Image recording apparatus

An image recording apparatus includes: a sheet conveying unit; an ink ejection head having a nozzle and an ink ejection surface; a pretreatment liquid ejection head; a purge unit; a wiping unit having a wiper; a paper jam detection unit detecting a position when the recording sheet is jammed; and a maintenance control unit, wherein, when the paper jam detection unit detects a paper jam on the downstream side from the pretreatment liquid ejection head, the maintenance control unit performs a first maintenance operation, in which the purge unit discharges ink from the ink ejection head, and the wiping unit wipes the ink ejection surface with the wiper, and in the first maintenance operation, the maintenance control unit performs control such that a discharge amount of ink to be discharged from the ink ejection head decreases or the wiping speed when the ink ejection surface is wiped decreases.

CROSS REFERENCE TO RELATED APPLICATION

The present application claims priority from Japanese Patent Application No. 2010-261268, which was filed on Nov. 24, 2010, the disclosure of which is herein incorporated by reference in its entirety.

TECHNICAL FIELD

The present invention relates to an image recording apparatus which ejects ink onto a recording sheet to perform recording.

BACKGROUND

Patent Document 1 describes an ink jet recording apparatus which ejects a reaction liquid (pretreatment liquid) containing a component capable of aggregating or precipitating ink components onto a recording sheet, and then ejects ink onto the recording sheet having the reaction liquid landed thereon to record an image on the recording sheet.

Patent Document 2 describes a technique in which, when a paper jam occurs in an ink jet recording apparatus and a user removes the jammed recording sheet, a purge operation is performed to discharge ink from a nozzle, and then ink attached to an ink ejection surface of an ink jet head is wiped by a wiper blade, thereby recovering the meniscus of the nozzle and removing ink on the ink ejection surface.

SUMMARY

In Patent Document 1, even when a paper jam occurs, it is necessary to recover the meniscus of the nozzle. At this time, it is considered that the same operation as described in Patent Document 2 is performed.

However, when a paper jam occurs in the ink jet recording apparatus described in Patent Document 1, the recording sheet having the reaction liquid landed thereon may come into contact with the ink ejection surface, and the reaction liquid may be attached to the ink ejection surface. If the reaction liquid is attached to the ink ejection surface, ink attached to the ink ejection surface is aggregated or precipitated, and the generated aggregate or precipitate (ink aggregated or precipitated by the pretreatment liquid) is solidly attached to the ink ejection surface. The aggregate or precipitate causes defective ink ejection.

For this reason, when a paper jam occurs in the inkjet recording apparatus described in Patent Document 1, even though the purge operation and wiping of the ink ejection surface by the wiper blade described in Patent Document 2 are performed, the aggregate or precipitate may not be sufficiently removed from the ink ejection surface. At the time of wiping of the ink ejection surface by the wiper, the aggregate or precipitate may spread over the ink ejection surface. As a result, defective ink ejection from the nozzle may occur. Further, wasteful ink consumption increases.

An object of the invention is to provide an image recording apparatus capable of reliably removing an aggregate or a precipitate attached to an ink ejection surface while suppressing wasteful ink consumption.

An image recording apparatus according to an aspect of the invention includes a sheet conveying unit for conveying a sheet along a sheet conveying path, an ink ejection head which has a nozzle ejecting ink onto the recording sheet being conveyed and an ink ejection surface in which an ejection port of the nozzle is formed, a pretreatment liquid ejection head which is arranged on the upstream side of the ink ejection head in the conveying direction of the recording sheet, and ejects a pretreatment liquid containing a component capable of aggregating or precipitating ink components onto the recording sheet being conveyed, a purge unit for forcibly discharging ink from the nozzle, a wiping unit having a wiper wiping the ink ejection surface, paper a jam detection unit for detecting a position in the sheet conveying path when the recording sheet is jammed, and a maintenance control unit for controlling the purge unit and the wiping unit. When the paper jam detection unit detects that a paper jam is detected on the downstream side from the pretreatment liquid ejection head in the conveying direction, the maintenance control unit performs a first maintenance operation, in which the purge unit forcibly discharges ink from the ink ejection head, and then the wiping unit wipes the ink ejection surface with the wiper, once or more. In the first maintenance operation, compared to a second maintenance operation capable of recovering the meniscus of the nozzle and removing ink attached to the ink ejection surface, the maintenance control unit performs control such that the discharge amount of ink to be discharged from the ink ejection head by the purge unit decreases or the wiping speed when the ink ejection surface is wiped by the wiping unit decreases.

According to the invention, in the first maintenance operation, when the amount of ink to be discharged by the purge unit is small compared to the second maintenance operation, the amount of ink remaining on the ink ejection surface immediately after ink discharge decreases, such that the frictional force between the wiper and the ink ejection surface increases. Therefore, when the recording sheet having the pretreatment liquid landed thereon is jammed, it is possible to reliably remove an aggregate or precipitate attached to the ink ejection surface while suppressing wasteful ink consumption. Further, the amount of ink consumption in the first maintenance operation decreases.

In the first maintenance operation, when the wiping speed when the ink ejection surface is wiped by the wiper is slow compared to the second maintenance operation, the recovery force when the wiper deformed by moving while coming into contact with the ink ejection surface returns to the original state increases, such that the force of the wiper for wiping the ink ejection surface increases. Therefore, it is possible to reliably remove an aggregate or precipitate attached to the ink ejection surface while suppressing wasteful ink consumption when purging or wiping is repeatedly performed many times.

Hereinafter, a preferred embodiment of the invention will be described.

As shown inFIG. 1, a printer101(image recording apparatus) has a casing101asubstantially having a rectangular parallelepiped shape, and a sheet discharge section30is provided at the upper part of the casing101a. The inside of the casing101ais divided into three spaces S1to S3in order from above. In the space S1are arranged four ink ejection heads2which eject ink of magenta, cyan, yellow, and black, an improvement liquid ejection head3(pretreatment liquid ejection head) which ejects an image quality improvement liquid (pretreatment liquid, and hereinafter, simply referred to as an improvement liquid) for improving image quality, a conveying mechanism15which conveys a recording sheet P in a conveying direction A, and the like. In the spaces S2and S3, a feeder unit10and a tank unit7which are detachably mounted in the casing101aare arranged. Inside the tank unit7, four ink tanks8and one improvement liquid tank9are accommodated. In the feeder unit10, a plurality of recording sheets P are arranged in an overlapping manner. In the space S1, a control device100which controls the operation of the printer101is provided.

As shown inFIGS. 1 and 2, the five heads2and3are so-called line heads which substantially have a rectangular parallelepiped shape elongated in a main scanning direction (a left-right direction ofFIG. 2) perpendicular to the conveying direction A, and are arranged along the conveying direction A. Specifically, in the conveying direction A, the improvement liquid ejection head3is arranged on the most upstream side, and the four ink ejection head2are arranged on the downstream side of the improvement liquid ejection head3. With regard to the four ink ejection heads2, the ink ejection heads2which eject ink of cyan, magenta, yellow, and black are arranged in order from the upstream side of the conveying direction A.

The heads2and3have the same configuration but store different types of liquids, and are laminates in which a flow channel unit and an actuator are bonded to each other. An ink flow channel including a pressure chamber is formed in the flow channel unit, and the actuator applies a pressure to ink in the pressure chamber. A surface of the flow channel unit facing the conveying mechanism15is an ejection surface in which ejection ports of nozzles20is formed. An ejection surface3aof the improvement liquid ejection head3has a plurality of ejection ports arranged in the main scanning direction, and the improvement liquid is ejected therefrom. An ejection surface2aof the ink ejection head2is the same as the ejection surface3a, and ink is ejected therefrom. The length of each of the ejection surfaces2aand3ain the main scanning direction is greater than the width of the recording sheet P.

As shown inFIG. 2, the five heads2and3are supported by a support frame5substantially having a rectangular shape. The five ejection surfaces2aand3aare exposed from a through hole5aformed inside the support frame5. The support frame can be moved up and down by an elevating mechanism34(seeFIG. 4), and is moved up and down along with the heads2and3.FIG. 2shows the arrangement form of the nozzles20when viewed from the front of the paper to the rear in the ejection surfaces2aand3aof the heads2and3which are primarily on the lower side in plan view and cannot be viewed.

The four ink tanks8respectively store ink of four colors, and the improvement liquid tank9stores the improvement liquid. Ink of a corresponding color is supplied from the ink tank8to the ink ejection head2, and the image quality improvement liquid is supplied from the improvement liquid tank9to the improvement liquid ejection head3. The tanks8and9and the heads2and3are connected through flexible tubes. When ink is pigment-based ink, the improvement liquid is a liquid which comes into contact with ink and aggregates ink. When ink is dye-based ink, the improvement liquid is a liquid which comes into contact with ink and precipitates ink.

Inside the printer101, as indicated by a bold arrow inFIG. 1, a sheet conveying path through which the recording sheet P is conveyed is formed from the feeder unit10to the sheet discharge section30. The feeder unit10has a feed roller12and a feed motor, in addition to a sheet feeding tray11which can store a plurality of recording sheets P. Of these, the sheet feeding tray11is detachably mounted in the casing101a. The feed motor is driven to rotate the feed roller12. The feed roller12feeds the uppermost recording sheet P in the sheet feeding tray11. The fed recording sheet P is sent to the conveying mechanism15by guides13aand13band a feed roller pair14.

The conveying mechanism15has two belt rollers16and17, an endless conveying belt18which is wound so as to be stretched between the two rollers16and17, and a conveying motor35(seeFIG. 4) which rotates the belt roller17. Outside the conveying belt18, a pressing roller24is arranged to face the belt roller16, and a separating member25is arranged to face the belt roller17. A platen21is arranged inside the conveying belt18.

As shown inFIG. 2, the width of the conveying belt18(the length in the main scanning direction) is slightly greater than the width of each of the heads2and3.

The platen21is formed to be slightly longer in the main scanning direction than the length of each of the recording sheet P and the conveying belt18.

As shown inFIG. 1, the upper surface of the platen21supports an upper loop of the conveying belt18from the inner circumference side. Thus, a conveying surface19of the upper loop of the conveying belt18faces the ejection surfaces2aand3ain parallel, and a gap suitable for image formation is formed between the ejection surfaces2aand3aand the conveying surface19.

On the upstream side of the conveying mechanism15, the pressing roller24is pressed toward the belt roller16by an elastic member (for example, a spring). The recording sheet P supplied from the feeder unit10is pressed against the conveying surface19by the pressing roller24. The pressing roller24is a driven roller and rotates with the rotation of the conveying belt18.

In the sheet conveying path, sheet sensors31to33are arranged on the direct upstream side and the direct downstream side of the improvement liquid ejection head3and on the direct downstream side of the most downstream-side ink ejection head2. The sheet sensor31is a sensor which detects the recording sheet P immediately before entering the arrangement region of the heads2and3. In this embodiment, the ejection timing from each of the heads2and3, or the like is determined on the basis of the leading end detection timing of the recording sheet P by the sheet sensor31, the conveying speed of the recording sheet P, or the like. As the sheet sensor31, a sensor having comparatively high precision is used such that the improvement liquid or ink is accurately landed.

The two sheet sensors32and33are arranged so as to sandwich the four ink ejection heads2therebetween. The upstream-side sheet sensor32detects the recording sheet P which is conveyed to the downstream side of the improvement liquid ejection head3. The downstream-side sheet sensor33detects the recording sheet P on which image formation is completed. Unlike the sheet sensor31, the sheet sensors32and33need not detect the leading end of the recording sheet P with satisfactory precision. It should suffice that the sheet sensors32and33detect the leading end or trailing end of the recording sheet P having passed. For this reason, as the sheet sensors32and33, sensors having low precision are used compared to the sheet sensor31.

The separating member25is provided on the direct downstream side of the conveying mechanism15. The separating member25is arranged such that the leading end thereof enters between the recording sheet P and the conveying belt18. The separating member25separates the recording sheet P from the conveying surface19and guides the recording sheet P to downstream-side guides29aand29b.

Two sets of feed roller pairs27and28and two sets of guides29aand29bare arranged between the conveying mechanism15and the sheet discharge section30. The feed roller pairs27and28are driven under the control of the control device100, such that the recording sheet P separated from the conveying surface19is guided and fed to the sheet discharge section30.

The printer101includes a cap unit41and a wiping unit42which are used for the maintenance of the heads2and3. In a state where purging or wiping described below is performed, the cap unit41and the wiping unit42are arranged laterally in relation to the heads2and3(on the left side ofFIG. 2) in the main scanning direction.

The cap unit41includes a substrate51, five purge caps52, and the like. The substrate51is a plate member substantially having a rectangular shape. The substrate51is supported by two guide rails43extending in the main scanning direction (the direction perpendicular to the sub scanning direction) at both end portions in the sub scanning direction, and is movable in the main scanning direction along the guide rails43by a cap unit moving mechanism46(seeFIG. 4).

The five purge caps52are arranged in the upper surface of the substrate51at the same intervals as the heads2and3. When the substrate51moves to a position facing the heads2and3, the five purge caps52respectively face the heads2and3. If the heads2and3are moved down by the elevating mechanism34in a state of facing the heads2and3, the five purge caps52respectively cover the ejection surfaces2aand3a.

A pressure pump53(seeFIG. 4) is connected to the halfway path of the heads2and3and the ink tanks8and9. If the pressure pump53is driven in a state where the ejection surfaces2aand3aof the heads2and3are covered with the purge caps52, the pressure in the heads2and3increases, and the improvement liquid, ink, air bubbles, and the like thickened in the heads2and3are forcibly discharged to the purge caps52(pressure purging). The purge caps52are connected to a waste liquid tank (not shown) through tubes54. The discharged improvement liquid, ink, and the like are stored in the waste liquid tank. In this embodiment, the combination of the cap unit41, the elevating mechanism34, and the pressure pump53correspond to a purge unit of the invention.

The wiping unit42is arranged on the right side of the cap unit41inFIG. 2, and includes a substrate61and a wiper62. The substrate61is a plate member substantially having a rectangular shape. The substrate61is supported by guide rails43at both end portions in the sub scanning direction, and is movable in the main scanning direction by a wiping unit moving mechanism47(seeFIG. 4).

The wiper62is a plate-shaped elastic member made of a rubber material to substantially have a rectangular shape elongated in the sub scanning direction. If the heads2and3are moved down by the elevating mechanism34in a state where the substrate61faces the heads2and3, the leading end portion of the wiper62comes into contact with the ejection surfaces2aand3aof the heads2and3. In this state, if the substrate61is moved in the main scanning direction, the ejection surfaces2aand3aare wiped by the wiper62, such that the improvement liquid and ink attached to the ejection surfaces2aand3aand ink aggregated or precipitated by the improvement liquid are removed (wiping). In this embodiment, the combination of the wiping unit42and the elevating mechanism34correspond to a wiping unit of the invention.

Next, the control device100which controls the printer101will be described. The control device100is constituted by hardware, such as a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory), software, such as a control program stored in the ROM or the like, and the like. Hardware, software, and the like constitute a printing control section111, a paper jam detection section112, an improvement liquid detection section113, a maintenance control section114, and the like.

When printing is performed in the printer101, the printing control section111controls the heads2and3, the conveying motor35(belt roller17), and the like on the basis of print data transferred from a host computer, or the like.

The paper jam detection section112detects whether or not a paper jam occurs in the printer101and whether the paper jam occurs on the upstream side or the downstream side of the improvement liquid ejection head3on the basis of the detection results of the sheet sensors31to33. Specifically, when the leading end of the recording sheet P has not been detected by the sheet sensor32within a predetermined time since the leading end of the recording sheet P has been detected by the sheet sensor31, it is detected that a paper jam has occurred on the upstream side from the improvement liquid ejection head3.

When the leading end of the recording sheet P has been detected by the sheet sensor32within a predetermined time since the leading end of the recording sheet P has been detected by the sheet sensor31, and then the trailing end of the recording sheet P has not been detected by the sheet sensor33within a predetermined time, it is detected that a paper jam occurs on the downstream side from the improvement liquid ejection head3, that is, a paper jam occurs when at least a part of a portion of the recording sheet P where the improvement liquid has landed is advanced to the downstream side from the improvement liquid ejection head3.

When a paper jam has been detected by the paper jam detection section112, the improvement liquid detection section113detects the improvement liquid landing on the jammed recording sheet P and the amount of the landed improvement liquid. Specifically, it is determined whether printing is performed on the recording sheet P using both the improvement liquid and ink or printing is performed using only ink from print data transferred from the host computer. When printing is performed using both the improvement liquid and ink, and when the paper jam detection section112detects the occurrence of a paper jam on the downstream side from the improvement liquid ejection head3, the improvement liquid landing on the recording sheet P is detected. The amount of the improvement liquid landed on the recording sheet P is detected on the basis of print data or the like.

The maintenance control section114has a purge amount determination section121, a wiping speed determination section122, a contact force determination section123, and a number-of-repetitions determination section124. The purge amount determination section121determines the amount (purge amount) of the improvement liquid and ink to be discharged from the heads2and3at the time of pressure purging. The wiping speed determination section122determines the moving speed (wiping speed) of the wiper62when wiping is performed.

The contact force determination section123determines the contact force of the wiper62with respect to the ejection surfaces2aand3a. The contact force of the wiper62with respect to the ejection surfaces2aand3achanges by moving up and down the heads2and3(support frame5). As the ejection surfaces2aand3abecome close to the wiping unit42, the contact force increases. The number-of-repetitions determination section124determines the number of repetitions of pressure purging and wiping.

The maintenance control section114controls the elevating mechanism34, the moving mechanisms46and47, the pressure pump53, and the like such that, at the time of pressure purging, the improvement liquid or ink is discharged by the amount determined by the purge amount determination section121, at the time of wiping, the wiper62comes into contact with the ejection surfaces2aand3awith the contact force determined by the contact force determination section123and the wiper62moves at the wiping speed determined by the wiping speed determination section122, and pressure purging and wiping are repeated by the number of repetitions determined by the number-of-repetitions determination section124.

Next, a printing operation by the printer101will be described below. If print data is transferred from the host computer to the control device100, the recording sheet P is fed from the sheet feeding tray11by the feed roller12, and the recording sheet P is conveyed toward the downstream side of the sheet conveying path by the feed rollers14,27, and28and the conveying mechanism15.

When printing is performed on the recording sheet P with high image quality, the improvement liquid ejection head3ejects the improvement liquid toward the recording sheet P, and a transparent image is formed on the recording sheet P with the same image pattern as that being ejected from the ink ejection head2. Thereafter, when the recording sheet P passes directly below the ink ejection head2, ink is ejected to print a color image on the recording sheet P. In this case, ink is landed onto the position of the recording sheet P where the improvement liquid has landed. For this reason, ink landed on the recording sheet P reacts with the improvement liquid and is aggregated or precipitated, and ink does not easily soak through the recording sheet P. Therefore, the edge of an image to be printed is not easily blurred, thereby increasing printing quality.

When printing is performed on the recording sheet P with low image quality, the improvement liquid is not ejected from the improvement liquid ejection head3, and only when the recording sheet P passes directly below the ink ejection head2, ink is ejected from the ink ejection head2to print a color image on the recording sheet P. In this case, since ink has landed on the recording sheet P on which the improvement liquid has not landed, landed ink easily soaks through the recording sheet P. For this reason, the edge of an image to be printed is easily blurred, and printing quality is degraded. Meanwhile, because the improvement liquid is not ejected from the improvement liquid ejection head3, the printing speed increases proportionately.

Thereafter, the recording sheet P on which an image is printed is discharged to the sheet discharge section30by the feed roller pairs27and28. In this way, the printing operation by the printer101ends.

Next, the maintenance operation of the printer101during printing will be described. If printing is performed in the printer101in the above-described manner, the recording sheet P may be bent and hung up on the heads2and3, and a paper jam may occur. When a paper jam occurs, the recording sheet P on which the improvement liquid or ink has landed comes into contact with the ejection surfaces2aand3aof the heads2and3, such that the meniscus of the nozzles20may be destroyed or the improvement liquid landed on the recording sheet P is attached to the ejection surface2aof the ink ejection head2to aggregate or precipitate ink. For this reason, the maintenance of the heads2and3is performed in the procedure shown in the flowchart ofFIG. 5. The processing flow of the maintenance operation shown inFIG. 5starts when printing starts.

In the printer101, while printing is continuing (Step S101: NO, hereinafter, simply referred to as S101), it is detected whether or not a paper jam occurs (Step S102). If a paper jam is detected by the paper jam detection section112(S102: YES), printing (conveying of the recording sheet P and ink ejection) is stopped (S103).

A stand-by state is maintained until the user removes the jammed recording sheet P and the recording sheet P is not detected by any of the sheet sensors31to33(S104: NO). When the recording sheet P is not detected by any of the sheet sensors31to33(S104: YES), and when the improvement liquid detection section113does not detect the improvement liquid landing on the jammed recording sheet P (S105: NO), the purge amount is set to D2(for example, 2 ml), the wiping speed is set to V2(for example, 125 mm/s), and the contact force is set to F2(S106).

At this time, the purge amount D2is the minimum amount at which the meniscus of the improvement liquid or ink of the nozzles20can be reliably recovered. The wiping speed V2is the wiping speed such that the improvement liquid or ink attached to the ejection surfaces2aand3acan be sufficiently removed over a temperature range which should secure the operation of the printer101when an experiment is performed in which wiping is performed in the printer101at various wiping speeds in various temperature environments with the contact force F2of the wiper62with respect to the ejection surfaces2aand3a.

Next, as shown inFIG. 6A, the heads2and3are moved up, and the cap unit41and the wiping unit42are moved to a position where the purge caps52face the heads2and3. Subsequently, as shown inFIG. 6B, the heads2and3are moved down to cover the ejection surfaces2aand3awith the purge caps52, and the pressure pump53is driven to perform pressure purging. At this time, ink or the improvement liquid is discharged from the heads2and3by the purge amount D2(S107).

Next, as shown inFIG. 7A, the heads2and3are moved up, and then the cap unit41is moved to the original position. Subsequently, as shown inFIG. 7B, the heads2and3are moved down to the position where the contact force of the wiper62with respect to the ejection surfaces2aand3abecomes F2. In this state, the wiping unit42is moved to the original position at the wiping speed V2set in S103to perform wiping (S108). Thus, the improvement liquid, ink, or the like attached to the ejection surfaces2aand3ais removed by pressure purging. After wiping, printing is continued (S109) and the processing returns to S101.

At this time, the maintenance operation including pressure purging in S107and wiping in S108corresponds to a second maintenance operation of the invention.

When it is detected that the improvement liquid has landed on the jammed recording sheet P (S105: YES), the purge amount is set to a purge amount D1(for example, 1 ml) smaller than the purge amount D2in the second maintenance operation, the wiping speed is set to a wiping speed V1(for example, 100 mm/s) lower than the wiping speed V2in the second maintenance operation, and the contact force of the wiper62with respect to the ejection surfaces2aand3ais set to a contact force F1greater than the contact force F2in the second maintenance operation (S110).

Next, the number of repetitions of pressure purging and wiping is determined such that the greater the amount of the improvement liquid detected by the improvement liquid detection section113, the greater the number of repetitions of pressure purging and wiping (S111).

As shown inFIGS. 6A to 7B, pressure purging (S112) and wiping (S113) are repeatedly performed by the number of repetitions determined in S111(S114: NO). At the time of pressure purging in S112, ink and the improvement liquid are discharged by the purge amount D1determined in S110, and at the time of wiping in S113, the wiping unit42is moved at the wiping speed V1determined in S110in a state where the heads2and3are moved down to the position where the contact force of the wiper62with respect to the ejection surfaces2aand3abecomes the contact force F1determined in S110. The maintenance operation including pressure purging and wiping in S112to S114corresponds to a first maintenance operation of the invention.

Thereafter, after the same maintenance operation (second maintenance operation) as in S106to S108is further performed, printing is continued (S109).

When the improvement liquid has landed on the jammed recording sheet P, and when the recording sheet P comes into contact with the ink ejection head2, the landed improvement liquid may be attached to the ejection surface2a. If the improvement liquid has landed on the ejection surface2a, ink attached to the ejection surface2amay react with the improvement liquid and may be aggregated or precipitated. Aggregated or precipitated ink has high viscosity compared to ink prior to aggregation or precipitation. For this reason, in this case, even when pressure purging and wiping are performed in the same manner as when the improvement liquid has not landed on the ejection surface2a, aggregated or precipitated ink on the ejection surface2amay not be sufficiently removed and may spread on the ejection surface2a, in which the ejection ports of the nozzles20are formed, by wiping, and as a result, ink may not be normally ejected from the nozzles20. Alternatively, pressure purging or wiping may be repeatedly performed many times so as to reliably remove aggregated ink on the ejection surface2a, causing wasteful ink consumption.

In contrast, in this embodiment, when it is detected that the improvement liquid has landed on the jammed recording sheet P (S102: YES, S105: YES), the purge amount decreases, the wiping speed decreases, and the contact force of the wiper62with respect to the ejection surface2aincreases compared to when it is not detected that the improvement liquid has landed (S102: NO, S105: NO).

If the purge amount decreases, after pressure purging, the amount of the improvement liquid or ink to be attached to the ejection surface2adecreases, and at the time of subsequent wiping, the frictional force between the wiper62and the ejection surface2aincreases. If the wiping speed of the wiper62decreases, the recovery force when the wiper62deformed by moving while coming into contact with the ejection surface2areturns to the original state increases. If the contact force of the wiper62with respect to the ejection surface2aincreases, the frictional force between the wiper62and the ejection surface2aat the time of wiping increases.

As a result, the force of the wiper62for wiping the ejection surface2aat the time of wiping increases, making it possible to reliably remove aggregated or precipitated ink on the ejection surface2awhile suppressing wasteful ink consumption when pressure purging or wiping is repeated many times.

As the amount of the improvement liquid landed on the jammed recording sheet P increases, the amount of the improvement liquid to be attached to the ejection surface2ais likely to increase, and a great amount of ink is likely to be aggregated or precipitated on the ejection surface2a. In contrast, in this embodiment, as the amount of the improvement liquid landed on the jammed recording sheet P increases, the number of repetitions of pressure purging and wiping increases. Thus, it is possible to reliably remove aggregated or precipitated ink from the ejection surface2a.

When it is detected that the improvement liquid has landed on the jammed recording sheet P, the purge amount decreases compared to when the improvement liquid is not detected. For this reason, at the time of pressure purging in S111, the meniscus of the improvement liquid or ink in the nozzles20may not be recovered.

However, in this embodiment, after the first maintenance operation (S111to S113), since the second maintenance operation is performed by the purge amount greater than in the first maintenance operation, it is possible to reliably recover the meniscus of the improvement liquid or ink in the nozzles20. In the second maintenance operation, since the wiping speed is high compared to the first maintenance operation, it is possible to quickly wipe ink or the improvement liquid on the ejection surfaces2aand3a.

In this embodiment, as described above, even when it is detected that the improvement liquid has landed on the jammed recording sheet P, similarly to when it is not detected that the improvement liquid has landed on the jammed recording sheet P, the second maintenance operation is performed. At this time, the meniscus of the improvement liquid or ink in the nozzles20is reliably recovered. Thus, in the first maintenance operation, it is preferable that pressure purging in S112is not performed (the purge amount D2is zero) because the frictional force between the wiper62and the ejection surface2aincreases.

When this happens, however, the ejection surfaces2aand3aare likely to be damaged at the time of wiping by the wiper62. For this reason, in this embodiment, in S112, pressure purging is performed by a purge amount smaller than in S107, such that the improvement liquid or ink is attached to the ejection surfaces2aand3a, thereby preventing the ejection surfaces2aand3afrom being damaged by the wiper62at the time of wiping.

At the time of pressure purging (S107) which is performed when it is not detected that the improvement liquid has landed on the jammed recording sheet P, the purge amount D1is the minimum amount at which the meniscus of the improvement liquid or ink in the nozzles20can be recovered. Thus, it is possible to significantly suppress the amount of the improvement liquid or ink to be discharged by pressure purging.

When a paper jam does not occur (S102: NO), printing continues until a predetermined time elapses since the maintenance operation was last performed (S115: NO), and when the predetermined time has elapsed, the same maintenance as in S106to S109is performed. The maintenance operation which is performed regardless of a paper jam corresponds to a third maintenance operation of the invention. In the third maintenance operation, the purge amount, the wiping speed, and the contact force of the wiper62with respect to the ejection surfaces2aand3aare respectively equal to the purge amount D2, the wiping speed V2, and the contact force F2in the second maintenance operation.

In this embodiment, as described above, in the second maintenance operation and the third maintenance operation, the purge amount, the wiping speed, and the contact force of the wiper62with respect to the ejection surfaces2aand3aare identical. Thus, it is possible to perform the second maintenance operation and the third maintenance operation under the same control, thereby simplifying the control of the printer101.

As described above, the third maintenance operation which is performed regardless of a paper jam may be performed each time a predetermined time elapses during printing or may be performed, for example, when a state where printing is not performed continues for a long time, when the user operates the printer101to instruct maintenance, or the like.

Next, modifications in which various changes are made to this embodiment will be described. The same parts as those in this embodiment are represented by the same reference numerals, and descriptions thereof will be appropriately omitted.

Although in the foregoing embodiment, in the first maintenance operation and the second maintenance operation, all the purge amount, the wiping speed, and the contact force of the wiper62with respect to the ejection surfaces2aand3aare changed, some of the purge amount, the wiping speed, and the contact force may be changed, and others may be identical.

Although in the foregoing embodiment, the number of repetitions of pressure purging and wiping changes depending on the amount of the improvement liquid landed on the jammed recording sheet P, the first maintenance operation may be performed such that pressure purging and wiping are performed once or repeatedly multiple times regardless of the amount of the improvement liquid landed on the jammed recording sheet P.

Although in the foregoing embodiment, when it is detected that the improvement liquid has landed on the jammed recording sheet P, after the first maintenance operation, the second maintenance operation is further performed, printing may be continued immediately after the first maintenance operation. This is applied when the landed amount of the improvement liquid is very small.

At the time of pressure purging (S112) of the first maintenance operation in which the purge amount is small, the meniscus of the improvement liquid or ink in the nozzles20may be recovered. In this case, after the first maintenance operation, pressure purging or the like is not further performed, thereby preventing the improvement liquid or ink from being wastefully discharged.

With pressure purging (S112) of the first maintenance operation, the meniscus of the improvement liquid or ink in the nozzles20cannot be recovered, and when the quality of an image to be subsequently printed is degraded, the third maintenance operation may be performed or the like in accordance with a user's instruction.

Although in the foregoing embodiment, at the time of pressure purging in the second maintenance operation, the purge amount D2is the minimum amount at which the meniscus of the improvement liquid or ink in the nozzles20can be recovered, the purge amount D2may be greater.

Although in the foregoing embodiment, in the first maintenance operation, pressure purging and wiping are performed for the improvement liquid ejection head3, the invention is not limited thereto. The improvement liquid ejection head3is arranged on the upstream side in the conveying direction A from the ink ejection head2. Thus, there is little possibility that, even when a paper jam occurs, a portion of the recording sheet P where ink has landed will come into contact with the ejection surface3a. That is, there is little possibility that aggregated or precipitated ink will be attached to the ejection surface3a.

Accordingly, for example, a wiper and a substrate supporting the wiper may be provided for each of the ink ejection head2and the improvement liquid ejection head3. In this case, in the first maintenance operation, pressure purging may be performed only for the ink ejection head2, and only the wiper corresponding to the ink ejection head2may be moved to perform wiping only for the ejection surface2aof the ink ejection head2.

Although in the foregoing example, when a paper jam occurs, the maintenance operation is performed uniformly for the ejection surfaces2aof the four ink ejection heads2, the invention is not limited thereto. For example, a sensor or the like which can detect the position of the recording sheet P in more detail when a paper jam occurs may be provided, and when a paper jam occurs, the maintenance operation may be performed for one or two adjacent ink ejection heads2in the conveying direction A with no ink ejection head2interposed therebetween with respect to the position where the paper jam occurs.

For example, although the sheet sensors32and33are arranged on the downstream side of the improvement liquid ejection head3so as to sandwich the four ink ejection heads2therebetween, the number of sheet sensors may increase and the sheet sensors may be arranged between the heads3. Therefore, the paper jam position is accurately detected, and after the paper jam is detected, it becomes possible to specify a head3for which the maintenance operation is required, thereby suppressing wasteful ink consumption compared to the foregoing embodiment.

Specifically, when a paper jam occurs between two adjacent ink ejection heads2, there is no other ink ejection head2between the two ejection heads2and the position where the paper jam occurs, and one of the two ink ejection heads2is sandwiched between the ink ejection head2other than the two ink ejection heads2and the position where the paper jam occurs. Thus, the maintenance operation is performed only for the two ink ejection heads2.

When a paper jam occurs on the upstream side of the ink ejection head2arranged on the most upstream side (the leftmost side ofFIG. 1) in the conveying direction A, there is no ink ejection head2on the upstream side from the position where the paper jam occurs. Thus, the maintenance operation is performed only for the single ink ejection head2on the most upstream side.

Similarly, when a paper jam occurs on the downstream side of the ink ejection head2arranged on the most downstream side (the rightmost side ofFIG. 1) in the conveying direction A, there is no ink ejection head2on the downstream side from the position where the paper jam occurs. Thus, the maintenance operation is performed only for the single ink ejection head2on the most downstream side.

When a paper jam occurs at a position facing any ink ejection head2, there is no other ink ejection head2between the head2and the position where the paper jam occurs, and the head2is sandwiched between the position where the paper jam occurs and another ink ejection head2. Thus, the maintenance operation is performed only for the single ink ejection head2facing the paper jam position.

In this case, the maintenance operation is performed only for the ink ejection head2which is near the position where the paper jam occurs and in which the improvement liquid is likely to be attached to the ejection surface2a. Meanwhile, the maintenance operation is not performed for the ink ejection head2which is distant from the position where the paper jam occurs and in which the improvement liquid is unlikely to be attached to the ejection surface2a. Therefore, it is possible to suppress wasteful ink consumption.

Although in the foregoing embodiment, the purge amount, the wiping speed, and the contact force of the wiper62with respect to the ejection surfaces2aand3ain the third maintenance operation which is performed regardless of a paper jam are respectively equal to the purge amount D2, the wiping speed V2, and the contact force F2in the second maintenance operation, the invention is not limited thereto. The purge amount in the third maintenance operation may be greater than the purge amount D2. The wiping speed in the third maintenance operation may be higher than the wiping speed V2. The contact force of the wiper62with respect to the ejection surfaces2aand3ain the third maintenance operation may be greater than the contact force F2.

Although in the foregoing embodiment, the image quality improvement liquid is ejected onto the recording sheet P before ink is ejected onto the recording sheet P, the pretreatment liquid which is ejected onto the recording sheet P before ink is ejected onto the recording sheet P may be a liquid other than the image quality improvement liquid.

Although in the foregoing embodiment, the improvement liquid or ink in the heads2and3is forcibly discharged by so-called pressuring purging in which ink or the improvement liquid in the heads2and3is pressurized to discharge ink from the nozzles20, the invention is not limited thereto. Ink or the improvement liquid in the heads2and3may be forcibly discharged by so-called suction purging in which a suction pump is connected to halfway of the tube54connected to the purge cap52, and the suction pump is driven in a state where the ejection surface2aor3ais covered with the purge cap52, such that the space surrounded by the ejection surface2aor3aand the purge cap52has a negative pressure, and ink or the improvement liquid is sucked from the nozzles20.

Although in the foregoing embodiment, both the ink ejection head2and the improvement liquid ejection head3are line heads, one of or both the ink ejection head2and the improvement liquid ejection heads3may be so-called serial heads which eject ink or the improvement liquid from the nozzles while reciprocating in the main scanning direction.