JPH0516359A - Driving method for liquid jet recording head - Google Patents

Abstract

PURPOSE:To realize improvement of image quality and high speed printing at a low cost. CONSTITUTION:When an auxiliary pulse is applied as shown at (a), a superposed oscillating voltage waveform, generated by a residual pressure wave, can be observed at section (A) as shown at (b). Assuming the period of the oscillating waveform is T and the amplitude thereof is V, motion of meniscus in the vicinity of the nozzle plane is synchronized with the period T of the residual pressure wave and the moving distance from the nozzle plane oscillates repeatedly in proportion to the amplitude V. Delivery of ink droplet can be varied by applying a main pulse in synchronization with the period T of the residual pressure wave after application of the auxiliary pulse.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for driving a liquid jet recording head.

[0002]

2. Description of the Related Art In an on-demand type ink jet recording apparatus, it is necessary to reduce the diameter of dots printed on the recording paper in order to perform high resolution recording with high density on the recording paper. For that purpose, it is necessary to reduce the size of the droplet discharged from the nozzle. In order to reduce the size of the liquid droplets ejected from the nozzle, it is conceivable to reduce the diameter of the nozzle opening. However, if the diameter of the nozzle opening is reduced, clogging of the nozzle easily occurs, and The friction of the ink liquid increases in the portion, and the ink liquid is less likely to be ejected from the nozzle. Due to the fluidity of the ink liquid passing through the nozzle, there is naturally a limit to reducing the diameter of the nozzle opening. The size of the droplet can be reduced to some extent by reducing the diameter of the nozzle opening, but the size cannot be freely controlled.

In order to solve this point, for example, JP-A-59-143652 and JP-A-59-14365.
A "liquid discharging device" is proposed in Japanese Patent Laid-Open No. In this publication, before applying the main pulse voltage, an auxiliary pulse having the same polarity as the main pulse voltage or the opposite polarity to determine the tip position of the liquid in the nozzle is applied.

Further, the "on-demand type ink jet recording apparatus" proposed in Japanese Patent Laid-Open No. 59-176055 discloses a pulse width or peak value of an auxiliary pulse applied prior to the main pulse, or the auxiliary pulse. The time interval with the main pulse is adjustable. Conventionally, in the on-demand type ink jet printer, as shown in FIG. 9, the ink discharge amount Mj greatly varies with respect to the frequency of the print signal, which causes the dot diameter on the image to vary. In particular, when solid printing is performed at the highest drive frequency, density unevenness of the image is caused and the image quality is significantly deteriorated.

A driving method in the present invention is described in the above-mentioned JP-A-59-176055 and JP-A-59-14365.
As disclosed in Japanese Patent Laid-Open No. 3 and Japanese Patent Laid-Open No. 59-143652, it is similar in that the position of the ink surface when applying a pulse for ejecting an ink droplet is controlled by an auxiliary pulse. Does not describe the specific relationship between the method of applying the auxiliary pulse and the ink surface and ink droplet size. Therefore, it is difficult to actually control the size of the ink droplet by the auxiliary pulse in the conventional technique described in the above publication.

Further, in the above publication, the behavior of the ink surface changes depending on the level of the voltage of the auxiliary pulse and the difference in the pulse width, and the time required for the ink solution to repeat one reciprocating motion in the nozzle. It is noted that (the cycle of ink liquid vibration) changes. However, it is considered that the vibration cycle of the ink liquid matches the vibration cycle of the residual pressure wave because the pressure wave generated by the applied auxiliary pulse remains in the flow path and the nozzle. The cause of the vibration of the residual pressure wave is that the ink liquid is caused by the natural vibration defined by the vibration system including the structure (size, material, shape) of the flow path and the nozzle, the elastic coefficient of the piezoelectric element, the viscosity of the ink liquid, and the mass. Because it resonates.
Therefore, even if the crest value and the pulse width of the auxiliary pulse are changed, the period of the ink liquid vibration does not change, and only the amplitude thereof changes, which is a point different from the above-mentioned conventional technique. Further, as described in the above publication, reversing the polarities of the auxiliary pulse signal and the main pulse signal only increases the cost of the drive circuit.

[0007]

An object of the present invention is to provide a method for driving a liquid jet recording head, which has been made in view of the above-mentioned circumstances, and which realizes an improvement in image quality and an increase in printing speed at low cost. It was done for the purpose.

[0008]

In order to achieve the above object, the present invention provides (1)
A plurality of parallel flow channels arranged at intervals in the longitudinal direction of the flow channels, nozzles connected to each of the parallel flow channels to eject droplets, and connections for supplying liquid to the parallel flow channels. And a piezoelectric element for changing the volume of the flow passage by displacing in the direction perpendicular to the longitudinal direction of the parallel flow passage, and a signal for holding the piezoelectric element so as to constantly reduce the flow passage volume. To the selected flow path, and then a pulse signal is applied to give a displacement to reduce the flow path volume again, and then a droplet is ejected from the nozzle corresponding to the flow path. In a method of driving a liquid jet recording head that ejects, applying auxiliary pulses having different pulse widths or peak values before applying the pulse signal, and applying the pulse signal in accordance with the cycle of the residual pressure wave, Or (2) with respect to the longitudinal direction of the flow path A plurality of parallel flow channels arranged at intervals, nozzles connected to each of the parallel flow channels to eject droplets, connection means for supplying liquid to the parallel flow channels, and the parallel flow channel Of a piezoelectric element for varying the volume of the flow passage by displacing in the direction perpendicular to the longitudinal direction of the piezoelectric element, and giving a signal for holding the piezoelectric element so that the flow passage volume is constantly reduced,
After displacing the selected channel in the direction of increasing the channel volume, a pulse signal is applied to give a displacement to reduce the channel volume again, and droplets are ejected from the nozzle corresponding to the channel. In a method of driving a liquid jet recording head, the crest value or pulse width of an auxiliary pulse is changed according to the dot diameter before the pulse signal is applied, and the pulse signal is applied according to the cycle of the residual pressure wave. And even,
(3) A plurality of parallel flow channels arranged at intervals in the longitudinal direction of the flow channels, nozzles connected to each of the parallel flow channels to eject droplets, and the parallel flow channels. A connecting means for liquid, and a piezoelectric element for varying the volume of the flow passage by displacing in the direction perpendicular to the longitudinal direction of the parallel flow passage,
In a method of driving a liquid jet recording head, which applies a pulse signal for displacing a piezoelectric element in a direction of reducing a flow channel volume to a selected flow channel to eject droplets from a nozzle corresponding to the flow channel, Before the pulse signal is applied, the auxiliary pulse described in (1) or (2) is applied, and the pulse signal is applied according to the cycle of the residual pressure wave. Hereinafter, description will be given based on examples of the present invention.

First, FIGS. 2A and 2B are configuration diagrams for explaining a liquid jet recording head, wherein FIG. 2A is a sectional view and FIG. 2B is A in FIG. FIG. 7 is an enlarged view taken along line A-A.
In the figure, 1 is a substrate, 2 is a piezoelectric element, 2a is a non-driving piezoelectric element, 2b is a driving piezoelectric element, 3 is a flow path plate, 3a is an ink flow path, 3b is a wall portion, 4 is a common liquid chamber constituent member, 4a is a common liquid chamber, 5 is an ink supply pipe, 6 is a nozzle plate, 6a
Is a nozzle, 7 is a drive circuit printed board (PBC), 8 is a lead wire, 9 is a drive electrode, 10 is a filler, 11 is a protective plate, 12 is a fluid resistance, 13 and 14 are internal electrodes, and 15 is an upper partition wall. Is.

In the integrated head, the internal electrode 1
The laminated piezoelectric element 2 having 3, 14 is subjected to groove processing in the direction of the flow path 3a corresponding to the flow path 3a.
It is divided into a driving piezoelectric element 2b and a non-driving piezoelectric element 2a.
A filling material is enclosed in the groove 10. The flow path plate 3 is bonded to the grooved piezoelectric element 2 through the upper partition wall 15. That is, the upper partition wall 15 is the non-driving piezoelectric element 2
It is supported by a and a wall portion 3b that separates the adjacent flow path. The width of the driving piezoelectric element 2a is slightly narrower than the width of the flow path 3a,
When a pulsed signal voltage is applied to the driving piezoelectric element 2b selected by the driving circuit on the driving circuit printed board (PCB), the driving piezoelectric element 2b is displaced in the thickness direction, and the flow path 3a is passed through the upper partition wall 15. Changes, and as a result, ink droplets are ejected from the nozzles 6a of the nozzle plate 6.

As described above, in the structure of the ink jet head shown in FIG. 2, the residual vibration has a pulse width of 2 L / Cs.
Can be significantly reduced by setting it to a natural multiple (L is the length of the pressurized liquid chamber, Cs is the velocity of the pressure wave) or by operating the pulse fall time according to the attenuation of the residual vibration. . However, even if the drive waveform is determined at the design or manufacturing stage, the residual vibration is due to the natural frequency of the liquid chamber structure and the system of the piezoelectric body and the ink fluid, and the operating environment of the head (temperature, humidity, aging When the deterioration) changes, the residual vibration also changes. Therefore, the drive waveform must also be adjusted accordingly.

FIGS. 1A and 1B are views for explaining a method of driving a liquid jet recording head according to the present invention, and a residual pressure wave and mechanics driving will be described. When the auxiliary pulse is applied as shown in FIG. 1A, the voltage oscillation waveform generated by the residual pressure wave as shown in FIG. The period of this vibration waveform is T,
When the amplitude is V, the movement of the meniscus near the nozzle surface is synchronized with the cycle T of the residual pressure wave, and the movement distance from the nozzle surface repeats vibration in proportion to the amplitude V. When the main pulse is applied after applying the auxiliary pulse in synchronization with the cycle T of the residual pressure wave, the ejection amount of the ink droplet can be changed.

3A to 3C are diagrams showing the residual pressure wave and the meniscus (the position of the ink liquid surface from the nozzle surface). In FIG. 1A, the main pulse is applied at time t = ta in FIG. 1B, the residual pressure wave has a maximum of positive pressure, and the position of the meniscus is as shown in FIG. It projects from the nozzle surface. FIG. 1B shows a state in which the main pulse is applied at time t = tb in FIG. 1B, the surface tension of the liquid surface and the atmospheric pressure are balanced, and the position of the meniscus is shown in FIG. 1B. As shown in, the position is almost the same as the nozzle surface. FIG. 1C shows time t = in FIG. 1B.
Since the main pulse is applied at the time of tc and the residual pressure wave has the maximum of negative pressure, the position of the meniscus is in a state of being drawn inward of the nozzle surface as shown in FIG. At this time, even if the pulse width Pw2 of the auxiliary pulse to be applied or the peak value Vp2 is changed, only the amplitude amount of the meniscus vibration is changed, and the vibration cycle is not changed.

FIGS. 4A to 4C are diagrams showing the relationship between the constant periodicity of meniscus vibration and the timing of main pulse application, and FIGS. 5A to 5C show the timing of main pulse application. It is a figure which shows the discharge state of an ink drop. 4 (a)-
(C) and FIGS. 5 (a)-(c) correspond to FIGS. 3 (a)-(c), respectively. In FIG. 4A, when the delay time between the auxiliary pulse (Pw2, Vp2) and the main pulse (Pw1, Vp1) is Td, Td = ta = T, and the position of the meniscus in that case is shown in FIG. (A),
Since the main pulse (Pw1, Vp1) is applied from that state, ink droplets are ejected as shown in FIG. The ink ejection amount Mj in this case is Mja. Figure 4 (b)
, The delay time between the auxiliary pulse (Pw2, Vp2) and the main pulse (Pw1, Vp1) is Td = Tb = (5 /
4) T, and the position of the meniscus in that case is as shown in FIG. 3 (b), and from that state, the main pulse (Pw1,
Since Vp1) is applied, ink droplets are ejected as shown in FIG. In this case, the ink ejection amount Mj is Mj
b. Comparing the case of FIG. 5A and the case of FIG. 5B, the ejection amount of the ink droplets is larger in the case of FIG. 5A. That is, Mja> Mjb.

In FIG. 4C, the auxiliary pulse (Pw
2, Vp2) and the main pulse (Pw1, Vp1) have a delay time of Td = tc = (3/2) T, and the position of the meniscus in this case is as shown in FIG. 3 (c). Since the main pulse (Pw1, Vp1) is applied, ink droplets as shown in FIG. 5C are ejected. In this case, the ink ejection amount Mj is Mjc. Comparing the case of FIG. 5B and the case of FIG. 5C, the ejection amount of the ink droplets in the case of FIG. 5B increases. That is, Mjb> Mj
c. In this way, according to the cycle of the residual pressure wave,
When the main pulse is applied after the auxiliary pulse is applied, the ink droplet ejection amount Mj can be changed as shown in FIG.

As can be seen from FIG. 6, Td for maximizing Mj is not limited to Td = T, and may be any integral multiple of T,
Further, Td for minimizing Mj is not limited to Td = (3/2) T, and may be an odd multiple of (1/2) T. If ink droplets are ejected by the application of the auxiliary pulse itself, the paper surface is stained and the image quality is impaired. Therefore, as shown in FIGS. 7 and 8, the pulse width Pw2 and its peak value Vp2 are limited. If Pw2 is set to a pulse width such that the maximum amplitude Vm of the residual pressure wave exceeds Vm0, the auxiliary pulse itself ejects ink droplets. If Vm <Vm0, the larger Pw2 is, the larger the Mj fluctuation amount ΔMj is. Similarly, for Vp2, if Vm> Vm0, ink droplets are ejected by the auxiliary pulse itself,
If m <Vm0, the larger Vp2 is, the larger ΔMj is. Especially when considering the configuration of the drive circuit, Vp1
= Vp2 is more advantageous for cost reduction.

Since the amplitude of the residual pressure wave can be changed by changing Pw2 and Vp2 as described above,
Although it is possible to change the position of the ink drop surface, if the amplitude of the pressure wave is changed, the vibration of the meniscus becomes unstable, and eventually the bubbles may be sucked and the ink drop may not be ejected by the main pulse. Therefore, Pw2 or V
It is preferable to change Td according to the cycle of the residual pressure wave rather than changing p2.

Next, a specific example of the present invention will be described.Specific example 1 In the head structure as shown in FIG. 2, the pulse peak value Vp1
= Vp2 = 22 (V), main pulse width Pw1 = 14 (μ
s), auxiliary pulse width Pw2 = 7 (μs), delay time Td
= T = 28 (μs) (T is the period of the residual pressure wave),
When driven, the ejection amount at f = 8 KHz was Mj = 90.
× 10^-9From (cc), Mj = 120 × 10^-9To (cc)
Increased density unevenness of solid image (printed at f = 8KHz)
The image quality is significantly improved.Example 2 In order to realize dot diameter modulation in the present invention, Td is a density signal.
Td = T to (3/2) T when changing according to the number
Can be varied up to a variation of ΔMj
To be Also, if you want to control the discharge amount more precisely
Is the amount of change ΔTd of Td using the attenuation of the residual pressure wave.
Is set to be large, and the maximum point and the minimum point of the amplitude V are set to many,
It is sufficient to increase the set point of Td.

[0019]

As is apparent from the above description, the present invention has the following effects. (1) Since only the delay time of the auxiliary pulse and the main pulse is set in accordance with the cycle of the residual pressure wave, the ejection amount of the ink droplet can be freely changed, so that the driving circuit is stable at a low cost. High image quality and high-speed printing can be realized. (2) By setting the crest value or pulse width of the auxiliary pulse and the delay time of the main pulse in accordance with the cycle of the residual pressure wave, the ejection amount of the ink droplet can be changed more efficiently. High image quality, high-speed printing, and gradation expression can be realized.

[Brief description of drawings]

FIG. 1 is a configuration diagram for explaining an example of a method of driving a liquid jet recording head according to the present invention.

FIG. 2 is a configuration diagram for explaining a liquid jet recording head.

FIG. 3 is a diagram showing a relationship between a residual pressure wave and a meniscus.

FIG. 4 is a diagram showing the relationship between the constant periodicity of meniscus vibration and the timing of main pulse application.

FIG. 5 is a diagram showing the timing of main pulse application and the state of ink droplet ejection.

FIG. 6 is a diagram showing the timing of main pulse application and changes in the ejection amount of ink droplets.

FIG. 7 is a diagram showing a relationship between a pulse width and an ink droplet ejection amount.

FIG. 8 is a diagram showing a relationship between a crest value and an ink droplet ejection amount.

FIG. 9 is a diagram showing the ejection amount of ink droplets with respect to the frequency of a print signal.

[Explanation of symbols]

1 ... Substrate, 2 ... Piezoelectric element, 2a ... Non-driving piezoelectric element, 2b
... Drive piezoelectric element, 3 ... Flow path plate, 3a ... Ink flow path, 3b
... Wall part, 4 ... Common liquid chamber constituent member, 4a ... Common liquid chamber, 5 ...
Ink supply pipe, 6 ... Nozzle plate, 6a ... Nozzle, 7 ... Drive circuit printed board (PBC), 8 ... Lead wire, 9 ... Drive electrode, 10 ... Filler, 11 ... Protect plate, 12
... Fluid resistance, 13, 14 ... Internal electrodes, 15 ... Upper partition wall.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Toshio Inada             1-3-3 Nakamagome, Ota-ku, Tokyo Stocks             Company Ricoh

Claims (3)

[Claims] 1. A plurality of parallel flow channels arranged at intervals in the longitudinal direction of the flow channels, nozzles connected to each of the parallel flow channels to eject droplets, and the parallel flow channels. And a piezoelectric element for changing the volume of the flow passage by displacing in the direction perpendicular to the longitudinal direction of the parallel flow passage, and the flow volume of the piezoelectric element is constantly reduced. Signal is applied to the selected channel to displace it in a direction that increases the volume of the channel, and then apply a pulse signal that gives a displacement to reduce the volume of the channel again. In a method for driving a liquid jet recording head that ejects liquid droplets from a nozzle, an auxiliary pulse having a different pulse width or peak value is applied before the pulse signal is applied, and the pulse signal is adjusted in accordance with the cycle of the residual pressure wave. To liquid jet recording characterized by applying How to drive the door. 2. A plurality of parallel flow passages arranged at intervals in the longitudinal direction of the flow passages, nozzles connected to each of the parallel flow passages to eject droplets, and the parallel flow passages. And a piezoelectric element for changing the volume of the flow passage by displacing in the direction perpendicular to the longitudinal direction of the parallel flow passage, and the flow volume of the piezoelectric element is constantly reduced. Signal is applied to the selected channel to displace it in a direction that increases the volume of the channel, and then apply a pulse signal that gives a displacement to reduce the volume of the channel again. In the method of driving a liquid jet recording head that jets liquid droplets from a nozzle, the peak value or pulse width of the auxiliary pulse is changed according to the dot diameter before the pulse signal is applied, and the cycle of the residual pressure wave is changed. In addition, the pulse signal is applied together Liquid ejection recording head driving method. 3. A plurality of parallel flow passages arranged at intervals in the longitudinal direction of the flow passages, nozzles connected to each of the parallel flow passages to eject droplets, and the parallel flow passages. And a piezoelectric element for varying the volume of the flow path by displacing the parallel flow path in a direction perpendicular to the longitudinal direction of the parallel flow path. In a method of driving a liquid jet recording head, in which a droplet signal is ejected from a nozzle corresponding to a flow path by applying a pulse signal for displacing a piezoelectric element in a direction of decreasing the amount of discharge, before applying the pulse signal. Or applying the auxiliary pulse described in 2,
A method for driving a liquid jet recording head, characterized in that the pulse signal is applied in synchronization with the cycle of the residual pressure wave.