JPH05131645A - Ink jet recording head - Google Patents

Abstract

PURPOSE:To obtain a highly reliable ink jet recording head capable of stably emitting ink by preventing the obstruction and stop of the supply of ink due to the air bubble trapped by the ink filter of the ink jet recording head. CONSTITUTION:An ink jet recording head constituted of nozzles 1, ink passages 2, a common ink chamber 10, an ink supply pipe 15 and the filter part communicating with them and the filter part consists of an ink filter 21, a filter ink chamber 22 and an ink stirring member (turbine) 23.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording apparatus, and more particularly to a head structure of the ink jet recording apparatus.

[0002]

2. Description of the Related Art Conventionally, as this type of technology, Japanese Patent Laid-Open No. 1-3 has been used.
Some were disclosed in No. 06257. In order to prevent the bubbles in the supplied ink from being trapped in the ink filtering filter section and blocking the flow of the ink, the bubble discharging channel and the filter are separately provided from the ink filtering filter. It was installed in.

[0003]

However, in the above-mentioned prior art, although the total area of the filter for ink filtration must be increased, the mesh size does not change when the area of the filter is increased. The number of (numerical aperture) increases. Since the force required to discharge the bubbles is the sum of the surface tensions of the meshes, the force required to discharge the bubbles increases as the number of meshes increases. Therefore, when the size of the filter is increased, large bubbles corresponding to the size of the filter are trapped in the filter due to the surface tension of the ink, which eventually hinders the flow of the supplied ink. If the flow of ink is obstructed, the supply of ink will be insufficient or will be stopped in the ink flow path, and stable ink ejection will not be possible or ink will not be ejected at all, resulting in defective operation of the head. And printing is impossible.

Further, even if the air bubbles do not obstruct the flow of the supplied ink initially, the air bubbles remain in the head in the above-mentioned conventional technique. This is because the flow of ink around the bubbles becomes a laminar flow and a large force does not act on the bubbles. In such a case, the laminar flow of the ink causes the bubbles to exist rather stably. It never passes through the filter and is discharged. Using these residual bubbles as nuclei, the minute dissolved gas in the ink and the evaporation of the ink,
Bubbles grow over time due to permeation of gas from the outside of the head, eventually obstructing the flow of the supplied ink.

In any case, when the air bubbles trapped in the filter block the flow of the supplied ink, stable ink ejection becomes impossible. Furthermore, if the ink supply is stopped, the ink ejection itself becomes impossible. These have a problem that printing reliability such as dot omission or printing becomes impossible and the reliability of the inkjet recording apparatus is significantly lowered.

Further, the above-mentioned prior art also has problems that the manufacturing of the ink jet recording head becomes difficult and the size of the apparatus is increased due to the complicated structure.

The present invention has been made to solve these problems, and it is an object of the present invention to prevent air bubbles in the supplied ink from being trapped by the ink filtering filter section and obstructing the flow of the supplied ink. To do so. Another object of the present invention is to obtain a highly reliable, small-sized and easy-to-manufacture inkjet recording head by making it possible to discharge trapped air bubbles to the outside of the head and to perform stable ink ejection for a long period of time. ..

[0008]

In an ink jet recording apparatus for recording information by ejecting ink droplets serving as a unit of a pixel, a nozzle, an ink channel communicating with the nozzle, and a common channel communicating with the channel. An ink chamber, a filter section that communicates with the common ink chamber, and an ink supply pipe that is provided at a position that communicates with the filter section and that supplies ink, and the filter section includes an ink filtration filter and a filter ink chamber. , And an ink stirring member installed upstream of the ink filtering filter upstream of the ink supply side. Further, the ink stirring member is a turbine.

[0009]

According to the above configuration of the present invention, the ink flow in the filter ink chamber caused by the pressurization of the ink from the supply tube to the ink jet recording head and the suction operation of the ink from the nozzle causes the ink flow in the front stage of the filter for ink filtration. Turbulence and wake flow are generated by the ink stirring member. The turbulent flow or wake of the ink generated in the filter ink chamber is blocked by the ink filtering filter, and the air bubbles stored in the filter ink chamber are agitated, divided, crushed, and dissolved. Since the number of meshes of the filter in contact with the finely divided bubbles is small, the total surface tension is small and it is possible to pass through the filter with a slight force. Will be able to pass through. Further, air bubbles crushed smaller than the mesh size of the filter and air bubbles dissolved in the ink can pass through the filter without any drag. Eventually, due to the pressurization / suction operation of the ink for the ink jet recording head, all the air bubbles that are blocked by the filter and stored in the filter ink chamber pass through the filter and are discharged to the outside of the head.

Further, the ink stirring member is a turbine (impeller).
In the case of, the turbine in the filter ink chamber is rotated by the flow of ink in the filter ink chamber caused by the pressurization / suction operation of the ink for the ink jet recording head, and turbulent flow of ink, wake flow / vortex is generated, and In addition to agitating, fragmenting, crushing, and dissolving the air bubbles that are blocked by the filtration filter and stored in the filter ink chamber, the turbine itself mechanically agitates, divides, crushes, and dissolves the air bubbles. Similar to the above, all the bubbles accumulated in the filter ink chamber pass through the filter and are discharged to the outside of the head.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. In all the drawings, the same reference numerals indicate the same components.

FIG. 1 is a schematic perspective view showing the construction of an embodiment of an ink jet recording head of the present invention. Also, in FIG.
It is a sectional view showing a section composition of an example of an ink jet recording head. Reference numeral 1 denotes a nozzle, 1a denotes a nozzle surface, and in this embodiment, nine nozzles 1 are provided on the nozzle surface 1a at equal intervals. Reference numeral 2 is an ink flow path, and 4 is a supply port, which is provided in a plurality of grooves corresponding to the nozzle 1. A common ink chamber 10 is connected to the ink flow path 2 through the supply port 4 in common.
Reference numeral 2a is a part of the ink flow path 2 and is a pressure chamber. Reference numeral 2b is a dummy flow path for discharging bubbles provided one above and one below the ink flow path 2. Reference numeral 5 denotes a substrate on which the nozzle 1, the ink flow path 2, the supply port 4, and the common ink chamber 10 are integrally formed. 6 is a second substrate (not shown in FIG. 1)
Then, the ink is sealed in the nozzle 1, the ink flow path 2, the supply port 4, and the common ink chamber 10 by being bonded to the substrate 5 to form an inkjet head. 3 is a piezoelectric element, and pressure chamber 2
It is provided on the surface of the second substrate 6 on a through a conductive member such as a metal thin film. 7 is an FPC, which is electrically connected to the piezoelectric element 3,
It is for applying a control voltage pulse. Reference numeral 100 is an ink droplet ejected from the nozzle 1.

The ink flow path 2 and the common ink chamber 10 are always filled with ink, and the piezoelectric element 3 is used.
Is bent in the direction in which a voltage is applied to retain the electric charge and remove the ink in the pressure chamber 2a. When the voltage of the piezoelectric element 3 is released and the electric charge is discharged according to a constant time constant, the piezoelectric element 3 returns to its original state, the volume of the pressure chamber 2a increases, and the pressure changes to a negative pressure. Ink is supplied by being supplied from the supply port 4. When voltage is applied to the piezoelectric element 3 again when the pressure chamber 2a is filled with ink to hold the charge, the piezoelectric element 3 bends in the direction of removing the ink in the pressure chamber 2a, and the ink is ejected from the nozzle 1. A drop 100 is ejected. The ejected ink droplets 100 reach a printing medium such as a paper surface and penetrate or adhere to the printing medium to print dots as pixels. In this embodiment, a piezoelectric element is used as a drive element of an inkjet recording head, but in the present invention, a heating resistor may be used as a drive element without any problem in the configuration, action and effect of the present invention.

In order to stably eject the ink droplet 100 during printing, the ejection speed of the ink droplet 100 needs to be fast to some extent. Therefore, in this embodiment of the present invention, the nozzle 1
The opening shape is a substantially rectangular shape with a length of 30 μm and a width of 70 μm, and has a shape dimension that is smaller than the sectional shape of the ink flow path 2.

Reference numeral 10a is an ink supply passage, and 15 is an ink supply pipe. Further, 21 is a filter for ink filtration, and 2
Reference numeral 2 is a filter ink chamber, and 23 is a turbine which is an ink stirring member. The ink supply pipe 15 communicates with the filter ink chamber 22, and the filter ink chamber 22 communicates with the ink supply passage 10 a and the common ink chamber 10 sequentially through the filter 21. The ink is supplied from the ink supply pipe 15, flows into the filter ink chamber 22, is filtered by the filter 21, and then is supplied to the common ink chamber 10 via the ink supply path 10a.

The supplied ink contains dust that is mixed in during the manufacture of the ink, deposits that are deposited from the ink during storage in the ink tank or ink cartridge, and foreign substances that are separated from the ink piping parts and are mixed in the ink. Be done. Filter 2
No. 1 secures the reliability of the inkjet recording head so that these minute foreign substances are removed and the nozzles 1 and the like are not clogged and ink droplet ejection failure does not occur. The filter 21 is made of polyamide resin, stainless steel or the like and has a mesh structure. The filter 21 is made of a material that is not corroded by the ink used and does not change the physical properties of the ink. Fineness, or the size of the mesh). In this embodiment, the filter 21 is made up of fibers having a diameter of 30 microns and the opening is set to 25 microns with respect to the depth of the nozzle 1 of 30 microns. Therefore, foreign matters contained in the supplied ink and clogged the nozzles 1 etc. are filtered by the filter 21.
Since it does not enter after that, the nozzle 1 is not clogged and the reliability of the head is secured.

On the other hand, however, since the filter 21 does not catch and pass not only minute foreign matter but also bubbles contained in the supplied ink, bubbles are accumulated in the filter ink chamber 22. (Bubbles are trapped by the filter 21.) When the bubbles are accumulated, they cover the entire surface of the filter 21 and hinder or stop the ink supply. Therefore, in this embodiment of the present invention, the turbine 23 is installed in the filter ink chamber 22 as an ink stirring member. The turbine 23 is made of a material that does not corrode the ink used and does not change the physical properties of the ink, and is made of a resin such as polyamide, polycarbonate, or polysulfone that is injection-molded.

An ink flow from the supply pipe 15 passing through the filter ink chamber 22 and the filter 21 caused by the pressurizing and discharging operation of the ink from the supply pipe 15 or the suction and discharge operation of the ink from the nozzle 1 is an ink stirring member. And collide with the turbine 23 to generate a turbulent flow, and a wake and a vortex are generated behind the turbine 23. The ink in the filter ink chamber 22 is agitated by these. When the ink in the filter ink chamber 22 is agitated, the air bubbles trapped and integrated in the filter 21 are agitated / divided / crushed / dissolved, pass through the filter 21, and pass through the common ink chamber 10 and the ink flow path 2. Alternatively, it is discharged to the outside of the head through the dummy flow path 2b and the nozzle 1.

Further, the ink supply pipe 15 is provided at a position eccentric with respect to the rotation center of the turbine 23, and the turbine 23 is guided along the inner wall of the filter ink chamber 22 and is rotatably held. The ink flow generated by the pressure / suction operation rotates in the direction of arrow A. The ink in the filter ink chamber 22 is agitated by the rotation of the turbine 23, and at the same time, the air bubbles trapped in the filter ink chamber 22 and integrated are mechanically divided and pulverized by the turbine 23, and a part thereof. Dissolves in the ink. This allows bubbles to pass through the filter 21 more easily.

The turbine 23 does not rotate during the printing operation because the ink flow rate per unit time is extremely small as compared with the pressurization or suction operation. As a result, during the printing operation, the bubbles that have inadvertently flowed into the filter ink chamber 22 during the printing operation do not flow to the ink flow path side, nor do large pressure fluctuations that affect ink ejection occur. Therefore, the turbine 23 has no influence on the printing quality and the printing operation during the printing operation, and a stable and good printing result can be obtained.

By the action of these turbines 23, all the bubbles in the filter ink chamber 22 are discharged or dissolved and disappeared, the flow of the ink is not blocked or stopped, and the bubble nuclei that cause bubble growth disappear. Ink can be ejected stably over a long period of time, and the reliability of the inkjet recording head is ensured.

In this embodiment, the nozzle 1, the ink flow path 2, the common ink chamber 10, the filter ink chamber 22, the ink supply pipe 15 and the like are integrally formed on the substrate 5. Further, after the turbine 23 is temporarily installed in the filter ink chamber 22, the filter 21 is fused to the substrate 5 by ultrasonic waves or heat, and the turbine 23 is rotatably installed in the filter ink chamber 22. The filter portion may be provided separately, but by integrally forming the filter portion as described above, the inkjet recording head can be easily manufactured in a large amount with stable quality. In addition, the inkjet recording head can be downsized.

Reference numeral 31 shown by a chain line in the drawing is an ink supply joint, 33 is an ink supply tube, and 32 is an O-ring. The ink supply joint 31 is fitted to the ink supply pipe 15 via an O-ring 32, and supplies ink to the ink supply pipe 15 without leaking from the ink supply tube 33. Further, 35 is a portion near the nozzle of the head case, and 34 is a nozzle packing. Since the head case 35 covers the nozzle portion of the substrate 5 while pressing the nozzle packing 34, the ink on the nozzle surface does not enter the outer peripheral portion of the head, and a suction cap (not shown) is applied to the head case 35. Air does not leak from the gap between the substrate 5 and the head case 5 even when they come into contact with each other and perform a suction operation with a suction pump or the like. With these configurations, the ink sealing around the head is surely performed, so that the ink is guided to the head at the initial stage or when the ink tank / ink cartridge is replaced, or at the time of sudden ink ejection failure, and bubbles are discharged. It is possible to perform pressure supply and pressure discharge by a pressure pump (not shown) or the like from the ink supply pipe 15 for this purpose, and suction supply and suction discharge from the nozzle 1.

FIG. 3 is a cross-sectional view of the vicinity of the filter section showing another embodiment of the present invention. The flow channel configuration and the like are the same as those in the above-described embodiment, but the configuration of the filter section is different. Reference numeral 24 denotes a screw which is an ink stirring member attached to the inner wall of the ink supply pipe 15. An ink flow is generated in the filter ink chamber 22 by the pressurization / suction operation by the pump outside the head, but the screw 24 causes the ink flow to form a vortex as shown by the arrow B and agitates the bubbles stored in the filter ink chamber 22.・ Crush, divide, and dissolve. Bubbles crushed, divided, and dissolved by the screw 24 can pass through the filter 22, so that the bubbles in the filter ink chamber 22 can be finally discharged. Even if the filter portion is configured in this way, the same effect as that of the above-described embodiment can be obtained.

FIG. 4 is a cross-sectional view of the vicinity of the filter section showing still another embodiment of the present invention. The flow channel configuration and the like are the same as those in the above-described embodiment, but the configuration of the filter section is different. Reference numeral 25 is a plate which is an ink stirring member. The filter ink chamber 2 is operated by pressurization / suction operation by a pump outside the head.
The ink flow generated in 2 flows by the plate 25 as shown by an arrow C, and a wake is generated. Bubbles stored in the filter ink chamber 22 are stirred, crushed, divided, and dissolved by this wake.
The flow of ink generated by the plate 25 crushes and
Since the divided / dissolved bubbles can pass through the filter 22, the bubbles in the filter ink chamber 22 can be eventually discharged. Even if the filter portion is configured in this way, the same effect as that of the above-described embodiment can be obtained.

FIG. 5 is a cross-sectional view of the vicinity of the filter section showing still another embodiment of the present invention. The flow channel configuration and the like are the same as those in the above-described embodiment, but the configuration of the filter section is different. Reference numeral 26 is a ball which is an ink stirring member, and has a large number of concave dimples on the surface. By the pressurization / suction operation by the pump outside the head, the ink flow generated in the filter ink chamber 22 collides with the ball 26 and flows as shown by an arrow D, and is separated by the dimple of the ball 26 to generate a turbulent flow. Due to this turbulent flow, the air bubbles stored in the filter ink chamber 22 are stirred, crushed, divided, and dissolved. Further, due to this turbulent flow, the ball 26 causes an irregular movement in the filter ink chamber 22.
The air bubbles are mechanically agitated by the balls 26 as well. Since the flow of ink generated by the balls 26 and the bubbles crushed, divided, and dissolved by the balls 26 can pass through the filter 22, the bubbles in the filter ink chamber 22 can be eventually discharged. Even if the filter portion is configured in this way, the same effect as that of the above-described embodiment can be obtained.

FIG. 6 is a schematic perspective view showing the structure of another embodiment of the present invention. The configuration in the vicinity of the filter portion is almost the same as that of the embodiment shown in FIG. Reference numeral 50 is a substrate on which a heating resistor and a circuit that conducts to the heating resistor are formed, and 51 is an orifice which is a nozzle. A common ink chamber 52 communicates with the above-mentioned orifice 51 and the flow path to supply ink.
Reference numeral 53 is an orifice plate, which is an orifice 51, a flow path,
The common ink chamber 52 and the like are formed in a groove shape, and the substrate 50
The ink is sealed by forming a head by being bonded to. In the ink jet head of the present embodiment, a voltage pulse is applied to the heating resistor on the surface of the substrate 50 on the lower surface of the ink flow path to generate heat to expand and evaporate the ink in the ink flow path to generate pressure. , Ink drop 1
00 is discharged from the orifice 51 for printing.

The common ink chamber 52 communicates with the filter chamber 22 and the ink supply pipe 15 via the filter 15, and ink is supplied by these. Similar to the above-described embodiment, even if the driving method of the head is changed, the ink in the filter ink chamber 22 of the turbine 23, which is the ink agitating member of the filter unit, is agitated and the air bubbles stored in the filter ink chamber 22 are agitated. The effects of dividing, crushing, and dissolving and passing through the filter 22 and the effect of ensuring stable ink ejection are the same.

[0029]

As described above, according to the present invention, even if the air bubbles in the supplied ink are trapped in the ink filtration filter, the air bubbles are agitated / divided / crushed / dissolved by the ink agitation member. When the air bubbles are divided, the area of the air bubbles contacting the ink filtration filter becomes smaller, so that the force required for the air bubbles to pass through the ink filtration filter, that is, the total surface tension becomes smaller. On the contrary, since the surface area of the bubble with respect to the volume increases due to the division, the ratio of the pressure that the bubble receives from the ink increases. Therefore, the bubbles easily pass through the ink filtering filter and are discharged to the outside of the head. The bubbles trapped and stored by these do not hinder or stop the ink supply. In addition, since the accumulated bubbles are completely discharged to the outside of the head by the return operation by the pressurization or suction of the head, the residual bubbles do not grow as nuclei, so that the ink supply is not obstructed or stopped in the long term. A smooth and stable ink supply can be performed. As a result, stable ink ejection is ensured for a long period of time, and a highly reliable inkjet recording head can be obtained.

Further, since it is not necessary to provide a separate filter portion for discharging bubbles, the number of constituent parts can be reduced and the structure can be achieved. Therefore, there is an effect that an ink jet recording head which is small and easy to manufacture can be obtained.

[Brief description of drawings]

FIG. 1 is a perspective view showing the configuration of an embodiment of the present invention.

FIG. 2 is a sectional view showing the configuration of an embodiment of the present invention.

FIG. 3 is a sectional view of the vicinity of a filter section showing the configuration of another embodiment of the present invention.

FIG. 4 is a sectional view of the vicinity of a filter section showing the configuration of still another embodiment of the present invention.

FIG. 5 is a cross-sectional view of the vicinity of a filter section showing the configuration of still another embodiment of the present invention.

FIG. 6 is a perspective view showing the configuration of another embodiment of the present invention.

[Explanation of symbols]

 1 Nozzle 2 Ink flow path 10 Common ink chamber 15 Ink supply pipe 21 Filter 22 Filter ink chamber 23 Ink stirring member (turbine)

Claims (2)

[Claims] 1. An ink jet recording apparatus for recording information by ejecting ink droplets as a unit of a pixel, a nozzle, an ink channel communicating with the nozzle, and a common ink chamber communicating with the channel. The filter unit communicates with the common ink chamber, and an ink supply pipe that is provided at a position communicating with the filter unit and supplies ink. The filter unit includes an ink filtration filter, a filter ink chamber, and an ink supply side. An ink jet recording head comprising an ink stirring member installed upstream of the upstream ink filtering filter. 2. The ink jet recording head according to claim 1, wherein the ink stirring member is a turbine.