JPS58175667A - Laminated ink jet head - Google Patents

Abstract

PURPOSE:To obtain an inexpensive ink jet head having a small thickness, by a method wherein a reinforcing member having a modulus of elasticity higher than that of a head substrate is adhered to the substrate. CONSTITUTION:A vibrating plate 2 made of the same material as that for the head substrate 1, which is made of an ABS resin or the like, is adhered to the substrate 1 by a dope adhesive, and the reinforcing plate 7 such as a steel plate is adhered to the substrate 1 by an epoxy resin. Accordingly, an ink jet head with little loss in pressure and having a small thickness can be obtained. In addition, by producing the head substrate 1 by injection molding and melt-bonding the vibrating plate 2 to the substrate 1, it is possible to mass-produce the head inexpensively, with less shrinkage upon injection molding, a higher degree of flatness and less possibility of collapse of a nozzle.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ink-on-demand type inkjet, and particularly to an inkjet head with low mass production cost.

The ink-on-demand type inkjet head has a head substrate 1, as shown in FIG. Vibration plate 2. It consists of a piezoelectric element 3 and has a very simple configuration. However, because the diameter of the nozzle 4 is small, it is quite difficult to actually mass-produce the head. At present, heads based on photoetching of photosensitive glass are in practical use, but they are difficult to mass produce and are expensive.

The inventors of the present invention have been developing plastic heads using injection molding in order to mass produce inkjet heads at low cost, but it has become clear that the thickness of the head substrate needs to be increased due to the low elastic modulus of plastic. . In other words, if the thickness of the head substrate is thin compared to the laminated plate of the piezoelectric element and the diaphragm, pressure will escape to the head substrate, and the electrical energy applied to the piezoelectric element will not be used sufficiently for ink ejection. To provide an inkjet head with a thin head thickness that can be manufactured at low cost.

The gist of the present invention is to suppress an increase in the thickness of the head by bonding a reinforcing member having a higher elastic modulus than the head substrate to the head substrate.

A schematic cross-sectional view of an embodiment of the invention is shown in FIG.

A nozzle 4, a pressurizing chamber 5. Ink flow paths such as the supply path 6 are formed as grooves. A diaphragm 2 made of the same material is bonded to the head substrate 1 with doped cement, and a piezoelectric element 3 is placed at a position corresponding to the pressurizing chamber 5.
is glued. The head substrate 1 is bonded with epoxy resin to a reinforcing plate 7 made of steel that has been punched into a predetermined shape using a press.

At the same time, a piezoelectric element 3' and a diaphragm 2' are mounted on the opposite side of the reinforcing plate 7.
The head substrate 1' laminated on is bonded. Here, the head substrate 1 and the diaphragm 2', and the head substrate 1' and the diaphragm 2 are the same parts, and the side to which the piezoelectric elements 3 and 3' are bonded functions as the diaphragm.

In the above configuration, in order to prevent the driving energy of the piezoelectric elements 3 and 6' from escaping due to the deflection of the opposing head substrates, the thicknesses of the head substrates 1 and 1' and the thickness of the reinforcing plate 7 must be sufficiently thick. . Quantitatively, the body for the same pressure on the diaphragm side and the head board side! Energy escape can be estimated based on the amount of change, that is, compliance.

Pressurized chamber 5. If the shape of the piezoelectric element 3 is calculated as a circle, the compliance of the laminated plate of the diaphragm 2 and the piezoelectric element 3 is 0,
can be expressed as follows. Here, the subscript P represents a piezoelectric element, and the subscript V represents a diaphragm.

h, = hυ+ to 11IhP I...
・■ However, α: radius of piezoelectric element, 'H, p, Ev: modulus of longitudinal elasticity, P, V: Boisson's ratio, hP t h v:
Thickness, hl: Equivalent thickness of laminate, kl! Equivalent coefficient to convert piezoelectric element thickness to diaphragm thickness.

Similarly, the compliance of the laminate of the head substrates 1, 1' and the reinforcing plate 7 is 0. can be expressed as follows. Here, the suffix R represents the reinforcing plate, and the suffix represents the head board, E, C, h.
etc. are the constants mentioned above.

h, = 2hh+ to 2h9rL ・
・・・・・・■ Note: Equivalent thickness of the laminate, k2: Equivalent coefficient for converting the thickness of the reinforcing plate into the thickness of the head substrate.

Since the pressure escape to the head substrate side can be considered as the ratio of the volume change on the substrate side and the diaphragm side due to the same pressure, in order to reduce the pressure escape to a predetermined ratio or less, 0, ≦KO1...
・・・■ It is sufficient if it holds true. Since the diaphragm and the head substrate are made of the same material, Eυ=Eh, υ=Shh, and when formulas 0 to 2 are summarized, the following is obtained.

Specifically, Ep=5.9×10”°N/normal 2.νP=0
, 3. h p = 0.15, M v = E
b = 2. I X 10'N/9rL", vv
=vb=0.57, hv=hh=0.3, verbosity=
2. I X 1011N/lyL”, ν poison ==
0.5, by substituting K=0,1 into the formula ■, we get h, ≧[
The length will be 23m. If this is to be satisfied by increasing the thickness of the head substrate without using a reinforcing plate, it will be necessary to increase the thickness by one time, which means hffl≧1rrrm. Therefore, assuming the thickness of the head substrate part as h m + 2 h b, it is 1.6
By inserting a steel plate as a reinforcing plate, the thickness of the head substrate part that was required for ++on can be reduced to 0.83 mm, and the same effect can be obtained.

As described above, by using a reinforcing plate with a thickness that satisfies formula (■) as an intermediate substrate, an inkjet head with low pressure loss and no adverse effects due to vibration leakage on both sides can be obtained, and the thickness of the head can be reduced. .

Note that formulas ■, ■, ■, and ■ are for the case where the diaphragm 2 and the head substrate 1 are supported circumferentially, and if the state of the connection between the diaphragm 2 and the head substrate 1 can be considered to be fixed circumferentially, it is better to calculate by substituting them into the formula ■. good. Specifically, when calculated using the same constants as those used previously, htrL≧0.13peng.

Further, when the pressurizing chamber 5 and the piezoelectric element 3 are rectangular,
When it can be considered as peripheral support, it is sufficient to substitute into formula ■. Specifically, when calculated using the same constant as before, h=≧0.22 tan.

Also, when it can be considered that the periphery is fixed, it is sufficient to substitute into formula ■. If we calculate as before, hfi≧0.13.

In each of the above calculation examples, K = o, 1, but in order to further suppress injection instability due to vibration leakage to the back side, the pressure loss is set to 5% or less, and if [=Q, Q5, then according to formula (■), If it is circular and can be considered as peripheral support, ktrL
≧0,32 rtun , if it can be considered as peripheral fixed,
kfn≧0.2 tan eIf the periphery is fixed in a rectangular shape, the thickness of the auxiliary plate should be selected to be ≧0.19 mm.

The embodiment shown in FIG. 2 shows a double-sided head in which the head substrate is bonded to both sides of the reinforcing plate, but if the head substrate is bonded to only one side of the reinforcing plate, 2hb may be replaced with hh in equation (2).

The value of K can take various values, but when priority is given to the thinness of the head, it should be set to 0.1. When prioritizing prevention of voltage rise and increase in instability, K = approximately 0.05 may be selected.

Ceramics and various metals can be used as the reinforcing plate, but steel plates, stainless steel plates, etc. having a high modulus of elasticity are particularly suitable.

In addition to ABS, materials such as A8TL resin, acrylic resin, and polysal 7on are suitable for the head substrate in terms of head assembly adhesion and transparency.

As can be seen from the embodiment shown in FIG. 2, according to the present invention, by bonding a reinforcing plate having a higher elastic modulus than the head substrate to the head substrate, an inkjet head with less pressure loss and a thinner thickness can be obtained. .

In particular, mass production of low-cost heads is possible by welding the diaphragm to the plastic head substrate made by injection molding. Furthermore, since the thickness of the diaphragm and head substrate can be thin, there are fewer sink marks during injection molding and flatness is achieved, so the amount of solvent cement applied during bonding can be reduced, and the nozzle can therefore be sealed with solvent cement. Nikugu naru. In addition, since the diaphragm and head substrate are thin, the pressing force required for assembly and deodorization can be weak, and the nozzle is less likely to collapse.

Also, compared to a head made only of plastic, since the pressurizing chamber is covered with a metal plate, it is less likely that ink will evaporate through the plastic or that air will enter.

Furthermore, the weight of the head can be reduced compared to a head made only of photosensitive glass or metal, and the energy and drive motor for moving the head are also advantageous.

Furthermore, since the head substrate can be made smaller, the width W of the front surface of the nozzle is reduced, the amount of ink accumulated is reduced, and the stability of ink ejection is increased. In particular, if a material with good ink wettability, such as a metal plate, is used as the reinforcing plate, the ink on the front surface of the plastic nozzle will be less likely to be pulled by the reinforcing plate and accumulate. In particular, if the reinforcing plate 7 is provided at a position lowered from the nozzle front surface 9 as in the embodiment shown in FIG.
The ink 10 is pulled by the reinforcing plate 7 like the ink 8, and is even more effective. For example, in the embodiment shown in FIG. 2, when the ink colors on both the left and right sides are red and black, the amount of color mixing between the red and black inks is reduced.

Furthermore, in the embodiment shown in FIG. 2, the right and left head parts are made common, and the only difference is the adhesive surface of the piezoelectric element.
There is an advantage in mass production that only one type of injection mold 9 assembly jig is required.

As described above, the present invention not only provides a thin head with low pressure loss, but also has many effects and can be widely applied to serial printers, line printers, plotters, copiers, facsimile machines, etc.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a conventional inkjet head, and FIG. 2 is a sectional view of an embodiment of the present invention. 1.1'... Head board 2.2'... Vibration plate 3.3'... Piezoelectric element 4... ...Nozzle 5...
・・・・・・・・・Pressurization chamber 7・・・・・・・・・・・・
...Reinforcement plate and above Applicant Shinshu Seiki Co., Ltd. Shuwa Seikosha Co., Ltd. Agent Patent attorney Tsutomu Mogami

Claims (1)

[Claims] A first substrate (1) with a low elastic modulus on which ink supply channels, pressure chambers, nozzles, etc. are formed on one surface, and a diaphragm made of the same material as the first substrate (1) laminated on the one surface. (2), a piezoelectric element (3) further laminated on the diaphragm (2) and placed opposite the pressure chamber, and a second substrate (1') made of the same material as the first substrate (1). ), a diaphragm (2') made of the same material as the second substrate (1'), which is laminated with the second substrate (1') and has an ink supply path, a pressure chamber, a nozzle, etc. formed on one surface thereof; A piezoelectric element (3') laminated on the other side of the diaphragm (2') and placed opposite the pressure chamber is tightly attached between the first substrate (1) and the second substrate (1'). A laminated inkjet head comprising a reinforcing plate (7) made of a material with a high elastic modulus and having an end face inward from a nozzle end face (9).