JP2008207354A - Inkjet head and inkjet recorder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet head which is free from cavitation, and to provide an ink jet recorder using the inkjet head. <P>SOLUTION: In the inkjet head, chambers to be ink chambers are formed in juxtaposition with a piezoelectric plate, and the ink is ejected by impressing a voltage to side walls of the chambers and utilizing the reverse piezoelectric phenomenon of the piezoelectric plate. The inkjet head has a driving circuit 30 which drives a head chip, and a predetermined electrical resistance 60 inserted on a piece of wiring led from a power supply to the driving circuit 30. The chamber side wall suppresses sudden deformation and reduces generation of the cavitation. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an ink jet recording head that performs recording by discharging ink onto a recording medium, and an ink jet recording apparatus using the ink jet head.

  2. Description of the Related Art Conventionally, an ink jet recording apparatus that records characters and images on a recording medium using an ink jet head having a plurality of nozzles that eject ink is known.

  FIG. 1 shows a configuration diagram of an inkjet head 1 used in such an inkjet recording apparatus. The inkjet head 1 includes at least a head chip 10 that ejects ink, a drive circuit 30 that drives the head chip 10, a wiring board 40 on which the drive circuit 30 is mounted, and a flexible substrate 20 that connects the drive circuit 30 and the head chip 10. And a base member 50 on which the above components are mounted.

  Next, FIG. 2 shows a schematic configuration of the head chip 10 used in the inkjet 1. 3 is a cross-sectional view taken along the line h-h ′ of FIG. 2, and FIG. 4 is a view of FIG. 2 viewed from the direction of the arrow X. As shown in FIGS. 2 and 3, chambers 104 are arranged in parallel on the piezoelectric plate 101, and each chamber is separated by a side wall 105. One end of the chamber 104 in the longitudinal direction extends to the end face of the piezoelectric plate 101, and the other end does not extend to the end face of the piezoelectric plate, but gradually becomes shallow as shown in FIG. .

  A cover plate 102 is bonded to the opening of the chamber 104 with an adhesive or the like. The cover plate 102 is provided with an ink supply port 107 for supplying ink to the chamber 102 at the shallow end of the chamber. In addition, a nozzle plate 106 is bonded to the end surface of the joined body of the piezoelectric plate 101 and the cover plate 102 with an adhesive or the like, and a nozzle hole 108 is formed at an opposing position. .

  Further, as shown in FIG. 4, an electrode 103 is formed on the surface of the side wall 105 in the chamber 104 for applying a driving voltage in the longitudinal direction. A wiring 109 is formed on the cover plate 102 side of the piezoelectric plate 101 so that a driving voltage can be applied to the electrode 103 through the driving circuit 30.

In the ink jet head configured as described above, each chamber 104 is filled with ink from the ink supply port 107, and when a voltage is applied to the electrode 103 provided on the surface of the side wall 105 in the chamber 104, the side wall 105 is formed by the reverse piezoelectric effect of the piezoelectric plate. The ink is ejected when the volume in the chamber 104 changes due to deformation.
JP 2002-347241 A

  In the conventional driving method, since the piezo element is charged instantaneously, the chamber side wall that is a pump is rapidly deformed. For this reason, a local negative pressure state occurs in the chamber, and cavitation occurs when the amount of dissolved gas in the ink is high, which causes a decrease in ejection stability.

  According to the present invention, by smoothly deforming the chamber side wall, the occurrence of cavitation is suppressed even in ink having a high dissolved gas amount, and the discharge stability is improved.

  In the first aspect of the invention for solving the problems as described above, a groove serving as an ink chamber is provided in the piezoelectric plate, and a voltage is applied to the side wall of the groove so as to make use of the reverse piezoelectric phenomenon of the piezoelectric plate. In the inkjet head, the drive circuit for driving the head chip and the resistor having a predetermined resistance value on the wiring from the power source to the drive circuit are arranged to increase the rise time of the drive waveform. Features.

  According to a second aspect of the present invention, in the first aspect, when the driving voltage is applied, an electric resistance of the resistor is 10Ω or more and 1 kΩ or less.

  According to a third aspect of the present invention, in the first or second aspect, the electrical resistance of the resistor is 10Ω or more and 1 kΩ or less.

  A fourth aspect of the present invention is characterized in that, in the first to third aspects, a material having a large resistance value is used for the wiring member, and the electrical resistance is set to 10Ω to 1 kΩ.

  A fifth aspect of the present invention is characterized in that, in the first to fourth aspects, a coil is connected in series with the resistor, the rise time of the drive waveform is lengthened, and the drive waveform is further gently raised. To do.

  The sixth aspect of the present invention is characterized in that the inductance value of the coil is 10 μH or more and 1 mH or less.

  The seventh aspect of the present invention is characterized in that a material having a large inductance is used for the wiring member and the inductance value is set to 10 μH or more and 1 mH or less.

  According to an eighth aspect of the present invention, there is provided an ink jet recording apparatus including the ink jet head according to any one of the first to seventh aspects.

  The present invention inserts a resistor or a resistance + coil between a power source and a drive circuit for driving the piezoelectric plate to increase the electric resistance to a predetermined magnitude, thereby extending the charging time for the piezoelectric plate and increasing the drive voltage rise time. Lengthen. As a result, it is possible to suppress abrupt deformation of the chamber side wall, which is a pump, and to drive the side wall smoothly.

  Therefore, cavitation generated in the chamber can be reduced, and the ejection stability is improved even for ink with a high amount of dissolved gas.

Hereinafter, embodiments of the present invention will be described in detail.

(Embodiment 1)
The structure of Embodiment 1 in this invention is demonstrated in detail. The basic configuration is the same as that of a conventional inkjet head.

  FIG. 1 is a configuration diagram of an ink jet head 1 according to the first embodiment, and FIG. 5 is a diagram illustrating how the ink jet head is driven.

  In FIG. 1, an inkjet head 1 includes at least a head chip 10 that discharges ink, a drive circuit 30 that drives the head chip 10, a wiring board 40 that mounts the drive circuit 30, and a flexible board that connects the drive circuit 30 and the head chip 10. 20 and a base member 50 on which the above components are mounted.

  Next, the ink ejection principle of such an ink jet head will be described. FIG. 5A and FIG. 5B are simple schematic diagrams showing the ink ejection principle.

  First, as shown in FIG. 5A, when a positive voltage is applied to the electrodes e and f and the other electrodes are grounded, the side wall is deformed in the direction of the arrow due to the reverse piezoelectric phenomenon of the head chip, and the volume of the chamber 104 increases. To do. Next, when the electrodes e and f are grounded to GND and a + voltage is applied to the other electrodes, the side wall is deformed as shown in FIG. Ink is ejected due to the volume difference in the chamber due to these two movements. The drive circuit 30 mounted on the wiring board 50 controls the side wall movement. The drive circuit 30 is disposed between the power supply and the head chip 10, and controls the voltage applied to each electrode by switching the power supply voltage and GND.

  Therefore, as shown in FIG. 5, when there is an electrical resistance of a predetermined value or more between the power supply on the wiring board 50 and the drive circuit 30, the charging time for the head chip is lengthened, and the rise time of the drive voltage for ejecting ink is increased. become longer.

  In the first embodiment, by inserting a resistor in the middle of wiring from the power supply on the wiring board 40 to the drive circuit 30, the electrical resistance when applying a drive voltage to each electrode is a predetermined value or more, specifically 10Ω to The rise time of the drive voltage is lengthened by 1 kΩ. FIG. 6A shows the relationship between the conventional drive voltage and time, and FIG. 6B shows the relationship between the drive voltage and time when the first embodiment is used.

  As shown in FIG. 6 (a), when the conventional electrical resistance is not more than a predetermined magnitude, the wiring board that applies the drive voltage is instantaneously increased to the maximum voltage V1 at time t1. When the electrical resistance on 40 is increased, the drive voltage rises at t2 while drawing a curve, as shown in FIG. 6B.

  Therefore, the drive waveform changes gently without rapidly increasing and decreasing. For this reason, the displacement of the side wall 105 accompanying the application of the driving voltage also becomes gentle, and a sudden pressure change does not occur in the chamber 104, and the occurrence of cavitation can be suppressed. Therefore, even if ink with a high dissolved gas amount is continuously ejected, ejection failure such as missing dots does not occur and ejection stability is improved.

  In the present invention, since only a resistor is inserted on the wiring board 40, no special IC or the like is required. Moreover, since it is possible to implement without requiring a large design change, it can be realized at low cost.

  In this embodiment, an example in which a resistor is inserted on the wiring board 40 has been introduced. However, the electrical resistance may be increased by using a material having a large resistance value for the wiring material itself of the wiring board 40.

(Embodiment 2)
Next, a second embodiment of the present invention will be described in detail. FIG. 7A is a diagram when a coil is connected in series with a resistor, and FIG. 7B is a diagram when a coil is connected in parallel with the resistor. The difference between the first embodiment and the second embodiment is that a coil is connected in series or in parallel with a resistor in the middle of wiring from the power supply on the wiring board 40 described in the first embodiment to the drive circuit 30. In FIG. 7A, the coil is connected after the resistor, but the coil may be connected before the resistor. FIG. 5C shows a driving voltage waveform when the electric resistance is increased and a coil is inserted.

  Here, the coil is not limited to a type such as a laminated chip type or a toroidal type. However, when the coil is inserted, the drive voltage is disturbed when only the coil is used. Therefore, it is necessary to insert a resistor having a predetermined size according to the inductance of the coil in series or in parallel with the coil. In this embodiment, for example, when a 220 μH coil is inserted, a resistance of 100Ω to 500Ω is inserted in series with the coil.

  In this embodiment, an example in which a resistor and a coil are inserted on the wiring board 40 has been introduced. However, a material having a large resistance value is used for the wiring material itself of the wiring board 40, and an electrical resistance and an inductance component are provided. An inductance may be provided.

It is a block diagram of the inkjet head which concerns on this invention. 1 is a schematic configuration diagram of a head chip according to the present invention. It is sectional drawing of the structure schematic of the head chip which concerns on this invention. It is the figure which looked at the structure schematic of the head chip concerning this invention from the X direction. (A) It is the figure which showed the discharge principle of the ink which concerns on this invention which concerns on this invention. (B) It is the figure which showed the discharge principle of the ink which concerns on this invention which concerns on this invention. It is the figure which showed the relationship between the drive voltage which concerns on this invention, and time. (A) It is the figure which connected the coil in series by the structure of Embodiment 2 which concerns on this invention. (B) It is the figure which connected the coil in parallel with the structure of Embodiment 2 which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inkjet head 10 Head chip 20 Flexible board 30 Drive circuit 40 Wiring board 50 Base member 60 Resistor 70 Coil 101 Piezoelectric plate 102 Cover plate 103 Electrode 104 Chamber 105 Side wall 106 Nozzle plate 107 Ink supply port 108 Nozzle 109 Wiring

Claims (8)

An ink jet head in which a groove serving as an ink chamber is attached to the piezoelectric plate, and a voltage is applied to the side wall of the groove to eject ink using the reverse piezoelectric phenomenon of the piezoelectric plate,
An ink-jet head characterized in that a drive circuit for driving a head chip and a resistor having a predetermined resistance value on a wiring from a power source to the drive circuit are arranged to lengthen the rise time of the drive waveform.   2. The inkjet head according to claim 1, wherein when the driving voltage is applied, an electric resistance of the resistor is 10Ω or more and 1 kΩ or less.   The inkjet head according to claim 1, wherein an electrical resistance of the resistor is 10Ω or more and 1 kΩ or less.   4. The ink jet head according to claim 1, wherein a material having a large resistance value is used for the wiring member and the electric resistance is set to 10Ω to 1 kΩ.   An ink jet head characterized in that a coil is connected in series or in parallel with the resistor so that the rise time of the drive waveform is lengthened and the drive waveform is gradually raised.   The inkjet head according to claim 5, wherein the inductance value of the coil is 10 μH or more and 1 mH or less.   7. The ink jet head according to claim 5, wherein a material having a large inductance is used for the wiring member, and the inductance value is set to 10 μH or more and 1 mH or less.   An ink jet recording apparatus equipped with the ink jet head according to claim 1.

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