JP2005131906A - Inkjet recording apparatus, and recovery method of inkjet recording apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a recovery method of effectively removing filter clogging by a simple constitution. <P>SOLUTION: Ink and the air are made to flow backward from nozzles of a head by a rapid stream, thereby removing most of the ink of the filter. The efficiency of cleaning is enhanced, and the filter clogging can be removed efficiently. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an ink jet recording apparatus and a method for recovering the ink jet recording apparatus.

  In general, an ink jet recording apparatus includes a carriage on which a recording head as a recording unit can be mounted, a conveying unit that conveys a recording medium, and a control unit that controls these. Then, while ejecting ink as, for example, droplets from a plurality of ejection openings formed in the recording head, the carriage is serially scanned in the main scanning direction, and the recording medium is set in a predetermined sub-scanning direction perpendicular to the main scanning direction. Images are sequentially formed on a recording medium by intermittently conveying them in an amount.

  This recording method is a recording method in which ink is ejected in accordance with a recording signal and recording is performed by the ejected ink landing on a recording medium, and is a low-impact and quiet recording method with a low running cost. Therefore, many recording apparatuses such as printers, copiers, facsimiles, word processors and the like to which the ink jet recording method is applied have been put into practical use. In addition, since this recording method does not require a particularly complicated mechanism for implementation, it is relatively easy to downsize the apparatus, colorize, etc., and in recent years, a color recording apparatus using a plurality of colors of ink. Many products that have been applied to have been put to practical use. In such an ink jet recording apparatus, there are various methods for ejecting ink. For example, as a typical example, a heating element such as an electrothermal conversion element is provided in an ink path in the vicinity of an ejection port for ejecting ink, and film boiling occurs in the ink by the heat energy generated by the heating element. There is a method of discharging ink by the rapid generation pressure of bubbles due to film boiling.

  FIG. 1 is a conceptual diagram showing a general ink jet recording head adopting the above-described method from the direction in which ink is ejected. Here, in one recording head, 1280 nozzles are arranged at a pitch of about 20 μm, and an image having a recording density of 1200 dpi (dot / inch; reference value) can be recorded at high speed. Yes. Furthermore, recording of a color image is also supported by arranging a plurality of recording heads capable of ejecting inks of different hues in the main scanning direction (arrow direction) as shown in the figure.

  There are mainly two methods for supplying ink to the recording head. One is to mount an ink tank for holding ink on the carriage and to supply ink directly to the head. The other is to supply ink by connecting between a tank holding ink and a head using a tube called a supply tube. The former is a means that is often applied in home printers and printers that are easy to carry because the main unit is relatively simple. On the other hand, since the latter does not require a tank to be mounted on the carriage, it is possible to use a large ink tank, and it is often applied as a printer for offices or professional use with a large print volume.

  FIG. 2 shows an example of a printing apparatus including a supply system using such a tube supply.

  Reference numerals 201a to 201f denote ink tanks that contain liquid ink. A supply tube 202 supplies ink to the head 203. The head 203 has nozzles as shown in FIG. 1, and performs recording by discharging ink. The recovery system 204 has a suction pump, and is used when filling the ink in the head, and has a role of sucking and removing dust and fixed matter attached to the head. FIG. 3 is a longitudinal sectional view of the head. The filter 309 has a role of preventing dust from entering the nozzle 312. For dust smaller than the nozzle 312, even if it passes through the filter, there is a high possibility that the nozzle will also pass through. For this reason, in order to prevent the nozzle from being clogged with dust, the hole diameter of the filter is usually designed to be smaller than the nozzle diameter. 310 is a damper made of rubber, which prevents a sudden change in internal pressure.

  Further, as the ink to be used, there are generally pigment ink and dye ink. Dye inks are excellent in color developability but poor in image fastness, and pigment inks are excellent in image fastness and are difficult to fade even when the printed matter is left outdoors for a long time. Recently, inkjet printers are used in many applications, and pigment inks with particularly high image robustness are used as office printers that require document reliability and large format printers for creating posters for outdoor exhibitions. Many are applied.

  As described above, various color materials are used according to various printer forms and applications. However, some of the color materials used may be in a slightly unstable but unstable dissolved state or dispersed state in the ink. When such a form of ink is used, the dispersion stability and dissolution stability of the ink may decrease due to long-term standing or the like, and the ink may stick from the ink supply path to the nozzle. In particular, the gap of the filter 309 in FIG. 3 has various sizes and may be clogged. If the filter gap is clogged, the ink has a large pressure loss when it reaches the nozzle, and the ejection becomes unstable, causing image degradation.

As a conventional technique, a method of cleaning a filter by reversing a pressure pump existing in a supply system is disclosed as an effective cleaning method for the filter (see, for example, Patent Document 1). However, this method cannot be applied to a general supply recovery system such as that shown in FIG. 2 without adding a pump, and it is relatively difficult to perform a simple pump reversal particularly when the degree of filter clogging is significant. In many cases, sufficient effects cannot be obtained.
Japanese Patent Laid-Open No. 07-052398

  Further, such a filter is clogged (hereinafter referred to as “filter clogging”). When ink that generates water is used, a method of removing the ink by suction or the like with a tube pump installed under the head is common. However, in order to remove the filter clogging or maintain the removed state, there is a possibility that an excessive number of times of suction is required rather than a frequency that is normally used. At this time, excessive suction may fill up the waste ink capacity of the printer at an early stage. In such a case, the total number of printable sheets of the printer is remarkably reduced, or it takes time and effort for the service person to replace the waste ink absorber, which is a great disadvantage for the user. Further, if the head becomes unusable due to clogging of the filter, the head or the entire apparatus will be replaced, which will be very expensive.

  The present invention has been made in view of the above points, and it is an object of the present invention to provide a recovery method that effectively removes filter clogging with a simple configuration.

The present invention relates to an ink jet recording apparatus that uses a recording head having a plurality of nozzles and performs recording by ejecting ink droplets from the nozzles onto a recording medium. The ink jet recording apparatus stores ink. Having a container, and further having a filter in at least one of the places where the ink passes,
Air and / or ink are allowed to pass from the nozzle side to the ink container side with respect to the filter.

  More preferably, the ink jet recording apparatus includes an ink supply unit that supplies the ink from the ink container to the recording head, an openable / closable valve that controls the flow of ink to the ink supply unit, and the ink from the nozzle. A suction pump for sucking, and in the recovery method, the ink in the supply means is depressurized by performing suction with the valve closed, and the ink between the filter and the suction pump. By opening the air to the atmosphere, the ink and / or air are passed through the filter from the nozzle side to the ink container side.

  More preferably, the ink jet recording apparatus has a cap that communicates with the suction pump and seals the nozzle, and the method of releasing the ink to the atmosphere includes opening the cap or an air communication port leading to the cap to the atmosphere. It is characterized by being.

  More preferably, the reduced pressure state is characterized in that the pressure in the supply means is reduced by ¼ atmosphere or more with respect to the atmospheric pressure.

  More preferably, in addition to the recovery method, the inkjet recording apparatus also has a normal recovery method by allowing the ink to pass from the ink container side to the nozzle side with respect to the filter. It is characterized by using both recovery methods properly.

  More preferably, in addition to the recovery method, the ink jet recording apparatus also has a normal recovery method by flowing the ink from the ink container side to the nozzle side with respect to the filter. And a recovery sequence to be performed.

  More preferably, the recovery sequence includes performing a recovery method for allowing air and / or ink to pass through the filter from the nozzle side to the ink container side at least once, and then performing the nozzle from the ink container side. 7. The ink jet recording apparatus according to claim 1, wherein a recovery method for allowing air and / or ink to pass to the side is performed at least once.

According to another aspect of the present invention, there is provided a method for recovering an ink jet recording apparatus in which a recording head having a plurality of nozzles is used and ink droplets are ejected from the nozzles onto a recording medium by the recording head. An ink container for storing the ink, and further having a filter in at least one of the places where the ink passes,
Air and / or ink are allowed to pass from the nozzle side to the ink container side with respect to the filter.

  More preferably, the ink jet recording apparatus includes an ink supply unit that supplies the ink from the ink container to the recording head, an openable / closable valve that controls the flow of ink to the ink supply unit, and the ink from the nozzle. A suction pump for sucking, and in the recovery method, the ink in the supply means is depressurized by performing suction with the valve closed, and the ink between the filter and the suction pump. The ink and / or air is allowed to pass through the filter from the nozzle side to the ink container side.

  More preferably, the ink jet recording apparatus has a cap that communicates with the suction pump and seals the nozzle, and the method of releasing the ink to the atmosphere is to open the cap or the air communication port that leads to the cap to the atmosphere. It is characterized by that.

  More preferably, the reduced pressure state is characterized in that the pressure in the supply means is reduced by ¼ atmosphere or more with respect to the atmospheric pressure.

  By adopting the above configuration, even when using ink that is relatively clogged, it is possible to remove most of the ink in the filter once by passing the air through the filter and refreshing the filter. As a result, the cleaning efficiency is improved, the clogging of the filter is efficiently removed, and a desired image density for the user can always be realized.

  The present invention is characterized by improving the efficiency of cleaning and removing clogging of filters efficiently by almost removing the ink of the filter by causing the ink and air to flow backward from the nozzle of the head in a rapid flow. Yes.

(Example)
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  First, FIG. 23 shows an example of the appearance of the ink jet recording apparatus used in this embodiment.

  FIG. 23 is a perspective view showing a configuration of an ink jet recording apparatus having a recording head for six colors. In FIG. 23, reference numeral 2301 denotes a carriage for attaching a recording head capable of printing black, light cyan, cyan, light magenta, magenta, and yellow ink to the printer body. In addition, a flexible tube (2302) for supplying a signal pulse current for driving and a head temperature adjusting current to the recording head is provided on the carriage, and a printed board (not shown) provided with an electric circuit for controlling the printer. Connected). Ink is supplied to the ink jet recording head from a six-color tank unit (not shown) via an ink supply tube (2303) attached to the flexible cable independently for each color.

  Printing is performed as follows. A recording object (2305) set on a paper feed tray (2304) is picked up by a paper feed roller (not shown), and is passed along a U-turn guide (not shown) to pass through a platen (2306). Send it up. Using the carriage moving encoder (2307), the carriage is moved in the sub-scanning direction along the guide shaft (2308), and the paper is fed by a paper feed roller (not shown). Printing is performed, and a non-printed material is discharged by a paper discharge roller (not shown) to complete the printing.

  FIG. 4 is a cross-sectional view showing details of the recording head 1, and a heater board 16 formed by a semiconductor manufacturing process is provided on the upper surface of the support 20. The heater board 16 is provided with a temperature adjustment heater (temperature increase heater) 17 formed by the same semiconductor process for keeping the recording head 1 warm and adjusting the temperature. Reference numeral 19 denotes a wiring board wired on the support 20, and the wiring board 19, the temperature adjustment heater 17 and the discharge heater 18 are wired by wire bonding or the like (wiring is not shown). Moreover, the heater 17 for temperature control may be obtained by attaching a heater member formed by a process different from the heater board 16 to the support 20 or the like.

  Reference numeral 14 denotes bubbles generated by being heated by the discharge heater 18. Reference numeral 15 denotes an ejected ink droplet. Reference numeral 13 denotes a common liquid chamber for discharging ink to flow into the recording head.

  The first embodiment of the present invention will be described below.

  FIG. 5 is a schematic diagram showing the configuration of the ink supply system used in this embodiment. Reference numeral 501 denotes an ink tank. Reference numeral 507 denotes a head. Reference numeral 512 denotes a nozzle that ejects ink. Reference numeral 508 denotes a liquid chamber. Reference numeral 509 denotes an in-head filter that functions to prevent dust from reaching the nozzle. Reference numeral 510 denotes a rubber damper, which is a buffer material for sudden changes in internal pressure. Reference numeral 503 denotes an ink supply tube. A valve 511 controls ink supply and is closed when the head is filled with ink or when transported at 2 o'clock. Reference numeral 504 denotes a supply pin through which ink in the tank is supplied. Reference numeral 505 denotes an air communication pin, and the air for the consumed ink is supplied through the pin to keep the internal pressure substantially constant. Reference numeral 506 denotes an ink meniscus, which is an air communication surface. The negative pressure applied to the head is formed by a water head difference between the nozzle 512 and the meniscus 506. In this embodiment, the negative pressure is set to -90 mmAq. Reference numeral 513 denotes a sub-buffer chamber that prevents ink from leaking through the air communication port even when the meniscus is broken due to an internal pressure change such as a sudden increase in ambient temperature. FIG. 6 shows an outline of a recovery device in a general head. Reference numeral 601 denotes a cap, which can prevent the ink from drying by being in close contact with the face surface of the head during printing standby. A state in which the face surface of the head is in close contact with the cap is called a capping state.

  In FIG. 6, reference numeral 602 denotes a tube pump. When ink in the nozzle is fixed, the tube 601 is rotated from a state in which the cap 601 is in close contact with the surface of the head to generate a strong decompression in the cap 601 and fix the ink. The removed ink can be removed by suction. Reference numeral 603 is called a wiper, and dust attached to the surface of the head is removed by moving the wiper back and forth.

  Incidentally, as described above, depending on the type of ink, continuous printing may cause the filter 509 in FIG. 5 to be clogged. This is a problem that occurs when the solubility and dispersibility of ink become unstable. FIG. 7 illustrates this possible mechanism.

  The ink 713 may be lowered in dissolution stability or decomposition stability due to long-term storage or transportation such that it experiences excessively high or low temperatures. When the ink 713 in such a state continuously passes through the filter by printing, the ink adsorbs on the filter as shown in FIG. 7B, or relatively large particles in the filter pores. It seems that the state becomes clogged.

  In this state where the ink is clogged, the flow path resistance of the filter increases. As the printing is repeated, the pressure loss due to the flow path increases, and the pressure of the ink existing in the liquid chamber 708 and the nozzle 712 decreases. When the ink pressure is drastically reduced, the ink is not ejected normally and the density of the image is lowered.

  FIG. 8 shows the relationship between the number of printed sheets and the image density when using a printer such as that shown in FIG. 23 and using ink that is relatively susceptible to filter clogging. The vertical axis represents the optical density of the image. The horizontal axis is the number of printed sheets. In this embodiment, a large format printer is used. In addition, this time, inkjet glossy paper was used, and yellow ink, which is relatively susceptible to filter clogging, was used. One image has an A0 size of 1189 mm in length and 841 mm in width. The print density is defined as 100% when 8.5 pl of ink is applied to a vertical 1/120 inch horizontal 1/600 inch square region, and printing is performed at a print density of 20%. As is apparent from the figure, the image density decreases as the number of printed sheets increases.

  As described above, cleaning using a suction pump has been conventionally performed. It is considered that the suction by the suction pump not only removes the stuck matter in the nozzle but also removes the clogging accumulated or adhered to the filter. FIG. 9 shows an example of a cleaning operation sequence. First, in step 901, the head is moved to the cap position. Next, in step 902, capping is performed. Next, in step 903, the suction pump is rotated forward. In this embodiment, suction is performed for 3 seconds. In step 904, the capping is canceled. Next, in order to prevent ink from entering the adjacent nozzles and mixing the colors, in step 905, wiping and preliminary ejection are performed. In the preliminary ejection, ejection is performed on the cap, not on the recording medium. Hereinafter, such cleaning is referred to as “normal cleaning”.

  FIG. 10 shows a control sequence in the case where such normal cleaning is performed once for a print of 5 sheets of A0 paper 20% duty pattern. First, before printing, in step 1001, the dot count Dy of yellow ink is referred to. In step 1002, the yellow ink dot count value Dy is compared with the threshold value Dt. Dt is a value corresponding to the dot count for printing 5 sheets of A0 paper 20% duty pattern. When Dy exceeds Dt, normal cleaning is performed (step 1003). When cleaning is performed, the yellow dot count value Dy is cleared (step 1004). Subsequently, in step 1005, printing is performed. The yellow dot count number δy used for printing is again added to the dot count value Dy in step 1006.

  FIG. 11 shows the relationship between the number of printed sheets and the image density when normal cleaning is performed once with a pattern of 20% duty on A0 paper for five sheets of printing. In the initial stage, a head that does not print at all, that is, a state in which almost no ink passes through the filter is used. As shown in FIG. 11, every time cleaning is performed, the image density slightly approaches the initial level, but the cleaning performance is insufficient and the density gradually decreases.

  Further, a cleaning method in which the valve is closed and suction is performed and the valve is released has been conventionally known. This method has been shown to be more effective for nozzle sticking. FIG. 12 shows an operation sequence of valve closing suction. First, in steps 1201 and 1202, the carriage is moved to the cap position and capped. Next, in step 1203, the supply valve is closed. Next, in step 1204, the suction pump is sufficiently rotated to reduce the pressure in the head. In this embodiment, the pump is rotated for 30 seconds. In this state, in step 1205, the suction pump stops rotating and the valve is released. Leave it on for 5 seconds before releasing the cap. Subsequently, in step 1207, wiping for preventing color mixture and preliminary discharge are performed. By releasing the valve at once from a state where the pressure has been sufficiently reduced by the operation sequence as described above, it is possible to realize a high flow rate with respect to the ink passing through the nozzle and to realize a high cleaning property. Hereinafter, this cleaning operation is referred to as “normal valve closing suction”.

  FIG. 13 shows the relationship between the number of printed sheets and the image density when this normal valve closing suction is applied once in 50 sheets for A0 size, 20% printed matter. In normal valve closing suction, the amount of ink consumed is large, so the frequency is reduced compared to the normal cleaning in FIG. Compared to FIG. 11, it can be seen that the recoverability of the image density is high. However, if you look closely at FIG. 13, the deterioration of the image density is worse after the history of cleaning with respect to the reduction of the image density from the initial state of the head. This is considered to be because the pressure loss of the filter is reduced to such an extent that the image is not affected by this cleaning, but what is completely adhered or deposited on the filter cannot be removed.

  From the above points, the present inventor has intensively studied a recovery sequence that improves the cleaning performance of the filter. As a result, the following cleaning sequence has been found to be very effective in suppressing the increase in filter pressure loss. FIG. 14 shows the cleaning operation sequence of this embodiment. First, also in this embodiment, the head is capped in step 1401 in the same manner. Next, in step 1403, the valve is closed. In step 1404, the suction pump is rotated to perform suction. As a result, the pressure of ink and air in the head and in the flow path is lowered. In this state, in step 1405, the cap is released. By performing this operation, the nozzle is released to the atmosphere. Since the pressure in the head and the flow path is reduced, the atmosphere flows from the nozzle, and the ink flows backward and flows toward the supply valve. Next, as shown in steps 1406 to 1409, normal valve closing suction is performed from this state. Normally, the valve closing suction releases the supply valve in a state where the pressure in the head is reduced, so that the air with high compression / expansion is sufficiently removed from the head and the ink supplied from the valve side can fill the head. Is possible. The operation sequence as described above is called “backflow cleaning”. In the operation sequence of this embodiment, the backflow of air into the head and the ink filling into the head are performed once each, but it goes without saying that the number is not limited to this.

  It has been found that filter deposits and deposits can be sufficiently removed by cleaning such as removing the nozzle and the ink in the filter and refilling them.

  FIG. 15 shows the relationship between the number of printed sheets and the image density when backflow cleaning is performed once in 50 sheets for a printing pattern of 20% A0 paper. Since the amount of ink consumption is large as in the case of normal valve closing suction, the frequency is lowered. In the inkjet recording apparatus of the present embodiment, it has been confirmed that the amount of ink consumption is almost the same as that when the normal valve closing suction is performed alone, and the cleaning is performed at the same frequency as the normal valve closing suction. Carried out. Compared with the normal valve closing suction in FIG. 13, the speed of image density reduction after cleaning is suppressed, and it is possible to realize almost the same situation as in the initial stage.

  16 to 17 are diagrams for explaining a possible mechanism. FIG. 16 shows a possible situation of the filter in the head when normal valve closing suction is performed. FIG. 16A shows a state before cleaning. On the other hand, FIG. 16B shows a state at the moment when the valve is opened after the valve is closed and suctioned. FIG. 16C shows a state in which the rapid ink flow is finished and the clogging in the filter is removed. Normally, valve closing suction causes the ink to rapidly pass through the filter by opening the valve. However, even if the ink speed is high, the flow rate of the narrow portion of the filter does not increase, and it is not possible to completely remove the filter deposits and deposits.

  On the other hand, FIG. 17 shows the situation in the head when backflow cleaning is performed. FIG. 17A shows the situation before cleaning. From this state, the valve is closed and suction is performed to reduce the pressure in the head. FIG. 17B shows the state at the moment when the cap is released from this state. By releasing the cap, air flows in rapidly. As a result, the ink flows backward, and the deposits in the filter can be removed in the same manner as the normal valve closing suction. Furthermore, air passes through the filter. Since air is much less viscous than ink, the speed of passing through the filter is high. It is believed that this air flow makes it possible to remove most of the clogging that has adhered or deposited in the narrow voids in the filter. FIG. 17C shows the state of the filter at the time when the backflow is completed. Moreover, it is predicted that the filter is likely to be clogged upstream due to its structure. Therefore, it is considered that the clogging can be removed relatively easily by the back flow.

  In this embodiment, the pressure is reduced by closing the valve. In order to release the atmosphere at once from the reduced pressure state, it is considered that the cleaning effect is enhanced by generating a rapid backflow of air and ink. The following table shows the amount of pressure reduction in the liquid chamber in the head with the valve closed and the recovery status. When the amount of decompression is low, the filter cannot be refreshed unless back-flow cleaning is performed repeatedly. In the table, A is a state in which the image density decrease curve is returned to the initial state. B is a state where there is almost no problem although the image density decrease curve is somewhat worse. C indicates a state where the deterioration of the image density decrease curve is remarkable.

In this embodiment, the reduced pressure is 3/4 atm, and the cleaning is repeated once.

  FIG. 18 shows an application method when applying the recovery sequence of this embodiment to an actual printer. First, before printing, in step 1801, the dot count value Dy of yellow ink is referred to. Next, in step 1802, the dot count value Dy of yellow ink is compared with the threshold value Dt. Dt is a value corresponding to a dot count for printing 50 sheets of a 20% duty pattern on A0 paper. When Dy exceeds Dt, reverse flow cleaning is performed. When cleaning is performed, the yellow dot count value Dy is cleared. Next, printing is performed. The yellow dot count number δy used for printing is again added to the dot count value Dy.

  In addition, when applying the dot count value of only ink that is likely to be clogged due to the configuration of the printer head, etc., when adopting the maximum value of all color inks for cleaning, and further, the dot count value of all colors. There are cases where the sum of the two is applied, but it goes without saying that either may be applied depending on the case.

  By adopting the configuration as described above, even when ink that tends to clog a filter is used, clogging that clogs the filter can be effectively removed by backflow cleaning, preventing image deterioration and use. It is possible to realize a desired image density for a person.

  This embodiment is characterized in that both normal valve closing suction and backflow cleaning are used in combination. In many printers that use tubes as the ink supply path, valve closing suction is usually an effective recovery means. This is because it becomes an effective means for removing air that has accumulated in the tube or the head through the tube wall or the like. In addition, as shown in the first embodiment, there is a recovery effect against filter clogging, although not as much as backflow cleaning. This embodiment is characterized in that the backflow cleaning is performed in synchronization with the normal valve closing suction.

  FIG. 19 shows an example of application of such a recovery sequence. First, before printing, the yellow dot count Dy is referenced in step 1901. Subsequently, in step 1902, backflow cleaning is performed when the yellow dot count Dy is larger than Dta. Dta is a value corresponding to a dot count for printing 50 sheets of a 20% duty pattern on A0 paper. Since the dot count Dy is not cleared at this time, the fact that the reverse flow cleaning has been performed is stored by setting the optional parameter α = 1. Thereafter, as long as α = 1, even if Dy is larger than Dta, backflow cleaning is not performed.

  Next, normal valve closing suction is performed when Dy exceeds Dtb. Dtb is a value corresponding to the dot count for printing 80 sheets of a 20% duty pattern on A0 paper. The reason why the normal valve closing suction is performed in accordance with the dot count is to remove bubbles due to bubbles mixed from the nozzles by printing, and to remove filter clogging by printing.

  FIG. 20 simply shows the dot count value and the cleaning timing. Reference numeral 2001 denotes a time axis, 2002 denotes a backflow cleaning timing, and 2003 denotes a normal valve closing cleaning timing. By alternately performing cleaning at approximately equal intervals, the interval between the cleaning and the next cleaning can be efficiently reduced.

  By adopting such a configuration, it is possible to perform backflow cleaning and normal valve closing suction cleaning with good timing, and it is possible to suppress a decrease in print density.

  In this embodiment, the backflow cleaning and the normal valve closing suction cleaning are synchronized using the dot count. However, in general, the suction may be performed every certain period. It goes without saying that the backflow cleaning and the normal valve closing suction cleaning may be synchronized with such time control.

  In addition, as for the dot count value, when applying the dot count value of only ink that is likely to clog the filter as in the first embodiment, when adopting the maximum value of all color inks for cleaning, and further for the dot count of all colors. There are cases where sums are applied, but either can be applied.

  In this embodiment, a pressure system is built in the head. In FIG. 21, when the filter is clogged, the pressure at the position in the head 2108 is greatly reduced by discharging. Reference numeral 2114 denotes a pressure gauge. This embodiment is characterized in that the ink flow is generated by performing preliminary ejection, and the backflow cleaning is performed only when the pressure loss value in that state exceeds a certain value.

  FIG. 22 shows a cleaning sequence using the above configuration. While performing preliminary discharge in step 2201, the value of the pressure gauge is checked in step 2202. When the increase in pressure loss increases by a certain value Pt or more, backflow cleaning is performed. In this embodiment, 0.03 atm, which is a range of pressure loss with little influence on the image density, is given as Pt. Further, when the pressure loss is small, printing is started. The same pressure loss check is repeated when about 10 sheets are printed on the A0 sheet again.

  By adopting the above-described configuration, the backflow cleaning can be performed only when pressure loss actually occurs. As a result, it is possible to perform the minimum necessary cleaning, and it is possible to suppress an increase in the amount of waste ink caused by the cleaning to a minimum.

  In this embodiment, the atmosphere of the nozzle is released through the atmosphere release valve provided in the recovery system cap. FIG. 24 shows a cap and a tube used in a general printer recovery system. In the figure, 2401 is a cap, and 2402 is a tube pump. Reference numeral 2403 denotes an air release valve. Usually, the ink in the cap can be removed by turning the suction pump with the air release valve opened.

  The present embodiment is characterized in that the atmosphere communication valve is opened instead of the cap opening in the first embodiment. Accordingly, it is possible to reduce the mechanical load by opening the atmospheric communication valve having a valve structure in advance, rather than releasing the cap in a decompressed state.

  The present embodiment is characterized in that the backflow cleaning and the normal valve closing cleaning are performed twice in the recovery sequence in the first embodiment. The cleaning sequence in this embodiment is shown in FIG. In contrast to the cleaning sequence shown in the first embodiment, in this embodiment, backflow is performed again in step 2507. Further, the normal valve closing suction performed thereafter is performed twice to ensure the ink filling in the head. Such a sequence can further enhance the cleaning effect due to the backflow. In particular, in step 2507, which is the second time in the backflow sequence, backflow is performed in a state where the amount of ink remaining in the head is small, so that a high cleaning effect by air can be obtained.

Front view of recording head Schematic diagram of supply system of ink jet recording apparatus according to the present invention Vertical section of recording head Vertical section of nozzle in recording head Schematic diagram of the supply system of the ink jet recording apparatus according to the present invention 1 is a schematic view of a recovery device for an ink jet recording apparatus according to the present invention. Schematic diagram showing the filter Graph showing the relationship between optical density and number of printed sheets when filter clogging occurs Flow chart showing normal cleaning sequence Flow chart showing the sequence for determining the implementation of normal cleaning Graph showing the relationship between optical density and number of printed sheets when normal cleaning is performed Flow chart showing normal valve closing suction sequence Graph showing the relationship between optical density and number of printed sheets when normal valve closing suction is performed Flow chart showing backflow cleaning sequence Graph showing the relationship between optical density and number of printed sheets when backflow cleaning is performed Expected filter and filter clogging when normal valve closing suction is performed Possible filter and filter clogging when backflow cleaning is performed Flow chart showing the sequence for determining the implementation of backflow cleaning Flow chart showing the sequence for determining the implementation of both reverse flow cleaning and normal valve closing suction The figure which shows the timing of cleaning in the case of performing both reverse flow cleaning and normal valve closing suction Vertical sectional view of the head used in Example 3 In Example 3, it is a flowchart which shows the sequence which determines implementation of backflow cleaning. Schematic perspective view of an ink jet recording apparatus according to the present invention Sectional drawing of the recovery apparatus of the inkjet recording device concerning Example 4. FIG. Flow chart showing cleaning sequence for backflow cleaning and valve closing suction twice.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Recording head 11 Nozzle part 13 Common liquid chamber 14 Bubble 15 Ink droplet 16 Heater board 17 Temperature control heater 18 Discharge amount heater 19 Wiring base 20 Support body 201,501 Ink tank 202,503,1003 Supply tube 203,507,707 2107 Recording head 204 Recovery system 309, 509, 709, 1401, 2109 Filter 310, 510, 710, 2110 Rubber damper 312, 512, 712, 2112 Nozzle 504 Supply pin 505 Atmospheric communication pin 506 Meniscus 508, 708, 2108 Liquid chamber 511 Supply valve 513 Sub tank 601 Cap 602 Tube pump 603 Wiper 713 Ink s901 to s905 Block for determining the recovery sequence s1001 to s1007 Recovery sea Block s1201 to s1207 block to determine the recovery sequence s1401 to s1409 block to determine the recovery sequence s1801 to s1807 block to determine the execution of the recovery sequence s1901 to s1908 block to determine the execution of the recovery sequence 2001 time axis 2002 Arrow indicating timing for performing reverse flow cleaning 2003 Arrow indicating timing for performing normal valve closing suction 2114 Pressure gauge s2201 to s2206 Block diagram for determining recovery sequence 2301 Carriage 2302 Flexible tube 2303 Supply tube 2304 Paper feed tray 2305 Recording Object 2306 Platen 2307 Carriage moving encoder 2308 Guide shaft 2401 Cap 24 Block to determine a second tube pump 2403 air release valve s2501~s2512 recovery sequence

Claims (11)

In an ink jet recording apparatus that uses a recording head having a plurality of nozzles to perform recording by discharging ink droplets from the nozzles onto a recording medium, the ink jet recording apparatus has an ink container for storing ink. And further having a filter in at least one of the places where the ink passes,
An ink jet recording apparatus comprising: a recovery method for allowing air and / or ink to pass from the nozzle side to the ink container side with respect to the filter.   The ink jet recording apparatus includes: an ink supply unit that supplies the ink from the ink container to the recording head; an openable / closable valve that controls an ink flow to the ink supply unit; and a suction pump that sucks the ink from the nozzle And the recovery method opens the ink between the filter and the suction pump to the atmosphere from the state in which the ink in the supply means is depressurized by performing suction with the valve closed. The ink jet recording apparatus according to claim 1, wherein the ink and / or air is passed through the filter from the nozzle side to the ink container side.   The ink jet recording apparatus has a cap that communicates with the suction pump and seals the nozzle, and the method of releasing the ink to the atmosphere is to open the cap or an air communication port leading to the cap to the atmosphere. The ink jet recording apparatus according to claim 2, wherein:   4. The ink jet recording apparatus according to claim 2, wherein the reduced pressure state is a state in which the pressure in the supply means is reduced by ¼ atmosphere or more with respect to the atmospheric pressure.   In addition to the recovery method, the ink jet recording apparatus also has a normal recovery method by allowing the ink to pass from the ink container side to the nozzle side with respect to the filter. The ink jet recording apparatus according to claim 1, wherein the ink jet recording apparatus is selectively used.   In addition to the recovery method, the inkjet recording apparatus also has a normal recovery method by flowing the ink from the ink container side to the nozzle side with respect to the filter, and recovery is performed by continuously performing both recovery methods. 6. The ink jet recording apparatus according to claim 1, further comprising a sequence.   In the recovery sequence, after the filter is subjected to a recovery method of passing air and / or ink from the nozzle side to the ink container side at least once, the air from the ink container side to the nozzle side and 7. The ink jet recording apparatus according to claim 6, wherein a recovery method for allowing ink to pass is performed at least once. In a recovery method of an ink jet recording apparatus that uses a recording head having a plurality of nozzles and performs recording by ejecting ink droplets from the nozzles onto a recording medium using the recording head, the ink jet recording apparatus is an ink container for storing ink And having a filter in at least one of the places where the ink passes,
A method for recovering an ink jet recording apparatus, wherein air and / or ink are passed from the nozzle side to the ink container side with respect to the filter.   The ink jet recording apparatus includes: an ink supply unit that supplies the ink from the ink container to the recording head; an openable / closable valve that controls an ink flow to the ink supply unit; and a suction pump that sucks the ink from the nozzle And the recovery method opens the ink between the filter and the suction pump to the atmosphere from the state in which the ink in the supply means is depressurized by performing suction with the valve closed. The method according to claim 8, wherein the ink and / or air is passed through the filter from the nozzle side to the ink container side.   The ink jet recording apparatus has a cap that communicates with the suction pump and seals the nozzle, and the method of releasing the ink to the atmosphere is to open the cap or an air communication port that leads to the cap to the atmosphere. The method for recovering an ink jet recording apparatus according to claim 9. 11. The method for recovering an ink jet recording apparatus according to claim 9, wherein the reduced pressure state is a state in which the pressure in the supply means is reduced by ¼ atmosphere or more with respect to the atmospheric pressure. .

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