JP4826210B2 - Inkjet recording device - Google Patents

Description

  The present invention relates to an inkjet recording apparatus that records an image on a recording medium by ejecting ink.

  As an apparatus for recording an image on a recording medium such as paper or cloth, there is an ink jet recording apparatus. An ink jet recording apparatus records an image by ejecting ink from an ink ejection port of a recording head toward a recording medium. In such an ink jet recording apparatus, since it is necessary to perform a cleaning operation at a predetermined timing so as not to clog the ink discharge port, a suction cap for sucking bubbles or the like inside the ink discharge port, or a recording head A wiping blade or the like for scraping off ink adhering to the ink discharge surface (surface provided with the ink discharge port) is provided.

  In general, as described in Patent Document 1, the suction is performed in a sequence in which suction is continued (so-called idle suction) in a state where the atmosphere is communicated with the inside of the cap.

  By the way, when printing or flushing is performed, minute ink droplets fluctuate or scatter due to the air flow and adhere to the ink ejection surface. In addition, after wiping in the cleaning operation, a minute ink droplet may adhere to the ink ejection surface as a wiping residue. Thus, the minute ink droplets adhering to the ink ejection surface may be dried and fixed. In particular, the sticking of the ink near the ink discharge port causes the ink droplet to be bent or non-discharge during discharge.

  Further, when a resin such as latex is contained in the ink, a thin film may be formed and fixed on the ink ejection surface. Due to the adhesion of ink droplets (including resin) in the vicinity of the ink ejection port, the ink repellency of the ink ejection surface is lowered and a large amount of residual ink is generated even when wiping is performed. Also in this case, the ink discharge is bent or non-discharge. In some cases, latex is laminated and fixed in the vicinity of the ink discharge port to cause bending or non-discharge of ink.

  The ink sticking cannot be removed even if the above-described normal cleaning such as suction or wiping is performed. Alternatively, the state may be deteriorated by laminating fixed ink.

  In order to solve such a problem, Patent Document 2 discloses that the first time after flushing, the first ink is slowly wiped (or stopped in the vicinity of the ink discharge port) to wet the thickened ink, and the second time wipe increases the viscosity. It has been proposed to scrape ink.

  Patent Document 3 proposes that the ink contact angle on the ink ejection surface be 60 ° or less in order to prevent the formation of a film of the ink in which the resin is dissolved.

Patent Document 4 proposes to wipe all the heads in a capped state by wet discharge.
Japanese Examined Patent Publication No. 3-61593 Japanese Patent Application Laid-Open No. 5-293973 JP 2004-167913 A JP-A-6-115082

  As described above, Patent Documents 2 and 4 propose a method of wiping the ink discharge surface by wetting it by flushing. However, wetness by flushing does not provide a sufficient effect because the amount of ink is not sufficient. In particular, it is necessary to sufficiently wet the ink adhering to the thin resin film.

  Further, when wiping twice consecutively as in Patent Document 2, the second wipe is empty, and the ink discharge surface may be damaged, or conversely, the resin may be thinly stretched.

  If the ink discharge surface is easily wetted as in Patent Document 3 to prevent the ink from being formed into a film, the wiping performance itself deteriorates, and discharge bending or non-discharge occurs due to wiping.

  An object of the present invention has been made in view of the above problems, and the cap member is separated while the ink is sufficiently adhered on the ink ejection surface by suction, and then the ink ejection surface is wet with the ink. It is an object of the present invention to provide an ink jet recording apparatus capable of removing the fixed ink by wiping.

The object of the present invention is achieved by the following configurations.
1
A recording head having an ink discharge port for discharging ink to a recording medium;
A cap member for capping the ink discharge port of the recording head;
A communication port communicating the inside of the cap of the cap member and the atmosphere;
A valve for opening and closing the communication port;
A suction means that communicates with the cap member and applies a suction force to the inside of the cap ;
A wiping member for wiping the recording head;
As a first cleaning mode of the recording head, ink is sucked from the ink ejection port by driving the suction means with the cap member capping the ink ejection port of the recording head and closing the valve. A first operation to be performed, a second operation for stopping the suction means, a third operation for separating the cap member from the recording head, and a fourth operation for wiping the recording head by the wiping member. And execute
As a second cleaning mode of the recording head, ink is sucked from the ink ejection port by driving the suction means with the cap member capping the ink ejection port of the recording head and closing the valve. A first operation to be performed, a second operation to perform suction of ink remaining in the cap member by driving the suction means in a state where the valve is opened, and the cap member from the recording head. An ink jet recording apparatus comprising: a control device configured to execute a third operation for separating and a fourth operation for wiping the recording head by the wiping member after the first cleaning mode .
2
The suction means includes a suction pump and a communication valve provided between the suction pump and the cap member,
The control device is characterized in that the suction means is stopped by closing the communication valve while the suction pump is operated, and the suction means is actuated by driving the suction means by opening the communication valve. 2. The inkjet recording apparatus according to 1.
3
The inkjet recording apparatus according to 1 or 2, wherein the cleaning is performed by repeating the first cleaning mode at least twice.
4
4. The ink jet recording apparatus according to any one of 1 to 3, wherein the first cleaning mode is performed on a regular basis.
5
The inkjet recording apparatus according to any one of 1 to 4, wherein the first cleaning mode is performed at predetermined time intervals.
6
The inkjet recording apparatus according to any one of 1 to 5, wherein the first cleaning mode is performed when the power is turned on.
7
The inkjet recording apparatus according to any one of 1 to 6, wherein the first cleaning mode is performed when the power is turned off.
8
The ink jet recording apparatus according to any one of 1 to 7, wherein the first cleaning mode is performed based on a user instruction.
9
The ink jet recording apparatus according to any one of 1 to 8, wherein the ink is an ink in which a resin is dissolved or dispersed in the ink.
10
10. The inkjet recording apparatus according to 9, wherein the number of repetitions of the first cleaning mode is set according to the content of the resin.
11
The ink jet recording apparatus according to claim 9 or 10, wherein the number of repetitions of the first cleaning mode is set according to the type of the resin.
12
The ink jet recording apparatus according to any one of 3 to 11, wherein the number of repetitions of the first cleaning mode is set in accordance with an elapsed time from the execution of the immediately preceding first cleaning mode.

  According to the present invention, the first cleaning mode is provided in which the cap member is separated in a state where the ink is sufficiently adhered on the ink ejection surface by suction, and then the wiping is performed in a state where the ink ejection surface is wet with the ink. Thus, the ink fixed on the ink discharge surface can be removed. Further, after the suction, the second cleaning is performed in which the cap member is connected to the atmosphere and the residual ink in the cap member, that is, the ink adhering to the ink ejection surface is sucked, and then the cap member is separated and then wiped. By having the mode, even if ink may remain on the ink ejection surface after the first cleaning mode is performed, the residual ink can be removed by the second cleaning mode. Accordingly, it is possible to provide an ink jet recording apparatus that can prevent the ejection bend or non-ejection due to the ink fixed on the ink ejection surface or the remaining ink after wiping.

  As a result, it is possible to realize a highly reliable ink jet recording apparatus that can always output a stable and high-quality image.

  It can be carried out only by changing the sequence of the conventional cleaning device, and since no new parts are generated, an increase in cost can be suppressed.

  Although the example of embodiment regarding this invention is shown below, the aspect of this invention is not limited to these.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows a schematic configuration diagram of the inside of the ink jet recording apparatus according to the present embodiment. 2 is a perspective view of the ink jet recording apparatus according to the present embodiment, FIG. 3 is a side view of the recording head 1, the ink supply device 28, and the cleaning unit 5 provided in the ink jet recording apparatus, and FIG. 4 is an ink jet recording apparatus. It is a block diagram of the control apparatus 2 with which it was equipped. 3 shows a side view of the recording head 1, the ink supply device 28, and the cleaning unit 5 for one color, these configurations are common to the respective colors. In FIG. 2, the suction pump 16 and the waste ink container 17 are omitted.

  In the following description, each component of the recording head 1, the ink supply device 28, and the cleaning unit 5 is provided for each color, but since the configuration is common to each color, subscripts Y, M, In some cases, C and K are omitted and explained collectively.

<Mechanical structure of the device>
As shown in FIG. 1, the ink jet recording apparatus includes a casing 10, a paper feeding unit 19, a transport unit 20, a head unit unit 100 including the recording head 1, a carriage 18, a paper discharge unit 21, and a cleaning unit as a cleaning unit. 5 etc.

  The paper supply unit 19 is provided with a paper supply tray 8 that stores a plurality of recording media 7 in a stacked manner below the inside of the ink jet recording apparatus. A take-out device 22 for taking out the recording medium 7 on which an image is to be recorded from the paper feed tray 8 one by one is provided above one end of the paper feed tray 8.

  The recording medium 7 may be in the form of a cut sheet made of various papers such as plain paper, recycled paper, and glossy paper, and various fabrics, various non-woven fabrics, resin, metal, glass, and the like.

  The transport unit 20 is disposed above the paper feed unit 19 and transports the recording medium 7. The transport unit 20 includes a transport belt 6, a tension roller 23, a pressing roller 24, a transport roller 25, and a transport path 26. A sub-scanning motor 31 (see FIG. 4) serving as a driving source is connected to the take-out device 22, the conveying roller 25, and the plurality of tensioning rollers 23, and each is configured to be driven by the sub-scanning motor 31. ing.

  The conveyance belt 6 is an annular belt that supports the recording medium 7 in a flat shape and conveys the recording medium 7 in the horizontal direction. The conveyance belt 6 is movably stretched by a plurality of tension rollers 23. As described above, the plurality of tensioning rollers 23 are connected to the sub-scanning motor 31 (see FIG. 4) serving as a driving source, and when the sub-scanning motor 31 rotationally drives the plurality of tensioning rollers 23 around the axis. The conveying belt 6 and the recording medium 7 stretched on the plurality of stretching rollers 23 are transported along the sub-scanning direction A. Here, the sub-scanning direction A is a direction orthogonal to the axis of the plurality of tensioning rollers 23.

  The pressing roller 24 is rotatably provided as a roller that presses the conveying belt 6 in order to convey the recording medium 7 in a plane at a position where the conveying belt 6 and the recording medium 7 start to contact each other.

  The transport path 26 is a path for transporting the recording medium 7 supplied from the paper feed tray 8 to the transport belt 6. The transport rollers 25 are provided as a plurality of pairs of rollers for transporting the recording medium in the sub-scanning direction A at a predetermined position on the transport path 26.

  A guide member (not shown) is disposed above the conveyor belt 6. The guide member is provided substantially parallel to the upper surface of the transport belt 6 and further provided so as to be orthogonal to the sub-scanning direction A. A longitudinal direction in which the guide member extends is referred to as a main scanning direction B. A carriage 18 is supported on the guide member. The carriage 18 is driven by a main scanning motor 32 (see FIG. 4) to reciprocate along the main scanning direction B while being guided by a guide member.

  On the carriage 18, four recording heads 1Y, 1M, 1C, and 1K for ejecting inks of process colors of yellow (Y), magenta (M), cyan (C), and black (K) are interchangeably mounted. Are arranged along the main scanning direction B.

  A plurality of ink discharge ports (not shown) are provided on the lower surface of the recording heads 1Y, 1M, 1C, and 1K, that is, the ink discharge surface 27, and the circumference of the ink discharge surface 27 of the recording head 1 and the conveyance belt 6 is provided. It arrange | positions so that a surface may oppose.

  The recording medium on which an image is formed by ejecting ink droplets from the ink ejection openings of the recording heads 1 is sequentially discharged to the paper discharge unit 21.

  The paper discharge unit 21 includes a paper discharge tray 9 provided on a side portion of the ink jet recording apparatus, and recording media on which images are formed are sequentially discharged.

  The ink ejection surface 27 of the recording head 1 is preferably ink repellency (for example, water repellency for water-based ink) in order to further enhance the effects of the present invention. In order to achieve ink repellency, usually, for example, the nozzle plate surface constituting the ink ejection surface is subjected to ink repellency.

  The surface of the nozzle plate is usually an ink-repellent surface obtained by applying an ink-repellent coating to a nozzle plate material such as plastic such as polyester or polyamide, glass, ceramic, or metal.

  With respect to a method of applying water-repellent and ink-repellent coating so that ink does not adhere to the ink ejection surface, for example, Japanese Patent Publication No. Sho 52-24821 and Japanese Patent Laid-Open Publication No. A coating of a material having an ink repelling property such as a resin or a silicone resin is disclosed in Japanese Patent Application Laid-Open Nos. 57-72866 and 60-255441 using a tetrafluoroethylene-hexafluoropropylene copolymer (FEP) as an ink repellent film. Each use is described. Although this FEP has low surface energy (ink repellency) equivalent to polytetrafluoroethylene (PTFE), its viscosity at the time of heating and melting is lower than that of PTFE, and it is uniform by applying an aqueous dispersion and heating and melting. When forming a film, a uniform film can be obtained in a short time at a lower temperature than PTFE, and the film forming processability is excellent. Japanese Patent Application Laid-Open No. 2001-71509 discloses a method in which an FEP aqueous dispersion and a silica sol particle dispersion are mixed and applied, dried and fired at 300 to 400 ° C., and Japanese Patent Application Laid-Open No. 10-505870 also contains fluorine. A method using a polysiloxane compound is described.

  Further, an ink supply device 28 is connected to each side of each recording head 1 for each color.

  The ink supply device 28 includes four main tanks 3 that store ink of process colors of yellow (Y), magenta (M), cyan (C), and black (K). The main tank 3 can be replaced.

  An ink supply pipe 11 that supplies ink from the main tank 3 to the intermediate tank 4 is connected to the main tank 3.

  The ink supply pipe 11 is provided with a supply valve 29. The supply valve 29 controls ink supply to the intermediate tank 4.

  The intermediate tank 4 is provided with a detection sensor 30 that detects the amount of ink inside the intermediate tank 4.

  An ink supply pipe 11 that supplies ink from the intermediate tank 4 to the recording head 1 is connected to the intermediate tank 4.

  The back pressure of each recording head 1 is preferably determined by each intermediate tank 4. An intermediate tank 4 made of a flexible bag or a container having an air communication valve is provided below the main tank 3 via a supply valve 29. If the air communication valve is opened and the supply valve 29 is closed, the ink in the intermediate tank 4 becomes atmospheric pressure. By placing the intermediate tank 4 below the recording head 1 by a predetermined height, the ink in the recording head 1 becomes a negative pressure by a predetermined water head value with respect to the atmospheric pressure, and stable ejection can be realized. A detection sensor 30 is provided in the intermediate tank 4, and when the amount becomes a predetermined amount or less, the supply valve 29 is opened to replenish ink from the main tank 3 to the intermediate tank 4. If the intermediate tank 4 is not refilled even after a predetermined time has elapsed since the supply valve 29 was opened, it can be detected that the main tank 3 is empty. Compared with determining the back pressure directly at the position of the main tank 3, there are advantages such as no influence of back pressure fluctuation due to fluctuations in the remaining amount of ink and empty detection of the main tank 3. When the main tank 3 is replaced, the replacement of the main tank 3 and the recording operation can be performed in parallel without interrupting the recording operation with the ink remaining in the intermediate tank 4.

  A damper 12 is provided between the recording head 1 and the intermediate tank 4.

  The damper 12 stabilizes the ejection operation of the recording head 1 by suppressing back pressure fluctuations due to the reciprocating operation of the carriage 18 and the ejection operation of the recording head 1.

  In addition, the ink jet recording apparatus includes a cleaning unit 5 for recovering the ejection failure of each recording head 1. The cleaning unit 5 is disposed below the recording head 1 and the carriage 18 and to the left of the conveyance belt 6.

  As shown in FIGS. 2 and 3, the cleaning unit 5 includes four warper blades 14 for each color which are wiping members for wiping the base member 33 and the lower surface (ink ejection surface 27) of each recording head 1. Four cap members 13 for each color for capping the ink discharge ports of the recording heads 1, four suction pumps 16 for each color as suction means for applying a suction force to the inside of the cap member 13, and a cap member 13, a communication port 48 communicating the inside of the cap with the atmosphere, an electromagnetic valve 15 serving as a valve for opening and closing the communication port 48, and ink sucked by the suction pump 16 through the cap member 13 by the suction pump 16. The waste ink tank 17 and the drive device 34 that moves the base member 33 back and forth while raising and lowering the base member 33 (FIG. 4). Provided with irradiation), the.

  The cap member 13 has a recess, and the recess is brought into close contact with the ink discharge surface 27 having the ink discharge port of the recording head 1 to cover the ink discharge port. A space formed by the recess and the ink discharge surface 27 corresponds to the inside of the cap (member) in the present embodiment.

  The base member 33 is moved in the front-rear direction in FIG. 2, that is, in the sub-scanning direction A by the driving device 34, and is further moved in the vertical direction (X direction in FIG. 3) by the driving device 34. ing. Note that the recording head 1 may be provided so as to be able to move up and down together with the carriage 18 instead of the base member 33 moving up and down.

  Four warper blades 14 made of an elastomer material such as silicone rubber, which is a wiping member, are provided on the rear end portion of the upper surface of the base member 33 in an upright state. These warper blades 14 are arranged along the main scanning direction B at the same intervals as the intervals of the recording heads 1, and the number of installed warper blades 14 is the same as the number of installation of the recording heads 1 (4 in this example). There is a one-to-one correspondence between the head 1 and the warper blade 14.

  The wiper blade 14 is selected from materials having elasticity, such as various rubbers (although it may be ink-philic (hydrophilic) or ink-repellent (water-repellent)). When a relatively hydrophilic blade such as urethane rubber is used, the ink can be attracted and wiped off due to its affinity. However, due to its hydrophilicity, ink droplets may be drawn out again (from the ink ejection port) to the cleaned ink ejection surface, and the blade is rather a material with low ink affinity and ink repellency. It is preferable to comprise. It is preferable that ink droplets are not drawn out from the ink discharge port and that the blade itself is less contaminated.

  As the material of the ink-philic (hydrophilic) blade, a silane compound is coated on a blade material such as urethane rubber or butyl rubber, or a hydrophilic polymer (for example, nylon, polyurethane, polyvinyl alcohol, etc.) is coated. As an example, a rubber surface that has been hydrophilized by so-called surface modification, in which plasma treatment is performed in advance. For example, an ink contact angle of 40 degrees or less is selected.

  Examples of the blade material having an ink-repellent and water-repellent surface include those made of silicone-based materials such as silicone rubber, silicone resin, room temperature curable silicone resin, and room temperature curable organic modified silicone resin. Further, the surface of a plastic substrate having elasticity may be made of a hydrophobic material, for example, a material made of a water-repellent polymer resin such as polytetrafluoroethylene or a coating of these resins. Of these, silicone materials are preferred. When the contact angle to ink is evaluated, a material of 50 degrees or more is preferable. As silicone rubber, for example, Irumagawa Rubber Co., Ltd. IS-825 50HS can be obtained.

  A cap member 13 is provided on the upper surface of the base member 33. Each cap member 13 is disposed in front of each warper blade 14. The number of installed cap members 13 is the same as that of the recording head 1, and the recording head 1 and the cap member 13 correspond one-to-one.

The suction pump 16 is arranged for each of the four cap members 13. Here, the suction pump 16 will be described as corresponding to one cap member 13. The suction pump 16 is disposed below the base member 33, and one waste ink tank 17 for each color that stores waste ink is disposed below the suction pump 16. A rubber tube 35 is arranged between the base member 33 and the waste ink tank 17. One end of the tube 35 communicates with the cap member 13 via the base member 33, and the other end of the tube 35 communicates with the waste ink tank 17. A suction pump 16 is disposed in the middle of the tube 35. The suction pump 16 generates a suction pressure inside the cap member 13 through the tube 35 by setting the space in the tube 35 to a reduced pressure state. In this embodiment, a tube pump is used as the suction pump 16, but
As the suction pump, other suction pumps such as a piston type may be used.

  Further, the suction means is constituted by the suction pump 16 and a communication valve provided between the suction pump 16 and the cap member 13, and the suction means is stopped by closing the communication valve while the suction pump 16 is operated. The suction means may be driven by opening the communication valve to apply a suction force to the cap member. The rise time of suction can be shortened.

  Under the cap member 13, a communication port 48 for communicating the inside of the cap member 13 with the atmosphere and an electromagnetic valve 15 for opening and closing the communication port 48 are disposed. In the present embodiment, an example in which the communication port 48 is formed in the cap member 13 is shown as a more preferable form, but the present invention is not limited to this, and the communication port 48 may be formed in the recording head 1.

  Here, only the suction pump 16 and the electromagnetic valve 15 related to one cap member 13 out of the four cap members 13 have been described. However, such a suction pump 16 and the electromagnetic valve 15 are each of the four cap members 13. In each cap member 13, the suction pressure and various suction sequences are appropriately changed for each color in accordance with the operation mode of the suction pump 16 of each color. Can be done.

<Electrical configuration of the device>
Next, the electrical configuration of the ink jet recording apparatus of FIG. 1 will be described.

  As shown in FIG. 4, the ink jet recording apparatus includes a control device 2 that controls the sub-scanning motor 31, the main scanning motor 32, the recording heads 1, the suction pumps 16, the electromagnetic valves 15, and the driving device 34.

The control device 2 includes a system controller 36, a main memory 37 that provides a work area for the system controller 36, a reception buffer memory 39 that temporarily stores data in order to exchange image data and the like with the host computer 38, An image buffer 40 that temporarily stores image data received from the host computer 38, a timer group 41 that performs various timings according to a clock signal, a main scanning drive driver 42 that drives and controls the main scanning motor 32, and a sub-scanning motor 31. A sub-scanning drive driver 43 for driving and controlling the suction pump 16, a suction pump driving driver 44 for driving and controlling the suction pump 16, a base member driving driver 45 for driving and controlling the driving device 34, and a valve driving driver 46 for driving and controlling the electromagnetic valve 15. According to the image data stored in the image buffer 40 A head drive driver 47 for driving the recording head 1, a power switch 50 of the apparatus main body, a print switch 51 for instructing start of recording (printing), a cleaning switch 52 for instructing start of cleaning, and the like. And a switch group 49 for receiving an input. When the user presses the cleaning switch 52, a cleaning start signal is input from the cleaning switch 52 to the control device 2. The power switch 50 is connected to a commercial power source (not shown) as a main power source. When the switch is turned on, the main power source is supplied to the recording apparatus. When the switch is turned off, the supply of main power to the recording apparatus is stopped.

  The ink jet recording apparatus of this embodiment includes a battery power source (not shown) as a sub power source in addition to a normal main power source, and supplies power to each part in the ink jet recording apparatus. The battery power supply is configured to supply power in place of the main power supply 41 to each part of the ink jet recording apparatus, particularly the control device 2 and the timer group 41, when the power switch 50 of the main power supply is off. Thus, even during the main power off period, the timer can be counted during the off period, and the recording head 1 can be cleaned when the main power is off. As the secondary power source, a rechargeable backup power source that can be charged when an outlet is connected can be used.

  The control device 2 uses the main memory 37 as a work area to perform arithmetic processing by the system controller 36, whereby the main scanning motor 32, the sub-scanning motor 31, the driving device 34, the suction pump 16, and the solenoid valve 15 are passed through the drivers 42 to 47. The recording head 1 is controlled. In addition, the control device 2 performs various types of time measurement using the timer group 41.

  The timer may be of a type that resets, or may be of a type that stores the time and the like at that time, and calculates and outputs the elapsed time from that time. When there is a timer that manages the date and time for control in the inkjet recording apparatus, the elapsed time is calculated from the display time of the timer for controlling the date and time. You can also

  In addition, the cleaning switch 52 selects one or more of the first cleaning mode and the second cleaning mode, which will be described later, or the order in the case of a plurality of the cleaning switches 52 according to the situation, and further repeats the number of repetitions. Is selected and can be instructed to the control device 2.

<Operation and action of the device>
Next, the operation / action of the ink jet recording apparatus will be described.

Hereinafter, the control of the recording head 1 is taken as an example, and Y, M, C, and K, which are subscripts representing colors, are omitted and explained collectively. Note that the operation example described for the recording head 1 is also applied to the recording heads 1Y, 1M, 1C, and 1K of four colors, and when actually recording a color image, each recording head 1Y, Control of 1M, 1C, and 1K is performed simultaneously.
[1. (Image recording operation)
When the control device 2 receives image data from the host computer 38 and receives an image recording start signal from the print switch 51, the control device 2 outputs a control signal to the sub-scanning motor 31, the main scanning motor 32, the recording head 1, and the like. The operation of each component is controlled as follows. That is, when the control device 2 repeats the operation and stop of the sub-scanning motor 31, the take-out device 22, the transport roller 25, and the transport belt 6 repeatedly rotate and stop by a predetermined amount, and the recording medium 7 moves in the transport direction A. It is moved intermittently along.

  In this state, when the movement of the recording medium 7 is temporarily stopped at a position facing the recording head 1, when the control device 2 operates the main scanning motor 32, the carriage 18 is directly above the recording medium 7 and each recording head 1. 2 is moved along the main scanning direction B from left to right in FIG. 2 (or from right to left). When the control device 2 causes the recording heads 1 to appropriately perform ejection operations according to the image data while the carriage 18 is moving, the ink ejection ports of the ink ejection surfaces 27 of the recording heads 1 move toward the recording surface of the recording medium 7. Ink is ejected as fine droplets.

  Thereafter, the control device 2 causes each member of the ink jet recording apparatus to repeatedly perform the above-described operation, and sequentially records an image on the image recording area of the recording surface of the recording medium 7 that has passed over the conveyance belt 6.

  When the image recording operation is not performed for a predetermined time or longer, the ink discharge surface 27 of the recording head 1 is sealed and held in a sealed state by the cap member 13 in a state where the electromagnetic valve 15 is closed. That is, in this state, the ink discharge surface 27 of the recording head 1 is sealed by the cap member 13 and is kept in a sealed state.

  Further, when a certain time has passed in the state of the image recording operation or the like where the cap member 13 is not in close contact with the recording head 1 or when the image recording is completed, the carriage 18 is returned from the image recording unit to the cleaning unit, and the recording head 1 is moved. A small amount of ink is ejected from all the ink ejection ports of the recording head 1 facing the cap member 13. That is, so-called flushing is performed.

  Here, in addition to the above-described image recording operation, the ink jet recording apparatus performs cleaning for recovering or preventing the ejection failure of the recording head 1. Note that ejection failure means non-ejection of ink droplets (meaning that ink is not ejected from the ink ejection port even though the recording head 1 has performed the ink ejection operation), and the landing and bending of the ejected ink droplets. Etc.

  Next, the operation of the ink jet recording apparatus at the time of cleaning the recording head 1, that is, a so-called cleaning sequence will be described with reference to FIGS.

  In this embodiment, the first cleaning mode shown in FIG. 5 is used as a basis, and the number of repetitions thereof can be changed. After the first cleaning mode is executed once or a plurality of times, the second cleaning mode shown in FIG. Perform the cleaning mode.

  Based on the first cleaning mode shown in FIG. 5 and the second cleaning mode shown in FIG. 6, any one or a plurality of these, and in the case of a plurality, the order is changed, and the number of repetitions of each is changed. Different types of cleaning modes may be provided.

This cleaning mode is performed when an ejection failure occurs at the ink ejection port of the recording head 1 or on a regular basis (periodically). 5 and 6, each line extending in the left-right direction is a time axis, and shows the passage of time from the left side to the right side of the figure. In FIGS. 5 and 6, it is assumed that the ink supply device 28 continuously supplies ink to the recording head 1.
[2. Cleaning operation)
When the power switch 50 of the ink jet recording apparatus 1 is turned on, when the power switch 50 is turned off, or when the user presses the cleaning switch 52 (for example, when the user finds a defect in the recorded image), the control device 2 from the host computer 38. When the image data is input, when the user presses the print switch 51, when the image recording is completed, every time when the timer group 41 measures a predetermined time, etc., the control device 2 performs the first cleaning mode of the recording head 1. Execute.

  A case where cleaning is performed at predetermined time intervals will be described.

  Even if the recording head 1 is left to dry and adhere too much, it becomes increasingly difficult to remove it from the ink ejection surface.

  Therefore, the most effective standing time (drying time) for removing the ink to be used is experimentally obtained in advance, and the time until the drying time elapses after the last cleaning is performed is measured by the timer group 41, The cleaning effect can be further enhanced by performing the cleaning. Thus, it is preferable to perform cleaning at a predetermined time interval corresponding to the drying time. By carrying out regular cleaning, strong ink sticking due to excessive drying can be prevented in advance.

The cleaning operation is as follows.
<First cleaning mode>
When the control device 2 operates the main scanning motor 32, the carriage 18 moves above the base member 33, and the recording head 1 is positioned on each cap member 13. Next, when the control device 2 operates the drive device 34, the base member 33 is raised and the cap member 13 is in close contact with the lower surface (ink ejection surface 27) of the recording head 1.

  When the controller 2 drives (activates) the suction pump 16 in a sealed state with the electromagnetic valve 15 closed after the cap member 13 is in close contact with the ink ejection surface 27 and capped, the inside of the cap member 13 is in a reduced pressure state. Ink is sucked from each ejection port of the recording head 1.

  That is, the air between the ink discharge surface 27 of the recording head 1 and the cap member 13 is sucked by the suction pump 16, so that ink is sucked from the ink discharge port of the recording head 1 and discharged to the waste ink tank 17. . As a result, the inside of the cap member 13 is filled with ink, and the ink is sufficiently adhered on the ink ejection surface 27 of the recording head 1.

  After a predetermined time T1 has elapsed in this state, the control device 2 stops the suction pump 16. After waiting for a predetermined time T2 in this state (the pressure in the cap gradually returns to atmospheric pressure during this time), when the control device 2 opens the solenoid valve 15, the inside of the cap member 13 communicates with the atmosphere. Since the pressure inside the cap member 13 becomes atmospheric pressure, the cap member 13 is separated almost simultaneously with the opening of the electromagnetic valve 15.

  Here, the communication valve 48 may be opened immediately after the suction pump 16 is stopped (in this case, T2 is substantially 0). However, as in the present embodiment, T2 may be provided for a predetermined time. preferable. When the cap member 13 is separated, a large amount of ink can be left on the ink discharge surface 27, and the wiping property can be improved. Although T1 and T2 are arbitrarily set, the waiting time (T1 + T2) is preferably set to be longer than the time for the fixed ink to swell. As the ink swells, the subsequent wiping property (ink removing ability) is improved.

  Further, it is not always necessary to open the electromagnetic valve 15, and the operation from the start of suction to the removal of the cap member may be performed with the electromagnetic valve 15 closed. In this case, after the suction pump 16 is stopped, it is only necessary to wait for the time until the inside of the cap member returns to the atmospheric pressure, and then the suction cap is separated.

  When the control device 2 operates the drive device 55, the base member 33 is lowered and returned to its original height. Thereby, the cap member 13 and the recording head 1 are separated from each other. In this state, the ink ejection surface 27 of the recording head 1 is wet with ink. Next, the base member 33 moves from rear to front (Y direction in FIG. 3). At this time, the upper part of the warper blade 14 moves while rubbing the ink discharge surfaces 27 of the respective recording heads 1, and the ink adhering to the ink discharge surfaces 27 is removed.

  Each time of T1 and T2 is measured by each timer of the timer group 41.

  In addition, it is preferable to provide a known ejection detection means to detect whether or not ink is normally ejected from all ink ejection ports of the recording head 1, for example, from all ink ejection ports of the recording head 1. This may be performed by discharging ink toward the recording medium 7 and detecting whether there is a discharge failure at the ink discharge port. As a method for detecting the presence or absence of ejection failure, there is a method for examining the ink landing state on the surface of the recording medium 7.

  If there is a discharge failure even at one discharge port according to the detection result, it is preferable to perform cleaning again.

  As described above, for example, as in the prior art disclosed in Japanese Patent Publication No. 3-61593, after the suction, in a state where the recording head 1 is capped by the cap member 13, the electromagnetic valve 15 is opened and the suction is continued (so-called Vacant suction), the ink inside the cap member 13 is discharged to the waste ink tank 17, and wiping is performed in a state where the ink discharge surface 27 of the recording head 1 is not wet with ink, Ink stuck to the ink ejection surface 27 cannot be removed.

  In the present embodiment, the cap member is separated without performing idle suction in a state where the ink is sufficiently adhered to the ink ejection surface by suction, and then the first wiping is performed in a state where the ink ejection surface is wet with ink. By having the cleaning mode, it is possible to remove the ink adhered to the ink ejection surface.

  The first cleaning mode is configured so that the number of repetitions can be changed, and cleaning can be performed two or more times.

  By repeating the first cleaning mode at least twice, it is possible to improve the ability to remove the ink adhered to the ink ejection surface. That is, the larger the number of repetitions, the more the ability to remove the stuck ink can be improved.

In the present embodiment, the first cleaning mode is performed once or a plurality of times, and then a second cleaning mode described later is performed to perform cleaning. Even if the ink may remain on the ink ejection surface after being performed once or a plurality of times, the residual ink can be removed by the second cleaning mode. Accordingly, it is possible to prevent the bending or non-ejection of ejection due to the residual ink after wiping, which is a preferable mode.
<Second cleaning mode>
When the control device 2 operates the drive device 34, the base member 33 is raised, and the cap member 13 is in close contact with the lower surface (ink ejection surface 27) of the recording head 1.

  When the controller 2 drives (activates) the suction pump 16 in a sealed state with the electromagnetic valve 15 closed after the cap member 13 is in close contact with the ink ejection surface 27 and capped, the inside of the cap member 13 is in a reduced pressure state. Ink is sucked from each ejection port of the recording head 1.

  That is, the air between the ink discharge surface 27 of the recording head 1 and the cap member 13 is sucked by the suction pump 16, so that ink is sucked from the ink discharge port of the recording head 1 and discharged to the waste ink tank 17. . As a result, the inside of the cap member 13 is filled with ink, and the ink is sufficiently adhered on the ink ejection surface 27 of the recording head 1.

  After a predetermined time T3 has elapsed in this state, the control device 2 stops the suction pump 16. After waiting for a predetermined time T4 in this state (the pressure in the cap gradually returns to atmospheric pressure during this time), the control device 2 opens the electromagnetic valve 15 so that the inside of the cap member 13 communicates with the atmosphere. In this state, the suction pump 16 is driven to suck the ink remaining in the cap member 13 (so-called idle suction). After a predetermined time T5 has passed in this state, the suction pump 16 is stopped, and then the cap member 13 is separated.

  Here, the cap internal pressure return process corresponding to T4 time is not necessarily required, and suction (T3) and idle suction (T5) may be continuously performed while the suction pump 16 is continuously driven. Alternatively, the cap member 13 may be separated while the suction pump 16 is being driven without stopping the suction pump 16 before the cap member 13 is separated.

  When the control device 2 operates the drive device 55, the base member 33 is lowered and returned to its original height. Thereby, the cap member 13 and the recording head 1 are separated from each other. Next, the base member 33 moves from rear to front (Y direction in FIG. 3). At this time, the upper part of the warper blade 14 moves while rubbing the ink discharge surfaces 27 of the respective recording heads 1, and the ink adhering to the ink discharge surfaces 27 is removed.

  Each time of T3, T4, and T5 is measured by each timer of the timer group 41.

  In addition, it is preferable to provide a known ejection detection means to detect whether or not ink is normally ejected from all ink ejection ports of the recording head 1, for example, from all ink ejection ports of the recording head 1. This may be performed by discharging ink toward the recording medium 7 and detecting whether there is a discharge failure at the ink discharge port. As a method for detecting the presence or absence of ejection failure, there is a method for examining the ink landing state on the surface of the recording medium 7.

  If there is a discharge failure even at one discharge port according to the detection result, it is preferable to perform cleaning again.

  As described above, in the present embodiment, after sucking, after sucking the residual ink in the cap member with the cap member communicating with the atmosphere, that is, ink adhering to the ink ejection surface, the cap member is separated, and then wiping is performed. By having the second cleaning mode, the residual ink can be removed by the second cleaning mode even if the ink may remain on the ink ejection surface after the first cleaning mode is performed. Accordingly, it is possible to prevent ejection bends and non-ejections due to residual ink after wiping.

As described above, in the present embodiment, the second cleaning mode is used as an additional cleaning performed after the first cleaning mode, but it is assumed that the ink adhering to the ink ejection surface has not been fixed. When performing the cleaning in the state, the cleaning may be performed in the second cleaning mode alone.
<Setting of cleaning mode and repeat count>
Next, a method for setting the cleaning mode and the number of repetitions in the present embodiment will be described in detail.

  As described above, when foreign matter such as ink droplets remaining on the ink ejection surface 27 is left on the ink ejection surface 27, the ink itself is thickened due to evaporation of evaporation components such as moisture of the ink. At the same time, it is fixed and cannot be easily removed even if it is wiped after being left. Further, when the resin is contained in a dissolved or dispersed state as an ink component, the evaporation component evaporates to form a resin film and firmly adhere.

  In this embodiment, when ink is attached to the ink ejection surface 27 of the recording head 1 and left to stand, the fixed ink (which may include resin may be included) by appropriately setting the number of repetitions of the first cleaning mode. ) Can be removed.

  That is, the cleaning is performed by executing the second cleaning mode after executing the first cleaning mode once or a plurality of times.

  Further, the degree of fixation depends on easiness of evaporation of the evaporated component in the ink, that is, the environment (temperature and humidity) in which it is left and the amount of the evaporated component in the ink. Further, when the ink contains a resin, it is easily fixed. Further, since the evaporating component evaporates as the leaving time elapses, the evaporating component adheres more firmly as the leaving time becomes longer. That is, the number of repetitions of the first cleaning mode suitable for removing the fixed ink exists in the type of ink used, the environmental conditions, and the standing time.

  Therefore, in the ink jet recording apparatus of the present embodiment, the number of repetitions of the first cleaning mode suitable for removing the ink to be used is experimentally obtained in advance, and the first number of times is determined according to the leaving time and the leaving environmental conditions. By changing the number of repetitions of the cleaning mode, the ink fixed by drying can be surely removed.

  Specifically, the longer the standing time is, the smaller the environmental humidity (which indicates absolute humidity) is, or the higher the environmental temperature is, the easier it is to firmly adhere. Therefore, for example, when the leaving time is relatively long, when the environmental temperature is relatively high, or when the environmental humidity is low, the number of repetitions of the first cleaning mode may be set large.

  For example, a temperature detection sensor or a humidity detection sensor is installed in the ink jet recording apparatus (for example, in the vicinity of the recording head 1), and the temperature and humidity in the vicinity of the recording head 1 are detected every predetermined period or every time. The temperature and humidity may be transmitted as information to the control device 2. The leaving time is measured by the timer group 41. As described above, the relationship between the environmental temperature, the humidity, the standing time, etc., and the optimum number of repetitions of the first cleaning mode is obtained for each type of ink in advance through experiments on the ink used in the recording apparatus. This data may be tabulated and stored in the main memory 37. That is, storage means (for example, main memory 37) is provided for storing a conversion table for converting the optimum number of repetitions of the first cleaning mode from the fixing parameters (ink type, environmental temperature, humidity, standing time, etc.). The control device 2 preferably obtains the optimum number of repetitions of the first cleaning mode with reference to the conversion table. The control device 2 may control each unit based on the optimum number of repetitions so as to perform the first cleaning mode and then execute the second cleaning mode.

  According to such a configuration, by storing the conversion table, it is possible to easily obtain the optimum number of repetitions of the first cleaning mode with reference to the conversion table. For example, it is desired to use inks having different characteristics. In this case, it is possible to cope with the same configuration by simply rewriting the value of the conversion table. Furthermore, the case of recording using a plurality of types of ink can be handled by storing a conversion table for each type of ink, so that the application range is wide.

For example, in the case of an ink in which a resin is dissolved or dispersed in the ink, the ease with which the ink is fixed is, for example, when the resin content increases, the glass transition temperature of the resin increases as the resin content increases. The lower the value, the easier the sticking due to the resin filming. Therefore, it is preferable to set the number of repetitions of the first cleaning mode in accordance with the content of the resin in the ink. As the content of the resin is larger, the number of repetitions of the first cleaning mode is set to be larger. Good. It is preferable to set the number of repetitions of the first cleaning mode according to the type of the resin. For example, the lower the glass transition temperature of the resin, the greater the number of repetitions of the first cleaning mode may be set.

  The conversion table may be a table in which one or more threshold values are set for each fixing parameter, and the number of repetitions of the first cleaning mode is changed in a plurality of stages based on the threshold values.

  In addition, as the standing time, an elapsed time after ink droplet ejection for image recording or flushing, an elapsed time from the immediately preceding first cleaning mode, or the like may be used. The elapsed time from the immediately preceding first cleaning mode means the elapsed time from the previous first cleaning mode to the current cleaning.

  For example, the first cleaning mode is executed when the power switch 50 is turned off, the elapsed time from this time until the power switch 50 is turned on is counted by a timer, and the power switch 50 is turned on according to the elapsed time. The number of repetitions of the first cleaning mode in the cleaning to be executed is changed. Therefore, when resuming image recording after the power switch 50 is turned on, the reliability of image recording can be ensured by performing optimal cleaning according to the downtime of the apparatus.

  In the above description, the number of repetitions of the first cleaning mode suitable for removing the ink to be used is experimentally obtained in advance, and the first cleaning mode is repeated according to the leaving time and the leaving environmental conditions. The present embodiment has been described in which the ink fixed by drying is reliably removed by changing the number of times.

  Here, regarding the number of repetitions of the first cleaning mode, the number of repetitions of the first cleaning mode is set in accordance with the leaving condition (leaving time and environmental condition of leaving) that is most likely to be fixed in the ink jet recording apparatus. May be. In this case, the leaving time is set in advance (for example, overnight), and when the standing time is exceeded, the cleaning operation may be performed by repeating the first cleaning mode.

<Ink>
Next, the ink used in the ink jet recording apparatus of this embodiment will be described.

  The ink is preferably an ink in which a resin is dissolved or dispersed in the ink.

  For example, when the ink contains resin fine particles such as emulsion and latex in the water-based ink using the water-soluble dye, the storability of the image after printing is remarkably improved. By applying the present invention, it is possible to prevent or remove a resin thin film formed on the ink ejection surface and fix it, and it is possible to improve image storability after printing.

  In the present embodiment, the resin dispersed in the ink refers to resin particles dispersed in a medium, for example, water, and is also called latex.

  The resin fine particles can be used in the form of an aqueous dispersion of various resins. Specifically, acrylic, styrene-acrylic, acrylonitrile-acrylic, vinyl acetate, vinyl acetate-acrylic, vinyl acetate-vinyl chloride, polyurethane, silicon-acrylic, acrylic silicon, polyester, Epoxy resins can be mentioned.

  Usually, these resin fine particles are obtained by an emulsion polymerization method. The surfactants, polymerization initiators, etc. used there may be those used in conventional methods. Regarding the synthesis method of the non-colored resin fine particles, U.S. Pat. Nos. 2,852,368, 2,853,457, 3,411,911, 3,411,912, 4,197,127. Belgian Patent Nos. 688,882, 691,360, 712,823, JP-B 45-5331, JP-A-60-18540, 51-130217, 58-137831, 55-50240 and the like.

  In the ink according to the present embodiment, the average particle diameter of the resin particles is 10 nm or more and 300 nm or less, and more preferably 10 nm or more and 100 nm or less. If the average particle diameter of the resin particles exceeds 300 nm, the glossiness of the image is deteriorated, and if it is less than 10 nm, the water resistance and scratch resistance become insufficient. The average particle diameter of the resin particles can be easily obtained using a commercially available particle size measuring instrument using a light scattering method, an electrophoresis method, a laser Doppler method, for example, Zetasizer 1000 (manufactured by Malvern) or the like. .

  The content of the resin particles in the ink is preferably 0.2 to 10% by mass, and more preferably 0.5 to 5% by mass.

  In the present embodiment, a dye-based water-based ink containing a resin is used, but a pigment-type ink may be used. In particular, in the case of pigment ink, when the solvent or moisture evaporates, the pigment is basically insoluble in the solvent and does not re-dissolve. The ink jet recording apparatus according to the present invention capable of performing the above is particularly effective when a pigment ink is used.

  In the present embodiment, the water-based ink is, for example, a water-based inkjet ink containing 10% by mass or more of water per total ink mass.

  In the present embodiment, it is particularly preferable to use a pigment ink as a colorant in view of causing a larger problem than cleaning with a dye ink as described above. Further, it is also preferable from the viewpoint of the storage stability of the obtained image record. As the pigment used in the pigment ink, insoluble pigments, organic pigments such as lake pigments, carbon black and the like can be preferably used.

  These pigments preferably contain a resin as a pigment dispersant as required. Specifically, styrene, a styrene derivative, a vinyl naphthalene derivative, acrylic acid, an acrylic acid derivative, maleic acid, a maleic acid derivative, itaconic acid, an itaconic acid derivative, fumaric acid, and a fumaric acid derivative. A block copolymer made of a monomer, a random copolymer, and a polymer dispersant made of a salt thereof are preferable. Among these, styrene, acrylic acid, acrylic ester, methacrylic acid having a molecular weight of 3,000 or more. A block copolymer or a random copolymer selected from methacrylic acid esters and the like is preferable. Examples of these include styrene-acrylic acid-methyl methacrylate copolymer (molecular weight 10,000, acid value 160), and acryl-styrene resin Jonkrill 61 (manufactured by Johnson) and the like are available. .

  The content of the resin particles in the ink is preferably 0.2 to 10% by mass, and more preferably 0.5 to 5% by mass.

  In the case of using a polymer dispersant, the electric double layer is firmly formed around the pigment particles, and the dispersion stability can be improved. By applying the present invention, it is possible to prevent or remove the formation of a resin thin film on the ink ejection surface, and to improve the dispersibility.

It is a schematic diagram which shows schematic structure inside an inkjet recording device. 1 is a perspective view illustrating a schematic configuration of an ink jet recording apparatus. FIG. 2 is a schematic diagram illustrating a recording head, an ink supply device, and a cleaning unit of an ink jet recording apparatus. It is a block diagram which shows the electrical structure of the control apparatus of an inkjet recording device. 6 is a time chart illustrating a sequence operation in a first cleaning mode of a recording head in an inkjet recording apparatus. 6 is a time chart showing a sequence operation in a second cleaning mode of the recording head in the inkjet recording apparatus.

Explanation of symbols

1, 1Y, 1M, 1C, 1K Recording head 2 Control device 3, 3Y, 3M, 3C, 3K Main tank 4, 4Y, 4M, 4C, 4K Intermediate tank 5 Cleaning unit 6 Conveying belt 7 Recording medium 8 Feeding tray 9 Paper discharge tray 10 Housing 11, 11Y, 11M, 11C, 11K Ink supply pipe 12, 12Y, 12M, 12C, 12K Damper 13, 13Y, 13M, 13C, 13K Cap member 14, 14Y, 14M, 14C, 14K Wiper blade 15, 15Y, 15M, 15C, 15K Solenoid valve 16, 16Y, 16M, 16C, 16K Suction pump 17 Waste ink tank 18 Carriage

Claims (12)

A recording head having an ink discharge port for discharging ink to a recording medium;
A cap member for capping the ink discharge port of the recording head;
A communication port communicating the inside of the cap of the cap member and the atmosphere;
A valve for opening and closing the communication port;
A suction means that communicates with the cap member and applies a suction force to the inside of the cap ;
A wiping member for wiping the recording head;
As a first cleaning mode of the recording head, ink is sucked from the ink ejection port by driving the suction means with the cap member capping the ink ejection port of the recording head and closing the valve. A first operation to be performed, a second operation for stopping the suction means, a third operation for separating the cap member from the recording head, and a fourth operation for wiping the recording head by the wiping member. And execute
As a second cleaning mode of the recording head, ink is sucked from the ink ejection port by driving the suction means with the cap member capping the ink ejection port of the recording head and closing the valve. A first operation to be performed, a second operation to perform suction of ink remaining in the cap member by driving the suction means in a state where the valve is opened, and the cap member from the recording head. An ink jet recording apparatus comprising: a control device configured to execute a third operation for separating and a fourth operation for wiping the recording head by the wiping member after the first cleaning mode . The suction means includes a suction pump and a communication valve provided between the suction pump and the cap member,
The control device is characterized in that the suction means is stopped by closing the communication valve while the suction pump is operated, and the suction means is actuated by driving the suction means by opening the communication valve. The inkjet recording apparatus according to claim 1. The inkjet recording apparatus according to claim 1, wherein the cleaning is performed by repeating the first cleaning mode at least twice. The inkjet recording apparatus according to claim 1, wherein the first cleaning mode is performed on a regular basis. The inkjet recording apparatus according to claim 1, wherein the first cleaning mode is performed at predetermined time intervals. The ink jet recording apparatus according to claim 1, wherein the first cleaning mode is performed when the power is turned on. The ink jet recording apparatus according to claim 1, wherein the first cleaning mode is performed when the power is turned off. The ink jet recording apparatus according to claim 1, wherein the first cleaning mode is performed based on a user instruction. 9. The ink jet recording apparatus according to claim 1, wherein the ink is an ink in which a resin is dissolved or dispersed in the ink. The inkjet recording apparatus according to claim 9, wherein the number of repetitions of the first cleaning mode is set according to the content of the resin. The inkjet recording apparatus according to claim 9 or 10, wherein the number of repetitions of the first cleaning mode is set according to the type of the resin. 12. The inkjet recording apparatus according to claim 3, wherein the number of repetitions of the first cleaning mode is set according to an elapsed time from the execution of the immediately preceding first cleaning mode.

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