Liquid-ejecting-apparatus maintenance method and liquid ejecting apparatus

A maintenance method that discharges liquid L collected in a liquid receiver 15 of a liquid ejecting apparatus includes a first step of causing a nozzle opening face 43a of a liquid ejecting head 3 to be disposed facing the liquid receiver 15 in a non-contact state and applying an electric field between both, a second step of ejecting liquid D from a nozzle 47 to the liquid receiver 15, a third step of detecting a voltage change based on electrostatic induction at the time of ejecting the liquid D to the liquid receiver 15, a fourth step of determining a liquid level height H of the liquid L collected in the liquid receiver on the basis of a result of detection of the voltage change, and a fifth step of discharging the liquid L collected in the liquid receiver when the liquid level height H reaches a predetermined height.

The entire disclosure of Japanese Patent Application No. 2007-032558, filed Feb. 13, 2007, is expressly incorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a maintenance method for use in a liquid ejecting apparatus such as an ink jet printer, and an ink jet printer.

2. Description of the Related Art

Liquid ejecting apparatuses have liquid ejecting heads capable of ejecting liquids as droplets, and eject various types of liquids from the ejecting heads.

Examples of typical liquid ejecting apparatuses include an image recording apparatus, such as an ink jet printer, having an ink jet recording head (hereinafter referred to simply as a recording head) as a liquid ejecting head, for performing recording by forming dots in such a manner that liquid ink is allowed to be discharged as ink droplets from nozzles (openings) of the recording head and to land on a discharge target such as recording paper.

In recent years, the liquid ejecting apparatuses have been applied not only to the image recording apparatuses but also to various manufacturing apparatuses such as an apparatus for manufacturing color filters of liquid crystal displays, etc.

In such an image recording apparatus, for example, ink stored in a liquid reservoir such as an ink tank or an ink cartridge is introduced into a pressure chamber of a recording head, and a driving signal is applied to drive a pressure generating source such as a piezoelectric vibrator, whereby a pressure change is caused to occur in the ink in the pressure chamber. By controlling the pressure change, an ink droplet can be discharged from a nozzle.

Regarding the recording head, on the basis of a driving voltage (potential difference from the lowest voltage to the highest voltage) of the driving signal supplied to the pressure generating source and a waveform thereof, a liquid amount (weight and volume) of an ink droplet discharged from the nozzle increases or decreases.

In a liquid ejecting apparatus, in order that each nozzle of the recording head may be maintained in a good state and that missing dots may be prevented from occurring in such a manner that a desired amount of ink droplets is always discharged, in a case such as before the start of recording (printing), during recording, or after finishing recording, so-called flushing processing in which, by discharging ink from each nozzle, ink having increased viscosity, etc., in the nozzle is discharged is performed

The liquid discharged by the flushing processing collects in a tray-shaped liquid receiver. When a predetermined amount of the liquid has collected in the liquid receiver, a pump is driven to discharge the liquid to a discharge ink tank. This processing is called idle suction processing (Japanese Unexamined Patent Application Publication No. 2006-248132).

The liquid that collects in the liquid receiver needs to be discharged before overflowing the liquid receiver. However, since the amount of the liquid that collects in the liquid receiver cannot be directly measured, conventionally, the amount of the liquid that collects is indirectly determined on the basis of the amount of the liquid discharged from the nozzle of the recording head and the number of times discharging has been performed. At this time, the liquid amount discharged from the nozzle changes according to environmental conditions such as temperature and humidity, and the liquid amount varies. Thus, the liquid amount is determined assuming the worst conditions (a case where the liquid amount is the largest).

In addition, to ensure avoidance of liquid leaking from the liquid receiver, at the time the amount of the liquid that is collecting has reached a predetermined liquid amount less than the volume (for example, approximately 80% of the volume of the liquid receiver) of the liquid receiver, the pump is driven. In addition, the volume of the liquid receiver is determined assuming that, when a liquid absorber disposed in the liquid receiver is used, the liquid absorber is clogged.

Accordingly, even if the liquid receiver can still sufficiently store liquid, the pump is driven. In other words, there is a problem in that a frequency of pump driving increases.

In particular, in a case where a driving motor for a pump for discharging (suction) liquid from the liquid receiver is also used as a driving motor for a paper feeding mechanism for feeding and expelling recording paper to a recording head, when liquid is discharged from the liquid receiver, it is necessary to interrupt recording processing including paper feeding and expelling. Thus, there is a problem in that efficiency of the recording processing decreases.

SUMMARY

The present invention has been made in view of the above circumstances. It is an object of the present invention to provide a liquid-ejecting-apparatus maintenance method and a liquid ejecting apparatus in which a frequency of discharging liquid collecting in a liquid receiver can be reduced, and in which it is ensured that leaking of liquid from the liquid receiver can be avoided.

To solve the above problems, a liquid-ejecting-apparatus maintenance method and liquid ejecting apparatus according to the present invention employ the following means.

A first invention provides a maintenance method for a liquid ejecting apparatus that ejects liquid from a nozzle of a liquid ejecting head to a liquid receiver and that, when a predetermined amount of the liquid collects in the liquid receiver, discharges the predetermined amount of the liquid, the maintenance method including a first step of allowing a nozzle opening face of the liquid ejecting head and the liquid receiver to face each other in a non-contact state and applying an electric field between the nozzle opening face and the liquid receiver, a second step of ejecting the liquid from the nozzle to the liquid receiver, a third step of detecting a voltage change based on electrostatic induction at the time of ejecting the liquid to the liquid receiver, a fourth step of determining a liquid level height of the liquid collected in the liquid receiver, and a fifth step of discharging the liquid collected in the liquid receiver when the liquid level height reaches a predetermined height.

This can detect the amount of the liquid collected in the liquid receiver, and can optimize timing for performing the step of discharging the liquid collected in the liquid receiver. Therefore, a frequency of the liquid discharging step is reduced, so that an efficiency of recording processing with the liquid ejecting head can be increased. In addition, by reducing the frequency of the liquid discharging step, an improvement in durability of a suction pump for discharging the liquid can be achieved.

In addition, the liquid level height is determined on the basis of, as to the voltage change, a voltage change in a case where the liquid ejected from the nozzle lands in the liquid receiver.

In addition, the liquid level height is determined on the basis of a time after the voltage change occurs until a voltage peak is reached.

This can accurately detect the amount of the liquid collected in the liquid receiver, so that it is ensured that the frequency of the liquid discharging step can be reduced.

In addition, the first step through the fourth step are performed after the liquid ejected to the liquid receiver reaches an amount set beforehand.

This can reduce a frequency of executing the step of detecting the liquid level height of the liquid receiver.

In addition, the method includes, between the fourth step and the fifth step, a sixth step of performing flushing processing that continuously ejects the liquid from the liquid ejecting head to the liquid receiver. In the sixth step, the amount of liquid that can be ejected and/or the number of times the liquid can be ejected before the predetermined height is reached are/is determined.

This can estimate timing for implementing a liquid discharging step to be subsequently performed.

In addition, in the sixth step, the flushing processing is performed periodically and/or aperiodically a plural number of times.

In addition, in the sixth step, the number of times the flushing processing can be performed until the predetermined height is reached is determined.

This can ensure that the liquid discharging step is implemented before the liquid collected in the liquid receiver overflows.

In the sixth step, in a case where the flushing processing is flushing processing at a discharging time, the predetermined height is set to be higher compared with other flushing processing.

This can optimize timing for implementing the liquid discharging step.

A second invention provides a liquid ejecting apparatus that ejects liquid from a nozzle of a liquid ejecting head to a liquid receiver and that, when a predetermined amount of the liquid collects in the liquid receiver, discharges the predetermined amount of the liquid, the liquid ejecting apparatus including a liquid detecting unit that, in a case where a nozzle opening face of the liquid ejecting head the liquid receiver are disposed facing each other in a non-contact state, applies an electric field between the nozzle opening face and the liquid receiver, a flushing processing unit that continuously ejects the liquid from the liquid ejecting head to the liquid receiver, a liquid discharging unit that discharges the liquid collected in the liquid receiver, and a maintenance processing unit that determines a liquid level height of the liquid collected in the liquid receiver on the basis of a result of detection of the voltage change, and that drives the liquid discharging unit when the liquid level height reaches a predetermined height.

This can detect the amount of the liquid collected in the liquid receiver, so that timing for implementing the step of discharging the liquid collected in the liquid receiver can be optimized. Accordingly, a frequency of the liquid discharging step is reduced, so that an efficiency of recording processing with the liquid ejecting head can be improved. In addition, by reducing the frequency of the liquid discharging step, an improvement in durability of a suction pump for discharging the liquid can be achieved.

In addition, the maintenance processing unit determines the liquid level height on the basis of, as to the voltage change, a voltage change in a case where the liquid ejected from the nozzle lands in the liquid receiver.

In addition, the liquid level height is determined on the basis of a time after the voltage change occurs until a voltage peak is reached.

This can accurately detect the amount of the liquid collected in the liquid receiver, so that it is ensured that the frequency of the liquid discharging step can be reduced.

In addition, the maintenance processing unit determines the amount of liquid that can be ejected and/or the number of times the liquid can be ejected before the predetermined height is reached.

This can ensure that the liquid discharging step is implemented before the liquid collected in the liquid receiver overflows.

In addition, the flushing processing unit continuously ejects the liquid to the liquid receiver periodically and/or aperiodically a plural number of times.

In addition, the maintenance processing unit determines the number of times the flushing processing can be performed before the predetermined height is reached, and drives the liquid discharging unit on the basis of the number of times the flushing processing can be performed.

This can ensure that the liquid discharging step is implemented before the liquid collected in the liquid receiver overflows.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A first embodiment of a liquid-ejecting-apparatus maintenance method and liquid ejecting apparatus according to the present invention will be described below with reference to the drawings. In this embodiment, an ink jet printer (hereinafter referred to as a printer1) is exemplified as a liquid ejecting apparatus according to the present invention.

FIG. 1is a partially exploded view showing printer1according to the embodiment of the present invention.

The printer1broadly includes a carriage4provided with subtanks2and a recording head3, and a printer body5.

The printer body5includes a carriage moving mechanism65(seeFIG. 5) for moving the carriage4in a reciprocating manner, a paper feeding mechanism66(seeFIG. 5) for transporting recording paper, which is not shown, a capping mechanism14that is used in an operation such as a cleaning operation for sucking ink L whose viscosity is increased from each nozzle of the recording head3, and an ink cartridge6that stores ink L to be supplied to the recording head3.

In addition, the printer1includes an ink droplet sensor7(seeFIGS. 4 and 5) capable of detecting an ink droplet D discharged from the recording head3. The ink droplet sensor7is configured to charge the ink droplet D discharged from the recording head3and to output, as a detection signal, a voltage change based on electrostatic induction in a case where the charged droplet D flies.

Details of the ink droplet sensor7will be described later.

The carriage moving mechanism65includes a guide shaft8provided in a width direction of the printer body5, a pulse motor9, a driven pulley10which is connected to a rotating shaft of the pulse motor9and which is driven to be rotated by the pulse motor9, an idling pulley11provided on the opposite side of the driven pulley10in the width direction of the printer body5, and a timing belt12which extends between the driven pulley10and the idling pulley11and which is connected to the carriage4.

The carriage4is configured so that, by driving the pulse motor9, the carriage4moves in a reciprocating manner in a main scanning direction along the guide shaft8.

In addition, the paper feeding mechanism66includes a paper feeding motor M and a paper feeding roller that is driven to rotate by the paper feeding motor M (both not shown). The paper feeding mechanism66sequentially feeds the recording paper onto a platen13in conjunction with a recording operation.

The capping mechanism14includes a cap member15and a suction pump16. The cap member15is formed by a member obtained by shapening an elastic material into a tray shape, and is disposed at a home position. This home position is set to be within a moving range of the carriage4and to be in an end region outside a recording region. The home position is a position at which the carriage4is positioned in a power-off time and in a case where recording (liquid ejecting processing) is not performed for a long time.

In a case where the carriage4is positioned at the home position, the cap member15performs sealing by abutting against a surface (that is, a nozzle opening face43a) of a nozzle substrate43(seeFIG. 3) of the recording head3. When the suction pump16is actuated in this sealing state, the inside (sealing hollow portion) of the cap member15is decompressed, so that the ink L in the recording head3is forcibly discharged from a nozzle47.

In addition, in cases such as before a recording operation by the recording head3and during a recording operation by the recording head3, in flushing processing that discharges the ink droplet D in order to discharge the ink L, whose viscosity is increased, bubbles, etc., the cap member15receives the ink droplet D.

FIG. 2is a section view illustrating the configuration of the recording head3.FIG. 3is a main-part section view of the recording head3.FIG. 4is a schematic view illustrating configurations of the recording head3, the ink cartridge6, and the ink droplet sensor7.

The recording head3in the embodiment has, as main constituent elements, an introduction needle unit17, a head case18, a channel unit19, and an actuator unit20.

Two ink introduction needles22are attached to an upper face of the introduction needle unit17side by side, with filters21provided therebetween. The subtanks2are respectively mounted to the ink introduction needles22. Also, in the introduction needle unit17, ink introduction paths23corresponding to the ink introduction needles22are formed.

An upper end of each ink introduction path23communicates with each ink introduction needle22through each filter21, and a lower end of the ink introduction path23communicates with each case channel25formed in the head case18through a packing24.

Since the embodiment uses two inks, two subtanks are provided. However, obviously, the present invention is applied to a configuration in which three or more inks are used.

The subtanks2are molded from a resin material such as polypropylene. In each subtank2, a depression that serves as an ink chamber27is formed. A transparent elastic sheet26is bonded to an opening face of the depression, whereby the ink chamber27is formed.

In addition, in a lower portion of each subtank2, a needle connection portion28into which the ink introduction needle22is inserted is downwardly provided in a protruding manner. The ink chamber27in the subtank2is shallow, cone-shaped. At a position slightly below a horizontal center of a side of the ink chamber27, an upstream opening of a connection channel29that communicates with the needle connection portion28is exposed. A tank-portion filter30that filtrates the ink L is attached to the upstream opening.

In an inside space of the needle connection portion28, a seal member31into which the ink introduction needle22is inserted in a liquid-tight manner is fitted. As shown inFIG. 4, the subtank2has an extension portion32having a communicating groove32′ that communicates with the ink chamber27, and, on an upper surface of the extension portion32, an ink inlet33is provided in a protruding manner.

An ink supply tube34for supplying the ink L stored in the ink cartridge6is connected to the ink inlet33. Accordingly, the ink L, which passes through the ink supply tube34, flows from the ink inlet33to the ink chamber27through the communicating groove32′.

The elastic sheet26can change in shape in a direction in which the ink chamber27contracts and in a direction in which the ink chamber27expands. A damper function by the shape change of the elastic sheet26absorbs a pressure change in the ink L. In other words, an operation of the elastic sheet26causes each subtank2to function as a pressure damper. Accordingly, the ink L is supplied to the side of the recording head3, with the pressure change absorbed.

The head case18is a hollow box member made of synthetic resin. The channel unit19is bonded to a lower end face of the head case18. The actuator unit20is accommodated in an accommodating portion37formed inside. The introduction needle unit17is attached to the head case18, with the packing24provided on an upper end face opposing the side of the channel unit19.

In the inside of the head case18, each case channel25is provided penetrating a height. An end of the case channel25can communicate with the ink introduction path23in the introduction needle unit17via the packing24.

A lower end of the case channel25can communicate with a common ink chamber44in the channel unit19. Accordingly, the ink L, which is introduced from the ink introduction needle22, is supplied to the common ink chamber44through the ink introduction path23and the case channel25.

The actuator unit20accommodated in the accommodating portion37of the head case18includes a plurality of piezoelectric vibrators38arranged in the form of a comb, a fixed plate39to which the piezoelectric vibrators38are bonded, and a flexible cable40as a wiring member that supplies a driving signal from the printer body side to the piezoelectric vibrators38. Each piezoelectric vibrator38has a fixed end side fixed to the fixed plate39and a free end side that protrudes outwardly from an end face of the fixed plate39. That is, the piezoelectric vibrator38is attached to the fixed plate39in a cantilever state.

In addition, the fixed plate39, which supports each piezoelectric vibrator38is formed of, for example, stainless steel having a thickness of approximately 1 mm. The actuator unit20is accommodated and fixed in the accommodating portion37by bonding a back face of the fixed plate39to an in-case wall surface delimiting the accommodating portion37.

The channel unit19is formed in such a manner that channel-unit constituent elements including a diaphragm (sealing plate)41, a channel substrate42, and a nozzle substrate43are joined to one another with an adhesive in a state in which the channel-unit constituent elements are stacked so as to be integrated. The channel unit19is a member that forms a continuous ink channel (liquid channel) from the common ink chamber44to nozzles47through an ink supply port45, and each pressure chamber46. The pressure chamber46is formed as an elongated chamber perpendicularly to a direction (nozzle-row direction) in which the nozzles47are arranged in a row. In addition, the common ink chamber44communicates with the case channel25. The ink L from the side of the ink introduction needle22is introduced into the common ink chamber44.

The ink L introduced into the common ink chamber44is distributed to each pressure chamber46through the ink supply port45.

The nozzle substrate43, which is disposed on the bottom of the channel unit19, is a thin metal plate on which the nozzles47are provided in rows in an open condition at a pitch (for example, 180 dpi) corresponding to a dot formation density. The nozzle substrate43in the embodiment is formed of a stainless steel plate material. In the embodiment, as rows of nozzles47(i.e., nozzle rows), a total of 22 rows of nozzles47are arranged in parallel so as to correspond to the subtanks2. One nozzle row consists of 180 nozzles47.

The channel substrate42, which is disposed between the nozzle substrate43and the diaphragm41, is a plate member in which a channel portion that becomes an ink channel, specifically, a hollow portion that becomes the common ink chamber44, the ink supply port45, and the pressure chamber46, is defined.

In the embodiment, the channel substrate42is formed by performing anisotropic etching on a silicon wafer that is a crystalline base material. The diaphragm41is a double structure composite plate formed by laminating an elastic film on a support plate of a metal such as a stainless steel. In a portion of the diaphragm41which corresponds to the pressure chamber46, the support plate is circularly removed by etching or the like, whereby an insular portion48to which an end face of the piezoelectric vibrator38is joined is formed. This portion functions as a diaphragm portion. In other words, the diaphragm41is configured so that the elastic film around the insular portion48can be elastically deformed in accordance with an operation of the piezoelectric vibrator38. In addition, the diaphragm41seals one opening face of the channel substrate42and also functions as a compliance portion49. Regarding a portion corresponding to the compliance portion49, similarly to the diaphragm portion, only the elastic film is allowed to remain by removing the support plate with etching or the like.

In the above recording head3, when a driving signal is supplied to the piezoelectric vibrator38through the flexible cable40, the piezoelectric vibrator38expands or contracts in an element longitudinal direction. This accordingly causes the insular portion48to move close to or away from the pressure chamber46. This changes the volume of the pressure chamber46, so that a pressure change occurs in the ink L in the pressure chamber46. The pressure change discharges the ink droplet D from the nozzle47.

As shown inFIG. 4, the ink cartridge6includes a case member51formed having a hollow box form and an ink pack52formed of a plastic material. The ink pack52is accommodated in an accommodation chamber in the case member51.

The ink cartridge6communicates with one end portion of the ink supply tube34. The ink cartridge6is configured so that a water head difference between the ink cartridge6and the nozzle opening face43aof the recording head3can supply the ink L in the ink pack52to the side of the recording head3. Specifically, a positional relationship in weight direction between the ink cartridge6and the recording head3is set to be in a state in which an extremely small negative pressure is applied to a meniscus of the nozzle47.

A pressure change caused by driving the piezoelectric vibrator38performs supply of the ink L to the pressure chamber46and discharge of the ink L in the pressure chamber46.

As shown inFIG. 4, the ink droplet sensor7includes the cap member15as a liquid droplet receiver disposed at the home position, an inspection region74provided in the cap member15, a voltage applying circuit75that applies a voltage between the inspection region74and the nozzle substrate43of the recording head3, and a voltage detecting circuit76that detects a voltage of the inspection region74.

The cap member15is a tray-shaped member having an open upper face and is formed of a member of elastic material such as elastomer. In the cap member15, an ink absorber77is provided. The ink absorber77has high retention of the ink L, and is formed of, for example, nonwoven fabric such as felt.

On an upper face of the ink absorber77, a mesh electrode member78is provided. A surface of the electrode member78corresponds to the inspection region74. The electrode member78is formed as latticed mesh formed of metal such as stainless steel. Accordingly, the ink droplet D, which has landed at the electrode member78, can be absorbed and retained in the absorber77, which is disposed below the electrode member78, through openings of the electrode member78in lattice form.

The voltage applying circuit75electrically connects, via a direct current power supply (for example, 400 V) and a resistance element (for example, 1 MΩ), the electrode member78and the nozzle substrate43of the recording head3so that the electrode member78is a positive electrode and the nozzle substrate43of the recording head3is a negative electrode.

The voltage detecting circuit76includes an amplification circuit81that amplifies and outputs a voltage signal of the electrode member78, and an A/D conversion circuit82that performs A/D conversion on a signal output from the amplification circuit81and outputs a converted signal to the side of a printer controller55. The amplification circuit81amplifies and outputs the voltage signal of the electrode member78at a predetermined amplification factor. The A/D conversion circuit82can convert an analog signal output from the amplification circuit81into a digital signal and can output the digital signal as a detection signal to the side of the printer controller55.

FIG. 5is an illustration showing the configuration of a suction pump16connected to the cap member15.

In a bottom wall of the cap member15, a drain portion126for draining the ink L, which is collected in the cap member15, is downwardly provided in a protruding manner. In the drain portion126, a drain path126ais formed.

One end portion of a drain tube127formed of a flexible material or the like is connected to the drain portion126, and the other end portion of the drain tube127is inserted into a waste ink tank128.

In the waste ink tank128, a waste ink absorber129formed of a porous member is accommodated, and the waste ink absorber129can absorb the ink L, which has been collected. The waste ink tank128is provided below the platen13.

A tube-pump suction pump16is provided between the cap member15and the waste ink tank128. The suction pump16has a cylindrical case130. In the case130, a pump wheel132that is circular in a plan view is accommodated so as to rotate around a wheel shaft131provided at the shaft center of the case130. In the case130, an intermediate portion127aof the drain tube127is accommodated along an inner circumferential wall130a.

In the pump wheel132, a pair of roller guiding grooves133and134each having an outwardly extending arc shape is formed so that both oppose each other, with the wheel shaft131provided therebetween. Each of the roller guiding grooves133and134has one end positioned on the outer circumferential side of the pump wheel132, and the other end positioned on the inner circumference side of the pump wheel132. In other words, each of the roller guiding grooves133and134extends so as to gradually move away from the outer circumference of the pump wheel132as the distance from the one to the other end increases.

In the roller guiding grooves133and134, rollers135and136as pressing means, which form a pair, are supported such that they are inserted into rotating shafts135aand136a. The rotating shafts135aand136acan slide in the roller guiding grooves133and134, respectively.

When the pump wheel132is rotated in a forward direction (the arrow direction), both rollers135and136move to ends (the outer circumferential side of the pump wheel132) of the roller guiding grooves133and134. The pump wheel132can rotate while sequentially squeezing (pressing) the intermediate portion127aof the drain tube127from an upstream side to a downstream side. This rotation can reduce the pressure of the inside of the drain tube127on an upstream side with respect to a tube pump123.

Accordingly, the ink L that collects in the cap member15can be gradually discharged to the direction of the waste ink tank128by a forward rotation operation of the pump wheel132.

In addition, when the pump wheel132is rotated in a reverse direction (the direction opposite to the arrow direction), both rollers135and136can move to the other end side (the inner circumferential side of the pump wheel132) of the roller guiding grooves133and134. This movement causes both rollers135and136to slightly touch the intermediate portion127aof the drain tube127, whereby the reduced pressure state in the inside of the drain tube127can be canceled.

The pump wheel132can be driven to rotate by the paper feeding motor M of the paper feeding mechanism66.

FIG. 6is a block diagram showing an electric configuration of the printer1.

The printer1in the embodiment broadly includes the printer controller55, a print engine56, and the ink droplet sensor7.

The printer controller55includes an external interface (external I/F)57to which print data or the like from an external apparatus such as a host computer is input, a RAM58for storing various types of data, etc., a ROM59storing a control program for various types of control, etc., a control unit60for performing overall control of each portion in accordance with a control program stored in the ROM59, an oscillating circuit61for generating a clock signal, a driving signal generating circuit62for generating a driving signal to be supplied to the recording head3, and an internal interface (internal I/F)63for outputting, to the recording head3, discharge data obtained by expanding print data for each dot, driving signals, etc.

The print engine56includes the recording head3, the carriage moving mechanism65, and the paper feeding mechanism66.

The recording head3includes a shift register67in which discharge data is set, a latch circuit68that latches the discharge data set in the shift register67, a decoder69that generates pulse selection data by translating the discharge data from the latch circuit68, a level shifter70that functions as a voltage amplifier, a switch circuit71that controls supply of a driving signal to the piezoelectric vibrator38, and the piezoelectric vibrator38.

The control unit60expands print data transmitted from the external apparatus to discharge data corresponding to a dot pattern, and transmits the discharge data to the recording head3. The recording head3is configured to discharge the ink droplet D on the basis of received discharge data.

In addition, the control unit60also functions as a flushing processing unit on the basis of flushing conditions stored in the ROM59. In the flushing processing, by discharging the ink L, whose viscosity is increased, or bubbles from each nozzle47of the recording head3, nozzle clogging is prevented. Discharge of the ink droplet D is performed a predetermined number of times from each nozzle47to the cap member15.

The flushing processing includes so-called pre-printing flushing that is performed before a recording operation by the recording head3is started after power is supplied to the printer1. The pre-printing flushing is set so that, for example, discharge of the ink droplet D is performed 3000 to 5000 times from all the nozzles47. The flushing conditions are stored in the ROM59.

Also, in addition to the pre-printing flushing, the flushing processing includes so-called periodic flushing that is performed during the recording operation by the recording head3. The flushing processing further includes paper-feeding-time flushing that is performed when recording paper is supplied toward the recording head3, and paper-expelling-time flushing that is performed immediately after recording paper is expelled.

In the periodic flushing, the paper-feeding-time flushing, and the paper-expelling-time flushing, the number of times discharge is performed is set to, for example, approximately several tens of times to several hundreds of times.

Further, the control unit60functions also as an idle suction processing unit (maintenance processing unit) that implements so-called idle suction processing in which, when a predetermined amount of the ink L collects in the cap member15, the tube-pump suction pump16is driven to discharge the ink L toward the waste ink tank128.

The idle suction processing is processing in which, since the ink L collects in the cap member15after the pre-printing flushing, the periodic flushing, or the like, is performed a plural number of times, the ink L is sucked and discharged so that the ink L is prevented from overflowing the cap member15.

The driving signal generating circuit62receives data that represents an amount of change in voltage of a discharge pulse to be supplied to the piezoelectric vibrator38of the recording head3and a timing signal that defines timing at which the voltage of the discharge pulse is changed, and generates a driving signal (discharge pulse) on the basis of the data and the timing signal.

By applying the discharge pulse DP to the piezoelectric vibrator38, the ink droplet D is discharged in the following manner. Specifically, when the discharge pulse is supplied, first, the piezoelectric vibrator38contracts and the pressure chamber46expands. After this expansion state of the pressure chamber46is maintained for an extremely short time, the piezoelectric vibrator38rapidly extends. In accordance therewith, the volume of the pressure chamber46contracts to be not greater than a reference volume, so that a meniscus exposed at the nozzle47is rapidly pressurized to the exterior. This discharges a predetermined liquid amount of the ink droplet D from the nozzle47. After that, the pressure chamber46returns to the reference volume so that meniscus vibration caused by discharge of the ink droplet D is allowed to converge.

The printer1having the above-described configuration is controlled so that, when the ink L collects in the cap member15after the flushing processing is performed, before the ink L overflows, the suction pump16is driven to discharge the ink L (idle suction processing).

As described above, since the suction pump16is driven by the paper feeding motor M, the idle suction processing needs to be performed in a state in which recording processing (printing) including paper feeding and expelling is stopped. Therefore, it is required that, by storing the ink L in the cap member15as much as possible, a frequency of the idle suction processing be reduced.

A method for reducing the frequency of the idle suction processing in the case of maintenance processing such as flushing will be described below.

FIG. 7is a flowchart illustrating maintenance processing using the ink droplet sensor7.

FIG. 8consists of schematic diagrams illustrating the principle of generation of induced voltage by electrostatic induction. (a) is a diagram showing a state immediately after the ink droplet D is discharged. (b) is a diagram showing a state in which the ink droplet D has landed in the inspection region74of the cap member15. (c) is a diagram showing a state in which the ink droplet D has landed when the ink L collects in the cap member15.

FIG. 9is a graph showing an example of a waveform of the detection signal (for one droplet of ink) output from the ink droplet sensor7.

After print data is transmitted from the external apparatus, the control unit60expands the print data to discharge data corresponding to a dot pattern and transmits the discharge data to the recording head3. On the basis of the discharge data, which is received, the recording head3executes recording processing (printing), that is, discharge of the ink droplet D onto recording paper (step S1).

If a preset time (periodic flushing time interval) has elapsed during the recording processing (step S2), the recording processing is interrupted and the periodic flushing processing is started.

In the periodic flushing processing, first, the carriage4is driven to move the recording head3to the home position, whereby the recording head3is positioned above the cap member15.

Next, by raising the cap member15by using an elevating mechanism, which is not shown, the nozzle opening face43aof the recording head3and the inspection region74(the electrode member78) are allowed to be close to and face each other (step S3) in a non-contact state.

A voltage is applied between the nozzle substrate43and the electrode member78by the voltage applying circuit75(step S4).

Next, in a state in which the voltage is applied between the nozzle substrate43and the electrode member78, by driving the piezoelectric vibrator38, an ink droplet D is discharged from any one nozzle (for example, #A1) among the nozzles47(step S5).

At this time, the nozzle substrate43is a negative electrode. Thus, as shown inFIG. 8(a), part of negative charge of the nozzle substrate43moves to the ink droplet D, and the ink droplet D discharged is negatively charged. As the ink droplet D approaches the inspection region74of the cap member15, positive charge increases in the inspection region74(the surface of the electrode member78) in accordance with electrostatic induction. This causes the voltage between the nozzle substrate43and the electrode member78to be higher than an initial voltage value in a state in which the ink droplet D is not discharged, due to an induced voltage generated by electrostatic induction.

After that, as shown inFIG. 8(b), after the ink droplet D lands at the electrode member78, the negative charge of the ink droplet D neutralizes the positive charge of the electrode member78. Accordingly, the voltage between the nozzle substrate43and the electrode member78is less than the initial voltage value.

After that, the voltage between the nozzle substrate43and the electrode member78returns to the initial voltage value.

Therefore, as shown inFIG. 9, regarding a detection waveform output from the ink droplet sensor7, after the voltage temporarily rises, it drops until it is less than the initial voltage value, and subsequently returns to the initial value.

As described above, a voltage change in a case where the ink droplet D is discharged from the nozzle47(for example, #A1) is detected by using the ink droplet sensor7(step S6).

In a case where the periodic flushing or the like has been performed a plural number of times, as shown inFIG. 8(c), the ink L collects in the cap member15. In this case, a time (landing time) after the ink droplet D moves away from the recording head3until it lands in the ink droplet sensor7(the inspection region74) is shorter than that in a case where the ink L does not collect.

When the landing time is shorter, also the detection waveform output from the ink droplet sensor7changes. This is because the level of the ink L collected in the cap member15is charged and becomes the inspection region74.

The landing time of the ink droplet D corresponds to a time until, in the detection waveform, the voltage begins to increase (a voltage change occurs) and reaches its peak. Accordingly, as shown inFIG. 9, time ΔT of detection waveform Z in a case where the ink L collects is shorter than ΔT0of detection waveform Z0in a case where the ink L does not collect (initial stage).

The level of the liquid and the landing time are proportional to each other. Thus, from landing time ΔT of detection waveform Z output from the ink droplet sensor7, a liquid level height H (seeFIG. 8(c)) of the ink L collected in the cap member15is found (step S7).

In addition, a liquid level height in a case where, for example, the ink L collects in the cap member15, occupying approximately 95% of its capacity limit, and a landing time ΔTx obtained in the case are found beforehand, and the landing time ΔTx is set as a threshold value. By comparing this threshold value (ΔTx) and the landing time ΔT, it is determined whether or not the ink L collected in the cap member15should be discharged (the idle suction processing) (step S8).

Next, in a case where the liquid level height H of the ink L collected in the cap member15is lower than a liquid level height obtained when the ink L collects (that is, the landing time ΔT is longer than ΔTx) occupying approximately 95% of the capacity limit, the periodic flushing processing is executed (step S10).

On the other hand, in a case where the liquid level height H of the ink L collected in the cap member15is not less than a predetermined height (that is, the landing time ΔT is within ΔTx), after the idle suction processing (step S9) is temporarily executed to discharge all the ink L collected in the cap member15, the periodic flushing processing is performed (step S10).

After the periodic flushing processing is completed, the recording head3returns to the recording processing again. In the recording processing, determination of whether or not the recording processing is to be completed (step S11) and determination of whether or not the periodic flushing processing is to be performed (step S2) are repeated.

As described above, according to the maintenance method in the embodiment, from the landing time ΔT of the detection waveform Z output from the ink droplet sensor7, the liquid level height H of the ink L collected in the cap member15can be determined. Thus, it is possible to sufficiently utilize the amount of ink capacity of the cap member15.

Conventionally, the liquid amount of the ink L collected in the cap member15is estimated from the number of times discharging is performed. Thus, at worst, to prevent the ink L from overflowing the cap member15, in the case of estimating that an amount of the ink L which is, for example, approximately 80% of the capacity limit of the cap member15has collected, the idle suction processing is performed (that is, a safety factor is set to be high).

Conversely, in the maintenance method in the embodiment, the ink capacity of the cap member15can be sufficiently utilized. Thus, a frequency of the idle suction processing can be reduced than before.

Specifically, conventionally, whenever the periodic flushing is performed, for example, 20 times, the idle suction processing is performed. However, in the maintenance method in the embodiment, it is only necessary to perform the idle suction processing whenever the periodic flushing is performed, for example, 30 times.

As described above, by reducing the frequency of the idle suction processing, a frequency (printing) and time of interrupting the recording processing is reduced, thus increasing the efficiency of the recording processing. In addition, since the frequency of the idle suction processing is reduced, an improvement in durability is achieved.

The above embodiment describes a case where, whenever the periodic flushing is performed, the liquid level height H of the ink L collected in the cap member15is determined on the basis of the detection waveform output from the ink droplet sensor7.

However, since the amount of the ink L that collects in the cap member15is small when the periodic flushing is performed once, as described below, a frequency of determining the liquid level height H may be minimized.

FIG. 10is a flowchart illustrating another example of the idle suction processing using the ink droplet sensor7.

Regarding processing identical to the above-described processing, its description will be simplified or omitted. In addition, in the following description, a case where processing is started from an empty state of the cap member15will be described.

First, a counter N for counting the number of times the periodic flushing is performed is initialized (N=0).

In addition, for example, in the case of the 26th flushing processing (after the flushing processing is performed 25 times), in order for the liquid level height H of the ink L collected in the cap member15to be determined by using the ink droplet sensor7, the number of times K that flushing has been performed is set so that K=25.

Further, the remaining number of times X that flushing is to be performed is set so that X=0 (step S101).

These values are stored in the RAM58. The recording processing (step S102) is performed, and it is determined whether or not the periodic flushing time interval has elapsed (step S103). If the periodic flushing time interval has elapsed, the recording processing is interrupted and a periodic flushing step is started.

In the periodic flushing step, it is determined whether or not the counter N represents 25 (K) (step S104).

If the counter N represents a value less than 25, furthermore, it is determined whether or not N=25+0 (N=K+X) (step S105).

If both determination results are negative, the flushing processing (step S106) is directly executed. One is added to the counter N (N=0+1) (step S107).

After the periodic flushing processing is completed, the recording head3returns to the recording processing again. In the recording processing, determination of whether or not the recording processing is to be finished (step S108) and determination of whether or not the periodic flushing is to be performed (step S103) are repeated.

In the case of the 2nd to 25th (N=0 to 24) lushing steps, processing is executed as described above.

If it has been determined that the present step is the 26th flushing step (step S104), processing (steps S109to S113) that determines the liquid level height H of the ink L collected in the cap member15by using the ink droplet sensor7is performed. These steps are identical to the above-described steps S3to S7.

When the liquid level height H of the ink L is found, at the same time, a remaining ink capacity amount (that is, how much the ink L can collect in the cap member15) of the cap member15is found.

Next, for the found remaining ink capacity amount, it is determined how many times the flushing processing can be performed (in other words, how many times the flushing processing should be performed to cause the cap member15to be full with the ink L (so that the ink L does not overflow)). This number of times (for example, 5 times) is set as the remaining number of times X that the flushing processing is performed (X=5) (step S114).

The 26th periodic flushing processing is executed (step S106), and one is added to the counter N (step S107).

The 26th to 30th lushing steps are performed similarly to the 1st to 24th lushing processing.

If it has been determined that the present flushing step is the 31st flushing step (N=25+5) (step S105), the idle suction processing (step S115) is started. This discharges the ink L from the cap member15before the ink L overflows (before the 31st flushing processing).

The counter N and the remaining number of times X that the flushing processing is performed are initialized (step S116). After the periodic flushing processing (step S106) and counter addition (step S107) are performed, the recording head3returns to the recording processing.

As described above, after the periodic flushing processing is performed a plural number of times, liquid-level-height detection is performed to predict a subsequent increase in liquid level height, whereby a frequency of detection by using the ink droplet sensor7can be minimized.

Compared with a case where, from initial flushing processing, a subsequent increase in liquid level height is predicted as in a conventional manner, a difference between the prediction and actuality is reduced. Thus, by causing a more amount of the ink L to collect in the cap member15, a frequency of executing the idle suction processing can be reduced.

By using, as a reference, the number of times the periodic flushing processing is performed, timing for executing liquid-level-height detection by using the ink droplet sensor7is set to optimize (reduce a frequency) timing for executing the idle suction processing. However, the number of times (amount of liquid) of the ink droplet D may be used as a reference.

In other words, by using, as a reference, the number of times (amount of liquid) the ink droplet D is discharged to the cap member15, when this number of times (amount) reaches a preset number of times (amount), liquid-level-height detection is performed. Further, instead of finding the remaining ink capacity amount of the cap member15and subsequently determining the remaining number of times the flushing processing is performed, a remaining number of times discharging is performed and a remaining amount of liquid can be determined.

This enables a much more amount of the ink L to further collect in the cap member15, so that the frequency of the idle suction processing can be reduced.

In addition, the case where processing is started from a state in which the cap member15is empty has been described. However, in a case where processing is started from a state in which the ink L collects in the cap member15after flushing is performed a plural number of times, it is preferable that, in the first flushing processing, liquid-level-height detection by using the ink droplet sensor7be performed. Alternatively, the number of times flushing has already been performed may be stored in the RAM58, and the stored number may be input to the counter N.

Although, in the above-described embodiment, various limitations are used as preferred specific examples, the present invention is not limited thereto. The present invention can be variously modified on the basis of the description in Claims.

In the above-described embodiment, a case where, when the periodic flushing processing is performed, the liquid level height of the ink L collected in the cap member15is detected by using the ink droplet sensor7has been described. However, the present invention is not limited thereto.

In the cases of the pre-printing flushing that is performed before the recording (printing) is started, and the paper-feeding-time flushing and the paper-expelling-time flushing that are performed when paper is fed and expelled, liquid-level-height detection by using the ink droplet sensor7may be performed.

In addition, a case where the number of times the periodic flushing processing is performed is counted has been described. However, also the number of times flushing processing (the paper-feeding-time flushing and the paper-expelling-time flushing) is irregularly performed may be counted.

In addition, the liquid-level-height detection by using the ink droplet sensor7is not limited to a case where the number of times the flushing processing is performed or the number of times (amount of liquid) an ink droplet is discharged is used as a reference. At worst, before timing at which the ink L collected in the cap member15is likely to overflow, liquid-level-height detection may be performed a minimum of once. For example, whenever a predetermined time elapses, liquid-level-height detection by using the ink droplet sensor7may be performed. This makes it possible to accurately determine a remaining ink capacity amount of the cap member15, so that idle suction processing on the cap member15can be optimized (frequency can be reduced).

In addition, the above-described embodiment describes a case where determination of the idle suction processing is performed by using, as a reference (threshold value), a liquid level height obtained when the ink L collects in the cap member15, occupying approximately 95% of its capacity limit. This reference (threshold value) may be changed in accordance with a type of flushing processing.

For example, the case of the paper-expelling-time flushing processing has a state immediately after the recording paper is expelled (printing is not being performed). Thus, after detecting the liquid-level height, the idle suction processing can be directly performed. Therefore, the liquid level height as the reference (threshold value) may be set to be higher (for example, 97%) than that in the case of other flushing processing.

In addition, in accordance with an installation state of the printer1, the liquid level height as the reference (threshold value) may be set. When the printer1is installed, with it inclined, the liquid level height as the reference (threshold value) is set to, for example, 90%.

In addition, the above-described embodiment exemplifies a configuration in which the cap member15in the capping mechanism14is used as the liquid droplet receiver in the present invention. However, the liquid droplet receiver is not limited thereto, and a separate liquid droplet receiver dedicated for discharging inspection may be provided.

In addition, the above-described embodiment shows an example in which the electrode member78and the nozzle substrate43of the recording head3are electrically connected to each other so that the electrode member78is a positive electrode and the nozzle substrate43is a negative electrode. However, the positive and negative polarities of both can be reversed.

In addition, the above-described embodiment describes a case where the tube-pump suction pump16(the pump wheel132) is driven to rotate by the paper feeding motor M of the paper feeding mechanism66. However, the embodiment is not limited to the case. A motor for driving the tube-pump suction pump16and the paper feeding motor M may differ from each other.

In addition, the tube-pump suction pump16is not limited to a tube pump, and another type of pump may be used.

In addition, in the above-described embodiment, the piezoelectric vibrator38having a so-called length-extension-vibration mode is exemplified as a pressure generator in the present invention. However, the pressure generator is not limited thereto. For example, the pressure generator may also be a piezoelectric vibrator capable of vibration in an electric field direction (direction in which a piezoelectric substance and an internal electrode are stacked). Also, the pressure generator is not limited to piezoelectric vibrators unitized for each nozzle row. The pressure generator may be one provided for each pressure chamber46, as a piezoelectric vibrator having a so-called flexural oscillation mode. Further, not only the piezoelectric vibrator, but also another pressure generating element, such as a heater element, may be used.

In the above-described first and second embodiments, a case where an ink jet recording apparatus is the printer1has been described as an example. However, the ink jet recording apparatus is not limited to the ink jet printer, and may be an ink jet recording apparatus for use in copying machines and facsimile machines.

Although each above-described embodiment exemplifies a case where the liquid ejecting apparatus is a liquid ejecting apparatus that ejects liquid such as ink, the liquid ejecting apparatus of the present invention is applicable to a liquid ejecting apparatus that ejects or discharges a different liquid other than ink. Liquids that can be ejected by the liquid ejecting apparatus include a liquid material in which particles of a high-performance material are dispersed or dissolved, and a granular material in gel form.

In each above-described embodiment, as the liquid (the liquid material or the granular material), not only ink, but also a liquid corresponding to a particular use is applicable. By providing the liquid ejecting apparatus with an ejecting head capable of ejecting the liquid corresponding to the particular use, ejecting the liquid corresponding to the particular use from the ejecting head, and causing the liquid to adhere to a predetermined object, a predetermined device can be produced. For example, the liquid ejecting apparatus (liquid material ejecting apparatus) of the present invention is applicable to liquid ejecting apparatuses that eject liquid (liquid material) in which materials, such as electrode materials and coloring materials, used in uses such as production of liquid crystal displays, EL (electroluminescent) displays, and surface-emitting displays (FED), are dispersed (dissolved) in a predetermined dispersion medium (solvent).

In addition, types of the liquid ejecting apparatus may include a liquid ejecting apparatus for ejecting a living organic material for use in production of biochips and a liquid ejecting apparatus which is used as a precision pipet and which ejects a liquid serving as a sample.

Furthermore, the types of the liquid ejecting apparatus may include a liquid ejecting apparatus that ejects lubricant to a precision machine such as a clock or a camera in a pinpoint manner, a liquid ejecting apparatus that ejects, on a substrate, transparent resin liquid, such as ultraviolet curing resin, for forming a microhemispherical lens (optical lens) for use in optical communication elements or the like, a liquid ejecting apparatus that ejects an etching solution, such as an acid or alkali, for etching a substrate or the like, a fluid material ejecting apparatus that ejects gel, and a toner recording apparatus that ejects a solid, for example, powder such as a toner. In addition, if there is a possibility that, among these, in any one type of liquid ejecting apparatus, liquid (liquid material, fluid material) to be ejected may have a viscosity increased due to drying or the like, the present invention can be applied to the type of liquid ejecting apparatus.