JPH0289648A - Ink-jet recording head - Google Patents

Abstract

PURPOSE:To reduce the return of ink to the ink feed side, and to stabilize the discharge of ink by partially throttling the width of an ink feed in the vicinity of the inlet of an ink pressure chamber and constituting an ink backflow preventive section. CONSTITUTION:Sections near the inlets of ink pressure chambers 2 in ink feeds 2 on a substrate 1 are throttled in the width direction, thus organizing backflow preventive sections 2a. When such backflow preventive sections 2a are mounted, no only passage resistance but also inertial resistance by the mass of ink can be balanced before and behind the ink pressure chambers 3 because the passage resistance on the ink supply side is adjusted easily, and the quantity of ink escaping to the ink supply side and the quantities of ink ejected from ink nozzles 5 are balanced when a piezoelectric element 10 is driven, thus stabilizing the discharge of ink. According to the backflow preventive sections 2a, the movement of ink in the direction of the nozzles and the movement of ink to the ink supply side are equilibrated, thus simultaneously satisfying the increase of discharge efficiency and the shortening of the ink return time after discharge.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to an on-demand inkjet recording head, and more particularly to means for preventing backflow of ink during ink ejection.

[Conventional technology]

An inkjet recording head performs recording by ejecting ink from minute nozzle holes and depositing the ink on a recording medium such as paper. Conventionally, an on-demand type inkjet recording head Are known. 3 and 4 show its general configuration, with FIG. 3 being a plan view showing the arrangement of the ink channels, and FIG. 4 being a cross-sectional view. In the inkjet recording head shown in the figure, a large number of ink flow paths consisting of an ink supply path 11, an ink pressurizing chamber 12, an ink ejection path 13, and an ink nozzle 14, and an ink reservoir 15 common to these are formed in the shape of a groove. A diaphragm 17 is laminated and integrated with a substrate 16, and a piezoelectric element 18 as an electromechanical transducer is adhered to a position of the diaphragm 17 corresponding to the ink pressurizing chamber 12. In such a structure, when an electric signal is applied to the piezoelectric element 18, the diaphragm 17 is displaced inside the ink pressurizing chamber 12, and the volume of the ink pressurizing chamber 12 is rapidly reduced. As a result, the reduced volume of ink is ejected from the ink nozzle 14 in the form of ink droplets, which are spotted on a recording medium (not shown) to perform printing.

[Problem to be solved by the invention]

By the way, in such an inkjet recording head, when an electric signal is applied to the piezoelectric element 18 and a rapid pulse-like volume change is given to the ink pressurizing chamber 12, the ink in the ink pressurizing chamber 12 becomes an ink droplet. While the ink is ejected from the ink nozzle 14, it is also pushed back toward the rear ink supply path 11. However, if the ink flows backward, there is a risk that ink droplets will be ejected from other ink nozzles. Therefore, if an attempt is made to form the ink supply path 11 wide and deep to absorb the ink backflow pulse, the flow path resistance at the rear of the ink pressurizing chamber 12 becomes smaller, and the flow path resistance at the rear of the ink pressurizing chamber 12 decreases. The amount of ink flowing back to the printer increases, resulting in a decrease in ink ejection. In addition, this makes it necessary to increase the deformation of the piezoelectric element, and this also impedes the miniaturization of ink nozzles and high integration due to the increase in the size of the piezoelectric element, and the increase in the voltage applied to the piezoelectric element. This will lead to deterioration. SUMMARY OF THE INVENTION An object of the present invention is to provide an ink side recording head that stabilizes ink ejection by leaving ink returning to the ink supply path side.

[Means to solve the problem]

In order to achieve the above object, the present invention provides an inkjet recording head in which a plurality of groove-shaped ink flow paths each consisting of an ink supply path, an ink pressure chamber, an ink ejection path, and an ink nozzle are formed on a substrate. The ink backflow prevention portion is configured by partially narrowing the width of the ink supply path near the entrance of the pressurizing chamber.

[For use]

By partially narrowing the width of the ink supply path near the inlet of the ink pressurizing chamber to form an ink backflow prevention section, the flow path resistance on the ink supply path side is increased and ink return is reduced.
As the impact on other ink nozzles becomes smaller and the amount of ink returned is reduced, the amount of ink transferred to the ink nozzle side increases, reducing the displacement of the piezoelectric element to eject the same amount of ink. can.

【Example】

1 and 2 show an embodiment of the present invention, FIG. 1 is a plan view showing the arrangement of ink flow paths, and FIG.
It is a sectional view along -H. In FIGS. 1 and 2, on a substrate l made of glass, there are a number of ink flow paths consisting of an ink supply path 2, an ink pressurizing chamber 3, an ink ejection path 4, and an ink nozzle 5, and a common ink flow path for these. A large number of ink reservoirs 6 are formed in the shape of grooves by photo-etching. In addition, a filter flow path 7 having approximately the same width and depth as the ink nozzle 5 is provided at a portion connecting the ink supply path 2 and the ink reservoir 6, and a filter flow path 7 having approximately the same width and depth as the ink nozzle 5 is provided at an inlet and an outlet of the ink pressurizing chamber 3. A pair of island-shaped protrusions 8 are provided to smooth the flow and to prevent the diaphragm from sagging as described later. A diaphragm 9 is bonded to the substrate 1 by adhesive, and a piezoelectric element 10 is further bonded to the diaphragm 9 at a position corresponding to the ink pressurizing chamber 3. In such an inkjet recording head, a portion of the ink supply path 2 near the inlet of the ink pressurizing chamber 3 is narrowed in width to constitute a backflow prevention portion 2a. In the illustrated embodiment, the width of the backflow prevention portion 2a is 0.1 mm, and the length is 1 to 2 m+++. Then, the ink supply path 2
The width is 0.5 to 0.9 mm, and the length is 3 to 5 mm.
And so. Here, the length of the backflow prevention part 2a or the width and length of the ink supply path 2 are different for each flow path depending on the flow path resistance on the ink ejection side from the ink pressurizing chamber 3 in each flow path. This is provided. As a result, the ratio of the flow path resistances before and after the ink pressurizing chamber 3 is constant throughout the entire flow path, and uniform ink droplets can be ejected from each nozzle. Further, as shown in FIG. 1, the connecting portions 2b and 3a between the ink supply path 2, the ink pressurizing chamber 3, and the backflow prevention portion 2a are tapered, but the connecting portion 2b has a small opening, and the connecting portion 3a has a small opening. By widening the opening, it is difficult for ink to flow from the ink pressure chamber 3 to the ink supply path 2 side, but it is easy to flow from the ink supply path 2 side to the ink pressure chamber 3 side, resulting in good ejection characteristics. I'm trying to get it. Note that the flow path resistance can also be increased by partially reducing the depth of the ink supply path 2 without narrowing the width.
If such processing is performed by etching, it is difficult to control the depth, causing problems with accuracy, and the process becomes complicated and labor-intensive, such as applying masking tape during the processing process, which is undesirable. When the section 2a is provided, the ink supply side (
Since it is easy to adjust the flow path resistance (on the front side of the ink pressurizing chamber 3), not only the flow path resistance but also the inertial resistance due to the ink fffi can be balanced before and after the ink pressurizing chamber 3. When the piezoelectric element 10 is driven, the amount of ink escaping to the ink supply side and the amount ejected from the ink nozzle 5 can be balanced to stabilize ink ejection. The greater the resistance on the ink supply side, the higher the ejection efficiency, but since the ink supply after ejection is performed by the action of the ink meniscus returning to the nozzle end surface due to the surface tension of the ink in the ink nozzle 5, the resistance on the ink supply side is large. If it is too long, the ink return time will increase, and the repetition cycle of ink ejection will become longer. However, according to the backflow prevention portion 2a that is narrowed in front of the ink pressurizing chamber 3, the amount of ink movement toward the nozzle and the amount of ink movement toward the ink supply side can be balanced, so that the ejection efficiency can be increased and At the same time, the ink return time can be shortened. Here, the backflow prevention part 2a is created immediately in front of the ink pressurizing chamber 3, and both sides are widened into a tapered shape with the narrowed part in between. At this time, the opening on the ink pressurizing chamber 3 side is used as the ink supply path By making the opening larger than the opening on the second side, backflow of ink during ink ejection can be more effectively suppressed without greatly affecting the time for the ink to return from the ink supply side to the ink pressurizing chamber 3 after ejection. can. Since the width of the ink supply path 2 can be determined by the width of the photomask, this method is more advantageous in terms of precision and man-hours than adjusting the depth by etching, as described above.

【Effect of the invention】

According to this invention, the width of the ink supply path is partially narrowed near the inlet of the ink pressurizing chamber to form an ink backflow prevention portion, thereby reducing the return of ink to the ink supply side.
Reduces the impact on other ink nozzles when ejecting ink.
Ink ejection can be stabilized, ink ejection efficiency can be improved, ink nozzle density can be increased by miniaturizing the piezoelectric element, and deterioration of the piezoelectric element due to a decrease in applied voltage can be prevented.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing the arrangement of ink flow paths in an embodiment of the present invention, FIG. 2 is a sectional view taken along II-II in FIG. 1, and FIG.
This figure is a plan view showing the arrangement of ink flow paths in a conventional example, and FIG. 4 is a longitudinal sectional view of FIG. 1. ■...Substrate, 2...Ink supply path, 2a...Backflow prevention portion, 3...Ink pressurizing chamber, 4...Ink ejection passage, 5...Ink nozzle, 9... Vibration plate, 10・
··Piezoelectric element. Figure 1 Figure 2

Claims (1)

[Claims] 1) In an inkjet recording head in which a plurality of ink flow paths each consisting of an ink supply path, an ink pressure chamber, an ink ejection path, and an ink nozzle are formed in a groove shape on a substrate, the ink supply path is formed near the entrance of the ink pressure chamber. An inkjet recording head characterized in that an ink backflow prevention portion is formed by partially narrowing the width of the inkjet recording head.