JP2012196881A - Method for controlling inkjet recorder, and inkjet recorder - Google Patents

Abstract

The temperature of a nozzle plate whose temperature has been lowered is made uniform.
An ink jet head having three or more nozzle rows and an element for discharging ink connected to each discharge nozzle generating heat in response to application of a drive waveform includes a recording area and an outside of the recording area. In the control method of the ink jet recording apparatus 1 for performing recording by selectively ejecting ink in the recording area, the ink jet head 11 moves in the folding area. During this time, a drive waveform of minute vibration that does not lead to ink ejection is applied to each piezoelectric element of the pair of nozzle rows 14 located at both outer ends so that the temperature of the three or more nozzle rows 14 becomes uniform. Apply.
[Selection] Figure 3

Description

  The present invention relates to an ink jet recording apparatus control method and an ink jet recording apparatus that perform drawing by discharging ink while reciprocating an ink jet head.

  Conventionally, as an ink jet recording apparatus of this type, an ink jet recording apparatus that performs drawing by ejecting ink from an ink jet head onto a work placed on a work table is known in which the ink jet head is heated by a heat retaining heater. (See Patent Document 1). In this ink jet recording apparatus, the thermal heater is energized in synchronism with the acceleration drive of the carriage motor every time image printing processing for one line (head temperature control) or immediately before the head temperature control is started. . Thereby, the ink jet head is heated at the time of drawing, the viscosity of the ink is lowered, and the occurrence of ejection failure is prevented.

  In addition, in an ink jet recording apparatus of a thermal ink jet recording system that discharges ink using bubbles, an amount of ink is insufficient to generate bubbles in a discharge heater provided in the vicinity of the discharge surface for a predetermined time before starting printing. There is known a technique for controlling the temperature of an ink jet head by applying thermal energy (see Patent Document 2). In this heat retention control, the temperature of the ink-jet head that is deprived of heat by a work table or the like with reciprocal scanning is suppressed, and the viscosity of the ejected ink is stabilized while maintaining the ink viscosity low. Yes.

Japanese Patent Laid-Open No. 4-85045 Japanese Patent Laid-Open No. 10-16228

By the way, although the ink is not actively heated as in the above prior art, in an inkjet head using a piezoelectric element (piezo element) or the like as a drive source, a voltage is applied to the piezoelectric element to drive it ( Ink discharge) and the piezoelectric element are known to generate heat. The piezoelectric element is provided facing the cavity, and when the piezoelectric element generates heat, the temperature of the ink in the cavity is increased by heat transfer.
When the conventional ink jet head has one or two nozzle rows, the ink ejected from each nozzle row also has the same temperature (same viscosity) by heating. That is, even if the piezoelectric element generates heat, the ink ejected from one or two nozzle rows can be managed at a uniform temperature (viscosity).
However, when the inkjet head has three or more nozzle rows, the heat of the piezoelectric element is more likely to accumulate in the inner nozzle row than in the outer nozzle row, and the temperature is controlled to a uniform temperature (viscosity). There arises a problem that cannot be done. That is, the nozzle row formed on the end portion side of the nozzle plate easily radiates heat, but as it goes toward the center, it becomes difficult to radiate heat, and the temperature in the nozzle plate becomes uneven. For this reason, the viscosity of the ejected ink differs between the nozzle row at the center and the nozzle row at the end, and the ejection amount and ejection speed also differ. Therefore, even if the ink is heated to a uniform temperature via the ink jet head or the ink is directly heated to a uniform temperature, the print quality may be deteriorated.

  The present invention relates to a method for controlling an ink jet recording apparatus and an ink jet recording apparatus capable of equalizing the temperatures of three or more nozzle rows even in the case where heat is generated in an element portion in an ink jet head having three or more nozzle rows. It is an issue to provide.

  The control method of the ink jet recording apparatus of the present invention includes an ink jet head having three or more nozzle rows and an ink discharge element unit that is connected to each discharge nozzle generating heat when a drive waveform is applied. In a control method of an ink jet recording apparatus that performs recording by selectively ejecting ink in a recording area and moving in a moving area composed of a folding area set outside the recording area, the inkjet head moves the folding area. Apply a slight vibration drive waveform that does not lead to ink ejection to each element of the pair of nozzle rows located at both outer ends so that the temperature of three or more nozzle rows is uniform during It is characterized by.

  In addition, the ink jet recording apparatus of the present invention includes three or more nozzle rows, an ink jet head in which an element unit for ink ejection connected to each ejection nozzle generates heat when a drive waveform is applied, and an ink jet head. And a head moving means for moving the recording area and a moving area composed of the folded area set outside the recording area, and a control means for controlling the ink jet head and the head moving means. While moving, recording is performed by selectively ejecting ink by applying a drive waveform in the recording area, and at the same time, the temperature of three or more nozzle rows is uniform while the inkjet head is moving in the folding area. So that each element portion of the pair of nozzle rows located at both outer end portions And applying the micro-vibration of the drive waveform that does not lead to discharge.

  In this case, the recording area is an area where the inkjet head is moved at a constant speed, and the folding area is an area where the inkjet head is decelerated, stopped and accelerated.

  According to these configurations, when the ink jet head is located in the folded area sandwiching the recording area, a drive waveform that does not lead to ink ejection is applied to each element part of the pair of nozzle rows formed at the outer end part that easily radiates heat. Therefore, the temperature of the three or more nozzle rows in the inkjet head can be made uniform efficiently. For this reason, the viscosity of the ejected ink can be made more stable and constant, and unevenness in the ejection amount and ejection speed does not occur for each nozzle row, and the print quality can be improved. In addition, since the application of the drive waveform for ink ejection and the application of the micro-vibration drive waveform for temperature adjustment do not overlap, the recording operation is not adversely affected.

  In this case, it is preferable to apply the necessary number of micro-vibration driving waveforms to the respective element portions of the pair of nozzle rows so that a heat quantity corresponding to the temperature difference caused by the movement is generated.

  According to this configuration, the temperature lost in the moving operation can be compensated immediately after the operation is completed, so that the temperatures of the three or more nozzle rows can be stably made uniform.

  Further, it is preferable to apply a drive waveform of slight vibration to each element portion of the pair of nozzle rows continuously while moving in the folding region.

  According to this configuration, it is possible to simplify the control system for applying the micro-vibration driving waveform. In this case, it is preferable to adjust the temperature uniformity by the magnitude (voltage) of the drive waveform of the minute vibration.

It is a top view of an inkjet recording device. It is a schematic diagram of a carriage unit. It is a perspective view of an inkjet head. It is a control block diagram of an inkjet recording device. It is a drive waveform figure applied to a piezoelectric element. It is a time chart which shows the reciprocation of an inkjet head. It is the graph which measured the temperature change of the nozzle row by a drive waveform. It is the graph which measured the temperature difference of the nozzle row of a center, and the nozzle row of an outer end part.

  Hereinafter, an inkjet recording apparatus according to an embodiment of the present invention will be described with reference to the accompanying drawings.

  As shown in FIG. 1, the inkjet recording apparatus 1 is mounted on a machine base 2, a drawing apparatus 3 that is widely mounted on the entire area of the machine base 2, and an inkjet head 11 is mounted on the drawing apparatus 3 on the machine base 2. And a maintenance device 4 attached thereto, and the maintenance device 4 performs maintenance processing (maintenance / recovery) of the inkjet head 11 and the drawing device 3 draws, for example, UV ink on the work W (recording medium). I try to do it.

  The drawing apparatus 3 includes an XY moving mechanism 21 including an X-axis table 22 and a Y-axis table 23 (head moving means) orthogonal to the X-axis table 22, a carriage unit 15 movably attached to the Y-axis table 23, have. The carriage unit 15 is equipped with an inkjet head 11 and a heating device 50 described later. On the other hand, the workpiece W is mounted in a state of being positioned on the X-axis table 22. In the present embodiment, a single inkjet head 11 is mounted, but the number thereof is arbitrary.

  The X-axis table 22 includes a motor-driven X-axis slider 24 that constitutes a drive system in the X-axis direction, and a set table 25 including a suction table 26 and a θ table 27 is movably mounted thereon. ing. Similarly, the Y-axis table 23 includes a motor-driven Y-axis slider 28 that constitutes a drive system in the Y-axis direction, and the carriage unit 15 is movably mounted thereon. The Y-axis table 23 includes the carriage unit 15 mounted on the Y-axis table 23 between the drawing area 31 positioned immediately above the X-axis table 22 and the maintenance area 32 positioned directly above the maintenance device 4. Move as appropriate.

  The ink jet recording apparatus 1 configured as described above appropriately performs maintenance processing on the ink jet head 11 by the maintenance device 4 and performs a drawing operation on the workpiece W by the drawing device 3. That is, the drawing device 3 intermittently feeds the workpiece W in the X-axis direction (sub-scanning) by the X-axis table 22 while being controlled by the control device, and the Y-axis table 23 moves the inkjet head 11 in synchronization with this. The ink jet head 11 is selectively driven while reciprocating in the Y-axis direction (main scanning), and drawing is performed on the workpiece W.

  FIG. 2 is a schematic diagram of the carriage unit 15. As shown in the figure, the carriage unit 15 includes a carriage plate 15a, an inkjet head 11 mounted downward on the carriage plate 15a, and a chamber-type heating device 50 for heating the inkjet head 11. Ink jet head 11 of the present embodiment is introduced with UV ink having a high viscosity. Therefore, ink jet head 11 is heated (heated) by heating device 50, and the viscosity of UV ink is lowered and discharged. Yes.

  The heating device 50 includes a chamber 51 that covers the upper space of the carriage plate 15 a so as to enclose the inkjet head 11, and a fan 52 and a heater 53 disposed in the chamber 51. Although not shown, the chamber 51 is provided with a temperature sensor, and the heater 53 is ON / OFF controlled based on the detection result of the temperature sensor. When the fan 52 and the heater 53 are driven, warm air circulates in the chamber 51 and the atmosphere in the chamber 51 is maintained at a constant temperature. As a result, the ink jet head 11 and the ink tubes 54 connected to the ink head 54 (actually, eight ink tubes 54 for each color) are heated, and the ink introduced into the ink jet head 11 and the ink tubes 54 is predetermined. Heated (heated) to temperature. That is, the ink ejected from the inkjet head 11 is warmed and its viscosity is lowered.

  As shown in FIGS. 1 and 3, the inkjet head 11 includes a case head 41 into which ink is introduced, and a pump unit 16 that is provided at the tip of the case head 41 and includes a piezoelectric element (element unit: not shown). And a nozzle plate 12 provided at the tip of the pump unit 16, and a drive board 42 and a flexible printed board 43 attached to the side surface of the case head 41. Further, the nozzle plate 12 is formed with eight nozzle rows 14a to 14h for each color extending in the X-axis direction and including one ejection row 13 (see FIG. 1). Each discharge nozzle 13 communicates with the cavity of the pump unit 16, and a drive waveform of a predetermined voltage is applied to the piezoelectric element provided facing the cavity via the drive board 42 and the flexible printed board 43. As a result, the piezoelectric element is deformed (pump action), and ink is ejected from each ejection nozzle 13.

  Next, the control device of the inkjet recording apparatus 1 will be described with reference to FIG. As shown in the figure, the inkjet recording apparatus 1 includes an operation unit 61 having a keyboard and a display (not shown), a print processing unit 62 having an inkjet head 11, an X-axis table 22, a Y-axis table 23, and a heating device 50. , A driving unit 63 having a head driver, a workpiece moving driver, a head moving driver and a heater driver, and a control unit 64 connected to each unit and controlling the entire inkjet recording apparatus 1.

  The control unit 64 has an interface 71, a recording area for temporary storage, a RAM 72 used as a work area for control processing, and various storage areas, and stores control programs and control data. The ROM 73 stores drawing data for performing predetermined drawing (recording) on the work W, various data, and the like, and stores a program for processing various data, etc., and stores in the ROM 73 and the hard disk 74. In accordance with the programmed program, it has a CPU 75 for arithmetic processing of various data, and a bus 76 for connecting them together.

  The control unit 64 inputs various data from each unit via the interface 71 and causes the CPU 75 to perform arithmetic processing according to a program stored in the hard disk 74 or the ROM 73, and the processing result is displayed on the driving unit 63 ( Output to each part via various drivers). Thereby, the whole apparatus is controlled and various processes of the inkjet recording apparatus 1 are performed.

  FIG. 5 shows a drive waveform applied to the piezoelectric element of the inkjet head 11 from the control unit 64 via the drive unit 63 (head driver) for ink ejection or the like. FIG. 5A shows a drive waveform (ejection waveform) for ejecting ink, which is a waveform in which a predetermined voltage (Vh) is applied and then ejected after being drawn. On the other hand, FIG. 5B shows a drive waveform (microvibration waveform) for preventing ink thickening and promoting heat generation, which will be described later, and is similar to the discharge waveform and has a voltage (for example, Vh) lower than the discharge waveform. X 30%) is applied. In this fine vibration waveform, the meniscus only vibrates and ink is not ejected. Further, the ejection waveform and the fine vibration waveform are applied according to a common driving cycle. The fine vibration waveform may be a plurality of pulses by dividing the drive cycle as shown in FIG.

  By the way, in the inkjet head 11 of this embodiment, when a piezoelectric element (piezo element) is driven (a drive waveform is applied), the piezoelectric element generates heat. As described above, the ink jet head 11 (the plurality of nozzle rows 14a to 14h) is uniformly heated by the heating device 50. However, when the piezoelectric element generates heat, it is easy to dissipate heat (mainly absorbed by the X-axis table 22). The temperature of the nozzle rows 14d and 14e located in the center where heat radiation is difficult is higher than the nozzle rows 14a and 14h located on both outer sides, and the viscosity of the ejected ink differs depending on the positions of the nozzle rows 14a to 14h. Become. That is, depending on whether the nozzle rows 14a to 14h are located outside or in the center of the nozzle plate 12, the ink ejection amount and ejection speed differ. Therefore, in the present embodiment, the above-described fine vibration waveform is appropriately applied to the nozzle rows 14a and 14h located on both outer sides so that the nozzle plate 12 (the plurality of nozzle rows 14) has a uniform temperature. ing.

  FIG. 6 shows a time chart of main scanning, that is, reciprocation of the carriage unit 15. As shown in the figure, the carriage unit 15 (inkjet head 11) accelerates from the stopped state in the forward movement, shifts to a constant speed at a constant speed (drawing speed), further decelerates and stops. . Subsequently, the operation shifts to the backward movement, and stops after acceleration, constant speed, and deceleration as described above. In the actual drawing operation, the discharge nozzle 13 of the inkjet head 11 is selectively driven at each constant speed movement while repeating the forward and backward movements with the sub-scan (intermittent feed of the workpiece W) interposed therebetween. And draw.

  That is, in the main scanning, an acceleration area 81, a constant speed area (drawing area) 82, a deceleration area 83, and a stop area 84 are set, and the acceleration area 81, the constant speed area 82, and the deceleration area 83 are added. Is the reciprocating region width. Further, the acceleration region 81 and the deceleration region 83 have the same region width, and include the stop region 84. The acceleration region 81 and the deceleration region 83 overlap each other by reciprocating motion, thereby forming a turn-back region 85.

  In the present embodiment, drawing based on the drawing data is performed in the constant speed region 82. Specifically, based on the drawing data, the discharge waveform is selectively applied to the discharge nozzles 13 (piezoelectric elements thereof) of the inkjet head 11 at the drive period described above, and desired drawing is performed. On the other hand, in the folded region 85, the fine vibration waveform is continuously applied in the above driving cycle to all the discharge nozzles 13 (piezoelectric elements) of the nozzle rows 14a and 14h located on both outer sides, and heating is performed. Is done.

  That is, when the inkjet head 11 is positioned in each folded region 85, ink ejection is performed only on the piezoelectric elements of the nozzle rows 14a and 14h formed at both outer end portions where the temperature drop is significant compared to the central nozzle rows 14d and 14e. A fine vibration waveform that does not reach is continuously applied. As a result, the temperature of the nozzle rows 14a and 14h rises, and in the nozzle rows 14a and 14h, heat dissipation in the constant speed region 82 and heat generation in the turn-back region 85 are offset. That is, the plurality of nozzle rows 14a to 14h are maintained at a uniform temperature, and the ink ejected from the plurality of nozzle rows 14a to 14h has the same temperature. In the present embodiment, the fine vibration waveform is continuously applied. However, it may be applied intermittently with a necessary number of times, or the duty ratio can be controlled.

  FIG. 7 shows the change in temperature of the nozzle rows 14d and 14e and the temperature of the nozzle rows 14a and 14h when the above-described fine vibration waveform is not applied (FIG. 7A and when applied) (FIG. 7B). In the figure, the solid line indicates the temperature change of the central nozzle rows 14d and 14e, the dotted line indicates the temperature change of the end nozzle rows 14a and 14h, and the horizontal axis indicates time. The vertical axis represents temperature.

  In FIG. 7A, immediately after the start of driving of the inkjet head 11, the temperatures of the central nozzle rows 14d and 14e and the end nozzle rows 14a and 14h are substantially the same between the temperature T1 and the temperature T2. In the constant speed region 82 where drawing is performed, the heat on the surface of the nozzle plate 12 is taken away by the X-axis table 22, and the temperature of the nozzle plate 12 is not uniform. Therefore, the temperature difference between the central nozzle rows 14d and 14e and the outer end nozzle rows 14a and 14h increases with time, and eventually becomes constant with the temperature difference open (equilibrium state).

In FIG. 7B, immediately after the start of driving of the inkjet head 11, it is almost the same as in the case of FIG. 7A. When the inkjet head 11 moves from the constant speed region 82 to the deceleration region 83, a drive waveform that does not lead to ink ejection is applied only to the piezoelectric elements of the nozzle rows 14a and 14h to cause slight vibration. As a result, the piezoelectric elements generate heat, and the nozzle rows 14a and 14h are heated to the same temperature as the nozzle rows 14d and 14e. The drive waveform is applied also in the stop region 84 and the acceleration region 81. Thereby, the surface temperature of the nozzle plate 12 becomes uniform.
As described above, in the present embodiment, the inkjet head 11 is formed at the outer end portion so that the temperatures of the nozzle rows 14a to 14h are uniform while moving in the folded region at both ends sandwiching the drawing region. Only the piezoelectric elements of the nozzle arrays 14a and 14h are applied with a drive waveform of minute vibration that does not lead to ink ejection.

FIG. 8 is a graph obtained by measuring the temperature difference of the nozzle row between the center and the outer end in FIGS. 7A and 7B, and the dotted line indicates the temperature difference when the fine vibration waveform is not applied. The solid line indicates the temperature difference when the fine vibration waveform is applied. The horizontal axis represents time, and the vertical axis represents the temperature difference.
Immediately after the inkjet head 11 is driven, the surface temperature of the nozzle plate 12 is the same for both the dotted line and the solid line. In the case of the dotted line, even if the surface temperature of the nozzle plate 12 decreases in the drawing region, the driving waveform is not applied to the nozzle rows 14a and 14h at the outer end portion in the folding region, but in the case of the solid line, the nozzle waveforms 14a and 14h are applied. The drive waveform is applied continuously or intermittently. For this reason, the temperature difference in the case of the dotted line is about 1.5 ° C., whereas in the case of the solid line, the temperature difference is generally within 1 ° C.

As described above, in the present invention, when the inkjet head is located in the folded area sandwiching the recording area, the drive waveform that does not lead to ink ejection is continuously applied to the piezoelectric elements of the pair of nozzle rows formed at both outer ends. Since the voltage is intermittently applied, the surface temperature of the nozzle plate 12 can be made uniform efficiently. For this reason, it is possible to perform drawing stably and to improve the printing quality.
In this embodiment, the drive waveform is applied only in the folding region. However, when the discharge waveform can be controlled for each discharge nozzle 13, the drive waveform may be applied also in the constant speed region 82.

DESCRIPTION OF SYMBOLS 1 ... Inkjet recording apparatus 11 ... Inkjet head 12 ... Nozzle plate 13 ... Discharge nozzle 14a-14h ... Nozzle row 22 ... X-axis table

Claims (5)

An ink jet head having three or more nozzle rows and an element portion for ink discharge connected to each discharge nozzle generating heat with application of a drive waveform;
In the control method of the ink jet recording apparatus, in which the recording is performed in the recording area and the moving area composed of the folded area set outside the recording area, and the ink is selectively ejected in the recording area.
While the inkjet head is moving in the folded region, ink is applied to each element portion of the pair of nozzle rows located at both outer ends so that the temperature of the three or more nozzle rows is uniform. A control method for an ink jet recording apparatus, wherein the drive waveform of minute vibration that does not lead to ejection is applied. The recording area is an area for moving the inkjet head at a constant speed,
The method of controlling an ink jet recording apparatus according to claim 1, wherein the folded area is an area where the ink jet head is decelerated, stopped, and accelerated.   3. The ink jet according to claim 1, wherein the drive waveform of the minute vibrations is applied to each element portion of the pair of nozzle rows so that a heat amount corresponding to a temperature difference caused by the movement is generated. Control method of recording apparatus.   3. The inkjet recording apparatus according to claim 1, wherein the drive waveform of the minute vibration is applied to each element portion of the pair of nozzle rows continuously while moving in the folding region. Control method. An ink-jet head having three or more nozzle rows and an element portion for ink discharge connected to each discharge nozzle generating heat with application of a drive waveform;
A head moving means for moving the inkjet head in a moving area composed of a recording area and a folded area set outside the recording area;
Control means for controlling the inkjet head and the head moving means,
The control means moves the inkjet head in the movement region,
In the recording area, recording is performed by selectively ejecting ink by applying the drive waveform,
While the inkjet head is moving in the folded region, ink is applied to each element portion of the pair of nozzle rows located at both outer ends so that the temperature of the three or more nozzle rows is uniform. An ink jet recording apparatus, wherein the drive waveform of minute vibration that does not lead to ejection is applied.

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