JP4617799B2 - Inkjet recording head maintenance method and inkjet recording apparatus - Google Patents

Description

  The present invention relates to an ink jet recording head maintenance method and an ink jet recording apparatus, and more particularly, to an ink jet recording head maintenance method for performing printing by discharging ink supplied through a circulation path for circulating ink and the ink jet recording thereof. The present invention relates to an ink jet recording apparatus including a head.

  In an inkjet recording apparatus that prints on a recording medium by ejecting ink droplets from the recording head, a serial scan that performs printing line by line by reciprocating the recording head in a direction perpendicular to the conveying direction while conveying the recording medium The so-called printing method is widely used mainly for personal use. In recent years, a non-scanning type recording head corresponding to a recording medium width in which a large number of ink discharge ports (nozzles) are arranged in a direction (width direction) orthogonal to the recording medium conveyance direction is used to continuously convey the recording medium. However, a so-called full-line head type ink jet recording apparatus has been commercialized, which performs printing while improving the printing speed to be compatible with office use.

  In these ink jet recording apparatuses, in order to prevent ink clogging due to ink drying or foreign matter in the ink, a vacuum operation (maintenance) is performed in which negative pressure is applied to the nozzle from outside to suck ink in the nozzle. . However, in the full line type print head as described above, the ink consumption during the vacuum operation increases as the number of nozzles increases, leading to an increase in running cost. Circulating and removing foreign matter in the ink with a filter provided in the circulation path makes it possible to reduce the number of vacuums so that nozzle clogging is less likely to occur, and to suppress an increase in running cost. is there.

In addition, as a technique for circulating the ink supplied to the recording head in the circulation path in this way, ink (recording body) made of an electrorheological fluid whose viscosity is changed by applying an electric field in the circulation path (supply channel) Circulating and applying an electric field to the ink with an electrode provided on the downstream side of the nozzle to increase the viscosity, the ink can be ejected from the nozzle (for example, see Patent Document 1), or an ink supply source (ink A circulation channel is formed by connecting the loop channel to the tip side of a plurality of common channels extended from the reservoir, and connected to the loop channel when ink is filled from the ink supply source to each common channel Ink is discharged from the nozzle when performing a purge operation, in which each common channel can be quickly filled with ink by sucking with a pump from the suction path formed (see, for example, Patent Document 2). For A purge channel is provided in communication with an ink flow path serving as an ink supply path to the nozzle, and an ink circulation path is configured by the ink flow path and the purge channel (see, for example, Patent Document 3). .
JP-A-2-212147 JP 2000-25218 A JP-A-3-150165

  By the way, in the recording head mounted on the above-described circulation type ink jet recording apparatus, if the ink is circulated with a uniform pressure when performing maintenance in the ink flow path, the ink in the nozzle remains in the nozzle and the ink is retained. It becomes difficult for the ink to flow backward in the flow path, and the ink is not circulated through the circulation path. For this reason, at the start of ink discharge (several dots from the start of discharge), the ink discharge characteristics differ from those at the time of continuous discharge, and there is a problem in that the image quality deteriorates. Further, in a nozzle that does not discharge ink for a long time during printing, the same problem occurs because the ink is easily dried.

  On the other hand, in the technique of Patent Document 1 described above, when performing maintenance of the circulation path, the operation of returning the ink in the nozzles to the circulation path is not performed, and the ejection characteristics at the start of ink ejection are not performed. The above-mentioned problem occurs because no operation is taken into consideration.

  In the case of the technique of Patent Document 2, only when ink is supplied from an ink supply source to each common flow path, a pump is connected to a suction path branched from the circulation path to suck ink, and ink is supplied to each common flow path and circulation path. Therefore, for example, it is not possible to circulate ink in the circulation path during maintenance of the circulation path or when ink is ejected in the printing operation. Therefore, the same problem occurs again.

  In the technique of Patent Document 3, ink flows from the ink flow path to the purge channel at the time of the purge operation, but ink is not circulated at the time of ink discharge. Since the operation for returning the ink in the nozzles to the circulation path at the time of maintenance and the operation considering the discharge characteristics at the start of the ink discharge are not performed, the above problem still occurs.

  In consideration of the above-mentioned fact, the present invention refreshes the ink staying in the nozzle when performing maintenance of the ink jet recording head mounted on the circulation type ink jet recording apparatus, and the ink discharge characteristics at the start of ink discharge It is an object of the present invention to provide an ink jet recording head maintenance method and an ink jet recording apparatus capable of preventing image quality deterioration of an image to be printed in the same manner as in the above. Inkjet recording that prevents ink drying at nozzles that do not discharge ink for a long time during printing, and prevents deterioration in image quality of printed images by setting the discharge characteristics at the start of ink discharge to the same level as during continuous discharge It is an object to provide an apparatus.

According to the first aspect of the present invention, there is provided an ink jet recording head that performs printing by discharging ink onto a recording medium, an ink storage unit that stores ink to be supplied to the ink jet recording head, the ink jet recording head, and the ink storage. And a circulation path for circulating ink supplied from the ink storage means while supplying the ink to the ink jet recording head, and a circulation means provided in the circulation path for circulating the ink in the circulation path in a predetermined direction. And an ink channel that is provided in the ink jet recording head and that allows the ink to flow from the upstream side of the circulation path and to flow the introduced ink to the downstream side of the circulation path, and communicated with the ink channel. It is provided in the ink discharge port and the ink flow path, and the discharge pressure is applied by increasing the pressure of the ink in the ink flow path. And pressurizing means to drive the circulating means to circulate the ink in the circulation path and drive the pressurizing means to vibrate the ink in the ink discharge port. It is characterized by that.

According to the first aspect of the present invention, when the circulation unit is driven, the ink stored in the ink storage unit is circulated through the circulation path and is supplied to the ink jet recording head along with the circulation. In the ink jet recording head, ink supplied through the circulation path flows into the ink flow path from the upstream side of the circulation path, and flows out through the ink flow path to the downstream side of the circulation path.

  In the printing operation by the ink jet recording head, when the pressurizing means provided in the ink flow path is driven, the pressure in the ink in the ink flow path is increased and ejection energy is applied. As a result, ink is ejected from the ink ejection port communicated with the ink flow path, and landed on the recording medium to perform printing.

  Further, during maintenance of the ink jet recording head, the ink staying in the ink discharge port by driving the pressure means provided in the ink flow path of the ink jet recording head while driving the circulation means to circulate the ink in the circulation path Vibrate. As a result, the ink in the ink discharge port is agitated and flows out into the circulation path, and new ink flows into the ink discharge port from the circulation path. By this maintenance, the ink staying in the nozzles is refreshed, so that the ejection characteristics at the start of ink ejection are the same as those at the time of continuous ejection, and it is possible to prevent the image quality of the printed image from being deteriorated.

The invention according to claim 2 is characterized in that the ink in the circulation path is circulated in the direction opposite to that during the printing operation during the maintenance.

In the second aspect of the invention, for example, in order to increase the ink discharge efficiency, in a configuration in which a throttle portion or the like that narrows the cross-sectional area of the flow path is provided downstream of the ink discharge port in the ink flow direction, When clogging occurs at the discharge port, if the ink in the circulation path is circulated in the same direction as during printing during maintenance, foreign matter that causes clogging will not easily flow out to the downstream side at the throttle. Since foreign matter or the like that has flowed out of the ink discharge port is likely to be clogged at the throttle portion, there is a possibility that the clogging cannot be eliminated.

  In contrast, when the ink in the circulation path is circulated in the direction opposite to that during the printing operation during maintenance as described above, the clogging is generated when clogging occurs in the ink discharge port and the throttle portion. Foreign matter or the like can be discharged from the ink jet recording head to the circulation path. As a result, clogging can be reliably eliminated at the ink discharge port and the aperture portion. In addition, foreign matter discharged to the circulation path can be easily removed from the ink by, for example, a filter unit provided in the circulation path, so even if the circulation path ink is circulated in the original direction during the printing operation, Foreign matter or the like does not return to the ink jet recording head, and clogging does not occur at the ink discharge port and the throttle portion.

The invention according to claim 2 is characterized in that a filter unit is provided on the upstream side of the ink jet recording head in the circulation path to remove impurities in the ink by passing the ink. .

According to the second aspect of the present invention, when the ink in the circulation path is circulated in the direction opposite to that during the printing operation at the time of maintenance, impurities discharged from the ink jet recording head to the circulation path are filtered by the filter provided in the circulation path. It is removed from the ink by passing through the unit. Thereby, even if the ink in the circulation path is circulated in the original direction during the printing operation, the impurities do not return to the ink jet recording head and the ink discharge port is not clogged.

  In addition, since the filter unit is disposed upstream of the ink jet recording head in the ink flow direction, the pressure generated by the pressure generating means affects the filter unit even when the pressure generating means is provided in the ink jet recording head. It will never be done.

  Since the ink jet recording head maintenance method and the ink jet recording apparatus of the present invention are as described above, the maintenance of the ink jet recording head mounted in the circulation type ink jet recording apparatus refreshes the ink staying in the nozzles and starts the ink discharge. It is possible to prevent the deterioration of the image quality of an image to be printed with the discharge characteristics being equal to those during continuous discharge. In addition, since the ink jet recording apparatus of the present invention having the circulation type ink jet recording head has the above-described configuration, ink drying at a nozzle that does not discharge ink for a long time during printing is prevented, and the discharge characteristics at the start of ink discharge are reduced. It is possible to prevent deterioration in image quality of an image to be printed, which is equivalent to that during continuous ejection.

  Hereinafter, an ink jet recording head and an ink jet recording apparatus according to embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
The inkjet recording head 10 of the present embodiment shown in FIG. 1 has a flat rectangular parallelepiped shape, and is a non-scanning full line head in which the longitudinal direction (width direction) indicated by the arrow W corresponds to the paper width. As shown in the figure, a piezoelectric element substrate 12, a resin film 14, a flow path substrate 16, and a nozzle substrate 18 stacked in four layers are provided.

  Inside the flow path substrate 16, a common liquid supply flow path 20 extending substantially along the longitudinal direction is formed on one end side (rear end side in FIG. 1) in the short direction indicated by the arrow L. On the other end side (the front end side in FIG. 1), a common drainage flow path 22 extending substantially along the longitudinal direction is formed.

  The common liquid supply flow path 20 penetrates the flow path substrate 16, the resin film 14, and the piezoelectric element substrate 12 downward from the bottom surface of the common liquid supply flow path 20, and the common liquid supply flow path 20 and the ink jet recording. An inflow path 36 that communicates with the outside of the head 10 is connected. One end of a liquid supply pipe 106 for supplying ink to the ink jet recording head 10 is connected to an inlet (not shown) of the inflow path 36 formed in the lower surface of the piezoelectric element substrate 12.

  The common drainage channel 22 penetrates the channel substrate 16, the resin film 14, and the piezoelectric element substrate 12 downward from the bottom surface of the common drainage channel 22, and the common drainage channel 22 and inkjet recording. An outflow path 38 that communicates with the outside of the head 10 is connected. One end of a drainage pipe 108 for discharging ink from the inkjet recording head 10 is connected to an outlet (not shown) of the outlet path 38 formed in the lower surface of the piezoelectric element substrate 12.

  Between the common liquid supply flow path 20 and the common drainage flow path 22, a plurality of individual flow paths 26 partitioned by a plurality of partition walls 24 extending along the short direction are formed. The plurality of individual channels 26 are in communication with the common liquid supply channel 20 and the common drainage channel 22.

  A rectangular opening 28 is formed at the center of the bottom surface of each individual flow channel 26. In each opening 28, a plurality of piezoelectric elements 30 mounted on the piezoelectric element substrate 12 positioned below the flow path substrate 16 are arranged in correspondence with each other, and each piezoelectric element 30 is connected to the piezoelectric element substrate 12 and flows. They are arranged in contact with the lower surface of the resin film 14 provided between the road boards 16. The resin film 14 serves as a protective layer, and each piezoelectric element 30 is protected from corrosion by ink filled in each individual flow path 26.

  A plurality of nozzles 32 corresponding to the individual flow paths 26 and arranged along the longitudinal direction are formed on the nozzle substrate 18 located in the upper layer of the flow path substrate 16.

  As shown in FIG. 2, the nozzle 32 is disposed closer to the common liquid supply flow path 20 than the piezoelectric element 30 (upstream in the ink flow direction). Further, the individual flow path 26 is provided with a throttle portion 34 on the common drain flow path 22 side (downstream side in the ink flow direction) with respect to the piezoelectric element 30. The narrowed portion 34 is formed in a tapered shape on the upstream side in the ink flow direction so as to be gradually reduced from the cross-sectional area (maximum cross-sectional area) of the individual flow path 26 to reach the minimum cross-sectional area. The area is larger than the cross-sectional area of the nozzle 32.

  Next, an ink jet recording apparatus according to this embodiment including the ink jet recording head 10 having the above-described configuration will be described.

  As shown in FIG. 3, the ink jet recording apparatus 100 of the present embodiment is provided with an ink tank 102 for storing liquid ink. One end of an ink supply pipe 104 is connected to the ink tank 102, and ink stored in the ink tank 102 can flow into the ink supply pipe 104.

  The other end of the liquid supply pipe 106 and the other end of the drain pipe 108 are connected to the other end of the ink supply pipe 104, respectively. The connection part 110 of the ink supply pipe 104, the liquid supply pipe 106, and the drainage pipe 108 is trifurcated as shown in the figure, and the liquid supply pipe 106 and the drainage pipe 108 are connected to supply liquid. A circulation path 112 is constituted by the pipe 106 and the drainage pipe 108.

  In the middle of the liquid supply pipe 106, an ink circulation pump 114 is connected to flow the ink flowing from the ink supply pipe 104 to the liquid supply pipe 106 through the connecting portion 110 to the ink jet recording head 10 side. A control valve 116 is connected in the vicinity of the connection portion 110 of the drainage pipe 108, and this control valve 116 closes the connection portion 110 side of the drainage pipe 108 to connect the drainage pipe 108 and the ink supply pipe 104. The communication state is cut off and the circulation path 112 is opened to the atmosphere, or the connection part 110 side of the drainage pipe 108 is opened to establish a communication state between the drainage pipe 108 and the ink supply pipe 104 and the release of the circulation path 112 to the atmosphere is stopped. Perform switching operation.

  Also, foreign matter or bubbles present in the ink are caught between the pump 114 and the ink jet recording head 10 in the liquid supply pipe 106 and between the ink jet recording head 10 and the control valve 116 in the drain pipe 108. Filter units 118 and 120 to be removed from the inside are connected. These filter units 118 and 120 are configured to be attachable to and detachable from the respective pipes.

  Further, the inkjet recording apparatus 100 is provided with a control unit 122 that controls each drive unit of the apparatus and controls the operation of the entire apparatus. The control unit 122 is connected to the ink jet recording head 10, the pump 114, and the control valve 116. By the control unit 122, each piezoelectric element 30 is individually driven and controlled by the ink jet recording head 10 from each nozzle 32. Ink droplet ejection is controlled, the pump 114 is controlled to be driven and stopped, and the control valve 116 is controlled to release the atmospheric air from the circulation path 112 and to stop it.

  Next, the ink supply (filling) operation to the ink jet recording head 10 by the ink jet recording apparatus 100 of the present embodiment configured as described above, the ink circulation operation in the circulation path 112, the printing operation, and the maintenance operation will be described. To do.

  In the ink jet recording apparatus 100, when the ink stored in the ink tank 102 is filled into the circulation path 112 and the ink jet recording head 10, the control unit 122 controls the control valve 116 to control the ink supply pipe 104 and the drain pipe 108. The communication state is cut off, the circulation path 112 is opened to the atmosphere, and the pump 114 is driven after the circulation path 112 is opened to the atmosphere.

  When the pump 114 is driven, ink flows from the ink tank 102 into the ink supply pipe 104, and the ink is supplied to the inkjet recording head 10 through the liquid supply pipe 106. Further, when the ink supplied to the inkjet recording head 10 flows into the drainage pipe 108 and the ink reaches the entire area of the inkjet recording head 10 and the circulation path 112, the control unit 122 controls the control valve 116 to discharge the drainage pipe. 108 is brought into communication with the ink supply pipe 104 to stop the circulation path 112 from being released to the atmosphere.

  Here, in the ink jet recording head 10, as shown in FIG. 1, the ink flows from the liquid supply pipe 106 to the inflow path 36, and the ink passes through the common liquid supply path 20 to each individual flow path 26. Inflow. Further, the ink flowing into each individual flow path 26 passes through the common drain flow path 22 and flows out from the outflow path 38 to the drain pipe 108. As described above, in each individual flow path 26, ink is introduced from the upstream side of the circulation path 112 and the inside of the flow path is filled with ink, and the introduced ink flows out to the downstream side of the circulation path 112. Further, the nozzle 32 communicated with the individual flow path 26 is filled with ink by the pressure in the individual flow path 26, and as shown in FIGS. 2 (A) and 2 (B), it is at a predetermined liquid level position. Quiesce.

  As a result, the circulation path 112 and the ink jet recording head 10 are filled with ink. In this ink filling, a vacuum operation (not shown) may be brought into close contact with the nozzle forming surface 10A of the ink jet recording head 10, and a vacuum operation of applying a negative pressure to the nozzle 32 by the vacuum device and sucking it may be used in combination.

  After ink filling, the pump 114 is continuously driven, and the ink is always supplied to the inkjet recording head 10 while being circulated in the circulation path 112. Further, foreign matters, bubbles, etc. existing in the ink are caught by the filter units 118 and 120 provided in the circulation path 112 and removed from the ink.

  In a printing operation by the inkjet recording apparatus 100, when a printing command is input to the control unit 122, the control unit 122 drives and controls each piezoelectric element 30 of the inkjet recording head 10 based on the printing data. As shown in FIG. 4, the driven piezoelectric element 30 presses the resin film 14 to be deformed so as to bulge into the individual flow path 26 and pressurizes the ink filled in the individual flow path 26. By this pressurization, ejection energy is applied to the ink, and the ink droplet id is ejected from the nozzle 32.

  With this ink ejection operation, in the ink jet recording head 10 of the present embodiment, for example, a diaphragm provided downstream in the ink flow direction compared to a case where a drive source such as a piezoelectric element is provided upstream in the ink flow direction from the nozzle. In the section 34, the fluid resistance is greater during pressurization than during ink flow (circulation). As a result, the pressure generated by the piezoelectric element 30 is applied more to the nozzle 32 side. Therefore, the ink ejection efficiency is improved and energy consumption for ejecting ink can be suppressed.

  In addition, after the ink is discharged, the ink circulates in the circulation path 112 and flows from the upstream side to the downstream side in the individual flow path 26. For example, compared with the case where the ink is not circulated during the printing operation, for example. The ink refilling speed to the nozzle 32 is increased. Therefore, the driving frequency of the piezoelectric element 30 can be increased, and the driving speed for ink ejection can be improved to increase the printing speed.

  Then, as shown in FIG. 3, the ink droplet id discharged from the nozzle 32 lands on the paper P that is located on the nozzle forming surface 10 </ b> A side of the inkjet recording head 10 and is conveyed in a predetermined direction. As a result, an image is recorded on the paper P by the inkjet recording apparatus 100. Further, the ink consumed by the ink ejection from the ink jet recording head 10 is replenished to the circulation path 112 by the ink supplied from the ink tank 102.

  Further, in the maintenance operation of the inkjet recording apparatus 100, the control unit 122 drives and controls the pump 114 so that the ink in the circulation path 112 is circulated in the direction opposite to that during the printing operation. As a result, as shown in FIG. 5, the ink is circulated in the circulation path 112 in the direction opposite to that during the printing operation.

  In addition, the control unit 122 performs drive control so that each piezoelectric element 30 of the inkjet recording head 10 is driven at a predetermined frequency with a smaller deformation amount than during the printing operation. When each piezoelectric element 30 is driven as described above, each nozzle 32 vibrates (slightly vibrates) as shown in FIG. 6 so that the ink staying in the nozzle 32 does not leak. Here, the meniscus M has a convex shape in the vicinity of the opening of the nozzle 32 as shown in FIG. 6B when pressurized, and is drawn into the individual flow path 26 as shown in FIG. 6C when decompressed. It becomes concave. As a result, the ink in the nozzle 32 is agitated, old ink flows out to the individual flow path 26, and new ink flows into the nozzle 32 from the individual flow path 26.

  In addition, when clogging occurs in the nozzle 32 or the narrowing portion 34, the ink in the circulation path 112 is circulated in the direction opposite to that during the printing operation, so that the foreign matter that has caused the clogging is The ink is discharged from the ink jet recording head 10 to the liquid supply pipe 106 and is removed from the ink by passing through a filter unit 118 provided in the liquid supply pipe 106.

  Next, the operation of the inkjet recording apparatus 100 including the inkjet recording head 10 described above will be described.

  In the ink jet recording apparatus 100 of this embodiment, during maintenance of the ink jet recording head 10, the ink staying in the nozzle 32 is vibrated while the ink in the circulation path 112 is circulated, whereby the ink is agitated and flows individually. The ink flows out from the passage 26 to the circulation passage 112 (liquid supply pipe 106), and new ink flows from the circulation passage 112 through the individual passage 26 into the ink discharge port. By this maintenance, the ink staying in the nozzle 32 is refreshed, so that the discharge characteristics at the start of ink discharge can be made equal to those at the time of continuous discharge, and deterioration of the image quality of the printed image can be prevented.

  Further, in the ink jet recording head 10 of the present embodiment, the piezoelectric element 30 is disposed downstream of the nozzle 32 in the ink flow direction during the printing operation, and the throttle portion 34 is further provided downstream of the piezoelectric element 30 in the ink flow direction. As described above, the ink ejection efficiency can be improved as described above. However, in the ink jet recording head having such a configuration, when the ink in the circulation path 112 is circulated in the same direction as in the printing operation during maintenance, the aperture is reduced. In the portion 34, foreign matter or the like that causes clogging is less likely to flow downstream, and foreign matter or the like that has flowed out of the nozzle 32 is likely to be clogged in the throttle portion 34, so that clogging may not be eliminated. There is.

  In contrast, in the present embodiment, the ink in the circulation path 112 is circulated in the direction opposite to that during the printing operation at the time of maintenance. Therefore, when the clogging occurs at the nozzle 32 and the throttle unit 34, the clogging occurs. The foreign matter or the like that has been discharged can be discharged from the ink jet recording head 10 to the circulation path 112 (liquid supply pipe 106). Thereby, clogging can be reliably eliminated by the nozzle 32 and the throttle part 34. In addition, since foreign matter discharged to the circulation path 112 is removed from the ink by the filter unit 118 provided in the liquid supply pipe 106 of the circulation path 112, the ink in the circulation path 112 is returned to the original direction during the printing operation. Even if it is circulated, foreign matter or the like does not return to the ink jet recording head 10 and clogging does not occur at the nozzle 32 and the throttle portion 34.

(Second Embodiment)
In the inkjet recording apparatus 100 according to the first embodiment, the second embodiment improves deterioration of ink ejection characteristics that occur in nozzles that are not ejected for a long time during printing. A printing operation according to the embodiment will be described.

  In the printing operation of the inkjet recording apparatus 100 according to the second embodiment, as in the first embodiment, the control unit 122 drives and controls the pump 114 so that the ink in the circulation path 112 is circulated in the forward direction ( (See FIG. 3).

  Further, the control unit 122 drives the piezoelectric element 30 corresponding to the nozzle 32 that does not eject ink during printing by the inkjet recording head 10 with a smaller deformation amount and a predetermined frequency than during the printing operation as in the maintenance. Drive control is performed. When the piezoelectric element 30 is driven as described above, the nozzle 32 that does not eject ink vibrates (finely vibrates) to an extent that the ink staying in the nozzle 32 does not leak out, as shown in FIG. Here, the meniscus M is convex in the vicinity of the opening of the nozzle 32 as shown in FIG. At the time of depressurization, since the pressure due to the ink circulation is applied from the upstream side, as shown in FIG. 7C, the pressure is retracted to the depth of the nozzle 32, and the convex shape is maintained near the individual flow path 26. Yes.

  With the above operation, in the present embodiment, the ink in the nozzle 32 that is not ejected during the printing operation is agitated to prevent drying. Therefore, when ink ejection is started at the nozzle 32, the ink is ejected. The discharge characteristics at the start of discharge can be made equal to those during continuous discharge. Thereby, it is possible to prevent the image quality of the printed image from being deteriorated.

(Third embodiment)
In the ink jet recording head 10 according to the first embodiment, the third embodiment is provided with pressure generating means for vibrating the ink in the nozzle 32 separately from the piezoelectric element 30. The configuration of the ink jet recording head according to the embodiment and the printing operation thereof will be described. In the inkjet recording head 50 of the present embodiment shown in FIG. 8, the same components as those of the inkjet recording head 10 according to the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  As shown in FIG. 8, the inkjet recording head 50 of the present embodiment is provided with a piezoelectric element 52 inside the flow channel wall surface 36 </ b> A constituting the inflow channel 36. The piezoelectric element 52 is smaller than the piezoelectric element 30 and is driven and controlled by the control unit 122 in the same manner as the piezoelectric element 30.

  In the printing operation by the inkjet recording head 50, as in the first and second embodiments, the control unit 122 drives and controls the pump 114 so that the ink in the circulation path 112 is circulated in the forward direction (see FIG. 3). .

  In addition, the control unit 122 performs drive control so that the piezoelectric element 52 is driven at a predetermined deformation amount and at a predetermined frequency during the printing operation. When the piezoelectric element 52 is driven as described above, each nozzle 32 of the ink jet recording head 50 vibrates (finely vibrates) so that the ink staying in the nozzle 32 does not leak out, as shown in FIG. . Here, the meniscus M is convex in the vicinity of the opening of the nozzle 32 as shown in FIGS. 8A and 8B when pressurized. Further, at the time of decompression, the pressure due to the ink circulation is applied from the upstream side as in the second embodiment, and therefore, as shown in FIG. 8C and FIG. A gentle convex shape is maintained in the vicinity of the individual flow path 26.

  With the above operation, in the present embodiment, the ink in each nozzle 32 is slightly vibrated during the printing operation, and the ink is agitated and prevented from drying in the nozzle 32 where ink is not ejected. When ink discharge is started, the discharge characteristics at the start of ink discharge can be made stable as in the case of continuous discharge. Thereby, it is possible to prevent the image quality of the printed image from being deteriorated.

  In the present embodiment, since the piezoelectric element 52 is disposed upstream of the nozzle 32 in the ink flow direction, the pressure generated by the piezoelectric element 52 does not hinder ink circulation. Thereby, since the ink is rapidly refilled in the nozzles 32 after ink discharge, the drive speed of ink discharge can be improved.

  In this embodiment, the piezoelectric element 52 corresponds to the plurality of nozzles 32 of the inkjet recording head 50, and the ink in the plurality of nozzles 32 is finely vibrated by one piezoelectric element 52. Compared with a configuration in which each pressure generating means is provided for each nozzle, the electrical wiring can be simplified, the flow path configuration and the like can be simplified, and the inkjet recording head 50 can be made smaller.

  In this embodiment, the piezoelectric element 52 is disposed upstream of the nozzle 32 in the ink flow direction. The piezoelectric element 52 is discharged from the ink jet recording head 50 to the liquid supply pipe 106 in the circulation path 112 during maintenance. Therefore, even when such a piezoelectric element 52 is provided in the circulation path, it is upstream of the nozzle 32 in the ink flow direction as in the present embodiment. In addition, the pressure generated by the piezoelectric element 52 can be applied to the ink in the nozzle 32 without being affected by the filter unit 118 by disposing it between the nozzle 32 and the filter unit 118, and a desired meniscus can be obtained. A slight vibration of M can be caused.

(Fourth embodiment)
In the inkjet recording head 10 according to the first embodiment, the fourth embodiment is configured by disposing pressure generating means for vibrating the ink in the nozzle 32 at a position different from that of the third embodiment. The configuration of the ink jet recording head according to the fourth embodiment and the printing operation thereof will be described. In addition, in the inkjet recording head 60 of this embodiment shown in FIGS. 9 and 10, the same components as those of the inkjet recording head 10 according to the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

  As shown in FIG. 9, the inkjet recording head 60 of the present embodiment is provided with two piezoelectric elements 62 </ b> A and 62 </ b> B on the surface of the piezoelectric element substrate 12. These piezoelectric elements 62A and 62B are arranged at positions corresponding to the common liquid supply channel 20 across the inflow path 36 to which the liquid supply pipe 106 of the circulation path 112 is connected (see FIG. 10). The drive is controlled by the control unit 122 in the same manner as the piezoelectric element 52 of the third embodiment.

  Also in the case of the ink jet recording head 60, in the printing operation, the control unit 122 drives and controls the pump 114 so as to circulate the ink in the circulation path 112 in the forward direction (see FIG. 3).

  Further, the control unit 122 performs drive control so as to drive the piezoelectric elements 62A and 62B with a predetermined deformation amount and with a predetermined frequency during the printing operation. As a result, as the piezoelectric elements 62 </ b> A and 62 </ b> B press and release the piezoelectric element substrate 12, the ink filled in the individual flow path 26 is repeatedly pressurized and depressurized, and is placed in each nozzle 32 of the inkjet recording head 60. It vibrates (slightly vibrates) so that the accumulated ink does not leak.

  With the above operation, the same operation and effect as in the third embodiment can be obtained also in the ink jet recording head 60 of the present embodiment. Furthermore, in the present embodiment, the piezoelectric elements 62A and 62B are disposed so as to correspond to the common liquid supply flow path 20, so that the piezoelectric elements 52A and 62B are disposed closer to the nozzle 32 than the piezoelectric element 52 of the third embodiment. Accordingly, the pressure generated by the piezoelectric elements 62A and 62B can be efficiently transmitted to the ink in the nozzle 32.

  As mentioned above, although the present invention was explained in detail by the 1st-3rd embodiment mentioned above, the present invention is not limited to those embodiments, and other various forms are within the limits of the present invention. It can be implemented.

1 is a perspective view showing an external appearance and an internal configuration of an ink jet recording head according to a first embodiment of the present invention with a partial break. FIG. (A) is a longitudinal sectional view schematically showing the vicinity of an individual flow path in the ink jet recording head of FIG. 1, (B) is an enlarged view of 2 (B) of (A), and (C) is (A). It is the enlarged view to which 2 (C) part of was expanded. 1 is a configuration diagram showing a schematic configuration of an ink jet recording apparatus according to a first embodiment of the present invention. (A) is a longitudinal sectional view schematically showing the vicinity of an individual flow path of an ink jet recording head during ink ejection corresponding to FIG. 2 (A), and (B) is an enlarged view of part (B) of (A). FIG. 4C is an enlarged view of a portion 4 (C) of FIG. It is explanatory drawing which shows the ink circulation direction at the time of the maintenance in the inkjet recording device of FIG. (A) is a longitudinal sectional view schematically showing the vicinity of an individual flow path of an ink jet recording head at the time of maintenance corresponding to FIG. 2 (A), and (B) is an enlarged view in which a meniscus in a nozzle at the time of pressurization is enlarged, (C) is the enlarged view which expanded the meniscus in the nozzle at the time of pressure reduction. (A) is a longitudinal sectional view schematically showing the vicinity of an individual flow path where ink is not discharged during a printing operation in the ink jet recording head corresponding to FIG. 2 (A), and (B) is a meniscus in the nozzle during pressurization. An enlarged enlarged view, (C) is an enlarged enlarged view of the meniscus in the nozzle during decompression. In the inkjet recording head according to the third embodiment, (A) schematically shows the vicinity of the individual flow path during the printing operation, (C) is a longitudinal sectional view at the time of pressurization, (C) is a longitudinal sectional view at the time of pressure reduction, (B). FIG. 4 is an enlarged view in which a meniscus in a nozzle corresponding to (A) is enlarged, and (D) is an enlarged view in which a meniscus in a nozzle corresponding to (C) is enlarged. It is a perspective view which shows the external appearance which looked at the inkjet recording head which concerns on the 4th Embodiment of this invention from the surface opposite to the nozzle formation surface side. It is the perspective view which shows the external appearance which looked at the inkjet recording head which concerns on the 4th Embodiment of this invention from the surface opposite to a nozzle formation surface side, and its internal structure by a partial fracture.

Explanation of symbols

10 Inkjet recording head 26 Individual channel (ink channel)
30 Piezoelectric element (pressurizing means)
32 nozzles (ink discharge ports)
50 Inkjet recording head 52 Piezoelectric element (pressure generating means)
60 Inkjet recording head 62A, 62B Piezoelectric element (pressure generating means)
100 Inkjet recording apparatus 102 Ink tank (ink storage means)
106 Liquid supply pipe (circulation path)
108 Drainage pipe (circulation path)
110 Connection (circulation path)
112 Circulation path 114 Pump (circulation means)
id ink drops

Claims (2)

An inkjet recording head that performs printing by discharging ink onto a recording medium;
Ink storage means for storing ink to be supplied to the inkjet recording head;
A circulation path connected to the ink jet recording head and the ink storage means for circulating the ink flowing from the ink storage means to the ink jet recording head;
A circulation means provided in the circulation path for circulating the ink in the circulation path in a predetermined direction;
An ink flow path that is provided in the ink jet recording head, allows ink to flow in from the upstream side of the circulation path, and causes the ink to flow out to the downstream side of the circulation path;
An ink discharge port communicated with the ink flow path;
A pressure unit that is provided in the ink flow path on the downstream side in the ink flow direction from the ink discharge port, and that increases the pressure of the ink in the ink flow path to apply discharge energy;
A throttle part provided in the ink flow path on the downstream side in the ink flow direction with respect to the pressurizing means, and narrowing a cross-sectional area of the ink flow path;
With
Driving the circulation means during maintenance of the ink jet recording head to circulate the ink in the circulation path and drive the pressure means to vibrate the ink in the ink discharge port;
Further, the ink jet recording apparatus characterized in that the ink in the circulation path is circulated in the direction opposite to that during the printing operation during the maintenance.   2. The ink jet recording apparatus according to claim 1, wherein a filter unit that removes impurities in the ink by passing the ink is provided upstream of the ink jet recording head in the circulation path in the ink flow direction.

Images