Liquid discharge apparatus

There is provided a liquid discharge apparatus, including: a conveyer; a head having a nozzle surface formed having a nozzle from which a liquid is discharged on a recording medium conveyed by the conveyer; a carriage carrying the head and configured to be movable in a scanning direction parallel to the nozzle surface in a movement range including a facing range that faces a passing area where the recording medium conveyed by the conveyer passes; a first conductor for detection arranged at a first side in the scanning direction relative to the passing area; and a second conductor for detection arranged at a second side, which is opposite to the first side, in the scanning direction relative to the passing area.

CROSS REFERENCE TO RELATED APPLICATION

The present application claims priority from Japanese Patent Application No. 2018-235505 filed on Dec. 17, 2018, the disclosure of which is incorporated herein by reference in its entirety.

BACKGROUND

Field of the Invention

The present disclosure relates to a liquid discharge apparatus.

Description of the Related Art

There is known an ink-jet printer including a platen that supports a recording sheet (recording medium), a carriage that reciprocates in a left-right direction, and a printing head that is carried on the carriage. The ink-jet printer includes an electrode (a conductor for detection for detection) at a position on the right of the platen. Ink is discharged from nozzles of the printing head in a state where the printing head is in a home position facing the electrode member. The ink discharged from the nozzles causes an electrical change in the electrical member. A nozzle inspection is executed based on a signal output from the electrode member to inspect a discharge state of the nozzle(s).

SUMMARY

In the above-described ink-jet printer, however, the carriage is required to move to the home position every time the nozzle inspection is executed. For example, the carriage may be in a position far away from the home position when the nozzle inspection is executed during image recording on a recording sheet. In this case, a time for moving the carriage to the home position is long, which consequently lengthens a time until the nozzle inspection starts. Thus, a technology in which the nozzle inspection is executed as soon as possible is conventionally requested. Alternatively, a technology in which the nozzle inspection is executed accurately is conventionally requested.

An object of the present disclosure is to provide a liquid discharge apparatus capable of shortening a time until determination of a discharge state of a nozzle starts, or provide a liquid discharge apparatus capable of determining the discharge state of the nozzle accurately.

According to an aspect of the present disclosure, there is provided a liquid discharge apparatus, including: a conveyer; a head having a nozzle surface in which a nozzle is opened; a carriage configured to carry the head, the carriage being movable in a scanning direction parallel to the nozzle surface in a movement range including a facing range that faces a passing area where a recording medium conveyed by the conveyer passes; a first conductor for detection arranged at a first side in the scanning direction relative to the passing area, and configured to generate an electrical detection signal responding to landing a liquid discharged from the nozzle onto the first conductor for detection; and a second conductor for detection arranged at a second side, which is opposite to the first side, in the scanning direction relative to the passing area.

DESCRIPTION OF THE EMBODIMENTS

A schematic configuration of an ink-jet printer1(corresponding to a liquid discharge apparatus of the present disclosure, hereinafter referred to as a printer1) according to an embodiment of the present disclosure is explained. As depicted inFIG. 1, the printer1includes a casing1ahaving a substantially rectangular parallelepiped shape. The casing1aaccommodates a conveyer2(corresponding to a conveyer of the present disclosure), a platen3, a carriage4, a holder5, a head unit6, a maintenance mechanism8, a driving-force switching mechanism23(seeFIG. 5), a flushing receiver25(corresponding to a liquid receiver of the present disclosure), a nozzle inspection apparatus40(seeFIG. 4), a controller100(seeFIG. 2), and the like. In the following, the fore side (front side) of the sheet surface ofFIG. 1is defined as up (upward) of the printer1, and the far side (the other side) of the sheet surface ofFIG. 1is defined as down (downward) of the printer1. Further, a front-rear direction and a left-right direction inFIG. 1are defined as a front-rear direction and a left-right direction of the printer1. The following explanation is made based on those definitions.

The conveyer2includes two conveyance rollers2aand2barranged in the front-rear direction. The two conveyance rollers2aand2bare driven in synchronization with each other by a conveyance motor21(seeFIG. 2). Driving the two conveyance rollers2aand2bby the conveyance motor21conveys a sheet P frontward, which is a conveyance direction. The sheet P is a recording medium.

The platen3is interposed between the two conveyance rollers2aand2bin the front-rear direction. The platen3supports the sheet P conveyed by the conveyer2from below. The sheet P conveyed by the conveyer2passes on the platen3. Two guide rails15and16extend parallelly to each other in the left-right direction (a scanning direction). The guide rails15and16are disposed above the platen3.

The carriage4, which is attached to the two guide rails15and16, is movable in the scanning direction along the two guide rails15and16. A driving belt17is attached to the carriage4. The driving belt17is an endless belt stretched between two pulleys18and19. The pully18is coupled to a carriage driving motor20(seeFIG. 2). Rotating and driving the pully18by the carriage driving motor20causes the driving belt17to run, which reciprocatingly moves the carriage4in the scanning direction. The head unit6carried on the carriage4also reciprocates in the scanning direction.

A movement range MR in the scanning direction of the carriage4includes a facing range CR positioned at a center portion in the scanning direction where the carriage faces the platen3, a non-facing range RR positioned at the right of the facing range CR, and a non-facing range LR positioned at the left of the facing range CR. The right of the facing range CR corresponds to a first side of the present disclosure, and the left of the facing range CR corresponds to a second side of the present disclosure. The carriage4does not face the platen3in the non-facing ranges RR and LR. The facing range CR includes a range facing a passing area where the sheet P conveyed by the conveyer2passes.

The holder5is disposed at the front of the carriage4and at the right of the platen3. Four ink cartridges42are removably installed in the holder5. The four ink cartridges42contain a black ink, a yellow ink, a cyan ink, and a magenta ink, respectively.

The head unit6is carried on the carriage4with a space in between the head unit6and the platen3. The head unit6and the carriage4reciprocatingly move in the scanning direction. The head unit6includes an ink-jet head30(hereinafter simply referred to as a head30) and buffer tanks35that are disposed on an upper surface of the head30and temporarily store the respective inks to be supplied to the head30. The respective buffer tanks35are removably connected to first ends of four flexible ink supply tubes45. Second ends of the four ink supply tubes45are connected to the holder5. The inks in the four ink cartridges42attached to the holder5are supplied to the respective buffer tanks35via the four ink supply tubes45.

As depicted inFIG. 3A, the head30includes a channel unit31and an actuator32. The channel unit31is formed having nozzles10and pressure chambers83that communicate with the respective nozzles10. The channel unit31is made using a metal material and is connected to the ground potential. The actuator32is placed on an upper surface of the channel unit31.

As depicted inFIG. 3C, the channel unit31is formed by stacking four plates. A lower surface of the channel unit31is a nozzle surface30awhere the nozzles10are open. The nozzle surface30ais parallel to a horizontal plane. As depicted inFIG. 3A, the nozzles10are aligned in the front-rear direction (the conveyance direction of the sheet P) to form a nozzle row9. Four nozzle rows9corresponding to the inks of four colors are arranged in the left-right direction. The black ink is discharged from the rightmost nozzle row9in the scanning direction, the yellow ink is discharged from the second rightmost nozzle row9, the cyan ink is discharged from the third rightmost nozzle row9, and the magenta ink is discharged from the leftmost nozzle row9. The pressure chambers83are aligned to form a pressure chamber row, similar to the nozzles10. Four pressure chamber rows are arranged in the left-right direction, similar to the four nozzle rows9.

As depicted inFIGS. 3A and 3B, the channel unit31includes four manifolds84extending in the front-rear direction. The inks of four colors are supplied to the four respective pressure chamber rows through the four manifolds84. The four manifolds84are connected to four ink supply openings85(corresponding to a liquid supply opening of the present disclosure) formed on the upper surface of the channel unit31. The inks of four colors are supplied from the buffer tanks35to the four ink supply openings85. The channel unit31thus includes individual channels each of which branches off from one of the manifolds84and reaches one of the nozzles10via one of the pressure chambers83.

As depicted inFIG. 3C, the actuator32includes a vibration plate87covering the pressure chambers83, a piezoelectric layer88disposed on an upper surface of the vibration plate87, and individual electrodes89corresponding to the respective pressure chambers83. The individual electrodes89positioned on an upper surface of the piezoelectric layer88are electrically connected to a driver IC90driving the actuator32.

The vibration plate87positioned on a lower surface of the piezoelectric layer88is made using a metal material. The vibration plate87functions as a common electrode, which faces the individual electrodes89with the piezoelectric layer88interposed therebetween. The vibration plate87is connected to a ground line of the driver IC90. The vibration plate87is always kept at the ground potential.

A driving signal having a predefined driving waveform is input from the driver IC90to the individual electrode89. This deforms the volume of the piezoelectric layer88corresponding to the individual electrode89to which the driving signal is input, which applies pressure (discharge energy) to the ink in the pressure chamber83. Ink droplets are thus discharged from the nozzle10.

As described above, in this embodiment, the actuator that applies the discharge energy, by which ink is discharged from the nozzle10, to ink is an actuator that deforms the volume of the pressure chamber83communicating with the nozzle10to apply the discharge energy. The present disclosure, however, is not limited thereto. For example, the actuator may be a heater that generates bubbles in the pressure chamber through heating to apply the discharge energy to ink.

Referring toFIG. 1, the maintenance mechanism8is configured to execute a maintenance operation for maintaining and recovering the discharge state of the head30. The maintenance mechanism8includes a cap unit50, a suction pump51, a waste liquid tank52, and the like.

The cap unit50is disposed on the right of the platen3. When the carriage4is positioned in a standby position, which is a right end of the movement range MR, the carriage4faces the cap unit50in an up-down direction. The cap unit50is movable in the up-down direction by being driven by a cap driving motor22(seeFIG. 2). The cap unit50includes a cap55that can be brought into contact with the head30. The cap55is made using, for example, a rubber material. As depicted inFIG. 4, the cap55includes a plate-like base portion55aand a cylindrical lip portion55bthat stands upward from the circumference of the base portion55a.For the convenience of explanation,FIG. 4depicts the head unit6, the cap55, the flushing receiver25, the nozzle inspection apparatus40, and the controller100. InFIG. 4, both the head30positioned in a right detection range DR and the head30positioned in a left detection range DL are depicted by solid lines.

When the carriage4faces the cap unit50, the cap55faces the nozzle surface30a.When the cap unit50moves upward in a state where the carriage4faces the cap unit50, the cap unit50is installed in the head30. In this situation, a tip55b1of the lip portion55bof the cap55is brought into contact with the head30. This causes the cap55to cover all the nozzles10belonging to the four nozzle rows9. When the printer1is on standby, all the nozzles10are capped with the cap55to inhibit the increase in viscosity of inks in the nozzles10. The suction pump51is connected to the cap55.

In the printer1, the controller100can control the maintenance mechanism8to execute a suction purge as the maintenance operation. The suction purge is a purge in which ink is forcibly discharged from the nozzles10. In the suction purge, the suction pump51is driven in a state where the nozzles10are covered with the cap55. This makes the pressure inside the cap55negative, forcibly discharging ink from the nozzles10. The ink discharged from the head30into the cap55through the suction purge is delivered to the waste liquid tank52connected to the suction pump51.

The driving-force switching mechanism23switches a state of the driving force of the conveyance motor21(corresponding to a driving source of the present disclosure) between a state where the driving force can be transmitted to the conveyance rollers2aand2b(corresponding to a driving object of the present disclosure) and a state where the driving force can be transmitted to the suction pump51(corresponding to the driving object of the present disclosure). Specifically, as depicted inFIGS. 5A and 5B, the driving-force switching mechanism23includes a shaft91, a switching gear92, a switching lever93, a urging spring94, a transmission shaft95, a transmission gear96(sheet-feeding transmission gear96), a transmission gear97(maintenance transmission gear97), and the like.

The shaft91extends in the left-right direction. The shaft91is supported by a support member99at the right of the platen3below the guide rail15. The shaft9lis inserted into the switching gear92such that the switching gear92is slidably and rotatably supported by the shaft91. The driving force of the conveyance motor21is transmitted to the switching gear92via an unillustrated transmission gear and the like. The shaft91is inserted into the switching lever93at the left of the switching gear92such that the switching lever93is slidably and rotatably supported by the shaft91. The switching lever93includes a contact portion93athat can be brought into contact with the carriage4. The guide rail15is formed having a guide groove15a(seeFIG. 1) into which the contact portion93ais inserted. The guide groove15aextends in the left-right direction. The contact portion93acan slide across the guide groove15ain the left-right direction.

The urging spring94is a coil spring. The shaft91is inserted into the urging spring94such that the urging spring94is positioned at the right of the switching lever93. A right end of the urging spring94is coupled to the support member99.

The transmission shaft95is positioned below the shaft91. The transmission shaft95is supported by an unillustrated support member such that the transmission shaft95is parallel to the shaft91. The transmission gear96is rotatably supported at a predefined position on the transmission gear95. The transmission gear96is coupled to driving shafts of the conveyance rollers2aand2bvia an unillustrated transmission gear and the like. The transmission gear97is rotatably supported on the transmission shaft95such that the transmission gear97is positioned at a predefined position at the right of the transmission gear96. The transmission gear97is connected to the suction pump51via an unillustrated transmission gear and the like. The switching gear92is configured to selectively mesh with the transmission gear96and the transmission gear97.

In the above configuration, as depicted inFIG. 5A, the switching gear92meshes with the transmission gear97when the carriage4is positioned in the standby position. This allows the driving force of the conveyance motor21to be transmitted to the suction pump51and does not allow the driving force of the conveyance motor21to be transmitted to the conveyance rollers2aand2b.In this situation, the contact portion93aof the switching lever93is brought into contact with a right end of the guide groove15a.

As depicted inFIG. 5B, when the carriage4moves leftward from the standby position, the urging spring94urges the switching gear92and the switching lever93, slidably moving the shaft91leftward. In this situation, the contact portion93aof the switching lever93moves leftward along the guide groove15a.

When the contact portion93aof the switching lever93is brought into contact with a left end of the guide groove15a,the leftward movement of the switching gear92and the switching lever93stops and the switching gear92and the switching lever93stay at this position. In this situation, the switching gear92meshes with the transmission gear96. This allows the driving force of the conveyance motor21to be transmitted to the conveyance rollers2aand2band does not allow the driving force of the conveyance motor21to be transmitted to the suction pump51.

When the carriage4moves rightward from the facing range CR to the standby position, the carriage4is brought into contact with the contact portion93aof the switching lever93to push the switching lever93and the switching gear92against the urging force of the urging spring94, thus slidably moving the shaft91rightward. When the carriage4is positioned in the standby position, the switching gear92meshes with the transmission gear97.

As described above, in this embodiment, the driving-force switching mechanism23switches the state of the driving force of the conveyance motor21between the state where the driving force of the conveyance motor21can be transmitted to the conveyance rollers2aand2band the state where the driving force of the conveyance motor21can be transmitted to the suction pump51. The switching of driving force of the conveyance motor21interlocks with the movement of the carriage4.

As depicted inFIG. 1, the flushing receiver25is disposed on the left of the platen3. As depicted inFIG. 4, the flushing receiver25includes a guide member26and a waste liquid tank29. The guide member26, which is made using a non-conductive plate-like member, has a vertical portion27and an inclined portion28. The vertical portion27extends in the up-down direction. A lower end of the inclined portion28is connected to an upper end of the vertical portion27. The inclined portion28is inclined to a horizontal plane so that its upper end is inclined rightward to its lower end. A second detection electrode62is placed on an upper surface28aof the inclined portion28, as described below in detail. An upper surface of the second detection electrode62is thus an inclined surface62ainclined to the horizontal plane. The waste liquid tank29is placed below the guide member26.

The printer1may execute a flushing operation when the carriage4is positioned in the left detection range DL. In the flushing operation, the actuator32of the head30is driven to discharge ink from the nozzles10to the flushing receiver25. In the flushing operation, the ink discharged from the nozzles10of the head30lands on the inclined surface62aof the second detection electrode62. The ink landing on the inclined surface62aslides down the inclined surface62a,the inclined portion28of the guide member26, and the vertical portion27in that order under its own weight, then held in the waste liquid tank29. In this embodiment, the flushing operation is executed during the leftward movement of the carriage4. The present disclosure, however, is not limited thereto. The flushing operation may be executed in a state where the carriage4is stopped.

The nozzle inspection apparatus40inspects the discharge state of the nozzles10. The nozzle inspection apparatus includes a first detection electrode61(corresponding to a first conductor for detection of the present disclosure), the second detection electrode62(corresponding to a second conductor for detection of the present disclosure), a high-voltage power circuit63, and a determination circuit64.

The first detection electrode61is a flat-plate electrode. The first detection electrode61is in the cap55at a position closer to the base portion55athan the tip55b1of the lip portion55b.The first detection electrode61is thus placed on the right of the platen3. An upper surface of the first detection electrode61is a facing surface61aparallel to a horizontal plane. When the carriage4is positioned in the standby position, the first detection electrode61faces the four nozzle rows9in the up-down direction at a spaced interval. When ink is discharged from the nozzle(s)10in a state where the carriage4is positioned in the standby position, the ink lands on the facing surface61aof the first detection electrode61.

The second detection electrode62is a flat-plate electrode. The second detection electrode62is placed on the inclined portion28of the guide member26. The second detection electrode62is thus placed on the left of the platen3. The upper surface of the second detection electrode62is the inclined surface62ainclined to a horizontal plane. The ink discharged from the nozzle(s)10lands on the inclined surface62aof the second detection electrode62in the flushing operation and a second discharge-state determination operation described below.

As viewed in the up-down direction, the width in the left-right direction of the first detection electrode61is larger than the width in the left-right direction of a nozzle formation area in the nozzle surface30awhere the nozzles10are formed. As viewed in the up-down direction, the width in the left-right direction of the second detection electrode62is smaller than the width in the left-right direction of the nozzle formation area.

The two detection electrodes61and62are connected to the high-voltage power circuit63via resistance R. The controller100can control the high-voltage power circuit63to make the electrical potential of the two detection electrodes61and62a predefined positive potential. This generates a predefined difference in electrical potential between the head30connected to the ground potential and the two detection electrodes61and62.

The determination circuit64compares a voltage value of a voltage signal output from each of the two detection electrodes61and62with a threshold value TH described below, and outputs its determination result to the controller100. The controller100determines the discharge state of the nozzle(s)10based on the determination result from the determination circuit64. The position of the determination circuit64is not especially limited, and the determination circuit64may be disposed at any position.

As depicted inFIG. 2, the controller100includes a Central Processing Unit (CPU)101, a Read Only Memory (ROM)102, a Random Access Memory (RAM)103, a flush memory104, an Application Specific Integrated Circuit (ASIC)105, and the like. The ROM102stores programs executed by the CPU101, a variety of fixed data, and the like. The RAM103temporarily memorizes data and image data required for execution of the programs. The flush memory104memorizes a proportion table104adescribed below. The ASIC105is connected to a variety of apparatuses and driving portions of the printer1, such as the head30, the carriage driving motor20, the conveyance motor21, and a communication interface110.

In the controller100, only the CPU101may execute a variety of processing, only the ASIC105may execute a variety of processing, or the CPU101may cooperate with the AISC105in a variety of processing. In the controller100, the CPU101may execute processing alone or multiple CPU101may execute processing in a shared fashion. In the controller100, the ASIC105may execute processing alone or multiple ASIC105may execute processing in a shared fashion.

The controller100controls the CPU101and the ASIC105to execute a variety of processing in accordance with programs stored in the ROM102. For example, when the controller100receives a recording instruction from an external apparatus200via the communication interface110, the controller100executes recording processing in which discharge processing and conveyance processing are alternately executed. In the discharge processing, ink is discharged from the nozzle(s)10during one movement (pass) in the scanning direction of the carriage4based on image data memorized in the RAM103. In the conveyance processing, the conveyance rollers2aand2bconvey the sheet P frontward by a predefined amount. Namely, the printer1of this embodiment is a serial-type ink-jet printer.

The printer1of this embodiment records an image on the sheet P using a unidirectional recording mode in which the discharge processing is executed only when the carriage4moves rightward. Thus, after the discharge processing is executed once during the rightward movement of the carriage4and before the next discharge processing starts, the controller100is required to execute a return operation in which the carriage4moves leftward while discharging no ink from the head30. As a modified example, an image may be recorded on the sheet P using a bidirectional recording mode in which the discharge processing is executed independently of whether the carriage4moves rightward or leftward in the scanning direction.

The controller100controls the head30, the nozzle inspection apparatus40, and the like to execute a discharge state determination operation in which the discharge state of the nozzle(s)10is determined. In the discharge state determination operation of this embodiment, it is determined whether all the nozzles10that are determination targets are normal nozzles from which ink can be discharged or whether at least one nozzle10that is the determination target is an abnormal nozzle from which ink can not be discharged.

In this embodiment, the discharge state determination operation includes a first discharge-state determination operation and the second discharge-state determination operation. In the first discharge-state determination operation, the controller100drives the head30to discharge ink from the nozzles10as the determination targets sequentially in a state where the carriage4is positioned in the right detection range DR included in the non-facing range RR. The controller100determines whether each nozzle10as the determination target is the normal nozzle based on a voltage signal that is output from the first detection electrode61depending on the driving of the head30.

The right detection range DR is a range in which the ink discharged from each nozzle10as the detection target can land on the first detection electrode61. In this embodiment, the right detection area DR is a range corresponding to the standby position of the carriage4. The position of a right end of the right detection range DR is the same as the position of the right end of the movement range MR.

In the second discharge-state determination operation, the controller100drives the head30to discharge ink from the nozzles10as the determination targets sequentially in a state where the carriage4is positioned in the left detection range DL included in the non-facing range LR. The controller100determines whether each nozzle10as the determination target is the normal nozzle based on a voltage signal that is output from the second detection electrode62depending on the driving of the head30.

The left detection range DL is a range in which the ink discharged from each nozzle10as the detection target can land on the second detection electrode62. A left end of the left detection range DL is at the right of a left end of the movement range MR. A distance between the left end of the left detection range DL and the left end of the movement range MR is thus longer than a distance between the right end of the right detection range DR and the right end of the movement range MR. When the carriage4is positioned at the right end of the movement range MR, the rightmost nozzle row9of the four nozzle rows9is positioned at the left of a right end of the first detection electrode61. When the carriage4is positioned at the left end of the movement range MR, the leftmost nozzle row9of the four nozzle rows9is positioned at the left of a left end of the second detection electrode62.

The controller100makes ink discharge timing of each nozzle10as the determination target in the first discharge-state determination operation different from that in the second discharge-state determination operation. More specifically, the controller100makes the ink discharge timing of each nozzle10in the first discharge-state determination operation different from that in the second discharge-state determination operation so that a period during which electrically change is caused in the detection electrodes61and62due to the ink discharged from a certain nozzle10does not overlap with a period during which electrically change is caused in the detection electrodes61and62due to the ink discharged from any other nozzle10than the certain nozzle10.

The timing at which the discharge state determination operation is executed is not especially limited. For example, the timing may be a timing at which the printer1is turned on, a timing at which a recording instruction is received, a timing at which recording is executed for a predefined number of pages in the recording processing, and a timing at which recording corresponding to a predefined number of passes is executed in the recording processing. When executing the discharge state determination operation, the controller100selectively executes any of the first discharge-state determination operation and the second discharge-state determination operation.

As described above, when the carriage4moves from the facing range CR to the standby position (right detection range DR), the carriage4is brought into contact with the contact portion93aof the switching lever93. If the movement velocity of the carriage4is fast, big contact noise would be caused and the carriage4and the switching lever93would be damaged when the carriage4is brought contact with the contact portion93a.

The landing surface of the first detection electrode61on which the ink discharged from the nozzle(s)10lands is the facing surface61aparallel to the nozzle surface30a(horizontal plane). When compared to a surface inclined to the horizontal plane such as the inclined surface62aof the second detection electrode62, the ink landing on the facing surface61aof the first detection electrode61easily bounces off the facing surface61a,so that the ink bounced off travels upward to the nozzle surface60a.When ink is discharged from the nozzle(s)10during the movement of the carriage4, inertial force is acted on the ink discharged from the nozzle(s)10to increase ink flying velocity. Thus, if the movement velocity of the carriage4is fast in the first discharge-state determination operation, the ink bounced off the first detection electrode61and the like in the cap55would easily scatter far and wide. The ink scattered is likely to adhere to the nozzle surface30aof the head30and/or the lip portion55bthat may be brought into contact with the head30.

When ink is discharged from the nozzle(s)10during the movement of the carriage4, an ink flying direction is not an exactly downward direction (ink does not fly exactly downward in a vertical direction) due to the inertial force acted on ink, but a direction containing components of a movement direction of the carriage4. In order to land ink on a desired position of the first detection electrode61in the cap55during the movement of the carriage4in the first discharge-state determination operation, ink is required to be discharged from a point of time at which the carriage4is positioned upstream in the movement direction from the standby position where the carriage4faces the cap55. The first detection electrode61, however, is in the cap55at the position closer to the base portion55athan the tip55b1of the lip portion55b.In that configuration, when the movement velocity of the carriage4is fast in the first discharge-state determination operation, the ink discharged from the nozzle(s)10is liable to land on the lip portion55brather than lands on the desired position of the first detection electrode61.

The movement velocity of the carriage4is required to decrease in the vicinities of ends in the movement range MR of the carriage4to inhibit the carriage4from overrunning beyond the movement range MR. The right end of the right detection range DR is the same as the right end of the movement range MR. The left end of the left detection range DL is at the right of the left end of the movement range MR.

In view of the above, in this embodiment, the movement velocity of the carriage4in the first discharge-state determination operation is slower than that in the second discharge-state determination operation. Specifically, in the first discharge-state determination operation, the controller100drives the head30to discharge ink from the nozzle(s)10while stopping the carriage4in the right detection range DR. In other words, the controller100executes the first discharge-state determination operation when the carriage4is in the standby position.

In the second discharge-state determination operation, the controller100drives the head30to discharge ink from the nozzle(s)10while moving the carriage4leftward at a predefined movement velocity. The second discharge-state determination operation is executed immediately after the return operation (details are described below). The second discharge-state determination operation is executed during the leftward movement of the carriage4that continues from the return operation. Namely, the leftward movement of the carriage4is not stopped between the second discharge-state determination operation and the return operation.

When the recording processing is being executed, the carriage4is not required to move to the standby position (right detection range DR) except in the case of executing the suction purge. Thus, when the discharge state determination operation is executed during the execution of the recording processing, the execution of the second discharge-state determination operation having faster movement velocity of the carriage4than the first discharge-state determination operation shortens a time for the recording processing.

The controller100thus executes the first discharge-state determination operation when the carriage4is in the right detection range DR (standby position). For example, when the controller100receives a recording instruction with the carriage4positioned in the right detection range DR, the controller100executes the first discharge-state determination operation before executing the recording processing for the recording instruction.

The controller100executes the second discharge-state determination operation when the recording processing is being executed with the carriage4not positioned in the right detection range DR. In this embodiment, when the carriage4moves from the facing range CR to the left detection range DL during the execution of the recording processing, the controller100executes any one of the flushing operation and the second discharge-state determination operation. More specifically, when the cumulative number of movement of the carriage4from the facing range CR to the left detection range DL is a multiple of three during the execution of the recording processing, the controller100executes the second discharge-state determination operation. In other cases, the controller100executes the flushing operation.

The viscosity of the ink in each nozzle10increases as a non-discharge period, in which no ink is discharged from each nozzle10, is longer. Thus, when a standby time of the printer1is long, the nozzles10of the head30are highly likely to be the abnormal nozzles due to the increase in viscosity of the ink in the nozzles10at the start of the recording processing. In order to solve that problem, the controller100sets all the nozzles10of the head30as the determination targets in the first discharge-state determination operation executed before the recording processing. When the controller100has determined in the first discharge-state determination operation that at least one nozzle10is the abnormal nozzle, the controller100controls the maintenance mechanism8to execute the suction purge. This allows all the nozzles10of the head30to be the normal nozzles before the recording processing starts.

The second discharge-state determination operation is a determination operation executed during the execution of the recording processing. In the second discharge-state determination operation of this embodiment, the controller100makes jetting timings of the respective nozzles10as the determination targets differ from each other. Thus, a time required for completing ink discharge from all the nozzles10as the determination targets is longer as the number of nozzles10set as the determination targets is larger. The width in the left-right direction of the second detection electrode62is smaller than the width in the left-right direction of the nozzle formation area as viewed in the up-down direction. Further, the controller100controls the carriage4to move leftward during the execution of the second discharge-state determination operation. Thus, the period during which the ink discharged from the nozzles10of the head30can land on the second detection electrode62is limited.

In order to allow the controller100to set all the nozzles10of the head30as the determination targets in the second discharge-state determination operation, the movement velocity of the carriage4during the execution of the second discharge-state determination operation is required to decrease. However, reducing the movement velocity of the carriage4lengthens the time required for the recording processing. Thus, in the second discharge-state determination operation of this embodiment, the controller100sets some of the nozzles10of the head30as the determination targets.

Whether the nozzle10easily has discharge failure may depend on the position where the nozzle10is formed. For example, the respective nozzles10belonging to each nozzle row9have different channel distances from the ink support opening85to the respective nozzles10. Further, the viscosity of ink typically increases due to, for example, the volatilization of a solvent, as the ink stays in channels of the head30for a longer time. The discharge failure is thus likely to occur in the nozzle10having a longer channel distance from the ink support opening85.

In order to solve the above problem, the controller100increases the frequency of setting, in which the nozzle10having a longer channel distance from the ink supply opening85is set as the determination target, in the second discharge-state determination operation. Specifically, the flush memory104memorizes the proportion table104ain which a proportion of setting each nozzle10as the determination target in the second discharge-state determination operation is specified. In the proportion table104a,the nozzle10having a longer channel distance from the ink supply opening85is made to have a larger proportion of being set as the determination target. The controller100determines in the second discharge-state determination operation which of the nozzle(s)10is/are set as the determination target(s) based on the proportion table104a.

Referring toFIG. 6, an exemplary processing operation related to the discharge state determination operation of the printer1is explained below. The carriage4is in the standby position (right detection range DR) at the start of the flowchart inFIG. 6.

When receiving a recording instruction from the external apparatus200(Si: YES), the controller100sets a variable N to zero (S2). Then, the controller100executes the first discharge-state determination operation (S3), which is explained below while referring toFIG. 7. When the controller100has determined in the first discharge-state determination operation that all the nozzles10as the determination targets are the normal nozzles (S4: YES), the controller100proceeds to processing in S6. When the controller100has determined that at least one nozzle10as the determination target is the abnormal nozzle rather than the normal nozzle (S4: NO), the controller100controls the maintenance mechanism8to execute the suction purge (S5). The suction purge makes all the nozzles10of the head30the normal nozzles. After completing the processing in S5, the controller100proceeds to the processing in S6.

In the processing of S6, the controller100feeds the sheet P from a feed unit (not depicted) to a position where the sheet P can face the carriage4. Then, the controller100controls the carriage driving motor20to move the carriage4leftward from the standby position to a position where the discharge processing starts (S7). Subsequently, the controller100executes the discharge processing, in which ink is discharged from the nozzles10of the head30, while controlling the carriage driving motor20, the head30, and the like to move the carriage4rightward (S8). Subsequently, the controller100determines whether the discharge processing in S8is the last discharge processing executed when an image is recorded on one sheet P (S9). When the controller100has determined that the discharge processing in S8is not the last discharge processing (S9: NO), the controller100controls the carriage driving motor20to start the return operation in which the carriage4moves leftward (S10). The controller100updates the variable N to [N+1] (S11), and determines whether the variable N after the update is three (S12). When the controller100has determined that the variable N is three (S12: YES), the controller100executes the second discharge-state determination operation (S13), which is explained below while referring toFIG. 9. When the controller100has determined in the second discharge-state determination operation that all the nozzles10as the determination targets are the normal nozzles (S14: YES), the controller100proceeds to processing in S17.

When the controller100has determined that at least one nozzle10as the determination target is the abnormal nozzle rather than the normal nozzle (S14: NO), the controller100drives the carriage driving motor20to move the carriage4to the standby position. Then, the controller100controls the maintenance mechanism8to execute the suction purge (S15). This suction purge makes all the nozzles10of the head30the normal nozzles. Then, the controller100moves the carriage4leftward from the standby position to a position where the next discharge processing starts (S16) and proceeds to processing in S17.

In the processing of S17, the controller100resets the variable N to zero. After completing the processing in S17, the controller100proceeds to processing in S19.

When the controller100has determined in the processing of S12that the variable N is not three (S12: NO), the controller100drives the head30to execute the flushing operation after the carriage4moves to the left detection range DL through the return operation (S18). After completing the processing in S18, the controller100proceeds to the processing in S19.

In the processing of S19, the controller100controls the conveyance motor21to execute the conveyance processing in which the sheet P is conveyed by a predefined conveyance amount. After that, the controller100returns to the processing in S8to execute the next discharge processing.

When the controller100has determined in the processing of S9that the discharge processing in S8is the last discharge processing executed when an image is recorded on one sheet P (S9: YES), the controller100controls the conveyance motor21to execute sheet-discharge processing (S20) in which the sheet P for which the image has been recorded is discharged on a discharge tray (not depicted). Then, the controller100determines whether the image recording on the sheet P related to the recording instruction is completed (S21). When the controller has determined that the image recording is completed (S21: YES), the controller100drives the carriage driving motor20to move the carriage4to the standby position (S22). Then, the controller100returns to the processing in51. When the controller100has determined that the image recording is not yet completed (S21: NO), the controller100returns to the processing in S6to record an image on the next sheet P.

Referring toFIGS. 7 and 8, the first discharge-state determination operation is explained. The carriage4is in the standby position (right detection range DR) at the start of the first discharge-state determination operation.

As indicated inFIG. 7, the controller100first controls the high-voltage power circuit63to generate a difference in electrical potential between the head30and the first detection electrode61(B1). Then, the controller100sets all the nozzles10of the head30as the determination targets (B2). Subsequently, the controller100sets one of the nozzles10as the determination targets as a discharge target (B3).

Subsequently, the controller100controls the head30to start non-discharge driving in which the ink in each nozzle10of the head30except for the discharge target is vibrated to an extent that no ink is discharged therefrom (B4). The first discharge-state determination operation thus inhibits the ink in each nozzle10except for the discharge target from thickening due to the drying of ink. Subsequently, the controller100drives the head30so that a predefined number of ink droplets are discharged from only the nozzle10as the discharge target (B5).

In B5, since the difference in electrical potential between the head30and the first detection electrode61is generated, the ink discharged from the nozzle10as the discharge target is charged with electricity. Electrical change is caused in the first detection electrode61when the charged ink approaches the first detection electrode61and lands thereon. The voltage value of the voltage signal output from the first detection electrode61changes depending on the electrical change caused in the first detection electrode61. Namely, as indicated inFIG. 8A, the voltage value of the voltage signal output from the first detection electrode61while the head30is driven is higher than a voltage value (hereinafter referred to as a reference voltage value) while the head30is not driven. When no ink is discharged from the nozzle10as the discharge target, as depicted inFIG. 8B, the voltage value of the voltage signal output from the first detection electrode61while the head30is driven is substantially the same as the reference voltage value. The determination circuit64thus sets the threshold value TH to distinguish the voltage value of the voltage signal output from the first detection electrode61and the reference voltage value. The determination circuit64compares the voltage value of the voltage signal output from the first detection electrode61while the head30is driven and the threshold value TH, and outputs the determination result to the controller100.

When the determination circuit64has determined that the voltage value of the voltage signal of the first detection electrode61while the head30is driven is equal to or more than the threshold value TH (B6: YES), the controller100determines that the nozzle10as the discharge target is the normal nozzle (B7). Then, the controller100determines whether all the nozzles10as the determination targets have been set as the discharge targets (B8). When the controller100has determined that there is a nozzle10that is not set as the discharge target (B8: NO), the controller100returns to the processing in B3to set the nozzle10that has not yet been set as the discharge target as the discharge target. When the controller100has determined that all the nozzles10as the determination targets have been set as the discharge targets (B8: YES), the controller100determines that all the nozzles10of the head30are the normal nozzles (B9) and ends the first discharge-state determination operation.

When the determination circuit64has determined in the processing of B6that the voltage value of the voltage signal of the first detection electrode61while the head30is driven is less than the threshold value TH (B6: NO), the controller100determines that the nozzle10as the discharge target is the abnormal nozzle, and at least one nozzle10as the determination target is the abnormal nozzle (B10). Then, the controller100ends the first discharge-state determination operation.

Referring toFIG. 9, the second discharge-state determination operation is explained below.

The controller100first controls the high-voltage power circuit63to generate a difference in electrical potential between the head30and the second detection electrode62(C1). Then, the controller100sets some of the nozzles10of the head30as the determination targets (C2) based on the proportion table104amemorized in the flush memory104.

After that, the controller100determines whether the carriage4has moved to the left detection range DL in the return operation (C3). When the controller100has determined that the carriage4has not moved to the left detection range DL (C3: NO), the controller100waits until the controller100determines that the carriage4has moved to the left detection range DL. When the controller100has determined that the carriage4has moved to the left detection range DL (C3: YES), the controller100sets one of the nozzles10as the determination targets as the discharge target (C4). The processing in C5to C11is substantially the same as the processing in B4to B10, and thus only the differences therebetween are explained below. Namely, in the second discharge-state determination operation, ink is discharged from the nozzle10to the second detection electrode62. The determination circuit64thus compares the voltage value of the voltage signal output from the second detection electrode62while the head30is driven and the threshold value TH, and outputs the result to the controller100. When the controller100has determined that the voltage value of the voltage signal of the second detection electrode62while the head30is driven is equal to or more than the threshold value TH, the controller100determines that the nozzle10as the discharge target is the normal nozzle. When the controller100has determined that the voltage value of the voltage signal of the second detection electrode62while the head30is driven is less than the threshold value TH, the controller100determines that the nozzle10as the discharge target is the abnormal nozzle.

In this embodiment, the discharge state of the nozzle(s)10can be determined in the right detection range DR and the left detection range DL included in the movement range MR of the carriage4. A time for moving the carriage4can thus be shortened when the determination of discharge state of the nozzle(s)10is executed. This consequently shortens a time until the determination of discharge state of the nozzle(s)10starts.

Although the embodiment of the present disclosure is explained above, the present disclosure is not limited to the above embodiment, and a variety of modifications are possible without departing from the claims. For example, the arrangement of the first detection electrode61and the second detection electrode62is not limited to that of the above embodiment. The first detection electrode61may be disposed at any other position than being disposed in the cap55. Like a modified embodiment depicted inFIG. 10, the second detection electrode62may be placed on a platen203. The modified embodiment depicted inFIG. 10is explained below. In the following, the constitutive parts or components, which are the same as or equivalent to those of the above embodiment, are designated by the same reference numerals, any explanation therefor will be omitted as appropriate.

A printer201according to the modified embodiment depicted inFIG. 10does not include the flushing receiver25. A flushing receiver225is formed on the platen203supporting the sheet P conveyed by the conveyer2. Specifically, the flushing receiver225is formed at a left end of the platen203. The flushing receiver225is a recess or concave portion that is recessed downward from a support surface203aof the platen203supporting the sheet P. The ink discharged from the nozzles10of the head30through the flushing operation is received by the flushing receiver225.

In this modified embodiment, the second detection electrode62is disposed in the flushing receiver225. Part of the left detection range DL belongs to the facing range CR, and the remaining part of the left detection range DL belongs to the non-facing range LR. The ink discharged from the nozzles10as the determination targets in the second discharge-state determination operation lands on the second detection electrode62in the flushing receiver225.

As described above, also in this modified embodiment, the discharge state of the nozzles10can be determined in the right detection range DR and the left detection range DL included in the movement range MR of the carriage4. This shortens the time for moving the carriage4when the determination of discharge state of the nozzles10is executed.

In the above modified embodiment, the second detection electrode62may be covered with the sheet P when the sheet width of the sheet P as a recording target is long and the sheet P is supported by the platen203. In this case, the second discharge-state determination operation can not be executed while the sheet P is supported by the platen203. Thus, the second discharge-state determination operation may be executed during a period, during which the second detection electrode62is not covered with the sheet P supported by the platen203, in the execution of the recording processing. The period may be, for example, a period before or after an image is recorded on one sheet P.

Other modified embodiments are explained below.

In the above embodiment, the first detection electrode (first conductor for detection) and the second detection electrode (second conductor for detection) are the detection electrodes on which the ink discharged from the nozzle10lands when the determination of discharge failure of the nozzle10is executed. The present disclosure, however, is not limited thereto. The first detection electrode (first conductor for detection) and the second detection electrode (second conductor for detection) may be any in which electrical change is caused by the ink discharged from the nozzle10. The first detection electrode (first conductor for detection) and the second detection electrode (second conductor for detection) may thus be, for example, conductors on which the ink discharged from the nozzle10does not land but in which an induced current is caused when the ink discharged from the nozzle10approaches them.

The standby position where the carriage4faces the cap unit50in the up-down direction is not limited to the right end of the movement range MR. The right end of the right detection range DR may thus be at the left of the right end of the movement range MR. In this case, the distance between the right end of the right detection range DR and the right end of the movement range MR may be longer than the distance between the left end of the left detection range DL and the left end of the movement range MR. Further, when the first discharge-state determination operation is executed in the above configuration, the head30may be driven to discharge the ink from the nozzles10while the carriage4moves in the right detection range DR. The movement velocity of the carriage4in the first discharge-state determination operation is preferably slower than the movement velocity of the carriage4in the second discharge-state determination operation in view of the contact between the carriage4and the switching lever93, the possibility that the nozzle surface30agets dirty due to the ink bouncing off the first detection electrode61, the arrangement of the first detection electrode61in the cap55, and the like. In the second discharge-state determination operation, the head30may be driven to discharge ink from the nozzle surface30ain a state where the carriage4is stopped.

In the above embodiment, the landing surface of the first detection electrode61on which ink lands is the facing surface61aparallel to the nozzle surface30a(horizontal plane). The present disclosure, however, is not limited thereto. Namely, the landing surface of the first detection electrode61may be a surface of which inclination angle with respect to the nozzle surface30ais gentler than the inclined surface62aof the second detection electrode62. In this case also, ink is more likely to bounce off the landing surface of the first detection electrode61than the inclined surface62a.In the above embodiment, the surface of the second detection electrode62on which ink lands is the inclined surface62ainclined to the nozzle surface30a.The present disclosure, however, is not limited thereto. The surface of the second detection electrode62on which ink lands may be a surface parallel to the nozzle surface30a.

In the above embodiment, the right detection range DR belongs to the non-facing range RR. The present disclosure, however, is not limited thereto. For example, part of the right detection range DR may belong to the facing range CR. In the first discharge-state determination operation, when ink is discharged from the nozzles10during the movement of the carriage4, inertial force is acted on the ink discharged from the nozzles10. Thus, also in the configuration in which the first detection electrode61is disposed on the right of the platen3, if the carriage4moves rightward, ink is capable of landing on the first detection electrode61with the carriage4positioned in the facing range CR. Similarly, the left detection range DL is not limited to the above, provided that the left detection range DL is disposed on the left of the right detection range DR.

The first discharge-state determination operation may be executed also during the execution of the recording processing. For example, when the discharge state determination operation is executed during the execution of the recording processing, whether the first discharge-state determination operation or the second discharge-state determination operation is executed may be determined depending on the position of the carriage4, the distance to the right detection range DR, and the distance to the left detection range DL.

In the above embodiment, the driving-force switching mechanism23operates through the movement of the carriage4. The present disclosure, however, is not limited thereto. The operation of the driving-force switching mechanism23may be controlled, for example, by the controller100.

In the first discharge-state determination operation of the above embodiment, all the nozzles10of the head30are set as the determination targets. Only some of the nozzles10, however, may be set as the determination targets. Further, all the nozzles10of the head30may be set as the determination targets in the second discharge-state determination operation.

In the first discharge-state determination operation of the above embodiment, the nozzles as the determination targets have mutually different discharge timings. The nozzles as the determination targets, however, may have the same discharge timing. Specifically, the electrical change in the first detection electrode61is larger as the number of nozzles10from which ink is discharged while the head30is driven is larger. Namely, the voltage value of the voltage signal output from the first detection electrode61while the head30is driven is higher as the number of nozzles10from which ink is discharged is larger. The controller100thus sets multiple nozzles10as the discharge targets and drives the head30so that a predefined number of ink droplets are discharged from the nozzles10as the discharge targets. The determination circuit64may compare the voltage value of the voltage signal output from the detection electrode61depending on the driving of the head30with a predefined threshold value. The predefined threshold value may be an intermediate value (average value) of a setting voltage value of a voltage signal when all the nozzles10as the discharge targets are the normal nozzles and a setting voltage value of a voltage signal when one nozzle10is the abnormal nozzle. The setting voltage values are voltage values obtained through experiment, simulation, or the like in advance. Similarly, in the second discharge-state determination operation, the nozzles as the determination targets may have the same discharge timing.

In the first and second discharge-state determination operations of the above embodiment, the difference in electrical potential between the head30and each of the detection electrodes61and62is caused. This is not indispensable. Namely, even when there is no difference in electrical potential between the head30and each of the detection electrodes61and62, the ink discharged from the nozzles10is slightly charged with electricity when separating from the nozzle surface30a.When the ink charged approaches each of the detection electrodes61and62and lands thereon, the voltage signal output from each of the detection electrodes61and62becomes higher than the reference voltage value. Accordingly, although determination accuracy may be lower than the above embodiment, the discharge state of the nozzles10can be determined when there is no difference in electrical potential between the head30and each of the detection electrodes61and62.

In the above embodiment, the abnormal nozzle is determined as a non-discharge nozzle from which no ink can be discharged. The present disclosure, however, is not limited thereto. For example, when the volume of ink discharged from the nozzle10is reduced, the voltage value of the voltage signal output from each of the detection electrodes61,62is lower by the reduced volume. Thus, it is possible to execute determination of the nozzle10from which a predefined volume of ink can not be discharged, provided that the threshold value TH in the determination circuit64is set appropriately. Thus, in addition to the non-discharge nozzle, the nozzle from which a predefined volume of ink can not be discharged may be set as the abnormal nozzle.

In the above embodiment, the conveyance system of the sheet P of the conveyer is a roller conveyance system using the conveyance rollers2aand2b.The present disclosure, however, is not limited thereto. The conveyance system may be any other conveyance system. For example, the conveyance system may be a belt conveyance system using a conveyance belt. In the belt conveyance system, the sheet P may be conveyed while being attracted to the conveyance belt. The attraction method of the sheet P is exemplified, for example, by an electrostatic attraction method in which static electricity is generated on a surface of the conveyance belt to attract the sheet P and an air attraction method in which through holes passing the conveyance belt in a thickness direction are provided to suction air through the through holes and to attract the sheet P.

When the conveyance system of the conveyer is the belt conveyance system, one of the detection electrodes (first conductor for detection) may be disposed at one side in the scanning direction from the passing area where the sheet P conveyed by the conveyance belt passes. The other of the detection electrodes (second detection conduction portion) may be disposed at the other side in the scanning direction from the passing area or at a position included in the passing area. For example, when the liquid receiver receiving the liquid discharged from the nozzle(s) is provided in the conveyance belt, the second conductor for detection may be disposed in the liquid receiver.

The conveyance system of the conveyer may be a system in which the sheet P is conveyed using both the conveyance rollers and the conveyance belt. The recording medium may be a roll of paper that is continuous paper wound like a roll. In this case, the conveyer may include a winding mechanism that winds the roll of paper at a downstream side in the conveyance direction from the ink-jet head (carriage).

In the above embodiment, the nozzle inspection apparatus40that inspects the discharge state of the nozzle(s)10includes the first detection electrode61and the second detection electrode62. The present disclosure, however, is not limited thereto. For example, as depicted inFIG. 11, the nozzle inspection apparatus140may include a detection electrode161, an optical detector162, and a hygrometer163. The detection electrode161is disposed in the cap55like the first detection electrode61of the above embodiment. Since the detection electrode161has the same structure as the first detection electrode61of the above embodiment, the explanation therefor is omitted here. The optical detector162is disposed at a position overlapping with a left end of the platen203. The optical detector162includes an irradiation unit162A that irradiates illumination light, and a light receiving unit162B that receives the light from the irradiation unit162A. The irradiation unit162A and the light receiving unit162B are arranged at an interval with the nozzle rows9interposed therebetween in the conveyance direction. The light from the irradiation unit162A is received by the light receiving unit162B, and the intensity thereof is measured. Unlike a case in which no ink is discharged from the nozzles10, flying ink droplets block the light when ink is discharged. This reduces the intensity of the light received by the light receiving unit162B. The optical detector162can thus detect whether ink is discharged from the nozzle(s)10.

The detection electrode161outputs a voltage signal based on a change in electrical potential generated in the detection electrode161due to charged ink. Here, it is known that the charge amount of ink changes depending on the surrounding humidity. When the humidity is high, ink is difficult to be charged. This makes an output value of the voltage signal small and makes detection accuracy low. In order to solve that problem, when the humidity measured by the hygrometer163is higher than a predetermined threshold, the controller100may inspect the discharge state of the nozzle(s)10by use of the optical detector162instead of the detection electrode161. Further, the controller100may inspect the discharge state of the nozzle(s)10by use of the detection electrode161, when the humidity measured by the hygrometer163is lower than a predetermined threshold.

In the above example, the detection electrode161is disposed in the cap55and the optical detector162is disposed at a position overlapping with the left end of the platen203. However, the detection electrode161may be disposed at a position overlapping with the left end of the platen203and the optical detector162may be disposed in the cap55.

In the above embodiment, the first electrode61and the second electrode62are parallel to the nozzle surface, and the length of the first detection electrode61in the scanning direction is longer than the length of the second detection electrode62in the scanning direction. Therefore, the length of the detection range of the first detection electrode61in the scanning direction is longer than the length of the detection range of the second detection electrode62in the scanning direction. The ink discharged from a certain nozzle10may be detected by the first detection electrode61, but may not be detected by the second detection electrode62. In this case, the controller100can determine that the ink discharged from the certain nozzle10is flying while curving or deviating in the scanning direction. Namely, the controller100can determine that the ink discharged from the certain nozzle10has a flying curve or flying deviation. In this case, since it is considered that foreign matter adheres to the certain nozzle10, the controller100can wipe the nozzle surface with a wiper W instead of the suction purge. When the ink discharged from the certain nozzle10is not detected by both the first detection electrode61and the second detection electrode62, the controller100can determine that no ink is discharged from the certain nozzle10. In this case, like the above embodiment, the suction purge solves the non-discharge of the certain nozzle.

When the optical detector162is used, the detection range of the optical detector162may be adjusted by adjusting the irradiation range in the scanning direction of the light from the irradiation unit162A or the light receiving range in the scanning direction of the light receiving unit162B. Thus, both when multiple optical detectors are combined together and when the optical detector and the detection electrode(s) are combined together, the flying curve of ink can be detected.

The optical detector is not limited to the above configuration. For example, the optical detector may include a light emitting unit that emits focused light such as laser light and a light receiving unit. In this case, the laser light can detect the ink discharged from nozzle(s) belonging to one nozzle row or several nozzle rows. Further, the optical detector may include an imaging unit that captures an image (moving image or still image). In this case, the presence or absence of ink discharge can be detected based on the image captured by the imaging unit.

The serial-type ink-jet head that performs printing during the movement of the head in the scanning direction is adopted in the above-described embodiment and modified embodiments of the present disclosure. Note that in the serial-type ink-jet head as described above, the head unit may be removably attached onto the carriage. The present disclosure, however, may be applied to a line-type ink-jet head that performs printing in a state where the head stands still. When a movable line-type ink-jet head is used, the nozzle inspection apparatus can be disposed outside the printing area as in the above embodiment. Further, when the ink-jet head is not movable, the nozzle inspection apparatus may be configured to be movable between a storage position away from the printing area and a detection position below the head. Both the head and the nozzle inspection apparatus may be configured to be movable. The printer that records an image on a sheet by discharging ink from nozzles is adopted in the above embodiment and the modified embodiments of the present disclosure. The present disclosure, however, is not limited thereto. The present disclosure is applicable to a liquid discharge apparatus that discharges liquid on any other recording medium than the sheet P. For example, the recording medium may be a T-shirt, a sheet for out-of-home advertising, and the like. The present disclosure can be applied to a liquid discharge apparatus that performs recording on a trace (wiring) board by discharging any other liquid than ink, such as a material of a trace (wiring) pattern. The present disclosure can be applied to a liquid discharge apparatus that performs recording on a medium, such as cases of mobile terminals including smartphones, cardboard, and resin, by discharging ink thereon.