JP2015150740A - Ink jet head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem in which an ink circulation type ink jet head that cannot hold the temperature in a pressure chamber uniform owing to an influence of a shift of a fitting part, caused depending upon to coefficients of thermal expansion of a head structure and a printer body-side structure due to heat generation of a drive IC, on ink.SOLUTION: An ink jet head according to an embodiment includes: a head body which has a plurality of nozzle holes and a liquid chamber for ink; a plurality of ink flow passages which have opening in the liquid chamber of the head body; a base part which has an ink supply path and an ink discharge path of the plurality of ink flow passages and a supply port and a discharge port for the ink to those ink supply path and ink discharge path; a driving circuit which is provided at the base part and drives the head body for discharging; a heat sink which emits heat of the driving circuit; a reference plate where those heat sink, driving circuit, base part, and head body are fixed; and a heat pipe which is connected to the reference plate.

Description

  One embodiment relates to an inkjet head.

  The ink jet recording apparatus includes an ink jet head, a tank of ink to the ink jet head, and an ink circulation mechanism between the ink jet head and the tank (see, for example, Patent Document 1). The inkjet head has a piezoelectric member having the same number of pressure chambers as the number of nozzles on the substrate. When an electric signal is supplied to the pressure chambers via a wiring circuit, the volume of the pressure chambers changes, and the volume changes. As a result, ink is ejected from the nozzle toward the paper.

  A reference plate and a heat sink for positioning and fixing the head main body to a mounting plate on the printer apparatus main body side are attached to the head main body of the inkjet head, and the temperature of the reference plate and the heat sink rises due to ejection driving by the driver IC. . When the thermal expansion coefficients of the heat sink and the reference plate are larger than the thermal expansion coefficient of the mounting plate, the reference plate is displaced by a dimension that cannot be ignored with respect to the nozzle pitch due to the thermal expansion. 2. Description of the Related Art Conventionally, there has been known a droplet discharge unit that connects a plurality of heat pipes to a driver IC for heat dissipation and improves the heat dissipation of each driver IC (see, for example, Patent Document 2).

JP 2009-18540 A JP 2007-203528 A

  However, in the ink circulation type ink jet head, the heat generation of the drive IC causes a displacement due to the thermal expansion coefficient between the head structure and the printer body side structure, which affects the ink, and the temperature of the pressure chamber is reduced. It cannot be kept uniform. Even if heat is dissipated by the heat pipe and the heat sink, the heat generated by the driver IC is transferred to the metal connection portion (connection) to the ink supply pipe and the discharge pipe. Heat generation raises the temperature of the ink flowing through these supply pipes and discharge pipes through the connecting portion. Ink viscosity has a temperature characteristic, and an increase in ink temperature affects print quality.

  In order to solve such a problem, according to one embodiment, a head body having a plurality of nozzle holes and an ink liquid chamber, a plurality of ink flow paths opening in the liquid chamber of the head body, An ink supply path and an ink discharge path in the ink flow path, a base part having the ink supply port and the ink discharge path to the ink supply path and the ink discharge path, and an ejection of the head main body provided in the base part An ink jet comprising: a drive circuit for driving; a heat sink for dissipating heat generated by the drive circuit; a reference plate for fixing the heat sink, the drive circuit, the base portion, and the head body; and a heat pipe connected to the reference plate A head is provided.

It is a perspective view of the ink-jet head concerning one embodiment. It is an upper surface perspective view showing an example of the head main part of the ink jet head concerning one embodiment. It is a longitudinal cross-sectional view of the inkjet head which concerns on one Embodiment. It is a partial exploded perspective view of the ink jet head concerning one embodiment. It is a disassembled perspective view before the fastening of the inkjet head which concerns on one Embodiment. FIG. 3 is a three-side view of an inkjet head according to an embodiment. It is a perspective view which shows the positional relationship of the inkjet head and ink path which concern on one Embodiment. It is a perspective view from another direction which shows the positional relationship of the inkjet head and ink path which concern on one Embodiment. It is a longitudinal cross-sectional view which follows CC of FIG. 6 of the inkjet head which concerns on one Embodiment. It is a longitudinal cross-sectional view which follows DD of FIG. 9 of the inkjet head which concerns on one Embodiment.

  Hereinafter, an inkjet head according to an embodiment will be described with reference to FIGS. 1 to 10. In the drawings, the same portions are denoted by the same reference numerals, and redundant description is omitted.

(One embodiment)
FIG. 1 is a perspective view of an inkjet head according to an embodiment. The ink jet head according to the present embodiment includes a head body 11 having a plurality of nozzle holes 51 and an ink liquid chamber, a plurality of ink flow paths each opening in the liquid chamber of the head main body 11, and among these ink flow paths. The ink supply path 80 and two ink discharge paths 81 from the liquid chamber, the ink supply port 82 to the ink supply path 80, and the base portion 12 having the ink discharge port 83 to the ink discharge path 81. The inkjet head is provided on the base portion 12 and includes a pair of drive circuits 18 including a driver IC 21 that discharges and drives the head body 11, a pair of heat sinks 14 and 15 that dissipate heat generated by the drive circuit 18, 15, a reference plate (datum plate: DATUM-PLATE-BLOCK) 13 for fixing the drive circuit 18, the base portion 12 and the head body 11, and two heat pipes 66 each connected to the reference plate 13 and sealed with a refrigerant. , 67.

  FIG. 2 is a top perspective view showing an example of the head body 11. 3 is a longitudinal sectional view of the inkjet head taken along line ZZ in FIG. The above described symbols represent the same elements. 2 does not show the frame member 53, and FIG. 3 shows only one of a plurality of pairs of piezoelectric elements.

  The head body 11 is an inkjet head body that ejects ink, and includes an orifice plate 52 in which a plurality of nozzle holes 51 are formed, and a frame member 53. The orifice plate 52 is a rectangular film made of polyimide. The nozzle holes 51 are each formed in two rows in the nozzle arrangement direction. The frame member 53 is made of, for example, a nickel alloy, and is bonded to the main surface of the base plate 54 and the orifice plate 52.

  The base portion 12 includes a base plate 54 having a hole 85 communicating with the ink supply path 80 and another hole 86 communicating with the ink discharge path 81, and these holes 85 and 86, the ink supply path 80, and two ink discharge paths. 81, a further one ink discharge path obtained by combining these two ink discharge paths 81, and a manifold 22 having a supply port 82 and a discharge port 83 formed therein. The manifold 22 is a branching and coupling part of the ink flow path. The manifold 22 supplies ink from the supply path 82 to the liquid chamber 55 through the ink supply path 80 and the hole 85. The manifold 22 discharges ink from the liquid chamber 55 through the pressure chamber 87 through the hole 86 to the discharge port 83 through an ink discharge path combined into one.

  Further, the base plate 54, the orifice plate 52 and the frame member 53 form a liquid chamber 55. Piezoelectric elements 87 are respectively provided below the plurality of nozzle holes 51. A plurality of piezoelectric elements 87 are provided along the nozzle arrangement direction of two rows, and one of the rows is shown on the left side of FIG. 3 (the piezoelectric elements 87 in the other row are not shown). Side walls of two piezoelectric elements 87 adjacent in the nozzle arrangement direction form one pressure chamber 88. Ink can flow between the pressure chamber 88 between the piezoelectric elements 87 and the liquid chamber 55. The wiring pattern 84 on the base plate 54 is connected to electrodes 89 formed on the side wall and bottom surface of the pressure chamber. The piezoelectric element 87 is driven by the driver IC 21 to change the volume of the pressure chamber 88. The ink fills the pressure chamber 88 and passes through the pressure chamber 88. Ink is projected from the nozzle hole 51 to the recording medium.

  FIG. 4 is a partially exploded perspective view of the ink jet head according to the embodiment, which is displayed with the top and bottom reversed from the example of FIG. The above described symbols represent the same elements. The manifold 22 of the base portion 12 supplies ink to the base plate 54 from above via the supply pipe 16 and discharges ink from below via the discharge pipe 17. The base portion 12 is provided with the supply pipe 16 and the discharge pipe 17 on the manifold 22 via a sealing member 24. The supply pipe 16 and the discharge pipe 17 are each connected to a tube.

  A pair of drive circuits 18 are provided symmetrically with the base plate 54 interposed therebetween, and these drive circuits 18 transmit and receive control signals between the head body 11 and the printer body side to drive the plurality of piezoelectric elements 87. . One drive circuit 18 includes a rigid printed wiring board (PCB) 19, two heat-resistant flexible printed wiring boards (FPC) 20, and a plurality of driver ICs (Dr. ICs) 21 for driving control. I have. The flexible printed wiring board 20 is a film wiring made of polyimide, for example. One end of the flexible printed wiring board 20 is connected to the rigid printed wiring board 19 and the other end is connected to the wiring pattern 84 (FIG. 3). The driver IC 21 is packaged on the flexible printed wiring board 20 by COF (chip on film). The driver IC 21 can apply a pulse voltage to each of the plurality of electrodes 89 (FIG. 3). The other drive circuit 18 has the same configuration as the one drive circuit 18. Each drive circuit 18 includes a connector 32 to the controller on the printer main body side and passive components 33 on the rigid printed wiring board 19.

  FIG. 5 is an exploded perspective view of an ink jet head according to an embodiment before fastening. The above described symbols represent the same elements. The heat sink 14 is fixed to the left side surface of the reference plate 13 with screws 54 and bolts 38 and 39, and the heat sink 15 is similarly fixed to the right side surface of the reference plate 13. The heat sinks 14 and 15 are caulked to each other by screws 54, bolts 38 and 39, and the like, and between the inner wall surface of the heat sink 14 and the inner wall surface of the heat sink 15, the reference plate 13, the ink supply tube 47, and the ink discharge tube. 48 and two heat pipes 66 and 67 are covered. For the heat sink 14, for example, aluminum or a molded product excellent in heat conduction is used. A plurality of fins may be formed on the heat sink 14. The heat sink 15 is the same as the heat sink 14. With these heat sinks 14 and 15 attached to each other, the flexible printed wiring board 20 is bent upward from its base. The lower ends of the tubes 47 and 48 are connected to the supply pipe 16 and the discharge pipe 17, respectively. The other upper ends of the tubes 47 and 48 are connected to the pipes 34 and 35, respectively. One end of each of the ink supply pipe 68 and the ink discharge pipe 69 is connected to each of the pipes 34, and the other end of each of the ink supply pipe 68 and the ink discharge pipe 69 is connected to the second end via the connection portions 64 and 65. The ink path 63 and the first ink path 62 are connected.

  The ink supply pipe 68 supplies ink from the second ink path 63 to the ink supply port 82 (FIG. 3). The ink discharge pipe 69 is provided in parallel with the ink supply pipe 68 and discharges ink from the ink discharge port 83 (FIG. 3) to the first ink path 62. The first heat pipe 66 and the second heat pipe 67 are provided outside the juxtaposed positions of the ink supply pipe 68 and the ink discharge pipe 69, respectively.

  FIG. 6 is a three-side view of the inkjet head according to the embodiment. FIG. 6A is a top view of the inkjet head. FIG. 6B is a front view of FIG. FIG.6 (c) is a right view by the BB line of FIG.6 (b). The above described symbols represent the same elements. As shown in FIG. 6B, the reference plate 13 is a metal plate for fixing the ink jet head to the iron mounting plate 40 on the printer main body side and positioning the ink jet head relative to the printer main body. For example, an aluminum molded product is used for the reference plate 13 and has a thermal expansion coefficient larger than that of the mounting plate 40. The thermal expansion coefficient is a volume expansion coefficient or a linear expansion coefficient, and is expressed by a dimension of the reciprocal of temperature (Celsius). The reference plate 13 (FIG. 4) includes through holes 25 and 26 inserted into the pipes 34 and 35, through holes 29 and 30 inserted into the heat pipes 66 and 67, respectively, and fastening at both ends in the longitudinal direction. Parts 27 and 28. The fastening portion 28 (FIG. 6) is screwed into the through hole of the fastening portion 28, the bolt hole on the mounting plate 40 side, and the spacer / stud 42 on the mounting plate 40 by bolts 44. Fix the head. The fastening portion 27 also screws the bolt 45 into the through hole, the bolt hole on the mounting plate 40 side, and the stud 43.

  FIG. 7 is a perspective view showing the positional relationship between the ink jet head and the ink path according to the embodiment. FIG. 8 is a perspective view from another direction showing the positional relationship between the ink jet head and the ink path according to the embodiment. The above described symbols represent the same elements. An ink tank 100 and an ink circulation mechanism (not shown) are provided on the printer main body side where the ink jet head is provided. The ink circulation mechanism is a mechanism that circulates ink from the ink tank 100 in the ink circulation direction, supplies ink to the inkjet head, circulates ink from the inkjet head in the ink circulation direction, and discharges the ink to the ink tank 100. . The ink circulation mechanism has a plurality of ink paths.

  7 and 8, a first ink path (ink path [out-port]) 62 that discharges ink discharged from the head main body 11 to the ink tank 100 and ink for supply from the ink tank 100 are supplied to the head. A second ink path (ink path [in-port]) 63 for supplying to the main body 11 is provided. The upper end of the first heat pipe 66 is connected to the first ink path 62 and the second ink path 63, and the lower end is connected to the reference plate 13. The upper end of the first heat pipe 66 may be connected to the first ink path 62 and the second ink path 63 by a heat pipe guide 60. The upper end of the second heat pipe 67 is connected to the first ink path 62 and the second ink path 63, and the lower end is connected to the reference plate 13. The upper end of the second heat pipe 67 may be connected to the first ink path 62 and the second ink path 63 by a heat pipe guide 61.

  The first heat pipe 66 has a flow path in the pipe and a refrigerant that moves up or down the flow path. The liquid-phase refrigerant is vaporized by absorption of heat from the reference plate 13 at one end side of the first heat pipe 66, that is, below, and moves to the other end side of the first heat pipe 66, that is, upward. The gas-phase refrigerant is cooled and condensed by releasing heat to the first ink flow path 62 or the second ink flow path 63, and flows down below the first heat pipe 66. Also in the second heat pipe 67, the liquid-phase refrigerant is vaporized by absorption of heat from the reference plate 13 and moves above the second heat pipe 67, and the gas-phase refrigerant is transferred to the first ink flow path. 62 or the second ink flow path 63 is cooled and condensed due to the release of heat, and flows down the second heat pipe 67.

  Further, the driver IC 21 is in close contact with the lower back of the heat sinks 14 and 15. Four driver ICs 21 (two driver ICs 21 are shown in FIGS. 7 and 8) exchange signals with the controller on the printer main body side via cables 36 and 37.

  FIG. 9 is a longitudinal sectional view taken along CC of FIG. 6A of the inkjet head according to the present embodiment. FIG. 10 is a longitudinal sectional view taken along DD of FIG. 9 of the ink jet head according to the present embodiment. The above described symbols represent the same elements. The lower end portions of the first heat pipe 66 and the second heat pipe 67 are bent, and these lower end portions are fixed in a state of being sandwiched by a gap between one side of the manifold 22 and one side of the reference plate 13. That is, the first heat pipe 66 and the second heat pipe 67 are connected to both the reference plate 13 and the manifold 22.

  Next, the operation of the inkjet head according to the present embodiment having the above-described configuration will be described. For ejection, each drive circuit 18 receives a drive signal from the printer main body, and any one of the driver ICs 21 supplies a plurality of pressure chambers 88. An electric field is generated by applying a pulse voltage signal, and the side walls of these pressure chambers 88 are deformed. In the head main body 11, the volume of the pressure chamber 88 is expanded and contracted to pressurize the ink, and the head main body 11 ejects droplets from the nozzle holes 51. The heat generated in the driver IC 21 when the inkjet head discharges is transmitted to the heat sinks 14 and 15, the first heat pipe 66 and the second heat pipe 67, and the heat sinks 14 and 15 and the reference plate 13 dissipate heat.

  Here, when the fastening portions 27 and 28 are bolted with a strong force and the driving period of the drive circuit 18 is short, the axial positions of the bolts 44 and 45 are displaced outward in the longitudinal direction of the reference plate 13 due to heat generation. However, it returns to its original state by cooling, and the head main body 11 is not deformed to the extent that it affects the print quality. The reference plate 13 also extends in the print feed direction orthogonal to the longitudinal direction, but even if the plate dimension in the feed direction is extended, the plate dimension is restored to the original by cooling. Alternatively, the deviation does not substantially contribute to the printing deviation.

  When the driver IC 21 dissipates heat due to an increase in the amount of heat generated by the drive circuit 18, since the heat sink material is made of aluminum, the reference plate 13 and the mounting plate 40 are transferred by heat transfer from the heat sinks 14 and 15 due to high heat conduction efficiency. ) Expands to the left and right. In a state where the fastening portions 27 and 28 are bolted with a strong force, the reference plate 13 expands larger than the mounting plate 40 outward in the longitudinal direction. If no countermeasure against heat generation is taken, the position of the nozzle hole 51 of the head main body 11 may be shifted outward in the longitudinal direction.

  As a result, the positional deviation of the inkjet head with respect to the printer body may occur, which may affect printing. Further, the heat generated in the driver IC 21 affects the temperature of the ink flowing through these connections through metal connection portions (connections) such as the heat sinks 14 and 15, the reference plate 13, the supply pipe 16 and the discharge pipe 17. The ink viscosity is changed to affect the print quality.

  The purpose of the ink-jet head using the ink circulation is to prevent clogging of the nozzle holes 51 formed on the orifice plate 52 by the ink circulation in the pressure chamber 88. Secondly, there is an object to keep the temperature of the pressure chamber 88 generated by the IC drive uniform by circulating the ink. However, there is a limit to the ink circulation amount, and it becomes difficult to keep the ink temperature uniform depending on the driving conditions (printing speed, pulse on / off duty ratio).

  Therefore, in order to eliminate the positional shift caused by the mounting portions such as the fastening portions 27 and 28 generated at the time of thermal expansion, and to reduce the influence of the heat generated by the driver IC 21 on the ink, in order to keep the temperature of the pressure chamber 88 uniform. The structure shown in FIGS. 4 to 10 is employed in the inkjet head according to the embodiment.

  As shown in FIG. 9, the ends of the first heat pipe 66 and the second heat pipe 67 are in contact with the manifold 22 and the reference plate 13, and the other ends of the heat pipes 66 and 67 are in contact with the manifold 22 and the reference plate 13. Heat exchange is performed by contacting the first ink path 62 and the second ink path 63 through the heat pipe guides 64 and 65.

These ink paths 62 and 63 are provided for supplying and discharging ink to and from each of the inkjet heads when a plurality of inkjet heads are attached to the mounting plate 40 of the printer main body. In the first ink path 62 and the second ink path 63, ink supplied to and discharged from the plurality of inkjet heads by a pump provided in the ink circulation mechanism flows, so that the ink temperature becomes constant. Adjusted. The heat pipe guides 64 and 65 are made of a material having good thermal conductivity, and have a structure that easily transfers heat due to the temperature of the ink in the ink paths 62 and 63.

  With such a structure, the temperature of the manifold 22 and the temperature of the reference plate 13 can be promoted by the ink temperature, and the base plate 54, the pressure chamber 88, and the driver IC 22 that are in contact with the manifold 22 and the reference plate 13 respectively. The temperature rise can be adjusted.

  As described above, according to the ink jet head according to the present embodiment, in the circulation type ink jet head, it is possible to reduce the displacement due to the mounting portion due to the thermal expansion coefficient between the head structure and the printer main body side structure. The influence of the heat generated by the driver IC 21 on the ink can be reduced, and the temperature of the pressure chamber 88 can be kept uniform.

  In the above embodiment, the cross-sectional structure of FIG. 3 is an example, and the structure of the ink supply path and the ink discharge path can be variously modified. Each end of the first heat pipe 66 is connected up and down, but the direction in which each end of the first heat pipe 66 is connected may be connected or coupled in a direction different from the up and down direction. Needless to say. The second heat pipe 67 is the same as the first heat pipe 66. The superiority of the ink jet head according to the embodiment is not impaired at all with respect to the embodiment that has been implemented with these changes.

  Although several embodiments have been described, these embodiments have been presented by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and the equivalents thereof.

  DESCRIPTION OF SYMBOLS 11 ... Head main body, 12 ... Base part, 13 ... Reference | standard plate, 14, 15 ... Heat sink, 18 ... Drive circuit, 21 ... Driver IC, 66 ... 1st heat pipe, 67 ... 2nd heat pipe.

Claims (5)

A head body having a plurality of nozzle holes and an ink liquid chamber;
A plurality of ink flow paths opening in the liquid chamber of the head body, an ink supply path and an ink discharge path among the plurality of ink flow paths, an ink supply port to the ink supply path and the ink discharge path, and A base portion having a discharge port;
A drive circuit provided in the base portion for driving the head body to discharge;
A heat sink that dissipates the heat generated by the drive circuit;
A reference plate for fixing these heat sink, drive circuit, base portion and head body;
A heat pipe connected to this reference plate;
An inkjet head comprising: An ink tank; a first ink path for discharging the ink from the head body to the ink tank; and a second ink path for supplying the ink from the ink tank to the head body.
The heat pipe is
A first heat pipe connected to the first ink path and the reference plate;
The inkjet head according to claim 1, further comprising: a second heat pipe connected to the second ink path and the reference plate. Each of the first heat pipe and the second heat pipe has a flow path in the pipe and a refrigerant that rises or falls in the flow path,
The liquid-phase refrigerant is vaporized by absorption of heat from the reference plate on each one end side and moves to the other end side, and the gas-phase refrigerant flows in the first ink flow path or the second ink flow. The inkjet head according to claim 2, wherein the inkjet head is cooled and condensed by releasing heat to the path and moves to one end side. The base portion includes a base plate having a hole communicating with the ink supply path and another hole communicating with the ink discharge path, and these holes, the ink supply path, the ink discharge path, the supply port, and the discharge port. A manifold having
The inkjet head according to claim 1, wherein the heat pipe is connected to the manifold. An ink supply pipe between the second ink path and the ink supply port;
An ink discharge pipe provided in parallel with the ink supply pipe and between the first ink path and the ink discharge port;
4. The ink jet head according to claim 3, wherein the first heat pipe and the second heat pipe are provided outside the juxtaposition position of the ink supply pipe and the ink discharge pipe, respectively.

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