JP2615319B2 - Inkjet head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet head used in an ink jet printer, and more particularly to a multi-nozzle type ink jet head having a plurality of ink ejection nozzles.

[0002]

2. Description of the Related Art As a method of a drop-on-demand type ink jet printer, according to a print information signal,
A pulse voltage is applied to a piezoelectric element, which is a pressurizing vibration mechanism attached to the ink chamber, to deform the piezoelectric element, change the volume of the ink chamber, and pressurize the ink liquid pressure therein.
2. Description of the Related Art A method has been adopted in which ink droplets are ejected from nozzles at the tip of a head that communicate with an ink chamber, and printing is performed on a recording medium such as recording paper that faces away.

In such a multi-nozzle type ink jet printer, it is desired to improve the recording density and reduce the size of the head. However, since the efficiency of converting the piezoelectric element from electric to mechanical deformation is low, the size of the piezoelectric element is small. Cannot be reduced,
It is difficult to increase the density and reduce the size.

[0004] At present, in order to realize the miniaturization and high-density recording of the ink jet head, a new pressurizing and vibrating mechanism replacing a pressurizing and vibrating mechanism using a piezoelectric element is being attempted. For example, as an ink jet head disclosed in Japanese Patent Application Laid-Open No. 63-57251, an apparatus using a combination of a shape memory alloy having large mechanical deformation and a heating means for heating the same is used as a pressure vibration mechanism. is there.

[0005]

In the pressure vibration mechanism using the above shape memory alloy, as a characteristic of a general shape memory alloy, the shape when heated to a transformation temperature or more and returned to the parent phase is stable. Although the shape of the so-called martensite phase below the transformation temperature is memorized by heat treatment or the like, it has an unstable surface. For this reason, below the transformation temperature, it is difficult to keep the volume of the ink chamber constant, and a certain degree of error occurs compared to the original shape. Since the ejection characteristics of the ink change due to this error, the printing quality deteriorates.

An object of the present invention is to improve the reliability, reduce the size, and increase the density of an ink jet head using a shape memory alloy.

[0007]

According to the present invention, a pressure vibrator is formed by laminating first and second shape memory alloys having different transformation temperatures, and the pressure vibrator is attached to an ink chamber and heated. By doing so, the above object is achieved by ejecting the ink liquid from a nozzle communicating with the ink chamber.

The pressurizing vibrator is deformed in a direction of increasing the volume of the ink chamber at a first temperature higher than room temperature or higher,
It is preferable that the ink chamber be deformed in a direction to reduce the volume of the ink chamber at a second temperature higher than the first temperature.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An ink jet head according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an explanatory view showing the configuration of the present invention. In FIG. 1, X is an ink jet head section, and FIG. 1 shows a cross section taken along line AA of FIG. 1 is an ink chamber having a length of 10
0 to 10000 μm, width 50 to 500 μm.

Reference numeral 2 denotes a first shape memory alloy, and 3 denotes a second shape memory alloy.
And pressurized vibrating body 4 is formed by laminating and fixing them. As these shape memory alloys, it is possible to use a Ni—Ti alloy, a Cu—Zn—Al alloy, or the like.
A system alloy is used.

The state of the hardness and temperature change of the Ni-Ti based shape memory alloy is as follows. For example, length 40m
m, width 8.9mm, thickness 0.32mm alloy,
The pressing force required to obtain a displacement of 1.5 mm in the length direction is about 0.3 at 20 ° C., which is a martensite phase.
Although it is 5N, it becomes about 1.9N in the parent phase at a temperature higher than the transformation temperature of 80 ° C., which is more than five times that in the martensite phase.

The transformation temperature is variable depending on the composition of the alloy. For example, the transformation temperature at 50 at% Ni is about 80 ° C., and if the Ni composition is shifted by 0.1 at%,
10 ° C lower.

The first shape memory alloy 2 made of a Ni—Ti based shape memory alloy having the above characteristics has a thickness of about 100 μm.
m, an area of 0.1 to 10 mm ² , laminated on the upper surface of the second shape memory alloy 3, and the shape in the martensite phase is
It is a planar shape, the transformation temperature is about 50 ° C., and the shape of the matrix exceeding the temperature is formed so as to bend upward in FIG.

Similarly, the second shape memory alloy 3 made of a Ni—Ti based shape memory alloy has a thickness of about 250 μm and an area of about 0.2 μm.
1 to 10 mm 2, which is attached to the upper surface of the ink chamber 1 and the outer periphery thereof is fixed, and the shape in the martensite phase is as follows:
It is a planar shape, the transformation temperature is about 60 ° C., and the shape of the parent phase exceeding that temperature is formed so as to bend downward.

The pressurizing vibrator 4 formed by laminating and fixing the first shape memory alloy 2 and the second shape memory alloy 3 changes its shape at the temperatures of 50 ° C. and 60 ° C. Is expanded or reduced, and the ink in the same is pressurized.

In this embodiment, the pressure vibrating body 4 is laminated and fixed with the first shape memory alloy 2 on top and the second shape memory alloy 3 on down. Can perform the same operation.

Reference numeral 5 denotes a drive circuit as a heating means, which receives a print information signal from a control circuit (not shown), applies a 1 kHz rectangular wave to the pressure vibrator 4, and heats the pressure vibrator 4. . Reference numeral 6 denotes an ink flow path as a supply means, and its depth is 10 to 100 μm. This communicates with the ink chamber 1 and supplies ink to the ink chamber 1. Reference numeral 7 denotes a nozzle having a diameter of 10 to 100 μm. This is ink chamber 1
And ejects the ink liquid pressurized by the pressure vibrating body 4.

Next, the operation will be described with reference to FIGS. 1, 3, and 4. FIG.

First, the drive circuit 5 receiving the print information signal from the control circuit (not shown) supplies a rectangular wave of 1 kHz to the pressure vibrator 4. The pressurized vibrating body 4 is heated by energization.

FIG. 3 shows a change in volume of the ink chamber 1 with a change in temperature. In the figure, the martensite phase is represented as martens, the shape is the same if the volume of the ink chamber 1 does not change, and the shape is enlarged if the volume is increased, and the volume is reduced. In the case of a shape, it is represented as reduced. Using the same figure, 60 ° from room temperature
Pressurized vibrating body 4 in accordance with the process of reaching C or higher and returning to room temperature
Will be described.

First, in the temperature range from room temperature to 50 ° C., the first shape memory alloy 2 and the second shape memory alloy 3
Are in a martensitic phase, and none of the shape memory alloys shows any change in shape. At this time, the shape of the ink chamber 1 becomes the shape of the initial state shown in FIG.

In a temperature range of 50 ° C. or higher and lower than 60 ° C., the first shape memory alloy 2 is a parent phase and changes to a shape stored in advance. Here, a shape that bends upward is shown. The second shape memory alloy 3 is in a martensitic phase and does not show a shape change.

At this time, the thickness of the first shape memory alloy 2 (1
00 μm) to the thickness of the second shape memory alloy (250 μm).
μm) is thick, but the change in the first shape memory alloy is due to the parent phase, and the pressing force in the parent phase is about five times that in the martensite phase. 2 changes the shape of the second shape memory alloy 3 upward,
The pressure vibrating body 4 bends upward. Thereby, the shape of the ink chamber 1 increases the volume as shown in FIG. Increasing the volume of the ink chamber 1 leads to an improvement in ink supply efficiency.

In a temperature range of 60 ° C. or higher, both the first shape memory alloy 2 and the second shape memory alloy 3 are in a parent phase, the first shape memory alloy 2 tends to bend downward, and The shape memory alloy 3 of 2 tries to bend upward. As described above, the first shape memory alloy 2 and the second shape memory alloy 3 try to change shapes in directions opposite to each other, but the thickness of the first shape memory alloy 2 (100 μm) corresponds to the second shape memory alloy 2. Is thick (250 μm), the second shape memory alloy 3 also bends the first shape memory alloy 2 downward, and the pressurized vibrator 4 bends downward. As a result, the pressurizing vibrator 4 reduces the volume of the ink chamber as shown in FIG. 4, pressurizes ink, and ejects ink droplets from the nozzle 7.

After the ejection of the ink droplets, the current supply from the drive circuit is stopped, and when the temperature starts to decrease, the state returns to the initial state through a process reverse to that of the heating. First, when the temperature is lower than 60 ° C., the second shape memory alloy becomes a martensite phase, and the volume of the ink chamber 1 is expanded by the first shape memory alloy. When the temperature is lower than 50 ° C., the first shape memory alloy also becomes a martensite phase and returns to the initial state.

As described above, the ink ejection operation of the pressurizing vibrator 4 involves two operations of expanding and reducing the ink chamber 1, and the respective shapes are formed of the first shape memory alloy and the second shape memory alloy. Since the shape is defined by the mother phase, the shape changes stably irrespective of the initial state, the ejection characteristics of the ink are stabilized, and the printing quality is stabilized. In addition, when cooling and returning to the initial state, since the operation of once expanding the volume of the ink chamber 1 is performed, the ink is supplied quickly and the speed can be increased.

In the above example, the transformation temperature of each of the first shape memory alloy 2 and the second shape memory alloy 3 is set to 50.
Although the temperature was set to ° C. and 60 ° C., the transformation temperature can be set and changed variously at the stage of forming the shape memory alloy.

For example, the transformation temperature of the first shape memory alloy 2 is set lower than room temperature, and at room temperature, the shape is always maintained in the matrix. As a result, the pressure vibrating body 4 has a shape that always increases the volume of the ink chamber 1 at room temperature, and the initial state shown in FIG. 4 showing the shape of the ink chamber 1 disappears. There are two operations, enlargement and reduction. Even with such a change, the same effect as in the above example can be obtained.

[0029]

According to the present invention, a first shape memory alloy and a second shape memory alloy having different transformation temperatures are used for the pressure vibrator, and the minimum volume and the maximum volume of the ink chamber are determined by the respective mother phases. , The change in volume required for pressurization is always constant, and the amount of ejected ink liquid, the ejection pressure, and the like become constant, and stable ink ejection can be performed. As a result, a small and highly reliable inkjet head can be realized.

In particular, a direction in which the pressure vibrator is deformed in a direction of increasing the volume of the ink chamber at a desired temperature or higher and a volume of the ink chamber is reduced at a predetermined temperature higher than the desired temperature. Since the change in volume required for pressurizing the ink liquid by the pressurizing vibrator is large by using a deformable member, the volume of the ink chamber itself can be formed small, which is effective in terms of miniaturization and high density.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a configuration of an inkjet head according to an embodiment of the present invention.

FIG. 2 is a plan view of a main part of FIG. 1;

FIG. 3 is an explanatory diagram for explaining the operation of FIG. 1;

FIG. 4 is an explanatory diagram for explaining the operation in FIG. 1;

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 ink chamber 2 first shape memory alloy 3 second shape memory alloy 4 pressurized vibrator 5 heating means 6 supply means 7 nozzle

Claims (3)

(57) [Claims] 1. An ink chamber, comprising a first shape memory alloy and a second shape memory alloy having different transformation temperatures laminated to each other, and a pressurizing means provided in the ink chamber for pressurizing an ink liquid pressure in the ink chamber. A pressure vibrator, heating means for heating the pressure vibrator, supply means for supplying ink to the ink chamber, and communication with the ink chamber for ejecting the ink liquid pressurized by the pressure vibrator. An inkjet head comprising a nozzle. 2. The pressurizing vibrator according to claim 1, wherein the first shape memory alloy becomes a parent phase at a first temperature higher than room temperature and deforms in a direction to increase the volume of the ink chamber, and the first temperature increases. 2. The ink jet head according to claim 1, wherein the second shape memory alloy becomes a parent phase at a temperature higher than a second temperature higher than the second temperature and deforms in a direction to reduce the volume of the ink chamber. 3. The pressure vibrating body has a first shape memory alloy as a matrix at room temperature, is deformed in a direction to increase the volume of the ink chamber, and has a third temperature higher than room temperature. 2. The ink jet head according to claim 1, wherein the second shape memory alloy becomes a parent phase and deforms in a direction to reduce the volume of the ink chamber.