JPS6144848Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ink supply system for an ink-on-demand type inkjet recording apparatus, and particularly to an ink supply system for an inkjet recording apparatus of the type in which a head cartridge is provided with an ink tank.

In an inkjet recording device, one method of ejecting minute ink droplets from the ink ejection holes of the inkjet head is to eject ink droplets toward the recording paper only when necessary for recording. A so-called ink-on-demand method is known. In this type of inkjet recording device, normally the ink liquid in the ink liquid chamber of the ink jet head is in equilibrium with the atmospheric pressure at the tip of the ink ejection hole, so that the ink liquid flows into the ink ejection hole. There is no leakage to the outside, and the ink liquid in the ink liquid chamber has a reverse piezoelectric effect caused by a piezoelectric element.
When momentary pressure is applied by suitable means,
When pressure waves are generated within the ink chamber, ink droplets are ejected from the ink ejection holes.

Therefore, in such an ink-on-demand type inkjet recording device, not only when the ink pressure in the ink chamber of the ink jet head fluctuates, but also when the ink supply path that sends ink to the ink chamber changes. Even if the ink liquid pressure at the time of printing changes slightly, undesirable phenomena such as ink liquid dripping from the ink ejection holes or air being sucked into the ink ejection holes occur. In particular, when air is sucked into the ink ejection holes due to a drop in ink liquid pressure and air bubbles are mixed in, the inkjet recording device becomes unable to eject, and this is the biggest drawback of in-on-demand type inkjet recording devices. This is an issue that should be improved. Generally, the ink jet head that defines the ink chamber is made of a rigid body such as metal, so the volume of the ink chamber does not change due to external force and the ink pressure does not fluctuate. If the ink supply path is composed of a flexible tube such as a rubber tube or a soft plastic tube, even if the volume of the ink supply path inside the tube changes slightly due to deformation due to bending or shaking of the tube during head operation, the above-mentioned problem will occur. This can lead to undesirable phenomena such as: For example, inner diameter 1
If a flexible tube with a length of about 50 mm shakes slightly due to acceleration of motion and a change in volume of about 1 x 10 ₃ ml occurs, the ink liquid inside the tube is essentially an incompressible liquid. This sensitively acts on the ink ejection holes of the ink jet head and the ink tank, and air is mixed in from the ink ejection holes to maintain balance.

In view of the above-mentioned circumstances, the present invention provides an improved ink-on-demand type inkjet recording that prevents even the slightest variation in the volume in the ink supply path and does not cause the above-mentioned undesirable phenomena. The purpose is to provide an ink supply system in the device.

This purpose is to provide an ink-on-demand type inkjet recording device equipped with an inkjet head that is mounted on a head carriage and has an ink chamber. and a main tank that is fixedly arranged on a stationary part of the recording device and supplies ink liquid to the sub-tank via the ink supply pipe. This is accomplished by an ink supply system.

According to this configuration, since the ink supply tube is made of a rigid body, the ink supply tube is prevented from being deformed due to shaking or bending during head scanning, and the inner path volume does not change. Furthermore, by dividing the ink tank into a main tank and a small-volume sub-ink tank mounted on the head carriage, the carriage can be made more compact and fluctuations in ink pressure when the carriage is moved are reduced. Fluctuations in ink pressure can be suppressed by dividing the sub-ink tank into a plurality of small-volume chambers using partition plates or by configuring the sub-ink tank to be compact.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a schematic vertical sectional view showing the main parts of an inkjet recording apparatus incorporating an ink supply system according to the present invention, and FIG. 2 is a schematic perspective view thereof. An inkjet head 1 of an inkjet recording apparatus is mounted on a head carriage (not shown) and scans a recording sheet. Inkjet head 1
is an ink liquid chamber divided into two, i.e. an internal liquid chamber 2.
and an external liquid chamber 3, and the external liquid chamber 3 has an ink ejection hole 4 that opens toward the front surface of the head. The internal liquid chamber 2 and the external liquid chamber 3 are connected to each other by a connecting passage 5 provided on the same axis as the ink ejection hole 4, and one side of the internal liquid chamber 2, that is, the external liquid chamber 3 The opposite side is defined by a metal diaphragm 6, and a piezoelectric element plate 7 is superimposed on the back side of this metal diaphragm 6. The ink liquid is supplied to the ink supply pipe 9 from the sub-ink tank 8 mounted on the head carriage.
The liquid is allowed to flow into the external liquid chamber 3 and the internal liquid chamber 2 through capillary action. The ink supply pipe 9 extends from the ink liquid intake port 10 of the ink jet head 1 to near the bottom of the sub-ink tank 8, and is entirely made of a substantially rigid body such as metal or hard plastic. The sub-ink tank 8 is appropriately supplied with ink liquid through an ink liquid supply pipe 12 from a main tank 11 which is fixedly disposed in a stationary part of the inkjet recording apparatus. The ink tank 8 is divided into a plurality of small chambers each having a small volume, and is provided with an air vent hole 13.

3 and 4 show another embodiment of an inkjet recording device equipped with an ink supply system according to the present invention, of which FIG. 3 is a schematic configuration diagram and FIG. 4 is a perspective view. . In FIGS. 3 and 4, parts that are similar to those in FIGS. 1 and 2 are designated by the same reference numerals as those in FIGS. 1 and 2. Also in this embodiment, the ink supply pipe 9
All of them are made of rigid bodies such as metal or hard plastic.

In the embodiment shown in FIG. 3, the sub-ink tank 8 has a small volume approximately equivalent to one small chamber of the tank 8 in the embodiment shown in FIG. Therefore,
In any of the embodiments, since the actual ink capacity in the sub-ink tank is small and the area of the ink liquid surface is small, the height of waves generated on the ink liquid surface in the sub-ink tank due to the movement of the head carriage is small. This suppresses fluctuations in the pressure of the ink liquid in the sub-ink tank due to wave motion.
Coupled with the fact that the ink supply pipe is made of a rigid body, adverse effects on the ink chamber of the head are prevented.

In any of the embodiments described above, when no voltage signal is applied between the piezoelectric element plate 7 and the metal diaphragm 6 through the lead wires 14 and 15, the ink liquid in the liquid chamber becomes ink. By balancing with the external atmospheric pressure at the tip of the ejection hole 4, the ink does not leak from the ejection hole 4 to the outside. On the other hand, when a predetermined voltage signal is applied between the piezoelectric element plate 7 and the metal diaphragm 6 through the lead wires 14 and 15, the metal diaphragm 6 moves into the internal liquid chamber 2 due to the reverse piezoelectric effect of the piezoelectric element plate 7. is displaced to reduce the internal volume of the ink, and in accordance with the displacement, the liquid pressure of the ink liquid in the internal liquid chamber 2 increases, and the pressure wave is transmitted through the coupling passage 5 to the external liquid chamber 3.
As a result, ink droplets smaller than the ink ejection holes 4 are ejected toward the recording paper (not shown in the figure).

[Brief explanation of the drawing]

FIG. 1 is a schematic vertical sectional view showing one embodiment of an inkjet recording device equipped with an ink supply system according to the present invention, FIG. 2 is a perspective view thereof, and FIG. FIG. 4 is a schematic diagram showing another embodiment of the inkjet recording apparatus, and FIG. 4 is a perspective view thereof. 1... Ink jet head, 8... Sub ink tank, 9... Ink supply pipe, 11... Main tank, 12... Ink liquid supply pipe.

Claims (1)

[Claims for Utility Model Registration] 1. In an ink-on-demand type inkjet recording device equipped with an inkjet head that is mounted on a reciprocating head carriage and has an ink chamber, a small-volume sub-jet recording device that is mounted on the head carriage. An ink tank, an ink supply pipe made of a rigid body that connects the ink liquid chamber and the sub-ink tank, and an ink supply pipe that is fixedly arranged on a fixed part of the ink-on-demand type inkjet recording device, and that connects the ink liquid chamber and the sub-ink tank. an ink supply system consisting of a main tank that supplies ink liquid to the sub-ink tank via the main tank; 2. The ink supply system according to claim 1, wherein the sub-ink tank is partitioned by a partition plate into a plurality of small-volume chambers that communicate with each other.