JPH0365348A - Ink jet head - Google Patents

Abstract

PURPOSE:To make compact an ink jet head by providing opening/closing means provided in an ink passage for coupling an ink vessel to an ink discharge port, and means for pressurizing ink by pressure gas, and forming the opening/closing means of a shutter member having an opening, and a shape memory alloy for driving the shutter member in response to a record signal. CONSTITUTION:After ink is filled in a whole ink passage to an ink discharge port 3, pressure ink is supplied to an ink passage 110 at the ink reservoir side from a shutter member 8. When image signals 6 are applied to both ends of a shape memory alloy member 7, the member 7 us heated, and when it reaches to a martensite transition point, it tends to return to its original shape, thereby pulling up the member 8. In this case, when a pinhole 10 provided at the member 8 reaches the passage 110, the pressure ink is discharged from the port 3. Then, after the signal is applied, the member 7 is cooled by the member 7, and when it is cooled to a martensite transition point or lower, the member 8 is returned by the recoiling force of an elastic member 9 to close the pinhole 10. Since, many nozzles each having simple structure are arranged in high density the structure is simplified and made compact.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an on-demand inkjet head that prints characters or figures on a recording medium by ejecting ink droplets in response to an image signal.

2. Description of the Related Art It is well known that a piezo element is used as one of pressure generating means for ejecting ink in a geo-on-demand ink jet head.

For example, a representative example is 'Mochiko Sho 53-12138.
Hereinafter, a conventional inkjet head using a piezoelectric element will be described with reference to FIG.

In FIGS. 5(a) and 5(b), reference numeral 2 denotes a strain chamber, which has an ink discharge port 3 on one side and an ink supply port 1 on the other side. A part of the wall surface of the pressure chamber 2 is made up of a piezoelectric plate 4 and a metal plate 5 pasted together.

1. When the image signal 6 is applied between the piezoelectric plate 4 and the metal plate 5 with the strain force chamber 2 filled with ink, the piezoelectric plate 4 and the metal plate 5 move into the pressure chamber 2 as shown in FIG. It warps to the side, causing a sudden change in volume, and the pressure generated at that time causes ink to be ejected from the ink ejection port 3.

Next, when an image signal 6 in a direction opposite to that at the time of ejection is applied between the piezoelectric plate 4 and the metal plate 5, the piezoelectric plate 4
The metal plate 5 is warped in the opposite direction, and the pressure inside the pressure chamber 2 is rapidly reduced, so that ink is forcibly supplied into the pressure chamber 2 from the ink supply path 1. In order to prevent air from being sucked into the pressure chamber 2 from the ink ejection port 3 during the operation shown in FIG. It is.

Note that even if the operation of applying the image signal in the opposite direction is omitted, the piezoelectric plate 4 and the metal plate 5 return to their original positions due to their inherent elasticity after the operation shown in FIG. For this reason, the same figure (1
The same effect as )) is performed, although there are differences in degree.

Problems to be Solved by the Invention However, in the above configuration, the amount of displacement of the piezoelectric element is extremely small, so in order to eject ink stably, the area of the piezoelectric plate must be at least 2 angles or 2 angles. Although the structure is simple, it is difficult to produce a multi-nozzle head with a nozzle density of 4 or more nozzles per head.

In addition, in order to drive the piezoelectric element, at least 100
A signal voltage of around V is required, which imposes a large cost burden on the drive circuit.

The present invention solves the above-mentioned problems, and provides an inkjet head that has a simple structure, has a large number of nozzles arranged at high density, is compact, and can be driven at a low voltage.

Means for Solving the Problems The present invention includes an opening/closing means provided in an ink flow path connecting an ink container containing ink and an ink discharge port, and a means for pressurizing the ink with pressurized gas. It consists of a shutter member having an opening and a shape memory alloy member that drives the shutter member in accordance with a recording signal.

Effect of the present invention With the above configuration, an image signal is applied to the shape memory alloy member to generate heat, thereby returning the shape to the shape before plastic working.

This shape memory alloy member is connected to an elastic member via a shutter member having a pinhole penetrating in the same direction as the ink flow path, and the shape memory alloy member attempts to return to its pre-processing shape (even if it was bent). (becomes straight), the pinhole provided in the roller member communicates with the ink flow path, and the pressurized ink passes through the pinhole and is ejected as ink droplets from the ink ejection port.

Next, when the shape memory alloy member drops below the martensitic transformation point due to heat radiation after the signal application is finished, the elastic member that was pulled through the shutter member returns to its original position by self-restoring force, and the shutter member also returns to its original position. In order to return to the position, the pinhole is removed from the ink flow path, and as the shutter member moves, it is closed by the cylindrical wall surface. In this series of operations, the ejection and stopping of ink droplets are controlled, and the head functions as an inkjet head.

EXAMPLES Hereinafter, examples of the present invention will be described in detail with reference to the drawings.

FIG. 2 is a conceptual diagram showing the overall configuration of an inkjet unit according to an embodiment of the present invention.

In FIG. 2, the inkjet unit 100 is composed of an ink reservoir section 101 and a bottom section 102. 105 is connected via a gas supply pipe 106.

As for the gas cylinder 103 used here, it is preferable to use a small cylinder filled with liquefied carbon dioxide gas in terms of safety, gas capacity, price, etc. A small cylinder of about 7 to 8 crn can be used. The gas cylinder 103 is detachable from the pressure regulator 104 and can be replaced.

High-pressure gas is kept at a constant pressure (2 to 3 hours/d) using a pressure regulator 104.
The ink in the ink reservoir 101 is pressurized through the on-off valve 105 and the gas supply pipe 106.

Note that the on-off valve 105 is opened and closed automatically or manually, and is in a closed state when the printer power is turned off.

Figure 1 shows the ink reservoir section 101 and head section 102 of Figure 2.
FIG. 3 is a cross-sectional view showing the detailed structure of

In FIG. 1, the ink container 107 has a gas supply pipe 10
6 is connected, and gas pressure P is applied to the ink 108. Then, the ink 108 reaches the ink discharge port 3 via the ink filter 109 and the ink channel 110, and the ink channel 110 is connected to the shape memory alloy member 7.
Due to the structure of the elastic member 9, and the round bar-shaped shutter member 8 that connects these two members 7 and 9, it can be opened and closed freely by the no-stain signal 6, and ink droplets are ejected and stopped.

FIG. 3 is an enlarged view of the head section in FIG. 2, and the ejection operation of ink droplets will be explained below with reference to the figures.

As shown in FIG.
A cylindrical hole about twice the size of the hole is made, and a shutter member 8 with a pinhole 10 of about the same diameter as the ink flow path 110 made at a predetermined position is inserted in the large direction of the hole, and one of both ends of the shutter member 8 is inserted. A wire or ribbon-shaped Ti-Ni shape memory alloy member 7 which has been processed and formed into a dogleg shape or an arch shape in advance is provided, and both ends are fixed to two fulcrums, and a similarly elastic wire is attached to the other end. Alternatively, a ribbon-shaped elastic member 9 is fixed. After filling the entire ink flow path leading to the ink discharge port 3 with ink, pressurized ink is supplied to the ink flow path 110 on the side of the ink reservoir from the shutter member 8, as shown in FIG. 3(b). Shape memory alloy member 7
When the image signal 6 is applied to both ends of the shape memory alloy member 7
Because it itself has a moderate electrical resistance (approximately 50 Ω crn), it can be heated to the martensitic transformation point (
In this case, when the temperature reaches around 100C), the shutter member 8 tries to return to its original shape and pulls up the shutter member 8.

At this time, when the pinhole 10 section provided in the shutter member 8 reaches the ink flow path 110 section, the pressurized ink acts on the ink discharge port 3 through the pinhole 10, and a droplet of ink is discharged from the ink discharge port 3. .

Next, after the application of the image signal is finished, the shape memory alloy member 7 is cooled by heat radiation, and when it becomes below the martensitic transformation point, it is easily deformed by the restoring force of the elastic member 9, and the shutter member 8 is pulled back. Pinhole 10 is closed. That is, it functions as an ink generator by repeating the processes shown in FIGS. 3(a) and 3(b).

In order to prevent ink from leaking from the insertion portion of the shutter member 8, a seal member 11 made of a polymeric material such as a soft silicone adhesive is used for sealing.

FIGS. 4(a) to 4(c) are enlarged views of a head portion showing a second embodiment of the present invention. The difference from the configuration shown in FIGS. 3(a) and 3(b) is that the same member as the shape memory alloy member 7 is used instead of the elastic member 9. That is, shape memory alloy members 7 are provided at both ends of the shutter member 8, respectively.
1.72 is formed, and an image signal 6.6' is applied to the shape memory alloy member 71 and the shape memory alloy member 72 as shown in FIG.
When no pressure is applied, the pinhole 10 of the shutter member 8 is positioned away from the ink flow path 110, and the pressurized ink is blocked by the shutter member 8.

Next, as shown in FIG. 3(b), when the image signal 6' is applied to the shape memory alloy member 72, the shape memory alloy member 72 straightens and shutters according to the same principle as in FIG. Pull member 8. As a result, ink is ejected from the ink ejection port 3 where the pinhole 10 overlaps the ink flow path 110. After the application of the image signal is completed, the shape memory alloy member 7 is
2 becomes below the mardenzite transformation point, the image signal 6 is applied to the shape memory alloy member 71 and the shutter member 8 is returned to its original position, as shown in FIG. From the flow path 110 1~,
Blocks Kaomi ink.

49, this configuration has shape memory alloy members 71 and 7.
2 and the elastic member 9, both 21 have diameters of 50 and 200.
It can be made into a wire shape of μm, and its driving voltage is several volts.
Compared to a piezo element, which requires only a few liters of volts, it is possible to obtain an extremely large stroke, making it possible to easily realize a high-density multi-nozzle.

Effects of the Invention As described in Section 2, according to the present invention, the pressure generating means for ejecting ink droplets is performed using a simple gas cylinder, so there is no need for a pressure generating means such as a piezo element. In addition, the nozzle density can be easily increased, and the drive voltage of the j7 can be reduced to several tens of volts or less, which greatly reduces the cost burden of the drive circuit.3.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional side view showing the structure of an inkjet henode according to the present invention, FIG. 2 is a conceptual diagram showing the overall structure of an inkjet unit using the inkjet henode according to the present invention, and FIGS. 3(a) and 3(b) ) is a cross-sectional side view showing a first embodiment of the shutter section of the inkjet head according to the present invention, and FIG. 4(a) = (e) is a second embodiment of the shutter section of the inkjet head according to the present invention. FIG. 5 is a schematic cross-sectional view of a conventional ink cartridge head. 3... Ink discharge port, 6.6'... Image signal, 7,
71゜72... Shape memory alloy member, 8... Shutter member, 9... Bullet 14L 10... Pinhole, 11
... Seal member, 101 ... Ink reservoir section, 102
... Hesode part, 103 ... Gas cylinder, 104 ...
- Pressure regulator, 106... Gas supply pipe, 107... Ink container, 108... Ink, 109... Ink filter, 110... Ink channel.

Claims (8)

[Claims] (1) An ink container storing ink, a means for pressurizing the ink with pressurized gas, an ink flow path having one end communicating with the ink container and the other end communicating with an ink discharge port, and an ink flow path disposed in the ink flow path. an inkjet head comprising: a shutter member having an opening; a shape memory alloy member provided at one end of the shutter member; and an elastic member provided at the other end of the shutter member. . (2) The inkjet head according to claim 1, wherein the shape memory alloy member is wire-shaped. (3) The inkjet head according to claim 1, wherein the shape memory alloy member is ribbon-shaped. (4) The inkjet head according to claim 1, wherein the elastic member is wire-shaped. (5) The inkjet head according to claim 1, wherein the elastic member is ribbon-shaped. (6) The inkjet head according to claim 1, wherein the shape memory alloy member is energized and heated in accordance with a recording signal to move the shutter member. (7) The inkjet head according to claim 1, wherein a shape memory alloy member is used instead of the elastic member. (8) A pressurizing means includes a gas cylinder, a gas supply pipe connecting the gas cylinder and the ink container, a pressure regulator arranged in the gas supply pipe to adjust the gas pressure of the gas from the gas cylinder, and a pressure regulator for adjusting the gas pressure of the gas from the gas cylinder. The inkjet head according to claim 1, further comprising an on-off valve that opens and closes the supply pipe.