JP2010105169A - Ink filling method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To surely fill inks into all of recording heads at the time of the initial filling of an inkjet printer or when the recording heads are exchanged in maintenance. <P>SOLUTION: The inkjet printer has a plurality of the recording heads 2, an upper tank 6 at a position higher than a nozzle plate 33, a first atmosphere opening valve 22 which makes the interior of the upper tank 6 communicate with an atmosphere or blocks the interior from the atmosphere, a pump 11 which sends the ink to the upper tank 6, a lower tank 7 at a position lower than the nozzle plate 33, a second atmosphere opening valve 26 which makes the interior of the lower tank 7 communicate with the atmosphere or blocks the interior from the atmosphere, and an ink cartridge 9 which supplies the ink to the lower tank 7. The inkjet printer has an ink circulation part 4 in which the ink flows from the upper tank 6 through the recording heads 2 to the lower tank 7 and is pumped up again by the pump 11 to the upper tank 6 to be circulated. The ink is filled into the ink circulation part 4 by controlling the sending action of the pump 11 and the opening and closing action of the first atmosphere opening valve 22. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an ink jet printer including an ink filling method for efficiently filling ink in an ink path.

  2. Description of the Related Art Conventionally, in general, an image recording apparatus (inkjet printer) using an inkjet recording method is equipped with a recording head such as a thermal head method or an electromechanical conversion element (piezo) method, and a recording medium such as a recording sheet by the recording head. Recording (printing) is performed by ejecting ink droplets on the top. Some of such image recording apparatuses include an ink circulation path for circulating ink.

  For example, an image recording apparatus disclosed in Patent Document 1 includes a recording head, a first ink chamber provided above the recording head, a second ink chamber provided below the recording head, and a recording head. An ink circulation path is formed by a pipe connecting each of the first ink chamber and the second ink chamber and a pump.

The supply and recovery of the ink inside the recording head is performed by the height difference between the two ink chambers of the first ink chamber and the second ink chamber, and the ink recovered in the second ink chamber is pumped. It is configured to pump up to the first ink chamber.
JP 2001-219580 A

Incidentally, Patent Document 1 describes that a plurality of recording heads may be used for each color. However, in the image recording apparatus having the ink circulation path described in Patent Document 1, when a plurality of recording heads are used for each color, the following problems occur.

  In an ink jet printer, generally, a recording head is not filled with ink at the time of initial installation on the user side after shipment from a factory. Even when the recording head is replaced due to a problem, the replaced recording head is not filled with ink. Therefore, it is necessary to fill all the recording heads with ink. However, since there is a recording head in which air is mixed at the time of initial filling or replacement of the recording head, it is not possible to fill all the recording heads with only a normal ink circulation operation.

  This is because the ink flows normally at a location where ink is filled because the load on the ink flow is small, but conversely, the location where the air stagnates increases the load on the ink flow and makes it difficult for the ink to flow. is there. In other words, at the time of initial filling, ink does not enter all the recording heads at the same time, and ink enters and exits with an irregular time difference, so that a recording head filled with ink and a recording head not filled with ink are generated. Ink flows only to the recording head at the location filled with ink. Further, when the recording head is replaced, since ink is filled other than the replaced recording head, the ink flows only to the recording head where the ink is filled. As a result, it is not possible to fill all the recording heads with ink.

However, Patent Document 1 only describes that all the recording heads are already filled with ink, and does not describe any ink filling method at the time of initial filling or when the recording head is replaced.

  Accordingly, in order to solve the above-described problems, the present invention provides an ink jet printer that has a plurality of recording heads for each color and performs image recording while circulating ink, so that all the recording heads are reliably filled with ink. An object of the present invention is to provide an ink filling method that can be used.

  In order to solve the above problems, an ink jet printer of the present invention includes a nozzle plate having a plurality of nozzle holes for discharging ink, a plurality of ink heads for printing on a recording medium, and a gravitational direction from the nozzle plate surface. The upper tank, which is disposed at a high position, temporarily stores ink to be supplied to the ink head, the first atmosphere release valve which allows the inside of the upper tank to communicate with and shut off the atmosphere, and the upper tank stores the ink. A liquid level sensor that detects the ink level to be discharged, a pump that supplies ink to the upper tank, and an ink that is disposed at a position lower in the gravitational direction than the nozzle plate surface, and is supplied from the ink head and supplied to the pump. A lower tank that temporarily stores the second tank, a second atmosphere release valve that allows the inside of the lower tank to communicate with and shut off the atmosphere, and the upper tank or the lower part An ink cartridge for supplying ink to the ink tank, and ink flowing out from the upper tank flows down to the lower tank through the ink head, and the ink that has flowed down to the lower tank is pumped up to the upper tank by a pump, thereby circulating the ink. In the ink jet printer having the ink path that enables the ink level of the ink stored in the upper tank by the liquid level sensor, and by controlling the liquid feeding operation of the pump and the opening and closing operation of the first atmosphere release valve, An ink filling method for filling ink in an ink path is provided.

  According to the present invention, there is provided an ink filling method capable of reliably filling all recording heads with ink in an ink jet printer that has a plurality of recording heads per color and performs image recording while circulating ink. be able to.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
(First embodiment)
FIG. 1 is a diagram schematically showing an ink path configuration of an ink jet printer according to a first embodiment of the present invention.

  In FIG. 1, a supply unit that supplies a recording medium, a conveyance mechanism that conveys the supplied recording medium, a discharge unit that unloads an image-formed recording medium, and maintenance of an ink head (hereinafter also referred to as a recording head). The illustration of a maintenance unit that performs the above and an apparatus control unit that controls the entire apparatus including ink ejection control is omitted.

  The ink jet printer 1 shown in FIG. 1 records an image on a recording medium using, for example, four kinds of inks of cyan (C), magenta (M), yellow (Y), and black (K). FIG. 1 typically shows the configuration of an ink circulation path related to ink of one color.

  The ink jet printer 1 roughly categorizes the ink circulation part 4, the ink cartridge holder part 10 for replenishing the ink circulation part 4, and the ink unnecessary in the ink circulation part 4 or the overflowed ink. The waste liquid tank section 48, the upper tank air chamber 19 that adjusts the pressure of the ink circulation section 4, and the pressure adjustment section 30 are configured.

First, the ink cartridge holder unit 10 will be described.
The ink cartridge holder portion 10 includes a joint portion 41 for detachably mounting the supply port 9a of the ink cartridge 9 filled with ink. When the supply port 9 a of the ink cartridge 9 is attached to the joint part 41, the ink in the ink cartridge 9 is supplied to the ink circulation part 4. A replenishment valve 43 is provided in the ink path connecting the ink cartridge holder 10 and the ink circulation unit 4, and ink supply to the ink circulation unit 4 is controlled by opening and closing the replenishment electromagnetic valve 43. Next, the ink circulation unit 4 will be described.

  FIG. 2 is a diagram schematically showing the configuration of the ink circulation unit 4 and enlarged from FIG. In FIG. 2, the same components as those in FIG. 1 are denoted by the same reference numerals as those in FIG. The configuration of the ink circulation unit 4 will be described with reference to FIGS. 1 and 2.

  The ink circulation unit 4 includes an image recording unit 3, an upper tank 6 serving as a first tank, a lower tank 7 serving as a second tank, a pump 11, a heat exchanger 12, a filter 13, and the like. And a tube (a path indicated by a thin line with an arrow in the figure) as an ink flow path for sequentially connecting the respective components. The arrows indicate the direction of ink flow when the ink circulates through the ink circulation unit 4. In the ink circulation unit 4, the ink flows from the upper tank 6 in the order of the image recording unit 3, the lower tank 12, the pump 11, the heat exchanger 12, and the filter 13, and returns to the upper tank 6.

  In the ink circulation unit 4 of this example, the upper tank 6 is disposed above the image recording unit 3. The lower tank 7 is disposed below the image recording unit 3. In addition, the ink circulation unit 4 of this example can be roughly divided into a first ink path 14 and a second ink path 15.

  The first ink path 14 is a path through which ink flows from the upper tank 6 to the lower tank 7 via the image recording unit 3. The second ink path 15 is a path through which ink is pumped by the pump 11 to the upper tank 6 via the lower tank 7, the pump 11, the heat exchanger 12, and the filter 13.

First, each configuration of the first ink path 14 will be described in detail.
The image recording unit 3 includes a recording head 2 that ejects ink, an ink supply bus 31 that distributes ink to the recording head 2, and an ink collection bus 32 that collects ink that has not been ejected by the recording head 2. ing.

  In the recording head 2 of this example, six short recording heads (K1 to K6) having a recording width (nozzle row length) less than the width of the recording medium are used, and these short recording heads are used as the recording medium. Are arranged in a zigzag pattern, for example, and fixed to a frame or the like to form a line head as a whole. Of course, the number of recording heads is not limited to six, and a plurality of recording heads may be used for each color.

  Each recording head 2 of the image recording unit 3 has a nozzle surface (nozzle plate) 33 in which nozzle holes (not shown) are formed. The recording head 2 performs image recording by ejecting ink onto a recording medium conveyed by a conveyance mechanism (not shown) to a position facing the nozzle plate 33. Further, the image recording unit 3 is provided with a temperature sensor 34 at or near each recording head 2 in order to control the heat exchanger 12 by detecting the difference between the target temperature of ink and the actual temperature. The

  The upper tank 6 is arranged to be above the image recording unit 3 in the direction of gravity. More specifically, the ink liquid surface 39 in the upper tank 6 is disposed so as to be above the nozzle plate 33 of the recording head 2 in the direction of gravity. The upper tank 6 is provided with an ink inlet port 6a, an ink outlet port 6b, and an atmospheric port 6c. In addition, a liquid level detector 35 is provided in the upper tank 6 in order to keep the position of the ink liquid level 39 at a predetermined height.

  The ink inlet port 6a is connected to the above-described filter 13 on the second ink path 15 side through a tube, and is provided so that the ink flowing out from the filter 13 flows into the upper tank 6.

  Note that the opening of the ink inlet port 6a in the upper tank 6 is located lower than the ink liquid level 39 in the upper tank 6 with respect to the vertical direction (gravity direction) so that bubbles do not easily enter the ink that flows in. Is provided.

  The ink outlet port 6 b is connected to the ink supply bus 31 via a tube, and the ink in the upper tank 6 flows to the ink supply bus 31. The ink that has flowed into the ink supply bus 31 is distributed to the recording heads 2 approximately equally.

  Since the amount of ink flowing into the recording head 2 via the ink supply bus 31 is set to exceed the amount of ink discharged from the nozzle holes of the recording head 2, the ink amount is not discharged from the nozzle holes and enters the recording head 2. The remaining ink flows into the ink recovery bus 32 and flows out to the lower tank 7 via a tube connected to the ink recovery bus 32.

  Further, the atmospheric port 6c is connected to the upper tank air chamber 19 through a tube. The upper tank air chamber 19 is connected to an overflow tank 8 of a waste liquid tank section 48 to be described later by a tube provided with an air release valve 22 as a first atmosphere release section. Since the overflow tank 8 is always exposed to the atmosphere, the upper tank air chamber 19 can be opened or closed (sealed) to the atmosphere by opening / closing (opening / blocking) the air release valve 22. . That is, since the upper tank air chamber 19 is connected to the atmosphere port 6c through the tube, the inside of the upper tank 6 can be opened to the atmosphere or sealed. Therefore, when the air release valve 22 is opened and the upper tank air chamber 19 is opened to the atmosphere, the ink in the upper tank 6 is transferred from the upper tank 6 to the image recording unit 3 by the water head difference. It will flow to 31. In the present embodiment, the upper tank air chamber 19 is also connected to an upper tank that handles other three colors of ink. In other words, the upper tank provided for each ink color to be used can be opened or sealed with respect to the atmosphere by one upper tank air chamber 19, and the pressure is equalized for all the upper tanks. be able to. Of course, the upper tank air chamber 19 may not be provided, and the upper tank of each color may be controlled to be opened or sealed with respect to the atmosphere.

  The liquid level detection unit 35 disposed in the upper tank 6 includes a float member 35a, a liquid level position sensor 35b, and a magnet 35c. The float member 35a swings up and down according to the height of the ink level in the upper tank 6.

  A magnet 35c is attached to the float member 35a. The liquid surface position sensor 35b is a magnetic sensor, and detects the position of the float member 35a, that is, the height of the ink liquid surface by detecting the magnet 35c attached to the float member 35a. The liquid level detection unit 35 is not limited to the above configuration, and for example, a part of the wall surface of the upper tank 6 is formed of a transparent member, and the position of the liquid level is directly detected by, for example, a reflective optical sensor. Also good.

  The lower tank 7 is arranged to be lower than the image recording unit 3 in the direction of gravity. More specifically, the ink liquid surface 40 in the lower tank 7 is arranged so as to be lower than the nozzle surface of the recording head 2 in the gravity direction. The lower tank 7 is provided with an ink inlet port 7a, an ink supply port 7b, an ink outlet port 7c, and an atmospheric port 7d. A liquid level adjuster 37 is provided in the lower tank 7.

  The ink inlet port 7a is connected to the ink recovery bus 32 of the image recording unit 3 through a tube. Therefore, the ink that has not been ejected by the recording head 2 is once collected by the ink collection bus 32 and flows down to the lower tank 7.

  The ink supply port 7b is connected to the ink cartridge holder portion 10 through a tube. When the amount of ink in the ink circulation unit 4 is smaller than a preset amount of ink, ink is supplied from the ink cartridge 9 to the lower tank 7.

The ink outlet port 7c is connected to a pump 11 described later via a tube. The atmospheric port 7d is connected to the pressure adjusting unit 30 via a tube.
The pressure adjusting unit 30 includes a lower tank air chamber 24 and a negative pressure adjusting mechanism 44.

  The lower tank air chamber 24 is connected to the overflow tank 8 by a tube provided with an atmosphere release valve 26 as a second atmosphere release section. Therefore, the inside of the lower tank air chamber 24 can be opened or closed (sealed) with respect to the atmosphere by opening and closing (opening / blocking) the atmosphere opening valve 26. That is, since the lower tank air chamber 24 is connected to the atmospheric port 7d through the tube, the lower tank 7 can be opened to the atmosphere or sealed.

  Further, the inside of the lower tank air chamber 24 is partitioned by a partition wall (not shown) that communicates only with the upper portion so that the ink cannot advance toward the negative pressure adjusting mechanism 44 even if the ink in the lower tank 7 overflows. In the tube communicating from the lower tank air chamber 24 to the negative pressure adjusting mechanism 44, only the movement of the gas is performed.

The negative pressure adjusting mechanism 44 is connected to the lower tank air chamber 24 via a tube, and includes a bellows portion 45, a weight portion 46, and a bellows lifting mechanism 47 that generate negative pressure.
The bellows part 45 is connected to the lower tank air chamber 24 by a tube, and can be brought into a negative pressure state in the lower tank air chamber 24 by extending and lowering. The negative pressure first opens the air release valve 26 and raises the bellows portion 45 and the weight portion 46 by the bellows lifting mechanism 47 with the lower tank air chamber 24 open to the atmosphere. And after raising the bellows part 45 and the weight part 46 to a predetermined position, the air release valve 26 is closed. When the air release valve 26 is closed in this way, the air portion of the lower tank 7, the lower tank air chamber 24, and the bellows portion 45 communicate with each other and become a closed space from the outside. When the bellows part 45 is expanded and contracted in this state, the volume of the closed space increases or decreases. That is, when the bellows lifting mechanism 47 is lowered, the bellows part 45 is pulled downward by the weight of the weight part 46, and the volume of the closed space increases. A negative pressure is generated that balances the applied gravity.

  The negative pressure generated in the lower tank chamber 24 gives the same negative pressure also in the lower tank 7 communicated with the tube. In the negative pressure state of the lower tank 7, a predetermined negative pressure is also applied to the recording head 2 communicating with the tube. With this predetermined negative pressure, a meniscus can be formed in the ink applied to the nozzle. The predetermined negative pressure also contributes to ink circulation. As described above, the pressure adjusting mechanism 44 applies a negative pressure to the recording head 2 to form a meniscus on the ink applied to the nozzles, thereby enabling a normal printing operation.

  In the present embodiment, the lower tank air chamber 24 is also connected to lower tanks in charge of the other three colors of ink. As a result, the pressure in the lower tank 7 for all colors can be simultaneously changed to an equal pressure by one negative pressure adjusting mechanism 44. Of course, the lower tank air chamber 24 may not be provided, and the negative pressure may be adjusted for each lower tank of each color.

  The liquid level adjuster 37 includes a float member 37a and a lower end protrusion member 37b extending downward from the float member 37a. The liquid level adjuster 37 floats in accordance with the vertical movement of the ink level, and self-adjusts the amount of ink pumped to the upper tank 6 by the pump 11 according to the height of the ink level of the lower tank 7. In this self-adjustment, when the ink level is lowered in the lower tank 7, the float member 37 a is also lowered and the lower end protrusion member 37 b closes the opening of the ink outlet port 7 c and is supplied from the lower tank 7 to the pump 11. The ink flow is blocked.

  Further, when the ink flows from the recording head 2 and the position of the ink liquid level of the lower tank 7 becomes higher, the float member 37a rises together with the ink liquid level, and the lower end protrusion member 37b exposes the opening of the ink outlet port 7c. . Thereby, the ink supply from the lower tank 7 to the pump 11 is started again. By repeating this operation, the ink is caused to flow out to the pump 11 while maintaining the position of the ink liquid level 40 in the lower tank 7 within a desired range, and the ink is supplied to the upper tank 6 through the second ink path 15. Can be sent to. In the present embodiment, the liquid level adjuster 37 slides along the ink outlet port 7c, and closes or exposes the opening of the ink outlet port 7c according to the ink liquid level.

Next, each configuration of the second ink path 15 will be described in detail.
The pump 11 is connected to the ink outlet port 7 c of the lower tank 7 by a tube, and is provided to send ink in the lower tank 7 to the upper tank 6.

  For example, a gear pump can be used as the pump 11, and all gear pumps can be operated with one pump drive source by connecting the rotation shafts of the gear pumps for each color with coupling members. Moreover, it is also possible to drive each pump individually by using a clutch or the like.

  In this embodiment, the liquid feeding capability of the pump 11 is designed so that more ink can be fed to the upper tank 6 than the amount of ink flowing into the lower tank 7. This is to prevent overflow of the lower tank 7.

  That is, the lower tank 7 is prevented from overflowing by increasing the ink flow rate that can be pumped out by the pump 11 rather than the ink flow rate that flows into the lower tank 7 in a normal use state.

  Here, in order to control the amount of ink pumped out by the pump 11, the liquid level adjuster 37 is provided opposite to the tip of the ink outlet port 7 c of the lower tank 7 as described above. Therefore, the pump 11 is provided with a constant pressure valve (not shown) so that the internal pressure between the ink outlet port 7c and the pump 11 does not exceed a set value.

  This is to prevent a suction force larger than the maximum buoyancy of the liquid level adjuster 37 from being applied to the ink outlet port 7c. In other words, the liquid level adjuster 37 that closed the ink outlet port 7c when the ink liquid level 39 is lowered is attracted to the ink outlet port 7c by the suction force of the pump 11 even though the ink liquid level 39 is subsequently raised. To prevent them from leaving.

  In the present embodiment, a gear pump capable of feeding a fixed amount of ink regardless of the viscosity of the ink is used as the pump 11. However, the present invention is not limited to this, and the ink flowing into the lower tank 7 as described above. Any pump may be used as long as it is capable of feeding more ink than the amount.

As a pump other than the gear pump, for example, a diaphragm pump, a piston pump, a tube pump, a rotary pump, or a spiral pump may be used.
A waste liquid tank portion 48 is disposed below the pump 11. The waste liquid tank section 48 includes a tank tray 49, a waste liquid tank 52, a waste ink amount detection section 53, a tank attachment detection section 54, and an overflow tank 8.

  The overflow tank 8 is formed in a tray shape and is disposed below the pump 11. Therefore, even if the pump 11 is damaged and ink leaks, the overflow tank 8 stores all the leaked ink and does not contaminate the inside of the apparatus. Further, the overflow tank 8 is connected to the upper tank air chamber 19 and the lower tank air chamber 24. Therefore, even if ink overflows from the upper tank 6 or the lower tank 7 due to an abnormality in the apparatus, the leaked ink can be stored in the overflow tank 8.

  The overflow tank 8 is connected to the waste liquid tank 52 through a tube. The waste liquid tank 52 is disposed on the tank tray 49 and is detachable from the tank tray 49. In the tank tray 49, a waste ink amount detection unit 53 that detects the amount of ink stored in the waste liquid tank 52, and a tank that detects whether the waste liquid tank 52 is mounted by weight detection or optical detection. A mounting detection unit 54 is provided. When a predetermined amount of waste liquid accumulates in the waste liquid tank 52, the waste ink amount detection unit 53 detects it and notifies the user to suggest replacement.

Further, from the ink cartridge holder 10, ink leaked to the outside when the ink cartridge 9 is replaced is sent to the waste liquid tank 52 as waste liquid through the tube.
The heat exchange unit 12 is connected to the pump 11 through a tube, and adjusts the temperature of the ink pumped up by the pump 11. Although not shown, the heat exchange unit 12 includes a heat sink unit, a cooling fan, a heater unit, and an ink channel unit. The constituent parts other than the ink flow path portion are shared by the ink flow paths for all four colors.

  In the ink circulation unit 4 of the present embodiment, the recording head 2 is heated by the heat generated by the piezo unit (not shown) and the heat generated by the recording head drive unit (not shown) as the recording head 2 ejects ink.

  However, the print head 2 is cooled by the heat transmitted to the outside by the ink flowing inside the print head 2 and consequently cooled. At this time, the temperature of the ink flowing out from the recording head 2 is higher than the temperature of the ink flowing into the recording head 2. If printing continues continuously in this state, the ink circulates, and the temperature of the ink and the recording head 2 rises, exceeding the temperature range in which the printing quality can be guaranteed, and the printing quality cannot be guaranteed.

At such a high temperature, in the heat exchanging unit 12, the ink is cooled by the heat sink unit and the cooling fan, and the temperature is lowered to a temperature at which the print quality can be guaranteed.
Conversely, in a low temperature environment where the ink is cold, such as in the winter morning, the ink temperature falls below the temperature range that guarantees the print quality, and the print quality may deteriorate. At such a low temperature, in the heat exchanging unit 12, the temperature of the ink is raised by the heater unit and heated to a temperature at which the print quality can be guaranteed.

  Thus, the heat exchanger 12 functions to control the temperature of the ink flowing in the ink circulation flow path 4 to a desired temperature. In this heat exchanging section 12, the ink flow path section is not particularly shown, but the outer shape is formed in a plate shape for each color, and the inside is partitioned by a plurality of walls, so that heat can be easily transferred to the ink. It is configured as follows.

  The heat exchanging unit 12 constantly monitors the temperature of the ink flowing in the recording head 2 by the temperature sensor 34 of the image recording unit 3, and if the ink temperature is outside the preset allowable range, the ink temperature is reduced. Adjust the temperature so that it is within the allowable range. Thereby, it is possible to record an image at an optimum ink temperature.

  The ink cooled by the heat exchanger 12 circulates in such a way that it takes heat from the recording head 2 that generates heat to perform image recording and is cooled by the heat exchange unit 12. Thereby, it is possible to prevent the print quality from being deteriorated due to the heat generated by the recording head 2.

  Next, the filter 13 will be described. The filter 13 is provided to remove foreign matters contained in the ink supplied to the recording head 2 and eliminate printing defects caused by clogging of nozzle holes.

  The filter 13 has a mesh-like member that allows ink to pass through, and the mesh having a mesh size that can remove even small foreign matters that can pass through the nozzle hole diameter of the recording head 2 without any problem. A shaped member is selected.

  Since the ink circulation unit 4 in the present embodiment is cleaned / assembled in a clean environment, foreign matter is not mixed in the path unit or is difficult to mix. However, there is a possibility that foreign matters drifting in the air may enter when the ink cartridge 9 is attached or detached or maintenance is performed at the installation location.

  When ink containing foreign matter is fed into the recording head 2, there is a high risk of clogging the nozzle holes and causing ink ejection failure. Therefore, a filter 13 is provided in the ink circulation unit 4 so that foreign matter that has entered the ink circulation unit 4 can be removed during the ink circulation.

  In the ink jet printer 1 configured as described above, based on an image signal input from the outside, recording is transported by a transport mechanism (not shown) from the nozzle holes formed in the nozzle plate of each recording head 2. Ink that is a liquid is ejected toward a medium (not shown).

  At this time, the atmosphere release valve 22 is opened to make the upper tank 6 open to the atmosphere, and the atmosphere release valve 26 is closed, and the pressure in the lower tank 7 is set to a predetermined negative pressure by the pressure adjusting unit 30. As a result, a meniscus that is recessed in a spherical shape is formed in the nozzle hole of the recording head 2 to enable normal printing operation.

  When the inkjet printer 1 is on standby, the atmosphere release valve 22 is closed to shut off the upper tank 6 from the atmosphere, and the atmosphere release valve 26 is opened, so that the lower tank 7 is opened to the atmosphere. At this time, since the lower tank 7 is arranged below the recording head 2 in the gravity direction as described above, a meniscus is formed in the nozzle hole of the recording head 2 due to a water head difference. That is, ink does not spill from the recording head 2 during standby.

Further, when the atmosphere release valve 22 and the atmosphere release valve 26 are closed, the tanks in all the ink circulation paths are sealed, and only the nozzle holes of the recording head 2 are opened to the atmosphere. In this state, the pressure in the closed space can be increased by compressing the bellows portion 45 from the extended state.

  Pressure can be applied to the nozzle holes by pressurizing the entire ink circulation path. Therefore, this pressure is applied to the nozzle holes of the recording head 2 that are clogged due to thickening of the ink to push the ink outward, thereby realizing a purge operation that eliminates clogging of the nozzle holes.

  In the present embodiment, the purge operation is performed simultaneously for all colors because the upper tank air chamber 19 and the lower tank air chamber 24 are shared. In order to perform the purge operation separately for each color, an independent upper tank air chamber 19 and lower tank air chamber 24 may be provided for each color so that communication or blocking with the atmosphere can be controlled for each color. .

  By the way, although the above-mentioned content was the description of the operation on the premise that the ink circulation unit 4 has already been filled, actually, when the ink jet printer 1 is installed (the user uses the ink jet printer 1 for the first time). In this case, the ink circulation unit 4 is empty without ink, so it is necessary to fill the ink circulation unit 4 with ink.

  In this example, the ink liquid level 39 of the upper tank 6 is located higher in the vertical direction (gravity direction) than the nozzle plate 33 of the recording head 2, and the water head between the ink liquid level 39 of the upper tank 6 and the nozzle plate 33. Due to the difference, a positive pressure is applied to the recording head 2.

  On the other hand, the ink liquid level 40 of the lower tank 7 is at a position lower in the vertical direction (gravity direction) than the nozzle plate 33 of the recording head 2, and due to the water head difference between the ink liquid level 40 of the lower tank 7 and the nozzle plate 33. A negative pressure is applied to the recording head 2.

  Therefore, normally, the ink replenished from the ink cartridge 9 to the lower tank 7 is sent to the upper tank 6 by the pump 11, and the ink sent to the upper tank 6 passes through the recording head 2 due to the water head difference. It flows to tank 7. As a result, the ink circulation unit 4 can be filled with ink.

  However, when a line head is configured by arranging a plurality of recording heads 2 (short heads) per color as in this embodiment, a plurality of inks connecting the ink supply bus 31 and the plurality of recording heads 2 are used. A route exists. In such a case, ink does not enter all the ink paths at the same time, but ink enters and exits with an irregular time difference. As a result, there arises a problem that a path that is not filled with ink occurs or that a bubble remains in the ink path.

  More specifically, since the ink path in which ink is filled does not change in volume with respect to positive pressure from above or negative pressure from below, the ink moves according to the pressure. . Accordingly, the load on the ink flow is reduced, and the ink easily flows.

  Conversely, in the ink path that is not filled with ink or the ink path in which bubbles remain, air that is a gas easily changes in volume with respect to positive pressure from above or negative pressure from below, and is irregular. Move to. That is, in the ink path in which only air or air bubbles are mixed, the ink cannot move according to the pressure.

  Therefore, an ink path that is not filled with ink or an ink path where bubbles remain is larger than an ink path that is filled with ink, and the ink path is difficult to flow.

Therefore, ink flows only in the path filled with ink first, and the path that is not filled with ink, or the path where air bubbles remain and the load on the ink flow is increased, the ink is not filled normally. Become. That is, it is not possible to fill all the recording heads 2 with ink.

Therefore, an ink filling process for eliminating this state will be described.
FIG. 3 is a flowchart illustrating a process for filling ink into all the recording heads 2 in this example, that is, the ink circulation unit 4. Note that the initial state of the ink circulation unit 4 immediately before the start of this process is as follows.

  The air release valve 22 is closed. The air release valve 26 is open. The pump 11 is stopped. The supply valve 43 is closed. Moreover, the bellows part 45 is compressed by the bellows raising / lowering mechanism 47 to the uppermost part which is a standby position. From this state, ink filling processing is performed.

In FIG. 3, execution of ink filling is started (STEP 1).
In this process, an ink filling operation is executed by a manual operation of a user or a serviceman who performs maintenance of the ink jet printer from an operation panel (not shown). When starting the ink filling, it is necessary to confirm whether or not there is a sufficient amount of ink necessary for the ink filling process because the ink is initially empty in the ink circulation unit 4.

Therefore, it is determined whether sufficient ink remains in the ink cartridge 9 (STEP 2).
In this process, whether or not the ink amount of the ink cartridge 9 is a sufficient amount necessary for the ink filling process is determined by a remaining amount detection unit (not shown).

  When it is determined that there is no ink in the ink cartridge 9 or insufficient (STEP2 is NO), the user is notified that there is no ink (STEP3), and the process returns to STEP2.

  In the processing of STEP3, the user or serviceman is prompted to replace the ink cartridge by using an operation panel (not shown) or other notification function, and the user is informed that ink refilling will be performed after the replacement.

  On the other hand, if the ink amount in the ink cartridge 9 is sufficient (YES in STEP 2), a maintenance unit (not shown) is moved to a position facing the recording head 2 in this embodiment (STEP 4).

  In this process, when ink is filled, the ink dropped from the nozzle holes is maintained in the maintenance section (see FIG. 5) so that the ink dropped from the nozzle holes formed in the nozzle plate 33 of the recording head 2 does not contaminate the transport mechanism (not shown). (Not shown).

Subsequently, the number N of repetitions of processing between STEP 12 to STEP 21 in which the ink filling operation is performed is arbitrarily set (STEP 5).
In this process, the number of times is set to 6 in this embodiment (N = 6), but this number of times N is set in the ink filling process according to the configuration (length and arrangement) of the ink circulation unit 4. A sufficient appropriate number of times may be set arbitrarily.

Next, the monitor value n of the number of repetitions is reset to “0” (STEP 6).
This process is a process of setting the monitor value n for counting how many times the process between STEP 12 to STEP 21 is performed to the initial value “n = 0”.

Then, driving of the pump 11 is started (STEP 7), and the air release valve 22 is opened (STEP 9).
As a result, the inside of the upper tank 6 is brought to atmospheric pressure via the upper tank air chamber 19, and a positive pressure corresponding to the water head difference between the ink liquid level 39 of the upper tank 6 and the nozzle plate 33 is applied to the recording head 2.

  Next, the supply valve 43 is opened when the liquid level position sensor 35b of the upper tank 6 is OFF, and the supply valve 43 is closed when the liquid level position sensor 35b is ON. (STEP 12).

  In this process, since the initial state in the ink circulation unit 4 is an empty state in which no ink is contained, the liquid level sensor 35b of the upper tank 6 is OFF, the replenishing valve 43 is opened, and the lower tank 7 is opened. The ink supply operation is started.

  When the ink supply operation to the lower tank 7 is started, the ink liquid level 40 of the lower tank 7 rises, and the liquid level adjuster 37 floats due to the buoyancy of the float member 37a. As the liquid level adjuster 37 floats, the ink outlet port 7 c is opened, and the ink in the lower tank 7 is pumped to the upper tank 6 by the pump 11.

  When ink is sent to the upper tank 6, the ink liquid level 39 in the upper tank 6 rises and the float member 35a floats. During this time, the ON / OFF state of the liquid level sensor 35b is determined.

That is, following STEP 12, it is determined whether or not the liquid level position sensor 35b of the upper tank 6 is ON (STEP 13).
If the liquid surface position sensor 35b is not ON (STEP 13 is NO), the process returns to STEP 12, and the processes of STEP 12 and STEP 13 are repeated.

As a result, the ink is continuously pumped from the lower tank 7 to the upper tank 6 by the pump 11, and the float member 35a rises higher.
Eventually, if the ink amount in the upper tank 6 increases to an appropriate amount and the liquid level sensor 35b of the upper tank 6 is turned on (YES in STEP 13), the driving of the pump 11 is immediately stopped (STEP 14).

In this embodiment, as described above, the operations are performed in the order of STEP 7, STEP 9, and STEP 12, but these STEPs are performed continuously in a short time.
Also, when heat generation due to the initial drive of the pump 11 due to the ink being empty becomes a problem, the replenishing valve 43 is opened before the pump 11 is driven, and the ink is supplied to the pump 11 (lower tank 7). Also good.

  FIG. 4 is a flowchart showing a process of opening the supply valve 43 and supplying ink to the pump 11 before driving the pump 11. Note that FIG. 4 shows processing that replaces the processing of STEP 7, STEP 9, and STEP 12 of FIG.

  In this process, following the process of STEP 6 in FIG. 3, as shown in FIG. 4, first, the atmosphere release valve 22 is opened to bring the upper tank 6 to atmospheric pressure (STEP 9), and then the refill valve 43 is opened. Ink is supplied to the pump 11 (lower tank 7) (STEP 27), and then the driving of the pump 11 is started (STEP 7). Thereafter, it is preferable to move to the processing of STEP 12 and STEP 13 shown in FIG.

Note that the order of the above STEP 9, STEP 27, and STEP 7 can be arbitrarily determined.
Returning to FIG. 3 again, it waits for a predetermined time to elapse after the operation of the pump 11 is stopped as described above (STEP 15).

  In this time waiting process, the atmosphere release valve 22 is open, and the upper tank 6 is in communication with the atmosphere via the upper tank air chamber 19. The atmosphere release valve 26 is opened from the beginning, and the lower tank 7 is in communication with the atmosphere via the lower tank air chamber 24.

  Accordingly, the ink in the upper tank 6 passes through the first ink path 14 due to gravity and flows down to the lower tank 7 positioned below the upper tank 6, and the ink is accumulated in the lower tank 7.

  The amount of ink that flows down is the maximum when the ink circulation unit 4 is normally filled with ink. Therefore, the above waiting time is a value that does not cause the lower tank 7 to overflow even when the amount of ink flowing down is maximum. Is set to

  For example, when 5 ml / sec of ink per color flows down, the capacity until the lower tank 7 overflows is 30 ml (the remaining amount obtained by subtracting the minimum ink amount that the liquid level adjuster 37 blocks the flow path from the total allowable amount) If the ink capacity in the upper tank 6 is 40 ml (the ink capacity in the upper tank 6 when the liquid level sensor 35b is ON), the ink in the upper tank 6 is not lost and the lower tank 7 does not overflow. What is necessary is just to set time shorter than 6 second used as time.

  In this embodiment, it is set to 4 seconds, and the lower tank 7 overflows, the ink in the upper tank 6 runs out, and the air does not flow into the first path 14. Further, the waiting time of STEP 15 may be set according to the ink temperature.

For example, the temperature of the supplied ink or the ink in the ink circulation unit 4 is detected by a temperature detection means (not shown), and the waiting time is calculated according to the temperature.
In particular, in the case of ink in which the viscosity, which is a physical property of the ink, varies greatly with temperature change, the amount of ink that flows down per unit time also changes. By performing this process, the lower tank 7 The amount of ink flowing down can be stabilized.

  Following the above-described time waiting process, the atmosphere release valve 22 is closed (STEP 16). As a result, the inside of the upper tank 6 communicating with the atmosphere via the upper tank air chamber 19 is blocked from the atmosphere, so that ink does not flow from the upper tank 6 to the lower tank 7.

Next, the driving of the pump 11 is resumed (STEP 17).
As a result, the ink remaining in the lower tank 7 is pumped up to the upper tank 6 at once, except for the minimum ink remaining amount where the liquid level adjuster 37 blocks the flow path of the ink outlet port 7c.

  Since the inside of the upper tank 6 is shut off from the atmosphere by closing the atmosphere release valve 22, the internal pressure of the upper tank 6 rapidly increases according to the volume of ink pumped from the lower tank 7.

As a result, the amount of ink fed from the upper tank 6 to the recording head 2 increases abruptly and remains even in a path that is not filled with ink in a normal ink circulation due to air remaining unevenly in the first ink path 14. The air that has been pushed out is pushed out toward the lower tank 7, and the inside of the first ink path 14 is filled with ink.

Then, it waits for a predetermined time to elapse (STEP 18).
This time waiting process is a time during which the pump 11 is driven. That is, the process waits for a time until ink supplied from the upper tank 6 is filled in the first ink path 14 (ink is pushed out from the upper tank 6).

  As time passes, the ink flows out from the upper tank 6, so that the air pressure in the upper tank 6 gradually decreases. Therefore, the force for pressing out the bubbles remaining in the recording head 2 (first ink path 14) is also reduced.

  For this reason, in this example, a waiting time corresponding to the ink push-out effect is set, and in this example, it is approximately 10 seconds. In addition, since it is only necessary to efficiently eject the remaining bubbles, an optimal value may be set as the waiting time depending on the configuration of the ink circulation unit 4. Similarly to STEP 15, an optimal waiting time may be calculated according to the ink temperature.

After the above waiting time has elapsed, the air release valve 22 is opened again (STEP 19).
As a result, the inside of the upper tank 6 is restored to the atmospheric pressure again via the upper tank air chamber 19, and the above-mentioned pressurization amount in the upper tank 6 is drastically reduced, so that the flow rate that flows out to the first ink path 14. Will decrease.

Subsequently, the repetition number monitor value n is incremented by “1”, that is, “n = n + 1” (STEP 20).
In this way, each time the process between STEP 12 to STEP 21 is performed, the repetition number monitor value n is incremented by “1”, and the repetition number of the process between STEP 12 to STEP 21 is counted.

Then, it is determined whether or not the repetition number monitor value n is not less than the arbitrarily set repetition setting value N, that is, “N ≦ n” (STEP 21).
If the repeat count monitor value n is less than the repeat set value N (STEP 21 is NO), the process returns to STEP 12 and the processes of STEP 12 to STEP 21 are repeated. Accordingly, all the recording heads 2, that is, the first ink paths 14 are filled with ink.

  Here, the ink filling speed into the ink path depends on the length and thickness of the flow path of the first ink path 14 and the flow path resistance that varies depending on how the ink is routed in the ink jet printer (the load received when a fluid flows). It affects the pressure loss) and fluctuates due to a water head difference that changes according to the arrangement of the upper tank 6, the recording head 2, and the lower tank 7 in the direction of gravity.

Therefore, the number of repetitions N may be set to a number suitable for each of the above configurations. In the present embodiment, N = 6 is set.
In addition, the time of STEP15 can be set long by increasing the volume of the upper tank 6 or the lower tank 7. This also allows a large amount of ink to flow from the upper tank 6 to the lower tank 7, so that the amount of ink pumped from the lower tank 7 to the upper tank 6 increases.

  Accordingly, the state in which the internal pressure of the upper tank 6 is increased can be set longer, that is, the waiting time of STEP 18 can be set longer, so that the value of the number of repetitions N can be reduced and the ink filling processing time can be shortened.

  If the repeat number monitor value n is greater than or equal to the repeat set value N as determined in STEP 21 (STEP 21 is YES), the replenishing valve 43 is opened when the liquid level position sensor 35b of the upper tank 6 is OFF. When the liquid level sensor 35b is turned on, the refill valve 43 is set to be closed (STEP 22).

  Then, it is confirmed whether or not the liquid level sensor 35b of the upper tank 6 is ON (STEP 23). If it is not ON (STEP 23 is NO), the process returns to STEP 22 and the processes of STEP 22 and STEP 23 are repeated.

As a result, if the amount of ink in the upper tank 6 is less than or equal to the proper amount, ink is fed from the lower tank 7 to the upper tank 6 until the amount reaches the proper amount.
If the liquid level sensor 35b of the upper tank 6 is turned on (YES in STEP 23), the driving of the pump 11 is immediately stopped (STEP 24).

  Thus, when the ink amount in the upper tank 6 increases to an appropriate amount and the liquid level sensor 35b is turned on, the replenishing valve 43 is closed, the ink replenishment to the lower tank 7 is stopped, and the pump 11 is stopped. Ink feeding to the upper tank 6 stops.

Subsequently, the air release valve 22 is closed (STEP 25).
After the pump 11 is stopped, the inside of the upper tank 6 is shut off from the atmosphere via the upper tank air chamber 19 by closing the atmosphere release valve 22. Thereby, the ink in the upper tank 6 does not flow down to the lower tank 7.

Then, head cleaning is performed (STEP 26).
In this process, since the ink droplets after the ink filling process are scattered on the nozzle plate 33 of the recording head 2, the nozzles of the recording head 2 are cleaned by a maintenance unit (not shown) to clean the scattered droplets. The plate 33 is cleaned. After cleaning, a meniscus is formed in the nozzle hole. This completes the ink filling process.

  FIG. 5 is a diagram illustrating pressure fluctuations inside the recording head 2 when the ink filling process of the present embodiment is performed. In the figure, the horizontal axis represents time (seconds), and the vertical axis represents the pressure inside the recording head 2.

Hereinafter, description will be made in comparison with the above-described processing STEP in FIG.
When STEP 1 to STEP 9 are being executed, there is no ink in the recording head 2 and communication with the atmosphere through the nozzle holes. ).

  When ink is fed into the ink circulation unit 4 at STEP 12 to STEP 13, the ink also flows down to the first ink path 14. At this time, a large amount of air still remains in the ink path, but the nozzle holes are blocked by the ink that has flowed down to the recording head 2, and the inside of the recording head 2 is blocked from the atmosphere.

  Ink is accumulated in the upper tank 6, and the internal pressure of the recording head 2 has a waveform 71-1 to a waveform 71-6 due to a water head difference between the nozzle plate 33 of the recording head 2 and the ink liquid level 39 of the upper tank 6. As shown in the figure, it becomes a slight positive pressure (pressure slightly higher than the atmosphere) of about +0.5 kPa.

In addition, since the pump 11 is also stopped between STEP14 to STEP15, the ink flows down from the upper tank 6 to the lower tank 7 through the first ink path 14. During this time, the pressure due to the water head difference acts in the same manner, so the internal pressure of the recording head 2 is approximately +0.5 kPa.

  Here, the same waveform is generated six times because in the present embodiment, the repetition count setting value N is set to 6 (STEP 5), and STEP 12 to STEP 21 are performed six times.

  Further, the intervals t1 to t6 of the waveforms 71-1 to 71-6 are narrowed as the repetition number monitor value n is increased. The ink circulation unit 4 is filled with ink each time the number of repetitions is increased. This is because the ink supply time in STEP 12 is shortened. When the number of repetitions is around 5, it is time to supply a small amount of ink dripped from the recording head 2.

When STEP 16 is executed, the upper tank 6 is shut off from the atmosphere, and the outflow of ink from the upper tank 6 stops.
Then, due to the water head difference between the nozzle plate 33 of the recording head 2 and the ink level 40 of the lower tank 7, the internal pressure of the recording head 2 is substantially short although it is a short time as shown by the waveforms 72-1 to 72-6. It approaches a slight negative pressure of -1.0 kPa (pressure slightly lower than the atmosphere).

  Next, when STEP 17 to STEP 18 are executed, the operation of STEP 14 to STEP 15 causes the ink to flow down to the lower tank 7 and the stored ink is pumped up to the upper tank 6 at once by the pump 11.

For this reason, the internal pressure of the upper tank 6 that is cut off from the atmosphere rapidly increases, and the internal pressure of the recording head 2 is approximately +6 kPa as shown by the waveforms 73-1 to 73-6.
Due to the influence of this pressure, the flow velocity of the ink flowing through the first ink path 14 is also increased, and bubbles remaining in the ink path are pressed out from the nozzle holes or in the lower tank 7 communicating with the atmosphere. Or is discharged from the first ink path 14 to the atmosphere.

In the present embodiment, since the number of repetitions is set to 6 times, an abrupt pressure waveform of approximately +6 kPa is generated 6 times.
While STEP 19 to STEP 21 are being executed, the internal pressure of the recording head 2 is approximately +0.5 kPa as in the waveforms 71-1 to 71-6, as in STEP 12 to STEP 13.

When the desired number of repetitions is completed, STEP 22 to STEP 24 are executed. At this time, the internal pressure of the recording head 2 is approximately +0.5 kPa as shown by the waveform 75.
When STEP 25 is executed, since the inside of the lower tank 7 has been at atmospheric pressure from the beginning, the water head via the second ink path 15 between the nozzle plate 33 of the recording head 2 and the ink liquid level 40 of the lower tank 7. Due to the difference, the internal pressure of the recording head 2 becomes a slight negative pressure (a pressure slightly lower than the atmosphere) of approximately −1.0 kPa as shown by a waveform 76.

In this state, head cleaning (STEP 26) for removing droplets from the nozzle plate 33 is performed, and the ink filling process is completed.
FIG. 6 is a flowchart showing a process of circulating the ink in the ink circulation unit 4 in order to maintain a printable state. The ink circulation process when the printing operation is performed will be described with reference to FIG.

As described with reference to FIG. 3 or 4, the ink circulation unit 4 is already filled with ink, and the nozzle holes of all the recording heads 2 are formed with a meniscus that is ready for printing.
In FIG. 6, first, a printing operation start command is issued (STEP 101).

  In this process, a print instruction (command) is issued to the inkjet printer via a USB port or LAN port serving as an interface with the outside by a user or a service person who performs maintenance of the inkjet printer.

As a result, the following processing is performed on the ink circulation unit 4 so as to shift from the standby state to the printable state.
First, it is confirmed whether or not the bellows lifting mechanism 47 is in the standby position (STEP 102). The position of the bellows lifting mechanism 47 is performed by a position sensor not shown. This process is a process for determining whether or not the negative pressure adjusting mechanism 44 necessary for generating a negative pressure in the lower tank 7 is in a standby state.

  If it is determined that the bellows lifting mechanism 47 is in the standby position (YES in STEP 102), the process proceeds to STEP 104, and if it is determined that the bellows lifting mechanism 47 is not in the standby position (NO in STEP 102), the bellows lifting / lowering is performed. After the mechanism 47 is moved to the upper standby position (STEP 103), the process proceeds to STEP 104.

As described above, when the bellows lifting mechanism 47 moves to the standby position, preparation for generating the negative pressure in the lower tank 7 is completed.
In the processing of STEP 104, the atmosphere release valve 26 is closed. As a result, the inside of the lower tank 7 is shut off from the atmosphere via the lower tank air chamber 24.

Subsequently, the air release valve 22 is opened (STEP 105). As a result, the inside of the upper tank 6 communicates with the atmosphere via the upper tank air chamber 19.
Next, the operation of the pump 11 is started (STEP 106). Then, the bellows lifting mechanism 47 is moved to the circulation position (STEP 107). In this process, the bellows lifting mechanism 47 is lowered to freely open the lower end portion of the bellows portion 45. The circulation position of the bellows lifting mechanism 47 is a position lower in the gravitational direction than the standby position, and is a position that is not supported by the bellows lifting mechanism 47 even if the bellows part 45 extends due to the weight of the weight part 46.

  As a result, due to the elasticity of the bellows part 45 and the weight part 46, a negative pressure is generated in the bellows part 45, and the pressure adjusting part 30 generates a negative pressure in the ink circulation state (the lower tank 7 via the lower tank air chamber 24). State). Note that the processing of STEP 104 to STEP 107 is performed substantially simultaneously or continuously in a short time. This is because the internal pressure of the upper tank 6 and the lower tank 7 fluctuates when the ink in the ink circulation unit 4 shifts from a static state to a dynamic state (circulation state). is there.

  In other words, fluctuations in the internal pressure of the upper tank 6 and the lower tank 7 also affect the internal pressure of the recording head 2, and there is a possibility that the meniscus formed in the nozzle holes of the recording head 2 may be broken. This is to prevent the occurrence.

  By the above four processing STEPs of STEP 104 to STEP 107, the upper tank 6 communicates with the atmosphere, the lower tank 7 is blocked from the atmosphere, and a pressure (negative pressure) lower than the atmosphere is generated by the pressure adjusting unit 30. The That is, the pressure inside the recording head 2 in the vicinity of the nozzle holes is set to a pressure suitable for printing by the water head differential pressure due to the opening of the upper tank 6 to the atmosphere and the negative pressure in the lower tank 7. Becomes a printable ink circulation state.

  FIG. 7 is a flowchart showing a process for stopping the ink circulation in the ink circulation unit 4 after the printing is completed. The ink circulation stop process when printing is completed will be described with reference to FIG.

  First, in the process of the printing operation completion (STEP 201), when the printing instructed by the printing operation start command is completed, a command to stop the ink circulation of the ink circulation unit 4 is issued to the ink jet printer. This command is automatically issued by a device control unit (not shown).

When the ink circulation stop command is issued, the operation of the pump 11 is stopped (STEP 202).
Then, after the operation of the pump 11 is stopped, a predetermined time is waited (STEP 203). This process is because the movement of the pump 11 does not stop suddenly even after the stop instruction is given due to inertia.

  In this embodiment, when a gear pump is used and, for example, a DC motor is used as a drive source, the rotation operation does not stop with the force of inertia even after the stop instruction is given, and the ink pumping operation to the upper tank 6 is also performed. do not stop.

  When the air release valve 22 is closed when the ink pumping operation is not stopped (there is no waiting time), the internal pressure of the upper tank 6 is increased by the pumped ink. There is a risk of breaking the meniscus formed in the hole.

  On the contrary, when the waiting time is set to be long, the ink in the upper tank 6 flows down from the first ink path 14 to the lower tank 7, so that the negative pressure in the lower tank 7 gradually decreases, and the meniscus in the nozzle hole There is a risk that the ink in the upper tank 6 is reduced and bubbles are mixed into the first ink path 14.

  Therefore, the waiting time takes into account the time from when the command to stop the operation of the pump 11 is issued to when the pumping operation of the pump 11 actually stops, and the nozzle hole pressure fluctuation of the recording head 2 and the upper tank A value with no problem in the ink amount of 6 may be set.

  In this embodiment, the waiting time is set to 1.5 seconds. It should be noted that the waiting time can be reduced to approximately 0 seconds (no waiting time) by separating the power by a motor having a brake function or a clutch.

Following the above, the atmosphere release valve 22 is closed (STEP 204). As a result, the inside of the upper tank 6 is shut off from the atmosphere via the upper tank air chamber 19.
Next, the atmosphere release valve 26 is opened (STEP 205). Thereby, the inside of the lower tank 7 is communicated with the atmosphere via the lower tank air chamber 24.

  The processing of STEP 203 to STEP 205 is performed substantially simultaneously or continuously in a short time. This is because it is necessary to keep the internal pressure of the recording head 2 at a pressure (negative pressure) lower than the atmosphere regardless of whether the ink circulation is stopped or not, so that the normal negative pressure can be maintained by switching quickly. Realized.

  That is, the air release valve 22 and the air release valve 26 are reversed during the ink circulation and the ink circulation stop, and the internal pressure of the recording head 2 is switched by switching both the air release valves substantially simultaneously or in a short time. The fluctuation is suppressed and the meniscus formed in the nozzle hole is prevented from being broken.

Following the above, a predetermined time is waited (STEP 206), and then the bellows lifting mechanism 47 is put into a standby state (STEP 207).
In the above processing, when the atmosphere release valve 26 is opened in STEP 205, the inside of the bellows part 45 of the negative pressure adjusting mechanism 44 also communicates with the atmosphere via the lower tank air chamber 24. This extends to a position supported by the bellows lifting mechanism 47 located below.

Then, by moving the bellows lifting mechanism 47 to the standby position in STEP 207, the ink circulation operation can be executed in a short time when the next printing operation is executed.
When the bellows lifting mechanism 47 is moved to the standby position, the bellows portion 45 of the negative pressure adjusting mechanism 44 is compressed, but if this operation is performed in a state where the atmosphere release valve 26 is not opened to the atmosphere, the lower tank Therefore, a waiting time is required until the atmosphere release valve 26 is completely opened. This waiting time is the waiting time of STEP206.

  As described above, according to this embodiment, it is possible to provide an ink filling method that can perform stable ink filling without air or bubbles remaining in the ink path when ink is filled in the ink circulation unit 4. Yes, it is possible to prevent a decrease in print quality of the ink jet printer.

  In addition, according to the present embodiment, since the ink filling process is performed with the minimum necessary ink amount, there is no overflow in the upper tank or the lower tank, and an ink jet printer that can suppress the discharged ink amount is provided. Is possible.

In the present embodiment, the recording head 2 is not limited to the fixed type, and a serial ink jet printer that has a scanning mechanism and scans and moves during image recording can be used as long as it can supply ink. It is also possible to apply the same. In this case, the ink supply system may have a scanning movable structure in which the ink circulating unit 4 and the recording head 2 are connected by a tube that has elasticity and can be bent, such as a spiral tube.
(Modification 1 of the first embodiment)
FIG. 8 is a flowchart for explaining a modified example of the ink filling process in the first embodiment described above.

  The setting of the waiting time of STEP 15 in the flowchart shown in FIG. 3 is replaced with a process of driving the pump 11 of STEP 500 in the reverse direction and a process of stopping the driving of the pump of STEP 501 as shown in FIG.

  According to this process, the pump 11 is used as means for ensuring the amount of ink that flows from the upper tank 6 to the lower tank 7 in STEP 15 of FIG. By performing the operation of rotating the pump 11 in the reverse direction, the ink in the upper tank 6 can be sent to the lower tank 7.

  Thus, according to this modification, since the liquid feeding capability of the pump 11 can be used, the ink in the upper tank 6 can be fed to the lower tank 7 in a short time, and the ink filling time can be shortened. Can be done. In particular, a large effect can be obtained in an industrial inkjet printer having a large amount of ink in both tanks.

In this embodiment, a gear pump is used as the pump 11 as an example of a pump capable of feeding a fixed amount of ink regardless of the viscosity of the ink.
Therefore, according to this modification, it is possible to send a desired amount of ink to the lower tank 7 within a unit time without being affected by the ink viscosity due to temperature change, and stable ink filling can be performed. It is possible to prevent printing defects caused by air or bubbles remaining in the path.

Needless to say, the same effects as those of the first embodiment can be obtained.
(Modification 2 of the first embodiment)
FIG. 9A is a diagram showing a modification of the ink circulation unit 4 in Modification 2 of the first embodiment, and FIG. 9B is a flowchart showing the control process. In FIG. 9A, the same components as those in FIGS. 1 and 2 are denoted by the same reference numerals as those in FIGS.

  In the second modification of the first embodiment, as shown in FIG. 9 (a), the upper tank 6 and the lower tank are compared with the configuration of the ink circulation section 4 of the first embodiment shown in FIG. Apart from the first ink path 14 and the second ink path 15, a third ink path 55 is provided between the tanks 7.

  The third ink path 55 is provided with a path opening / closing valve 56 that can open and close the ink path. Accordingly, the ink in the upper tank 6 is directly transferred to the lower tank 7 between the upper tank 6 and the lower tank 7 by the third ink path 55 and the path opening / closing valve 56 separately from the first ink path 14. The liquid can be sent.

  In the ink filling process in the second modification, the waiting time setting process in STEP 15 of the flowchart shown in FIG. 3 of the first embodiment is changed to a path opening / closing valve 56 as shown in FIG. Is replaced with a process for opening / closing the path opening / closing valve 56, such as a process for opening an arbitrary time (STEP 510) and a process for closing the path opening / closing valve 56 (STEP 511).

  According to the second modification, even when the liquid feeding direction of the pump 11 is restricted to only one direction, the ink in the upper tank 6 can flow down to the lower tank 7. Therefore, since stable ink filling can be performed, it is possible to prevent printing defects caused by air or bubbles remaining in the ink path 4.

  Further, according to the second modification, the ink in the upper tank 6 can be sent to the lower tank 7 by the third ink path 55 in a short time, and the ink filling time can be performed in a short time. become. In particular, a large effect can be obtained in an industrial inkjet printer having a large amount of ink in both tanks.

Needless to say, the same effects as those of the first embodiment can be obtained.
(Modification 3 of the first embodiment)
FIG. 10 is a diagram illustrating a modified example of the ink circulation unit 4 in the modified example 3 of the first embodiment. In FIG. 10, the same components as those in FIGS. 2 and 9 (a) are denoted by the same reference numerals as those in FIGS. 2 and 9 (a).

  In the third modification of the first embodiment, as shown in FIG. 10, the third ink that bypasses the pump 11 instead of the third ink path 55 and the circuit opening / closing valve 56 of the second modification described above. A path 57 and a path opening / closing valve 58 are provided.

  Also in the third modification, the ink in the upper tank 6 can be directly fed to the lower tank 7 by opening the path opening / closing valve 58 when the upper tank 6 is opened to the atmosphere and the pump 11 is closed. Yes.

That is, in the ink filling process in the third modification, in the process of the flowchart shown in FIG. 9B, the path opening / closing valve 58 is opened / closed instead of opening / closing the path opening / closing valve 56, whereby the ink in the upper tank 6 is lowered. By allowing the ink to flow directly into the tank 7, stable ink filling can be performed quickly, and printing defects caused by air and bubbles remaining in the ink path 4 can be prevented.
(Modification 4 of the first embodiment)
FIG. 11A is a diagram illustrating a modification of the ink circulation unit 4 in Modification 4 of the first embodiment, and FIG. 11B is a flowchart illustrating the control process. In FIG. 11A, the same components as those in FIGS. 1 and 2 are given the same reference numerals as those in FIGS.

  In the fourth modification of the first embodiment, as shown in FIG. 11 (a), the upper tank 6 and the ink are different from the configuration of the ink circulation section 4 of the first embodiment shown in FIG. A path opening / closing valve 59 is provided in the ink path connecting to the supply bus 31.

  In the ink filling process according to the fourth modification, the path opening / closing valve 59 is set between the process of STEP 16 and STEP 17 and the process of STEP 17 and STEP 18 in the flowchart shown in FIG. 3 of the first embodiment. A closing process (STEP 520) and a process for opening the path opening / closing valve 59 (STEP 521) are additionally inserted. FIG. 12 is a diagram showing the internal pressure fluctuation of the recording head 2 in the ink filling process shown in FIG. 11B in the fourth modification of the first embodiment.

  In the ink filling process shown in FIG. 11 (b) in the configuration of the modified example 4, when the pump 11 is driven and ink is pumped up to the upper tank 6 (STEP 17), the path opening / closing valve 59 is closed immediately before. (STEP 520), the internal pressure of the upper tank 6 rapidly increases. Therefore, when the path opening / closing valve 59 is opened (STEP 521), ink is fed to the recording head 2 at a high pressure.

  The rising waveform of the waveform 73-1 that appears as the internal pressure of the recording head 2 shown in FIG. 5 in the first embodiment is affected by the ink flowing out from the first ink path 14, and is inclined as shown by the broken line in FIG. However, in the fourth modification, the internal pressure of the recording head 2 suddenly rises as shown by the solid line in FIG.

  As described above, according to the fourth modification, since a rapid pressure change can be applied to the recording head 2, more stable ink filling can be performed. As a result, it is possible to prevent printing defects caused by air and bubbles remaining in the ink path.

(Second Embodiment)
FIG. 13 is a flowchart for describing processing for filling ink into the ink circulation path of the ink jet printer according to the second embodiment.

  The configuration of the ink jet printer in this example is the same as the configuration shown in FIGS. In addition, the ink filling process described in this example is performed in the case where ink is filled again into the ink circulation unit 4 in which ink is once filled, that is, in the ink circulation path 4. The process when the ink amount is unknown is shown.

  The case where ink is once again filled in the ink jet printer once filled with ink corresponds to, for example, the case where some of the plurality of recording heads are replaced.

In addition, when the ink circulation operation of the ink circulation unit 4 is not performed, that is, in a state other than during the printing operation, each part is normally in the following state.
The air release valve 22 is closed. The air release valve 26 is open. The pump 11 is stopped. The supply valve 43 is closed. Moreover, the bellows raising / lowering mechanism 47 is in a standby position, and the bellows part 45 is compressed to the uppermost part. From this state, ink refilling is performed.

In the processing STEP shown in FIG. 13, the same or similar processing STEP as the processing STEP shown in FIG. 3 is indicated by the same STEP number as in FIG.
Also, the processing shown in FIG. 13 and the processing shown in FIG. 3 differ greatly in that the processing of STEP 8 is inserted between STEP 7 and STEP 9 of FIG. 3 and between STEP 9 and STEP 12 of FIG. Then, the processing of STEP11 is inserted.

  The other STEP processes in FIG. 13 are the same as or similar to those in FIG. 3 as described above. Therefore, here, only the STEP processes different from those in FIG. 3 are reproduced (the STEP processes before and after that are reproduced as necessary). Explain).

First, the ink filling operation is started by a manual operation of a user or a serviceman who performs maintenance of the ink jet printer from an operation panel (not shown) (STEP 1).
Initially, it is unclear what the inside of the ink circulation unit 4 is, so replenishment is possible assuming that the ink in the path is empty or a state where many bubbles have entered the path. In order to know whether or not sufficient ink is present in the ink cartridge 9, the ink amount of the ink cartridge 9 is checked (STEP 2).

  If it is determined that the ink in the ink cartridge 9 is insufficient, the user or service person is prompted to replace the ink cartridge by an operation panel (not shown) or other notification function, and the ink is filled again after the replacement. Notification is made (STEP 3).

Since STEP4 to STEP7 are the same processing as in FIG.
After the operation of the pump 11 is started in the above STEP 7, a predetermined time is waited until the operation to open the atmosphere release valve 22 (STEP 8). The reason for waiting for the predetermined time in this way is to prevent ink exceeding the allowable amount in the upper tank 6 from being sent to the upper tank 6 by the operation of the pump 11 and overflowing the upper tank 6. is there.

  That is, in this example, the pump 11 is configured to be able to pump a larger amount of ink into the upper tank 6 than the amount of ink flowing down to the lower tank 7. Accordingly, the ink remaining in the lower tank 7 tends to be pumped up to the upper tank 6 at once, except for the minimum ink amount that the liquid level adjuster 37 blocks the flow path of the ink outlet port 7c. Here, when ink is filled again, the amount of ink remaining in the ink circulation unit 4 is indefinite, so that there is a possibility that sufficient ink remains in the upper tank 6 and the lower tank 7 to fill the ink path. There is. In this state, when the air release valve 22 is opened directly after the pump is driven (STEP 7) (STEP 9), excess ink remaining in the lower tank 7 is pumped up to the upper tank at once, and the liquid level of the upper tank 6 rises. To do. Then, the upper tank 6 overflows where the allowable ink amount is exceeded.

  Therefore, as in this embodiment, after the pump is driven (STEP 7), the waiting time (STEP 8) is set, and the atmosphere release valve 22 is kept closed even after the pump is driven, so that the inside of the upper tank 7 is Since the sealed space is cut off from the atmosphere, even if excess ink remaining in the lower tank 7 is pumped up to the upper tank, the rise in the liquid level in the upper tank 6 is suppressed at a height that does not overflow. This is because the ink in the upper tank 6, which is a sealed space, is raised by the pumped ink, so that the ink in the upper tank 6 is pressed out from the ink outlet port 6 b and drops outside from the nozzle holes of the recording head 2. Or by flowing down to the lower tank 6, the liquid level rise in the upper tank 6 can be suppressed, and overflow can be prevented.

The waiting time of STEP 8 is set so that the upper tank 6 does not overflow regardless of the amount of ink remaining in the lower tank 7 in consideration of the flow rate that flows as the internal pressure of the upper tank 6 increases.

  Following the time waiting process of STEP 8, after opening the air release valve 22 (STEP 9), the ON / OFF state of the liquid level sensor 35b is confirmed (STEP 11). And if the liquid level sensor 35b of the upper tank 6 is ON, it will progress to STEP14. If not, the process proceeds to STEP12.

Hereinafter, STEP12 to STEP26 are the same as those in FIG.
FIG. 14 is a diagram showing pressure fluctuations inside the recording head 2 when the ink filling process in the present embodiment is performed. Hereinafter, description will be made in comparison with the processing STEP in FIG.

  When STEP 1 to STEP 6 are executed, as shown by a waveform 77, the internal pressure in the recording head 2 is such that when the meniscus is formed because the nozzle holes are blocked by the ink remaining in the ink circulation unit 4. The pressure is equivalent, that is, approximately −1 kPa.

However, when air enters the ink circulation unit 4 and a printing operation is performed, a normal ink circulation operation cannot be performed, and a printing failure occurs.
When STEP 7 to STEP 8 are executed, the ink remaining in the lower tank 7 is pumped up to the upper tank 6 by the pump 11 as shown by a waveform 78, and the internal pressure of the upper tank 6 is increased, and the recording head 2 is about 5 kPa. Is pressurized.

  When STEP 9 is executed, the upper tank 6 becomes atmospheric pressure, and the internal pressure of the recording head 2 becomes approximately +0.5 kPa due to the water head difference between the nozzle plate 33 of the recording head 2 and the ink liquid level 39 of the upper tank 6.

  It should be noted that ink is supplied into the ink circulating unit 4 in the steps of STEP 11 to STEP 13, but at this time, the recording head is also different due to the water head difference between the nozzle plate 33 of the recording head 2 and the ink level 39 of the upper tank 6. The internal pressure 2 is a slightly positive pressure (a pressure slightly higher than the atmosphere) of approximately +0.5 kPa, as shown by a waveform 71-1.

Further, since the hydraulic head differential pressure acts similarly between STEP14 to STEP15, the internal pressure of the recording head 2 is approximately +0.5 kPa as shown by the waveform 71-1.
Here, the same waveform is generated six times in the present embodiment, in the processing of STEP5, the set value N of the number of repetitions is set to six times (N = 6), and STEP12 to STEP21. This is because the process is performed six times.

  Further, the intervals t1 to t6 of the waveforms 71-1 to 71-6 are narrowed every time the repetition number monitor value n is increased. The ink circulation unit 4 is filled with ink each time the number of repetitions is increased. This is because the ink supply time in STEP 12 is shortened.

When the number of repetitions is around 3, it is time for a small amount of ink dripped from the recording head 2 to be supplied.
With respect to the internal pressure waveform in the case of the first embodiment shown in FIG. 5, the time from t1 to t6 is shortened from the early stage because it remains in the ink path when the ink filling process is started. This is because the filling time is shortened due to the amount of ink that is present.

The subsequent waveforms are the same as those in the case of the first embodiment, and thus description thereof is omitted.
In the ink filling process of this example, as in the case of the first embodiment, the waiting time of STEP 15 may be set according to the ink temperature. Further, as in the case of the first embodiment, the present invention can also be applied to Modifications 1 to 4.

  According to the embodiment of the present invention or a modification thereof, when ink is empty in the ink circulation portion at the beginning of use of the ink jet printer or when the recording head is replaced during maintenance work, the ink is empty only in the replaced recording head. Even at this time, the head tank, the nozzle surface of the recording head, the water head difference between the lower tanks, the opening and closing of the valve in the ink path, and the drive control of the pump can always give a sudden pressure change in the recording head, All the recording heads, that is, the ink circulation portions can be reliably filled with ink. As a result, it is possible to prevent printing defects caused by air or bubbles remaining in the ink circulation unit.

  In addition, this invention is not limited to the said embodiment, In the implementation stage, it can change variously in the range which does not change the summary.

FIG. 2 is a diagram schematically showing an ink path configuration of the ink jet printer according to the first embodiment of the present invention. It is a figure which shows typically the structure of the ink circulation path | route of the inkjet printer in 1st Embodiment, and expanded. 6 is a flowchart for describing processing for filling ink into an ink circulation path of the ink jet printer according to the first embodiment. FIG. 4 is a flowchart showing a process when the ink is supplied to the pump by opening the refill valve before driving the pump in the process of FIG. It is a figure which shows the pressure fluctuation inside a recording head when performing the ink filling process of the inkjet printer in 1st Embodiment. 3 is a flowchart illustrating a process of circulating ink in an ink circulation path in order to maintain a printable state of the ink jet printer according to the first embodiment. 4 is a flowchart illustrating a process of stopping ink circulation in an ink circulation path after printing by the ink jet printer according to the first embodiment. It is a flowchart explaining the modification of the ink filling process in 1st Embodiment. (a) is a diagram showing a modified example of the ink circulation path as modified example 2 of the first embodiment, and (b) is a flowchart showing the control process. It is a figure which shows the modification of the ink circulation path as the modification 3 of 1st Embodiment. (a) is a figure which shows the modification of the ink circulation path as the modification 4 of 1st Embodiment, (b) is a flowchart which shows the process of the control. It is a figure which shows the internal pressure fluctuation | variation of the recording head in the ink filling process of the modification 4 of 1st Embodiment. It is a flowchart explaining the process which fills with ink in the ink circulation path | route of the inkjet printer in 2nd Embodiment. It is a figure which shows the pressure fluctuation inside a recording head when performing the ink filling process of the inkjet printer in 2nd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inkjet printer 2 Recording head 3 Head holder part (image recording part)
4 Ink circulation path 6 Upper tank 6a Ink inlet port 6b Ink outlet port 6c Atmospheric port 7 Lower tank 7a Ink inlet port 7b Ink supply port 7c Ink outlet port 7d Atmospheric port 8 Overflow tank 9 Ink cartridge 9a Supply port 10 Ink cartridge holder DESCRIPTION OF SYMBOLS 11 Pump 12 Heat exchange part 13 Filter 14 1st ink path 15 2nd ink path 19 Upper tank air chamber 22 Atmospheric release valve 24 Lower tank air chamber 26 Atmospheric release valve 30 Pressure adjustment part 31 Ink supply bus 32 Ink collection bus 33 Nozzle plate 34 Temperature sensor 35 Liquid level detector 35a Float member 35b Liquid level position sensor 35c Magnet 37 Liquid level adjuster 37a Float member 37b Lower end protrusion member
39, 40 Ink liquid level 41 Joint part 43 Supply valve 44 Negative pressure adjustment mechanism 45 Bellows part 46 Weight part 47 Bellows lifting mechanism 48 Waste liquid tank part 49 Tank tray 52 Waste liquid tank 53 Waste ink amount detection part 54 Tank installation detection part

Claims (10)

A plurality of ink heads having a nozzle plate formed with a plurality of nozzle holes for discharging ink, and performing printing on a recording medium;
An upper tank that is disposed at a position higher in the gravitational direction than the nozzle plate surface and temporarily stores ink to be supplied to the ink head;
A first atmosphere release valve that allows the inside of the upper tank to communicate with and shut off the atmosphere;
A liquid level sensor for detecting the ink liquid level stored in the upper tank;
A pump for feeding ink to the upper tank;
A lower tank that is disposed at a position lower in the gravitational direction than the nozzle plate surface, and that temporarily stores ink that is fed from the ink head and fed to the pump;
A second atmosphere release valve that allows the interior of the lower tank to communicate with and shut off the atmosphere;
An ink cartridge for supplying ink to the upper tank or the lower tank;
Have
Ink jet having an ink path that enables ink circulation by allowing ink flowing out of the upper tank to flow down to the lower tank through the ink head and pumping the ink flowing down to the lower tank back to the upper tank by the pump. In the printer
The liquid level sensor detects the level of ink stored in the upper tank, and controls the liquid feeding operation of the pump and the opening / closing operation of the first atmosphere release valve, thereby allowing the ink to flow into the ink path. An ink jet printer having an ink filling method for filling.   2. The ink jet printer according to claim 1, wherein during the printing operation, the pump is operated, the first atmosphere release valve is opened, and the second atmosphere release valve is closed to perform an ink circulation operation. .   While the printing operation is not performed, the operation of the pump is stopped, the first atmosphere release valve is closed, the second atmosphere release valve is opened, and the entire apparatus is in a standby state. The inkjet printer according to claim 1. A plurality of ink heads having a nozzle plate formed with a plurality of nozzle holes for discharging ink, and performing printing on a recording medium;
An upper tank that is disposed at a position higher in the gravitational direction than the nozzle plate surface and temporarily stores ink to be supplied to the ink head;
A first atmosphere release valve that allows the inside of the upper tank to communicate with and shut off the atmosphere;
A liquid level sensor for detecting the ink liquid level stored in the upper tank;
A pump for feeding ink to the upper tank;
A lower tank that is disposed at a position lower in the gravitational direction than the nozzle plate surface, temporarily stores ink that is fed from the ink head and fed to the pump;
A second atmosphere release valve that allows the inside of the lower tank to communicate with and shut off the atmosphere;
An ink cartridge for supplying ink to the upper tank or the lower tank;
Have
Ink jet having an ink path that enables ink circulation by allowing ink flowing out of the upper tank to flow down to the lower tank through the ink head and pumping the ink flowing down to the lower tank back to the upper tank by the pump. In the printer
The liquid level sensor detects the ink level stored in the upper tank,
Stop the liquid feeding operation of the pump for an arbitrary waiting time A in a state where the first atmosphere release valve communicates with the atmosphere,
The ink in the upper tank flows down to the lower tank,
Closing the first atmosphere release valve to shut off from the atmosphere;
By starting the liquid feeding operation of the pump,
An ink jet printer having an ink filling method for performing ink filling processing into an ink circulation path.   5. The ink jet printer according to claim 4, wherein during the printing operation, the pump is operated, the first atmosphere release valve is opened, and the second atmosphere release valve is closed to perform an ink circulation operation. .   The operation of the pump is stopped while the printing operation is not being performed, the first atmosphere release valve is closed, the second atmosphere release valve is opened, and a standby state is established. Inkjet printer described in   5. The ink jet printer according to claim 4, wherein the waiting time A is set according to an ink temperature in a circulation path. Detecting the liquid level sensor;
Bringing the first atmosphere release valve into communication with the atmosphere;
The operation to reverse the operation of the pump with respect to the circulation operation is performed for an arbitrary time,
The ink in the upper tank flows down to the lower tank,
Closing the first atmosphere release valve to shut off from the atmosphere;
By operating the pump in the same liquid feeding direction as the circulation operation,
The ink jet printer according to claim 4, wherein an ink filling process into the ink circulation path is performed. A plurality of ink heads having a nozzle plate formed with a plurality of nozzle holes for discharging ink, and performing printing on a recording medium;
An upper tank that is disposed at a position higher in the gravitational direction than the nozzle plate surface and temporarily stores ink to be supplied to the ink head;
A first atmosphere release valve that allows the inside of the upper tank to communicate with and shut off the atmosphere;
A liquid level sensor for detecting the ink liquid level stored in the upper tank;
A pump for feeding ink to the upper tank;
A lower tank that is disposed at a position lower in the gravitational direction than the nozzle plate surface, and that temporarily stores ink that is fed from the ink head and fed to the pump;
A second atmosphere release valve that allows the inside of the lower tank to communicate with and shut off the atmosphere;
An ink cartridge for supplying ink to the upper tank or the lower tank;
A first path for sending ink from the upper tank to the lower tank via the ink head;
A second path for feeding ink from the outlet port of the lower tank to the upper tank by a pump;
A third path through which the ink in the upper tank can flow down to the lower tank by the opening / closing operation of the path opening valve A;
Ink jet having an ink path that enables ink circulation by allowing ink flowing out of the upper tank to flow down to the lower tank through the ink head and pumping the ink flowing down to the lower tank back to the upper tank by the pump. In the printer
The liquid level sensor detects the ink level stored in the upper tank,
Bringing the first atmosphere release valve into communication with the atmosphere;
Stop the pumping operation of the pump,
Open the path opening valve A for an arbitrary time,
The ink in the upper tank flows down to the lower tank,
Closing the first atmosphere release valve to shut off from the atmosphere;
By starting the liquid feeding operation of the pump,
An ink jet printer having an ink filling method for performing ink filling processing into an ink circulation path. A plurality of ink heads having a nozzle plate formed with a plurality of nozzle holes for discharging ink, and performing printing on a recording medium;
An upper tank that is disposed at a position higher in the gravitational direction than the nozzle plate surface and temporarily stores ink to be supplied to the ink head;
A first atmosphere release valve that allows the interior of the upper tank to communicate with and shut off the atmosphere;
A liquid level sensor for detecting the ink liquid level stored in the upper tank;
A pump for feeding ink to the upper tank;
A lower tank that is disposed at a position lower in the gravitational direction than the nozzle plate surface, and that temporarily stores ink that is fed from the ink head and fed to the pump;
A second atmosphere release valve that allows the inside of the lower tank to communicate with and shut off the atmosphere;
An ink cartridge for supplying ink to the upper tank or the lower tank;
A path opening / closing valve B capable of opening and closing the ink path from the upper tank into the ink path of the ink head;
Have
Ink jet having an ink path that enables ink circulation by allowing ink flowing out of the upper tank to flow down to the lower tank through the ink head and pumping the ink flowing down to the lower tank back to the upper tank by the pump. In the printer
The liquid level sensor detects the ink level stored in the upper tank,
The pumping operation of the pump is stopped for an arbitrary waiting time A in a state where the first atmosphere release valve communicates with the atmosphere,
The ink in the upper tank flows down to the lower tank,
Closing the first atmosphere release valve to shut off from the atmosphere;
Close the path opening / closing valve B;
Start the pumping operation of the pump,
By opening the path opening / closing valve after an arbitrary time,
10. The ink jet printer according to claim 1, further comprising an ink filling method for performing an ink filling process into the ink circulation path.