JP2658161B2 - Ink jet recording device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an ink jet recording apparatus, and more particularly, to an ink jet recording apparatus using hot melt ink.

(Prior Art) An ink jet recording apparatus in which a nozzle plate having a plurality of nozzle openings and a piezoelectric converter behind the nozzle plate for directly contacting the ink and pressurizing the ink are disclosed in Japanese Patent Publication No. 60-8953. I have. In this recording apparatus, since the vibrator constituting the piezoelectric transducer vibrates in a direction substantially perpendicular to the nozzle plate and the ink flow path between the nozzles is short, the ejection efficiency and safety of ink droplets are high, and Even if gas or dust is mixed in the ink, it operates normally without being affected,
Furthermore, as a cantilever-type vibrator, there is an advantage that the rigidity is small, the electromechanical conversion efficiency is high, and the movable part displacement required for the vibrator can be obtained with a small amount of power.
However, on the other hand, in this type of device, since it is necessary to deposit the piezoelectric transducer in the ink, a non-conductive ink, for example, an oil-based ink containing an organic solvent as a main component must be used as the ink. For this reason, when printing on rough paper or the like using this kind of ink, if ink droplets adhere to the recording paper, they will ooze out to the surroundings, and the outline will be unclear and the density will be low, and the printing quality will be reduced. Have a problem.

Of course, for such a problem, for example,
By using an ink jet recording apparatus as disclosed in -98547, the printing quality can be maintained at a high level because the ink used is a hot melt type,
On the other hand, this type of ink always generates bubbles when it undergoes a phase change from a solid phase to a liquid phase, and as a result of this being mixed into the ink, even if the ink is pressurized by a piezoelectric converter, the bubbles generate this pressure. There is a problem that the ink cannot be discharged normally due to absorption.

(Problems to be Solved by the Invention) The present invention has been made in view of such a problem, and an object of the present invention is to enable accurate ejection of a hot-melt type ink, thereby providing advantages of this type of ink. Another object of the present invention is to provide a new ink jet recording apparatus capable of sufficiently exhibiting a high printing function.

(Means for Solving the Problems) That is, the present invention provides, as an ink jet recording apparatus for achieving the above object, a housing made of a heat conductive material provided with a heat source and opposed to a recording medium. A plate-shaped member having a plurality of nozzle openings disposed in the housing, a piezoelectric conversion means disposed on a base rear surface of the plurality of vibrators via an interval regulating member, and the plate-shaped member and the piezoelectric conversion means. A hot melt ink is provided by a gap regulating member provided so as to form a gap that allows ink to be pumped up by a capillary action, and having a passage for supplying ink from the ink reservoir to the gap. The ink is ejected accurately and effectively to exhibit a high printing function which is an advantage of this type of ink.

(Embodiment) Therefore, an embodiment illustrated below will be described.

FIG. 1 shows a cross section of an ink jet head, and the ink jet head 1 is mounted on a carriage (not shown) that runs in the axial direction of a platen 2.

Reference numeral 3 denotes a casing of the ink jet head 1 formed of a metal material having a good thermal conductivity in a container shape. A heating element 4 is attached to a lower surface of the casing 1, and a surface 5 on the pteran 2 side has a platen axis direction. A required number of ink droplet ejection holes 6 # are arranged in a row, and a nozzle plate 8 having a plurality of nozzles 7 # arranged in a position corresponding to the ink droplet ejection holes 6 inside the surface 5 is provided. They are integrally attached via a spacer 9.

Reference numeral 10 denotes a piezoelectric transducer mounted on the back surface of the nozzle plate 8 via a spacer 17. As shown in FIG. 2, the piezoelectric transducer 10 has a common electrode 1 on one surface of a piezoelectric element 11 made of PZT.
2 is formed by depositing a pattern electrode 13 on the other surface, and a plurality of vibrators 15 に are formed on one side of the support base 16 by making cuts 14 間隔 from one side thereof at intervals equal to the pitch of the nozzle 7. ‥ is configured as a comb-shaped protrusion. And the piezoelectric transducer configured in this way
10, each tip of each vibrator 15 ‥‥ is a nozzle 7 ‥‥
Is mounted on the back surface of the nozzle plate 8 with a minute interval corresponding to the thickness of the spacer 17 with the support base 16 facing upward, and the lead wires 18
When a voltage is selectively applied through the nozzle, the corresponding vibrator 15 vibrates in a direction perpendicular to the surface of the nozzle plate 8, and presses ink interposed between the nozzle plate 8 and the vibrator 15. This is configured to be discharged from the nozzle 7 onto the platen 2 toward the recording paper s.

On the other hand, behind the piezoelectric transducer 10, a reservoir tank 20
A regulating plate 22 for regulating the gap D between the ink chambers 21 is provided between the nozzle plate 8 and the regulating plate 22 by a projection 23 for supporting the nozzle plate 8 from behind. The ink chambers 21 having the interval D are formed. This gap D is provided in this apparatus in which the ink level L is always located below the axis of the nozzle 7 as will be described later, and the ink in the ink chamber 21 is always moved along the axis of the nozzle 7 by capillary action. At the same time, the gap must be small enough to suppress fluctuations in the ink surface during the movement of the carriage, and on the other hand, bubbles generated from the melted and liquefied ink must be removed. In addition to being able to escape, the ink must be free from ink shortage due to continuous ink ejection, and must have a gap enough to respond to ink ejection at a high frequency. Therefore, the restricting plate 22 is positioned by the above-described protrusion 23 so that a gap D satisfying the above condition is formed between the restricting plate 22 and the nozzle plate 8.

By the way, the casing 3 described above is provided with a cover 31 that covers the reservoir tank 20 at a position lower than the axis of the nozzle 7 so that the liquid level L of the liquefied ink is always lower than the axis of the nozzle 7. Be managed.
Although not shown, the reservoir tank 20 is provided with a lower limit liquid level detection sensor, and when the ink level reaches the lower limit and is detected by this sensor, the nozzle is removed from the solid ink storage tank (not shown). An ink mass having a volume that does not exceed 7 axes is
It is configured to be supplied into.

In the drawing, reference numeral 24 indicates an ink flow path connecting the reservoir tank 20 and the ink chamber 21, and 25 indicates the flow path 24.
Shows a filter stretched at the entrance of the device.

In the printing apparatus thus configured, when the heating element 4 on the lower surface of the casing 3 is energized to perform a printing operation, the entire casing 3 made of a heat conductive material is heated equally, and first the narrow gap of the ink chamber 21 is formed. The coagulated ink is melted while being sealed in D to make it ready for printing.

Therefore, when the pattern electrode 13 is selectively energized in this state in accordance with the recorded information, the piezoelectric transducer 10 mounted so that most of the piezoelectric transducer 10 is exposed above the ink with the support base 16 facing upward has a comb-like shape. The corresponding vibrator 15 among the plurality of vibrators 15 is efficiently and stably vibrated toward the nozzle plate 8, and the ink pumped by the capillary action between the nozzle plate 8 and the regulating plate 22. Is efficiently ejected as an ink droplet from a nozzle 7 opened immediately before the ink and adheres to the recording paper s on the platen 2.

On the other hand, the ink in the solid phase in the reservoir tank 20 is quickly melted from below by the heat generating element 4 on the lower surface of the casing 3, and eventually liquefies and transmits heat to each part by its convection effect, The ink is supplied to the ink chamber 21 sequentially without entering the flow passage 24 of the metal casing 3 that has been uniformly heated.

In this way, the specified printing operation is completed, and finally the power is turned off.
When turned off, the ink chamber 21
The small amount of ink inside quickly solidifies due to its small heat capacity and fixes the vibrator 15, and then enters a rest state while preventing deformation of the vibrator 15 from the contraction force of the other solidified ink by ink .

(Effects) As described above, according to the present invention, a plate member having a plurality of nozzles is provided in a casing made of a heat conductive material provided with a heat source, and the piezoelectric conversion means is disposed on the back surface thereof via a spacer. The ink that has been melted and liquefied is pressurized and ejected from the nozzle opening, so that when a heat source is energized, a small amount of ink remaining between the plate-shaped member and the piezoelectric conversion means can be quickly liquefied and printed in a short time. In addition to the state, at the end of printing, by solidifying the ink in this part quickly and fixing the piezoelectric conversion means, it is possible to prevent the piezoelectric conversion means from being deformed by the condensing force of the other parts, Further, the ink ejection path is made as short and accurate as possible so that the ink pumped up by the capillary action is effectively and stably ejected as ink droplets, and hot ink is discharged. A clear image can be formed on a recording medium while utilizing the characteristics of the melt-type ink.

[Brief description of the drawings]

FIG. 1 is a side view of an apparatus showing one embodiment of the present invention, and FIG. 2 is a perspective view of a piezoelectric transducer. DESCRIPTION OF SYMBOLS 1 ... Ink jet head 2 ... Platen 3 ... Casing 4 ... Heating element, 7 ... Nozzle 8 ... Nozzle plate, 9 ... Spacer 10 ... Piezoelectric transducer, 15 ... Vibrator 16 ... Support Substrate, 17 Spacer 18 Lead wire 20 Reservoir tank 22 Gap regulating plate 24 Ink passage

 ────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-55-139268 (JP, A) JP-A-1-145156 (JP, A) JP-A-1-150550 (JP, A) JP-A-1- 108049 (JP, A) Full-scale sho 61-83925 (JP, U)

Claims (1)

(57) [Claims] 1. A housing made of a heat conductive material provided with a heat source and opposed to a recording medium, a plate-like member having a plurality of nozzle openings provided in the housing, and a plurality of vibrators. A piezoelectric conversion means provided on the rear surface of the base via a space regulating member, and a gap formed between the plate-like member and the piezoelectric conversion means so as to be able to pump ink by capillary action. And a gap regulating member provided with a passage for supplying the gap ink from the ink reservoir.