JPS63242553A - Ink jet head - Google Patents

Abstract

PURPOSE:To enable sucked bubbles to be easily discharged outside a pressure- propagation path to increase the ink-replenishment speed and to enhance a recording speed to a great extent, by a method wherein an ink supply path and a pressure- propagation path are directly connected through one or more connecting paths. CONSTITUTION:Due to the negative pressure generated in a pressure chamber 14 just after the jetting of an ink drip, an ink is sucked from an ink reservoir 12 to the side of a pressure-propagation path 13 and the pressure chamber 14 through an orifice 11. Bubbles are sucked into the pressure-propagation path 13 together with the ink. When a head is disposed with the pressure-propagation path 13 set horizontal, the sucked bubbles move upwards in the pressure-propagation path 13 due to the buoyancy, thereafter being easily discharged to the atmosphere through a connecting path 17, an ink supply path 15 and the ink reservoir 12, which are disposed upwards of the pressure-propagation path 13. In addition, the sucking of the ink into the pressure- propagation path 13 due to the negative pressure, etc. can be carried out not only through the orifice 11 from the ink reservoir 12 but also through the connecting path 17, which is formed upwards of the orifice 11, directly from the ink supply path 15. In this manner, the replenishment of ink is enhanced at high speed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention This invention relates to an inkjet head installed in an inkjet printer.

2. Description of the Related Art Inkjet printers, which perform printing by ejecting ink droplets and flying them to the surface of recording paper, have various advantages such as less noise than the currently mainstream dot impact printers. There are two types of inkjet heads installed in such inkjet printers: continuous jet type and drop-on-demand type.
The latter type is considered to be promising in terms of the small size and simplicity of the device.

There are various types of drop-on-demand type inkjet heads, but a type having an ink reservoir in front of an orifice as shown in FIG. 2 has been developed as a high-performance head.

This inkjet head has an orifice 21 and...
An ink reservoir 22 having a rear end face including the orifice 21 and a front end face in contact with the atmosphere, a pressure chamber 24 filled with ink and pressurized by an electro/a-mechanical conversion element 26, and a pressure chamber 24 extending from the pressure chamber 24 in front of the The pressure propagation path 23 extends and is connected to the ink reservoir 22 via the orifice 21, and the ink supply path 25 is connected to the ink reservoir 22 at a peripheral portion thereof. In this inkjet head, by forming an ink reservoir 22 in front of the orifice 21, it is possible to control the direction and speed of ink droplet jetting that occurs when excess ink adheres to the vicinity of the orifice in an inkjet head that does not have this. It has a configuration that effectively prevents fluctuations.

Problems to be Solved by the Invention In the above conventional inkjet head, the orifice 2
By forming an ink reservoir 22 in front of the ink droplet 1, the direction and speed of ink droplet jetting are stabilized.

However, when an impact is applied to the head or the head is driven in an abnormal state, air bubbles are often sucked into the pressure propagation path 23. When the head shown in FIG. 2 is arranged so that its pressure propagation path 23 is horizontal, the bubbles sucked into the head move upward due to buoyancy, making it difficult for them to be discharged to the outside through the orifice. As a result, quite large air bubbles are accumulated above the orifice 21, as illustrated by B in the enlarged cross-sectional view of FIG.

The air bubbles accumulated in this way absorb and weaken the pressure propagating inside the pressure propagation path 23, causing deterioration of the head characteristics such as a decrease in the ejection speed of ink droplets, or in extreme cases, making ejection impossible. I'll do it.

Furthermore, in the conventional apparatus shown in FIG. 2, the ink discharged to the outside of the head during ejection is replenished from the ink reservoir 22 only through the orifice 21, so the number of ejected droplets per unit time is increased to achieve high-speed recording. When attempting to do so, there is a problem in that ink replenishment cannot keep up with this, making it difficult to improve the recording speed.

Means for Solving the Problems The inkjet head of the present invention is configured such that the ink supply path and the pressure propagation path are directly connected via one or more communication paths.

Operation In the inkjet head of the present invention, air bubbles sucked into the pressure propagation path through the orifice etc. are easily discharged to the outside of the pressure propagation path through the communication path formed between the ink supply path and the ink supply path. Therefore, deterioration of characteristics such as a decrease in injection speed due to air bubbles does not occur.

Furthermore, in the inkjet head of the present invention, the ink discharged to the outside of the head during jetting is replenished not only from the ink reservoir through the orifice, but also directly from the ink supply path through the communication path, so the ink replenishment speed is is increased, thus significantly increasing the recording speed.

Hereinafter, further details of the present invention will be explained in detail together with examples.

Embodiment FIG. 1 is a sectional view showing the structure of an inkjet head according to an embodiment of the present invention.

This inkjet head includes an orifice 11 and an ink reservoir 12 having a rear end face including the orifice 11 and a front end face in contact with the atmosphere. Furthermore, this inkjet head has a pressure chamber 14 that is filled with ink and pressurized by an electromechanical transducer 16.
, a pressure propagation path 13 extending from the pressure chamber 14 forward thereof, and an ink supply path 15 connected to the ink reservoir 12 in a peripheral portion thereof.

The ink reservoir 12 and the pressure propagation path 13 are connected by an orifice 11 formed near the axes of both.

Furthermore, the pressure propagation path 13 and the ink supply path 15 are interconnected by a communication path 17 formed above the orifice 11. Such a change in the cross-sectional shape along the ejection direction can be easily realized by configuring the inkjet head as a laminated structure formed by stacking thin plates.

An electrical/mechanical transducer element 16 composed of a piezo element or the like is attached to the rear wall forming the pressure chamber 14, and pressure waves are generated by pulsed electrical signals that are intermittently applied to this element. occurs within the pressure chamber 14. This pressure wave is
The pressure is propagated through the pressure propagation path 13 to the orifice 11, from where it breaks through the ink reservoir 12 in front and ejects ink droplets.

The front end surface of the ink reservoir 12 in contact with the atmosphere is the orifice 11.
Since the cross-sectional area is set to be larger than the area of the orifice 11, the amount of ink and the shape of the liquid surface in front of the orifice 11 are maintained stably, and the ejection direction and speed of the ink droplets are stabilized.

Due to the negative pressure generated in the pressure chamber 14 immediately after the ink droplet is ejected, ink is sucked from the ink reservoir 12 through the orifice 11 into the pressure propagation path 13 and the pressure chamber 14 side. Air bubbles may be sucked into the pressure propagation path 13 together with this ink. When the head shown in FIG. 1 is arranged so that its pressure propagation path 13 is horizontal, the air bubbles sucked here move above the pressure propagation path 13 due to buoyancy, and a communication path is formed above the head. 17, the ink is easily discharged into the atmosphere through the ink supply path 15 and the ink reservoir 12.

In addition, suction of ink into the pressure propagation path 13 due to negative pressure or the like is performed not only from the ink reservoir 12 through the orifice 11 but also directly from the ink supply path 15 through the communication path 17 formed above it. replenishment becomes extremely fast.

Although the configuration in which the communication path is formed only above the orifice has been exemplified above, one or more communication paths may be added diagonally above the orifice for the purpose of promoting ink supply.

Effects of the Invention As explained in detail above, the inkjet printer of the present invention
Since the head has a structure in which the ink supply path and the pressure propagation path are interconnected via the communication path, even if bubbles are once sucked into the pressure propagation path, they can easily escape to the outside of the pressure propagation path through the communication path. This effectively prevents the deterioration of injection characteristics due to bubble inhalation.

In addition, the ink discharged to the outside of the head during jetting is refilled not only from the ink reservoir through the orifice, but also directly from the ink supply path through the communication path, which greatly improves the ink replenishment speed and, therefore, the recording speed. This effect is also produced.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the structure of an inkjet head according to an embodiment of the present invention, and FIG. 2 is a sectional view showing the structure of a conventional inkjet head. 11... Orifice, 12... Ink reservoir, 13.
...Pressure propagation path, 14...Pressure chamber, 15...Ink supply path, 16...Electrical/mechanical conversion element, 17...Communication path. Patent applicant: NEC Home Electronics Co., Ltd.

Claims (3)

[Claims] (1) A pressure chamber filled with ink and pressurized by an electrical/mechanical conversion element; A pressure propagation path extending from this pressure chamber forward; and connected to this pressure propagation path via an orifice. An ink reservoir having a rear end surface and a front end surface in contact with the atmosphere, and an ink supply path connected to the ink reservoir in a peripheral portion of the ink reservoir, and one or more connections between the pressure propagation path and the ink supply path. An inkjet head characterized by having a passage formed therein. (2) The inkjet head according to claim 1, wherein only one communication path is formed above the orifice. (3) The inkjet head according to claim 1, wherein the communication path is formed one above and one above and below the orifice.