JP2002273882A - Ink jet printing head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink jet printing head which can prevent the throughput of a printer from decreasing and can reduce an amount of ink to be wasted as much as possible by efficiently removing bubbles which affect printing among bubbles. SOLUTION: The ink jet printing head 42Y is provided with a plurality of discharge energy generating elements, ink discharge openings 13, a substrate 10 with ink supply ports 11, a common liquid chamber 17 communicating with the ink supply ports 11, an ink supply channel 3 for supplying ink from an ink supply source by communicating with the common liquid chamber 17, a discharge opening plate 12 provided with the ink discharge openings 13, and ink channels 18 formed between the substrate 10 and the discharge opening plate 12 by joining the substrate 10 and the discharge opening plate 12. The ink supply channel 3 is made to communicate horizontally or upwardly with the common liquid chamber 17.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an ink jet print head used in an ink jet recording system for ejecting ink droplets and recording on a recording medium.

[0002]

2. Description of the Related Art An ink discharge method using an ink jet recording method which is widely and widely used today includes a method using an electrothermal conversion element (heater) as a discharge energy generating element used for discharging ink droplets. There is a method using a piezoelectric element (piezo), and any of these methods can control the ejection of ink droplets by an electric signal. For example, the principle of an ink droplet discharging method using an electrothermal conversion element is that an ink near an electrothermal conversion element is instantaneously boiled by giving an electric signal to the electrothermal conversion element, and is caused by a phase change of the ink at that time. Ink droplets are ejected at high speed by rapid growth of bubbles.

On the other hand, the principle of a method of ejecting ink droplets using a piezoelectric element is that the piezoelectric element is displaced by applying an electric signal to the piezoelectric element, and the ink droplet is ejected by the pressure at the time of this displacement.

In particular, in an ink droplet discharging method using an electrothermal transducer, it is relatively easy to increase the discharge density of ink droplets, and it is most suitable for a printer for high-density printing of small droplets. At present, printers using an ink jet print head according to these methods are increasingly used. In these printers, residual bubbles generated in the head due to printing or other causes have an adverse effect on ink droplet ejection characteristics and images. Therefore, bubbles are periodically removed by a suction operation of the printer body.

FIG. 6 shows a conventional example of an ink jet print head.

[0006] In the ink jet print head shown in FIG.
The ejection energy generating elements arranged in rows and the ink supply ports 11 which are 0.155 mm × 11 mm through holes extending along the arrangement direction are formed. The plate 14 joined to the upper portion of the substrate 10 in the drawing has an ink supply channel 15 having a through hole having a diameter of 1 mm, and supplies ink to a common liquid chamber 17 formed by the ink supply port 11.

[0007] A metal mesh filter 16 is welded to the other end of the ink supply channel 3, and an ink tank 21 as an ink supply source is directly connected to the metal mesh filter 16. A discharge port plate 12 bonded to a lower portion of the substrate 10 in the figure has a discharge port 13 having a diameter φ
And an ink flow path 18 communicating the discharge port 13 and the common liquid chamber 17.

When a desired electric pulse is applied to an energy generating element (not shown), ink droplets are ejected from the ejection port 13. Bubbles B generated at the top of the common liquid chamber 17 due to repetition of ejection, intake of air at the time of standing, inflow from the ink tank, and the like are brought into close contact with the cap member 19 to the ejection port plate 12 to perform a suction operation. Is discharged from the discharge port 13.

[0009]

However, in the above-mentioned prior art, in order to remove the generated bubbles, the suction of the bubbles is frequently performed by pumping from the discharge port. Naturally, printing cannot be performed at the time of pumping, which greatly affects the throughput of the printer. At the same time, the ink is also sucked and wasted. Therefore, it is preferable that the number of times of pumping be small.

As a method of reducing the number of times of pumping, a method of enlarging the common liquid chamber to reduce the influence of bubbles accumulated in the upper part of the common liquid chamber is considered.

However, in this case, there is a problem in that the bubbles accumulated in the upper portion of the common liquid chamber cannot be removed well at the time of suction, and the effect is small because the amount of waste ink is rather increased.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to efficiently remove bubbles which have a bad influence on printing among bubbles generated by printing or other causes even in a relatively large common liquid chamber. An object of the present invention is to provide an ink jet print head which can reduce the amount of wasted ink as much as possible without lowering the throughput of the printer by removing the ink well.

[0013]

To achieve the above object, the present invention provides a plurality of ejection energy generating elements for generating energy used for ejecting ink droplets,
A substrate having an ink discharge port for discharging ink droplets, an ink supply port including a plurality of discharge energy generating elements arranged in a row, and a through-hole extending along an arrangement direction of the discharge energy generating elements; A common liquid chamber that communicates with the ink supply port, an ink supply channel that communicates with the common liquid chamber to supply ink from an ink supply source, an ejection port plate including the ink ejection port, the substrate and the ejection port. In an ink jet print head having an ink flow path between a substrate and a discharge port plate to which an outlet plate is joined, the ink supply flow path is horizontally or upwardly communicated with the common liquid chamber.

[0014]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 5 is a cutaway perspective view of an ink jet printer having an ink jet print head according to the present invention.

The ink jet printer shown in FIG.
A transport device 30 intermittently transporting a sheet 28 as a recording medium provided in the casing 38 along the longitudinal direction in the direction of arrow C in the drawing, and a transport direction of the sheet 28 by the transport device 30 (direction of arrow C). The recording unit 40 is configured to include a recording unit 40 that is reciprocated in a direction parallel to the orthogonal direction, and a recording unit movement driving unit 36 as a driving unit that reciprocates the recording unit 40.

The transfer device 30 includes a pair of roller units 22a and 22b, which are arranged in parallel and opposed to each other, a pair of roller units 24a and 24b, and a drive unit 20 for driving these. Thereby, the driving unit 2
When 0 is in the operating state, the sheet 28 is nipped and conveyed by the respective roller units 24a and 4b in the direction of arrow C in FIG.

The movement drive unit 36 is provided with pulleys 26a, 26b disposed on rotating shafts opposed to each other at a predetermined interval.
Belt 46 wound around the roller unit 22
a and a guide shaft 44 arranged in parallel to 22b to guide the movement of the carriage member 40a of the recording unit 40 in parallel.
And a motor 4 for driving a belt 46 connected to a carriage member 40a in the recording unit 40 in a forward direction and a reverse direction.
8 is included.

When the motor 48 is activated and the belt 46 is rotated in the direction of arrow S in FIG. 5, the carriage member 40a of the recording unit 40 moves by a predetermined amount in the same direction. Is activated, and the belt 46 rotates in the direction opposite to the direction of the arrow S in FIG. 5, the carriage member 40a of the recording unit 40 moves by a predetermined amount in the direction opposite to the direction of the arrow S in FIG.

Further, at one end of the movement driving unit 36, a recovery unit 26 for performing the discharge recovery processing of the recording unit 40 at a position to be the home position of the carriage member 40a faces the ink discharge port arrangement of the recording unit 40. It is provided.

In the recording section 40, ink tanks 21Y and 21 which supply inks of respective colors to ink jet print heads 42Y, 42M, 42C and 42B, respectively.
M, 21C, and 21B are the carriage members 40 of the recording unit 40.
It is provided detachably with respect to a. Here, an ink tank directly attached to the head is shown, but ink may be supplied from an ink tank placed at another location by a tube or the like.

The ink-jet print heads 42Y, 4
Since 2M, 42C, and 42B have the same structure, only the inkjet print head 42Y will be described below, and description of the other inkjet print heads 42M, 42C, and 42B will be omitted.

FIG. 1 is a configuration diagram of an ink jet print head 42Y according to the present invention.

The substrate 10 of the ink jet print head 42Y shown in FIG.
The ejection energy generating elements arranged in rows and the ink supply ports 11 which are 0.155 mm × 11 mm through holes extending along the arrangement direction are formed.

Plate 1 bonded to upper part of substrate 10 in the figure
4, a 1.0 mm × 12.5 mm slit-shaped opening is opened, and the sub ink tank 1 joined to the upper part of the plate 14 in the drawing has a width of 1.8 mm × length 12.5 mm ×
There is a space of 3.5 mm in height, and the ink supply port 1
1 together form a common liquid chamber 17.

The discharge port plate 12 joined to the lower part of the substrate 10 in the drawing has a discharge port 13 having a diameter of 21 μm and a discharge port 13 and a common liquid chamber 17 communicating with each other on a discharge energy generating element (not shown). An ink flow path 18 is formed.
The water-repellent layer 2 is provided on the surface (the lower part in the figure) of the discharge port plate 12. The sub-ink tank 1 stores ink from the ink tank 21Y, which is an ink supply source, in the common liquid chamber 17.
And a metal mesh filter 16 is welded to an end of the ink supply passage 3 which is in contact with the ink tank 21Y. At the junction between the ink supply channel 3 and the common liquid chamber 17, the ink supply channel 3 is in continuous contact with the ceiling 15 of the common liquid chamber 17 at an elevation angle θ = about 30 degrees. Here, the ceiling 15 is formed of a three-dimensional curved surface, and is smoothly connected to the side wall of the common liquid chamber 17.

Hereinafter, a method of filling the ink will be described.

As shown in FIG. 3A, in the initial state, the common liquid chamber 17 in the ink jet print head 42Y is filled with about 0.06 cc of ink, and the upper part of the common liquid chamber 17 is filled with about 0.06 cc. 0.02 cc of gas G is present. The gas G includes air, water vapor, vapor of a solvent component in the ink, and the like.

By repeating printing with the printer, bubbles are generated and float (see FIGS. 3B and 4) and accumulate in the upper portion of the common liquid chamber 17. The cause of the bubble generation is that the dissolved air and water in the ink and the solvent component in the ink are turned into gas by heat. At this time, the gas G in the upper portion of the common liquid chamber 17 is sufficiently separated from the ink supply port 11, so that there is no significant adverse effect on printing, such as discharge failure. Conversely, the presence of the bubbles has the effect of absorbing the vibration caused by the ejection of the ink inside the common liquid chamber 17, which may rather improve the print quality.

By continuing printing, the common liquid chamber 1
7, the gas G in the upper part increases, and most of the common liquid chamber 17 is
(See FIG. 3C). In this case, the ink flowing out of the ink supply flow path 3 into the common liquid chamber 17 flows from the junction to the bottom and is supplied to the ink supply port 11 even in the full discharge state where the flow rate is maximum. If the number of bubbles increases to this point, there is a concern that printing will be adversely affected. Accordingly, the bubbles in the common liquid chamber 17 are reduced by periodically performing suction from the discharge port 13 with the recovery unit 26.

When the carriage member 40a is at the home position, the recovery unit 26 closely contacts the ejection port plate 12 of the ink jet print head 42Y to generate a negative pressure, thereby sucking ink from the ejection ports 13. At this time, the ink flow rate is much larger (10 times or more) than the maximum flow rate at the time of ejection. It flows along the wall (see FIG. 3D). The ink flowing along the wall of the ceiling 15 of the common liquid chamber 17 is supplied to the ink supply passage 3 of the common liquid chamber 17.
The common liquid chamber 17 is filled with ink from the opposite side of the joint. At this time, the ink moves in a lump at this magnitude of the flow without being scattered due to surface tension. Further, a part of the bubbles in the common liquid chamber 17 is simultaneously sucked and discharged from the discharge port 13 (see FIG. 3E).

After suction for a certain period of time, the flow of ink in the common liquid chamber 17 is in a steady state (see FIG. 3 (f)), so that the suction recovery operation is completed and the initial state shown in FIG. 3 (a) is reached. .
Since the ink flows along the ceiling 15 of the common liquid chamber 17,
It is possible to reduce the amount of gas G remaining in the common liquid chamber 17.

Even if there is no ink in the common liquid chamber 17 of the ink jet print head 42Y for some reason, it is possible to shift to the initial state of FIG. 3A by the above-mentioned recovery suction operation.

In the embodiment described above, by making the ceiling 15 of the common liquid chamber 17 more hydrophilic than the side wall, the ink can flow more stably along the ceiling 15.

Second Embodiment Next, a second embodiment of the present invention will be described.

FIG. 2 is a configuration diagram of an ink jet print head 42Y according to a second embodiment of the present invention. The difference between the ink jet print head 42Y of the first embodiment and the ink jet print head 42Y of the first embodiment is that the ink supply flow is different. The third embodiment is basically the same as the first embodiment except that the passage 3 is joined to the ceiling 15 of the common liquid chamber 17 in the horizontal direction.

In the first and second embodiments described above, the ink supply passage 3 is connected so as to be in contact with the ceiling 15 of the common liquid chamber 17, but it is not always necessary to be in contact. However, in this case, in order to form an ink flow toward the upper part of the common liquid chamber 15, a strong suction recovery force for forming a faster ink flow is required.

[0038]

As is apparent from the above description, according to the present invention, it is possible to efficiently remove bubbles which are generated by printing or the like and which have an adverse effect on printing accumulated in a common liquid chamber without requiring complicated operations. Thus, an effect is obtained that the throughput of the printer is not reduced and the amount of waste ink can be reduced as much as possible.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an inkjet print head according to Embodiment 1 of the present invention.

FIG. 2 is a configuration diagram of an inkjet print head according to Embodiment 2 of the present invention.

FIG. 3 is a cross-sectional view illustrating an ink filling method.

FIG. 4 is a partial cross-sectional view of the inkjet print head according to the present invention.

FIG. 5 is a cutaway perspective view of an ink jet printer including the ink jet print head according to the present invention.

FIG. 6 is a configuration diagram of a conventional inkjet print head.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Sub-ink tank 2 Water-repellent layer 3 Ink drawing path 16 Filter 10 Substrate 11 Ink supply port 12 Discharge port plate 13 Discharge port 14 Plate 17 Common liquid chamber 18 Ink flow path 19 Cap member 21Y Ink tank

Claims (2)

[Claims] A plurality of ejection energy generating elements for generating energy used for ejecting ink droplets;
A substrate having an ink discharge port for discharging ink droplets, an ink supply port including a plurality of discharge energy generating elements arranged in a row, and a through-hole extending along an arrangement direction of the discharge energy generating elements; A common liquid chamber communicating with the ink supply port, an ink supply channel communicating with the common liquid chamber to supply ink from an ink supply source, an ejection port plate including the ink ejection port, the substrate and the ejection port An ink jet print head having an ink flow path between a substrate and a discharge port plate to which an outlet plate is joined, wherein the ink supply flow path is horizontally or upwardly communicated with the common liquid chamber. Print head. 2. The ink jet print head according to claim 1, wherein the ink supply flow path communicates with a direction in contact with a ceiling of the common liquid chamber.