JP2005238742A - Ink-jet head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To restrain the temperature of ink in a specific ink-chamber from rising with a simple structure and make the ink-temperature in each ink-chamber uniform. <P>SOLUTION: The ink-jet head is formed with the material of which thermal conductance is larger than the one of a substrate 3 in a common ink-chamber 8 to which the ink is supplied from an ink-feeding portion in communicating with two or more ink-chambers 14 arranged in the longitudinal direction of the substrate 3. A thermal conductive member 9, which extends to the position covering the arrangement area of the ink-chamber 14 along the arrangement direction of the ink-chamber 14, is retained, and the retainment is carried out by pressing the thermal conductive member 9 to the substrate 3 using an elastic member 16. Thereby, the ink-temperature rising in the specific ink-chamber 14 is suppressed, and the ink-temperature in each ink-chamber is made uniform, and then the failures, such as an unevenness of image density caused by the unevenness of the ink-temperature in each ink-chamber 14 and a non-discharge of ink or irregular discharge-direction caused by the remarkable rising of the ink temperature in some ink-chamber 14, can be prevented. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an ink jet head in which a plurality of ink chambers are arranged.

  The inkjet head has a plurality of ink chambers arranged in the longitudinal direction of the substrate, ejects ink droplets from nozzles provided corresponding to the respective ink chambers, and adheres the ejected ink droplets to a recording medium. Thus, image formation is performed.

  At the time of image formation by the ink jet head, energy for ejecting ink droplets is applied, and application of this energy raises the ink temperature in the ink chamber where ink is ejected. When the ink temperature in the ink chamber rises, the viscosity of the ink decreases, and the amount of ink ejected when the same energy is applied for ejecting ink droplets increases.

  FIG. 6 shows a case where ink is continuously ejected from all the nozzles of the inkjet head A to form an image. The ink in each ink chamber is reduced by the ejection of the ink, and the reduced amount of ink is supplied to the inkjet head A. The supplied ink flows in the common ink chamber B toward each ink chamber as indicated by an arrow.

  The temperature of the ink supplied to the inkjet head A is lower than the temperature of the ink in the ink chamber, and the temperature of the supplied ink gradually increases in the process of flowing in the common ink chamber B toward the ink chamber.

  However, the ink supplied to the ink chamber near the center and the ink chambers on both ends of the ink jet head A has different distances flowing through the common ink chamber B, so that there is a difference in temperature rise until reaching each ink chamber. Occurs. FIG. 6B is a graph showing a comparison result of ink temperatures in the ink chamber near the center and the ink chambers on both ends. The ink temperature in the ink chamber near the center is low, and the ink temperature in the ink chambers on both ends is high. For this reason, when image formation is performed by discharging ink from all nozzles, the ink discharge amount increases and the image density increases because the viscosity of the ink is lower at both ends compared to the vicinity of the center. Become. Furthermore, in the ink chambers at both ends, the ink viscosity decreases as the ink temperature rises, causing the meniscus amplitude on the ink liquid surface formed on the nozzle to increase or the meniscus to oscillate. Disturbance in the ejection direction is likely to occur.

  7 and 8 show a case where image formation is performed by ejecting ink from nozzles in a specific range, and then image formation is performed by ejecting ink from all nozzles. When ink is ejected from a specific range of nozzles to form an image, as shown in FIG. 7B, the ink temperature in the ink chamber where the ink is ejected rises above the ink temperature in the other ink chambers. . For this reason, when an image is formed by ejecting ink from a specific range of nozzles and then ink is ejected from all nozzles, the ink is ejected in advance as shown in FIG. In the area, the image density formed is higher than in other areas. This is presumably because the ink temperature in the ink chamber where ink was previously ejected was higher than the ink temperature in the other ink chambers, which lowered the viscosity of the ink and increased the amount of ink ejected.

  In order to prevent such inconvenience, a method of forcibly cooling the ink jet head by flowing a cooling liquid on the outer surface of the ink jet head has been proposed (see, for example, Patent Document 1).

JP 2002-67329 A

  However, in the cooling method proposed in Patent Document 1 described above, it is necessary to secure a space for flowing a cooling liquid, and it is difficult to reduce the size of the inkjet head. Further, the provision of the cooling mechanism complicates the structure of the entire inkjet head including the cooling mechanism.

  An object of the present invention is to suppress an increase in the ink temperature in a specific ink chamber and to make the ink temperature uniform in each ink chamber with a simple configuration.

  The inkjet head of the present invention is formed of a material having a larger thermal conductivity coefficient than the substrate on which the ink chamber is formed, in a common ink chamber that is communicated with a plurality of ink chambers and supplied with ink from an ink supply unit. The heat conductive member extending to a position covering the ink chamber arrangement region along the ink chamber arrangement direction is held, and this holding is performed by pressing the heat conductive member against the substrate by the elastic member. Yes.

  Therefore, even if there is a difference in the ejection frequency of ink from each ink chamber and a difference in the distance from the location where ink is supplied from the ink supply unit to the common ink chamber to each ink chamber, the heat of the ink in each ink chamber is heated. It is transmitted to the conductive member. Further, the ink flowing in the common ink chamber can be evenly warmed by the heat from the heat conductive member. As a result, an increase in the ink temperature in a specific ink chamber is suppressed, and the ink temperature in each ink chamber is made uniform.

  According to the ink jet head of the present invention, it is possible to suppress an increase in the ink temperature in a specific ink chamber and to maintain a uniform ink temperature in each ink chamber by a simple configuration in which the heat conducting member is held in the common ink chamber. Can be achieved.

  A first embodiment of the present invention will be described with reference to FIGS. The inkjet head 1 according to the present embodiment includes a substrate 3 on which a plurality of ink chamber grooves 2 are arranged in the longitudinal direction, a lid member 5 on which a common ink chamber recess 4 is formed, and a plurality of nozzles 6. The nozzle plate 7 is bonded, and a heat conductive member 9 is held in a common ink chamber 8 to be described later.

  The substrate 3 is formed by laminating piezoelectric members 10 and 11 polarized in opposite directions in the thickness direction, and the groove 2 for the ink chamber is formed by performing groove processing on a portion on one end side of the substrate 3. ing. Electrodes 12 are formed on the side surfaces of the ink chamber grooves 2, and wiring patterns 13 connected to these electrodes 12 are formed on the upper surface of the other end side of the substrate 3. When the ink has conductivity, an insulating layer is formed on the surface of the electrode 12 formed in the ink chamber groove 2.

  The lid member 5 is formed of a material whose linear expansion coefficient is close to that of the substrate 3, and when the substrate 3 is formed of piezoelectric members 10 and 11 having a low linear expansion coefficient, the lid member 5 is the same as the substrate 3. Material is preferred. An approximate low linear expansion coefficient material such as alumina can also be used.

  By bonding the substrate 3, the lid member 5, and the nozzle plate 7, the ink chamber groove 2 is surrounded by the lid member 5 and the nozzle plate 7 to form a plurality of ink chambers 14, and the common ink chamber recess 4. The common ink chamber 8 is formed by closing the opening portion of the substrate 3 by the substrate 3. The common ink chamber 8 communicates with all the ink chambers 14. The lid member 5 has an ink supply hole 15 for supplying ink from an ink supply unit (not shown) to the common ink chamber 8.

  The thermally conductive member 9 is formed of a material having a larger thermal conductivity coefficient than the piezoelectric members 10 and 11 forming the substrate 3, and for example, a metal such as copper or aluminum, carbon, aluminum nitride, or the like is used. When using a metal, it is preferable to form a coating layer such as a resin on the surface in order to prevent the surface from being corroded by the ink.

  The thermally conductive member 9 is placed on the surface of the substrate 3 and pressed against the surface of the substrate 3 via an elastic member 16 such as fluoro rubber interposed between the lid member 5 and the thermally conductive member 9. It is held by being. The elastic member 16 has a concave portion (not shown) formed on the inner surface of the concave portion 4 for the common ink chamber in the lid member 5, and is fixed in position by fitting one end side into the concave portion.

  Further, the heat conductive member 9 extends to a position covering the arrangement region of the ink chambers 14 along the arrangement direction of the ink chambers 14. The term “extends to a position covering the arrangement region of the ink chambers 14” not only extends to a position beyond the ink chambers 14 at both ends as shown in the figure, but also to the same positions as the ink chambers 14 at both ends. In the case of extending, the case of extending to the inside of the ink chamber 14 on both ends is included.

  In such a configuration, in the inkjet head 1 of the present embodiment, when the ink temperature in the ink chamber 14 rises due to ink ejection, the heat from the ink is transferred to the heat conductive member 9, so that the specific ink chamber 14 The ink temperature of the ink chamber 14 is suppressed from significantly increasing as compared with the ink temperatures in the other ink chambers 14. The ink supplied from the ink supply hole 15 flows in the direction of the arrow shown in FIG. 2, and the ink is evenly warmed by the heat from the heat conductive member 9 in the process of flowing through the common ink chamber 8. For this reason, an increase in the ink temperature in a specific ink chamber 14 can be suppressed, and the ink temperature in each ink chamber 14 can be made uniform. As a result, variations in image density caused by variations in the ink temperature in each ink chamber 14, ink non-ejection and disturbance in the ejection direction caused by a large increase in the ink temperature in a certain ink chamber 14 are caused. Can be prevented.

  In particular, since the heat conductive member 9 extends to a position that covers the arrangement region of the ink chambers 14 along the arrangement direction of the ink chambers 14, the inside of the ink chambers 14 at both ends along the arrangement direction of the ink chambers 14. This ink temperature is also made uniform with the ink temperature in the other ink chambers 14.

  In addition, since the heat conductive member 9 is held in the common ink chamber 8 by pressing the heat conductive member 9 against the substrate 3 by the elastic member 16, the heat conductive member 9 and the substrate 3 are thermally expanded. Even if a dimensional difference occurs, only a slip occurs on the pressing surface between the heat conductive member 9 and the substrate 3, and no warpage occurs, and the performance degradation of the inkjet head 1 caused by the warpage is prevented.

  In the present embodiment, the case where fluorine rubber is used as the elastic member 16 has been described as an example. However, the elastic member can exert a function of pressing the heat conductive member 9 against the surface of the substrate 3. For example, a spring or the like can be used.

  A second embodiment of the present invention will be described with reference to FIGS. The same parts as those described in FIGS. 1 and 2 are denoted by the same reference numerals, and description thereof is omitted (the same applies to the following embodiments). The basic structure of the inkjet head 21 of the present embodiment is the same as that of the inkjet head 1 of the first embodiment. The difference between the present embodiment and the first embodiment is that the common ink chamber 8 This is a method for holding the heat conductive member 9 at.

  In the present embodiment, the heat conductive member 9 is fixed to the substrate 3 with the elastic adhesive 22. As the elastic adhesive 22, for example, a silicone-based adhesive or a polyurethane adhesive can be used.

  By fixing the heat conductive member 9 to the substrate 3 with such an elastic adhesive 22, in addition to the functions and effects described in the first embodiment, in this embodiment, the substrate 3 and the heat conductive member are used. Even if a dimensional difference due to thermal expansion occurs with respect to 9, the dimensional difference is absorbed by the elastic adhesive 22, so that the occurrence of stress can be prevented.

  Further, by fixing the heat conductive member 9 to the substrate 3 with the elastic adhesive 22, the structure for holding the heat conductive member 9 in the common ink chamber 8 is simplified. Further, the interval between the heat conductive member 9 and the inner peripheral surface of the common ink chamber recess 4 in the lid member 5 can be set to the minimum interval necessary for supplying ink, and the inkjet head 21 is thin. Can be achieved.

  A third embodiment of the present invention will be described with reference to FIG. The basic structure of the inkjet head 31 of the present embodiment is the same as that of the inkjet head 1 of the first embodiment. The difference between the inkjet head 31 of the present embodiment and the inkjet head 1 of the first embodiment is that, in the present embodiment, the substrate 3 in the heat conductive member 9 held in the common ink chamber 8 is not opposed. The uneven surface 32 is formed on the side surface, that is, the surface in contact with the ink flowing in the common ink chamber 8. The concavo-convex portion 32 is formed in a shape having a plurality of grooves extending along the flow direction of the ink flowing through the common ink chamber 8. A part of the ink flowing toward the common ink chamber 8 toward each ink chamber 14 flows in the groove.

  By forming the concavo-convex portion 32 and the ink flowing in the groove formed by the concavo-convex portion 32, the contact area between the ink flowing in the common ink chamber 8 and the heat conductive member 9 increases, and each ink chamber The performance of making the temperature of the ink supplied into the nozzle 14 uniform can be improved. Further, since the temperature of the ink supplied to each ink chamber 14 is made more uniform, the variation in image density caused by the variation in the ink temperature in each ink chamber 14, Ink non-ejection and turbulence in the ejection direction caused by a large rise in the ink temperature can be further prevented.

1 is an exploded perspective view showing an ink jet head according to a first embodiment of the present invention. It is a vertical side view which shows the inkjet head. It is a disassembled perspective view which shows the inkjet head of the 2nd Embodiment of this invention. It is a vertical side view which shows the inkjet head. It is a disassembled perspective view which shows the inkjet head of the 3rd Embodiment of this invention. A change in ink temperature in each ink chamber in the case where image formation is performed by continuously ejecting ink from all nozzles in a conventional inkjet head will be described. (A) is a plan view of the inkjet head, (b) ) Is a graph showing the temperature change of each ink chamber. A change in ink temperature in each ink chamber in the case where image formation is performed by continuously ejecting ink from some of the nozzles in a conventional inkjet head will be described. (A) is a plan view of the inkjet head; b) is a graph showing a temperature change of each ink chamber. FIG. 8 is an explanatory diagram illustrating a sheet on which light and shade are generated in an image formed when ink is continuously ejected from all nozzles after ink ejection illustrated in FIG. 7 is performed.

Explanation of symbols

3 Substrate 8 Common ink chamber 9 Thermally conductive member 14 Ink chamber 16 Elastic member 22 Elastic adhesive 32 Concavity and convexity

Claims (3)

A plurality of ink chambers arranged in the longitudinal direction of the substrate;
A common ink chamber communicated with the ink chamber and supplied with ink from an ink supply unit;
It is made of a material having a higher thermal conductivity than the substrate, extends to a position covering the ink chamber arrangement region along the ink chamber arrangement direction, and is pressed against the substrate by an elastic member and held in the common ink chamber. A thermally conductive member,
An inkjet head comprising: A plurality of ink chambers arranged in the longitudinal direction of the substrate;
A common ink chamber communicated with the ink chamber and supplied with ink from an ink supply unit;
The ink chamber is formed of a material having a larger thermal conductivity than the substrate on which the ink chamber is formed, extends to a position covering the arrangement region of the ink chamber along the arrangement direction of the ink chamber, and is disposed in the common ink chamber. A thermally conductive member fixed to the substrate by an elastic adhesive;
An inkjet head comprising: The inkjet head according to claim 1, wherein a concavo-convex portion is formed on a surface of the thermal conductive member that is not opposed to the substrate.

Images