JP2002113858A - Method for controlling liquid ejector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for controlling a liquid ejector in which ink is prevented from being thickened or dried and the driving frequency can be enhanced. SOLUTION: In the method for controlling a liquid ejector comprising a pressure generating chamber 32 communicating with a nozzle opening 33 and having a Helmholtz oscillation frequency of period Tc, and a pressure generating means 38 for imparting a pressure to ink in the pressure generating chamber 32 and stirring ink in the vicinity of the nozzle opening 33 by driving the pressure generating means 38 of the liquid ejector ejecting ink drops thereby exciting a meniscus to perform microoscillation, a microoscillation driving process 61 is provided in order to stir ink in the vicinity of the nozzle opening by imparting a pressure to ink in the pressure generating chamber 32 without ejecting an ink drop from the nozzle opening 33 thereby exciting the meniscus to perform Helmholtz oscillation of period Tc. According to the arrangement, ink is prevented from being thickened or dried and high speed printing is realized by performing the microoscillation process in a short time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a liquid ejecting apparatus having a head for applying pressure to ink supplied to a pressure generating chamber communicating with a nozzle opening to eject ink droplets from the nozzle opening. In particular, the present invention relates to a method for controlling an ink jet recording head that discharges ink droplets from nozzle openings by pressurizing ink in a pressure generating chamber via a piezoelectric element or a heating element.

[0002]

2. Description of the Related Art As a liquid ejecting apparatus, for example, a plurality of pressure generating chambers for generating pressure for ejecting ink droplets by a piezoelectric element or a heating element, a common reservoir for supplying ink to each pressure generating chamber, There is an ink jet recording apparatus having an ink jet recording head having a nozzle opening communicating with each pressure generating chamber. In this ink jet recording apparatus, ink is ejected to ink in the pressure generating chamber communicating with a nozzle corresponding to a print signal. Energy is applied to eject ink droplets from the nozzle openings.

As described above, such an ink jet type recording head includes a bubble jet (registered trademark) type in which a resistance wire for generating Joule heat is provided in a pressure generating chamber as a pressure generating means as described above. A part of the pressure generating chamber is composed of a vibration plate, and the vibration plate is roughly classified into two types of a piezoelectric vibration type in which the vibration plate is deformed by a piezoelectric element to discharge ink droplets from nozzle openings. There are two types of ink jet recording heads, one using a longitudinal vibration mode piezoelectric element that expands and contracts in the axial direction of the piezoelectric element, and the other using a flexural vibration mode piezoelectric element.

In these ink jet recording heads, ink is supplied from, for example, an ink cartridge or the like filled with ink to a pressure generating chamber of the ink jet recording head through a flow path, and is driven by a driving signal from a driving circuit. When driving energy is applied to the piezoelectric element or the like at a predetermined timing, the ink in the pressure generating chamber is pressurized and discharged from the nozzle opening.

In addition, such an ink jet recording head has a problem that the viscosity of the ink increases due to a change in the temperature of the ink due to a change in the surrounding environmental temperature, and the nozzle openings are clogged. Therefore, in order to reliably discharge the ink droplets while maintaining the ink at a predetermined viscosity, prior to the ink discharge, the meniscus, that is, the free surface of the ink exposed at the nozzle opening is moved to such an extent that the ink droplets are not discharged. A fine vibration drive for fine vibration is performed. This agitates the ink near the nozzle opening,
The ink is maintained at a predetermined viscosity.

Further, since the viscosity of ink is relatively easy to increase, it is desirable to execute this fine vibration drive at predetermined intervals even during ink ejection.

[0007]

However, the length of such a signal for micro-vibration drive is generally longer than the interval between drive signals for continuous ink ejection. For this reason, if the micro-vibration drive is performed during ink ejection, the drive frequency of the head must be reduced to increase the interval between drive signals, which causes a problem that the ejection speed (throughput) is reduced. Such a problem also exists in other liquid ejecting apparatuses.

In view of such circumstances, an object of the present invention is to provide a method of controlling a liquid ejecting apparatus which can prevent thickening and drying of ink and improve a driving frequency.

[0009]

According to a first aspect of the present invention, there is provided a pressure generating chamber which communicates with a nozzle opening and has a Helmholtz oscillation frequency of a period Tc, and applies pressure to ink in the pressure generating chamber. And driving the pressure generating means of the liquid ejecting apparatus which ejects ink droplets by driving the pressure generating means to excite vibrations in the meniscus to drive ink in the vicinity of the nozzle opening. In the control method of the stirring liquid ejecting apparatus, by applying a pressure to the ink in the pressure generating chamber without ejecting the ink droplet from the nozzle opening, the meniscus excites Helmholtz oscillation having a period of Tc and the vicinity of the nozzle opening. The method for controlling a liquid ejecting apparatus according to claim 1, further comprising a fine vibration driving step of stirring the ink.

[0010] In the first aspect, the Helmholtz oscillation is excited in the meniscus, whereby the ink near the nozzle opening can be surely agitated with a short period of minute oscillation. The “meniscus” means the free surface of the ink exposed at the nozzle opening.

According to a second aspect of the present invention, in the first aspect, in the micro-vibration driving step, the time for increasing the pressure of the ink in the pressure generating chamber and the time for decreasing the pressure of the ink are each Helmholtz. A method for controlling a liquid ejecting apparatus, wherein the method is shorter than the oscillation period Tc.

In the second aspect, Helmholtz oscillation is reliably excited in the meniscus.

[0013] In a third aspect of the present invention based on the second aspect, in the fine vibration driving step, each of the time for increasing the pressure of the ink in the pressure generating chamber and the time for decreasing the pressure of the ink is determined by Helmholtz. 1 / of vibration cycle Tc
A control method for the liquid ejecting apparatus, wherein the control method is shorter than 2.

In the third aspect, Helmholtz oscillation is reliably excited in the meniscus, and the ejection of minute ink droplets (ink mist) due to the oscillation is prevented.

According to a fourth aspect of the present invention, in any one of the first to third aspects, in the micro-vibration driving step, the total time t during which the pressure in the ink in the pressure generating chamber is increased or decreased is changed. Is n × Tc <t <n × Tc + Tc / 2 (n is an integer) in the control method of the liquid ejecting apparatus.

In the fourth aspect, the Helmholtz vibration is reliably excited in the meniscus, and the ejection of the ink mist due to the vibration is more reliably prevented.

According to a fifth aspect of the present invention, in the fourth aspect, in the fine vibration driving step, the total time t during which the pressure in the ink in the pressure generating chamber is increased or decreased is changed by:
A method of controlling a liquid ejecting apparatus, wherein the method is shorter than 1/2 of the Helmholtz oscillation period Tc.

In the fifth aspect, the fine vibration driving step can be performed without lowering the frequency of the ejection waveform.

According to a sixth aspect of the present invention, in any one of the first to fifth aspects, the driving voltage applied to the pressure generating means in the micro-vibration driving step is such that a discharge voltage for discharging ink droplets from the nozzle opening is provided. In the method for controlling a liquid ejecting apparatus, the driving voltage may be 1/5 or less of the driving voltage applied to the pressure generating means in the step.

In the sixth aspect, the ejection of the ink mist by the fine vibration drive is reliably prevented.

According to a seventh aspect of the present invention, in any one of the first to sixth aspects, the driving voltage applied to the pressure generating means in the micro-vibration driving step is such that the driving voltage applied to the pressure generating means is such that an ink droplet is discharged from the nozzle opening. In the method for controlling a liquid ejecting apparatus, the driving voltage may be 1/20 or more of a driving voltage applied to the pressure generating means in the step.

In the seventh aspect, the ink in the vicinity of the nozzle opening can be surely agitated by executing the microvibration driving step at a drive voltage of 1/20 or more.

According to an eighth aspect of the present invention, in any one of the first to seventh aspects, the driving voltage applied to the pressure generating means in the fine vibration driving step is changed according to an environmental temperature. A method for controlling a liquid ejecting apparatus.

[0024] In the eighth aspect, an optimal micro-vibration driving step can be executed according to a change in environmental temperature.

According to a ninth aspect of the present invention, in the control method of the liquid ejecting apparatus according to any one of the first to eighth aspects, the fine vibration driving step is performed during the discharging step. is there.

In the ninth aspect, high-speed printing can be realized while maintaining good ink ejection characteristics.

According to a tenth aspect of the present invention, in any one of the first to ninth aspects, the fine vibration driving step is performed during a discharging step of discharging ink droplets from the nozzle openings. The present invention provides a method for controlling a liquid ejecting apparatus.

In the tenth aspect, by performing fine vibration drive on the nozzles that are not ejected during the printing operation, the ink in the vicinity of the nozzle openings is reliably agitated, and good ink ejection characteristics are maintained. And high-speed printing can be realized.

An eleventh aspect of the present invention is the piezoelectric element according to any one of the first to tenth aspects, wherein the pressure generating means is disposed on a diaphragm provided on one surface of the pressure generating chamber. The control method of the liquid ejecting apparatus is characterized in that:

In the eleventh mode, Helmholtz oscillation is excited in the meniscus by driving the piezoelectric element.

[0031]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail based on embodiments.

(Embodiment 1) FIG. 1 is a view showing a schematic configuration of a liquid ejecting apparatus according to Embodiment 1. The liquid ejecting apparatus according to the present embodiment is, for example, an ink jet recording apparatus, and is schematically constituted by a printer controller 11 and a print engine 12, as shown in FIG.

The printer controller 11 includes an external interface 13 (hereinafter referred to as an external I / F 13), a RAM 14 for temporarily storing various data, a ROM 15 for storing a control program and the like, and a control system including a CPU and the like. Unit 16 and an oscillation circuit 1 for generating a clock signal
7, a drive signal generating circuit 19 for generating a drive signal to be supplied to the ink jet recording head 18, and a dot pattern data (bitmap data) developed based on the drive signal and print data, etc.
To the internal interface 20 (hereinafter referred to as internal I /
F20).

The external I / F 13 receives print data composed of, for example, character codes, graphic functions, image data, and the like from a host computer (not shown). Also, a busy signal (BUSY) and an acknowledge signal (ACK) are transmitted through the external I / F 13.
Is output to a host computer or the like.

The RAM 14 functions as a receiving buffer 21, an intermediate buffer 22, an output buffer 23, and a work memory (not shown). The receiving buffer 21 temporarily stores the print data received by the external I / F 13, the intermediate buffer 22 stores the intermediate code data converted by the control unit 16, and the output buffer 23 stores the dot pattern data. . The dot pattern data is composed of print data obtained by decoding (translating) gradation data.

The ROM 15 stores font data, graphic functions, and the like, in addition to a control program (control routine) for performing various data processing.

The control unit 16 reads the print data in the reception buffer 21 and stores the intermediate code data obtained by converting the print data in the intermediate buffer 22.
Further, the intermediate code data read from the intermediate buffer 22 is analyzed, and the intermediate code data is developed into dot pattern data with reference to the font data and graphic functions stored in the ROM 15. After performing the necessary decoration processing, the control unit 16 stores the developed dot pattern data in the output buffer 23.

Then, the ink jet recording head 18
Is obtained, the dot pattern data for one line is converted to the internal I / O
The image is output to the ink jet recording head 18 through F20. When one line of dot pattern data is output from the output buffer 23, the expanded intermediate code data is erased from the intermediate buffer 22, and the expansion processing for the next intermediate code data is performed.

The print engine 12 includes an ink jet recording head 18, a paper feed mechanism 24, and a carriage mechanism 25.

The paper feed mechanism 24 is composed of a paper feed motor, a paper feed roller and the like, and sequentially feeds a print storage medium such as a recording paper in conjunction with the recording operation of the ink jet recording head 18. That is, the paper feed mechanism 24 relatively moves the print storage medium in the sub-scanning direction.

The carriage mechanism 25 includes a carriage on which the ink jet recording head 18 can be mounted, and a carriage driving unit for moving the carriage along the main scanning direction. The head 18 is moved in the main scanning direction. Note that the carriage drive unit may have any configuration as long as it can move the carriage, such as one using a timing belt.

The ink jet recording head 18 has a large number of nozzle openings along the sub-scanning direction, and discharges ink droplets from each nozzle opening at a timing specified by dot pattern data and the like.

Next, the ink jet recording head 18 will be described in detail. FIG. 2 is a diagram showing a mechanical configuration of the ink jet recording head, and FIG.
FIG. 2 is a diagram showing the electrical configuration.

The ink jet recording head 18 of this embodiment is a so-called vertical vibration type ink jet recording head. As shown in FIG. 2, a pressure generating chamber 32 is formed in a spacer 31, and both sides of the spacer 31 are formed. Are sealed by a nozzle plate 34 having a nozzle opening 33 and a vibration plate 35. Further, a reservoir 37 is formed in the spacer 31 so as to communicate with the pressure generating chamber 32 via the ink supply port 36, and an ink tank (not shown) is connected to the reservoir 37.

On the other hand, the tip of the piezoelectric element 38 is in contact with the side of the vibration plate 35 opposite to the pressure generating chamber 32. The piezoelectric element 38 includes a piezoelectric material 39 and electrode forming materials 40 and 41.
Are alternately sandwiched between them so as to form a laminated structure, and an inactive region that does not contribute to vibration is fixed substrate 4.
2 is fixed. The fixed substrate 42 and the diaphragm 3
5, the spacer 31 and the nozzle plate 34
3 are integrally fixed.

An electric signal, for example, a drive signal (COM) and print data (SI), which will be described later, are supplied to the piezoelectric element 38 of the ink jet recording head 18 via a flexible cable (not shown).

When a voltage is applied to the electrode forming materials 40 and 41 of the piezoelectric element 38, the piezoelectric element 38 contracts, the diaphragm 35 is displaced, and the pressure is generated in the ink jet type recording head 18 thus configured. The chamber 32 expands. Then, when the application of the voltage is released from this state, the pressure generating chamber 3
2 contracts, and ink droplets can be ejected from the nozzle openings 33.

In such an ink jet recording head, vibration is excited in the ink in the vicinity of the nozzle opening 33 by applying pressure to the ink in the pressure generating chamber 32 at a predetermined timing so that the ink droplet is not ejected. Is performed. This stirs the ink near the nozzle opening 33, thereby preventing the ink near the nozzle opening 33 from thickening and drying.

In this embodiment, the pressure is applied to the ink in the pressure generating chamber 32 by driving the piezoelectric element 18 as described above. That is, by charging the piezoelectric element 18 with a voltage, the pressure generating chamber 32 is expanded to reduce the pressure of the ink inside. Thereafter, by discharging the voltage charged in the piezoelectric element 18, the pressure generating chamber 32 is contracted to increase the pressure of the ink inside and return to the original state. Therefore, the time for reducing the pressure of the ink in the pressure generating chamber 32 is the time for charging the piezoelectric element 18 with a voltage,
The time for increasing the pressure of the ink in the pressure generating chamber 32 is a time for discharging the charged voltage of the piezoelectric element 18.

Although this fine vibration drive will be described later in detail, in this embodiment, the ink near the nozzle opening 33 is stirred by exciting the meniscus with a Helmholtz vibration period Tc.

Next, the ink jet recording head 1
8 will be described.

This ink jet recording head 18
As shown in FIG. 1, the shift register 51, the latch circuit 5
2. Level shifter 53, switch 54, and piezoelectric element 38
Etc. are provided. Further, as shown in FIG. 3, these shift register 51, latch circuit 52, level shifter 5
3, the switch 54 and the piezoelectric element 38 are respectively provided with shift register elements 51A to 51N and a latch element 5 provided for each nozzle opening 33 of the ink jet type recording head 18.
2A to 52N, level shifter elements 53A to 53N, switch elements 54A to 54N, and piezoelectric elements 38A to 38N, a shift register 51, a latch circuit 52,
The level shifter 53, the switch 54, and the piezoelectric element 38 are electrically connected in this order.

The shift register 51, the latch circuit 52, the level shifter 53, and the switch 54 generate a driving pulse from the ejection driving signal and the micro vibration driving signal generated by the driving signal generating circuit 19. Here, the drive pulse is an applied pulse actually applied to the piezoelectric element 38.

Next, control of the ink jet type recording head 18 having such an electrical configuration will be described.
First, a procedure for applying a drive pulse to the piezoelectric element 38 will be described.

Here, in the present embodiment, the fine vibration drive is executed during the printing, but this fine vibration drive is executed, for example, in correspondence with the nozzle opening 33 that does not eject ink droplets.

The procedure for applying the drive pulse during the fine vibration drive and the procedure for applying the drive pulse during the ink discharge are as follows. The fine vibration drive signal is applied to the piezoelectric element 38 as a drive pulse at the time of stirring the ink, and the drive pulse is applied at the time of the ink discharge. The difference is that a drive pulse generated based on the ejection drive signal is applied to the piezoelectric element 38, but the procedure is basically the same. For this reason,
In the following description, a procedure at the time of ink ejection will be described as an example.

In the ink jet recording head 18 having the above-described electrical configuration, as shown in FIG. 4, a printing process for forming dot pattern data is first synchronized with the clock signal (CK) from the oscillation circuit 17. Data (S
I) is serially transmitted from the output buffer 23 to the shift register 51 and is sequentially set. In this case, first, the data of the most significant bit in the print data of all the nozzle openings 33 is serially transmitted, and when the data serial transmission of the most significant bit is completed, the data of the second most significant bit is serially transmitted. . Similarly, the data of the lower bits are sequentially transmitted in a serial manner.

When the print data of the bit is set in the shift register elements 51A to 51N for all the nozzles, the control section 16 outputs a latch signal (LAT) to the latch circuit 52 at a predetermined timing. With this latch signal, the latch circuit 52 latches the print data set in the shift register 51. The print data (LATout) latched by the latch circuit 52 is applied to a level shifter 53 which is a voltage amplifier. When the print data is, for example, “1”, this level shifter 53
The print data is boosted to a voltage value at which the switch 54 can be driven, for example, several tens of volts. The boosted print data is applied to the switch elements 54A to 54N, and the switch elements 54A to 54N are connected by the print data.

Each of the switch elements 54A to 54N has an ejection drive signal (C) generated by the drive signal generation circuit 19.
OM) is also applied, and the switch elements 54A to 54N
Are connected, the switch elements 54A to 54N
The ejection drive signal is applied to the piezoelectric elements 38A to 38N that are connected to the piezoelectric elements 38A to 38N.

As described above, in the illustrated ink jet recording head 18, whether or not the ejection drive signal is applied to the piezoelectric element 38 can be controlled based on the print data. For example, since the switch 54 is connected by the latch signal (LAT) during the period when the print data is “1”, the drive signal (COMout) can be supplied to the piezoelectric element 38, and the supplied drive signal (COMOUT) COMou
Due to t), the piezoelectric element 38 is displaced (deformed). Further, since the switch 54 is in a non-connected state during a period in which the print data is “0”, the supply of the drive signal to the piezoelectric element 38 is cut off. Note that, during the period in which the print data is “0”, each piezoelectric element 38 holds the immediately preceding charge, so that the immediately preceding displacement state is maintained.

Accordingly, when the ejection drive signal is composed of a plurality of pulses, print data is set for each pulse, and by selecting "1" or "0" of the print data, a plurality of types of drive pulses can be obtained. Is generated, and ink droplets of different sizes can be ejected by the driving pulse.

Although not shown in FIG. 4, the basic drive signal (COM) is composed of a discharge drive signal and a fine vibration drive signal, and the discharge drive or the fine vibration drive is selectively performed according to print data. Be executed. That is, when the print data of the ejection drive signal portion is “1”, ink droplets are ejected from the nozzle openings as described above, and when the print data of the ejection drive signal portion is “0”, “1” is set in the print data of the driving portion. Then, the micro-vibration drive signal is applied to the piezoelectric element as a drive pulse, and the piezoelectric element 38 is deformed to vibrate the meniscus.

Hereinafter, such a drive signal, particularly a fine vibration drive signal for stirring the ink, will be described in detail. FIG. 5A is a diagram illustrating a waveform shape of a drive signal according to an embodiment of the present embodiment, FIG. 5B is an enlarged view of a waveform shape of the micro-vibration drive signal, and FIG. FIG. 5 is a diagram showing a waveform representing a position of a meniscus with respect to a nozzle opening surface due to Helmholtz oscillation.

The drive signal according to the present embodiment is shown in FIG.
As shown in FIG. 5, the method includes a discharge driving step 61 which is a discharge driving signal for discharging ink droplets, and a fine vibration driving step 62 which is a fine vibration driving signal for stirring ink near the nozzle opening 33. In the embodiment, the drive signal is configured by a combination of three ejection drive processes and one fine vibration drive process. Of course, a fine vibration driving step may be provided for each ejection driving step.

Here, the time t of the fine vibration driving step 62 is
As shown in FIG. 5B, since the period is shorter than の of the Helmholtz oscillation period Tc, the micro-vibration driving step 62 is executed substantially during one ejection driving step 61.
Therefore, even if the micro-vibration drive is performed during the printing, the printing speed is not reduced. Here, the time of the micro-vibration driving step 62 specifically means the entire time during which the pressure of the ink in the pressure generating chamber 32 is changed by driving the piezoelectric element 38 to increase or decrease.

The micro-vibration driving step 62 includes an expansion step a for charging the piezoelectric element 38 with a voltage to expand the pressure generating chamber 32, a holding step b for holding the voltage charged in the piezoelectric element 38, A contraction step c is performed in which the voltage charged in the piezoelectric element 38 is discharged to contract the pressure generating chamber 32, and is set so that Helmholtz oscillation can be excited in the meniscus. That is, the time t1 of the expansion step a and the time t2 of the contraction step c are set to be shorter than the Helmholtz oscillation period Tc.
Further, it is preferable that at least the time t1 of the expansion step a is shorter than 1/2 of the Helmholtz oscillation period Tc.
In the present embodiment, the time t of the fine vibration driving step 62 is set to be shorter than の of the Helmholtz oscillation period Tc, and the time t1 of the expansion step a and the time t1 of the contraction step c are set.
2 is set to be shorter than the Helmholtz oscillation period Tc.

By performing such a micro-vibration step, Helmholtz oscillation is surely excited in the meniscus without moving the entire meniscus in the nozzle. In addition, the micro-vibration driving step 6 which is a signal of this relatively short cycle
By agitating the ink in the vicinity of the nozzle opening 33 by the Helmholtz vibration excited by the meniscus by the method 2, the ink can be efficiently agitated to prevent thickening and drying.

In the driving of the piezoelectric element 38 in the micro-vibration driving step 62, no fine ink droplet (ink mist) is ejected from the nozzle opening 33. As described above, in the present embodiment, the time t in the fine vibration driving process 62 is
However, since it is shorter than 1/2 of the Helmholtz oscillation period Tc, the entire meniscus does not move in the nozzle,
As shown by the waveform A in FIG. 5C, Helmholtz oscillation is excited in the meniscus.

Also, in the present embodiment, the micro-vibration driving step 6
2 is shorter than の of the Helmholtz oscillation cycle Tc, and therefore, the time (t1 + t3) of the expansion step a and the holding step b of the fine vibration driving step 62 is naturally shorter than １ ／ of the Helmholtz oscillation cycle Tc. Is also short. Therefore, while the meniscus is moving toward the pressure generating chamber side of the nozzle opening (the direction opposite to the ink ejection direction) by the driving of the piezoelectric element 38 in the expansion step a, that is, the meniscus reaches the peak P1 on the pressure generating chamber side. Before reaching, the contraction step c is performed. Therefore, a part of the force acting in the ink ejection direction by the driving of the piezoelectric element 38 in the contraction step c is canceled by the force acting in the direction opposite to the ink ejection direction in the expansion step a. Therefore, the force acting in the ink ejection direction is weakened, and as shown by the waveform B in FIG. 5C, the slope becomes gentler than the waveform A, and the peak P2 of the meniscus on the nozzle opening side is changed to the nozzle opening surface. Never exceed. Therefore, no ink droplet is ejected from the nozzle opening 33.

On the other hand, when the time t of the fine vibration driving step 62 is longer than 1/2 of the Helmholtz vibration period Tc, for example, as shown in FIG. And the time of the holding step b (t1 + t3)
However, when it is longer than 1/2 of the Helmholtz oscillation period Tc, the meniscus starts to move in the ink ejection direction by driving the piezoelectric element 38 in the expansion step a, that is, the meniscus changes the peak P3 on the pressure generating chamber side. too much,
The contraction step c is executed after the movement in the ink ejection direction starts. In this case, the force by which the meniscus moves in the ink ejection direction is amplified, and FIG.
As shown in the waveform C of FIG. 3B, the slope becomes steeper than the waveform A, and the peak P4 of the meniscus on the nozzle opening 33 side exceeds the nozzle opening surface. Therefore, the nozzle opening 3
There is a possibility that ink mist is ejected from the nozzle 3.

Actually, the time t1 of the expansion step a
Is shorter than の of the Helmholtz oscillation period Tc, the time t of the fine vibration driving step 62 is n × Tc <t <n
If the length satisfies the relationship of × Tc + Tc / 2 (n is an integer), the ejection of the ink mist can be prevented, but the time t of the micro-vibration driving step 62 is shorter in consideration of the speeding up of the head. Is more preferred. That is, it is desirable that the signal be short enough to be executed during one ejection driving step 61 without increasing the interval between the ejection driving steps 61. Therefore, the time t of the fine vibration driving step 62 is
It is preferable that the length be shorter than 1/2 of the Helmholtz oscillation period Tc.

The voltage (small vibration drive voltage) applied to the piezoelectric element in the fine vibration drive step 62 is the voltage (ejection drive voltage) applied to the piezoelectric element in the ejection drive step 61.
Is preferably set to 1/5 or less (20% or less). In the present embodiment, the fine vibration drive voltage is set to about 10% of the ejection drive voltage. Thus, it is possible to prevent the ink mist from being discharged by the fine vibration driving step 62. Furthermore, the conventional micro-vibration driving voltage is 40% of the ejection driving voltage.
On the other hand, in the present embodiment, in the present embodiment, the cost can be significantly reduced to 20% or less, whereby the cost can be reduced. Note that in order to obtain the effect of micro-vibration that prevents thickening and drying of the meniscus, 1/2 of the ejection voltage is required.
It is preferable to drive at a voltage of 0 or more (5% or more).

As described above, in the present embodiment, the time of the fine vibration driving step 62 is set to 1/1 / Helmholtz vibration Tc.
By setting the length to be shorter than 2, the Helmholtz oscillation is excited in the meniscus, and the ink near the nozzle opening is stirred by the Helmholtz oscillation. Accordingly, the viscosity increase and drying of the ink near the nozzle opening 33 can be reliably prevented, and the ink near the nozzle opening 33 can be stirred in a short time. Therefore, without increasing the interval of the ejection driving step 61 for ejecting ink droplets,
Substantially, the micro-vibration driving step 62 is replaced by one ejection driving step 6
1, the driving frequency of the head can be increased.

Further, since the same agitation effect can be obtained by keeping the micro-vibration driving voltage lower than that of the conventional one, the cost can be reduced.

In contrast to the fine vibration driving step according to the present embodiment, the conventional fine vibration driving step 162 includes, as shown in FIG. 7, a time t4 of the expansion step a1 and a time t5 of the contraction step c1. Is the Helmholtz oscillation period Tc
The meniscus surface moves up and down in the nozzle by this fine vibration driving step 162. Since the time of each of the micro-vibration driving processes 162 is relatively long, it is difficult to execute the micro-vibration driving process 162 without substantially changing the ejection timing in the ejection driving process 161. The drive frequency must be reduced.

Here, Helmholtz oscillation period Tc = 7.
When a head of about 5 μs is used, specifically, the time t1 of the expansion step a is 1 μs, the time t3 of the hold step b is 1.5 μs, and the time t2 of the contraction step c is 1 μs. By setting the time t to about 3.5 μs, good fine vibration driving can be performed. On the other hand, in the conventional micro-vibration driving step, the expansion step a1
Time t4 of 8 μs, and time t6 of hold process b1 is 2 μs.
μs, the time t5 of the contraction step c1 is required to be about 8 μs, and the time t7 of the entire fine vibration driving step is about 18 μs.
Required. That is, the micro-vibration driving step of the present embodiment reduces the time by 1 / compared to the conventional micro-vibration driving step.
Since the driving frequency can be reduced to about 5, the driving frequency can be increased.

(Other Embodiments) In the ink jet recording head described above, the pressure generating chamber is expanded by applying a voltage to the piezoelectric element. However, the present invention is not limited to this. The control method of the present invention can also be applied to an ink jet recording head that contracts the pressure generating chamber by applying the pressure.

FIG. 8 shows an example of an ink jet recording head having such a structure. The ink jet recording head shown in FIG. 8 has a similar structure except that a piezoelectric element 138 is provided instead of the piezoelectric element 38 shown in FIG. Piezoelectric element 1
Numeral 38 is configured so as to sandwich the piezoelectric material 139 and the electrode forming materials 140 and 141 alternately on the opposite side of the pressure generating chamber 32 of the diaphragm to form a laminated structure.
An inactive region that does not contribute to vibration is fixed to the fixed substrate 32. Therefore, when a voltage is applied to the electrode forming materials 140 and 141 of the piezoelectric element 138, the piezoelectric element 38 expands toward the nozzle plate 34, so that the vibration plate 3
5 is displaced, and the volume of the pressure generating chamber 32 is compressed. For example, the voltage is removed from a state where a voltage of 30 V is applied in advance,
By contracting the piezoelectric element 138, the ink can flow from the reservoir 37 into the pressure generating chamber 32 via the ink supply port 36. Thereafter, by applying a voltage, the piezoelectric element 38 expands, and the diaphragm 35 is deformed, so that the pressure generating chamber 32 contracts and the ink droplet is ejected from the nozzle opening 33. Therefore, by performing the charging and discharging of the voltage at the time of expansion and contraction of the control method described above in reverse,
A similar control method can be implemented.

In this embodiment, in the expansion step, the piezoelectric element 138 is charged with a voltage to increase the pressure of the ink in the pressure generating chamber 132, and in the contraction step, the piezoelectric element 138 is charged. By discharging the voltage, the pressure of the ink in the pressure generating chamber 132 is reduced.

Further, for example, in the micro-vibration driving step of the above-described embodiment, the driving voltage applied to the piezoelectric element may be appropriately adjusted according to the environmental temperature. Specifically, in a high-temperature environment where the ink viscosity is relatively low, a relatively weak vibration may be used, so that the driving voltage is adjusted to be lower.
In a low-temperature environment where the ink viscosity is relatively high, relatively strong vibration is required. Therefore, by adjusting the drive voltage to be increased, an optimum micro-vibration effect can always be obtained.

Further, the structure of the ink jet recording head capable of realizing the driving method of the present invention is not limited to the longitudinal vibration type ink jet recording head, and may be, for example, a flexural vibration type ink jet recording head or a bubble jet type recording head. The present invention can be applied to various types of liquid ejecting apparatuses such as an ink jet recording head.

[0082]

As described above, according to the present invention, by applying pressure to the ink in the pressure generating chamber without ejecting the ink from the nozzle opening to excite the meniscus to Helmholtz oscillation, the ink is finely vibrated. The ink near the nozzle opening was agitated. This makes it possible to stir the ink near the nozzle opening reliably in a short time, prevent thickening and drying of the ink near the nozzle opening, and increase the driving frequency of the head to realize high-speed printing. .

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a schematic configuration of an ink jet recording apparatus according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view of the ink jet recording head according to the first embodiment of the present invention.

FIG. 3 is a circuit diagram illustrating a circuit configuration of the ink jet recording head according to the first embodiment of the present invention.

FIG. 4 is a diagram illustrating an example of a waveform of a drive signal according to the first embodiment of the present invention.

FIG. 5 is a schematic diagram illustrating an example of a drive signal and a micro-vibration drive signal according to the first embodiment of the present invention.

FIG. 6 is a schematic diagram illustrating a fine vibration drive signal to be compared with the fine vibration drive signal according to the first embodiment of the present invention.

FIG. 7 is a schematic diagram illustrating a conventional drive signal and a micro-vibration drive signal.

FIG. 8 is a cross-sectional view illustrating an example of an ink jet recording head according to another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 31 Spacer 32 Pressure generating chamber 34 Nozzle plate 35 Vibration plate 38 Piezoelectric element

Continued on the front page (72) Inventor Hironobu Hasei 3-3-5 Yamato, Suwa-shi, Nagano F-term in Seiko Epson Corporation (reference) 2C057 AF02 AF74 AG12 AL26 AM16 AR06 AR07 BA04 BA14

Claims (11)

[Claims] 1. A pressure generating chamber which communicates with a nozzle opening and has a Helmholtz oscillation frequency of a period Tc, and a pressure generating means for applying pressure to ink in the pressure generating chamber, and the pressure generating means is driven. A method of controlling a liquid ejecting apparatus that excites vibration in a meniscus by driving the pressure generating means of the liquid ejecting apparatus that ejects ink droplets to stir ink near the nozzle opening, wherein the ink droplet is ejected from the nozzle opening A liquid that includes a micro-vibration driving step of applying Helmholtz oscillation with a period Tc to the meniscus by applying pressure to the ink in the pressure generating chamber without stirring, and agitating the ink near the nozzle opening. Control method of the injection device. 2. The micro vibration driving step according to claim 1, wherein the time for increasing the pressure of the ink in the pressure generating chamber and the time for decreasing the pressure of the ink are each shorter than the Helmholtz oscillation period Tc. A method for controlling a liquid ejecting apparatus. 3. The method according to claim 2, wherein in the fine vibration driving step, the time for increasing the pressure of the ink in the pressure generating chamber and the time for decreasing the pressure of the ink are each smaller than の of the Helmholtz oscillation period Tc. A method for controlling a liquid ejecting apparatus, wherein the method is also short. 4. The method according to claim 1, wherein in the fine vibration driving step, the total time t during which the pressure in the ink in the pressure generating chamber is increased or decreased is n × Tc <.
A control method for a liquid ejecting apparatus, wherein t <n × Tc + Tc / 2 (n is an integer). 5. The method according to claim 4, wherein in the micro-vibration driving step, the total time t during which the pressure of the ink in the pressure generating chamber is increased or decreased is changed to a Helmholtz oscillation period T.
A method for controlling a liquid ejecting apparatus, wherein the method is shorter than 1/2 of c. 6. The method according to claim 1, wherein the driving voltage applied to the pressure generating means in the fine vibration driving step is applied to the pressure generating means in an ejection step of ejecting ink droplets from the nozzle openings. A method of controlling the liquid ejecting apparatus, wherein the driving voltage is not more than 1/5 of the driving voltage to be applied. 7. The method according to claim 1, wherein the driving voltage applied to the pressure generating means in the fine vibration driving step is applied to the pressure generating means in an ejection step of ejecting ink droplets from the nozzle openings. A method for controlling the liquid ejecting apparatus, wherein the driving voltage is 1/20 or more of the driving voltage. 8. A control method for a liquid ejecting apparatus according to claim 1, wherein a driving voltage applied to said pressure generating means in said fine vibration driving step is changed in accordance with an environmental temperature. 9. The control method for a liquid ejecting apparatus according to claim 1, wherein the fine vibration driving step is performed during a discharge step of discharging ink droplets from the nozzle openings. 10. The fine vibration driving step according to claim 1, wherein the fine vibration driving step is performed only for a nozzle opening in which ink droplets are not discharged in a discharging step of discharging ink droplets from the nozzle opening. A method for controlling a liquid ejecting apparatus, comprising: 11. The liquid according to claim 1, wherein the pressure generating means is a piezoelectric element disposed on a diaphragm provided on one surface of the pressure generating chamber. Control method of the injection device.