JP5268804B2 - Mist jet recording head - Google Patents

Description

  The present invention relates to a mist jet type recording head that ejects liquid in a mist form using ultrasonic vibration.

  The mist ejection technique is a technique for ejecting a liquid in a mist form by introducing ultrasonic waves generated from a vibrator such as a piezoelectric vibrator into a liquid and focusing the acoustic energy of the ultrasonic waves. As a mist jet type recording head using such a mist discharge technique, for example, there is one disclosed in Patent Document 1 below.

  In the mist jet recording head described in Patent Document 1, a nozzle plate having a continuous through-hole along the longitudinal direction of the vibration reflector is provided on the ink chamber front aperture side of the vibration reflector, and the bottom surface of the ink chamber of the vibration reflector is provided. A vibrator is provided on the side. The vibration wave from this vibrator is reflected by the side wall surface of the vibration wave reflector and focused on the through hole of the nozzle plate. By focusing the vibration wave in this way, the energy density of the vibration wave emitted into the ink is increased, and mist-like ink is ejected from the through hole.

JP 2001-353889 A Masayoshi Tateno and two others, “Method of calculating droplet shape using droplet geometry conditions by image measurement”, Surface Science, 2001, Vol. 22, no. 6, p. 388-396

  In the mist jet type recording head, as one countermeasure for increasing the mist discharge amount, it is conceivable to increase the pressure of the ink in the ink chamber. However, when the pressure of the ink is increased, the contact angle between the meniscus (the convex surface shape of the droplet) and the surface of the mist discharge part of the nozzle exceeds the limit, and the mist discharge part of the nozzle holds the meniscus. There is a problem that the ink cannot be discharged, and the ink overflows on the nozzle surface, making it impossible to discharge the ink.

  The present invention has been made in view of the above, and an object of the present invention is to obtain a mist jet type recording head capable of stably increasing a mist discharge amount.

In order to solve the above-described problems and achieve the object, a mist jet type recording head according to the present invention includes a pair of vertically long linear members arranged close to each other in parallel, and the sides of the members facing each other. The wall surface is formed in a concave shape, and a vibration wave reflector in which a liquid chamber having a cross-sectionally narrowed shape is formed between the side wall surfaces, and the vibration wave reflector is disposed on the surface of the liquid crystal chamber on the front-drawing side. A nozzle plate having a through hole continuous in the longitudinal direction of the pair of vertically long linear members along the longitudinal direction of the member, and provided on a surface of the vibration wave reflector on the side opposite to the front aperture side. A vibrator for discharging a mist-like liquid from the through hole of the nozzle plate by applying a vibration wave to the liquid filled in the liquid chamber, and in a direction of discharging the liquid from the through hole plane as the nozzle play orthogonal And wherein the angle between the outer surface of an acute angle.

  According to the present invention, it is possible to stably increase the mist discharge amount.

FIG. 1 is a schematic perspective view of a mist jet recording head according to Embodiment 1 of the present invention. FIG. 2 is a schematic cross-sectional view showing a cross section orthogonal to the longitudinal direction of the vertically long linear member of the mist jet recording head according to the first embodiment of the present invention. FIG. 3 is a schematic cross-sectional view of a mist jet recording head as a comparative example of Embodiment 1 of the present invention. FIG. 4 is an enlarged schematic diagram of a comparative example of Embodiment 1 of the present invention. FIG. 5 is an enlarged schematic diagram of the mist jet recording head according to the first embodiment of the present invention. FIG. 6 is a graph showing the relationship between the major axis ellipse radius of the spheroid and the droplet volume. FIG. 7 is a schematic cross-sectional view of a mist jet recording head according to the second embodiment of the present invention. FIG. 8 is a schematic cross-sectional view of a mist jet recording head according to the third embodiment of the present invention.

  Hereinafter, a mist jet recording head according to an embodiment of the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment 1 FIG.
FIG. 1 is a schematic perspective view of a mist jet type recording head according to Embodiment 1 of the present invention. As shown in FIG. 1, a mist jet recording head 1 includes a vibration wave reflector 5 including a pair of vertically long linear members 2 arranged close to each other in parallel, and an upper surface of the vibration wave reflector 5 in FIG. A piezoelectric vibrator 11 joined via an insulating material 9 and a nozzle plate 8 joined to the lower surface of the vibration wave reflector 5 in FIG. 1 are configured.

  In the cross section orthogonal to the longitudinal direction of the pair of vertically long linear members 2 constituting the vibration wave reflector 5, the side wall surfaces 2 a facing each other of the vertically long linear members 2 are concave (preferably parabolic). 1), and has a tapered shape toward the lower side in FIG. 1 between the side wall surfaces 2a. The liquid (here, ink) is filled in the liquid chamber 3 formed by the side wall surface 2 a of the vibration wave reflector 5 and the insulating material 9.

  FIG. 2 is a schematic cross-sectional view showing a cross section of the mist jet recording head 1 perpendicular to the longitudinal direction of the vertically long linear member 2. The upper surface of the vertically long linear member 2 in FIG. 2 is formed horizontally in the left-right direction in FIG. 2, a substantially flat insulating material 9 is disposed on the surface, and piezoelectric vibration is further provided on the insulating material 9. A child 11 is arranged.

  When a high-frequency voltage corresponding to the recording target data is applied to the piezoelectric vibrator 11, ultrasonic waves are emitted from the piezoelectric vibrator 11 in the downward direction in FIG. This ultrasonic wave is reflected by the side wall surface 2a and focused on the point P1. When the side wall surface 2a is formed in a paraboloid shape, the point P1 matches the focal point of the paraboloid.

  The lower surfaces in FIG. 2 of the pair of vertically long linear members 2 are formed so as to be inclined from the side portions in FIG. 2 toward the center portion in FIG. A letter-shaped nozzle plate 8 is arranged. As shown in FIGS. 1 and 2, near the center of the nozzle plate 8, a through hole 8 a is formed in the gap between the pair of vertically long linear members 2 along the longitudinal direction of the member. The through-hole 8a is formed so as to be located below the point P1 in FIG. 2, and mist is discharged from the through-hole 8a downward in FIG.

As shown in FIG. 2, an angle θ formed by a plane orthogonal to the mist discharge direction and the outer surface of the nozzle plate 8 (the lower surface in FIG. 2) is an acute angle (0 ° <θ <90 °). In consideration of the symmetry of the shape of the liquid droplet, the vicinity of the through hole 8a of the nozzle plate 8 is preferably symmetrical in FIG.

  FIG. 3 is a schematic cross-sectional view of a mist jet type recording head as a comparative example of the present embodiment. This comparative example includes a pair of vertically long linear members 22, a piezoelectric vibrator 31 disposed on an upper surface in FIG. 3 of the pair of vertically long linear members 22 via an insulating material 29, and a pair of vertically long linear members 22. The nozzle plate 28 is disposed on the lower surface in FIG. In this comparative example, the bottom surfaces in FIG. 3 of the pair of vertically long linear members 22 are arranged so as to be substantially orthogonal to the mist discharge direction. The nozzle plate 28 has a flat plate shape and is arranged so as to be substantially orthogonal to the mist discharge direction.

FIG. 4 is an enlarged schematic view of a comparative example, and a contact angle formed by an extension line of the outer surface (the lower surface in FIG. 4) of the nozzle plate 28 and a meniscus of the droplet 32 (the convex surface shape of the droplet 32). Is represented by θ ₁ .

FIG. 5 is an enlarged schematic diagram of the mist jet recording head according to the present embodiment. As shown in FIG. 5, in the mist jet type recording head according to the present embodiment, the contact angle formed by the extension line of the outer surface of the nozzle plate 8 (the lower surface in FIG. 5) and the meniscus of the droplet 12 is θ2. As shown, the outer surface of the nozzle plate 8 (the lower surface in FIG. 5) is horizontal in the left-right direction in FIG. 5 as in the comparative example (see FIG. 4) (the plane and the nozzle perpendicular to the mist discharge direction) The apparent contact angle when the angle θ formed with the outer surface of the plate 8 is 0 ° is represented by θ3.

  Non-Patent Document 1 describes that a droplet shape can approximate a spheroid under predetermined conditions.

  FIG. 6 is a graph showing the relationship between the major axis ellipse radius of the spheroid calculated by Table 2 of Non-Patent Document 1 and the volume of the droplet. FIG. 6 shows a case where the contact angle is 77.18 ° and a case where the contact angle is 101.93 °. As shown in FIG. 6, the larger the contact angle, the longer the ellipse radius of the long axis can be suppressed, and the volume of the droplet can be increased, and the meniscus can be held without overflowing the large droplet. Obviously it is possible. That is, it can be seen that the larger the contact angle, the higher the pressure of the liquid in the liquid chamber.

Referring to FIGS. 4 and 5 again, the relationship between the contact angle θ _{1 of the} comparative example shown in FIG. 4 and the contact angle θ ₃ of the present embodiment shown in FIG.
θ ₃ > θ ₁ (1)
It is. Therefore, the relationship between the volume of the droplet 32 in the comparative example shown in FIG. 4 and the droplet 12 in the present embodiment shown in FIG.
(Volume of droplet 12)> (Volume of droplet 32) (2)
It is.

In order to increase the amount of mist discharge, it is only necessary to increase the drive voltage, increase the wave number, increase the burst frequency, or increase the duty ratio (ratio of drive signal activation time to unit time). . However, when an ultrasonic wave is applied at a high duty ratio, the ink pressure reaches the limit pressure for holding the meniscus due to the radiation pressure even at a voltage lower than that at which mist starts to be ejected, and the ink overflows to the nozzle surface. In order to apply a high sound pressure to the meniscus, it is important to keep the meniscus behavior stable due to the radiation pressure associated therewith. As in this embodiment, to the angle theta formed by the outer surface of the plane and the nozzle plate 8 perpendicular to the discharge direction of the liquid at an acute angle (0 ° <θ <90 ° ) leads to a stable meniscus. Therefore, the meniscus can be held up to a larger droplet, and thus the meniscus can be effectively prevented from overflowing with a high ink pressure. As a result, the effect of increasing the mist discharge amount can be achieved.

Embodiment 2. FIG.
FIG. 7 is a schematic cross-sectional view of a mist jet recording head according to the second embodiment of the present invention. Differences with respect to the configuration of the first embodiment shown in FIG. 2 are as follows.

  In the mist jet recording head according to the second embodiment shown in FIG. 7, the bottom surfaces of the pair of vertically long linear members 2 in FIG. 7 are formed substantially horizontally in the left-right direction in FIG. In addition, the lower surface in FIG. 7 of a pair of vertically long linear member 2 does not necessarily need to be formed substantially horizontally. For example, it may be formed inclined as shown in FIG.

  A substantially flat nozzle plate 13 is disposed substantially horizontally in the left-right direction in FIG. 7 on the lower surface of the pair of vertically long linear members 2 in FIG. The nozzle plate 13 is not necessarily formed in a substantially flat plate shape. For example, as shown in FIG.

  Near the center of the nozzle plate 13, a through hole is formed in the gap between the pair of vertically long linear members 2 along the longitudinal direction of the member. The through hole is formed so as to be located below the point P1 in FIG. 7, and mist is discharged from the through hole in the lower direction in FIG.

As shown in FIG. 7, on the outer surface of the nozzle plate 13, a groove 13a is formed along the longitudinal direction of the through hole, and the through-hole side of the plane and the groove 13a perpendicular to the mist ejection direction The formed angle θ is an acute angle (0 ° <θ <90 °). In consideration of the symmetry of the droplet shape, it is preferable that the vicinity of the through hole of the nozzle plate 13 is symmetrical in FIG.

  In addition, about others, it is the same as that of the structure of Embodiment 1, or equivalent, attaches | subjects the same code | symbol and abbreviate | omits detailed description.

As described above, according to this embodiment, by forming along the groove 13a on the outer surface of the nozzle plate 13 in the longitudinal direction of the through hole, to achieve the same effect as in the first embodiment it can.

  Further, by adjusting the cutting angle of the groove 13a, it is possible to more easily and flexibly cope with the droplet size, mist discharge amount, etc. required as product specifications.

  If the bottom surfaces in FIG. 7 of the pair of vertically long linear members 2 are formed substantially horizontally, the members can be easily processed. Further, if the nozzle plate 13 is formed in a substantially flat plate shape, the nozzle plate 13 can be easily processed. Moreover, the assembly process of the pair of vertically long linear members 2 and the nozzle plate 13 is facilitated.

Embodiment 3 FIG.
FIG. 8 is a schematic cross-sectional view of a mist jet recording head according to the third embodiment of the present invention. Differences with respect to the configuration of the second embodiment shown in FIG. 7 are as follows.

In the mist jet recording head according to the third embodiment shown in FIG. 8, on the outer surface of the nozzle plate 14, projections 14a are formed along the longitudinal direction of the through hole, perpendicular to the mist ejection direction The angle θ formed by the flat surface and the surface on the through hole side of the protrusion 14a is an acute angle (0 ° <θ <90 °). The protruding portion 14a may be formed by attaching a protruding member to the nozzle plate 14, or may be formed by bending the nozzle plate 14 or the like. In consideration of the symmetry of the shape of the liquid droplets, the vicinity of the through hole of the nozzle plate 14 is preferably symmetric in FIG.

  In addition, about others, it is the same as that of the structure of Embodiment 1, 2, or equivalent, attaches | subjects the same code | symbol and abbreviate | omits detailed description.

As described above, according to this embodiment, by forming along the protruding portion 14a in the longitudinal direction of the through hole on the outer surface of the nozzle plate 14, achieving the same effect as Embodiments 1 and 2 can do.

  Further, by adjusting the protrusion angle of the protrusion 14a, it is possible to more easily and flexibly cope with the droplet size, mist discharge amount, and the like required as product specifications.

  In addition, if the lower surface in FIG. 8 of a pair of vertically long linear member 2 is formed substantially horizontal, the process of this member will become easy. Further, if the nozzle plate 14 is formed in a substantially flat plate shape, the nozzle plate 14 can be easily processed. Moreover, the assembly process of the pair of vertically long linear members 2 and the nozzle plate 14 is facilitated.

  As described above, the mist jet recording head according to the present invention is suitable for a mist jet recording head that discharges liquid in a mist form using ultrasonic vibration.

DESCRIPTION OF SYMBOLS 1 Mist jet type recording head 2, 22 Longitudinal linear member 2a Side wall surface 3 Liquid chamber 5 Vibration wave reflector 8, 13, 14, 28 Nozzle plate 8a Through-hole 9, 29 Insulating material 11, 31 Piezoelectric vibrator 12, 32 Droplet 13a Groove 14a Projection

Claims (4)

A pair of vertically long linear members arranged close to each other in parallel are formed, the side wall surfaces of the members facing each other are formed in a concave shape, and a liquid chamber having a tapered tip is formed between the side wall surfaces. Vibration wave reflector,
A nozzle plate that is disposed on a surface of the vibration wave reflector on the front diaphragm side of the liquid chamber, and has a through-hole that is continuous along the longitudinal direction of the member in the gap between the pair of vertically long linear members;
The oscillating wave reflector is provided on the surface of the liquid chamber on the side opposite to the front diaphragm side, and a mist-like liquid is removed from the through hole of the nozzle plate by applying a vibration wave to the liquid filled in the liquid chamber. A vibrator to be discharged;
With
Wherein a plane perpendicular to the discharge direction of the liquid from the through-hole, the mist jet recording head, wherein the angle between the outer surface of the nozzle plate is an acute angle. A pair of vertically long linear members arranged close to each other in parallel are formed, the side wall surfaces of the members facing each other are formed in a concave shape, and a liquid chamber having a tapered tip is formed between the side wall surfaces. Vibration wave reflector,
A nozzle plate that is disposed on a surface of the vibration wave reflector on the front diaphragm side of the liquid chamber, and has a through-hole that is continuous along the longitudinal direction of the member in the gap between the pair of vertically long linear members;
The oscillating wave reflector is provided on the surface of the liquid chamber on the side opposite to the front diaphragm side, and a mist-like liquid is removed from the through hole of the nozzle plate by applying a vibration wave to the liquid filled in the liquid chamber. A vibrator to be discharged;
With
Wherein the outer surface of the nozzle plate is formed with a groove along the longitudinal direction of the pair of longitudinal rectilinear member,
Wherein a plane perpendicular to the discharge direction of the liquid from the through-hole, features and to Rumi strike jet recording head that faces and the angle of the through-hole side of the groove is an acute angle. A pair of vertically long linear members arranged close to each other in parallel are formed, the side wall surfaces of the members facing each other are formed in a concave shape, and a liquid chamber having a tapered tip is formed between the side wall surfaces. Vibration wave reflector,
A nozzle plate that is disposed on a surface of the vibration wave reflector on the front diaphragm side of the liquid chamber, and has a through-hole that is continuous along the longitudinal direction of the member in the gap between the pair of vertically long linear members;
The oscillating wave reflector is provided on the surface of the liquid chamber on the side opposite to the front diaphragm side, and a mist-like liquid is removed from the through hole of the nozzle plate by applying a vibration wave to the liquid filled in the liquid chamber. A vibrator to be discharged;
With
In the portion where the through hole of the nozzle plate is formed, a protrusion protruding in the liquid discharge direction from the through hole is formed along the longitudinal direction of the pair of vertically long linear members,
Wherein a plane perpendicular to the discharge direction, wherein the features and to Rumi strike jet recording head that faces the angle between the protruding portions is an acute angle. The nozzle plate, mist jet recording head according to claim 2 or 3, characterized in that it is arranged in a plane substantially orthogonal previously Ki吐 out direction.

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