JP2002019104A - Ink jet recording - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink jet recorder capable of suppressing increase of a viscosity of ink and preventing clogging of a nozzle at low cost in the electrostatic type ink jet recorder that comprises the nozzle for ejecting ink drops, an ink passage communicating with the nozzle, a diaphragm forming a wall face of the ink passage and an electrode provided in opposition to the diaphragm and ejects the ink drops from the nozzle by deforming the diaphragm by the electrostatic force. SOLUTION: A second driving waveform Bp that generates deformation on the diaphragm whereby the ink drop is not ejected and a meniscus is vibrated is applied to a nozzle which does not eject the ink drop during the driving.

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.

By the way, such an ink-jet head discharges ink droplets from nozzles. Therefore, when the ink viscosity changes depending on the environment, stable ink droplet discharge characteristics (drop speed Vj, droplet volume Mj, bending of the droplet ejection direction) are obtained. Cannot be obtained, and the image quality deteriorates. In addition, when the ink viscosity increases during non-printing as well as the environmental change, 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.

[0005]

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.

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 an increase in ink viscosity and nozzle clogging are reduced at low cost.

[0007]

In order to solve the above problems, an ink jet recording apparatus according to the present invention comprises means for vibrating a meniscus of a nozzle which does not discharge ink droplets at least once when driven.

[0008] The ink jet recording apparatus according to the present invention comprises:
A means is provided for vibrating the meniscus by giving a drive waveform that does not discharge ink droplets to a nozzle that does not discharge ink droplets at least once during driving.

[0009] The ink jet recording apparatus according to the present invention comprises:
A means is provided for vibrating the meniscus by giving a drive waveform at which the ink droplet is not ejected at least once when the ink jet head is in the non-printing area.

Here, the driving waveform in which the ink droplet is not ejected can be a pulse having a narrower pulse width than the driving waveform in which the ink droplet is ejected. Further, the drive waveform in which the ink droplet is not ejected may be a pulse having a longer pulse fall time than the drive waveform in which the ink droplet is ejected. Further, the drive waveform in which the ink droplet is not ejected may be a pulse having a pulse width between the pulse width at which the ink droplet ejection characteristic becomes the first peak and the pulse width at which the ink droplet ejection characteristic becomes the next peak.

[0011]

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 (the direction perpendicular to the plane of FIG. 2) by 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 recording 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 facing downward. Above the carriage 13, ink tanks (ink cartridges) 15 for supplying ink of each color to the recording head 14 are exchangeably mounted.

Here, the carriage 13 is slidably fitted on the main guide rod 11 on the rear side (downstream side in the paper transport direction), and the slave guide rod 1 on the front side (upstream side in the paper transport direction).
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 recording heads 14 of each color are used here as recording heads, a single head having nozzles for ejecting ink droplets of each color may be used. Further, as described later, the ink jet head used as the recording head 14 is an electrostatic head that presses ink by displacing the vibration plate with an electrostatic force between a vibration plate forming an ink flow path wall surface and an electrode opposed thereto. The type is used.

On the other hand, the paper 3 set in the paper feed cassette 4
And a friction pad 22 for separating and feeding the paper 3 from the paper cassette 4, a guide member 23 for guiding the paper 3, and A transport roller 24 that reverses and transports the sheet 3, a transport roller 25 pressed against the peripheral surface of the transport roller 24, and a tip roller 26 that defines an angle at which the sheet 3 is sent out from the transport roller 24 are 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 sent 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 recording head 14 is provided on the right end side in the moving direction of the carriage 13.
Has been arranged. The carriage 13 is moved to the subsystem 37 side during printing standby, and the recording head 14 is capped by a capping unit or the like. Carriage 1
3 is located on the subsystem 37 side when the inkjet head (head 14) is located in the non-printing area.

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

The ink jet head 40 includes a flow channel substrate 41 using a single crystal silicon substrate, a silicon substrate such as an SOI substrate or the like, a silicon substrate provided below the flow channel substrate 41, and a Pyrex (registered trademark) glass substrate. A nozzle 44 for discharging a plurality of ink droplets, a nozzle 44 for discharging a plurality of ink droplets, A common liquid chamber flow path 48 and the like are formed to communicate with the chamber 46 and each of the liquid chambers 46 via a fluid resistance part 47 also serving as an ink supply path.

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 serves 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.
For the formation of the insulating film, the surface of the diaphragm can be thermally oxidized to form an oxide film, or a film forming technique can be used.

Further, 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. Furthermore, the flow path substrate 41 and the electrode substrate 42 can be bonded by eutectic bonding in which a binder such as gold is interposed between bonding surfaces 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 has a discharge surface 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, 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 extends 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.

A joint member 70 for connecting to the ink cartridge 15 is connected to the frame member 65 of the recording head 14, and the ink is supplied from the ink cartridge 15 to the common liquid chamber channel 48 through the ink supply hole 66 through the filter 71. Is supplied.

In the ink-jet head 40, the diaphragm 50 is used as a common electrode, and the electrode 55 is used as an individual electrode (the configuration may be reversed). A driving voltage (driving) is applied between the diaphragm 50 and the electrode 55. (Waveform), the diaphragm 50 is deformed and displaced toward the electrode 55 by an electrostatic force generated between the diaphragm 50 and the electrode 55, and the electric charge between the diaphragm 50 and the electrode 55 is discharged from this state. As a result, the diaphragm 50 is returned and deformed, and the internal volume (volume) / pressure of the liquid chamber 46 changes, so that the nozzle 44
Ink droplets are ejected from.

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 deformed and displaced toward the electrode 55 in accordance with the magnitude of the applied voltage. After that, the applied pulse voltage falls, whereby the diaphragm 50 is restored, and the pressure in the liquid chamber 46 is increased by the restoring force, so that the ink droplet is ejected from the nozzle 44. in this case,
The diaphragm 50 is connected to the electrode 55 (actually, the surface of the insulating protective film 57).
The contact drive method is a method of displacing to the position where it contacts
A method in which the diaphragm 50 is displaced to a position where it does not contact the electrode 55 is referred to as a non-contact drive method.

Here, in the case of driving by the contact driving method, when the diaphragm 50 displaced by the application of the driving waveform voltage reaches the position of １ ／ of the gap length between the diaphragm 50 and the electrode 55, the diaphragm 50 Due to the balance between the mechanical force acting on 50 and the electrostatic force, it comes into contact with the electrode 55. Thereafter, by lowering the applied driving waveform, the displacement of the diaphragm 50 is restored, and the ink droplets are ejected by the restoring force as described above.

As shown in FIG. 6, when a pulse-like drive waveform is applied, after the diaphragm 50 contacts the electrode 55, if the pulse width of the drive waveform is increased, the current waveform oscillates. The vibration is attenuated (hereinafter referred to as “residual vibration”).

Looking at the relationship between the residual vibration and the ink droplet ejection characteristics, as shown in FIG. 7, the pulse is cut at any timing of the residual vibration seen in the residual vibration waveform of FIG. It can be seen that the ink droplet ejection characteristics (ejection droplet speed Vj, ejection droplet mass Mj) vary depending on whether the ink droplets fall.

In the example shown in FIG. 7, when the pulse width PW of the driving waveform is set to be smaller than 4 μsec, the pulse width at which the discharge droplet speed Vj and the discharge droplet volume Mj become the first peak and the next pulse width are obtained. In the case where the pulse width is set to a pulse width between the two pulse widths, it can be seen that no ink droplet is ejected.

That is, the application of the pulse voltage causes the diaphragm 5
A short-time (narrow pulse width PW) 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 out With the pulse width PW, 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 reduced.

Next, the outline of the 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.

The PIO port 84 receives various information such as image data from the host, various instruction information such as reliability recovery instruction information from an operation panel (not shown), and a paper presence / absence sensor for detecting the start and end of the paper. , 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 vibration plate 50 and the electrode 55 of the ink jet head 40, that is, the vibration plate 5
0 is displaced to the electrode 55 side at the displacement amount and timing at which the ink droplet is ejected, and a first drive waveform to be restored and energy for vibrating the meniscus without ejecting the ink droplet are generated. And a second drive waveform for displacing and restoring to the electrode 55 side at the timing when the meniscus vibrates without ejecting ink droplets and at the timing.
Generate and output in chronological order.

The head drive circuit 88 includes a PIO port 86
The first drive waveform or the second drive waveform is applied to the energy generating means (diaphragm 50 and electrode 55) corresponding to each nozzle 44 of the recording head 14 based on various data and signals given via the. Further, the driver 89
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, the carriage 13 is moved and scanned in the main scanning direction, and the transport roller 24 is rotated to rotate the paper 3 Is transported by a predetermined amount.

Next, a part related to head drive control in this control unit will be described with reference to FIG. The head drive control unit includes the CPU 80, ROM 81,
A main control unit 91 including a RAM 82 and peripheral circuits, a waveform generation circuit 87, an amplifier 92, and a drive circuit (driver I
C) 93 and the like.

The main control section 91 supplies data for generating the first drive waveform and the second drive waveform to the waveform generation circuit 87 and print signals (serial data) SD, shift signals to the driver IC 93. A clock CLK, a latch signal LAT, and the like are provided.

As described above, the waveform generation circuit 87 generates the first driving waveform for generating energy for discharging the ink droplets from the nozzles 44 to the actuator section of the ink jet head 40, and the meniscus without discharging the ink droplets from the nozzles 44. A second drive waveform for vibrating the surface is generated in time series. The output from the waveform generation circuit 87 is defined as a drive waveform (drive voltage) Pv. The waveform generation circuit 87 uses a D / A converter to perform D / A conversion on voltage data supplied from the main control unit 91 to generate and output drive waveforms having different pulse widths in time series.

That is, here, as shown in FIG. 10A, the drive waveform Pv has a first drive pulse Dp which is a first drive waveform having a pulse width PW1 and a pulse width narrower than the first drive pulse Dp. Two second drive pulses Bp, which are the second drive waveforms of the pulse width PW2, are generated in a time series repeated in one drive cycle of the head. Therefore, the meniscus can be vibrated one or more times (here, twice) by giving the second drive pulse Bp to the nozzles (the channels that are not driven) that do not eject ink droplets.

The driver IC 93 selects the first drive pulse Dp or the second drive pulse Bp from the drive waveform Pv input in time series according to the print signal, and selects each of the individual ink jet heads 40 constituting the recording head 14. It is applied to the electrode 55. 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 96
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, a print signal (serial data) SD is taken into the shift register circuit 95 according to the shift clock CLK, and the latch circuit 96 latches the latch signal LAT.
Thus, the print signal SD captured by the shift register circuit 95 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) is supplied with the drive waveform Pv from the waveform generation circuit 87 via the amplifier (AMP) 92. Therefore, when the analog switch ASm (m = 1 to m) is turned on, the drive waveform Pv
(The first drive pulse Dp or the second drive pulse Bp) is applied to the individual electrode 55.

Next, FIG. 10 shows the first embodiment of the present invention in the ink jet recording apparatus thus configured.
This will be described with reference to FIG. First, as described above, from the waveform generation circuit 87, as shown in FIG. 10A, the first drive pulse Dp having the pulse width PW1 and the two second drive pulses Bp having the pulse width PW2 within one drive cycle are output. Are generated and output in time series, and this is the analog switch A of the driver IC 93.
S1 to ASm.

Therefore, by supplying a print signal SD from the main control unit 91 at the time of driving, for example, as shown in FIG. 3B, the analog switch ASn () of the driver IC 93 corresponding to the bit (channel) for ejecting ink droplets. n
= 1 to m) is turned on and the analog switch AS
The first drive pulse Dp or the second drive pulse Bp input while n is on is applied to the individual electrode 55 of the inkjet head 40 as shown in FIG.

FIG. 10C shows a pulse applied to the individual electrode 55 corresponding to one nozzle 44 at the time of driving, and this nozzle 44 is driven in the first driving cycle shown in FIG. Because it is printing (driving), the first
When the drive pulse Dp is given, ink droplets are ejected, and in the next drive cycle, printing is not performed (ink droplets are not ejected). Therefore, the analog switch ASn is turned off and the second drive pulse B
Give p to vibrate the meniscus of the nozzle.

Note that, specifically, the liquid chamber length is about 1000 μm.
m, a diaphragm thickness of about 2 μm, and a nozzle diameter of about 20 μm. A first drive pulse D used for ink droplet ejection is manufactured by referring to the pulse width characteristics shown in FIG.
The experiment was performed with the pulse width of p set to 6 μm for PW1, the pulse width PW2 for the second drive pulse Bp used for meniscus oscillation to 2 μs, and the voltage to 30 V for both pulses. No ink droplet ejection characteristics were obtained, and it was confirmed that the change in the droplet ejection characteristics due to the increase in ink viscosity was reduced.

Since means for oscillating the meniscus of the nozzle that does not eject ink droplets during driving as described above is provided, for example, even with a nozzle having a low ink ejection frequency, the change in the droplet ejection characteristics due to thickening of the ink is reduced. Stable ink droplet ejection characteristics can be obtained. As a result, dot disturbance immediately after the start of printing is eliminated, and a good printed image with high dot position accuracy is obtained. In this case, by applying a drive waveform that does not eject ink droplets to vibrate the meniscus, it is possible to reduce the drop in ink droplet ejection characteristics due to thickening of ink with a simple configuration and at low cost.

Next, a second embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG. In this embodiment, when the meniscus of the non-ejection nozzle (nozzle that does not eject ink droplets) is vibrated during driving in the first embodiment, the carriage 13 is moved to the subsystem 37 side. That is, when the head 14 is in the non-printing area, a process of vibrating the meniscus of all the nozzles 44 is performed.

That is, the timer T1 is set and started when the head 14 is at the print standby position (reliability maintaining / recovering position by the subsystem 37) which is a non-printing position. Perform maintenance and recovery processing. In this reliability maintaining and recovering process, as is known, the suction means is driven while the head 14 is capped by the cap means to suction and discharge the ink from the nozzles 44 of the head 14, thereby discharging the ink having the thickened nozzles 44. Or all nozzles 44
Is driven to eject ink droplets, thereby
To discharge the thickened ink.

Then, after the reliability maintenance / recovery operation, the timer T
1. Set and start T2, determine whether or not there is a print command, and if there is no print command, return to the process of determining whether or not the timer T1 has timed out.

Here, if the timer T1 has not expired, it is determined whether or not the timer T2 has expired. If the timer T2 has expired, the same head as described in the first embodiment is used. The first drive pulse Dp generated and output in time series by the drive control
By selecting only the second drive pulse Bp of the drive pulses Bp and applying the selected drive pulse Bp to the head 14, only the meniscus vibration is performed during the reliability maintaining / recovering operation to suppress the viscosity increase of the ink in the nozzles 44. Do.

As described above, as a part of the reliability maintenance / recovery operation, by performing the maintenance / recovery process in which only the meniscus vibration is performed without ejecting the ink droplets every predetermined time, the increase in the viscosity of the ink can be suppressed. It is possible to reduce the number of times of the maintenance / recovery processing accompanied by the ejection of the droplets (the number of times of the cleaning operation), thereby reducing wasteful ink consumption.

The head drive for the meniscus vibration is generated in time series with the first drive waveform and the second drive waveform.
By selecting only the second drive waveform from the drive waveforms and applying it to the head, the configuration is simplified and the cost can be reduced. Further, it can be combined with the configuration in which the meniscus vibration is performed even during the printing operation (during driving) as in the above-described embodiment, whereby the viscosity increase of the ink can be suppressed at low cost.

Returning to FIG. 11, when a print command is given, meniscus vibration is performed immediately before the start of the printing operation to recover the ink viscosity in the nozzle 44, and then the printing process is started. Thus, stable printing can be started quickly.

Next, a third embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG. In this embodiment, the meniscus vibration in the non-printing area of the head is performed as part of the reliability maintenance / recovery operation in the above-described second embodiment. The head 14 is moved to the non-printing area on the subsystem 37 side, and the meniscus vibration (1
Or multiple times), the head 1 is scanned for the next scan.
4 is moved to the print area. It should be noted that not all the nozzles that perform meniscus vibration may be divided into a plurality of regions (nozzle groups), and the meniscus vibration of the nozzles of the nozzle groups may be sequentially performed for each scan.

Also in this case, it is possible to prevent the ink droplet ejection characteristics from being deteriorated due to the increase in the viscosity of the ink, to reduce the number of times of the reliability maintenance / recovery operation, and to reduce wasteful ink consumption.

In the above embodiments, the first drive waveform and the second drive waveform output in time series are used. However, the present invention is not limited to this. For example, as shown in FIG. An array of terminal switches 100 is used as a driver IC, and a first drive pulse Dp is applied to one of the three-terminal switches 100 and a second drive pulse Bp is applied to the other. 14
Can be selected.

In each of the above embodiments, FIG.
As shown in FIG. 14, two pulse driving pulses Bp having a pulse width PW narrower than the driving pulse Dp for meniscus vibration are used, but the pulse width PW of the first driving pulse Dp shown in FIG. It is also possible to use one narrow second drive pulse Bp shown in FIG. As described above, the second drive pulse Bp has a pulse width PW smaller than the first drive pulse Dp.
By using narrow pulses, pulse generation can be realized with a simple circuit configuration.

As shown in FIG. 7D, the second drive pulse Bp has a valley portion of the pulse width characteristic shown in FIG. 7 (the residual pressure vibration when the diaphragm 55 is pulled and the vibration of the diaphragm 55). Pulse width PW, ie, the pulse width between the pulse width at which the droplet ejection volume Mj and the droplet ejection speed Vj become the first peak and the pulse width at which the droplet ejection speed becomes the next peak. What is set to PW can also be used. Further, as shown in FIG. 3C, a pulse whose fall is made slower (the fall time is longer) than the first drive pulse Dp can be used.

In each of the above embodiments, the meniscus vibration is performed using a drive waveform that deforms the diaphragm with a displacement amount and timing that does not discharge ink droplets. Vibration means for vibrating the ink in the room may be provided to perform meniscus vibration. Further, in the above-described embodiment, the diaphragm and the liquid chamber are formed of the same member as the flow path substrate in the ink jet head, but the diaphragm and the member forming the liquid chamber are formed by different members and joined. You can also.

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, but the nozzle is moved in the direction intersecting with the direction of displacement of the diaphragm. May be an edge shooter type inkjet head formed so as to discharge ink.

[0073]

As described above, according to the ink jet recording apparatus of the present invention, the means for vibrating the meniscus of the nozzle which does not eject ink droplets at least once at the time of driving is provided. Fluctuations in the ink droplet ejection characteristics due to thickening of the ink can be suppressed even in nozzles that eject less frequently, and disturbance of the printed image can be prevented, so that a higher quality image can be obtained.

The ink jet recording apparatus according to the present invention is provided with a means for vibrating the meniscus by giving a drive waveform that does not discharge ink droplets to the nozzles that do not discharge ink droplets at least once, when driving, so that the meniscus is vibrated. At cost,
Fluctuations in ink droplet ejection characteristics due to thickening of ink can be suppressed even for nozzles that do not eject ink frequently.
Disturbance of the printed image can be prevented, and a higher quality image can be obtained.

According to the ink jet recording apparatus of the present invention, there is provided means for vibrating the meniscus by giving a drive waveform at which the ink droplet is not ejected at least once when the ink jet head is in the non-printing area. so,
It is possible to eliminate dot disturbance immediately after printing starts,
A good printed image with high dot position accuracy can be obtained, and the disturbance of the image is reduced, the number of operations for maintaining and recovering the reliability is reduced, and wasteful ink consumption can be reduced. Can be planned together.

In this case, the drive waveform that does not eject ink droplets is a pulse whose pulse width is narrower than the drive waveform that ejects ink droplets, or has a longer fall time, or the first droplet ejection characteristic is By using a pulse having a pulse width between the pulse width that becomes the peak and the pulse width that becomes the next peak, two types of driving waveforms can be easily generated.

[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 illustrating a relationship among a pulse width, a current waveform, and a pulse voltage of a drive waveform of the head.

FIG. 7 is an explanatory diagram for explaining a relationship between a pulse width of a driving waveform of the head, a droplet speed, and a droplet volume.

FIG. 8 is a block diagram illustrating an example of a control unit of the recording apparatus.

FIG. 9 is a block diagram showing an example of a head drive control unit in the control unit;

FIG. 10 is an explanatory diagram for explaining a first embodiment of the present invention in the recording apparatus.

FIG. 11 is a flowchart for explaining a second embodiment of the present invention;

FIG. 12 is a flowchart for explaining a third embodiment of the present invention;

FIG. 13 is an explanatory diagram for explaining another example of the head drive control unit in the recording apparatus.

FIG. 14 is an explanatory diagram for explaining another different example of a driving waveform that does not eject ink droplets;

[Explanation of symbols]

13: carriage, 14: recording head, 24: transport roller, 33: discharge roller, 40: inkjet head,
41: channel substrate, 42: electrode substrate, 43: nozzle plate, 4
4 Nozzle, 46 liquid chamber, 47 fluid resistance section, 48 common flow path liquid chamber, 50 diaphragm, 55 electrode, 56 gap, 87 waveform generation circuit, 91 main control section, 60 93
... Driver IC, 95 ... Shift register, 96 ... Latch circuit, 97 ... Level conversion circuit, 98 ... Analog switch array.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2C057 AF72 AG14 AM03 AM17 AM21 AM32 AN01 AP02 AP25 AP27 AP28 AP34 AP38 AP56 AP60 AQ01 AQ02 AQ06 AR08 BA03 BA15

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; In an ink jet recording apparatus having an ink jet head for ejecting ink droplets from the nozzles by deforming the diaphragm with electrostatic force, a means for vibrating a meniscus of a nozzle that does not eject ink droplets at least once when driving is provided. Characteristic inkjet recording device. A plurality of nozzles for discharging ink droplets, an ink flow path communicating with the nozzles, a vibration plate provided in a part of the flow path, and an electrode facing the vibration plate. In an ink jet recording apparatus including an ink jet head that discharges ink droplets from the nozzles by deforming the vibration plate with electrostatic force, a drive waveform that does not discharge ink droplets to nozzles that do not discharge ink droplets when driven is performed once. An ink jet recording apparatus comprising means for vibrating the meniscus given above. A plurality of nozzles for ejecting ink droplets, an ink flow path communicating with the nozzles, a vibration plate provided in a part of the flow path, and an electrode facing the vibration plate. In an ink jet recording apparatus including an ink jet head that discharges ink droplets from the nozzles by deforming the vibration plate with electrostatic force, a drive waveform in which ink droplets are not discharged when the ink jet head is in a non-printing area is output once. An ink jet recording apparatus comprising means for vibrating the meniscus given above. 4. The ink-jet recording apparatus according to claim 2, wherein a drive waveform from which the ink droplet is not ejected has a pulse width narrower than a drive waveform from which the ink droplet is ejected. 5. The ink jet recording apparatus according to claim 2, wherein a drive waveform in which the ink droplet is not ejected has a longer pulse fall time than a drive waveform in which the ink droplet is ejected. Recording device. 6. The ink jet recording apparatus according to claim 2, wherein the drive waveform in which the ink droplet is not ejected is a pulse width in which an ink droplet ejection characteristic has a first peak and a pulse width at which a next peak occurs. An ink jet recording apparatus having a pulse width between the two.