JPH03295657A - Ink jet printing head - Google Patents

Abstract

PURPOSE:To stabilize high speed printing operation by providing projections in ink passageways so that fluid resistance in the reverse direction is higher than fluid resistance in the forward direction in each of the ink passageways. CONSTITUTION:Before making a printing, an ink is fed from an ink tank to ink passageways 3 through a common ink chamber 2, the ink is fed to ink nozzles 5 through ink chambers 4 and filled with them. If a pulse signal is applied to a selected piezo-electric element 8 corresponding to dots to be printed, the piezo-electric element 8 deforms and makes a cover plate 7 flex so that the ink in the ink chamber 4 is pressurized and discharged out of the ink chamber. Then, the projection 6 in the ink passageway 3 allows the ink to easily flow in the forward direction and interrupts the flow of the ink in the reverse direction. Therefore, the ink is efficiently discharged from the nozzles 5 toward a printing paper. After that, the piezo-electric element 8 and the cover plate 7 returns to their normal state, and the ink chamber 4 is depressurized and sucks in the ink from outside of the ink. Consequently, it is possible to prevent the ink from flowing in the reverse direction and realize stable high speed printing operation.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an inkjet printer.

[Prior Art] Conventionally, an on-demand method or a charge control method has been generally adopted as a method for inkjet printers. This on-demand printer head is
It consists of a substrate on which an ink channel is formed and a lid plate fixed to the channel surface of the substrate. An ink chamber is provided in the ink flow path, and a piezoelectric element is provided on the cover plate at a position facing the ink chamber. During printing, a pulse voltage is applied to the piezoelectric element, the piezoelectric element is deformed, the cover plate is bent, and the ink in the ink chamber is pressurized, causing the ink to be ejected from the nozzle.

[Problems to be Solved] In the conventional example described above, when the ink ejection plate piezoelectric element and the cover plate are restored, the pressure inside the ink chamber decreases, so that the ink chamber is replenished with ink.

At this time, ink flows in from the rear of the ink chamber, and at the same time, ink from the front of the ink chamber is also pulled back.

Therefore, a meniscus is generated at the nozzle tip. If an attempt is made to eject ink before this meniscus is replenished with ink, sufficient ink may not be ejected, making stable printing impossible. In order to prevent such printing failures, it is necessary to apply the next pulse voltage after the ink is sufficiently replenished by the pressure within the ink flow path, but this makes high-speed printing impossible. Furthermore, when ink is ejected, the ink within the ink chamber flows almost equally in the forward direction and the reverse direction, so the efficiency of ink ejection from the nozzle is low. Therefore, a large pressure must be applied to the ink chamber, which increases the size of the pressure device and makes it difficult to increase the density and reduce the size of the print head.

An object of the present invention is to provide an inkjet printer head that is capable of stable high-speed printing by reducing backflow of ink.

[Means for Solving the Problems] In order to achieve the above object, the inkjet printer head of the present invention has a flow resistance in the ink flow path in the opposite direction than the flow resistance in the forward direction. A protrusion is provided to increase road resistance.

[Operation When the coin ink chamber is reduced, ink is ejected from the tip of the nozzle in the form of small droplets. When the ink chamber is restored to its original state, the pressure within the ink chamber decreases and the ink within the ink flow path is sucked. The ink flow path is provided with protrusions that have low flow path resistance in the forward direction of the ink flow and high flow path resistance in the reverse direction, so that the ink at the front of the ink chamber is pulled back in the opposite direction. It is faster for the ink to be pushed out from the rear of the ink chamber in the forward direction than to be pushed out. Therefore, a meniscus is unlikely to occur at the tip of the nozzle flow path. Further, when ink is ejected, the amount of ink flowing back to the rear of the ink chamber is reduced for the same reason as described above, so that less energy is required to be applied to the ink chamber to eject the same amount of ink.

[Embodiment] An example in which the present invention is applied to an on-demand inkjet printer head will be described below with reference to the drawings.

As shown in FIG. 1, a channel pattern is formed by etching on the upper surface of a glass substrate 1 constituting a multi-nozzle head. This flow path pattern is formed so that a plurality of ink flow paths 3, which will be described below, communicate with each other from the common ink chamber 2.

Each ink flow path 3... has a common ink chamber 2 as an inlet, is meandered in order to adjust the flow path resistance, and has an ink chamber 4 formed by widening the flow path in the middle.

The part from the ink chamber 4 to the nozzle 5 is relatively straight.
It has been extended to

In a place located slightly downstream (front) of the ink chamber 4, a planar shape is provided so that the flow path resistance in the opposite direction to the ink flow is greater than the flow path resistance in the forward direction. (
An isosceles triangular projection 6 facing toward the rear) side is provided. Similar protrusions 6 are also provided near the inlet of each ink flow path 3.

As shown in FIG. 2, a lid plate 7 is placed over the patterned surface of the substrate 1 on which the ink channels 3 and the like are formed, and the two are bonded together using an epoxy resin adhesive or the like. A piezoelectric element 8 is provided on the upper surface of the cover plate 7 so as to face the ink chamber 4 .

Electrodes (not shown) of the piezoelectric element 8 are connected to a printer control circuit (not shown) via lead wires (not shown).

In the inkjet printer head configured as described above, ink is first supplied from an ink tank (not shown) into the ink flow path 3 via the common ink chamber 2 prior to printing. That is, ink is filled from the common ink chamber 2 through the ink chamber 4 to the nozzle 5. When a pulse signal is applied to the piezoelectric element 8 selected corresponding to the dot to be printed, the piezoelectric element 8 is deformed and the cover plate 7 is bent.
The ink in the ink chamber 4 is momentarily pressurized and pushed out of the ink chamber. At this time, due to the protrusion 6 provided in the ink flow path 3, the ink flows well toward the front of the ink chamber, or does not flow back to the rear of the ink chamber very much. Therefore, ink is efficiently ejected from the nozzle 5 toward the recording paper (not shown). Thereafter, the piezoelectric element 8 and the cover plate 7 return to their normal states, and the ink chamber 4 is depressurized to suck ink and ink from outside the room. This suction force acts equally on the front and rear of the ink chamber 4 of the ink flow path 3, but from the rear of the ink chamber, the flow path resistance due to the protrusion 6 is small, so the ink easily flows and is sucked into the ink chamber 4. However, from the front of the ink chamber, the flow path resistance caused by the protrusions is large and prevents ink suction. Therefore, the ink in the front of the ink chamber 4 hardly flows backward in the ink flow path 3, and the ink in the ink chamber 4
The front of the printer remains filled with ink. Therefore, a large meniscus is not generated, and the time for replenishing the meniscus with ink is shortened, so that preparations for the next pulse application can be made in a short time.

In this embodiment, the protrusions are provided at two locations, one immediately in front of the ink chamber 4 and the other near the entrance of the ink flow path 3, but the protrusions may be provided at only one of the locations. Note that the installation position of the protrusion 6 is also not particularly limited. Further, the shape of the protrusion is not limited to the triangular shape as in the present embodiment, but may be any shape as long as the flow path resistance in the reverse direction is greater than the flow path resistance in the forward direction. For example, a half-moon shape as shown in Figure 3(a).

As shown in Figure (b), the ink flow path is cut on both sides and both ends of the triangular base are widened to the full width of the flow path, and as shown in Figure (C), slopes are protruded from both sides of the ink flow path. Alternatively, the flow path area may be gradually narrowed.

Note that the present invention is not limited to on-demand type heads, but can also be applied to other inkjet printer heads such as charge control type and bubble jet type.

[Effects] As explained above, the present invention is provided with a protrusion in the ink flow path that increases the flow resistance in the reverse direction than the flow resistance in the forward direction with respect to the ink flow. Even immediately after ejection, a large meniscus does not occur at the tip of the ink flow path, reducing ink replenishment time and allowing the next ink to be ejected immediately, making stable high-speed printing possible. Furthermore, the ink jetting efficiency is improved and less energy is applied to the ink chamber, so there are effects such as miniaturization of the device and higher density of the inkjet printer head.

[Brief explanation of the drawing]

FIG. 1 is a plan view of a substrate of an inkjet printer head showing one embodiment of the present invention, FIG. 2 is an enlarged sectional view taken along line A-A in FIG. 1, and FIG. 3 is another embodiment of the protrusion. FIG. 3. Ink flow path, 6... Protrusion. that's all

Claims (1)

[Claims] An inkjet printer head characterized in that an ink flow path is provided with a protrusion that increases flow path resistance in the reverse direction of the ink flow than in the forward direction.