JP5566072B2 - Liquid discharge head block and recording apparatus having the same - Google Patents

Description

  The present invention relates to a liquid discharge head block equipped with a plurality of liquid discharge heads and a recording apparatus that includes the liquid discharge head block and prints an image.

  In recent years, printing apparatuses using inkjet recording methods such as inkjet printers and inkjet plotters are not only printers for general consumers, but also, for example, formation of electronic circuits, manufacture of color filters for liquid crystal displays, manufacture of organic EL displays It is also widely used for industrial applications.

  In such an ink jet printing apparatus, a liquid discharge head for discharging liquid is mounted as a print head. This type of print head includes a heater as a pressurizing unit in an ink flow path filled with ink, heats and boiles the ink with the heater, pressurizes the ink with bubbles generated in the ink flow path, A thermal head system that ejects ink as droplets from the ink ejection holes, and a part of the wall of the ink channel filled with ink is bent and displaced by a displacement element, and the ink in the ink channel is mechanically pressurized, and the ink A piezoelectric method for discharging liquid droplets from discharge holes is generally known.

  In addition, in such a liquid discharge head, a serial type that performs recording while moving the liquid discharge head in a direction (main scanning direction) orthogonal to the conveyance direction (sub-scanning direction) of the recording medium, and main scanning from the recording medium There is a line type in which recording is performed on a recording medium conveyed in the sub-scanning direction with a liquid discharge head that is long in the direction fixed. The line type has the advantage that high-speed recording is possible because there is no need to move the liquid discharge head as in the serial type.

  In order to print droplets at a high density in any of the serial type and line type liquid discharge heads, the density of the liquid discharge holes for discharging the droplets formed in the liquid discharge head must be increased. There is a need to.

  Accordingly, the liquid discharge head includes a manifold and a flow path member having a liquid discharge hole that connects the manifold via a plurality of liquid pressurization chambers, and a plurality of displacement elements provided so as to cover the liquid pressurization chambers. A structure in which the actuator units are stacked is known (see, for example, Patent Document 1). In this liquid ejection head, the liquid pressurizing chambers connected to the plurality of liquid ejection holes are arranged in a matrix, and the displacement elements of the actuator unit provided so as to cover the chambers are displaced so that each liquid ejection chamber Ink is ejected and printing is possible at a resolution of 600 dpi in the main scanning direction.

JP 2003-305852 A

  When the liquid discharge head described in Patent Document 1 is used in a serial recording apparatus, in order to perform multicolor printing, increase the resolution, and increase the throughput, the liquid discharge head includes a plurality of liquid discharge heads. It is conceivable to reciprocate the head block with respect to the recording medium. In such a case, it is difficult for heat to escape between the plurality of liquid discharge heads, and the temperature may become high. Due to the temperature, there is a fluctuation in discharge characteristics between the liquid discharge heads or within the liquid discharge heads. As a result, there is a problem that the recording accuracy deteriorates.

  Accordingly, an object of the present invention is to provide a liquid discharge head block capable of cooling the liquid discharge head with high efficiency and a recording apparatus using the liquid discharge head block.

The liquid discharge head block of the present invention is a liquid discharge head block including a plurality of liquid discharge heads each having a liquid discharge hole surface in which a plurality of liquid discharge holes are arranged, and is adjacent to each other among the plurality of liquid discharge heads. The liquid discharge heads are arranged so that the side surfaces of the liquid discharge heads face each other with a space therebetween, and the liquid discharge head is moved when the liquid discharge head block is moved in a direction intersecting the side surfaces. An air introduction part that guides ambient air to the space between the liquid discharge head, the side surface of the liquid discharge head is made of a metal plate, and a driver IC that controls the discharge of the liquid contacts the inner surface of the metal plate. contact with and, in the space between a plurality of said liquid discharge head adjacent one of said liquid discharge head, the abutment of the driver IC of the flow of air the metal plate Characterized in that comprises an air rectification section leading to the side of the outer part.

The plurality of liquid discharge holes are long in one direction, the liquid discharge head has a rectangular parallelepiped shape that is long in the one direction, and the side surfaces are long in the one direction. It is preferable that the side surfaces of the adjacent liquid discharge heads are arranged substantially in parallel .

Further, the air introduction section causes the air in the space between the adjacent liquid ejection heads to flow from one to the other in the one direction when the liquid ejection head block is moved in a direction orthogonal to the side surface. Are provided in both one and the other of the one direction ,
The number of the liquid discharge heads is three or more, and when the liquid discharge head block is viewed from a direction orthogonal to the side surface, It is preferable that the air introduction part is larger than the air introduction part that guides air to the space on the near side .

  Furthermore, the air rectifying plate having substantially the same shape as the side surface of the liquid discharge head is disposed substantially parallel to the outermost side surface among the side surfaces of the plurality of liquid discharge heads and facing each other with a space therebetween. In addition, it is preferable that a second air introduction unit for introducing ambient air into a space between the air rectifying plate and the liquid discharge head is provided.

  In the recording apparatus of the invention, the liquid ejection head block, a transport unit that transports the recording medium to the liquid ejection head, and the liquid ejection head block are parallel to the direction of transporting the recording medium. A reciprocating mechanism that reciprocates in a direction substantially perpendicular to the side surface of the liquid ejection head in a direction that is not, and a control unit that controls driving of the liquid ejection head.

  According to the liquid discharge head block of the present invention, the liquid discharge head block having a plurality of liquid discharge heads each having a rectangular parallelepiped shape that has a liquid discharge hole surface in which a plurality of liquid discharge holes are arranged long in one direction. The liquid discharge heads are arranged such that adjacent ones of the liquid discharge heads are opposed to each other with the side surfaces longer in the one direction being substantially parallel to each other with a space therebetween, and the liquid discharge head block The liquid ejection head block is arranged in a direction substantially orthogonal to the side surface by providing an air introduction part that guides ambient air to the space between the liquid ejection heads when the liquid ejection head is moved in a direction orthogonal to the side surface. As a result, the air flows into the space between the liquid discharge heads, and the temperature of the liquid discharge head can be lowered.

  Further, the side surface of the liquid discharge head is made of a metal plate, and a driver IC that controls the discharge of the liquid is in contact with the inner surface of the metal plate, and between the adjacent liquid discharge heads. In the case where the air flow rectifying unit that guides the air flow to the side surface outside the contacted portion of the driver IC of the metal plate is provided in the space, the portion of the contacted portion of the driver IC that is a heat generation source Since the air flow can be concentrated on the metal plate, the efficiency of waste heat is improved and the temperature of the liquid discharge head can be lowered.

  Further, the air introduction section causes the air in the space between the liquid ejection heads to flow from one side to the other side when the liquid ejection head block is moved in a direction orthogonal to the side surface. In this case, the heat transfer direction is one direction, the efficiency of waste heat is improved, and the temperature of the liquid discharge head can be lowered.

  Still further, the number of the liquid discharge heads is three or more, and when the liquid discharge head block is viewed from a direction orthogonal to the side surface, When the air introduction part on the side is larger than the air introduction part that guides air to the space on the near side, the air introduction part between the plurality of liquid ejection heads is larger Since the ambient air can be guided to each of the spaces, each liquid discharge head can be efficiently cooled, and the temperature of the liquid discharge head can be lowered.

  Furthermore, the air rectifying plate having substantially the same shape as the side surface of the liquid discharge head is disposed substantially parallel to the outermost side surface among the side surfaces of the plurality of liquid discharge heads and facing each other with a space therebetween. In addition, since the second air introduction unit that introduces ambient air into the space between the air rectifying plate and the liquid ejection head is provided, the temperature of the liquid ejection head can be lowered.

  In the recording apparatus of the invention, the liquid ejection head block, a transport unit that transports the recording medium to the liquid ejection head, and the liquid ejection head block are parallel to the direction of transporting the recording medium. A reciprocating mechanism that reciprocates in a direction substantially orthogonal to the side surface of the liquid ejection head in a direction that is not, and a control unit that controls the driving of the liquid ejection head. It is possible to suppress fluctuations in the liquid ejection characteristics between the liquid ejection heads and within the liquid ejection head caused by the temperature rise. Recording quality is improved.

1 is a schematic configuration diagram of a printer that is a recording apparatus according to an embodiment of the present invention. FIG. 2 is a plan view showing a head body that constitutes the liquid ejection head of FIG. 1. FIG. 3 is an enlarged view of a region surrounded by an alternate long and short dash line in FIG. 2. FIG. 3 is an enlarged view of a region surrounded by an alternate long and short dash line in FIG. It is a longitudinal cross-sectional view along the VV line of FIG. FIG. 2 is a perspective view of the liquid ejection head in FIG. 1. FIG. 7 is a longitudinal sectional view of the liquid discharge head of FIG. 6 taken along line XX. (A) is the perspective view which showed one Example of the liquid discharge head block of this invention, (b) is the top view of (a), (c) is the liquid discharge head block of (a) It is the perspective view which showed a part of. It is another Example of the liquid discharge head block of this invention. (A) is another embodiment of the liquid discharge head block of the present invention, and (b) is another embodiment of the liquid discharge head block of the present invention.

  FIG. 1 is a schematic configuration diagram of a color inkjet printer which is a recording apparatus according to an embodiment of the present invention. The color inkjet printer 1 (hereinafter referred to as printer 1) includes a liquid discharge head block 18 including four liquid discharge heads 2. These liquid discharge heads 2 have a rectangular parallelepiped shape that is long in one direction, and have a liquid discharge hole surface on the printing paper P side. On the surface of the liquid discharge hole, the liquid discharge hole 8 is arranged long in the one direction.

  Four liquid discharge heads 2 are mounted on the liquid discharge head block 18, and the liquid discharge heads 2 are arranged so as to overlap each other with a space therebetween in a substantially parallel manner. The liquid ejection head block 18 reciprocates in a direction that is not parallel to the conveyance direction of the printing paper P, for example, a direction that is orthogonal to the one direction.

  In the printer 1, a paper feed unit 114, a transport unit 120, and a paper receiver 116 are sequentially provided along the transport path of the printing paper P. In addition, the printer 1 is provided with a control unit 100 for controlling the operation of each unit of the printer 1 such as the liquid discharge head 2 and the paper feeding unit 114.

  The paper supply unit 114 includes a paper storage case 115 that can store a plurality of printing papers P, and a paper supply roller 145. The paper feed roller 145 can send out the uppermost print paper P among the print papers P stacked and stored in the paper storage case 115 one by one.

  Between the paper feed unit 114 and the transport unit 120, two pairs of feed rollers 118a and 118b and 119a and 119b are arranged along the transport path of the printing paper P. The printing paper P sent out from the paper supply unit 114 is guided by these feed rollers and further sent out to the transport unit 120.

  The transport unit 120 includes an endless transport belt 111 and two belt rollers 106 and 107. The conveyor belt 111 is wound around belt rollers 106 and 107. The conveyor belt 111 is adjusted to such a length that it is stretched with a predetermined tension when it is wound around two belt rollers. Thus, the conveyor belt 111 is stretched without slack along two parallel planes each including a common tangent line of the two belt rollers. Of these two planes, the plane closer to the liquid ejection head 2 is a transport surface 127 that transports the printing paper P.

  As shown in FIG. 1, a conveyance motor 174 is connected to the belt roller 106. The transport motor 174 can rotate the belt roller 106 in the direction of arrow A. The belt roller 107 can rotate in conjunction with the transport belt 111. Therefore, the conveyance belt 111 moves along the direction of arrow A by driving the conveyance motor 174 and rotating the belt roller 106.

  In the vicinity of the belt roller 107, a nip roller 138 and a nip receiving roller 139 are arranged so as to sandwich the conveyance belt 111. The nip roller 138 is urged downward by a spring (not shown). A nip receiving roller 139 below the nip roller 138 receives the nip roller 138 biased downward via the conveying belt 111. The two nip rollers are rotatably installed and rotate in conjunction with the conveyance belt 111.

  The printing paper P sent out from the paper supply unit 114 to the transport unit 120 is sandwiched between the nip roller 138 and the transport belt 111. As a result, the printing paper P is pressed against the transport surface 127 of the transport belt 111 and is fixed on the transport surface 127. The printing paper P is transported in the direction in which the liquid ejection head 2 is installed according to the rotation of the transport belt 111. The outer peripheral surface 113 of the conveyor belt 111 may be treated with adhesive silicon rubber. Thereby, the printing paper P can be securely fixed to the transport surface 127.

  Each liquid discharge head 2 has a head body 13 at the lower end. A large number of liquid ejection holes 8 for ejecting liquid are provided on the lower surface of the head body 13 (see FIG. 3).

  Liquid droplets (ink) of the same color are ejected from the liquid ejection holes 8 provided in one liquid ejection head 2. Since the liquid ejection holes 8 of each liquid ejection head 2 are arranged at equal intervals in one direction (a direction parallel to the printing paper P and perpendicular to the conveyance direction of the printing paper P and the longitudinal direction of the liquid ejection head 2), Printing can be performed without gaps in one direction. The colors of the liquid ejected from each liquid ejection head 2 are magenta (M), yellow (Y), cyan (C), and black (K), respectively. Each liquid ejection head 2 is disposed with a slight gap between the lower surface of the head body 13 and the transport surface 127 of the transport belt 111.

  The printing paper P transported by the transport belt 111 passes through the gap between the liquid ejection head 2 and the transport belt 111. At that time, droplets are ejected from the head main body 13 constituting the liquid ejection head 2 toward the upper surface of the printing paper P. As a result, a color image based on the image data stored by the control unit 100 is formed on the upper surface of the printing paper P.

  A separation plate 140 and two pairs of feed rollers 121a and 121b and 122a and 122b are arranged between the transport unit 120 and the paper receiver 116. The printing paper P on which the color image is printed is conveyed to the peeling plate 140 by the conveying belt 111. At this time, the printing paper P is peeled from the transport surface 127 by the right end of the peeling plate 140. Then, the printing paper P is sent out to the paper receiving unit 116 by the feed rollers 121a to 122b. In this way, the printed printing paper P is sequentially sent to the paper receiving unit 116 and stacked on the paper receiving unit 116.

  Note that a paper surface sensor 133 is installed between the liquid ejection head 2 and the nip roller 138 that are the most upstream in the transport direction of the printing paper P. The paper surface sensor 133 includes a light emitting element and a light receiving element, and can detect the leading end position of the printing paper P on the transport path. The detection result by the paper surface sensor 133 is sent to the control unit 100. The control unit 100 can control the liquid ejection head 2, the conveyance motor 174, and the like so that the conveyance of the printing paper P and the printing of the image are synchronized based on the detection result sent from the paper surface sensor 133.

  Next, the liquid discharge head 2 of the present invention will be described. FIG. 6 is a perspective view of the liquid discharge head 2. The liquid discharge head 2 includes a liquid discharge head main body 13 and a housing 90. The casing 90 is made of metal, and a hole 99 through which a signal cable for transmitting a driving signal is partially opened. In the example of FIG. 6, a hole 99 is opened in a part of the upper surface, and a signal cable (not shown) through which a drive signal connected to the control unit 100 is transmitted passes through the hole 99 and is closed with a resin lid or the like. Can be removed. A liquid introduction hole 98 is opened in the liquid discharge head 2, and a liquid discharged from the liquid introduction hole 98 is put therein. A side plate 91 is attached to a part of the head body 2 by screwing or bonding.

  FIG. 7 is a cross-sectional view of the liquid ejection head 2 shown in FIG. The liquid discharge head main body 13 includes a flow path member 4, a branch flow path member 93, a piezoelectric actuator unit 21, a flexible flat cable (hereinafter sometimes abbreviated as FPC) 92, a driver IC 55, and a side plate 92. A branch flow path member 93 is overlaid on the liquid discharge head body 13, and the branch flow path member 93 includes a frame 96 with a heat insulating elastic member 97 and a substrate 94 on which a connector 95 is mounted. It is fixed. The frame 96 is not connected in the cross-sectional view of FIG. 7, but is fixed at a portion other than this cross-section. A drive signal sent from the control unit 100 to the board 232 via a signal cable (not shown) is sent to the FPC 92 via the connector 95. The driver IC 55 mounted on the FPC 92 processes the drive signal, and the processed drive signal drives the liquid discharge element 50 of the piezoelectric actuator unit 21 described later through the FPC 92 to pressurize the liquid inside the flow path member 4. Thus, a droplet is ejected. For example, the substrate 94 may divide the ejection signal into a plurality of driver ICs 55 or rectify the ejection signal. However, the substrate 94 is not provided, and the signal cable from the control unit 100 is directly connected to the FPC 92. It may be. The FPC 92 has a flexible belt-like shape, has a metal wiring inside, and a part of the wiring is exposed on the surface of the FPC 92, and the connector 95, the driver IC 55, and the piezoelectric actuator unit are exposed by the exposed wiring. 21 is electrically connected.

  The driver IC 55 generates heat when performing the above-described drive signal processing. When this heat is transmitted to the flow path member 4, a temperature difference occurs between the flow path member 4 and the liquid inside the flow path member 4. Since the viscosity of the liquid changes as the temperature changes, even if the pressure from the pressurizing means is constant, the discharge speed and amount of the droplets change. If the speed and amount of the ejected droplets change, the landing position on the printing paper P shifts, and the size of the pixels formed by the spreading of the droplets after landing changes, so the accuracy of the printed image is low. May be. However, since the driver IC 55 is pressed by the heat insulating elastic member 97 through the FPC 92 and pressed against the metal casing 90, the generated heat is mainly transmitted to the casing 90, and further the entire casing 90. It spreads quickly and is dissipated to the outside.

  Next, the head main body 13 constituting the liquid discharge head 2 of the present invention will be described. FIG. 2 is a top view showing the head main body 13 shown in FIG. FIG. 3 is an enlarged top view of a region surrounded by the alternate long and short dash line in FIG. 2 and is a part of the head main body 13. FIG. 4 is an enlarged perspective view of the same position as in FIG. 3, in which some of the flow paths are omitted so that the position of the liquid discharge holes 8 can be easily understood. 3 and 4, in order to make the drawings easy to understand, the liquid pressurizing chamber 10 (liquid pressurizing chamber group 9), the squeezing 12, and the liquid discharge holes which are to be drawn by broken lines below the piezoelectric actuator unit 21. 8 is drawn with a solid line. FIG. 5 is a longitudinal sectional view taken along line VV in FIG.

  The head body 13 includes a flat plate-like flow path member 4 and a piezoelectric actuator unit 21 that is an actuator unit on the flow path member 4. The piezoelectric actuator unit 21 has a trapezoidal shape, and is disposed on the upper surface of the flow path member 4 so that a pair of parallel opposing sides of the trapezoid is parallel to the longitudinal direction of the flow path member 4. Further, two piezoelectric actuator units 21 are arranged on the flow path member 4 as a whole in a zigzag manner, two along each of two virtual straight lines parallel to the longitudinal direction of the flow path member 4. Yes. The oblique sides of the piezoelectric actuator units 21 adjacent to each other on the flow path member 4 partially overlap in the short direction of the flow path member 4. In the area printed by driving the overlapping piezoelectric actuator unit 21, the droplets ejected by the two piezoelectric actuator units 21 are mixed and landed.

  A manifold 5 that is a part of the liquid flow path is formed inside the flow path member 4. The manifold 5 has an elongated shape extending along the longitudinal direction of the flow path member 4, and an opening 5 b of the manifold 5 is formed on the upper surface of the flow path member 4. A total of ten openings 5 b are formed along each of two straight lines (imaginary lines) parallel to the longitudinal direction of the flow path member 4. The opening 5b is formed at a position that avoids a region where the four piezoelectric actuator units 21 are disposed. The manifold 5 is supplied with liquid from a liquid tank (not shown) through the opening 5b.

  The manifold 5 formed in the flow path member 4 is branched into a plurality of branches (the manifold 5 at the branched portion may be referred to as a sub-manifold 5a). The manifold 5 connected to the opening 5 b extends along the oblique side of the piezoelectric actuator unit 21 and is disposed so as to intersect with the longitudinal direction of the flow path member 4. In a region sandwiched between two piezoelectric actuator units 21, one manifold 5 is shared by adjacent piezoelectric actuator units 21, and the sub-manifold 5 a branches off from both sides of the manifold 5. These sub-manifolds 5 a extend in the longitudinal direction of the head main body 13 adjacent to each other in regions facing the piezoelectric actuator units 21 inside the flow path member 4.

  The flow path member 4 has four liquid pressurizing chamber groups 9 in which a plurality of liquid pressurizing chambers 10 are formed in a matrix (that is, two-dimensionally and regularly). The liquid pressurizing chamber 10 is a hollow region having a substantially rhombic planar shape with rounded corners. The liquid pressurizing chamber 10 is formed so as to open on the upper surface of the flow path member 4. These liquid pressurizing chambers 10 are arranged over almost the entire surface of the upper surface of the flow path member 4 facing the piezoelectric actuator unit 21. Accordingly, each liquid pressurizing chamber group 9 formed by these liquid pressurizing chambers 10 occupies a region having almost the same size and shape as the piezoelectric actuator unit 21. Further, the opening of each liquid pressurizing chamber 10 is closed by adhering the piezoelectric actuator unit 21 to the upper surface of the flow path member 4.

  In the present embodiment, as shown in FIG. 3, the manifold 5 branches into four rows of E1-E4 sub-manifolds 5a arranged in parallel with each other in the short direction of the flow path member 4, and each sub-manifold The liquid pressurizing chambers 10 connected to 5a constitute a row of liquid pressurizing chambers 10 arranged in the longitudinal direction of the flow path member 4 at equal intervals, and the four rows are arranged in parallel to each other in the short direction. Yes. Two rows of liquid pressurizing chambers 10 connected to the sub-manifold 5a are arranged on both sides of the sub-manifold 5a.

  As a whole, the liquid pressurizing chambers 10 connected from the manifold 5 constitute rows of the liquid pressurizing chambers 10 arranged in the longitudinal direction of the flow path member 4 at equal intervals, and the rows are 16 rows parallel to each other in the short direction. It is arranged. The number of liquid pressurizing chambers 10 included in each liquid pressurizing chamber row is arranged so as to gradually decrease from the long side toward the short side, corresponding to the outer shape of the displacement element 50 that is an actuator. ing. The liquid discharge holes 8 are also arranged in the same manner. As a result, it is possible to form an image with a resolution of 600 dpi in the longitudinal direction as a whole. That is, the individual flow paths 32 are connected to each sub-manifold 5a at intervals corresponding to 150 dpi on average. This is because the individual flow paths 32 connected to the sub-manifolds 5a are not necessarily connected at equal intervals when the liquid ejection holes 8 for 600 dpi are divided and connected to the four sub-manifolds 5a. This means that the individual flow paths 32 are formed at intervals of an average of 170 μm (25.4 mm / 150 = 169 μm intervals if 150 dpi) in the extending direction of 5a, that is, the main scanning direction.

  Drive electrodes 35 to be described later are formed at positions facing the respective liquid pressurizing chambers 10 on the upper surface of the piezoelectric actuator unit 21. The drive electrode 35 is slightly smaller than the liquid pressurizing chamber 10, has a shape substantially similar to the liquid pressurizing chamber 10, and fits in a region facing the liquid pressurizing chamber 10 on the upper surface of the piezoelectric actuator unit 21. Is arranged.

  A large number of liquid discharge holes 8 are formed in the liquid discharge surface on the lower surface of the flow path member 4. These liquid discharge holes 8 are arranged at a position avoiding a region facing the sub-manifold 5 a arranged on the lower surface side of the flow path member 4. Further, these liquid discharge holes 8 are arranged in a region facing the piezoelectric actuator unit 21 on the lower surface side of the flow path member 4. These liquid discharge hole groups 7 occupy an area having almost the same size and shape as the piezoelectric actuator unit 21, and the liquid discharge holes 8 are made to drop liquid by displacing the displacement element 50 of the corresponding piezoelectric actuator unit 21. Can be discharged. The arrangement of the liquid discharge holes 8 will be described in detail later. The liquid discharge holes 8 in each region are arranged at equal intervals along a plurality of straight lines parallel to the longitudinal direction of the flow path member 4.

  The flow path member 4 included in the head body 13 has a stacked structure in which a plurality of plates are stacked. These plates are a cavity plate 22, a base plate 23, an aperture (squeezing) plate 24, supply plates 25 and 26, manifold plates 27, 28 and 29, a cover plate 30 and a nozzle plate 31 in order from the upper surface of the flow path member 4. is there. A number of holes are formed in these plates. Each plate is aligned and laminated so that these holes communicate with each other to form the individual flow path 32 and the sub-manifold 5a. As shown in FIG. 5, the head main body 13 has a liquid pressurizing chamber 10 on the upper surface of the flow path member 4, the sub-manifold 5a on the inner lower surface side, and the liquid discharge holes 8 on the lower surface. Each portion constituting the path 32 is disposed close to each other at different positions, and the sub manifold 5 a and the liquid discharge hole 8 are connected via the liquid pressurizing chamber 10.

  The holes formed in each plate will be described. These holes include the following. First, the liquid pressurizing chamber 10 formed in the cavity plate 22. Second, there is a communication hole that forms a flow path that connects from one end of the liquid pressurizing chamber 10 to the sub-manifold 5a. This communication hole is formed in each plate from the base plate 23 (specifically, the inlet of the liquid pressurizing chamber 10) to the supply plate 25 (specifically, the outlet of the sub manifold 5a). The communication hole includes the aperture 12 formed in the aperture plate 24 and the individual supply flow path 6 formed in the supply plates 25 and 26.

  Third, there is a communication hole that constitutes a flow channel that communicates from the other end of the liquid pressurizing chamber 10 to the liquid discharge hole 8, and this communication hole is referred to as a descender (partial flow channel) in the following description. . The descender is formed on each plate from the base plate 23 (specifically, the outlet of the liquid pressurizing chamber 10) to the nozzle plate 31 (specifically, the liquid discharge hole 8). Fourthly, there is a communication hole constituting the sub-manifold 5a. The communication holes are formed in the manifold plates 27-30.

  Such communication holes are connected to each other to form an individual flow path 32 from the liquid inflow port (the outlet of the submanifold 5a) from the submanifold 5a to the liquid discharge hole 8. The liquid supplied to the sub manifold 5a is discharged from the liquid discharge hole 8 through the following path. First, from the sub-manifold 5a, it passes through the individual supply flow path 6 and reaches one end of the aperture 12. Next, it proceeds horizontally along the extending direction of the aperture 12 and reaches the other end of the aperture 12. From there, it reaches one end of the liquid pressurizing chamber 10 upward. Further, the liquid pressurizing chamber 10 proceeds horizontally along the extending direction of the liquid pressurizing chamber 10 and reaches the other end of the liquid pressurizing chamber 10. While moving little by little in the horizontal direction from there, it proceeds mainly downward and proceeds to the liquid discharge hole 8 opened on the lower surface.

  As shown in FIG. 5, the piezoelectric actuator unit 21 has a laminated structure including two piezoelectric ceramic layers 21a and 21b. Each of these piezoelectric ceramic layers 21a and 21b has a thickness of about 20 μm. The total thickness of the piezoelectric actuator unit 21 is about 40 μm. Each of the piezoelectric ceramic layers 21a and 21b extends so as to straddle the plurality of liquid pressurizing chambers 10 (see FIG. 3). The piezoelectric ceramic layers 21a and 21b are made of a lead zirconate titanate (PZT) ceramic material having ferroelectricity.

  The piezoelectric actuator unit 21 has a common electrode 34 made of a metal material such as Ag—Pd and a drive electrode 35 made of a metal material such as Au. The drive electrode 35 is disposed at a position facing the liquid pressurizing chamber 10 on the upper surface of the piezoelectric actuator unit 21 as described above. One end of the drive electrode 35 is drawn out of a region facing the liquid pressurizing chamber 10 to form a connection electrode 36. The connection electrode 36 is made of, for example, gold containing glass frit, and has a convex shape with a thickness of about 15 μm. The connection electrode 36 is electrically joined to an electrode provided in an FPC (Flexible Printed Circuit) (not shown). Although details will be described later, a drive signal (drive voltage) is supplied to the drive electrode 35 from the control unit 100 through the FPC. The drive signal is supplied in a constant cycle in synchronization with the conveyance speed of the print medium P.

  The common electrode 34 is formed over almost the entire surface in the area between the piezoelectric ceramic layer 21a and the piezoelectric ceramic layer 21b. That is, the common electrode 34 extends so as to cover all the liquid pressurizing chambers 10 in the region facing the piezoelectric actuator unit 21. The thickness of the common electrode 34 is about 2 μm. The common electrode 34 is grounded in a region not shown, and is held at the ground potential. In the present embodiment, a surface electrode (not shown) different from the drive electrode 35 is formed on the piezoelectric ceramic layer 21b at a position avoiding the electrode group composed of the drive electrodes 35. The surface electrode is electrically connected to the common electrode 34 through a through hole formed in the piezoelectric ceramic layer 21b, and is connected to another electrode on the FPC, like the many drive electrodes 35. ing.

  As shown in FIG. 5, the common electrode 34 and the drive electrode 35 are disposed so as to sandwich only the uppermost piezoelectric ceramic layer 21b. A region sandwiched between the drive electrode 35 and the common electrode 34 in the piezoelectric ceramic layer 21b is referred to as an active portion, and the piezoelectric ceramic in that portion is polarized. In the piezoelectric actuator unit 21 of the present embodiment, only the uppermost piezoelectric ceramic layer 21b includes an active portion, and the piezoelectric ceramic 21a does not include an active portion and functions as a diaphragm. The piezoelectric actuator unit 21 has a so-called unimorph type configuration.

  As will be described later, when a predetermined drive signal is selectively supplied to the drive electrode 35, pressure is applied to the liquid in the liquid pressurizing chamber 10 corresponding to the drive electrode 35. As a result, droplets are discharged from the corresponding liquid discharge ports 8 through the individual flow paths 32. That is, the portion of the piezoelectric actuator unit 21 that faces each liquid pressurizing chamber 10 corresponds to an individual displacement element 50 (actuator) corresponding to each liquid pressurizing chamber 10 and the liquid discharge port 8. That is, in the laminate composed of two piezoelectric ceramic layers, the displacement element 50 having a unit structure as shown in FIG. 5 is provided immediately above the liquid pressurizing chamber 10 for each liquid pressurizing chamber 10. Are formed by a diaphragm 21a, a common electrode 34, a piezoelectric ceramic layer 21b, and a drive electrode 35. The piezoelectric actuator unit 21 includes a plurality of displacement elements 50. In the present embodiment, the amount of liquid ejected from the liquid ejection port 8 by one ejection operation is about 5 to 7 pL (picoliter).

  The multiple drive electrodes 35 are individually electrically connected to the actuator control means via contacts and wirings on the FPC so that the potentials can be individually controlled.

  A method for driving the piezoelectric actuator unit 21 in the present embodiment will be described first with respect to a drive voltage (drive signal) supplied to the drive electrode 35. When the drive electrode 35 is set to a potential different from that of the common electrode 34 and an electric field is applied to the piezoelectric ceramic layer 21b in the polarization direction, the portion to which the electric field is applied functions as an active portion that is distorted by the piezoelectric effect. At this time, the piezoelectric ceramic layer 21b expands or contracts in the thickness direction, that is, the stacking direction, and tends to contract or extend in the direction perpendicular to the stacking direction, that is, the surface direction, due to the piezoelectric lateral effect. On the other hand, since the remaining piezoelectric ceramic layer 21a is an inactive layer that does not have a region sandwiched between the drive electrode 35 and the common electrode 34, it does not spontaneously deform. In other words, the piezoelectric actuator unit 21 uses the upper piezoelectric ceramic layer 21b (that is, the side away from the liquid pressurizing chamber 10) as a layer including the active portion and the lower side (that is, close to the liquid pressurizing chamber 10). This is a so-called unimorph type configuration in which the piezoelectric ceramic layer 21a on the side) is an inactive layer.

  In this configuration, when the drive electrode 35 is set to a predetermined positive or negative potential with respect to the common electrode 34 by the actuator controller so that the electric field and the polarization are in the same direction, a portion sandwiched between the electrodes of the piezoelectric ceramic layer 21b. (Active part) contracts in the surface direction. On the other hand, the piezoelectric ceramic layer 21a, which is an inactive layer, is not affected by an electric field, so that it 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 21b and the piezoelectric ceramic layer 21a, and the piezoelectric ceramic layer 21b is deformed so as to protrude toward the liquid pressurizing chamber 10 (unimorph deformation). .

  One of the actual driving procedures in the present embodiment is called “strike”. The driving electrode 35 is set to a potential higher than the common electrode 34 (hereinafter referred to as “high potential”) in advance, and the driving electrode 35 is provided each time there is a discharge request. Is once set to the same potential as the common electrode 34 (hereinafter referred to as a low potential), and then set to a high potential again at a predetermined timing. As a result, the piezoelectric ceramic layers 21a and 21b return to the original shape at the timing when the drive electrode 35 becomes a low potential, and the volume of the liquid pressurizing chamber 10 is compared with the initial state (the state where the potentials of both electrodes are different). To increase. At this time, a negative pressure is applied to the liquid pressurizing chamber 10 and the liquid is sucked into the liquid pressurizing chamber 10 from the manifold 5 side. Thereafter, at the timing when the drive electrode 35 is set to a high potential again, the piezoelectric ceramic layers 21a and 21b are deformed so as to protrude toward the liquid pressurizing chamber 10 side. Becomes a positive pressure, the pressure on the liquid rises, and droplets are ejected. That is, a drive signal including a pulse with a high potential as a reference is supplied to the drive electrode 35 in order to discharge the droplet. The ideal pulse width is AL (Acoustic Length), which is the length of time during which the pressure wave propagates from the manifold 5 to the liquid discharge hole 8 in the liquid pressurizing chamber 10. According to this, when the inside of the liquid pressurizing chamber 10 is reversed from the negative pressure state to the positive pressure state, both pressures are combined, and the liquid droplet can be ejected with a stronger pressure.

  On the contrary, a driving method called pushing can be used. In the pushing, the drive electrode 35 is set to the same potential (low potential) as the common electrode 34, and the drive electrode 35 is set to a higher potential (high potential) than the common electrode 34 every time there is an ejection request. Thereby, the liquid column pushed out from the liquid discharge hole 8 due to the increase in the volume of the liquid pressurizing chamber 10 causes the liquid pressurization when the inside of the liquid pressurizing chamber 10 is reversed from the positive pressure state to the negative pressure state. The volume of the chamber 10 is increased, the root of the liquid column is cut, and the separated droplets are discharged.

  In gradation printing, gradation expression is performed by the number of droplets ejected continuously from the liquid 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 specified gradation expression is continuously performed from the liquid discharge hole 8 corresponding to the specified 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.

  When the liquid discharge head block 18 in which a plurality of liquid discharge heads 2 are arranged as described above is used, the driver IC 55 generates heat, and there is a possibility that the discharge characteristics vary. Heat tends to be trapped between the two liquid ejection heads 2. In addition, when three or more liquid discharge heads 2 are arranged, the temperature of the liquid discharge head 2 inside may increase.

  In order to release such heat to the outside, the liquid discharge head block 18 of the present invention shown in FIGS. 8A to 8C is a liquid in which a plurality of liquid discharge holes are arranged long in one direction in a frame 80. The liquid discharge head 2 includes a plurality of rectangular liquid discharge heads 2 having a discharge hole surface and long in the one direction, and each of the liquid discharge heads 2 is adjacent to each other on the long side in the one direction of the liquid discharge hole surface. Are arranged in parallel with each other with a space between them, and when the liquid discharge head block 18 is moved in a direction perpendicular to the side surface, the space between the liquid discharge heads 2 Air introduction parts (first air layer entry parts) 60A to 60C for introducing air are provided. The air introduction units 60A to 60C have a surface that changes the flow of the surrounding air when the liquid discharge head block 18 is moved, and the air whose direction of flow has changed on the surface is adjacent to the adjacent liquid discharge head 2. Introduced into the space between.

  The frame 80 is open at a portion corresponding to the surface of the liquid discharge head 2 having the liquid discharge holes.

  When the liquid discharge head block 18 is moved in the direction of the arrow shown in FIG. 8B, which is a direction perpendicular to the side surface, the liquid discharge head 2 is opened from the openings formed by the air introduction portions 60A to 60C. It is possible to effectively cool the liquid discharge head 2 by guiding the air passing through to the space between the liquid discharge heads 2 and flowing the air mainly from the right side to the left side in FIG. it can.

  Note that the moving direction of the liquid discharge head 18 in actual operation does not have to be perpendicular to the side surface, and may be moved so that air is introduced.

  Further, in the liquid discharge head 18, the side surface is made of a metal plate, the driver IC 55 is brought into contact with the surface on the opposite side of the metal plate, and air flows into the space between the liquid discharge heads 2. An air rectifying unit 62 is provided to guide the metal plate driver IC 55 to a contact portion. In this way, the air flow is concentrated on the metal plate on the side surface outside the portion where the driver IC 55 as a heat source is in contact, and the cross-sectional area of the air rectifying unit 62 is the portion where the driver IC is located. Since the flow velocity of the air flow is increased, the efficiency of waste heat is improved and the temperature of the liquid discharge head can be lowered.

  When the number of liquid ejection heads is three or more, it is preferable to provide the air introduction part 60 in each of the spaces between the liquid ejection heads 2. At that time, when the liquid ejection head block 18 is viewed from the direction orthogonal to the side surface, that is, when viewed from the side opposite to the arrow in FIG. 8B, the liquid ejection head block 18 is moved forward. In this case, in the air introduction part 60 on the side for sending ambient air into the space between the liquid discharge heads, that is, the right air introduction part 60 in FIGS. It is preferable that the air introduction part 60 that introduces air into the inner space is larger than the air introduction part that introduces air. This is because the air introduction part 60C spreads outward than the air introduction part 60B, the air introduction part 60C spreads outward than the air introduction part 60C, and the air introduction part 60B. 60C is preferably spread outward. By doing so, ambient air can be guided to each of the spaces between the plurality of liquid ejection heads 2, so that each liquid ejection head 2 can be efficiently cooled.

  In addition, an air rectifying plate 64 having substantially the same shape as the side surface of the liquid discharge head 2 is disposed substantially parallel to the outermost side surface of the liquid discharge head 2 with a space therebetween, and air rectification. It is preferable to include a second air introduction portion 66 that introduces ambient air into the space between the plate 64 and the liquid ejection head 2. In this way, when the liquid ejection head block 18 is moved forward, air is also introduced into the back side of the rearmost liquid ejection head 2, so that the temperature of the liquid ejection head 2 is lowered. be able to. In addition, since the air that hits the front liquid discharge head 2 is blocked by the front air rectifying plate 64, the cooling state of the front liquid discharge head 2 becomes closer to the other liquid discharge heads 2.

  The openings formed by the first air introduction part 60 and the second air introduction part 66 that guide air to each space preferably have the same area when viewed from the direction orthogonal to the side surface. That is, in FIG. 8B, the intervals A are preferably all the same. By doing so, the amount of air flowing into each space becomes close, and the temperature difference between the liquid ejection heads 2 is reduced.

  FIG. 9 is a perspective view of another example of the liquid discharge head block 218 of the present invention. The liquid discharge head block 218 is provided with a lid 268 so that the air introduced into the first air introduction part 260 and the first air introduction part 266 does not escape.

  FIG. 10A is a cross-sectional view of another example of the liquid discharge head block 318 of the present invention. When the liquid discharge head block 318 is moved in the left-right direction in the drawing, the air introduction unit 360 causes air to be introduced into the space between the liquid discharge heads 302 attached to the frame 380, so that the air discharge head block 318 moves from bottom to top. The liquid discharge head 302 can be cooled by the flowing air. Since the flow of air is the same as the direction in which warm air moves, efficiency is improved and this is preferable.

  FIG. 10B is a cross-sectional view of another example of the liquid discharge head block 418 of the present invention. When the liquid discharge head block 418 is moved in the left-right direction in the figure, the air introduction unit 460 causes air to be introduced into the space between the liquid discharge heads 402 attached to the frame 480, so that the air discharge head block 418 moves from bottom to top. The liquid discharge head 402 can be cooled by the flowing air.

  The liquid discharge head block 18 as described above is manufactured as follows, for example.

  A tape composed of a piezoelectric ceramic powder and an organic composition is formed by a general tape forming method such as a roll coater method or a slit coater method, and a plurality of green sheets that become piezoelectric ceramic layers 21a and 21b after firing are produced. . An electrode paste to be the common electrode 34 is formed on a part of the green sheet by a printing method or the like. Further, if necessary, a via hole is formed in a part of the green sheet, and a via conductor is inserted into the via hole.

  Next, each green sheet is laminated to produce a laminate, and pressure adhesion is performed. The laminated body after pressure contact is fired in a high-concentration oxygen atmosphere, and then the individual electrodes 25 are printed on the fired body surface using an organic gold paste, fired, and then the connection electrode 36 is printed using an Ag paste. And the piezoelectric actuator unit 21 is produced by baking.

  Next, the flow path member 4 is produced by laminating plates 22 to 31 obtained by a rolling method or the like. Holes to be the manifold 5, the individual supply flow path 6, the liquid pressurizing chamber 10, the descender, and the like are processed in the plates 22 to 31 into a predetermined shape by etching.

  These plates 22 to 31 are preferably formed of at least one metal selected from the group consisting of Fe—Cr, Fe—Ni, and WC—TiC, particularly when ink is used as a liquid. Since it is desired to be made of a material having excellent corrosion resistance against ink, Fe-Cr is more preferable.

  The piezoelectric actuator 21 and the flow path member 4 can be laminated and bonded via an adhesive layer, for example. A well-known adhesive layer can be used as the adhesive layer. However, in order not to affect the piezoelectric actuator 21 and the flow path member 4, an epoxy resin, a phenol resin, or a polyphenylene ether having a thermosetting temperature of 100 to 150 ° C. It is preferable to use at least one thermosetting resin adhesive selected from the group of resins. By heating to the thermosetting temperature using such an adhesive layer, the piezoelectric actuator 21 and the flow path member 4 can be heat-bonded.

  Thereafter, in order to electrically connect the piezoelectric actuator upper 21 and the control unit 100 as necessary, an electrode such as FPC is joined to the connection electrode 36, and the casing 90, the side plate 91, the branch flow channel member 93, the substrate 94, the connector 95, the frame 96, and the heat insulating elastic member 97 are assembled to obtain the liquid ejection head 2.

  Furthermore, if the liquid discharge head 2, the air introduction part 60, the rectification part 62, and the second air introduction part 66 are screwed into the metal frame 80, the liquid discharge head block 18 is obtained.

DESCRIPTION OF SYMBOLS 1 ... Printer 2 ... Liquid discharge head 4 ... Flow path member 5 ... Manifold 5a ... Sub manifold 5b ... Opening 6 ... Individual supply flow path 8 ... Liquid discharge hole DESCRIPTION OF SYMBOLS 9 ... Liquid pressurization chamber group 10 ... Liquid pressurization chamber 11a, b, c, d ... Liquid pressurization chamber row | line | column 12 ... Squeezing 13 ... Head main body 15a, b, c, d ... Liquid ejection hole array 18, 218, 318, 418 ... Liquid ejection head block 21 ... Piezoelectric actuator unit 21a ... Piezoelectric ceramic layer (vibrating plate)
21b ... Piezoelectric ceramic layer 22-31 ... Plate 32 ... Individual flow path 34 ... Common electrode 35 ... Drive electrode 36 ... Connection electrode 50 ... Displacement element 55 ... Driver IC
60, 260, 360, 460 ... air introduction part 62 ... rectification part 66, 266 ... second air introduction part 80, 280, 380 ... frame 90 ... casing 91 ... Side plate 92 ... Flexible flat cable 93 ... Branch channel member 94 ... Substrate 95 ... Connector 96 ... Frame 97 ... Thermal insulation elastic member 98 ... Liquid introduction hole 99 ...・ Hole

Claims (5)

A liquid discharge head block including a plurality of liquid discharge heads having a liquid discharge hole surface on which a plurality of liquid discharge holes are arranged,
The liquid discharge heads adjacent to each other among the plurality of liquid discharge heads are arranged so that the side surfaces of the liquid discharge heads face each other with a space therebetween, and the liquid discharge head block intersects the side surface. An air introduction part that guides ambient air to the space between the liquid ejection heads when moved in the direction;
The side surface of the liquid ejection head is made of a metal plate, and a driver IC that controls liquid ejection is in contact with the inner surface of the metal plate ,
An air rectifying unit is provided in a space between the liquid ejection heads adjacent to each other among the plurality of liquid ejection heads to guide the air flow to the side surface outside the contacted portion of the driver IC of the metal plate. A liquid discharge head block. The plurality of liquid ejection holes are arranged long in one direction,
The liquid discharge head has a rectangular parallelepiped shape that is long in the one direction,
The side surface is arranged long in the one direction,
The liquid discharge head block according to claim 1, wherein the side surfaces of the liquid discharge heads adjacent to each other are arranged substantially in parallel. The air introduction unit is configured to cause the air in the space between the adjacent liquid ejection heads to flow from one side of the one direction to the other when the liquid ejection head block is moved in a direction orthogonal to the side surface. Provided in both one and the other in one direction,
The number of the liquid discharge heads is three or more, and when the liquid discharge head block is viewed from a direction orthogonal to the side surface, 3. The liquid ejection according to claim 2, wherein the air introduction portion is larger in the air introduction portion that introduces air into the space on the back side than the air introduction portion that introduces air into the space on the near side. Head block. An air rectifying plate having substantially the same shape as the side surface of the liquid discharge head is disposed substantially parallel to the outermost side surface among the side surfaces of the plurality of liquid discharge heads and facing each other with a space therebetween. together, the liquid discharge according to any one of claims 1 to 3, characterized in that it comprises a second air introduction portion for introducing the ambient air into the space between the air guide plate and the liquid discharge head Head block. A liquid discharge head block according to any one of claims 1 to 4, a conveyance unit for conveying the recording medium to the liquid ejecting head, the liquid ejection head block with respect to the direction of conveying the recording medium A recording system comprising: a reciprocating mechanism that reciprocates in a direction substantially orthogonal to the side surface of the liquid ejection head in a direction that is not parallel; and a control unit that controls driving of the liquid ejection head. apparatus.

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