JPH08309971A - Ink jet printing head - Google Patents

Abstract

PURPOSE: To provide an ink jet printing head capable of emitting ink droplets in clear multistage capacity under the same drive condition without altering multistage gradation expression, resolving power and the speed of ink droplets. CONSTITUTION: In an ink jet printing head, a plurality of pumping chambers 17 are connected to one nozzle 14 and the side walls constituting the pumping chambers 17 form spriral shapes having the same rotary direction to be connected to a communication hole 12. The ink streams generated by a PZT element receive rotary action by the side walls of the pumping chambers 17 to become vortex streams to flow in the communication hole 12 and ink is emitted from the nozzle 14. Even when ink streams are generated at the same time by a plurality of the pumping chambers, the fluxes of the ink streams donot interfere and offset each other and vortex streams are superposed one upon another in the communication hole 12 to emit large ink droplets from the nozzle 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet printer head used in an ink jet recording apparatus for ejecting ink droplets for printing and recording.

[0002]

2. Description of the Related Art As a conventional inkjet head,
The drop-on-demand method is well known. For example, when piezoelectric ceramics is used as an energy generating element and the volume of the ink flow path is changed by the deformation of the piezoelectric ceramics, the ink in the ink flow path is reduced when the volume decreases. There is a nozzle in which ink is ejected as a droplet from a nozzle and ink is introduced into the groove from an ink inlet when the volume is increased. Then, ink droplets are ejected from a nozzle at a required position in accordance with required print data to form a desired character or image on a paper surface facing the inkjet head.

As an ink jet head of this type,
For example, JP-A-63-247051, JP-A-63-63
There are those described in JP-A-252750 and JP-A-2-150355.

Conventionally, an actuator portion of an ink jet printer head mainly includes a nozzle plate having nozzles for ejecting ink, a cavity plate having an ink cavity forming an ink flow path, and an ink in the ink flow path. It is composed of a drive source such as an energy element for discharging and an ink supply system such as an ink manifold, and each component is assembled by a method such as adhesion. Then, a so-called bubble jet type print head that uses a heating element that is an electro-thermal conversion element as an energy generating element, or a piezo-type print head that uses a piezoelectric element that is an electro-mechanical conversion element as described above is practically used. Has been converted.

Further, the cavity plate having a plurality of concave groove portions serving as individual ink flow paths has been formed by a method such as etching of a metal plate, resin molding, or optical molding of a photosensitive resin. The ink flow path formed by such a method can be accurately formed with uniform dimensions.

[0006]

However, although the conventional ink jet head can eject uniform and stable ink drops, it is difficult to largely change the driving condition in order to change the drop diameter. In particular, it has not been possible to control the drop capacity without changing the ink drop speed to express a clear gradation or change the resolution.

As a method of changing the drop diameter, there is a method of changing the voltage signal supplied to the energy generating element. Specifically, the drop diameter is controlled by changing the magnitude and pulse width of the applied pulse voltage. However, for that purpose, it is necessary to have multiple power supplies, or a power supply with adjustable output,
It has a problem that the circuit configuration and control related to the power source are complicated and the cost is increased.

Further, in Japanese Utility Model Publication No. 54-8747, a plurality of ink flow paths are connected to one ejection hole, and a piezoelectric vibrator is arranged corresponding to each ink flow path to eject ink droplets. A device is disclosed. Ink droplets can be ejected from the ejection holes by superimposing pressure changes from multiple piezoelectric vibrators. Therefore, the size of the ink droplets obtained from the ejection holes can be controlled by adjusting the number of piezoelectric vibrators to be driven. Is said to be possible.

However, in the case where a plurality of ink flow paths are connected to only one ejection hole, such as the above-mentioned ink ejection device, ink droplets ejected when one piezoelectric vibrator is driven. Comparing the capacity of No. 1 with the capacity of the ink droplets ejected when a plurality of piezoelectric elements are simultaneously driven, the ink capacity does not always increase by being multiplied by the number of driven piezoelectric vibrators. . This is because changes in pressure given by the piezoelectric vibrators interfere with each other and are attenuated.

The present invention has been made in order to solve the above-mentioned problems, and a drop-on-demand type ink jet printer which can obtain a discharge characteristic that enables clear gradation expression and resolution change by a flow path configuration. The purpose is to provide a head.

[0011]

In order to achieve this object, an ink jet printer head of the present invention has a nozzle for ejecting ink and an ink filled with ink, which has a communication hole communicating with the nozzle. A cavity and an energy generating element that adds energy for ejecting ink in the ink cavity, and a plurality of the ink cavities are provided to one nozzle through one communication hole. While connected
At least the side wall of the ink cavity near the communication hole is connected to the communication hole while forming a spiral shape having the same rotation direction.

The ink cavity may be connected to the communication hole while forming one side surface of the ink cavity while forming an involute curve.

Two ink cavities are connected to each of the communication holes connected to the nozzles, and the two ink cavities face each other with the communication hole as a center and are offset in opposite directions. And may be connected to the communication hole.

The communicating hole may have a taper shape which gradually becomes thinner toward the nozzle.

[0015]

According to the ink jet printer head of the first aspect of the present invention having the above structure, one ink nozzle is connected to a plurality of ink cavities through one communication hole, and the ink cavity is The side wall at least near the communication hole constituting the above is connected to the communication hole while forming a spiral shape having the same rotation direction. Therefore, the ink flow generated by the energy generating element in the ink cavity is rotated by the side wall to become a vortex flow and flow into the communication hole, and the ink is ejected from the nozzle. Further, even if the ink flows are simultaneously generated from the plurality of ink cavities, the respective flow velocities do not interfere with each other and cancel each other out, and the vortex flows can be superposed in the communication hole to eject a large amount of ink from the nozzle. . As a result, the size of the ink drop ejected from the nozzle is larger than that of a single ink cavity, and it is possible to change the drop speed without changing the drop speed, such as multi-step gradation expression or resolution change. Under the same driving condition, clear multi-stage drop capacities can be discharged.

Further, by imparting rotation to the ink flow flowing from the cavity toward the nozzle, it is possible to prevent the retention of air bubbles, and at the same time, stabilize the ejection direction and ejection characteristics of the drop from the nozzle.

In the ink jet head according to the second aspect, the ink cavity is connected to the communication hole while forming one side surface of the ink cavity with an involute curve. Therefore, the ink flow generated from the energy generating element is guided by the side wall and flows into the communication hole with high efficiency without killing the momentum thereof, and generates a vortex flow having a high rotation speed there. Therefore, it is possible to more strongly prevent the retention of bubbles and stabilize the discharge direction and discharge characteristics of drops from the nozzles with high accuracy.

In the ink jet head according to a third aspect of the present invention, two ink cavities are connected to each communication hole connected to the nozzle, and the two ink cavities face each other with the communication hole as a center, and It is coupled to the communication hole by offsetting them in opposite directions. That is, the most effective arrangement is provided in which the ink flows from the respective ink cavities do not interfere with each other. In addition, when a multi-nozzle is used, the nozzles can be arranged in extremely high density.

In the ink jet head according to the fourth aspect, the communication hole has a taper shape which gradually becomes thinner toward the nozzle. Therefore, the ejection pressure of the ink is gradually increased as the ink proceeds in the nozzle direction, so that a vibrant ink drop can be ejected from the nozzle, and the ejection direction and ejection characteristics of the drop can be stabilized with high accuracy.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 4 shows a main part of an ink jet printer equipped with an ink jet head which is an embodiment of the present invention. A platen 110 in the figure is rotatably attached to a frame 113 by a shaft 112, and is driven by a motor 114. Paper 111 is set on the platen 110, and the inkjet head 10 is provided so as to face the platen 110. The inkjet printer head 10 is mounted on the carriage 118 together with the ink supply device 116. The carriage 118 is slidably supported by two guide rods 120 arranged parallel to the axis of the platen 110, and
A timing belt 124 wound around a pair of pulleys 122 is coupled. And one pulley 12
2 is rotated by the motor 123, and the timing belt 124 is sent, so that the carriage 118 is moved along the platen 110.

FIG. 1 shows a sectional view of an ink jet printer head 10 of an embodiment of the present invention, and FIG. 2 shows a configuration diagram of an ink flow path of a cavity plate 11 of this embodiment. The cavity plate 11 is photosensitive glass, and its thickness is 0.5 to 2 mm. The cavity plate 11 is formed with communication holes 12 connected to the nozzles 14 at predetermined positions by a predetermined number of nozzles. Communication hole 1
In FIG. 2, two ink cavities (pumping chambers 17) for each one are formed at positions facing each other, and the pumping chambers 17 are installed so as to be offset in opposite directions with respect to the communication holes 12. ing. And each pumping chamber 17
At least the side wall near the communication hole 12 constituting the above is connected to the communication hole 12 while forming a spiral shape (clockwise vortex flow in the figure) having the same rotation direction.

Communication hole 12 of the cavity plate 11
, A nozzle plate 13 having a row of nozzles 14 is bonded by an epoxy adhesive, and a vibration plate 15 is also bonded by an epoxy adhesive on the surface of the cavity plate 11 facing the nozzle plate 13. . In addition, the communication holes 12 each have a tapered shape that gradually becomes thinner toward the nozzle 14.

A PZT (lead zirconate titanate) element 16 is also attached by an epoxy adhesive at a position corresponding to the pumping chamber 17 of the diaphragm 15. The material of the cavity plate 11 is not limited to the photosensitive glass, but can be formed by metal etching or ceramics molding.
Further, the adhesive is not limited to the epoxy adhesive, and a silicone adhesive or another adhesive can be used depending on the application.

The ink jet printer head 10 having such a structure has the ink supply pipe 19 and the ink filter.
A head unit is completed by mounting an ink tank (not shown) and an ink tank (not shown). In the ink in the ink tank, dust and bubbles are removed by an ink filter on the way, the ink is guided to the manifold 18 from the ink supply hole 20, and branched into individual pumping chambers 17 to be filled therein.

Next, the operation of the ink jet printer head 10 having the above structure will be described. Printer head 1
In the case of 0, the ink flow generated by the predetermined drive of each PZT element 16 is rotated by the side wall and becomes a vortex flow into the communication hole, and the ink droplets have a predetermined volume / speed. It is uniformly and stably discharged from the nozzle 14. In particular, since the communication hole of this embodiment has a tapered shape in which the communication hole is gradually narrowed toward the nozzle, the ejection pressure of the ink is gradually increased as it progresses in the nozzle direction, so that a vigorous ink drop is achieved. Can be ejected from the nozzle, and the ejection direction and ejection characteristics of the drop can be stabilized with high accuracy.

Further, even if an ink flow is simultaneously generated from the pumping chamber 17 communicated with the same communication hole 12, since the respective ink flows take the same rotation direction at the communication hole 12, the respective ink flows almost interfere with each other. -Large-sized ink can be ejected from the nozzle by superimposing vortexes in the communication holes without canceling each other. At this time, since the driving voltage waveform of the PZT element 16 is constant, the ink drop speed becomes substantially stable regardless of the capacity.

As described above, of the two PZT elements 16 installed on the two pumping chambers 17 connected to one communication hole 12, only one of the two PZT elements 16 is driven by a predetermined pulse voltage waveform or two of them are driven. By selecting whether to drive simultaneously, it is possible to stably change the capacity of the ink drop ejected from the nozzle 14 in two steps. Then, due to the two-step change in ink drop capacity, for example, two-step gradation expression or, for example, 300 dpi and 6
Since the resolution of 00 dpi can be changed, a high-definition print image can be realized, and a high-quality and high-performance printer can be provided.

Further, in the ink jet printer head 10 of the present embodiment, as described above, the two pumping chambers 17 are formed at the positions facing each other with respect to the one communication hole 12, respectively. The communication holes 12 are offset from each other in opposite directions. Therefore, the ink flow generated from one pumping chamber 17 is not disturbed by affecting or being affected by the other pumping chamber 17. Also, each pumping chamber 1
With this arrangement, the nozzles 7 can be arranged with a high density of nozzles as shown in FIG. 2, and it is possible to provide a small head for printing with higher resolution.

Further, in order to improve the above effect, it is preferable that the side surface of the pumping chamber 17 near the communication hole has an involute curve shape. The involute curve is expressed by the following equation (involute function). FIG. 3 shows the shape.

Θ = inv α = tan α + α Although only one pumping chamber 17 is shown in FIG. 3, it is assumed that another pumping chamber 17 is provided on the opposite side in the same shape. With the involute curve shape, the ink flux generated from the pumping chamber 17 efficiently creates a vortex in the communication hole, and the ink is guided particularly to the central portion where the nozzle is provided. Therefore, it is possible to more strongly prevent the retention of bubbles and stabilize the discharge direction and discharge characteristics of drops from the nozzles with high accuracy.

The present invention is not limited to the structures shown in the above embodiments, and various modifications can be made without departing from the spirit of the invention. For example, although two pumping chambers 17 are communicated with one communication hole 12 in the above-described embodiment, three or more pumping chambers are communicated with one communication hole 12. Good.

Further, the ink jet printer head 10 according to the present invention has the PZT element 1 exemplified in the above embodiment.
Ink jet printer head of so-called bubble jet type that ejects ink by using the electro-thermal conversion element is not limited to the one that ejects ink by using the modification of 6. Further, the ink jet printer head is not limited to the drop-on-demand type ejection type, and may be a continuous jet type ejection type.

[0034]

As is apparent from the above description, according to the ink jet printer head of the present invention, in addition to the conventional method of forming an ink flow path by a member having high rigidity, a plurality of inks are formed for one nozzle. The cavity has a structure in which it is connected through one communication hole, and further, at least a side wall of the ink cavity near the communication hole is
Each of them is connected to the communication hole while forming a spiral shape having the same rotation direction. As a result, the plurality of ink flow paths do not interfere with each other due to their driving, and
For example, a clear multi-stage drop capacity can be ejected under the same driving condition without changing the drop speed, such as multi-stage gradation expression or changing the resolution between 300 dpi and 600 dpi.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an inkjet printer head according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of an ink flow path of a cavity plate according to an embodiment of the present invention.

FIG. 3 is an enlarged view of an essential part near a communication hole of a cavity plate according to another embodiment of the present invention.

FIG. 4 is a perspective view showing a main part of an inkjet printer equipped with an inkjet printer head according to an embodiment of the present invention.

[Explanation of symbols]

 10 inkjet printer head 11 cavity plate 12 communication hole 13 nozzle plate 14 nozzle 15 diaphragm 16 PZT element 17 pumping chamber

Claims (4)

[Claims] 1. A nozzle for ejecting ink, an ink cavity having a communication hole communicating with the nozzle and filled with ink, and energy for adding energy for ejecting ink in the ink cavity. In an inkjet printer head including a generating element, a plurality of the ink cavities are connected to one nozzle via one communication hole, and at least a side wall of the ink cavity near the communication hole is formed. An ink jet printer head, wherein the ink jet printer head is connected to the communication hole while forming a spiral shape having the same rotation direction. 2. The ink jet printer head according to claim 1, wherein the ink cavity is connected to the communication hole while forming one side surface of the ink cavity while forming an involute curve. 3. Two ink cavities are connected to each of the communication holes connected to a nozzle, and the two ink cavities are opposed to each other with the communication hole as a center and offset in opposite directions. The ink jet printer head according to claim 1, wherein the ink jet printer head is connected to the communication hole. 4. The communication hole has a taper shape that gradually becomes thinner toward the nozzle.
4. The inkjet printer head according to any one of items 1 to 3.