JP2004243664A - Ink jet head and ink jet recorder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink jet head and an ink jet recorder capable of detecting suitability of ink filling the ink jet head. <P>SOLUTION: The ink jet head is arranged to eject ink filling an ink channel 12 formed in a piezoelectric ceramic plate 11 from a nozzle opening 27 by applying a driving voltage to an electrode 15 mounted on the side wall 13 of the ink channel 12 thereby varying the volume in the ink channel 12. The ink jet head comprises a means 53 for detecting conduction between the electrodes 15 of the ink channels 12 when a voltage is applied thereto, and a means 54 for judging suitability of ink based on the detection results from the detecting means 53. According to the arrangement, conductivity of ink can be detected. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an ink jet head and an ink jet recording apparatus capable of detecting compatibility of ink filled in an ink jet head mounted on an ink jet recording apparatus applied to, for example, a printer, a facsimile, and the like.
[0002]
[Prior art]
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 that ejects ink from a plurality of nozzles has been known.
[0003]
As a conventional inkjet head, for example, there is one described in the following Patent Document 1, that is, Japanese Patent Application Laid-Open No. 10-322652.
[0004]
In such an ink jet type recording apparatus, an ink jet head facing a recording medium is provided on a head holder, and the head holder is mounted on a carriage and scanned in a direction orthogonal to a conveying direction of the recording medium.
[0005]
FIG. 8 shows an outline of an example of such an ink-jet head, and FIG. As shown in FIGS. 8 and 9, a plurality of grooves 102 are provided in the piezoelectric ceramic plate 101, and each groove 102 is separated by a side wall 103. One end in the longitudinal direction of each groove 102 extends to one end surface of the piezoelectric ceramic plate 101, and the other end does not extend to the other end surface, but gradually decreases in depth. Further, electrodes 105 for applying a driving electric field are formed on the opening side surfaces of both side walls 103 in each groove 102 in the longitudinal direction.
[0006]
A cover plate 107 is joined to the opening side of the groove 102 of the piezoelectric ceramic plate 101 via an adhesive 109. The cover plate 107 has an ink chamber 111 serving as a recess communicating with the shallow other end of each groove 102, and an ink supply port 112 penetrating from the bottom of the ink chamber 111 in a direction opposite to the groove 102. .
[0007]
A nozzle plate 115 is joined to an end face of the joined body of the piezoelectric ceramic plate 101 and the cover plate 107 where the groove 102 is open, and a nozzle opening is provided at a position facing each groove 102 of the nozzle plate 115. 117 are formed.
[0008]
A wiring substrate 120 is fixed to the surface of the piezoelectric ceramic plate 101 opposite to the nozzle plate 115 and opposite to the cover plate 107. A wiring 122 connected to each electrode 105 by a bonding wire 121 or the like is formed on the wiring substrate 120, and a driving voltage can be applied to the electrode 105 via the wiring 122.
[0009]
In the ink jet head configured as described above, ink is filled into each groove 102 from the ink supply port 112, and a predetermined driving electric field is applied to the side walls 103 on both sides of the predetermined groove 102 via the electrode 105. 103 deforms to change the volume in a predetermined groove 102, whereby the ink in the groove 102 is ejected from the nozzle opening 117.
[0010]
[Patent Document 1]
JP-A-10-322652
[Problems to be solved by the invention]
However, in such an ink jet head, the ink filled for the electrode structure must be non-conductive. That is, when a highly conductive ink is filled in the ink jet head, when a predetermined voltage is applied to each electrode for the ink discharging operation, a current flows between the electrodes through the ink that is in direct contact with the electrodes. Would. For this reason, there is a problem that an overcurrent flows and the inkjet head may be broken.
[0012]
In view of such circumstances, an object of the present invention is to provide an ink jet head and an ink jet recording apparatus which can detect the conductivity even if the ink is filled with highly conductive ink.
[0013]
[Means for Solving the Problems]
According to a first aspect of the present invention for solving the above-described problems, a volume in the ink flow path is changed by applying a drive voltage to an electrode provided on a side wall of the ink flow path formed in the piezoelectric ceramic plate. In an ink jet head that discharges the ink filled therein from a nozzle opening, a detection unit that detects a state of conduction between the electrodes when a voltage is applied between the electrodes of the ink flow path, and the detection unit detects the conduction state between the electrodes. An ink jet head having a determination unit for determining ink compatibility.
[0014]
A second aspect of the present invention is the ink jet head according to the first aspect, wherein the detecting means detects a current value between the electrodes when the voltage is applied.
[0015]
According to a third aspect of the present invention, in any one of the first and second aspects, the detecting means applies a voltage to approximately half of the electrodes every other one or approximately one-third of the electrodes every two. And detecting the current value.
[0016]
A fourth aspect of the present invention is the ink jet head according to any one of the first to third aspects, wherein the voltage applied to the electrode by the detection means is a DC voltage.
[0017]
According to a fifth aspect of the present invention, in any one of the first to fourth aspects, the detection unit is activated at a predetermined timing, and the determination unit determines the conductivity of the ink. In the head.
[0018]
According to a sixth aspect of the present invention, the volume in the ink flow path is changed by applying a drive voltage to an electrode provided on a side wall of the ink flow path formed in the piezoelectric ceramic plate to fill the inside of the ink flow path. An ink-jet recording apparatus having an ink-jet head that discharges the discharged ink from a nozzle opening, a detecting unit that detects an energized state between the electrodes when a predetermined voltage is applied between the electrodes of the ink flow path of the ink-jet head, Determining means for determining the suitability of the ink filled in the inkjet head based on the detection result of the detecting means.
[0019]
A seventh aspect of the present invention is the ink jet recording apparatus according to the sixth aspect, wherein the detecting means detects a current value between the electrodes when the voltage is applied.
[0020]
According to an eighth aspect of the present invention, in any one of the sixth to seventh aspects, the detection means applies a voltage to approximately half of the electrodes every other one or approximately one-third of the electrodes every two. And detecting the current value.
[0021]
A ninth aspect of the present invention is the ink jet recording apparatus according to any one of the sixth to eighth aspects, wherein the voltage applied to the electrode by the detection means is a DC voltage.
[0022]
According to a tenth aspect of the present invention, there is provided an ink jet recording apparatus, wherein the detecting means is activated at a predetermined timing, and the determining means determines the conductivity of the ink.
[0023]
According to the present invention, the conductivity of the ink filled in the inkjet head can be detected, and the inkjet head can be prevented from being broken.
[0024]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail based on embodiments of the present invention.
[0025]
(Embodiment 1)
FIG. 1 is an exploded perspective view of a head chip according to Embodiment 1 of the present invention. As shown in FIG. 1, a plurality of grooves 12 are provided in a piezoelectric ceramic plate 11, and each groove 12 is separated by a side wall 13. One end in the longitudinal direction of each groove 12 extends to one end surface of the piezoelectric ceramic plate 11, and the other end does not extend to the other end surface, but gradually decreases in depth. In addition, electrodes 15 for applying a driving electric field are formed on the opening side surfaces of both side walls 13 in each groove 12 in the longitudinal direction.
[0026]
Here, each groove 12 formed in the piezoelectric ceramic plate 11 is formed by, for example, a disk-shaped die cutter, and a portion whose depth is gradually reduced is formed using the shape of the die cutter. The electrode 15 formed in each groove 12 is formed, for example, by deposition from a known oblique direction.
[0027]
A cover plate 17 is joined to the opening side of the groove 12 of the piezoelectric ceramic plate 11. The cover plate 17 has an ink chamber 21 serving as a recess communicating with the shallow other end of each groove 12, and an ink supply port 22 penetrating from the bottom of the ink chamber 21 in a direction opposite to the groove 12. .
[0028]
Here, in the present embodiment, each groove 12 is divided into groups corresponding to inks of black (B), yellow (Y), magenta (M), and cyan (C). One supply port 22 is provided for each.
[0029]
The cover plate 17 can be formed of a ceramic plate, a metal plate, or the like. However, in consideration of deformation after joining with the piezoelectric ceramic plate 11, it is preferable to use a ceramic plate having an approximate coefficient of thermal expansion.
[0030]
A nozzle plate 25 is joined to an end face of the joined body of the piezoelectric ceramic plate 11 and the cover plate 17 where the groove 12 is open, and a nozzle opening is provided at a position facing each groove 12 of the nozzle plate 25. 27 are formed.
[0031]
In the present embodiment, the nozzle plate 25 is larger than the size of the end face where the groove 12 of the joined body of the piezoelectric ceramic plate 11 and the cover plate 17 is open. The nozzle plate 25 is formed by forming a nozzle opening 27 in a polyimide film or the like using, for example, an excimer laser device.
[0032]
In the present embodiment, a nozzle support plate 28 is disposed around an end of the joined body of the piezoelectric ceramic plate 11 and the cover plate 17 where the groove 12 is open. The nozzle support plate 28 is bonded to the outside of the bonded body end face of the nozzle plate to stably hold the nozzle plate 25. Of course, the nozzle support plate 28 need not be provided.
[0033]
Further, there is no particular limitation on how to provide wirings and the like for driving such a head chip 30, but an example is shown below.
[0034]
2 and 3 show an example of a manufacturing process of the inkjet head 40 using the head chip 30 described above.
[0035]
As shown in FIG. 2, a wiring pattern (not shown) connected to the electrode 15 is formed at an end of the piezoelectric ceramic plate 11 opposite to the nozzle opening side. The flexible cable 32 is joined via the base 31. An aluminum base plate 33 on the piezoelectric ceramic plate 11 side and a head cover 34 on the cover plate 17 side are attached to the rear end side of the nozzle support plate 28 of the joined body of the piezoelectric ceramic plate 11 and the cover plate 17. . The base plate 33 and the head cover 34 are fixed by engaging a locking shaft 34a of the head cover 34 with a locking hole 33a of the base plate 33, and sandwich the joined body of the piezoelectric ceramic plate 11 and the cover plate 17 therebetween. The head cover 34 is provided with an ink introduction path 35 communicating with each of the ink supply ports 22 of the cover plate 17.
[0036]
That is, the ink is supplied from the ink introduction path 35 of the head cover 34 to the inside of the inkjet head 40, and is filled from the ink supply port 22 of the head chip 30 into each groove 12, that is, the ink flow path. Is discharged from the nozzle opening 27.
[0037]
Next, as shown in FIG. 3A, a wiring board 36 is fixed on the base plate 33 projecting to the rear end side of the piezoelectric ceramic plate 11. Here, a drive circuit 37 such as an integrated circuit for driving a head chip is mounted on the wiring board 36, and the drive circuit 37 and the flexible cable 32 are connected via an anisotropic conductive film 38. Thus, the inkjet head 40 shown in FIG. 3B is completed.
[0038]
In the present embodiment, a detection circuit for detecting the state of conduction between the electrodes 15 is provided on the wiring board 36 of the inkjet head 40. Hereinafter, this detection circuit will be described. FIG. 4 is a schematic diagram showing the detection circuit, and a control register and a control signal for controlling the switching circuit 51 included in the drive circuit 37 are omitted for simplification of the description.
[0039]
As shown in FIG. 4, wirings 50 (50a, 50b,...) Are drawn out from the drive circuit 37 to the electrodes 15 (15a, 15b,. The wiring 50 is connected to a power supply 52 via a switching circuit 51 for selectively applying a voltage to each electrode 15. Further, between the switching circuit 51 and the power supply 52, a detecting means 53 and a determining means 54 are connected. Note that, in the present embodiment, the switching circuit 51 forms an output stage of the drive circuit 37 formed of an IC (integrated circuit).
[0040]
The detecting means 53 detects a state of conduction between the electrodes 15 when a voltage is applied between the electrodes 15 on both sides of each side wall 13, that is, a current value between the electrodes 15.
[0041]
Further, the determination unit 54 determines the conductivity of the ink filled in each groove 12 and in contact with each electrode 15 based on the detection result of the detection unit 53.
[0042]
Here, an example of detection of the energization state between the electrodes 15 by the detection unit 53 and the determination unit 54 and determination of the conductivity of the ink will be described.
[0043]
First, by switching the switching circuit 51 by a control signal (not shown), a voltage of a predetermined magnitude is applied from the power supply 52 to each of the electrodes 15a to 15d via the wirings 50a to 50d. For example, in the present embodiment, as shown in FIG. 4, a DC voltage of a predetermined magnitude is applied to the electrodes 15a and 15c connected to the wirings 50a and 50c.
[0044]
At this time, the detecting means 53 detects the current value flowing between the electrodes 15, that is, the ink filled in the ink flow path, that is, the grooves 12, from the electrodes 15 a and 15 c to which a DC voltage is applied and has a positive potential. The current flowing through the electrodes 15b and 15d, which are at the ground potential, is detected.
[0045]
The method of applying the voltage to the electrode 15 is such that the method of alternately repeating the electrode of the positive potential and the electrode of the ground potential as in the present embodiment is such that the current flowing through the ink flow path becomes the largest and the current can be easily detected. For example, the electrodes 15a and 15b may be at a positive potential and the electrodes 15c and 15d may be at a ground potential. Needless to say, it is good in principle that only one electrode can be set to a positive potential.
[0046]
Further, when a voltage is applied to every other electrode as in the present embodiment, and there is a possibility that ink is ejected when a large voltage is applied, a voltage is applied to every other electrode. May be.
[0047]
Here, FIG. 5A shows an example of the waveform of the voltage applied to the electrode, and FIG. 5B shows an example of the waveform of the current flowing at that time.
[0048]
As shown by the solid line in FIG. 5B, when the ink filled in the ink jet head has no conductivity, the positive potentials of the electrodes 15a and 15c are changed from the positive potentials of the electrodes 15b and 15d to the ground potentials of the electrodes 15b and 15d. There is almost no current flowing. However, when the ink is conductive as shown by the broken line in FIG. 5B, a current flows between the electrodes via the ink.
[0049]
In FIG. 5B, a large current flows when the voltage waveform rises because of the capacitance between the positive electrode and the ground electrode. Therefore, if the rise of the voltage waveform is made smooth, this steep current can be reduced.
[0050]
Further, in the present embodiment, the detecting means 53 converts such a current value into a digital signal by performing an analog-digital conversion (A / D conversion), and the judging means 54 refers to the digital signal to obtain a digital signal. Is determined.
[0051]
In order to A / D convert a current value, a method of detecting a current flowing through a resistance of several ohms to several tens of ohms as a voltage value and performing A / D conversion is generally used because the resistance value of the ink is very large. .
[0052]
FIG. 6 shows an embodiment of the determining method of the determining means 54.
[0053]
First, the determination unit 54 measures a current I ₁ when the ground potential of all the electrodes in step 1 · S1. This is because the current flowing through the ink is a very small current and is measured in order to cancel the offset current and the like of the circuit and improve the measurement accuracy.
[0054]
Next, to measure the current I ₂ at the time of applying a DC voltage to half of the electrodes are alternately in step 2 · S2.
[0055]
Then, I subtracted current _{I 1} measured from the current _{I 2} measured at Step 2 · S2 in Step 1 · S1 in Step 3 · S3, and calculates the current _{I ink} flowing through the actual ink.
[0056]
Finally, in steps S4 and S4, the current _Iink flowing through the ink calculated in step S3 is compared with a predetermined reference value _Iref. If the current _Iink is larger than this value, it is determined that the ink is unusable.
[0057]
Specifically, when the resistance value of the ink filled in the ink jet head needs to be 100 kΩ or more, if the applied voltage is 10 V, the upper limit of the current value flowing through the ink is 0.1 mA. In this case, the determination unit 54 determines that the ink has conductivity when the current _Iink flowing through the _ink is 0.1 mA or more.
[0058]
The reference value for determining the conductivity in the determination unit 54 changes depending on the shape of the inkjet head, that is, the contact area between the ink and the electrode, the number of electrodes, the applied voltage, and the like. Therefore, this reference value may be determined as appropriate.
[0059]
In the present embodiment, the detection of the conductivity of the ink by the detection unit 53 and the determination unit 54 is performed, for example, when the power is turned on, or when the ink is initially charged into the ink jet head for the first time. When the conductivity of the ink is detected, an abnormal signal is generated from the determination means 54, and the user is warned by an alarm or the like mounted on a device for controlling the head.
[0060]
As described above, the detection means 53 and the determination means 54 are provided in the ink-jet head 40 and the conductivity of the ink filled between the respective electrodes 15 is detected, so that the ink-jet head 40 can be used without actually performing the printing operation. It is possible to detect that the ink filled in is inappropriate. Therefore, it is possible to prevent a discharge operation by abnormal ink from being performed, and to prevent a worst case of damage to the inkjet head due to an overcurrent. Also, the user can recognize that the wrong ink has been filled.
[0061]
Note that such an ink jet head 40 is, for example, assembled to a tank holder that detachably holds an ink cartridge, and is then used by being mounted on a carriage of an ink jet recording apparatus. FIG. 7 schematically shows an example of this use mode.
[0062]
As shown in FIG. 7, the carriage 61 is mounted on a pair of guide rails 62a and 62b so as to be movable in the axial direction, and is provided at one end of the guide rail 62 and connected to the carriage drive motor 63 by a pulley 64a. And a pulley 64b provided on the other end side, and are conveyed via a timing belt 65 stretched over the pulley 64b. A pair of transport rollers 66 and 67 are provided on both sides in a direction orthogonal to the transport direction of the carriage 61 along guide rails 62a and 62b, respectively. These transport rollers 66 and 67 transport the recording medium S below the carriage 61 in a direction orthogonal to the transport direction of the carriage 61.
[0063]
In such an ink jet type recording apparatus, characters and images are recorded on the recording medium S by the ink jet head by scanning the carriage 61 in a direction perpendicular to the feeding direction while feeding the recording medium S.
[0064]
(Other embodiments)
As described above, one embodiment has been described, but the present invention is not limited to such a configuration.
[0065]
For example, in the above-described embodiment, the determination unit for determining the conductivity of the ink is incorporated in the inkjet head. However, the determination unit is formed separately from the inkjet head, and is used as a configuration provided in the inkjet recording apparatus. You may.
[0066]
Also, a part of the detecting means for detecting the state of conduction between the electrodes of the inkjet head may be used, for example, as a configuration in which an A / D converter of a detection circuit is provided inside the inkjet recording apparatus.
[0067]
【The invention's effect】
As described above, in the present invention, the conductivity of the ink filled between the electrodes is detected by the detection means and the determination means. Thus, when the ink having high conductivity is accidentally filled, it is possible to detect an abnormality of the head without actually driving the inkjet head, thereby preventing damage to the inkjet head and the like. .
[Brief description of the drawings]
FIG. 1 is an exploded perspective view and a sectional view of a head chip according to a first embodiment of the present invention.
FIG. 2 is an exploded perspective view of the inkjet head according to the first embodiment of the present invention.
FIG. 3 is a perspective view showing an assembly process of the inkjet head according to the first embodiment of the present invention.
FIG. 4 is a schematic diagram illustrating a detection circuit according to the first embodiment of the present invention.
FIG. 5 is a diagram illustrating an example of a waveform of a voltage applied to an electrode and a waveform of a current flowing at that time.
FIG. 6 is a diagram illustrating an example of a determination method of a determination unit according to the first embodiment of the present invention.
FIG. 7 is a perspective view showing a use mode of the inkjet head according to one embodiment of the present invention.
FIG. 8 is an exploded perspective view showing an outline of an inkjet head according to a conventional technique.
FIG. 9 is a cross-sectional view illustrating an outline of an inkjet head according to a conventional technique.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 Piezoelectric ceramic plate 12 Groove 13 Side wall 15 Electrode 17 Cover plate 25 Nozzle plate 27 Nozzle opening 28 Nozzle support plate 30 Head chip 33 Base plate 34 Head cover 36 Wiring board 40 Inkjet head 50 Wiring 51 Switching circuit 52 Power supply 53 Detecting means 54 Determination means

Claims (10)

By applying a drive voltage to electrodes provided on the side walls of the plurality of ink flow paths formed in the piezoelectric ceramic plate, the volume in the ink flow paths is changed, and the ink filled therein is discharged from the nozzle openings. Ink jet head
It has a detecting means for detecting an energized state between the electrodes when a voltage is applied between the electrodes of the ink flow path, and a determining means for determining compatibility of the ink from a detection result of the detecting means. Ink jet head. 2. The ink-jet head according to claim 1, wherein the detecting means detects a current value between the electrodes when the voltage is applied. 3. A method according to claim 1, wherein said detecting means detects a current value by applying a voltage to approximately half of the electrodes every other electrode or approximately one third of the electrodes every two electrodes. Inkjet head. The ink jet head according to any one of claims 1 to 3, wherein the voltage applied to the electrode by the detection means is a DC voltage. 5. An ink jet head according to claim 1, wherein said detecting means is activated at a predetermined timing, and said determining means determines the conductivity of said ink. By applying a drive voltage to electrodes provided on the side walls of the plurality of ink flow paths formed in the piezoelectric ceramic plate, the volume in the ink flow paths is changed, and the ink filled therein is discharged from the nozzle openings. In an ink jet recording apparatus equipped with an ink jet head,
Detecting means for detecting an energized state between the electrodes when a predetermined voltage is applied between the electrodes of the ink flow path of the ink jet head, and determining the compatibility of the ink filled in the ink jet head from the detection result of the detecting means. An ink jet recording apparatus, comprising: a determination unit. 7. The ink jet recording apparatus according to claim 6, wherein the detecting means detects a current value between the electrodes when the voltage is applied. 8. The method according to claim 6, wherein the detecting unit detects a current value by applying a voltage to approximately half of the electrodes every other electrode or approximately one third of the electrodes every two electrodes. Ink jet recording apparatus. 9. An ink jet recording apparatus according to claim 6, wherein a voltage applied to said electrode by said detection means is a DC voltage. The ink jet recording apparatus according to any one of claims 6 to 9, wherein the detecting means is started at a predetermined timing, and the determining means determines the conductivity of the ink.

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