JP2011235480A - Inkjet recording head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inkjet recording head which can reduce variation of a temperature distribution inside the inkjet recording head and is also capable of cooling.SOLUTION: The inkjet recording head has a substrate 101 in which a plurality of grooves are formed and arranged side by side on one surface, and at least part of a side wall 102 of the groove is formed of a piezoelectric material. The plurality of grooves constitute a plurality of ink channels 103 which communicate with ejection openings 109 for ejecting ink and ink chambers 112 to which the ink is supplied. Moreover, the plurality of grooves constitute a plurality of channels 104 exclusive for cooling which are arranged alternately with the ink channels 103 and which have end parts connected with a supply port of a fluid exclusive for cooling or a discharge port 112, and end parts connected with each other via connection parts 115.

Description

  The present invention relates to an ink jet recording head that ejects liquid from an ejection port using displacement of a piezoelectric element.

  In an ink jet recording apparatus having an ink jet recording head, electric power is supplied to an energy generating element, for example, a piezoelectric material, formed on a substrate of the recording head in accordance with a recording signal to be deformed. Recording is performed by ejecting ink from the ejection port by pressurizing ink in the ejection port of the recording head by deformation of the piezoelectric material.

  Conventionally, print heads have various temperatures in order to prevent deterioration of displacement characteristics and loss of piezoelectric characteristics due to heat generation when power is supplied to the piezoelectric material, and to reduce variations in ink discharge characteristics due to temperature distribution in the print head. A thing provided with the adjustment means is proposed. For example, in Patent Document 1, an air flow path is provided between ink flow paths, and a wall between the ink flow path and the air flow path is formed by flowing temperature-adjusted air into the air flow path. Since the heat of the air is transmitted to the ink in the ink flow path, the temperature of the recording head can be adjusted.

JP 2006-181819 A

  However, when high-viscosity ink is ejected at a high ejection frequency, the amount of heat generated by the piezoelectric material increases, so that the variation in temperature within the recording head increases. In the above-mentioned Patent Document 1, in order to reduce the variation in the temperature distribution generated in the recording head, the temperature of the air flowing through each air flow path must be individually controlled, and the variation in the temperature distribution in the recording head. Is difficult to reduce.

  Accordingly, an object of the present invention is to provide an ink jet recording head that can be cooled while easily reducing variations in temperature distribution in the ink jet recording head.

  The ink jet recording head of the present invention has a plurality of grooves formed side by side on one surface, and at least a part of the side walls of the grooves has a substrate made of a piezoelectric material. The plurality of grooves constitute a plurality of ink flow paths that communicate with an ejection port that ejects ink and an ink chamber to which ink is supplied. Further, the plurality of grooves are alternately arranged with the ink flow paths, and have a plurality of ends connected to the supply port or the discharge port of the cooling-dedicated fluid and ends connected to each other through the connecting portion. A cooling-only flow path is configured.

  According to the present invention, it is possible to reduce the variation in temperature distribution in the ink jet recording head while lowering the temperature in the ink jet recording head.

1 is a schematic configuration diagram of an embodiment of an ink jet recording head according to the present invention. It is a cross-sectional schematic diagram of a piezoelectric substrate. It is an example of the other structure of a piezoelectric substrate. It is an example of the temperature distribution of an inkjet recording head. It is an example of the structure which reduces the dispersion | variation in the temperature in an inkjet recording head. 1 is a schematic perspective view of an embodiment of an ink jet recording head.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. In addition, the same number is attached | subjected to the structure which has the same function in an accompanying drawing, and the description may be abbreviate | omitted.

  FIG. 1 shows a schematic configuration diagram of an embodiment of an ink jet recording head according to the present invention. A piezoelectric substrate 101 made of a piezoelectric material that constitutes a part of the recording head of the present invention is a laminate of two first and second piezoelectric plates that are polarized in opposite directions. After the groove processing for the flow path and the formation of the electrodes, the two piezoelectric plates are bonded together using an adhesive, pressed, and heated. As the piezoelectric substrate 101, it is preferable to use lead zirconate titanate (hereinafter referred to as PZT) which is a non-metallic material and is formed through processes such as molding and firing.

  As shown in FIG. 1, a plurality of concave grooves arranged in parallel at a predetermined interval are formed in the piezoelectric substrate 101, and the grooves are separated from each other by a side wall 102. This groove is a groove which becomes the ink flow path 103 for discharging ink from the discharge port and the cooling dedicated flow path 104 for flowing a cooling dedicated fluid for cooling the piezoelectric element. The grooves that become the flow paths 104 are alternately arranged. An ink flow path 103 and a cooling dedicated flow path 104 are formed by bonding a top plate 106 to be described later to the piezoelectric substrate 101. A groove of each ink flow path 103 extends from one end face of the piezoelectric substrate 101 to the other end face. One end in the longitudinal direction of the groove of each cooling dedicated flow path 104 extends to one end face of the piezoelectric substrate 101, and the other end has a groove depth that gradually decreases. It does not extend to the other end surface of the substrate 101. In addition, electrodes 105 are formed on both side surfaces of each side wall 102 in the longitudinal direction.

  The grooves of the ink flow path 103 and the cooling dedicated flow path 104 formed on the piezoelectric substrate 101 are formed in a concave shape by cutting or grinding at a predetermined interval using, for example, a disk-shaped dicing blade. ing. The groove of the ink flow path 103 is formed by penetrating and moving a disk-shaped dicing blade from one end face of the piezoelectric substrate 101 to the other end face at the same depth. The groove of the cooling dedicated flow path 104 is formed so that the depth of the groove is gradually reduced while moving the disk-shaped dicing blade from one end face of the piezoelectric substrate 101 and does not penetrate to the other end face. The electrodes 105 formed on both side surfaces of each side wall 102 are formed by, for example, electroless plating.

  A top plate 106 is bonded to the upper surface of the piezoelectric substrate 101 via an adhesive. The top plate 106 is composed of three plates 106A to 106C, and has a structure for supplying and discharging a cooling-dedicated fluid. The first plate 106A has a restriction 123 for the cooling dedicated flow path 104, the second plate 106B has a cooling dedicated fluid chamber 121, and the third plate 106C has a cooling dedicated fluid discharge port 122 and a supply port ( (Not shown). Note that the cooling dedicated fluid chamber 121 and the cooling dedicated flow path 104 communicate with each other through the throttle 123. The top plate 106 can be formed of ceramic, metal, or the like, but considering the deformation after bonding with the piezoelectric substrate 101, the top plate 106 has a thermal expansion coefficient similar to that of PZT of the non-metallic material forming the piezoelectric substrate 101. It is preferable to use ceramic.

  When the piezoelectric substrate 101 and the top plate 106 are joined, an opening communicating with each ink flow path 103 or each cooling dedicated flow path is formed at one end. The discharge port plate 108 in which the discharge port 109 and the opening 117 are formed is bonded to one end of the joined body of the piezoelectric substrate 101 and the top plate 106. Discharge ports 109 are formed at positions corresponding to the respective ink flow paths 103 of the discharge port plate 108, and openings 117 are formed at positions corresponding to the respective cooling dedicated flow paths 104 of the discharge port plate 108. The discharge port plate 108 is formed by forming the discharge port 109 and the opening 117 in a metal, a resin, or the like by, for example, pressing using a punch.

  A flow path plate 114 is joined to the discharge port plate 108. An opening 118 larger than the discharge port 109 is formed in the flow path plate 114 at a position corresponding to the discharge port 109. In addition, a connecting portion 115 is formed on the flow path plate 114 so as to connect the two cooling dedicated flow paths 104.

  Further, a cover plate 116 is joined to the flow path plate 114, and an opening 119 larger than the discharge port 109 is formed in the cover plate 116 at a position corresponding to the discharge port 109.

  A rear plate 110 is bonded to an end opposite to one end of the piezoelectric substrate 101 to which the discharge port plate 108 is bonded. At positions corresponding to the respective ink flow paths 103 on the rear plate 110, openings 120 smaller than the openings formed by the top plate 106 and the ink flow paths 103 are formed.

  A common ink chamber plate 111 is joined to the rear plate 110. The common ink chamber plate 111 is provided with a common ink chamber 112 and an ink supply port 113. The common ink chamber 112 is connected to the ink flow path 103 via the opening 120 of the rear plate 110, and is also connected to an ink tank (not shown) via the ink supply port 113. Ink is supplied from the ink tank to the common ink chamber 112 via the ink supply port 113, and ink is supplied to each ink flow path 103 via the opening 120.

  Next, a method for ejecting ink will be described. 2A and 2B are schematic cross-sectional views of the piezoelectric substrate 101, where FIG. 2A shows a state where no voltage is applied to the electrode 105, and FIG. 2B shows a state where a voltage is applied to the electrode 105.

  As shown in FIG. 2A, side walls 102 are formed so as to sandwich the ink flow path 103, and electrodes 105 are provided on both side surfaces of the side walls 102. Further, as described above, the polarization directions of the two bonded piezoelectric plates are opposite to each other. As shown in FIG. 2B, when a voltage is applied between the electrodes 105, a driving electric field in the direction of the ink flow path 103 acts on the side wall 102. When the driving electric field is orthogonal to the polarization direction of the side wall 102, the side wall 102 is deformed in the direction of the ink flow path 103. As a result, the volume in the ink flow path 103 changes, and the ink filled in each ink flow path 103 is discharged from the discharge port 109. The ink droplets ejected from the ejection port 109 fly to the recording medium through the large opening 118 of the flow path plate 114 and the opening 119 of the cover plate 116.

  In the above configuration, the piezoelectric substrate 101 has been described as being bonded with piezoelectric plates polarized in opposite directions, but the present invention is not limited to this. An example of another configuration of the piezoelectric substrate 101 is shown in FIG. For example, instead of bonding two piezoelectric plates, one piezoelectric plate may be used and the polarization direction may be one direction. In this case, an electrode 105 is provided on the top plate side on both sides of the side wall 102 as shown in FIG. 3A, or both the top plate side and the piezoelectric substrate side on both sides of the side wall 102 are shown in FIG. 3B. In addition, a configuration in which two electrodes 105A and 105B are provided and different electric fields are applied can be considered.

  Next, the reason why variation in temperature distribution in the ink jet recording head can be reduced in the ink jet recording head of this embodiment will be described below.

  FIG. 4 is an example of a temperature distribution when the horizontal axis is the position in the direction in which the ejection ports are arranged, that is, the position in the width direction of the recording head, and the vertical axis is the temperature. A curve X in FIG. 4 is a temperature distribution of a conventional recording head. The temperature distribution of the conventional recording head is such that the temperature is high at the center of the recording head and the temperature is not as high at the center as at the side. When the entire recording head is cooled, not only the central portion of the recording head having a high temperature but also the side portion having a lower temperature than the central portion is cooled, so that the temperature of the entire recording head is lowered (curve Y in FIG. 4). ). Therefore, with this method, the temperature of the entire recording head cannot be made uniform.

  In the present embodiment, first, the position having the highest temperature without cooling the recording head is set as a point T, and the high-temperature side cooling dedicated flow path 104 near the point T and the low-temperature side cooling dedicated flow path 104 far from the point T are used. Are connected by a connecting portion 115. Then, the cooling dedicated fluid is caused to flow from the high temperature side cooling dedicated flow path 104 to the low temperature side cooling dedicated flow path 104 via the connecting portion 115. By doing so, it is possible to cause the cooling dedicated fluid to flow at a low temperature through the cooling dedicated flow path 104 on the high temperature side, and to allow the heated cooling dedicated fluid to flow through the cooling dedicated flow path 104 at the low temperature side. The temperature difference between the part and the side part becomes small (curve Z in FIG. 4).

  An example of a configuration for reducing temperature variations in the recording head will be described with reference to schematic configuration diagrams of the discharge port plate 108 and the flow path plate 114 in FIG.

  For example, in the recording head having the ejection port plate 108 as shown in FIG. 5A, a description will be given of a case where the temperature difference between the central portion and the side portion of the recording head is suppressed as shown by the curve X in FIG. To do.

  First, in the arrangement direction of the ejection ports 109, the central portion from one side portion of the recording head is set with reference to the position of the point T having the highest temperature without cooling the recording head (in this embodiment, the central portion of the recording head). The cooling dedicated flow paths 104A to 104D in the region up to are defined as a group. The cooling dedicated flow paths 104E to 104H in the region from the other side of the recording head to the center are defined as b group. In this way, it is divided into two groups. In addition, it is preferable that the total number of the cooling-only flow paths 104 of each group a and b is an even number.

  Next, in the cooling dedicated flow paths 104A to 104D in the group a, the cooling dedicated flow path 104D closest to the reference point T and the farthest cooling dedicated flow path 104A are connected via the connection path 115. Next, the cooling dedicated flow path 104 </ b> C that is second closest to the reference point T and the cooling dedicated flow path 104 </ b> B that is second furthest are connected via the connection path 115. The same operation is also performed in the group b, and the cooling dedicated flow path 104E and the cooling dedicated flow path 104H, and the cooling dedicated flow path 104F and the cooling dedicated flow path 104G are connected via the connection path 115.

  That is, in each group, the Nth cooling dedicated flow path 104 counted from the reference point T (N is an integer equal to or greater than 1) and the Nth cooling dedicated flow path 104 counted from the side of the recording head are provided. And connected through the connecting portion 115. For example, when N is 1, in the a group, the cooling dedicated flow path 104A and the cooling dedicated flow path 104D are connected via the connecting part 115, and in the b group, the cooling dedicated flow path 104H and the cooling dedicated flow path 104E are connected. 115 is connected. Thus, the connection part 115 is formed in the flow-path plate 114 (refer FIG.5 (b)).

  Thus, each flow path plate 114 and the connection part 115 are connected (refer FIG.5 (b)).

  The flow of the cooling dedicated fluid flowing in the cooling dedicated flow path 104 connected by the connecting portion 115 will be described below with reference to FIG. FIG. 6 is a schematic perspective view of an embodiment of the ink jet recording head. In the direction of the arrow, the dotted line is the direction in which the ink flows, and the solid line is the direction in which the cooling dedicated fluid flows.

  The temperature of the cooling dedicated fluid is adjusted by a temperature adjusting means (not shown), and supplied to a supply port (not shown) by a pressure generating means (not shown). The supplied cooling-only fluid is a group of cooling-only fluids 104 that are located on the side of the two cooling-only flow paths 104 connected by the connecting portion 115 that are at a high temperature when not cooled. It flows to the channel group 501. The cooling-dedicated fluid that has cooled the piezoelectric element is a cooling-dedicated flow path that is a collection of cooling-dedicated fluids 104 located away from the high temperature side when not cooled through the connecting portion 115. It flows into the group 502. Thereafter, the cooling only fluid is discharged from the discharge port 122 through the common cooling fluid chamber 121.

  The cooling fluid used here is preferably pure water having a higher heat transfer coefficient than the ink flowing in the ink flow path 103.

  By circulating the cooling-dedicated fluid in the recording head in this way, the temperature difference of each cooling-dedicated flow path 104 due to the difference in the heat generation amount of the piezoelectric element is reduced. Therefore, it is possible to reduce the temperature distribution variation that occurs in the recording head.

  The present invention is mainly applicable to a printing apparatus, a coating apparatus, or a modeling apparatus that discharges highly viscous droplets at a high frequency.

DESCRIPTION OF SYMBOLS 101 Piezoelectric substrate 102 Side wall 103 Ink flow path 104,104A-H Cooling exclusive flow path 109 Discharge port 112 Common ink chamber 115 Connection part

Claims (8)

A plurality of grooves are formed side by side on one surface, and at least a part of the side walls of the grooves has a substrate made of a piezoelectric material,
The plurality of grooves are alternately arranged with a plurality of ink flow paths communicating with an ejection port for ejecting ink, an ink chamber to which the ink is supplied, and the ink flow path. An ink jet recording head, comprising: a plurality of cooling dedicated flow paths each having an end connected to a discharge port and an end connected to each other via a connecting portion.   The inkjet recording head according to claim 1, wherein the substrate is formed by bonding two piezoelectric plates polarized in opposite directions to each other.   The ink jet recording head according to claim 1, wherein electrodes are provided on both side surfaces of the side wall that separates the ink flow path and the cooling dedicated flow path.   The electrodes on both sides of the side wall that separates the ink flow path and the cooling fluid are divided into two on the top plate side and the substrate side, and both the top plate side and the substrate side, or the top plate The ink jet recording head according to claim 3, wherein the electrode is provided only on the side.   The groove of the ink flow path is formed from one end face of the substrate to the other end face, and one end portion in the longitudinal direction of the groove of the cooling dedicated flow path is formed to one end face of the substrate. 5. The inkjet recording head according to claim 1, wherein the other end portion has a groove depth that is gradually reduced and is not formed to the other end face of the substrate. A plurality of ink flow paths communicating with an ejection port for ejecting ink, an ink chamber to which the ink is supplied, and the ink flow path are alternately arranged, and are connected to a supply port or a discharge port for a cooling-dedicated fluid. A cooling method for an ink jet recording head, comprising: a plurality of cooling-dedicated flow paths each having an end portion and an end portion connected to each other via a coupling portion,
In the arrangement direction of the ink ejection ports, the position where the temperature becomes highest from one side of the ink jet recording head through the cooling dedicated flow path with reference to the position where the temperature becomes highest when the ink jet recording head is not cooled. Divided into a group arranged in a region up to and a group arranged in a region from the other side portion of the inkjet recording head to the position where the temperature becomes highest. Connecting the cooling dedicated flow path at a position close to a higher position and the cooling dedicated flow path at a position farther from the position where the temperature is highest, via a connecting portion;
Supplying the cooling-dedicated fluid to the cooling-dedicated flow channel at a position close to the position where the temperature becomes highest, and via the connecting portion, to the cooling-dedicated flow path at a position far from the position where the temperature becomes highest. A method of cooling an ink jet recording head that is caused to flow.   The cooling dedicated fluid is supplied from the end of the cooling dedicated flow channel at a position close to the position where the temperature becomes highest, from the end opposite to the end connected to the connecting portion, and from the position where the temperature becomes highest. The inkjet recording head cooling method according to claim 6, wherein the cooling dedicated flow path at a distant position is discharged from an end opposite to the end connected to the connecting portion.   In each of the groups, the Nth dedicated cooling channel counted from the side of the inkjet recording head is connected to the Nth dedicated cooling channel counted from the highest temperature position. The method for cooling an ink jet recording head according to claim 6, wherein the ink jet recording head is connected via a section.

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