JPH01278357A - Ink jet recording system - Google Patents

Abstract

PURPOSE:To prevent ejection of a second droplet or taking-in of a bubble from occurring, by rapidly expanding an electro-mechanical converting element, maintaining the element in the expanded state for a predetermined time, then rapidly contracting the element, maintaining the element in the contracted state for a predetermined time, then rapidly expanding the element in an amount corresponding to the temperature of an ink, and gradually returning the element to an initial state. CONSTITUTION:An electro-mechanical converting element 11 is rapidly expanded by a rapid voltage drop, and the expanded state is maintained. The element 11 is then rapidly contracted by a rapid voltage rise, and the contracted state is maintained for a period of time of 2(l1+2l2)/c, wherein l1 is the distance from the element 11 to the tip of a jet nozzle, l2 is the distance from the element 11 to an ink-supplying port, and c is the propagation velocity of a pressure wave in a glass tube 22. The element 11 is rapidly expanded by an amount corresponding to the temperature of an ink, and is then gradually returned to an initial state. A meniscus 20 after the ejection of an ink droplet 14 can be returned without moving in a forward or backward direction of an orifice 15, so that ejection of a second droplet or taking-in of a bubble will not occur.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention is capable of ejecting ink from the tip of an ink jet nozzle using pressure generated by an electromechanical transducer provided along an ink flow path of the nozzle. The present invention relates to an on-demand inkjet recording method that performs recording by ejecting droplets.

[Prior Art] In an on-demand inkjet recording system, as a method of driving an inkjet recording head, for example, a method of applying a voltage as shown in FIG. 5 to a piezoelectric element as an electromechanical conversion system is known (particularly 62-25058)
. In this method, an inkjet recording head is configured as shown in FIG. 6, and a voltage as described above is applied to a piezoelectric element 11 using a circuit block 12. In this case, first,
The piezoelectric element 11 is expanded with the voltage step a, and the expansion of the piezoelectric element 11 is maintained for a predetermined time with a constant voltage.

At this time, the meniscus 20 of the orifice 15 is slightly pulled back into the nozzle. After a predetermined period of time has elapsed, the piezoelectric element 11 is rapidly contracted by voltage step C, and the orifice 15 is closed.
The ink droplets 14 are ejected.

Furthermore, there is also known an inkjet recording head similar to that described above, which applies a voltage waveform as shown in FIG. In this case, in the process of returning to the state before operation after ejecting ink droplets, d.

The waveforms shown by e and f are added, and the meniscus 2
In order to stabilize the behavior of zero, the piezoelectric element 11 is contracted and expanded.

[Problems to be Solved by the Invention] All of the above driving methods use an inkjet recording head having the structure shown in FIG. 2
It was suitable for structures with 1.

The filter 21 absorbs the pressure waves propagating in the ink in the ink flow path 13 and removes the meniscus 2 after the ink is ejected.
It is useful for stabilizing the motion of 0 and damping it early.

However, the above-described driving method cannot be directly applied to an inkjet recording head that does not include a filter at the rear end of the ink flow path 13. In addition, the filter is expensive and needs to be attached to the rear end of the glass tube 22 and welded, requiring a large number of man-hours to manufacture.

The present invention provides an inkjet recording method that can stably operate an inkjet recording head that is not equipped with a filter at the rear end of a glass tube that constitutes an ink flow path, thereby preventing the ejection of harmful second droplets and the incorporation of air bubbles. The primary purpose is to

A second object of the present invention is to provide an inkjet recording method that enables stable ejection over a wide temperature range.

[Means for Solving the Problems] The present invention provides a solution to pressure waves generated in the ink in the ink flow path by contraction and expansion of an electromechanical transducer provided along the ink flow path of an ink jet nozzle. , in an on-demand inkjet recording method in which recording is performed by jetting ink from the tip of the ink liquid jetting nozzle,
The electromechanical transducer is rapidly expanded and held for a predetermined time, then rapidly contracted and held for a predetermined time, and then
The gist is an inkjet recording method characterized by rapidly expanding an electromechanical transducer by an amount corresponding to the temperature of the ink and then gradually returning it to its pre-operation state.

In the above, the predetermined time T when the electromechanical transducer is rapidly contracted and held for a predetermined time is the distance from the electric aI carpet transducer to the ink liquid jet nozzle of 121
s If the distance to the ink supply port is 12 and the propagation speed of the pressure wave is C, it is preferable to set T=2 (u, +2°C2)/c.

[Function] According to the inkjet recording method of the present invention, reflected waves of pressure waves caused by contraction and expansion of the electromechanical transducer can be canceled in the step of releasing the contraction of the electromechanical transducer. As a result, it is possible to drive an inkjet recording head that does not have a filter at the rear end of the ink flow path.

Furthermore, since the electromechanical transducer is rapidly expanded by an amount corresponding to the temperature of the ink, stable ink ejection is possible over a wide temperature range.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings. 1st
The figure shows the voltage waveform that drives the electromechanical transducer 11.
The inkjet recording head was operated as shown in the figure. In FIG. 2, 12 is a drive circuit that drives the electromechanical transducer 11, 14 is an ink droplet, 15 is an orifice,
22 is a glass tube whose rear end 23 opens into the ink tank 17 without providing a filter.

First, at time 1=0, the electromechanical transducer 11 was rapidly expanded by a sudden voltage drop a, and the expanded state was maintained in step b. During this time, meniscus 2 of orifice 15
0 was slightly pulled back into the ink flow path.

After that, due to the sudden voltage rise C, the electromechanical transducer 1
1 is rapidly shrunk to 2 (°C.

The condition was maintained for a time of +2l2)/c. Here 1
1 is the distance from the electromechanical transducer 11 to the orifice, that is, the tip of the ink droplet ejecting nozzle, fl2 is the distance from the rear end 23 of the glass tube 22, that is, the ink supply port, and C is the distance within the glass tube 22. is the propagation velocity of the pressure wave. During this time, the meniscus 20 flew out from the orifice 15 and an ink droplet 14 was formed.

Then, after the time 2 (fl, +2J2.)/c has elapsed, the contraction of the electromechanical transducer 11 is rapidly released in step g, and then the electric mw transducer 11 is gradually returned to the state before operation in step h. Ta. As a result, the meniscus 20 after ejecting the ink droplet 14 can be returned to the equilibrium state before ejection very quietly without violently moving in the front-rear direction of the orifice 15, and the ejection of the second droplet, No air bubbles were introduced.

At the time 2 (J2+ +2J22)/c, in Step C, a positive pressure wave (a pressure portion higher than the surroundings) propagating behind the glass tube 22 in the direction @23 is reflected at the rear end 23 and becomes a negative pressure wave ( The wave propagates in the direction of the orifice 15 as a pressure wave (lower pressure than the surrounding area), is reflected as it is at the orifice 15, reaches the rear end 23, is reflected again as a positive pressure wave at the rear end 23, and reaches the electromechanical transducer element 11. It is time that is required as time. Note that, acoustically, the orifice 15 is considered to be a closed end, and the rear end 23 is considered to be an open end.

When this time elapses, if the conventional driving method as shown in FIG. 5 is adopted without operating step g, the reflected pressure wave will reach the orifice 15 again and eject the second ink liquid. Even if the liquid is not ejected, air bubbles are captured by the movement of the meniscus, making subsequent ejection impossible.

In the above, it goes without saying that the height of step g may be lower than the height of step C, because the pressure wave reflected and propagated in the ink flow path transfers part of its energy to the ink. This is because it is attenuated by discharge into the flow path or by internal friction, which is a physical property of the ink (mainly due to the viscosity of the ink). Therefore, the viscosity of the ink is the fourth
As shown in the figure, it depends on the temperature, so by detecting the temperature of the ink and giving the electromechanical transducer 11 the amount of expansion necessary to cancel the energy of the reflected wave, taking into account the viscosity. good.

Step g is lower than the height of Stella C as described above, so to return to the equilibrium state, operate as in step h,
It must be ensured that no new pressure waves are generated within the ink flow path.

Now, in step C, there is also another positive pressure wave traveling to the orifice 15. However, since this pressure wave reaches the orifice 15 and is absorbed as energy to form the ink droplet 14, no reflected wave is formed and there is no adverse effect on the movement of the meniscus.

FIGS. 3(a) and 3(b) show an example in which the electromechanical transducer 11 is constituted by an inductance circuit element such as a magnetostrictive element, where (a) shows the voltage waveform and (b) shows the current waveform. ing.

The current waveform is the same as in the previous embodiment at step a.

b, c, g, and h were formed, and stable operation of the meniscus 20 was possible. In addition, in the voltage waveform (a), m takes into consideration the internal resistance of the electromechanical transducer element in the gentle voltage slope.

[Effects of the Invention] As explained above, according to the present invention, since the reflected waves of the pressure waves propagating through the ink flow path are canceled, a filter is installed at the rear end of the glass tube that constitutes the ink flow path. This has the effect of stably operating the inkjet recording head that is not equipped with the inkjet recording head, thereby preventing the ejection of harmful second droplets and the intake of air bubbles.

Furthermore, since the electromechanical transducer is rapidly expanded by an amount corresponding to the temperature of the ink, stable ink ejection is possible over a wide temperature range.

[Brief explanation of the drawing]

FIG. 1 is a voltage waveform diagram of an embodiment of the present invention, FIG. 2 is a structural diagram of an inkjet recording head used in an embodiment of the present invention, and FIG. 3(a) is a voltage waveform diagram of another embodiment of the present invention. Figure 3(b) is a current waveform diagram, Figure 4 is a graph showing the relationship between ink viscosity and temperature, Figure 5 is a voltage waveform diagram of the conventional drive method, and Figure 6 is a graph of conventional inkjet recording. FIG. 7, which is a structural diagram of the head, is a voltage waveform diagram of another conventional drive method. 11... Electric relative conversion element, 14... Ink droplet,
15... Orifice, 20... Meniscus, 21.
··filter. Figure 1 Figure 3 $4 Figure

Claims (2)

[Claims] (1) Pressure waves generated in the ink in the ink flow path due to contraction and expansion of an electromechanical transducer provided along the ink flow path of the ink jet nozzle cause ink to flow from the tip of the ink jet nozzle. In an on-demand inkjet recording method that performs recording by injecting ink, the electromechanical transducer is rapidly expanded and held for a predetermined time, then rapidly contracted and held for a predetermined time, and then adjusted to the temperature of the ink. An inkjet recording method that is characterized by rapidly expanding an electromechanical transducer by an amount that causes the electromechanical transducer to expand, and then gradually returning it to its pre-operation state. (2) The time T for rapidly contracting and holding the electromechanical transducer is T=2(l_1+2l_2)/c l_1: Distance from the electromechanical transducer to the tip of the ink jet nozzle l_2: Ink supply from the electromechanical transducer The inkjet recording method according to claim 1, wherein the distance c to the mouth is the propagation speed of the pressure wave.