JPH0516352A - Ink jet head - Google Patents

Abstract

PURPOSE:To realize high quality printing by suppressing mutual interference due to propagation of pressure wave, generated at a distorted part of a piezoelectric element, to other channel. CONSTITUTION:In an ink jet head wherein a piezoelectric element 2 having distorted parts 7 and supporting parts 8 formed alternately through a plurality of parallel slits 5 is jointed integrally with a channel board 1 having channels 4 partitioned through barrier parts 3 corresponding with the distorted parts 7, depth (d) of the slit 5 and average depth (ds) of the distorted part 7 are set to satisfy a relation (1/4) d>=ds or (3/4) d<=ds.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a piezoelectric body drive type on-demand type ink jet head, and more particularly, to an ink jet head having a structure that suppresses mutual interference between a plurality of flow paths and reduces pressure reflected waves. Regarding

[0002]

2. Description of the Related Art An ink jet recording apparatus has a feature that it is possible to use an inexpensive ordinary recording paper which is capable of high-speed printing with extremely low noise. In particular, a piezoelectric body is provided and an electric signal is applied thereto. An on-demand type ink jet recording apparatus that forms a pressure wave in a pressure chamber (ink flow path) by utilizing the resulting piezoelectric displacement and ejects ink particles as needed is a simple and small recording apparatus.

3 (a), 3 (b) and 3 (c) are views showing the basic structure of an ink jet head of an ink jet recording apparatus, FIG. 3 (a) is a perspective view showing the constituent elements, and FIG. 3 (b) is a flow chart. The perspective view which shows the back surface of a road board, FIG.6 (c) is a perspective view when a component is joined together. In the figure, 11 is a flow path plate, 1
2 is a piezoelectric body, 13 is an ink supply port, 14 is an orifice,
Reference numeral 15 is a flow path, 16 is an ink chamber, 17 is a strained portion, 18 is a partition slit, 18a is a filler, and 19 is a substrate.

In the figure, the flow path plate 11 is provided with an ink chamber 16 for receiving ink supplied from the ink supply port 13 and storing the ink therein, as shown in FIG. A nozzle 1 that communicates with the ink chamber 16 and serves as an ink flow path, and ejects ink particles by pressurization.
A plurality of flow paths 15 having 4 at their ends are provided in parallel.

The piezoelectric body 12 is composed of stacked piezoelectric elements that are distorted in the thickness direction by the application of a driving voltage, and has one surface fixed on the substrate 19 and the other surface at a position facing the flow path 15. The strained portions 17 are provided as many as the number of the flow paths 15. The strained portion 17 is a channel 1 that is slightly narrower than the channel 15.
5 is a convex portion extending in the longitudinal direction and is formed by providing a plurality of slits 18 parallel to the piezoelectric body 12. The slit 18 is filled with a filler 18a made of a soft elastic material having a low Young's modulus. The flow path plate 11, the piezoelectric body 12, and the substrate 19 are overlapped and integrally bonded so that the flow path 15 and the strained portion 17 face each other as shown in FIG.

4 (a), (b) and (c) are views showing an orifice surface and a head section of an ink jet head. FIG. 4 (a) is a sectional view of the orifice surface, and FIG. 2A and 2C are cross-sectional views taken along the line AB of FIG. 2A, and reference numerals in the drawings are the same as those in FIG.

In the figure, the strained portion 17 forming a convex portion is an actuator which, when a voltage is applied, causes strain to be displaced in the thickness direction, that is, in the direction of decreasing the cross-sectional area of the flow path 15 having the length L. , Channel 1 due to the strain
A pressure wave is generated in the nozzle 5, and ink particles are ejected from the orifice 14. However, in the case of an inkjet head provided with a plurality of flow paths 15, there is a difference in the ink particle formation characteristics of ejecting ink particles from the nozzles 14 when the flow paths 15 are driven independently and when a plurality of the flow paths 15 are driven at the same time. This is because mutual interference (crosstalk) occurs between the flow paths 15. When mutual interference occurs, the dot position accuracy is deteriorated as a result, the dot diameter varies, and the recording image quality deteriorates.

[0008] Japanese Patent Application Laid-Open No. 1-242 proposed by the present applicant
The "Liquid jet recording head" of Japanese Patent No. 261 has a pressure wave absorbing member disposed in an ink chamber communicating with a plurality of ink channels in order to eliminate mutual interference when ejecting ink particles. As the pressure wave absorbing member, a porous organic material such as polyethylene that passes through the ink but is difficult to elute, an inorganic material such as a porous ceramics material, or a metal material woven from a stainless wire in a mesh shape is used. . However, since the above-described conventional technique disposes the pressure wave absorbing member inside the ink chamber, it is effective for mutual interference caused by the pressure wave transmitted to the non-driving flow path through the ink chamber, but It has no effect on vibrations and resonance phenomena through the parts, and it cannot be said to be sufficient as a measure for reducing mutual interference.

[0009]

[Purpose] The present invention has been made in view of the above situation, and reduces the mutual interference of pressure waves of straight traveling and reflection propagating in a piezoelectric body, which is a solid part, by reducing the propagation distance, The purpose of the present invention is to provide an inkjet head that enables quality printing.

[0010]

In order to achieve the above object, the present invention provides (1)
A piezoelectric body in which a plurality of parallel slits are provided and convex portions formed by the slits are alternately arranged so as to be a strained portion and a support portion, and a flow having a groove corresponding to the strained portion and partitioned by a partition wall portion. In the path plate, the partition wall portion of the flow path plate and the support portion of the piezoelectric body, the slit is filled with an elastic body and directly joined, or indirectly joined through a thin film member,
It is composed of parallel flow channels formed corresponding to the grooves of the flow channel plate, drives the strained portion to cause displacement in a direction perpendicular to the surface of the flow channel, and a nozzle communicating with the flow channel is used. In an inkjet head recording device that ejects liquid droplets, the depth d of the slit of the piezoelectric body and the depth d of the center of the strained portion of the piezoelectric body.
The relationship with _S is (1/4) d ≧ d _S , or
(2) A piezoelectric body in which a plurality of parallel slits are provided, and convex portions formed by the slits are alternately arranged as a strained portion and a support portion; A flow path plate having a groove, in the partition wall portion of the flow path plate and the support portion of the piezoelectric body, by filling the elastic body in the slit and directly bonded, or via a thin film member A nozzle that is indirectly joined to form a parallel flow path corresponding to the groove of the flow path plate, drives the strained portion to cause displacement in a straight direction on the surface of the flow path, and communicates with the flow path. In an inkjet head recording apparatus that ejects more droplets, the relationship between the depth d _S of the slit of the piezoelectric body and the depth d _{S of the} center of the strained portion of the piezoelectric body is set to (3/4) d ≦ d _S It is characterized by that. Hereinafter, description will be given based on examples of the present invention.

FIG. 1 is a sectional view as seen from the nozzle side for explaining the propagation of pressure waves in the ink jet head of the present invention. In the figure, 1 is a flow path plate, 2 is a piezoelectric material, 3 is a partition wall portion, 4 Is a flow path, 5 is a slit, 6 is a filler, 7 is a strained portion,
Reference numeral 8 is a support portion, and 9 is a groove.

In the figure, the piezoelectric body 2 is provided with a plurality of parallel slits 5 in a direction perpendicular to the plane of the drawing. Due to the slits 5, the piezoelectric body 2 forms a piezoelectric body having a convex cross-section, and the convex-shaped portion has the strained portions 7 and the support portions 8 arranged alternately. In addition, the flow path plate 1 includes the piezoelectric body 1
A groove 9 corresponding to the strained portion 7 is provided, and each groove 9 is partitioned by the partition wall portion 3. The flow path plate 1 and the piezoelectric body 2 are joined and integrated by the partition wall portion 3 of the flow path plate 1 and the support portion 8 of the piezoelectric body 2, and the groove 9 becomes the flow path 4 by being joined. , Forming ink flow paths.

In the slit 5 of the piezoelectric body 2,
The filler 6 having low elasticity and high insulation is filled. In the illustrated piezoelectric body 1, a laminated piezoelectric element is usually used in order to obtain a large piezoelectric strain even when a low voltage is applied, but the filler 6 enhances insulation between electrodes in the slit 5 of the laminated piezoelectric element. It is a thing. Further, when the number of slits 5 per unit length is increased in order to increase the integration density, the width of the convex portion between the strained portion 7 and the support portion 8 becomes narrower and the damage easily occurs, but the filler 6 serves as a reinforcing material. Therefore, prevent damage. Further, the piezoelectric body 2 is displaced in the thickness direction in the strained portion 7 by the application of a voltage, and the filler 6 is also elastically deformed in accordance with the displacement of the strained portion 7, which is directly or through the support portion 8. Although the partition wall 3 is lifted to reduce the volume change efficiency of the flow path 4 and cause mutual interference, by using the filler 6 as a soft elastic material having a low Young's modulus, the mutual interference by the flow path plate 1 is prevented. It is decreasing.

The operation of the ink jet head having the above structure will be described with reference to FIG. FIG. 2 is a diagram for explaining the operation of the inkjet head. In FIG.
Reference numeral 0 is a substrate, and other parts having the same functions as those in FIG. In the figure, when a voltage pulse is applied to the strained portion 7 of the selected piezoelectric body 1 based on the image information, the strained portion 7 is displaced in the thickness direction shown by the arrow and the volume of the pressure variation 4 is A sudden change occurs and a pressure wave is generated in the flow path 4. The pressure wave ejects ink droplets from a nozzle (not shown) provided at the end of the flow path 4.

The strained portion 7 of the piezoelectric body 1 generates a pressure wave in the flow path 4 as described above, but the pressure wave propagates downward through the strained portion 7 and goes to another channel. The arrow shown in FIG. 1 indicates a straight pressure wave propagating downward. On the other hand, the pressure wave generated by the displacement of the strained portion 7 is reflected by the end surface of the strained portion 7 and propagates the reflected pressure wave indicated by the arrow to another channel. Therefore, the rectilinear pressure wave and the reflected pressure wave are superimposed to form a composite pressure wave.

Now, let the depth of the slit 5 of the piezoelectric body 1 be d,
Assuming that the central depth of the strained portion 7 is d _S and the sound velocity in the piezoelectric body 1 is C _S , the reflected pressure wave is reflected at the open end of the strained portion 7 on the flow path 4 side, and therefore 2 d with respect to the straight pressure wave. _The pressure wave has a time delay of _S / C _S and the phase is inverted. Therefore, the phase of the reflected pressure wave with respect to the rectilinear pressure wave changes depending on the size of the central depth d _S of the strained portion 7. Further, the reflected pressure wave originating from the 0-0 line shown in the drawing, which is the central depth of the strained portion 7, and the straight traveling pressure wave are superposed and passed through the piezoelectric strained portion 7 which is the same medium as a synthetic wave, Turn to another channel.

The circulated synthetic pressure wave propagates to the strained portion 7 of the other channel and causes mutual interference. Therefore, when the rectilinear pressure wave and the reflected pressure wave are strengthened and the combined pressure wave has the maximum amplitude, mutual interference is maximum. On the contrary, when the amplitude of the synthetic pressure wave disappears, the mutual interference disappears. The combined pressure wave of the straight pressure wave and the reflected pressure wave is the depth d of the slit 5 and the central depth d _S of the strained portion 7.
The relationship is changed as follows, but this relationship is shown below. (1) d _S = d / 2; In this case, the rectilinear pressure wave and the reflected pressure wave overlap each other so as to strengthen each other, and wrap around to another channel to form a standing wave. (2) d _S «d or d _S ≒ d; In this case, the straight pressure wave almost the reflected pressure waves or generated from the same position, or the reflected pressure wave is synthesized in substantially the same phase , Each pressure wave strengthens each other. Further, when the above conditions are applied to the strained portion 7, the piezoelectric element strained portion 7 is formed sufficiently thin with respect to the depth d of the slit 5 and is arranged at the upper end portion or the lower end portion of the strained portion 7. It will be difficult to implement. (3) d _S ≦ d / 4 or d _S ≧ 3d / 4; this condition shows the relationship between the depth d of the slit 5 of the piezoelectric body 1 and the central depth of the strained portion 7 in the inkjet head of the present invention. However, since the phase is a phase that avoids the constructive strengthening due to the superposition of the rectilinear pressure wave and the reflected pressure wave, the amplitude of the combined pressure wave becomes a small value, and the mutual interference is reduced.

[0018]

[Effect] As is clear from the above description, in the ink jet printer of the present invention, the straight pressure wave emitted from the position of the average depth of the strained portion of the piezoelectric body and the reflected pressure wave reflected by the upper end surface are obtained. Separated, the straight pressure wave propagates through the piezoelectric strained part → downward propagation → shunt path to other channels, and the reflected pressure wave reflected by the open end face of the strained part is the piezoelectric strained part → top surface reflection → Propagation downward → Propagates a path around another channel, but the relationship between the slit depth d of the piezoelectric body and the average depth d _S is (1/4) d ≧ d _S or (3/4) d ≦ By selecting the value of d _S , the respective pressure waves were superposed in the other channels without strengthening each other, so that the amplitude of the synthetic pressure wave could be reduced. Therefore, the pressure wave generated by driving the strained portion can reduce mutual interference caused by the synthesized pressure wave generated by propagating through the strained portion 7, and high-quality printing can be performed.

[Brief description of drawings]

FIG. 1 is a cross-sectional view seen from a nozzle side for explaining pressure wave propagation in an inkjet head of the present invention.

FIG. 2 is a diagram for explaining the operation of the inkjet head.

FIG. 3 is a diagram showing a basic configuration of an inkjet head of an inkjet recording apparatus.

FIG. 4 is a diagram showing an orifice surface and a head cross section of an inkjet head.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Flow path plate, 2 ... Piezoelectric body, 3 ... Partition part, 4 ... Flow path, 5 ...
Slit, 6 ... Filler, 7 ... Distorted part, 8 ... Support part, 9 ...
groove.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Shunren Hirata             1-3-3 Nakamagome, Ota-ku, Tokyo Stocks             Company Ricoh (72) Inventor Koji Izumi             1-3-3 Nakamagome, Ota-ku, Tokyo Stocks             Company Ricoh

Claims (2)

[Claims] 1. A piezoelectric body in which a plurality of parallel slits are provided, and convex portions formed by the slits are alternately arranged as a strained portion and a support portion, and a partition portion corresponding to the strained portion. In the flow path plate having the groove, and in the partition wall portion of the flow path plate and the support portion of the piezoelectric body, the slit is filled with an elastic body to be directly bonded, or indirectly bonded via a thin film member. And the parallel flow paths formed corresponding to the grooves of the flow path plate, driving the strained portion to cause displacement in the direction perpendicular to the surface of the flow path and communicating with the flow path. In the inkjet head recording apparatus that ejects liquid droplets from the nozzle, the relationship between the depth d _S of the slit of the piezoelectric body and the depth d _{S of the} center of the strained portion of the piezoelectric body is (1/4) d ≧ d _S An inkjet head characterized in that 2. A piezoelectric body in which a plurality of parallel slits are provided, and convex portions formed by the slits are alternately arranged as a strained portion and a support portion, and a partition wall portion corresponding to the strained portion. A flow path plate having a groove formed, and in the partition wall portion of the flow path plate and the support portion of the piezoelectric body, an elastic body is filled in the slit and directly bonded, or a thin film member is formed. To form a parallel flow path corresponding to the groove of the flow path plate by driving through the distorted portion to cause displacement in the straight direction on the surface of the flow path and to communicate with the flow path. In an inkjet head recording device that ejects liquid droplets from a nozzle
The inkjet head is characterized in that the relationship between the depth d of the slit of the piezoelectric body and the depth d _{S of the} center of the strained portion of the piezoelectric body is (3/4) d ≦ d _S.