JP2958392B2 - Ink tank for inkjet printer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cartridge-type ink tank used for an ink jet printer.

[0002]

2. Description of the Related Art In an ink cartridge of an ink jet printer, the ink level of an ink tank may be higher than the nozzle level of a recording head due to the structure of the printer. In such a case, a water head pressure difference due to a difference in height is applied to the nozzle surface of the recording head, and ink flows out of the nozzle. In order to prevent this, a method of applying a negative pressure in the ink tank is used, and a negative pressure generating means is required.

As a method of storing ink in an ink tank, as described in JP-A-63-87242 and JP-A-2-34349, a porous material such as a sponge is provided in the ink tank. In general, a method of arranging an elastic member and holding ink by utilizing the capillary force is widely used.

[0004] However, this method has a problem that the sponge cannot be completely filled with ink, and only about 70% of the volume of the ink tank can be filled with ink. The portion remains on the sponge, and there is a problem that only about 80% of the filled ink is used. For this reason, the utilization efficiency of the volume of the ink tank is only about 50 to 60%, and it has been difficult to reduce the size of the cartridge.

Further, as disclosed in Japanese Patent Application Laid-Open No. 62-231759, a method of providing a pressure regulating valve between an ink tank and a recording head has been proposed. The pressure regulating valve is liable to fail due to clogging or the like due to clogging, etc., and if the failure occurs, ink leaks from the ink tank, which is not suitable for actual use.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and it is possible to make the ink pressure supplied to the recording head appropriate, thereby increasing the efficiency of ink use. It is another object of the present invention to provide an ink tank for an ink jet printer that can improve reliability.

[0007]

According to the present invention, there is provided an ink jet printer having an ink tank in which a recording head portion and an ink tank are separable, wherein the ink tank mainly stores ink and has an opening to the atmosphere. A first chamber, a sealed second chamber having a joint portion with a recording head and a porous member, one end of which opens into the ink of the first chamber, and the other end of which opens the ink in the second chamber. Characterized by having a capillary tube arranged so as to drip.

[0008]

The ink is stored in the first chamber of the ink tank. One end of the capillary tube is opened in the ink, and the other end is the second chamber.
Open to the room. The first chamber is open to the atmosphere and the second chamber is closed. Therefore, at the capillary end of the second chamber, there is a height difference between the ink liquid level and the capillary end,
The pressure difference between the atmosphere and the second chamber acts. The second chamber is connected to the recording head via a joint, and a porous member is arranged near the joint. The ink pressure acting on the recording head is the sum of the height difference between the nozzle surface and the porous material, the pressure difference between the atmosphere and the second chamber, and the capillary force of the porous material. The ink at the capillary end of the second chamber is usually
It is held at the capillary end by its own surface tension.
When ink is consumed by printing and ink is sent from the porous material in the second chamber to the recording head, the second chamber is under negative pressure unless the ink in the capillary moves. When the negative pressure in the second chamber increases, the balance due to the surface tension at the end of the capillary is lost, and ink flows out from the end of the capillary to form droplets. The chamber is supplied with ink. When the negative pressure in the second chamber is alleviated by this ink supply, the balance due to the surface tension of the capillary end is restored, and the supply of the ink is stopped.

In this way, the ink stored in the first chamber is supplied to the second chamber by the capillary tube connecting the first chamber and the second chamber. A pressure holding unit is provided in the ink flow path from the first chamber to the recording head by surface tension, and the capillary force is cut off once in the second chamber in the same gravitational arrangement as at the time of printing. To prevent the pressure (positive pressure) of the height difference between the recording head and the recording head from acting on the recording head, and apply the holding pressure (negative pressure) of the porous material in the second chamber to the recording head. A suitable negative pressure.

[0010]

FIG. 1 is a sectional view schematically showing an ink tank according to a first embodiment of the present invention. In the figure, 1 is a recording head, 2 is a head chip, 3 is a housing, 4 is a heat sink, 5 is a manifold, 6 is joint packing,
7 is a printed wiring board, 8 is a housing guide, 10 is an ink tank section, 11 is a first chamber, 12 is an air communication hole,
13 is a membrane member, 14 is a capillary tube, 15 is a second chamber, 16 is a porous member, 17 is a joint, and 20 is ink. The recording head unit 1 and the ink tank unit 10 are configured to be separable, and the casing of the ink tank unit 10 is positioned by being guided by a housing guide 8 formed on the housing 3 of the recording head unit 1. A heat sink 4 to which the head chip 2 is attached, a printed wiring board 7 for supplying an electric signal to the head chip 2, and a manifold 5 for supplying ink to the head chip 2 are attached to the housing 3 of the recording head unit 1. And a housing guide 8 is formed. A large number of nozzles (not shown) are formed in the head chip 2 at a high density. In this embodiment, 128 nozzles are formed at a density of 300 spi. Each nozzle has
A heating element (not shown) is provided for generating bubbles by energization and ejecting ink droplets. In FIG. 1, the ejection of ink droplets is performed downward.

The ink tank 10 has a first chamber 11 for storing ink 20 and a second chamber 15 having a porous member 16.
It consists of In this example, urethane foam having an average bore size of 200 μm was used as the porous member 16. The ink tank 10 was formed of polyethylene terephthalate (PET). The first chamber 11 has an atmosphere communication hole 1 for keeping the pressure of the first chamber equal to the atmospheric pressure.
2 is provided, and a film member 13 that allows only air and does not allow ink to pass therethrough is disposed below the atmosphere communication hole 12 in order to prevent the ink 20 from flowing out from the atmosphere communication hole 12. Below the second chamber 15, there is provided a joint 17 for connection with the recording head 1. First
The chamber 11 and the second chamber 15 are connected by a capillary 14, and the second chamber 15 is closed when the capillary 14 and the joint 17 are closed. One end of the capillary 14 extends to the bottom of the first chamber 11. If a depression is provided in the bottom wall of the first chamber 11 facing this end, the remaining amount of ink when the ink runs out can be reduced. The other end of the capillary 14 protrudes into the space of the second chamber 15, and the other end is formed as a protrusion when the ink tank is used, and ink droplets drop onto the porous member 16 from the tip. It is arranged to be. The capillary 14 is made of stainless steel (SUS) whose main body has an inner diameter of 200 μm.
It is a pipe, and the protruding portion is made of glass having a tip outer shape of 300 μm and an inner diameter of 100 μm.

The operation will be described. First, a case where the ink tank unit 10 is separated from the recording head unit 1 will be described. The capillary 14 is filled with ink by the capillary force. The pressure in the first chamber 11 and the second chamber 15 is equal to the atmospheric pressure, and a pressure difference between the liquid level of the ink 20 and the tip of the capillary 14 acts on the tip of the capillary 14. This pressure balances the force due to the surface tension of the ink at the tip of the capillary 14, and the ink is held inside the capillary 14. The geometric dimensions of the ink tank section 10 are designed such that ink is retained inside the capillary tube 14 regardless of the orientation of the ink tank section 10. Even when vibration is applied to the ink tank, the ink is held inside the capillary tube 14 because the flow resistance inside the capillary tube 14 is large and the action time of the vibration acceleration is short. Therefore, the ink in the first chamber 11 does not move to the second chamber.

Next, a case where the ink tank unit 10 is attached to the recording head unit 1 will be described. Manifold 5
Is a polyethersulfone (PEC) in this example.
The tip is formed of stainless steel (SUS). This tip is inserted into the porous member 16 through the opening of the joint 17, and the joint is sealed with the joint packing 6. Butyl rubber was used for the joint packing 6. When a negative pressure is applied from the nozzle portion of the head chip 2 for initial filling after the ink tank unit 10 is attached to the recording head unit 1, the pressure in the second chamber 15 decreases. First chamber 11 and second chamber 15
When the pressure difference exceeds the force caused by the surface tension of the ink at the tip of the capillary 14, the ink flows out from the tip of the capillary 14 and drops on the porous member 16. The dropped ink is
The porous member 16 is filled and sent to the head chip 2 via the manifold 5. When the negative pressure acting on the nozzle portion of the head chip 2 is stopped, the pressure in the second chamber 15 approaches the atmospheric pressure with the dropping of the ink, and the pressure difference between the first chamber 11 and the second chamber 15 is reduced. However, when the surface tension of the ink at the tip of the capillary 14 is balanced, the dropping of the ink stops. At this time,
The pressure in the second chamber 15 is a weak negative pressure close to the atmospheric pressure.
The pressure of the ink acting on the nozzle portion of the head chip 2 is the first pressure.
And the pressure difference between the pressure of the porous member 16 and the pressure of the second chamber, and this value is a value suitable for printing, for example, -20 to -1
The bore size of the porous member 16 is selected so as to be 30 mmH ₂ O.

The printing operation will be described. When the ink is consumed by printing, the porous member 1 of the second chamber 15 is
The ink filled in 6 is sent to the head chip 2. As a result, the pressure in the second chamber 15 decreases, and when the pressure difference between the first chamber 11 and the second chamber 15 exceeds the force due to the surface tension of the ink at the tip of the capillary 14, the ink from the tip of the capillary 14 Flows out and drops on the porous portion 16. When printing is completed, the pressure in the second chamber 15 approaches the atmospheric pressure with the dropping of the ink, and the pressure difference between the first chamber 11 and the second chamber 15 becomes the surface of the ink at the tip of the capillary tube 14. When the tension is balanced, the dropping of the ink stops. In this way, the same amount of ink as the amount of ink consumed by printing is
It is supplied from the first chamber 11 to the second chamber 15.

FIG. 2 is a sectional view schematically showing an ink tank according to a second embodiment of the present invention. In the figure, the same parts as those in FIG. In this embodiment, the second chamber 15 is arranged below the first chamber 11. In this arrangement, since the pressure due to the height difference between the ink 20 and the tip of the capillary 14 is large, the pressure applied to the tip of the capillary 14 is large. Therefore, it is necessary to make the tip diameter of the capillary tube 14 smaller than in the first embodiment. This embodiment has an advantage that the ink tank section 10 can be formed more compactly.

As is apparent from the above description of the embodiment, in the present invention, the ink flow path from the first chamber to the recording head needs to be once interrupted by surface tension, and the ink holding at the tip of the capillary tube is required. The condition is important. In the first and second examples, one capillary was used. However, the reason is not limited to one, and two or more may be used. As described above, when the ink is held at the tip of the capillary when the tubular body is used as the capillary, as shown in FIG. 3, when the meniscus of the ink is generated from the capillary 14, the contact angle is set to θ and the surface tension of the ink is set to θ. When γ, the radius of the capillary is r, and the pressure difference is P, P = (2γ cos θ) / r, θ = 60 °, γ = 30 dyn / cm, r = 50
In μm, the holding pressure is P = 60 mm H ₂ O.

As shown in FIG. 4, when the meniscus is held at the outer diameter of the capillary, if r = 150 μm,
The holding pressure is P = 20 mm H ₂ O, which is １ ／.

In order to stably maintain the ink holding state at the tip of the capillary, it is effective to apply a surface treatment. As shown in FIG. 5, when the outer surface is subjected to the surface treatment with the ink-repellent coating 18 by coating or the like, the ink is stably held on the inner wall of the capillary, and as a result, the ink supply to the recording head is also stabilized. It is done. As an ink-repellent coating material,
For example, silicone resin SR2410 (manufactured by Dow Corning Toray Co., Ltd.) or KP-80 of fluorinated silicon
1 (manufactured by Shin-Etsu Chemical Co., Ltd.) is suitable.

As shown in FIG. 6, when the tip of the capillary 14 is tapered to reduce the outer diameter of the tip of the capillary 14, even if the meniscus changes to the outer diameter side, the change is small. Effectively reduces the change in capillary diameter,
This is effective in suppressing the fluctuation of the ink holding pressure.

Further, providing a piezoelectric element or the like in the capillary tube and applying a small pulsation of pressure to the tip of the capillary has the effect of stably dropping ink from the tip of the capillary. As shown in FIG. 7, a piezoelectric element 21 that expands and contracts in the radial direction is provided on the outer periphery of
When a vibration of 0 to 20 KHz is given, the size of the ink droplet to be dropped is stabilized, and the holding pressure can be made constant. The piezoelectric element 21 is made of cylindrical PZT ceramics, and has electrodes 22 on the inside and the outside.
Was applied. The amplitude of the vibration may be a very small value, and is a size that does not cause dripping unless ink flows out from the tip of the capillary tube 14. The driving of the piezoelectric element is performed continuously during the operation of the recording head, regardless of the presence or absence of printing.

FIG. 8 is a sectional view schematically showing a third embodiment of the ink tank of the present invention. In the figure, the same parts as those in FIG. Reference numeral 24 denotes a polymer electrostrictive plate. In this embodiment, the second chamber 15 is arranged below the first chamber 11 as in the second embodiment.
The chamber 11 and the second chamber 15 are partitioned by a polymer electrostrictive plate 24 having many fine openings. As the porous member 16, a polyvinyl alcohol (PVA) foam having an average bore size of 200 μm was used. The main body of the ink tank 10 is made of polyether sulfone (PE
Although these materials were formed in S), these materials are merely examples, and the materials used in the first or second embodiment and other appropriate materials can be selected.

The polymer electrostrictive plate will be described with reference to FIG.
(A) is a plan view, and (B) is a sectional view. Thickness 1
Aluminum electrodes 26 are provided on both sides of a 00 μm polyvinylidene fluoride (PVF2) 25 by vapor deposition, and a large number of holes 27 having a diameter of about 50 μm are provided in the aluminum electrodes 26. Furthermore, an insulating coating 28 made of a urethane coating is applied to the side facing the first chamber, and an ink-repellent film 29 made of the KP-801 coating is applied to the side facing the second chamber. ing.

Returning to FIG. Polymer electrostrictive plate 24
Forms the upper surface of the second chamber 15 and the second chamber 15
A porous member 16 is arranged on the lower side, and a joint portion 17 is further provided on the lower side. A high-frequency AC voltage of 50 V and 100 KHz is applied to the electrode 26 (FIG. 9) of the polymer electrostrictive plate 24.
Oscillates minutely up and down. As in the other embodiments described above, when the ink in the second chamber 15 is consumed by printing and the second chamber 15 becomes negative pressure, the fine holes 27 (FIG. 9) of the polymer electrostrictive plate 24 are opened. It acts as a capillary from which ink is drawn and supplied. In this embodiment, the dropping of the ink is stably performed by the ink-repellent treatment film and the vibration of the polymer electrostrictive plate even if the opening is not a nozzle. Further, in order to increase the holding pressure of the polymer electrostrictive plate 24 connecting the first chamber 11 and the second chamber 15, the micropore diameter is reduced, so that the number of micropores can be increased even if the flow path resistance increases. Can be increased, so that a necessary ink supply amount can be secured.

[0024]

As is apparent from the above description, according to the present invention, the pressure difference caused by the difference in height between the ink tank and the recording head is temporarily interrupted by the capillary force in the flow path, and the pressure holding unit is operated by the surface tension. Is provided to hold the ink, so there is no need to fill most of the ink tank with the porous member of the sponge, there is no waste in the ink tank volume, and the ink remains in the porous member. And almost 100% of the ink can be used for printing. In addition, since the outflow of ink from the ink tank is suppressed by the flow path resistance of the capillary and the surface tension of the end of the capillary, the ink from the ink tank is not only statically exposed, but also when vibration acceleration is applied. There is an effect that outflow can be effectively prevented.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a first embodiment of an ink tank according to the present invention.

FIG. 2 is a schematic sectional view of a second embodiment of the ink tank of the present invention.

FIG. 3 is an explanatory diagram of an ink holding force by a capillary tube.

FIG. 4 is an explanatory diagram in the case where ink is held at the outer diameter of a capillary.

FIG. 5 is a cross-sectional view of one embodiment of a capillary tube.

FIG. 6 is a cross-sectional view of another embodiment of a capillary tube.

FIG. 7 is a cross-sectional view of an embodiment in which vibration is applied to a capillary.

FIG. 8 is a schematic sectional view of a third embodiment of the ink tank of the present invention.

FIG. 9 is an explanatory diagram of a polymer electrostrictive plate.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Recording head part, 2 head chips, 3 housings, 4 heat sinks, 5 manifolds, 6 joint packing, 7 printed wiring boards, 8 housing guides, 10 ink tank sections, 11 first chambers, 12
Atmospheric communication hole, 13 membrane member, 14 capillary tube, 15 second
Chamber, 16 porous members, 17 joints, 20
Ink, 24 polymer electrostrictive plate.

Continued on the front page (72) Inventor Masaki Kataoka 2274 Hongo, Ebina-shi, Kanagawa Prefecture Fuji Xerox Co., Ltd.Ebina Office (72) Inventor Masafumi Hiratsuka 2274 Hongo, Ebina-shi, Kanagawa Prefecture Fuji Xerox Co., Ltd.Ebina Office (72 ) Inventor Nobuyuki Takao 2274 Hongo, Ebina City, Kanagawa Prefecture Fuji Xerox Co., Ltd. Ebina Office Surveyed field (Int.Cl. ⁶ , DB name) B41J 2/175

Claims (1)

(57) [Claims] An ink tank of an ink jet printer in which a recording head portion and an ink tank are configured to be separable, wherein the ink tank mainly stores ink and has a first chamber having an opening to the atmosphere, and a recording head. A sealed second chamber having a joint portion with the first member and a porous member, and a capillary arranged such that one end side is opened into the ink of the first chamber and the other end side is configured to drip ink into the second chamber. An ink tank for an ink jet printer, comprising: