JP2013121665A - Device and method for discharging droplet, printing device including the droplet discharge device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a variation in droplet speed due to a drive frequency while preventing an increase in a waveform length by adding a pulse other than a fine drive pulse for preventing thickening, in a droplet discharge device.SOLUTION: In a droplet discharge device, a drive control part 100 selects a discharge drive waveform for droplet discharge or a fine drive waveform for imparting micro vibration for each time period element to perform discharge control of a droplet, wherein the drive control part 100 adjusts a time interval between the rising of the fine drive waveform and the rising of the discharge drive waveform in one time period element immediately thereafter so that a droplet discharge speed at a low frequency is approximately equal to a droplet discharge speed at a high frequency.

Description

  The present invention relates to a droplet discharge device, specifically, for example, a serial type printing device that mounts a droplet discharge head on a carriage and performs printing while reciprocating, and a state in which the droplet discharge head is installed on a line. The present invention relates to a drop-on-demand type droplet discharge apparatus, a droplet discharge method, and a printing apparatus including the droplet discharge apparatus, which form an image using a line head type printing apparatus for printing.

Conventionally, in a droplet discharge apparatus such as an ink jet recording apparatus, a piezoelectric element is deformed by a driving pulse, and an instantaneous pressure is applied to ink in the pressure chamber in accordance with the deformation, and an ink droplet is discharged from a nozzle opening to be covered. Characters, figures, etc. are recorded on a landing medium (recording medium).
In this conventional droplet discharge device, depending on the discharge timing of the ink droplet, vibration due to the previous discharge remains in the pressure chamber, thereby causing a problem that the ink discharge amount and the ink discharge speed vary.

In order to cope with this problem, an inkjet recording apparatus that applies a stop pulse voltage to a piezoelectric member has been proposed in order to eliminate vibrations caused by the previous deformation of the piezoelectric element in the inkjet recording apparatus (see Patent Document 1). ).
However, in this conventional ink jet recording apparatus, in order to suppress the residual vibration, it is necessary to use a pulse that is used only for suppressing the vibration, not for discharging the droplet, which is useless in that respect. Consume power. In addition, since the pulse is added at the time of recording, the entire waveform length required for the recording is increased, which causes another problem that it is disadvantageous for high-speed recording.

  The present invention has been made by paying attention to the above-mentioned problems of the prior art, and its purpose is to eliminate the adverse effects such as an increase in waveform length caused by using a new pulse as in the prior art in a droplet discharge device. It is to reduce the fluctuation of the droplet velocity due to the driving frequency.

  The present invention includes a droplet discharge head that discharges a droplet by changing a volume of a pressure chamber by a pressure generation unit, and a drive control unit that applies a drive waveform that changes the volume of the pressure chamber to the pressure generation unit. A liquid droplet ejection apparatus capable of ejecting liquid droplets at a high frequency and a low frequency, wherein the drive control unit ejects a liquid ejection drive waveform and a liquid ejection waveform when the liquid droplet is ejected at the low frequency When selecting a fine drive waveform one period before the timing and discharging a droplet at the high frequency, a waveform selection means for selecting the discharge drive waveform at the discharge timing, and a droplet discharge speed at the low frequency Adjusting means for adjusting a time interval between the rising edge of the fine driving waveform and the rising edge of the discharge driving waveform in the one-period element immediately thereafter so that the droplet discharge speeds at the high frequency are substantially equal. 1 period required A droplet ejection apparatus for controlling the ejection of droplets by selecting fine drive waveform for applying a discharge driving waveform or micro-vibration for droplet ejection in each.

  According to the present invention, in the droplet discharge device, the fine drive pulse that is currently used to prevent thickening of the recording liquid such as ink is used as it is, thereby preventing an increase in the waveform length during discharge. However, fluctuations in the droplet velocity due to the driving frequency can be reduced.

It is sectional drawing of the droplet discharge head used by embodiment of this invention. It is a drive waveform of the drive pulse applied to a piezoelectric vibrator by the drive control part used by embodiment of this invention. Is a graph showing the driving frequency and the relationship between the droplet velocity of the ejection pulse P ₀ when performed using the driving waveform of FIG. It is a wave form diagram which shows the waveform selected when droplets are discharged at a low frequency. It is the graph which showed the relationship between the time of pitch T between pulses in the case of discharging a droplet at low frequency, and a droplet velocity. It is a graph which shows the measurement result of the relationship between a drive frequency and a droplet velocity, Comprising: The measurement result of the relationship between the drive frequency and droplet velocity after time correction of the pitch T between pulses. It is a wave form diagram which shows the waveform selected at the time of droplet discharge. A graph showing the driving frequency and the relationship between the droplet velocity of the ejection pulse P ₀ when performed using the drive waveform, the droplet at the droplet velocity VL> frequency in the case of droplet discharge in the low frequency The case where the speed is VH is shown. It is a graph which shows the relationship between the droplet velocity after time correction | amendment to the pitch T between pulses, and a drive frequency.

Embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view of a droplet discharge head 1 using a piezoelectric vibrator 61 used in an ink jet recording apparatus according to an embodiment of the present invention.
The droplet discharge head 1 is mainly composed of a flow path substrate 2, a frame 50, and pressure generating means 60. The flow path substrate 2 controls a nozzle plate 10 having a large number of nozzle openings 11 in a direction perpendicular to the paper surface, a pressure chamber 21 communicating with the nozzle openings 11, and a liquid inflow amount into the pressure chamber 21. The restrictor plate 20 having the fluid resistance portion 22, the diaphragm plate 30 on which the diaphragm 31 for efficiently transmitting the pressure of the pressure generating means 60 to the pressure chamber 21, and the ink in the common ink chamber 51 are used. It consists of a manifold plate 40 for diverting to each nozzle opening 11.

  The frame 50 has the common ink chamber 51 that holds the flow path substrate 2 and introduces and stores ink from the outside, and the opening faces the manifold plate 40. In the pressure generating means 60, for example, one end of a piezoelectric vibrator 61 in which conductive material and piezoelectric material are alternately laminated is fixed to a support member 62, and the other end of the piezoelectric vibrator 61 is bonded to the diaphragm plate 30 with an adhesive. It is a structured.

Electrodes are formed on the piezoelectric vibrator 61 and are electrically connected to the drive control unit 100. The drive control unit 100 includes a waveform selection unit 101 and an adjustment unit 102 described later. Printing material, for example, ink is supplied from an ink supply pipe or a head connection pipe (not shown), enters the common ink chamber 51, passes through the manifold plate 40, passes through the fluid resistance portion 22, the pressure chamber 21, and the nozzle opening. It flows to 11 in order.
The piezoelectric vibrator 61 of the pressure generating means 60 expands and contracts by applying a predetermined drive pulse from the drive control unit 100, and returns to the state before expansion and contraction when the application of the drive pulse is stopped. The ink in the pressure chamber 21 receives a momentary pressure due to the deformation of the piezoelectric vibrator 61 and lands on the adherend as a droplet from the nozzle opening 11.

  The droplet discharge head 1 configured as described above has compliance (reciprocal of elastic modulus) determined by the shape of the nozzle opening 11, the pressure chamber 21, and the fluid resistance portion 22 from the nozzle opening 11 to the fluid resistance portion 22. It has a natural oscillation period determined by inertance (the degree of influence that the unit pressure has on the time variation of the flow rate), that is, the Helmholtz period Tc.

FIG. 2 is a drive waveform diagram of drive pulses applied to the piezoelectric vibrator 61 by the drive control unit 100 used in the embodiment of the present invention.
One printing cycle includes a period A including an ejection pulse P ₀ for ejecting droplets, a period B for maintaining an intermediate potential, and ink without ejecting droplets to prevent thickening of ink in the nozzles. consists each time element of the time C that contains fine driving pulse P ₁ is swung.
The drive control unit 100 selects these three periods A, B, and C (period elements) according to printing information, and performs printing at appropriate positions.

The ejection pulse P ₀ in the period A expands the volume of the pressure chamber 21 at the voltage falling portion D ₁ and maintains the state for a predetermined time, and then contracts the volume of the pressure chamber 21 at the voltage rising portion U _1. Thus, a droplet (ink droplet) is ejected from the nozzle.

Voltage rising portion U ₂ of the second stage is used to shrink the satellite length of the droplets, the last of the voltage falling portion D ₂ in the period A are those to suppress residual vibration after the ejection. In the period B, the piezoelectric vibrator 61 is charged in a predetermined manner so that the reference displacement of the piezoelectric vibrator is always constant. Period fine driving pulse P ₁ of C, after the droplets to expand the volume of the pressure chamber 21 by the voltage falling part D ₃ to the extent not discharging, and held for a predetermined time that state, the pressure chamber at a voltage rising portion U ₃ By contracting the volume of 21, the ink in the vicinity of the nozzle is agitated, the ink in the vicinity of the nozzle surface is thickened, and the phenomenon that the ink is not normally discharged by the next application of the discharge pulse P ₀ is prevented. Is for.

Figure 3 is a graph showing the driving frequency and the relationship between the droplet velocity of the ejection pulse P ₀ when performed using the driving waveform of FIG.
The waveform selection means 101 of the drive control unit 100 selects the period A of FIG. 2 every 25 usec at the high frequency in FIG. 3, here the drive frequency 40 kHz, and similarly every 50 usec at low frequency, here 20 kHz. Period A is selected.
As is apparent from FIG. 3, the droplet velocity differs by about 0.4 m / s between a low frequency of 20 kHz or less and a high frequency at 40 kHz. This is because, at high frequency, the next droplet discharge is started in a state where the residual vibration after the droplet discharge is still large, so that the droplet velocity can be obtained by combining the pressure fluctuation due to the residual vibration and the pressure fluctuation due to the discharge pulse. It is. As described above, when the droplet velocity fluctuates depending on the frequency, a uniform printed image cannot be obtained.

Therefore, conventionally, as described above, in order to eliminate fluctuations in the droplet velocity due to the driving frequency, a method of applying a pulse that cancels residual vibration after droplet ejection has been adopted. However, if a pulse is newly added to reduce the residual vibration, one printing cycle becomes longer, and it becomes impossible to cope with high-speed printing.
Incidentally, since the fine drive pulse P ₁ for preventing ink thickening is used as a pulse that does not eject ink (droplet) that has already been used, the fine drive pulse P ₁ is used to cancel the residual vibration. If possible, an increase in one printing cycle can be prevented. However, until now, it has been difficult to achieve the two actions of vibration suppression of the ejection pulse P ₀ and prevention of ink thickening with this one fine driving pulse P ₁ .

This embodiment selects the driving pulse waveform in response to a low high-ink ejection frequency, the time, when possible to reduce the variation in droplet velocity by the driving frequency by utilizing the vibration generated by the fine driving pulse P ₁ It was devised based on this knowledge.
Hereinafter, this point will be described.

FIG. 4 is a waveform diagram showing waveforms selected when droplets are ejected at a low frequency based on the above knowledge.
That is, the waveform selected by the drive control unit 100 (waveform selection unit 101) when ink is ejected at a low frequency is shown.
In the present embodiment, a pulse waveform in which the ejection pulse P _{0 in the} period A and the fine driving pulse P ₁ in the period C are combined is used.
That is, the waveform selection unit 101 of the drive control unit 100 selects the ejection pulse P ₀ in the period A in FIG. 2 when ejecting ink at a low frequency, and the period C immediately before that is the period C. to select the fine driving pulse _{P 1.}
Here, from this time the pressure chamber pressure starts in the fine driving pulse P ₁ (when the voltage rising unit start), the ejection pulse P ₀ at the start of the pressure chamber pressure at the time the pulse pitch up (voltage rising portion at the beginning) T.

FIG. 5 is a graph showing the relationship between the time of the pitch T between pulses and the droplet velocity when droplets are ejected at a low frequency.
The Helmholtz period Tc of the droplet discharge head used in this embodiment is about 3.1 usec. From the graph of FIG. 5, the droplet velocity is 9.6 usec, which is substantially an integral multiple (about 3 times) thereof. The maximum and the minimum droplet velocity are about 8.2 us and about 11.4 us, and it can be seen from these values that the droplet velocity fluctuates in substantially the same period as the Helmholtz period Tc.

From FIG. 5, it can be seen that the droplet velocity is 7 m / s when the pulse pitch T is 9.3 usec, which is the same as the droplet velocity at the high frequency of 40 kHz shown in FIG. Therefore, as a condition for setting the arrangement of the ejection pulse P ₀ and the fine driving pulse P ₁ in one printing cycle to be a pulse-to-pulse pitch 9.3 (3 Tc) usec and performing ejection by the ejection pulse P ₀ , When discharging at a high frequency, only the period A in one printing cycle is used for discharging, and when discharging at a low frequency, the period A is selected as the period element for discharging, and the period element immediately before is selected. The relationship between the driving frequency and the droplet velocity was measured under the condition that the period C of the fine driving pulse was selected.

FIG. 6 is a graph showing the measurement result of the relationship between the driving frequency and the droplet velocity, and the measurement result of the relationship between the driving frequency and the droplet velocity after the time correction of the pitch T between pulses.
As is apparent from FIG. 6, in this case, a constant droplet velocity of approximately 7 m / s could be obtained regardless of the driving frequency.
From the above, it was found that the conditions for ejecting droplets at a constant droplet velocity are as follows.
That is, first, a droplet when the positional relationship between the immediately preceding fine driving pulse P ₁ and the ejection pulse P ₀ within one printing cycle is low-frequency ejection and ejection is performed using two pulses P ₁ and P _0. speed and, the drop velocity when ejected using only ejection pulse P ₀ at a high frequency discharge is adjusted to be the same. The waveform is selected as shown in FIG. FIG. 7 is a waveform diagram showing waveforms selected at the time of droplet discharge.

That is, the drive control unit 100 controls the ink ejection by selecting the ejection driving waveform for ejecting ink or the fine driving waveform for giving fine vibration for each period element by the waveform selection means. That is, (1) ejection of ink at a high frequency, as shown in FIG. 7A, in one period element using the ejection pulse P ₀ selects the period A in FIG. (2) ejection of ink at low frequencies, as shown in FIG. 7B, in one period element using the ejection pulse P _0, select the period A in FIG. 2, the fine driving pulse in one period element immediately before The period C in FIG. 2 that is P ₁ is selected. (3) When not eject droplets, in order to prevent the ink can not be normally discharged when thickened with the necessary, as shown in FIG. 7C, is a fine driving pulse P ₁ is a first period element The period C in FIG. 2 is selected.

In FIG. 7C, the period C (fine drive pulse P ₁ ) is always selected as one period element. However, the number of fine drive pulses P ₁ should be reduced as much as possible within a range in which ejection failure due to thickening does not occur. It is desirable because power consumption can be reduced. Depending on the type of ink, the fine driving pulse may be selected every other period element or once every three period elements.
Also in the case shown in FIG. 7B, it is desirable to reduce the number of fine driving pulses as much as possible in order to reduce power consumption. That is, as shown in FIG. 7B, the fine driving pulse P ₁ + the ejection pulse P ₀ is necessary for low-frequency ejection, but there is no adverse effect even if the fine driving pulse P ₁ is not present in the period elements before and after that. it is desirable to not put the fine driving pulse P _1.

  The above embodiment is a case where the relationship between the droplet velocity VL in the low frequency ejection and the droplet velocity VH in the high frequency is VL <VH. In this case, the inter-pulse pitch T in FIG. As is clear from the relationship between the droplet speeds, the variation in the droplet speed due to the driving frequency is increased by adopting a place where the inter-pulse pitch T is close to an integral multiple of the Helmholtz period Tc to increase the droplet speed in the low frequency discharge. Can be reduced.

Depending on the waveform and the head ink, as shown in the graph of FIG. 8, there are cases where the droplet velocity VL in the low frequency ejection> the droplet velocity VH in the high frequency ejection. In this case, from the relationship between the pitch between pulses and the droplet velocity in FIG. 5, a method for lowering the droplet velocity at a low frequency by employing an odd multiple (including the vicinity thereof) of the pulse pitch T as Tc / 2. Take.
That is, when the droplet velocity VL in the low frequency discharge is decreased, the pitch T between the pulses is shifted by Tc / 2 from that when the droplet velocity VL is increased, and the portion where the droplet velocity falls below the center of the droplet velocity fluctuation in FIG. In particular, the pitch T between the pulses of the smallest part is taken. Thereby, as shown in FIG. 9, the fluctuation | variation of the droplet speed by a drive frequency can be reduced. FIG. 9 is a graph showing the relationship between the droplet velocity after the time correction to the pitch T between pulses and the driving frequency.
As described above, the inter-pulse pitch T between the fine driving pulse P ₁ and the ejection pulse P ₀ is adjusted by the relationship between the droplet velocity VL in the low frequency ejection and the droplet velocity VH in the high frequency ejection, thereby depending on the driving frequency. Variations in droplet velocity can be reduced. This adjustment can be performed by the adjusting means 102 (FIG. 1) of the drive control unit 100.

  Note that both the waveform selection unit 101 and the adjustment unit 102 of the drive control unit 100 can be configured as function realizing units realized by causing the computer of the drive control unit 100 to read a program.

  DESCRIPTION OF SYMBOLS 1 ... Droplet discharge head, 2 ... Channel board, 10 ... Nozzle plate, 11 ... Nozzle opening, 21 ... Pressure chamber, 22 ... Fluid resistance part, 31 ... Diaphragm, 51 ... Common ink chamber, 60 ... Pressure generating means, 61 ... Piezoelectric vibrator, 100 ... Drive controller.

JP 10-291308 A

Claims (5)

A droplet discharge head that discharges droplets by changing the volume of the pressure chamber by the pressure generating means; and a drive control unit that applies a drive waveform that changes the volume of the pressure chamber to the pressure generating means. A droplet discharge device capable of discharging droplets at a low frequency,
When discharging the droplet at the low frequency, the drive control unit selects a discharge drive waveform and a fine drive waveform one period element before the discharge timing of the discharge drive waveform, and discharges the droplet at the high frequency. When discharging, waveform selection means for selecting a discharge drive waveform at the discharge timing; and
The time between the rise of the fine drive waveform and the rise of the discharge drive waveform in one period element immediately thereafter so that the droplet discharge speed at the low frequency and the droplet discharge speed at the high frequency are substantially equal. Adjusting means for adjusting the interval;
Have
A droplet discharge device that performs droplet discharge control by selecting a discharge drive waveform for droplet discharge or a fine drive waveform for giving fine vibration for each period element. In the droplet discharge device according to claim 1,
The Helmholtz period of the droplet ejection device is Tc, the droplet velocity when ejecting ink at the low frequency is VL, the droplet velocity when ejecting droplets at the high frequency is VH, and VL <VH. when,
The drive control unit is a droplet discharge device that adjusts the time interval to an integral multiple of Tc. In the droplet discharge device according to claim 1,
The Helmholtz period of the droplet ejection device is Tc, the droplet velocity when ejecting ink at the low frequency is VL, the droplet velocity when ejecting droplets at the high frequency is VH, and VL> VH. when,
The drive control unit is a droplet discharge device that adjusts the time interval to an odd multiple of Tc / 2.   A printing apparatus comprising the droplet discharge device according to claim 1. A droplet discharge head that discharges droplets by changing the volume of the pressure chamber by the pressure generating means; and a drive control unit that applies a drive waveform that changes the volume of the pressure chamber to the pressure generating means. A droplet discharge method in a droplet discharge apparatus capable of discharging droplets at a low frequency,
When ejecting droplets at the low frequency, select the ejection drive waveform and the fine drive waveform one period before the ejection timing of the ejection drive waveform, and when ejecting droplets at the high frequency, A waveform selection step for selecting the ejection drive waveform at the timing;
The time between the rise of the fine drive waveform and the rise of the discharge drive waveform in one period element immediately thereafter so that the droplet discharge speed at the low frequency and the droplet discharge speed at the high frequency are substantially equal. An adjustment process for adjusting the interval;
Have
A droplet discharge method for controlling droplet discharge by selecting a discharge drive waveform for discharging a droplet or a fine drive waveform for giving fine vibration for each period element.

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