Liquid discharge device and inspection method

Abstract

To provide a liquid discharge device and inspection method that can be miniaturized and cost-reduced, and capable of detecting whether or not the ink circulation flow is normal.SOLUTION: A liquid discharge device performs a discharge operation by making the output of a first circulation pump 1002 lower than the output during normal recording by a recording device 1100, and determines whether or not the circulation is being performed normally on the basis of the result.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a liquid ejection device and an inspection method.

Background Art

[0002] Patent Document 1 discloses an inkjet recording apparatus including a supply tank, a main tank, and a recovery tank, and circulating a liquid in a liquid ejection head. In the inkjet recording apparatus of Patent Document 1, it is described that the ink circulation flow in the circulation is monitored by a pressure sensor, and if the ink circulation flow is not appropriate, the output of the pump is adjusted based on the pressure sensor to obtain an appropriate ink circulation flow.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in a configuration having a pressure sensor in the circulation path, there is a problem that it is difficult to miniaturize the liquid ejection head or the inkjet recording apparatus and reduce costs.

[0005] Therefore, the present invention provides a liquid ejection device and an inspection method that can be miniaturized and cost-reduced, and can detect whether the ink circulation flow is normal.

Means for Solving the Problems

[0006] Therefore, the liquid ejection apparatus of the present invention is a liquid ejection apparatus including a recording unit that ejects a liquid from an ejection port to perform recording, a pump that circulates the liquid supplied to the ejection port, and a control unit that controls driving of the recording unit and the pump. The control unit drives the pump with a first output in a recording operation of recording an image on a recording medium, and drives the pump with a second output that provides a smaller liquid feed amount than the first output in a circulation inspection of inspecting a circulation state of the liquid.

Advantages of the Invention

[0007] According to the present invention, it is possible to provide a liquid ejection apparatus and an inspection method that enable miniaturization and cost reduction and can detect whether an ink circulation flow is normal.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

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Figure 6

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Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Embodiments for Carrying Out the Invention

[0009] (First Embodiment) Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. In the following description, a recording apparatus using an inkjet recording method will be described as an example of a liquid ejection apparatus. The recording apparatus may be, for example, a single function printer having only a recording function, or a multi-function printer having a plurality of functions such as a recording function, a FAX function, and a scanner function. Further, it may be a manufacturing apparatus for manufacturing a color filter, an electronic device, an optical device, a micro-structure, etc. by a predetermined recording method.

[0010] In the following description, "recording" refers not only to the case of forming significant information such as characters and figures, but also regardless of whether it is significant or not. Further, it also represents the case of forming an image, a pattern, a pattern, a structure, etc. on a recording medium widely or performing processing of the medium, regardless of whether it is made apparent so that a human can perceive it visually.

[0011] Further, the "recording medium" represents not only paper used in a general recording apparatus, but also cloth, plastic film, metal plate, glass, ceramics, resin, wood, leather, etc., which can receive ink.

[0012] Furthermore, "ink" should be interpreted widely in the same way as the above definition of "recording". Therefore, it represents a liquid that can be used for forming an image, a pattern, a pattern, etc., processing the recording medium, or treating the ink (for example, coagulating or insolubilizing a colorant in the ink applied to the recording medium) by being applied on the recording medium.

[0013] Furthermore, the "recording element" (sometimes referred to as a "nozzle") generally refers to an ink ejection port, a liquid path communicating therewith, and an element (ejection element) that generates energy used for ink ejection, unless otherwise specified.

[0014] Recording apparatuses include a serial type that performs recording by alternately moving a liquid ejection head and a recording medium, and a line type that fixes the liquid ejection head and conveys the recording medium to perform recording. This embodiment can be applied to both serial type recording apparatuses and line type recording apparatuses.

[0015] FIG. 1(a) is a schematic diagram showing a recording apparatus 1000 equipped with a serial type head to which this embodiment can be applied. The recording apparatus 1000 supplies the liquid in the main tank 1006 to the liquid connection portion 111 of the liquid ejection head 3 via the pump 1004. The ink that has passed through the liquid connection portion 111 passes through the filter 221, passes through the negative pressure control unit 230 on the high pressure side (denoted as H in FIG. 1), is in fluid communication with the liquid supply unit 220, and is supplied to the recording element substrate 10 where nozzles are formed. A part of the ink supplied to the recording element substrate 10 is ejected from the nozzles, but the ink that has not been ejected passes through the discharge flow path of the liquid supply unit 220 again and reaches the negative pressure control unit 231 on the low pressure side (denoted as L in FIG. 1). Due to the pressure difference between the negative pressure control unit 230 on the high pressure side and the negative pressure control unit 231 on the low pressure side, the ink circulates inside the liquid ejection head 3.

[0016] Furthermore, the recording apparatus 1000 includes a pump 1001 that returns the ink of the negative pressure control unit 231 on the low pressure side to the negative pressure control unit 230 on the high pressure side, and ink circulation is also possible by driving the pump 1001. The pump 1001 is integrated with the liquid ejection head 3, and in view of performing a scanning operation, it is desirable to be small and lightweight. For example, a small diaphragm pump or a piezoelectric pump is preferable.

[0017] Here, when the output of the pump 1001 is large and the amount of ink returned to the negative pressure control unit 230 on the high pressure side is larger than the amount of ink flowing to the recording element substrate 10, the bypass flow path 240 compensates for the insufficient amount of ink. A check valve (not shown) is installed in the bypass flow path 240, and the ink flows only in the direction from the negative pressure control unit 230 on the high pressure side to the negative pressure control unit 231 on the low pressure side.

[0018] FIG. 1(b) is a schematic diagram showing a recording apparatus 1100 equipped with a line head to which the present embodiment is applicable. In FIGS. 1(a) and 1(b), the same members are denoted by the same reference numerals. In the recording apparatus 1100, the main tank 1006 is connected to the buffer tank 1003 via the replenishing pump 1005. The buffer tank 1003 has an air communication port (not shown) that communicates the inside and outside of the tank, and discharges air bubbles in the ink to the outside. When the liquid is consumed at the liquid discharge head 3 by discharging (discharging) the ink from the discharge port of the liquid discharge head 3 for recording by discharging the ink or for suction recovery, etc., the replenishing pump 1005 transfers the consumed amount of ink from the main tank 1006 to the buffer tank 1003.

[0019] The first circulation pump 1002 draws ink from the liquid connection portion 111 of the liquid discharge head 3 and flows it to the buffer tank 1003. As the first circulation pump 1002, a positive displacement pump having a quantitative liquid feeding ability is preferable. Specifically, a tube pump, a gear pump, a diaphragm pump, a syringe pump, etc. may be mentioned. For example, a form in which a general constant flow rate valve or relief valve is arranged at the pump outlet to ensure a constant flow rate may also be used. When the liquid discharge head 3 is driven, a certain amount of ink flows through the common supply channel 211 and the common recovery channel 212 by the first circulation pump 1002.

[0020] As this flow rate, since the temperature difference between each recording element substrate 10 in the liquid discharge head 3 affects the recording image quality if it affects the adjacent recording element substrate 10, it is preferable to set the temperature difference between the recording element substrates 10 so as not to affect the adjacent recording element substrate 10. Further, if the flow rate is set too large, due to the influence of the pressure loss of the flow path in the liquid discharge unit 300, the negative pressure difference becomes too large in each recording element substrate 10, and density unevenness of the image may occur. Therefore, it is preferable to set the flow rate while considering the temperature difference and the negative pressure difference between each recording element substrate 10.

[0021] The negative pressure control units 230 and 231 are provided in the path between the second circulation pump 1007 and the liquid discharge unit 300. Even when the flow rate of the circulation system fluctuates due to the difference in Duty during recording, the negative pressure control units 230 and 231 maintain the pressure on the downstream side (i.e., the liquid discharge unit 300 side) at a preset constant pressure. As the two pressure adjustment mechanisms constituting the negative pressure control units 230 and 231, any mechanism may be used as long as it can control the pressure downstream of itself within a certain range below a desired set pressure centered on the desired set pressure.

[0022] As an example of the pressure adjustment mechanism, a mechanism similar to the so-called "pressure reducing regulator" can be adopted. When using a pressure reducing regulator, as shown in Fig. 1(b), it is preferable to pressurize the upstream side of the negative pressure control units 230 and 231 via the liquid supply unit 220 by the second circulation pump 1007. By doing so, the influence of the head pressure on the liquid discharge head 3 of the buffer tank 1003 can be suppressed, and the degree of freedom in the layout of the buffer tank 1003 in the recording apparatus 1000 can be increased.

[0023] The second circulation pump 1007 may be any pump that has a lift pressure equal to or higher than a certain pressure within the range of the ink circulation flow rate used when driving the liquid discharge head 3, and a turbo pump, a positive displacement pump, etc. can be used. Specifically, a diaphragm pump or the like is applicable. Further, instead of the second circulation pump 1007, for example, a head tank arranged with a certain head difference with respect to the negative pressure control unit 230 is also applicable.

[0024] As shown in Fig. 1(b), the negative pressure control units 230 and 231 are two pressure adjustment mechanisms with different control pressures set for each. Among the two negative pressure adjustment mechanisms, the negative pressure control unit 230 with a relatively high pressure setting and the negative pressure control unit 231 with a relatively low pressure setting are respectively connected to the common supply flow path 211 and the common recovery flow path 212 in the liquid discharge unit 300 via the inside of the liquid supply unit 220.

[0025] The liquid ejection unit 300 is provided with a common supply channel 211, a common recovery channel 212, an individual supply channel 213a and an individual recovery channel 213b that communicate with each recording element substrate 10. The individual channels 213 communicate with the common supply channel 211 and the common recovery channel 212, and a part of the liquid flows from the common supply channel 211 through the internal channels of the recording element substrate 10 to the common recovery channel 212 (the arrow in FIG. 1(b)). Since a negative pressure control unit 230 on the high-pressure side is connected to the common supply channel 211 and a negative pressure control unit 231 on the low-pressure side is connected to the common recovery channel 212, a differential pressure is generated between the common supply channel 211 and the common recovery channel 212.

[0026] In this way, in the liquid ejection unit 300, while flowing the liquid through the common supply channel 211 and the common recovery channel 212, a part of the liquid passes through each recording element substrate 10. In this manner, the heat generated in each recording element substrate 10 is discharged to the outside of the recording element substrate 10 by the flow in the common supply channel 211 and the common recovery channel 212.

[0027] In this way, when recording is being performed by the liquid ejection head 3, in order to cause the flow of ink also in the ejection ports and pressure chambers where recording is not being performed, it is possible to suppress the thickening of the ink in the ejection ports and pressure chambers where recording is not being performed. As a result, high-speed and high-quality recording becomes possible.

[0028] Note that this embodiment is applicable to both the recording apparatus 1000 equipped with the serial type head shown in FIG. 1(a) above and the recording apparatus 1100 equipped with the line type head shown in FIG. 1(b). Hereinafter, the recording apparatus 1100 equipped with the line type head will be described as an example.

[0029] FIGS. 2(a) to (c) are diagrams showing the recording element substrate 10.

[0030] FIG. 2(a) shows a plan view of the side of the discharge port forming member 12 where the discharge ports 13 of the recording element substrate 10 are formed. FIG. 2(b) shows an enlarged view of the portion indicated by IIb in FIG. 2(a). FIG. 2(c) shows a plan view of the lid member 20 on the back surface of FIG. 2(a). The recording element substrate 10 includes a substrate (not shown), a discharge port forming member 12, and a lid member 20. The lid member 20 is provided on the side opposite to the discharge port forming member 12 with respect to the substrate.

[0031] As shown in FIG. 2(a), four rows of discharge port rows 14 corresponding to each ink color are formed in the discharge port forming member 12 of the recording element substrate 10. Hereinafter, the direction in which the discharge port rows 14 in which a plurality of discharge ports 13 are arranged extends is referred to as the "discharge port row direction".

[0032] As shown in FIG. 2(b), at positions corresponding to each discharge port 13, a heater 15, which is a heat generating element that foams ink by thermal energy, is arranged. A pressure chamber 23 that includes the heater 15 inside is partitioned by a partition wall 22. The heater 15 is electrically connected to the terminal 16 in FIG. 2(a) by an electrical wiring (not shown) provided on the recording element substrate 10.

[0033] The heater 15 generates heat based on a pulse signal input from the control circuit of the recording apparatus 1100 via an electrical wiring substrate (not shown) or a flexible wiring substrate (not shown) to boil the ink. The ink is discharged from the discharge port 13 by the force of foaming due to boiling. As shown in FIG. 2(b), along each discharge port row 14, a liquid supply path 18 and a liquid recovery path 19 extend and communicate with the discharge port 13 via a supply port 17a and a recovery port 17b, respectively.

[0034] As shown in Fig. 2(c), a sheet-like lid member 20 is laminated on the back surface of the surface of the recording element substrate 10 where the discharge port 13 is formed. A plurality of openings 21 communicating with the liquid supply path 18 and the liquid recovery path 19 are provided in the lid member 20. In the present embodiment, three openings 21 are provided for one of the liquid supply paths 18, and two openings 21 are provided in the lid member 20 for one of the liquid recovery paths 19. The lid member 20 functions as a lid that forms a part of the walls of the liquid supply path 18 and the liquid recovery path 19 formed on the substrate of the recording element substrate 10.

[0035] The lid member 20 preferably has sufficient corrosion resistance against ink. Also, from the viewpoint of preventing color mixing, high precision is required for the opening shape and opening position of the opening 21. Therefore, as the material of the lid member 20, it is preferable to use a photosensitive resin material or a silicon plate and provide the opening 21 by a photolithography process. Such a lid member 20 desirably has a small thickness in consideration of pressure loss and is preferably composed of a film-like member.

[0036] Next, the flow of ink in the recording element substrate 10 will be described. The recording element substrate 10 is laminated with a substrate formed of Si and a discharge port forming member 12 formed of a photosensitive resin, and the lid member 20 is joined to the back surface of the substrate. A heater 15 is formed on one surface side of the substrate, and grooves constituting the liquid supply path 18 and the liquid recovery path 19 extending along the discharge port row 14 are formed on the back surface side thereof.

[0037] Ink flows from a common supply channel (not shown) in the liquid supply unit 220 through the opening 21 of the lid member 20 into the liquid supply path 18, and then flows into the pressure chamber 23 through the supply port 17a and the supply-side common liquid chamber 25 in the discharge port forming member 12. A part of the ink in the pressure chamber 23 is discharged from the discharge port 13, and the ink that has not been discharged flows into the liquid recovery path 19 through the recovery-side common liquid chamber 26 and the recovery port 17b. The ink in the liquid recovery path 19 flows through the opening 21 of the lid member 20 into a common recovery channel (not shown) in the liquid supply unit 220.

[0038] FIG. 3 is a block diagram showing the configuration of the recording apparatus 1100. The recording apparatus 1100 includes a control unit 30 having a CPU 30a such as a microprocessor, and a RAM 30b that is used as a work area for the CPU 30a and stores various data such as recording data and registration adjustment values. The control unit 30 includes a ROM 30c that stores the control program and various data of the CPU 30a. Further, the recording apparatus 1100 includes an interface 31, an operation panel 32, and drivers 35 and 36. The driver 35 drives and controls a motor 34 for driving a conveyance roller and a circulation pump 1002 of an ink supply passage, and the driver 36 drives a liquid ejection head 3.

[0039] The recording data received by the recording apparatus 1100 is stored in the RAM 30b of the control unit 30. According to the recording data stored in the RAM 30b, the control unit 30 outputs an ON / OFF signal for driving the motor 34 to the driver 35 and a discharge signal or the like to the driver 36, respectively, to form an image on the recording medium. Further, the control unit 30 outputs a signal for driving the circulation pump 1002 to the driver 35 according to a control sequence described later, and controls the circulation pump 1002.

[0040] FIG. 4 is a flowchart showing the processing of a circulation inspection, which is an inspection for detecting in advance whether ink is circulating normally (circulation state). The series of processes shown in FIG. 4 is performed by the CPU 30a of the recording apparatus 1100 expanding and executing the program code stored in the ROM 30c in the RAM 30b. Alternatively, some or all of the functions of the steps in FIG. 4 may be realized by hardware such as an ASIC or an electronic circuit. Note that the symbol "S" in the description of each process means that it is a step in the flowchart.

[0041] FIG. 5(a) is a diagram showing an inspection pattern when the ink is circulating normally in the circulation inspection, and FIG. 5(b) is a diagram showing an inspection pattern when the ink is not circulating normally in the circulation inspection. FIG. 6 is a graph showing the relationship between the circulation flow rate and the pump output during normal circulation and abnormal circulation.

[0042] In this embodiment, a circulation inspection is performed to detect whether the circulation of the ink flowing in the discharge port 13 and the pressure chamber 23 is normal. In the circulation inspection, a test pattern is recorded, and by checking the test pattern, it is determined whether normal circulation is achieved. If normal circulation is achieved, a test pattern as shown in Fig. 5(a) is recorded. However, if normal circulation is not achieved, a test pattern as shown in Fig. 5(b) is recorded. Note that the black circles in Figs. 5(a) and 5(b) indicate the dots where the discharged droplets ejected from each discharge port 13 landed on the recording medium.

[0043] In this embodiment, in the circulation inspection, the inspection is performed by reducing the output of the first circulation pump 1002 below the output when normally recording with the recording device 1100. By reducing the output of the first circulation pump 1002, the amount of liquid to be fed decreases, and the ink circulation amount flowing in the discharge port 13 and the pressure chamber 23 also decreases. In such a state where the ink circulation amount has decreased, a test pattern is recorded. If the ink circulation amount is appropriate, dots are recorded at the desired positions starting from the first discharge after a long pause as shown in Fig. 5(a), whereas if the ink circulation amount is small, the droplets ejected at the first discharge after a long pause are recorded shifted from the desired positions as shown in Fig. 5(b). The reason for the discharged droplets shifting from the desired positions is that normal circulation is not achieved during the long pause due to the influence of pump deterioration or the like, the ink near the discharge port 13 becomes highly viscous, and the timing of the first discharge is delayed.

[0044] Note that the pump output mentioned here corresponds to, for example, the rotation speed of the roller that crushes the tube of the tube pump to feed the liquid if the pump is a tube pump, and corresponds to the drive voltage if the motor that drives the tube pump is a DC motor. Also, if the pump is a piezoelectric pump, the pump output corresponds to the drive frequency or voltage of the piezoelectric element for feeding the liquid, and by changing these, the amount of liquid fed per unit time can be changed. Thus, the output is a parameter for changing the amount of ink to be fed.

[0045] When the circulation inspection shown in FIG. 4 is started, the CPU 30a reduces the output from the output Pp when normally recording the output of the first circulation pump 1002 by the recording device 1100 to a lower inspection output Pt. With the output of the first circulation pump 1002 reduced, the CPU 30a controls to record an inspection pattern in S402. Then, in S403 (determination means), the CPU 30a determines whether the recorded inspection pattern is normal. If it is determined that the recorded inspection pattern is normal (Yes), the CPU 30a proceeds to S404 and determines that the ink is circulating normally. If it is determined that the recorded inspection pattern is not normal (No), the CPU 30a proceeds to S405 and determines that the ink is not circulating normally. This ends the present process.

[0046] When the ink is circulating normally, as shown by the solid line in FIG. 6, at the time of the normal recording pump output Pp, the circulation flow velocity in the pressure chamber 23 is VPp1. Also, at the time of the circulation inspection pump output Pt, the circulation flow velocity in the pressure chamber 23 is VPt1. Here, let the minimum circulation flow velocity in the pressure chamber 23 at which the desired discharge operation is achieved be Vth. When the ink is circulating normally, whether the pump output is Pp or Pt, a circulation flow exceeding the threshold value Vth is achieved and no discharge failure occurs.

[0047] On the other hand, when the ink is not circulating normally for some reason, the relationship between the pump output and the circulation flow velocity in the pressure chamber is, for example, as shown by the dotted line in FIG. 6. In this case, at the time of the normal recording pump output Pp, the circulation flow velocity in the pressure chamber 23 is VPp2, which exceeds the threshold value Vth. However, at the time of the circulation inspection pump output Pt, the circulation flow velocity in the pressure chamber 23 is VPt2, which is lower than the threshold value Vth. That is, when the ink is not circulating normally, even if no discharge failure is confirmed in the actual recording operation, when the pump output for the circulation inspection is Pt, the circulation flow velocity is lower than the threshold value Vth and a discharge failure is confirmed.

[0048] When the ink is circulating normally (solid line in Fig. 6), even if the pump output is reduced to Pt, the circulation flow rate becomes VPt1, which is faster than Vth. That is, the relationship is V Pp1 > V Pt1 ≥ Vth. However, when the ink is not circulating normally (dashed line in Fig. 6), at the pump output Pp during normal recording, the circulation flow rate V Pp2 is faster than Vth (V Pp1 ≥ Vth). However, when the pump output is reduced to Pt, the circulation flow rate V Pt2 during the circulation inspection becomes slower than Vth (V Pt2 < Vth), and the desired recording result cannot be obtained.

[0049] In the state where the above ink circulation is not performed normally, since a good recording result can be obtained during normal recording, it is impossible to determine whether the ink circulation is normal. However, by reducing the pump output and performing a circulation inspection, in the state where the ink circulation is not performed normally, a recording defect occurs in the recording of the inspection pattern, so it can be determined that the ink circulation is not performed normally.

[0050] In this embodiment, by performing the inspection by reducing the pump output during the circulation inspection in this way, it is possible to detect whether the ink circulation is performed normally. When it is detected that the ink circulation is not performed normally, first, a recovery operation such as sucking the ink in the liquid discharge head 3 from the discharge port 13 is performed to attempt to remove bubbles and foreign matters in the discharge port and the flow path and to eliminate the thickening of the ink. If the ink still does not circulate normally even with such a recovery operation, it is assumed that the pump is deteriorating or the flow paths in the liquid discharge head 3 are approaching an unresolvable blocked state. Therefore, operations such as prompting the replacement of the first circulation pump 1002 or the replacement of the liquid discharge head 3 are performed.

[0051] Here, regarding the relationship between Pp, which is the output of the first circulation pump 1002, and Pt, the closer the values of Pp and Pt are, the lower the frequency of the recovery operation and the frequency of replacement of the first circulation pump 1002 and the liquid ejection head 3 can be, improving convenience. However, if the values of Pp and Pt are too close, there is a risk of false detection due to fluctuations in the circulation flow rate, and there is an increased risk that the ink circulation will further decrease and become defective during the recording operation until the next circulation inspection. Also, if the values of Pp and Pt are too far apart, it will be immediately determined that there is an ink circulation defect, increasing the frequency of the recovery operation and the replacement frequency of the first circulation pump 1002 and the liquid ejection head 3, which is disadvantageous in terms of convenience and cost. Therefore, it is desirable to set the relationship between Pp and Pt as 0.5Pp ≦ Pt ≦ 0.95Pp. That is, the pump output Pt for circulation inspection is preferably set to an output that can obtain a liquid delivery amount that is 0.5 to 0.95 times the liquid delivery amount obtained by the normal recording pump output Pp in normal circulation.

[0052] Also, in the present embodiment, in S403 of FIG. 4, it is determined whether the ink is circulating normally from the recording result of the inspection pattern. Regarding the determination of this recording result, it may be in a form that accepts a visual judgment from the user, or it may be in a form that reads the inspection pattern with a scanner (reading means) mounted on the recording apparatus 1100 and makes a judgment by image processing.

[0053] Thus, according to the present embodiment, the ejection operation is performed with the output of the first circulation pump 1002 lowered from the output during normal recording by the recording apparatus 1100, and it is determined whether the circulation is being performed normally based on the result. That is, it is not necessary to provide a pressure sensor in the circulation path. As a result, miniaturization and cost reduction are possible, and a liquid ejection apparatus and an inspection method capable of detecting whether the ink circulation flow is normal can be provided.

[0054] (Second Embodiment) Hereinafter, a second embodiment of the present invention will be described with reference to the drawings. Since the basic configuration of the present embodiment is the same as that of the first embodiment, the characteristic configuration will be described below.

[0055] In the first embodiment, it was determined whether the ink was circulating normally by recording an inspection pattern on a recording medium. In this embodiment, no recording is performed on the recording medium, the heater 15 is driven, and it is determined whether the ink is circulating normally by detecting the ejection state of the ink.

[0056] FIG. 7 is a flowchart showing the process of the circulation inspection in this embodiment. The series of processes shown in FIG. 7 are performed by the CPU 30a of the recording apparatus 1100 expanding and executing the program code stored in the ROM 30c in the RAM 30b. Alternatively, some or all of the functions of the steps in FIG. 7 may be realized by hardware such as an ASIC or an electronic circuit. Note that the symbol "S" in the description of each process means that it is a step in the flowchart.

[0057] FIG. 8 is a diagram for explaining the detection of droplets by the sensor in this embodiment. FIG. 9(a) is a diagram showing an example of a cross-sectional configuration of the heater 15 and the temperature detection element 905 formed on the recording element substrate 10, and FIG. 9(b) is a diagram showing an example of a planar configuration of the heater 15 and the temperature detection element 905. Note that FIG. 9(a) is a cross-section taken along line IXa-IXa of FIG. 9(b), and FIG. 9(b) is a perspective view from the Si substrate 901 side showing the positional relationship of the temperature detection element 905. Here, for convenience of explanation, the illustration of the nozzle portion such as the ejection port 13 and some films is omitted. FIG. 10 is a diagram showing the temperature profiles during normal ejection and non-ejection when a driving voltage is applied to the heater 15 obtained by the temperature detection element 905.

[0058] In this embodiment, reducing the output of the first circulation pump (hereinafter also simply referred to as the pump) 1002 during the circulation inspection is the same as in the first embodiment. By reducing the output of the pump 1002, discharging ink based on an inspection pattern, and separately detecting the discharged droplets with a sensor, it is possible to determine whether the discharge is normal (discharge state). As the sensor, for example, an optical sensor as shown in FIG. 8 can be used. As shown in FIG. 8, a light source 401 and an optical sensor 402 are installed in the recording apparatus 1100 in the direction in which ink is discharged from the liquid discharge head 3, and the light irradiated from the light source 401 is received by the optical sensor 402. Then, since the discharged droplets discharged from the liquid discharge head 3 pass between the light source 401 and the optical sensor 402, the light received by the optical sensor 402 is blocked, and it is possible to detect the discharge by detecting this light blocking. More specifically, it is possible to determine whether the circulation is being performed normally based on the timing of driving the heater 15 and the timing at which the optical sensor 402 detects light blocking.

[0059] Furthermore, by detecting the light blocking time and using a plurality of light sources 401 and optical sensors 402, it is possible to detect the discharge speed and volume of the discharged droplets, so that the determination accuracy of whether the discharge is normal can be improved.

[0060] When the circulation inspection shown in FIG. 7 is started, the CPU 30a reduces the output of the pump 1002 in S701 to be lower than the output when normally recording with the recording apparatus 1100. With the output of the pump 1002 reduced, the CPU 30a controls to discharge ink droplets in the inspection pattern in S702. Thereafter, in S703, the CPU 30a determines whether normal discharge has been performed by the optical sensor at the timing when the ink droplets were discharged in S702. If it is determined that normal discharge has been performed (Yes), the CPU 30a proceeds to S704 and determines that the ink is circulating normally. If it is determined that normal discharge has not been performed (No), the CPU 30a proceeds to S705 and determines that the ink is not circulating normally. The processing ends here.

[0061] Although an example of ejecting ink droplets based on an inspection pattern during ejection has been described, the present invention is not limited thereto, and ejection may be simply performed without being based on an inspection pattern.

[0062] As another example of the determination method in S703, it is also possible to use a temperature detection element built in the recording element substrate 10 of the liquid ejection head 3. As shown in FIG. 9(a), in the recording element substrate 10, a plurality of layers are formed on the Si substrate 901. Specifically, on the Si substrate 901, an insulating film PSG903 is formed via a field oxide film 902 such as SiO2. On the insulating film PSG903, a temperature detection element 905 formed of a thin film resistor such as Al, Pt, Ti, Ta, etc. is provided, and an AL1 wiring 904 for connecting the temperature detection element 905 is provided. Further, an interlayer insulating film 906 such as SiO is provided in the upper layer, and on the interlayer insulating film 906, a heater 15 for electrothermal conversion such as TaSiN and an AL2 wiring 908 for connecting the heater 15 and the drive circuit formed on the Si substrate 901 are provided. In addition, a passivation film 909 such as SiO2 and a cavitation-resistant film 910 such as Ta and Ir for enhancing the cavitation resistance on the heater 15 are provided.

[0063] As shown in FIG. 9(b), on the plane of the recording element substrate 10, there are regions indicating the region 911 of the heater 15, the region indicating the AL2 wiring 912 connecting the heater 15 and the drive circuit, and the region indicating the AL1 wiring 914 of the individual wiring of the temperature detection element 905. Such a configuration of the recording element substrate 10 is formed by a semiconductor process. The recording element substrate 10 according to the present embodiment can be manufactured by placing the temperature detection element 905 in the AL1 layer and performing film formation and patterning, so that it can be manufactured without changing the structure of the conventional recording element substrate.

[0064] In FIG. 9(b), the temperature detection element 905 is shown in a meandering shape, but it is not limited to this. The temperature detection element 905 may be formed in a rectangular shape, for example. When the temperature detection element 905 has a zigzag shape as shown in FIG. 9(b), the detection signal increases as the resistance value of the temperature detection element 905 increases, so the advantage of being able to accurately detect temperature changes can be obtained.

[0065] When the ejection operation is normally performed as in the temperature profile of FIG. 10, the temperature detected by the temperature detection element 905 shows a characteristic point where the temperature drops rapidly after reaching the maximum temperature (solid line graph). In contrast, when there is no ejection, such a characteristic point does not appear (dotted line graph). This is because when a normal ejection operation is performed, when the heater 15 is driven to eject ink from the ejection port 13, a force that pulls the ejected droplets into the pressure chamber 23 acts during the process of contraction after the volume of the film boiling bubbles generated on the heater 15 reaches its maximum. As a result, a part of the ejected droplets falls onto the heater 15. From the state where the heater 15 was heated to a high temperature due to film boiling, when a part of the cold ejected droplets falls onto the heater 15, a rapid temperature change occurs, and the aforementioned characteristic point appears. By detecting the presence or absence of this characteristic point, it is possible to determine whether ejection has been performed normally.

[0066] As described above, since it is possible to judge only by ejection without recording on a recording medium, there is an advantage that a recording medium for landing droplets is not required. Further, since there is no need to record on a recording medium, for example, ejection may be performed on a cap or the like provided in the recording apparatus 1100 to prevent ink drying from the nozzles of the liquid ejection head 3.

[0067] As described above, according to the present embodiment, recording on a recording medium is not performed, the heater 15 is driven, ink is ejected from the ejection port 13, and it is determined whether the ink is circulating normally from the ejection state. That is, it is not necessary to provide a pressure sensor in the circulation path. As a result, miniaturization and cost reduction are possible, and a liquid ejection device and an inspection method capable of detecting whether the ink circulation flow is normal can be provided.

[0068] (Third Embodiment) Hereinafter, a third embodiment of the present invention will be described with reference to the drawings. Since the basic configuration of this embodiment is the same as that of the first embodiment, the characteristic configuration will be described below.

[0069] In each of the above embodiments, during the circulation inspection, the output of the first circulation pump (hereinafter also simply referred to as the pump) 1002 was reduced from Pp, which is the output during normal recording, to Pt for discharging. In this embodiment, the output of the pump 1002 is set to Pta, which is lower than Pp, and it is determined whether the discharge is normal. If the discharge is normal, the output of the pump is further set to Ptb, which is lower than Pta, and it is determined whether the discharge is normal or not. That is, the circulation inspection is performed by reducing the output of the pump in multiple steps from the output during normal recording.

[0070] FIG. 11 is a flowchart showing the processing of the circulation inspection in this embodiment. The series of processes shown in FIG. 11 are performed by the CPU 30a of the recording device 1100 expanding and executing the program code stored in the ROM 30c in the RAM 30b. Alternatively, some or all of the functions of the steps in FIG. 11 may be realized by hardware such as an ASIC or an electronic circuit. Note that the symbol "S" in the description of each process means that it is a step in the flowchart. FIG. 12 is a graph showing the relationship between the circulation flow rate and the pump output in state 1, which is the normal circulation state, state 2, in which the usage period has elapsed, and state 3, in which the usage period has further elapsed.

[0071] In state 1, regardless of whether the output of the pump 1002 during recording is Pp, Pta with the output reduced, or Ptb with the output further reduced, the circulation flow rates (VPp1, VPta1, Vptb1) in the pressure chamber 23 are higher than the minimum circulation flow rate Vth at which a desired recording can be obtained. Here, the relationship of the output of the pump 1002 is Pp > Pta > Ptb.

[0072] After passing through the usage period from State 1, in State 2 where the circulation flow velocity has decreased, let the circulation flow velocities in the pressure chamber 23 at the time of the output Pp of the pump 1002 during recording, Pta with the output decreased, and Ptb with the output further decreased be VPp2, VPta2, and Vptb2 respectively. In that case, the circulation flow velocities have the relationship of VPp2 > VPta2 > Vth > VPtb2.

[0073] In State 2, at Pta with the output decreased from Pp, since the circulation flow velocity is VPta > Vth, it can be judged that the ink is still circulating normally. However, at Ptb with the output further decreased, the circulation flow velocity is Vth > VPtb2, and since it is lower than the minimum circulation flow velocity Vth, it can be judged that the ink will soon stop circulating normally.

[0074] When such a state is detected, by estimating how much normal recording can be obtained from here on, it becomes possible to perform a recovery operation at an appropriate timing, optimize the number of recovery operations, and shorten the recording stop time due to the recovery operation. When estimating, by conducting a test in advance and obtaining the time for normal recording and the degree of recovery in the recovery process according to the first circulation pump 1002 and the liquid ejection head 3, an optimal number of recovery operations can be obtained.

[0075] After passing through the usage period from State 2, in State 3 where the circulation flow velocity has decreased further, let the circulation flow velocities in the pressure chamber 23 at the time of the output Pp of the pump 1002 during recording, Pta with the output decreased, and Ptb with the output further decreased be VPp3, VPta3, and Vptb3 respectively. In this case, the circulation flow velocities have the relationship of VPp3 > Vth > VPta3 > VPtb3.

[0076] In State 3, already at Pta with the output decreased from Pp, Vth > VPta3, and since it is lower than the minimum circulation flow velocity, the ink is not circulating normally, so it becomes necessary to perform a recovery operation immediately.

[0077] When the circulation inspection shown in FIG. 11 is started, the output of the pump 1002 is set to Pta, which is lower than the output Pp when normally recorded by the recording device 1100 at S1101. With the output of the pump 1002 lowered, ink droplets of the inspection pattern are ejected at S1102. Then, at S1103, it is determined by the optical sensor whether normal ejection has been performed. If it is determined that normal ejection has been performed (Yes), the process proceeds to S1104, and it is determined that the ink is circulating normally. If it is determined that normal ejection has not been performed (No), the process proceeds to S1105, and it is determined that the ink is not circulating normally. When the process proceeds to S1104, thereafter, the process proceeds to S1106, and the output of the pump 1002 is lowered below Pta to Ptb. At S1107, ink droplets of the inspection pattern are ejected. Then, at S1108, it is determined by the optical sensor whether normal ejection has been performed. If it is determined that normal ejection has been performed (Yes), the process proceeds to S1109, and it is determined that the ink is circulating normally and the process ends. If it is determined that normal ejection has not been performed (No), the process proceeds to S1110, and it is determined that the ink will soon stop circulating normally and the process ends.

[0078] In this way, by changing the pump output in two stages during the circulation inspection mode, not only can it be detected whether the ink is not circulating normally, but it is also possible to predict whether the ink is likely to stop circulating normally.

[0079] In this embodiment, the pump output is changed in two stages, but it may be changed in three stages, four stages, or more stages than two stages. In the case of more stages, the state of ink circulation can be grasped in more detail. Also, recovery processing with different degrees may be executed according to the result of the determination.

[0080] Also, in the same manner as the second embodiment that detects ejection, an example was described in which it is determined whether normal ejection has been performed by an optical sensor or a temperature detection element. However, as in the first embodiment, it may be implemented by recording an inspection pattern on a recording medium and making a determination by visual inspection or the like. In that case, as shown in FIG. 11, it takes time to make a determination of the inspection pattern every time the output of the pump 1002 is changed. Therefore, after finishing recording all the inspection patterns in which the output of the pump 1002 is changed in several steps, the landing states of the plurality of inspection patterns may be finally determined by visual inspection or the like.

[0081] As described above, according to the present embodiment, the output of the pump is set to Pta which is lower than Pp, and it is determined whether ejection has been performed normally. If ejection has been performed normally, the output of the pump is further set to Ptb which is lower than Pta, and it is determined whether ejection has been performed normally. As a result, it is possible to reduce the size and cost without providing a pressure sensor in the circulation path, and it is possible to provide a liquid ejection device and an inspection method capable of detecting whether the ink circulation flow is normal.

[0082] (Modification example) Hereinafter, a modification example of the third embodiment will be described. In each of the above embodiments, during the circulation inspection, the output of the pump 1002 was not set to be equal to or higher than the pump output Pp at the time of recording. However, for example, when the state becomes state 2 or state 3 of the third embodiment and it is determined that the state remains state 2 or state 3 even after the recovery operation is performed, the pump output may be set to Ptc which is larger than Pp which is the output at the time of recording, and the second circulation inspection may be performed. If there is a change such that the state approaches state 1 from state 2 or the state approaches state 2 from state 3 when the output of the pump is set to Ptc, an operation is performed to reset the pump output at the time of recording from Pp to Ptc based on the result.

[0083] By appropriately changing the setting of the pump output at the time of recording in this way, the pump 1002 and the liquid ejection head 3 can be used further, so that it is possible to expect an extended service life of the pump 1002 and the liquid ejection head 3.

[0084] The disclosure of this embodiment includes the following configurations and methods.

[0085] (Configuration 1) Recording means for discharging liquid from a discharge port to perform recording, A pump for circulating the liquid supplied to the discharge port, Control means for controlling the driving of the recording means and the pump, A liquid discharge device comprising: In the recording operation of recording an image on a recording medium, the control means drives the pump with a first output, and in a circulation inspection for inspecting the circulation state of the liquid, the control means drives the pump with a second output that results in a liquid feed amount smaller than the first output. The liquid discharge device is characterized by this.

[0086] (Configuration 2) The liquid discharge device according to Configuration 1, wherein the output for driving the pump is a voltage applied to a motor.

[0087] (Configuration 3) The liquid discharge device according to Configuration 1, wherein the output for driving the pump is at least one of a voltage applied to a piezoelectric element or a frequency applied to the piezoelectric element.

[0088] (Configuration 4) In the circulation inspection, the control means drives the recording means while driving the pump with the second output, The liquid discharge device according to any one of Configurations 1 to 3, comprising determination means for determining the circulation state of the liquid based on the discharge state of the recording means.

[0089] (Configuration 5) The liquid discharge device according to Configuration 4, wherein the determination means determines the circulation state based on the discharge state obtained from an inspection pattern recorded on a recording medium.

[0090] (Configuration 6) The liquid discharge device according to Configuration 5, comprising means for reading the inspection pattern recorded on a recording medium.

[0091] (Configuration 7) The liquid ejecting apparatus according to Configuration 5, comprising means for receiving the result of the user visually observing the inspection pattern recorded on the recording medium.

[0092] (Configuration 8) The liquid ejecting apparatus according to Configuration 4, wherein the determination means determines the circulation state based on the ejection state obtained by detecting the liquid ejected by the recording means with a sensor.

[0093] (Configuration 9) The liquid ejecting apparatus according to Configuration 8, wherein the sensor is an optical sensor.

[0094] (Configuration 10) The liquid ejecting apparatus according to Configuration 4, wherein the determination means determines the circulation state based on the ejection state detected by a temperature detection element provided in the ejection element of the recording means.

[0095] (Configuration 11) In the circulation inspection, the control means drives the recording means while driving the pump with the second output, and further drives the recording means while driving the pump with a third output smaller than the second output. The liquid ejecting apparatus according to Configuration 4.

[0096] (Configuration 12) In the recording operation after the circulation inspection, the control means drives the recording means while driving the pump with an output larger than the first output. The liquid ejecting apparatus according to Configuration 1.

[0097] (Configuration 13) The liquid ejecting apparatus according to Configuration 4, which performs a recovery operation of a circulation path including the discharge port based on the result of the determination by the determination means.

[0098] (Method 1) Recording means for discharging liquid from a discharge port to perform recording, A pump for circulating the liquid supplied to the discharge port, A method for inspecting the circulation of liquid in a liquid ejecting apparatus including: In a circulation inspection for inspecting the circulation state of a liquid, the inspection method is characterized by driving the pump so as to achieve a smaller liquid feed amount than a recording operation for recording an image on a recording medium.

Explanation of Signs

[0099] 10 Recording element substrate 300 Liquid discharge unit 1002 First circulation pump 1100 Recording apparatus

Claims

1. Recording means for performing recording by discharging liquid from a discharge port, A pump for circulating the liquid supplied to the discharge port, Control means for controlling the driving of the recording means and the pump, A liquid discharge device comprising: In the recording operation of recording an image on a recording medium, the control means drives the pump with a first output, and in a circulation inspection for inspecting the circulation state of the liquid, the control means drives the pump with a second output that provides a liquid feed amount smaller than the first output. A liquid discharge device characterized by this.

2. The liquid discharge device according to claim 1, wherein the output for driving the pump is a voltage applied to a motor.

3. The liquid discharge device according to claim 1, wherein the output for driving the pump is at least one of a voltage applied to a piezoelectric element and a frequency applied to the piezoelectric element.

4. In the circulation inspection, the control means drives the recording means while driving the pump with the second output, The liquid discharge device according to claim 1, further comprising determination means for determining the circulation state of the liquid based on the discharge state of the recording means.

5. The liquid discharge device according to claim 4, wherein the determination means determines the circulation state based on the discharge state obtained from an inspection pattern recorded on a recording medium.

6. The liquid discharge device according to claim 5, further comprising means for reading the inspection pattern recorded on a recording medium.

7. The liquid discharge device according to claim 5, further comprising means for receiving the result of a user visually observing the inspection pattern recorded on a recording medium.

8. The liquid discharge device according to claim 4, wherein the determination means determines the circulation state based on the discharge state obtained by detecting the liquid discharged by the recording means with a sensor.

9. The liquid discharge device according to claim 8, wherein the sensor is an optical sensor.

10. The liquid discharge device according to claim 4, wherein the determination means determines the circulation state based on the discharge state detected by a temperature detection element provided in a discharge element of the recording means.

11. In the circulation inspection, the control means drives the recording means while driving the pump with the second output, and further drives the recording means while driving the pump with a third output smaller than the second output. The liquid discharge device according to claim 4.

12. The liquid ejection apparatus according to claim 1, wherein in the recording operation after the circulation inspection, the control means drives the recording means while driving the pump with an output larger than the first output.

13. The liquid ejection apparatus according to claim 4, wherein a recovery operation of a circulation path including the discharge port is performed based on a determination result of the determination means.

14. Recording means for performing recording by ejecting liquid from a discharge port; A pump for circulating the liquid supplied to the discharge port; An inspection method for inspecting the circulation of liquid in a liquid ejection apparatus including: In the circulation inspection for inspecting the circulation state of the liquid, the pump is driven so that the liquid feed amount is smaller than that in the recording operation for recording an image on a recording medium.

Images