JP2687352B2 - Ink jet recording device - Google Patents

Description

The present invention relates to ink jet recording, and more particularly to an ink jet recording apparatus that drives a pressure generator in ink to eject the ink from a nozzle orifice for printing. . [Prior Art] Various systems have been announced and put into practical use for ink jet recording, and the above-mentioned printing mechanism is known from Japanese Patent Publication No. Sho 60-8953. According to this known example, since the ink is a non-conductor, it is generally limited to an oil-based ink containing an organic solvent as a main component. In the case of oil-based ink, it is possible to obtain good print quality by forming uniform dots if special paper is selected.
When printing on plain paper, there is a drawback that it is difficult to obtain good print quality because the ink droplets adhere to the paper and at the same time bleed in the peripheral direction, the ring is unclear and the print density is light. A hot-melt type ink jet recording apparatus is known as a means for obtaining good print quality on plain paper, but when solid ink is heated to cause a phase change from a solid phase to a liquid phase, When air bubbles are generated and remain in the flow path without disappearing, pressure is often absorbed by the air bubbles and is not propagated normally, which often causes defective ejection of ink. [Problems to be Solved by the Invention] An object of the present invention is to solve these problems,
An object of the present invention is to provide an ink jet recording apparatus that can obtain good print quality on any print paper without selecting the paper quality. Another object of the present invention is to provide an ink jet recording apparatus that is less likely to cause printing defects and can efficiently use ink without any problem. [Means for Solving the Problems] An ink jet recording apparatus of the present invention is a frame member having a substrate on which a plurality of nozzle orifices are formed and a heat insulating member that is joined to the substrate to form a single ink chamber. A plurality of pressure generators for ejecting ink from the nozzle orifices by applying an applied voltage arranged in the single ink chamber and facing the nozzle orifices; And heating means for changing to a phase state. [Operation] With the configuration described above, by disposing a plurality of pressure generators in one ink chamber, the heat conduction to the ink is uniform, so that the molten state of the hot melt ink can be changed by each pressure generator. You can make no difference between
No variation occurs in the ink droplets ejected from each nozzle orifice. Further, the ink inside the ink is agitated by the vibration of the pressure generator when the ink is discharged, so that a more uniform molten state can be maintained. Further, the heat capacity can be smaller than that of the recording apparatus of the multi-nozzle orifice type having the ink chambers individually partitioned. Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an embodiment showing the configuration of the print recording apparatus of the present invention. By the head 3 which is guided by the guide shaft 1 and the timing belt 2 to move in the width direction of the printing paper, the ink supply device 5 which supplies ink from the ink cartridge 4 to the head, and the paper feeding mechanism 6 which moves the printing paper 7. It is configured. FIG. 2 is a block diagram showing the outline of the head of the present invention,
A nozzle plate 9 having a large number of nozzle orifices 8, a piezoelectric element 10 and a metal plate 11 having a thickness of 20 to 50 μm which are joined to each other to form a piezoelectric vibrator having two members, and a ceramic member having a high heat insulating effect. It is composed of a frame 12 and a Posister (trademark Murata Manufacturing Co., Ltd.) 1313 which is a heating means. The metal plate also functions as a common electrode of the piezoelectric vibrator, and a metal conductor wire is grounded on the surface of each piezoelectric element and electrically connected to the outside. The nozzle plate and the metal plate are bonded via the spacer 14, but according to the experiment, the thickness of the spacer has a great influence on the ink supply time to the nozzle orifice and the pressure propagation from the piezoelectric vibrator to the nozzle orifice. I know, 20
It is desirable to set the thickness to 50 μm. FIG. 3 shows a sectional view of the head according to the present invention. The nozzle plate 9 has a nozzle orifice 8 formed in a cone shape or a funnel shape, and a piezoelectric element is arranged corresponding to the nozzle orifice. When an electric charge is applied to the posistor 13 mounted on the frame surface, the heat is generated, the entire head is heated, and the ink 15 which is in a solid state at room temperature is melted and changes into a liquid state. At this time, even if bubbles are generated from the ink, they move smoothly above the piezoelectric element and are taken into the air pocket 16 because of the simple structure that the pressure chambers are integrated. The ink used in this example is a non-conductive solid ink obtained by adjusting stearone, stearic acid amide, and a dye, and has a melting point of 100 ° C. and a viscosity of 3.5 mPas at 120 ° C.
・ S, surface tension is 30dyn / cm. When the ink temperature is kept constant at 120 ° C and a voltage is applied to the piezoelectric element,
When the piezoelectric element contracts in the length direction and forms a bimetal structure with the metal plate, the displacement is changed in the thickness direction as shown in FIG. 3 (b). Due to this displacement, pressure propagates to the ink that fills the space between the piezoelectric vibrator and the nozzle plate, ink droplets are formed from the nozzle orifice, and ejected to the outside. When the ink droplets reach the recording paper, they immediately undergo a phase change and adhere in a solid state, so that they do not cause print stains and are excellent in quick drying. The piezoelectric strain constant is one of the parameters indicating the characteristics of the piezoelectric element and is represented by the following equation. Where k: electromechanical coupling coefficient ε ^T : permittivity Y: Young's modulus In general, the permittivity ε ^T increases as the temperature rises and reaches its maximum at the Curie point, but the electromechanical coupling coefficient K depends on the temperature of the piezoelectric element. The characteristics are different. Since the piezoelectric strain constant d changes according to the above equation, as shown in FIG. 4, there are various types of material a in which the piezoelectric strain constant increases as the temperature rises, and the material b decreases. The Curie point is 300 ° C. or higher because the piezoelectric element used here exhibits the characteristic of the material a and the practical use temperature limit of the piezoelectric element is about 1/2 of the Curie point. Therefore, when the ink is held at a high temperature, the piezoelectric vibrator arranged in the ink is also exposed to the high temperature, the piezoelectric strain constant increases, and a larger displacement can be obtained. Also, a piezoelectric element having a linear expansion coefficient of 1.0 × 10 ⁻⁶ or more and 3.0 × 10 ⁻⁶ or less,
When a piezoelectric vibrator formed by joining with a metal plate that is 1.0 × 10 ^-6 or more and 2.0 × 10 ^-6 or less is changed in temperature from normal temperature to high temperature, a linear expansion coefficient of Deforms to the large metal plate side. However, here, nickel was used as the material of the metal plate. It is advantageous to increase the displacement amount of the piezoelectric vibrator because it is constantly changed and held in a shape curved in one direction. FIG. 5 shows another embodiment of the present invention. In this embodiment, the structure of the vibrator portion is different from that of the bimorph structure shown in FIG. 3, and the piezoelectric elements are arranged at both ends of the metal plate to expand and contract the both ends, so that the central portion of the metal plate is vertically displaced. To generate a pressure for ejecting ink droplets. During standby, the metal plate is curved upward (Fig. 5 (a)), and when an electric charge is applied, the piezoelectric element contracts and the metal plate becomes straight (Fig. 5 (b)). Are discharged from the nozzle orifice. Furthermore, another embodiment is shown in FIG. Unlike the above-mentioned embodiment, a magnet 21 is used as a drive source of the pressure generator instead of the piezoelectric element. A magnet is joined to a part of the vibrator placed in the ink, and it is excited when electric charge is applied to the electromagnet 22 attached to the ink chamber wall, and when the polarities are the same, a repulsive force is generated in the vibrator, causing vibration. By displacing the child downward, ink droplets can be ejected from the nozzle orifice. FIG. 7 is an embodiment showing the outline of the ink supply unit of the ink jet recording apparatus according to the present invention. The ink 23 is solid at room temperature, is contained in the ink cartridge 4 in the form of particles, and is supplied to the head by an ink supply device having a spiral pushing mechanism. The ink is pressurized in the cartridge by the spring 25 and drops into the cylinder 26, which is a heater provided on the outer wall of the cylinder.
Heated by 27. When the small motor 28 is driven, the screw 29 is rotated and the ink is pushed out to the nozzle 24. When the screw rotates, the ink in the clearance between the cylinder and the cylinder generates frictional heat due to shear stress and is melted. By utilizing this action, the minimum required amount of ink can be continuously and efficiently supplied. Although the ink supply port of the head is always closed, it is opened when ink is replenished and is supplied in a liquid state by the above-mentioned ink supply device. Further, a filter is provided at the ink supply port to prevent foreign matter such as dust from entering. [Advantages of the Invention] As described above, according to the inkjet recording apparatus of the present invention, a substrate on which a plurality of nozzle orifices are formed,
A frame member having a heat insulating property that is joined to the substrate to form a single ink chamber, and from the nozzle orifice by applying an applied voltage that is arranged in the single ink chamber and facing the nozzle orifice. Since a plurality of pressure generators for ejecting the ink and a heating means for changing the ink in the solid state at room temperature to the liquid state are provided, the heat conduction to the ink is uniform and the hot melt There can be no difference in the melted state of the ink between the pressure generators, and there is no variation in the ink droplets ejected from each nozzle orifice. Further, the ink inside the ink is agitated by the vibration of the pressure generator when the ink is discharged, so that a more uniform molten state can be maintained. Further, the heat capacity can be smaller than that of the recording apparatus of the multi-nozzle orifice type having the ink chambers individually partitioned. Furthermore, it is also a configuration in which printing defects due to bubbles are unlikely to occur. Furthermore, in the case of a piezoelectric vibrator in which the pressure generator is formed by joining a metal plate and a piezoelectric element, it is possible to obtain an effect that the piezoelectric efficiency can be increased and the applied voltage can be reduced by raising the temperature of the piezoelectric element itself. As a result, the total energy consumption can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram of an inkjet recording apparatus of the present invention, FIG. 2 is a configuration diagram of an inkjet head which is an embodiment of the present invention, and FIG. b) is a sectional view of the head when a voltage is applied, FIG. 4 is a temperature characteristic diagram of the piezoelectric strain constant, and FIG. 5 is another embodiment.
6B is a sectional view of the head when a voltage is applied, FIG. 6 is a sectional view of the head of another embodiment, and FIG. 7 is a sectional view of the ink supply device of the embodiment of the present invention. 3 ... Recording head 4 ... Ink cartridge 5 ... Ink supply device, 6 ... Paper feeding mechanism 7 ... Printing paper 8 ... Nozzle orifice 9 ... Nozzle plate, 10 ... Piezoelectric element 11 ... Metal plate, 12 …… frame 13 …… positor, 14 …… spacer 15 …… ink, 16 …… air reservoir 17,18 …… driving circuit, 19 …… ink drop 20 …… filter, 21 …… magnet 22 …… electromagnet, 23 …… Ink particles 25 …… Spring, 27 …… Heater 28 …… Motor, 29 …… Screw

Claims (1)

(57) [Claims] A substrate on which a plurality of nozzle orifices are formed, a frame member having heat insulation properties that is joined to the substrates to form a single ink chamber, and arranged in the single ink chamber and facing the nozzle orifice An ink jet recording apparatus comprising: a plurality of pressure generators for ejecting ink from a nozzle orifice by applying the applied voltage; and heating means for changing the ink in a solid phase state at room temperature to a liquid phase state.