JP2015066864A - Liquid discharge head and recording device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid discharge head in which crosstalk through common flow passages or variation in discharge property by resonance of a liquid inside the common flow passages is difficult to occur, and to provide a recording device using the same.SOLUTION: A liquid discharge head has: at least two common flow passages 5, 16; a plurality of pressurizing chambers 10 respectively connected with the two common flow passages 5, 16; flow passage members 4, 6 provided with a plurality of flow passage groups having a plurality of discharge holes 8 respectively connected with the plurality of pressurizing chambers 10; and a plurality of pressurizing parts 30 respectively pressurizing liquid inside the plurality of pressurizing chambers 10. When having viewed a discharge hole face 6-1 in which the plurality of discharge holes 8 are bored in a plan view, the common flow passages 5, 16 belonging to one flow passage group are disposed such that the common flow passages 5, 16 do not overlap each other, and the common flow passages 5, 16 belonging to the one flow passage group and the common flow passages 5, 16 belonging to the other flow passage group are disposed such that they overlap.

Description

  The present invention relates to a liquid discharge head that discharges droplets and a recording apparatus using the same.

  Conventionally, as a liquid ejection head, for example, an inkjet head that performs various types of printing by ejecting a liquid onto a recording medium is known. The liquid discharge head is provided so as to cover, for example, a manifold (common flow path) and a flat plate-like flow path member having discharge holes connected from the manifold via a plurality of pressure chambers, and the pressure chamber, respectively. A head main body configured by stacking actuator substrates having a plurality of displacement elements, and a reservoir for supplying liquid to the head main body are included (see, for example, Patent Document 1).

  In this liquid discharge head, the common flow path for supplying the liquid to the pressurizing chamber and the common flow path 10 for discharging the liquid from the pressurizing chamber are arranged to overlap each other.

JP 2008-290292 A

  However, in the liquid ejection head described in Patent Document 1, since the common supply channel and the common discharge channel connected to one pressurizing chamber are arranged close to each other, vibration is transmitted between them. If the vibration of the liquid driven at the same timing is transmitted, the resonance will increase in the same way, and the vibration may be transmitted to the pressurizing chamber and affect the discharge characteristics. was there.

  Accordingly, an object of the present invention is to provide a liquid discharge head in which variations in discharge characteristics are difficult to occur due to crosstalk through a common flow path and resonance of liquid in the common flow path, and a recording apparatus using the liquid discharge head.

  The liquid discharge head of the present invention has at least two common flow paths, a plurality of pressure chambers connected to the two common flow paths, and a plurality of discharge holes respectively connected to the plurality of pressure chambers. A liquid discharge head having a flow path member in which a plurality of flow path groups are provided and a plurality of pressurization units that pressurize liquid in the plurality of pressurization chambers, respectively, wherein the plurality of discharge holes are open. The common flow passages belonging to one flow passage group are arranged so as not to overlap each other when the discharge hole surface is viewed in plan view, and the common flow passage belonging to one flow passage group and the other flow passage The common flow path belonging to the flow path group is disposed so as to overlap.

  The recording apparatus of the invention includes the liquid discharge head, a transport unit that transports a recording medium to the liquid discharge head, and a control unit that controls the plurality of pressurizing units. And

According to the present invention, the pressure wave when one pressurizing chamber is pressurized is transmitted to the two common flow paths. However, since the two common flow paths are not overlapped, mutual vibrations are generated. Since it is difficult to transmit, the liquid in the vicinity of the discharge hole surface can be easily discharged by increasing the temperature, or the discharge characteristics can be stabilized by making the temperature almost constant, and the liquid in the common supply path is Since it is difficult to warm or the temperature is lowered by cooling, it is difficult for the viscosity of the liquid to be lowered and it is difficult to precipitate pigments in the liquid.

(A) is a side view of a recording apparatus including a liquid ejection head according to an embodiment of the present invention, and (b) is a plan view. FIG. 2 is a perspective view of a head body that is a main part of the liquid ejection head of FIG. 1. (A) is the partial longitudinal cross-section of the head main body of FIG. 2, (b) is the partial longitudinal cross-sectional view seen from the XX direction of (a). It is a longitudinal cross-sectional view of the head main body which is the principal part of the other liquid discharge head of this invention.

  FIG. 1A is a schematic side view of a (color inkjet) printer 1 which is a recording apparatus including a liquid discharge head 2 according to an embodiment of the present invention, and FIG. 1B is a schematic plan view. It is. The printer 1 moves the printing paper P relative to the liquid ejection head 2 by transporting the printing paper P that is a recording medium from the transporting roller 80 a to the transporting roller 80 b. The control unit 88 controls the liquid ejection head 2 based on image and character data, ejects liquid toward the recording medium P, causes droplets to land on the printing paper P, and prints on the printing paper P. Record such as.

  In the present embodiment, the liquid discharge head 2 is fixed to the printer 1, and the printer 1 is a so-called line printer. As another embodiment of the recording apparatus of the present invention, the operation of moving the liquid ejection head 2 by reciprocating in the direction intersecting the transport direction of the printing paper P, for example, the direction substantially orthogonal, and the printing paper P There is a so-called serial printer that alternately conveys.

  A flat plate (head mounting) frame 70 is fixed to the printer 1 so as to be substantially parallel to the printing paper P. The frame 70 is provided with 20 holes (not shown), and the 20 liquid discharge heads 2 are mounted in the respective hole portions, and the portion of the liquid discharge head 2 that discharges the liquid is the printing paper P. It has come to face. The distance between the liquid ejection head 2 and the printing paper P is, for example, about 0.5 to 20 mm. The five liquid ejection heads 2 constitute one head group 72, and the printer 1 has four head groups 72.

  The liquid discharge head 2 has a long and narrow shape in the direction from the front to the back in FIG. 1A and in the vertical direction in FIG. This long direction is sometimes called the longitudinal direction. Within one head group 72, the three liquid ejection heads 2 are arranged along a direction that intersects the conveyance direction of the printing paper P, for example, a substantially orthogonal direction, and the other two liquid ejection heads 2 are conveyed. Each of the three liquid ejection heads 2 is arranged at a position shifted along the direction. The liquid discharge heads 2 are arranged so that the printable range of each liquid discharge head 2 is connected in the width direction of the print paper P (in the direction intersecting the conveyance direction of the print paper P) or the ends overlap. Thus, printing without gaps in the width direction of the printing paper P is possible.

  The four head groups 72 are arranged along the conveyance direction of the recording paper P. Liquid (ink) is supplied to each liquid discharge head 2 from a liquid tank (not shown). The liquid ejection heads 2 belonging to one head group 72 are supplied with the same color ink, and four color inks can be printed by the four head groups. The colors of ink ejected from each head group 72 are, for example, magenta (M), yellow (Y), cyan (C), and black (K). A color image can be printed by printing such ink under the control of the control unit 88.

  The number of liquid ejection heads 2 mounted on the printer 1 may be one if it is a single color and the range that can be printed by one liquid ejection head 2 is printed. The number of the liquid ejection heads 2 included in the head group 72 and the number of the head groups 72 can be appropriately changed according to the printing target and printing conditions. For example, the number of head groups 72 may be increased to perform multicolor printing. Also, by arranging a plurality of head groups 72 that print in the same color and printing alternately in the transport direction, the printing speed (transport speed) can be increased. Alternatively, a plurality of head groups 72 for printing in the same color may be prepared and arranged so as to be shifted in a direction crossing the transport direction, so that the resolution in the width direction of the print paper P may be increased.

  Further, in addition to printing colored inks, a liquid such as a coating agent may be printed for surface treatment of the printing paper P.

  The printer 1 performs printing on a printing paper P that is a recording medium. The printing paper P is wound around the paper feed roller 80a, passes between the two guide rollers 82a, passes through the lower side of the liquid ejection head 2 mounted on the frame 70, It passes between the two conveying rollers 82b and is collected by the collecting roller 80b. When printing, the printing paper P is conveyed at a constant speed by rotating the conveyance roller 82 b and printed by the liquid ejection head 2. The collection roller 80b winds up the printing paper P sent out from the conveyance roller 82b. The conveyance speed is, for example, 75 m / min. Each roller may be controlled by the controller 88 or may be manually operated by a person.

  In addition to the printing paper P, the recording medium may be a cloth or the like. In addition, the printer 1 is configured to convey a conveyance belt instead of the printing paper P, and the recording medium is not only a roll-shaped one, but also a sheet, cut cloth, wood, It may be a tile. Furthermore, a wiring pattern of an electronic device may be printed by discharging a liquid containing conductive particles from the liquid discharge head 2. Still further, the chemical may be produced by discharging a predetermined amount of liquid chemical agent or liquid containing the chemical agent from the liquid discharge head 2 toward the reaction container or the like and reacting.

  In addition, a position sensor, a speed sensor, a temperature sensor, and the like may be attached to the printer 1, and the control unit 88 may control each part of the printer 1 according to the state of each part of the printer 1 that can be understood from information from each sensor. In particular, if the discharge characteristics (discharge amount, discharge speed, etc.) of the liquid discharged from the liquid discharge head 2 are affected by the outside, the temperature of the liquid discharge head 2, the temperature of the liquid in the liquid tank, the liquid tank Depending on the pressure applied by the liquid to the liquid ejection head 2, the drive signal for ejecting the liquid in the liquid ejection head 2 may be changed.

  Next, the liquid discharge head 2 according to an embodiment of the present invention will be described. FIG. 2 is a perspective view of the head main body 2a including the main part of the function of discharging liquid, which is located at the lower end of the liquid discharge head 2. 3A is a partial vertical cross-sectional view of the head main body 2a in FIG. 2, and FIG. 3B is a partial vertical cross-sectional view as viewed from the XX direction in FIG. 3A. In FIG. 3 (b), in order to make the figure easy to understand and understand, the pressurizing chamber 10, the squeezing 14 and the like to be represented by a chain line are drawn with solid lines. Further, the detailed structure is drawn only on the structure on the front side of the common supply flow path 5 (flow path and electrode), and the structure on the back side of the common supply flow path 5 is only the pressurizing chamber 10. Is drawn with a chain line so that the positional relationship can be understood.

The lower end of the liquid discharge head 2 has a head body 2a that discharges liquid. The lower surface of the head main body 2a is a discharge hole surface 6-1 in which a large number of discharge holes 8 for discharging liquid are opened. In addition to the head main body 2a, the liquid ejection head 2 includes an electrical member including a driver IC that generates a drive signal for ejecting liquid, and a housing that covers a portion other than the electrical member and the ejection hole surface 6-1.

  The head main body 2a includes a flat-plate nozzle module 6 whose one main surface is the discharge hole surface 6-1 where the discharge holes 8 are open, and a main surface opposite to the discharge hole surface 6-1 of the nozzle module 6. It includes four rectangular parallelepiped discharge units 3 arranged above. The discharge unit 3 is disposed on the nozzle module 2 in a substantially parallel manner with a gap therebetween.

  The discharge unit 3 is provided with two common flow paths, one of which is a common supply flow path 5 (sometimes referred to as a supply flow path) and the other is a common discharge flow path 16 (abbreviated as a supply flow path). May be called). The discharge unit 3 further has two supply channel openings 5 a that are connected to the supply channel 5, and two discharge channel openings 16 a that are connected to the discharge channel 16. Although details will be described later, the liquid to be discharged is supplied from the outside through one of the openings 5a of the supply flow path of one discharge unit, and a part of the liquid passes through the supply flow path 5 to the other supply flow path. A part of the liquid is discharged from the discharge hole 8 and the remaining liquid is discharged to the outside through the discharge flow path of the adjacent discharge unit 3 and from the opening 16a of the discharge flow path. . The liquid is supplied and discharged by pressurizing, depressurizing, or both from the outside with a pump or the like. The liquid discharged to the outside can be reused after passing through a filter or the like. That is, the liquid discharge head 2 has a structure through which the liquid to be discharged can pass, and can circulate the liquid in the printer 1. The direction of liquid circulation may be reversed from that described above.

  Since the head main body 2a has a structure that allows liquid to pass through, the head main body 2a can flow more liquid than the amount to be discharged. By doing in this way, the flow rate of the liquid in the head main body 2a is increased, and the problem due to sedimentation hardly occurs even when using a liquid containing inclusions that are likely to settle. Further, the temperature of the head main body 2a can be adjusted by flowing a temperature-controlled liquid.

  First, the liquid circulation structure will be described. The discharge unit 3 has a rectangular parallelepiped shape that is long in the longitudinal direction of the head body 2a, and has substantially the same length as the head body 2a. One surface of the discharge unit 3 is joined to the nozzle module 6. The discharge unit 3 includes a flow path unit (flow path member of the discharge unit) 4 and an actuator unit 21. The flow path unit 4 has a rectangular parallelepiped shape that is long in the longitudinal direction of the head main body 2a, and occupies most of the discharge unit 3. One of the actuator units 21 having a rectangular planar shape is bonded to each of two surfaces that are substantially orthogonal to the nozzle module 6 along the longitudinal direction of the flow path unit 4. The liquid is discharged by driving the displacement element 30 built in the actuator unit 21.

  The channel unit 4 is configured by laminating plates 4a to 4d (of the channel unit). The thickness of the plate 4d (the thickness in the left-right direction in FIG. 3A) is about 1 to 10 mm, and the thickness of the plates 4a to 4c is about 10 to 500 μm. The plate 4d can be produced by molding a resin, for example. The plates 4a to 4c are made of metal, for example, and holes and grooves serving as flow paths are formed by etching or punching.

The flow path arranged in the flow path unit 4 includes a pressurizing chamber 10, a part of a descender (partial flow path) 12, a throttle 14, a (common) supply flow path 5, and a (common) discharge flow path 16. is there. The pressurizing chamber 10, descender 12, and throttle 14 will be described in detail later. The supply flow path 5 and the discharge flow path 16 are provided in the discharge unit 3 along the longitudinal direction, and the discharge flow path 16 is disposed on the side close to the nozzle module 6 of the flow path unit 4. A supply flow path 5 is disposed on the side far from the module 6. The supply channel 5 and the discharge channel 16 having an elongated shape extending from one end to the other end in the longitudinal direction of the discharge unit 3 by sealing the left and right sides of the holes opened in the plate 4d with the plate 4c. Is configured. On the left and right plates 4c, a plate 4b and a plate 4a are further stacked in this order. A hole which is a part of the aperture 14 is opened in the plate 4c, and the aperture 14 and the supply flow path 5 are connected. The supply flow path 5 is opened to the outside through the respective openings 5a at both ends, and the liquid is supplied from one opening 5a to supply the liquid to the pressurizing chamber 10 through the squeezing 14, and the remaining liquid is the other liquid. It is discharged outside through the opening 5a.

  The discharge channel 16 is opened at a plurality of locations on the nozzle module 6 side, and is connected to the plurality of descenders 12. However, the connected descender 12 is connected not from the descender 12 connected from the pressurizing chamber 10 of the discharge unit 3 having the discharge flow path 16 but from the pressurizing chamber 10 in the discharge unit 3 adjacent to the discharge unit 3. This is the descender 12. The discharge channel 16 is opened to the outside through an opening 16a at one end, and the liquid flowing from the descender 12 is collected in the discharge channel 16 and discharged to the outside. You may make it discharge from both the opening 16a of a discharge flow path made in both ends.

  The nozzle module 6 is configured by laminating flat nozzle module plates 6a to 6d. The nozzle module plates 6a to 6d are provided with holes and grooves, which are connected to form a flow path. The nozzle module plates 6a to 6d have a thickness of about 10 to 500 [mu] m, and the nozzle module 6 has a thickness of about 200 to 2 mm. The nozzle module plates 6a to 6d are made of metal, for example, and the holes and grooves described above can be processed by etching or punching. Alternatively, only the nozzle module plate 6d in which the discharge holes 8 are opened may be made of metal, and the other parts may be made of ceramics such as alumina. In that case, the aforementioned holes and grooves are processed in the state of the green sheet before firing, and the laminate of the nozzle module plates 6a to 6c can be produced by laminating and firing the green sheets.

  A large number of discharge holes 8 are opened in the discharge hole surface 6-1 which is the lower surface of the nozzle module 6, and a large number of descenders 12 respectively connected to the discharge holes 8 are arranged inside the nozzle module 6. ing. Further, a connecting flow path 18 that branches from the middle of each descender 12 and is connected to the discharge flow path 16 is disposed. The entire descender 12 is configured by combining a portion formed in the nozzle module 6 and a portion formed in the discharge unit 3, so that it is precisely arranged in the nozzle module 6. , Part of descender 12. The descender 12 has a shape penetrating the nozzle module 6 vertically. The connection flow path 18 is a substantially linear flow path extending in the plane direction of the nozzle module 6 in a direction intersecting with the longitudinal direction of the head main body 2a (preferably substantially perpendicular). The connection flow path 18 connects the descender 12 connected from the pressurizing chamber 10 in one discharge unit 3 and the discharge flow path 16 in the other discharge unit 3 between the adjacent discharge units 3. Conversely, the descender 12 connected from the pressurizing chamber 10 in the other discharge unit 3 and the discharge flow path 16 in the one discharge unit 3 are connected. By connecting the two discharge units 3 to each other, when the number of discharge units 3 is an even number, the supply flow path 5 can be obtained without preparing the supply flow path 5 and the discharge flow path 16 in addition to the discharge units 3. And the discharge flow path 16 is connected. The discharge hole 8 and the descender 12 will be described in detail later.

With the configuration as described above, the flow of the liquid passing through the head body 2 a is supplied from the outside to one of the openings 5 a of the supply channel of the single discharge unit 3, the supply channel 5, the squeezing 14, the pressurizing chamber 10, and the descender 12. Part, connection flow path 18, discharge flow path 16 of discharge unit 3 next to discharge unit 3 to which liquid has been supplied, and opening 18 a of the discharge flow path in this order. The entire flow path connected in this way may be collectively referred to as a flow path group. In the head main body 2a shown in FIG. 2, when the discharge heads 3 are numbered in order from the left, the head main body 2 receives the supply of liquid from the first discharge unit 3 and discharges it from the second discharge unit 3. One channel group receives liquid supply from the second discharge unit 3, one channel group discharges from the first discharge unit 3, receives liquid supply from the third discharge unit 3, 4 A total of four channels, one channel group discharging from the third discharge unit 3, receiving a liquid supply from the fourth discharge unit 3, and one channel group discharging from the third discharge unit 3. There are groups. Because of such a configuration, when the discharge hole surface 6-1 is viewed in plan, the discharge flow paths 16 belonging to the same flow path group as the supply flow paths 5 belonging to one flow path group are arranged so as not to overlap. In addition, the supply flow path 5 belonging to one flow path group and the discharge flow path 16 belonging to another flow path group are arranged to overlap. It should be noted that if a plurality of supply flow passage openings 5a at one end, a plurality of supply flow passage openings 5a at the other end, and a discharge flow passage opening 16a are provided together, the external It is preferable because it can be easily connected to

  Next, a structure for discharging liquid will be described. A plurality of pressurizing chambers 10 are opened on both sides of the flow path unit 4 of the discharge unit 3 in the left-right direction. The pressurizing chamber 10 opened on both sides is sealed by joining the actuator unit 21 to each side. The pressurizing chambers 10 are arranged over substantially the entire length of the discharge unit 3 at equal intervals corresponding to, for example, 50 dpi on each surface. In the nozzle module 6, a discharge hole 8 is provided almost directly below the pressurizing chamber 10, and 50 dpi printing is possible in the pressurizing chamber 10 on one side of the discharge unit 3. The pressure chambers 10 on both sides of the discharge unit 3 are alternately arranged in the longitudinal direction. For example, if the pressure chambers 10 on both sides are arranged at a distance corresponding to 100 dpi in the longitudinal direction, printing at 100 dpi is possible in the pressure chambers 10 on both sides. Further, if four such discharge units 3 are arranged at a distance corresponding to 400 dpi in the longitudinal direction, 400 dpi can be printed by the entire liquid discharge head 2.

  It should be noted that a dummy pressurization chamber is further provided on the outer side so that the difference between the discharge characteristics from the pressurization chamber 10 located at the end of the discharge unit 3 in the longitudinal direction and the discharge characteristics of the other pressurization chambers 10 is reduced. May be provided so that the difference in the rigidity of the surroundings is reduced.

  The pressurizing chamber 10 has a shape spreading in a direction orthogonal to the stacking direction of the discharge units 3. That is, it has a shape spreading in the direction substantially perpendicular to the discharge hole surface 6-1 and the longitudinal direction of the discharge unit 3. With this shape, the size of the head body 2a in the short direction (left and right direction in FIG. 2) can be reduced. The pressurizing chamber 10 is long in the direction orthogonal to the discharge hole surface 6-1. This is because the size of the pressurizing chamber 10 in the direction orthogonal to the discharge hole surface 6-1 is larger than the size in a plane orthogonal to the direction (that is, a plane parallel to the discharge hole surface 6-1). is there. The specific planar shape of the pressurizing chamber 10 is, for example, a rectangular shape with rounded corners.

  A descender 12 (exactly part of the descender 12) extends from the pressurizing chamber 10 toward a portion where the discharge unit 3 and the nozzle module 6 are joined. The descender 12 is connected to the end portion on the side close to the discharge hole surface 6-1 in the end portion in the longitudinal direction of the pressurizing chamber 10. The descender 12 extends in a direction substantially orthogonal to the discharge hole surface 6-1. The descender 12 arranged in the discharge unit 3 and the descender 12 arranged in the nozzle module 6 are connected to form a descender 12 connecting the pressurizing chamber 10 and the discharge hole 8.

  When the displacement element 30 provided on the actuator substrate 21 at a position overlapping the pressurizing chamber 10 is displaced, the volume of the pressurizing chamber 10 changes, and pressure is applied to the liquid therein. This pressure is transmitted through the descender 12, reaches the discharge hole 8, and the liquid is discharged. A specific driving method will be described in detail later.

The actuator substrate 21 has a laminated structure composed of two piezoelectric ceramic layers 21a and 21b which are piezoelectric bodies. Each of these piezoelectric ceramic layers 21a and 21b has a thickness of about 20 μm. The thickness from the upper surface of the piezoelectric ceramic layer 21a of the actuator substrate 21 to the lower surface of the piezoelectric ceramic layer 21b is about 40 μm. Both of the piezoelectric ceramic layers 21 a and 21 b extend so as to straddle the plurality of pressure chambers 10. These piezoelectric ceramic layers 21a and 21b are made of, for example, a lead zirconate titanate (PZT) ceramic material having ferroelectricity. The piezoelectric ceramic layer 21b functions as a vibration plate and does not necessarily need to be a piezoelectric body. Instead, another ceramic layer or metal plate that is not a piezoelectric body may be used.

  The actuator substrate 21 has a common electrode 24 made of a metal material such as Ag—Pd and an individual electrode 25 made of a metal material such as Au. The individual electrodes 25 are arranged at positions facing the pressurizing chamber 10 on the upper surface of the actuator substrate 21. The individual electrode 25 includes an individual electrode body that overlaps the pressurizing chamber 10 and an extraction electrode that is extracted therefrom. A wiring to which a drive signal is supplied is connected to the extraction electrode. A drive signal sent from the control unit 88 is supplied to the individual electrode 25. A drive signal generated by a driver IC or the like provided in the liquid ejection head 2 based on a control signal sent from the control unit 88 may be sent to the individual electrode 25. The drive signal is supplied in a constant cycle in synchronization with the conveyance speed of the print medium P.

  The common electrode 24 is formed over almost the entire surface in the region between the piezoelectric ceramic layer 21a and the piezoelectric ceramic layer 21b. That is, the common electrode 24 extends so as to cover all the pressurizing chambers 10 in the region facing the actuator substrate 21. The thickness of the common electrode 24 is about 2 μm. The common electrode 24 is connected to the common electrode surface electrode formed on the piezoelectric ceramic layer 21a so as to avoid the electrode group composed of the individual electrodes 25 through via holes formed through the piezoelectric ceramic layer 21a. Are grounded and held at the ground potential. The common electrode surface electrode is directly or indirectly connected to the control unit 88 in the same manner as the large number of individual electrodes 25.

  A portion sandwiched between the individual electrode 25 and the common electrode 24 of the piezoelectric ceramic layer 21a is polarized in the thickness direction, and becomes a displacement element 30 having a unimorph structure that is displaced when a voltage is applied to the individual electrode 25. Yes. More specifically, when an electric field is applied in the polarization direction to the piezoelectric ceramic layer 21a by setting the individual electrode 25 to a potential different from that of the common electrode 24, an active portion where the electric field is applied is distorted by the piezoelectric effect. Work as. In this configuration, when the control unit 88 sets the individual electrode 25 to a predetermined positive or negative potential with respect to the common electrode 24 so that the electric field and the polarization are in the same direction, the portion sandwiched between the electrodes of the piezoelectric ceramic layer 21a. (Active part) contracts in the surface direction. On the other hand, the piezoelectric ceramic layer 21b, which is an inactive layer, is not affected by an electric field, and therefore does not spontaneously shrink and tries to restrict deformation of the active portion. As a result, there is a difference in strain in the polarization direction between the piezoelectric ceramic layer 21a and the piezoelectric ceramic layer 21b, and the piezoelectric ceramic layer 21b is deformed so as to be convex toward the pressurizing chamber 10 (unimorph deformation).

  Next, the liquid discharge operation will be described. The displacement element 30 is driven (displaced) by a drive signal supplied to the individual electrode 25 through a driver IC or the like under the control of the control unit 88. In the present embodiment, liquid can be ejected by various driving signals. Here, a so-called strike driving method will be described.

The individual electrode 25 is set to a potential higher than the common electrode 24 (hereinafter referred to as a high potential) in advance, and the individual electrode 25 is once set to the same potential as the common electrode 24 (hereinafter referred to as a low potential) each time there is a discharge request, and then a predetermined potential is set. At this timing, the potential is set again. Thereby, the piezoelectric ceramic layers 21a and 21b return to the original (flat) shape at the timing when the individual electrode 25 becomes low potential (beginning), and the volume of the pressurizing chamber 10 is in an initial state (the potentials of both electrodes are different). Increase compared to the state). As a result, a negative pressure is applied to the liquid in the pressurizing chamber 10. Then, the liquid in the pressurizing chamber 10 starts to vibrate with the natural vibration period. Specifically, first, the volume of the pressurizing chamber 10 begins to increase, and the negative pressure gradually decreases. Next, the volume of the pressurizing chamber 10 becomes maximum and the pressure becomes almost zero. Next, the volume of the pressurizing chamber 10 begins to decrease, and the pressure increases. Thereafter, the individual electrode 25 is set to a high potential at a timing at which the pressure becomes substantially maximum. Then, the first applied vibration overlaps with the next applied vibration, and a larger pressure is applied to the liquid. This pressure propagates through the descender 12 to discharge the liquid from the discharge hole 8.

In other words, a droplet can be ejected by supplying a pulse driving signal that is a low potential for a certain period with the high potential as a reference to the individual electrode 25. If this pulse width is AL (Acoustic Length), which is half the natural vibration period of the liquid in the pressure chamber 10, in principle, the discharge speed and discharge amount of the liquid can be maximized. The natural vibration period of the liquid in the pressure chamber 10 is greatly influenced by the physical properties of the liquid and the shape of the pressure chamber 10, but besides that, from the physical properties of the actuator substrate 21 and the characteristics of the flow path connected to the pressurizing chamber 10. Also affected by.

  Note that the pulse width is actually set to a value of about 0.5 AL to 1.5 AL because there are other factors to consider, such as combining the ejected droplets into one. Further, since the discharge amount can be reduced by setting the pulse width to a value outside of AL, the pulse width is set to a value outside of AL in order to reduce the discharge amount.

  In gradation printing, gradation expression is performed by the number of droplets ejected continuously from the ejection holes 8, that is, the droplet amount (volume) adjusted by the number of droplet ejections. For this reason, the number of droplet discharges corresponding to the designated gradation expression is continuously performed from the discharge holes 8 corresponding to the designated dot region. In general, when liquid ejection is performed continuously, it is preferable that the interval between pulses supplied to eject liquid droplets is AL. As a result, the period of the residual pressure wave of the pressure generated when discharging the previously discharged liquid droplet coincides with the pressure wave of the pressure generated when discharging the liquid droplet discharged later, and these are superimposed. Thus, the pressure for discharging the droplet can be amplified. In this case, it is considered that the speed of the liquid droplets ejected later increases, but this is preferable because the landing points of a plurality of liquid droplets are close.

  In the liquid discharge head 2 of the present embodiment as described above, when the liquid in the pressurizing chamber 10 is pressurized in one flow path group, the pressure is transmitted to the supply flow path 5 through the aperture 14. Also, it is transmitted to the discharge channel 16 via the descender 12. However, since the supply flow path 5 and the discharge flow path 16 of one flow path group are arranged so as not to overlap when the discharge hole surface 6-1 is viewed in plan, vibrations are hardly transmitted to each other. Yes. Although it is possible to arrange the supply flow path 5 and the discharge flow path 16 included in the liquid discharge head 2 so as not to overlap, the size of the liquid discharge head 2 in the plane direction, more specifically, the liquid discharge head This is not preferable because the size in the lateral direction of 2 becomes large. When the liquid discharge head 2 is disposed in the printer 2, if the liquid discharge head 2 is rotated and fixed in the plane direction (with an angle), the printing accuracy is lowered. An increase in size is not preferable because a decrease in printing accuracy increases even at the same angle.

  Therefore, by making the supply flow path 5 and the discharge flow path 16 belonging to different flow path groups overlap, the size of the liquid discharge head 2 can be reduced while suppressing the influence of the vibration generated during the above-described discharge. can do. Note that vibration is easily transmitted between the supply flow path 5 and the discharge flow path 16 belonging to different flow path groups. However, pressure applied between the different flow path groups due to a difference in images to be printed or the like. Since the vibrations are different, the degree of influence can be made smaller than when the supply flow path 5 and the discharge flow path 16 belonging to the same flow path group are overlapped.

  Moreover, in this embodiment, since the supply flow path 5 and the discharge flow path 16 which belong to the same flow path group are arrange | positioned in the different discharge unit 3, it becomes difficult to transmit a vibration more.

  The pressure applied to the pressurizing chamber 10 is transmitted not only through the vibration of the liquid but also through the flow path unit 4. Therefore, when the pressurizing chamber surface 4-1 in which the pressurizing chamber 10 is provided is viewed in plan, the pressurizing chamber 10 and the same channel group as the pressurizing chamber 10 are arranged in one channel unit 4. The area where the supply flow path 5 belonging to the pressure chamber 10 overlaps is made smaller than the surface area where the pressurization chamber 10 and the discharge flow path 16 belonging to a flow path group different from the pressurization chamber 10 overlap. That is, since any one of the supply flow path 5 and the discharge flow path 16 belonging to the same flow path group as the pressurizing chamber 10 existing in the flow path unit 4 exists in one flow path unit 4, The area in which any one of the flow channels and the pressurizing chamber 10 overlaps is determined as any of the discharge flow channel 16 and the supply flow channel 5 belonging to a different flow channel group from the pressurizing chamber 10 existing in the flow channel unit 4. Therefore, the area is smaller than the area where one of the flow paths and the pressurizing chamber 10 overlap. By doing so, vibration transmitted from the pressurizing chamber 10 through the flow path unit 4 can be hardly transmitted to the flow path group to which the pressurizing chamber 10 belongs. In other words, the pressure is transmitted well in the left-right direction in FIG. 2A, and the discharge flow channel is a flow channel having a large overlapping area when the pressurizing chamber surface 4-1 that is easy to transmit vibration is viewed in plan view. Reference numeral 16 denotes a flow path group different from the flow path group to which the pressurizing chamber 10 belongs (the flow path group to which the pressurizing chamber 10 of the adjacent discharge unit 3 belongs). It can reduce the impact. The pressurizing chamber 10 and the supply channel 5 or the discharge channel 16 that belong to the same flow path group as the pressurizing chamber 10 and exist in the discharge unit 4 where the pressurizing chamber surface 10 exists are provided. It is more preferable to arrange so as not to overlap. By doing so, vibrations through the flow path unit 4 can be made harder to be transmitted to the flow paths belonging to the same flow path group.

  In the above description, the liquid is supplied from the supply flow channel 5 side and the liquid is discharged from the discharge flow channel 16 side. However, the discharge flow channel 5 is used as the supply flow channel and the discharge flow channel 16 side is used. The liquid may be supplied, and the supply flow path 5 may be used as the discharge flow path to discharge the liquid from the supply flow path 5 side.

  In the above description, the common flow path is divided into two types from the viewpoint of supply and discharge. However, the supply flow path is divided into two types depending on whether or not the supply flow path is connected to the descender 12 (flow path connected to the discharge hole 8). You may think. In the above-described embodiment, the common flow path connected to the descender 12 will be described as the first common flow path 16, and the supply flow path not connected to the descender 12 will be described as the second common flow path 5.

  When the discharge hole surface 6-1 is viewed in plan, the first common flow path 16 and the second common flow path 5 belonging to the same flow path group do not overlap with each other. Since vibration is hardly transmitted between the first common flow path 16 and the second common flow path 5, the influence on the discharge characteristics can be reduced. In addition, since the common flow paths of the different flow path groups are arranged so as to overlap, the length of the liquid discharge head 2 in the short direction can be reduced. In this case, in the structure in which the common channels are overlapped, one common channel is the first common channel 16 and the other common channel is the second common channel 5. It becomes easy to arrange the flow path in the inside.

  Further, the flow path member includes a flat-plate nozzle module 6 having the discharge hole surface 6-1 as one main surface, and a plurality of flow path units 4 joined to the other main surface of the nozzle module 6. The first common flow path 16 belonging to one flow path group and the second common flow path 5 belonging to another flow path group are arranged in one flow path unit 4. The vibration can be made more difficult to be transmitted between the first common channel 16 and the second common channel 5 belonging to the same channel group. Furthermore, as described above, in the structure in which the common flow channels overlap, by setting one common flow channel as the first common flow channel 16 and the other common flow channel as the second common flow channel 5, Since the arrangement of the flow paths of the respective flow path units 3 can be made the same, the same flow path unit 4 can be manufactured, and therefore the flow path unit 4 can be easily manufactured.

Furthermore, in one flow path unit 4, one of the second common flow path 5 and the first common flow path 16 belonging to the same flow path group as the pressurizing chamber 10 existing in the flow path unit 4. Therefore, the area where one of the flow channels and the pressurizing chamber 10 overlap is defined as a first common flow belonging to a group of flow channels different from the pressurizing chamber 10 existing in the flow channel unit 4. Since either the channel 16 or the second common flow path 5 exists, the area is smaller than the area where the flow path and the pressurizing chamber 10 overlap each other. By doing so, vibration transmitted from the pressurizing chamber 10 through the flow path unit 4 can be hardly transmitted to the flow path group to which the pressurizing chamber 10 belongs. The pressurizing chamber 10 and the second common channel 5 or the first channel belonging to the same flow path group as the pressurizing chamber 10 and present in the discharge unit 4 where the pressurizing chamber surface 10 exists. It is more preferable to arrange so that the common channel 16 does not overlap. By doing so, it is possible to make it difficult for vibrations through the flow path unit 4 to be transmitted to the flow paths belonging to the same flow path group.

  In addition to the above-described embodiment, a plate-shaped flow path member in which plates are stacked is used, the lower surface is a discharge hole surface, a displacement element is disposed on the upper surface, a pressure chamber, a supply flow path, In addition, the liquid discharge head may be configured by arranging a discharge channel. If the arrangement of the discharge hole surface, the pressurizing chamber, the supply flow path, and the discharge flow path satisfies the same relationship as shown in the above-described embodiment, the same effect can be obtained with respect to the difficulty of transmitting vibrations. .

  FIG. 4 shows a head body 102a according to another embodiment of the present invention. The same parts as those in the above embodiment are given the same reference numerals, and the description thereof is omitted. The head body 102 a is composed of a plurality of ejection units 103. Similarly to the discharge unit 3 in FIG. 2, the discharge units 103 that are long in one direction are arranged in the short direction. The number of discharge units 103 can be changed according to the resolution, and is, for example, four. Further, the head main body may be configured with only one ejection unit 103.

  The discharge unit 103 includes a flow path unit 104, a piezoelectric actuator substrate 21, and a nozzle module plate 106. One nozzle module plate 106 may be provided for each flow path unit 4, or one nozzle module plate 106 may be provided for the entire head body 102 a. The flow path unit 104 is configured by stacking flow path plates 104a to 104g. In the discharge uni and 103, the discharge channel 16 (first common channel 16) is arranged on one side (left side in FIG. 4) of the pressurizing chamber 10, and the supply channel 5 (second common channel) is arranged on the opposite side. Since the flow paths 5) are arranged, the common flow paths belonging to the same flow path group do not overlap. And if the several discharge unit 103 is joined, the liquid discharge head with which the common flow path which belongs to a different flow path group overlapped can be comprised.

DESCRIPTION OF SYMBOLS 1 ... (Color inkjet) Printer 2 ... Liquid discharge head 2a, 102a ... Head main body 3, 103 ... Discharge unit 4, 104 ... Flow path unit (flow path member of discharge unit)
4a to d, 104a to g (plate unit) 5 (common) supply channel, second common channel 5a (common discharge channel, second common channel) 6) Nozzle module 6a-d, 106 ... Nozzle module plate 6-1, 106-1 ... Discharge hole surface 8 ... Discharge hole 10 ... Pressurizing chamber 12 ... Descender (partial flow path)
14 ... Squeeze 16 ... (Common) discharge channel, first common channel 16a ... Opening (common discharge channel, first common channel) 18 ... Connection channel 21 .... (Piezoelectric) actuator substrate 21a ... Piezoelectric ceramic layer 21b ... Piezoelectric ceramic layer (vibrating plate)
24 ... Common electrode 25 ... Individual electrode 30 ... Displacement element (pressure part)
70 ... (head mounting) frame 72 ... head group 80a ... paper feed roller 80b ... collection roller 82a ... guide roller 82b ... transport roller 88 ... control unit P ... Printing paper

Claims (8)

A plurality of flow path groups having at least two common flow paths, a plurality of pressurization chambers connected to the two common flow paths, and a plurality of discharge holes respectively connected to the plurality of pressurization chambers are provided. A liquid discharge head having a flow path member and a plurality of pressurizing units that pressurize the liquid in the plurality of pressurizing chambers, respectively.
When the discharge hole surface in which the plurality of discharge holes are open is viewed in plan view,
The common flow paths belonging to one flow path group are arranged so as not to overlap each other, and the common flow path belonging to one flow path group and the common flow path belonging to another flow path group A liquid discharge head characterized in that the two are overlapped. One of the two common flow paths is a common supply flow path for supplying a liquid from the outside and supplying the liquid to the plurality of pressurizing chambers, and the other is a common discharge for discharging a part of the plurality of liquids to the outside. Discharge channel,
In the structure in which the common flow paths of the different flow path groups are overlapped, one of the common flow paths is the common supply flow path, and the other common flow path is the common discharge flow path. The liquid discharge head according to claim 1, wherein the liquid discharge head is a liquid discharge head.   The flow path member includes a flat plate-like nozzle module having the discharge hole surface as one main surface, and a plurality of flow path units joined to the other main surface of the nozzle module. 3. The common supply flow path belonging to one of the flow path groups and the common discharge flow path belonging to another of the flow path groups are arranged in the flow path unit. The liquid discharge head described. The plurality of pressurizing chambers are disposed on the pressurizing chamber surface substantially orthogonal to the nozzle module of the flow path unit,
When the pressure chamber surface is viewed in plan view,
The common supply flow path that exists in the discharge unit in which the pressurization chamber surface and the pressurization chamber surface belong to the same flow path group as the pressurization chamber surface and the pressurization chamber surface exists. Or the area where the common discharge channel overlaps,
The common discharge flow which exists in the discharge unit where the pressurizing chamber surface exists and belongs to the flow path group different from the pressurizing chamber surface and the pressurizing chamber surface. The liquid discharge head according to claim 3, wherein the liquid discharge head is smaller than an area where the path or the common supply flow path overlaps. One of the two common flow paths is a first common flow connected to the pressurizing chamber via a plurality of partial flow paths connecting the plurality of pressurizing chambers and the plurality of discharge holes, respectively. The other is a second common flow channel connected to the pressurizing chamber without passing through the partial flow channel,
In the structure in which the common flow paths of the different flow path groups are overlapped, one of the common flow paths is the first common flow path, and the other common flow path is the second common flow path. The liquid discharge head according to claim 1, wherein the liquid discharge head is a path.   The flow path member includes a flat plate-like nozzle module having the discharge hole surface as one main surface, and a plurality of flow path units joined to the other main surface of the nozzle module. The first common flow path belonging to one flow path group and the second common flow path belonging to another flow path group are arranged in the flow path unit. The liquid discharge head according to claim 5. The plurality of pressurizing chambers are disposed on the pressurizing chamber surface substantially orthogonal to the nozzle module of the flow path unit,
The pressurization chamber existing on the pressurization chamber surface, and the second common that belongs to the same flow path group as the pressurization chamber and exists in the discharge unit where the pressurization chamber surface exists. The area where the flow path or the first common flow path overlaps,
The first chamber existing in the discharge unit having the pressurizing chamber surface and the pressurizing chamber existing on the pressurizing chamber surface, and belonging to the flow path group different from the pressurizing chamber. The liquid discharge head according to claim 6, wherein the liquid discharge head is smaller than an area where the common flow path or the second common flow path overlaps.   A liquid discharge head according to claim 1, a transport unit that transports a recording medium to the liquid discharge head, and a control unit that controls the plurality of pressure units. A recording apparatus.

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