Liquid ejection apparatus and circulation state determination method

Abstract

To provide a liquid ejection apparatus and a circulation state determination method capable of helping prevent problems caused by a malfunction.SOLUTION: An ejection state detected after a lapse of a first period of time and an ejection state detected after a lapse of a second period of time shorter than the first period of time are compared with each other to detect whether an ink circulation operation is performed faultily.SELECTED DRAWING: Figure 9

Description

[Technical Field]

[0001] The present invention relates to a liquid ejection device that ejects circulating liquid and a circulation state determination method. [Background technology]

[0002] In a liquid ejection device equipped with a circulation mechanism for circulating liquid such as ink, continued use without proper circulation can cause ink to solidify or settle in the pressure chamber, making it necessary to replace the liquid ejection head, etc. Examples of cases where circulation is not proper include when the circulation mechanism stops working, or when the circulation mechanism is working properly but a blockage occurs in the path along the way. Furthermore, the timing at which circulation stops being proper can vary, from immediately after the circulation mechanism is put into operation to while the liquid is being ejected.

[0003] As such, there are various reasons and timing for circulation to become disrupted, making it difficult to detect the state of circulation in a timely manner with high accuracy.

[0004] Patent Document 1 discloses a method for detecting an abnormality in the circulation flow path by measuring the supply amount and the recovery amount from the pressure difference in the ink flow path and the rotation speed of the circulation pump. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-183806 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the method of Patent Document 1 cannot detect changes in the ejection state caused by a decrease in circulation capacity. Specifically, it cannot detect solidification of liquid components at the ejection ports and the resulting ejection defects. As a result, there is a risk of a decrease in the quality of the output of the liquid ejection device. For example, in the case of an inkjet recording device, there is a risk of a decrease in image quality.

[0007] Therefore, the present invention provides a liquid ejection device and a circulation state determination method that can appropriately detect a change in the ejection state due to a decrease in circulation capacity. [Means for solving the problem]

[0008] Therefore, the liquid ejection device of the present invention is a liquid ejection device comprising an ejection means for ejecting liquid in a pressure chamber from an ejection port by the action of a pressure generating element, a replacement means for replacing the liquid in the pressure chamber, and an ejection state detection means for detecting the ejection state of the liquid from the ejection port, and is characterized by further comprising a malfunction detection means for detecting a malfunction in the operation of the replacement means based on the ejection state of the liquid detected by the ejection state detection means. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a liquid ejection device and a circulation state determination method that can prevent problems caused by breakdowns from occurring. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a perspective view schematically illustrating a liquid ejection device. [Figure 2] FIG. 2 is a block diagram showing the configuration of a printing control system in the liquid ejection apparatus. [Figure 3] FIG. 2 is an exploded perspective view of the liquid ejection head. [Figure 4] FIG. 2 is a diagram showing a flow path configuration of a liquid ejection head. [Figure 5] FIG. 2 is a schematic diagram showing the flow path configuration for one color of the liquid ejection head. [Figure 6] FIG. 4 is a schematic diagram showing the structure of a second pressure adjusting means. [Figure 7] 6A and 6B are diagrams illustrating the flow of ink in the liquid ejection head for each operation of the circulation pump. [Figure 8] FIG. 2 is a schematic diagram showing a discharge speed measuring unit and a part of a liquid discharge head. [Figure 9] 10 is a flowchart showing a process of a circulation operation confirmation sequence. [Figure 10] FIG. 2 is a schematic diagram showing the vicinity of a discharge port. [Figure 11] 10 is a flowchart showing a process of a circulation operation confirmation sequence. [Figure 12] FIG. 4 is a schematic diagram showing a discharge state detection unit. [Figure 13] 10 is a graph showing temperature profiles during normal ejection and non-ejection. [Figure 14] 10 is a flowchart showing a process of a circulation operation confirmation sequence. [Figure 15] 10 is a flowchart of a recovery sequence and a table showing drive frequencies. DETAILED DESCRIPTION OF THE INVENTION

[0011] A first embodiment of the present invention will be described below with reference to the drawings.

[0012] 1 is a perspective view that schematically shows a liquid ejection device 50 that can mount a liquid ejection head 1. The liquid ejection device 50 is a serial type inkjet recording device that performs recording on a recording medium P by ejecting ink as a liquid while scanning the liquid ejection head 1. The liquid ejection head 1 is mounted on a carriage 53, which moves back and forth in the X direction along a guide shaft 51. The recording medium P is transported in the Y direction, which is perpendicular to the X direction, by transport rollers 55, 56, 57, and 58. Ink is supplied to the liquid ejection head 1 from an ink supply tube 59 that is connected to an ink tank (not shown).

[0013] The liquid ejection head 1 includes a circulation unit 54 and an ejection unit 3 (see FIG. 3) described later. The specific configuration will be described later, but the ejection unit 3 is provided with a plurality of ejection ports and energy generating elements (hereinafter referred to as standing thermal resistance elements) that generate ejection energy for ejecting liquid from each of the ejection ports.

[0014] FIG. 2 is a block diagram showing the configuration of a print control system in the liquid ejection device 50. The liquid ejection device 50 is connected to a data supply device such as a host PC 406 via an interface 407. Various data and print-related control signals transmitted from the host PC 406 are input to a print control unit 401 of the liquid ejection device 50. The print control unit 401 includes a memory 403 that stores input image data, multi-value gradation data of intermediate products, and a multi-pass mask pattern, and a CPU 402 (which may be an ASIC) that serves as a control and arithmetic unit. The print control unit 401 controls a motor driver and a liquid ejection head driver 412 (described below) in accordance with the control signals input via the interface 407. The print control unit 401 includes an image processing unit 404 and a data processing unit 405, and performs predetermined image processing on the input image data.

[0015] A conveying motor 413 rotates and drives conveying rollers 55, 56, 57, and 58 that convey the recording medium P. A carriage motor 414 reciprocates a carriage 53 that carries the liquid ejection head 1. A recovery unit motor 415 is a motor mounted in the recovery unit and operates a suction pump and the like. A circulation pump motor 416 drives a circulation motor within the liquid ejection head 1. Motor drivers 408, 409, 410, and 411 drive the conveying motor 413, carriage motor 414, recovery unit motor 415, and circulation pump motor 416, respectively. A liquid ejection head driver 412 drives the liquid ejection head 1, and when multiple liquid ejection heads are mounted, multiple liquid ejection head drivers 412 are provided corresponding to the number of liquid ejection heads.

[0016] The recording control unit 401 controls the light emitting element 202 and the light receiving element 203 in the discharge speed measuring unit 708 .

[0017] 3 is an exploded perspective view of the liquid ejection head 1 of this embodiment. The liquid ejection head 1 includes a circulation unit 54 and an ejection unit 3 for ejecting ink supplied from the circulation unit 54 onto a recording medium P.

[0018] In this embodiment, four colors of ink can be ejected from the liquid ejection head 1. An ink connector insertion port 53a is provided corresponding to each ink supply tube, and an individual supply path is formed.

[0019] The ejection unit 3 includes two ejection modules 100, a first support member 4, a second support member 7, and an electrical wiring member 5. The ejection module 100 of the ejection unit 3 includes a silicon substrate and a plurality of heat generating resistor elements (heaters) provided on one side of the silicon substrate as energy generating elements used to eject ink. Furthermore, in the ejection module 100, electrical wiring for supplying power to each heat generating resistor element is formed on the silicon substrate using a film formation technique. The silicon substrate is formed with a plurality of ink flow paths corresponding to the heat generating resistor elements and a pressure chamber provided with a plurality of ejection ports for ejecting ink. An ink supply port and an ink recovery port for supplying ink to the plurality of ink flow paths are opened on the back surface of the silicon substrate. The energy generating elements are not limited to heat generating resistor elements (heaters), and piezoelectric elements may also be used. Ink is ejected from the ejection ports by the action of the energy generating elements.

[0020] The ejection module 100 is adhesively fixed to a first support member 4 that has an ink supply port and an ink recovery port. A second support member 7 that has an opening is adhesively fixed to the first support member 4. An electrical wiring member 5 is held on the second support member 7 so that it is electrically connected to the recording element substrate. The electrical wiring member 5 applies an electrical signal to the ejection module 100 to eject ink. Power to the electrical wiring member 5 is supplied from an electrical contact substrate 6 provided on the side of the carriage 53.

[0021] FIG. 4 is a cross-sectional view taken along the line IV-IV in FIG. 3, illustrating the flow path configuration of the liquid ejection head 1. The liquid ejection head 1 has an ejection port array consisting of a plurality of ejection ports 13 arranged in the Y-row direction. The liquid ejection head 1 is provided with individual supply flow paths 19 and individual recovery flow paths 18 that circulate ink from each ejection port, and the individual supply flow paths 19 and individual recovery flow paths 18 are provided along the ejection port array. The first support member 4 has a supply flow path 20 formed in one cross section, which is connected to the individual supply flow path 19, and the individual supply flow path 19 is connected to the circulation unit 54 for each color via the supply flow path 20 and a joint member 8. In addition, a recovery flow path 21 is formed in another cross section of the first support member 4, which is connected to the individual recovery flow path 18 and is connected to the circulation unit 54 for each color via the joint member 8.

[0022] The arrows in the figure indicate the direction of ink flow. Ink flows from the circulation unit 54 via the supply port of the joint portion 8 to the supply flow path 20, the individual supply flow path 19, and the ejection port 13. A portion of the ink supplied to the ejection port 13 is ejected from the ejection port 13, and the ink that is not ejected flows in this order through the individual recovery flow path 18, the recovery flow path 21, and the recovery port of the joint portion 8, before returning to the circulation unit 54. The electrical wiring member 5 is supported by a second support member (not shown), and is electrically connected to the ejection module 100. A flow path configuration similar to that described above is provided for the circulation unit 54 of each color.

[0023] FIG. 5 is a schematic diagram showing the flow path configuration for one color of the liquid ejection head 1, and corresponds to the ink circulation unit 54 and ejection module 100 in FIG. 4. The arrows in the figure indicate the direction of ink flow. Ink supplied from an ink tank (not shown) is pressurized by a pressure pump provided in the main body of the liquid ejection device 50, passes through a filter 110 at positive pressure, and is then reduced to a predetermined negative pressure by a first pressure adjustment means 120. The reduced pressure ink is supplied to the ejection module 100 via a supply flow path 130 and supplied to a pressure chamber 123 provided with an ejection port 13. Unejected liquid is supplied via a recovery flow path 140 to a second pressure control chamber 152 provided in a second pressure adjustment means 150. A circulation pump 500 is provided downstream of the second pressure control chamber 152 and returns the ink to the first pressure adjustment means 120. This completes the circulation path. The supply flow path 130 and the recovery flow path 140 correspond to the supply path 20 and the recovery path 21, including the joint portion 8, in FIG. 4.

[0024] The first pressure adjustment means 120 and the second pressure adjustment means 150 are connected via a bypass flow path 160, and ink is supplied from the first pressure adjustment means 120 to the second pressure adjustment means 150. The ink that has flowed into the second pressure control means 150 via the bypass flow path 160 and the ink recovered from the recovery flow path 140 are sucked into the circulation pump 500 by driving the circulation pump 500. The ink that has been sucked into the circulation pump 500 then flows into the first pressure control means 120 again.

[0025] 6(a) to 6(c) are schematic diagrams showing the structure of the second pressure adjustment means (pressure adjustment mechanism) 150 of this embodiment. Note that the first pressure adjustment means 120 shown in FIG. 5 has the same configuration as the second pressure adjustment means 150, and therefore a description of the first pressure adjustment means 120 will be omitted.

[0026] The second pressure adjustment means 150 includes a second valve chamber 151 and a second pressure control chamber 152 that communicates with the second valve chamber 151 via a communication port 191. A valve 190 that can open and close the communication port 191 is provided in the second valve chamber 151, and the valve 190 is biased by a valve spring 200 in a direction that closes the communication port 191. A portion of the valve 190 is formed from an elastic body, and the communication port 191 can be put into a closed state by the valve spring 200 pressing the elastic body portion in the X direction.

[0027] On the other hand, one open surface of the second pressure control chamber 152 is covered with a flexible member 230 and a pressure plate 210, and the pressure plate 210 is configured to be displaceable in the X direction in accordance with the displacement of the flexible member 230. For example, the pressure plate 210 is made of a resin molded part, and the flexible member 230 is made of a resin film, and the pressure plate 210 is heat-welded to the flexible member 230. The flexible member 230 and the pressure plate 210 are urged by a pressure adjustment spring 220 in a direction in which the volume of the second pressure control chamber 152 expands (X direction). When the negative pressure in the second pressure control chamber 152 increases, the pressure plate 210 and the flexible member 230 are displaced in a direction in which the volume decreases (-X direction). Furthermore, when the second pressure control chamber 152 reaches a certain negative pressure, the pressure plate 210 abuts against the tip of the valve 190. When the negative pressure further increases, the valve 190 moves in the −X direction against the biasing force of the valve spring 200, and the communication port 191 opens (see FIG. 6(b)).

[0028] By setting the pressure in second valve chamber 151 higher than the pressure in second pressure control chamber 152, ink flows from second valve chamber 151 to second pressure control chamber 152 when communication port 191 is in the open state. When ink flows from second valve chamber 151 to second pressure control chamber 152, flexible member 230 and pressure plate 210 are displaced in the direction (X direction) in which the volume of second pressure control chamber 152 increases, and communication port 191 is in the closed state (see FIG. 6(c)).

[0029] In this way, when the second pressure control chamber 152 reaches a certain negative pressure or higher, ink flows in from the second valve chamber 151 through the communication port 191, preventing the negative pressure from increasing any further, making it possible to control the pressure inside the second pressure control chamber 152 within a certain range.

[0030] 7(a) to 7(d) are diagrams illustrating the flow of ink in the liquid ejection head 1 during each operation of the circulation pump 500. The liquid ejection head 1 includes a first pressure control chamber 122 communicating with one side of the pressure chamber 123 and a second pressure control chamber 152 communicating with the other side of the pressure chamber 123. Each operation will be described below with reference to FIG. 7(a). FIG. 7(a) schematically illustrates the circulation flow during an ejection operation. During an ejection operation, the circulation pump 500 is turned on, and ink discharged from the first pressure control chamber 122 is supplied to the supply flow channel 130 and the bypass flow channel 160. The ink supplied to the supply flow channel 130 passes through the ejection module 100, which includes the pressure chamber 123, before being supplied to the recovery flow channel 140 and then to the second pressure control chamber 152. Meanwhile, the ink supplied from the first pressure control chamber 122 to the bypass flow channel 160 is supplied to the second pressure control chamber 152 via the second valve chamber 151. The ink supplied to the second pressure control chamber 152 is supplied to the first pressure control chamber 122 via the pump inlet flow path 170, the circulation pump 500, and the pump outlet flow path 180. In this way, the liquid in the pressure chamber 123 is circulated between the outside and the inside by the difference between the negative pressure caused by the first pressure control chamber 122 and the negative pressure caused by the second pressure control chamber 152.

[0031] By setting the control pressure of the first pressure control chamber 122 higher than the control pressure of the second pressure control chamber 152, the ink supplied to the first pressure control chamber 122 is supplied to the ejection module 100 via the supply flow path 130. Thereafter, the ink is circulated in the liquid ejection head 1 to the second pressure control chamber 152 via the recovery flow path 140. The amount of ink passing through the ejection module 100 by circulation is determined by the differential pressure between the control pressures of the first pressure control chamber 122 and the second pressure control chamber 152. Therefore, the control pressures of the first pressure control chamber 122 and the second pressure control chamber 152 are set to an amount of ink that can suppress an increase in viscosity of the ink near the ejection ports in the ejection module 100. In addition, the amount of ink consumed by ejection is replenished by being supplied from an ink tank (not shown) to the first pressure control chamber 122 via the filter 110 and the first valve chamber 121.

[0032] FIG. 7B shows the circulation flow when the discharge operation is completed and the circulation pump 500 is turned off. When the discharge operation is completed and the circulation pump 500 is turned off, the pressures in the first pressure control chamber 122 and the second pressure control chamber 152 remain the same as their respective control pressures during discharge. Therefore, ink continues to circulate as shown in FIG. 7B in accordance with the differential pressure. Specifically, ink is supplied from the first pressure control chamber 122 to the discharge module 100 via the supply flow path 130, and then circulates within the discharge module 100 to the second pressure control chamber 152 via the recovery flow path 140. Furthermore, ink circulates within the bypass flow path 160 from the first pressure control chamber 122 to the second pressure control chamber 152 via the bypass flow path 160 and the second valve chamber 151. The amount of ink that circulated from the first pressure control chamber 122 to the second pressure control chamber 152 is supplied from an ink tank (not shown) to the first pressure control chamber 122 via the filter 110 and the first valve chamber 121. Therefore, the internal volume of the first pressure control chamber 122 is kept constant.

[0033] On the other hand, the pressure in the second pressure control chamber 152 changes over time in response to a change in the volume of ink contained in the second pressure control chamber 152 due to the inflow of ink from the first pressure control chamber 122. Specifically, the pressure changes from the state shown in Fig. 7(b) until the communication port 191 is closed and the second valve chamber 151 and the second pressure control chamber 152 are not in communication with each other, as shown in Fig. 7(c). Thereafter, the pressure plate 210 and the valve 190 are not in contact with each other, and the pressure changes until the pressure plate 210 and the flexible member 230 are displaced to the maximum volume of the second pressure control chamber 152, as shown in Fig. 7(d).

[0034] 7(c), no flow occurs in the bypass flow path 160 from the first pressure control chamber 122 to the second pressure control chamber 152 via the bypass flow path 160 and the second valve chamber 151. Then, ink is supplied from the first pressure control chamber 122 to the ejection module 100 via the supply flow path 130, and then circulates through the ejection module 100 to the second pressure control chamber 152 via the recovery flow path 140. The movement of ink from the first pressure control chamber 122 to the second pressure control chamber 152 occurs according to the pressure difference between the first pressure control chamber 122 and the second pressure control chamber 152, and therefore stops when the pressure in the second pressure control chamber 152 becomes equal to the pressure in the first pressure control chamber 122.

[0035] FIG. 8 is a schematic diagram showing a discharge speed measurement unit 708, which is an ink discharge state detection unit according to this embodiment, and a portion of the liquid discharge head 1. FIG. 8 shows the liquid discharge head 1 as viewed from the X direction. The discharge speed measurement unit 708 includes a light-emitting element 202, a light-receiving element 203, an aperture 205 for the light-emitting element, an aperture 204 for the light-receiving element, and an ink absorber 206 that absorbs discharged ink droplets 207. The light-emitting element 202 and the light-receiving element 203 are positioned so that a light beam 209 intercepts the ink droplets 207 discharged from the liquid discharge head 1. For example, a narrow-directivity infrared LED is used as the light-emitting element 202, and a voltage of 5 V is applied to cause it to emit light. The light-receiving element 203 then reads the amount of light from the light-emitting element 202 incident on the light-receiving element 203.

[0036] When detecting the ejection velocity of the ink droplet 207, a voltage is applied to the light-emitting element 202. The light-receiving element 203 is, for example, a photodiode that exhibits spectral sensitivity characteristics with the highest sensitivity in the infrared region. When detecting the ejection velocity of the ink droplet 207 ejected from the ejection orifice 13, each ejection orifice 13 is sequentially driven (heater is heated), and the ink droplet 207 is ejected from each ejection orifice 13. The ejected ink droplet 207 passes through the light beam 209 (is shielded from light) and lands on the sponge-like ink absorber 206 where it is absorbed. In this configuration, the distance from the ejection orifice 13 to the light beam 209 is defined as L. When the ink droplet 207 passes through the light beam 209, the light-receiving element 203 detects it. The time difference between the rising edge of the ejection signal and the rising edge of the detection signal is defined as T. The ejection velocity v of the ink droplet 207 in this case can be calculated from v = L / T. In this manner, the ejection velocity measurement unit 708 is configured to acquire the ejection velocity of the ink droplet 207.

[0037] If circulation is not performed normally, even if the ejection immediately after the preliminary ejection is performed without any problems, the ejection speed may decrease or the ejection may not be performed after a certain time has passed since the preliminary ejection. It is known that this is because some of the ink components evaporate from the ejection port 13 during the certain time period, causing the ink to thicken.

[0038] Therefore, in this embodiment, the ejection speed is compared between the ejection immediately after the preliminary ejection and the ejection a predetermined time after the preliminary ejection, and the result is used to determine whether circulation is occurring normally (circulation state determination).

[0039] FIG. 9 is a flowchart showing the processing of the circulation operation confirmation (circulation operation detection) sequence in this embodiment. The series of processes shown in FIG. 9 is performed by the CPU 402 of the liquid ejection device 50 expanding and executing program code stored in the memory 403. Alternatively, some or all of the functions of the steps in FIG. 9 may be realized by hardware such as an ASIC or electronic circuit. Note that the symbol "S" in the explanation of each process indicates a step in the flowchart. Below, the processing of the circulation operation confirmation sequence in this embodiment will be explained using the flowchart in FIG. 9.

[0040] When the circulation operation check sequence starts, in S901 the CPU 402 checks whether the circulation pump 500 is operating using the recording control unit 401. If the circulation pump 500 is not operating, the CPU 402 proceeds to S911 and operates the circulation pump 500. If the circulation pump 500 is operating, the CPU 402 proceeds to S902.

[0041] In S902, in order to measure the ejection speed, the recording control unit 401 controls the motor driver 409 to move the carriage 53 carrying the liquid ejection head 1 to the ejection speed measurement position. The CPU 402 then proceeds to S903, where the recording control unit 401 controls the liquid ejection head driver 412 to perform a preliminary ejection to refresh the ink before measuring the ejection speed. This preliminary ejection constitutes the "previous ejection" in the ejection operation of S904. The CPU 402 then proceeds to S904, where it controls the liquid ejection head driver 412 to measure the ejection speed "v0." Specifically, the ejection operation and ejection speed measurement are performed for each of the multiple ejection ports 13 in turn, and the average value of the ejection speeds of the multiple ejection ports is set to "v0." In this way, the ejection speed "v0" is measured immediately after the preliminary ejection.

[0042] In S905, the CPU 402 performs preliminary ejection again, and in S906, the recording control unit 401 waits for a predetermined time. In this embodiment, the wait time is set to 2 seconds. After waiting for the predetermined time, the CPU 402 proceeds to S907, controls the liquid ejection head driver 401 to eject again, and measures the ejection speed "v1". The method for acquiring the ejection speed "v1" is the same as for the ejection speed "v0". In this way, the ejection speed "v1" is measured after a predetermined time has elapsed since the preliminary ejection.

[0043] Next, the CPU 402 proceeds to S908 and determines whether the difference between the discharge speeds "v0" and "v1", "|v0-v1|", is equal to or greater than a threshold (a predetermined value). If the difference between the discharge speeds "v0" and "v1" is equal to or less than the threshold, it is considered that there is not much difference between the discharge speeds "v0" and "v1", and the process proceeds to S910, where it is determined that the circulation mechanism is operating without problems, and the process ends. On the other hand, if the difference between the discharge speeds "v0" and "v1" is equal to or greater than the threshold, it is considered that the discharge speed "v1" is decreasing because the circulation is not normal, and the process proceeds to S909, where it is determined that there is a malfunction, and the process ends.

[0044] In this manner, in this embodiment, by measuring the discharge speed for each discharge port, the state of the circulation operation can be detected with high accuracy.

[0045] In this embodiment, the ejection speed v0 immediately after the preliminary ejection is about 10 m / sec, and if the circulation mechanism fails and circulation is not performed, two seconds after the preliminary ejection, no ejection occurs (v1 = 0 m / sec), and |v0 - v1| = 10 m / sec. In this embodiment, the threshold value is set to 5 m / sec, and a malfunction of the circulation mechanism is determined before complete ejection failure occurs.

[0046] If it is determined that the circulation mechanism is faulty, an error is displayed on the display panel of the main body of the liquid ejection device 50. This may also be an audible warning. Note that although it is preferable to measure the ejection speed "v0" from preliminary ejection to continuous ejection, it may also be measured after a waiting time from preliminary ejection as long as this is shorter than the waiting time when measuring the ejection speed "v1". Also, in this embodiment, the waiting time before measuring the ejection speed "v1" is set to 2 seconds, but it does not have to be 2 seconds as long as the ejection speed decreases or ejection stops due to evaporation from the ejection port.

[0047] In this embodiment, the above-mentioned circulation operation confirmation sequence is performed when the circulation mechanism is operated to determine whether the circulation is good or bad, and in the event of a bad circulation, problems such as poor image quality or sticking are prevented from occurring.

[0048] In this way, the ejection state after a first time has elapsed since the previous ejection, such as a preliminary ejection, is compared with the ejection state after a second time has elapsed, which is shorter than the first time, to detect malfunction of the ink circulation. This makes it possible to provide a liquid ejection device and a circulation state determination method that can appropriately detect a decrease in circulation capacity.

[0049] (Second embodiment) The second embodiment of the present invention will be described below with reference to the drawings. Note that the basic configuration of this embodiment is the same as that of the first embodiment, so only the characteristic configuration will be described below.

[0050] 10 is a schematic diagram showing the vicinity of the ejection port in this embodiment. In this embodiment, a heat generating element (pressure generating element) 304 that does not contribute to the ejection of ink is provided in a flow path 303 connected to a pressure chamber 123. Note that a piezoelectric element may also be used for the heat generating element 304.

[0051] A flow path 303 is connected to each pressure chamber 123, and ink is supplied to the pressure chamber 123 from the common liquid chamber 305 and the flow path 303. When ejecting ink droplets, a voltage is applied to the heating resistor element 301 to cause bubbles to form in the ink near the heating resistor element 301, and the pressure generated causes the ink in the pressure chamber 123 to be ejected from an ejection port (not shown). After the bubbles form, the bubbles disappear, and ink is supplied to the pressure chamber 123 from the flow path 303 and the common liquid chamber 305.

[0052] The heating element 304 is used to replace the ink in the pressure chamber 123 when ink is not being ejected. Applying a voltage to the heating element 304 causes bubbles to form, and the pressure causes the ink in the flow path 303 to move, pushing out the ink in the pressure chamber 123 and replacing it with the ink in the flow path 303. By repeating this operation at appropriate times, new ink can be supplied to the pressure chamber 123.

[0053] (Third embodiment) The third embodiment of the present invention will be described below with reference to the drawings. Note that the basic configuration of this embodiment is the same as that of the first embodiment, so only the characteristic configuration will be described below.

[0054] Fig. 11 is a flowchart showing the processing of the circulation operation confirmation sequence in this embodiment. The series of processing shown in Fig. 11 is performed by the CPU 402 of the liquid ejection device 50 expanding and executing program code stored in the memory 403. Alternatively, some or all of the functions of the steps in Fig. 11 may be realized by hardware such as an ASIC or electronic circuit. Note that the symbol "S" in the explanation of each process indicates that it is a step in the flowchart. The processing from S1101 to S1107 is the same as the processing in the first embodiment, so explanation will be omitted.

[0055] In S1108, the CPU 402 compares the rate of change in the ejection speed calculated by the recording control unit by dividing the difference between the ejection speed "v0" and the ejection speed "v1", "|v0-v1|", by the ejection speed "v0", with a threshold value to determine whether the circulation operation is working properly. If the calculated rate of change is below the threshold, it is considered that there is not much difference between the ejection speed "v0" and the ejection speed "v1", and the CPU 402 proceeds to S1110, determines that the circulation mechanism is operating without problems, and ends the process. On the other hand, if the calculated rate of change is above the threshold, it is considered that there is some problem with the circulation, causing the ejection speed "v1" to decrease, and the CPU 402 proceeds to S1109, determines that the circulation mechanism is malfunctioning, and ends the process.

[0056] (Fourth embodiment) A fourth embodiment of the present invention will be described below with reference to the drawings. The basic configuration of this embodiment is the same as that of the first embodiment, so only the characteristic configuration will be described below. Note that this embodiment is limited to a heat generating resistance element (heater), and a piezoelectric element cannot be used.

[0057] 12 is a schematic diagram showing the ejection state detection means in this embodiment. In this embodiment, a non-ejection inspection is performed using a temperature sensor 308. Whether poor circulation has occurred is determined based on the results of the non-ejection inspection. The method of non-ejection inspection in this embodiment will be described below.

[0058] A voltage is applied to the heating resistor elements 301 to generate bubbles 307, which then eject ink droplets 207 from the ejection ports 13. A temperature sensor 308 is installed below each heating resistor element 301. The temperature sensor 308 measures the temperature in the vicinity of the heating resistor element 301 during ejection.

[0059] 13 is a graph showing the temperature profile (temperature change) obtained by the temperature sensor 308 when a drive voltage is applied to the heating resistor element 301 during normal ejection and when no ejection occurs. The horizontal axis represents time, and the vertical axis represents temperature. When ink is ejected, a voltage is applied to the heating resistor element 301, causing the temperature in the vicinity of the heating resistor element 301 to rise suddenly. After that, if ink is ejected normally, the ejected ink droplets 207 carry heat and ink that has not risen in temperature is supplied, causing the temperature in the vicinity of the heating resistor element 301 to drop rapidly. On the other hand, if ink is not ejected, the ink droplets 207 are not ejected and ink that has not risen in temperature is not supplied, so the temperature in the vicinity of the heating resistor element 301 drops gradually rather than suddenly.

[0060] As shown in the temperature profile of Figure 13, when the ejection operation is performed normally, the temperature detected by the temperature sensor 308 reaches a maximum temperature and then a characteristic point where the temperature drops suddenly appears (solid line graph). In contrast, when ejection is not performed, no characteristic point where the temperature drops suddenly appears (dotted line graph). In this way, by detecting the presence or absence of a characteristic point in the temperature profile, it is possible to determine whether or not the ink has been ejected normally.

[0061] FIG. 14 is a flowchart showing the processing of the circulation operation confirmation sequence in this embodiment. The series of processes shown in FIG. 14 is performed by the CPU 402 of the liquid ejection device 50 expanding and executing program code stored in the memory 403. Alternatively, some or all of the functions of the steps in FIG. 14 may be realized by hardware such as an ASIC or electronic circuit. Note that the symbol "S" in the description of each process indicates that it is a step in the flowchart. Below, the processing of the circulation operation confirmation sequence in this embodiment will be described using the flowchart in FIG. 14. The processing from S1401 to S1403 is the same as the processing in the first embodiment, so description thereof will be omitted.

[0062] In S1404, the CPU 402 performs ejection and acquires the number of non-ejecting nozzles. Specifically, for each of the multiple ejection ports 13, the presence or absence of the characteristic points described in FIG. 14 is detected, and the number of ejection defects is set to "n0." In this way, the number of ejection defects (number of ejection ports with ejection defects) "n0" is measured immediately after the preliminary ejection.

[0063] In S1405, the CPU 402 performs preliminary ejection again, and in S1406, the recording control unit 401 waits for a predetermined time. In this embodiment, the wait time is 2 seconds. After waiting for the predetermined time, the CPU 402 proceeds to S1407, controls the liquid ejection head driver 401 to eject again, and measures the number of defective ejections "n1". The method for acquiring the number of defective ejections "n1" is the same as for the number of defective ejections "n0". In this way, the number of defective ejections "n1" is measured after a predetermined time has elapsed since the preliminary ejection.

[0064] Next, the CPU 402 proceeds to S1408 and determines whether "n1-n0", which is the difference between the number of defective discharges "n0" and the number of defective discharges "n1", is 1 or more. If the difference between the number of defective discharges "n0" and the number of defective discharges "n1" is 0, the CPU 402 proceeds to S1410 and determines that the circulation mechanism is operating without problems, and ends the process. On the other hand, if the difference between the number of defective discharges "n0" and the number of defective discharges "n1" is 1 or more, the circulation is not normal, so the CPU 402 proceeds to S1409 and determines that there is an operational malfunction, and ends the process.

[0065] In this way, a non-ejection inspection is performed using the temperature sensor 308, and if the number of non-ejections increases after waiting for a predetermined time, it is determined that poor circulation has occurred. This makes it possible to provide a liquid ejection device that can appropriately detect a decrease in circulation capacity.

[0066] (Fifth embodiment) A fifth embodiment of the present invention will be described below with reference to the drawings. The basic configuration of this embodiment is the same as that of the first embodiment, so only the characteristic configuration will be described below. In this embodiment, a recovery sequence to be performed when a "fail" is determined in the circulation operation confirmation sequence will be described.

[0067] FIG. 15(a) is a flowchart showing the processing of the circulation failure recovery sequence in this embodiment. FIG. 15(b) is a table showing the drive frequency of the circulation pump. The series of processing shown in FIG. 15(a) is performed by the CPU 402 of the liquid ejection device 50 expanding and executing program code stored in the memory 403. Alternatively, some or all of the functions of the steps in FIG. 15(a) may be realized by hardware such as an ASIC or electronic circuit. Note that the symbol "S" in the explanation of each process indicates a step in the flowchart.

[0068] If the circulation operation check sequence determines that the circulation pump 500 is malfunctioning, the CPU 402 drives the circulation pump 500 at S1501, increasing the drive frequency by one step from the reference 20 kHz to 30 kHz. In this embodiment, one step is 10 kHz (see FIG. 15(b)), and the frequency is increased by 10 kHz from the reference 20 kHz. Increasing the drive frequency of the circulation pump 500 increases the circulation speed of the liquid. Thereafter, in S1502, the CPU 402 performs the circulation operation check sequence described in the above embodiment. In S1503, the CPU 402 determines whether the circulation operation check sequence is malfunctioning. If the circulation operation check sequence is malfunctioning, the CPU 402 proceeds to S1505. If the circulation operation check sequence is not malfunctioning, the CPU 402 proceeds to S1504.

[0069] When the process proceeds to S1505, it is determined whether the drive frequency of the circulation pump 500 is at the upper limit. If it is not at the upper limit, the process returns to S1501 and repeats. If it is at the upper limit, the CPU 402 proceeds to S1506, determines that there is a malfunction, displays an error on the panel of the main body, and ends the process. In this embodiment, the upper limit of the drive frequency is 60 kHz (see FIG. 15(b)). When the process proceeds from S1503 to S1504, 30 kHz is set as the condition for the drive frequency of the circulation pump 500 thereafter, and the process ends.

[0070] In this way, when the malfunction of the circulation mechanism is at a level that can be recovered from, the configuration of this embodiment can prolong the life of the malfunctioning circulation mechanism.

[0071] The disclosure of this embodiment includes the following configurations and methods.

[0072] (Configuration 1) a discharge means for discharging the liquid in the pressure chamber from the discharge port by driving the pressure generating element; a circulation means for circulating the liquid in the pressure chamber between the pressure chamber and the outside; a discharge state detection means for detecting a discharge state of the liquid from the discharge port; a circulation state determination means for determining a state of circulation by the circulation means; A liquid ejection device comprising: A liquid ejection device characterized in that the circulation state determination means determines the circulation state based on the difference between the result detected by the ejection state detection means after a first time has elapsed since the previous ejection operation by the ejection means and the result detected by the ejection state detection means after a second time, which is longer than the first time, has elapsed since the previous ejection operation by the ejection means.

[0073] (Configuration 2) the ejection state detection means detects the ejection speed of the liquid ejected from the ejection port, The liquid ejection device according to configuration 1, wherein the circulation state determination means determines that the circulation state is poor when the difference between the ejection speed after the first time has elapsed since the previous ejection operation by the ejection means and the ejection speed after the second time has elapsed since the previous ejection operation by the ejection means is equal to or greater than a predetermined threshold value.

[0074] (Configuration 3) the ejection state detection means detects the ejection speed of the liquid ejected from the ejection port, The liquid ejection device according to configuration 1, wherein the circulation state determination means determines that the circulation state is poor when the rate of change between the ejection speed after the first time has elapsed since the previous ejection operation by the ejection means and the ejection speed after the second time has elapsed since the previous ejection operation by the ejection means is equal to or greater than a predetermined threshold value.

[0075] (Configuration 4) the ejection state detection means detects the number of non-ejecting ejection ports among the plurality of ejection ports, The liquid ejection device according to configuration 1, wherein the circulation state determination means determines that the circulation state is poor if the number of non-ejecting outlets after the second time has elapsed since the previous ejection operation by the ejection means is greater than the number of non-ejecting outlets after the first time has elapsed since the previous ejection operation by the ejection means.

[0076] (Configuration 5) the pressure generating element is a heat generating resistor element, 5. The liquid ejection device according to configuration 4, wherein the ejection state detection means detects whether the ejection is good or bad based on a temperature change of the heat generating resistor element that accompanies an ejection operation.

[0077] (Configuration 6) a first pressure-generating element provided in the pressure chamber, and a second pressure-generating element provided in a flow path communicating with the pressure chamber; 6. The liquid ejection device according to any one of configurations 1 to 5, wherein the circulation means circulates the liquid in the pressure chamber between the outside and the pressure chamber by a second pressure generating element provided in a flow path communicating with the pressure chamber.

[0078] (Configuration 7) A liquid ejection device described in any one of configurations 1 to 5, wherein the circulation means has a first pressure adjustment mechanism communicating with one side of the pressure chamber and a second pressure adjustment mechanism communicating with the other side of the pressure chamber, and circulates the liquid in the pressure chamber by the difference between the negative pressure caused by the first pressure adjustment mechanism and the negative pressure caused by the second pressure adjustment mechanism.

[0079] (Configuration 8) The liquid ejection device according to configuration 6, wherein the second pressure generating element in the flow path is a heater made of a heat generating element or a piezoelectric element.

[0080] (Configuration 9) 9. The liquid ejection device according to any one of configurations 1 to 8, wherein an error is displayed when the circulation state determination means determines that the circulation state is poor.

[0081] (Configuration 10) 10. The liquid ejection device according to configuration 9, wherein the circulation means increases the circulation speed when the circulation state determination means determines that the circulation state is poor.

[0082] (Configuration 11) 11. The liquid ejection device according to configuration 10, wherein the circulation state determination means determines that the circulation state is poor and displays an error when the circulation speed is at the upper limit.

[0083] (Method 1) a discharge means for discharging the liquid in the pressure chamber from the discharge port by driving the pressure generating element; a circulation means for circulating the liquid in the pressure chamber between the pressure chamber and the outside; a discharge state detection means for detecting a discharge state of the liquid from the discharge port; A circulation state determination method for determining a circulation state by the circulation means in a liquid ejection device comprising: a first detection step of causing the discharge state detection means to detect a discharge state of the liquid from the discharge port after a first time has elapsed since the previous discharge operation by the discharge means; a second detection step of causing the ejection state detection means to detect the ejection state of the liquid from the ejection port after a second time period longer than the first time period has elapsed since the previous ejection operation by the ejection means; and determining the state of circulation based on the difference between the results of the first detection step and the second detection step. [Explanation of symbols]

[0084] 1 Liquid ejection head 50 Liquid dispensing device 123 Pressure Chamber 301 Heating resistance element 304 Heating element 402 CPU 500 Circulation Pump

Claims

1. a discharge means for discharging the liquid in the pressure chamber from the discharge port by driving the pressure generating element; a circulation means for circulating the liquid in the pressure chamber between the pressure chamber and the outside; a discharge state detection means for detecting a discharge state of the liquid from the discharge port; a circulation state determination means for determining a state of circulation by the circulation means; A liquid ejection device comprising: A liquid ejection device characterized in that the circulation state determination means determines the circulation state based on the difference between the result detected by the ejection state detection means after a first time has elapsed since the previous ejection operation by the ejection means and the result detected by the ejection state detection means after a second time, which is longer than the first time, has elapsed since the previous ejection operation by the ejection means.

2. the ejection state detection means detects the ejection speed of the liquid ejected from the ejection port, The liquid ejection device described in claim 1, wherein the circulation state determination means determines that the circulation state is poor when the difference between the ejection speed after the first time has elapsed since the previous ejection operation by the ejection means and the ejection speed after the second time has elapsed since the previous ejection operation by the ejection means is greater than or equal to a predetermined threshold value.

3. the ejection state detection means detects the ejection speed of the liquid ejected from the ejection port, The liquid ejection device described in claim 1, wherein the circulation state determination means determines that the circulation state is poor when the rate of change between the ejection speed after the first time has elapsed since the previous ejection operation by the ejection means and the ejection speed after the second time has elapsed since the previous ejection operation by the ejection means is greater than or equal to a predetermined threshold value.

4. the ejection state detection means detects the number of non-ejecting ejection ports among the plurality of ejection ports, The liquid ejection device described in claim 1, wherein the circulation state determination means determines that the circulation state is poor when the number of non-ejecting ejection ports after the second time has elapsed since the previous ejection operation by the ejection means is greater than the number of non-ejecting ejection ports after the first time has elapsed since the previous ejection operation by the ejection means.

5. the pressure generating element is a heat generating resistor element, 5. The liquid ejection apparatus according to claim 4, wherein the ejection state detection means detects whether the ejection is good or bad based on a change in temperature of the heat generating resistor element that accompanies an ejection operation.

6. a first pressure-generating element provided in the pressure chamber, and a second pressure-generating element provided in a flow path communicating with the pressure chamber; 2. The liquid ejection apparatus according to claim 1, wherein the circulation means circulates the liquid in the pressure chamber between the pressure chamber and the outside by means of a second pressure generating element provided in a flow path communicating with the pressure chamber.

7. 2. The liquid ejection device according to claim 1, wherein the circulation means has a first pressure adjustment mechanism communicating with one side of the pressure chamber and a second pressure adjustment mechanism communicating with the other side of the pressure chamber, and circulates the liquid in the pressure chamber by the difference between the negative pressure caused by the first pressure adjustment mechanism and the negative pressure caused by the second pressure adjustment mechanism.

8. 7. The liquid ejection device according to claim 6, wherein the second pressure generating element in the flow path is a heater or a piezoelectric element made of a heat generating element.

9. The liquid ejection device according to claim 1 , wherein an error is displayed when the circulation state determining means determines that the circulation state is poor.

10. The liquid ejection device according to claim 9, wherein the circulation means increases the circulation speed when the circulation state determination means determines that the circulation state is poor.

11. 11. The liquid ejection device according to claim 10, wherein the circulation state determination means determines that the circulation state is poor and displays an error when the circulation speed is at the upper limit.

12. a discharge means for discharging the liquid in the pressure chamber from the discharge port by driving the pressure generating element; a circulation means for circulating the liquid in the pressure chamber between the pressure chamber and the outside; a discharge state detection means for detecting a discharge state of the liquid from the discharge port; A circulation state determination method for determining a circulation state by the circulation means in a liquid ejection device comprising: a first detection step of causing the discharge state detection means to detect a discharge state of the liquid from the discharge port after a first time has elapsed since the previous discharge operation by the discharge means; a second detection step of causing the ejection state detection means to detect the ejection state of the liquid from the ejection port after a second time period longer than the first time period has elapsed since the previous ejection operation by the ejection means; and determining the state of the circulation based on the difference between the results of the first detection step and the second detection step.

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