JP2012232447A - Inkjet recording apparatus and method for recovering the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inkjet recording apparatus in which clogging of a filter can be treated efficiently.SOLUTION: The inkjet recording apparatus includes an ink tank 40, a recording head 13, a feed passage 52, a filter 42, a first pressure measuring unit 44, a second pressure measuring unit 45, a heater 43, a pump 50, and controlling unit 46. The controlling unit 46 causes the pump 50 to perform a first sucking processing and measure pressure drop Poe at the first sucking processing when the recording head 13 does not perform recording. When the pressure drop Poe exceeds an admissible value, the pump causes the heater 43 to heat ink. Thereafter, the controlling unit measures pressure drop again, and when the re-measured pressure drop Pts satisfies Pts>Pob (wherein Pob=Poe×ηt/ηo, ηt denotes ink viscosity after heating and ηo denotes ink viscosity before heating), the controlling unit causes the pump 50 to perform a second sucking processing in which the ink is sucked at negative pressure larger than that of the first sucking processing.

Description

  The present invention relates to an inkjet recording apparatus in which a filter is provided in the middle of a supply path for supplying ink from an ink tank to a recording head, and a method for recovering the inkjet recording apparatus.

In an inkjet recording apparatus including a recording head in which a plurality of ejection ports (hereinafter also referred to as nozzles) that eject ink are formed, ejection failure may occur due to clogging of the ejection ports. The causes of the clogging of the discharge outlet include the following.
(1) When a small piece of a porous member used as an ink holding member or an ink tank containing ink is replaced, fine dust or the like is mixed in the ink supply path.
(2) Dust generated from the recording medium or the like adheres directly to the discharge port. Alternatively, the ink solvent adhering to the vicinity of the ejection port that has not been used for a long time evaporates and the viscosity of the ink increases.
(3) Fine bubbles stay in the discharge port due to precipitation of dissolved gas in the ink or intrusion from outside the discharge port.

  As a method of removing dust in the ink along the path from the ink tank to the ejection port, there is a method of filtering the ink by disposing a filter in the middle of the ink supply path. As a method for eliminating clogging of the discharge port due to bubbles in the liquid chamber, there is a method of sucking out the bubbles together with the ink to the outside of the recording head by sucking ink from the discharge port.

  When a filter is used, bubbles mixed in the ink supply path gather on the filter along the ink flow from the ink tank toward the recording head. The bubbles are, for example, air that has entered from the outside when the ink tank is replaced, or dissolved air in the ink. Air bubbles collected in the filter make the ink supply unstable by obstructing the flow of ink or intermittently closing the filter. In view of this, an ink jet recording apparatus capable of detecting clogging of a filter provided in the middle of an ink supply path is disclosed in Patent Document 1. In this ink jet recording apparatus, pressure sensors are arranged on the upstream side and the downstream side of the filter, respectively, and it is determined that the filter is clogged when the pressure value difference between the pressure sensors is large.

JP 05-116337 A

  However, the ink jet recording apparatus disclosed in Patent Document 1 cannot determine whether the filter is clogged with dust or bubbles. Therefore, when the cause of clogging of the filter is dust, even if a suction operation for removing bubbles is performed, the solid dust cannot pass through the filter and cannot be removed. As a result, the suction operation is wasted and the efficiency is poor.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an ink jet recording apparatus capable of efficiently dealing with filter clogging and a method for recovering the ink jet recording apparatus.

  In order to achieve the above object, an ink jet recording apparatus of the present invention includes an ink tank capable of storing ink, a recording head that performs a recording operation for discharging the ink onto a recording medium, and the ink from the ink tank to the recording head. Supply path, a filter provided in the middle of the supply path, a first pressure measuring unit for measuring the pressure of the ink before passing through the filter in the supply path, and the supply path A second pressure measuring unit that measures the pressure of the ink after passing through the filter, a heater provided on the upstream side of the filter, a pump communicating with the recording head, the recording head, the first 1 pressure measurement unit, the second pressure measurement unit, the heater, and a control unit connected to the pump, wherein the control unit is the recording head When the recording operation is not being performed, the pump is caused to perform a first suction operation for sucking ink flowing through the supply path from the recording head, and the first pressure measurement unit in the first suction operation is performed. The pressure loss obtained by subtracting the measurement value of the second pressure measurement unit from the measurement value is measured, and when the measured pressure loss Poe exceeds a predetermined allowable value, the heater is heated with the ink, Thereafter, the pressure loss is measured again, and the measured pressure loss Pts satisfies Pts> Pob (where Pob = Poe × ηt / ηo, ηt: ink viscosity after heating, ηo: ink viscosity before heating) The pump is caused to perform a second suction operation for sucking the ink at a negative pressure larger than that of the first suction operation.

  In order to achieve the above object, an ink jet recording apparatus recovery method according to the present invention includes an ink tank capable of storing ink, a recording head that performs a recording operation for discharging the ink onto a recording medium, and the ink tank to the recording head. In a recovery method of an ink jet recording apparatus, comprising: a supply path for supplying the ink to the filter; and a filter provided in the middle of the supply path, from the recording head when the recording head is not performing the recording operation The first step of performing a first suction operation for sucking ink flowing through the supply path, the second step of measuring the pressure loss of the filter in the first suction operation, and the second step A third step of heating the ink upstream of the filter when the pressure loss Poe exceeds a predetermined allowable value. Then, after the third step, the fourth step of measuring the pressure loss again, and the pressure loss Pts measured in the fourth step is Pts> Pob (where Pob = Poe × ηt / ηo, a second step of performing a second suction operation for sucking the ink with a negative pressure larger than that of the first suction operation when ηt: ink viscosity after heating and ηo: ink viscosity before heating); It is characterized by having.

  According to the present invention, the bubbles expand unlike the dust by heating the ink. Therefore, by measuring the pressure loss before and after heating the ink, it is possible to specify that the cause of the filter clogging is air bubbles. Since the second suction operation is performed after it is determined that the cause of the filter clogging is air bubbles, if the cause of the filter clogging is dust, the second suction operation is not performed. Can be transferred to the treatment to remove Therefore, it becomes possible to cope with clogging of the filter efficiently.

1 is a front view showing an internal configuration of an ink jet recording apparatus according to a first embodiment of the present invention. FIG. 2 is a diagram illustrating a flow path of the ink jet recording apparatus according to the first embodiment of the present invention and constituent elements attached thereto. It is the figure which showed the change in the filter box accompanying the heating in the inkjet recording device shown in FIG. It is a graph which shows the relationship between the pressure loss and the ink temperature of each state shown in FIG. It is a flowchart which shows the procedure of the foam removal operation | movement of 1st Embodiment. It is the figure which showed the change in the filter box accompanying the heating in the inkjet recording device of 2nd Embodiment. It is a figure which shows the flow path of the inkjet recording device in the 3rd Embodiment of this invention, and the component incidental to it. It is a graph which shows the relationship between the elapsed time after starting sucking ink, and the measured value of a pressure measurement part.

(First embodiment)
FIG. 1 is a front view showing an internal configuration of the ink jet recording apparatus according to the first embodiment of the present invention. In the ink jet recording apparatus of the present embodiment, the housing 4 is supported on the upper ends of the gantry 2A and the gantry 2B that are arranged to face each other. In the housing 4, a support plate 20A and a support plate 20B are provided opposite to each other with a predetermined interval. A carriage rail member 16 that slidably supports the carriage 14 is disposed between the support plate 20A and the support plate 20B. The carriage rail member 16 is supported by the support plate 20A and the support plate 20B so that the central axis thereof is substantially parallel to the central axis of the conveyance roller 34, that is, substantially orthogonal to the conveyance direction of the recording medium 36. . Both ends of the carriage rail member 16 are fixed to the support plates 20A and 20B, respectively. Between the carriage rail member 16 and the conveyance roller 34, a conveyance path through which the recording medium 36 is carried toward the recording head 13 is formed.

  A recording head 13 is mounted on the upper surface side of the carriage 14. For example, ink such as yellow, magenta, cyan, and black is supplied to the recording head 13 through a tube (not shown) from an ink tank 40 that can store these inks. The recording operation in which the recording head 13 ejects ink onto the recording medium 36 is controlled by a drive pulse signal corresponding to image data formed on the recording surface of the recording medium 36. The carriage 14 reciprocates corresponding to the recording operation of the recording head 13.

  The carriage 14 is provided with a support shaft (not shown), and a roller 26 is rotatably supported at one end of the support shaft. The roller 26 is engaged with an inner peripheral portion of the roller guide rail 22 having a rectangular cross-sectional shape with a predetermined gap. Thus, the carriage 14 is guided by the carriage rail member 16 and the roller guide rail 22 so as to be movable. As shown in FIG. 1, a standby area 8 of the recording head 13 is provided at a position away from the end of the recording medium 36 toward the support plate 20A.

  A recovery processing unit 6 that performs recovery processing of the recording head 13 is provided at a predetermined reference position (home position) in the standby area unit 8. The recovery processing unit 6 is arranged to face the discharge port surface of the recording head 13 and has a structure including a capping mechanism that selectively covers and sucks the discharge port surface. The recovery processing unit 6 is controlled based on a drive control signal supplied at a predetermined timing from a recovery processing drive control unit (not shown).

  FIG. 2 is a diagram showing a flow path of the ink jet recording apparatus shown in FIG. 1 and components attached thereto. FIG. 2 shows a configuration for one color. In the ink jet recording apparatus of the present embodiment, the ink stored in the ink tank 40 having the valve 53 and the atmosphere communication port 54 is supplied to the recording head 13 through the supply path 52. When the ink is initially filled in the recording head 13, the suction cap 49 is brought into contact with the ejection port surface of the recording head 13, the valve 53 is opened, the atmosphere communication port 54 is opened, and the pump 50 is driven. The ink sucked by the pump 50 is discharged to the waste liquid tank 56 through the flow path 55. After the initial filling, every time ink is ejected, the ink is refilled by the capillary force of the nozzles of the recording head 13. A filter box 41 is provided in the middle of the supply path 52. The filter box 41 includes a filter 42 for filtering ink and a heater 43 for heating ink. Ink passes through the filter 42 to prevent dust from entering the recording head 13. In the ink jet recording apparatus of the present embodiment, when removing ink or dust adhering to the nozzles of the recording head 13 or bubbles remaining in the liquid chamber 48 provided on the upstream side of the filter 42, the suction cap 49 and the pump 50 are removed. Operate to suck ink.

  The ink jet recording apparatus of the present embodiment further includes a pressure measurement unit 44 (first pressure measurement unit), a pressure measurement unit 45 (second pressure measurement unit), a control unit 46, a temperature measurement unit 47, Have The pressure measurement unit 44 measures the pressure of the ink before passing through the filter 42 in the supply path 52. The pressure measurement unit 45 measures the pressure of the ink after passing through the filter 43 in the supply path 52. By measuring a value obtained by subtracting the measurement value of the pressure measurement unit 45 from the measurement value of the pressure measurement unit 44, the pressure loss through the filter 42 can be measured. The temperature measurement unit 47 measures the temperature of the ink in the liquid chamber 48. The control unit 46 includes a CPU (Central Processing Unit) and a memory. The control unit 46 is connected to measurement elements (pressure measurement units 44 and 45, temperature measurement unit 47) and drive elements (recording head 13, pump 50, heater 43). The control unit 46 receives a signal from the measurement element and outputs a control signal to the drive element.

  FIG. 3 is a diagram showing changes in the filter box 41 accompanying heating. FIG. 3A shows a state in which only the bubbles 60 remain in the liquid chamber 48. FIG. 3B shows a state where bubbles 60 and dust 61 are mixed and stay in the liquid chamber 48. FIG. 3C shows a state where only the dust 61 stays in the liquid chamber 48.

  When the bubble 60 stays in the liquid chamber 48, when the heater 43 generates heat, the bubble 60 expands (see FIGS. 3A and 3B). Due to the expansion of the bubbles 60, the area that blocks the filter 42 increases. Therefore, the flow path resistance of the filter 42 increases. When only the dust 61 stays in the liquid chamber 48, the area that blocks the filter 42 is unchanged even if the heater 43 generates heat. Therefore, the flow path resistance of the filter 42 does not change (see FIG. 3C).

  FIG. 4 is a graph showing the relationship between the pressure loss (difference between measured values of the pressure measuring units 44 and 45) and the ink temperature in each state shown in FIG. (A)-(c) in a graph respond | corresponds to each state of Fig.3 (a)-(c).

  In general, when an ink is heated, its viscosity decreases, so that the pressure loss after heating is lower than the pressure loss before heating. On the other hand, as described above, the amount of increase in pressure loss due to temperature rise increases as the ratio of the bubbles 60 out of the accumulated matter in the liquid chamber 48 increases. Therefore, if the pressure loss in the filter 42 at the temperature To is Poe, the graph of each state shown in FIG. 3 is as shown in FIG. In the state shown in FIG. 3C, there is no bubble expansion factor, and only the viscosity factor affects the pressure loss. Therefore, when the ink temperature is heated from To to Tt, the pressure loss becomes Poe × ηt / ηo (ηo: ink viscosity at temperature To before heating, ηt: ink viscosity at temperature Tt after heating). In the state shown in FIGS. 3A and 3B, there is a bubble expansion factor as an effect on the pressure loss. For this reason, the pressure loss Poe at the temperature Tt is larger than the state shown in FIG. 3C (see FIG. 4). In FIG. 4, the pressure loss Poa indicates the pressure loss when nothing stays in the liquid chamber 48 at the temperature To.

  Next, the operation of the ink jet recording apparatus of this embodiment will be described. Hereinafter, a bubble removal operation for removing bubbles collected in the liquid chamber 48 will be described. FIG. 5 is a flowchart showing the procedure of the bubble removal operation of the present embodiment. This bubble removal operation is performed based on the control of the control unit 46.

  In the present embodiment, the start timing of the bubble removal operation is determined based on the amount of ink discharged from the recording head 13, that is, dot count data. The start timing of the bubble removal operation may be any physical quantity that is correlated with the amount of accumulated matter in the filter 42, such as the cumulative driving time of the recording head 13 and the number of printed sheets.

  When the ejection amount from the recording head 13 reaches a predetermined amount, the recording head 13 stops the ejection operation, and the carriage 14 moves to the position of the recovery processing unit 6. Next, the suction cap 49, which is one of the components of the recovery processing unit 6, closes the ejection port surface of the recording head 13, and the pump 50 is driven at a predetermined rotational speed (first suction operation). Thereby, the ink flowing through the supply path 52 is sucked from the recording head 13 (step S1). In step S1, the valve 53 is opened and the atmosphere communication port 54 is opened to the atmosphere. During the ink suction, the temperature measuring unit 47 measures the ink temperature To in the liquid chamber 48 (step 2). At this time, the control unit 46 monitors the pressure loss obtained by subtracting the measurement value of the pressure measurement unit 45 from the measurement value of the pressure measurement unit 44, and sets the value when the pressure loss becomes constant as Poe (step S3). ). FIG. 8 is a graph showing the relationship between the elapsed time from the start of ink suction and the measured values of the pressure measuring units 44 and 45. As shown in FIG. 8, in order to determine that the differential pressure difference between the measured value Pα of the pressure measuring unit 44 and the measured value Pβ of the pressure measuring unit 45 has become constant (from time t1 to time t2 in FIG. 8). Time). That is, in order to keep the ink flowing through the filter 42 from the time 0 when the ink starts to be sucked to the time t2, it is necessary to continue sucking the ink from the suction cap 49.

  Subsequently, the control unit 46 determines whether or not the pressure loss Poe measured in step S3 exceeds a predetermined allowable value (step S4). In the present embodiment, the allowable value is the pressure loss Poa when there is no accumulated matter in the filter 42. Since the pressure loss Poa is a value that varies depending on the ink temperature, data indicating the pressure loss value in association with the ink temperature is stored in the memory of the control unit 46 in advance.

  In the case of Poe = Poa, the control unit 46 determines that there is no accumulated matter, and stops the pump 50 without causing the bubble removal operation. When Poe> Poa, the controller 46 determines that the filter 42 is clogged and causes the heater 43 to heat the ink (step S5). The above equations and inequalities actually have a predetermined amount of margin α which is a measurement error or a detection error, and strictly speaking, Poe = Poa + α and Poe> Poa + α. However, for the sake of simplification, such a margin shall be included even if there is no particular notice for the equations and inequalities that will appear in the future. In the present embodiment, the pump 50 is driven from step S4 to step S5. However, during this period, the pump 50 may be temporarily stopped and the operation may be resumed after step S5 ends.

  Next, the temperature measuring unit 47 measures the heated ink temperature (step 6). When the measured value of the temperature measuring unit 47 reaches a predetermined temperature Tt, the control unit 46 measures the pressure loss again as in step S3 (step S7). The temperature Tt is desirably in a temperature range in which the ink is not denatured as much as possible, specifically in a range of about 35 to 50 ° C.

  Subsequently, the control unit 46 determines whether or not the pressure loss Pts measured in Step S7 is Pts <Pob (Step S8). Pob is calculated by Poe × ηt / ηo. Data indicating the ink viscosity in association with the ink temperature is stored in the memory of the control unit 46 in advance.

  When Pts = Pob, the control unit 46 determines that there are not enough bubbles to be removed in the filter 42 (the cause of clogging of the filter 42 is dust), and stops the pump 50. Thereafter, the control unit 46, for example, causes a warning means (not shown) to present to the user by voice or image that the filter 42 is clogged with dust.

  When Pts> Pob, the control unit 46 determines that there are bubbles to be removed, and causes the heater 43 to generate heat so that the temperature of the ink flowing through the filter 42 becomes a temperature T1 higher than the above-described temperature Tt (step S40). 9). In the present embodiment, the temperature T1 is set to the ink heating limit temperature in consideration of the influence on the image. Subsequently, by increasing the drive rotation speed of the pump 50 as compared to before heating (step S10), ink is sucked with a negative pressure larger than the suction operation of step S1 (second suction operation). By this suction operation, the flow velocity of the ink flowing through the filter 42 becomes faster than before heating. As a result, the bubbles 60 are sucked through the filter 42. Thereafter, when a predetermined time has elapsed, the control unit 46 stops the pump 50. (Step S11).

  In the present embodiment, when the cause of clogging of the filter 42 is the dust 61, the dust 61 does not expand even when the ink is heated. Therefore, the pressure loss Pts after heating the ink decreases as the ink viscosity decreases. . On the other hand, when the cause of clogging of the filter 42 is the bubble 60, when the ink is heated, the bubble 60 expands unlike the dust 42. Therefore, the pressure loss Pts after heating the ink decreases the viscosity of the ink. Not only does it decrease, but it also increases the volume of expansion. Therefore, when the cause of clogging of the filter 42 is the bubble 60, the pressure loss Pts after heating the ink satisfies the relationship Pts> Pob (where Pob = Poe × ηt / ηo).

  According to the present embodiment, after the pressure loss before and after heating the ink is measured and the cause of clogging of the filter 42 is specified as the bubble 60, the bubble removal operation (second suction operation) is performed. Is going. Therefore, when the cause of clogging of the filter 42 is the dust 61, it is possible to shift to a procedure for removing the dust 61 without performing the bubble removal operation. Therefore, the filter 42 can be effectively dealt with clogging. Furthermore, according to this embodiment, it is possible to reduce the viscosity of the ink passing through the filter 42 by using the heater 43 that is a part of the bubble detection means during the bubble removal operation. Therefore, the flow rate during the bubble removal operation can be further increased, and the bubble removal effect can be improved.

(Second Embodiment)
FIG. 6 is a diagram showing changes in the filter box accompanying heating in the ink jet recording apparatus according to the second embodiment of the present invention. FIG. 6A shows a state in which only the bubbles 60 remain in the liquid chamber 48. FIG. 6B shows a state where bubbles 60 and dust 61 are mixed and stay in the liquid chamber 48. FIG. 6C shows a state where only the dust 61 stays in the liquid chamber 48.

  In the present embodiment, a heater 43 is provided on the wall portion of the liquid chamber 48 facing the filter 42. When the liquid chamber 48 is viewed in a cross section parallel to the length direction of the supply path 52, the length L1 from the filter 42 to the wall portion is a flat shape shorter than the length L2 of the wall portion (see FIG. 6 (a)). Therefore, the bubble 60 heated by the heater 43 expands so as to spread in a plane. As a result, since the area covered by the filter 42 becomes large, the difference in pressure loss before and after the ink is heated becomes remarkable, so the detection sensitivity of the bubble 60 is improved.

(Third embodiment)
FIG. 7 is a diagram illustrating a flow path and components attached to the ink jet recording apparatus according to the third embodiment of the present invention. FIG. 7 shows the configuration for one color, similar to FIG. The ink jet recording apparatus according to the present embodiment is different from the ink jet recording apparatus according to the first embodiment in that the recording head 13 and the ink tank 40 form a circulation channel. Specifically, the ink jet recording apparatus of this embodiment has a circulation path 57 between the pump 50 and the ink tank 40. In the ink jet recording apparatus of the present embodiment shown in FIG. 7, the suction cap 49 and the recovery processing unit 6 are not shown, but even if they are present, there is no influence on the gist of the present invention.

  In the ink jet recording apparatus of the first embodiment, as shown in FIG. 2, the ink sucked by the pump 50 is discharged to the waste liquid tank 56. Therefore, if the time from the time t0 (see FIG. 8) at which ink suction starts to the time t2 (see FIG. 8) for measuring the pressure loss Poe compared to the pressure loss Poa becomes longer, the amount of ink waste liquid increases. If the time t2 (see FIG. 8) is advanced in order to reduce the amount of ink waste, the measurement accuracy of the pressure loss Poe may decrease.

  On the other hand, in this embodiment, the ink sucked by the pump 50 is returned to the ink tank 40 through the circulation path 57. With this configuration, the amount of waste ink can be reduced to zero when measuring the pressure loss Poe described above. Therefore, it is not necessary to advance the time t2 described above, and the value when the pressure loss Poe becomes constant can be measured. Therefore, it is possible to increase the measurement accuracy of the pressure loss Poe. Furthermore, it is possible to increase the measurement accuracy of the pressure loss Pts necessary to determine whether the accumulated matter in the liquid chamber 48 is the bubble 60 or not. Therefore, the detection sensitivity of the bubble 60 is improved.

13 Recording head 40 Ink tank 42 Filter 43 Heater 44 Pressure measurement unit 45 Pressure measurement unit 46 Control unit 50 Pump 54 Supply path

Claims (5)

An ink tank capable of storing ink, a recording head for performing a recording operation for discharging the ink onto a recording medium, a supply path for supplying the ink from the ink tank to the recording head, and a midway in the supply path. A first pressure measuring unit that measures the pressure of the ink before passing through the filter in the supply path, and the pressure of the ink after passing through the filter in the supply path. A second pressure measuring unit; a heater provided upstream of the filter; a pump communicating with the recording head; the recording head; the first pressure measuring unit; the second pressure measuring unit; A heater, and a control unit connected to the pump,
The controller causes the pump to perform a first suction operation for sucking ink flowing through the supply path from the recording head when the recording head is not performing the recording operation, and the first suction operation. When the pressure loss obtained by subtracting the measurement value of the second pressure measurement unit from the measurement value of the first pressure measurement unit is measured, and the measured pressure loss Poe exceeds a predetermined allowable value The ink is heated by the heater, and then the pressure loss is measured again. The measured pressure loss Pts is Pts> Pob (where Pob = Poe × ηt / ηo, ηt: ink viscosity after heating, ηo: An ink jet recording apparatus that causes the pump to perform a second suction operation for sucking the ink with a negative pressure larger than that of the first suction operation when the ink viscosity before heating is satisfied.   2. The inkjet recording apparatus according to claim 1, wherein, when Pts> Pob is satisfied, the control unit causes the pump to perform the second suction operation after further heating the ink to the heater.   A liquid chamber provided with the heater on the wall facing the filter, and when the liquid chamber is viewed in a cross section along the length direction of the supply path, from the filter to the wall; The ink jet recording apparatus according to claim 1, wherein a length of the ink jet recording apparatus is shorter than a length of the wall portion.   4. The ink jet recording apparatus according to claim 1, further comprising a circulation path that is located between the pump and the ink tank and returns the ink sucked by the pump to the ink tank. 5. An ink tank capable of storing ink, a recording head for performing a recording operation for discharging the ink onto a recording medium, a supply path for supplying the ink from the ink tank to the recording head, and a midway in the supply path. A recovery method for an ink jet recording apparatus comprising:
A first step of performing a first suction operation for sucking ink flowing through the supply path from the recording head when the recording head is not performing the recording operation;
A second step of measuring a pressure loss of the filter in the first suction operation;
A third step of heating the ink upstream of the filter when the pressure loss Poe measured in the second step exceeds a predetermined allowable value;
A fourth step of measuring the pressure loss again after the third step;
When the pressure loss Pts measured in the fourth step satisfies Pts> Pob (where Pob = Poe × ηt / ηo, ηt: ink viscosity after heating, ηo: ink viscosity before heating), the first A fifth step of performing a second suction operation for sucking the ink with a negative pressure greater than the suction operation of
A method for recovering an ink jet recording apparatus, comprising:

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