JPH03193456A - inkjet head - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an inkjet recording apparatus such as a printer that forms an ink image on a medium such as a recording paper by flying ink droplets, and more particularly to an inkjet printer head.

[Conventional technology]

It includes a nozzle forming member having a plurality of nozzle openings, and a piezoelectric diaphragm disposed to face each of the nozzle openings and spread in the ink. An on-demand inkjet head that ejects ink from a nozzle to fill a gap with a forming member is disclosed in Japanese Patent Publication No. 60-8953, for example, and is highly stable and does not allow foreign matter such as air bubbles or dust to get mixed into the ink. It has the advantage that normal operation is possible without being affected by this even if the A cantilevered or double-sided beam structure is used as the piezoelectric diaphragm, which has advantages such as high electromechanical conversion efficiency and the ability to obtain the necessary vibration displacement with a low voltage.

[Problem to be solved by the invention]

However, on the other hand, in this type of device, the gap between the nozzle forming member and the diaphragm has a large effect on the ink ejection characteristics, so it is necessary to maintain a minute gap, and the high precision of this gap is required in head manufacturing. Management was a problem.

Further, in order to expand the permissible size range of the gap, there is a method of increasing the area of the diaphragm, but in this case, a small and high-density head cannot be designed.

Therefore, the object of the present invention is to solve these problems.The purpose of the present invention is to make it possible to alleviate the need for highly accurate control of the minute gap between the nozzle forming member and the diaphragm in head manufacturing, and at the same time to make it possible to The purpose of the present invention is to provide an inkjet head capable of increasing density.

[Means to solve Tan U]

The inkjet head of the present invention includes a nozzle forming member having a plurality of nozzle openings, and a plurality of diaphragms that are arranged to face each of the nozzle openings and vibrate in response to a print signal, and the inkjet head has a plurality of diaphragms that vibrate in response to a print signal. The inkjet head for ejecting ink from the nozzle opening has an ink flow path that supplies ink to the nozzle opening through a space between the diaphragm filled with ink and an adjacent diaphragm, and the diaphragm The print signal that vibrates the diaphragm has a time difference with respect to the adjacent diaphragm that is at least 574 times the natural vibration period of the diaphragm in the ink.

[Effect]

When one diaphragm vibrates in response to a print signal and moves in a direction that reduces the gap between the diaphragm and the nozzle forming member,
Due to the reduction in space, some of the ink in the area sandwiched between the diaphragm and the nozzle forming member flows from the nozzle opening to the recording paper, and some of the ink flows through the ink supply channel constructed between the diaphragm and the diaphragm. flows to the supply side. In order to suppress changes in the ratio of the amount of ink flowing into the nozzle opening and the ink supply section due to variations in the gap size between the diaphragm and the nozzle forming member, the flow path resistance of the ink supply system is It needs to be approximately equal to the road resistance and have little dependence on variations in the gap size between the diaphragm and the nozzle forming member.

According to the above configuration of the present invention, even when the gap between adjacent diaphragms is narrowed so that the gap between adjacent diaphragms functions as a flow path resistance that satisfies the above conditions, the printed signal applied to the adjacent diaphragms is affected by the natural vibration of the diaphragm. Since the time difference is more than 574 times the period, it is possible to suppress interaction with the movement of adjacent diaphragms, and stable ejection characteristics can be obtained that are independent of changes in the gap size between the nozzle forming member and the diaphragm. .

Furthermore, since the size of the diaphragm and the gap between the diaphragms are reduced, a small, high-density inkjet head can be constructed.

〔Example〕

The details of the present invention will be explained below using specific examples with reference to the drawings.

FIG. 1 is a perspective view showing the structure of an inkjet head according to the present invention, which is made by bonding a Ni elastic plate and a PzT piezoelectric element plate, has a radius of 400 μm, a thickness of 150 μm, and a length of 4 m.
m diaphragms 1 have one end joined to a support base 2 to form a cantilever diaphragm. As shown in FIG. 1, the diaphragms 1 are arranged at regular intervals of 450 μm to form a diaphragm row, and the diaphragm rows are arranged in two opposing rows. A print signal from a drive circuit (not shown) is applied to the PZT piezoelectric element plate of the diaphragm 1 via a connection line 9, thereby exciting flexural vibrations in the diaphragm 1.

A plurality of nozzle openings 3 are arranged in a manner that matches the arrangement of the diaphragm 1.
The nozzle forming member 4 provided with the diaphragm 1 has a step formed on the surface facing the diaphragm 1 to form a small gap between the diaphragm 1 and the diaphragm 1, and is bonded onto the diaphragm row. Next, the ink flow path and the ink flow of the inkjet head according to the present invention shown in FIG. This will be explained using FIG. 3, which is a cross-sectional view taken along the arrangement direction. In FIG. 2, an ink channel 5 that supplies ink directly below the diaphragm 1 is formed by a minute gap formed between a channel base 6 and a support base 2, and one end 7 of the channel is not shown. It is connected to a missing ink tank. Ink guided from the ink tank around the diaphragm 1a by capillary action passes through a flow path 8 formed between adjacent diaphragms 1b to the gap between the diaphragm 1a and the nozzle forming member 4, as shown in FIG. and fills the periphery of the diaphragm 1a and the nozzle opening 3. In the inkjet head of the present invention, the operation of the diaphragm 1 when the driving pulse voltage of the print signal is applied,
There are two drive systems. One is the pulling method, in which when a driving pulse is applied, the diaphragm 1 moves in the direction of increasing the gap with the nozzle forming member 4, and then vibrates in the direction of decreasing the gap, filling the gap. This is a driving method in which a part of the ink is ejected as ink dots from the nozzle opening 3, and a part of the ink flows out to the side of the flow path 8 formed between the adjacent diaphragm 1. The other type is a push type, which is a driving method in which the diaphragm 1 moves in a direction to reduce the gap with the nozzle forming member 4 when a driving pulse is applied. In the embodiment of the present invention shown in FIG. 1, the diaphragm l is divided into two series of even numbers and odd numbers in the arrangement direction, and the time difference between the printing signals applied to the two series is changed, so that the nozzle opening 3 is The results of measuring the amount of ink dots ejected are shown in FIGS. 4 and 5. The horizontal axis is the time difference between the print signals normalized by the natural vibration period of the diaphragm 1 in the ink, and the vertical axis is the ink dot amount normalized by the ink dot amount when no print signal is applied to one of the diaphragm series. be. Fig. 4 shows the above-mentioned pulling driving method, and Fig. 5 shows the pushing driving method, which is a six-car drive method, in which the print signal applied to the adjacent diaphragm 1 is applied to the diaphragm 1 in the ink. When the time difference is 5/4 times or more the natural vibration period of 1
The length of the flow path 8 formed between the
Since the gap between the diaphragm 1 and the nozzle forming member 4 was sufficiently large with respect to the dimensional change, the flow path resistance did not change within the gap manufacturing error of ±15 μm, and constant ejection characteristics were obtained.

In FIG. 6, which is another embodiment of the present invention, a rectangular prism shape with a thickness of 150 μm on which an electrode for applying an electric field in the thickness direction is deposited.
The diaphragms 11 made of PZT piezoelectric element plates with a radius of 300 μm and a length of 2 mm are two-dimensionally arranged at constant intervals with a spacing regulating plate 19 in between. Wiring (not shown) is disposed on the surface of the spacing regulating plate 19 that is in contact with the diaphragm 11, and drive voltage pulses can be selectively applied to the diaphragm 11 from a drive circuit (not shown). By applying the drive voltage pulse, the diaphragm 11 vibrates in the length direction,
Part of the ink filling the gap between the free end surface of the diaphragm 11 and the nozzle forming member 4 having the nozzle opening 3 is ejected from the nozzle opening 3, and the other part is ejected from the nozzle forming member 4 formed between the adjacent diaphragm 11. flow out to the flow path side. The support base 12 that fixes the diaphragm 11 and the nozzle forming member 4 is provided with a slit-shaped opening 15, which allows ink to flow from an ink tank (not shown) into the ink supply channel formed by the diaphragm 11. Supplied. 1! ! The moving plate 11 is driven by a series 11 with hatching on the free end surface of the diaphragm 11, as shown in FIG. 6, so that adjacent diaphragms 11 belong to different series.
It is divided into two series: a and series 11b, which are not hatched. FIG. 7 shows the results of measuring the amount of ink dots ejected from the nozzle entrance 3 by varying the time difference between the print signals added to the two series. The horizontal axis is the time difference of the print signal normalized by the natural vibration period of the diaphragm 11 in the ink, and the vertical axis is the ink dot amount normalized by the ink dot amount when no print signal is applied to one side of the diaphragm series. be. As in the previous embodiment, when the print signals applied to the adjacent diaphragms 11 have a time difference of 574 times or more the natural vibration period of the diaphragms 11 in the ink, the amount of ink dots is determined regardless of the state of the adjacent diaphragms 11. , exhibits constant ejection characteristics. Furthermore, constant ejection characteristics were exhibited when the gap between the diaphragm 11 and the nozzle forming member 4 was in the range of 10 μm to 30 μm.

〔Effect of the invention〕

As described above, according to the above structure of the present invention, in the structure in which ink is supplied through the space between adjacent diaphragms,
Since the ink ejection characteristics are not affected by the movement of the adjacent diaphragm, the flow path resistance on the supply side formed by the adjacent diaphragm is not affected by dimensional changes in the gap between the diaphragm and the nozzle forming member. The distance between adjacent diaphragms can be reduced to provide resistance. Therefore, the above configuration has the effect of providing an inkjet head with a wide allowable gap size range. Furthermore, since the density of the diaphragm increases as a result, it is possible to provide a small, high-density inkjet head.

[Brief explanation of drawings]

FIG. 1 is a main perspective view showing an embodiment of an inkjet head according to the present invention. 2 and 3 are main sectional views of the embodiment of the inkjet head according to the present invention shown in FIG. 1. 4 and 5 are diagrams showing measurement results of characteristics of the embodiment of the inkjet head according to the invention shown in FIG. 1. FIG. FIG. 6 is a main perspective view showing an embodiment of an inkjet head according to the present invention. FIG. 7 is a diagram showing measurement results of characteristics of the embodiment of the inkjet head of the present invention shown in FIG. 6. 11... Vibration plate 12... Support base... Nozzle opening... Nozzle forming member or more

Claims (1)

[Claims] A nozzle forming member having a plurality of nozzle openings, and a plurality of diaphragms that are arranged opposite to each of the nozzle openings and vibrate in response to a print signal, and ink is ejected from the nozzle openings by the vibration of the diaphragm. The inkjet head has an ink flow path that supplies ink to the nozzle opening through between the diaphragm filled with ink and an adjacent diaphragm, and the print signal that vibrates the diaphragm is . An inkjet head having a time difference between adjacent diaphragms that is at least 5/4 times the natural vibration period of the diaphragm in ink.