JPH01105746A - Ink jet head - Google Patents

Abstract

PURPOSE:To enable enlargement of a gradation width using a single electricity/ machine conversion means by providing a reflective plate which changes its shape in accordance with deformation of the electricity/machine conversion means and also each orifice and a pressurized liquid chamber on both surfaces of the flexible plate. CONSTITUTION:An electricity/machine conversion means 1 and an elastic sheet 2 are integrally connected to constitute a flexible plate with one end fixed as a cantilever. When a pulse is applied to the electricity/machine conversion means 1, the flexible plate is displaced by the gradual rising of the applied pulse. At that time, although meniscuses 3, 4 change, recording medium liquid 9 is not ejected from an orifice 4. Next, the flexible plate returns to a standstill condition due to the steep falling of pulse, and recording medium liquid 9 is ejected from an orifice 3.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Criticism 91 The present invention relates to an inkjet head, and more particularly, to an inkjet head using an electromechanical transducer element.

Because it is difficult to stably change the volume of ejected droplets from large to small with one nozzle in the disaster technology inkjet head,
Conventionally, gradation expression has been satisfied by using a dither method (reducing resolution) or by increasing the number of heads and using heads of the same color but different densities (reducing cost). for example,
The invention described in Japanese Unexamined Patent Publication No. 52-11712 has a plurality of inkjet heads that eject ink of different concentrations, and the ink is ejected from these inkjet heads according to the level of an image signal. Although it is possible to increase the resolution and obtain gradation, it requires a plurality of heads, which increases the cost and makes it difficult to downsize.

” - Kazumasa ・The present invention was made in view of the above-mentioned circumstances,
In particular, it is intended to provide means for expanding the gradation width that can be expressed by one electromechanical conversion means.

Structure In order to achieve the above object, the present invention provides an inkjet head that applies an electric pulse to the electromechanical conversion means to change the volume of a pressure chamber and ejects a recording medium liquid from an orifice. It is characterized by having a flexible plate that deforms as it deforms, and having orifices and pressurized liquid chambers on both sides of the flexible plate. Hereinafter, the present invention will be explained based on examples.

1 and 2 are cross-sectional configuration diagrams for explaining the present invention in detail, FIG. 3 is a diagram showing an example of the electric pulse of the drive signal source, and FIG. 4 is a diagram for explaining the gradation expression. These are diagrams for explaining the effect. Throughout the diagrams, 1 is an electromechanical conversion means, and 2 is an elastic thin plate.

3.4 is an orifice, 5 and 6 are pressurized liquid chambers, 7 and 8 are recording medium liquid supply channels, 9 and 10 are recording medium liquid, and 11 is a drive signal source, as shown in FIGS. 2 and 3 below. The operation of the present invention will be explained with reference to the following.

The electromechanical conversion means 1 and the elastic thin plate 2 are integrally connected to form a flexible plate, and in the case of the embodiment shown in FIG. 2, it is a cantilever beam with one end fixed. FIG. 2(a) shows a stationary state, and at this time, the electromechanical conversion means 1
The voltage applied to is Vo in FIG. Now, when a pulse as shown at 3a in FIG. 3(a) is applied to the electromechanical conversion means 1, the flexible plate moves as shown in FIG. 2(b) due to the gradual rise of this applied pulse. Displace as shown. At this time, the menisci 3 and 4 change as shown in FIG. 2(b), but the recording medium liquid is not ejected from the orifice 4. At the 0th order, due to the steep fall of the pulse 3a, the flexible plate It returns to a stationary state, and at this time, the pressure in the pressurized liquid chamber 5 rises rapidly, and the recording medium liquid 9 is injected from the orifice 3. Further, the pressure in the pressurized liquid chamber 6 becomes negative, and the recording medium liquid 9 is sucked into the pressurized liquid chamber 6 from the supply channel 8 and the orifice 4, resulting in the state shown in FIG. 2(c). After this, the meniscus of the orifice passes through the state shown in FIG.
) Returns to the state of 0 Next, when the electric pulse 3b shown in FIG. 3(a) is applied, the flexible plate is displaced in the opposite direction and the orifice
Spray more. Electric pulses 3c and 3d in FIG. 3(b) are different driving examples.

In 3c, the injection occurs from the orifice 4 at a steep rise, but since the flexible plate returns to its original position with a gentle fall, there is no injection from the orifice 3.The opposite is true for 3d. By selecting the pulses to be applied in this way, the orifice to which the injection will be made can be selected.

Note that FIG. 2(e) is a cross section taken along the line A-A in FIG. 2(a), and the gap between the flexible plate and the wall surface of the pressurized liquid chamber must be minute.

The embodiment shown in FIG.
are separated by an elastic thin plate 2, and different recording medium liquids are supplied to both liquid chambers, and the recording medium liquid is ejected in the same manner as in the embodiment shown in FIG.

Figure 4 shows the optical density expression range by taking the optical density (0, D) on the vertical axis and the peak value (Vp) of the applied pulse on the horizontal axis. In A, orifices 3 and 4 are used simultaneously. In this case, B shows the case where only orifice 3 is used, and C shows the case where only orifice 4 is used.As is clear from this figure, in Figs. Different droplet volume adjustment ranges (optical density expression ranges) can be obtained by reducing the opening area and by selecting application pulses corresponding to each orifice.

5 and 6 are sectional views showing modified embodiments of the embodiment shown in FIG. 2, respectively, and the embodiment shown in FIG.
Although two electromechanical conversion means 1 are used to form a flexible plate, an elastic thin plate may be provided between these electromechanical conversion means. In addition, FIG. 6(b) shows the line B-B in FIG. 6(a).
In this embodiment, which is a line sectional view, the elastic thin plate 2 of the embodiment shown in FIG. 2 is changed from a cantilever beam to a beam supported at both ends. In the embodiment shown in FIGS. 1 and 2, the orifices 3 and 4 eject droplets in the same direction and are close to each other, so the orifices 3 and 4 are arranged in the direction of relative movement between the recording medium and the head. By providing a slight delay between the two applied pulses, recording can be performed at a desired position. Also, orifices 3 and 4
The range of gradation expression can be further expanded by ejecting and recording droplets of 1 to 100% overlapping each other at the same position on the recording medium (either by varying the orifice diameter or by varying the concentration of the recording medium liquid). Furthermore, in the embodiment shown in FIG. 1, by changing the concentrations of the recording medium liquids 9 and 10, the optical density can be similarly changed even with the same orifice and applied pulse. Furthermore.

It is also possible to make the recording medium liquids 9 and 10 different colors,
By providing two of these heads, yellow, magenta, cyan, and black can be ejected.

In the embodiment shown in FIGS. 1 and 2, it is necessary to make the recording medium liquid non-conductive or to coat the elastic thin plate 2 with an insulation coating.

Effects As is clear from the above description, according to the present invention, (a) the head shown in FIG. 1 can select two types of recording medium liquids of different colors with one head.

(b) Selecting two types of recording medium liquids with different concentrations and expanding the gradation width as shown in FIG. 4 can be realized with the head shown in FIG. 1.

(c) By using the head shown in Figures 1 and 2, in which both orifices have different opening areas, it is possible to select ejected droplets with different volumes, and it is possible to expand the gradation width as shown in Figure 4. can.

There are advantages such as

[Brief explanation of the drawing]

FIG. 1 and FIG. 2 are a cross-sectional configuration diagram for explaining an embodiment of an inkjet head according to the present invention, and FIG.
The figure shows an example of the electric pulse of the drive signal source, FIG. 4 is a diagram for explaining the effect on gradation expression, and FIGS. 5 and 6 are examples of the embodiment shown in FIG. 2, respectively. FIG. 3 is a cross-sectional configuration diagram for explaining a modified example of FIG. 1... Electromechanical conversion means, 2... Elastic thin plate, 3, 4
... Orifice, 5, 6... Pressurized liquid chamber, 7, 8...
- Recording medium liquid supply channel, 9.10... Recording medium liquid, 1
1... Drive signal source. Patent applicant Ricoh Co., Ltd. 1! Portrait←

Claims (4)

[Claims] (1) In an inkjet head that applies electric pulses to an electromechanical transducer to change the volume of a pressure chamber and eject recording medium liquid from an orifice, a flexible plate that deforms as the electromechanical transducer deforms is used. An inkjet head comprising: an inkjet head having an orifice and a pressurized liquid chamber on both sides of the flexible plate. (2) The inkjet head according to claim (1), wherein both pressurized liquid chambers are separated by the flexible plate. (3) The inkjet head according to claim (2), wherein the recording medium liquids in both pressurized liquid chambers are different. (4) Claims (1) or (2) or (2) characterized in that the opening areas of the orifices are different.
The inkjet head described in item 3).