JP2001315332A - Driving method of inkjet printer - Google Patents

Abstract

(57) [Problem] To provide an inkjet printer using a fixed head having a large number of nozzles, the number of nozzles becomes 1000 or more, and a recovery operation in which all actuators are driven simultaneously increases power consumption and decreases durability. There is a problem to do. SOLUTION: In a printing process of an ink jet printer, a first voltage pulse is applied to a pressure generating means in accordance with a recorded content, and an ink droplet is ejected from a nozzle.
Instead of applying the second pulse to all other pressure generating means, the second pulse is applied to different pressure generating means for each printing process.
Is applied. As a result, the number of pressure generating means for simultaneously applying a voltage pulse can be reduced, so that an increase in the viscosity of ink in a nozzle that is used less frequently can be suppressed without increasing power consumption.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet printer that discharges minute ink droplets and records characters, symbols, images, and the like, and in particular, prevents nozzles from being clogged by viscous ink near the nozzles. The present invention relates to a method for controlling an inkjet printer.

[0002]

2. Description of the Related Art Conventionally, an ink jet recording apparatus is disclosed in Japanese Patent Publication No. 2-51734, in which the driving means is a piezoelectric element, or as described in Japanese Patent Publication No. 61-59911, an ink jet recording apparatus. And a method of discharging ink from nozzles using an electrostatic actuator that vibrates a vibration plate by electrostatic force as disclosed in Japanese Patent Application Laid-Open No. 7-81088. Proposed and put to practical use.

Generally, in these ink jet printers, an image signal is developed in a storage means such as a memory, and based on the developed data, a piezoelectric element, a heating element, or The pressure generating means composed of an electrostatic actuator is selectively driven to perform printing on a recording medium.

[0004] A common problem with such an ink-jet printer is that if ink droplets are not ejected from a nozzle for a certain period of time or longer, water, which is a solvent of the ink, evaporates from the nozzle and the viscosity of the ink near the nozzle becomes low. Rising.

When the viscosity of the ink near the nozzle increases,
Nozzles are clogged, and ink is not ejected at the time of printing, or even when ejected, ink droplets of the original size and speed are not ejected. Also, as the viscosity of the ink increases, the refill speed of the ink with respect to the nozzles decreases, and the refill amount cannot keep up with the amount of the ejected ink.
Ink droplets may not be ejected due to the inclusion of bubbles in the ink.

For this reason, in many ink jet printers, when recording is not performed, the nozzle is covered with a cap to prevent the nozzle from drying and increasing the viscosity of the ink near the nozzle.

In addition to the method of covering the nozzles with the cap as described above, in addition to the printing process, in order to prevent clogging of the ink near the nozzles, fine droplets are periodically discharged from all the discharge ports. Many methods for maintaining and recovering printing performance have been proposed.

For example, Japanese Patent Publication No. 6-39163 discloses that the frequency of driving an ink jet head during a recovery ejection operation is set lower than the maximum driving frequency at the time of recording characters, images, etc. There is disclosed a recovery processing method that reliably discharges ink having increased viscosity without taking in bubbles from the nozzles even if the pressure rises.

[0009] In addition to the method of discharging ink having increased viscosity and performing a nozzle recovery process, International Publication W097 / 3
As disclosed in U.S. Pat. No. 2,728, a first cycle of a reference signal is generated, and in synchronization with the reference signal, a first electric pulse having an amplitude at which an ink droplet can be ejected, and an amplitude of the first electric pulse. A method has been proposed in which one of the second voltage pulses, which is smaller and causes the ink in the nozzle to flow in the nozzle, is applied to each pressure generating means. According to this method, even if the second electric pulse having a smaller amplitude than the first electric pulse is applied to the pressure generating means, the ink droplet is not ejected,
By applying the second electric pulse, the ink near the nozzle flows, and the ink at the tip of the nozzle having the highest viscosity mixes with the ink having a lower viscosity at the back of the nozzle, and the ink near the nozzle as a whole is There is disclosed a recovery method of reducing the viscosity.

[0010]

However, these methods have the following problems.

1) In order to prevent clogging of nozzles, it is necessary to drive all actuators regardless of whether an ink droplet is ejected or a small pulse which is not ejected. Increases power consumption.

Particularly, in an ink jet printer using a fixed head having a large number of nozzles, the number of nozzles is 100.
It becomes 0 or more, which is an important problem.

2) Since the actuator is driven irrespective of discharge or not, the durability is reduced. this is,
This is a problem common to ink jet printers.

[0014]

In the printing process of the ink jet printer, the second voltage pulse is used as follows. That is, the first voltage pulse is selectively applied to the pressure generating means in accordance with the content of the recording, the ink droplet is ejected from the nozzle, and the pressure generating means other than the pressure generating means to which the first voltage pulse is applied. Instead of applying the second pulse to all, the second voltage pulse is applied to the different pressure generating means for each printing process. As a result, the number of pressure generating means for simultaneously applying a voltage pulse can be reduced, so that an increase in the viscosity of ink in a nozzle that is used less frequently can be suppressed without increasing power consumption. This method is particularly effective for a color line printer having a large number of nozzles.

By changing the amplitude of the electric pulse applied to the pressure generating means, a pressure generating means of a type capable of discharging ink droplets or flowing ink in the nozzles without discharging ink droplets is employed. The present invention can be applied to any inkjet printer as long as it is an inkjet printer.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of an ink jet printer according to the present invention will be described below with reference to FIGS. FIG. 1 is a block diagram showing an example of the ink jet printer of the present invention, and FIG. 2 is a perspective view and a side view showing one embodiment of a printing unit 10 in FIG.

As shown in FIG. 1, the ink jet printer of the present invention comprises a printing section 10 and a control section 100 for controlling the printing section 10 based on an image signal sent from a host.

For example, as shown in FIG. 2, the printing unit 10 comprises the following. Reference numeral 300 denotes a platen that conveys the recording paper 105, and reference numeral 301 denotes an ink tank that stores ink therein. The ink is supplied to the inkjet head 30 via an ink supply tube 306.

The ink jet head 30 includes a piezoelectric element,
A pressure generating means such as a heating element and an electrostatic actuator is provided. The platen 300 moves the recording paper 105 in the transport direction by driving the motor 15 (FIG. 1).
Reference numeral 303 denotes a pump, which is connected to the inkjet head 3 via a cap 302 and a waste ink collecting tube 308.
It has a function of sucking the ink in 0 and collecting it in the discharged ink reservoir 305.

The recovery process using the pump 303 is performed on an ink jet head that cannot be recovered by the recovery ejection process described later. For example, when recording is not performed for a long time, or when bubbles are mixed in the nozzles. When done. The cap 302 is a cap that covers all the nozzle rows of the inkjet head 30 having a width substantially equal to the width of the recording paper 105, and includes a print position P and a cap position R.
Move between. In the ink jet head 30, the cap 302 performs ejection for recording at the printing position P, and performs the recovery ejection at the cap position R to prevent nozzle clogging. This cap position R is normally used as a standby state of the printer. After power is turned on, the printer stands by at the cap position R with a nozzle covered with the cap 302 until a print command is issued.

The receiving port 170 shown in FIG. 1 is a serial or parallel communication port for receiving an image signal from a host, and the image data included in the image signal received by the receiving port 170 is, for example, a RAM or the like. It is stored in the print pattern storage unit 110. When the print pattern storage unit 110 is configured by a RAM, data of the address designated by the print operation processing unit (CPU) 200 is sequentially output to the next stage using an address signal and a read / write signal.

The recovery driving pattern generation means 160 is for generating driving pattern data for performing recovery driving, that is, generating data for designating an ejection port for performing recovery driving, and outputting the data to the next stage. I do. Combining means 150
Is for combining the output of the print pattern storage means 110 and the output of the recovery drive pattern generation means 160 and outputting it to the next stage.

The driving signal generating means 180
0 based on the data output created at 0
Nn drive data signals D1 to Dn are generated, and a signal in which the energizing width and timing of a drive pulse given to the pressure generating element of the nozzle are specified is output to the next stage. That is, the drive signals D1 to Dn are output in synchronization with the timing pulse output from the CPU 200.

The storage means 210 is composed of a RAM for storing a print command and the like included in the image signal, a ROM for storing a program for controlling each of the above-described means, and the like.
The PU 200 appropriately controls each of the above units according to a program stored in the storage unit 210.

The timer 220 comprising a timer or the like starts counting after the recovery discharge, and outputs a timer up signal for instructing the output of the recovery discharge signal when a preset time or the number of times of driving has elapsed. Or
A flag is set to notify that a predetermined time has elapsed.

The driver 190 is provided with a drive signal generating means 18.
0 is a driver for driving the inkjet head 30 by boosting the drive signal output from the
Is a driver for driving the motor 15, and the motor 15 is controlled by a control signal output from the CPU 200.

The driving voltage selecting means 130 supplies a driving pulse having a large amplitude for ejecting ink droplets to the pressure generating element in the ink jet head 30 and an amplitude for causing the ink in the nozzle to flow without ejecting the ink droplets. This is for generating a small driving pulse, and the driving signal generating means 1
In accordance with the drive signal output from the driver 80, the driver 180 applies a large-amplitude voltage to a pulse to be ejected and a small-amplitude voltage to a recovery drive pulse.
Control.

Next, an example of an ink jet head applied to the present invention will be described.

FIG. 3 is a sectional view of an ink jet head applied to the present invention, FIG. 4 is a plan view thereof, and FIG.
Is a partial sectional view thereof.

As shown in these figures, the ink jet head 30 has a silicon substrate 1, a nozzle plate 2 also made of silicon on the upper side, and a borosilicate glass substrate 3 whose thermal expansion coefficient is close to that of silicon on the lower side. 3 stacked
It has a layer structure. In the central silicon substrate 1, a plurality of independent ink chambers 5, a common ink chamber 6 provided in common therewith, and an ink supply path 7 connecting the common ink chamber 6 to the plurality of ink chambers 5, respectively. Are formed by etching from the surface (upper surface in the figure). These grooves are closed by the nozzle plate 2, and each part 5, 6,
7 are sectioned.

In the nozzle plate 2, nozzles 11 are formed at positions corresponding to the front end portions of the respective ink chambers 5, and these nozzles communicate with the respective ink chambers 5. In addition, an ink supply port 12 communicating with the common ink chamber 6 is formed in the glass substrate 3.

The ink is supplied from the ink tank 301 (FIG. 2) to the common ink chamber 6 through the ink supply port 12 via the ink supply tube 306 (FIG. 2). The ink supplied to the common ink chamber 6 is supplied to the independent ink chambers 5 through the ink supply path 7.

The ink chamber 5 is formed so as to be thin so that the bottom wall 8 functions as a diaphragm which can be elastically displaced vertically in FIG. Therefore, the portion of the bottom wall 8 may be referred to as a diaphragm 8 for convenience of the following description.

Next, in the upper surface of the glass substrate 3 which is in contact with the lower surface of the silicon substrate 1, that is, in the bonding surface with the silicon substrate 1, the glass substrate 3 is shallow at a position corresponding to each ink chamber 5 of the silicon substrate 1. An etched recess 9 is formed. Therefore, the bottom wall 8 of each ink chamber 5 is separated from the surface 92 of the concave portion 9 of the glass substrate 3 by a very small gap.
And confront. Part of the surface of the concave portion 9 on the nozzle 11 side is provided with a surface 92b protruding from the surface 92 toward the bottom wall 8, and the distance between the surface 92b and the bottom wall 8b is different from the surface 92 other than this portion and the bottom wall 8b. 8a is smaller than the interval.

Here, the bottom wall 8 of each ink chamber 5 functions as an electrode for storing a charge. A segment electrode 10 is formed on the concave surface 92 of the glass substrate 3 so as to face the bottom wall 8 of each ink chamber 5. The surface of each segment electrode 10 is covered with an insulating layer 15 made of inorganic glass and having a thickness G0 (see FIG. 5). The purpose of the insulating layer 15 is to insulate the bottom wall 8 described later and the segment electrode 10 when the segment electrode 10 is to be brought into close contact, and may be formed so as to cover the bottom wall 8 on the segment electrode 10 side.

As described above, the segment electrodes 10 and the bottom walls 8 of the respective ink chambers form opposed electrodes partially different from each other with the insulating layer 15 interposed therebetween. That is, the inter-electrode distance of the counter electrode is G2 near the nozzle, and G1 in other portions. As shown in FIG. 4, a driver 190 for driving the ink-jet head charges and discharges between these counter electrodes in response to a drive signal output from the drive signal generation unit 180 and a control signal output from the CPU 200. Do.

One output of the driver 190 is directly connected to each segment electrode 10, and the other output is connected to a common electrode terminal 22 formed on the silicon substrate 1. Since impurities are implanted into the silicon substrate 1 and the silicon substrate 1 itself has conductivity, charges can be supplied from the common electrode terminal 22 to the bottom wall 8. When it is necessary to supply a voltage to the common electrode with a lower electric resistance, for example, a thin film of a conductive material such as gold may be formed on one surface of the silicon substrate by vapor deposition or sputtering.

In this embodiment, since the silicon substrate 1 and the glass substrate 3 are bonded by anodic bonding, a conductive film is formed on the flow channel forming surface side of the silicon substrate 1 because of the necessity.

FIG. 5 shows a section taken along line III-III of FIG. When a driving voltage is applied between the opposing electrodes from the driver 190, Coulomb force is generated between the opposing electrodes, the bottom wall (diaphragm) 8 bends toward the segment electrode 10, and the volume of the ink chamber 5 increases ( FIG. 5 (b)). Next, by the driver 190,
When the electric charge between the opposing electrodes is rapidly discharged, the diaphragm 8 is restored by its elastic restoring force, and the volume of the ink chamber 5 is contracted rapidly (FIG. 5C). At this time, due to the pressure generated in the ink chamber, a part of the ink filling the ink chamber 5 is ejected as ink droplets from the nozzle 11 communicating with the ink chamber. As described above, the small gap G2 and the large gap G1 are formed between the opposing electrodes. The portion 8b corresponding to the gap G2 of the diaphragm 8 is easily attracted to and adhered to the opposing wall 92b only by applying a smaller driving voltage than the other portions 8a.
Therefore, the diaphragm 8 is largely vibrated by two types of driving voltages, a driving voltage having such a size that the entire area of the diaphragm is in close contact with the opposing wall 92 and a driving voltage having such a magnitude that only the portion 8b of the diaphragm 8 is in close contact with the wall 92. In addition, a vibration mode in which ink droplets are ejected and a vibration mode in which the vibration plate 8 is partially vibrated and ink near the nozzles flows can be obtained.

In the case of driving by the two types of driving voltages,
Since the vibrating plate 8 and the segment electrode 10 repeat the operation of closely contacting via the insulating layer 15, the vibration plate 8 and the segment electrode 10 are repeatedly exposed to the mechanical shock of the close contact operation and a high electric field. As a result, the insulating layer 15 deteriorates and reaches the end of its durability. Therefore, in order to secure a durable life, it is effective means to reduce the number of times of close contact operation.

Next, an example of a driving method will be described.

FIG. 6 shows an example of a driving waveform of the ink jet head of the present invention. For example, when a dot of ink to be printed on a recording paper (hereinafter referred to as a dot) is composed of two ink droplets, a voltage pulse applied to the segment electrode 10 while holding the diaphragm 8 at V0 is shown. I have.

When the ejection pulse rises to VH1, the diaphragm 8 is attracted to the segment electrode 10, and when returning from VH1 to V0, the diaphragm 8 separates from the segment electrode 10 and ejects ink as described above. Next, when the ejection pulse drops to VL1 and returns to V0, the potential relationship is reversed, but ink is ejected similarly.

On the other hand, in the recovery drive pulse, a pulse of a voltage VH2 lower than VH1 is applied, but ink is not ejected by this drive.

The waveform of the synthesized pulse is an example of the output waveform from the synthesizing means 150 (FIG. 1), and one dot is printed by adding a recovery drive pulse to the ejection pulse. In the illustrated waveform, the recovery drive pulse is applied prior to the ejection pulse, but the ejection pulse may be applied prior to the ejection pulse.

FIG. 7 is an example of a drive waveform time chart diagram for each nozzle. In the figure, the broken lines extending over the nozzle numbers indicate the positions of the timing signals for each print dot line created from the reference signal.

For example, when a recovery drive pulse is applied to one of four nozzles, the recovery drive pulse can be reduced to １ ／. At this time, if a print command is sent to the nozzle # 5 in the dot line 1, an ejection pulse is applied as shown in the figure.

Further, as shown in FIG. 8, when the ejection pulse and the recovery drive pulse are combined, the recovery drive pulse can be omitted, and the number of times of driving can be further reduced.

The required application frequency for recovery by the recovery drive pulse greatly varies depending on environmental conditions, nozzle shape, nozzle dimensions, ink physical properties, etc., but as an example, the recovery drive is performed more than 200 times within one second from the previous ejection. Experiments have shown that recovery can be achieved by applying a pulse. If the driving frequency of the ejection driving pulse is 10 kHz, 1/50 frequency can be calculated from the above knowledge. That is, 5
By applying a recovery drive pulse to one or more of the 0 nozzles, it is possible to reduce the increase in ink viscosity in the nozzles.

The number and order of the nozzles to which the recovery drive pulse is applied need not be constant as long as all the nozzles are driven at a predetermined frequency or more. Further, the driving frequency can be changed according to the environmental conditions.

FIG. 9 is a control flowchart for each nozzle, and shows a drive control method for further reducing the number of drives from the above knowledge.

In step 1, the ejection data is confirmed, and if there is data, the flow advances to step 4 to perform ejection driving.

If there is no ejection data in step 1, the flow advances to step 2 to determine whether the elapsed time from the previous ejection is equal to or longer than a predetermined time. If the elapsed time is equal to or longer than a predetermined time, the process proceeds to step 3, and if the elapsed time is equal to or shorter than the predetermined time, the process proceeds to step 6. In step 3, it is determined whether or not there is data for recovery driving. If there is data for recovery driving, the process proceeds to step 5, and the recovery driving is performed. If there is no data for recovery driving, the process proceeds to step 6. In step 6, no driving is performed.

As described above, by selecting whether to perform the ejection drive, the recovery drive, or the non-drive for each nozzle and each dot cycle, when there is no ejection data and the elapsed time since the previous ejection, If the predetermined time has not elapsed, the recovery drive is omitted, and the number of times of drive is reduced.

[0055]

As described above, according to the present invention, even in a line ink jet printer having a large number of nozzles, a printer can be realized without increasing power consumption and without deteriorating durability. Therefore, the control method of the inkjet printer of the present invention is suitable for an output terminal of a computer, a color printing apparatus, and the like, and is particularly suitable as a control method of an inkjet printer in a field where high-speed printing, low running cost, and high reliability are required. is there.

[Brief description of the drawings]

FIG. 1 is a block diagram of an inkjet printer to which the present invention is applied.

FIG. 2 is a perspective view and a side view of an inkjet printer to which the present invention is applied.

FIG. 3 is a sectional view of an inkjet head to which the present invention is applied.

FIG. 4 is a plan view of an inkjet head to which the present invention is applied.

FIG. 5 is a partial sectional view of an inkjet head to which the present invention is applied.

FIG. 6 is a driving waveform diagram of the ink jet head of the present invention.

FIG. 7 is a first driving waveform time chart of the present invention.

FIG. 8 is a time chart of a second driving waveform according to the present invention.

FIG. 9 is a control flowchart of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 10 printing unit 30 inkjet head 302 cap 100 control unit 130 drive voltage selection unit 150 synthesis unit 160 recovery drive pattern generation unit 200 print operation control unit (CPU) 220 timing unit

Claims (4)

[Claims] A plurality of nozzles for ejecting ink droplets; and a pressure generating means provided for each of the nozzles for applying pressure to ink in the nozzles. In a method of driving an inkjet printer that performs printing while moving relatively, in synchronization with a reference signal,
A first voltage pulse having an amplitude capable of ejecting an ink droplet and an amplitude smaller than the amplitude of the first voltage pulse are supplied to the pressure generating means corresponding to the nozzle having a command to eject the ink droplet. A second voltage pulse is applied to a part of the nozzle which does not have a command to eject ink droplets, and the second voltage pulse is applied to the pressure generating means corresponding to a part of the nozzle which does not have a command to eject ink droplets. . 2. A printing apparatus comprising: a plurality of nozzles for ejecting ink droplets; and pressure generating means provided corresponding to each of the nozzles and applying pressure to ink in the nozzles. In a method of driving an ink jet printer which performs printing while moving relatively, a first voltage having an amplitude capable of discharging ink droplets is supplied to a pressure generating means corresponding to a nozzle instructed to discharge ink droplets in synchronization with a reference signal. Applying a pulse to a pressure generating means corresponding to a part of the nozzle for which there is no command to eject ink droplets, causing the ink in the nozzle to flow within the nozzle, the amplitude being smaller than the amplitude of the first voltage pulse; A method for driving an ink jet printer, comprising applying a voltage pulse. 3. A method for driving an ink jet printer according to claim 1, wherein a first predetermined number of nozzles are grouped, and the pressure generating means corresponding to a second predetermined number of nozzles in each nozzle group. A second voltage pulse is applied in synchronization with the reference signal, and the second voltage pulse is applied to pressure generating means corresponding to a second predetermined number of nozzles among nozzles to which the second voltage pulse has not been applied. A method for driving an ink-jet printer, wherein the method is applied in synchronization with a next reference signal and sequentially drives all nozzles. 4. The method according to claim 1, 2 or 3.
In the driving method of the ink jet printer described above, for each nozzle, an elapsed time from the previous ink ejection or an elapsed reference signal pulse number is measured, and a second time is elapsed until a predetermined time or a predetermined reference signal pass number has elapsed from the previous ink ejection. A method for driving an ink jet printer, wherein a voltage pulse is not applied to pressure generating means corresponding to the nozzle.