JP5011603B2 - Inkjet printer - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an ink jet printer that performs printing by discharging ink from a head unit.
[0002]
[Prior art]
In a conventional inkjet printer, when a head that discharges ink at the time of printer cleaning is cleaned for maintenance, the head discharge portion is sucked for one or two color heads to prevent clogging of discharge nozzles. Such cleaning is sequentially performed for the four color heads.
[0003]
However, after the cleaning of the head is completed, the first suctioned and cleaned head increases the viscosity of the ink on the head ejection surface, and the ink may not be ejected sufficiently or may not be ejected. . For this reason, it takes a long time to maintain the inkjet printer. Also, providing the capping on the head ejection surface to prevent an increase in ink viscosity complicates the apparatus configuration.
[0004]
[Problems to be solved by the invention]
An object of the present invention is to provide an ink jet printer capable of preventing an increase in the viscosity of ink in a discharge portion of a head in view of the above-described problems of the prior art.
[0005]
[Means for Solving the Problems]
In order to achieve the above object, an ink jet printer according to the present invention includes a plurality of head units each having a discharge unit for discharging ink, and a plurality of head units that are independently provided to discharge ink from the discharge unit. A plurality of drive units for driving the head unit with a non-discharge signal that drives the head unit with a discharge signal to cause the ink to not be discharged from the discharge unit when the head unit is not used; And a suction unit for sucking ink from the ejection unit, wherein the ejection signal and the non-ejection signal are respectively applied to electrodes of the head unit to expand the head unit and the head It is a voltage signal consisting of an OFF waveform that contracts the unit, and the voltage level of the ejection signal Absolute value greater than a threshold voltage which divides the discharge and non-discharge of ink, the absolute value of the voltage level of the non-ejection signals is smaller than the threshold voltage, during suction by the suction unit, other than the head unit during aspiration When the head unit is driven by the non-ejection signal, only one of the ON waveform or the OFF waveform of the ejection signal is applied to each head unit as the non-ejection signal .
[0006]
According to this ink jet printer, when the head unit is not used, the head unit is driven with a non-ejection signal in a state where ink is not ejected from the ejection part, so that an increase in ink viscosity at the ejection part can be effectively prevented. .
[0007]
Further, in this case , it is possible to independently drive for each head unit to prevent ink viscosity increase due to the non- ejection signal.
[0008]
Further, while the cleaning sucks the ink remaining and the like from the ejection unit by a suction unit such as for preventing clogging of the ink ejection detecting portion, to drive the other head unit that are not attracted by the non-ejection signals Thus, for example, an increase in the viscosity of the ink can be prevented in the head unit that has completed the suction, and the cleaning effect can be maintained well, and the suction by the suction unit is easier to perform in the head unit before the suction.
[0009]
Furthermore, during the suction by the suction unit, the head unit being sucked can also be configured to be driven by the non-ejection signal. According to this, since the head unit that has been suctioned and cleaned by the suction unit by the suction unit can be driven by the non-discharge signal, the cleaning effect by the suction unit can be further increased.
[0010]
The ejection signal and the non-ejection signal are respectively applied to the electrodes of the head unit, and are voltage signals having an ON waveform for expanding the head unit and an OFF waveform for contracting the head unit. The absolute value of the level is larger than a threshold voltage that partitions ink ejection / non-ejection, and the absolute value of the voltage level of the non-ejection signal is smaller than the threshold voltage . In this case, for example, the ON waveform can be a positive voltage and the OFF waveform can be a negative voltage.
[0011]
As the non-ejection signals to the each head unit, ON waveform of the discharge signal, or by configuring such that said adding one of OFF waveform only, as it is non-eject ON waveform or OFF waveform of the ejection signal can be a signal, the voltage change at the time of driving at the time of non-ejection is not required, easily ing circuit configuration of such a head driver.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a schematic configuration of a head unit and a suction unit of an ink jet printer according to an embodiment of the present invention, and FIG. 2 is a block diagram showing a drive and control system of each head unit of FIG. FIG. 3A shows an ON waveform and an OFF waveform when ink is ejected, FIG. 3B shows an ON waveform and an OFF waveform when ink is not ejected, and shows these ON and OFF waveforms in consideration of positive and negative. FIG. 4 is a perspective view (a) partially showing the discharge part of the head unit of FIG. 1, front views (b), (c) for explaining the operation of the electrodes of the discharge part, FIG. FIG. 5D is a front view (d), (e), and (f) for explaining the ejection / non-ejection driving states of the ejection unit.
[0013]
As shown in FIG. 1, the ink jet printer includes a first head unit 1 having a plurality of ejection portions 1a arranged in a line on the ejection surface so as to eject Y (yellow) ink, and M (magenta) ink. A second head unit 2 having a plurality of ejection portions 2a aligned in a row on the ejection surface, and a plurality of ejection portions 3a aligned in a row on the ejection surface so as to eject C (cyan) ink. A third head unit 3 having a plurality of discharge portions 4a arranged in a line on the discharge surface so as to discharge K (black) ink, and a decompression unit (not shown). The first and second suction units 21 and 22 are connected to suck ink from the ejection portions 1a to 4a of the head units 1 to 4 and prevent clogging.
[0014]
Each head unit 1 to 4 is driven on the basis of each ejection signal as described later while moving in the horizontal direction in the figure to eject each ink of Y, M, C, and K onto a recording sheet such as paper for color printing. It is supposed to be. Further, when not in use such as cleaning for maintenance, one or two of the head units 1 to 4 move to the first and second suction units 21 and 22, and ink is ejected from these ejection units. It comes to suck.
[0015]
As shown in FIG. 2, the drive and control system for driving and controlling the head units 1 to 4 includes a voltage setting circuit 15 that sets a drive source voltage for each head unit 1 to 4, and a voltage setting circuit 15. 3A and 3B based on the voltage control circuit 16 for controlling the voltage based on the driving source voltage from the voltage and converting the level of each driving voltage, respectively, and on the driving voltage from the voltage control circuit 16. First, second, third and fourth head drivers 11 for outputting drive signals (ejection signals, non-ejection signals) having such driving waveforms (ON waveform, OFF waveform) to the head units 1 to 4, respectively. 12, 13, and 14. In FIGS. 3A and 3B, the ON waveform of the drive waveform is a positive signal and the OFF waveform is a negative signal.
[0016]
As shown in FIG. 3A, the ejection drive voltages Vh and -Vh of the drive signal (ejection signal) at the time of ejection are threshold voltages that separate ink ejection and non-ejection from the ejection units 1a to 4a of the head unit. The voltage level (absolute value) is larger than Vth and −Vth, and ink can be ejected by continuously outputting the ON waveform a1 and the OFF waveform b1. Further, as shown in FIG. 3B, the non-ejection drive voltages Vm and -Vm of the non-ejection drive signal (non-ejection signal) have a voltage level (absolute value) smaller than the threshold voltages Vth and -Vth. By continuously outputting the ON waveform c1 and the OFF waveform d1, the ejection units 1a to 4a can be driven without ejecting ink.
[0017]
As shown in FIG. 4A, the first head unit 1 is surrounded by piezoelectric elements 31 and 32 and piezoelectric elements 33 and 34 in which discharge portions 1a formed on the discharge surface 1b are arranged in the vertical direction in the figure. It is configured as described. As shown in FIG. 4B, the piezo element 31 includes a pair of electrodes 31a and 31b provided on both wall surfaces. When a drive voltage of a drive signal (ejection signal, non-ejection signal) as shown in FIG. 3 is applied from the head driver 11 to the electrodes 31a and 31b, the piezo element 31 changes from the undeformed state of FIG. As shown in 4 (c), it undergoes shear deformation. The mode of the shear deformation changes depending on the positive / negative polarity applied to the electrodes 31a and 31b, and the degree of deformation changes depending on the voltage level.
[0018]
In the ejection unit 1a of the first head unit 1, the piezo elements 31 to 34 have a drive signal of zero when the ejection drive voltage Vh is applied to the electrode 31a with the ON waveform a1 of the ejection signal of FIG. 4 (f) from the undeformed state as shown by the solid line in FIG. 4 (d), each is subjected to shear deformation so as to expand as a whole, and the electrode 31b is then subjected to an ejection drive voltage − with an OFF waveform b1 of the ejection signal. When Vh is added, as shown by the solid line in FIG. 4E, each of them undergoes shear deformation so as to contract as a whole, and ink is ejected from the ejection section 1a by this deformation operation. Further, further discharge can be performed by adding the ON waveform a2 and the OFF waveform b2.
[0019]
As described above, the piezoelectric elements 31 to 34 are deformed as shown in FIG. 4 (f) → FIG. 4 (d) → FIG. 4 (e) → FIG. 4 (f) →. When the ON waveforms a1 and a2 and the OFF waveforms b1 and b2 of the discharge signal are shown in consideration of their positive and negative, they are as shown in FIG. 3C, and each of the piezo elements 31 to 34 has an ON waveform discharge drive voltage. Shear deformation occurs when a drive voltage of 2 Vh, which is the difference between Vh and the discharge drive voltage −Vh of the OFF waveform, is applied.
[0020]
In addition, when the non-ejection drive voltage Vm is applied to the electrode 31a in the piezo element 31 with the ON waveform c1 of the non-ejection signal in FIG. 3B, the piezo elements 31 to 34 are changed from the undeformed state in FIG. As shown by the broken line in FIG. 4D, each of the electrodes 31b undergoes shear deformation so as to expand slightly to the extent below the discharge time, and then the electrode 31b has a non-ejection drive voltage − When Vm is added, as shown by the broken line in FIG. 4E, the respective parts undergo shear deformation so as to shrink slightly as a whole to the extent of the above-mentioned discharge, and ink is not discharged inside the discharge part 1a by this deformation operation. However, it is moved and flows. Further, the non-ejection state can be further driven by adding the ON waveform c2 and the OFF waveform d2.
[0021]
As described above, each of the piezo elements 31 to 34 is driven in a non-ejection state. At this time, the ON waveforms c1 and c2 and the OFF waveforms d1 and d2 of the non-ejection signal are shown in consideration of positive and negative. (C) It becomes like a dashed-dotted line, and each piezo element 31 to 34 is applied with a non-ejection drive voltage of 2 Vm, which is the difference between the non-ejection drive voltage Vm of the ON waveform and the non-ejection drive voltage −Vm of the OFF waveform. Shear deformation in the applied state.
[0022]
The other piezo elements 32, 33, and 34 are configured in the same manner as the piezo element 31, and the second, third, and fourth head units 2, 3, and 4 are also the first head. The configuration is the same as that of the unit 1.
[0023]
Next, the operation of the ink jet printer as described above will be described. For example, when the ink jet printer is started at the start of work (such as at the start of work in the morning), the head units 1 to 4 are sequentially moved by the suction units 21 and 22 in FIG. Cleaning by sucking residual ink. Thereby, the clogging of the ink in the discharge part can be prevented and the clogging can be eliminated.
[0024]
Then, the non-ejection signal (ON waveform c1 and the OFF waveform d1) as shown in FIG. 3B is added from the head driver 11 to the head unit 1, for example, which has been cleaned, and the next non-ejection signal (ON waveform c2). And the OFF waveform d2) are added, and the ink is not ejected by repeating the expansion and contraction in the ejection part 1a as shown by the broken lines in FIGS. 4D and 4E, but the ink is not ejected inside the ejection part 1a. Move to flow. This ink flow can effectively prevent the viscosity of the ink from increasing particularly at the tip of the discharge portion 1a, and the cleaning effect by the suction units 21 and 22 can be maintained well.
[0025]
In this way, the maintenance of the head units 1 to 4 can be performed easily and effectively without taking time. Further, no special capping or the like is required in order to prevent an increase in the viscosity of the ink in the ejection part of the head unit after the cleaning by the suction units 21 and 22, and there is no problem of complication of the apparatus configuration.
[0026]
The head unit that is being suctioned by the suction units 21 and 22 may be driven by a non-discharge signal as shown in FIG. 3B, and the head unit before the suction by the suction units 21 and 22 is also non-discharged. You may make it drive with a signal.
[0027]
After the suction by the suction units 21 and 22 is completed and the driving for preventing the increase in the viscosity of the ink by the non-ejection signal as shown in FIG. 3B is finished, each of the head units 1 to 4 is illustrated. By driving with an ejection signal such as 3 (a), each ink can be ejected from each ejection section 1a to 4a and color printed on a recording sheet. At this time, the ink in each ejection section 1a to 4a Therefore, good color printing can be performed.
[0028]
Next, a modification of the present embodiment will be described with reference to FIGS. In this example, as shown in FIG. 5, the ejection drive voltage Vh of the ON waveform at the time of ejection is not changed, and the ON waveform of the non-ejection signal at the time of non-ejection is used as it is, while the OFF waveform is not added at the time of non-ejection. It is a thing. Accordingly, when the voltage Vh is applied to the electrode 31a with the ON waveform a1 of FIG. 5 in the piezoelectric element 31, the piezoelectric elements 31 to 34 from the undeformed state of FIG. 6A as shown in FIG. Similar to FIG. 4D, shear deformation is performed, but since no OFF waveform is applied, the state returns to the undeformed state of FIG. Further, when the voltage Vh is applied with the ON waveform a2, it is similarly deformed.
[0029]
Each of the piezo elements 31 to 34 is subjected to shear deformation in a state where the ON waveform voltage Vh is applied, and the applied voltage level is about half that in the normal ejection shown in FIG. Even in this case, it becomes a non-discharge state. As a result, the ink can be moved and flowed inside the discharge portion 1a as described above, and the ink flow can be prevented from increasing in the discharge portion 1a due to the flow of the ink. In this case, the discharge drive voltage −Vh of the OFF waveform at the time of discharge may not be changed, and the OFF waveform at the time of non-discharge may be used as it is, and the ON waveform may not be added. At this time, each of the piezo elements 31 to 34 undergoes shear deformation as shown in FIG. 4E from the undeformed state of FIG.
[0030]
As described above, the present invention has been described with reference to the embodiments. However, the present invention is not limited to these embodiments, and various modifications can be made within the scope of the technical idea of the present invention. For example, the configuration of the head unit may use another element other than the piezo element, and can also be applied to a monochromatic head unit such as black.
[0031]
Further, the voltage level of the ejection signal and the voltage level of the non-ejection signal can be appropriately set according to the threshold voltage as shown in FIG. In addition, for each of the plurality of head units, the voltage level of the non-ejection signal can be changed to appropriately change the degree of ink flow in the non-ejection state, and the time for driving with the non-ejection signal can be set as appropriate.
[0032]
【Effect of the invention】
According to the ink jet printer of the present invention, it is possible to effectively prevent an increase in the viscosity of the ink in the ejection unit of the head unit. In addition, when a suction unit that sucks ink in the ejection part of the head unit is provided, the cleaning effect by the suction can be maintained well.
[Brief description of the drawings]
FIG. 1 is a diagram showing a schematic configuration of a head unit and a suction unit of an ink jet printer according to an embodiment of the present invention.
2 is a block diagram showing a drive and control system of each head unit in FIG. 1. FIG.
3A is a diagram showing an ON waveform and an OFF waveform when the head unit of FIG. 1 is driven when ink is ejected, FIG. 3B is a diagram showing an ON waveform and an OFF waveform when the head unit is driven when ink is not ejected, and FIG. FIG. 6C is a diagram (c) illustrating the ON waveform and the OFF waveform of FIG.
4 is a perspective view (a) partially showing the discharge part of the head unit of FIG. 1, front views (b) and (c) for explaining the operation of the electrodes of the discharge part, and the discharge part; It is a front view (d), (e), (f) for demonstrating each drive state of discharge / non-discharge.
FIG. 5 is a diagram illustrating an ON waveform and an OFF waveform when ink is not ejected in a modified example.
FIGS. 6A and 6B are front views (a) and (b) of a discharge unit for explaining each non-discharge driving state in the modification of FIG. 5;
[Explanation of symbols]
1, 2, 3, 4 First to fourth head units 1a, 2a, 3a, 4a Discharge units 11, 12, 13, 14 of each head unit First to fourth head drivers (drive units)
21, 22 First, second suction units 31, 32, 33, 34 Piezo elements 31a, 31b A pair of electrodes a1, b1, a2, b2 Discharge signal c1, d1, c2, d2 Non-discharge signal Vh Discharge drive voltage Vm Non-ejection drive voltage Vth threshold voltage

Claims (2)

A plurality of head units each having a discharge unit that discharges ink; and a plurality of head units that are independently provided corresponding to the plurality of head units, driving the head unit with a discharge signal that discharges ink from the discharge unit, A plurality of drive units that drive the head unit with a non-ejection signal that does not eject ink from the ejection unit when not in use;
A suction unit for sucking ink from the ejection unit when the head unit is not used, and
The ejection signal and the non-ejection signal are respectively applied to the electrodes of the head unit, and are voltage signals having an ON waveform for expanding the head unit and an OFF waveform for contracting the head unit. The absolute value of the level is larger than a threshold voltage that partitions ink ejection / non-ejection, and the absolute value of the voltage level of the non-ejection signal is smaller than the threshold voltage,
When a head unit other than the head unit being sucked is driven by the non-ejection signal during suction by the suction unit, one of the ON waveform and the OFF waveform of the ejection signal is used as the non-ejection signal for each head unit. Inkjet printer characterized by adding only .   2. The ink jet printer according to claim 1, wherein the head unit that is being suctioned by the suction unit is also driven by the non-ejection signal.

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