JPH03239561A - Ink jet printer - Google Patents

Abstract

PURPOSE:To melt a solid ink into liquid ink irreducible minimum for supply and prevent the ink deterioration by providing a structure comprising a finely divided solid ink, an ink container having the wall surface low in heat conductivity, a heating means, an ink supply passage and an ink jet delivering part having a plurality of nozzles positioned above the liquid ink. CONSTITUTION:When a heater 8 is energized to heat a head frame 6, a solid ink 1 near a bottom part is melted into a liquid ink 2, which is then sent by capillary action from small holes in the bottom of an ink container 3 through an ink supply passage 7 into an ink jet delivering part A so as to be filled therein. On the other hand, the temperature of the ink container 3 changes gradually from the bottom thereof and approaches the ambient temperature at the top thereof. According to such temperature gradient, the ink in the ink container 3 changes gradually from the liquid ink 2 of a low viscosity at the bottom thereof through the liquid ink 2a of a higher viscosity into a solid ink at the top thereof. During this time, the liquid ink 2a of higher viscosity is adhered to the inner wall of the ink container 3 to serve as a damper, so that the ink 2 of lower viscosity will not be subjected to the pressure of the solid ink 1 under the weight thereof.

Description

Detailed Description of the Invention [Industrial Application Field 1] The present invention is directed to ink that is solid at room temperature (hot melt ink).
The present invention relates to an ink supply system for an inkjet printer that melts ink and causes ink droplets to fly in a liquid state to form an ink image on a medium such as recording paper.

[Prior Art 1] In general, an inkjet recording device using hot melt ink has the advantage of being highly compatible with paper types and being free from clogging due to ink evaporation during rest periods. Ink supply systems used in this type of device include those that supply block-shaped ink that is not mounted on the carriage to a head on the carriage in fixed amounts (described in U.S. Pat. No. 4,636,803); One in which a rod-shaped ink is advanced and supplied to the head and melted (described in U.S. Pat. No. 4,682,185), and another in which a cartridge containing solid ink is attached to the head and is melted by a heater in the head (U.S. Pat. No. 4,631,557).
(described in the publication) etc.

[Problems to be Solved by the Invention] The conventional ink supply system described above includes a mechanism for advancing solid ink, an ink reservoir for liquefying and storing the solid ink, and a detection means for determining the amount of ink in the ink reservoir. This method requires a large heater to keep the ink in the ink reservoir in a liquid state, resulting in a problem that the device becomes complicated and large. Furthermore, both methods have the problem that because a large amount of ink is contained in the head or ink reservoir in a liquid state, the ink is exposed to high temperatures for a long time, leading to deterioration of the ink. .

An object of the present invention is to solve the above problems and provide an inkjet printer equipped with a simple ink supply system.

[Means for Solving the Problems 1] The inkjet printer of the present invention is an inkjet printer that heats and liquefies ink that is solid at room temperature and makes it fly. an ink container having a wall surface with a low ratio, an ink discharge section that discharges ink from a plurality of nozzles, a heating means, and an ink supply section that supplies liquefied ink to the ink discharge section; The bottom nozzle is
It is characterized in that it is located above the liquefied ink in the ink container.

[Operation 1] According to the above structure of the present invention, a temperature gradient is generated inside the ink container, and only the ink near the heating means is liquefied and supplied, and the ink away from the heating means is kept in a solid state. By making the lowest nozzle higher than the liquefied ink in the ink container, ink overflow can be prevented.

1 Example 1 Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a sectional view of an inkjet printer showing an embodiment of the present invention. In the figure, an ink container 3 made of heat-resistant resin is filled with solid ink 1 in the form of fine particles. The ink container 3 has its bottom surface in close contact with the head frame 6. 4 is a cap with a small hole, and 5 is a packing. The head frame 6 made of aluminum alloy, which is a good thermal conductor, houses a heater 8 therein, which heats the bottom surface of the ink container 3 and also heats the ink supply path 7 and the ink discharge section A, thereby discharging the melted liquid ink 2. (The shaded area in the figure) is kept in a liquid state until it is discharged. B, indicated by a two-dot chain line - in the figure, is the boundary between the solid ink 1 and the liquid ink 2. 9 is a heater cable connected to the board 26; Reference numeral 11 denotes a carriage on which the head frame 6 is mounted via a heat insulating plate 14. 12 is a belt that moves the carriage 11 along the guide shaft 13. The recording paper 31 is fed through a paper guide 34, and is fed through a paper feed roller 32 and a paper press roller 33.
It is held in the middle and transported in the direction of arrow (A) in the figure.

FIG. 2 shows in detail the configuration of the ink discharge section A, in which a plurality of cantilever-shaped vibrators 23 made of electrostrictive elements are joined to a base 43 made of a ceramic member. An electrode pattern 44 for electrically connecting the vibrator 23 and the head cable 24 is provided on the upper surface of the base 43 which is an insulating material. The head cable 24 is connected to a connector 25 on a board 26 shown in FIG. 1, and is connected to a control circuit by a carriage cable 27. Each vibrator 23
The nozzle plate 21 has a plurality of nozzles 22 corresponding to
The spacer 41 maintains a constant gap with the vibrator 23 and the sealing material 42 is sandwiched between the vibrator 23 and the vibrator 23 . 22a is
This is the lowest nozzle among the nozzles 22.

FIG. 3 is a perspective view of the inkjet printer of the present invention. In the figure, 16 is a carriage motor that reciprocates the carriage 11 along the guide shaft 13 via the belt 12, 15 is a pulley, and 35 is a reduction gear 36 fixed to one end of the paper feed roller 32. It is a paper feed motor.

Next, the operation will be explained. In FIG. 1, heater 8
Electric power is supplied to heat the head frame 6. As a result, the bottom of the ink container 3 in contact with the head frame 6 receives heat, and the solid ink 1 near the bottom quickly melts and becomes liquid ink 2. The liquid ink 2 fills the inside of the ink discharge part A from the small hole in the bottom of the ink container 3 via the ink supply path 7 due to capillary force. On the other hand, in the ink container 3, the higher the position is from the bottom, the lower the thermal conductivity of the resin forming the ink container 3, the thermal insulation of the air layer existing between the fine particles of the solid ink 1, and the heat radiation. Close to outside temperature. According to this temperature gradient, the ink inside the ink container 3 is gradually distributed from the bottom to the liquid ink 2 with lower viscosity.
, the state changes to high viscosity liquid ink 2a and solid ink 1. At this time, the high viscosity liquid ink 2a comes into close contact with the wall surface of the ink container 3, and acts as a damper so that the weight of the solid ink 1 does not apply pressure to the low viscosity ink 2.

Since the lowermost nozzle 22a shown in FIG. 2 is located above the boundary B between the liquid ink 2 and the solid ink 1 formed as described above, the meniscus of all the nozzles 22 becomes a negative pressure, and the liquid ink 2 It doesn't overflow.

After the liquid ink 2 is filled into the ink discharge part A, when an electric field is applied to the vibrator 23 through the wiring 24, the vibrator 23
The tip is displaced in a direction away from the nozzle plate 21.

Next, when this electric field is released, the liquid ink 2 is ejected from the nozzles 22 of the nozzle plate 21 due to the pressure generated by the elastic restoring force of the vibrator 23. Repeat this operation for each nozzle.
Repeat according to the recording signal. By performing this ink ejection operation in synchronization with the scanning of the carriage 11 using the carriage motor 16 as the power source and the conveyance of the recording paper 31 using the paper feed motor 35 as the power source, as shown in FIG. Records are obtained.

As the recording progresses, as the liquid ink 2 in the ink container 3 is consumed, the solid ink 1 becomes a highly viscous liquid ink 2a.
Then, the liquid ink 2a with high viscosity sequentially undergoes a phase change to the liquid ink 2 with low viscosity, and ink is supplied. However, since the boundary B between the solid ink 1 and the liquid ink 2 always moves up and down between the bottom surface of the ink volume M3 and the lowest nozzle 22a,
There will be no excess or shortage of supply. Eventually, when the ink in the ink container 3 becomes empty, the solid ink 1 can be added or the ink container 3 can be replaced with a new one.

In this embodiment, the bottom surface of the ink container 3 is made of the same material as the wall surface, but in order to increase the melting speed of the ink depending on the type of ink and the increase in the number of nozzles in the ink ejection part A,
The bottom surface may be formed of a good thermal conductor.

[Advantageous Effects of the Invention 1] As described above, the components include finely divided solid ink, an ink container having a wall surface with low thermal conductivity, a heating means, an ink supply path, and a plurality of units located above the liquefied ink. The present invention, which is comprised of an ink discharge unit equipped with a nozzle, melts and liquefies only the minimum amount of ink required from within an ink container without requiring a complicated mechanism that uses power to move solid ink. Since the ink is supplied at high temperatures, it requires only a small amount of electricity, and also prevents the ink from deteriorating due to long-term exposure to high temperatures.

[Brief explanation of drawings]

FIG. 1 is a sectional view of an inkjet printer showing an embodiment of the present invention. FIG. 2 is a partially detailed perspective view of the same inkjet printer as above. FIG. 3 is a perspective view of the same inkjet printer as above. Solid ink Liquid ink Ink container Head frame Ink supply path Ink discharge section a: Above the lowest nozzle

Claims (2)

[Claims] (1) In an inkjet printer that heats and liquefies ink that is solid at room temperature and jets it, it includes finely divided solid ink, an ink container with a wall surface with low thermal conductivity that stores the solid ink, and a plurality of nozzles. An inkjet printer comprising: an ink ejecting section that ejects ink from the ink jetting section; a heating means; and an ink supply section that supplies liquefied ink to the ink ejecting section. (2) The inkjet printer according to item 1, wherein the lowest nozzle of the ink discharge section is located above the liquefied ink in the ink container.