Fluid ejecting apparatus and cleaning method

A printer includes: a fluid ejecting head provided with multiple nozzles that eject ink; an ink supply tube that supplies the ink to the fluid ejecting head; and a pressure application mechanism that pressurizes the ink to swell from the nozzles by pressurizing the ink within the ink supply tube and then depressurizes the interior of the ink supply tube while the ink is swelling from the nozzles.

BACKGROUND

1. Technical Field

The present invention relates to fluid ejecting apparatuses and cleaning methods for such fluid ejecting apparatuses.

2. Related Art

Ink jet printers have been widely known for some time as fluid ejecting apparatuses that eject a fluid onto a medium. Such printers carry out processes for printing onto a medium by ejecting ink (a fluid) from nozzles formed in a fluid ejecting head.

In such printers, there have been occurrences of missing dots in printed images, which are caused by attempting to eject ink in a state in which bubbles have entered into a nozzle and the nozzle thus experiences blank ejections. There are printers that execute a cleaning process in which ink is discharged along with the bubbles within the nozzle in order to suppress the occurrence of printing problems caused by missing dots (for example, see JP-A-2007-152725).

Such a cleaning process consumes a large amount of ink in order to discharge the bubbles, and thus in JP-A-2007-152725, the amount of ink supplied is changed depending on the severity of the printing problem. Nevertheless, a significant amount of ink is still consumed by this cleaning process, and thus the further reduction of the amount of ink consumed is still an issue.

SUMMARY

An advantage of some aspects of the invention is to provide a fluid ejecting apparatus and a cleaning method capable of discharging bubbles while suppressing the consumption of fluid.

A fluid ejecting apparatus according to an aspect of the invention includes: a fluid ejecting head provided with multiple nozzles that eject a fluid; a fluid supply channel that supplies the fluid to the fluid ejecting head; and a pressure application mechanism that causes the fluid to swell from the nozzles by pressurizing the fluid within the fluid supply channel, and then depressurizes the interior of the fluid supply channel while the fluid is swelling from the nozzles.

According to this configuration, some of the fluid is caused to swell from the nozzles by the pressure application mechanism pressurizing the fluid within the fluid supply channel, making it possible to push bubbles that have intermixed with the fluid at the swollen area out to the atmospheric side, which is outside of the nozzle openings. The pressure application mechanism depressurizes the interior of the fluid supply channel immediately after the pressurization, which then pulls the fluid that has swollen from the nozzles due to the pressurization back into the fluid ejecting head, so that the fluid is not wastefully consumed by falling from the nozzle openings or the like. Accordingly, the bubbles can be discharged while suppressing the consumption of fluid.

In the fluid ejecting apparatus according to another aspect of the invention, a depressurizing time for which the pressure application mechanism carries out the depressurization is longer than a pressurizing time for which the pressure application mechanism carries out the pressurization.

According to this configuration, by pressurizing for a short amount of time so as to ensure the bubble discharge properties while also making the depressurizing time longer than the pressurizing time, it is possible to suppress bubbles from being sucked in through the nozzle openings.

In the fluid ejecting apparatus according to another aspect of the invention, the pressure application mechanism carries out the pressurization by causing the volume of the fluid supply channel to decrease, and carries out the depressurization by causing the volume of the fluid supply channel to increase.

According to this configuration, by the pressure application mechanism reducing the volume of the fluid supply channel, an amount of fluid equivalent to the reduced volume is pushed out, thus making it possible to transmit the pressure toward the nozzles side. Because depressurization is carried out by increasing the volume of the fluid supply channel, the depressurization can be carried out immediately after the pressurization by returning the volume, which has been reduced for pressurization, to its original state.

In the fluid ejecting apparatus according to another aspect of the invention, the volume of the fluid supply channel caused to increase by the pressure application mechanism for the depressurization is less than the volume of the fluid supply channel caused to decrease by the pressure application mechanism for the pressurization.

According to this configuration, when bubbles are discharged from the nozzles through pressurization, an equivalent air gap is produced within the nozzles; however, the volume of the fluid supply channel increased for depressurization is lower than the volume of the fluid supply channel reduced for pressurization, making it possible to suppress the occurrence of empty nozzles caused by the air gaps.

In a fluid ejecting apparatus according to another aspect of the invention, multiple fluid ejecting heads are provided, and the apparatus further includes a fluid holding chamber that holds the fluid supplied via the fluid supply channel and supplies the held fluid to the multiple fluid ejecting heads.

According to this configuration, the meniscuses of the nozzles can be unified by adjusting the backpressure of the nozzles in the fluid holding chamber. The pressure application mechanism is provided upstream from the fluid holding chamber in the fluid flow channel, and thus increasing the number of fluid ejecting heads does not complicate the configuration.

In the fluid ejecting apparatus according to another aspect of the invention, the pressurizing time for which the pressure application mechanism carries out the pressurization is between 0.025 seconds and 0.5 seconds.

According to this configuration, the pressurizing time for which the pressure application mechanism carries out pressurization is between 0.025 and 0.5 seconds, and is thus extremely short; accordingly, it is possible to dislodge bubbles that have adhered to the inner walls of the nozzles and discharge those bubbles.

A cleaning method according to another aspect of the invention is a cleaning method for a fluid ejecting apparatus, the apparatus including a fluid ejecting head provided with multiple nozzles that eject a fluid and a fluid supply channel that supplies the fluid to the fluid ejecting head, and the method including: pressurizing the fluid to swell from the nozzles by pressurizing the fluid within the fluid supply channel; and after the pressurization, depressurizing the interior of the fluid supply channel while the fluid is swelling from the nozzles.

According to this configuration, the same effects as those of the aforementioned fluid ejecting apparatus can be achieved.

A fluid ejecting apparatus according to another aspect of the invention includes: a fluid ejecting head provided with multiple nozzles that eject a fluid; a fluid supply channel that supplies the fluid to the fluid ejecting head; an on-off valve provided in the fluid supply channel; and a pressure application mechanism that pressurizes the fluid to swell from the nozzles by pressurizing the fluid within the fluid supply channel downstream from the closed on-off valve.

According to this configuration, some of the fluid is pressurized to swell from the nozzles by the pressure application mechanism pressurizing the fluid within the fluid supply channel, making it possible to push bubbles that have intermixed with the fluid at the swollen area out to the atmospheric side, which is outside of the nozzle openings. Because the on-off valve is closed at this time, fluid is not supplied to nozzles from the fluid supply channel that is upstream therefrom. Accordingly, bubbles can be discharged from the nozzles while suppressing the consumption of fluid.

In the fluid ejecting apparatus according to another aspect of the invention, the pressure application mechanism depressurizes the interior of the fluid supply channel in a state in which the on-off valve is closed and the fluid is swelling from the nozzles due to the pressurization.

According to this configuration, because the pressure application mechanism depressurizes the interior of the fluid supply channel after pressurization while maintaining the closed state of the on-off valve, fluid that is swelling from the nozzles can be pulled back into the fluid ejecting head without being consumed wastefully due to dripping down from the nozzle openings and so on. Accordingly, the meniscuses of the nozzles can be suppressed from breaking, and the consumption of fluid can be suppressed as well. The pressure can be increased by the amount of fluid that is pulled back due to the depressurization, thus making it possible to improve the bubble discharge properties.

In a fluid ejecting apparatus according to another aspect of the invention, multiple fluid supply channels are provided and the same number of pressure application mechanisms as the fluid supply channels is provided.

According to this configuration, multiple pressure application mechanisms are provided in accordance with the number of fluid supply channels that are installed, thus making it possible to discharge bubbles for each of the fluid supply channels.

A cleaning method according to another aspect of the invention is a cleaning method for a fluid ejecting apparatus, the apparatus including a fluid ejecting head provided with multiple nozzles that eject a fluid, a fluid supply channel that supplies the fluid to the fluid ejecting head, and an on-off valve provided in the fluid supply channel, and the method including: closing the on-off valve; and after closing the on-off valve, pressurizing the fluid to swell from the nozzles by pressurizing the fluid within the fluid supply channel downstream from the on-off valve.

According to this configuration, the same effects as those of the aforementioned fluid ejecting apparatus can be achieved.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

First Embodiment

Hereinafter, a first embodiment, in which the invention is embodied as an ink jet printer (called simply a “printer” hereinafter) serving as a type of fluid ejecting apparatus, will be described with reference toFIGS. 1 through 10. Note that the terms “depth direction”, “horizontal direction”, and “vertical direction” as used in the descriptions hereinafter refer respectively to the depth direction, horizontal direction, and vertical direction indicated by the arrows in the drawings.

As shown inFIG. 1, a printer11includes a transport unit12that transports paper P serving as a medium, a line head13that executes a printing process on the paper P, an ink supply unit14that supplies ink serving as a fluid to the line head13, and a maintenance unit15.

The transport unit12includes a pair of paper feed rollers16, an endless transport belt17, a driving roller18, a slave roller19, a driving motor20connected to the driving roller18, and a pair of discharge rollers21. The transport belt17is wrapped upon the driving roller18and the slave roller19, and moves cyclically when the driving roller18rotates in the clockwise direction inFIG. 1due to the driving of the driving motor20. The paper feed rollers16, transport belt17, and discharge rollers21transport the paper P along a transport direction X. Multiple transport belts17(for example, two) are provided so as to support at least both ends of the paper P in a width direction Y (the depth direction), and the maintenance unit15is disposed between the transport belts17that are arranged in the depth direction.

The line head13includes a base unit23and fluid ejecting heads24supported by the base unit23. As shown inFIG. 2, the fluid ejecting heads24are arranged in a staggered pattern so as to form two rows of lines that extend along the width direction Y of the paper P. The first row, located upstream in the transport direction X (that is, on the left side), is configured of four fluid ejecting heads24arranged along the width direction Y, whereas the second row, located downstream in the transport direction X (that is, on the right side), is configured of four fluid ejecting heads24arranged along the width direction Y.

Each fluid ejecting head24is provided with multiple nozzles25for ejecting ink. Two nozzle rows N that extend along the width direction Y are formed in a nozzle formation surface24a, located on the bottom surface (base surface) of the fluid ejecting head24, by nozzle openings25aof the multiple nozzles25. As shown in the enlarged area ofFIG. 2, the nozzle openings25aare disposed in a staggered manner so that the intervals at which the two nozzle rows N are disposed along the width direction Y are shifted by ½ pixel. The first and second rows of fluid ejecting heads24are arranged so that, when projected in the transport direction X, at least one nozzle25at the respective ends of the rows overlap, or so that the nozzles25at the respective ends of the rows are continuous with a space equivalent to the nozzle pitch provided therebetween.

Accordingly, the printer11is capable of printing across the maximum paper width range even with the line head13remaining in a fixed state. In this embodiment, a single fluid ejecting head24corresponds to 1.1 inches of paper, and thus eight fluid ejecting heads24cover the horizontal width of A4 (297 mm×210 mm) paper (that is, approximately 8.3 inches). A single nozzle row N is configured of 330 nozzles25. Accordingly, a single line head13has 8 (the number of fluid ejecting heads24in the width direction Y)×2 (the number of nozzle rows N)×330 (the number of nozzles25of which each nozzle row N is configured), or 5,280 nozzles25.

In the case where four-color printing using, for example, cyan (C), magenta (M), yellow (Y), and black (K) is to be carried out, one pair of the line heads13and the ink supply unit14is provided for each of the colors (however, for the sake of simplicity,FIGS. 1 and 2show only one of each). A printing process can be carried out at a resolution of 600 dpi by superimposing ink droplets of the four colors from the four line heads13onto the transported paper P.

As shown inFIG. 1, the ink supply unit14includes an ink cartridge26that holds ink, an ink supply tube27that configures a fluid supply channel for supplying the ink from the ink cartridge26to the fluid ejecting head24, and a pressure pump28that pressure-transfers the ink. The ink cartridge26is mounted in a cartridge holder (not shown) in a removable state and is connected to the ink supply tube27. A pressure application mechanism29is provided partway along the ink supply tube27.

A common ink chamber30, which temporarily holds the ink supplied from the ink cartridge26via the ink supply tube27, is provided in the base unit23of the line head13. Multiple branch channels31, corresponding to respective fluid ejecting heads24, are connected to the common ink chamber30. The ink held within the common ink chamber30is supplied to multiple fluid ejecting heads24via the branch channels31.

As shown inFIG. 3, each fluid ejecting head24includes a flow channel formation member32, a vibrating plate33, a flow channel formation member34, and a nozzle plate35, all stacked in the vertical direction. The branch channel31that communicates with the common ink chamber30, a reservoir36, and a holding chamber37are formed in the flow channel formation member32. A communication hole38is provided in the vibrating plate33in a location that corresponds with the reservoir36. A cavity39that communicates with the reservoir36via the communication hole38is formed in the flow channel formation member34.

A piezoelectric element40is provided on the upper surface side of the vibrating plate33in a location that is above the cavity39. The nozzle25, which communicates with the cavity39, is formed in the nozzle plate35. In other words, the ink distributed to the fluid ejecting heads24from the common ink chamber30through the branch channels31is held in the reservoir36, and is then supplied to the nozzles25from the reservoir36via the communication hole38and the cavity39.

The vibrating plate33is provided so as to be capable of vibrating vertically. The vibrating plate33is caused to vibrate vertically by the piezoelectric element40extending/shrinking due to the application of a driving signal thereto. When the vibrating plate33vibrates vertically, the volume of the cavity39expands/shrinks. When the volume of the cavity39shrinks, the ink within the cavity39is ejected from the nozzle25as an ink droplet Fb. The nozzle formation surface24aof the fluid ejecting head24is configured of the bottom surface (base surface) of the nozzle plate35. In this embodiment, the diameter of each nozzle opening25ais approximately 20 micrometers, and the thickness of the nozzle plate35in the vertical direction is approximately 100 micrometers.

Here, the ink cartridge26is provided in a position that is lower than the line head13. Accordingly, the region within the fluid ejecting head24(the ink flow channel) has a negative pressure of approximately −1 kPa due to head differential. This negative pressure is for suppressing the ink from dripping down from the nozzle25and for stabilizing ejection operations by forming a concave-shaped meniscus within the nozzle25.

Next, the maintenance unit15will be described.

The maintenance unit15includes a capping unit41for capping the nozzle formation surface24aof the fluid ejecting head24(seeFIG. 4) and a wiping unit42for wiping the nozzle formation surface24a(seeFIG. 5). The capping unit41and wiping unit42may be provided for each fluid ejecting head24, or the multiple fluid ejecting heads24may be capped and wiped at the same time.

In addition to being used for capping that prevents the nozzles25from drying, the capping unit41is used when executing suction cleaning, in which ink within the ink cartridge26is sucked from the nozzles25, thus discharging bubbles, thickened ink, and so on from the nozzles25. Furthermore, the capping unit41is also used for catching ink discharged from the nozzles25during pressure cleaning, in which ink within the ink cartridge26is discharged from the nozzles25by the pressure pump28. Meanwhile, the wiping unit42is used when wiping the nozzle formation surface24ain order to remove objects stuck thereto, such as paper dust, ink, or the like, and when executing wiping for unifying the meniscuses of the nozzles25.

As shown inFIG. 4, the capping unit41includes a closed-end square box-shaped cap43, a raising/lowering mechanism44that raises/lowers the cap43, and a suction mechanism45. A square frame-shaped sealing member46, configured of a flexible material, is provided on the entirety of the top surfaces of the circumferential walls of the cap43, whereas a discharge pipe47is provided protruding downward from the base wall of the cap43.

One end of a discharge tube48, which is composed of a flexible material and partially configures the suction mechanism45, is connected to the discharge pipe47. The other end of the discharge tube48is inserted into a waste ink tank49. The waste ink tank49contains a waste ink absorption member50that is composed of a porous member.

A tube pump51of which the suction mechanism45is partially configured is disposed between the cap43and the waste ink tank49. The tube pump51includes a cylindrical case52, a pump wheel53that is circular when viewed from above, a wheel shaft54, and a pair of pressure rollers55. The pump wheel53is housed within the case52so as to be capable of rotation central to the wheel shaft54, which in turn is provided central to the axis of the case52. The middle portion of the discharge tube48is housed within the case52so as to follow the inner circumference of the walls of the case52.

A pair of roller guidance grooves56having arc shapes are formed in the pump wheel53so as to oppose each other with the wheel shaft54therebetween. Each of the roller guidance grooves56has one end positioned on the inner side of the circumference of the pump wheel53and the other end positioned on the outer side of the circumference of the pump wheel53. In other words, the roller guidance grooves56extend so as to gradually become further from the wheel shaft54as the groove progresses from one end to the other end. The pair of pressure rollers55are insertedly supported in the roller guidance grooves56via rotational shafts57. Both rotational shafts57are capable of sliding freely within their respective roller guidance grooves56.

When the pump wheel53rotates in the forward direction (the clockwise direction, indicated by the arrow inFIG. 4), the pressure rollers55in the outbound direction move to the other end of the roller guidance grooves56(that is, toward the outer circumferential side of the pump wheel53), continuously pressing down the middle portion of the discharge tube48from the upstream side to the downstream side while rotating. Due to this rotation, the interior of the discharge tube48that is upstream from the tube pump51is depressurized.

However, when the pump wheel53rotates in the backward direction (that is, the counter-clockwise direction inFIG. 4), the pressure rollers55return in the inbound direction to the one end of the roller guidance grooves56(that is, toward the inner circumferential side of the pump wheel53). Due to this movement, the pressure rollers55make light contact with the middle portion of the discharge tube48, thus canceling the depressurized state of the interior of the discharge tube48.

The raising/lowering mechanism44includes a cam member58that makes contact with the cap43from below, a motor59for rotating the cam member58, and a driving force transmission mechanism60. When the motor59is driven in the forward direction, the cam member58is rotated via the driving force transmission mechanism60, and the cap43makes contact with the nozzle formation surface24a.

Accordingly, when the pump wheel53is driven in the forward direction while the cap43is in contact with the nozzle formation surface24a, negative pressure arises in a space R formed between the cap43and the nozzle formation surface24a. Through this, suction cleaning, in which ink is discharged from the nozzles25, is executed. The negative pressure in the space R is canceled when the pump wheel53is rotated in the backward direction. Thereafter, when the motor59of the raising/lowering mechanism44is driven in the backward direction, the cap43drops, thus removing the cap43from the transport path of the paper P.

The wiping mechanism61includes a holder63, a lead screw64erected in the holder63so as to extend along the depth direction, a motor65for rotating the lead screw64, a support member66, and a plate-shaped wiper67configured of an elastic material such as rubber. The wiper67is supported by the support member66so as to be erect thereabove, and the support member66is supported by the lead screw64. A holding cavity66ais formed in the upper surface side of the support member66.

The raising/lowering mechanism62includes a cam member68that makes contact with the holder63of the wiping mechanism61from below, a motor69for rotating the cam member68, and a driving force transmission mechanism70. When the motor69is driven in the forward direction, the cam member68is rotated via the driving force transmission mechanism70, and the wiping mechanism61rises to a position in which the wiper67makes contact with the nozzle formation surface24a.

When the motor65is driven in the forward direction and the lead screw64rotates in the forward direction, the wiper67slides along the nozzle formation surface24awhile moving along the depth direction with the support member66. Wiping, in which the nozzle formation surface24ais wiped clean, is executed in this manner. At this time, ink, paper dust, and so on wiped off from the nozzle formation surface24afall along the wiper67and are held in the holding cavity66a.

Next, the pressure application mechanism29will be described.

As shown inFIGS. 6A and 6B, the pressure application mechanism29includes a flow channel formation member71of a fixed shape. A connection portion72is provided on the left end of the flow channel formation member71, connecting to the ink supply tube27on the upstream side, whereas a connection portion73is provided on the right side of the flow channel formation member71, connecting to the ink supply tube27on the downstream side. A recessed portion71a, which is circular in shape when viewed from above, is formed in the upper surface side of the flow channel formation member71. An inflow channel72athat allows the ink supply tube27on the upstream side to communicate with the recessed portion71ais formed in the connection portion72. Meanwhile, an outflow channel73athat allows the ink supply tube27on the downstream side to communicate with the recessed portion71ais formed in the connection portion73.

A flexible film member74is affixed on the upper surface side of the flow channel formation member71in a flexible state so as to seal the opening of the recessed portion71a. Meanwhile, a disk-shaped depression plate74awhose surface area is smaller than the area of the opening of the recessed portion71ais affixed approximately in the center of the outer surface side of the film member74. A pressure chamber75is enclosed and formed by the film member74and the recessed portion71a. The pressure chamber75configures part of the fluid supply channel by communicating with the ink supply tube27through the inflow channel72aand the outflow channel73a.

A biasing member76that biases the film member74in a direction that expands the interior volume of the pressure chamber75is disposed within the pressure chamber75. The biasing member76can be configured from, for example, a coil spring, a plate spring, or the like. A cam member77that makes contact with the depression plate74ais disposed above the depression plate74a. The cam member77is supported by a rotational shaft78, and rotates along with the rotational shaft78in accordance with the driving of a motor79.

Accordingly, when the motor79is driven in the forward direction in the state shown inFIG. 6A, the cam member77rotates in the counter-clockwise direction inFIG. 6Aagainst the biasing force of the biasing member76. As a result, as shown inFIG. 6B, the film member74displaces in a direction that reduces the interior volume of the pressure chamber75, and the ink within the ink supply tube27is pressurized by the ink pushed out from the pressure chamber75. When the motor79is then driven in the backward direction in the state shown inFIG. 6B, the cam member77rotates in the clockwise direction inFIG. 6B. As a result, the film member74displaces in a direction that increases the interior volume of the pressure chamber75due to the biasing force of the biasing member76, and the interior of the ink supply tube27is depressurized by the ink being sucked into the pressure chamber75.

Next, maintenance operations in the printer11will be described.

In the printer11, missing dots occur when bubbles infiltrate the ink supply tube27when the ink cartridge26is replaced, and the nozzles25become clogged due to ink thickening when the printer11is left standing with the power turned off. In order to suppress a drop in printing quality caused by such missing dots and clogs, the printer11executes suction cleaning, pressure cleaning, and so on using the capping unit41. Hereinafter, cleaning in which ink is discharged from the nozzles25while supplying ink from the ink cartridge26will be referred to as “ink supply cleaning”.

In the case where paper dust and so on has stuck to the nozzle formation surface24adue to the printing process, the nozzle formation surface24ais wiped using the wiping unit42. Because discharged ink sticks to the nozzle formation surface24a, convex meniscuses are formed in the nozzle openings25a, and so on after ink supply cleaning, this wiping is carried out immediately after ink supply cleaning.

However, when such wiping is carried out, there are situations where the wiper67pushes air into the nozzles25and fine bubbles are produced in the nozzles25. These bubbles are much smaller compared to the bubbles that infiltrate when replacing the ink cartridge26and so on, and thus these bubbles often accumulate in the vicinity of the nozzles25. Accordingly, the printer11executes non-ink-supply cleaning using the pressure application mechanism29in order to discharge the fine bubbles in the vicinity of the nozzles25.

Next, the non-ink-supply cleaning performed by the pressure application mechanism29will be described in detail.

The non-ink-supply cleaning is configured of a pressurizing step, in which the pressure application mechanism29pressurizes the ink in the ink supply tube27and causes ink to swell from the nozzles25, and a depressurizing step, carried out after the pressurizing step, in which the pressure application mechanism29depressurizes the interior of the ink supply tube27while the ink is swelling from the nozzles25. In other words, in the pressurizing step, the pressure application mechanism29propagates pressure to within the nozzles25by expelling ink from the pressure chamber75all at once, thus dislodging bubbles that have stuck to the inner walls of the nozzles25, as shown inFIG. 7A. As shown inFIG. 7B, causing the ink to swell from the nozzles25pushes the bubbles toward the atmosphere side, which is the outside of the nozzle openings25a.

In the depressurizing step, the pressure application mechanism29causes the volume of the pressure chamber75to increase, thus pulling the volume of ink that has been pushed out back into the pressure chamber75. Through this, the ink that has swelled out in a convex shape from the nozzles25is collected back into the nozzles25, as shown inFIG. 7C, before the ink droplets Fb are ejected, fall (drip), or the like from the nozzles25. When the bubbles are discharged, an air gap equivalent to the volume of the bubbles arises in the nozzles25, but the ink within the common ink chamber30feeds into the nozzles25as shown inFIG. 7Ddue to capillarity if the printer11is left standing for a short amount of time.

By executing this pressurizing and depressurizing in the non-ink-supply cleaning multiple times in repetition, even bubbles that are difficult to be discharged can be gradually moved to the outside. For example, in the case where the pressurizing and depressurizing are repeated multiple times, bubbles present in the fluid ejecting head24, the common ink chamber30, and so on can also be discharged, in addition to the bubbles within the nozzles25. Furthermore, even in the case where an air gap has been produced in the nozzles25due to the discharge of bubbles, the positions of the liquid surfaces of the nozzles25are gradually unified by repeating the pressurizing and the depressurizing.

In the depressurizing step, the volume that was reduced in the pressurizing step may be restored to its original volume, or the volume increased for the depressurizing may be smaller than a volume that has been reduced for the pressurizing. For example, in the case where comparatively large bubbles present within the common ink chamber30have been discharged by repeating the pressurizing and the depressurizing multiple times, there is also the risk of empty nozzles arising, in which the entire nozzle25is taken up by an air gap. When an empty nozzle has arisen in this manner, there are cases where it is difficult for the ink to fill through capillarity, and thus it is preferable to reduce the amount of ink that is sucked in, particularly during the final depressurization after pressurization and depressurization have been repeated multiple times.

Here, as shown inFIG. 8, it is preferable for a depressurizing time Td for which depressurizing is carried out during the depressurizing step to be set longer than a pressurizing time Ta for which pressurizing is carried out during the pressurizing step. If the pressurizing time Ta is too short, there is a risk of the ink droplets Fb being ejected due to the propagated pressure and ink being wastefully consumed, the depressurizing starting too early and causing the ink to be sucked back before the bubbles have been pushed out, and so on. Conversely, if the pressurizing time Ta is too long, there is a risk of the ink flow speed slowing and the bubbles not being dislodged from the inner walls of the nozzles25, the ink not being pulled back in a timely manner by the depressurizing and the ink being consumed, and so on.

On the other hand, if the depressurizing time Td is too long, there is a risk of the ink not being pulled back in a timely manner and the ink being consumed. Conversely, if the depressurizing time Td is too short, there is a risk of air being sucked in from outside of the nozzles25, producing bubbles.

A proper pressurizing time Ta for suppressing the ejection of ink droplets Fb and ensuring the discharge properties for bubbles is an extremely short amount of time, such as 0.05 to 0.5 seconds. On the other hand, carrying out depressurization in such a short amount of time will suck air in, and thus with a pressurizing time Ta from 0.05 to 0.5 seconds, it is preferable for the pressurizing time Ta to be less than the depressurizing time Td.

In this embodiment, the pressurization and depressurization are executed by causing the volume of the pressure chamber75to fluctuate to a degree at which ink droplets Fb are not ejected from the nozzles25. Accordingly, the appropriate values for the amount of ink pushed out due to the volume fluctuation caused by the pressurization (called a “pressurized ink amount Vd” hereinafter), the pressurizing time Ta, and the depressurizing time Td fluctuate depending on flow channel conditions, such as the number of nozzles25, fluid ejecting heads24, and so on that are installed. A range of appropriate values for the pressurized ink amount Vd, the pressurizing time Ta, and the depressurizing time Td, as well as the flow channel conditions, will be described next.

As shown inFIG. 9, the following can be given as an example of flow channel conditions of the printer11according to this embodiment (called “flow channel condition 1” hereinafter): an interior volume of the ink cartridge26(region No. 1) of approximately 50 cc; and an interior volume of the ink supply tube27from the ink cartridge26to the pressure chamber75(region No. 2) of approximately 3.5 cc. Furthermore, the volume of the pressure chamber75capable of fluctuating (region No. 3) is approximately 1.0 cc; the interior volume of the ink supply tube27downstream from the pressure chamber75(region No. 4) is approximately 1.9 cc; the interior volume of the common ink chamber30(region No. 5) is approximately 3.1 cc; and the total interior volume of the eight fluid ejecting heads24(region No. 6) is approximately 0.9 cc.

An appropriate range of the pressurized ink amount Vd when carrying out non-ink-supply cleaning under the flow channel condition 1 is illustrated inFIG. 10A, whereas appropriate ranges for the pressurizing time Ta and the depressurizing time Td are illustrated inFIG. 10B.

With respect to the pressurized ink amount Vd, it is preferable to carry out pressurization so that the approximately 1.0 cc volume of the pressure chamber75is reduced to a volume in the range of 0.22 cc≦Vd≦0.62 cc. If 0.22 cc>Vd, there is a risk that sufficient pressurizing for discharging the bubbles cannot be obtained, whereas if 0.62 cc<Vd, there is a risk of consuming ink.

In the case where 0.22 cc≦Vd≦0.62 cc, it is preferable for the pressurizing time Ta to be 0.05 seconds≦Ta≦0.5 seconds and for the depressurizing time Td to be 0.09 seconds≦Td≦0.7 seconds (assuming, however, that Ta<Td).

With the non-ink-supply cleaning performed by the pressure application mechanism29, the risk of ink sticking to the nozzle formation surface24aafter the cleaning is executed is low, and the meniscuses of the nozzles25can be unified, which makes it unnecessary to carry out wiping as post-processing, as is the case with ink supply cleaning. Ink consumption can be reduced to nearly zero, and the cleaning can be carried out in an extremely short amount of time.

According to the embodiment described thus far, the following effects can be obtained.

(1) Some ink is caused to swell from the nozzles25by the pressure application mechanism29pressurizing the ink within the ink supply tube27, making it possible to push bubbles that have intermixed with the ink at the swollen area out to the atmospheric side, which is outside of the nozzle openings25a. The pressure application mechanism29depressurizes the interior of the ink supply tube27immediately after the pressurization, which then pulls the ink that has swollen from the nozzles25due to the pressurization back into the fluid ejecting heads24, so that the ink is not wastefully consumed by falling from the nozzle openings25aor the like. Thus according to the non-ink-supply cleaning performed by the pressure application mechanism29, bubbles can be discharged while also suppressing the consumption of ink.

(2) By pressurizing for a short amount of time so as to ensure the bubble discharge properties while also making the depressurizing time Td longer than the pressurizing time Ta, it is possible to suppress bubbles from being sucked in through the nozzle openings25a.

(3) By the pressure application mechanism29reducing the volume of the pressure chamber75, an amount of ink equivalent to the reduced volume is pushed out, thus making it possible to transmit the pressure toward the nozzles25. Because depressurization is carried out by increasing the volume of the pressure chamber75, the depressurization can be carried out immediately after the pressurization by returning the volume, which has been reduced for pressurization, to its original state.

(4) When bubbles are discharged from the nozzles25through pressurization, an equivalent air gap is produced within the nozzles25; however, by reducing the volume of the pressure chamber75increased for depressurization beyond the volume of the pressure chamber75reduced for pressurization, the occurrence of empty nozzles caused by the air gaps can be suppressed.

(5) The meniscuses of the nozzles25can be unified by adjusting the backpressure of the nozzles25in the common ink chamber30. For example, the flow of ink caused by pressurization and depressurization in the non-ink-supply cleaning is transmitted to the nozzles25through the common ink chamber30. Accordingly, even in the case where an air gap has been produced within a single nozzle25from which bubbles have been discharged, repeating the pressurization and depressurization unifies the position of the liquid surface with the other nozzles25. The pressure application mechanism29is provided upstream from the common ink chamber30in the ink flow channel, and thus increasing the number of fluid ejecting heads24does not complicate the configuration.

(6) The pressurizing time Ta for which the pressure application mechanism29carries out pressurization is, under the flow channel condition 1, between 0.05 and 0.5 seconds, and is thus extremely short; accordingly, it is possible to dislodge bubbles that have adhered to the inner walls of the nozzles25and discharge those bubbles.

Second Embodiment

Next, a second embodiment of the invention will be described based onFIGS. 11 to 13.

With the printer11according to the first embodiment, the regions No. 1 through No. 6 of which the ink flow channel is configured communicate with each other, and thus ink that has been pushed out of the pressure chamber75moves not only into the regions No. 3 through No. 6 that are downstream, but also into the regions No. 1 and No. 2 that are upstream. For this reason, the pressure extending to the nozzles25weakens by the amount by which the pressure is transmitted upstream. Accordingly, in the second embodiment, a printer11A capable of causing the ink that has been pushed out to flow downstream only will be described.

As shown inFIG. 11, the printer11A according to the second embodiment includes an ink supply unit14A in place of the ink supply unit14of the printer11. In the ink supply unit14A, a differential pressure regulating valve80and an on-off valve81are provided in the ink supply tube27.

The on-off valve81is a valve that can be opened or closed as desired, and is provided immediately upstream from the pressure application mechanism29. A solenoid valve, a valve that operates mechanically, or the like can be employed as the on-off valve81. When executing non-ink-supply cleaning, putting the differential pressure regulating valve80into a closed state causes the ink that has been pushed out from the pressure chamber75to flow downstream only.

The differential pressure regulating valve80is a diaphragm-type self-sealing valve that opens and closes using a differential pressure between the atmospheric pressure and the ink pressure, and is disposed between the ink cartridge26and the on-off valve81. In the printer11A, the ink cartridge26(the cartridge holder, which is not shown) is provided in a higher position than the line head13. Accordingly, the interior of the fluid ejecting head24has a negative pressure of approximately −1 kPa due to the differential pressure regulating valve80.

As shown inFIG. 12A, the differential pressure regulating valve80includes a flow channel formation member82of a fixed shape. A connection portion83is provided on the left end of the flow channel formation member82, connecting to the ink supply tube27on the upstream side, whereas a connection portion84is provided on the right side of the flow channel formation member82, connecting to the ink supply tube27on the downstream side. A recessed portion82a, which is circular in shape when viewed from above, is formed in the upper surface side of the flow channel formation member82, and a single protruding portion82bhaving a conical trapezoidal shape is formed in a location of the inner base surface of the recessed portion82athat is shifted to the left of the center. An inflow channel83athat allows the ink supply tube27on the upstream side to communicate with the recessed portion82ais formed in the connection portion83, so that an opening into the recessed portion82ais formed in the upper end surface of the protruding portion82b. Meanwhile, an outflow channel84athat allows the ink supply tube27on the downstream side to communicate with the recessed portion82ais formed in the connection portion84.

A flexible film member85is affixed on the upper surface side of the flow channel formation member82in a flexible state so as to seal the opening of the recessed portion82a. Meanwhile, a disk-shaped depression plate86whose surface area is smaller than the area of the opening of the recessed portion82ais affixed approximately in the center of the inner surface side of the film member85that faces toward the recessed portion82a. A pressure chamber87is enclosed and formed by the film member85and the recessed portion82a.

A base section88, an arm member89supported by the base section88in a tillable state, and a biasing spring90that biases one end of the arm member89(the left end) toward the protruding portion82bare housed within the pressure chamber87. Under the constant biasing force of the biasing spring90, the one end of the arm member89seals the opening of the inflow channel83aprovided in the upper end surface of the protruding portion82b, while the other end (the right end) pushes the depression plate86in the upward direction. Accordingly, the film member85is flexed in a direction that expands the interior volume of the pressure chamber87, and thus the pressure chamber87and the interior of the fluid ejecting head24positioned in an area downstream therefrom have a negative pressure of approximately −1 kPa.

Ink is supplied to the inflow channel83ain a pressurized state by the pressure pump28, and the inflow of ink into the pressure chamber87is suppressed by the one end of the arm member89, which constantly receives the biasing force from the biasing spring90. The negative pressure within the pressure chamber87increases as ink is consumed by ejection from the nozzles25or outflow, and as shown inFIG. 12B, the film member85flexes, against the biasing force of the biasing spring90, in a direction that reduces the interior volume of the pressure chamber87. Upon doing so, the other end of the arm member89tilts so as to press upon the film member85through the depression plate86and the one end opens the opening of the inflow channel83a, and as a result, the ink pressurized within the pressure chamber87flows in through the inflow channel83a.

As the negative pressure within the pressure chamber87decreases due to the inflow of ink, the arm member89and the film member85return to their original positions due to the biasing force of the biasing spring90. Accordingly, an amount of ink in accordance with the amount that has been consumed is supplied to the fluid ejecting head24.

Next, non-ink-supply cleaning according to this embodiment will be described.

This non-ink-supply cleaning is configured of a valve closing step in which the on-off valve81is closed, a pressurizing step of causing ink to swell from the nozzles25by the pressure application mechanism29carrying out pressurization after the valve closing step, and a depressurizing step of the pressure application mechanism29carrying out depressurization in a state in which the ink has swelled from the nozzles25as a result of the pressurization.

By carrying out the pressurizing step and the depressurizing step while the on-off valve81is closed in this manner, ink is not supplied from upstream from the on-off valve81and is thus not ejected and does not drip down from the nozzle openings25a; accordingly, ink is not consumed during the non-ink-supply cleaning.

In the printer11A, it is assumed that the differential pressure regulating valve80is in a closed state when the non-ink-supply cleaning is executed (this state will be referred to as a “flow channel condition 2” hereinafter). Under the flow channel condition 2, of the regions illustrated inFIG. 9, the regions aside from the regions No. 1 and 2, or the regions No. 3 through 6, correspond to the range that is affected by the pressurization and depressurization.

An appropriate range of the pressurized ink amount Vd when carrying out non-ink-supply cleaning under the flow channel condition 2 is illustrated inFIG. 13A, whereas appropriate ranges for the pressurizing time Ta and the depressurizing time Td are illustrated inFIG. 13B.

With respect to the pressurized ink amount Vd, it is preferable to carry out pressurization so that the approximately 1.0 cc volume of the pressure chamber75is reduced to a volume in the range of 0.18 cc≦Vd≦0.48 cc. In other words, because a loss in the pressure arising when ink flows toward the regions No. 1 and 2 is eliminated, bubbles can be discharged with a lower pressurized ink amount Vd under the flow channel condition 2 than under the flow channel condition 1. In this case, because 5,280 nozzles25are provided in a single line head13, a favorable ink swell range for a single nozzle is approximately 3.5×10−5cc to 9.0×10−5cc. It has been confirmed that particularly favorable results can be obtained by pressurizing at Ta=0.15 seconds and depressurizing at Td=0.35 seconds with Vd=0.33 cc.

In the case where 0.18 cc≦Vd≦0.48 cc, it is preferable for the pressurizing time Ta to be 0.025 seconds≦Ta≦0.2 seconds and for the depressurizing time Td to be 0.1 seconds≦Td≦0.5 seconds (assuming, however, that Ta<Td). In other words, considering the flow channel conditions 1 and 2, it is preferable to set the pressurizing time Ta at which the pressure application mechanism29carries out pressurization in the pressurizing step to 0.025 seconds to 0.5 seconds.

According to the embodiment described thus far, the following effects can be obtained in addition to effects similar to those in the aforementioned (1) to (5).

(6) Some ink is caused to swell from the nozzles25by the pressure application mechanism29pressurizing the ink within the ink supply tube27, making it possible to push bubbles that have intermixed with the ink at the swollen area out to the atmospheric side, which is outside of the nozzle openings25a. Because the on-off valve81is closed at this time, ink is not supplied to nozzles from the ink supply tube27that is upstream from the on-off valve81. Accordingly, bubbles can be discharged from the nozzles25while suppressing the consumption of ink.

(7) Because the pressure application mechanism29depressurizes the interior of the ink supply tube27after pressurization while maintaining the closed state of the on-off valve81, ink that is swelling from the nozzles25can be pulled back into the fluid ejecting head24without being consumed wastefully due to dripping down from the nozzle openings25aand so on. Accordingly, the meniscuses of the nozzles25can be suppressed from breaking, and the consumption of ink can be suppressed as well. The pressure can be increased by the amount of ink that is pulled back due to the depressurization, thus making it possible to improve the bubble discharge properties.

(8) Multiple pressure application mechanisms29are provided in accordance with the number of ink supply tubes27that are installed, thus making it possible to discharge bubbles for each of the ink supply tubes27.

(9) The pressurizing time Ta for which the pressure application mechanism29carries out pressurization is between 0.025 and 0.2 seconds, and is thus extremely short; accordingly, it is possible to dislodge bubbles that have adhered to the inner walls of the nozzles25and discharge those bubbles.

The aforementioned embodiments may be changed to the embodiments described hereinafter as well.

The pressure application mechanism29may have the configuration of a pressure application mechanism29A, as illustrated inFIG. 14.

The pressure application mechanism29A includes a flow channel formation member91of a fixed shape. A connection portion92is provided on the left end of the flow channel formation member91, connecting to the ink supply tube27, whereas a connection portion93is provided on the right side of the flow channel formation member91, connecting to the ink supply tube27. A recessed portion91a, which is circular in shape when viewed from above, is formed in the upper surface side of the flow channel formation member91. An inflow channel92athat allows the ink supply tube27to communicate with the recessed portion91ais formed in the connection portion92. Meanwhile, an outflow channel93athat allows the ink supply tube27to communicate with the recessed portion91ais formed in the connection portion93.

A piston94is housed in the recessed portion91aof the flow channel formation member91so as to be capable of sliding. One end (the lower end) of the piston94configures a disk-shaped mobile portion94athat in turn configures one wall surface of the pressure chamber75, whereas the other end (the upper end) of the piston94configures a disk-shaped pressure receiving portion94b. The pressure chamber75is enclosed and formed by the mobile portion94aof the piston94and the recessed portion91aof the flow channel formation member91.

The biasing member76, composed of a spring, is disposed between the upper surface side of the flow channel formation member91and the lower surface side of the pressure receiving portion94b. Accordingly, when the motor79is driven in the forward direction and the cam member77rotates in the counter-clockwise direction inFIG. 14, the mobile portion94aof the piston94moves in a direction away from the rotational shaft78. Upon doing so, the volume of the pressure chamber75decreases, and the ink within the ink supply tube27is pressurized by the ink that has been pushed out from the pressure chamber75. When the motor79is driven in the backward direction and the cam member77rotates in the clockwise direction inFIG. 14, the mobile portion94aof the piston94moves in a direction toward the rotational shaft78due to the biasing force of the biasing member76. Upon doing so, the volume of the pressure chamber75increases, and the inner of the ink supply tube27is depressurized by the ink that has been pulled into the pressure chamber75.

With respect to the pressure application mechanism29, the piston94of the pressure application mechanism29A may be configured of a movable core, and a solenoid may be provided in the periphery thereof. In this case, the piston94configured of the movable core can be moved by flowing a current to the solenoid and generating a magnetic field.

The pressure application mechanism may include a piezoelectric element, and the pressurization and depressurization may be carried out by changing the volume of the fluid supply channel using the piezoelectric element.

The ink supply tube27capable of elastic deformation may be pressurized by the cam member77pressing down thereupon. In this case, the flow channel formation member71need not be provided, which makes it possible to simplify the configuration.

For example, rather than including the common ink chamber30, one end of the ink supply tube27(a base end) may be connected to the ink cartridge26, and the other end (a leading end) of the ink supply tube27may be connected to the fluid ejecting head24via multiple branches. In this case, the pressure application mechanism29may be provided on the base end, or the pressure application mechanism29may be provided on the branched leading end.

The pressure application mechanism may be provided between the common ink chamber30and the reservoir36, or may be provided between the reservoir36and the cavity39.

The liquid flow channel may be configured of rigid tubing that does not easily experience elastic deformation. In this case, pressure fluctuations caused by the pressurization in the pressurizing step and the depressurization in the depressurizing step can be transmitted to the nozzles25without being absorbed by the elastic deformation of the tubing.

In the case where the flow channel conditions, the fluid that is ejected, or the like has been changed, the friction resistance, flow channel resistance, viscosity, and so on change, and it is thus preferable to adjust the pressurized ink amount Vd, the pressurizing time Ta, and the depressurizing time Td to values appropriate thereto.

The number of fluid ejecting heads24, nozzles25, nozzle rows N, and so on can be set as desired.

A non-removable ink tank may be employed for a fluid holding unit.

The invention may be realized using a full-line type line head printer having a long fluid ejecting head, a lateral printer, or a serial printer.

Although the fluid ejecting apparatus is embodied as an ink jet printer in the aforementioned embodiment, a fluid ejecting apparatus that ejects or discharges a fluid aside from ink may be employed as well, and the invention can be applied to various types of liquid ejecting apparatuses that include liquid ejecting heads or the like that discharge miniature-sized liquid droplets. “Droplet” refers to the state of the liquid ejected from the liquid ejecting apparatus, and is intended to include granule forms, teardrop forms, and forms that pull tails in a string-like form therebehind. The “liquid” referred to here can be any material capable of being ejected by the liquid ejecting apparatus. For example, any matter can be used as long as the matter is in its liquid state, including liquids having high or low viscosity, sol, gel water, other inorganic agents, organic agents, liquid solutions, liquid resins, and fluid states such as liquid metals (metallic melts); furthermore, in addition to liquids as a single state of a matter, liquids in which the molecules of a functional material composed of a solid matter such as pigments, metal particles, or the like are dissolved, dispersed, or mixed in a liquid carrier are included as well. Ink, described in the above embodiment as a representative example of a liquid, liquid crystals, or the like can also be given as examples. Here, “ink” generally includes water-based and oil-based inks, as well as various types of liquid compositions, including gel inks, hot-melt inks, and so on. The following are specific examples of liquid ejecting apparatuses: liquid ejecting apparatuses that eject liquids including materials such as electrode materials, coloring materials, and so on in a dispersed or dissolved state for use in the manufacture and so on of, for example, liquid-crystal displays, EL (electroluminescence) displays, front emission displays, and color filters; liquid ejecting apparatuses that eject bioorganic matters used in the manufacture of biochips; liquid ejecting apparatuses that eject liquids to be used as samples for precision pipettes; printing equipment and microdispensers; and so on. Furthermore, the invention may be employed in liquid ejecting apparatuses that perform pinpoint ejection of lubrication oils into the precision mechanisms of clocks, cameras, and the like; liquid ejecting apparatuses that eject transparent resin liquids such as ultraviolet light-curable resins onto a substrate in order to form miniature hemispheric lenses (optical lenses) for use in optical communication elements; and liquid ejecting apparatus that eject an etching liquid such as an acid or alkali onto a substrate or the like for etching. The invention can be applied to any type of these ejecting apparatuses.