JPH08174824A - Ink-jet type recording head - Google Patents

Abstract

PURPOSE: To improve the energy efficiency at the time of ink spouting and quickly restore meniscus. CONSTITUTION: An ink-jet type recording head is provided with a pressure generating chamber 4 with a pressure generator 3, a common ink chamber 12 where ink is supplied from an ink tank, and a nozzle opening 19 that communicates with the pressure generating chamber 4. The pressure generating chamber 4 and the common ink chamber 12 are connected by an ink feed port 9 consisting of a tapered part that expands toward the pressure generating chamber 4 side and a straight part. When ink flows out from the ink feed port 9 to the common ink chamber 12, relatively high fluid resistance occurs because eddies arise in the common ink chamber 23, causing an increase in pressure loss. When ink flows into the pressure chamber 4 from the common ink chamber 12, eddies do not arise because ink flows smoothly along the tapered part, so that ink flows into the pressure generating chamber 4 quickly with a low fluid resistance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides a pressure generating means in a pressure generating chamber which communicates with a common ink chamber and a nozzle opening through an ink supply port, and supplies ink from the common ink chamber. The present invention relates to an inkjet recording head that ejects droplets onto a recording medium.

[0002]

2. Description of the Related Art For example, as disclosed in Japanese Patent Laid-Open No. 6-40035, a piezoelectric vibrating plate is attached to a partial area of an elastic plate that constitutes a pressure generating chamber, and the piezoelectric vibrating plate is flexibly displaced. The ink jet recording head that generates ink droplets by changing the volume of the pressure chamber is capable of displacing a large area of the pressure generating chamber, and thus has the characteristic that ink droplets can be generated stably. There is. In such a recording head, since the pressure generating chamber and the common ink chamber communicate with each other through the ink supply port formed by the pores, the pressure in the pressure generating chamber generated by the piezoelectric vibrating plate is In order to effectively use the ink for discharging from the nozzle opening, it is necessary to reduce the amount of return from the ink supply port to the pressure generating chamber. Since it is also necessary to quickly fill the pressure generating chamber with ink from the ink chamber to 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 improve energy efficiency during 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 lowered. On the contrary, if the ink supply port is widened in order to increase the meniscus return speed, the utilization rate of the energy in the pressure generating chamber for ejecting ink droplets will decrease, and the flow path resistance of the ink supply port will increase. That is, the driving frequency and the energy efficiency are in conflict with each other.

On the other hand, in order to improve the printing speed and to express the gradation in such a recording head, the dynamic characteristic of the meniscus, that is, the vibration amplitude of the meniscus generated after ink droplet ejection is increased, and 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 the pressure generating chamber for ink ejection, and further after ink ejection. It is an object of the present invention to provide a novel ink jet recording head capable of promptly flowing ink from a common ink chamber into a pressure generating chamber.

A second object of the present invention is to make the vibration amplitude of the meniscus in the vicinity of the nozzle opening after ink droplet ejection as large as possible so that the dynamic characteristic of the meniscus can be positively utilized. An object is to provide an ink jet recording head.

[0007]

In order to solve such a problem, in the present invention, a pressure generating chamber having a pressure generating means, a common ink chamber for receiving ink from an ink tank, 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 have a fluid resistance with respect to a flow from the common ink chamber to the pressure generating chamber, The connection is made by an ink supply port having a fluid resistance having a direction in which the fluid resistance to the flow from the pressure generating chamber side to the common ink chamber side becomes large.

[0008]

When a pressure is applied to the pressure generating chamber to eject the ink droplet, a part of the ink in the pressure generating chamber is ejected as an ink droplet from the nozzle opening, and a part of the ink is ejected 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 generating chamber side to the common ink chamber, the pressure in the pressure generating chamber is effectively used for ejecting ink droplets. On the other hand, when the ink flows from the common ink chamber into the pressure generating chamber due to the expansion of the pressure generating chamber after the ink is ejected, the fluid resistance decreases, so that the ink is rapidly supplied to the pressure generating chamber and the meniscus drops into 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 the structure in the vicinity of a pressure generating chamber that is connected to one common ink chamber according to an embodiment of the present invention. In the figure, reference numeral 2 is a first cover plate and has a thickness of 1
It is composed of a thin plate of zirconia with a thickness of about 0 μm, and the driving electrode 5 is provided on the surface thereof so as to face the pressure generating chamber 4 described later.
And a piezoelectric vibrating plate 3 made of PZT is fixed thereon.

A spacer 7 is a zirconia (Z) having a thickness suitable for forming the pressure generating chamber 4, for example, 150 μm.
The 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 which seals the other surface of the spacer 7, and one end of the pressure generating chamber 4 is connected to a common ink chamber 12 and a pressure generating chamber 4 which will be described later. A supply port 9 is provided, and a communication hole 10 connected to the nozzle opening 19 is provided on the other end side of the pressure generating chamber 4.

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

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

Reference numeral 13 denotes the above-mentioned common ink chamber forming plate,
A thickness suitable for forming the common ink chamber 12, for example, 1
A plate member having corrosion resistance such as 50 μm of stainless steel or ceramic is provided with a through hole corresponding to the shape of the common ink chamber 12 and a communication hole 16 for connecting the nozzle opening.

Reference numeral 18 is 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 the pressure generating chambers 4 and the nozzle openings 19 are communicated 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 connected to the communication hole 10,
It reaches the nozzle opening 19 via 15 and 16 and is ejected from there as an ink droplet.

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 portion 9b is narrowed down by the taper portion 9a on the pressure generating chamber side. Since it flows through to the common ink chamber 12, the flow velocity in the common ink chamber 12 becomes extremely high, and a vortex C (FIG. 3A) is generated in the common ink chamber 12.

Therefore, a large pressure loss occurs in the vicinity of the common ink chamber 12, and a large fluid resistance acts on the outflow from the pressure generating chamber 4 to the common ink chamber 12. The increase in fluid resistance caused by this vortex is due to the pressure generation chamber 4
Since it acts so as to block the ink that is about to flow out from the nozzle to the common ink chamber 12, the pressure generated in the pressure generating chamber 4 is effectively used for ejecting the ink droplet from the nozzle opening 19. .

When the drive signal is removed after ink droplet formation, the piezoelectric vibrating plate 3 returns to its 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
Through the pressure generating chamber 4.

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 through the straight portion 9b of the ink supply port 9 by the taper portion 9a while being gradually expanded, no vortex is generated in the pressure generating chamber 4. Therefore, the pressure loss due to the flow of ink from the common ink chamber 12 to the pressure generating chamber 4 becomes extremely smaller than that in the case of ejecting ink droplets, the ink smoothly flows into the pressure generating chamber 4, and the meniscus quickly forms It is possible to return to the original state and to shorten the time until the next ink droplet ejection.

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

The ink supply port 25 is formed of the taper portion 25a which expands on the side of the pressure generating chamber 23 and the straight portion 25b which is connected to the taper portion 25a and communicates with the common ink chamber 24 as in the above-described embodiment. There is.

Reference numeral 28 denotes the above-mentioned piezoelectric vibrator, one end of which is fixed to the base 30 and which is moved by the vibration in the longitudinal vibration mode to the second position.
The cover plate 29 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 ink droplets are ejected from the nozzle openings 26.

At the same time, 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 where the pressure generating chamber side is expanded.
Since it flows into the common ink chamber 24 through the thin straight portion 25b while being squeezed by the common ink chamber 24,
The flow velocity of the ink in the inside becomes extremely high, 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 ejecting ink droplets from the nozzle openings 26.

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

In this case, since the ink in the common ink chamber 24 flows into the pressure generating chamber 23 from the straight portion 25b of the ink supply port 25 via the taper portion 25a while the flow cross-sectional area is enlarged, Vortices are not generated in the generation chamber, and therefore the ink smoothly flows in, and the meniscus is quickly returned to the original state.

FIG. 5 shows an embodiment of the spacer. In the figure, reference numeral 30 is a through hole forming a common ink chamber, and reference numeral 31 is a through hole forming a pressure generating chamber. The through hole 31 side is widened so that these can communicate with each other, 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 at the ink supply port, the ink ejection amount, and the meniscus return time after ink droplet ejection. The ink droplet ejection amount has a taper angle of about 50 degrees. In this case, the maximum value is obtained, and the ink ejection amount is larger in the taper angle range of 5 to 60 degrees than in other angles.

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

From the above, the taper angle of the taper portion that expands into the pressure generating chamber formed in the ink supply port is 5 to 6
When selected in the range of about 0 degree, a large amount of ink is ejected and high speed driving becomes possible.

FIG. 7 is a cross-sectional view showing the structure in the vicinity of the pressure generating chamber for connecting one embodiment of the present invention to one common ink chamber, in which reference numeral 2 is a first cover plate, It is composed of a thin plate of zirconia with a thickness of about 10 μm, a drive electrode 5 is formed on the surface thereof so as to face a pressure generating chamber 4 described later, and a piezoelectric vibrating plate 3 made of PZT is fixed thereon.

A spacer 7 is a zirconia (Z) having a thickness suitable for forming the pressure generating chamber 4, for example, 150 μm.
The 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 lid plate that seals the other surface of the spacer 7, and a common ink chamber 12 and a pressure generating chamber 4 which will be described later are provided on one end side of the pressure generating chamber 4. 8, a taper portion 35a that expands toward the common ink chamber side,
An ink supply port 35 including a narrowed straight portion 35b is provided on the side facing the pressure generating chamber 12, and a communication hole 10 connected to the nozzle opening 19 is provided on the other end side of the pressure generating chamber 4. ing.

Reference numeral 11 denotes a common ink chamber constituent plate 13 which will be described later.
A heat-welding film for joining the second lid plate 8 and
A communication hole 14 and a communication hole 10 that correspond to the common ink chamber 12 are provided.

Reference numeral 13 denotes the above-mentioned common ink chamber forming plate,
A thickness suitable for forming the common ink chamber 12, for example, 1
A plate member having corrosion resistance such as 50 μm of stainless steel or ceramic is provided with a through hole corresponding to the shape of the common ink chamber 12 and a communication hole 16 for connecting the nozzle opening.

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 the pressure generating chambers 4 and the nozzle openings 19 are communicated 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 lid 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 connected to the communication hole 10,
It reaches the nozzle opening 19 via 15 and 16 and is ejected from there as an ink droplet.

When the drive signal is removed after ink droplet formation, the piezoelectric vibrating plate 3 returns to its 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
It flows into the pressure generation chamber 4 via 5.

During this inflow process, the common ink chamber 12 side flows into the pressure generating chamber 4 through the thin straight portion 35b while being squeezed by the widened tapered portion 35a in the process, so that the pressure in the pressure generating chamber 4 is increased. The flow velocity becomes extremely high, and the 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 that is about to flow into the pressure generating chamber 4 from the common ink chamber 12. As a result, the meniscus formed in the nozzle opening 19 after ejecting the ink droplets is largely drawn in, and the ejection failure such as satellite due to unnecessary post-vibration of the piezoelectric vibrating plate 3 is not concerned.

Further, the vibration amplitude of the meniscus becomes large, and particularly in the case of an ink jet recording head in which the piezoelectric vibrating plate 3 is oscillated and vibrated greatly, it becomes an effective measure for suppressing the post vibration, and the ejection of the next ink droplet is suppressed. It becomes easier to take timing.

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

Although the laminated type ink jet recording head has been described in this embodiment, the ink supply port 37 in the ink jet recording head using the longitudinal vibration mode piezoelectric vibrator as shown in FIG.
It is apparent that the same effect can be obtained even if the taper portion 37a that expands to the common ink chamber 24 side and the straight portion 37b that connects to the pressure generating chamber 23 are configured.

According to the ink supply port having the taper portion which expands to the common ink chamber side as described above, the ink droplet is ejected when the taper angle is set in the range of 5 to 60 degrees as shown in FIG. It was found that the vibration of the meniscus afterward became large and the dynamic characteristics of the meniscus could be positively utilized. In the above-mentioned embodiments, the example in which the piezoelectric vibrator is used as the pressure generating means has been described, but a heater is provided in the pressure generating chamber to instantly vaporize the ink solvent by Joule heat, and the pressure at this time is It is obvious that the same effect can be obtained even when applied to a bubble jet recording head that ejects ink droplets.

[0046]

As described above, in the present invention,
In an ink jet recording head having a pressure generating chamber provided with 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, an ink common to the pressure generating chamber Ink having a fluid resistance having a direction in which the fluid resistance to the flow from the pressure generation chamber side to the common ink chamber side is larger than the fluid resistance to the flow from the common ink chamber to the pressure generation chamber Since the ink supply port is connected, the ink supply port exhibits a large fluid resistance when ejecting ink droplets, and when the pressure generating chamber is filled with ink, the fluid resistance is reduced to eject ink droplets with high efficiency. At the same time, the meniscus can be quickly restored.

[Brief description of drawings]

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

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

3A and 3B are diagrams schematically showing the ink flow in the vicinity of the ink supply port when ejecting an ink droplet and when filling the 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 the vicinity of an ink supply port of an embodiment of a spacer used in the ink jet recording head.

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

FIG. 7 is a diagram showing another embodiment of the ink jet 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 above embodiment.

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

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

[Explanation of symbols]

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

Claims (10)

[Claims] 1. An ink jet recording head comprising: a pressure generating chamber having a pressure generating means; a common ink chamber for receiving ink from an ink tank; and a nozzle opening communicating with the pressure generating chamber. The pressure generation chamber and the common ink chamber have a fluid resistance with respect to the flow from the pressure generation chamber side to the common ink chamber side that is greater than a fluid resistance with respect to the flow from the common ink chamber to the pressure generation chamber. An ink jet recording head connected by an ink supply port having a fluid resistance having a large directionality. 2. The ink jet recording head according to claim 1, wherein the ink supply port is formed of a taper portion and a straight portion which expand toward the pressure generating chamber. 3. The ink jet recording head according to claim 2, wherein the taper angle of the taper portion is 5 to 60 degrees. 4. 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, and the pressure generating chamber. A lid member that seals the other of the forming members and that has a communication hole that communicates at both ends of the pressure generation chamber, and a flow path restriction that has an ink supply port that has a tapered portion that expands to the pressure generation chamber side. A common ink chamber forming plate including a plate, a common ink chamber communicating with the pressure generating chamber via the ink supply port, and a communication hole communicating with the pressure generating chamber, and a common ink chamber forming plate An ink jet recording head comprising: a nozzle plate having a nozzle opening that seals the other surface and is connected to the pressure generating chamber through each of the communication holes; 5. An elastic plate on the surface of which the piezoelectric vibrator contacts, one side of which is sealed by the elastic plate to form a common ink chamber and pressure generating chamber, and expands to the pressure generating chamber side. A spacer that forms an ink supply port that connects the common ink chamber and the pressure generating chamber, a nozzle plate that seals the other surface of the spacer, and has a nozzle opening that is connected to the pressure generating chamber. An inkjet recording head that is laminated in order and integrally molded. 6. An ink jet recording head comprising a pressure generating chamber having a pressure generating means, a common ink chamber for receiving ink from an ink tank, and a nozzle opening communicating with the pressure generating chamber, The pressure generation chamber and the common ink chamber have a fluid resistance with respect to the flow from the common ink chamber to the pressure generation chamber, rather than a fluid resistance with respect to the flow from the pressure generation chamber side to the common ink chamber side. An ink jet recording head connected by an ink supply port having a fluid resistance having a large directionality. 7. The ink jet recording head according to claim 6, wherein the ink supply port is formed of a taper portion and a straight portion that widen toward the common ink chamber side. 8. The ink jet recording head according to claim 7, wherein the taper angle of the taper portion is 5 to 60 degrees. 9. 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, and the pressure generating chamber. A lid member that seals the other of the forming members and that has a communication hole that communicates at both ends of the pressure generating chamber, and a flow path that has an ink supply port that has a tapered portion that expands to the common ink chamber side. A common ink chamber forming plate having a limiting plate, a common ink chamber communicating with the pressure generating chamber via the ink supply port, and a communication hole communicating with the pressure generating chamber, the common ink chamber forming plate And a nozzle plate having a nozzle opening that seals the other surface and is connected to the pressure generating chamber through each of the communication holes. 10. An elastic plate on the surface of which a piezoelectric vibrator abuts, one side of which is sealed by the elastic plate to form a common ink chamber and a pressure generating chamber, and to expand to the common ink chamber side. A spacer that forms an ink supply port that connects the common ink chamber and the pressure generating chamber, and a nozzle plate that includes a nozzle opening that seals the other surface of the spacer and that is connected to the pressure generating chamber. An inkjet recording head that is laminated in order and integrally molded.