JPH0699578A - Ink jet recording head - Google Patents

Abstract

PURPOSE:To realize the stable and high reliable emission of ink, to realize the uniform ink emitting speed between respective nozzles in a high density multinozzle head and to prevent the deterioration of the shape of an ink droplet due to the vibration of an ink passage constituting member. CONSTITUTION:A reinforcing member 2 having nozzle communication orifices 8 corresponding to a plurality of pressure chambers 9 and a plurality of ink emitting nozzles 7 is arranged between the pressure chamber forming member 3 having the pressure chambers 9 arranged thereto and the nozzle forming member 1 having the ink emitting nozzles 7 corresponding to the respective pressure chambers.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording head, and more particularly to an ink jet recording head in which the density and size of ink ejection nozzles are increased.

[0002]

2. Description of the Related Art An ink jet recording head for ejecting ink using a longitudinal vibration type piezoelectric element is disclosed in Japanese Patent Laid-Open No. 1-1156.
No. 38 publication. The configuration is shown in FIG. The vibrating surfaces of the laminated vibrator 5, which is a piezoelectric element that vibrates in the vertical direction, in other words, in the direction perpendicular to the vibrating surface, faces the plurality of pressure chambers 9 and is fixed to the elastic plate 4 of each pressure chamber. It On the other hand, the other end of the vibrator is fixed to the vibrator holder 6. The vibrator holder is fixed to an ink flow path forming member composed of a pressure chamber, an elastic plate, and a single plate or a multi-layer plate having an ink discharge nozzle 7, and the vibrator is sandwiched between the ink flow path forming member and the vibrator holder. It will be a structured structure. In the above structure, the ink flow path constituent member is fixed by the vibrator holder on the surface excluding the region where the plurality of pressure chambers are formed, and the region where the pressure chambers are formed is fixed only by the vibrator. There is nothing to support.

[0003]

In the conventional structure, if the density of the ink discharge nozzle and the pressure chamber is increased,
The wall of the pressure chamber that supports the nozzle forming member becomes thinner, and its rigidity eventually depends on the nozzle forming member. Further, if the density of ink ejection nozzles is increased, the pressure inside the pressure chamber must be increased in order to obtain the required ink dot amount.

On the other hand, in the general ink jet recording head, the ink flight characteristics that govern the printing quality are very important, and the ink droplets ejected from each nozzle must ensure a uniform shape. Therefore, extremely high accuracy is required for the shape and position of the ink ejection nozzle. Therefore, it is better to design the nozzle forming portion thin in view of processing accuracy. In order to accurately open the ink ejection nozzle, there is a method of etching a material having high ink resistance such as silicon wafer, glass, and stainless. However, in the forming method by etching, it is desirable to perform etching from both sides of the plate in order to obtain hole diameter accuracy, which increases the number of steps and increases the cost.

As another method, there is a method in which a polymer resin film is perforated with an excimer laser or the like, or a metal such as stainless steel is perforated with a press. In each of these methods, the accuracy of the ink ejection nozzle is ensured by using a thin plate, and the number of steps is small, which is advantageous in cost.

However, in the above-mentioned conventional structure, even if the ink discharge nozzle of the nozzle forming member having the above-mentioned restriction is opened accurately, in the region where the pressure chamber is formed, there is no supporting member other than the vibrator. When a large number of vibrators are driven by the driving force of the vibrator and the pressure applied to the ink in the pressure chamber, the vibrator has a large function of deforming the pressure chamber constituent region. That is, the ink flight characteristics change depending on the number of vibrators driven even in the same nozzle. Also,
Due to the deformation of the nozzle forming member, the flight speed of ink droplets ejected from each nozzle is not uniform. Further, the vibration of the nozzle forming member deteriorates the shape of the ink droplet. For this reason, the ink flight characteristics are significantly deteriorated, and the print quality is deteriorated.

The deformation modes of the ink flow path forming member in the conventional structure are shown in FIGS. The ink flow path constituent member is composed of stainless steel having a thickness of 60 μm in the nozzle forming portion, photosensitive resin for the pressure chamber forming member, and thickness of 2 μm for the elastic wall.
Uses nickel. There are 24 nozzles and the pitch is 0.1411 mm. FIG. 10 shows the case where 24 vibrators are driven, and FIG. 11 shows the case where 3 vibrators are driven.
Maximum displacement when driving 24 oscillators is 1.5 μm
And the maximum displacement amount when driving three rods is 0.1 μm. In addition, the displacement distribution becomes a dome shape with the fixed part (shaded part in the figure) by the vibrator holder as a fulcrum, and the place where the maximum displacement occurs is the surface where the vibrator is joined to the elastic wall as the ink flow path constituent member. It is the projected part. This deformation is in synchronization with the ink ejection, and the deformation direction and the ejection direction are the same. Therefore, if the deformation amount of the ink flow path forming member for each nozzle is different, the ink speed ejected from each nozzle is different. Become.

The actual ink ejection state is shown in FIG. 12 by the ink ejection speed. The ink speed is faster near the fixed part of the oscillator holder and slower at the farther part.

As another problem, the phenomenon that ink is ejected from nozzles that do not drive the vibrator appears depending on the drive pattern of the vibrator. This is a phenomenon caused by the thin elastic plate of the ink flow path forming member and the deformation of the ink flow path forming member. This phenomenon will be described in detail with reference to FIG. FIG. 13 shows the movement of the ink flow path forming section having the vibrator that is not driven when 23 of the 24 vibrators are driven. FIG. 13A shows a standby state. In FIG. 13B, the ink flow path constituent member is drawn to the vibrator side. At this time, since the vibrator is contracted in about 100 μsec, ink is not ejected even if the volume in the pressure chamber becomes small. The next driving oscillator is 1
It returns to the original length within about 0 μsec (Fig. 13).
(C)). At that time, the ink flow path forming member overshoots, but since the vibrator is fixed, the elastic plate expands and the volume in the pressure chamber increases (FIG. 13D). After that, the ink flow path constituting member repeats at a cycle of about 20 μsec, and the ink is ejected because the volume of the pressure chamber changes (FIG. 13E). In addition, the I-A line in FIG.
The position of the nozzle surface in the standby state is shown.

As another problem, it is ideal that the ejected ink droplet has a large diameter and one droplet in view of print quality, but the shape of the ink droplet is a two-step shape as shown in FIG. 14 due to the vibration of the nozzle forming member. And becomes a long droplet having a small ink droplet diameter. Such ejected ink droplets are disadvantageous in quick-drying the ink, and the dot diameter when printed on a recording medium is also small.

In order to solve the problem, a reinforcing member is added to a region where the joint surfaces of a plurality of piezoelectric elements are projected on the nozzle forming member of the ink flow path forming member to realize stable and highly reliable ink ejection, Furthermore, it is an object of the present invention to achieve a uniform ink ejection speed among the nozzles in a large number of high-density nozzle heads and to prevent deterioration of ink droplet shape due to vibration of ink flow path forming members.

[0012]

Therefore, in the present invention, a piezoelectric element vibrating in the vertical direction is used in an ink jet recording head for recording on a recording medium by causing a volume change of a pressure chamber using the piezoelectric element vibrating in the vertical direction. In the structure in which is fixed to the ink flow path forming member and the vibrator holder, a reinforcing member is added to a region where the bonding surfaces of the plurality of piezoelectric elements are projected on the ink flow path forming member.

[0013]

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is an exploded perspective view showing the basic structure of a first embodiment of an ink jet recording head according to the present invention.
A nozzle forming member 1 shown in FIG. 1 includes a reinforcing member 2, a pressure chamber forming member 3 including a pressure chamber 9 and a common ink chamber 10, and a pressure chamber 9.
The elastic plates 4 for transmitting the displacement of the vibrator 5 are laminated on each other to form an ink flow path forming member. An ink supply port 11 is connected to an ink supply pipe (not shown).
The reinforcing member 2 has a nozzle communication passage 8 through which ink passes from the pressure chamber 9 to the ink discharge nozzle 7. The vibrator 5 is joined to the pressure chamber 9 substantially at the center thereof. The vibrator holder 6 fixes the vibrator 5 and the ink flow path forming member. In this embodiment, the material of the ink flow path forming member is the nozzle forming member 1
As a reinforcing member 2 with a thickness of 0.06 mm
A stainless steel plate having a thickness of 0.1 mm was used as the elastic plate 4, nickel having a thickness of 2 μm was used as the elastic plate 4, and the others were made of a photosensitive resin. The communication passage 8 of the reinforcing member has a pitch of 0.1411.
mm. The hole diameter is φ0.08 to φ0.1 mm.

As the material of the nozzle forming member 1, in addition to a metal having a high ink resistance such as stainless steel, a polymer resin having a high ink resistance such as polysulfone, polyimide, polycarbonate, polyacetal, polyetherimide or polyether is used. Ether ketone, ABS resin, epoxy resin, silicone resin and the like can also be used. When a polymer resin is used as the nozzle forming member 1, it is necessary to change the thickness of the reinforcing member 2 depending on the elastic modulus of the resin. The material of the pressure chamber forming member 3 may be a material that can form the pressure chamber 9 at low cost and with high precision, such as a photosensitive resin, a polymer resin having ink resistance, glass, a silicon wafer, a metal, or the like. Either one will do.

With the configuration shown in FIG. 1, the printing density is 360 dpi,
FIG. 2 shows the flight state of an ink jet recording head having two rows of 24 nozzles and the ink ejection speed. Reinforcement member 2
By using, the flight distribution of ink drops became constant. The thickness of the reinforcing member 2 at this time is 0.1 mm.
As shown in FIG. 3, the flying state of the ink droplet becomes one spherical shape, and does not become a long gourd-shaped liquid column. Further, the maximum displacement amount of the nozzle forming member 1 at this time was 0.1 μm. At this time, the pressure applied to the flow path forming region of the ink flow path forming member was 1.5 atm, considering the ink flow path forming member as one flat plate. The maximum displacement amount of the piezoelectric element 5 at this time is 1 μm, and in order to design the reinforcing member 2, the maximum displacement amount of the ink flow path constituting member including the reinforcing member 2 is 10% of the maximum displacement amount of the vibrator 5. The strength of the reinforcing member 2 is calculated as follows.

In the first embodiment, as shown in FIG.
The same effect can be obtained in a configuration in which the vibrating surface of the vibrator 5 is arranged to face the nozzle hole opening.

FIG. 5 is an exploded perspective view showing another embodiment. The difference from the first embodiment is that the photosensitive resin 12 is laminated on the nozzle forming member 1, the hole 13 into which the reinforcing member 2 is inserted and the nozzle communication passage 14 are formed in advance, and then the reinforcing member 2 is inserted into the hole 13. Then, it is joined to the nozzle forming member 1, and a photosensitive resin 15 is further laminated to seal the pressure chamber 9, and the nozzle communication passage 16 is opened. The end face of the reinforcing member 2 on the ink ejection nozzle 7 side is the elastic plate 4 of the vibrator 5.
It suffices that the surface joined to the nozzle forming member 1 is closer to the ink ejection nozzle 1 side than the area projected on the nozzle forming member 1. However, in this embodiment, the nozzle communicating passages 14 and 16 are φ0.1 mm, and the nozzle communicating passage 14 and the reinforcing member The partition wall 2 was 0.15 mm, and the end surface of the reinforcing member 2 was 0.2 mm from the ink discharge nozzle 7. In this case, the thickness of the reinforcing member 2 was 0.2 mm. The material of the nozzle forming member 1 is the same as that of the first embodiment, but when the polymer forming resin 1 is used as the nozzle forming member 1, the reinforcing member 2 must be designed so as to hang on the fixed end of the vibrator holder 6. I have to. According to this embodiment, there is an effect that it is not necessary to intentionally form the nozzle communication path in the reinforcing member 2 that is difficult to drill. Further, as shown in FIG. 6, the end portion of the vibrator holder 6 is fixed from the common ink chamber 10 to the ink supply portion of the pressure chamber 9 (a place that does not act as an elastic wall), and the reinforcing member 2 is used as the common ink. If the chamber 10 is not covered, the pressure absorbing capacity of the common ink chamber 10 is increased, and there is an effect that the stable ink supply is not sacrificed.

FIG. 7 shows another embodiment of the present invention. The difference of the present invention from the first embodiment is that the reinforcing member 2, the nozzle forming member 1, and the pressure chamber forming member 3 are laminated in this order. A window 17 for ejecting ink is opened in the reinforcing member 2. As shown in FIG. 7, the window 17 of the reinforcing member 2 is inclined from the vicinity of the nozzle 7 for cleaning the nozzle surface 18. There is. When paper fluff, dust, and the like are deposited near the nozzle 7, the ejected ink is drawn by them and causes flight bending. Therefore, it is necessary to clean the nozzle 7 portion. Since the cleaning is performed with a rubber flat plate or the like, the reinforcing member 2 needs to be inclined as in the present embodiment.
The reinforcing member 2 also has an effect of preventing the nozzle surface 18 from being damaged by a recording medium (paper or the like) and preventing paper fluff or the like from directly adhering to the nozzle 7.

[0020]

As described above, the ink jet recording head for recording on the recording medium by causing the volume change of the pressure chamber by using the piezoelectric element vibrating in the longitudinal direction according to the present invention,
As a result of adding a strengthening member to the area where the joint surface of a plurality of piezoelectric elements is projected on the nozzle forming member of the ink flow path forming member, stable and reliable ink ejection is realized, and moreover, a large number of high density nozzle heads. In the above, the uniform ink ejection speed between the nozzles is realized, and the deterioration of the ink droplet shape due to the vibration of the ink flow path constituent member is prevented.

[Brief description of drawings]

FIG. 1 is an exploded perspective view showing a basic structure of a first embodiment.

FIG. 2 is a relationship diagram of each nozzle and ink ejection speed.

FIG. 3 is a view showing a flying state of ejected ink.

FIG. 4 is an exploded perspective view showing another embodiment.

FIG. 5 is an exploded perspective view of the second embodiment.

FIG. 6 is an exploded perspective view of a third embodiment.

FIG. 7 is a sectional view of the third embodiment.

8 is a cross-sectional view taken along the line AA of FIG.

FIG. 9 is a sectional view showing a basic structure of a conventional example.

FIG. 10 is a deformation diagram of an ink flow path constituent member when 24 vibrators are driven.

FIG. 11 is a deformation diagram of an ink flow path constituent member when three vibrators are driven.

FIG. 12 is a relationship diagram of each nozzle and ink ejection speed in a conventional example.

FIG. 13 is an explanatory diagram of a volume change state of the pressure chamber.

FIG. 14 is a diagram showing a ejected ink flying state in a conventional example.

[Explanation of symbols]

 1. Nozzle forming member 2. Reinforcement member 3. Pressure chamber forming member 4. Elastic plate 5. Multilayer piezoelectric element (vibrator) vibrating in the vertical direction 6. Transducer holder 7. Ink ejection nozzle 8. Nozzle communication hole 9. Pressure chamber 10. Common ink chamber 11. Ink supply port 12. Photosensitive resin 13. Hole 14. Nozzle communication passage 15. Photosensitive resin 16. Nozzle communication passage 17. Reinforcement member window 18. Nozzle surface 19. Ink flow path component

Claims (6)

[Claims] 1. A nozzle forming member having an ink discharge nozzle, a pressure chamber forming member having a pressure chamber communicating with the nozzle, and one wall surface of the pressure chamber, and transmitting energy from the pressure generating member to the pressure chamber. In an inkjet recording apparatus having an elastic plate, an ink jet recording head, wherein a reinforcing member is arranged in a region where the joint surfaces of the plurality of piezoelectric elements and the elastic plate are projected onto the nozzle forming member. 2. The ink jet recording head according to claim 1, wherein the reinforcing member is closely attached between the nozzle forming member and the pressure chamber forming member. 3. The ink jet recording head according to claim 1, wherein the strengthening member is projected on a surface of the vibrator holder that fixes the piezoelectric element, to which the ink flow path forming member is joined. . 4. The ink jet recording head according to claim 1, wherein the reinforcing member does not cover a common ink chamber. 5. The ink jet recording head according to claim 1, wherein the nozzle forming member is made of polymer resin. 6. The reinforcing member has a rigidity such that a maximum amount of bending of the nozzle forming member caused by deformation of the piezoelectric element is 10% or less of a maximum amount of displacement of the piezoelectric element. 1. The inkjet recording head according to 1.