Liquid ejecting apparatus

The piezoelectric vibrators 33 respectively have the active parts 33a capable of performing piezoelectric deformation joined to the elastic walls 26a forming one face of each of the pressure chambers 34 via the insular parts. On both sides of the active parts 33a in the vibrator width direction perpendicular to the arrangement direction of a plurality of nozzle openings 23, a pair of unit fixing parts 30 and 33b are installed. The pair of unit fixing parts 30 and 33b are joined to the parts of the flow path unit 21 other than a plurality of elastic walls 26a. According to the present invention, without increasing the rigidity of the case for storing the piezoelectric actuator unit, the cross talk is effectively prevented.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a liquid ejecting apparatus for ejecting liquid drops from a nozzle opening thereof. As a typical example of a conventional liquid ejecting apparatus, there is an ink jet recording apparatus having an ink jet recording head for image recording available. As other liquid ejecting apparatuses, for example, an apparatus having a coloring material ejecting head used to manufacture a color filter of a liquid crystal display, an apparatus having an electrode material (conductive paste) ejecting head used for electrode forming of an organic EL display and a face emission display (FED), an apparatus having a biological organic matter ejecting head used to manufacture biological chips, and an apparatus having a sample ejecting head as a precise pipette may be cited.

2. Description of Related Art

An ink jet recording apparatus which is a typical example of a liquid ejecting apparatus produces a comparatively low noise during printing and can form small dots at high density, so that it has been used recently in many printings including color printing.

The ink jet recording apparatus generally has an ink jet recording head (liquid ejecting head) which is loaded on a carriage and moves back and forth in the width direction (head scanning direction) of a recording medium such as recording paper and a feed means for moving the recording medium in the direction (medium feed direction) perpendicular to the head scanning direction.

In this ink jet recording apparatus, ink drops (liquid drops) are ejected from the recording head to the recording medium in correspondence to print data to print it. And, the recording head loaded on the carriage is formed so as to eject ink of colors such as black, yellow, cyan, and magenta, thereby not only text printing by black ink but also by changing the 4-color-ink ejection rate, full-color printing can be carried out.

FIG. 16is a sectional view showing an example of the recording head of a conventional ink jet recording apparatus.

A recording head70has a case71made of synthetic resin and a flow path unit72stuck on the bottom of the case71. The flow path unit72is formed by laminating and unifying by adhesion a nozzle plate74having many bored nozzle openings73in two rows, a flow path forming plate75made of silicon, an elastic plate76, and a vibration plate77. The bottom of the nozzle plate74forms a nozzle forming face78.

The case71is a block member having a storing space79opened on the top and bottom. In the storing space79, a pair of right and left piezoelectric actuator units80are installed and each of the piezoelectric actuator units80is fixed to the inner wall surface of the case71by each fixing substrate81. To each of the actuator units80, each tape carrier package83having a drive integrated circuit82is connected.

In the storing space79, furthermore, as shown inFIGS. 16 and 17, between the pair of right and left piezoelectric actuator units80, a central rib84is arranged. The central rib84, at both ends thereof in the nozzle arrangement direction (the direction perpendicular to the paper surface ofFIG. 16and the vertical direction ofFIG. 17), is fixed to the flow path unit72. And, a part of the force applied to the flow path unit72when the piezoelectric actuator units are driven is received by the central rib84.

Each of the piezoelectric actuator units80has a plurality of piezoelectric vibrators85arranged in one row in the nozzle arrangement direction. The piezoelectric vibrators85are formed by alternately laminating electrode players and piezoelectric material layers in the direction parallel with the nozzle forming face78and vibrate in the direction perpendicular to the lamination direction of both layers.

On the flow path forming plate75, a plurality of pressure chambers86formed in two rows in the nozzle arrangement direction, a common ink chamber87formed for each ink kind, and an ink feed port88for interconnecting the pressure chambers86and the common ink chambers87for each of the pressure chambers86are formed. The opening on the top of each of the pressure chambers87is sealed by the elastic plate76and on the top of the part of the elastic plate76corresponding to each of the pressure chambers87, an insular thick part89composed of a part of the vibration plate77is formed. The part of the elastic plate76corresponding to each of the pressure chambers87is deformed according to the deformation of the piezoelectric vibrator85of the piezoelectric actuator unit80, thereby the volume of the pressure chamber86is changed and ink drops can be ejected from the nozzle opening73.

In the case71, an ink feed path90for feeding ink to the common ink chambers87are formed for each ink kind. The ink feed path90passes through the elastic plate76and interconnects to the common ink chambers87.

AsFIG. 16shows, in the recording head of a conventional ink jet recording apparatus mentioned above, the loop of force generated when the piezoelectric vibrators85are expanded and contracted is completed only on the side of each of the fixing substrates81of the piezoelectric actuator units80. On the opposite side of each of the fixing substrates81, the force applied to the flow path unit72is received by the central rib84of the case71. However, the rigidity of the central rib84is insufficient, so that the force cannot be received sufficiently.

Therefore, for example, in the piezoelectric actuator units80, when the piezoelectric vibrators85are all driven simultaneously, the flow path unit72is deformed due to force generated at the time of drive and cross talk is caused. The cross talk produces an ejection characteristic difference between when a small number of piezoelectric vibrators85are driven and when a large number of piezoelectric vibrators85are driven.

Further, in a conventional recording head, due to deformation of the central rib84, the deformation is propagated also to the pressure chambers86in the opposite side of the drive side and so called inter-row cross talk may be generated.

For example, in Japanese Patent Laid-Open Publication No. 2001-71486, to prevent deformation and vibration of the central rib, a method for inserting a metal into the central rib is proposed (FIGS. 1 and 2of the publication). By this method, a cross talk prevention effect may be obtained to some extent, though another problem arises that the manufacturing steps are complicated and the manufacturing cost is increased.

Further, as shown inFIG. 16, in the conventional recording head, the fixing substrates81are joined to the case71, so that to the case71, in addition to the function of ink feed to the flow path unit72and protection of the piezoelectric actuator units80, the rigidity of receiving force generated when the piezoelectric vibrators85are driven and of preventing deformation and the high dimensional accuracy for positioning the piezoelectric vibrators85with high accuracy are required. Therefore, conventionally, for example, using a material that thermoset epoxy resin is kneaded with a glass fiber as a filler, the case71is manufactured by injection molding.

However, use of this manufacturing method causes problems that as compared with a case of general plastics, the material cost is increased, and the molding ability is low due to kneading of a filler, and the yielding rate is reduced, and the manufacturing cost is increased.

Further, the case71made of resin is different in the coefficient of linear expansion from the flow path forming plate75made of silicon and the piezoelectric vibrators85. Furthermore, since the case71is made of resin, moisture absorption expansion is caused at high humidity. Under such conditions, if the case is made of general plastics, the rigidity thereof is low, so that the case is easily deformed and follows the flow path forming substrate75and the piezoelectric vibrators85which are highly rigid, thus the members will not be peeled off from each other. However, as mentioned above, since the case71is made of a highly rigid material, a problem arises that the case is not deformed easily and the members are peeled off from each other.

SUMMARY OF THE INVENTION

The present invention was developed with the foregoing in view and is intended to provide a liquid ejecting apparatus having a liquid ejecting head capable of effectively preventing cross talk without increasing the rigidity of a case for storing a piezoelectric actuator unit.

The present invention is a liquid ejecting apparatus comprising a liquid ejecting head having a plurality of nozzle openings for ejecting liquid drops arranged in line, wherein: said liquid ejecting head has a flow path unit having a plurality of pressure chambers respectively interconnected to said plurality of nozzle openings, a plurality of elastic walls for respectively forming one face of each of said plurality of pressure chambers, and a nozzle plate where said plurality of nozzle openings are formed and a piezoelectric actuator unit which includes a plurality of piezoelectric vibrators respectively joined to said plurality of elastic walls via insular parts, deforms said elastic walls by deformation of said piezoelectric vibrators, and changes the volume of said pressure chambers, said plurality of piezoelectric vibrators are respectively formed by alternately laminating piezoelectric material layers and electrode layers and have active parts capable of performing piezoelectric deformation which are joined to said elastic walls, and said piezoelectric actuator unit further has a pair of unit fixing parts installed on both sides of said active parts in a vibrator width direction perpendicular to an arrangement direction of said plurality of nozzle openings, and said pair of unit fixing parts are joined to parts other than said plurality of elastic walls of said flow path unit, thereby said piezoelectric actuator unit is fixed to said flow path unit.

Preferably, at least one of said pair of unit fixing parts comprises a plurality of inactive parts incapable of performing piezoelectric deformation formed integrally with said active parts in said vibrator width direction as a part of each of said plurality of piezoelectric vibrators.

Preferably, at least one of said pair of unit fixing parts comprises a fixing member which is formed as a separate member from said plurality of piezoelectric vibrators and is joined to said plurality of piezoelectric vibrators.

Preferably, said fixing member is joined to said plurality of piezoelectric vibrators via a base member joined to said plurality of piezoelectric vibrators.

Preferably, said plurality of piezoelectric vibrators are respectively formed independently and are integrally fixed by said base member.

Preferably, the liquid ejecting apparatus further comprises a tape carrier package electrically connected to said plurality of piezoelectric vibrators, wherein said tape carrier package includes an integrated circuit for driving said plurality of piezoelectric vibrators and a rear of said integrated circuit is fixed to said base member at least partially.

Preferably, said base member is formed by free-cutting ceramics.

Preferably, said piezoelectric material layers and said electrode layers are laminated perpendicularly to said nozzle plate and said piezoelectric vibrators vibrate in a lamination direction of both layers.

Preferably, the liquid ejecting apparatus further comprises a plurality of said piezoelectric actuator units, wherein: a plurality of nozzle rows composed of said plurality of nozzle openings are formed, and said piezoelectric actuator units are respectively arranged for each nozzle row.

Preferably, said plurality of elastic walls comprise a part of an elastic plate covering all of said plurality of pressure chambers, and a plurality of insular movable thick parts which are formed in correspondence with said plurality of pressure chambers and to which respective said active parts of said plurality of piezoelectric vibrators are joined, first fixed thick parts to which said inactive parts of said piezoelectric vibrators are joined, and second fixed thick parts to which said unit fixing parts are joined are installed on a face of said elastic plate on a side of said actuator unit.

Preferably, a total width of said pair of unit fixing parts in said vibrator width direction is wider than a width of said active part in said vibrator width direction.

Preferably, at least one of said pair of unit fixing parts is joined to an end of said active part in said vibrator width direction and parts of said fixing members joined to said ends of said active parts are formed integrally with said plurality of piezoelectric vibrators in a comb-teeth shape.

Preferably, said plurality of nozzle openings are formed in two rows and are staggered between said nozzle rows, and each of said plurality of piezoelectric vibrators includes a half on one side in said vibrator direction and a half on the other side in said vibrator width direction, either of said half on one side and said half on the other side forms said active part, and the other half forms an inactive part incapable of performing piezoelectric deformation, an arrangement of said active part and said inactive part is opposite between adjacent piezoelectric vibrators, and said active parts are arranged in correspondence with said nozzle openings.

As mentioned above, according to the present invention, a liquid ejecting apparatus having a liquid ejecting head capable of effectively preventing the cross talk without increasing the rigidity of the case for storing the piezoelectric actuator units can be provided.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

An ink jet recording apparatus as an embodiment of the liquid ejecting apparatus of the present invention will be explained below with reference to the accompanying drawings.

FIG. 1is a perspective view showing a rough constitution of an ink jet recording apparatus of the present embodiment. InFIG. 1, numeral 1 indicates a carriage, and the carriage1is structured so as to be guided by a guide member4and driven by a carriage motor2via a timing belt3to move back and forth in the axial direction of a platen5. The platen5supports recording paper6(a kind of recording medium) from the rear thereof and defines the position of the recording paper6with respect to an ink jet recording head (liquid ejecting head)12.

The carriage1, the carriage motor2, the timing belt3, and the guide member4form the carriage mechanism for allowing the recording head12to scan in the head scanning direction together with the carriage1.

The recording head12is loaded on the side of the carriage1opposite to the recording paper6. On the carriage1, an ink cartridge7for feeding ink to the recording head12is mounted in a removable state.

In the home position (the right side ofFIG. 1) which is a non-printing area of the ink jet recording apparatus, a cap member13is arranged and the cap member13is structured so as to be pressed to the nozzle forming face of the recording head12and form a closed space between the recording head12and the nozzle forming face, when the recording head12loaded on the carriage1moves to the home position. And, under the cap member13, a suction pump10for giving negative pressure to the closed space formed by the cap member13is arranged.

In the neighborhood of the cap member13on the printing area side, a wiping member11composed of an elastic plate (elastic blade) such as rubber is arranged so as to move back and forth, for example, horizontally for the moving track of the recording head12and is structured so as to wipe out the nozzle forming face of the recording head12as required, when the carriage1moves from the side of the cap member13to the printing area side.

The ink jet recording apparatus further has a medium feeding mechanism for intermittently feeding the recording paper6to be printed (recorded) by the recording head12in the medium feeding direction perpendicular to the head scanning direction.

Next, by referring toFIGS. 2 to 6, the recording head (liquid ejecting head)12of the ink jet recording apparatus of this embodiment will be described in detail.

As shown inFIG. 2andFIG. 3which is the sectional view of the line A—A shown inFIG. 2, the recording head12has a case20made of synthetic resin and a flow path unit21stuck on the bottom of the case20. The case20is formed by general plastics without using a reinforced material like a conventional recording head. The flow path unit21is formed by laminating a nozzle plate24having many bored nozzle openings23in line, a flow path forming plate25made of silicon, an elastic plate26, and a vibration plate27and unifying them by adhesion.

As shown inFIG. 4, the nozzle plate24is a thin laminal member in which many nozzle openings23are bored in one row in the nozzle forming direction (the sub-scanning direction) and the bottom of the nozzle plate24forms a nozzle forming face22(FIG. 2).

The case20is a block member in which a storing space28opened on the top and bottom is formed. In the storing space28, a piezoelectric actuator unit29and a fixing member (unit fixing member)30for fixing the piezoelectric actuator unit29to the flow path unit21are stored. The fixing member30is formed by free-cutting ceramics.

To the piezoelectric actuator unit29, a tape carrier package32having a drive integrated circuit31is electrically connected. One face of the drive integrated circuit31is stuck to the piezoelectric actuator unit29, thereby a cooling effect for the drive integrated circuit31is obtained.

As shown inFIGS. 3 and 6, the piezoelectric actuator unit29has a plurality of piezoelectric vibrators33made of PZT arranged in one row. The piezoelectric vibrators33, as shown inFIG. 2, are composed of individual electrode layers43, common electrode layers44, and piezoelectric material layers49which are alternately laminated in the direction perpendicular to the nozzle forming face22, vibrate in the lamination direction of both layers, and have a piezoelectric strain constant d33. The individual electrode layers43are electrode layers of the piezoelectric vibrators33on the drive voltage input side and the common electrode layers44are electrode layers on the reference potential side.

Each of the individual electrode layers43is exposed on one side (the side on the left ofFIG. 2) of each of the piezoelectric vibrators33and each of individual external electrodes45is electrically connected to the exposed part of each of the individual electrode layers43. Further, each of the common electrode layers44is exposed on the other side (the side on the right ofFIG. 2) of each of the piezoelectric vibrators33and each of common external electrodes46is electrically connected to the exposed part of each of the common electrode layers44. The common external electrodes46are electrically connected commonly to all the common electrode layers44of the plurality of vibrators33.

The piezoelectric actuator unit29has a base member47installed on the upper part of the plurality of piezoelectric vibrators33and the plurality of piezoelectric vibrators33which are separated and formed independently from each other are integrally fixed by the base member47. The base member47is formed by free-cutting ceramics.

Further, as a modified example, a constitution that the cutting-in depth when forming the plurality of piezoelectric vibrators33is made slightly shallow, and the cutting is stopped before reaching the base member47, and the plurality of piezoelectric vibrators33are joined to each other on the upper part thereof may be used.

In either case, the upper part of the piezoelectric unit29is formed by the base member47made of ceramics without using an expensive piezoelectric material and electrode material, thereby the manufacturing cost of the piezoelectric unit29can be controlled.

The common external electrodes46pass through the side and top of the base member47and are pulled out up to the side of the individual external electrodes45. The drive integrated circuit31of the tape carrier package32is fixed to the side of the base member47on the side of the individual external electrodes45.

And, in this embodiment, as shown inFIG. 2, the lamination area of the individual electrode layers43and the common electrode layers44is limited to a half on one side of each of the piezoelectric vibrators33in the width direction, thereby the piezoelectric vibrators33respectively have the active parts33acapable of performing piezoelectric deformation and the inactive parts33bincapable of performing piezoelectric deformation. Further, inFIG. 2, also in the inactive parts33b, the electrode layers are displayed in the same plane as that of the common electrode layers44. However, the electrode layers are electrically interrupted from the common electrode layers44and are just used to make the active parts33aand the inactive parts33bequal to each other in thickness.

Further, the recording head12of this embodiment is structured so that the total width of the inactive parts33bin the vibrator width direction perpendicular to the arrangement direction of the plurality of nozzle openings23and the fixing member30is made wider than the width of the active parts33ain the vibrator width direction. By doing this, the strength on the fixing end side is ensured sufficiently and the force generated when the piezoelectric vibrators33are driven will not be absorbed at the fixing end.

As shown inFIGS. 2,3, and4, on the flow path forming plate25, a plurality of pressure chambers34, a common ink chamber35formed for each ink kind, and ink feed ports36for interconnecting the pressure chambers34and the common ink chambers35for each of the pressure chambers34are formed. The pressure chambers34are isolated by partitions37.

As shown inFIGS. 3 and 5, the opening on the top of each of the pressure chambers34is sealed by each of elastic walls26acomposed of a part of the single elastic plate26. The elastic wall26ais deformed according to the deformation of the piezoelectric vibrator33of the piezoelectric actuator unit29, thereby the volume of the pressure chamber34is changed and ink drops can be ejected from the nozzle opening23.

AsFIGS. 3 and 5show, insular movable thick parts38to which the tips of the active parts33a(shown inFIG. 2) of the piezoelectric vibrators22are joined, elastic thin parts (compliance parts)39formed so as to surround the movable thick parts38, a first fixed thick part40A to which the tips of the inactive parts33b(shown inFIG. 2) of the plurality of piezoelectric vibrators33are joined, and a second fixed thick part40B to which the tip of the fixing member30is joined are formed by the elastic plate26and the vibration plate27.

AsFIGS. 2 and 5show, the piezoelectric actuator unit29is fixed to the top of the flow path unit21by the inactive parts33bof the plurality of piezoelectric vibrators33and the fixing plate30, and the case20and the piezoelectric actuator unit29are not fixed to each other. As mentioned above, according to this embodiment, the inactive parts33bof the plurality of piezoelectric vibrators33and the fixing plate30form a unit fixing part for fixing the piezoelectric actuator unit29to the flow path unit21.

As shown inFIG. 2, in the case20, an ink feed path41for feeding ink to the common ink chambers35is formed for each ink kind. The ink feed paths41pass through the elastic plate26and the vibration plate27and interconnect to the common ink chambers35.

As mentioned above, according to this embodiment, the piezoelectric actuator unit25and the flow path unit21are fixed by the inactive parts33bof the piezoelectric vibrators33on one side with respect to the pressure chamber row and are fixed by the fixing member30on the other side with respect to the pressure chamber row. Therefore, the loop of force generated when the piezoelectric vibrators33are expanded and contracted is completed in the piezoelectric actuator unit29and the flow path unit21, thereby the deformation amount of the flow path unit21is reduced and the cross talk is suppressed.

Further, unlike a conventional recording head, there is no need to fix the piezoelectric actuator unit29to the case20, so that the requirements for rigidity and dimensional accuracy to the case20are reduced, and the degree of freedom of material and structure of the case20is increased, thereby the manufacturing cost of the case20can be decreased.

Furthermore, according to this embodiment, by the flow path forming plate25made of silicon, the piezoelectric vibrators33made of PZT, and the base member47and the fixing member30which are made of free-cutting ceramics, the surrounding of the drive part is formed, and these members are made of materials which have coefficients of linear expansion close to each other and cause no swell due to moisture absorption, so that the members are not separated from each other and high reliability can be ensured.

Another embodiment of the present invention may have a constitution shown inFIG. 7, in one recording head, two or more piezoelectric actuator units29are installed, and two or more rows composed of a plurality of nozzle openings23and pressure chambers34are formed, and the piezoelectric actuator units29correspond to each row.

As shown inFIG. 7, the tape carrier package32is pulled out vertically, so that even if the number of piezoelectric actuator units29to be installed is increased as mentioned above, wires can be easily laid.

According to this embodiment shown inFIG. 7, the loop of force generated when the piezoelectric vibrators33are driven is completed in the piezoelectric actuator unit29and the flow path unit21thereof, thereby the cross talk between the pressure chamber rows can be prevented.

In still another embodiment of the present invention, as shown inFIGS. 8 and 9, in place of the fixing member30shown inFIG. 2, additional inactive parts33care formed integrally with the active parts33aas a part of the piezoelectric vibrators33on the side in the vibrator width direction opposite to the side of the inactive parts33bwhile sandwiching the active parts33aof the piezoelectric vibrators33. And, the additional active parts33care joined to the second fixed thick part40B shown inFIG. 5.

This embodiment can produce the same effect as that of the embodiment shown inFIG. 2. Further, the operation of forming the fixing member30separately from the piezoelectric actuator unit29and joining it to the piezoelectric actuator unit29is not required and the manufacturing steps can be simplified.

Further,FIG. 10shows a modified example of the embodiment shown inFIG. 2and in this modified example, the fixing member30is joined to not only the base member47but also the ends of the active parts33aof the piezoelectric vibrators33. And, the parts of the fixing member30joined to the ends of the active parts33aare formed integrally with the plurality of piezoelectric vibrators33in a comb-teeth shape.

An example of the ink jet recording apparatus which is a kind of liquid ejecting apparatus is explained above. However, the present invention can be applied to a liquid ejecting apparatus having other liquid ejecting heads such as a liquid crystal ejecting head or a coloring material ejecting head.

Further,FIG. 11shows another modified example of the embodiment shown inFIG. 2and in this modified example, the piezoelectric vibrators33are composed of only the active parts33awith the inactive parts33bthereof omitted. And, in the parts in which the inactive parts33bare omitted, another fixing member30is installed and the base member47is fixed so as to be held between a pair of fixing members30on both sides in the vibrator width direction.

In this modified example, after the plurality of piezoelectric vibrators33are processed in a comb-teeth shape, the fixing members30may be stuck on the base member47or the fixing members30are stuck on the base member47beforehand and then the fixing members30may be processed in a comb-teeth shape together with the piezoelectric vibrators33. Further, the fixing members30may be formed so as to make the tops of the fixing members30and the top of the base member47flush with each other.

Further,FIG. 12shows still another modified example of the modified example shown inFIG. 11and in this modified example, each of the pair of fixing members30is joined to not only the base member47but also each end of the active parts33aof the piezoelectric vibrators33.

In this modified example, when forming the plurality of vibrators33by the comb-teeth process, the fixing members30are simultaneously processed in a comb-teeth shape.

Further,FIGS. 13 and 14show still another modified example of the embodiment shown inFIG. 2. In this modified example, as shown inFIG. 15, a plurality of nozzle openings23A and23B are formed in two rows and between the nozzle rows, the nozzle openings23A and23B are alternately arranged in a zigzag shape. The plurality of pressure chambers34A and34B, in correspondence to the arrangement of the nozzle openings23A and23B, are also alternately arranged in a zigzag shape.

Each of the plurality of piezoelectric vibrators33includes a half on one side in the vibrator width direction and a half on the other side in the vibrator width direction, and either of the half on one side and the half on the other side forms the active parts, and the other half forms the inactive parts incapable of performing piezoelectric deformation.

And, in the adjacent piezoelectric vibrators33, the arrangement of the active parts and inactive parts is opposite, and the active parts are arranged in correspondence with the nozzle openings23A and23B. Further, in this modified example, the plurality of fixed thick parts40are formed in an insular shape in correspondence with the respective inactive parts33bof the plurality of piezoelectric vibrators33and arranged in a zigzag shape.

Also in this modified example, as shown inFIG. 11, the fixing members30may be arranged on both sides of the piezoelectric vibrators33.

The preferred embodiments of the present invention are described above in detail to a certain degree. However, it is clear that many changes and modifications can be made. Therefore, it can be understood that without being deviated from the scope and spirit of the present invention, in configurations other than those specifically described here, the present invention can be executed.