JP3679865B2 - Inkjet recording device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a recording apparatus using an on-demand type ink jet recording head, and more particularly to a technique for preventing clogging of nozzle openings of the recording head.
[0002]
[Prior art]
The on-demand ink jet recording head includes a plurality of nozzle openings and a pressure generation chamber communicating with each nozzle opening, and is configured to pressurize the pressure generation chamber in response to a print signal to generate ink droplets. Yes. In such a recording head, since new ink is sequentially supplied to the nozzle openings where the printing operation is performed, clogging hardly occurs. However, there is a great opportunity for ink droplet ejection like the nozzle openings at the upper and lower ends, for example. Clogging is likely to occur when the output is low or when the print signal is stopped and released from the capping device.
[0003]
For this reason, when the printing operation is continued for a certain period of time, the recording head is retracted to the capping means in the non-printing area, where a drive signal is applied to the pressure generating means, for example, a piezoelectric vibrator, to the cap. It has been proposed to perform a flushing operation for ejecting ink droplets from all nozzle openings regardless of printing.
[0004]
[Problems to be solved by the invention]
However, if such measures are taken, there is a problem that the printing operation is interrupted, resulting in a decrease in printing speed and consumption of ink.
In order to solve such problems, a minute drive signal that does not cause ink droplets to be ejected is applied to the pressurizing means in the pressure generating chamber that communicates with the nozzle openings that do not generate ink droplets at regular intervals during the printing operation. Many techniques have been proposed to prevent clogging by minutely vibrating the meniscus in the vicinity of the nozzle opening (Japanese Patent Laid-Open Nos. 55-123476, 57-61576, US Pat. No. 4350989). ).
[0005]
If this method of microvibration of the meniscus is used in combination, the number of flushing operations can be reduced to prevent a reduction in printing speed and ink consumption. In the nozzle openings where ink droplets are not ejected during the printing period, the ink solvent volatilization is accelerated by the minute vibrations of the meniscus, and there is a problem that the timing of clogging is advanced.
Furthermore, since the viscosity of such ink that is easily formed into a film greatly depends on the temperature, when the environmental temperature rises and the viscosity of the ink decreases, the amount of movement of the meniscus due to minute vibrations becomes too large and the nozzle When the ink droplets are ejected for printing, there is a problem that the flight path of the ink droplets is bent.
The present invention has been made in view of such a problem, and the object of the present invention is to cause the nozzle opening to become clogged without causing a flying curve of ink droplets regardless of a change in environmental temperature. It is an object of the present invention to provide an ink jet recording apparatus capable of extending the period of time to the maximum.
[0006]
[Means for Solving the Problems]
In order to solve such a problem, a pressure generating chamber having an elastically deformable region that can be elastically deformed, a nozzle opening that communicates with the pressure generating chamber and discharges ink droplets, and the elastically deformable region are provided. An ink jet recording head constituted by a piezoelectric vibrator, temperature detecting means for detecting the temperature of the environment, and a signal applied to the pressure generating means based on a signal from the temperature detecting means to adjust the nozzle opening. Means for adjusting a pressure change that causes microvibration of the meniscus to prevent clogging, and a signal that generates the microvibration of the meniscus changes at a constant speed to expand the pressure generation chamber; and a signal for contracting said pressure generating chamber is changed at a constant speed, the change rate of change of the signal for expanding said pressure generating chamber of a signal for contracting said pressure generating chamber It is configured to be larger than the degree.
[0007]
[Action]
The amplitude of the minute vibration of the meniscus to prevent clogging of the nozzle opening is changed according to the outside air temperature, so that the nozzle plate does not get wet at high temperatures and ink solvent evaporation due to minute vibration is unnecessary The meniscus is minutely vibrated with an optimum amplitude without being accelerated and without losing the high viscosity at a low temperature.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Therefore, details of the present invention will be described below based on the illustrated embodiment.
FIG. 1 shows a structure around a printing mechanism of a printer of the present invention. In FIG. 1, reference numeral 1 denotes a carriage, which is connected to a pulse motor 3 via a timing belt 2 and guided to a guide member 4. Thus, the recording paper 5 is configured to reciprocate in the paper width direction.
[0009]
An ink jet recording head 6 to be described later is attached to the carriage 1 on the surface facing the recording paper 5, in this embodiment on the lower surface. The ink jet recording head 6 receives ink replenishment from an ink cartridge 7 mounted on the upper portion of the carriage 1, and ejects ink droplets onto the recording paper 5 in accordance with the movement of the carriage 1. To print.
[0010]
8 is a capping device that is provided in a non-printing area and seals the nozzle openings of the recording head 6 during a pause while receiving ink droplets from the recording head 6 by a flushing operation performed during the printing operation. It is. In the figure, reference numeral 9 denotes a cleaning means.
[0011]
FIG. 2 shows an embodiment of the recording head 6. In the figure, reference numeral 11 denotes a vibration plate, which is a thin plate that abuts against the tip of the piezoelectric vibrator 12 and elastically deforms. The flow path unit 18 is configured by being liquid-tightly fixed integrally with the nozzle plate 17 with the flow path forming plate 16 partitioning the ink chambers 14 and 1 and the ink supply ports 15 and 15 therebetween.
[0012]
Reference numeral 19 denotes a base, and the flow path unit 18 and the piezoelectric vibrator 12 are arranged so that the tip of the piezoelectric vibrator 12 is brought into contact with the vibration plate 11 in an accommodation chamber 20 having an opening for supporting the flow path unit 18 at the top. Are fixed.
[0013]
In the recording head configured as described above, when the piezoelectric vibrator 12 is charged and contracts, the pressure generation chamber 13 expands, and the ink in the common ink chambers 14 and 14 passes through the ink supply ports 15 and 15. It flows into the pressure generation chamber 13.
[0014]
When the electric charge of the piezoelectric vibrator 12 is discharged and returns to the original state after a lapse of a predetermined time, the pressure generating chamber 13 contracts, compresses the ink here, and discharges it as an ink droplet from the nozzle opening 21 to the recording paper. Form dots.
[0015]
On the other hand, if the piezoelectric vibrator 12 is contracted by a small amount so as not to eject ink droplets to the piezoelectric vibrator 12, the pressure generating chamber 13 expands slightly, so that the meniscus in the vicinity of the nozzle opening 21 is drawn into the pressure generating chamber 13 side. . Next, when the piezoelectric vibrator 12 is returned to the original state, the pressure generating chamber 13 is slightly contracted and the meniscus is pushed back slightly toward the nozzle opening 21 side.
[0016]
When the piezoelectric vibrator 12 is expanded and contracted by a minute amount in this way, the meniscus in the vicinity of the nozzle opening 21 vibrates with a minute amplitude without ejecting ink droplets, and the ink in the vicinity of the nozzle opening has a low viscosity in the pressure generating chamber 13. Since the ink is replaced, the time until the nozzle opening is clogged is greatly extended.
[0017]
FIG. 3 shows an embodiment of a control device for driving the recording head 6 described above. In FIG. 3, reference numeral 30 denotes a control means, which receives a print command signal and print data from the host and generates a drive signal which will be described later. The circuit 31, the head drive circuit 32, and the carriage drive circuit 33 are controlled to execute the printing operation, and the timing for minute oscillation of the meniscus described above is determined based on the timing data of the print timer 34 described later, and the storage means 37 described later. Based on these data, a drive signal is output from the head drive circuit to the piezoelectric vibrator so that the meniscus performs minute vibrations at a drive frequency, pressure change, and duration suitable for the current situation.
[0018]
Reference numeral 34 denotes a print timer which starts when the printing operation is started and resets when the minute vibration starts. Reference numeral 35 denotes an ink cartridge mounting time detection unit that receives a signal from a unit that detects attachment / detachment of the ink cartridge 7 in the cartridge housing portion, starts when the cartridge 7 is newly mounted, and resets when the cartridge 7 is removed. It is configured. Reference numeral 36 denotes temperature detecting means for detecting the outside air temperature and the temperature of the recording head.
[0019]
Reference numeral 37 denotes the storage means described above, which is a ratio for increasing the amplitude of the meniscus at the time of minute vibration in proportion to the mounting period of the ink cartridge as shown in FIG. Data indicating the ratio for increasing the amount, data for reducing the pressure change in the pressure generating chamber 13 for generating minute vibrations as the temperature increases as shown in FIG. 5, and further as shown in FIG. It stores data that lowers the driving frequency of minute vibrations as the temperature increases.
[0020]
Since the pressure change for causing the minute vibration can be adjusted by the voltage of the driving signal applied to the pressure generating means, for example, the piezoelectric vibrator, for the minute vibration, the ratio to the driving voltage at the time of printing as shown in FIG. Depending on the temperature, for example, in the low temperature range (10 to 15 ° C), the drive voltage at the time of printing is 0.3 times, and in the normal temperature range (15 to 25 ° C), it decreases linearly to 0.25 times with the temperature. For example, the temperature is further reduced by 0.25 times in the first high temperature region (25 to 30 ° C.) and further linearly by 0.2 times in the second high temperature region (30 to 40 ° C.), for example. The attenuation rate of a variable attenuator or the like can be adjusted and controlled.
[0021]
On the other hand, the frequency of the minute vibration of the meniscus is an integral multiple of 1 / integer of the maximum drive frequency during printing in the low temperature region (10 to 15 ° C.) as shown in FIG. The frequency is 7.2 KHz which is 16 times 16 times, 5.4 KHz which is 12 times in the normal temperature range (15 to 30 ° C), and 3.6 KHz which is 8 times in the first high temperature range (30 to 35 ° C). Thus, in the second high temperature region (35 to 40 ° C.), it can be easily controlled by selecting a driving frequency that is 4 times 1/16 of the maximum driving frequency. In this way, by using a frequency that is an integral multiple of 1 / integer of the driving frequency at the time of printing, a special oscillation circuit is not required only for minute vibration, and the structure can be simplified.
[0022]
Of course, it is obvious that clogging can be prevented more effectively by providing a circuit capable of finely changing the amplitude and frequency of the minute vibration with respect to the temperature if the structure is not complicated.
[0023]
In this embodiment, when a print command is input from the host, the control unit 30 detects the temperature of the recording head 6 based on a signal from the temperature detection unit 36 and selects a vibration form suitable for minute vibrations.
[0024]
That is, when the temperature is higher than the room temperature, the viscosity of the ink is lowered and the meniscus is likely to vibrate. Therefore, the pressure change that causes minute vibration is small, that is, the voltage of the drive voltage applied to the piezoelectric vibrator 12 is low. In addition to setting, the frequency of the minute vibration is lower than that at normal temperature, for example, 8 times 3.6 KHz in the first high temperature region (30 to 35 ° C), and the highest in the second high temperature region (35 to 40 ° C). A drive frequency that is four times 1/16 of the drive frequency is selected, and minute vibration is continued while avoiding evaporation of the ink solvent caused by high-speed movement of the meniscus and suction of gas from the nozzle opening.
[0025]
In addition, since the viscosity of the ink is low and the diffusion speed is high at high temperatures, the volatilization of the ink solvent from the nozzle opening induced by minute vibrations can be suppressed quickly by suppressing the total number of vibrations for one process to a small number. In addition, the viscosity of the ink in the vicinity of the nozzle opening can be reduced.
[0026]
Then, the minute vibration of the meniscus is performed in such a manner that the pressure generating chamber 13 is slightly expanded at the start and then returned to the original state. As a result, the meniscus vibrates around the position where the meniscus is slightly drawn from the nozzle opening 21 toward the pressure generating chamber side, so that the meniscus can be used for the ink even if the ink is low in viscosity due to an increase in temperature. The meniscus does not move to the nozzle opening 21 until the plate 17 is wetted, and the meniscus vibrates with a sufficient amplitude to diffuse the ink in the vicinity of the nozzle opening into the ink in the pressure generating chamber 13.
[0027]
By continuing such a process for a predetermined time, the thickened ink in the vicinity of the nozzle opening 21 is gradually replaced with the ink in the pressure generating chamber 13 to reduce its viscosity, and is restored to a printable viscosity.
[0028]
On the other hand, when the temperature is lower than room temperature, the viscosity of the ink is increased and the meniscus is difficult to vibrate. Therefore, the pressure change in the pressure generating chamber 13 for minute vibration is increased, that is, applied to the piezoelectric vibrator 12. The voltage of the drive voltage is set high and the drive frequency is also increased. For example, it is set to 16 times the 1/16 of the maximum drive frequency during printing.
[0029]
Accordingly, even when the outside air temperature is lower than the normal temperature and the viscosity of the ink is increased, the meniscus of the nozzle opening 21 receives a pressure stronger than that at the normal temperature to prevent clogging regardless of the increase in the viscosity of the ink. The ink that vibrates slightly with an amplitude suitable for the above and thickened in the vicinity of the nozzle opening 21 is diffused into the ink in the pressure generating chamber 13 and its viscosity is lowered. Needless to say, since the temperature of the ink is low, the evaporation of the ink solvent is low, and the viscosity is high, so that bubbles are not drawn into the nozzle opening 21 even if the frequency of the minute vibration is increased.
[0030]
On the other hand, when the elapsed time since the cartridge 7 is mounted is long, the amount of ink solvent evaporated from the container constituting the cartridge 7 is increased, and the ink of the cartridge 7 itself is also thickened. Therefore, it is desirable to increase the degree of pressure change due to minute vibrations based on the data from the ink cartridge mounting time detecting means 35, and to slightly increase the meniscus vibration frequency if necessary. As a result, the meniscus can be minutely vibrated with an amplitude and drive frequency suitable for preventing clogging regardless of evaporation of the ink solvent in the ink cartridge 7 and change in ink viscosity caused by changes in the outside air temperature.
[0031]
In this way, when there is no fear of clogging and printing is possible, a print signal is output, and a drive signal for ejecting ink droplets is output to each piezoelectric vibrator 12. The print timer 34 is activated with the start of printing, and a signal is output when the printing time reaches the timing of minute vibration. The control means 30 estimates the point in time when the recording head 6 reaches the vicinity of the end of the print line and the carriage 1 moves to the deceleration process, and when the environmental temperature is high as described above, the pressure change due to minute vibrations. The frequency of micro vibrations is lower than that at room temperature, and when the ambient temperature is low, the pressure change for micro vibrations is increased and the frequency of micro vibrations is higher than that at normal temperatures. Further, a signal is output so as to change the pressure for causing minute vibrations corresponding to the passage of time after the ink cartridge is mounted.
[0032]
As a result, minute vibrations are executed by the drive frequency and pressure corresponding to the time since the outside air temperature or the ink cartridge was mounted in the time zone when the printing operation is impossible.
[0033]
Then, while continuing this minute vibration state, the carriage 1 stops at a predetermined position, and then reverses to accelerate the next printing line toward the printing area. Then, the minute vibration of the meniscus that has been continued immediately before the carriage 1 moves to a constant speed printable state is stopped.
[0034]
In this way, by extending the execution time of the minute vibration for preventing clogging during the printing period until the carriage 1 enters the deceleration process for the return operation, it is possible without interrupting the printing operation. The minute vibration can be executed at an early stage, and not only can the nozzle opening be clogged without causing a decrease in the recording speed, but also the recording head 6 that occurs due to the return operation of the carriage 1 can be prevented. It is possible to prevent the ink from thickening the nozzle opening 21.
[0035]
When the predetermined amount of printing is completed, the control unit 30 moves the recording head 1 to the home position and waits. Even during this standby, the meniscus is periodically finely vibrated to prevent ink thickening of the nozzle openings 21.
[0036]
When a print command is input during the duration of the minute vibration during standby, the control means 30 starts acceleration toward the printing region without interrupting the minute vibration, and minutely immediately before entering the constant speed running. Stop the vibration and go to the printing process.
[0037]
On the other hand, when a print command is input during a period in which no micro-vibration of the meniscus is performed in the standby state, the control unit 30 starts acceleration of the carriage 1 toward the print area in preparation for a printing operation, and simultaneously causes the recording head 1 to A signal for minute vibration is supplied to cause the meniscus to perform minute vibration.
[0038]
Immediately before the acceleration process of the carriage 1 is finished and the process moves to a constant speed capable of printing, the minute vibration is stopped to prepare the printing system. When a print signal is input in this state, the recording head 6 ejects ink droplets according to the print data.
[0039]
As a result, immediately before printing, the viscosity of the ink in the nozzle opening 21 is reduced to a viscosity suitable for printing, and printing can be performed in an optimum state.
[0040]
In the embodiment described above, the amplitude of the minute vibration is controlled by the magnitude of the drive signal applied to the piezoelectric vibrator, but the voltage of the drive signal applied to the piezoelectric vibrator 21 as shown in FIG. By adjusting the change rates α and β, the expansion speed and contraction speed of the pressure generating chamber 13 at the time of minute expansion can be adjusted to adjust the pressure at the time of minute expansion.
[0041]
Further, as shown in FIG. 8, by setting the voltage change rate β at the time of minute contraction smaller than the voltage change rate α at the time of minute expansion, the meniscus is rapidly drawn into the pressure generating chamber 13 and the nozzle opening The ink in the vicinity of the ink 21 can be diffused into the pressure generating chamber 13, and when it is pushed back, the kinetic energy of the meniscus can be reduced, and the meniscus can be minutely oscillated without causing swell or protrusion from the nozzle opening 21.
[0043]
Further, in the above-described embodiment, the description has been made by taking an example of a recording apparatus in which the ink cartridge is mounted on the carriage. It is clear that the same effect can be obtained even when applied to an apparatus.
[0044]
【The invention's effect】
As described above, according to the present invention, the amplitude of the meniscus for preventing clogging of the nozzle opening is changed according to the outside air temperature without inducing the wetting of the nozzle plate or the evaporation of the ink solvent at a high temperature. Further, the meniscus can be vibrated minutely without losing the high viscosity at low temperatures, and the time until the nozzle opening is clogged can be extended.
[Brief description of the drawings]
FIG. 1 is a diagram showing an embodiment of an ink jet recording apparatus to which the present invention is applied.
FIG. 2 is a cross-sectional view showing an embodiment of an ink jet recording head.
FIG. 3 is a block diagram of an apparatus showing an embodiment of the present invention.
FIG. 4 is a diagram showing a relative ratio of a pressure change in a pressure generating chamber for generating minute vibrations with respect to an ink cartridge mounting period.
FIG. 5 is a diagram showing a relationship between an environmental temperature and a driving voltage applied to pressure generating means for minute vibrations.
FIG. 6 is a diagram showing a relationship between an environmental temperature and a driving frequency of minute vibration.
FIGS. 7A and 7B are waveform diagrams showing signals for adjusting the amplitude of minute vibrations, respectively.
FIG. 8 is a waveform diagram showing an example of a signal for generating minute vibrations.
[Explanation of symbols]
6 Inkjet recording head 8 Capping device 9 Cleaning device 12 Piezoelectric vibrator 13 Pressure generating chamber 21 Nozzle opening

Claims (7)

Inkjet recording comprising a pressure generating chamber having an elastically deformable region capable of elastic deformation, a nozzle opening communicating with the pressure generating chamber and discharging ink droplets, and a piezoelectric vibrator provided in the elastically deformable region Head,
A temperature detecting means for detecting the temperature of the environment, and a signal applied to the pressure generating means based on a signal from the temperature detecting means to adjust a minute vibration of the meniscus for preventing clogging of the nozzle opening. Means for adjusting the pressure change,
Signal to generate a minute vibration of the meniscus, and a signal for expanding said pressure generating chamber is changed at a constant speed, and a signal for contracting said pressure generating chamber is changed at a constant rate, the pressure generating chamber An ink jet recording apparatus configured such that a changing speed of a signal for expanding is higher than a changing speed of a signal for contracting the pressure generating chamber . 2. The ink jet recording apparatus according to claim 1, further comprising an ink cartridge mounting time detecting unit, wherein a signal for generating a minute vibration of the meniscus is adjusted according to the mounting time of the ink cartridge. The signal for generating minute vibrations of the meniscus is adjusted so that a pressure change due to the minute vibrations is larger than a normal temperature region in a low temperature region and smaller than a normal temperature region in a high temperature region. 2. An ink jet recording apparatus according to 1.   2. The ink jet recording apparatus according to claim 1, wherein the frequency of the minute vibration of the meniscus is set to be higher than a normal temperature region in a low temperature region and lower than a normal temperature region in a high temperature region. 2. The ink jet recording according to claim 1, wherein the frequency of the minute vibration of the meniscus is selected by a signal from the temperature detection unit so as to be an integral multiple of 1 / integer of a maximum drive frequency of a drive signal during printing. apparatus. 2. The ink jet recording apparatus according to claim 1, wherein the number of microvibrations of the meniscus in one process is set to be smaller in a high temperature region than in a normal temperature region.   The ink jet recording apparatus according to claim 1, wherein the minute vibration of the meniscus is performed in an acceleration / deceleration process of the carriage.

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