Liquid ejecting apparatus

A liquid ejecting apparatus, including: a head having an ejection surface; a head holder; a capping mechanism for capping the ejection surface, having: a facing member with a facing surface to face the ejection surface; and a protrusion provided on the head holder for isolating, from an external space, an ejection space formed between the ejection surface and the facing surface when a tip of the protrusion contacts the facing surface; and a humidifying mechanism having: a circulation passage whose first and second ends are open to the ejection space through openings thereof provided in one of the head and the head holder; and a humidifier for humidifying an air in the passage, the humidifying mechanism being configured to collect an air in the ejection space from the opening of the first end and to supply an air humidified by the humidifier into the ejection space from the opening of the second end.

CROSS REFERENCE TO RELATED APPLICATION

The present application claims priority from Japanese Patent Application No. 2010-077747, which was filed on Mar. 30, 2010, the disclosure of which is herein incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a liquid ejecting apparatus configured to eject a liquid such as ink.

2. Discussion of Related Art

An ink-jet printer as one example of a liquid ejecting apparatus includes a head having an ejection surface in which a multiplicity of ejection openings are open for ejecting ink therethrough. When a situation in which the ink is not ejected from the ejection openings continues for a long period of time, the viscosity of the ink increases in the vicinity of the ejection openings due to evaporation, thereby causing clogging of the ejection openings. To prevent the clogging of the ejection openings, there is known a technique in which the ejection surface is covered by a cap (capping portion) and an operation for humidifying an air in the cap by an air conditioning device (humidification maintenance) is performed.

SUMMARY OF THE INVENTION

The above-indicated technique, however, suffers from the following problems. Since a humidifying mechanism needs to be provided in the cap, the cap tends to become large-sized and accordingly the printer tends to become large-sized. Further, when the humidification maintenance is performed, the cap needs to come into contact with the ejection surface of the head at a predetermined position so as to surround a group of the ejection openings, requiring a high degree of accuracy for positioning the head and the cap relative to each other. Accordingly, it undesirably takes a long time to position the head and the cap relative to each other, hindering prompt initiation of the humidification maintenance.

It is therefore an object of the invention to provide a liquid ejecting apparatus which realizes reduction in both of a time relating to initiation of a humidification maintenance and a size of the apparatus.

The above-indicated object may be attained according to a principle of the invention, which provides a liquid ejecting apparatus, comprising:

a head having an ejection surface in which ejection openings are open through which a liquid is ejected to a recording medium;

a head holder for holding the head;

a capping mechanism which is configured to cap the ejection surface and which has: a facing member having a facing surface to face the ejection surface; and a protrusion provided on the head holder and having a tip, the protrusion being configured such that the protrusion isolates, from an external space, an ejection space formed between the ejection surface and the facing surface when the tip contacts the facing surface; and

a humidifying mechanism which has: a circulation passage having, at opposite ends thereof, a first end and a second end that are open to the ejection space; and a humidifier configured to humidify an air in the circulation passage, an opening of the first end and an opening of the second end being provided in one of the head and the head holder, the humidifying mechanism being configured to collect an air in the ejection space from the opening of the first end and to supply an air humidified by the humidifier into the ejection space from the opening of the second end.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

There will be hereinafter described preferred embodiments of the invention with reference to the drawings.

Referring first toFIG. 1, there will be explained an overall structure of an ink-jet printer1, as a liquid ejecting apparatus, constructed according to a first embodiment of the invention.

As shown inFIG. 1, the ink-jet printer1has a casing1ahaving a rectangular parallelepiped shape. A discharged-sheet receiving portion31is provided on a top plate of the casing1a. An inner space of the casing1ais divided into three spaces A, B, and C which are arranged in this order in a direction from the top to the bottom of the casing1a. In the spaces A and B, there is formed a sheet traveling route connecting to the discharged-sheet receiving portion31. In the space C, there are accommodated ink cartridges39as an ink supply source from which respective inks are supplied to respective ink-jet heads10.

In the space A, there are disposed the four heads10, a conveyor unit21for conveying a sheet P as a recording medium, a guide unit for guiding the sheet P, a humidifying mechanism50(FIG. 5) used in humidification maintenance described below, and so on. A controller1pis disposed in an upper portion of the space A. The controller1pis configured to control operations of various parts of the printer1so as to control the printer1as a whole.

The controller1pcontrols, on the basis of image data supplied from an external device, a conveyance operation of the sheet P, an ink ejecting operation synchronized with the conveyance of the sheet P, a maintenance operation relating to recovery and maintenance of ejection performance, and so on, which are performed by various parts of the printer1. The maintenance operation includes flushing, purging, wiping, and the humidification maintenance. The flushing is an operation in which ink is forcibly ejected from all ejection openings14aby activating all actuators of the heads10on the basis of flushing data different from the image data. The purging is an operation in which ink is forcibly ejected from all ejection openings14aby giving a pressure to the ink in the heads10by a pump or the like. The wiping is an operation in which ejection surfaces10aof the heads10are wiped by a wiper after the flushing or the purging so as to remove foreign substances from the ejection surfaces10a. The humidification maintenance is an operation in which a humidified air is supplied into an ejection space S1(FIG. 5) partially defined by an enclosing member40. The humidification maintenance will be later explained in detail.

The conveyor unit21as a medium support portion includes belt rollers6,7, an endless conveyor belt8wound around the two belt rollers6,7, a nip roller4and a separation plate5disposed outside the conveyor belt8, and a platen9disposed inside the conveyor belt8. The belt roller7is a drive roller configured to rotate clockwise inFIG. 1by driving of a conveyance motor (not shown). In accordance with the rotation of the belt roller7, the conveyor belt8moves or runs in a direction indicated by bold arrows inFIG. 1. The belt roller6is a driven roller configured to rotate clockwise inFIG. 1by the movement of the conveyor belt8. The nip roller4is disposed so as to be opposed to the belt roller6with the conveyor belt8interposed therebetween. The sheet P supplied from an upstream side of a sheet conveyance direction in which the sheet P is conveyed is pressed by the nip roller4onto a sheet support surface8awhich is an outer surface of the conveyor belt8. The sheet P is subsequently conveyed toward the belt roller7in accordance with the movement of the conveyor belt8while being supported on the sheet support surface8a. Thus, the sheet support surface8afunctions as a medium support surface. The separation plate5is disposed so as to be opposed to the belt roller7and is configured to separate the sheet P from the sheet support surface8aand guide the sheet P to a downstream side in the sheet conveyance direction. The platen9is disposed so as to be opposed to the four heads10and supports an upper portion of the loop of the conveyor belt8from inside the loop.

Each of the four ink-jet heads10is a line head having a generally rectangular parallelepiped shape that is long in a main scanning direction. The lower surface of each head10is formed as the ejection surface10ain which a multiplicity of the ejection openings14a(FIGS. 3 and 4) are open. In a recording or image forming operation, a magenta ink, a cyan ink, a yellow ink, and a black ink are ejected from the ejection surfaces10aof the respective four heads10. The four heads10are arranged in a sub scanning direction perpendicular to the main scanning direction at a suitable pitch and are supported by the casing1avia a head holder3. The head holder3holds the heads10such that the ejection surfaces10aare opposed to the sheet support surface8aat the upper portion of the loop of the conveyor belt8and such that a clearance suitable for the recording operation is formed between the ejection surfaces10aand the sheet support surface8a. Thus, the conveyor belt8serves as a facing member having the sheet support surface8aas a facing surface that faces the ejection surfaces10a. On the head holder3, there are provided enclosing members40for the respective four heads10such that each enclosing member40surrounds the corresponding head10, specifically, the outer periphery of the ejection surface10aof the corresponding head10. The structure of each head10and the structure of the head holder3will be explained in detail.

The guide unit includes an upstream guide portion and a downstream guide portion disposed so as to sandwich the conveyor unit21therebetween. The upstream guide portion includes two guides27a,27band a pair of feed rollers26. The upstream guide portion connects a sheet supply unit1bthat will be explained and the conveyor unit21. The downstream guide portion includes two guides29a,29band two pairs of feed rollers28. The downstream guide portion connects the conveyor unit21and the discharged-sheet receiving portion31.

In the space B, the sheet supply unit1bis disposed so as to be attachable to and detachable from the casing1a. The sheet supply unit1bincludes a sheet tray23and a sheet supply roller25. The sheet tray23is a box-like member opening upward and is capable of accommodating sheets P with a plurality of kinds of size. The sheet supply roller25is configured to pick up an uppermost one of the sheets P in the sheet tray23and supply the sheet P to the upstream guide portion.

As described above, the sheet traveling route is formed in the spaces A and B so as to extend from the sheet supply unit1bto the discharged-sheet receiving portion31via the conveyor unit21. The controller1pdrives a sheet supply motor (not shown) for the sheet supply roller25, a feed motor (not shown) for the feed rollers of each guide portion, the conveyance motor, etc., on the basis of record commands received from the external device. The sheet P supplied from the sheet tray23is fed to the conveyor unit21by the feed rollers26. When the sheet P passes immediately below the heads10in the sub scanning direction, the inks are ejected from the respective ejection surfaces10a, so that a color image is formed on the sheet P. The ink ejecting operation is carried out on the basis of a detection signal from a sheet sensor32. Thereafter, the sheet P is separated from the sheet support surface8aof the conveyor belt8by the separation plate5and fed upward by the two feed rollers28. The sheet P is finally discharged onto the discharged-sheet receiving portion31through an upper opening30of the casing1a.

Here, the sub scanning direction is a direction parallel to the direction of conveyance of the sheet P by the conveyor unit21and the main scanning direction is a direction parallel to the horizontal plane and perpendicular to the sub scanning direction.

In the space C, an ink unit1cis disposed so as to be attachable to and detachable from the casing1a. The ink unit1cincludes a cartridge tray35and four ink cartridges39accommodated in the tray35. The inks in the respective cartridges39are supplied to the corresponding heads10through respective ink tubes (not shown).

Referring next toFIGS. 2-4and7, the structure of the head10will be explained. InFIG. 3, pressure chambers16and apertures15which are located under actuator units17and should be indicated by a dotted line are indicated by a solid line.

Each head10includes a reservoir unit11and a flow-passage unit12that are superposed on each other (FIG. 6), eight actuator units17(FIG. 2) fixed to an upper surface12xof the flow-passage unit12, and a flat flexible printed circuit (FPC)19(FIG. 4) bonded to each actuator unit17. In the reservoir unit11, there are formed ink passages that include a reservoir in which the ink supplied from the corresponding cartridge39is temporarily stored. In the flow-passage unit12, there are formed ink passages extending from the corresponding opening12y(FIG. 2) formed in the upper surface12xand reaching the corresponding ejection openings14aformed in the lower surface (ejection surface10a). Each actuator unit17includes piezoelectric actuators for the respective ejection openings14a.

The lower surface of the reservoir unit11has projecting portions and recessed portions. The projecting portions are bonded to respective regions of the upper surface12xof the flow-passage unit12at which the actuator units17are not disposed, namely, respective regions including the respective openings12yand enclosed by a two-dot chain line inFIG. 2. On the top of each projecting portion, there are formed openings which are connected to the reservoir and which face the corresponding openings12yof the flow-passage unit12. According to the arrangement, the reservoir and individual ink channels14are held in communication with each other through the openings. The recessed portions are opposed to the upper surface12xof the flow-passage unit12, the surfaces of the actuator units17, and the surface of the FPC19with a slight clearance therebetween.

The flow-passage unit12is a laminated body composed of nine rectangular metal plates12a,12b,12c,12d,12e,12f,12g,12h,12i(FIG. 4) which are superposed on and bonded to one another and which have substantially the same size. As shown inFIGS. 2-4, each ink passage of the flow-passage unit12includes a manifold13having at one end thereof the opening12y, sub manifolds13abranched from the manifold13, and the individual ink channels14each extending from an outlet of the corresponding sub manifold13ato the corresponding ejection opening14avia the corresponding pressure chamber16. As shown inFIG. 4, the individual ink channels14are formed for the respective ejection openings14aand include the respective apertures15each functioning as an orifice for adjusting a resistance to the ink flow. In regions of the upper surface12xto which the actuator units17are respectively bonded (hereinafter referred to as “bonded regions” where appropriate), there are formed, in matrix, openings having a generally rhombic shape and defining the respective pressure chambers16. In regions of the lower surface (the ejection surface10a) which respectively correspond to the above indicated bonded regions of the upper surface12x, the ejection openings14aare formed, in matrix, in the same pattern as the pressure chambers16.

As shown inFIG. 2, the actuator units17each having a trapezoidal shape in plan view are disposed on the upper surface12xof the flow-passage unit12in two rows such that the actuator units17of the two rows are arranged in a zigzag fashion. As shown inFIG. 3, each of the actuator units17entirely covers the openings of a group of the pressure chambers16formed within a corresponding one of the bonded regions of the upper surface12xto which the actuator units17are respectively bonded. While not shown, each actuator unit17includes a plurality of piezoelectric layers extending over the group of the pressure chambers16and electrodes which sandwich each piezoelectric layer in the thickness direction. The electrodes include individual electrodes16provided for the respective pressure chambers16and a common electrode that is common to the group of the pressure chambers16. The individual electrodes are formed on an uppermost one of the plurality of piezoelectric layers.

The FPC19includes wires that correspond to the respective electrodes of each actuator unit17, and a driver IC (not shown) is mounted on the FPC19so as to be connected to the wires. The FPC19is fixed at one end thereof to the actuator units17and at another end thereof to a control board (not shown) of the head10disposed above the reservoir unit11. Under the control of the controller1p, the FPC19transmits drive signals outputted from the control board to the driver IC and transmits signals generated by the driver IC to the actuator units17.

Referring next toFIGS. 2,5, and6, the structure of the head holder3will be explained.

The head holder3is a metal frame. To the head holder3, there are attached four enclosing members40and four pairs of joints51. One enclosing member40and one pair of joints51are provided for one head10.

As shown inFIG. 5, one pair of the joints51constitute opposite ends, i.e., a first end and a second end, of a circulation passage in a humidifying mechanism50. The joints51are disposed so as to be located adjacent to respective longitudinally opposite ends of the corresponding head10. In the humidification maintenance, an air is collected from an opening51aat the lower surface of one of the pair of joints51, namely, the left-side joint51inFIG. 5, and a humidified air is supplied from an opening51bat the lower surface of the other of the pair of joints51, namely, the right-side joint51inFIG. 5. Hereinafter, the left-side joint51(FIG. 5) relating to air collection is referred to as “the first joint” and the right-side joint51(FIG. 5) relating to humidified-air supply is referred to as “the second joint” where the two joints51need to be distinguished from each other.

As shown inFIG. 6, the joint51is generally cylindrical and includes a base portion51xand an extending portion51ythat extends from the base portion51x. A hollow space51zhaving a cylindrical columnar shape is formed through the base portion51xand the extending portion51yso as to extend in the vertical direction. The base portion51xand the extending portion51yhave mutually different outside diameters, namely, the outside diameter of the base portion51xis larger than that of the extending portion51y. The hollow space51zhas a constant diameter in the vertical direction. The extending portion51yhas, at its upper end, a cut portion formed around the entire outer circumference thereof, so as to have a tapered shape, thereby facilitating connection of tubes55,57to the extending portions51yof the respective joints51.

Each of the joints51is fixed to the head holder3such that the extending portion51yis inserted into a through-hole3aof the head holder3. The through-holes3aare formed so as to correspond to the positions of the respective joints51, namely, so as to be adjacent to one and the other of the longitudinally opposite ends of the corresponding head10. The outside diameter of the extending portion51yof the joint51is somewhat smaller than the diameter of the through-hole3a, so that there exists a slight spacing between the outer circumferential surface of the extending portion51yand the wall of the head holder3that defines the through-hole3a. This spacing is closed by being filled with a sealer or the like when the joint51is fixed to the head holder3.

The enclosing member40is formed so as to surround the periphery of the ejection surface10aof the corresponding head10in plan view, in other words, as seen from the direction orthogonal to the ejection surface10a, and includes: an elastic body41which is supported, through its fixed portion41c, on the head holder3; and a movable body42which is movable up and down. The enclosing member40may be referred to as a cap, a skirt, or a sleeve.

The elastic body41is made of an elastic material such as rubber and includes a base portion41x, a protrusion41awhich protrudes downward from the lower surface of the base portion41xand which has an inverted triangular shape in cross section, the fixed portion41cwhich is fixed to the head holder3and which has a “T” shape in cross section, and a connecting portion41D which connects the base portion41xand the fixed portion41c. The elastic body41having the above-indicated portions is formed so as to surround the periphery of the ejection surface10aof the head10in plan view. The fixed portion41cis fixed to the head holder3at its upper end with an adhesive or the like interposed therebetween, and is held by and between the head holder3and the base portion51xof the joint51in the vicinity of the through-hole3a. The connecting portion41dextends from the lower end of the fixed portion41coutwardly, i.e., in a direction away from the ejection surface10ain plan view, in a curved manner, and is connected to the lower end of the base portion41x. The connecting portion41dhas flexibility that permits deformation thereof in accordance with the up-down movement of the movable body42. There is formed, in the upper surface of the base portion41x, a recess41bin which the lower end of the movable body42is fitted.

The movable body42is made of a rigid or stiff material and is formed so as to surround the periphery of the ejection surface10aof the head10in plan view, like the elastic body41. The movable body42is configured to be movable in the vertical direction relative to the head holder3while being supported by the head holder3through the elastic body41. More specifically, the movable body42is connected to a plurality of gears43and is configured to be movable up and down in accordance with rotation of the gears43by a motor being driven under the control of the controller1p. When the movable body42is moved up and down, the base portion41xis also moved up and down together with the movable member42since the lower end of the movable body42is fitted in the recess41bof the elastic body41. That is, when the movable body42is moved up and down, the elastic body41is moved such that the base portion41xincluding the protrusion41ais moved up and down together with the movable body42while the fixed portion41cis fixed to the head holder3. Accordingly, a relative position of a tip41a1of the protrusion41awith respect to the ejection surface10ain the vertical direction changes.

By the up-down movement of the movable body42, the protrusion41aof the elastic body41is selectively placed at one of a contact position (shown inFIG. 5) at which the tip41a1of the protrusion41acontacts the sheet support surface8aof the conveyor belt8and a retracted position (shown inFIG. 6) at which the tip41a1is separated away from the sheet support surface8a. As shown inFIG. 5, when the protrusion41ais located at the contact position, an ejection space S1formed between the ejection surface10aand the sheet support surface8ais isolated from an exterior space S2. As shown inFIG. 6, when the protrusion41ais located at the retracted position, the tip41a1of the protrusion41ais located between the ejection surface10aand the sheet support surface8a, namely, the tip41a1is located nearer to the sheet support surface8a, as compared with the ejection surface10a. That is, when the protrusion41ais located at the retracted position, a distance by which the tip41a1is distant from the sheet support surface8ais smaller than a distance by which the ejection surface10ais distant from the sheet support surface8a.

The protrusion41ais separated away from the ejection surface10a(the lower surface of the head10shown inFIG. 2) over the entire periphery of the ejection surface10a, in plan view, namely, as seen from the direction orthogonal to the ejection surface10a. Further, the protrusion41asurrounds the periphery of the ejection surface10aso as to form a trapezoidal shape, in plan view, having its upper base which is located in the vicinity of the one of the longitudinally opposite end portions of the head10(i.e., the lower end of the head10as seen inFIG. 2) and its lower base which is located in the vicinity of the other of the longitudinally opposite end portions of the head10(i.e., the upper end of the head10as seen inFIG. 2). In other words, the contour of the protrusion41ain plan view is a trapezoidal shape.

Here, the positional relationship between the protrusion41aand the ejection surface10a, i.e., the lower surface of the head10shown inFIG. 2, is considered in terms of a distance, in plan view, namely, a distance as seen from a direction orthogonal to the ejection surface10a(as seen from the bottom of the head10), by which the ejection surface10aand the tip41a1of the protrusion41aare spaced apart from each other. The distance may be hereinafter referred to as “separation distance” where appropriate. More specifically, a separation distance D2by which the ejection surface10aand the tip41a1of the protrusion41aare spaced apart from each other in the sub scanning direction is smaller than a separation distance D1by which the ejection surface10aand the tip41a1of the protrusion41aare spaced apart from each other in the main scanning direction across the opening51b. The above-indicated separation distance D1in the main scanning direction is the same at opposite ends of the ejection surface10ain the main scanning direction and is constant along the sub scanning direction. On the other hand, the above indicated separation distance D2in the sub scanning direction is the same at opposite ends of the ejection surface10ain the sub scanning direction, but is not constant along the main scanning direction. That is, the above-indicated separation distance D2in the sub scanning direction gradually decreases from the opening51btoward the opening51aalong the main scanning direction.

A pair of regulating plates60as a regulator are provided at the other of the longitudinally opposite end portions of the head10(i.e., the upper end portion of the head10inFIG. 2). The regulating plates60are fixed to respective side surfaces of the flow-passage unit12at the other of the longitudinally opposite end portions and extend along the sub scanning direction from the respective side surfaces near to the tip41a1of the protrusion41a. According to the arrangement, an area that encloses the opening51bis defined, in plan view, in other words, as seen from the direction orthogonal to the ejection surface10a, by an end of the ejection surface10athat constitutes the other of the longitudinally opposite end portions of the head10, the pair of regulating plates60, and the tip41a1of the protrusion41a. The lower end of each regulating plate60is located at the same height level as the ejection surface10a.

Referring next toFIGS. 5 and 7, the humidifying mechanism50will be explained.

As shown inFIG. 5, the humidifying mechanism50includes the joints51, tubes55,56,57, a pump53, and a tank54. One pair of joints51, namely, two joints51, are provided for one head10while one pump53and one tank54are provided in the printer1so as to be common to the four heads10, as shown inFIG. 7. The tube55has a main portion55acommon to the four heads10and four branched portions55bwhich are branched from the main portion55aand which extend to the first joints51of the respective four heads10while the tube57has a main portion57acommon to the four heads10and four branched portions57bwhich are branched from the main portion57aand which extend to the second joints51of the respective four heads10.

One end of the tube55, in other words, each of ends of the respective branched portions55bof the tube55, is fitted to the extending portion51yof the first joint51(the left-side joint51inFIG. 5) of the corresponding head10while another end of the tube55, in other words, an end of the main portion55aremote from the branched portions55b, is connected to the pump53. That is, the tube55connects the hollow spaces51zof the first joints51of the respective heads10and the pump53for allowing fluid communication therebetween. The tube56connects the pump53and the tank54for allowing fluid communication therebetween. One end of the tube57, in other words, each of ends of the respective branched portions57bof the tube57, is fitted to the extending portion51yof the second joint51(the right-side joint51inFIG. 5) of the corresponding head10while another end of the tube57, in other words, an end of the main portion57aremote from the branched portions57b, is connected to the tank54. That is, the tube57connects the hollow spaces51zof the second joints51of the respective heads10and the tank54for allowing fluid communication therebetween.

The tank54stores, at its lower space, water and, at its upper space, an air humidified by the water stored in the lower space. The tube56is connected to the tank54at a height level lower than the water surface of the tank54and is in communication with the lower space of the tank54The tube57is connected to the tank54at a height level higher than the water surface of the tank54and is in communication with the upper space of the tank54. A check valve (not shown) is provided on the tube56so as to prevent the water in the tank54from flowing into the pump53, thereby allowing an air to flow only in a direction indicated by arrows inFIG. 5.

Referring next toFIGS. 5-7, there will be explained operations of various parts of the printer1during the humidification maintenance. The humidification maintenance is carried out after the ink ejecting operation has not been carried out for a predetermined time, for instance.

During a series of procedure in the humidification maintenance, the heads10, the head holder3, and the conveyor belt8are kept fixed at respective locations. The head holder3is fixed so as to hold each head10such that a predetermined clearance suitable for the recording operation is formed between the ejection surface10aand the sheet support surface8aof the conveyor belt8. It is noted that the following explanation will be made with respect to the humidification maintenance performed on one head10.

In the humidification maintenance, the controller1pinitially controls such that the movable body42of the enclosing member40is moved downward by the rotation of the gears43. The protrusion41aof the enclosing member40is kept located at the retracted position shown inFIG. 6except when the humidification maintenance is carried out. For instance, the protrusion41ais kept located at the retracted position during the recording operation. The downward movement of the movable body42causes the protrusion41ato be moved to the contact position shown inFIG. 5, so that the ejection space S1isolated from the external space S2is formed.

Subsequently, the controller1pdrives the pump53, whereby the air in the ejection space S1is collected from the opening51aof the first joint51(the left-side joint51inFIG. 5). The air collected from the opening51areaches the pump53through the hollow space51zof the first joint51and the space of the tube55, and reaches the tank54through the space of the tube56. The air is supplied to the lower space of the tank54, namely, to the underwater. The air is humidified by the water in the tank54and is discharged from the upper space of the tank54. The humidified air passes through the space of the tube57and is supplied into the ejection surface S1from the opening51bof the second joint51(the right-side joint51inFIG. 5). InFIG. 5, solid arrows indicate a flow of the air before humidified while hollow arrows indicate a flow of the air after humidified. Thus, the humidified air is supplied into the ejection space S1, thereby preventing thickening of the ink in the vicinity of the ejection openings14aand clogging of the ejection openings14a. Further, even if the ink in the vicinity of the ejection openings14ais thickened, the water component owing to the humidified air is supplied to the thickened ink, whereby the ink thickening is eliminated and the condition of the ink recovers.

The controller1pis configured to control, together with the driving of the pump53, switching valves58(FIG. 7) as an adjustor provided on the respective branched portions55b,57b, to thereby selectively adjust respective air flows in the branched portions55b,57b. Accordingly, the humidification maintenance may be performed on only desired one or ones of the heads10. Alternatively, the humidification maintenance may be performed on all of the heads10at one time.

After the pump53has been driven for a predetermined time, the controller1pcontrols the pump53to stop driving. Thus, the humidification maintenance is completed. Thereafter, the controller1pcontrols such that the movable body42of the enclosing member40is moved upward by the rotation of the gears43, whereby the protrusion41ais moved from the contact position shown inFIG. 5to the retracted position shown inFIG. 6, and the printer1is placed in a state in which the recording operation can be restarted.

In the present embodiment, each enclosing member4and the conveyor belt8constitute a capping mechanism configured to cap the ejection space S1. The first and second joints51and the tubes55,56,57constitute a circulation passage of the humidifying mechanism50. The pump53and the tank54constitute a humidifier. The main portion55aof the tube55, the tube56, and the main portion57aof the tube57constitute a main passage portion of the circulation passage. The branched portions55bof the tube55constitute respective branched air-collect passage portions of the circulation passage while the branched portions57bof the tube57constitute respective branched air-supply passage portions of the circulation passage.

According to the printer1of the present embodiment, the capping mechanism is realized by providing each enclosing member40on the head holder3, thereby eliminating the conventionally required positioning of the head and the conventional cap relative to each other before initiation of the humidification maintenance and accordingly shortening a time required before the initiation of the humidification maintenance. Further, the present printer1in which the openings51a,51bof the respective ends of the circulation passage of the humidifying mechanism50are formed in the head holder3does not need a large-sized cap in which the humidifying mechanism50is disposed, resulting in a size reduction of the printer1. Moreover, owing to the humidification mechanism50constructed as described above, the air in the ejection space S1is collected from the opening51aof the first end (the first joint51) of the circulation passage and the air humidified by the water in the tank54is supplied into the ejection space S1from the opening51bof the second end (the second joint51) of the circulation passage, so that the air in the ejection space S1can be promptly replaced with the humidified air.

In the present printer1, the ejection space S1is isolated from the external space S2by abutting contact of the tip41a1of the protrusion41awith the sheet support surface8aof the conveyor belt8, whereby the ejection surface10ais capped. Accordingly, there is no need to move each head10between a recording position at which the ejection surface10ais opposed to the sheet support surface8aand a cap standby space which is distant from each head10and in which the above-described conventional cap is kept located during standby. Therefore, the humidification maintenance can be promptly initiated and the recording operation after the humidification maintenance can be promptly restarted. That is, it is possible to shorten a time relating to the humidification maintenance, namely, a time before and after the humidification maintenance. Further, it is not required to ensure the standby space as required by the above described conventional cap and a route through which the head10is moved for the humidification maintenance between the recording position and the standby space. Therefore, the printer1can be downsized with higher reliability. In addition, since the openings51a,51bof the respective joints51are formed in the head holder3, there is no need to form any opening in the conveyor belt8or the platen9, obviating a trouble that would hinder supporting and conveyance of the sheet P in the recording operation.

The air in the ejection space S1is circulated through the tubes55-57, etc., so as to allow humidification of the air while reducing a water consumption amount.

Where the openings of the first and second ends of the circulation passage are formed in the conveyor belt8or the platen9, there may arise a risk that the openings are closed by the ink ejected onto the conveyor belt8or the platen9in flushing or purging. The printer1according to the present embodiment does not suffer from such a problem.

As shown inFIG. 2, the openings51a,51bof the respective joints51are disposed such that the ejection surface10ais located therebetween in plan view, in other words, as seen from the direction orthogonal to the ejection surface10a. Accordingly, the humidified air can be promptly supplied around the ejection openings14a, resulting in efficient humidification with respect to the entirety of the ejection openings14a.

As shown inFIG. 2, the openings51a,51bof the respective joints51are disposed such that the ejection surface10ais located therebetween in the longitudinal direction of the ejection surface10a, i.e., in the main scanning direction, in plan view, in other words, as seen from the direction orthogonal to the ejection surface10a. Accordingly, the humidified air can be promptly supplied around the ejection openings14a, and effective humidification is realized with respect to the entirety of the ejection openings14aeven where the ejection surface10ais long in one direction (the main scanning direction).

As shown inFIG. 2, the above-indicated separation distance D2by which the ejection surface10aand the tip41a1of the protrusion41aare spaced apart from each other in the sub scanning direction is smaller than the above indicated separation distance D1by which the ejection surface10aand the tip41a1of the protrusion41aare spaced apart from each other in the main scanning direction across the opening51b. According to the arrangement, the humidified air supplied from the opening51bis not likely to flow toward widthwise opposite sides of the ejection surface10a, namely, regions S1aand S1bin the ejection space S1indicated inFIG. 2, in plan view, but tends to flow in a region of the ejection space S1facing the ejection surface10a. Therefore, more effective humidification is realized with respect to the entirety of the ejection openings14a.

Further, in the present embodiment, the separation distance D2by which the ejection surface10aand the tip41a1of the protrusion41aare spaced apart from each other in the sub scanning direction gradually decreases from the opening51btoward the opening51aalong the main scanning direction. Thus, the separation distance D2is gradually decreased along the flow of the humidified air in the ejection space S1, whereby the humidified air can be effectively supplied to the ejection openings14alocated on the downstream side of the flow, namely, the ejection openings14alocated at the lower portion of the ejection surface10as seen inFIG. 2.

FIG. 2shows the positional relationship between the tip41a1of the protrusion41aand the flow-passage unit12of the head10. The effects owing to the above-described separation distances are the most remarkable in a case in which the conditions of the separation distances are satisfied with respect to an average value of separation distances between the protrusion41aand the ejection surface10ain the vertical direction. This is because the flow of the humidified air in the ejection space S1is three dimensional including the vertical direction and depends on a cross-sectional area in the vertical direction of a space in which the humidified air flows.

The flow of the humidified air supplied into the ejection space S1from the opening51bis regulated by the regulating plates60. That is, the humidified air supplied from the opening51bis restrained from flowing toward the widthwise opposite sides of the ejection surface10a, namely, the regions S1aand S1bin the ejection space S1inFIG. 2, in plan view, but tends to flow in the region of the ejection space S1facing the ejection surface10a. Therefore, more effective humidification is realized with respect to the entirety of the ejection openings14a.

Where the head holder3is considered as including the enclosing member40and the joints51, a recess3xis formed in the head holder3as shown inFIG. 6and the openings51a,51bof the joints51are located at the bottom of the recess3x. The recess3is formed between the ejection surface10aand the tip41a1of the protrusion41aso as to surround the ejection surface10a, in plan view. The bottom of the recess3xat which the openings51a,51bare formed is located at a height level higher than the ejection surface10a. Accordingly, the foreign substances such as ink held on the top of a wiper during wiping are prevented from adhering to the openings51a,51b. Hence, it is possible to avoid operation failures in the humidification maintenance which would be otherwise caused by adhesion of the foreign substances to the openings51a,51b.

The openings51a,51bof the first and second joints51which constitute respectively the first and second ends of the circulation passage are formed in the head holder3. Accordingly, the adhesion of the foreign substances to the openings51a,51bduring wiping can be more easily restrained, as compared with an arrangement in which the openings51a,51bare formed in the head10.

In the present printer1constructed as described above, the protrusion41amoves up and down, together with the movable body42. Accordingly, the capping can be conducted, in other words, the ejection space S1can be isolated from the external space S2, by moving only the protrusion41aup and down with the head10and the conveyor belt8kept fixed. Where the head10and/or the conveyor belt8is/are moved, a relatively large moving mechanism and a relatively long time for the movement are required. In the present embodiment, however, the protrusion41acan be moved by a relatively simple moving mechanism and a time required for the movement of the protrusion41ais shortened. Therefore, the humidification maintenance can be more promptly initiated and the recording operation after the humidification maintenance can be more promptly restarted.

As shown inFIG. 2. the protrusion41ais formed to surround the entire periphery of the ejection surface10ain plan view and is separated away from the ejection surface10aover the entire periphery thereof. Accordingly, it is possible to prevent the wiper from coming into contact with the protrusion41aduring wiping.

Where four pumps53and four tanks54are used, namely, where the pump53and the tank54are provided for each of the four heads10and the tubes55,57are provided for each of the four heads10, the humidifying mechanism50inevitably becomes large-sized. In contrast, in the present embodiment, one pump53and one tank54are provided so as to be common to the four heads10and the tubes55,57include the respective main portions55a,57aand the respective four branched portions55b,57b, as shown inFIG. 7. Accordingly, the humidifying mechanism50can be downsized even where the printer1includes a plurality of heads10.

The controller1pis configured to control the switching valves58provided on the respective branched portions55b,57bshown inFIG. 7so as to selectively adjust the respective air flows in the branched portions55b,57b, thereby making it possible to allow the air flows in only a part of the branched portions55b,57b. In other words, the humidified air can be supplied only to the ejection space(s) S1of desired one or ones of the heads10, permitting appropriate humidification maintenance depending upon various situations.

The controller1pis configured to control driving of the pump53such that the humidified air whose volume is not smaller than the volume of the ejection space S1is supplied form the opening51binto the ejection space S1. Accordingly, the air in the ejection space S1is entirely replaced with the humidified air, so that the humidified air can be appropriately supplied into the ejection space S1.

The upper space of the tank54, i.e., the space above the water surface, has a volume not smaller than a total of the volumes of the ejection spaces S1of the respective four heads10. Accordingly, the air in the ejection spaces S1of all of the four heads10can be speedily replaced. In other words, the humidified air can be speedily and efficiently supplied into the ejection surfaces S1of all of the four heads10.

The sheet support surface8aof the conveyor belt8with which the tip41a1of the protrusion41ais to come into contact is entirely flat, ensuring reliable capping. Other structure is similar to that in the illustrated first embodiment.

Referring next toFIG. 8, there will be explained an ink-jet printer according to a second embodiment of the invention. The printer in this second embodiment differs from the printer in the illustrated first embodiment only in the shape, in plan view, formed by the protrusion of the enclosing member.

A protrusion241aof the enclosing member in the second embodiment extends so as to form a rectangular shape, in plan view, similar to the contour of the ejection surface10a, i.e., the lower surface of the head10shown inFIG. 8. In other words, the contour of the protrusion241ain plan view is a rectangular shape. A separation distance, in plan view, namely, a separation distance as seen from the direction orthogonal to the ejection surface10a, by which the ejection surface10aand a tip241a1of the protrusion241aare spaced apart from each other is determined in a similar manner to that in the illustrated first embodiment. More specifically, a separation distance D2by which the ejection surface10aand the tip241a1of the protrusion241aare spaced apart from each other in the sub scanning direction is smaller than a separation distance D1by which the ejection surface10aand the tip241a1are spaced apart from each other in the main scanning direction across the opening51b. The separation distance D1in the main scanning direction is the same at opposite ends of the ejection surface10ain the main scanning direction and is constant along the sub scanning direction. The separation distance D2in the sub scanning direction is the same at opposite ends of the ejection surface10ain the sub scanning direction and is constant along the main scanning direction.

The present embodiment enjoys the same effects as in the illustrated first embodiment except for the effect offered by the separation distance D2which is arranged to gradually decrease from the opening51btoward the opening51aalong the main scanning direction.

Referring next toFIG. 9, there will be explained an ink-jet printer according to a third embodiment of the invention. The printer in this third embodiment differs from the printer in the illustrated first embodiment only in that the openings of the circulation passage are formed not in the head holder3, but in the head10. Other structure is similar to that in the illustrated first embodiment.

In the third embodiment, vertically extending through-holes351are formed in the head10, in place of the joints51. Two through-holes351are formed in one head10at respective positions corresponding to those of the joints51. Each through-hole351consists of a cylindrical through-hole352formed in the reservoir unit11and a cylindrical through-hole353formed in the flow-passage unit12. The through-holes352,353have the same center axis and mutually different diameters. That is, the diameter of the through-hole353is larger than that of the through-hole352.

A recess310xpartially provides the through holes353is formed in the surface of the head10, i.e., the ejection surface10a, and two openings of the circulation passage are formed in the bottom of the recess310x. While only one (351a) of the two openings is shown inFIG. 9, the other of the openings is similarly formed. In this arrangement, the bottom of the recess310xin which the openings (351a) are formed is located at a height level higher than the ejection surface10a, thereby preventing the foreign substances such as ink held on the top of a wiper during wiping from adhering to the openings (351a). Hence, it is possible to avoid operation failures in the humidification maintenance which would be otherwise caused by adhesion of the foreign substances to the openings (351a).

As in the illustrated first embodiment, the humidification maintenance can be promptly initiated and the recording operation after the humidification maintenance can be promptly restarted without causing a trouble to supporting and conveyance of the sheet P during the recording operation while ensuring downsizing of the printer. More specifically, since the enclosing member40is provided on the head holder3so as to realize the capping mechanism, there is no need to move the head10to the above-described cap standby position which is distant from the head10and in which the above-described conventional cap is kept located during standby. Therefore, the humidification maintenance can be promptly initiated and the recording operation after the humidification maintenance can be promptly restarted. Further, it is not required to ensure the standby space as required by the above-described conventional cap and a route through which the head10is moved for the humidification maintenance between the recording position and the standby space. Therefore, the printer1can be downsized. In addition, since the openings of the circulation passage are formed in the head10, there is no need to form any opening in the conveyor belt8or the platen9, obviating a trouble that would hinder supporting and conveyance of the sheet P during the recording operation.

According to the third embodiment, the openings of the circulation passage are formed in the head10. In particular, the other of the openings from which the humidified air is supplied is formed in the head10, whereby the opening can be disposed nearer to the ejection openings14a, resulting in effective supply of the humidified air to the ejection openings14a.

In the third embodiment, the openings of the circulation passage are disposed such that a group of the ejection openings14aconsisting of all ejection openings14aformed in the ejection surface10aare located between the two openings in plan view, namely, the openings are respectively disposed on outer sides of the two outermost actuator units17which are located at opposite ends in the main scanning direction shown inFIG. 2. Accordingly, the entirety of the ejection openings14acan be effectively humidified.

In the third embodiment, a separation distance, in plan view, namely, a separation distance as seen from the direction orthogonal to the ejection surface10a, by which the group of the ejection openings (corresponding to the eight actuator units17) and the tip41a1of the protrusion41aare spaced apart from each other in the sub scanning direction is smaller than a separation distance, in plan view, by which the group of the ejection openings and the tip41a1of the protrusion41aare spaced apart from each other in the main scanning direction across the other opening. According to the arrangement, the humidified air supplied from the other opening is not likely to flow toward widthwise opposite sides of a region of the group of the ejection openings in the ejection space S1, in plan view, but tends to flow in a region of the ejection space S1facing the group of the ejection openings, namely, in a region of the ejection space S1corresponding to the actuator units17. Therefore, more effective humidification is realized with respect to the entirety of the ejection openings14a.

Further, in the third embodiment, the above-indicated separation distance by which the group of the ejection openings (corresponding to the eight actuator units17) and the tip41a1of the protrusion41aare spaced apart from each other in the sub scanning direction gradually decreases from the other of the openings to the one351aof the openings along the main scanning direction. Thus, the separation distance is gradually decreased along the flow of the humidified air in the ejection space S1, whereby the humidified air can be effectively supplied to the ejection openings14alocated on the downstream side of the flow, namely, the ejection openings14alocated at the lower portion of the ejection surface10as seen inFIG. 2.

The third embodiment offers effects similar to those in the illustrated first embodiment by the structure similar to that in the illustrated first embodiment.

The elastic body41of the enclosing member40in the third embodiment is held by the head holder3such that the fixed portion41cis fitted in a fitting recess3bof the head holder3, as shown inFIG. 9. Further, one end of each of the tubes55,57is fixed to the surface of the reservoir unit11in which the upper open end of the corresponding through-hole352is formed, so as to cover the through-hole352.

Referring next toFIG. 10, there will be explained an ink-jet printer according to a fourth embodiment of the invention. The printer in this fourth embodiment differs from the printer in the illustrated first embodiment only in that the surface with which the tip41a1of the protrusion41acomes into contact is not the sheet support surface8aof the conveyor belt8. Other structure is similar to that in the illustrated first embodiment.

In the printer of the fourth embodiment, a plate member70formed of metal, plastic, or the like is used as the facing member to face the ejection surface10aof each head10. The ejection space S1is isolated from the external space S2by abutting contact of the protrusion41awith an upper surface70a, as the facing surface, of the plate member70, whereby the ejection surface10ais capped. For permitting the upper surface70aof the plate member70to face the ejection surface10a, in a state in which the head10and the conveyor unit21are kept fixed, the plate member70disposed at a position at which the plate member70does not overlap, in plan view, the head10and the conveyor unit21may be horizontally moved so as to be inserted between the ejection surface10aand the sheet support surface8a. Instead, in a state in which the plate member70is kept fixed at a position at which the plate member70does not overlap, in plan view, the head10and the conveyor unit21and in which the conveyor unit21is kept fixed, the head10may be horizontally moved such that the ejection surface10afaces the upper surface70aof the plate member70. Further, in a state in which the plate member70is kept fixed below the conveyor belt8and in which the head10is kept fixed, the conveyor unit21may be horizontally moved such that the upper surface70aof the plate member70faces the ejection surface10aof the head10.

As in the illustrated embodiments, the capping mechanism is realized in this fourth embodiment by providing each enclosing member40on the head holder3, thereby eliminating the conventionally required positioning of the head10and the above-described conventional cap relative to each other before initiation of the humidification maintenance and accordingly shortening a time required before the initiation of the humidification maintenance. Further, the openings51a,51bof the respective ends of the circulation passage of the humidifying mechanism50are formed in the head holder3, so that a large-sized cap in which the humidifying mechanism50is disposed is not needed, resulting in a size reduction of the printer1. Moreover, owing to the humidification mechanism50constructed as described above, the air in the ejection space S1is collected from the opening51aof the first end of the circulation passage and the air humidified by the water in the tank54is supplied into the ejection space S1from the opening51bof the second end of the circulation passage, so that the air in the ejection space S1can be promptly replaced with the humidified air.

While the presently preferred embodiments of the invention have been explained, it is noted that the invention is not limited to the details of the illustrated embodiments, but may be embodied with various changes and modifications, which may occur to those skilled in the art, without departing from the spirit and scope of the invention defined in the attached claims.

The material, the shape, the position, etc., of the regulator are not particularly limited. For instance, the regulator may be formed to extend in any arbitrary direction other than the sub scanning direction. The regulator may be fixed to the head holder3or the enclosing member40, in place of the head10. The regulator is not limited to the illustrated plate-like shape, but may have any shape.

The regulator may be eliminated.

As the moving mechanism for moving the protrusion, the gears43are utilized in the illustrated embodiments. Any other means such as a solenoid and a cam mechanism using a link may be utilized.

In the illustrated embodiments, when the protrusion41ais located at the retracted position, the tip41a1of the protrusion41ais located between the ejection surface10aand the sheet support surface8aas shown inFIG. 6, namely, the tip41a1is located nearer to the sheet support surface8a, as compared with the ejection surface10a. The tip41a1may be otherwise located when the protrusion41ais located at the retracted position. For instance, for preventing paper jamming, it is preferable that the tip41a1be preferably located at a height level higher than the ejection surface10a, namely, the tip41a1is preferably more distant from the sheet support surface8a, as compared with the ejection surface10a.

In the illustrated embodiments, the protrusion is arranged to be movable. However, the protrusion may be otherwise arranged. For instance, the protrusion may be immovably fixed to the head holder, and the relative position of the tip of the protrusion with respect to the ejection surface may be made constant. In this instance, the relative position of the tip of the protrusion with respect to the ejection surface may be changed by moving up and down the head holder or the medium support surface of the medium support portion, thereby allowing the protrusion to be selectively placed at one of the contact position and the retracted position.

The material, the shape, etc., of the protrusion are not particularly limited. For instance, the protrusion may be formed of a rigid material, in place of the elastic material. The protrusion may protrude in a direction inclined with respect to the vertical direction. The cross-sectional shape of the protrusion may have a rectangular shape, in place of the inverted triangular shape. That is, the protrusion may not be tapered. The protrusion may not be separated away from the ejection surface over the entire periphery of the ejection surface, in plan view, but may partially contact the ejection surface or may contact the ejection surface over the entire periphery thereof, in plan view. The protrusion may extend so as to form any shape, in plan view, other than the trapezoidal shape and the rectangular shape. In other words, the contour of the protrusion in plan view may not limited to the illustrated trapezoidal shape and rectangular shape. The separation distance, in plan view, by which the ejection surface10a(or the group of the ejection openings in the case where the openings of the circulation passage are formed in the head) and the tip of the protrusion are spaced apart from each other may not be particularly limited. For instance, the above-indicated separation distance D2in the sub scanning direction may be zero. The manner in which the protrusion is held by the head holder may be variously changed.

The recess3xformed in the head holder and the recess310xformed in the head may not be formed so as to surround the periphery of the ejection surface10ain plan view. For instance, the recess may be formed only at a portion where the opening of either one of the two opposite ends (the first and second ends) of the circulation passage is formed or only at portions where the openings of the respective two opposite ends of the circulation passage are formed.

The shape and the position of the opening of each of the first and second ends of the circulation passage are not particularly limited as long as the opening is formed in the head or the head holder and is open to the ejection surface. For instance, one of the openings may be formed in the head and the other of the openings may be formed in the head holder. Each opening may be formed in the protrusion. In place of forming the recess3x,310xin the head holder or the head, the opening of at least one of the two opposite ends of the circulation passage may be formed at the same height level as the ejection surface10a. The openings may be disposed such that the ejection surface10a(or the group of the ejection openings in the case where the openings are formed in the head) is located between the openings in the sub scanning direction in plan view. Alternatively, the openings may be disposed such that the ejection surface10a(or the group of the ejection openings in the case where the openings are formed in the head) is not located between the openings in plan view. For instance, the openings may be disposed on the same one of opposite sides of the ejection surface10aor the group of the ejection openings.

The pump53and the tank54may be provided for each of the four heads10, and the tube55and the tube57may be provided for each of the four heads10.

In the illustrated embodiments, the pump53and the tank54function as the humidifier. Various other means may be employed as the humidifier as long as the humidifier is configured to humidify the air in the circulation passage. For instance, the pump53may be eliminated, and only the tank54may be utilized for humidification. A heating means such as a heater may be additionally used. An ultrasonic humidifier may be used. A porous member such as a sponge impregnated with water, a cloth or the like may be disposed in the circulation passage for humidification.

The positions of the constituent elements of the humidifying mechanism are not particularly limited. For instance, some (the joints51, etc.,) of those may be provided on the head or the head holder and the rest (the tubes55-57, the pump53, the tank54, etc.,) may be provided at arbitrary positions in the printer.

The medium support portion is not limited to the illustrated conveyor unit including the conveyor belt, but may be a platen roller, a drum or the like, as long as the medium support portion is configured to support the recording medium. The medium support portion may not be configured to move, like the conveyor belt, for conveying the recording medium. The head may be moved for performing the recording operation on the recording medium supported by a stationary medium support portion.

The facing member is not limited to the illustrated conveyor belt and plate member, but any suitable member may be used as long as the facing member has the facing surface that is to face the ejection surface.

The ejection surface or the group of ejection openings may not be long in one direction.

The present invention is applicable to both of a line-type printer and a serial-type printer. Further, the present invention is applicable to a facsimile machine, a copying machine, etc., other than the printer. The present invention is applicable to apparatus configured to eject a liquid other than the ink.

The recording medium is not limited to the illustrated sheet P, but may be any kind of recordable medium.