JPS6140160A - Recording head - Google Patents

Abstract

PURPOSE:To densely integrate an energy application portion and to enhance a practical dependability by providing fluid resistive bodies of different coefficients of resistance abuttingly with the energy application portion. CONSTITUTION:A resistive body 7 which has different coefficients corresponding to flowing directions of a fluid is provided adjacent to a heat transformation body 6, between the heat transformation body 6 which generates thermal energy and an orifice for ink to flow in, in such a manner as to decrease a resistance coefficient when a flow is from the orifice to the heat transformation body, and as to increase the resistance coefficient when the flow is reversed. When the heat transformation body 6 is heated, the bubbles generated on its surfaces grow pushing the ink around the bubbles, however, interrupted by the resistance of the resistive body 7, the ink finds it difficult to flow to the direction of the orifice, and the bubbles grow, and with their counter-force push the ink of the side of the discharge orifice 3. Therefore, the moving direction of the pressure wave generated on the heat transformation body 6 is diverted to the discharge orifice 3, and an ink discharge speed increases. Pressure waves will not cause mutual interferences by transmission to the ink in other nozzles.

Description

[Detailed description of the invention] [Field of application of the invention] The present F! AI/'i is a recording head unit applied to an on-demand inkjet recording device that uses various methods to reduce recording liquid, generally called ink, into small droplets and performs recording by adhering these ink droplets to a recording surface. Concerning configuration.

[Background of the invention]

Among the various recording methods currently known, the non-impact recording method generates almost no noise during recording, is capable of high-speed recording, and does not require special fixing treatment on plain paper. The so-called inkjet recording method, which allows recording without printing, is recognized as an extremely useful recording method. Various methods have been proposed for this inkjet recording method, some have been improved and commercialized, and others are still being worked on to put them into practical use. be.

In short, the inkjet recording method involves ejecting and flying droplets of a recording liquid called ink.
Recording is performed by attaching it to a recording member such as paper. The inkjet recording method is roughly divided into several types depending on the method of generating ink droplets and the control method for controlling the flight direction of the generated ink droplets. Among them, one of the representative methods is, for example, USP 35
96275 (Sweet method), USP 329803
0 (Lswis and Brown method), etc., in which an ink droplet flow with a controlled amount of charge is generated by a continuous vibration generation method, and this ink droplet flow with a controlled amount of charge is uniformly distributed. By causing the droplet to fly between deflection electrodes to which an electric field is applied, recording is performed on a recording member such as paper while controlling the flight trajectory of the droplet. This method is also generally referred to as a continuous method.

Other typical methods to be compared with this are, for example, USP
3747120 (Stemme method). In this method, an electrical recording signal is applied to a piezo vibrating element attached to the RAD, which has an orifice for ejecting ink for recording, and this electrical recording signal is transmitted to the mechanical vibration of the piezo vibrating element. Recording is performed by ejecting and flying ink droplets from the orifice and attaching them to the recording member whenever necessary according to the mechanical vibrations.

This is the so-called on-demand method.

In addition, a new recording method different in principle and idea from these methods has also been proposed in Japanese Patent Laid-Open No. 54-59936. In short, this new method applies a thermal pulse as an information signal to the ink introduced into a working chamber, and the ink changes its state. This is a method in which recording is performed by ejecting the liquid into small droplets, causing them to fly, and depositing the droplets on a recording member.

By the way, technical problems that are common to all of the various inkjet recording methods exemplified above still remain to be solved. Among these, particularly important issues are the establishment of multi-array recording heads and high-density integration technology for the purpose of highly efficient inkjet recording. However, in the continuous method, the ejected flying ink droplets must be electrically deflected according to the recording information signal, so the overall system configuration is complex, and the electrical control of the ink droplets requires advanced technology and precision. There are some drawbacks.

Regarding the on-demand method, there is no need to control the ejected ink droplets, so the system as a whole is simple, but the flying speed of the ink droplets is slower than that of the Coy7-Nias method, and the multi-array type In the recording head, the pressure wave generated in one ink droplet ejecting nozzle propagates to the ink in the other adjacent nozzles, which causes variations in the size of the ink droplets ejected from the other nozzles. However, there is a drawback that mutual interference between the ink droplet ejecting nozzles is likely to occur, such as changing the ink droplet ejection speed and causing the ejection timing to be out of order.

[Purpose of the invention]

The main object of the present invention is to provide an on-demand type in which a sharp state change is caused in the recording liquid by the action of thermal energy, and the acting force based on the state change causes the recording liquid to fly as droplets and adhere to the recording surface for recording. In other words, it is an object of the present invention to provide a highly reliable high-density external recording head by eliminating the conventional drawbacks of recording heads for inkjet recording devices, especially multi-array type recording heads. For example, it is an object of the present invention to provide a recording output device whose operating parts are highly integrated and which is highly reliable in practical use.

[Summary of the invention]

In order to achieve the above object, the present invention provides an orifice for ejecting and forming liquid and flying droplets, communicating with the orifice, being filled with the liquid, and forming the flying droplets in the liquid. In a recording head that is equipped with an energy application section that applies energy and an energy generator that generates the energy, when liquid flows downstream of the energy application section upstream, the resistance coefficient is small. , a record characterized in that a fluid resistance body is attached such that the resistance coefficient becomes large when the flow flows upstream, and the fluid resistance body is provided substantially in contact with the energy acting portion. provide the head. Finally, in the recording head of the present invention, a component of the pressure wave generated in the ink in a predetermined nozzle that propagates toward the ink supply system is reflected by the inner wall surface of the relay liquid chamber, and the wave is propagated again into the ink jet nozzle. The internal structure of the recording head has been improved to prevent the ink from spreading to the existing ink.

In the present invention, a resistance object having a different resistance coefficient (depending on the direction of fluid flow) is installed in the vicinity of the heat converter that generates the pressure waves. Conversely, when ink is supplied from the inflow orifice side, the resistance is reduced, so most of the pressure waves generated in the heat converter head towards the discharge orifice side.

Therefore, not only is mutual interference between the ink droplet ejecting nozzles less likely to occur, but also the ejection speed of ink droplets is increased, making it possible to improve ink ejection responsiveness to the input of a recording signal.

The fluid resistance body is constituted by a member whose cross-sectional area in a direction perpendicular to the direction in which the liquid flows becomes smaller toward the upstream side.

[Embodiments of the invention]

Hereinafter, the present invention will be explained according to specific examples shown in the drawings.

First, with reference to FIG. 4, an example of the structure of an ink droplet ejection nozzle in a print head of a conventional on-demand ink jet printing apparatus and an ink ejection principle will be described.

In FIG. 4, reference numeral 1 denotes a groove cover constituting the upper member of the ejection nozzle of the recording head, 2 an ink supply port provided in the groove cover, 3 an ejection orifice for ejecting ink, and 4 the ejection nozzle. A substrate constituting the lower member; 5 is an electrode provided on the substrate; and 6 is a heat converter provided on the substrate. The groove cover 1 and the substrate 4'' are bonded together with an adhesive so that the heat converter 6 is aligned with the groove formed in the groove cover 1.

Ink is introduced through the ink supply port 2 provided in the groove lid 1 of the recording head formed as described above, and a recording signal is input to the heat converter 6, and when heated, it comes into contact with the surface of the heat converter 6. When the ink is exposed to thermal energy, it undergoes a sudden change in state and evaporates, forming bubbles. At this time, a pressure wave is generated due to the volume increase due to the rapid vaporization, and droplets corresponding to the volume increase are discharged and flown through the discharge orifice 3 formed by the groove cover and the substrate 4. Bubbles with increased volume are
The heat is carried away by the ink in the cartridge and the ink is cooled, resulting in volumetric contraction (-1 disappears). 6. The shorter the time for vaporization and the time for the bubbles formed by vaporization to disappear, the faster the response to input of a recording signal will be.

According to the present invention, in the recording head of the above type, a resistance coefficient is provided between the heat converter 6 that generates thermal energy and the inflow orifice into which the ink flows, when the ink flows from the inflow orifice toward the heat converter. A resistance object 7 having a different resistance coefficient depending on the flow direction of the fluid is arranged close to the heat exchanger 6 so that the resistance coefficient is small and the resistance coefficient is large when moving from the heat exchanger toward the inflow orifice.

An embodiment of the recording head according to the present invention is shown in FIGS.
It is shown in Figure 3.

1 is a partially enlarged view of an ink ejection nozzle of a recording head according to the present invention, FIG. 2 is a partial cross-sectional view of FIG. 1 taken along a dashed line XX, and FIG. It is an enlarged sectional view.

In FIG. 1, the resistor object 7 is formed on the groove cover 1, but the present invention is not limited to this type of resistor object, and the method of forming the resistor object, shape, size, material, etc. is optional.

In FIG. 2, ink flows from right to left. Due to the resistance of the resistive object 7 provided when the electrode 5 is energized and the heat converter 6 is heated, the ink becomes difficult to flow in the direction of the inflow orifice. It grows by pushing the button. Therefore, the force that pushes the ink, that is, the pressure wave, is not divided into the inlet orifice side and the discharge orifice side as in the conventional recording head shown in FIG. 4, so the pressure generated on the heat converter 6 The traveling direction of the waves is directed toward the ejection orifice, and the ink ejection speed is improved. Furthermore, since the force acting in the direction of the inflow orifice is reduced, pressure waves do not propagate to ink in other nozzles and cause mutual interference. When ink is supplied to the ejection orifice after ink droplets are ejected, the resistance object 7 has less resistance from the inflow orifice side toward the heat converter 6, so that the ink flows smoothly.

FIG. 3 shows the shape of a columnar object as an example of a resistance object whose resistance coefficient differs depending on the direction of fluid flow. In the shape shown, dl / dl ”1 + r/ (Ill
When ==0,021, C is the resistance coefficient of this resistive object
The D value is CD=2.0 when the flow direction is a, and C=1.2 when the flow direction is b.

The force f due to viscous resistance is determined by the following equation.

In the above equation, l is the size of the object, η is the viscosity coefficient, and τ is the velocity of the fluid. In the figure, assuming that 11η and τ are constant, if the flow direction is reversed, the resistance will change by about 1.67 times.

The greater the resistance ratio of the resistance object used in the present invention that changes depending on the flow direction, the more it contributes to the present invention.

〔Effect of the invention〕

As described in detail above, according to the present invention, the responsiveness of ink droplet ejection to information signal input and the ink droplet ejection condition are very stable and good, and high-speed and high quality can be achieved without causing so-called crosstalk. It is possible to provide an in-jet recording head that provides recording of .

[Brief explanation of the drawing]

1 is a partially enlarged view of an ink ejection nozzle in an embodiment of the recording head according to the present invention, FIG. 2 is an enlarged view of a partial cross section taken along the dashed line XX in FIG. This figure is an enlarged cross-sectional view of the resistive object in FIG. 2, and FIG. 4 is a perspective view showing an example of the structure of an ink droplet ejection nozzle in a recording head of a conventional on-demand type inkjet recording apparatus. 1 is a groove cover, 2 is an ink supply port, 3 is an ejection orifice, 4 is a substrate, 5 is an electrode, 6 is a heat converter, and 7 is a resistance object.

Claims (1)

[Claims] 1. An orifice for ejecting and forming a liquid as flying droplets, communicating with the orifice, being filled with the liquid, and applying energy to the liquid to form the flying droplets. In a recording head equipped with an energy application section and an energy generating body for generating the energy, when the liquid flows downstream of the energy application section, the resistance coefficient becomes small; A recording head characterized in that a fluid resistance body having a large resistance coefficient is attached, and the fluid resistance body is provided substantially in contact with the energy application portion. 2. The recording head according to claim 1, wherein the cross-sectional area of the fluid resistance body in a direction perpendicular to the direction in which the liquid flows becomes smaller toward the upstream side. .