JP2002113863A - Ink jet recorder and apparatus for controlling driving head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that a discharge quantity of ink drops cannot be efficiently controlled to a driving voltage. SOLUTION: A deformed diaphragm 50 is recovered in a time while a pressure change inside a pressure chamber 46 brought about after the diaphragm 50 contacts an electrode 55 generates a positive pressure.

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 a head drive control apparatus, and more particularly to an ink jet recording apparatus equipped with an electrostatic ink jet head and a head drive control apparatus for driving and controlling the 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 vibrating plate forming a wall surface of the ink flow path, and an electrode opposed to the vibrating plate. 2. Description of the Related Art There is known an ink jet head equipped with an electrostatic ink jet head that ejects ink droplets from nozzles by deforming and displacing.

As a method of driving a head in a conventional ink jet recording apparatus, for example, as described in JP-A-9-39235, a head is formed between a diaphragm and a wall (electrode) facing the diaphragm. Configuration of the gap part
In some cases, a large gap, a middle gap, and a small gap are separately formed in a stepwise manner so that the ink droplet ejection amount can be controlled, and drive waveforms having different drive voltage values are applied to the inkjet head. .

Further, as described in, for example, Japanese Patent Application Laid-Open No. 10-193610, in order to control the amount of ink ejected from an ink-jet head, the pulse width of a pulse There is known an apparatus in which the discharge amount is variably controlled.

[0005]

However, in the above-described ink jet head in which the gap between the diaphragm and the electrode is formed in a step shape, the head configuration is complicated in the first place, and the manufacturing process is complicated. In addition, when controlling the ink ejection amount by mounting the inkjet head, it is necessary to apply complicated drive waveforms having different drive voltage values, and the configuration of a drive circuit for generating such drive waveforms is also required. It becomes complicated and costly. Further, since the ink ejection amount changes only by the volume change in the step-shaped gap portion, it is difficult to control the ink ejection amount to be able to greatly change several times, and the control range of the ink ejection amount is very large. narrow.

Further, since the ejection speed of the ink droplet has a property of changing according to the magnitude of the ink ejection amount of one droplet, generally, when printing with a larger ink ejection amount is desired, the ink is generally used. There is a problem that it becomes difficult to print at a higher speed or land an ink droplet at a desired position on a recording medium because a desired ink discharge speed cannot be obtained due to a decrease in the droplet discharge speed. .

Further, in an apparatus for changing the pulse width of the pulse waveform of the head driving means to change the ink discharge amount, the pixel (dot) shape obtained by changing the ink discharge amount greatly changes to an oblique elliptical shape. However, even if the pulse width is changed, the pixel shape changes non-uniformly. In particular, since the change in the pixel width direction is constant, a good pixel shape or image cannot be obtained even if the ink ejection amount is increased. .

Also, in this case, when printing is performed with a large ink ejection amount as described above, a desired constant ink droplet ejection speed cannot be obtained. There is a problem that the problem described above occurs. In order to avoid this problem, when the pulse width of the pulse waveform is changed, it is necessary to adjust the voltage value of the pulse waveform and the like so as to obtain a desired ink droplet ejection speed.

Further, in the conventional ink jet recording apparatus, it is insufficient to understand the driving method peculiar to the ink jet head for controlling the ink ejection amount at a timing which is efficient with respect to the driving voltage.

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 and a head drive control apparatus capable of obtaining stable ejection characteristics of ink droplets at an efficient timing.

[0011]

In order to solve the above-mentioned problems, in the ink jet recording apparatus according to the present invention, the pressure fluctuation in the ink flow path generated after the diaphragm comes into contact with the electrode is a positive pressure. In this configuration, the diaphragm is restored within a period of time, and means for ejecting ink droplets is provided.

Here, the diaphragm is restored at a timing when the change in the charging / discharging current generated between the diaphragm and the electrode becomes substantially zero during the time when the pressure fluctuation in the ink flow path is a positive pressure. Preferably.

Further, a pulse-like drive waveform is applied between the diaphragm and the electrode, and the pulse width of the drive waveform is restored within a time when the pressure fluctuation in the ink flow path becomes a positive pressure. It is preferable to set the pulse width.

In this case, it is preferable that a pulse-like drive waveform is applied a plurality of times within one pixel, and the diaphragm is restored a plurality of times within a period in which the pressure fluctuation in the ink flow path is a positive pressure. Note that “within one pixel” has the same meaning as “within one drive cycle”.

Here, a plurality of pressure waves can be generated by restoring the diaphragm a plurality of times within one pixel, and one ink droplet can be ejected by superimposing the plurality of pressure waves. Also,
A plurality of pressure waves can be generated by restoring the diaphragm a plurality of times within one pixel, and a plurality of ink droplets can be separately ejected from the nozzle for each pressure wave. In this case, a plurality of ink droplets separately ejected from the nozzle can be integrated during flight.

The head drive control device according to the present invention generates and outputs a drive waveform for restoring the diaphragm within a time period in which the pressure fluctuation in the ink flow path generated after the diaphragm contacts the electrode is positive. It is configured to include means for performing

Here, the diaphragm is restored at a timing when the change in the charging / discharging current generated between the diaphragm and the electrode becomes substantially zero during the time when the pressure fluctuation in the ink flow path is a positive pressure. It is preferable to generate and output a driving waveform to be generated.

Further, it is also possible to generate and output a drive waveform for restoring a diaphragm deformed in one pixel a plurality of times. Note that “within one pixel” has the same meaning as “within one drive cycle”. In this case, a plurality of pressure waves can be generated by restoring the diaphragm a plurality of times within one pixel, and a drive waveform can be generated and output so that a plurality of pressure waves are superimposed to eject one ink droplet. In addition, a plurality of pressure waves can be generated by restoring the diaphragm a plurality of times within one pixel, and a drive waveform for separating and discharging ink droplets from the nozzle can be generated and output for each pressure wave. In this case, it is also possible to generate and output a drive waveform that integrates a plurality of ink droplets separately ejected from the nozzle during flight.

[0019]

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 includes a carriage movable in the main scanning direction inside the recording apparatus main body 1, an ink jet head including an ink jet head mounted on the carriage, an ink cartridge for supplying ink to the ink jet head, and the like. The paper feed cassette 4 or the manual feed tray 5 takes in the paper 3, and records the required image by the print mechanism 2, and then the output tray mounted on the rear side. 6 is discharged.

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 ink jet head for discharging ink droplets of each color of yellow (Y), cyan (C), magenta (M), and black (Bk) with the ink droplet discharge direction facing 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 on the main guide rod 11 on the rear side (downstream side in the paper transport direction), and the front side (upstream side in the paper transport direction) on 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 head 14 of each color is used here as the ink jet head, a single head having a nozzle for ejecting ink droplets of each color may be used. Further, the head 14 is an electrostatic ink jet head that presses ink by displacing the vibration plate with an electrostatic force between the vibration plate forming the ink flow path wall surface and an electrode (electrode portion) facing the vibration plate.

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 sent from the transport roller 24 below the ink jet head 40 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, the conveying roller 3 that is driven to rotate in order to send out the sheet 3 in the sheet discharging direction.
1, a spur 32 is provided, and further, a paper discharge roller 33 and a spur 34 for sending the paper 3 to the paper discharge tray 6 and guide members 35 and 36 forming a paper discharge path are provided.

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 explanatory cross-sectional view of the inkjet head in the longitudinal direction of the diaphragm, and FIG. 4 is an enlarged cross-sectional view of a main part of the head in the lateral direction of the diaphragm.

This ink jet head includes a first substrate 41 which is a flow path substrate, a second substrate 42 which is an electrode substrate provided below the first substrate 41, and a lid provided above the first substrate 41. A nozzle hole 44 for discharging a plurality of ink droplets; a pressurizing chamber 46 serving as an ink flow path communicating with the nozzle holes 44; and each pressurizing chamber 46 also serves as an ink supply path. A common liquid chamber flow path 48 and the like communicating with each other via the fluid resistance part 47 are formed.

As the first substrate 41, a single crystal silicon substrate is used, a nozzle hole 44 is formed at one end, and a pressurizing chamber 46 communicating with the nozzle hole 44 and a bottom portion which is a wall surface of the pressurizing chamber 46 are formed. , A groove forming the fluid resistance portion 47, and a recess forming the common liquid chamber flow path 48.

The use of a single-crystal silicon substrate as the first substrate 41 facilitates processing when the thin diaphragm 50 having a thickness of about several μm is formed by etching, and has a very small size of about several μm. The gap can be formed with high accuracy by anodic bonding with the second substrate 42. Further, when the diaphragm 50 is vibrated, it is necessary to apply a voltage to the electrode to generate an electrostatic force. However, since silicon is semiconductive, the diaphragm 50 can also serve as an electrode. Therefore, there is an advantage that there is no need to provide a separate electrode on the diaphragm 50 side.

A recess 54 is formed in the second substrate 42 by using Pyrex (registered trademark) glass (borosilicate glass). The electrode 55 is formed by, for example, sputtering gold or the like, and an actuator section is constituted by the diaphragm 50 and the electrode 55. Note that the electrode 55 extends outside to integrally form an electrode terminal portion 55a. Further, the use of Pyrex glass for the second substrate 42 facilitates anodic bonding with the silicon substrate.

On the surface of the electrode 55, a dielectric insulating layer (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 used to improve the durability of the electrode 55. Although the electrode protection film 57 is formed, the electrode protection film 57 is not formed on the surface of the electrode 55, or the electrode protection film 57 is formed on the surface of the electrode 55 and the insulating film is formed on the diaphragm 50 side. Can also.

As the third substrate 43, a stainless steel substrate is used, and the third substrate 43 is bonded to the first substrate 41 with an adhesive. By the bonding of the third substrate 43, the nozzle holes 44 and the ink discharge chambers 4 are formed.
6, the fluid resistance part 47 and the common liquid chamber flow path 48 are configured. Further, an ink supply port 61 for supplying ink to the common liquid chamber flow path 48 from outside is formed in the third substrate 43, and the above-described ink is supplied through an ink supply pipe 62 connected to the ink supply port 61. Ink is supplied from the cartridge 15.

Next, a method of joining the first substrate 41 and the second substrate 42 will be described. A small gap of about several μm is formed with high precision like an electrostatic inkjet head,
As a method of assembling (joining), it is preferable to use an anodic bonding method. This anodic bonding method can be expected to ensure the dimensional accuracy of the gap more than other bonding methods (brazing, fusion welding, etc.), and a voltage is applied between the first substrate 41 and the second substrate 42 (− By applying about 300 V to -500 V), precise bonding can be performed at a relatively low temperature (300 to 400 ° C.).

In order to reliably perform such anodic bonding, the first substrate 41 or the second substrate 42 is so formed that covalent bonding between the substrates occurs at the bonding interface between the first substrate 41 and the second substrate 42. Either must be a substrate that contains a large amount of alkali ions, and when anodic bonding, a material whose coefficient of thermal expansion is relatively consistent between substrates so that distortion between the substrates due to thermal stress is reduced. It is preferable to select.

In this embodiment, as described above, a single crystal silicon substrate is used for the first substrate 41, and a large amount of alkali ions such as Na is contained in the second substrate 42, and the thermal expansion coefficient of the silicon substrate is relatively equal to that of the silicon substrate. Since a Pyrex glass (borosilicate glass) substrate is used, reliable bonding with little thermal distortion between the substrates can be obtained.

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 from an operation panel (not shown), a detection signal from a paper presence / absence sensor for detecting the start and end of the paper, Signals from various sensors such as a home position sensor for detecting a home position (reference position) are input.
Required information is transmitted to the host and the operation panel via the port 84.

The waveform generating circuit 87 generates a driving waveform between the vibration plate 50 and the electrode 55 of the head 14 such that the vibration plate 50 is displaced toward the electrode 55 with a displacement amount enough to eject ink droplets and at a timing. appear. By using a D / A converter for D / A converting the drive waveform data from the CPU 80 as the waveform generation circuit 87, a required drive waveform can be generated and output with a simple configuration.

The head drive circuit 88 includes a PIO port 86
The driving waveform is applied to the energy generating means (diaphragm 50 and electrode 55) corresponding to each nozzle hole 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 portion of the control section relating to the head drive control section as the head drive control apparatus according to the present invention will be described with reference to the block diagram of 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 drive waveform to be applied to the head to the waveform generation circuit 87, and print signals (serial data) SD, shift clock CLK, A latch signal LAT and the like are provided. As described above, the waveform generation circuit 87 generates a drive waveform that generates energy for ejecting ink droplets from the nozzles 44 to the actuator section of the inkjet head in a time series. That is, the main control unit 91 and the waveform generation circuit 87 constitute a means for generating and outputting a drive waveform.

The driver IC 93 is a control means for selecting a drive waveform input in time series in accordance with a print signal and controlling the selection of the drive waveform applied to each individual electrode 55 of the ink jet head constituting the head 14. That is, the driver IC 9
Reference numeral 3 denotes a shift register 95 for inputting a serial clock CLK and a serial signal SD as a print signal from the main control unit 91, and a latch circuit 96 for latching a register value of the shift register 95 with a latch signal LAT from the main control unit 91. A level conversion circuit 97 for changing the level of the output value of the latch circuit 96;
And an analog switch array 98 whose turning-off is controlled. 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 ink jet head 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) is supplied with a drive waveform from the waveform generation circuit 87 via the amplifier 92, so that the analog switch ASm (m = m)
1 to m) are turned on, the drive waveform is selectively applied to the individual electrodes 55.

Next, the operation of the ink jet head will be described with reference to FIGS. When a positive pulse voltage is applied to the electrode 55 from the head drive circuit 88, the surface of the electrode 55 is charged to a positive potential, and the lower surface of the diaphragm 50 facing the electrode 55 is charged to a negative potential. I do. Therefore, as shown by the arrow in FIG. 7A, the diaphragm 50 is caused to act on the electrode 55 facing the diaphragm 50 by an electrostatic attraction function (electrostatic attraction force).
Deflection in the direction. Here, the magnitude P of the electrostatic attraction force generated on the diaphragm 50 is expressed by the following equation (1).

[0047]

(Equation 1)

In the equation (1), ε is the permittivity of the air existing between the diaphragm 50 and the electrode 55, S is the effective area of the electrostatic force acting between the diaphragm 50 and the electrode 55,
V indicates a drive voltage value applied to the electrode 55, and d indicates an effective gap distance between the diaphragm 50 and the electrode 55.

Here, the effective gap distance d is expressed by equation (2) when a substance having a dielectric constant other than air is interposed between the diaphragm 50 and the electrode portion 55.

[0050]

(Equation 2)

[0051] However, in the equation (2), a dielectric insulating layer between the d _a diaphragm 50 and the distance of the gap existing between the electrodes 55, the d _epsilon diaphragm 50 and the electrode portion 55 5
The thickness of 7 and ε _r indicate the relative permittivity of the dielectric insulating layer 57.

That is, when a substance having a certain dielectric constant is interposed between the diaphragm 50 and the electrode 55, as shown in the equation (2), the thickness d _{ε of the} interposed dielectric substance and the dielectric substance By changing the relative permittivity ε _r of
Electric field intensity E (E (E) generated between diaphragm 50 and electrode 55
= V / d), and the magnitude P of the electrostatic attraction force generated thereby changes.

Therefore, as shown in the equation (1), the magnitude P of the electrostatic attractive force is such that the smaller the effective gap distance d between the diaphragm 50 and the electrode 55 is, the larger the electrostatic attractive force is on the diaphragm 50. Works. Further, as the drive voltage value V to the electrode 55 is increased, the diaphragm 50 bends toward the electrode 55, and as shown in FIGS.
Side is in contact via a dielectric insulating layer 57. The state where the diaphragm 50 is in contact with the electrode 55 in this manner is referred to as a contact state.

When the application of the pulse voltage, which is a pulse-like voltage, to the electrode 55 is turned off, FIGS.
As shown in (2), the flexed (deformed) diaphragm 50 is restored, and the pressure in the pressurizing chamber 46 rises sharply, so that ink droplets 65 are formed from the nozzle holes 44 and the ink is directed toward the paper 3. Drops 65 are ejected. When a pulse voltage is applied to the electrode 55 (ON), the diaphragm 50 bends again in the direction of the electrode section 55, so that the ink flows from the common liquid chamber flow path 48 through the fluid resistance section 47 to the pressure chamber 46. Will be replenished within.

Next, a first embodiment relating to head drive control in the ink jet recording apparatus thus configured will be described with reference to FIGS. First, FIG.
As shown in (a), the pulse-like voltage V of the drive voltage value V1
Is applied to the electrode 55, each time point t of the pulsed voltage V
The meniscus in the nozzle hole 44 serving as a non-ejection nozzle (meaning a nozzle that does not eject ink droplets) at 0 to t7 vibrates as shown in FIG. Further, the diaphragm 50
During the contact state (while the diaphragm 50 is in contact with the electrode 55), the current value oscillates positively and negatively as shown in FIG. It is observed that a charge / discharge current is flowing. Further, the pressure in the pressurizing chamber 46 is observed to fluctuate in the positive and negative directions as shown in FIG.

As described above, when the pulse-like voltage V1 is applied, the vibration phenomenon occurs in the meniscus, the diaphragm-electrode current (charge / discharge current), and the pressure in the pressurizing chamber. As described with reference to FIG.
At the same time when the diaphragm 50 is bent in the five directions to be in the contact state, ink flows into the pressurizing chamber 46 from the nozzle hole 44 side and the fluid resistance part 47 side, and the diaphragm 50 is in the contact state by the flow of each ink. It was found through experiments that a strong pressure wave was generated in the pressurizing chamber 46.

Further, the pulse width (voltage application time) of the pulse-like voltage is determined from time t1 to time t7 with reference to time t0 in FIG.
When it is changed to the above, the discharge characteristic value of the ink droplet (the discharge speed Vj and the discharge amount of the ink droplet = drop volume Mj) changes as shown in FIG. That is, it has been confirmed by experiments that the ejection characteristic value of the ink droplet fluctuates greatly by changing the pulse width.

Here, it was experimentally confirmed that the oscillation cycle of the ink droplet ejection characteristic value corresponds to the oscillation cycle of the pressure fluctuation in the pressurizing chamber 46. That is, as shown in the pressure fluctuation waveform of the pressurized chamber shown in FIG.
From time t1 to time t1, the inside of the pressurizing chamber 46 is in a negative pressure state. In this case, as shown in FIG.
Is canceled by the negative pressure P2 generated in the pressurizing chamber 46, and acts in a direction in which the ink flow velocity in the direction of the nozzle hole 44 decreases, so that the negative pressure P2 is in a stronger time region (time t0 to t0). During t1), a state occurs in which no ink droplet is ejected.

Further, since the diaphragm 50 is in the contact state at the time t1, a positive current generated at the time of the contact at the time ta as shown in the charge / discharge current waveform shown in FIG. 9C flows. In addition, since the pressure fluctuation value (negative pressure P2) becomes zero, ink droplet ejection is started. Further, the pressure chamber 46 is in a positive pressure state from the time point t1 to the time point t3. In this case, as shown in FIG.
A state occurs in which the positive pressure P3 generated in the pressurizing chamber 46 is superimposed, and the ink flow speed in the direction of the nozzle hole 44 is increased.

Therefore, in this ink jet head, after the diaphragm 50 is in the contact state (after the contact).
The discharge characteristic value of the ink droplet fluctuates in accordance with the magnitude of the positive and negative pressure fluctuations generated in the pressurizing chamber 46, and the positive pressure P3 in the pressurizing chamber 46 peaks (maximum) at time t2. The ejection characteristic value of the ink droplet reaches a peak (maximum) corresponding to t6, and the negative pressure P2 in the pressurizing chamber 46 peaks (minimum).
It has been found that the discharge characteristic value of the ink droplet has a peak (minimum value) corresponding to the time point t4 when

Therefore, in the present embodiment, the main control unit 9 utilizes such properties of the ink jet head.
9 (e) to 9 (f) by the waveform generation circuit 87 and FIG.
As shown in FIG. 5, the pressure chamber 4 generated after the diaphragm 50 comes into contact with the pressure chamber 4.
The drive voltage falls in the time region where the pressure fluctuation in 6 is positive pressure (within the positive pressure time: time t1 to t3, time t5 to t7), that is, the deformed diaphragm 50 is restored. Drive waveform (drive pulse) P having pulse width
v1 or the drive waveform Pv2 is generated and output.

As described above, the drive waveform generated and restored by the deformed diaphragm during the time when the pressure fluctuation in the pressurizing chamber generated after the diaphragm comes into contact with the electrode is positive pressure is output and applied. Accordingly, ink droplets can be ejected in a timing region where ejection efficiency of ink droplets is relatively high with respect to a constant drive voltage. Conversely, by adjusting the pulse width of such a pulsed drive waveform while maintaining a constant drive voltage, it is also possible to control the ink droplet ejection characteristic values Mj and Vj.

Here, the pressure chamber 46 as shown in FIG.
The time point t2 in FIG. 9 at which the positive pressure P3 of FIG.
t6 has a property that coincides with the timing (time tb, tc) at which the value of the charging / discharging current flowing and vibrating between the diaphragm 50 and the electrode portion 55 becomes substantially zero, as seen in FIG. Have.

Therefore, utilizing this property, the pressure chamber 46
The pulse width of the diaphragm 50 restored at the timing when the value of the charge / discharge current generated between the diaphragm 50 and the electrode portion 55 becomes substantially zero as described above within the time when the pressure fluctuation in the inside becomes the positive pressure. By using the drive waveform, it is possible to always discharge ink droplets at a timing at which the ink droplet discharge efficiency is the best for a constant drive voltage. The drive waveform P shown in FIG.
v1 is to restore the diaphragm 50 at time t2,
The drive waveform Pv2 shown in FIG.
0 is restored.

Next, a second embodiment relating to head drive control in the above-described ink jet recording apparatus will be described with reference to FIGS. In this embodiment, a driving waveform Pv composed of two driving pulses for one pixel signal is generated and output, and applied to the inkjet head. That is, as shown in FIG. 3A, when a driving waveform Pv composed of two driving pulses is applied to one pixel signal, the ink meniscus oscillates as shown in FIG. The pressure in the pressurizing chamber 46 vibrates as shown in FIG.

The driving pulse is applied to the electrode 55 by the following method.
It is not limited to two times for one pixel signal, and it is also possible to apply three or more times for one pixel signal within the repetition frequency range (within one driving cycle) of the pixel to be printed.

Here, each drive pulse of the drive waveform Pv shown in FIG.
The pulse widths T2 and T6 are set in advance in accordance with the time during which the pressure fluctuation generated in the pressurizing chamber 46 after the contact with the pressure chamber 5 becomes positive pressure. In the case of this ink jet head, the vibration cycle of the pressure fluctuation generated in the pressurizing chamber 46 after the vibration plate 50 abuts is usually a very short cycle of about 10 to 20 μsec. If the drive waveform can follow, it is possible to form ink droplets at a higher drive frequency.

In order to follow the oscillation cycle of such a short pressure fluctuation, a pulse waveform is used. Here, when the rising time T1 and the falling time T3 are changed while keeping the pulse width T2 of the driving pulse constant, the ink droplets increase as the rising time T1 or the falling time T3 increases as shown in FIGS. Discharge characteristic value (discharge speed Vj
And the discharge amount Mj) tend to gradually decrease.

Therefore, the fall time T1 of the drive pulse
When the time is 5 μs or less, the ink droplet can be stably ejected, and the ink droplet can be formed at a higher frequency.
If the fall time T3 of the drive pulse is 6 μs or less, there is no problem because the ink droplet ejection amount Mj can be stably ejected almost uniformly, but more preferably 2 μs or less is the ink droplet ejection speed Vj and the ejection amount Mj. Both of them can be ejected stably and almost unchanged, and ink droplets can be formed at a higher frequency.

As described above, a driving pulse is applied to the electrode 55 twice for one pixel signal by following the positive pressure of the pressure fluctuation generated in the pressurizing chamber 46 as shown in FIG. In this case, two large positive pressure waves PT1 and PT2 can be generated as shown in FIG.

Therefore, when a plurality of pressure waves are generated to eject ink droplets, one pixel (one pixel signal =
One ink droplet is ejected with a plurality of pressure waves (this is referred to as a “first example”) or a plurality of ink droplets is ejected with a plurality of pressure waves (this is referred to as “a first example”). Second example ”). A first example and a second example will be described with reference to FIGS. 16 and 17, taking an example in which ink droplets are ejected by two pressure waves PT1 and PT2.

First, in the first example shown in FIG. 16, a plurality of pressure waves are generated by restoring the diaphragm a plurality of times within one pixel, and a plurality of pressure waves are superposed to eject one ink droplet. It was made. That is, the first pressure wave PT1
Before the ink Pa1 raised from the nozzle hole 44 is ejected separately from the nozzle hole 44, the ink Pa2 raised by the next pressure wave PT2 is overlapped,
The ink droplets Pa are separated and ejected from the nozzle holes 44 to form one ink droplet D1 which lands on the paper 3 to form a dot D1 'on the paper 3. Therefore, in this case, the pulse width of the driving pulse applied to the diaphragm 50 in one pixel is adjusted and set so that the inks of the next pressure wave overlap before the ink raised by the plurality of pressure waves is separated. .

Next, in a second example shown in FIG. 17, a plurality of pressure waves are generated by restoring the diaphragm a plurality of times within one pixel, and a plurality of ink droplets are separately ejected from the nozzle for each pressure wave. It is like that. That is, one ink droplet Pb1 is separated and discharged by the first pressure wave PT1 from the nozzle hole 44, and another ink droplet Pb2 is separated and discharged by the next pressure wave PT2, and two ink droplets D2 and D3 are formed. The dots D2 'and D3' are overlapped on the paper 3 by being made to fly and land on the paper 3 sequentially. Therefore, in this case, the pulse width of the driving pulse applied to the diaphragm 50 within one pixel is set so that the ink droplets are separated and ejected by a plurality of pressure waves and then the ink droplets are ejected by the next pressure wave. To adjust.

As described above, the ink droplet is formed by restoring the diaphragm a plurality of times for one pixel signal, and the ink droplet is formed by restoring the diaphragm once for one pixel signal. In comparison, the ejection amount Mj of the ink droplet can be further increased, and the dot diameter can be increased. Therefore, the problem of a large decrease in the ink droplet ejection speed due to an increase in the amount of ink droplet ejection unlike the related art hardly occurs. This means that one pressure wave is formed at a timing with a very good ejection efficiency, and one ink droplet is surely protruded out of the nozzle hole 44 corresponding to each pressure wave, or The nozzle hole 4
This is because there is almost no decrease in the ink flow velocity in the vicinity of No. 4.

Here, the difference between the formation of ink droplets according to the first example and the formation of ink droplets according to the second example will be described with reference to FIGS. First, FIG. 18 illustrates the relationship between the number of pulses of the drive waveform for one pixel and the ink ejection amount Mj. A line Ga indicates the case where ink droplets are formed in the first example shown in FIG. 17 shows the case where ink droplets are formed in the second example shown in FIG. As can be seen from the above, the ink droplet formation according to the second example has a larger increase in the ink droplet volume Mj with respect to the number of drive pulses than the ink droplet formation according to the first example. It can be seen that the ink drop formation according to the second example is preferable.

FIG. 19 illustrates the relationship between the ink droplet ejection amount Mj and the dot diameter. The change from the point a to the point b was achieved by forming ink droplets according to the first example with three driving pulses. In the case, the change from the point a to the point c indicates the change width of the pixel diameter obtained with respect to the change amount of the ink droplet ejection amount when the ink droplet formation according to the second example is performed by three driving pulses. I have. Accordingly, the ink droplet formation according to the second example is more efficient than the first one.
It can be seen that the control range of the dot diameter (pixel diameter) is wider than the ink droplet formation according to the example.

FIG. 20 illustrates the dot shape formed on the paper when the ink droplet formation according to the first example is performed. FIG. 20A shows the ink droplet formation by one driving pulse. (B) in FIG. 3 (c) when the ink droplet formation according to the first example is performed with two driving pulses.
Indicates the respective dot shapes when the ink droplet formation according to the first example is performed with three drive pulses.

Similarly, FIG. 21 illustrates a dot shape formed on a sheet when ink droplet formation according to the second example is performed. FIG. 21A shows an ink droplet formed by one drive pulse. FIG. 4B shows the case where the ink droplets are formed by the second example using two driving pulses when the ink droplets are formed.
Indicates the respective dot shapes when the ink droplet formation according to the second example is performed with three drive pulses.

From the above, since the dot shape of the ink droplet formation according to the first example is closer to a circle than that of the ink droplet formation according to the second example, the control width of the pixel diameter is narrow, but relatively uniform and clean. It can be seen that an image is obtained. In addition,
The dot shapes in FIGS. 20 and 21 are the dot shapes when dye ink is printed on coated paper using a drive pulse having a voltage value of 50V.

Next, a third example of the second embodiment will be described with reference to FIGS. In the third example, a plurality of pressure waves are generated by restoring the diaphragm a plurality of times within one pixel, and a plurality of ink droplets are separated and ejected from a nozzle for each pressure wave. The ink droplets are combined (integrated). That is, one ink droplet Pb1 is separated and discharged from the nozzle hole 44 by the first pressure wave PT1, and another ink droplet Pb2 is separated and discharged by the next pressure wave PT2, and these two ink droplets Pb1 and Pb2 are discharged. Are integrated into the ink droplets Pb during flight, and landed as one ink droplet D4 on the paper 3 to form a dot droplet D4 'on the paper 3.

As described above, in order to integrate a plurality of ink droplets during flight, the ejection speeds of the plurality of ink droplets may be adjusted. For example, the ejection speed of the ink droplet separated and ejected as the first droplet is made slower than a desired ejection speed, and the ink droplet collides with the ink droplet separately ejected as the second droplet to be integrated into one droplet, or the second droplet. The ejection speed of the ink droplets separated and ejected is faster than the desired ejection speed, and the first droplet catches up with the ink droplets separately ejected, and is integrated into one droplet, or a combination of these methods is used. Thus, a plurality of ink droplets can be integrated into one droplet while flying. in this case,
In order to adjust the ejection speed Vj of each ink droplet, the pulse width and fall time of each drive pulse may be adjusted.

FIG. 23 illustrates the dot shape formed on the paper when the ink droplet formation according to the third example is performed. FIG. 23A illustrates the formation of the ink droplet by one driving pulse. FIG. 6B shows the case where the ink droplet formation according to the third example is performed with two driving pulses, and FIG.
Each dot shape when the ink droplet formation according to the third example is performed by the number of drive pulses is shown. It should be noted that this dot shape is also the dot shape when printing is performed with dye ink on coated paper using a drive pulse having a voltage value of 50V.

As can be seen by comparing the dot shape of FIG. 23 according to the third example with the dot system of FIG. 21 according to the second example, the dot shape according to the second example has an elliptical shape. In contrast to the above, an uneven image is obtained. On the other hand, the dot shape according to the third example has a relatively circular shape, and the variation width of the pixel diameter is large, so that a more uniform and clear image can be obtained. Become like

In the above embodiment, the shapes, arrangements, and forming methods of the nozzles, the pressurizing chambers, the fluid resistance portions, and the common channel liquid chambers of the ink jet head can be appropriately changed. For example, in the above-described embodiment, the edge shooter type inkjet head is formed such that the nozzles eject the ink droplets in a direction intersecting the displacement direction of the diaphragm. A side shooter type inkjet head formed to discharge may be used.

[0085]

As described above, according to the ink jet recording apparatus according to the present invention, the vibration in the ink flow path generated after the vibration plate comes into contact with the electrode during the time when the pressure fluctuation is positive pressure is obtained. Since the ink droplets are ejected by restoring the plate, stable ink droplets can be ejected at a timing that is efficient with respect to the driving voltage, and stable printing quality can be obtained at a lower voltage.

Here, the diaphragm is restored at the timing when the change in the charging / discharging current generated between the diaphragm and the electrode becomes substantially zero during the time when the pressure fluctuation in the ink flow path is a positive pressure. By ejecting the ink droplets in this manner, stable ink droplets can be ejected at a more efficient timing with respect to the driving voltage, and stable printing quality can be obtained at a lower voltage.

Further, a pulse-like drive waveform is applied between the diaphragm and the electrode, and the pulse width of the drive waveform is restored to the time when the pressure fluctuation in the ink flow path is positive. By setting the pulse width to a certain value, even at a higher driving frequency, ink droplets can be ejected efficiently with desired ink droplet ejection characteristics, and high-speed printing can be performed with constant print quality.

In this case, a pulse-like drive waveform is applied a plurality of times within one pixel, and the diaphragm is restored a plurality of times each time the pressure fluctuation in the ink flow path becomes a positive pressure. Print quality can be controlled, and an image of stable print quality without any pixel displacement or the like can be printed at high speed on a recording medium.

Here, a plurality of pressure waves are generated by restoring the diaphragm a plurality of times within one pixel, and a plurality of pressure waves are superimposed to eject one ink droplet, whereby a substantially constant ink droplet is ejected. The size of the pixel can be changed by changing the desired ink discharge amount by the discharge speed, and a relatively clear pixel shape can be stably obtained, so that a high-quality image with higher print quality can be printed.

Also, the diaphragm is restored a plurality of times within one pixel to generate a plurality of pressure waves, and a plurality of ink droplets are separated and ejected from the nozzle for each pressure wave, so that a substantially constant ink droplet ejection speed is obtained. Since the desired ink ejection amount can be changed more greatly and the pixels can be changed more greatly, the control range of the printing quality is expanded, and from the image that emphasizes the image quality with richer gradation, it is important to print at higher speed. It is possible to cope with a wider range of printing quality up to a printed image.

In this case, by integrating a plurality of ink droplets separately ejected from the nozzle during the flight, the control range of the printing quality can be expanded with a larger pixel change, and a more uniform and clear pixel shape can be obtained. Can be
It is possible to cope with a wider range of print quality with a high-quality image having more excellent gradation and excellent print quality.

According to the head drive control device of the present invention, the drive waveform generation for restoring the diaphragm within the time during which the pressure fluctuation in the ink flow path generated after the diaphragm comes into contact with the electrode is positive pressure. Since the output means is provided, stable ink droplets can be ejected at a timing that is efficient with respect to the drive voltage, and stable print quality can be obtained at a lower voltage.

Here, the diaphragm is restored at the timing when the change in the charging / discharging current generated between the diaphragm and the electrode becomes substantially zero within the time when the pressure fluctuation in the ink flow path is positive pressure. By generating and outputting a driving waveform, stable ink droplets can be ejected at more efficient timing with respect to the driving voltage, and stable printing quality can be obtained at a lower voltage.

Further, by generating and outputting a drive waveform in which a diaphragm deformed within one pixel is restored a plurality of times, print quality can be controlled in accordance with an image signal, and the position of a pixel on a recording medium can be controlled. It is possible to print an image of stable print quality without any deviation at a high speed.

In this case, the vibration plate is restored a plurality of times within one pixel to generate a plurality of pressure waves, and the plurality of pressure waves are superimposed to generate and output a drive waveform for discharging one ink droplet. It is possible to change the pixel size by changing the ink discharge amount to a desired amount at a substantially constant ink droplet discharge speed, and to obtain a relatively clear pixel shape stably, and to obtain a high-quality image with more excellent print quality. Can be printed.

Further, the diaphragm is restored a plurality of times within one pixel to generate a plurality of pressure waves, and a drive waveform is generated and output, in which ink droplets are separated and ejected from the nozzle for each pressure wave. With the ink droplet ejection speed, the desired ink ejection amount can be changed more greatly and the pixel can be changed more greatly, so that the control range of the printing quality is expanded, and from the image that emphasizes the image quality with richer gradation, It is possible to cope with a wider range of printing quality, even for images where printing is important.

In this case, by generating and outputting a drive waveform in which a plurality of ink droplets separately ejected from the nozzles are integrated during the flight, the control range of the print quality is expanded with a larger pixel change, and a more uniform print quality is obtained. A clear pixel shape can be obtained, and a high-quality image with richer gradation and excellent print quality can be applied to a wider range of print quality.

[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 explanatory cross-sectional view in the longitudinal direction of a diaphragm showing an example of a head of the recording apparatus.

FIG. 4 is an enlarged sectional explanatory view of a main part of the head in the transverse direction of the diaphragm.

FIG. 5 is a block diagram illustrating an example of a control unit of the recording apparatus.

FIG. 6 is a block diagram of a part related to a head drive control unit of the recording apparatus.

FIG. 7 is an explanatory diagram for explaining an operation of the head up to contact with the diaphragm;

FIG. 8 is an explanatory diagram for explaining an operation of the head from a diaphragm restoration;

FIG. 9 shows a first example relating to head drive control in the recording apparatus.
Explanatory drawing for explanation of embodiment

FIG. 10 is an explanatory diagram for explaining a pulse width of a driving waveform and an ink droplet ejection characteristic value.

FIG. 11 is an explanatory diagram for explaining pressure fluctuation of the head.

FIG. 12 is an explanatory diagram for explaining pressure fluctuation of the head.

FIG. 13 is an explanatory diagram which is used for describing a second embodiment relating to head drive control in the recording apparatus.

FIG. 14 is an explanatory diagram illustrating a relationship between a rising time of a driving pulse and an ink droplet ejection characteristic value in the embodiment.

FIG. 15 is an explanatory diagram illustrating a relationship between a fall time of a drive pulse and an ink droplet ejection characteristic value in the embodiment.

FIG. 16 is an explanatory diagram illustrating an ink droplet forming process in the first example of the embodiment.

FIG. 17 is an explanatory diagram illustrating an ink droplet forming process in a second example of the embodiment.

FIG. 18 is an explanatory diagram illustrating the relationship between the number of drive pulses and the increase ratio of the ink ejection amount in the first and second examples.

FIG. 19 is an explanatory diagram illustrating the relationship between the ink droplet ejection amount and the dot diameter in the first and second examples.

FIG. 20 is an explanatory diagram illustrating an example of a dot shape formed in an ink droplet forming process according to the first example.

FIG. 21 is an explanatory diagram illustrating an example of a dot shape formed in an ink droplet forming process according to the second example.

FIG. 22 is an explanatory diagram illustrating an ink droplet forming process in a third example of the embodiment.

FIG. 23 is an explanatory diagram illustrating an example of a dot shape formed in an ink droplet forming process according to the third example.

[Explanation of symbols]

13: carriage, 14: head, 24: transport roller,
33: paper ejection roller, 40: ink jet head, 41
... first substrate, 42 ... second substrate, 43 ... third substrate, 44 ...
Nozzle hole, 46 ... pressurized chamber, 47 ... fluid resistance part, 48 ... common flow path liquid chamber, 50 ... diaphragm, 55 ... electrode, 57 ... electrode protective film, 87 ... waveform generation circuit.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Mitsuru Shinginai 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (72) Masanori Kusunoki 1-3-6 Nakamagome, Ota-ku, Tokyo No. Ricoh Co., Ltd. (72) Inventor Taeko Murai 1-3-6 Nakamagome, Ota-ku, Tokyo F-term (reference) 2C057 AF23 AF30 AF39 AF42 AG12 AG54 AM17 AR08 BA05 BA14 BA15 CA01 CA04

Claims (13)

[Claims] A nozzle for discharging ink droplets, an ink flow path communicating with the nozzle, a vibration plate provided in a part of the ink flow path, and an electrode facing the vibration plate; In an ink jet recording apparatus provided with an ink jet head for deforming a diaphragm toward an electrode by electrostatic force and restoring the deformed diaphragm to eject ink droplets from the nozzles, the vibration occurs after the diaphragm comes into contact with the electrode. An ink jet recording apparatus, comprising: means for restoring a diaphragm during a period in which the pressure fluctuation in the ink flow path is a positive pressure to eject the ink droplets. 2. The charging / discharging current generated between the diaphragm and the electrode during a period in which the pressure fluctuation in the ink flow path is a positive pressure in the ink jet recording apparatus according to claim 1. An ink jet recording apparatus for restoring the diaphragm at a timing when the change of the vibration becomes substantially zero. 3. The ink jet recording apparatus according to claim 1, wherein a pulse-like drive waveform is applied between the diaphragm and the electrode, and the pulse width of the drive waveform is changed to the ink flow. An ink jet recording apparatus, wherein the diaphragm is set so as to be restored within a time period in which the pressure fluctuation in the path is positive. 4. The ink-jet recording apparatus according to claim 3, wherein the pulse-like drive waveform is applied a plurality of times within one pixel, and the diaphragm is driven every time the pressure fluctuation in the ink flow path becomes a positive pressure. An ink jet recording apparatus characterized by restoring a plurality of times. 5. The ink jet recording apparatus according to claim 4, wherein a plurality of pressure waves are generated by restoring the diaphragm a plurality of times within one pixel, and one ink droplet is ejected by superimposing the plurality of pressure waves. An ink jet recording apparatus characterized in that: 6. The ink jet recording apparatus according to claim 4, wherein the diaphragm is restored a plurality of times within one pixel to generate a plurality of pressure waves, and a plurality of ink droplets are separated from the nozzle for each pressure wave. An ink jet recording apparatus characterized by discharging. 7. An ink jet recording apparatus according to claim 6, wherein a plurality of ink droplets separately ejected from said nozzles are integrated during flight. And a nozzle for discharging ink droplets, an ink flow path communicating with the nozzle, a vibrating plate provided in a part of the ink flow path, and an electrode opposed to the vibrating plate. In a head drive control device that deforms the diaphragm toward the electrode with electrostatic force and restores the deformed diaphragm to drive an ink jet head that ejects ink droplets from the nozzles, after the diaphragm comes into contact with the electrode, A head drive control device comprising: a drive waveform generation / output unit for restoring the diaphragm within a time when the generated pressure fluctuation in the ink flow path is a positive pressure. 9. The head drive control device according to claim 8, wherein charge and discharge generated between the vibration plate and the electrode during a time when the pressure fluctuation in the ink flow path is a positive pressure. A head drive control device comprising: a drive waveform generation / output unit that restores a diaphragm at a timing when a change in current becomes substantially zero. 10. The head drive control device according to claim 8, further comprising a drive waveform generation output unit that restores the diaphragm a plurality of times within one pixel. 11. The head drive control device according to claim 10, wherein a plurality of pressure waves are generated by restoring the diaphragm a plurality of times within one pixel, and a plurality of pressure waves are superimposed to form one ink droplet. A head drive control device comprising: a drive waveform generation / output unit for discharging. 12. The head drive control device according to claim 10, wherein the diaphragm is restored a plurality of times within one pixel to generate a plurality of pressure waves, and ink droplets are separately ejected from the nozzle for each pressure wave. A head drive control device, comprising: a drive waveform generation / output means for causing the drive to generate. 13. The head drive control device according to claim 12, further comprising: a drive waveform generation output unit that integrates a plurality of ink droplets separately ejected from the nozzle during flight. Drive control device.