JP3244941B2 - Ink tank - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink tank used in an ink jet recording apparatus for supplying ink to a recording head and recording on a recording medium.

[0002]

2. Description of the Related Art An ink jet recording apparatus is configured to supply ink to a recording head fixedly mounted on a carriage via a tube which is turned around in the apparatus. There is an ink tank that employs a detachable ink tank configuration, or an ink tank that is integrally formed with a print head and that is detachable from a carriage.

The former employs a form in which ink is supplied by providing a head difference to a recording head.
In the latter case, a negative pressure source is provided on the ink tank side to supply ink to the recording head.

[0004] In recent years, from the viewpoint of downsizing of the apparatus and easiness of maintenance, many apparatuses using the latter type of ink tank have been proposed.

[0005] It is required that such an ink tank be able to satisfactorily supply ink corresponding to the amount of ink ejected from the recording head during recording, and that there be no leakage of ink from the ejection port during non-recording. Is done.

[0006] An example of such an ink tank is a cartridge in which a recording head and an ink tank are integrated and can be detachably mounted on a carriage. The ink tank is filled with a foam material (absorber). Have been. By filling the ink tank with the absorber in this manner, it is possible to maintain a stable ink meniscus at the ink ejection portion of the recording head, and to hold the ink in the ink tank by the capillary force of the absorber. I have. In this case, it is necessary that the ink tank is almost completely filled with the absorber, and by holding the ink amount slightly smaller than the maximum ink amount that the absorber can hold, the capillary force is reduced. Since the internal negative pressure is generated by using this, even when mechanical shock such as vibration or thermal shock such as temperature change is applied to the print head and ink tank, the print head ejection part and air communication part of the ink tank The ink can be stably held with little leakage of ink from the ink.

However, in the method in which the ink tank is entirely filled with the absorber, the negative pressure of the absorber increases with the consumption of ink, and the amount of ink remaining in the ink tank without being supplied to the recording head is increased. There was a problem that efficiency was poor.

[0008] The absorber contained in this type of ink tank includes, for example, a foam made of urethane resin. Here, a film is formed such that the urethane foam includes a hollow portion (pore) when the urethane foam is formed. If such a large number of pores are separated from each other by the membrane, the function as the ink impregnating absorber cannot be achieved as it is, so that a film removal treatment such as heating and washing is performed.

When the urethane foam subjected to the film removal treatment as described above is used as an absorber in an ink tank, the urethane foam may be stored in a compressed state with respect to the storage space of the ink tank, or may be connected to the ink outlet portion. The portion may be compressed to provide an appropriate negative pressure gradient at the communication with the member. However, it is extremely difficult to completely remove the film even by the film removal treatment, and in fact, film residues are considerably attached to the pores. Therefore, when the absorber is compressed, the residue of the membrane complements between the adjacent pores, hindering the flow of ink in the absorber that should be generated with the consumption of ink, and improving the ink supply to the outside of the ink tank. A problem that causes trouble occurs.

If these foams such as urethane resin are immersed in the ink for a long period of time, the solute of the foam components in the ink will deteriorate the urethane resin itself and change the physical properties of the ink. There are also problems such as hindrance to stable supply of ink to the recording head and deterioration of print quality.

Japanese Patent Application Laid-Open No. 2-258353 discloses an example of a structure for solving the above-mentioned various problems in an ink tank constituted by filling an absorber into the ink tank.
The configuration of an ink tank disclosed in Japanese Patent Application Laid-Open Publication No. H10-26095 is cited.

As schematically shown in FIGS. 7, 8A and 8B, the liquid ink is directly filled in the ink tank container without filling the ink tank with the absorber. . That is, as shown in FIG. 7, FIG. 8A, and FIG. 8B, the configuration of the ink tank in which the liquid ink is directly filled into the ink tank is the same as that of the ink jet printing apparatus 110 having the ink storage 112 and the print head 130. Orifice 1 as first pressure control means for restricting the negative pressure of ink reservoir 112 to a part of cylindrical portion 128 connecting reservoir 112 and print head 130
And a bag 126 as second pressure control means for limiting the negative pressure in the ink reservoir 112 by further changing the volume. In addition, inkjet
The printing apparatus 110 further has an opening 142 serving as an ink filling port and a plug 144 inserted and sealed in the opening at the upper part thereof, and an overflow reservoir 138 and an overflow reservoir 138 for storing the ink overflowing from the orifice 136 outside the orifice 136. 138 communicates with the atmosphere.

With this configuration, when ink is ejected from the print head 130 and ink is consumed from the ink reservoir 112, the pressure of the ink reservoir 112 is reduced while the meniscus formed in the orifice 136 is maintained.
As a result, a suitable negative pressure can be applied to the print head 130. Further, the ink discharge continues, and the negative pressure in the ink reservoir 112 increases. When the threshold value is exceeded, the meniscus of the orifice 136 is broken, and air is introduced from the meniscus into the ink reservoir 112 to return to a preferable negative pressure range. . This is repeated, and good ejection of ink is executed.

[0014]

[SUMMARY OF THE INVENTION Incidentally, when measuring the change of the negative pressure in the ink tank configuration in which only the orifice 136 is a first negative pressure control means shown in FIG. 7,
The negative pressure indicated by the solid line A in FIG.
It turned out that 30 was given. That is, an excessive negative pressure (peak value) is applied to the print head 130 in the initial stage of the use disclosure of the ink, and in the vicinity of this peak value, the ink supply to the print head 130 is insufficient and the ejection is unstable. , Causing print blurring.

Further, depending on the diameter of the orifice 136, the ink in the ink reservoir 112 leaks out of the orifice 136 due to the weight of the ink, so that a negative pressure cannot be generated. In our experiments, the inner diameter of the orifice 136 was 0.38 mm, and the surface tension was 30 dyne / cm and 40 dyne / c.
When ink of 50 m / dyne / cm was used and the liquid level was raised up to 40 mm from the print head 130, the ink leaked from the orifice.

When the diameter of the orifice 136 is further reduced (for example, 0.2 m) so as to prevent ink leakage.
Below m, this configuration tends to further increase the peak value. The peak value can be suppressed by providing the bag 126 in a part of the ink reservoir 112. The bag 126 is configured to have a restoring force in the direction of increasing the volume of the ink storage 112 or to be urged by a spring member in that direction. Therefore, this bag 126
As a result, the initial negative pressure peak is eliminated, and the broken line B in FIG.
The negative pressure has a behavior as indicated by.

However, in the ink tank having such a configuration, it is necessary to design the diameter of the orifice 136 and the restoring force of the bag 126 in accordance with the ink to be used. Also tend to be expensive.

The present invention solves the above-mentioned various problems,
An object of the present invention is to provide an ink tank capable of obtaining high-quality printing due to good ink supply and obtaining high reliability capable of maintaining a stable negative pressure with a simple configuration.

[0019]

SUMMARY OF THE INVENTION The present inventors have made intensive studies to achieve the above-mentioned object, and as a result, the configuration of the meniscus forming portion for adjusting the negative pressure in the ink tank causes a negative pressure peak. We came to the knowledge that there was.

The present invention has been made on the basis of the above findings, and has an ink storage section for storing ink, an ink supply section for supplying ink to a recording head section, and an atmosphere having one end for taking air into the ink storage section. A hollow thin tube that opens out of the ink storage section as a communication port and the other end opens into the ink storage section near the bottom of the tank, the ink being different from the atmosphere communication port.
Arranged for the opening configured to communicate outside the storage section,
Only in the direction from the inside of the ink storage unit to the outside,
Equipped with a valve body that allows movement and a gas-permeable membrane having water repellency
Further comprising an alleviating means for storing ink in the capillary.
By forming a meniscus at the end opened in the part,
While maintaining the negative pressure in the ink storage unit,
The method is characterized in that a rise in internal pressure in the ink storage section is reduced in steps.

According to the above arrangement, the air intermittently flows into the ink tank from the opening in the ink tank as the ink in the ink tank is consumed. At this time, due to the pressure reduction of the air portion formed by the inflow of air due to ink consumption and the meniscus force of the air at the opening, the ink tank moves the ink into the ink supply portion or the ink ejection port of the recording head portion. A negative pressure is generated in the direction of drawing. As a result, an appropriate negative pressure is applied to the recording head, so that not only stable supply of ink but also good print quality can be obtained.

Further, the negative pressure remains even after the ink consumption is interrupted, and the leakage of the ink from the recording head can be prevented.

[0023]

Further, since means is provided for alleviating an increase in the internal pressure of the ink tank so as to sufficiently cope with a case where the volume of the air portion is increased or decreased due to environmental changes.
The negative pressure is favorably maintained without the inside of the ink tank being pressurized.

[0025]

Here, in the present invention, the meniscus M is formed at the opening 5 (hole 5) at the tip of the hollow thin tube 4. The behavior of this meniscus is shown in FIGS. 11a and 11b. FIG. 11A shows a state at the initial stage of ink ejection. The meniscus M is formed inside the thin tube 4.

As the ink is consumed from this state, the ink level in the thin tube 4 reaches the position shown in FIG. When the ink is further consumed and the decompression of the air portion 8 in the ink tank is increased, the meniscus M is broken and the atmosphere is taken into the ink tank, and the inside of the tank is maintained at a desired decompression range, and an abnormal decompression state is caused. prevent.

On the other hand, the behavior of the meniscus M of the orifice 136 in the ink tank disclosed in JP-A-2-258353 disclosed in the prior art is shown in FIGS.
b, shown in FIG. 12c. In this configuration, the orifice 1
The upper part 136b and the lower part 136a of the members constituting 36
A meniscus M occurs at the two positions. Thus, in the early stage of meniscus M ink consumption, the orifice 1
36, and is formed at the upper portion 136b of the orifice 136 as the ink is consumed. As described above, the meniscus M is generated at two points above and below the orifice 136, and thus a peak value is generated in the negative pressure in the ink tank.

[0029]

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

FIG. 1 is a premise of the ink tank of the present invention.
It is sectional drawing showing an example of a structure .

The ink tank 1 has a supply section 2 for supplying ink to the recording head section RH and an atmosphere communication port 3 through which the atmosphere flows into the ink tank 1. The other portions of the ink tank 1 are isolated from the outside air. The thin tube 4 is hollow, and has one end above the liquid level of the stored ink and the air communication port 3.
The other end is a hole 5 that opens into the ink tank near the bottom in the ink tank 3. Further, a gas permeable membrane 6 having a water-repellent side surface facing at least the inside of the tank is disposed in the atmosphere communication port 3.

According to the above configuration, air flows intermittently into the ink tank 1 from the hole 5 as the ink 7 in the ink tank 1 is consumed. At this time, due to the pressure reduction of the air portion 8 due to ink consumption and the meniscus force of the air in the hole 5, the ink tank 1 causes the ink ejection port of the recording head portion RH to draw the ink 7 into the ink tank 1 in a negative direction. Generate pressure. As a result, an appropriate negative pressure acts on the recording head, so that not only stable supply of ink but also good print quality can be obtained.

Further, the negative pressure remains even after the ink consumption is interrupted, and the leakage of the ink from the recording head RH can be prevented.

Further, the gas permeable membrane 6 is provided so that the ink does not splash out of the air communication port 3 when the ink tank is vibrated while being carried.

Using an ink having a surface tension of 48 dyne / cm, an ink tank having an inner diameter of the hole 5 of 0.38 mm was manufactured by using polypropylene for the material of the thin tube 4 and the hole 5, and a supply section of the ink tank 1 was manufactured. The negative pressure at 2 was measured. Negative pressure in the print, respectively -48mmH ₂ O holding negative pressure in the still state, was negative pressure of about -42mmH ₂ O. Table 1 shows negative pressures when inks of other compositions having different surface tensions (surface tensions of 30 dyn / cm and 40 dyne / cm) were used in this system.

[0036]

[Table 1]

The same negative pressure can be obtained for inks of other compositions by changing the inner diameter and material of the hole 5. For example, for ink having a low surface tension, the inner diameter of the hole 5 is reduced.

According to the experiment, these negative pressures showed almost constant values from the initial stage to immediately before use up as shown in FIG. 10 irrespective of the liquid level of the ink. Also, no excessive negative pressure value was generated in the initial stage of use. In other words, it provides a substantially constant and stable print quality from the beginning to just before the end of use.

Even when ink enters the thin tube 4 during distribution, a negative pressure is generated as soon as the ink in the thin tube 4 is completely absorbed by the recovery pump when the printer is installed in the ink tank ( FIG. 1 ) . In the premise configuration shown in FIG .
9cc, pump capacity 1.3cc).

As the gas permeable membrane of the present example, a material made of polytetrafluoroethylene, which was stretched to form countless micropores, and further subjected to an oil-repellent treatment was used. In addition, a gas permeable membrane having a pore size of 0.1 μm to 3.0 μm was used.

Further, as for the positional relationship between the ink supply section 2 and the hole 5 of the thin tube 4, as shown in FIGS. This is because a meniscus can be effectively formed even when the ink tank is inclined to the posture as shown in FIGS. 13B and 14. 13A, when the supply unit 2 is tilted so that the supply unit 2 is at the bottom and the hole 5 is at the top, the air part 8 in the tank and the atmosphere outside the tank are directly communicated through the hole 5. For example, if the ink discharge port of the head section (usually has a size that does not leak ink due to meniscus force) comes into contact with paper etc. and the soniscus is broken, the ink discharge port of the head section Leaks. However, if the hole 5 and the ink supply unit 2 are arranged as shown in FIGS. 1 and 14, the ink is not supplied to the air unit 8 even if the meniscus of the discharge port is torn as shown in FIG. Will not leak out.

Embodiment 1 FIG. 2 is a sectional view showing a first embodiment of the present invention.

In the first embodiment, the principle of generation of a negative pressure on the recording head is the same as the above-described premise , but in order to obtain higher reliability, the inside of the ink tank 1 is provided with a means for alleviating the rise in pressure. A flexible bag 9 is arranged. The bag 9 communicates with the atmosphere at the opening 10 and is otherwise sealed. In the initial state, the bag 9 is arranged so as to be inflated to its maximum volume. Even if the pressure in the ink tank becomes low with respect to the atmosphere, the bag 9 does not inflate any further. Does not affect negative pressure. On the other hand, when the surrounding environment of the ink tank 1 changes, for example, when the ink tank 1 is placed under a reduced pressure environment for distribution or when the surrounding environmental temperature rises due to heat radiation inside the printer, the air unit The expansion of the air 8 is absorbed by the volume shrinkage of the bag 9 to mitigate an increase in the tank internal pressure and prevent ink from leaking from the recording head. When the environment returns to the original state, the volume of the bag 9 also returns to the initial maximum inflated state, and does not affect the negative pressure on the recording head unit thereafter.

During distribution (a considerably severe environmental change is conceivable), air may flow into the ink tank 1 from the thin tube 4 due to shocks such as vibrations, and the maximum inflated state of the bag 9 may not be secured in the initial state. Therefore, it is preferable that the air communication port 3 and the upper opening of the gas permeable membrane 6 be sealed with tape or the like during distribution, that is, until the printer is mounted.

Embodiment 2 FIG. 3 is a sectional view showing a second embodiment of the present invention.

In this embodiment, instead of the flexible bag of the first embodiment, at least one valve body 11 and at least one ink inner surface are formed of a water-repellent material as means for reducing the internal pressure. The gas permeable membrane 12 is provided.

The valve element 12 allows only the direction of the arrow in the figure, that is, the direction in which the internal air is discharged from the inside of the ink tank 1 to the outside. Normally, since the valve element 11 is closed, it does not affect the generation of negative pressure in the thin tube 4. On the other hand, when the environment around the ink tank 1 changes, for example, when the ink tank 1 is placed under a reduced pressure environment for distribution or when the surrounding environmental temperature rises due to heat radiation inside the printer,
By discharging the expansion of the air in the air section 8 from the valve body 11, an increase in the tank internal pressure is mitigated, and leakage of ink from the recording head section is prevented. Then, when the environment returns to the original state, the air is replenished from the contraction tube 4 of the air in the air section 8, so that the subsequent negative pressure on the recording head section is not affected.

FIGS. 4 and 6 show specific examples of the structure of the valve element 12. FIG.

FIG. 4 is a sectional view showing an example of the valve element 12.

A circular opening 16 is provided in the support portion 15 which is constituted by utilizing a part of the ink tank.
Are arranged to cover the opening 16. The thin film 13 and the support 15 are in close contact with each other via a viscous sealant 14 such as silicone oil. At this time, the viscous sealant 14 generates an adhesive force and maintains the obstruction when there is almost no pressure difference. As the viscous sealant, a liquid substance having no volatility such as silicone oil and having a viscosity of about 500 to 5000 cst can be preferably used.

Next, this operation will be described. Ink tank 1
When the internal pressure inside increases relative to the external pressure, the thin film 13 is pushed up to the outside of the tank. When the pressure of the thin film 13 reaches a predetermined pressure, a part of the viscous sealant 14 between the thin film 13 and the support portion 15 is opened, and a ventilation path is formed as shown in FIG. When the internal pressure rise is reduced by this opening, the thin film 1
The ventilation path is quickly closed by the elasticity of 3 and the surface tension of the viscous sealant 14.

The material of the thin film 13 is a polyethylene terephthalate (PET) film, a circular one having a thickness of 25 μm and a diameter of 13 mm.

FIG. 6 is a sectional view showing another example of the valve element 12. As shown in FIG.

The elastic valve 17 is made of an elastic material such as butyl rubber. When the pressure in the ink tank is relatively increased with respect to the outside air, the elastic valve 17 is deformed to support the support portion 15 and the elastic valve 17. Is broken and a ventilation path is formed, and the air in the tank is discharged to the outside due to the expansion.

[0055]

According to the configuration of the ink tank of the present invention,
As the ink in the ink tank is consumed, air intermittently flows into the ink tank from an opening in the ink tank. At this time, due to the pressure reduction of the air portion formed by the inflow of air due to ink consumption and the meniscus force of the air at the opening, the ink tank moves the ink into the ink supply portion or the ink ejection port of the recording head portion. A negative pressure is generated in the direction of drawing. As a result, an appropriate negative pressure is applied to the recording head portion, and it is possible to provide an ink tank that not only provides a stable supply of ink but also obtains good print quality.

Further, the negative pressure remains even after the ink consumption is interrupted, and an ink tank can be provided which can prevent the ink from leaking from the recording head.

[0057]

Further, a means is provided for alleviating an increase in the internal pressure of the ink tank so as to sufficiently cope with a case where the volume of the air portion is increased or decreased due to environmental changes.
It is possible to provide an ink tank in which the inside of the ink tank is not pressurized and the negative pressure is favorably maintained.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view illustrating an example of a configuration that is a premise of the present invention.

FIG. 2 is a schematic sectional view showing a first embodiment of the present invention.

FIG. 3 is a schematic sectional view showing a second embodiment of the present invention.

FIG. 4 is a schematic cross-sectional view showing an example of a pressure rise mitigation means.

FIG. 5 is a diagram showing the operation of FIG. 5;

FIG. 6 is a schematic cross-sectional view showing another example of the pressure rise mitigation means.

FIG. 7 is a schematic sectional view showing an example of a conventional ink tank.

FIGS. 8A and 8B are schematic sectional views showing an example of a conventional ink tank.

FIG. 9 is a diagram showing a relationship between a negative pressure generated by a conventional ink tank and an amount of ink used.

FIG. 10 is a diagram illustrating a relationship between a negative pressure generated by an ink tank to which the present invention is applied and an amount of ink used.

11A and 11B are diagrams illustrating a meniscus state of an ink tank to which the present invention is applied.

FIGS. 12A, 12B and 12C are diagrams showing a state of a meniscus of an ink tank to which a conventional invention is applied.

13A and 13B are diagrams showing another example of the arrangement of the thin tubes.

FIG. 14 is a view showing a preferred example of the position of the thin tube of the present invention.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Torachika Nagata 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Yoichi Taniya 3-30-2 Shimomaruko, Ota-ku, Tokyo Within Non Co., Ltd. (72) Inventor Yu Ikeya 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Kazuaki Masuda 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (56) References JP-A-1-136752 (JP, A) JP-A-61-139446 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B41J 2/175

Claims (2)

(57) [Claims] An ink supply section for containing ink; an ink supply section for supplying ink to a recording head section; and one end opening outside the ink storage section as an atmosphere communication port for introducing air into the ink storage section. A hollow thin tube having the other end opened into the ink storage portion near the bottom of the tank; and an air communication port outside the ink storage portion separate from the atmosphere communication port.
Inside the ink storage portion, which is arranged with respect to the configured opening
A valve that allows air to move only in the direction from
And a mitigation means comprising a water-repellent gas permeable membrane.
A meniscus at the end of the capillary that opens into the ink container.
To maintain a negative pressure in the ink storage section.
At the same time, the internal pressure in the ink storage section is increased by the relaxation means.
An ink tank characterized by reducing rising . 2. The ink tank according to claim 1, wherein a water-repellent gas permeable film is disposed in the air communication port.