JP2001353865A - Ink jet recorder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem that a meniscus does not oscillate to cause clogging of a nozzle. SOLUTION: When an ink drop is ejected, an oscillation pulse Bp for imparting meniscus oscillation is applied and then a drive pulse Dp for ejecting an ink drop is applied.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording apparatus, and more particularly, to an ink jet recording apparatus equipped with an electrostatic ink jet head.

[0002]

2. Description of the Related Art As an ink jet recording apparatus used as an image recording apparatus (image forming apparatus) such as a printer, a facsimile, a copying apparatus, and a plotter, a nozzle for discharging ink droplets and an ink flow path (discharging chamber, A pressure chamber, a pressurized liquid chamber, a liquid chamber, etc.), a diaphragm forming the wall of the ink flow path, and an electrode facing the diaphragm, and the diaphragm is deformed by electrostatic force. 2. Description of the Related Art There is known an ink jet head that is mounted with an electrostatic ink jet head that ejects ink droplets from nozzles when displaced.

[0003] Ink jet heads eject ink droplets from nozzles. Therefore, if the ink viscosity changes due to the environment, stable ink droplet ejection characteristics (drop speed V
j, the droplet volume Mj, and the curvature of the droplet ejection direction), and the image quality deteriorates. In addition to environmental changes,
If the viscosity of the ink increases during non-printing, nozzle clogging occurs and the image deteriorates significantly. In particular, since the size of the ejected ink droplets must be reduced in order to improve the image quality, the diameter of the nozzle has been reduced, and nozzle clogging is more likely to occur. Further, even if nozzle clogging does not occur, a difference occurs in the ink droplet ejection characteristics when a print signal is input next, depending on the length of the non-printing time, and image quality deteriorates.

Therefore, for example, a republished patent WO 97/32
As described in Japanese Patent Application Publication No. 728, a first electric pulse having an amplitude capable of ejecting ink droplets in synchronization with a single-cycle reference signal, and an amplitude smaller than the amplitude of the first electric pulse,
2. Description of the Related Art There is known an ink jet recording apparatus that applies one of a second voltage pulse that causes ink in a nozzle to flow in the nozzle to each pressure generating unit during a recovery process operation for preventing nozzle clogging and during a printing process. I have.

Japanese Patent Application Laid-Open No. 9-39236 discloses a state in which a diaphragm is vibrated by a pre-vibration that does not cause ink droplets to be ejected, and the pre-vibration causes the diaphragm to approach an individual electrode (a gap is narrow). There is known an apparatus which induces a vibration sufficient to eject ink droplets and provides a drive signal.

[0006]

However, in an ink jet recording apparatus for selectively applying the first electric pulse and the second electric pulse to the respective pressure generating means at the same timing, the energy of the ink jet head is reduced. Among the common electrode (diaphragm) and the individual electrode forming the generation means, there are provided switch means for switching the voltage applied to the common electrode, and switch means for switching the voltage of the individual electrode, and the individual electrode has two levels of voltage. Must be switched and provided, which increases the cost.

Further, in an ink jet recording apparatus which previbrates the diaphragm and applies a drive pulse at a timing when the diaphragm approaches the electrode side, the diaphragm is deformed even if the drive pulse is applied without the previbration. Therefore, it is necessary to always provide a pulse for driving the pre-vibration and a driving pulse.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above problems, and has as its object to provide an ink jet recording apparatus in which the rise of ink clay and clogging of nozzles are reduced at low cost.

[0009]

In order to solve the above problems, an ink jet recording apparatus according to the present invention comprises means for vibrating a meniscus at least once before ejecting ink droplets.

[0010] The ink jet recording apparatus according to the present invention comprises:
A head drive control unit that applies one or a plurality of vibration pulses for vibrating the meniscus without discharging the ink droplets and then applies a drive pulse for discharging the ink droplets when discharging the ink droplets. .

[0011] The ink jet recording apparatus according to the present invention comprises:
When ejecting ink droplets, after applying one or a plurality of vibration pulses for vibrating the meniscus without ejecting ink droplets, applying a drive pulse for ejecting ink droplets and continuously ejecting ink droplets In some cases, the apparatus is provided with head drive control means for applying a drive pulse for ejecting ink droplets without applying a vibration pulse.

In an ink jet recording apparatus using these vibration pulses, the vibration pulse for vibrating the meniscus without ejecting ink droplets has a narrower pulse width than the drive pulse, or has a longer pulse fall time than the drive pulse. And the pulse width of the ink droplet ejection characteristic is preferably between the pulse width at which the first peak is reached and the pulse width at which the next peak is reached.

[0013]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a schematic perspective explanatory view of a mechanism of an ink jet recording apparatus according to the present invention, and FIG. 2 is a side explanatory view of the mechanism.

This ink jet recording apparatus comprises a carriage movable in the main scanning direction inside the recording apparatus main body 1, a recording head including an ink jet head mounted on the carriage, an ink cartridge for supplying ink to the recording head, and the like. A paper feed cassette (or a paper feed tray) 4 capable of loading a large number of sheets 3 from the front side is detachably attached to a lower portion of the apparatus main body 1. In addition, the manual tray 5 for manually feeding the paper 3 can be opened, and the paper 3 fed from the paper feed cassette 4 or the manual tray 5 is taken in. After recording the image, the sheet is discharged to the sheet discharge tray 6 mounted on the rear side.

The printing mechanism 2 slides the carriage 13 in the main scanning direction (vertical direction in FIG. 2) with a main guide rod 11 and a sub guide rod 12 which are guide members which are laterally mounted on left and right side plates (not shown). This carriage 1
3 is provided with a head 14 composed of an inkjet head for ejecting ink droplets of each color of yellow (Y), cyan (C), magenta (M), and black (Bk) with the ink droplet ejection direction directed downward. Above 13, each ink tank (ink cartridge) 15 for supplying each color ink to the head 14 is exchangeably mounted.

Here, the carriage 13 is slidably fitted to the main guide rod 11 on the rear side (downstream side in the sheet conveying direction), and the front side (upstream side in the sheet conveying direction) of the slave guide rod 1.
2 slidably mounted. The main scanning motor 1 is moved to scan the carriage 13 in the main scanning direction.
A timing belt 20 is stretched between a driving pulley 18 and a driven pulley 19, which are driven to rotate by 7, and the timing belt 20 is fixed to the carriage 13.

Although the heads 14 of the respective colors are used here as recording heads, a single head having nozzles for ejecting ink droplets of the respective colors may be used. Furthermore, head 1
The ink jet head used as 4 is of an electrostatic type that presses ink by displacing the diaphragm with electrostatic force between a diaphragm forming the ink flow path wall surface and an electrode facing the diaphragm.

On the other hand, the paper 3 set in the paper feed cassette 4
Roller 21 and a friction pad 22 for separating and feeding the paper 3 from the paper feed cassette 4 and a guide member 23 for guiding the paper 3
A transport roller 24 that reverses and transports the fed paper 3, a transport roller 25 that is pressed against the peripheral surface of the transport roller 24, and a tip roller 26 that defines an angle at which the paper 3 is fed from the transport roller 24. Is provided. The transport roller 24 is driven to rotate by a sub-scanning motor 27 via a gear train.

An image receiving member 29 is provided as a paper guide member for guiding the paper 3 fed from the transport roller 24 below the recording head 14 in accordance with the moving range of the carriage 13 in the main scanning direction. I have. On the downstream side of the printing receiving member 29 in the sheet conveying direction, a conveying roller 31 and a spur 32, which are driven to rotate in order to send out the sheet 3 in the sheet discharging direction.
And a paper discharge roller 33 and a spur 34 for feeding the paper 3 to the paper discharge tray 6 and guide members 35 and 36 for forming a paper discharge path.

A reliability maintenance / recovery mechanism (hereinafter referred to as a "subsystem") 37 for maintaining and recovering the reliability of the head 14 is disposed on the right end side in the moving direction of the carriage 13. The carriage 13 is moved to the subsystem 37 side during printing standby, and the head 14 is capped by capping means or the like.

Next, an ink jet head constituting the head 14 of the ink jet recording apparatus will be described with reference to FIGS. 3 is an exploded perspective view of the head 14, FIG. 4 is a cross-sectional view of the head 14 in a direction orthogonal to the nozzle arrangement direction, and FIG. 5 is an enlarged cross-sectional view of a main part of the head 14 in the nozzle arrangement direction. .

The ink jet head 40 includes a flow path substrate 41 using a single crystal silicon substrate, a silicon substrate such as an SOI substrate or the like, and a silicon substrate, a Pyrex glass substrate, a ceramic substrate, etc. provided below the flow path substrate 41. And a nozzle plate 43 provided above the flow path substrate 41, a nozzle 44 for discharging a plurality of ink droplets, a liquid chamber 46 as an ink flow path to which each nozzle 44 communicates, Fluid resistance part 4 also serving as ink supply path in liquid chamber 46
A common liquid chamber flow path 48 and the like that communicate with each other through the air passage 7 are formed.

The flow path substrate 41 has a liquid chamber 46 and the liquid chamber 4.
6, a recess for forming a diaphragm 50 (which will be a first electrode) forming a bottom, which is a wall surface, is formed on the nozzle plate 43, a groove for forming a fluid resistance portion 47 is formed, and a flow path substrate 41 is formed. The electrode substrate 42 has a penetrating portion for forming the common liquid chamber flow path 48.

Here, for example, when a single crystal silicon substrate is used as the flow path substrate 41, boron is injected in advance to the diaphragm thickness to form a high-concentration boron layer serving as an etching stop layer. After bonding, the concave portion serving as the liquid chamber 46 is anisotropically etched using an etching solution such as a KOH aqueous solution, whereby the high-concentration boron layer becomes an etching stop layer, and the diaphragm 50 is formed with high precision. You.

Although an electrode film may be separately formed on the diaphragm 50, the diaphragm also functions as an electrode by diffusion of impurities as described above. Further, the diaphragm 50
An insulating film can be formed on the surface on the electrode substrate 42 side. As this insulating film, an oxide-based insulating film such as SiO ₂
A nitride insulating film such as i ₃ N ₄ can be used.
The insulating film can be formed by thermally oxidizing the surface of the diaphragm to form an oxide film, or by using a film forming technique.

An oxide film layer 42a is formed on the electrode substrate 42, a concave portion 54 is formed in the portion of the oxide film layer 42a, and an electrode 15 facing the diaphragm 50 is formed on the bottom surface of the concave portion 54.
(To be a second electrode), and the diaphragm 50 and the electrode 55
A gap 56 is formed between the vibration plate 50 and the electrode 55 to form an actuator section.
An electrode protection film 57 made of an oxide-based insulating film such as a SiO ₂ film or a nitride-based insulating film such as a Si ₃ N ₄ film is formed on the surface of the electrode 55. Membrane 5
An insulating film can be formed on the diaphragm 50 side without forming the layer 7.

When a single crystal silicon substrate is used as the electrode substrate 42, a normal silicon wafer can be used. The thickness varies depending on the diameter of the silicon wafer, but in the case of a 4-inch diameter silicon wafer, the thickness is about 500 μm, and in the case of a 6-inch diameter silicon wafer, the thickness is often about 600 μm. When a material other than the silicon wafer is selected, the smaller the difference in thermal expansion coefficient from silicon of the flow path substrate, the more the reliability can be improved when bonding to the diaphragm.

The bonding between the flow path substrate 41 and the electrode substrate 42 can be performed by an adhesive, but a more reliable physical bonding, for example, when the electrode substrate 42 is formed of silicon, A direct bonding method via an oxide film can be used. This direct bonding is performed at a high temperature of about 1000 ° C. When the electrode substrate 42 is made of glass, anodic bonding can be performed. When the electrode substrate 42 is formed of silicon and anodic bonding is performed, Pyrex glass may be formed between the electrode substrate 42 and the flow path substrate 41, and anodic bonding may be performed via this film. Further, the flow path substrate 41 and the electrode substrate 42 can be joined by eutectic joining in which a binder such as gold is interposed on the joining surface using a silicon substrate.

The electrodes 55 of the electrode substrate 42 include:
A commonly used in the process of forming a semiconductor element
Metal materials such as l, Cr, and Ni, high melting point metals such as Ti, TiN, and W, and polycrystalline silicon materials whose resistance has been reduced by impurities can be used. When the electrode substrate 42 is formed of a silicon wafer, it is necessary to form an insulating layer (the above-described oxide film layer 42a) between the electrode substrate 42 and the electrode 55. When an insulating material such as glass is used for the electrode substrate 42, there is no need to form an insulating layer between the electrode 55 and the electrode 55.

When a silicon substrate is used as the electrode substrate 42, an impurity diffusion region can be used as the electrode 55. In this case, an impurity used for diffusion is an impurity having a conductivity type opposite to the conductivity type of the substrate silicon, a pn junction is formed around the diffusion region, and the electrode 55 and the electrode substrate 42 are formed.
Are electrically insulated from each other.

The nozzle plate 43 is formed by arranging a large number of nozzles 44 in two rows, and the ejection surface is subjected to a water-repellent treatment. Here, the nozzle plate 43 is manufactured by the Ni electroforming method, but a nozzle having a multilayer structure of a resin and a metal layer can also be used. This nozzle plate 43
Are bonded to the flow path substrate 41 with an adhesive.

In the ink jet head 40, the nozzles 44 are arranged in two rows, and the liquid chambers 4 correspond to the respective nozzles 44.
6, the diaphragm 50, the electrodes 55, etc. are also arranged in two rows, a common liquid chamber flow path 48 is arranged at the center of each nozzle row, and ink is supplied to the left and right liquid chambers 46. This makes it possible to configure a multi-nozzle head having a large number of nozzles with a simple head configuration.

The electrode 55 of the ink-jet head 40 is extended outside to form a connection portion (electrode pad portion) 55a, and an FPC cable 61 on which a driver IC 60 as a head drive circuit is mounted is connected to an anisotropic conductive film or the like. Connected through. At this time, the electrode substrate 42 and the nozzle plate 43
As shown in FIG. 4, airtight sealing is performed with a gap sealing agent 62 using an adhesive such as an epoxy resin.

Further, the entire ink jet head 40 is joined onto the frame member 65 with an adhesive. The frame member 65 has an ink supply hole 66 for supplying ink from outside to the common liquid chamber flow path 48 of the inkjet head 40, and the FPC cable 61 and the like have holes 67 formed in the frame member 65. Is stored in.

The gap between the frame member 65 and the nozzle plate 43 is sealed with a gap sealing agent 68 using an adhesive such as an epoxy resin as shown in FIG. The ink is applied to the electrode substrate 42 and the FPC cable 6
It is prevented from going around to 1st mag.

The frame member 6 of the head 14
5 includes a joint member 70 with the ink cartridge 15.
Are connected to the common liquid chamber flow path 48 through the ink supply hole 66 from the ink cartridge 15 via the filter 71.
Is supplied with ink.

In the ink-jet head 40, a driving voltage is applied between the vibration plate 50 and the electrode 55 by using the vibration plate 50 as a common electrode and the electrode 55 as an individual electrode (the configuration may be reversed). As a result, the diaphragm 50 is deformed and displaced toward the electrode 55 due to an electrostatic force generated between the diaphragm 50 and the electrode 55, and in this state, the electric charge between the diaphragm 50 and the electrode 55 is discharged, whereby the diaphragm 50 is deformed by return, and the internal volume (volume) of the liquid chamber 46 /
When the pressure changes, ink droplets are ejected from the nozzles 44.

That is, when a pulse voltage is applied to the electrode 55 serving as an individual electrode, a potential difference occurs between the electrode 50 and the diaphragm 50 serving as a common electrode, and an electrostatic force is generated between the individual electrode 55 and the diaphragm 50. As a result, the diaphragm 50 is displaced according to the magnitude of the applied voltage. After that, the applied pulse voltage is dropped, the displacement of the diaphragm 50 is restored, and the restoring force increases the pressure in the liquid chamber 46, and the nozzle 4
4 ejects ink droplets. In this case, a method in which the diaphragm 50 is displaced until it comes into contact with the electrode 55 (actually, the surface of the insulating protective film 57) is a contact driving method, and the diaphragm 50 is
The method of displacing to a position where it is not brought into contact with 5 is referred to as a non-contact driving method.

When the pulse voltage is applied and the diaphragm 50 is attracted, a negative pressure is generated in the liquid chamber 46. Since the pressure oscillates at the natural frequency of the liquid chamber 46, the pressure at the time of the falling of the pulse is a superposition of the residual pressure vibration at the time of the rising of the pulse and the restoring pressure.

Accordingly, in the electrostatic ink jet head 40, a difference occurs in the ink droplet ejection characteristics depending on the pulse width of the applied pulse voltage. That is, for example,
As shown in FIG. 6, the ejection characteristics (ejected droplet speed Vj, ejected droplet mass Mj) fluctuate according to the timing of superposition of pressures based on the pulse width PW.

In the case of the example shown in FIG. 6, when the pulse width PW is set to be smaller than 4 μsec, the pulse width at which the ejection droplet speed Vj and the ejection droplet volume Mj reach the first peak and the next second
It can be seen that ink droplets are not ejected when the pulse width is set to a pulse width between the pulse widths at which the peak of.

That is, the application of the pulse voltage causes the diaphragm 5
This corresponds to a short-time (narrow pulse width) pulse, such as a pulse falling within the time from when 0 starts to be displaced to reach a position of 1/3 of the gap length, or a timing at which pressure oscillation is canceled. With the pulse width, the diaphragm 50 does not have a restoring force enough to eject ink droplets, and therefore only the meniscus in the nozzle 44 vibrates without ejecting ink droplets.

Also, it is possible to vibrate only the meniscus in the nozzle 44 without ejecting ink droplets by increasing the pulse falling time and slowly restoring the displacement of the diaphragm 50. By actively utilizing these characteristics, clogging of nozzles due to thickening of ink can be prevented.

Next, an outline of a control section of the ink jet recording apparatus will be described with reference to FIG. The control unit includes a microcomputer (hereinafter, referred to as a “CPU”) 80 for controlling the entire recording apparatus, a ROM 81 storing required fixed information, a RAM 82 used as a working memory, and the like. An image memory 83 for storing data obtained by processing the transferred image data;
A parallel input / output (PIO) port 84, an input buffer 85, a parallel input / output (PIO) port 86, a waveform generation circuit 87, a head drive circuit 88, and a driver 89
Etc. are provided.

Here, various information such as image data from the host side, various instruction information such as reliability recovery instruction information from an operation panel (not shown) from the host side, and a paper presence / absence sensor for detecting the start and end of the paper are provided to the PIO port 84. , A signal from various sensors such as a home position sensor for detecting the home position (reference position) of the carriage 13 and the like, and a required signal to the host and the operation panel through the PIO port 84. Information is sent.

The waveform generating circuit 87 generates energy for ejecting ink droplets between the diaphragm 50 and the electrode 55 of the ink jet head 40, that is, the diaphragm 5
A drive pulse for displacing 0 to the electrode 55 side at a displacement amount and timing for ejecting the ink droplet and energy for vibrating the meniscus without ejecting the ink droplet are generated.
In other words, a displacement amount and a vibration pulse for displacing the vibration plate 50 toward the electrode 55 at the timing when the meniscus vibrates without ejecting ink droplets are generated in a time series.

The head drive circuit 88 includes a PIO port 86
A driving pulse or the like is applied to the energy generating means (diaphragm 50 and electrode 55) corresponding to each nozzle 44 of the head 14 based on various data and signals given via the. Further, the driver 89 moves and scans the carriage 13 in the main scanning direction by controlling the driving of the main scanning motor 17 and the sub-scanning motor 27 in accordance with the driving data supplied via the PIO port 86, respectively. Is rotated to convey the sheet 3 by a predetermined amount.

Next, a part related to the head drive control means in this control unit will be described with reference to FIG. The head drive control unit includes the CPU 80 and the ROM 8 described above.
1, a main control unit 91 including a RAM 82, peripheral circuits, and the like;
It includes a waveform generation circuit 87, an amplifier 92, a drive circuit (driver IC) 93, and the like.

The main control section 91 supplies data for generating a vibration pulse and a drive pulse to the waveform generation circuit 87 and print signals (serial data) SD, shift clock CLK, and latch to the driver IC 93. Signal L
Give AT etc.

As described above, the waveform generating circuit 87 generates the vibration pulse for vibrating the meniscus surface of the nozzle 44 without discharging the ink droplet from the nozzle 44 to the actuator section of the ink jet head 40 and the energy for discharging the ink droplet. The drive pulses to be generated are generated in time series. The output from the waveform generation circuit 87 is defined as a drive waveform (drive voltage) Pv. This waveform generation circuit 87 has a D / A
By using a converter to perform D / A conversion of voltage data supplied from the main control unit 91, drive pulses having different pulse widths are generated and output in time series.

That is, in this case, as shown in FIG. 9A, the driving waveform Pv is such that two pulses having a pulse width PW2 are used as the vibration pulse Bp, and a pulse having a pulse width PW1 wider than the vibration pulse Bp is used as the driving pulse. Dp, the vibration pulse Bp and the drive pulse Dp are generated in a time series by repeating one head driving cycle. Therefore, by applying the vibration pulse Bp and the drive pulse Dp to the bit (channel) to be driven, it is possible to vibrate the meniscus one or more times (here, twice) before ejecting the ink droplet.

The driver IC 93 selects a drive waveform Pv input in time series in accordance with a print signal, and
Individual electrodes 55 of the inkjet head 40 constituting the
Give to. The driver IC 93 is provided with a shift register 95 for inputting a serial clock CLK from the main controller 91 and serial data SD as a print signal, and a latch for latching a register value of the shift register 95 with a latch signal LAT from the main controller 91. Circuit 96 and latch circuit 9
6 comprises a level conversion circuit 97 for changing the level of the output value, and an analog switch array 98 whose on / off is controlled by the level conversion circuit 97. The analog switch array 98 includes analog switches AS1 to ASm connected to m individual electrodes 55 of the inkjet head 40 (the number of nozzles is m). The diaphragm 50 serving as a common electrode of the inkjet head 40 is grounded.

Then, serial data (print signal) SD is fetched into the shift register 95 in accordance with the shift clock, and the serial data SD fetched into the shift register circuit 95 by the latch signal LAT by the latch circuit 96.
Is latched and input to the level conversion circuit 98. The level conversion circuit 98 turns on / off the analog switch ASm (m = 1 to m) connected to the individual electrode 55 of each actuator according to the content of the data.

This analog switch ASm (m = 1 to
m), the drive waveform Pv is given from the waveform generation circuit 87 via the amplifier 92, so that the analog switch ASm
When (m = 1 to m) is turned on, the drive waveform (the vibration pulse Bp and the ejection pulse Dp) is given to the individual electrode 55.

Next, the operation of the head drive control unit in the ink jet recording apparatus thus configured will be described with reference to FIG.
This will be described with reference to FIG. First, as described above, two vibration pulses Bp having a pulse width PW2 and one driving pulse Dp having a pulse width PW1 are output from the waveform generation circuit 92 within one driving cycle as shown in FIG. 9A. The analog switch AS1 of the driver IC 93 is generated and output in time series.
~ ASm.

Therefore, by giving a print signal from the main control section 91, for example, as shown in FIG. 7B, the analog switch ASn (n = 1 to m) of the driver IC 93 corresponding to the bit for ejecting the ink droplet. Is turned on, and the vibration pulse Bp and the ejection pulse Dp input while the analog switch ASn is on are given to the individual electrodes 55 of the inkjet head 40 as shown in FIG.

FIG. 9C shows a pulse applied to an individual electrode corresponding to one nozzle. Since this nozzle performs printing (driving) in the first driving cycle shown in FIG. After applying the two vibration pulses Bp to vibrate the meniscus twice, the drive pulse Dp is applied to eject the ink droplets. In the next drive cycle, the analog switch ASn is turned off for the entire period and the ejection pulse Dp and the meniscus Neither of the vibration pulses Bp is applied, and printing (driving) is performed in the next driving cycle, so that two vibration pulses Bp are applied to vibrate the meniscus twice, and then a driving pulse Dp is applied and ink droplets are applied. Discharge.

Note that, specifically, the liquid chamber length is about 1000 μm.
m, an ink jet head having a vibration plate thickness of about 2 μm and a nozzle diameter of about 20 μm, and referring to the pulse width characteristics shown in FIG.
The experiment was conducted with the pulse width PW2 of 2 μs, the pulse width of the drive pulse Dp used for ink droplet ejection being 6 μm, the voltage of both pulses being 30 V, and no difference in the ink droplet ejection characteristics regardless of the frequency of application of the drive pulse. Is obtained,
The change in the drop ejection characteristics due to the increase in the viscosity of the ink was reduced.

As described above, by causing the meniscus to vibrate at least once before ejecting the ink droplets and then ejecting the ink droplets, the change in the droplet ejection characteristics due to the thickening of the ink is reduced, and the stable ink droplets are formed. Discharge characteristics can be obtained.

Next, a second embodiment of the present invention will be described with reference to FIG.
0 will be described. In this embodiment, at the time of non-continuous ejection (when ejection is not performed twice or more) and the first ejection of continuous ejection, at least one or more ejection of ink droplets to the diaphragm is performed. A vibration pulse Bp for deforming the meniscus without vibrating and a driving pulse Dp for deforming the vibrating plate to discharge ink droplets are applied, and the driving is performed without applying the vibration pulse Bp in the second and subsequent discharges of the continuous discharge. Only the pulse Dp is applied.

That is, as shown in FIG. 10A, a waveform consisting of two vibration pulses Bp and a drive pulse Dp is given as the drive waveform Pv in the same manner as in FIG. As the SD, the analog switch ASn is turned on for one driving cycle during the first non-continuous discharge and the continuous discharge, and the analog switch ASn is turned off during the two or more vibration pulses Bp during the second and subsequent discharges. That is, during non-printing, a signal for turning off the analog switch ASn for one driving cycle is generated and output.

As a result, the analog switch ASn is turned on for one driving cycle during the first non-continuous discharge and the continuous discharge as shown in FIG. 6B, and as shown in FIG. Two vibration pulses Bp and a drive pulse Dp are continuously applied. On the other hand, in the second and subsequent consecutive ejections, the analog switch ASn is turned off and then turned on during the period corresponding to the vibration pulse Bp, so that only the drive pulse Dp is applied without applying the vibration pulse Bp. Applied.

In this case, even if the vibration pulse is not applied to the bit (the bit to be printed) which continuously discharges the ink droplets from the second time on, the ink viscosity in the nozzle is suppressed by the first ink droplet discharge. Therefore, stable ejection characteristics can be obtained. Rather, unnecessary power consumption and delay of ink refill can be prevented by not applying a vibration pulse.

As described above, when ejecting ink droplets,
After applying one or more vibration pulses that vibrate the meniscus without ejecting ink droplets, apply a drive pulse to eject ink droplets, and do not apply a vibration pulse when ejecting ink droplets continuously. By applying a drive pulse to eject ink droplets, changes in ink droplet ejection characteristics due to thickening of ink are reduced, stable ink droplet ejection characteristics are obtained, and unnecessary electrode consumption and delay of ink refill are reduced. can do.

In this case, the configuration for applying different pulses to the ejection (drive) bit is not limited to the one that changes the opening / closing timing of the switch, as described above. For example, as shown in FIG. 100 array as a driver IC, a first drive waveform P including a vibration pulse Bp and a drive pulse Dp in one of the three-terminal switches 100.
v1 on the other hand, the second drive waveform Pv having only the drive pulse Dp.
2 and switching the three-terminal switch 100 according to the print signal to select the first drive waveform Pv1 for the first non-continuous discharge and the continuous discharge, and the second drive waveform pv2 for the second and subsequent consecutive discharges. It can also be done.

In each of the above embodiments, the vibration pulse B
As for p, two pulses having a pulse width PW narrower than the driving pulse Dp are used, but the driving pulse D shown in FIG.
It is also possible to use one vibration pulse Bp shown in FIG. As described above, by making the vibration pulse a pulse having a pulse width narrower than the drive pulse, pulse generation can be realized with a simple circuit configuration.

As the vibration pulse Bp, as shown in FIG. 6C, the valley portion of the pulse width characteristic shown in FIG. Pulse width, ie, the droplet ejection volume Mj and the droplet ejection speed V
It is possible to use a pulse width in which j is set to a pulse width between the pulse width at the first peak and the pulse width at the next peak. Further, as shown in FIG. 3D, a pulse whose fall is slower than the drive pulse can be used. Alternatively, a pulse having a peak value smaller than that of the drive pulse may be used.

In each of the above-described embodiments, the meniscus vibration is performed by applying a vibration pulse to the vibration plate. In addition, another meniscus vibration may be performed by providing another pressing means. it can. Further, in each of the above-described embodiments, the vibration plate and the liquid chamber are formed of the same member as the flow path substrate in the ink jet head. However, the vibration plate and the liquid chamber forming member may be formed of different members and joined. .

In the ink jet head mounted on the ink jet recording apparatus, the shapes, arrangements, and forming methods of the nozzles, liquid chambers, fluid resistance portions, and common flow path liquid chambers formed in the flow path substrate can be appropriately changed. it can. For example, in the above embodiment, the nozzle is a side shooter type ink jet head formed so that ink droplets are ejected in the direction of displacement of the diaphragm. An edge shooter type inkjet head formed so as to discharge may be used.

[0070]

As described above, according to the ink jet recording apparatus of the present invention, when the ink droplet is ejected, the meniscus is vibrated at least once and then the ink droplet is ejected. As a result, clogging of the nozzle due to thickening of the ink can be prevented, the ink droplet ejection characteristics can be stabilized at a low cost with a simple configuration, and a high-quality image can be obtained.

According to the ink jet recording apparatus of the present invention, when an ink droplet is ejected, a driving pulse for ejecting the ink droplet is applied after applying a vibration pulse for vibrating the meniscus without ejecting the ink droplet. So that the meniscus can be vibrated to prevent clogging of the nozzle due to thickening of the ink.
The ink droplet ejection characteristics can be stabilized at low cost, and a high-quality image can be obtained.

Further, in the ink jet recording apparatus according to the present invention, when an ink droplet is ejected, a driving pulse for ejecting the ink droplet is applied after applying a vibration pulse for vibrating the meniscus without ejecting the ink droplet. When ejecting ink droplets continuously, a driving pulse is applied without applying a vibration pulse, so that the meniscus can be vibrated to prevent clogging of the nozzle due to thickening of the ink. Thus, the ink droplet ejection characteristics can be stabilized at low cost, and a high-quality image can be obtained.

In this case, by making the vibration pulse a pulse having a pulse width narrower than the drive pulse, two vibration pulses and a drive pulse can be easily generated, and the circuit configuration is simplified. Further, by making the vibration pulse a pulse whose fall time is longer than that of the drive pulse, two of the vibration pulse and the drive pulse can be easily generated, and the circuit configuration is simplified. Further, the vibration pulse has a pulse width between the pulse width at which the droplet discharge characteristic reaches the first peak and the pulse width at which the droplet discharge characteristic reaches the next peak, thereby easily generating two vibration pulses and a driving pulse. And the circuit configuration is simplified.

[Brief description of the drawings]

FIG. 1 is a schematic perspective explanatory view of a mechanism section of an ink jet recording apparatus according to the present invention.

FIG. 2 is an explanatory side view of the mechanism.

FIG. 3 is an exploded perspective view of a head of the recording apparatus.

FIG. 4 is an explanatory cross-sectional view of the head in the longitudinal direction of the diaphragm.

FIG. 5 is an enlarged sectional explanatory view of a main part of the head in the transverse direction of the diaphragm;

FIG. 6 is an explanatory diagram for explaining a relationship between a pulse width of a driving pulse of the head, a discharged droplet speed, and a discharged droplet volume.

FIG. 7 is a block diagram showing an example of a control unit of the recording apparatus.

FIG. 8 is a block diagram showing an example of a head drive control unit in the control unit;

FIG. 9 is an explanatory diagram for explaining the operation of the head drive control unit;

FIG. 10 is an explanatory diagram for explaining a second embodiment of the present invention;

FIG. 11 is an explanatory diagram for explaining another example of the embodiment;

FIG. 12 is an explanatory diagram for explaining another example of the vibration pulse;

[Explanation of symbols]

13: carriage, 14: head, 24: transport roller,
33: paper ejection roller, 40: ink jet head, 41
... channel substrate, 42 ... electrode substrate, 43 ... nozzle plate, 44 ...
Nozzle, 46: liquid chamber, 47: fluid resistance part, 48: common flow path liquid chamber, 50: diaphragm, 55: electrode, 56: gap,
87: waveform generation circuit, 91: main control unit, 93, 101,
103: driver IC, 95: shift register, 96:
Latch circuit, 97: level conversion circuit, 98: analog switch array.

Claims (6)

[Claims] A nozzle for discharging ink droplets, an ink flow path communicating with the nozzle, a vibration plate provided in a part of the flow path, and an electrode facing the vibration plate; An ink jet recording apparatus for ejecting ink droplets from said nozzles by deforming a vibration plate by electrostatic force, comprising means for vibrating a meniscus at least once before ejecting ink drops. . A nozzle for ejecting ink droplets, an ink flow path communicating with the nozzle, a vibration plate provided in a part of the flow path, and an electrode facing the vibration plate; In an ink jet recording apparatus that ejects ink droplets from the nozzles by deforming a diaphragm with electrostatic force, when ejecting ink droplets, one or a plurality of vibration pulses that vibrate a meniscus without ejecting ink droplets were applied. And a head drive control unit for applying a drive pulse for ejecting ink droplets. A nozzle for discharging ink droplets, an ink flow path communicating with the nozzle, a vibrating plate provided in a part of the flow path, and an electrode facing the vibrating plate; In an ink jet recording apparatus that ejects ink droplets from the nozzles by deforming a diaphragm with electrostatic force, when ejecting ink droplets, one or a plurality of vibration pulses that vibrate a meniscus without ejecting ink droplets were applied. After that, a head drive control means for applying a drive pulse for discharging the ink droplet and applying a drive pulse for discharging the ink droplet without applying the vibration pulse when continuously discharging the ink droplet is provided. An ink jet recording apparatus characterized by the above-mentioned. 4. The ink jet recording apparatus according to claim 2, wherein the pulse width of the vibration pulse is narrower than that of the drive pulse. 5. The ink jet recording apparatus according to claim 2, wherein a fall time of the vibration pulse is longer than that of the drive pulse. 6. The ink jet recording apparatus according to claim 2, wherein the vibration pulse has a pulse width between a pulse width at which the ink droplet ejection characteristic reaches a first peak and a pulse width at which a next peak occurs. An ink jet recording apparatus, comprising: