Ink jet recording head maintenance apparatus and ink jet recording apparatus

An ink jet recording head maintenance apparatus of this invention is provided with a plurality of wiping members having different wiping forces to remove residual ink or foreign substances from the nozzle face of the nozzle plate of the recording head. When performing wiping operation, the optimum wiping member is selected from among the plurality of wiping members in accordance with a change in the kind of adhering substances and adhering condition. It is therefore possible to select the optimum wiping member and achieve a good wiping effect without increasing the number of counts of wiping operation.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to an ink jet recording head maintenance apparatus and more particularly to a maintenance apparatus of an ink jet recording head which ejects drops of ink drops through a nozzle provided in a nozzle plate, and an ink jet recording apparatus having the maintenance apparatus.

2. Discussion of the Background

There has been in widespread use an ink jet recording apparatus which performs printing by selectively ejecting ink drops to a recording medium from a plurality of nozzles arranged in a nozzle plate. In such an ink jet recording apparatus, the ink is likely to remain around the nozzles after the ejection of ink drops. The ink thus remaining, if dried/solidified, will cause deviation of direction of ink ejection or blocking of nozzles, and accordingly, defective ink ejection and defective printing are easy to occur. Furthermore, foreign substances such as dusts on the recording medium and dusts in the air will attach around the nozzles, similarly causing the deviated direction of ink ejection and the blocked nozzles to consequently result in the defective ink ejection and defective printing.

Therefore, there have been conventionally proposed various kinds of ink jet recording apparatus designed to remove ink or foreign substances remaining around the nozzles. For example, there has been proposed the technology that, with a wiping member formed of an elastic material or other pressed against the nozzle plate (a nozzle face of the nozzle plate), the wiping member is slid on the nozzle plate in this state to thereby wipe off the foreign substances holding on the nozzle plate. Furthermore, in Japanese Unexamined Patent Publications No. 2001-219567 and No. 2002-283590, there has been disclosed the technology that an improved adhering substance wiping effect is achieved by using a single wiping member at an increased wiping frequency. Furthermore, to achieve the adhering substance wiping effect, there has been disclosed the technology in Japanese Unexamined Patent Publication No. 2000-127417 that a groove is formed in a single wiping member to enable adjusting the angle of contact of the wiping member in relation to the nozzle face by utilizing the elastic deformation of the wiping member.

Furthermore, in Japanese Unexamined Patent Publication No. Hei 9-76517, there has been disclosed the technology that the optimum wiping effect is gained by setting the rubber hardness of a single wiping member within the range of 40 to 60 degrees of A Hardness specified in JIS K6301. Furthermore, to ensure the same wiping force of the wiping member notwithstanding a change in a distance between the recording head and the recording medium, a technology is disclosed that has achieved the wiping effect by the optimum arrangement of a plurality of wiping members of different free length and thickness so that the amount of deflection of the wiping member and the angle of contact of the wiping member with the nozzle face will vary in synchronization with a change in a distance between the recording head and the recording medium, in Japanese Unexamined Patent Publication No. 2000-177113.

The single wiping member, however, sometimes fails to properly function in response to a change in the kind of adhering substances (ink, fine particles of paper, dusts, etc.) or change in the substance conditions (e.g., an increase in ink adhesion caused by environmental changes, and an increase in ink adhesion by the length of time when ink deposit is left unremoved). The increased wiping frequency of the single wiping member, as previously stated for example in Japanese Unexamined Patent Publications No. 2001-219567 and No. 2002-283590, can remove a firmly adhering substance only to some extent. It becomes necessary to improve the wiping operating force of the wiping member, which, however, will further increase the wiping frequency, causing such drawbacks as an easy-to-abrade wiping member, a shortened wiping member life, and consequently a deteriorated wiping effect.

Furthermore, setting the rubber hardness of the single wiping member within 40 to 60 degrees of A Hardness specified in JIS K6301 as stated in Japanese Unexamined Patent Publication No. Hei 9-76517, the wiping member will not be applicable to the case where a greater wiping operating force of the wiping member is needed. Furthermore, in Japanese Unexamined Patent Publication No. 2000-177113, although nearly the same wiping member operating force is adopted in accordance with the operating condition, application to a condition where the greater operating force of the wiping member is needed is not performed.

SUMMARY OF THE INVENTION

An object of this invention, therefore, is to achieve a good wiping effect by selecting the optimum wiping member without increasing the wiping frequency in case of a change in the kind of adhering substances (ink, fine particles of paper, dust, etc.) and a change in an adhering condition (an increase in ink adhesion caused by environmental changes, and an increase in ink adhesion caused by the length of time when ink deposit is left unremoved).

Another object of this invention is to prolong the life of the wiping member, and to maintain a good wiping performance of the wiping member for a prolonged period of time.

Another object of this invention is to maintain a good ink ejection performance at the time of printing for a prolonged period of time to thereby improve reliability of printing.

These objects of this invention are achieved by the provision of new ink jet recording head maintenance apparatus and ink jet recording apparatus of this invention.

Therefore, according to the new ink jet recording head maintenance apparatus and the ink jet recording apparatus, there are provided a plurality of wiping members at least one of which differs in the wiping force against the nozzle face, to thereby remove ink and foreign substances remaining on the nozzle face of the nozzle plate of the ink jet recording head. Thus the optimum wiping member can be selected from among a plurality of wiping members to achieve a good wiping effect in accordance with a change in the type of adhering substances (ink, fine particles of paper, dust, etc.) and a change in an adhering condition (an increase in ink adhesion caused by environmental changes, and an increase in ink adhesion caused by the length of time when the ink deposit is left unremoved).

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of this invention will be described with reference to the accompanying drawings.

FIG. 1is a longitudinal sectional side view schematically showing one embodiment of an ink jet recording apparatus according to this invention.FIG. 2is a schematic view showing a wiping mechanism of the ink jet recording apparatus. The ink jet recording apparatus of the present embodiment performs color printing on paper which is a recording medium. For the paper, ordinary paper, coated paper, OHP sheet, etc. are usable.

As shown inFIG. 1, an ink jet recording apparatus1has a sheet conveying route P in a chassis2for conveying a sheet. The sheet conveying route P is a route from a manual feed tray3or a paper cassette4to a lower sheet discharge tray6or an upper sheet discharge tray7through a printing section5. The printing section5is comprised of a drum8and a printing unit9.

In the manual feed tray3and the paper cassette4, a sheet feed mechanism10is provided which feeds sheets stacked on the manual feed tray3or the paper cassette5one by one in a separating manner to the sheet conveying route P. In the sheet conveying route P is mounted a sheet conveying mechanism11for conveying the sheet fed by the sheet feed mechanism10from the manual feed tray3or the paper cassette4toward the lower sheet discharge tray6or the upper sheet discharge tray7. The sheet conveying mechanism11has a sheet discharge mechanism12for discharging the printed paper from the printing section5.

The printing section5performs printing, with the paper held on the outer periphery of the drum8, by the printing unit9in accordance with a printing data while rotating the drum8at a predetermined speed. The printing unit9is provided with four nozzles units:13C (cyan),13Y (yellow),13M (magenta), and13B (black). The nozzle units13C,13Y,13M and13B are provided with an ink jet recording head15(seeFIG. 2) which selectively ejects ink to the paper fed from the conveying mechanism11, from a plurality of nozzles14(seeFIG. 2).

The printing unit9is located above the drum8so that the nozzles14provided in the ink jet recording head15will face the drum8from above. The nozzle units13C,13Y,13M and13B are positioned around the drum8along the direction of drum rotation:13C (cyan),13Y (yellow),13M (magenta) and13B (black) in order of mention from the upstream side in the direction of rotation of the drum8. Furthermore, the nozzle units13C,13Y,13M and13B are arranged so that the direction of arrangement of the nozzles14in the ink jet recording head15will be in parallel with the axial direction of the drum8. The ink jet recording apparatus1has a control section16which drives to control each part of the ink jet recording apparatus1.

As shown inFIG. 2, the ink jet recording apparatus1is provided with an ink feed mechanism17for feeding ink to the ink jet recording head15, an ink pressure control section18for controlling the feed pressure of ink to be supplied from the ink feed mechanism17, and a wiping mechanism19which is a maintenance mechanism for the maintenance of the ink jet recording head15.

The ink jet recording head15is provided with a plurality of pressure chambers (not shown) for holding ink to be supplied from the ink feed mechanism17, and a nozzle plate20forming a part of these pressure chambers and having the nozzles14which communicate with the pressure chambers. The ink jet recording head15thus structured performs printing on paper with drops of ink ejected from the pressure chambers through the nozzles14by utilizing volume changes in the pressure chambers.

The pressure chamber comprises: a plurality of grooves which are formed in a board, opening at the front and upper sides; a top plate which closes these grooves at the upper side; and the nozzle plate20which closes the plurality of grooves at the front side. The board with a plurality of grooves is formed by bonding two piezoelectric members each polarized in the direction of thickness of the board in such a manner that the direction of polarization will be opposite. The plurality of grooves in the board are formed along the direction of lamination of the piezoelectric members. The grooves are parallelly separated from one another by a side wall disposed between grooves. Inside of each groove is provided an electrode, which is formed by for instance an electroless nickel plating process. The board is provided with a wiring pattern for connection to the electrode.

In a top plate, a common ink chamber communicating with each pressure chamber and an ink supply port21for supplying ink to the common ink chamber are formed. To the common ink chamber, ink is supplied through the ink supply port21by means of the ink supply mechanism17. Ink used in the present embodiment is a liquid-type ink such as water-color ink, oil-based ink, ultraviolet-curing ink, etc. The ink used in the present embodiment contains for instance pigments or dyes as color materials.

In the nozzle plate20, a plurality of nozzles (through holes)14are formed through in the direction of plate thickness. In the nozzle plate20, the surface in which the plurality of nozzles14are formed functions as a nozzle face20a. The nozzles14are provided corresponding to the pressure chambers. Each pressure chamber communicates with the outside through the nozzle14. The nozzle plate20is provided with an ink-repellent layer (not shown) having an ink-repellent characteristic. The ink-repellent layer is provided on the entire surface of the nozzle plate20, including the peripheral surface of the nozzle14, to thereby achieve the stabilized straightforward ejection of ink drops.

In the present embodiment, no protective member for the protection of the nozzle plate20is provided. It should be understood, however, that this invention is not to be limited thereto, and a protective member for example may be adopted. Adopting the protective member can prevent a failure in maintaining the basic characteristics of the recording head likely to be caused by a flaw or breakage of the nozzle plate20. Furthermore, the protective member can prevent the occurrence of a damage, such as a flaw, in the nozzle plate20when adjusting a gap between the printing surface (paper) and the ink jet recording head15. Furthermore, the protective member functions to protect the nozzle plate20in the case there is the likelihood that an external force will be applied to the nozzle plate20during for example the transport of the ink jet recording head15.

The ink supply mechanism17has ink tanks (not shown) for holding cyan, yellow, magenta and black ink, and a filter (not shown) for removing foreign substances included in the ink held in the ink tanks. The ink supply mechanism17supplies the ink of a needed color to the ink jet recording head15of each of the nozzle units13C,13Y,13M and13B. At this time, the ink pressure control section18controls the supply pressure of ink to be supplied to the ink jet recording head15, thereby enabling the adjustment of the position of ink liquid level in the nozzle14.

The wiping mechanism19is provided with a plurality of wiping members22a,22band22cfor wiping the nozzle plate20(nozzle face20a), a wipe support member23for supporting the wiping members22a,22band22c, a moving mechanism24which movably supports the wipe support member23in the direction of arrangement of the nozzle14of the nozzle plate20and moves the wipe support member23along the nozzle plate20, and a positioning mechanism25which positions the wiping members22a,22band22cin their contact positions in which the wiping members come into contact with the nozzle plate20while the wipe support member23is being moved along the nozzle plate20by the moving mechanism24.

The wiping members22a,22band22care formed in a shape of plate of an elastic material or a porous material. For example, the wiping members22a,22band22care produced of a rubber material, such as an acrylonitrile-butadiene rubber (NBR) and a fluororubber (FPM). The wiping members22a,22band22cdiffer in thickness, hardness, material, porous density, wipe length (free length: length of free deflection), wiping depth, wiping speed, etc. That is, the wiping members22a,22band22care so formed as to vary in the wiping force to be applied to the nozzle faces20a(e.g., a contact pressure to be applied to the nozzle faces20a). In the present embodiment, three wiping members for example are provided, but it should be noted that the number of these wiping members is not limited thereto. Furthermore, the wiping members22a,22band22care formed to wipe the nozzle faces20awith different wiping forces, but it also should be noticed that the wiping forces are not limited thereto. For example, the wiping members22a,22band22cmay be formed so that at least one of the wiping forces against the nozzle faces20amay vary.

The wipe support member23has wipe holders26a,26band26cfor supporting the wiping members22a,22band22crespectively, and a wiper housing case27for holding the wipe holders26a,26band26c. The wiping members22a,22band22c, aligned along the direction of movement of the wipe support member23, are removably housed in the wiper housing case27. The wiper housing case27is supported by the wipe support member23so as to be movable along the direction of alignment of the wiping members22a,22band22c, that is, along the direction of movement of the wipe support member23.

The wipe support member23is of a cartridge type, and is removable together with the wiper housing case27and the wiping members22a,22band22cfrom the ink jet recording apparatus1. The wiper housing case27also is of a cartridge type, and is removably supported in the wipe support member23. That is, the wipe holders26a,26band26cis removably supported in the wiper housing case27, thereby enabling the replacement of the wiping members22a,22band22cin accordance with ink characteristics in the case where ink replacement (color and characteristics) is needed. In the present embodiment, therefore, the wipe support member23, the wiper housing case27, and the wiping members22a,22band22care removable. However, it should be understood that the present embodiment is not limited thereto; for example, the wipe support member23may be unremovably fixed.

The moving mechanism24comprises: a guide screw28which supports the wipe support member23, to guide and move the wipe support member23in the direction of arrangement of the nozzles14; and a driving motor29which drives to rotate the guide screw28. The moving mechanism24reciprocates the wipe support member23in the direction of arrangement of the nozzles14along the nozzle plate20by driving the driving motor29to change the direction of rotation of the guide screw28.

The positioning mechanism25has a wiping member moving mechanism30which moves the wiping members22a,22band22cas far as a predetermined pressing position, and a pressing mechanism31which presses, against a contact position, the wiping members22a,22band22cwhich have been moved to the predetermined pressing position by the wiping member moving mechanism30.

The wiping member moving mechanism30is comprised of a spring32mounted in the wiper housing case27for pressing the wiper housing case27rightward from the left inFIG. 2, and a cam33which is rotatably mounted in the wipe support member23and in contact with the wiper housing case27being pressed by the spring32. The cam33, driven to rotate by the control section16, is moved in the direction of arrangement of the wiping members22a,22band22c, that is, in the direction of movement of the wipe support member23.

The pressing mechanism31comprises a pressing member34for pressing the wiping members22a,22band22cinto contact with the nozzle plate20, and a cam35connected to the pressing member34and rotatably installed to the wipe support member23. In the bottom27aof the wiper housing case27, a hole27bis provided to allow the insertion of the pressing member34. The hole27b, which may, for example, be a long narrow hole in bottom27aof the wiper case27, is formed in such a manner that the wiping members22a,22band22cmay be pressed from below by the pressing member34. In the present embodiment, the wiper housing case27is moved by the wiping member moving mechanism30toward the pressing mechanism31, to thereby move the wiping members22a,22band22calong the direction of arrangement; therefore it is possible to move the optimum wiping members22a,22band22cto the pressing position in which these wiping members will come into contact with the nozzle plate20. There may be provided a plurality of special pressing mechanisms31respectively under the wiping members22a,22band22c. In this case, the wiping member moving mechanism30is not needed.

The pressing member34is installed so as to be vertically (inFIG. 2) moved in and out of the hole27bof the wiper housing case27. It is also so structured as to be insertable and removable through the hole27bat the bottom27aside. As the cam35is rotated by the control section16, the pressing member34vertically (inFIG. 2) moves in and out of the hole27b. With the movement of the pressing member34, the wiping members22a,22band22ccan be pressed to selectively push out the tips of the wiping members22a,22band22cinto contact with the nozzle plate20. Here, with positions of the wiping members22a,22band22choused in the wiper housing case27being as housing positions (22band22cinFIG. 2), the positions of the wiping members22a,22band22cthat have been pushed by the pressing member34out of the wiper housing case27into contact with the nozzle plate20are to be the contact positions (22ainFIG. 2).

The ink jet recording apparatus1has a home position sensor36whose output varies depending on whether or not the wipe support member23is in its home position, and an end position sensor37whose output varies depending on whether or not the wipe support member23is in the end position. The home position sensor36and the end position sensor37function as position detectors which detect the positions of the wiping members22a,22band22cin the wiping direction (from left to right inFIG. 2). In the present embodiment, the wiping direction is from left to the right inFIG. 2. It, however, should be understood that, in the present embodiment, the wiping direction is not limited thereto, but may be, for example, from right to left inFIG. 2.

The home position sensor36and the end position sensor37can be realized by for example a photo-interrupter, receiving by a light-receiving element the light emitted from a light-emitting element. The light-emitting and -receiving elements are oppositely positioned on both sides of a path of movement of the wipe support member23. That is, the output of these light-emitting and -receiving elements varies with the passage or non-passage of the wipe support member23between these elements.

When executing maintenance operation, the moving mechanism24moves the wipe support member23from its home position to the end position in accordance with a change in the output of the home position sensor36and the end position sensor37, and then returns the wipe support member23from the end position to its home position. While the wipe support member23is moved to the end position, the cam35of the pressing mechanism31is positioned to hold the tip of the wiping member22ain contact with the nozzle plate20. In this state, the wipe support member23is moved in the direction of wiping. While the wipe support member23returns to its home position after the wiping operation, the cam35of the pressing mechanism31is positioned such that the tips of the wiping members22a,22band22cdo not contact the nozzle plate20. Alternatively, the wipe support member23may be so structured as to move downward, to thereby move the tips of the wiping members22a,22band22caway from the nozzle plate20.

In the present embodiment, the wipe support member23is timed to be reset to its home position in accordance with a change in the output of the end position sensor37. It is to be understood, however, that the present embodiment is not limited thereto, and the wipe support member23may be so timed as to be reset to its home position, by, for example, controlling the travel of the wipe support member23in relation to a distance in the direction of arrangement of the nozzle14.

Here, the structure of the tip of the wiping member22will be explained as an example.FIG. 3is a schematic view showing the wiping member22awhich is in contact with the nozzle plate20. As shown inFIG. 3, at the tip of the wiping member22ais formed an edge portion38along a direction intersecting the direction of movement of the wipe support member23. The wiping member22ais supported in such a manner that the edge portion38will be pressed against the nozzle plate20. The edge portion38of the wiping member22ais pressed by an elastic force of its own against the nozzle plate20. The wiping member22ais being pressed in such a manner that its tip portion will be positioned at the rear side in the direction of wiping (the direction of arrow c inFIG. 3) in which the wipe support member23moves first when the wipe support member23is reciprocated by the moving mechanism24.

Next, the home position of the wipe support member23of the wiping member22awill be described. The wipe support member23is reciprocally movable along the direction of arrangement of the nozzle14. Except during the execution of maintenance operation, however, the wipe support member23is waiting in its home position. The home position of the wipe support member23is a position in which for example the edge portion38of the tip of the wiping member22ais off the nozzle plate20. Here,FIG. 4is an explanatory view explaining the home position of the wipe support member23, andFIG. 5is an explanatory view explaining the other home position (different fromFIG. 4) of the wipe support member23.

For example, as shown inFIG. 4, the home position of the wipe support member23may be outside of the nozzle14where the edge portion38at the tip of the wiping member22awill be in the outermost position in the direction of arrangement of the nozzle14, and may be in a position where it is in contact with the nozzle plate20. InFIG. 4, P1indicates a distance, in the direction of arrangement of the nozzle14, from the nozzle14ato the contact position where the edge portion38of the wiping member22acontacts the nozzle plate20. P1is set shorter than a distance from the nozzle14ato one end (the left end inFIG. 4) of the nozzle plate20in the direction of arrangement of the nozzle14.

Furthermore, for example, as shown inFIG. 5, the home position of the wipe support member23may be outside the nozzle14awhere the edge portion38of the wiping member22awill be in the outermost position in the direction of arrangement of the nozzle14, and may be in a position not opposite to the nozzle plate20. InFIG. 5, P2indicates a distance in the direction of arrangement of the nozzles14from the nozzle14ato the edge portion38of the wiping member22a. P2is set longer than the distance from the nozzle14ato one end (the left end inFIG. 5) of the nozzle plate20in the direction of arrangement of the nozzle14.

In executing the maintenance operation of wiping, of the nozzle plate20of the ink jet recording head15, the wiping member22ais in contact with the nozzle plate20only when moved in a direction (from the left to the right in the direction of wiping inFIG. 2) of moving away from its home position.

When the wipe support member23is placed in its home position shown inFIG. 5, the wiping member22amay be positioned for example in a position indicated by a solid line inFIG. 5, and also may be positioned in a position indicated by a dotted line inFIG. 5. Also when the wiping member22ais in the position indicated by the dotted line inFIG. 5, the wiping member22ais placed in a contact position in which the wipe support member23is in contact with the nozzle plate20while the wipe support member23is being moved by the moving mechanism24along the nozzle plate20. In the present embodiment, the position indicated by the solid line inFIG. 5is the home position of the wipe support member23.

FIG. 6is a block diagram schematically showing an electric connection of each part of the ink jet recording apparatus1. As shown inFIG. 6, the control section16of the ink jet recording apparatus1is comprised by connecting, through an I/O port54, a CPU50which drives to control each part of the ink jet recording apparatus1by executing various kinds of control programs, a memory51such as a ROM for the storage of various kinds of control programs and a RAM which functions as a work area of the CPU50, an operating section52which operates in accordance with the operator's operation, and a control circuit53.

To the control circuit53, are connected a printing section5(the ink jet recording head15), a driving source55, an ink pressure control section18, a driving motor29, a cam33, a cam35, a home position sensor36, an end position sensor37, an environment sensor56for detecting temperature and humidity, and wiping member identifying sensors57a,57band57cwhich identify the operating condition (whether operated or not) of the wiping members22a,22band22c. The driving source55is for driving the sheet feed mechanism10and the sheet conveying mechanism11.

As the wiping member identifying sensors57a,57band57c, mechanical switches are used. For example, three mechanical switches are installed in the wiper housing case27correspondingly to the wiping members22a,22band22c. Thus it is possible to identify the wiping members22a,22band22cplaced in the contact position, that is, in use for wiping, by detecting the on/off operation of these mechanical switches.

The control section16controls each part of the ink jet recording apparatus1to execute printing and maintenance operations. In the present embodiment, the maintenance operation is a wiping operation executed by the wiping mechanism19. The control section16functions to perform the printing and maintenance operations in accordance with signals outputted from the operating section52operated by the operator's key operation.

In the memory51an area for the storage of various data to be referred to in executing the maintenance operation is provided. In the area are stored such data as cumulative number of counts of maintenance operation executed after the execution of preceding maintenance operation, cumulative unexecuted maintenance time after the execution of preceding maintenance operation, temperature history, humidity history, and number of printed sheets after the preceding maintenance operation. Further stored in the area are data referred to at the time of up-down motions of the tips of the wiping members22a,22band22cby the pressing mechanism31, such as data of upward motion and data of downward motion relative to displacements. In addition, the memory51is provided with various counter areas for use in executing the maintenance operation. Furthermore, table data are stored for selecting the optimum wiping member from among a plurality of wiping members22a,22band22cin accordance with such data as cumulative number of counts of maintenance operation executed after the execution of the preceding maintenance operation, cumulative unexecuted maintenance time after the execution of the preceding maintenance operation, temperature history, humidity history, and number of printed sheets after the preceding maintenance operation.

Next, a selection processing for selecting the optimum wiping member from among the wiping members22a,22band22cfrom the condition of adhering substances on the nozzle plate20(the nozzle face20a) will be explained. The wiping members22a,22band22care formed, for example, of the same material (e.g., fluororubber). The wiping member22ais 0.5 mm thick; the wiping member22bis 1.0 mm thick; and the wiping member22cis 2.0 mm thick.

A first selection processing will be explained. Upon receiving a command for the execution of wiping, the control section16refers to the memory51relative to data about the unexecuted wiping time after the preceding execution of wiping, and compares the data with a table data prepared, thereby selecting the optimum wiping member from among the wiping members22a,22band22c. That is, the control section16performs the function as the selecting means. The table data is stored so that when the unexecuted wiping time after the preceding execution of wiping operation is within one hour, the wiping member22awill be selected; when the unexecuted wiping time exceeds one hour and within 8 hours, the wiping member22bwill be selected; and when the unexecuted wiping time exceeds 8 hours, the wiping member22cwill be selected. It is because the longer the unexecuted wiping time after the preceding wiping is, the firmer the adhering substance (residual ink) on the nozzle plate20dries/solidifies and accordingly the greater wiping force will be needed. When the wiping members22a,22band22chave the same hardness, length (free length: length of free deflection), wiping depth, and wiping speed, the wiping force will increase with an increase in the thickness of the wiping members22a,22band22c, gaining a higher wiping performance. It is to be noted that the selection of the wiping members22a,22band22cis not limited thereto; a similar wiping effect can be obtained even when the wiping member22ahas the hardness of 35 degrees, the wiping member22bhas the hardness of 60 degrees, and the wiping member22chas the hardness of 80 degrees, or when the wiping member22ais 7.0 mm long. (in free length), when the wiping member22bis 5.5 mm long (in free length), and when the wiping member22cis 3.0 mm long (in free length).

Next, a second selection processing will be explained. Upon receiving a command for execution of wiping, the control section16refers to the preceding environmental history (temperature and humidity) data of the memory51, and compares the data with a table data prepared in advance in the memory51, thus enabling the selection of the optimum wiping member from among the wiping members22a,22band22c. That is, the function as the selecting means will be executed. The table data is so stored that the wiping member22ais selected when, for example, the environmental histories (temperature and humidity) after the preceding wiping operation are 25° C. and 50%; the wiping member22bis selected in the case of 35° C. and 70%; and the wiping member22cis selected in the case of 45° C. and 85%. Generally, it is known that the ink is apt to solidify because moisture attaches to the ink at high humidities. Also it is generally known that the ink becomes less viscous and hard to solidify at high temperatures. Therefore it is hard to determine the condition of adhering substances only from temperatures and humidities. The condition of the adhering substances varies with a combination of temperature and humidity. The environmental history (temperature and humidity) table data from the preceding operations is one example verified by experiments. When the wiping members22a,22band22chave the same hardness, length (free length: length of free deflection), wiping depth, and wiping speed, the wiping force increases with an increase in the thickness of the wiping members22a,22band22c, and therefore a high wiping performance is achieved. The selection of the wiping members is not limited to the example described above.

Next, a third selection processing will be explained. The control section16, receiving a command for execution of wiping, refers to a data on the number of printed sheets from the preceding data in the memory51, and compares the data with the table data prepared in advance in the memory51, thus selecting the optimum wiping member from among the wiping members22a,22band22c. The table data is stored so that the wiping member22ais selected for example when the number of A4-sized printed sheets from the preceding operation is within 500 sheets; the wiping member22bis selected in the case of 500 up to 2000 sheets; and the wiping member22cis selected in the case of 1000 sheets or over. Generally, the more the number of printed sheets increases, the more the paper dust tend to attach on the nozzle plate20. Besides, with an increase in the amount of paper dust, adhering substances become likely to solidify in synergy with residual ink. Therefore, a greater wiping force is needed with an increase in the number of printed sheets from the preceding operation. The number of printed sheets from the preceding operation stated above is one example verified by experiments. When the wiping members22a,22band22chave the same hardness, length (free length: length of free deflection), wiping depth, and wiping speed, the thicker the wiping members22a,22band22cincrease, the greater the wiping force becomes, resulting in a higher wiping performance. It should be noticed, however, that the selection of the wiping members22a,22band22cis not limited to the example stated above.

In the ink jet recording apparatus1, the electric voltage is applied to an electrode corresponding to a pressure chamber from which the ink will be ejected in printing operation in accordance with printing data. A pair of side walls in the pressure chamber applied with the voltage, therefore, is so deflected to increase and then reduce the volume of the pressure chamber interior. With the change in the volume of the pressure chamber, a part of the ink drawn in the pressure chamber will be ejected as drops of ink from the nozzle14.

In such a printing operation, the ink thus ejected sometimes remains around the nozzle14. The residual ink, if dried/solidified, is likely to bend the direction of ejection or to block the nozzle14, or to cause defective ink ejection. It is, therefore, necessary to remove the residual ink.

In the ink jet recording apparatus1of the present embodiment, the wiping mechanism19performs maintenance operation to remove residual ink and foreign substances from the nozzle plate20. Now, the maintenance operation by the wiping mechanism19will be explained. That is, the maintenance procedure to be executed by the control section16(CUP50) in accordance with a program stored in the memory51will be described by referring toFIG. 7.FIG. 7is a flowchart showing the flow of the maintenance procedure.

The wiping mechanism19is waiting until the execution of maintenance operation is declared. Upon judging the declaration of the execution of the maintenance operation, the control section16controls the wiping mechanism19to carry out the maintenance operation. The maintenance operation is executed when for example the execution of maintenance operation is declared by the operator's key manipulation.

As shown inFIG. 7, the control section16reads (in S2to S4) data relative to the unexecuted maintenance time after the preceding maintenance, the temperature history, the humidity history, and the number of printed sheets after the preceding maintenance which are stored in the memory51, when it is determined that the execution of maintenance operation has been declared (Y in S1), during standby for the declaration of execution of maintenance operation (N in S1). The control section16compares data concerning the unexecuted maintenance time after the execution of the preceding maintenance, the temperature history, the humidity history, and the number of printed sheets after the preceding maintenance, with table data for selecting the optimum wiping material from among a plurality of wiping members22a,22band22c. Thus the optimum wiping member (a wiping member selecting means) is selected; the cam33is controlled in accordance with data on the wiping member identifying sensors57a,57band57c, and the optimum wiping member thus selected is moved to the pressing position (S5).

The control section16then controls the moving mechanism24to set the optimum wiping member in its home position, thereby moving the wipe support member28to a position in which the home position sensor36will be on (S6to S8). Next, the control section16drives the cam35to move the optimum wiping member up to the contact position until it determines that the optimum wiping member has been raised to the upper limit position in accordance with the UP data stored in the memory51(S9). After raising the optimum wiping member to the upper limit position in accordance with the UP data, the control section16drives the moving mechanism24to move the optimum wiping member toward wiping (from left to right inFIG. 2) until it determines that the optimum wiping member, i.e. the wipe support member23, has reached its end position, in accordance with an output change from the end position sensor37(S10to S11).

At this time, the edge portion38of the optimum wiping member comes into contact with the nozzle plate20as shown inFIG. 3. In this state, the wipe support member23is moved in the direction of wiping, thereby enabling the optimum wiping member to move as if rubbing against the nozzle plate20. Thus it is possible to remove the residual ink or foreign substances from around the nozzles14of the nozzle plate20. Furthermore, at this time, in the case of the wiping members22a,22band22cformed of an elastic or porous material, it is possible to prevent giving damage to the nozzle plate20if the wiping members22a,22band22care moved with their edge portions38pressed against the nozzle plate20.

The control section16stops driving the moving mechanism24(S12) when it is determined in accordance with an output change from the end position sensor37that the optimum wiping member, i.e. the wipe support member23, has reached the end position (Y in S11). At the same time, the control section16drives the cam35to move the optimum wiping member downward until it is determined in accordance with the DOWN data stored in the memory51that the optimum wiping member has moved down to the lower limit position. Then, the control section16drives to control the moving mechanism24until it is determined in accordance with the output change from the home position sensor36that the optimum wiping member, i.e. the wipe support member23, has been moved to its home position (S13to S14).

When it is determined in accordance with the output change from the home position sensor36that the optimum wiping member, i.e. the wipe support member23, has moved to its home position (Y in S14), the control section16stops driving the moving mechanism24(S15), clears a data concerning an unexecuted maintenance time after the preceding maintenance stored in the memory51, temperature history, humidity history, and the number of printed sheets after the execution of the preceding maintenance operation, and increments a counter, or counts up the number of counts of maintenance operation (number of counts of wiping operation) executed by the optimum wiping member used (S16to S19).

The control section16determines whether or not the number of counts registered has reached the preset number of counts of maintenance operation (S20). When it is determined that the number of counts registered has not reached the preset number of counts of maintenance operation (N in S20), the processing will end. When the number of counts registered is determined to have reached the preset number of counts of maintenance (Y in S20), the wiping members22a,22band22cthat have reached the preset number of counts of maintenance will be replaced (S21). The number of counts of maintenance of the wiping members22a,22band22cthus replaced will be cleared (S22), ending the processing.

According to the present embodiment, a plurality of wiping members22a,22band22cwhich have different wiping forces to be applied to the nozzle face20aare provided to remove ink and foreign substances remaining on the nozzle face20aof the nozzle plate20of the ink jet recording head15. It is possible to select the optimum wiping member without increasing the number of counts of wiping operation and accordingly to achieve a good wiping effect, by selecting the optimum wiping member from among the plurality of wiping members22a,22band22caccording to changes in the kind of adhering substances (ink, fine particles of paper, dust, etc.) and adhering condition (an increase in ink adhesion caused by environmental changes, and an increase in ink adhesion by the length of time when ink deposit is left unremoved). The wiping effect is not improved by increasing the number of counts of wiping operation; therefore it is possible to increase the life of the wiping member and maintain a good wiping performance of the wiping members for a prolonged period of time. Consequently, it is possible to maintain a good ink ejection performance at the time of printing, to thereby improve printing reliability.

When the ink jet recording head15has been replaced or when the ink to be supplied thereto has been changed, for example from the water-color ink to the oil-based ink, from the oil-based ink to the UV ink (the ultraviolet-curing ink), etc., there will occur such a trouble as ink solidification and accordingly defective printing if ink remaining unchanged is used. Also if new ink and the unchanged wiping members22a,22band22care used, the wiping members22a,22band22care likely to swell and the components of these wiping members22a,22band22cwill melt out to alter ink performance. Furthermore, it will become necessary to use the wiping members22a,22band22cmade of such a material as is capable of responding to the condition of the nozzle plate surface (the presence or absence of an ink-repellent film, or the strength of the ink-repellent film). Therefore, as in the ink jet recording apparatus1of the present embodiment, the wiping members22a,22band22c, when configured removable, will be replaceable.

According to the present embodiment, the wiping mechanism19includes: the wipe support member23supporting a plurality of wiping members22a,22band22c; the moving mechanism24supporting the wipe support member23movable along the nozzle face20a, and moving the wipe support member23thus supported, along the nozzle face20a; and the positioning mechanism25for positioning the optimum wiping member selected by the wiping member selecting means, in a contact position in which the optimum wiping member comes into contact with the nozzle face20a, in the state that the wipe support member23is being moved along the nozzle face20aby the moving mechanism24. It is therefore possible to achieve a good wiping effect without complicating the configuration of the wiping mechanism19.

Furthermore, according to the present embodiment, the positioning mechanism25has the wiping member moving mechanism30for moving the optimum wiping member to a predetermined pressing position, and the pressing mechanism31for pressing toward the contact position the optimum wiping member thus moved to the predetermined pressing position by the wiping member moving mechanism30. Therefore, a good wiping effect is obtainable without complicating the configuration of the positioning mechanism25. Also when the positioning mechanism25has a plurality of pressing mechanisms31for pressing a plurality of wiping members22a,22band22ceach toward the contact position, it is possible to achieve a good wiping effect without complicating the configuration of the positioning mechanism25.

Furthermore, according to the present embodiment, a plurality of wiping members22a,22band22chave, on their tips, the edge portion38along the direction intersecting the direction of movement. The positioning mechanism25also functions to position the optimum wiping member in a contact position so that the edge portion38of the optimum wiping member will come into contact with the nozzle face20a. It is therefore possible to enhance the wiping performance of the wiping members22a,22band22cwithout complicating their configuration.

Furthermore, according to the present embodiment, a plurality of wiping members22a,22band22care formed of an elastic material. The positioning mechanism25functions to position the optimum wiping member in such a manner that the edge portion38may be pressed toward the nozzle face20aby the elastic force of the optimum wiping member. Therefore it is possible to further enhance the wiping performance of the wiping members22a,22band22cwithout complicating the configuration of the positioning mechanism25.

Furthermore, according to the present embodiment, a plurality of wiping members22a,22band22care formed so that the wiping force to be applied to the nozzle face20amay vary. Therefore, it becomes possible to move the optimum wiping member into contact with the nozzle face20aof the nozzle plate20correspondingly to a change in the kind of adhering substances and adhering condition and also to maintain a good wiping effect for a prolonged period.

Furthermore, according to the present embodiment, a plurality of wiping members22a,22band22c, being formed of an elastic material, will never impair the nozzle face20aof the nozzle plate20if firmly pressed into contact with the nozzle face20a.

Furthermore, according to the present embodiment, a plurality of wiping members22a,22band22c, being formed of a porous material, will never impair the nozzle face20aof the nozzle plate20if firmly pressed into contact with the nozzle face20a.

Furthermore, according to the present embodiment, a plurality of wiping members22a,22band22c, being removably formed in relation to the wipe support member23, can be replaced according to ink characteristics in the case when the ink needs a change (in color and characteristic).

Furthermore, according to the present embodiment, since the wipe support member23are removably formed in relation to the moving mechanism24, a plurality of wiping members22a,22band22ccan easily be replaced by replacing the wipe support member23.

Furthermore, according to the present embodiment, the wipe selecting means selects the optimum wiping member in accordance with an elapsed time after the execution of the preceding wiping operation. It is therefore possible to properly select the optimum wiping member in accordance with a change in the type of adhering substances and adhering condition, and consequently to gain a good wiping effect.

Furthermore, according to the present embodiment, the wiping member selecting means selects the optimum wiping member on the basis of an environmental history after the execution of the preceding wiping operation, and therefore it is possible to properly select the optimum wiping member in accordance with a change in the kind of adhering substances and adhering condition, and accordingly to obtain a good wiping effect.

Furthermore, according to the present embodiment, the wiping member selecting means selects the optimum wiping member in accordance with the number of counts of printed sheets after the execution of the preceding wiping operation. It is therefore possible to properly select the optimum wiping member in accordance with a change in the kind of adhering substances and adhering condition, and consequently to obtain a good wiping effect.