 3 when recording is not in operation. For this reason, adhesive, sealant, filler, etc., may be applied to the frame to fill the gap between it and the recording head 3 to be capped.

[0042] As shown in Figure 6, the flow channel member 210 is made up of multiple (in this case, three) plate materials 50, 60, and 70 with grooves and / or openings formed therein, and is capable of distributing the ink supplied from the supply unit 220 to the individual ejection modules 200. The flow channel member 210 can also return the ink that has passed through the ejection modules 200 to the supply unit 220. The flow channel member 210 is fixed to the ejection unit support part 81 with screws to suppress warping and deformation.

[0043] Figures 7(a) to 7(f) are schematic diagrams showing examples of the configuration of the plate materials 50, 60, and 70 that form the flow path member 210. Figure 7(a) shows an example of the configuration of the upper surface (the surface on the discharge module 200 side) of plate material 50, and Figure 7(b) shows an example of the configuration of the lower surface (the surface on the discharge unit support part 81 side) of plate material 50. Figure 7(c) shows an example of the configuration of the upper surface of plate material 60, and Figure 7(d) shows an example of the configuration of the lower surface of plate material 60. Figure 7(e) shows an example of the configuration of the upper surface of plate material 70, and Figure 7(f) shows an example of the configuration of the lower surface of plate material 70.

[0044] The plate material 50 has a communication opening 51 and individual flow channel grooves 52 formed therein. The plate material 60 has a communication opening 61 (communication openings 61-1 and 61-2) and individual flow channel grooves 62 formed therein. The plate material 70 has a common supply channel 211 (common supply channels 211a, 211b, 211c, 211d), a common recovery channel 212 (common recovery channels 212a, 212b, 212c, 212d), a common channel groove 71, and a communication port 72 formed therein. In the figure, communication port 61-1 is shown as communicating with the common supply channel 211, and communication port 61-2 is shown as communicating with the common recovery channel 212.

[0045] These plate materials 50, 60, and 70 are stacked and in contact with each other to form the ink flow channels of the flow channel member 210. For example, plate materials 50 and 60, in contact with each other, form a part of the ink flow channels of the flow channel member 210 (see Figures 7(b) and 7(c)). Similarly, plate materials 60 and 70, in contact with each other, form another part of the ink flow channels of the flow channel member 210 (see Figures 7(d) and 7(e)).

[0046] With this configuration, common channels (common supply channels 211a, 211b, 211c, and 211d, and common recovery channels 212a, 212b, 212c, and 212d) extending longitudinally are formed from the common channel grooves 62 and 71 for each color. For example, the common supply channels 211a, 211b, 211c, and 211d, and the common recovery channels 212a, 212b, 212c, and 212d are each extended longitudinally from the recording head 3 to correspond to the four colors of ink. As an example, ink of a certain color supplied to the ejection module 200 through the common supply channel 211a is recovered through the common recovery channel 212a.

[0047] More specifically, the communication opening 72 of the plate material 70 (see Figure 7(f)) communicates with each hole provided in the joint rubber 100 and flows to the supply unit 220 (see Figure 6). This communication opening 72 communicates with one end of the individual flow channel groove 52 of the plate material 50 via a communication opening 61 provided on the lower surface of the common flow channel groove 62 of the plate material 60, and further communicates with multiple discharge modules 200 via a communication opening 51 at the other end. Such individual flow channel grooves 52 make it possible to form an ink flow channel in the central part of the flow channel member 210 (see Figure 7(b)).

[0048] The plate materials 50, 60, and 70 should be made of a material that has corrosion resistance to ink and a low expansion rate. Examples include composite materials or resin materials that use alumina, LCP (liquid crystal polymer), PPS (polyphenyl sulfide), PSF (polysulfone), etc. as the base material and to which inorganic fillers such as silica fine particles and fibers are added. The flow channel member 210 may be formed by welding or bonding the laminated plate materials 50, 60, and 70.

[0049] Figure 8 is an enlarged schematic diagram of a portion α of the flow channel member 210, which is formed by laminating the above-mentioned plate materials 50, 60, and 70 (see Figure 7(a)). As shown in Figure 8, the common supply channel 211 and the common recovery channel 212 are arranged alternately in the longitudinal direction.

[0050] Multiple individual supply channels 213 (213a, 213b, 213c, and 213d), formed by individual channel grooves 52, are connected to the common supply channel 211 (211a, 211b, 211c, and 211d) via a communication port 61. Similarly, multiple individual recovery channels 214 (214a, 214b, 214c, and 214d), formed by individual channel grooves 52, are connected to the common recovery channel 212 (212a, 212b, 212c, and 212d) via a communication port 61. With this channel configuration, ink can be guided from the common supply channel 211 to the central part of the channel member 210 via the individual supply channels 213 and supplied to each recording element substrate 10, and the ink can be recovered from each recording element substrate 10 to the common recovery channel 212 via the individual recovery channels 214.

[0051] Figure 9 is a schematic cross-sectional view of the section IX-IX in Figure 8. Individual recovery channels 214a and 214c communicate with the discharge module 200 via the communication port 51 (the same applies to the individual supply channel 213 and the other individual recovery channels 214).

[0052] Figure 10(a) is a perspective view showing an example configuration of a single ejection module 200, and Figure 10(b) is an exploded perspective view thereof. The ejection module 200 includes a recording element substrate 10, as well as a support member 30 and a sealing member 110. The support member 30 is provided with a communication port 31 through which ink passes.

[0053] The support member 30 and the recording element substrate 10 have channels formed in them for guiding the ink flowing in from the flow channel member 210 to the recording element 15 (see Figure 11(b)), and for recovering some or all of the ink supplied to the recording element 15 back into the flow channel member 210.

[0054] Here, the common supply channel 211 corresponding to each ink color is connected to the pressure control unit 230 (high pressure side) via the supply unit 220, and the common recovery channel 212 is connected to the pressure control unit 230 (low pressure side) via the supply unit 220. This pressure control unit 230 creates a pressure difference (differential pressure) between the common supply channel 211 and the common recovery channel 212. Therefore, in the recording head 3, as shown in Figures 8-9, the ink channels are formed so that the ink flows in the following order: common supply channel 211, individual supply channel 213, recording element substrate 10, individual recovery channel 214, and common recovery channel 212.

[0055] The ejection module 200 is obtained by bonding the recording element substrate 10 and the flexible wiring board 40 onto the support member 30, electrically connecting them, and then covering the connection with a sealing member 110 to seal it. The electrical connection between the recording element substrate 10 and the flexible wiring board 40 can be achieved by connecting the terminal 16 of the recording element substrate 10 and the terminal 41 of the flexible wiring board 40 by wire bonding. The terminal 42 on the flexible wiring board 40 opposite to the side connected to the recording element substrate 10 is electrically connected to the connection terminal 93 of the wiring board 90 (see Figure 6).

[0056] The support member 30 supports the recording element substrate 10 and is configured to connect the recording element substrate 10 and the flow channel member 210. Therefore, the support member 30 is preferably made of a material that can achieve high flatness and can be properly bonded to the recording element substrate 10, and examples of such materials include alumina and resin materials.

[0057] (Explanation of the structure of the recording element substrate) Figure 11(a) shows a plan view of the upper surface of the recording element substrate 10 (the side on which the ejection port 13 is formed), and Figure 11(b) shows an enlarged schematic diagram of part A of Figure 11(a). Figure 11(c) shows a plan view of the lower surface of the recording element substrate 10 (the side opposite to that shown in Figure 11(a)). The recording element substrate 10 includes an ejection port forming member 12 and a cover plate 20, with the ejection port forming member 12 located on the upper side and the cover plate 20 located on the lower side.

[0058] The nozzle-forming member 12 has multiple rows of nozzles (four in this case) corresponding to multiple ink colors, and each nozzle row consists of multiple nozzles 13 arranged in one direction. In the following description, the direction of arrangement of the nozzles 13 (the direction in which the nozzle row extends) can be expressed as the nozzle row direction.

[0059] As shown in Figure 11(b), a supply channel 18 extends along one side of each row of discharge ports, communicating with the discharge port 13 via a supply port 17a. Similarly, a recovery channel 19 extends along the other side of each row of discharge ports, communicating with the discharge port 13 via a recovery port 17b. A recording element 15 is provided in a pressure chamber 23 partitioned by a partition wall 22 at a position corresponding to each discharge port 13. The recording element 15 is electrically connected to a terminal 16 (see Figure 10(b)) and is driven based on a drive signal input via a wiring board 90 (see Figure 6) and a flexible wiring board 40. In response, ink is discharged from the corresponding discharge port 13.

[0060] As shown in Figure 11(c), the cover plate 20 is provided with a plurality of openings 21 that communicate with the supply passage 18 and the recovery passage 19. Each opening 21 communicates with a communication port 51 (see Figure 7(a)). In this embodiment, three openings 21 are provided for a single supply passage 18, and two openings 21 are provided for a single recovery passage 19. The cover plate 20 should be made of a material that has corrosion resistance to ink and allows for the formation of the opening 21 with high precision in terms of shape and position. Examples include photosensitive resin materials and silicon, which allow for the formation of the opening 21 by a photolithography process. The cover plate 20 should be thin (sheet-like or film-like) to reduce pressure loss when the pitch of the ink flow path is changed by the opening 21.

[0061] Figure 12 is a cross-sectional perspective view along the cutting line XII-XII in Figure 11(a). In the recording element substrate 10, a base 11, typically made of silicon, is placed between the ejection port forming member 12 and the cover plate 20. The recording element 15 is formed on the upper surface of the base 11 (the surface on the ejection port forming member 12 side), and the supply path 18 and the recovery path 19 are formed on the lower surface of the base 11 (the surface on the cover plate 20 side). The cover plate 20 is joined to the base 11 and functions as a lid that seals the supply path 18 and the recovery path 19, or the base 11 and the cover plate 20 are joined to form the supply path 18 and the recovery path 19. The supply path 18 and the recovery path 19 are connected to the common supply path 211 and the common recovery path 212 of the flow path member 210, respectively, and a pressure difference is generated between them by the pressure control unit 230. During recording, regardless of whether ink is ejected or not at the ejection port 13, the ink in the supply path 18 flows through the supply port 17a, the pressure chamber 23, and the recovery port 17b to the recovery path 19 due to this pressure difference, as shown by arrow C. Subsequently, the ink recovered in the recovery path 19 passes through the opening 21 of the cover plate 20 and the communication port 31 of the support member 30, and then sequentially passes through the communication port 51, the individual recovery path 214, and the common recovery path 212 in the flow path member 210 (see Figure 9).

[0062] To summarize the ink circulation, first, ink flows from the connection part 111 in the recording head 3 to the supply unit 220. The ink then passes through the joint rubber 100, the communication port 72 and common flow channel groove 71 of the plate material 70, the common flow channel groove 62 and communication port 61 of the plate material 60, and the individual flow channel groove 52 and communication port 51 of the plate material 50 in that order (see Figures 6-8). The ink then passes through the communication port 31 of the support member 30, the opening 21 of the cover plate 20, and the supply path 18 and supply port 17a of the base 11 in that order before being supplied to the pressure chamber 23 (see Figures 9-12). Of the ink supplied to the pressure chamber 23, some / all of the ink that is not discharged from the discharge port 13 passes sequentially through the recovery port 17b and recovery path 19 of the base 11, the opening 21 of the cover plate 20, and the communication port 31 of the support member 30 (see Figures 9-12). The ink then flows sequentially through the communication port 51 and individual flow channel grooves 52 of the plate material 50, the communication port 61 and common flow channel groove 62 of the plate material 60, the common flow channel groove 71 and communication port 72 of the plate material 70, and the joint rubber 100 (see Figures 6-8). The ink then flows out of the supply unit 220 from the connection part 111 and is thus returned from the recording head 3 to the buffer tank 1003 (see Figure 3).

[0063] Figure 13 is an enlarged schematic diagram of the boundary or adjacent area between two adjacent ejection modules 200 (between two adjacent recording element substrates 10). In this embodiment, the recording element substrate 10 has a substantially parallelogram shape. The ejection port rows 14a to 14d, which consist of multiple ejection ports 13 arranged on each recording element substrate 10, are arranged at a predetermined angle with respect to the longitudinal direction of the recording head 3. At the boundary, the ejection port rows 14a to 14d are arranged such that at least one ejection port 13 overlaps in the transport direction of the recording medium 2. In this example, as shown in Figure 13, two ejection ports 13 on line D overlap each other.

[0064] With this arrangement, even if the recording element substrate 10 is misaligned, the overlapping ejection ports 13 can compensate for this, thereby suppressing black streaks and white spots in the recorded image. This is not limited to the above-described arrangement of multiple recording element substrates 10, but is also true for other arrangements. In this embodiment, a recording element substrate 10 with a substantially parallelogram shape is exemplified, but other shapes such as rectangles and trapezoids may also be used, and in such cases, it is preferable that the ejection port rows 14a to 14d be arranged so that the ejection ports 13 overlap.

[0065] Figure 14(a) is a perspective view of the recording element substrate 10. Figure 14(b) is a schematic plan view showing the ink flow path in the recording element substrate 10. Figure 14(c) is a schematic cross-sectional view along the cutting line AA of Figure 14(b). As described above, the base 11 is provided with a recording element 15, and the ejection port forming member 12 is provided with an ejection port 13 (see Figure 12). In Figures 14(a) and 14(c), the side of the ejection port forming member 12 on which the ejection port 13 is provided (i.e., the side facing the recording medium 2) is shown as the ejection port forming surface (ejection port surface) 12a.

[0066] Multiple discharge ports 13 are arranged in one direction, and ink flow paths 24 facing the recording element 15 and the discharge ports 13 are formed between the base 11 and the discharge port forming member 12 (see Figures 14(b) and 14(c)). Adjacent ink flow paths 24 are separated by walls 26. Of the ink flow paths 24, the space where the recording element 15 and the discharge ports 13 are located corresponds to the pressure chamber 23.

[0067] Furthermore, the height h of the ink flow path 24 can be set based on the ink refill characteristics and circulation characteristics, and for example, in the case of a high-density recording head 3 equivalent to 600 dpi or higher, it can be set within the range of 3 to 25 μm.

[0068] The supply path 18 and the recovery path 19 are provided so as to penetrate the base 11. The supply path 18 is connected to the inlet end 24a of the ink flow path 24, enabling the supply of ink to the ink flow path 24. The recovery path 19 is connected to the outlet end 24b of the ink flow path 24, enabling the recovery of ink that was not discharged from the discharge port 13 from the ink flow path 24. The recording element 15 and the discharge port 13 are preferably formed in the ink flow path 24 at positions approximately equidistant from the inlet end 24a and the outlet end 24b. The pressure difference ΔP generated between the inlet pressure Pin of the supply path 18 and the outlet pressure Pout of the recovery path 19 is set such that the inlet pressure Pin is greater than the outlet pressure Pout. This generates a circulating flow f so that ink is supplied from the supply path 18 through the ink flow path 24 onto the recording element 15 and then flows through the ink flow path 24 to the recovery path 19. The inlet pressure Pin and outlet pressure Pout may be positive or negative pressure.

[0069] (Regarding the quality of ink in the circulation channel) Ink in the circulating channel may evaporate near the discharge port 13, for example, due to contact with air, increasing its viscosity and potentially raising the ink concentration. The accumulation of thickened ink near the discharge port 13 can be suppressed by increasing the flow rate of the circulating flow f (circulation flow rate). On the other hand, the thickened ink generated in the circulating channel flows along the circulating flow f from the ink channel 24 through the outlet end 24b to the recovery channel 19 and then to the common recovery channel 212, where it is subsequently recovered in the buffer tank 1003.

[0070] Such thickened ink can be discharged outside the circulation path by being ejected from the ejection port 13. However, if the amount of ink ejected to the recording medium 2 (the amount of ink ejected from the ejection port 13) is small, the thickened ink will return to the buffer tank 1003 through the recovery path 19, causing the quality of the ink in the circulation path to deteriorate. For example, if the viscosity of the ink exceeds the allowable value (e.g., 8 cp), it becomes difficult to properly eject the ink from the ejection port 13. Therefore, this can cause so-called non-discharge, and consequently, a decrease in the quality of the recording. In response to this, it is conceivable to restore the ink quality by discharging the ink from the discharge port 13 and removing it from the circulation channel through recovery processes such as pre-discharge or suction treatment, based on the degree of deterioration in the ink quality within the circulation channel. For this reason, there is a general need for technology to accurately identify the quality of the ink within the circulation channel or the degree of its deterioration (for example, the degree of increase in ink concentration, the degree of ink evaporation, the degree of ink viscosity increase, etc.).

[0071] When circulating ink, the circulation flow rate can be controlled by adjusting the driving force of the pump 1002 (in this embodiment, the duty cycle of the drive signal of the diaphragm pump). The circulation flow rate is continuously detected during ink circulation and can be measured by the flow sensor 1009b (see Figure 3).

[0072] When determining ink quality, the driving force of pump 1002 is fixed to a predetermined value, and in this embodiment, the duty cycle of the drive signal may also be fixed to a predetermined value. The driving force of pump 1002 is set higher than the standard driving force during recording (for example, the driving force between the driving force in the case of no discharge and the driving force in the case of full discharge) to increase the circulating flow rate. This enables highly accurate measurement of the circulating flow rate by the flow sensor 1009b, and consequently, as will be described in detail later, it becomes possible to determine the ink quality with high accuracy. Additionally, the amount of ink in the buffer tank 1003 may be detected by the liquid level sensor 1009a, and / or the temperature of the ink in the circulation channel may be detected by the temperature sensor 1009c.

[0073] Figure 18 shows the relationship between the circulating flow rate (represented as circulating flow rate S, in units of [ml / min]) and the viscosity of the ink (represented as ink viscosity η, in units of [cp]) in the driving force of a certain pump 1002. Here, the cases where the duty cycle of the diaphragm pump's drive signal (drive DUTY) is 43% and 48% are shown as the driving force of pump 1002. From Figure 18, S=-11.4*η+514...Equation (1) You can obtain this.

[0074] Figure 19 shows the relationship between the liquid level in the buffer tank 1003 (let's call it liquid level H, in units of [cm]) and the circulating flow rate S when the amount of ink in the buffer tank 1003 is detected by the liquid level sensor 1009a. When the liquid level H increases, the circulating flow rate S may change due to pressure loss in the circulation system, including the pump 1002. From Figure 19, S=6*H+368...Formula (2) You can obtain this.

[0075] Figure 20 shows the relationship between the degree of ink evaporation at a temperature of 25°C (denoted as ink evaporation rate V, in units of [%]) and ink viscosity η. In this example, ink evaporation rate V represents the degree of deterioration of the ink in the main tank 1006 (unused ink) due to water evaporation. For example, since no water has evaporated from the unused ink (in other words, 0% of the water has evaporated), V=0, and if 10% of the water has evaporated from the unused ink, V=10. Furthermore, ink concentration is the amount of ink components (e.g., colorants such as pigments) contained in a unit volume of water, and can be calculated based on the ink evaporation rate V. Here, when the concentration of the components of unused ink is Nref, the ink concentration N is calculated using the ink evaporation rate V. N = 100 / (100 - V) * Nref It can be expressed as follows.

[0076] And from Figure 20, η = 0.2 * V + 5 ... Equation (3a) This is obtained, that is, V=5*η-25...Formula (3b) You can obtain this.

[0077] In this way, at any given time, V=-0.439*S+2.63*H+173...Equation (4) This is obtained. When the amount of ink in the buffer tank 1003 is kept constant (when the amount of ink discharged from the discharge port 13 and consumed is replenished from the main tank 1006 to the buffer tank 1003 by the pump 1001), the liquid level height H is a fixed value. Figure 21 shows the relationship between the ink evaporation rate V and the circulation flow rate S based on the above equation (4).

[0078] As described above, the circulating flow rate S and the ink viscosity η are related in a way that approximates a linear function, and when the ink temperature is constant, the ink viscosity η and the ink evaporation rate V are related in a way that approximates a linear function. Furthermore, when the liquid level height H is constant, the circulating flow rate S and the ink evaporation rate V are related in a way that approximates a linear function. Therefore, according to this embodiment, the quality of the ink can be determined based on the circulating flow rate S measured by the flow sensor 1009b while the driving force of the pump 1001 is fixed.

[0079] In the above explanation, the liquid level height H was mentioned as an example of the amount of ink in the buffer tank 1003 detected by the liquid level sensor 1009a, but there are several possible methods for detecting the liquid level height H. For example: As illustrated in Figure 15, multiple sensors capable of detecting the presence or absence of ink may be arranged as liquid level sensors 1009a at multiple heights within the buffer tank 1003. Increasing the number of these sensors makes it possible to detect the liquid level height H with high accuracy. Furthermore, as illustrated in Figure 16, a strain gauge capable of detecting strain caused by the weight of the buffer tank 1003 and the amount of ink contained within it may be provided as a liquid level sensor 1009a. Based on this amount of strain, the liquid level height H can be continuously detected. Furthermore, as illustrated in Figure 17, the configuration of Figure 15 and the configuration of Figure 16 may be combined. With such a configuration, the liquid level height H can be detected with high accuracy and continuously. Furthermore, if the amount and weight of ink in the buffer tank 1003 can be detected with high accuracy, the specific gravity of the ink can be determined. Therefore, the quality of the ink in the buffer tank 1003 (ink concentration N, etc.) can be calculated as the quality of the ink in the circulation channel.

[0080] (Regarding the time required and timing) Ink quality identification is preferably performed while recording is suppressed (during non-recording periods), and especially before recording begins and after sufficient ink circulation has occurred. In this case, the driving force of pump 1002 is fixed to a predetermined value, and the ink temperature is approximately constant, making it possible to identify ink quality with high accuracy.

[0081] The quality of the ink can be determined, for example, during the initial setup of the recording device 1000. After ink is supplied from the main tank 1006 to the buffer tank 1003 and the circulation channel is filled with ink, the ink is circulated until the temperature of the ink in the circulation channel stabilizes (until it becomes approximately constant), and the ink evaporation rate V at this time is set to V=0. Here, the coefficients in equation (4) above can be corrected based on the relationship between the circulation flow rate S corresponding to the driving force of the pump 1002 and the ink viscosity η (see Figure 18), and the relationship between the ink evaporation rate V and the ink viscosity η (see Figure 20). By this method, the quality of unused ink can be determined in a way that also accommodates manufacturing variations.

[0082] If the system is configured to maintain the temperature of the ink in the circulation channel at a desired temperature (e.g., 25°C) (see Figure 34), it is preferable that the ink circulation be performed over a predetermined period of time in advance so that the temperature of the entire ink becomes uniform or homogeneous and the circulation flow rate stabilizes.

[0083] If ink circulation has not been performed for a relatively long period before recording is initiated (for example, if the recording device 1000 has been powered off for a relatively long period), the time required to stabilize the circulating flow rate when ink circulation is performed may be longer. Therefore, ink circulation should be performed until the amount of fluctuation in the circulating flow rate measured by the flow sensor 1009b falls within a predetermined range. This amount of fluctuation can correspond to the time derivative.

[0084] Figure 22 illustrates, for ease of understanding, the time course of absorbance of white ink, which tends to settle when not circulated, as an example of ink concentration. The absorbance of the white ink shown is that of the ink intake port in buffer tank 1003. Here, the time course of absorbance is shown for periods of 15 minutes, 30 minutes, and 45 minutes when ink circulation was stopped (non-circulation time), and then as the time of subsequent ink circulation (circulation time) progresses until the absorbance stabilizes. As shown in the figure, the absorbance is low immediately after the start of circulation, and returns to its original value as the circulation time progresses.

[0085] Figure 23 shows the circulating flow rate measured over the same time axis as Figure 22. When the stopped circulation is restarted, as shown in the figure, the circulating flow rate initially increases, then gradually decreases and stabilizes. Also, as shown in the figure, the time required for the circulating flow rate to stabilize is substantially the same as the time required for the absorbance to stabilize. From this, it can be said that the sedimentation of the white ink is resolved by stabilizing the circulating flow rate. In Figure 23, the stabilized circulation flow rate has decreased slightly from 420 ml / min to 400 ml / min. This is because the liquid level in buffer tank 1003 dropped by about 5 cm when ink was acquired during the absorbance measurement.

[0086] As another example, ink circulation may be performed for a period of time corresponding to the non-circulation time. As yet another example, the time for ink circulation may be determined by analyzing the mode of stabilization of the circulating flow rate based on the measurement results of the flow sensor 1009b, for example, it may be determined based on the time until the amount of fluctuation in the circulating flow rate falls within an acceptable range.

[0087] (Regarding the case where the main tank is replaced) Ink quality can also be determined when the main tank 1006 is replaced. Ink is supplied from the new main tank 1006 to the buffer tank 1003, and the circulating flow path, including the recording head 3, is filled with ink. In this case as well, the ink quality can be determined using the same procedure. After the main tank 1006 is replaced, the quality of the ink remaining in the circulation channel and the quality of the unused ink in the main tank 1006 may differ. Therefore, when ink is supplied from the main tank 1006 to the buffer tank 1003 (when ink is replenished in the circulation channel), it is desirable to determine the quality of the ink accordingly. In this way, the quality of the ink in the circulation channel can be managed through replacement.

[0088] (Ink quality restoration process in the circulation channel) If the ink density N in the circulating channel becomes high, it can cause a decrease in recording quality, such as the image on the recording medium 2 becoming an unintended density or color. Therefore, if the ink density N, which has been identified as one element of ink quality, is high, the signal for controlling the drive of the recording head 3 may be corrected. For example, by adjusting the drive signal (e.g., pulse width) for driving each recording element 15, it is possible to control the amount of high-density N ink ejected and form an image on the recording medium 2 with the desired density or color. On the other hand, if the ink concentration N exceeds the acceptable range, the highly concentrated ink can be discharged from the discharge port 13 by recovery processes such as pre-discharge or suction.

[0089] Figure 24 is a flowchart of the control process performed based on the identified ink concentration N. This flowchart is mainly performed by the controller unit 410, but may be performed by other computing devices as needed (the same applies to other flowcharts described later). In step S51, it is determined whether the ink density N is greater than the upper limit of the acceptable range (threshold density) Px (whether N > Px). The upper limit Px is assumed to be pre-stored in a predetermined memory, as exemplified in Table 1.

[0090] [Table 1]

[0091] If the ink concentration N is greater than the upper limit Px, the ink discharge process is performed in step S52. This process is carried out by recovery processes such as pre-discharge and suction. Pre-discharge is achieved by discharging ink from each discharge port 13 and discharging the ink into a waste liquid tank (not shown) built into the recording device 1000. Suction is achieved by applying negative pressure suction to each discharge port 13 using a recovery unit (not shown) built into the recording device 1000. After that, ink is replenished into the buffer tank 1003 from the main tank 1006 by the pump 1001, and in this way the quality of the ink in the circulation channel is restored.

[0092] (summary) According to this embodiment, the quality of the ink in the circulation channel is identified, and recovery processing is performed according to the identification result to restore the quality of the ink in the circulation channel, thereby enabling the appropriate maintenance of the ink concentration in the circulation path. The identification of the ink quality is performed based on the circulation flow rate when the driving force of the pump 1002 is fixed, thereby accurately identifying the ink viscosity η, ink evaporation rate V, and ink concentration N as indicators of ink quality. Therefore, according to this embodiment, unnecessary recovery processing is not performed.

[0093] Furthermore, in a relatively stable environment, or in a configuration with chillers or heat exchangers set to a predetermined temperature (see Figure 34), the ink temperature is approximately constant (e.g., 25°C). In such cases, fluctuations in ink viscosity η (=η0*exp(E / kT)), which depend on the ink temperature T, are suppressed. On the other hand, when the temperature T fluctuates, the ink viscosity η at that time can be converted to an equivalent value for, for example, when the ink temperature is 25°C (see Figure 25). This makes it possible to refer to Figure 20, which shows the relationship between the ink evaporation rate V and the ink viscosity η at a temperature of 25°C, and to determine the quality of the ink.

[0094] ≪Second Embodiment≫ During recording, the ink temperature may rise locally within the circulation channel due to factors such as the temperature rise of the recording head 3, and the temperature of the entire ink channel may not be uniform. Furthermore, this temperature may differ from the temperature detected by the temperature sensor 1009c. The second embodiment differs from the first embodiment described above in that it identifies the ink quality during the recording process.

[0095] Figure 26 shows the relationship between the duty cycle (drive DUTY) of the diaphragm pump drive signal, which is the driving force of pump 1002, and the circulating flow rate S for several ink viscosities η. As shown in the figure, within the range of usable drive DUTY, the relationship between drive DUTY and circulating flow rate S is approximately linear for any ink viscosity η.

[0096] Figure 27 shows the relationship between drive duty cycle and ink viscosity η at a certain circulation flow rate S (here, S = 460 [ml / min]). Since the drive duty cycle is controlled so that the circulation flow rate remains approximately constant even during recording, the ink viscosity η can be determined based on the drive duty cycle at that time. Figure 28 shows the relationship between the ratio of the drive duty cycle to the circulation flow rate S and the ink viscosity η. If there are fluctuations within the allowable range in the circulation flow rate S, referring to Figure 28 can help suppress the error in determining the ink viscosity η due to fluctuations in the circulation flow rate S.

[0097] In addition to the ink viscosity η determined in this way, if the temperature of the ink in the circulation channel is determined, the ink concentration N can be determined with high accuracy. On the other hand, as mentioned above, the temperature of the entire ink channel may not be uniform, and this temperature may differ from the temperature detected by the temperature sensor 1009c. Therefore, in this embodiment, the temperature of the ink in the circulating channel is calculated based on multiple temperature detection results. For example, the detection result of the temperature sensor 1009c may be corrected based on the temperature of the recording head 3 (the detection result of a head temperature sensor that may be provided on the recording head 3) and the room temperature (the detection result of an external temperature sensor that may be provided on the housing of the recording device 1000) to obtain the temperature of the ink in the circulating channel. As yet another example, the temperature of the ink in the circulating channel may be calculated by weighted addition of the detection result of the temperature sensor 1009c, the temperature of the recording head 3, and the room temperature. Since these calculation methods may differ depending on the configuration of the recording device 1000, it is preferable to determine them through predetermined experiments.

[0098] ≪Third Embodiment≫ In the third embodiment, another method for determining ink quality during recording is illustrated. This method involves determining ink quality by calculating the amount of water evaporated from the ink in the circulating channel. In this embodiment, ink quality is determined based on the amount of ink evaporation during recording, and based on the circulating flow rate using the same procedure as in the first embodiment described above when recording is not performed. In other words, there are two modes for determining ink quality, and one of them is selectively performed depending on whether recording is in progress or not. Here, the aforementioned ink evaporation rate (unit [%]) indicates the percentage of water lost due to evaporation from the original state of the ink, whereas the evaporation rate indicates the amount of water lost due to evaporation itself.

[0099] (Regarding the amount of ink that evaporates in the circulation channel) Figure 29 is a flowchart showing the calculation process when the recording device 1000 receives a print job (a job instructing recording to be performed). The outline of this flowchart is to calculate or measure the number of ink droplets (ink dots) to be ejected onto the recording medium 2 based on the image data (hereinafter referred to as dot counting). For example, one ink droplet ejected from a corresponding ejection port 13 by driving a certain recording element 15 is defined as one dot (that is, the dot value obtained by dot counting corresponds to the number of times ink is ejected from the ejection port 13). The evaporation amount is calculated based on this dot counting.

[0100] In response to receiving a print job, step S1 performs a dot count for each color on the page by analyzing the image data included in the print job. Here, the dot count is performed collectively for the 15 recording element plates 10 arranged longitudinally in the recording head 3, but it may also be performed for each recording element plate 10.

[0101] In step S2, the non-discharge rate Hx is calculated for each color. The non-discharge rate Hx represents the ratio of the number of non-discharges to the number of discharges in the case of total discharge. For example, the dot value D in the case of total discharge. ALL And the dot value D indicates the actual number of times the product was dispensed. ON Using this, the non-discharge ratio Hx is, Hx=(D ALL -D ON ) / D ALL This is the result.

[0102] Figure 30 is a flowchart showing the details of the calculation process for determining the evaporation rate. Prior to executing this calculation process, as shown in Table 2, the amount of water evaporated per unit time from a single ejector port 13 while the ink is circulating under predetermined temperature conditions is measured as the evaporation rate Zx (unit [μg / sec]) and stored in a predetermined memory. In step S11, the evaporation rate Zx corresponding to the temperature of the recording head 3 is referenced.

[0103] [Table 2]

[0104] Then, in step S12, the recording time Tx required to record one page is calculated. The recording time Tx can be calculated by dividing the transport speed by the transport length (page length) of the recording medium 2. After that, in step S13, the evaporation amount Vx is calculated. The evaporation amount Vx is obtained by multiplying the evaporation rate Zx, the recording time Tx, and the non-discharge ratio Hx. Vx = Zx * Tx * Hx This is the result.

[0105] The above calculation process is repeated for all pages recorded in the print job, thereby calculating the amount of evaporation Vx from the recording head 3 during recording.

[0106] (Regarding evaporation rate when recording is not performed) While it has been stated that ink quality is determined based on the circulation flow rate when recording is not in progress, ink quality may also be determined based on the evaporation rate even when recording is not in progress. When recording is not in progress, the individual ejection ports 13 of the recording head 3 are capped by the cap members, so the evaporation rate when recording is not in progress (denoted as evaporation rate Zy for distinction; unit [μg / min]) is smaller than the evaporation rate Zx, as shown in Table 3.

[0107] [Table 3]

[0108] As shown in Figure 31, in step S21, the evaporation rate Zy corresponding to the temperature of the recording head 3 is referenced. Then, in step S22, the elapsed time Ty when recording is not being performed is calculated. Subsequently, in step S23, the evaporation amount Vy is calculated. The evaporation amount Vy is obtained by multiplying the evaporation rate Zy by the recording time Ty. Vy=Zy*Ty This is the result.

[0109] In this case, the total evaporation amount up to that point is calculated by cumulatively adding the evaporation amount Vx during recording and the evaporation amount Vy during non-recording periods. Total This can be calculated.

[0110] (Calculation of ink consumption) Figure 32 is a flowchart showing the calculation process for determining the amount of ink consumed, which is one of the parameters referenced to determine the ink concentration. In step S31, it is determined whether there is a print job. If there is a print job, the process proceeds to step S32; otherwise, it proceeds to step S34. In step S32, the amount of ink consumed during recording is calculated based on the dot count calculation result described above. In step S33, the amount of ink consumed during recording is added to the total ink consumption (In). In step S34, it is determined whether there is a recovery execution job that instructs the execution of the recovery process. If there is a recovery execution job, the process proceeds to step S35; otherwise, this flowchart ends. In step S35, the amount of ink consumed during the recovery process is obtained (it is assumed that the amount of ink consumed during the recovery process is already stored in memory). In step S36, the amount of ink consumed during the recovery process is added to the amount of ink consumed In.

[0111] In this way, the amount of ink consumed (In) is accumulated each time a print job or recovery job occurs, making it possible to determine the amount of ink in the circulation channel.

[0112] (Identifying ink density) In this embodiment, based on the results calculated as described above, the ink concentration can be identified as the quality of the ink in the circulation channel, and the identified ink concentration can be updated. As mentioned above, the ink concentration is the amount of ink components (pigments, etc.) contained in water per unit volume.

[0113] Figure 33 is a flowchart showing the calculation process for determining the ink concentration in the circulating channel. In step S41, it is determined whether or not there is a print job. If there is no print job, this flowchart ends; if there is a print job, the process proceeds to step S42. In step S42, the previous ink concentration Nx is read from memory. Here, the initial value of the unused ink concentration Nref for the ink concentration Nx is pre-set as shown in Table 4.

[0114] [Table 4]

[0115] In step S43, it is determined whether the recording is complete, and if so, the process proceeds to step S44. In step S44, the evaporation amount Vx, the amount of ink consumed after recording is complete In, and the amount of ink in the circulation channel Jn shown in Table 5 are referenced.

[0116] [Table 5]

[0117] In step S45, the ink concentration Nx is updated based on the evaporation rate Vx, the amount of ink consumed In, and the amount of ink Jn in the circulation channel, as referenced above. For ease of understanding, let Nx be the ink concentration before the update and Nx' be the ink concentration after the update. Nx'=(Nx*(Jn-In)) / (Jn-In-Vx) This is how it is calculated. In this way, the ink density Nx is updated and stored in memory in step S46.

[0118] According to this embodiment, the ink quality can be determined based on the amount of evaporation during recording. Thereafter, as in the first embodiment described above, a recovery process can be performed based on the determination result (based on the degree of deterioration of the ink quality). Here, a diaphragm pump is used as an example for pump 1002, and an embodiment is shown in which the circulating flow rate is controlled by adjusting the duty cycle of its drive signal. However, this embodiment is advantageous when the circulating flow rate is controlled by other methods.

[0119] The above examples illustrate a configuration in which two modes are selectively executed: one that identifies ink quality based on circulation flow rate and another that identifies ink quality based on evaporation rate. However, these two modes may be executed side by side or simultaneously. These two modes can be executed side by side, regardless of whether recording is in progress or not. In such cases, one of the two results identified in each of the two modes described above, the one with the greater degree of quality degradation (in the example above, the one with the higher identified ink concentration), may be used as the reference. This makes it possible to appropriately maintain the quality of the ink in the circulation channel, regardless of the identification accuracy of the two modes described above.

[0120] ≪Program≫ The present invention may be implemented by supplying a program that implements one or more of the functions of the above embodiments to a system or device via a network or storage medium, and by a process in which one or more processors in the computer of the system or device read and execute the program. For example, the present invention may be implemented by a circuit (e.g., an ASIC) that implements one or more functions.

[0121] ≪Other≫ In the embodiments, individual elements are named using expressions based on their primary function, but the functions described in the embodiments may also be secondary functions, and the expressions are not strictly limited to these. Furthermore, these expressions can be replaced with other similar expressions. In the same vein, the expression "unit" can be replaced with "tool," "component," "member," "structure," "assembly," etc. Alternatively, these terms may be omitted or included.

[0122] Furthermore, the two or more elements exemplified as selectable in the embodiment are not strictly limited to those examples and may be combined arbitrarily. For example, each of the two or more exemplified elements may be additionally selected or substituted for others. For example, when arbitrarily combining two elements A and B, it may be expressed as "A and / or B" or "at least one of A and B" to indicate that it is either A only, B only, or both A and B.

[0123] Summary of the Embodiments Some of the features illustrated in the embodiment are as follows: (Item 1) A recording device comprising: a recording head that ejects ink to perform recording; a tank for storing ink to be supplied to the recording head; and a pump disposed in the ink circulation path that passes through the tank and the recording head, A measuring means for measuring the flow rate of ink circulating through the circulation channel by the pump as the circulating flow rate, The system further comprises a determination means for determining the quality of ink in the circulation channel based on the circulation flow rate measured by the measurement means. A recording device characterized by the following features.

[0124] (Item 2) The aforementioned identification means determines the degree of ink evaporation in the circulation channel based on the circulation flow rate measured by the measurement means. A recording device according to item 1, characterized in that it is a recording device.

[0125] (Item 3) The identification means determines the viscosity of the ink in the circulation channel based on the circulation flow rate measured by the measuring means. A recording device according to item 1 or item 2, characterized in that it is a recording device according to item 1 or item 2.

[0126] (Item 4) The aforementioned identification means further determines the quality of the ink in the circulation channel based on the amount of ink in the tank. A recording device according to any one of items 1 to 3, characterized in that it is the recording device described in any one of items 1 to 3.

[0127] (Item 5) The system further comprises a temperature detection means for detecting the temperature of the ink in the circulation channel, The aforementioned identification means further determines the quality of the ink in the circulation channel based on the temperature detected by the temperature detection means. A recording device according to any one of items 1 to 4, characterized by the above.

[0128] (Item 6) The pump is further provided with a drive control means for controlling the drive of the pump, The aforementioned identification means further determines the quality of the ink in the circulation path based on the driving force of the pump by the drive control means. A recording device according to any one of items 1 to 5, characterized by the above.

[0129] (Item 7) The drive control means sets the driving force of the pump to a fixed value when circulating the ink in the circulation channel. A recording device according to item 6, characterized in that it is a recording device.

[0130] (Item 8) The aforementioned identification means identifies the quality of the ink in the circulation channel after the circulation of ink in the circulation channel has started and the amount of fluctuation in the circulation flow rate measured by the measuring means has fallen within a predetermined range. A recording device according to item 6 or item 7, characterized in that it is a recording device according to item 6 or item 7.

[0131] (Item 9) The recording head starts recording after the circulation of ink in the circulation channel has begun and the amount of fluctuation in the circulation flow rate measured by the measuring means falls within a predetermined range. A recording device according to any one of items 6 to 8, characterized by the above.

[0132] (Item 10) The drive control means is When circulating the ink in the aforementioned circulation channel, the driving force of the pump is set to a fixed value. When recording is performed by the recording head, the driving force of the pump is controlled based on the circulation flow rate measured by the measuring means. A recording device according to item 9, characterized by the features described herein.

[0133] (Item 11) The pump is positioned in the flow path from the recording head to the tank in the direction of ink circulation within the circulation path. A recording device according to item 10, characterized in that it is a recording device.

[0134] (Item 12) The recording control means for controlling the drive of the recording head is further provided, The recording control means corrects the signal for controlling the drive of the recording head based on the quality of the ink in the circulation path identified by the identification means. A recording device according to any one of items 6 to 11, characterized by the following:

[0135] (Item 13) The system further comprises an update means for updating the ink in the circulation channel based on the results of the identification means. A recording device according to any one of items 1 to 12, characterized by the above.

[0136] (Item 14) The update means updates the ink in the circulation channel by ejecting ink from the recording head. A recording device according to item 13, characterized in that it is a recording device.

[0137] (Item 15) The aforementioned tank is connected to the main tank for storing ink. The renewal means renews the ink in the circulation channel by supplying ink from the main tank to the tank. A recording device according to item 13 or item 14, characterized by the above.

[0138] (Item 16) The system further comprises a calculation means for calculating the amount of ink evaporated in the circulation channel, The aforementioned identification means further identifies the quality of the ink in the circulation channel based on the evaporation amount calculated by the calculation means. A recording device according to any one of items 1 to 15, characterized by the above.

[0139] (Item 17) The aforementioned identification means identifies the sedimentation state of the ink components in the tank based on the circulation flow rate measured by the measurement means. A recording device according to any one of items 1 to 16, characterized in that

[0140] (Item 18) The system further comprises a determination means for determining the time for circulating the ink in the circulation channel based on the circulation flow rate measured by the measurement means. A recording device according to item 17, characterized in that it is a recording device.

[0141] (Item 19) The determination means determines the time for circulating the ink in the circulation channel based on the amount of fluctuation in the circulation flow rate measured by the measurement means. A recording device according to item 18, characterized by the features described above.

[0142] (Item 20) The aforementioned quality is concentration. A recording device according to any one of items 1 to 19, characterized by the above.

[0143] (Item 21) A recording head that ejects ink to perform recording, a tank for storing ink to be supplied to the recording head, and a pump arranged in the ink circulation path that passes through the tank and the recording head, A drive control means for controlling the drive of the pump, The system includes a determination means for determining the quality of the ink in the circulation channel based on the driving force of the pump by the drive control means, A recording device characterized by the following features.

[0144] (Item 22) The aforementioned quality is concentration and / or viscosity. A recording device according to item 21, characterized in that it is a recording device.

[0145] (Item 23) A program for causing a computer to function as one of the means of a recording device as described in any one of items 1 through 22.

[0146] The invention is not limited to the embodiments described above, and various modifications and variations are possible without departing from the spirit and scope of the invention. Accordingly, claims are attached to disclose the scope of the invention. [Explanation of symbols]

[0147] 1000: Recording device, 3: Recording head, 1003: Buffer tank, 1002: Pump.

Claims

1. A recording device comprising: a recording head that ejects ink to perform recording; a tank for storing ink to be supplied to the recording head; and a pump disposed in the ink circulation path that passes through the tank and the recording head, A measuring means for measuring the flow rate of ink circulating through the circulation channel by the pump as the circulating flow rate, The system further comprises a determination means for determining the quality of ink in the circulation channel based on the circulation flow rate measured by the measurement means. A recording device characterized by the following features.

2. The aforementioned identification means determines the degree of ink evaporation in the circulation channel based on the circulation flow rate measured by the measurement means. The recording device according to claim 1, characterized in that it is a recording device.

3. The identification means determines the viscosity of the ink in the circulation channel based on the circulation flow rate measured by the measuring means. The recording device according to claim 1, characterized in that it is a recording device.

4. The aforementioned identification means further determines the quality of the ink in the circulation channel based on the amount of ink in the tank. The recording device according to claim 1, characterized in that it is a recording device.

5. The system further comprises a temperature detection means for detecting the temperature of the ink in the circulation channel, The aforementioned identification means further determines the quality of the ink in the circulation channel based on the temperature detected by the temperature detection means. The recording device according to claim 1, characterized in that it is a recording device.

6. The pump is further provided with a drive control means for controlling the drive of the pump, The aforementioned identification means further determines the quality of the ink in the circulation path based on the driving force of the pump by the drive control means. The recording device according to claim 1, characterized in that it is a recording device.

7. The drive control means sets the driving force of the pump to a fixed value when circulating the ink in the circulation channel. The recording device according to claim 6.

8. The aforementioned identification means identifies the quality of the ink in the circulation channel after the circulation of ink in the circulation channel has started and the amount of fluctuation in the circulation flow rate measured by the measuring means has fallen within a predetermined range. The recording device according to claim 6.

9. The recording head starts recording after the circulation of ink in the circulation channel has begun and the amount of fluctuation in the circulation flow rate measured by the measuring means falls within a predetermined range. The recording device according to claim 6.

10. The drive control means is When circulating the ink in the aforementioned circulation channel, the driving force of the pump is set to a fixed value. When recording is performed by the recording head, the driving force of the pump is controlled based on the circulation flow rate measured by the measuring means. The recording device according to claim 9, characterized in that it is a recording device.

11. The pump is positioned in the flow path from the recording head to the tank in the direction of ink circulation within the circulation path. The recording device according to claim 10, characterized in that it is a recording device.

12. The recording control means for controlling the drive of the recording head is further provided, The recording control means corrects the signal for controlling the drive of the recording head based on the quality of the ink in the circulation path identified by the identification means. The recording device according to claim 6.

13. The system further comprises an update means for updating the ink in the circulation channel based on the results of the identification means. The recording device according to claim 1, characterized in that it is a recording device.

14. The update means updates the ink in the circulation channel by ejecting ink from the recording head. The recording device according to claim 13, characterized in that it is a recording device.

15. The aforementioned tank is connected to the main tank for storing ink. The renewal means renews the ink in the circulation channel by supplying ink from the main tank to the tank. The recording device according to claim 13, characterized in that it is a recording device.

16. The system further comprises a calculation means for calculating the amount of ink evaporated in the circulation channel, The aforementioned identification means further identifies the quality of the ink in the circulation channel based on the evaporation amount calculated by the calculation means. The recording device according to claim 1, characterized in that it is a recording device.

17. The aforementioned identification means identifies the sedimentation state of the ink components in the tank based on the circulation flow rate measured by the measurement means. The recording device according to claim 1, characterized in that it is a recording device.

18. The system further comprises a determination means for determining the time for circulating the ink in the circulation channel based on the circulation flow rate measured by the measurement means. The recording device according to claim 17, characterized in that it is a recording device.

19. The determination means determines the time for circulating the ink in the circulation channel based on the amount of fluctuation in the circulation flow rate measured by the measurement means. The recording device according to claim 18, characterized in that it is a recording device.

20. The aforementioned quality is concentration. The recording device according to claim 1, characterized in that it is a recording device.

21. A recording head that ejects ink to perform recording, a tank for storing ink to be supplied to the recording head, and a pump arranged in the ink circulation path that passes through the tank and the recording head, A drive control means for controlling the drive of the pump, The system includes a determination means for determining the quality of the ink in the circulation channel based on the driving force of the pump by the drive control means, A recording device characterized by the following features.

22. The aforementioned quality is concentration and / or viscosity. The recording device according to claim 21, characterized by the features described above.

23. A program for causing a computer to function as one of the means of a recording device according to any one of claims 1 to 22.

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