JP2007076113A - Liquid ejection head and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid ejection head which realizes the preferable ejection and refilling of a liquid, adaptable to high-speed ejection, and an image forming apparatus. <P>SOLUTION: In the ejection of the liquid, when a channel opening/closing member 30 is moved downward in response to the motion of an actuator 26, a nozzle opening/closing part 34, which is provided on the member 30, moves downward to open a nozzle 12, and a supply throttle opening/closing part 36 moves downward to close a supply throttle 28. Ejection efficiency can be enhanced by closing the supply throttle 28 so as to increase supply-side channel resistance. In the refilling, when the member 30 is moved upward, the opening/closing part 34 moves upward to close the nozzle 12, and the opening/closing part 36 moves upward to open the supply throttle 28. Thus, refilling efficiency can be enhanced by decreasing the supply-side channel resistance, and the drying of a meniscus can be suppressed by closing the nozzle 12. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a liquid discharge head and an image forming apparatus, and more particularly to a flow path structure of a liquid discharge head used in a liquid discharge apparatus such as an ink jet recording apparatus.

  In an ink jet recording apparatus, a drive signal is supplied from a drive signal generation source, and a drive element provided in each discharge element of a recording head (liquid discharge head) is driven to discharge ink droplets from the head. It is configured. When ink droplets are ejected from each ejection element, the ink is refilled into the ejection element via the supply-side flow path.

  When the ejection energy is given to the ink in each ejection element, there is not only the ink ejected from the nozzle but also the ink pushed back to the supply side ink flow path. The drive element needs to apply energy (ejection force) to the ejection element, including not only energy for ejecting ink from the nozzles but also energy for pushing ink back to the ink flow path on the supply side. In order to reduce the amount of ink pushed back to the ink flow path on the supply side at the time of ejection, the flow path resistance of the ink flow path on the supply side may be increased. It takes a long time, and refilling during high-speed ejection may not be in time. In an ink jet recording apparatus, various methods have been proposed in order to efficiently perform ink ejection and refilling.

  The inventions described in Patent Documents 1 and 2 include a structure (weir) that is deformed in conjunction with the operation of a valve structure (sphere) or an actuator (drive element) between the pressure chamber and the flow path on the supply side. The discharge efficiency is improved by preventing the back flow of ink to the supply-side flow path during discharge.

Further, the invention described in Patent Document 3 includes independent bimorphs that are deformed on the fluid supply side and the fluid ejection side, respectively, and drives these bimorphs with a time difference so that the flow path on the fluid supply side The flow path on the fluid ejection side is configured to be controlled.
JP-A-8-58085 JP-A-4-341854 Japanese Patent Application No. 5-80270

  However, in the inventions described in Patent Documents 1 and 2, even if the back flow of ink to the supply side during discharge can be prevented, the flow path on the discharge side is not controlled during refill, so the refill efficiency is improved. In addition, there is a high possibility that bubbles will be mixed into the discharge element through the flow path on the discharge side during refilling.

  Further, in the invention described in Patent Document 3, it is necessary to provide bimorphs on the fluid supply side and the fluid discharge side, respectively, and furthermore, since the two bimorphs need to be controlled independently, the system becomes complicated.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a liquid discharge head and an image forming apparatus that can realize preferable liquid discharge and refill corresponding to high-speed discharge.

  In order to achieve the above object, a liquid discharge head according to the present invention includes a nozzle that discharges liquid, a pressure chamber provided corresponding to the nozzle, a supply-side flow path that communicates with the pressure chamber, A supply side flow which is provided in the pressure chamber and closes at least a part of the supply side flow path at the time of discharge for discharging the liquid from the nozzle and opens the supply side flow path at the time of refill to supply the liquid to the pressure chamber. A flow path having a path opening / closing portion and a nozzle opening / closing portion that operates to open the nozzle when discharging liquid from the nozzle and close at least a part of the nozzle when refilling to supply liquid to the pressure chamber And an opening / closing means.

  According to the present invention, at the time of discharge operation in which liquid is discharged from the nozzle, at least a part of the supply side flow path communicating with the pressure chamber is closed and the nozzle is opened, and the liquid is supplied to the pressure chamber through the supply side flow path. At the time of refilling supplied, the flow path opening / closing member provided in the pressure chamber operates so as to open at least a part of the flow path on the supply side and close the nozzle, thereby improving the discharge efficiency and refill efficiency. Sometimes the nozzle is closed to prevent nozzle clogging and air bubbles entering the nozzle and pressure chamber.

  The supply side flow path includes a mode including a liquid flow path (main flow) common to the pressure chambers, and a correspondence including an individual flow path (branch flow) communicating with the pressure chambers from the liquid flow path. A supply restrictor (supply port) is provided in the supply side channel.

  Further, the nozzle may include at least an opening through which liquid is discharged, and may include a discharge-side flow path that communicates with the opening. That is, there are a mode in which the nozzle is closed and a mode in which the opening is closed by the nozzle opening / closing portion and a mode in which the discharge-side flow path is closed by the nozzle opening / closing portion.

  Note that a part of the nozzle may be open to the extent that liquid is not discharged from the nozzle during non-ejection including refilling, but it is preferable that the nozzle be completely closed during non-ejection.

  The liquid ejection head includes a line type head having an ejection hole array having a length corresponding to the entire width of the recording medium (image forming width of the recording medium), and an ejection hole having a length less than the entire width of the recording medium. There is a serial type head that scans a short head provided with a row in the width direction of a recording medium.

  The line type liquid discharge head has a length corresponding to the full width of the recording medium by arranging short heads having short discharge hole arrays that are less than the length corresponding to the full width of the recording medium in a staggered arrangement. It is good.

  A second aspect of the present invention relates to an aspect of the liquid discharge head according to the first aspect, wherein the flow path opening / closing means includes an actuator that applies a discharge force to the liquid stored in the pressure chamber, and the actuator. It includes a movable member that moves in a direction substantially orthogonal to the discharge direction of the liquid discharged from the nozzle in response to the operation.

  According to the second aspect of the present invention, it is possible to open and close the nozzle and open and close the supply-side flow path with a simple configuration, and to move the movable member that moves according to the operation of the actuator in a direction substantially orthogonal to the liquid discharge direction. By configuring so as to move, the nozzles can be arranged with high density.

  As the actuator, a ceramic piezoelectric element (piezoelectric actuator) such as PZT (lead zirconate titanate) is preferably used.

  A third aspect of the present invention relates to an aspect of the liquid ejection head according to the second aspect, wherein the nozzle opening / closing portion is formed on a surface on which the nozzle on the pressure chamber side is formed in response to the operation of the actuator. It moves along, and the said nozzle is opened and closed, It is characterized by the above-mentioned.

  At least at the time of non-ejection, the nozzle opening / closing part comes into contact with the nozzle forming surface inside the pressure chamber so that the nozzle is closed. During discharge, the nozzle opening / closing part may be in contact with the nozzle forming surface inside the pressure chamber, or there may be a space between the nozzle opening / closing part and the nozzle forming surface.

  A fourth aspect of the present invention relates to an aspect of the liquid ejection head according to the second or third aspect, wherein the supply-side flow path opening / closing portion has a cross-sectional area of the supply-side flow path according to the operation of the actuator. The supply-side flow path is varied to open and close.

  A portion where the cross-sectional area is varied in the discharge side channel functions as a supply throttle. It is preferable to completely close the supply-side flow path (supply throttle) during the discharge operation, and to completely open the supply-side flow path (supply throttle) during refilling (the cross-sectional area of the supply-side flow path is in the maximum state). preferable.

  A fifth aspect of the invention relates to an aspect of the liquid ejection head according to the second, third, or fourth aspect, wherein the nozzle opening / closing portion includes a first protrusion provided on the movable member, and the first The area of the protrusion corresponding to the nozzle is equal to or larger than the area of the nozzle.

  The shape of the portion of the first protrusion corresponding to the nozzle may be a substantially square shape, or a shape other than a substantially circular shape or a square shape that is substantially the same shape as the nozzle may be applied.

  According to a sixth aspect of the invention, there is provided the liquid ejection head according to the fifth aspect, further comprising a regulating member that regulates a moving range of the movable member.

  By providing the regulating member within the movable range of the movable member (for example, the stop position of the movable member or the end of the movable range), the movable member (first protrusion) is reliably stopped (moved) at the predetermined stop position. Can be made. Note that at least one regulating member may be provided in the movement range. The restricting member only needs to be provided at least at the stop position (position where the nozzle is closed) of the movable member during non-ejection.

  A seventh aspect of the invention relates to an aspect of the liquid ejection head according to any one of the second to sixth aspects, wherein the supply-side flow path opening / closing portion is a second protrusion provided on the movable member. It is characterized by including a part.

  The second protrusion is provided in the vicinity of the boundary between the supply-side flow path and the pressure chamber, and has a surface that contacts the surface that forms the supply-side flow path and the surface that forms the pressure chamber. That is, the supply-side flow path is closed by contacting the surface forming the second protrusion, the surface forming the supply-side flow path, and the surface forming the pressure chamber.

  Further, by combining the inventions according to claims 5 to 7, it is possible to easily open and close the nozzle and the supply side flow path (supply throttle) at the time of discharge and refill with a simple configuration.

  The invention according to an eighth aspect relates to an aspect of the liquid ejection device according to any one of the first to seventh aspects, wherein the nozzle opening / closing portion and the supply-side flow path opening / closing portion are arranged at the time of ejection. There is a predetermined time difference between the timing for opening the nozzle and the timing for closing the supply-side flow path, and there is a predetermined time difference between the timing for closing the nozzle and the timing for opening the supply-side flow path during refilling. It has a structure.

  According to the eighth aspect of the present invention, by providing a time difference between the opening / closing timing of the nozzle and the opening / closing timing of the supply-side flow path, it is possible to control the period during which the nozzle is open other than during liquid discharge.

  A ninth aspect of the present invention relates to an aspect of the liquid ejection head according to any one of the first to eighth aspects, wherein the supply side flow path opening / closing part is closed by the nozzle opening / closing part. It is characterized by having a structure that opens the discharge side flow path for a predetermined period after being used.

  According to the ninth aspect of the present invention, since the nozzle opening / closing part and the supply side flow path opening / closing part (movable member) have a structure in which the supply side flow path is opened after closing the nozzle, bubbles are mixed from the nozzle during refilling. Can be prevented.

  A tenth aspect of the present invention relates to an aspect of the liquid ejection head according to any one of the first to ninth aspects, wherein the nozzle opening / closing portion is configured to supply the supply side flow by the supply side flow path opening / closing portion. The nozzle is opened after a predetermined period has elapsed since the cross-sectional area of the passage has decreased.

  According to the tenth aspect of the present invention, since the period during which the nozzles are open can be shortened other than during the liquid ejection, drying of the meniscus is suppressed, and nozzle clogging and ejection abnormalities due to this are prevented.

  In order to achieve the above object, an image forming apparatus according to claim 11 is in communication with a nozzle that discharges liquid, a pressure chamber provided corresponding to the nozzle, and the pressure chamber. Supply side flow path, provided in the pressure chamber, closes at least a part of the supply side flow path at the time of discharge for discharging liquid from the nozzle, and on the supply side compared to at the time of discharge at the time of refill to supply liquid to the pressure chamber A supply-side channel opening / closing section that opens the channel, and a nozzle opening / closing operation that opens the nozzle when discharging liquid from the nozzle and closes at least a part of the nozzle when refilling the pressure chamber. And a liquid discharge head having a channel opening / closing means having a portion.

  According to the invention described in claim 11, preferable liquid discharge corresponding to high-speed discharge is realized, and a high-quality image can be obtained. The image here includes, for example, a wiring pattern formed on a printed wiring board, a mask pattern using a mask (resist or the like) used for masking, and the like.

  According to the present invention, the discharge efficiency is improved, the refilling property is improved, and stable liquid discharge is realized even at a high discharge frequency. Further, nozzle clogging due to meniscus drying and air bubbles mixing into the nozzle and the pressure chamber are prevented.

[First Embodiment, Configuration of Liquid Discharge Head]
FIG. 1 is a perspective view showing an appearance of a liquid discharge head (hereinafter referred to as a head) 10 according to the present invention. As shown in FIG. 1, a head 10 is an ink jet head mounted on an ink jet recording apparatus, and has a nozzle forming surface 14 on which a large number of nozzles (discharge holes) 12 for discharging liquid are formed. A liquid is ejected onto a recording medium (not shown) located at a position facing the surface 14 to form a desired image on the image forming surface of the recording medium.

  The head shown in FIG. 1 is a full-line head having two nozzle rows 16 and nozzle rows 18 having a length corresponding to the width direction of the recording medium (image forming width of the recording medium). For the arrangement, a staggered arrangement in which the nozzle rows 16 and the nozzle rows 18 are arranged with their phases shifted in the length direction of each nozzle row (longitudinal direction of the head 10) is applied.

  As shown in FIG. 1, when the nozzles 12 (nozzle row 16 and nozzle row 18) are arranged in a staggered arrangement in which the phases of the two nozzle rows are shifted, the substantial inter-nozzle pitch in the longitudinal direction of the head 50 Can be densified. For example, the nozzle density of the nozzle row 16 and the nozzle row 18 is 300 dpi, and the nozzle row 16 and the nozzle row 18 are arranged with a ½ pitch shift in the arrangement direction of each nozzle row, whereby the nozzle density in the longitudinal direction of the head However, the head 10 of substantially 600 dpi is realized. The nozzle density is merely an example, and the nozzle row 16 and the nozzle row 18 may have a nozzle density of about 100 dpi (substantially about 200 dpi).

  FIG. 2 is a perspective view showing the internal structure of the head 10. The head 10 includes a nozzle plate 29 in which a plurality of openings (holes) serving as nozzles 12 are formed, and a pressure chamber 20 that is a space (gap) in which liquid ejected from each nozzle is accommodated corresponding to each nozzle 12. And an actuator 26 formed on the pressure plate 22 and provided with an individual electrode 24 to which a drive signal is applied on the upper surface opposite to the pressure plate 22 to give a discharge force to the liquid in the pressure chamber 20, and the operation of the actuator 26 Accordingly, a flow path opening / closing member 30 (movable member) that moves in the pressure chamber 20 to open and close the nozzle 12 and the supply throttle 28 is provided.

  The pressure chamber 20 has the flow path opening / closing member 30 and the regulating member 42 as a top surface, a nozzle plate 29 on which the nozzles 12 are formed, a partition wall 20A between adjacent pressure chambers, and a bottom plate 20C (see FIG. 3A). ), And the liquid supplied from the common liquid chamber 38 (see FIG. 3A) via the supply restrictor 28 in FIG. 2 is discharged from the nozzle 12 by operating the actuator 26. It is configured.

  For the actuator 26, a piezoelectric element (piezoelectric actuator) such as PZT (lead zirconate titanate) or PVDF (polyvinylidene fluoride) is preferably used. In this example, electrodes are provided on the upper surface and the lower surface, and when a drive signal is applied between the electrodes, the piezoelectric element is deflected in the lateral direction (a direction substantially perpendicular to the direction in which the drive signal is applied), and the pressure plate 22 is moved up and down. A bender type piezoelectric element using a d31 mode displacement that is deformed in the direction is applied. When a metal material is used for the pressure plate 22, the common electrode of the actuator 26 is also used as the pressure plate 22.

  The actuator 26 applied to the present invention is a bimorph type piezoelectric element in which two piezoelectric elements are laminated such that one piezoelectric element deflects in the expansion direction and the other piezoelectric element in the contraction direction. A piezoelectric element such as an element may be applied. Note that the pressure plate 22 is not necessary in the embodiment using the bimorph piezoelectric element.

  The nozzle plate 29 is a plate having the nozzle forming surface 14 shown in FIG. 1, and a metal material such as SUS is preferably used. The nozzle 12 in FIG. 2 represents an opening through which liquid is discharged, but in this specification, the nozzle 12 may indicate an opening through which liquid is discharged, and the opening from the pressure chamber 20 may be the same. A pipe line (discharge-side flow path in FIG. 2, the thickness portion of the nozzle plate 29) may be shown. When these are not confused, the term “nozzle” is used without particular notice.

  Note that the discharge-side flow path described above may have a tapered portion in which the flow path diameter gradually decreases from the pressure chamber 20 side to the outside of the head 10, or includes a plurality of pipe lines having different flow path diameters. May be. Of course, a conduit having a substantially uniform channel diameter over the entire region may be applied.

  The flow path opening / closing member 30 is joined to the pressure plate 22 and the actuator 26 via the joining member 32. The flow path opening / closing member 30 includes a nozzle opening / closing portion 34 (first protrusion) that opens and closes the nozzle 12 and a supply throttle opening / closing portion 36 (second protrusion, supply throttle opening / closing portion 36) that opens and closes the supply throttle 28. 3), and a material such as resin or metal is used. The flow path opening / closing member 30 is subjected to a predetermined surface treatment so as to ensure predetermined liquid resistance and wear resistance. When a material excellent in liquid resistance and wear resistance is used, the surface treatment is unnecessary.

  Next, the ejection operation of the head 10 of this example will be described. The second actuator 26A from the right in FIG. 2 is in a discharge operation state to which a drive signal is applied, and is a flow path opening / closing member 30A (a nozzle opening / closing portion included in the flow path opening / closing member 30A) joined to the actuator 26A in the discharge operation state. 34A) is pushed downward in FIG. 2, the nozzle 12A corresponding to the actuator 26A in the discharge operation state is opened, and the liquid is discharged from the nozzle 12A.

  The discharge operation state here is a state from when a drive signal is supplied to the actuator 26 to discharge the liquid until the actuator 26 operates and the liquid is discharged from the nozzle 12.

  Further, in the state where the actuator 26 is not operating (static state, initial state of the pressure chamber 20, state of three actuators excluding the second actuator 26A from the right in FIG. 2), it is provided in the flow path opening / closing member 30. The nozzle 12 is closed from the inside of the pressure chamber 20 by the nozzle opening / closing part 34. In other words, the nozzle opening / closing part 34 functions as a cover for the nozzle 12 in the initial state of the pressure chamber 20 where the actuator 26 is not operating.

[Description of liquid ejection (droplet ejection) operation]
Next, the liquid discharge operation of the head 10 shown in this example will be described in detail. FIG. 3 shows a state of the pressure chamber 20 at the time of discharge, and FIG. 4 shows a state of the pressure chamber 20 (an initial state of the pressure chamber) when the actuator 26 is in a static state.

  3 (a) and 4 (a) are perspective views (transverse sections) viewed from the direction indicated by X in FIG. 2, and FIGS. 3 (b) and 4 (b) are indicated by Y in FIG. It is the perspective view (upper section) seen from the direction shown. 3B and 4B, the actuator 26, the pressure plate 22, the joining member 32, and the regulating member 42 are not shown.

  As shown in FIG. 3A, a predetermined drive signal is applied to the actuator 26 during the liquid discharging operation, and the pressure plate 22 joined to the actuator 26 is deformed and joined via the pressure plate 22 and the joining member 32. The flow path opening / closing member 30 to be moved moves downward (shown by an arrow line) in FIG.

  As described above, when the flow path opening / closing member 30 moves downward in FIG. 3A, the nozzle opening / closing portion 34 moves downward in FIG. 3A and the nozzle 12 is opened. Further, the volume of the pressure chamber 20 is reduced, and an amount of liquid corresponding to the volume change of the pressure chamber 20 is discharged from the nozzle 12 to the outside of the head 10. Furthermore, the supply throttle opening / closing section 36 moves downward in FIG. 3A, whereby the supply throttle 28 is closed.

  In this way, by moving the flow path opening / closing member 30 so as to open the nozzle 12 and close the supply throttle 28 during the liquid discharge, the supply throttle 28 to the common liquid chamber 38 (supply-side flow path) is discharged during the discharge operation. The backflow of liquid is prevented and the discharge efficiency is expected to improve. 3A and 3B show a state in which the supply throttle 28 is completely closed during the discharge operation (discharge timing), the flow path resistance of the supply throttle 28 (of the supply side flow path) is shown. If the state in which the flow path resistance) is sufficiently smaller than the flow path resistance of the nozzle 12 (flow path resistance of the discharge side flow path) is maintained, a part of the supply throttle 28 may be opened.

  The nozzle opening / closing part 34 has a surface that comes into contact with the pressure chamber side surface (nozzle formation surface 46) of the nozzle plate 29, and the shape of this contact surface is substantially rectangular. Of course, it is good also as a substantially circular shape similarly to the nozzle 12, and shapes other than a substantially square shape or a substantially circular shape may be applied. This contact surface is at least substantially the same as or larger than the nozzle 12. In order to achieve both adhesion and slidability between the nozzle plate 29 and the nozzle opening / closing part 34, a groove having a size corresponding to the nozzle opening / closing part 34 is formed on the portion of the nozzle plate 29 that contacts the nozzle opening / closing part 34. It is good to apply.

  The throttle opening / closing section 36 shown in this example has a shape that protrudes from the common liquid chamber 38, and has a surface that contacts the bottom surface 40 of the common liquid chamber 38 when the supply-side flow path is closed. That is, in a state where the bottom surface 40 of the common liquid chamber 38 and the throttle opening / closing part 36 are in contact, the cross-sectional area of the supply throttle 28 is zero.

  Further, the flow path opening / closing member 30 has an inclined surface 41 in the vicinity of the boundary between the pressure chamber 20 and the common liquid chamber 38, and the pressure chamber 20 has a structure that does not have an angular (right angle) shape in the ink flow path. Generation of bubbles near the boundary between the liquid chamber 38 and the common liquid chamber 38 is prevented.

  4A and 4B show an initial state of the pressure chamber 20 after the refill is completed. After the liquid is discharged from the nozzle 12, the liquid is supplied from the common liquid chamber 38 to the pressure chamber 20 via the supply throttle 28 (the liquid supply direction is indicated by an arrow line). When refilling, the actuator 26 returns to the initial state. When the flow path opening / closing member 30 moves upward in FIG. 4A by using the operation, the nozzle opening / closing portion 34 also moves upward, and the nozzle 12 is moved inside the pressure chamber 20 by the nozzle opening / closing portion 34. It will be in a state of being blocked from.

  Further, when the flow path opening / closing member 30 is moved upward in FIG. 4 (a), the supply throttle opening / closing portion 36 is also moved upward in FIG. 4 (a), and the supply throttle 28 shown in FIG. Opened.

  That is, in the initial state of the pressure chamber 20 shown in FIGS. 4A and 4B, the state where the nozzle 12 is closed by the nozzle opening / closing portion 34 and the supply throttle 28 is opened (discharge operation). The state in which the cross-sectional area of the supply restrictor 28 is larger than that of the case is maintained.

  The flow path opening / closing member 30 has a position where the supply throttle opening / closing portion 36 contacts the bottom surface 40 of the common liquid chamber 38 (that is, a position where the supply throttle 28 shown in FIG. 3A is completely closed). 4 (a), the nozzle opening / closing portion 34 is in contact with a regulating member 42 that regulates the upper end of the nozzle opening / closing portion 34 provided inside the pressure chamber 20 (ie, shown in FIG. 4A). The nozzle 12 has a movement range in which the position where the nozzle 12 is completely closed) is set as the other end (non-ejection end), and the nozzle side end (tip end) 44 of the nozzle opening / closing portion 34 is pressurized. While contacting the nozzle formation surface 46 of the chamber 20, it is configured to be movable in the vertical direction in FIGS. 3A and 4A along the nozzle formation surface 46. FIG.

  4 (a) and 4 (b) show a state in which the nozzle 12 is completely closed in the initial state of the pressure chamber 20, the flow resistance of the nozzle 12 (the flow resistance of the discharge side flow path). ) Is maintained sufficiently smaller than the flow resistance of the supply restrictor 28 (flow resistance of the supply-side flow path), and a part of the nozzle 12 is opened if it is within an allowable range from the viewpoint of preventing meniscus drying. It may be. However, the nozzle 12 is preferably completely closed in the initial state of the pressure chamber 20.

  Further, in this example, the mode in which the static state of the actuator 26 shown in FIGS. 4A and 4B is set to the initial state of the pressure chamber 20 is shown, but a drive signal having a predetermined constant voltage is applied to the actuator 26. A state in which a constant negative pressure is generated in the pressure chamber 20 by applying the pressure chamber 20 may be an initial state of the pressure chamber 20.

  Next, the state transition of the pressure chamber 20 during the discharge operation and the refill operation will be described with reference to FIGS. FIG. 5 shows the relationship between the passage of time and the cross-sectional area of the opening of the nozzle 12 (cross-sectional area of the discharge-side flow path) and the cross-sectional area of the supply restrictor 28 (cross-sectional area of the supply-side flow path) during the discharge operation. . 5 and 6, the cross-sectional area of the opening portion of the nozzle 12 and the cross-sectional area of the supply restrictor 28 are expressed as relative cross-sectional areas when the maximum cross-sectional area is 1.

  As shown in FIG. 5, the state in which the opening portion of the nozzle 12 has the maximum cross-sectional area is a state in which the flow path opening / closing member 30 is located at the above-described discharge end (lower end), and the supply throttle 28 has the maximum cross-sectional area. This state is a state in which the flow path opening / closing member 30 is located at the above-described non-ejection end (upper end).

  The timing t0 in FIG. 5 is the discharge operation off state, the nozzle 12 is completely closed (that is, the sectional area of the opening portion is 0), and the supply throttle 28 is in the maximum sectional area (that is, , State of cross-sectional area 1). In other words, the timing t0 in FIG. 5 is the initial state of the pressure chamber 20 where the flow path opening / closing member 30 shown in FIG.

  When a drive signal for the discharge operation is given to the actuator 26, the flow path opening / closing member 30 moves downward in FIGS. 3 (a) and 4 (a), and the cross-sectional area of the opening portion of the nozzle 12 is corresponding to the time. The cross-sectional area of the supply restrictor 28 gradually decreases as time passes. The flow path opening / closing member 30 moves downward in FIGS. 3 (a) and 4 (a) and is positioned at the discharge end shown in FIG. 3 (a) at the timing t1 in FIG. ), The cross-sectional area of the opening of the nozzle 12 is the maximum (that is, the state of the cross-sectional area 1), the cross-sectional area of the supply restrictor 28 is the minimum (in this example, the state of the cross-sectional area 0), and the liquid from the nozzle 12 Is discharged.

  FIG. 6 shows the relationship between the passage of time and the cross-sectional areas of the nozzle 12 and the supply restrictor 28 during the refill operation.

  The timing t10 in FIG. 6 is the discharge operation on state, the nozzle 12 is in the maximum cross-sectional area, and the supply restrictor 28 is completely closed. That is, the timing t10 during the refilling operation is the state shown in FIGS. 3A and 3B, and in this state, the liquid is ejected from the nozzle 12.

  When a drive signal for the refill operation is given to the actuator 26 after the liquid is discharged from the nozzle 12, the flow path opening / closing member 30 in the state shown in FIGS. 3 (a) and 3 (b) is shown in FIGS. 3 (a) and 4 (a). ) And the cross-sectional area of the opening of the nozzle 12 gradually decreases with time as the flow path opening / closing member 30 moves upward in FIGS. 3 (a) and 4 (a). The sectional area of the supply restrictor 28 gradually increases with time. The flow path opening / closing member 30 moves upward in FIGS. 3 (a) and 4 (a), and at the timing t11 in FIG. 6, the pressure chamber 20 located at the non-ejection end portion shown in FIG. 4 (a). In the initial state (discharging operation off), the cross-sectional area of the opening of the nozzle 12 is minimum (in this example, the cross-sectional area is 0), and the cross-sectional area of the supply restrictor 28 is maximum.

  As described above, the flow path opening / closing member 30 (having the nozzle opening / closing function and the supply throttle opening / closing function) having the nozzle opening / closing portion 34 and the supply throttle opening / closing portion 36 is set according to the operation of the actuator 26 (in response to the discharge operation and the refill operation). The nozzle 12 is opened and closed and the supply throttle 28 is opened and closed by moving the pressure chamber 20.

  The liquid discharge head 10 configured as described above improves the discharge efficiency by closing at least a part of the supply restrictor 28 and preventing the liquid from flowing back to the supply-side flow path during the discharge operation. Further, during non-ejection (for example, the initial state of the pressure chamber 20), the nozzle 12 is closed by the nozzle opening / closing part 34, thereby preventing the meniscus drying and the liquid thickening due to the meniscus drying. In addition, it is not necessary to add a function (for example, meniscus vibration) for avoiding ink thickening due to drying of the meniscus to the head, and the structure and system (control) of the head 10 can be simplified. Furthermore, since the possibility of occurrence of an abnormal discharge (non-discharge) phenomenon due to bubble mixing or meniscus solidification can be reduced, the reliability of the head 10 is expected to be improved.

  In addition, at least in the initial state of the pressure chamber 20, the nozzle 12 is blocked by the nozzle opening / closing part 34, so that a structure that is not affected by fluid crosstalk generated by driving other parts is realized. This facilitates the high-density arrangement of the nozzles 12.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. Note that, in the second embodiment, the same or similar parts as those of the first embodiment described above are denoted by the same reference numerals, and the description thereof is omitted.

  7A and 7B show the state of the head 100 during ejection, and FIGS. 8A, 8B, and 9 are diagrams showing the state of the head 100 during non-ejection. That is, FIGS. 7A and 7B correspond to FIGS. 3A and 3B of the first embodiment described above, and FIGS. 8A, 8B, and 9 show FIGS. ), (b).

  During the discharge operation of the head 100, the flow path opening / closing member 30 is moved downward in FIG. 7A from the non-discharge end portion according to the operation of the actuator 26 (moved to the discharge end portion). And the supply throttle 28 is closed. As the flow path opening / closing member 30 moves, the volume of the pressure chamber 20 decreases, and an amount of liquid corresponding to the volume change of the pressure chamber 20 is discharged from the nozzle. Further, since the supply throttle 28 is closed, the backflow of liquid from the pressure chamber 20 to the common liquid chamber 38 is prevented.

  8A and 8B show the state of the pressure chamber 20 on the way to the initial state of the pressure chamber 20 from the time of discharge shown in FIG. 7, and FIG. 9 shows the initial state of the pressure chamber 20. . In the state shown in FIG. 8, the nozzle 12 is completely closed by the nozzle opening / closing part 34, but since there is a gap between the nozzle opening / closing part 34 and the regulating member 42, the nozzle opening / closing part 34 (flow The road opening / closing member 30) is further movable upward in FIG. 8A from the state shown in FIG. That is, the pressure chamber 20 shown in FIG. 8A is in a state where the flow path opening / closing member 30 is positioned between the discharge end portion and the non-discharge end portion.

  The state shown in FIG. 8A is a static state where the drive signal is not applied to the actuator 26, and the actuator 26 and the pressure plate 22 are in a flat state where no deformation (deflection) occurs.

  FIG. 9 shows the pressure chamber in the second embodiment in which the flow path opening / closing member 30 is further moved from the state shown in FIG. 8A toward the non-ejection end portion (upper side in FIGS. 8A and 9). 20 shows an initial state. In the liquid ejection head 100 according to the second embodiment, the actuator 26 is driven so that the pressure plate 22 protrudes upward in FIG. 9 (outward direction of the pressure chamber 20), from the state shown in FIG. 8A and 9, the flow path opening / closing member 30 is moved in the upward direction, and the state where the nozzle opening / closing portion 34 is moved to a position where the nozzle opening / closing portion 34 is in contact with the regulating member 42 (that is, the end portion at the time of non-ejection) is shown. There are 20 initial states.

  That is, in the liquid discharge head 100 according to the second embodiment, the position of the regulating member 42 that regulates the position of the flow path opening / closing member 30 (nozzle opening / closing section 34) in the initial state of the pressure chamber 20 The position of the discharge end portion is located closer to the pressure plate 22 (upper side) than the liquid discharge head 10 according to the first embodiment, and the nozzle 12 is completely closed even when the nozzle 12 is completely closed. It is possible to move the flow path opening / closing member 30 further upward in FIG. 8 while maintaining the closed state.

  Next, the state transition of the pressure chamber 20 during the discharge operation and the refill operation will be described with reference to FIGS. FIG. 10 shows the relationship between the passage of time, the cross-sectional area of the opening of the nozzle 12 and the cross-sectional area of the supply restrictor 28 during the discharge operation. As in the first embodiment, in FIGS. 10 and 11, the cross-sectional area of the opening portion of the nozzle 12 and the cross-sectional area of the supply restrictor 28 are relative to each other when the maximum cross-sectional area is 1. It is represented by

  As shown in FIG. 10, the state in which the opening portion of the nozzle 12 has the maximum cross-sectional area is a state in which the flow path opening / closing member 30 illustrated in FIGS. 7 (a) and 7 (b) is located at the discharge end. The state in which the supply restrictor 28 has the maximum cross-sectional area includes a state in which the flow path opening / closing member 30 is in the position shown in FIG. 8A and a state in which the flow restrictor 30 is located at the non-ejection end portion shown in FIG. State).

  At timing t20 in FIG. 10, the discharge operation is off, the nozzle 12 is completely closed (that is, the opening has a cross-sectional area of 0), and the supply throttle 28 has the maximum cross-sectional area (that is, , State of cross-sectional area 1). In other words, the timing t20 in FIG. 10 is the initial state of the pressure chamber 20 where the flow path opening / closing member 30 shown in FIG. 9 is located at the non-ejection end.

  Further, at timing t21 in FIG. 10, the discharge operation is on, the nozzle 12 is in the maximum cross-sectional area, and the supply restrictor 28 has the minimum cross-sectional area (in the example shown in FIG. 10, the cross-sectional area is zero). is there.

  When a drive signal for the discharge operation is given to the actuator 26 at timing t20, the flow path opening / closing member 30 moves downward in FIG. 7 (a) and the like, and the flow path opening / closing member 30 in the downward direction in FIG. 7 (a) and the like. The cross-sectional area of the supply restrictor 28 gradually decreases with the passage of time in accordance with the movement of. On the other hand, when the sectional area of the opening portion of the nozzle 12 is maintained to the minimum until the timing t22, and the flow path opening / closing member 30 continues to move downward in FIG. It gradually increases with time and reaches its maximum at timing t21.

  FIG. 11 shows the relationship between the passage of time during the refilling operation and the cross-sectional areas of the nozzle 12 and the supply restrictor 28. At timing t30 in FIG. 11, the discharge operation is on, the nozzle 12 has the maximum cross-sectional area, and the supply throttle 28 has the minimum cross-sectional area. That is, at the timing t30 shown in FIG. 11, the pressure chamber 20 is in the state shown in FIGS. 7 (a) and 7 (b).

  When a drive signal for the refill operation is given to the actuator 26, the flow path opening / closing member 30 in the state shown in FIGS. 7A and 7B moves upward in FIG. In accordance with the upward movement in FIG. 7 and the like, the cross-sectional area of the opening portion of the nozzle 12 gradually decreases with time, and the cross-sectional area of the supply restrictor 28 gradually increases with time.

  The timing t31 in FIG. 11 is the initial state (discharging operation off) of the pressure chamber 20 where the flow path opening / closing member 30 shown in FIG. 9 is located at the non-ejection end, and the sectional area of the opening portion of the nozzle 12 is minimized. The cross-sectional area of the supply restrictor 28 is maximized.

  When the refill operation is started at the timing t30, the nozzle 12 has a minimum cross-sectional area at the timing t32. In the period from the timing t32 to the timing t31, the nozzle 12 has a minimum cross-sectional area. Maintained. On the other hand, the cross section of the supply restrictor 28 gradually increases with time in the period from timing t30 to timing t31.

  That is, in the head 100 of this example, the nozzle 12 is quickly closed and the supply throttle 28 is slowly opened during the refilling operation, so that air bubbles are prevented from entering the pressure chamber 20 from the outside of the head via the nozzle 12 during the refilling operation. In addition, since the nozzle 12 is closed for a predetermined period from the start of the discharge operation during the discharge operation, meniscus drying and ink thickening are prevented.

[Description of manufacturing method]
Next, a method for manufacturing the liquid ejection head 10 according to the first embodiment and the head 100 according to the second embodiment will be described. In addition, the manufacturing method of the liquid discharge heads 10 and 100 is common, and here, the manufacturing method of the head 10 will be described.

  As shown in FIG. 12, it has a structure in which the structure 10 having the nozzle array 16 shown in FIG. 1 and the head 10 and the structure 202 having the nozzle array 18 are overlapped. It has almost the same structure.

  As shown in FIG. 12, the structure 200 and the structure 202 have a laminated structure in which a plurality of cavity plates 220 and 222 are laminated, and the structure 200 and the structure 202 are configured to share a common liquid chamber 204. Has been. Reference numerals 206 and 208 denote actuator covers for protecting the actuators 26 formed on the structures 200 and 202, respectively. The actuator covers 206 and 206 are formed with recesses 210 and 212 corresponding to the positions where the actuators 26 are disposed.

  FIGS. 13A and 13B show an example of a cavity plate constituting the head 10 shown in FIG. FIG. 13A shows the planar shape of the cavity plate 220, and FIG. 13B shows the planar shape of the cavity plate 222.

  After the cavity plates 220 and 222 shown in FIGS. 13A and 13B are stacked, the pressure plate 22 to which the actuator 26 and the flow path opening / closing member 30 are joined is joined, and the actuator covers 206 and 208 are joined. The nozzle plate 29 on which the nozzles 12 are formed is joined to form the head 10.

  Metal plates such as SUS, resin materials, silicon, etc. are liquid resistant, wear resistant, and insulated for the cavity plates 220 and 222 shown in FIGS. 13 (a) and 13 (b) and other cavity plates constituting the liquid flow path. It is appropriately selected from conditions such as performance. Of course, one type of material may be selected from these materials, or cavity plates of different materials may be combined.

[Description of Other Embodiments]
Next, another embodiment according to the present invention will be described. 14 and 15 show a mode in which a laminated piezoelectric element is applied to an actuator that functions as an ejection force applying means.

  FIG. 14 is a plan view of the head 300 as viewed from the nozzle forming surface, and FIG. 15 is a cross-sectional view showing the three-dimensional structure of the head 300. As shown in FIG. 14, the head 300 includes a head structure 304 in which the nozzle row 302 is formed and a head structure 308 in which the nozzle row 306 is formed, and a structure in which these head structures 304 and 308 are overlapped. have. In the head 300, a laminated piezoelectric element 310 is disposed on the side opposite to the joint portion of each head structure 304, 308 corresponding to each nozzle 12. A constraining member 312 for restricting displacement of the multilayer piezoelectric element 310 in the direction opposite to the pressure plate 22 is provided on the side opposite to the pressure plate 22 (illustrated by a broken line) of the multilayer piezoelectric element 310.

  The stacked piezoelectric element 310 has a structure in which piezoelectric layers and electrode layers are alternately stacked, and a drive signal is applied so as to generate a d33 mode displacement in each piezoelectric layer. Such a multilayer piezoelectric element 310 can obtain a large energy when the same voltage is applied as compared with a single-layer piezoelectric element or a bimorph piezoelectric element.

  As shown in FIG. 15, the head structure 304 and the head structure 308 have the same structure, and the head 300 can be manufactured by combining two head structures formed in the same process. Simplification of the manufacturing process is expected.

  Next, a mode in which a matrix array is applied to the nozzle array will be described. The head 400 shown in FIGS. 16 and 17 includes nozzles 12 arranged in a matrix composed of six nozzle rows.

  FIG. 16 is a plan view of the head 400 as viewed from the nozzle forming surface 14 side, and FIG. 17 is a perspective view of the head 400. As shown in FIG. 16, the head 400 includes a head structure 404 in which the nozzle row 402 is formed, a head structure 408 in which the nozzle row 406 is formed, a head structure 412 in which the nozzle row 410 is formed, A head structure 416 in which the nozzle row 414 is formed, a head structure 420 in which the nozzle row 418 is formed, and a head structure 424 in which the nozzle row 422 is formed, and each head structure 404, 408, 412, 426, and 420 are arranged with the phase shifted in the nozzle arrangement direction.

  In order to increase the dot pitch formed on the recording medium, it is necessary to increase the nozzle pitch in the head 400. The head 400 of this example has a structure in which the nozzles 12 are arranged in a matrix, thereby achieving a high density of the substantial nozzle interval (projection nozzle pitch) projected so as to be aligned along the longitudinal direction of the head. ing.

  That is, in the head 400 shown in this example, even if the nozzle density of the nozzle rows 402, 406, 410, 414, 418, 422 formed in the head structures 404, 408, 412, 416, 420 is not increased, The nozzle arrangement density as the head 400 can be increased.

  For example, by arranging a large number in a grid pattern in a constant array pattern along a row direction along the longitudinal direction of the head 400 and an oblique column direction having a constant angle θ not orthogonal to the longitudinal direction of the head 400, The head 400 in which the nozzles are arranged at high density in this example is realized.

  That is, with a structure in which a plurality of nozzles 12 are arranged at a constant pitch d along the direction of an angle θ with respect to the longitudinal direction of the head 400, the pitch P of the nozzles 12 projected so as to be aligned in the longitudinal direction of the head 400 is d × cos θ, and in the longitudinal direction of the head 400, each nozzle 12 can be treated equivalently as a linear arrangement with a constant pitch P.

  In this example, the space (surface) formed by the flow path opening / closing member 30 (throttle opening / closing portion 36) and the bottom surface 40 of the common liquid chamber 38 becomes the supply throttle 28, and the flow path opening / closing member 30 is moved in the vertical direction. In the above embodiment, the cross-sectional area of the supply restrictor 28 is varied. However, the flow path opening / closing member 30 (the restrictor opening / closing part 36) is moved along the restrictor plate having the opening serving as the supply restrictor 28, and the area of the opening (supply The cross-sectional area of the diaphragm 28 may be varied.

  In the above embodiment, a page-wide full-line head having a nozzle row having a length corresponding to the entire width of the recording medium has been described. However, the scope of application of the present invention is not limited to this, and a short recording head is reciprocally moved. The present invention can also be applied to a shuttle head that records an image while the image is being recorded.

  The liquid ejection head according to the present invention forms an image (three-dimensional shape) with a liquid other than ink, such as a resist, in addition to an ink jet recording apparatus that ejects ink onto a recording medium to form a desired image on the recording medium. The present invention can also be widely applied to image forming apparatuses, liquid discharge apparatuses such as dispensers that discharge chemicals, water, and the like from nozzles (discharge holes).

1 is an overall configuration diagram of a liquid discharge head according to the present invention. FIG. 2 is a perspective view showing the internal structure of the liquid ejection head shown in FIG. Sectional drawing which shows the three-dimensional structure of the liquid discharge head which concerns on 1st Embodiment of this invention. The figure explaining operation | movement of the liquid discharge head shown in FIG. The figure explaining the relationship between passage of time at the time of discharge operation of the liquid discharge head shown in FIG. The figure explaining the relationship between time passage at the time of the refill operation | movement of the liquid discharge head shown in FIG. 3, and a flow-path cross-sectional area. Sectional drawing which shows the three-dimensional structure of the liquid discharge head which concerns on 2nd Embodiment of this invention. The figure explaining operation | movement of the liquid discharge head shown in FIG. The figure explaining the initial state of the pressure chamber of the liquid discharge head which concerns on 2nd Embodiment of this invention. The figure explaining the relationship between passage of time at the time of discharge operation of the liquid discharge head shown in FIG. The figure explaining the relationship between the passage of time and the cross-sectional area of the flow path during the refilling operation of the liquid ejection head shown in FIG. Diagram explaining the laminated structure The top view which shows an example of the cavity plate which comprises the laminated structure shown in FIG. The top view of the liquid discharge head which concerns on other embodiment of this invention. Sectional view of the liquid ejection head shown in FIG. The top view of the liquid discharge head which concerns on other embodiment of this invention. The perspective view of the liquid discharge head shown in FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10,100,300,400 ... Head, 12 ... Nozzle, 20 ... Pressure chamber, 22, 22A ... Pressure plate, 24, 24A ... Individual electrode, 26, 26A ... Actuator, 28 ... Supply restriction, 30 ... Flow path opening / closing member 34 ... Nozzle opening / closing part, 36 ... Supply throttle opening / closing part, 42 ... Restriction member

Claims (11)

A nozzle for discharging liquid;
A pressure chamber provided corresponding to the nozzle;
A supply-side flow path communicating with the pressure chamber;
Supply side that is provided in the pressure chamber and closes at least a part of the supply-side flow path at the time of discharge for discharging liquid from the nozzle, and opens the supply-side flow path at the time of refill to supply liquid to the pressure chamber compared to at the time of discharge A flow path opening / closing section, and a nozzle opening / closing section that operates to open at the time of discharging for discharging liquid from the nozzle and to close at least a part of the nozzle at the time of refilling to supply liquid to the pressure chamber. Road opening and closing means;
A liquid discharge head comprising: The flow path opening / closing means includes an actuator that applies a discharge force to the liquid stored in the pressure chamber;
The liquid discharge head according to claim 1, further comprising a movable member that moves in a direction substantially orthogonal to a discharge direction of the liquid discharged from the nozzle in response to the operation of the actuator.   The liquid discharge head according to claim 2, wherein the nozzle opening and closing unit opens and closes the nozzle by moving along a surface on the pressure chamber side where the nozzle is formed in response to an operation of the actuator. .   4. The liquid ejection according to claim 2, wherein the supply side flow path opening / closing section opens and closes the supply side flow path by changing a cross-sectional area of the supply side flow path according to an operation of the actuator. head.   The nozzle opening / closing portion includes a first protrusion provided on the movable member, and an area of a portion corresponding to the nozzle of the first protrusion is equal to or larger than an area of the nozzle. The liquid discharge head according to 2, 3 or 4.   The liquid ejection head according to claim 5, further comprising a regulating member that regulates a moving range of the movable member.   7. The liquid ejection head according to claim 2, wherein the supply-side flow path opening / closing portion includes a second protrusion provided on the movable member.   The nozzle opening / closing section and the supply side flow path opening / closing section have a predetermined time difference between the timing of opening the nozzle during discharge and the timing of closing the supply side flow path, and the timing of closing the nozzle during refilling. 8. The liquid ejection head according to claim 1, wherein the liquid ejection head has a structure in which a predetermined time difference exists between the timing of opening the supply-side flow path and the timing at which the supply-side flow path is opened.   The said supply side flow path opening / closing part has a structure which opens the said discharge side flow path for a predetermined period after the said nozzle is closed by the said nozzle opening / closing part, The any one of Claims 1 thru | or 8 characterized by the above-mentioned. The liquid discharge head described in 1.   The nozzle opening / closing part has a structure that opens the nozzle after a lapse of a predetermined period after the cross-sectional area of the supply side channel is reduced by the supply side channel opening / closing part. The liquid discharge head according to any one of the above. A nozzle for discharging liquid;
A pressure chamber provided corresponding to the nozzle;
A supply-side flow path communicating with the pressure chamber;
Supply side that is provided in the pressure chamber and closes at least a part of the supply-side flow path at the time of discharge for discharging liquid from the nozzle, and opens the supply-side flow path at the time of refill to supply liquid to the pressure chamber compared to at the time of discharge A flow path opening / closing section, and a nozzle opening / closing section that operates to open at the time of discharging for discharging liquid from the nozzle and to close at least a part of the nozzle at the time of refilling to supply liquid to the pressure chamber. Road opening and closing means;
An image forming apparatus comprising a liquid discharge head having

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