JP3296391B2 - Ink jet recording head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure generating means provided in a pressure generating chamber which communicates with a common ink chamber and a nozzle opening through an ink supply port. The present invention relates to an ink jet recording head for discharging droplets onto a recording medium.

[0002]

2. Description of the Related Art For example, as shown in Japanese Patent Application Laid-Open No. 6-40035, a piezoelectric vibrating plate is adhered to a partial area of an elastic plate constituting a pressure generating chamber, and a flexural displacement of the piezoelectric vibrating plate is applied. An ink jet recording head that generates ink droplets by changing the volume of a pressure chamber has a feature that ink droplets can be stably generated because a large area of the pressure generation chamber can be displaced. I have. In such a recording head, the pressure in the pressure generating chamber generated by the piezoelectric vibrating plate is related to the pressure generating chamber and the common ink chamber communicating with each other through an ink supply port formed by a fine hole. In order to effectively use the ink for discharging from the nozzle opening, it is necessary to reduce the return amount from the ink supply port to the pressure generating chamber. Since it is necessary to quickly fill the pressure generating chamber with ink from the ink chamber and restore the meniscus in a short time, the performance of the recording head depends on the ink supply port.

For this reason, in order to increase the energy efficiency at the time of ink ejection, if the ink supply port is narrowed, it takes time to fill the pressure generating chamber with ink and the return of the meniscus is delayed, so the drive frequency of the recording head must be reduced. However, if the ink supply port is widened to increase the return speed of the meniscus, the flow rate resistance of the ink supply port decreases, such that the utilization rate of the energy of the pressure generating chamber for discharging the ink drops decreases. This is in opposition to raising the drive frequency and raising the energy efficiency.

On the other hand, in order to improve the printing speed and to express the gradation in such a recording head, the dynamic characteristics of the meniscus, that is, the vibration amplitude of the meniscus generated after ink droplet ejection is increased, and the following is required. It is necessary to increase the margin for the timing of ink droplet ejection.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of these problems, and an object of the present invention is to make it possible to effectively use the pressure in a pressure generating chamber for discharging ink, and to further reduce the pressure after discharging ink. An object of the present invention is to provide a novel ink jet type recording head which can quickly flow ink from a common ink chamber into a pressure generating chamber.

A second object of the present invention is to provide a novel method in which the vibration amplitude of the meniscus near the nozzle opening after the ejection of ink droplets is made as large as possible so that the dynamic characteristics of the meniscus can be positively utilized. An object of the present invention is to provide an ink jet recording head.

[0007]

According to the present invention, there is provided a pressure generating chamber provided with pressure generating means, a common ink chamber receiving ink supplied from an ink tank, and In an ink jet recording head having a nozzle opening communicating with a pressure generating chamber, the pressure generating chamber and the common ink chamber are expanded toward the pressure generating chamber and a large diameter side is connected to the pressure generating chamber. a tapered portion having one end continuous with the small-diameter side of the tapered portion, the other end is connected by said common straight portion from a Louis down <br/> click supply port connected to the ink chamber.

[0008]

When pressure is applied to the pressure generating chamber for discharging ink droplets, a part of the ink in the pressure generating chamber is discharged as an ink droplet from the nozzle opening, and a part is discharged from the ink supply port to the common ink chamber. However, since a large fluid resistance is generated with respect to the flow from the pressure generation chamber side to the common ink chamber, the pressure in the pressure generation chamber is effectively used for discharging the ink droplets. On the other hand, when ink flows from the common ink chamber to the pressure generating chamber due to expansion of the pressure generating chamber after ink ejection, the fluid resistance is reduced, so that the ink is quickly supplied to the pressure generating chamber and the meniscus becomes ink droplets. It quickly returns to the dischargeable position.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to the illustrated embodiments. FIG. 1 is a cross-sectional view showing a structure in the vicinity of a pressure generating chamber connecting one embodiment of the present invention to one common ink chamber. In the drawing, reference numeral 2 denotes a first cover plate having a thickness of 1.
A drive electrode 5 is formed of a thin plate of zirconia having a thickness of about 0 μm,
Is formed, and a piezoelectric vibration plate 3 made of PZT is fixed thereon.

Reference numeral 7 denotes a spacer which is a zirconia (Z) having a thickness suitable for forming the pressure generating chamber 4, for example, 150 μm.
A pressure generating chamber 4 is formed by forming a through hole in a ceramic plate such as rO2) and sealing both surfaces with a second lid 8 and a first lid 2 described later.

Reference numeral 8 denotes the above-mentioned second cover plate for sealing the other surface of the spacer 7. One end of the pressure generating chamber 4 has an ink connecting a common ink chamber 12 and a pressure generating chamber 4 described later. A supply port 9 is provided, and a communication hole 10 connected to the nozzle opening 19 is provided at the other end of the pressure generating chamber 4.

As shown in FIG. 2, the ink supply port 9 is formed as a funnel-shaped through hole, and has a tapered portion 9a that expands toward the pressure generating chamber and a side that faces the common ink chamber 12. Has a narrowed straight portion 9b.

Reference numeral 11 denotes a common ink chamber constituting plate 13 described later.
A heat-sealing film for joining the second lid plate 8 and
A through hole 14 and a communication hole 10 corresponding to the common ink chamber 12 are provided.

Reference numeral 13 denotes the common ink chamber forming plate described above.
A thickness suitable for forming the common ink chamber 12, for example, 1
A through hole corresponding to the shape of the common ink chamber 12 and a communication hole 16 for connecting a nozzle opening are formed in a corrosion-resistant plate material such as stainless steel or ceramic of 50 μm.

Reference numeral 18 denotes a nozzle plate, and a nozzle opening 19 communicating with each pressure generating chamber 4 is provided near one side of the pressure generating chamber 4.
And a common ink chamber forming plate 13 with an adhesive layer 20 such as a heat welding film so that each pressure generating chamber 4 and the nozzle opening 19 communicate with each other through the communication holes 10, 15, 16.
Adhered to.

In this embodiment, when a drive signal is applied to the piezoelectric vibrating plate 3, the first cover plate 2 bends so that the pressure generating chamber 4 side is convex, and the pressure generating chamber 4 is contracted.
As a result, a part of the ink in the pressure generating chamber 4 is
The ink reaches the nozzle opening 19 via the nozzles 15 and 16 and is ejected from the nozzle opening 19 as ink droplets.

At the same time, ink flows from the pressure generating chamber 4 into the common ink chamber 12 via the ink supply port 9, and in the process, the thin straight section 9b is narrowed down while being narrowed by the tapered section 9a with the pressure generating chamber side expanded. Therefore, the flow velocity in the common ink chamber 12 becomes extremely large, and a vortex C (FIG. 3A) is generated in the common ink chamber 12.

For this reason, a large pressure loss occurs near the common ink chamber 12, and a large fluid resistance acts on the flow from the pressure generating chamber 4 to the common ink chamber 12. The increase in fluid resistance due to the vortex is caused by the pressure generation chamber 4
The pressure generated in the pressure generating chamber 4 is effectively used for discharging the ink droplet from the nozzle opening 19 because the ink acts to prevent the ink from flowing out to the common ink chamber 12. .

When the drive signal is removed after the ink droplets are formed, the piezoelectric vibration plate 3 returns to the original position, and the pressure generating chamber 4
Expands. As a result, the ink consumed by the formation of the ink droplets is supplied from the common ink chamber 12 to the ink supply port 9.
And flows into the pressure generating chamber 4 via.

When the ink flows from the common ink chamber 12 to the pressure generating chamber 4, the ink is supplied to the common ink chamber 12.
Since the ink flows into the pressure generating chamber 4 while gradually increasing the cross-sectional area of the ink flow by the tapered portion 9a through the straight portion 9b of the ink supply port 9, no vortex is generated in the pressure generating chamber 4. Therefore, the pressure loss caused by the flow of ink from the common ink chamber 12 to the pressure generating chamber 4 is extremely small as compared with the case of ejecting ink droplets, so that the ink flows smoothly into the pressure generating chamber 4 and the meniscus is quickly generated. Then, the time until the ink droplet is ejected can be set shorter.

FIG. 4 shows another embodiment of the present invention. In the drawing, reference numeral 22 denotes a pressure generating chamber 23, a common ink chamber 24, and an ink supply port 25 connecting these. One surface of the spacer is sealed with a first cover plate 27 having a nozzle opening 26, and the other surface is sealed with a second cover plate 29 that can be elastically deformed by a piezoelectric vibrator 28 described later. ing.

The ink supply port 25 is formed by a tapered portion 25a on the pressure generating chamber 23 side and a straight portion 25b connected to the tapered portion 25b and communicating with the common ink chamber 24, as in the embodiment described above. I have.

Reference numeral 28 denotes the above-described piezoelectric vibrator, one end of which is fixed to the base 30, and the second vibrator is vibrated in a longitudinal vibration mode.
Is pressed to expand and contract the pressure generating chamber 23.

In this embodiment, when the piezoelectric vibrator 28 expands, the pressure generating chamber 23 contracts and an ink droplet is ejected from the nozzle opening 26.

At the same time, the ink flows from the pressure generating chamber 23 into the common ink chamber 24 via the ink supply port 25, and in the process, the taper portion 25a is expanded at the pressure generating chamber side.
Flows into the common ink chamber 24 through the thin straight portion 25b while being squeezed.
The flow velocity of the ink inside the ink chamber becomes extremely large, and a vortex C (FIG. 3A) is generated in the common ink chamber 24.
The ink supply port 25 develops a large fluid resistance.

As a result, the pressure in the pressure generating chamber 23 is effectively used for discharging the ink droplet from the nozzle opening 26.

When the piezoelectric vibrator 28 returns to its original position and the pressure generating chamber 23 expands, it flows into the pressure generating chamber 23 from the common ink chamber 24 via the ink supply port 25.

In this case, the ink in the common ink chamber 24 flows from the straight portion 25b of the ink supply port 25 into the pressure generating chamber 23 while expanding the cross-sectional area of the flow via the tapered portion 25a. No vortex is generated in the generation chamber, so that the ink flows smoothly, and the meniscus quickly returns to the original state.

FIG. 5 shows an embodiment of the spacer. In the figure, reference numeral 30 denotes a through hole for forming a common ink chamber, and reference numeral 31 denotes a through hole for forming a pressure generating chamber. The through hole 31 side is expanded so as to connect them, and the through hole 30 side is provided with a groove 32 narrowed by a straight portion. FIG. 6 shows the relationship between the taper angle formed in the ink supply port, the ink discharge amount, and the return time of the meniscus after the ink droplet discharge. The discharge amount of the ink droplet is such that the taper angle is about 50 degrees. In this case, the maximum value is obtained, and the ink discharge amount is larger in the taper angle range of 5 to 60 degrees than in other angles.

The meniscus return time is also the shortest when the taper angle is about 50 degrees. When the taper angle is in the range of 5 to 60 degrees, the meniscus return time is shorter than at other angles.

For these reasons, the taper angle of the tapered portion expanding to the pressure generating chamber formed in the ink supply port is set to 5 to 6
When selected in the range of about 0 degrees, the ink ejection amount is large, and high-speed driving is possible.

FIG. 7 is a sectional view showing the structure near the pressure generating chamber connecting one embodiment of the present invention to one common ink chamber. In the drawing, reference numeral 2 denotes a first cover plate, A driving electrode 5 is formed on a surface of the zirconia thin plate having a thickness of about 10 μm so as to face a pressure generating chamber 4 described later, and a piezoelectric vibration plate 3 made of PZT is fixed thereon.

Reference numeral 7 denotes a spacer which is a zirconia (Z) having a thickness suitable for forming the pressure generating chamber 4, for example, 150 μm.
A pressure generating chamber 4 is formed by forming a through hole in a ceramic plate such as rO2) and sealing both surfaces with a second lid 8 and a first lid 2 described later.

Reference numeral 8 denotes the above-mentioned second cover plate for sealing the other surface of the spacer 7, and a common ink chamber 12 and a pressure generation chamber 4, which will be described later, are provided at one end of the pressure generation chamber 4. 8, a tapered portion 35a that expands toward the common ink chamber,
On the side facing the pressure generating chamber 12, there is provided an ink supply port 35 including a narrowed straight portion 35 b, and on the other end side of the pressure generating chamber 4, a communication hole 10 connected to the nozzle opening 19 is provided. ing.

Reference numeral 11 denotes a common ink chamber constituting plate 13 described later.
A heat-sealing film for joining the second lid plate 8 and
A through hole 14 and a communication hole 10 corresponding to the common ink chamber 12 are provided.

Reference numeral 13 denotes the common ink chamber forming plate described above.
A thickness suitable for forming the common ink chamber 12, for example, 1
A through hole corresponding to the shape of the common ink chamber 12 and a communication hole 16 for connecting a nozzle opening are formed in a corrosion-resistant plate material such as stainless steel or ceramic of 50 μm.

Numeral 18 denotes a nozzle plate. Near one side of the pressure generating chamber 4, a nozzle opening 19 communicating with each pressure generating chamber 4 is provided.
And a common ink chamber forming plate 13 with an adhesive layer 20 such as a heat welding film so that each pressure generating chamber 4 and the nozzle opening 19 communicate with each other through the communication holes 10, 15, 16.
Adhered to.

In this embodiment, when a drive signal is applied to the piezoelectric vibrating plate 3, the first cover plate 2 bends so that the pressure generating chamber 4 side is convex, and the pressure generating chamber 4 is contracted.
As a result, a part of the ink in the pressure generating chamber 4 is
The ink reaches the nozzle opening 19 via the nozzles 15 and 16 and is ejected from the nozzle opening 19 as ink droplets.

When the driving signal is removed after the formation of the ink droplet, the piezoelectric vibration plate 3 returns to the original position, and the pressure generating chamber 4
Expands. As a result, the ink consumed by the formation of the ink droplets is supplied from the common ink chamber 12 to the ink supply port 3.
5 flows into the pressure generating chamber 4.

In the course of the inflow, the common ink chamber 12 flows into the pressure generating chamber 4 through the thin straight portion 35b while being narrowed by the expanded tapered portion 35a in the process. The flow velocity becomes extremely large, and a vortex C (FIG. 9) is generated in the pressure generating chamber 4.

The increase in the fluid resistance caused by the vortex gives resistance to the ink flowing into the pressure generating chamber 4 from the common ink chamber 12. As a result, the meniscus formed in the nozzle opening 19 after the ejection of the ink droplet is largely drawn, and the occurrence of satellites or the like due to unnecessary post-vibration of the piezoelectric vibration plate 3 can be prevented.

Further, the piezoelectric vibrating plate 3 is vibrated greatly to
In the case of an ink jet recording head used by increasing the vibration amplitude of the varnish, this is an effective measure for suppressing post-vibration, and the timing of the next ink droplet ejection becomes easier.

When the meniscus reaches a predetermined position, that is, when it reaches a position suitable for controlling the gradation, when the piezoelectric vibrator 28 expands, the pressure generating chamber 23 contracts and the ink from the nozzle opening 26 passes through the nozzle opening 26. Drops are ejected.

In this embodiment, the description has been given of the laminated ink jet recording head. However, as shown in FIG. 10, the ink supply port 37 in the ink jet recording head using the vertical vibration mode piezoelectric vibrator is connected to the ink supply port 37.
It is apparent that the same operation is achieved even when the common ink chamber 24 is formed by the tapered portion 37a expanding toward the ink chamber 24 and the straight portion 37b connected to the pressure generating chamber 23.

According to the ink supply port having the tapered portion expanding toward the common ink chamber as described above, when the taper angle is set in the range of 5 to 60 degrees as shown in FIG. It has been found that the later vibration of the meniscus increases, and the dynamic characteristics of the meniscus can be easily used positively. In the above-described embodiment, an example in which a piezoelectric vibrator is used as the pressure generating means has been described.However, a heater is provided in the pressure generating chamber, and the ink solvent is instantaneously vaporized by Joule heat. It is apparent that the same effect can be obtained even when the present invention is applied to a bubble jet type recording head that discharges ink droplets.

[0046]

As described above, according to the present invention, the ink supply port exhibits large fluid resistance when ejecting ink droplets, and reduces the fluid resistance when filling the pressure generating chamber with ink. To eject ink droplets with high efficiency,
The meniscus can be quickly returned.

[Brief description of the drawings]

FIG. 1 is a diagram showing one embodiment of an ink jet recording head of the present invention with a cross-sectional structure of a pressure generating chamber.

FIG. 2 is an enlarged sectional view showing an ink supply port.

FIGS. 3A and 3B are diagrams schematically showing the flow of ink near an ink supply port when ejecting ink droplets and when filling a pressure generating chamber with ink, respectively.

FIG. 4 is a sectional view showing another embodiment of the ink jet recording head of the present invention.

FIG. 5 is an enlarged view showing an example of a spacer used in the ink jet recording head in the vicinity of an ink supply port.

FIGS. 6A and 6B are diagrams showing a relationship between a taper angle of a tapered portion formed in an ink supply port, an ink ejection amount, and a meniscus return time.

FIG. 7 is a view showing another embodiment of the ink jet type recording head of the present invention with a sectional structure of a pressure generating chamber.

FIG. 8 is an enlarged sectional view showing an ink supply port in the embodiment.

FIG. 9 is a diagram schematically showing the flow of ink near the ink supply port when filling the pressure generating chamber with ink.

FIG. 10 is a sectional view showing another embodiment of the present invention.

[Explanation of symbols]

 2 First lid plate 3 Piezoelectric vibrating plate 4 Pressure generating chamber 7 Spacer 8 Second lid plate 9 Ink supply port 9a Tapered section 9b Straight section 13 Common ink chamber forming plate 18 Nozzle plate 19 Nozzle opening 35 Ink supply port 35a Tapered part 35b Straight part

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-1-152068 (JP, A) JP-A-4-148936 (JP, A) JP-A-6-286142 (JP, A) JP-A-6-286142 40035 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) B41J 2/045

Claims (8)

(57) [Claims] 1. An ink jet recording head comprising: a pressure generating chamber having a pressure generating means; a common ink chamber receiving ink supplied from an ink tank; and a nozzle opening communicating with the pressure generating chamber. A pressure generating chamber and the common ink chamber are expanded toward the pressure generating chamber, and a large-diameter side is connected to the pressure generating chamber; a tapered portion; one end is continuous with the small-diameter side of the tapered portion; Is connected to the straight section connected to the common ink chamber.
Ink jet recording head are connected by Louis ink supply port. 2. The ink jet recording head according to claim 1, wherein the taper angle of the tapered portion is 5 to 60 degrees. 3. An elastic plate having a piezoelectric vibrating plate on its surface to form a vibrating member, a pressure generating chamber forming member having one surface sealed by the elastic plate to form a pressure generating chamber, A lid member that seals the other of the forming members and has communication holes that communicate with both ends of the pressure generation chamber; a tapered part that expands toward the pressure generation chamber and has a large diameter side connected to the pressure generation chamber When one end continuous with the small-diameter side of the tapered portion, the flow path limiting plate having a straight portion from a Louis ink supply port and the other end is connected to a common ink chamber, said through the ink supply opening pressure A common ink chamber forming plate having the common ink chamber communicating with the generating chamber, and a communication hole communicating with the pressure generating chamber, sealing the other surface of the common ink chamber forming plate, and connecting each of the communication A nozzle connected to the pressure generating chamber through a hole Nozzle plate with Le opening, formed by molding integrally laminated capital to turn each ink jet recording head. 4. An elastic plate having a piezoelectric vibrator on its surface, one surface of which is sealed by the elastic plate to form a common ink chamber and a pressure generating chamber, and expanded to the pressure generating chamber side. and a tapered portion which is the large diameter side connected to the pressure generating chambers, one end continuous with the small-diameter side of the tapered portion, Louis down <br/> click such from the straight portion to which the other end is connected to said common ink chamber A nozzle forming a supply port, a nozzle plate sealing the other surface of the spacer and having a nozzle opening connected to the pressure generating chamber, and are sequentially laminated and integrally molded. . 5. An ink jet type recording head comprising: a pressure generating chamber provided with a pressure generating means; a common ink chamber receiving supply of ink from an ink tank; and a nozzle opening communicating with the pressure generating chamber. A pressure generating chamber and the common ink chamber, a tapered portion that expands toward the common ink chamber and has a large-diameter side connected to the common ink chamber, and one end continuous with the small-diameter side of the tapered portion; ink jet recording head and the other end is connected by the straight portion from a Louis ink supply port that communicates with said pressure generating chamber. 6. The ink jet recording head according to claim 5, wherein the taper portion has a taper angle of 5 to 60 degrees. 7. An elastic plate having a piezoelectric vibrating plate on its surface to form a vibrating member, a pressure generating chamber forming member having one surface sealed by the elastic plate to form a pressure generating chamber, A lid member that seals the other of the forming members and has communication holes communicating with both ends of the pressure generating chamber; a taper that expands to the common ink chamber and has a large-diameter side connected to the common ink chamber; parts and one end continuous with the small-diameter side of the tapered portion, said common ink chamber other end via a Louis ink supply port, such from a straight portion connected to said pressure generating chamber communicating with said pressure generating chamber A common ink chamber forming plate having a communication hole communicating with the pressure generating chamber, and sealing the other surface of the common ink chamber forming plate and connecting to the pressure generating chamber via the communication holes. Nozzle plate with nozzle opening An ink jet recording head formed by molding integrally laminated preparative each in turn. 8. An elastic plate having a piezoelectric vibrator on its surface, one surface of which is sealed by the elastic plate to form a common ink chamber and a pressure generating chamber, and expand toward the common ink chamber. that Do from the tapered portion is larger diameter communicates with said common ink chamber, one end continuous with the small-diameter side of the tapered portion, a straight portion to which the other end is connected to the pressure generating chambers Te
Spacer forming the i ink supply port, a nozzle plate with nozzle openings for connecting to the pressure generating chamber while sealing the other surface of the spacer, the capital of each stacked sequentially inkjet formed by molding integrally Recording head.