JP3246905B2 - Print head of inkjet printer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a printer,
More specifically, the present invention relates to a print head of a piezoelectric ink jet printer.

[0002]

2. Description of the Related Art A conventional print head of a piezoelectric ink-jet printer employs a Kaiser method in which the wall of a pressure chamber filled with ink is deformed by using the flexure of a piezoelectric element by a bimorph, and the ink is projected by an increase in pressure. What is described is described in, for example, Japanese Patent Publication No. 57-20904.

A shear mode system in which a partition of a channel-shaped pressure chamber filled with ink is deformed by utilizing the deformation of a piezoelectric element in a shear mode, and the ink is protruded by an increase in pressure of the pressure chamber due to this, for example, is disclosed in Japanese Patent Application Laid-Open No. H10-163,873. It is described in JP-A-63-247051.

Further, a thickness vertical deformation mode system in which the volume of a pressure chamber filled with ink is changed by utilizing the deformation due to a dimensional change in the thickness direction of a piezoelectric element, and the ink is projected by a rise in the pressure of the pressure chamber, for example, is a special feature. Ganpei 2-3039
This is described in the specification attached to the 535 application.

[0005]

In all of the above-mentioned methods, eradication of ejection failure due to drying of ink, reduction of the driving voltage of the piezoelectric element, and miniaturization of the ejection means improve the reliability of the ink jet printer, respectively. Simplification of
It is required to reduce the weight and improve the resolution of the printing pattern. However, it is not easy to satisfy these requirements with the conventional technology. The fundamental reason is that the piezoelectric driving means has the property that it can output force but hardly displaces, but in order to increase the pressure of the ink before ejecting it, the pressure chamber filled with ink to increase the compression ratio of the ink Is required to be considerably deformed. That is, in the prior art, the conversion coefficient of the drive voltage to the ink pressure is originally low, and the conversion coefficient tends to decrease due to the miniaturization of the ejection means. SUMMARY OF THE INVENTION In order to solve such a fundamental problem, an object of the present invention is to increase the pressure of the ink filled in the pressure chamber without increasing the drive voltage of the piezoelectric element in the print head of the piezoelectric ink-jet printer.

[0006]

In order to solve the above-mentioned problems, a print head of an ink jet printer according to the present invention is provided with a pressure chamber for applying pressure to ink filled by driving a piezoelectric element, and is provided or attached to the pressure chamber. In a print head of a piezoelectric ink jet printer having an ejection hole means and an ink supply means for supplying ink to the pressure chamber, a spacer made of a material having a lower compression ratio than ink such as glass, ceramics, etc. is arranged in the pressure chamber. It is characterized by becoming.

(Operation) According to this structure, the volume of the ink filled in the pressure chamber is reduced by the presence of the spacer in the pressure chamber, and the ink is filled so as not to hinder the deformation of the wall surface of the pressure chamber due to the driving of the piezoelectric element. If an object is arranged, the volume change of the pressure chamber can be made the same as before.
By the way, the compression ratio of a material having a high elastic modulus such as glass and ceramics is as low as 1/10 to 1/100 of that of ink.
When the pressure chamber is compressed, the volume of the spacer may not be reduced, but may be approximated to that of the ink only. Therefore, if attention is paid to ink, although the volume itself is smaller than in the past, the decrease in that volume during piezoelectric driving is the same as in the past because the decrease in the spacer volume can be ignored. As a result, the rate of volume change of the ink is increased over the previous one. In general, when a liquid is compressed, a pressure proportional to the volume change rate of the liquid is generated. Therefore, in the case of the present invention, the pressure of the ink in the pressure chamber is increased without increasing the driving voltage of the piezoelectric element. be able to. In addition, since the pressure is increased while the amount of change in volume in the pressure chamber is kept constant, as a secondary effect, the responsiveness of ink inflow and outflow is increased, which is suitable for high-speed printing.

[0008]

(Embodiment 1) The first embodiment of the present invention will be described below.
Will be described with reference to the drawings. This embodiment is an embodiment of the present invention in a print head of a type in which a partition of a pressure chamber is deformed by utilizing deformation of a piezoelectric element in a shear mode. The piezoelectric head shown in FIG. 1, FIG. 2, FIG. Grooves 31, 32, 33 and partition walls 51, 52 forming a plurality of pressure chambers are formed in the substrate 1 made of a conductive material, and the upper end surface of the partition wall is connected to the lid 6 via an elastic member 9. The partition is polarized in the direction of the arrow in FIG. 1, and electrodes 41, 42, and 43 are provided on the inner surfaces of the grooves 31, 32, and 33, respectively. As shown in FIG.
As shown in FIG. 7, a common groove 81 for supplying ink is formed, and communicates with a joint 82 to supply ink to the pressure chamber from outside. The other ends of the grooves 31, 32, and 33 of the pressure chamber are opened at one end face of the substrate 1, and a nozzle plate 60 is attached to the end face of the substrate 1 so as to close this opening. The nozzle plate 60 is provided with injection holes 61, 62, 63 corresponding to the grooves 31, 32, 33, respectively. A spacer 95 made of glass is provided inside each pressure chamber.
Are arranged with a margin enough to cause some backlash, and the remaining gaps are filled with ink. Spacer 9
Numeral 5 can move within the range regulated by the wall surface as ink flows into and out of the pressure chamber, and acts to suppress an increase in fluid resistance. However, its end is sloped, and ink flows when it comes into contact with the wall surface. The road is not blocked. FIG. 1 shows a state before a voltage is applied to the electrodes 41, 42 and 43. When a positive voltage is applied to the electrodes 41 and 42 with respect to the electrode 42, the partition walls 51 and 52 are deformed in the clockwise and counterclockwise shear modes on a plane parallel to the paper surface as shown in FIG. As a result, the volume of the pressure chamber 92 formed by the groove 32 is reduced, the pressure of the filled ink is increased, and the ejection holes 62 provided in the nozzle plate 60 are formed.
Inject more ink.

When the upper end of the partition of the pressure chamber having the groove width X is displaced by ΔX due to the deformation in FIG. 2, if the volume of the pressure chamber is V and the change in volume is ΔV, the volume change rate ΔV / V is ΔV / V = ΔX / X (1) When the spacer 95 does not exist in the pressure chamber as in the conventional example shown in FIG. 12, the compression ratio F of the ink is: F = ΔV / V (2) The spacer 9 having a volume V ₀ in the pressure chamber as in this embodiment.
In the case where No. 5 is present, if it is assumed that the volume V ⁰ of the spacer does not change during compression for the reason already extended, F = ΔV / (V−V ₀ ) (3). The pressure P of the compressed ink is proportional to the compression ratio F, and if its bulk modulus is B, it is generally expressed as P = BF (4) From the formulas (2), (3), and (4), the ink pressure P ₀ when no filling object is present in the pressure chamber and the pressure P ₁ when the filling object is present are obtained, and the ratio is calculated as P ₁ / P ₀ = V / (V−V ₀ ) (5) Equation (5) shows that the pressure of the ink increases due to the presence of the filling object, and also increases as the volume V _{0 of the} filling object increases. In this embodiment, the volume V _{0 of the} filling object is ／ of the volume V of the pressure chamber, and the effect of increasing the pressure of the ink three times as compared with the conventional case is obtained. In addition, since the pressure is increased while the amount of change in volume in the pressure chamber is kept constant, the response speed of ink inflow and outflow has been improved three times as compared with the related art as a secondary effect.

(Embodiment 2) Hereinafter, a second embodiment of the present invention will be described with reference to the drawings. This embodiment is also an embodiment of the present invention in a print head of a type in which a partition of a pressure chamber is deformed by utilizing deformation of a piezoelectric element in a shear mode as in the first embodiment, and is shown in FIG. 10 and FIG. Grooves 531, 53 forming a plurality of pressure chambers in a substrate 501 made of a piezoelectric material
2, 533 and partition walls 551, 552 are formed, and the upper end surface of the partition wall is connected to the lid 506 via an elastic member 509. The partition is polarized in the direction of the arrow in FIG.
Electrodes 541 and 5 are provided on the inner surfaces of 1,532 and 533, respectively.
42, 543 are provided. Groove 5 constituting pressure chamber
As shown in FIG. 11, a common groove 581 for supplying ink is formed in communication with one end of 31, 31, 532, 533 to supply ink from outside to the pressure chamber. The other ends of the grooves 531, 532 and 533 of the pressure chamber are opened at one end face of the substrate 501, and a nozzle plate 560 is attached to the end face of the substrate 501 so as to close this opening.
The nozzle plate 560 is provided with injection holes 561, 562, and 563 corresponding to the grooves 531, 532, and 533, respectively. Inside each pressure chamber, a spherical spacer 595 made of glass is arranged with a margin enough to cause some backlash, and the remaining gap is filled with ink. Lid 5
In 06, stoppers 503 and 504 are provided to hold the spacer 595 in the pressure chamber and not to block the injection hole. Regarding specific dimensions in this example, when the groove width is h and the depth is d, d = 60 to 250 μm h: d = 2 to 3 is preferable. Now, for the electrode 542, the electrodes 541 and 542
When a positive voltage is applied to the partition wall 551 and 552, deformation in the clockwise and counterclockwise shear modes occurs in a plane parallel to the paper in exactly the same manner as described in the first embodiment. As a result, the volume of the pressure chamber formed by the groove 532 decreases, the pressure of the filled ink increases, and the ink is ejected from the ejection holes 562 provided in the nozzle plate 560. At this time, since the pressure is reduced along the flow in the direction of the arrow in FIG. 11 and a pressure gradient is generated, the spacer moves along the flow by receiving a force in the direction of the arrow due to the pressure difference between the two sides. As a result, unlike the case where the spacer is fixed, the ink and the spacer flow together as a single piece without forcibly passing through the gap between the pressure chamber wall and the spacer, thereby preventing an increase in fluid resistance. I can do it. When the drive voltage is released after the ejection of the ink and the deformation of the partition is restored, the pressure in the pressure chamber becomes negative with respect to the external pressure, the ink flow is in the opposite direction to the arrow, and the spacer is also in the opposite direction to the arrow. Moving. Also in this embodiment, the compression ratio of the ink is increased by the presence of the spacer 595, so that the ink pressure can be increased and the response speed for entering and exiting can be improved by the same principle as in the first embodiment.

(Embodiment 3) Next, a third embodiment of the present invention will be described. This embodiment is an embodiment of the present invention in a print head of a system in which a wall of a pressure chamber filled with ink is deformed by using bending of a piezoelectric element in a bending mode.
In FIG. 5, a groove 206 constituting a pressure chamber is formed in a substrate 201.
To form the bottom and side walls of the pressure chamber. An ejection hole 202 is provided on one wall of the side wall orthogonal to the longitudinal direction of the groove 206, and an introduction port 203 communicating with an ink introduction tube 205 is provided on the other wall. A bead spacer 209 of ceramic smaller in size than the groove is placed in the groove 206, and a lid 204 made of an elastic material is put on and fixed to the side wall portion. A plate-shaped piezoelectric element 211 which has an electrode 212 on one surface and an electrode 213 on the other surface and is polarized in the thickness direction is joined to the outer surface of the lid 204. The piezoelectric element 211 itself generates a compressive force in the longitudinal direction when a positive voltage is applied to the electrode 213 with respect to the electrode 212, and this generates a moment with respect to the plate of the lid 204 due to a shift of the neutral axis, and FIG. As shown, the lid 204 deforms in a bending mode to reduce the volume of the pressure chamber, thereby increasing the pressure of the ink filled therein and ejecting the ink from the ejection holes 202. Also in this embodiment, the compression ratio of the ink is increased by the presence of the spacer 209, so that the ink pressure can be increased and the response speed for entering and exiting can be improved by the same principle as in the first embodiment.

(Embodiment 4) Next, a fourth embodiment of the present invention will be described. This embodiment is an embodiment of the present invention in a print head of a system in which the volume of a pressure chamber filled with ink is changed by utilizing the deformation due to a dimensional change in the thickness direction of a piezoelectric element. As shown in FIG. 7 and FIG.
Reference numerals 0, 340 and 360 denote pressure chambers 321, 341 and 361 and ink reservoirs 322 and 34 respectively communicating with the pressure chambers.
2,362 are hollowed out to release in the thickness direction. The partition plates 330 and 350 have ink reservoirs 332 and 3 respectively.
52 is hollowed out so as to be released in the thickness direction. Electrodes 325, 326, 345, 346, 365 and 366 are attached to both surfaces of the plate-like piezoelectric members 320, 340 and 360, respectively, and the plate-like piezoelectric members are polarized in the directions of arrows. Next, the plate-like piezoelectric members 320, 340, 360 and the partition plate 3
30 and 350 are stacked alternately and sequentially with pressure spacers 321, 341, and 361 having spacers 390 made of ceramics having a size smaller than that of the pressure chambers 321, 341, and 361 inserted therein so as to obtain an appropriate play.
2, 342, 352, 362 are laminated and arranged so as to correspond to each other and are joined to form a common ink reservoir,
Further, the upper substrate 380 and the lower substrate 370 are attached with these components interposed therebetween. An ink supply hole 381 is provided in the upper substrate 380, from which ink is supplied, and the common ink reservoir and each pressure chamber are filled with ink. Pressure chambers 321, 341, 36
A nozzle plate 310 having ejection holes 311, 312, and 313 corresponding to the respective ink reservoirs is attached to the end opposite to the ink reservoir. Now, when a positive voltage is applied to the electrode 326 attached to the plate-shaped piezoelectric body 320 and an electric field is applied in a direction opposite to the direction of polarization indicated by the arrow, the thickness of the plate-shaped piezoelectric body 320 is reduced and the plane direction is changed. Approximately 1 in the compression ratio in the thickness direction
As shown in FIG. 4, the cross section of the pressure chamber 321 changes from a solid line 327 to a dotted line 328, and the cross-sectional area decreases because the rate of decrease in the dimension in the thickness direction exceeds the rate of increase in the dimension in the longitudinal direction. Therefore, the volume of the pressure chamber 321 decreases.
As a result, the pressure of the ink filled in the pressure chamber 321 is increased, and the ink is ejected from the ejection holes 311. Also in the present embodiment, the compression ratio of the ink can be increased by the presence of the spacer 390, and the pressure of the ink filled in the pressure chamber can be increased by the same principle as in the first embodiment.

[0013]

According to the present invention, in a piezoelectric ink jet printer, the driving pressure of the ink filled in the pressure chamber can be reduced without changing the driving voltage and the driving means, or independently of them. And can be significantly increased. In addition, it is possible to increase the responsiveness of ink inflow and outflow. Therefore, according to the present invention, it becomes possible to solve the problem of the ink ejection failure which has conventionally been a problem in this type of printer, reduce the voltage of the drive power supply, and solve the ejection means for increasing the resolution of the print pattern. This makes it possible to perform printing at a higher speed, which is extremely advantageous.

[0014]

[Brief description of the drawings]

FIG. 1 is a sectional view perpendicular to the longitudinal direction of a pressure chamber showing a structure of a first embodiment of the present invention.

FIG. 2 is a sectional view perpendicular to the longitudinal direction of the pressure chamber showing the operation of the first embodiment of the present invention.

FIG. 3 is a cross-sectional view parallel to the longitudinal direction of the pressure chamber showing the structure of the first embodiment of the present invention.

FIG. 4 is a perspective view showing a part of the structure of the first embodiment of the present invention.

FIG. 5 is a sectional view showing the structure of a second embodiment of the present invention.

FIG. 6 is a sectional view showing the operation of the second embodiment of the present invention.

FIG. 7 is an exploded perspective view showing the structure of a third embodiment of the present invention.

FIG. 8 is a sectional view showing a structure of a third embodiment of the present invention.

FIG. 9 is an explanatory diagram showing the operation of the third embodiment of the present invention.

FIG. 10 is a sectional view perpendicular to the longitudinal direction of a pressure chamber showing a structure of a second embodiment of the present invention.

FIG. 11 is a cross-sectional view parallel to the longitudinal direction of a pressure chamber showing a second embodiment of the present invention.

FIG. 12 is a sectional view showing the structure of a conventional example (corresponding to the first embodiment of the present invention).

[Explanation of symbols]

1,501 Piezoelectric substrate 6,506,204 Lid 9,509 Elastic member 31,32,33,531,532,533,206
Grooves 41, 42, 43, 541, 542, 543, 212,
213,325,326,345,346,365,3
66 electrode 51,52,53,51,52,53 partition wall 60,560,310 nozzle plate 61,62,63,561,562,563,202,
311, 312, 313 Injection hole 95, 595, 209, 390 Spacer 201 Substrate 203 Inlet hole 211 Piezoelectric element 320, 340, 360 Plate-like piezoelectric body 321, 341, 361 Pressure chamber 322, 332, 342, 352, 360 Ink reservoir 370 Lower substrate 380 Upper substrate

Claims (11)

(57) [Claims] 1. A piezoelectric ink jet printer comprising: a pressure chamber for applying pressure to ink by driving a piezoelectric element; ejection hole means attached to or provided in the pressure chamber; and ink supply means for supplying ink to the pressure chamber. in the print head, Ri Na glass, than the small substance serving compression ratio than ink such as ceramics in the pressure chamber, and the pressure
A print head for an ink jet printer, comprising a plurality of spacers movably arranged with a size that causes slight backlash with respect to a partition wall of a chamber . 2. The pressure chamber is provided at each end of a rectangular groove.
Having a configuration provided with an ejection hole and an ink supply hole;
Note that the spacers are arranged side by side in the groove.
The inkjet printer according to claim 1,
Print head. 3. The volume of the spacer is equal to the volume of the pressure chamber.
The product is approximately 2/3 of the product.
Or printing by an ink jet printer according to claim 2.
head. 4. The spacer has a rectangular shape with a rectangular cross section.
The jetting means of the spacer and the ink
The surface facing the supply means is prevented from blocking the ink flow path.
A bezel characterized by forming a slope for stopping
The ink jet according to any one of claims 1 to 3,
Print head of printer. 5. The method according to claim 1, wherein the spacer is wider than the width of the rectangular groove.
Characterized by a spherical spacer with a slightly smaller diameter
The printing of the ink jet printer according to claim 2
Good. 6. The method according to claim 6, wherein the spherical spacer is provided with a rectangular groove.
6. The method according to claim 5, wherein a plurality of crabs are arranged.
The print head of the inkjet printer according to the above. 7. The spherical groove near the end of the rectangular groove.
Holding the pacer in the pressure chamber and closing the injection hole
Note that a stopper is provided to prevent
7. The ink jet printer according to claim 5, wherein
Print head of printer. 8. A substrate is provided with a pressure chamber and a groove forming a side wall of the pressure chamber, and one side wall intersecting the longitudinal direction of the groove communicates with an ejection hole, and the other side wall communicates with an ink introduction pipe. An inlet is provided, a lid of the pressure chamber made of an elastic plate material is attached to an upper surface of the substrate, and a plate-shaped piezoelectric element which is polarized in a thickness direction and has drive electrodes on both surfaces is attached to an outer surface of the lid. the voltage by changing the volume of the pressure chamber by deformation due to the bending mode of the lid by applying, in a print head for ejecting ink filled in the pressure chamber from the injection hole, the glass to the pressure chamber, the ink of ceramics Ri Na than the small substance serving compression ratio and of the pressure chamber
Duplicate spacers with dimensions that may cause slight backlash
A print head for an ink jet printer, wherein several print heads are movably arranged. 9. The pressure chamber is provided at each end of a rectangular groove.
Having a configuration provided with an ejection hole and an ink supply hole;
Note that the spacers are arranged side by side in the groove.
The inkjet printer according to claim 8, wherein
Print head. 10. The pressure chamber has a volume of the spacer.
9. The method according to claim 8, wherein the volume is approximately 2/3.
Or the mark of the ink jet printer according to claim 9.
Character head. 11. The shape of the spacer is spherical.
The ink according to claim 8 or 9, wherein
Print head for jet printer.