JP3163864B2 - Ink supply device - 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 supply apparatus for supplying ink to a recording head in an ink jet recording apparatus.

[0002]

2. Description of the Related Art Conventionally, as an ink supply mechanism used in an ink jet recording apparatus, for example, as described in JP-A-63-87242, the entire area inside an ink tank connected to a recording head is connected. There is known an ink absorber in which ink is previously impregnated and held in the ink absorber, and the ink in the ink absorber is supplied to a recording head. As the ink absorber, a sponge which is a porous material or a felt which is a fibrous material is used. In such an ink supply mechanism, about 4% of the volume in the ink tank is required.
Only the ink amount of 0% to 60% can be used, and the usage efficiency is low. For this reason, there is a problem in that if the service life of the ink tank is to be extended, the ink tank is inevitably increased in size and does not meet the demand for downsizing.

In the above-described conventional ink supply mechanism,
Since the ink is held by the capillary force of the ink absorber, an appropriate negative pressure is generated for the print head. Therefore, as the amount of ink held by the ink absorber decreases as the ink is consumed, the negative pressure acting on the ink impregnated in the ink absorber gradually increases due to a decrease in the ink head pressure, and the ink applied to the recording head is reduced. There is a problem that the supply of ink is hindered. When this phenomenon progresses and the negative pressure applied to the ink exceeds a certain value, bubbles flow backward from the print nozzle portion of the recording head, and the ink is ejected in a state where ink is not supplied to the recording head. There is a problem that a defect causes a defect in a recorded image due to a defect, thereby causing a deterioration in image quality. This phenomenon also lowers the ink use efficiency.

To solve such a problem, for example,
JP-T-59-500609, JP-A-1-1485
No. 59, JP-A-3-180357, etc., in an ink supply device, only a closed ink tank is filled with ink, and a capillary tube having one end open to the atmosphere is connected to the ink tank. , One provided with a small hole has been proposed. According to this ink supply device, when the negative pressure in the ink tank increases as the ink in the ink tank is consumed, air is introduced into the ink tank through a capillary tube or a small hole, and the negative pressure value in the ink tank is reduced. Is kept substantially constant, and the ink in the ink tank can be stably supplied to the recording head.

When the surrounding environment changes and, for example, the air in the upper space in the ink tank expands, the ink in the ink tank flows back through the capillary. For this reason, in one example of the ink supply device described in JP-T-59-500609 and the ink supply device described in JP-A-1-148559, the atmosphere is supplied only through a capillary tube. And the ink tank communicate with each other, there is a possibility that the ink that has flowed backward may be ejected, which is a problem. It is conceivable to lengthen the capillary, but the structure becomes complicated.

An example of another ink supply device described in JP-A-1-148559 and JP-A-3-1803 are disclosed.
The ink supply device described in Japanese Patent Application Publication No. 57-57 has a small chamber, and when the air in the upper space in the ink tank expands, the ink in the ink tank temporarily retreats to the small chamber. As a result, the pressure in the ink tank is reduced, so that ink leakage from the recording head and ink leakage from a capillary or a small hole communicating with the atmosphere are effectively prevented.

However, in the ink supply device having a structure having these small chambers, the small chambers are arranged below the main ink chamber. Therefore, in order to alleviate the pressure fluctuation inside the ink tank, when the ink moved from the main ink chamber to the small chamber returns to the main ink chamber again, it is necessary to overcome the capillary force and move it against the direction of gravity. There is. Therefore, the ink in the small chamber cannot completely transfer to the main ink chamber and remains in the small chamber. That is, the volume efficiency is reduced by the amount of the remaining ink.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and has been made in consideration of the stabilization of ink supply performance,
It is another object of the present invention to provide an ink supply device that realizes suppression of the influence of a change in the surrounding environment and has an improved ink storage efficiency.

[0009]

According to the present invention, there is provided an ink supply apparatus which is connected to an ink jet head and supplies ink to the ink jet head. A sub-ink storage chamber which is disposed adjacent to the side of the ink storage chamber and communicates with the main ink storage chamber through a communication hole in a lower space and has an air communication port opened in an upper side; And an ink absorbing member arranged at least laterally in close contact with the inner wall of the sub-ink storage chamber, and provided to cover the communication hole of the sub-ink storage chamber to form a meniscus and reduce bubbles. It is characterized by having a meniscus forming portion that generates.

According to another aspect of the present invention, there is provided an ink supply device that is connected to an ink jet head and supplies ink to the ink jet head. A sub-ink storage chamber that is disposed adjacent to the side and communicates with the main ink storage chamber through a communication hole in a lower space and has an air communication port opened on an upper side, and is disposed inside the sub-ink storage chamber. An ink absorbing member arranged so that at least a side thereof is in close contact with an inner wall of the sub-ink storage chamber; a meniscus forming section provided so as to cover a communication hole of the sub-ink storage chamber; and a lower surface of the meniscus forming section And an ink guide portion extending into a lower space in contact with the main ink storage chamber. The ink guide section has one end in contact with the meniscus forming section,
The other end can be configured to be in contact with the bottom of the lower space communicating with the main ink storage chamber, and the ink guide is formed to have a smaller cross section than the communication hole,
An arrangement may be made wherein a region not in contact with the ink guiding portion is formed in the meniscus forming portion.

Further, the meniscus forming section can be formed of a mesh-like body or a porous body, and a filter having a higher filtration accuracy than the meniscus forming section between the main ink storage chamber and the ink jet head. Can also be arranged.

[0012]

According to the present invention, the main ink storage chamber and the sub ink storage chamber are provided, and the ink absorbing member is inserted into the sub ink storage chamber. The pressure can be controlled, and the negative pressure applied to the inkjet head can be maintained within a desired range.

The ink absorbing member in the sub-ink storage chamber can absorb ink up to the limit of the holding capacity of the absorbing member by capillary action in an initial stage, and functions as an ink chamber. There is an air communication port at the top, and communicates with the main ink storage chamber in the lower space of the ink absorbing member inserted closely into the sub ink storage chamber, so that the negative pressure generated due to the consumption of ink in the recording head causes The ink in the sub ink storage chamber moves to the main ink storage chamber. When the ink in the sub ink storage chamber is almost exhausted, air bubbles are generated from the meniscus forming portion, and the air bubbles are supplied to the main ink storage chamber through the lower space, thereby increasing the negative pressure in the main ink storage chamber. suppress. As a result, an appropriate negative pressure is always generated in the recording head, and excellent printing can be compensated.

Furthermore, when the surrounding environment changes and the pressure in the main ink storage chamber rises, the pressure in the main ink storage chamber can be kept substantially constant by flowing the ink into the sub ink storage chamber. Even in such a case, the ink flowing into the sub ink storage chamber moves to the main ink storage chamber due to a decrease in pressure due to ink consumption, so that the amount of ink remaining in the sub ink storage chamber can be reduced.
Volumetric efficiency can be increased.

By forming the meniscus forming portion from a mesh or a porous body, a meniscus of the ink can be formed in the mesh or the pore portion of the porous body. A bubble is generated at a desired pressure difference between the main ink storage chamber and the main ink storage chamber can be maintained at a substantially constant negative pressure.

Even if both surfaces of the meniscus forming section come into contact with an air layer due to bubbles or the like generated in the meniscus forming section, the ink guide section sucks up ink and supplies it to the meniscus forming section. Thus, the negative pressure in the main ink storage chamber can be kept substantially constant by the surface tension of the ink in the meniscus forming portion. Further, even when the amount of ink is low and the liquid level is lower than that of the meniscus forming portion, the meniscus forming portion can similarly be kept wet with the ink, and the residual amount of the ink can be reduced.

The ink guide section is configured such that one end thereof is in contact with the meniscus forming section and the other end thereof is in contact with the bottom of a lower space communicating with the main ink storage chamber, so that the amount of ink remaining is small. Even so, the ink is supplied to the meniscus forming section by the ink guiding section, and the pressure in the main ink storage chamber is kept substantially constant by the meniscus forming section, so that the ink can be used up and the ink use efficiency is further improved. Can be done.

Further, the ink guide portion is formed to have a smaller cross section than the communication hole, and by forming a non-contact area with the ink guide portion in the meniscus forming portion.
Bubbles can be generated in this region, and the generated bubbles can be smoothly moved to the lower space.

Further, by disposing a filter having higher filtration accuracy than the meniscus forming portion between the main ink storage chamber and the ink jet head, the absorbing member, the meniscus forming portion,
It is possible to promote the adjustment of the pressure by the ink guide section and the like, and to prevent the outflow of the ink from the ink jet head.

[0020]

FIG. 1 is a sectional view showing an embodiment of an ink supply apparatus according to the present invention, and FIG. 2 is an enlarged view of a lower portion of a sub ink chamber. In the figure, 1 is an ink jet head, 2 is an ink tank, 3 is ink, 4 is a main ink chamber, 5 is a communication path, 6 is a sub ink chamber, 7 is a communication hole, 8 is an air communication hole, 9 is an absorbing member, 10 is a meniscus forming section, 11 is an ink guiding section, 1
2 is a supply path. In this embodiment, the ink jet head 1 and the ink tank 2 are integrally formed. Around the ink jet head 1, there are a heat sink (not shown) to which the head itself is attached, a printed wiring board (not shown) for supplying an electric signal to the ink jet head 1, and the like. In the inkjet head 1, a large number of nozzles (not shown) are formed at a high density. For example, 128 nozzles can be formed at a density of 300 spi. Each of the nozzles is provided with a heating element (not shown) for generating air bubbles by energization and ejecting ink droplets. In FIG. 1, the ejection of ink droplets is performed downward.

The interior of the ink tank 2 includes a main ink chamber 4
And a sub ink chamber 6. The housing of the ink tank 2 is made of a material having good ink resistance so as to have rigidity and enable long-term ink holding. Main ink chamber 4
Contains only ink. Ink is supplied from the main ink chamber 4 to the inkjet head 1 via the supply path 12.

A communication hole 7 is provided in a lower portion of the sub ink chamber 6 and communicates with the main ink chamber 4 through a communication path 5. The cross-sectional shape of the communication hole 7 can be various shapes such as a circle, an ellipse, a polygon, a star, a cross, and a slit. The upper wall of the communication passage 5 may be flat, but as shown in the drawing, the communication wall 7 is formed obliquely so as to be gradually higher toward the main ink chamber 4.
Can be smoothly moved to the main ink chamber 4. An absorbing member 9 is arranged inside the sub ink chamber 6. As a material of the absorbing member 9, a fibrous material having a two-dimensional structure, a porous material having a three-dimensional structure,
A felt obtained by spinning a fibrous material in a three-dimensional shape, a nonwoven fabric material, or the like can be used. Specifically, for example,
A batting material in which polyester fibers are bundled in one direction can be used. As the batting material, for example, a polyester felt having a density (= weight / volume) of 800 g / m ³ can be used. The volume density is 5% to 15%
It is preferable to use a material having such a value from the viewpoints of fluid resistance and capillary force. In addition, the composition of the material is not limited to the polyester fiber, a material having an appropriate capillary force and a material having ink resistance, for example, a porous member such as polyurethane, melamine foam, or one-dimensional, A two-dimensional fiber structure can also be used.

At the top of the sub ink chamber 6, an air communication hole 8 is provided, which can communicate with the absorbing member 9 by air. In this embodiment, the diameter of the air communication hole 8 is configured to be larger than the hole of the absorbing member 9 or the gap between the fibers. Absorbing member 9
Communicates with the atmosphere at the top, and is released from the atmosphere.
The ink in the absorbing member 9 is pushed by the atmospheric pressure and is drawn out from below the absorbing member 9 by the negative pressure toward the main ink chamber, so that the ink in the absorbing member 9 can be used efficiently. At this time, the negative pressure in the main ink chamber 4 is kept constant by the capillary force of the absorbing member 9. It is also possible to provide a sheet in the atmosphere communication hole 8 that does not allow ink to pass through and allows air to pass through, so that the ink does not fly out from the atmosphere communication hole 8. Alternatively, the air communication hole 8 may be configured by arranging a large number of fine holes from which ink does not flow. The periphery of the absorbing member 9 is inserted in close contact with the inner wall of the sub ink chamber 6. The purpose is to prevent air introduced from the atmosphere communication hole 8 from entering along the inner wall of the sub ink chamber 6.

The meniscus forming portion 10 is disposed so as to cover the communication hole 7 and to contact the bottom of the absorbing member 9. For example, the absorbing member 9 can be installed so as to protrude from the bottom surface of the absorbing member 9 by several millimeters. In this case, the absorbing member 9 is pressed against the meniscus forming portion 10 and the surface of the meniscus forming portion 10 is immersed in the absorbing member 9. And a better fluid connection is obtained. Meniscus forming part 1
For 0, a mesh-like body such as a wire net or a resin net, a porous body, or the like can be used. As a specific example of the mesh-like body, a metal mesh filter, a metal fiber, for example, a SUS fine wire is made into a felt shape, and further, a filter having a base material obtained by compression sintering, an electroforming metal filter, or the like is used. be able to. Further, a filter made of a knitted resin fiber or a filter having a high-definition hole diameter by laser beam processing, electron beam processing, or the like can be used. The meniscus forming section 10 can be configured to be thermally fused to the absorbing member 9.

When the ink is absorbed in the absorbing member 9, the ink passes through the meniscus forming section 10 and moves to the main ink chamber 4. The meniscus forming section 10 prevents unnecessary air from entering the main ink chamber 4 even when the ink is exhausted in the absorbing member 9. As more ink is consumed,
The air that has entered through the air communication hole 8 passes through the absorbing member 9, and due to an increase in the negative pressure in the main ink chamber 4, the liquid of the ink caught on the meniscus forming portion 10 that is in close contact with the absorbing member 9. It pushes the surface and overcomes surface tension and passes through it, forming bubbles. The generated bubbles move to the main ink chamber 4 through the communication holes 7. The pressure at which bubbles are generated (bubble point pressure) depends on the filtration accuracy of the meniscus forming unit 10. By optimizing the filtration accuracy, the negative pressure in the main ink chamber 4, that is, the inkjet head 1 The ink supply pressure to the ink can be kept constant. The filtering accuracy of the meniscus forming section 10 may be, for example, about 70 μm. Meniscus forming part 1
0 also has the function of removing dust and the like larger than the filtration accuracy.

FIG. 3 is an explanatory diagram of an example of a mesh-like body that can be used for the meniscus forming section 10. When a wire mesh is used as the meniscus forming section 10, there are various methods for weaving the wire mesh. FIG. 3 shows a tatami twill weave (Twill
ed Dutch Weave). The tatami twill uses thick vertical lines, and the horizontal lines are adjacent to each other, and are woven so as to cross two vertical lines at a time. FIG.
As seen from the front, the horizontal lines are in contact with each other as shown in FIG. However, looking diagonally,
As shown in FIG. 3C, a triangular aperture is formed by a horizontal line running obliquely from the back to the front or from the front to the back, an adjacent straight horizontal line, and a vertical line. Ink passes through the triangular openings, and bubbles are generated at these portions. As described above, the tatami twill wire mesh can be finely woven, has uniform eyes, and can generate uniform air bubbles. Further, it has a feature that it has higher mechanical strength and is stronger than other wire nets having the same filtration accuracy. Usually, such a wire mesh is usually used for filtration. In the present invention, in addition to the filtration, as described above, the wire mesh also has a function of adjusting the pressure due to the generation of bubbles.

FIG. 4 is an explanatory diagram of the characteristics of the tatami twill wire mesh. In the tatami twill wire mesh indicated by A in the figure, the filtration particle size is 1
0 μm, and the liquid resistance average difference is 10.3 × 1
0 ⁴ g / cm ⁴ s, the pressure loss is ₂ O about 4.2CmH. Further, in the tatami twill wire mesh shown in B, the filtration particle size is about 5 μm, and the average difference in liquid resistance is 56.1 × 1.
0 ⁴ g / cm ⁴ s and pressure loss is about 23.1 cmH ₂ O. As described above, the liquid resistance and the pressure loss change depending on the roughness of the wire mesh used. Therefore, an optimal wire mesh may be used in consideration of the ink pressure applied to the head.

Returning to FIGS. 1 and 2, the ink guiding section 11
It is in contact with the meniscus forming portion 10 and extends downward through the communication hole 7. When bubbles accumulate on the lower surface of the meniscus forming section 10 to form an air layer, or when the amount of ink in the main ink chamber 4 decreases and the liquid level of the ink becomes lower than the diameter of the communication path 5, meniscus formation occurs. The part 10 will be exposed to air on both sides. However, since the pressure in the main ink chamber 4 needs to be maintained at a negative pressure, it is necessary to form a liquid surface of the ink in the meniscus forming section 10 even in such a case. Therefore, the ink guiding section 11 sucks ink from the bottom of the communication path 5 and supplies the ink to the meniscus forming section 10 to keep the meniscus forming section 10 wet and maintain a negative pressure in the main ink chamber 4. Can be. By extending the lower surface of the ink guiding portion 11 until it contacts the bottom of the communication hole 7, that is, the bottom of the communication passage 5, the best state can be maintained until the ink is used up. The ink guiding portion 11 is made of a material capable of raising ink to the meniscus forming portion 10 by capillary force. For example, a batting material in which polyester fibers are bundled in one direction, a porous member such as polyurethane, melamine foam, A two-dimensional or three-dimensional fiber structure can be used. The shape is arbitrary, and may be a slit shape, a rectangular parallelepiped, a prism such as a triangular prism, a cylindrical shape, or an elliptical column shape.
Further, as shown in FIG. 2, the gap A is provided around the ink guiding section 11 by making the cross-sectional dimension of the ink guiding section 11 smaller than the opening dimension of the meniscus forming section 10. Thereby, the movement of the air bubbles generated in the meniscus forming section 10 to the main ink chamber 4 can be facilitated.
The gap A is desirably 0.5 mm or more in width. The ink guiding portion 11 may be configured to be directly attached to the meniscus forming portion 10 or may be configured to be fixed to the side wall of the communication hole 7 by a rib.

The volume efficiency of the ink supply device having such a configuration will be described. In this embodiment, the volume ratio between the main ink chamber 4 and the sub ink chamber 6 is set to 1: 1. In the initial state of the ink tank 2, the main ink chamber 4 is filled with 100% ink. On the other hand, the inside of the sub ink chamber 6 is filled with the amount of ink that the absorbing member 9 can impregnate. As the material of the ink absorbing member 9, for example, a batting material in which polyester fibers are bundled in one direction can be used. When this material is used, the ink retention efficiency (= ink filling amount / total ink chamber volume) is about 80%. Further, the ink use efficiency (= suppliable ink amount / ink filling amount) of the sub ink chamber 6 is about 70%. On the other hand, the ink retention efficiency in the main ink chamber 4 (= ink filling amount / ink absorbing member volume)
Is about 100%, and the ink use efficiency (suppliable ink amount / ink filling amount) is also about 100%. Accordingly, the volume efficiency of the ink tank 2 (= suppliable ink amount / total ink chamber volume) is about 78%. As described above, the ink supply device of the present invention has very good ink use efficiency.

The size of the main ink chamber and the size of the sub ink chamber need not be the above-described 1: 1 volume ratio, and the size may be determined based on the amount of ink and the like. At this time, as described later, the air layer formed above the main ink chamber 4
If it expands due to temperature rise or pressure drop,
Since the amount of ink necessary to maintain the negative pressure in the main ink chamber 4 is stored in the absorbing member 9 in the sub ink chamber 6, the volume of the absorbing member 9 is set in consideration of the amount of ink stored at this time. There is a need.

The positional relationship between the main ink chamber and the sub ink chamber is, as shown in FIG. 1, not only in a shape in which the ink tank is divided into two, but also in two or three sides of the sub ink chamber. A configuration in which the ink chamber is surrounded, or a configuration in which the sub ink chamber is arranged on the island in the main ink chamber may be adopted. In these configurations, by forming all or a part of the side surface of the ink tank with a transparent body, it is possible to check the liquid level in the main ink chamber from any direction. How to confirm
Visual recognition, a method using an optical sensor, or the like can be used.

The operation of the ink supply device of the present invention will be described. The state shown in FIG. 1 described above indicates the time of ink filling. In this state, approximately 80% of the internal volume of the absorbing member 9 and 100% of the internal volume of the main ink chamber 4 are stored in the ink tank 2.
% Is filled with ink. Inkjet head 1
Can be, for example, −20 mmH ₂ O. This ink pressure is realized by the capillary force of the absorbing member 9, and the ink is held. As a state at the start of use, it is desirable to fill the ink in the ink tank 2 as much as possible from the viewpoint of ink use efficiency. However, in order to generate a negative pressure due to the capillary force of the absorbing member 9, Some unfilled parts are required. Before use, a confidential seal can be attached to the nozzle portion of the inkjet head 1 and the atmosphere communication hole 8. Packaged in this state.

When printing starts, the ink jet head 1
And the ink is supplied to the inkjet head 1 from the main ink chamber 4 via the supply path 12 by the amount of the consumed ink. Accordingly, while the absorbing member 9 holds the ink, the ink in the absorbing member 9 moves to the main ink chamber 4 through the communication passage 5, and the air is gradually released from the atmosphere communication hole 8. Spread inside.

FIG. 5 is an explanatory diagram of the process of ink consumption. FIG. 5A shows a state in which the ink has been consumed and the air has reached the meniscus forming section 10. Until this state, the meniscus forming portion 10 prevents air from entering the main ink chamber 4. Therefore, the absorbing member 9
It is possible to reduce the remaining amount of ink inside. At this point, a meniscus in contact with the ink and the air is formed on the meniscus forming section 10. Even when the air is in contact with the upper surface of the meniscus forming unit 10, the ink continues to move while the air is trapped on the meniscus forming unit 10 because the filtering accuracy of the meniscus forming unit 10 is finer than that of the absorbing member 9.

As the ink is further consumed, the negative pressure gradually increases from the decrease in the ink head pressure, and a certain negative pressure value (the filter and ink bubble point determined by the filtration accuracy of the meniscus forming unit 10). When the pressure is applied to the meniscus forming unit 10, air is generated as fine bubbles through the meniscus of the ink formed on the meniscus forming unit 10. The generated fine bubbles combine with the fine bubbles generated adjacently and the subsequent bubbles,
The bubbles move into the main ink chamber 4 through the communication path 5 while becoming large bubbles. At this time, since the upper wall of the communication path 5 is formed obliquely toward the main ink chamber 4, the bubbles smoothly move in the communication path 5 and reach the main ink chamber 4. The pressure at the time of bubble generation (bubble point pressure) depends on the filtration accuracy of the meniscus forming unit 10. By optimizing the filtration accuracy, the ink supply pressure to the ink jet head 1 is kept constant thereafter. be able to. The air bubbles that have moved to the main ink chamber 4 accumulate in the upper part of the main ink chamber 4. This state is shown in FIG.

The process of generating bubbles in the meniscus forming section 10 at this time will be described. FIG. 6 is an explanatory diagram of the process of generating bubbles in a tatami twill wire mesh. The case where the woven twill wire net shown in FIG. 3 is used as the meniscus forming section 10 will be described as an example. As shown in FIG. 3C, a tatami twill wire mesh has triangular openings. If this portion is wet with the ink, an ink film is formed due to the surface tension of the ink. While the pressures on both sides of the wire mesh are balanced, the ink film is flat as shown in FIG. In FIG. 4, when the pressure on the front side of the wire mesh decreases, the air on the back surface of the wire mesh pushes the ink film due to the pressure difference, and becomes convex as shown in FIG. 4B. When the pressure on the surface side of the wire mesh further decreases, FIG.
As shown in FIG. 4C, the protruding portions protrude, and eventually form bubbles and separate into the ink as shown in FIG. At this point, the pressure in the ink rises by the volume of the bubble, canceling the decrease in the pressure on the surface side of the wire mesh, and the ink film becomes flat. The air bubbles separated into the ink merge with air bubbles similarly generated from nearby eyes and move to the main ink chamber 4 while forming large air bubbles.

Returning to FIG. 5, when the ink is further consumed, the liquid level of the ink does not fill the communication path 5. This state is shown in FIG. In this state, both surfaces of the meniscus forming section 10 are exposed to air. But,
Since the ink guiding section 11 is immersed in the ink, the ink is raised to the meniscus forming section 10 by the capillary action of the ink guiding section 11, and the meniscus forming section 10 is kept in a wet state. Therefore, the meniscus forming section 10 includes
The ink film continues to be formed, and the operation of maintaining the pressure in the main ink chamber 4 due to the generation of bubbles operates effectively. From this state,
Until the ink in the main ink chamber 4 is completely exhausted, the ink supply pressure to the inkjet head 1 is kept constant. Therefore, a highly efficient ink supply device can be realized.

As described above, since the meniscus forming section 10 is always immersed in the ink, the meniscus of the ink formed on the meniscus forming section 10 is destroyed until the ink is exhausted after the bubble generation starts. However, the negative pressure in the main ink chamber 4 is kept almost constant.

FIG. 7 is an explanatory diagram showing the relationship between the ink amount and the ink pressure in the ink jet head. Fluctuations in the ink pressure in the ink jet head will affect the ejection characteristics of the ink from the nozzles. In FIG. 7, thick lines and thick dotted lines show variations in the ink static pressure and the ink dynamic pressure in the ink jet head with respect to the ink amount measured using the ink supply device of the embodiment of the present invention shown in FIG. The ink static pressure is a pressure when printing is not performed. This pressure is the pressure at which the capillary force of the absorbing member or the meniscus forming portion is generated,
It is generated by the water head pressure from the ink surface. Also, the ink dynamic pressure can be considered to be the sum of the pressure loss generated by the flow rate of the ink and the fluid resistance of the flow path system, and the static ink pressure. The measurement of the ink dynamic pressure in the figure is for solid printing.

FIG. 7 shows the same dimensions as those of the ink supply apparatus of the embodiment of the present invention used for measurement.
It measured similarly. The variation of the ink static pressure and the ink dynamic pressure with respect to the ink amount at this time is shown by a thin line and a thin dotted line for comparison.

Referring to FIG. 7, there is no significant difference between the pressure loss caused by the fluid resistance of the flow path system, that is, the difference between the solid line and the broken line, but the ink static pressure is considerably different. I have. First, in the embodiment of the present invention, the initial filling amount of ink is larger, because the ink tank can be filled with more ink.

Further, in the conventional ink tank, the static ink pressure increases almost in proportion to the decrease in the remaining amount of ink. This is because the head pressure of the ink from the head surface decreases. However, in the case of the embodiment of the present invention, the ink static pressure rises at the same inclination at the beginning, but the ink is consumed from the absorbing member, and the bubbles are generated from the meniscus forming portion. , The ink static pressure becomes constant. It is considered that the ink pressure at this time is represented by the following equation. Phead = Pair−4γcos θ / D + ρ · g · h2 where Phead is the pressure at the inkjet head,
Pair is the atmospheric pressure, γ is the interfacial tension between the ink and the meniscus forming portion, θ is the wetting angle, D is the void diameter of the meniscus forming portion,
ρ is the density of the ink, g is the gravitational acceleration, and h2 is the height from the ink liquid level of the meniscus forming portion to the inkjet head. One and two items of this equation are determined by the atmospheric pressure and the meniscus forming part. The head pressures of the three inks from the head surface also have a constant value because the height h2 is constant, so that the ink static pressure is constant. As a result, the ink dynamic pressure, which is the sum of the ink flow and the pressure loss generated by the fluid resistance of the flow path system and the ink static pressure, is also constant, realizing an efficient ink supply device with a large amount of usable ink. ing.

In this example, when the negative pressure value in the ink jet head exceeds 125 mmH ₂ O, refilling of the ink is hindered, causing a reduction in the amount of ink droplets ejected from the nozzles. It has been found to cause a decrease. For this reason, in the embodiment of the present invention, the ink pressure is kept in an appropriate range with respect to the change in the remaining amount of ink, and good printing can be performed until the ink is used up.

By the way, there is a case where the surrounding environment changes, for example, the outside air pressure fluctuates or the outside air temperature fluctuates. First, when the main ink chamber is completely filled with ink and the ink is supplied from the sub ink chamber, the atmospheric pressure received by the absorbing member from the air communication hole and the atmospheric pressure received by the tip of the nozzle of the inkjet head are equal to each other. Since they are the same, the pressure balance does not collapse even if the atmospheric pressure changes, and the influence is small.

Next, consider a case where an air layer is formed in the main ink chamber. FIG. 8 and FIG. 9 are explanatory diagrams of the state inside the ink tank due to a change in the surrounding environment. In the figure, 1
3 is an air layer. When the outside air pressure falls or the outside air temperature rises, the air layer 13 above the main ink chamber 4
The negative pressure value in the main ink chamber 4 tends to be relatively small due to the expansion of the volume. Therefore, as shown in FIG. 8, the ink in the main ink chamber 4 passes through the meniscus forming section 10 through the communication hole 7 and is absorbed by the absorbing member 9 in the sub ink chamber 6. Thus, the pressure difference between the pressure in the main ink chamber 4 and the atmospheric pressure is maintained, and the ink does not leak.

When the outside air pressure rises or the outside air temperature falls, the air layer 13 above the main ink chamber 4 contracts, so that the negative pressure value in the main ink chamber 4 becomes relatively large. Try to be. In this case, as shown in FIG. 9, as in the case of ink consumption, the ink passes through the absorbing member 9 from the air communication hole 8, further passes through the meniscus forming portion 10, and passes through the communication hole 7.
By introducing air into the main ink chamber 4 through the, the pressure difference inside the main ink chamber 4 is kept constant. When ink is present in the sub ink chamber 6, the ink moves into the main ink chamber 4, and the negative pressure in the main ink chamber 4 is maintained. In either case, no ink leaks.

FIG. 10 is an explanatory diagram of the relationship between the atmospheric pressure and the ink static pressure. The ink supply device shown in FIG. 1 is installed in a decompression chamber, and the ambient pressure is set to 0.02 atm / hour.
At a varying speed of that. FIG.
Indicates a change in the ink negative pressure value generated in the ink jet head 1 at this time. However, the remaining amount of ink in the ink tank 2 is 40% of the internal volume of the ink tank 2, and the air layer 13 is formed in the main ink chamber 4 in about half the internal volume of the main ink chamber 4. As described with reference to FIG. 9, the air layer is generated by the movement of air into the ink chamber through the meniscus forming portion.

In the state before the pressure reduction, that is, in the state where the atmospheric pressure is 1 atm, the ink negative pressure value of the ink jet head is a negative pressure of 60 mmH ₂ O. As the ambient atmospheric pressure is gradually reduced, the negative pressure value inside the ink tank becomes relatively smaller. At this time, as described above, since the pressure of the air layer 13 in the main ink chamber 4 relatively increases and expands, ink flows through the ink guide section 11 provided in contact with the meniscus forming section 10. Movement from the main ink chamber 4 into the sub ink chamber 6 is started, and the moved ink is absorbed by the absorbing member 9. When the ink is supplied to the absorbing member 9 again, the interfacial tension with the ink becomes
It is determined by the inter-fiber void diameter of the absorbing member 9.
At this time, it is considered that an ink negative pressure value corresponding to the amount of ink in the sub ink chamber 6 acts on the inkjet head 1 according to the ink static pressure curve before the start of bubble generation shown in FIG.

In FIG. 10, the ink is moved from the main ink chamber 4 to the sub ink chamber 6 until the atmospheric pressure becomes 0.8 atm, so that the ink jet head 1 has a negative pressure value of 20 mmH ₂ O or more. It is kept in. When the atmospheric pressure falls below this, the amount of ink that has moved to the sub ink chamber 6 exceeds the amount that the absorbing member 9 can hold the negative pressure, and the negative pressure cannot be maintained any more. And ink leakage occurs. At this time, the atmospheric pressure at which ink leakage occurs can be further reduced by increasing the capacity of the absorbing member 9 capable of holding ink. As described above, by changing the volume ratio between the main ink chamber 4 and the absorbing member 9 in the sub ink chamber 6, the resistance to the change in the outside air pressure and the change in the outside air temperature changes.

In the above description of the volume efficiency, the volume ratio between the main ink chamber 4 and the sub ink chamber 6 is set to 1: 1. The ink retaining efficiency of the absorbing member 9 in the sub ink chamber 6 is not 100%, but is, for example, about 80%. Therefore, considering the volume efficiency of the ink supply device, the smaller the volume of the absorbing member 9 is, the better. However, in consideration of the above-described variation in the atmospheric pressure, the larger the capacity of the absorbing member 9, the higher the ability to absorb the variation in the atmospheric pressure. Therefore, the volumes of the main ink chamber 4 and the absorbing member 9 need to be determined in view of both the ink use efficiency and the resistance to fluctuations in the outside air pressure and outside temperature.

The volume ratio between the main ink chamber 4 and the sub ink chamber 6 is
Let's try a trial calculation under certain conditions. Here, consider the case where the atmospheric pressure decreases and the case where the ambient temperature increases. In the reverse case, there is no problem because the air layer 13 in the main ink chamber 4 contracts and the negative pressure is maintained in the same manner as during normal ink consumption. In the following description, the fluctuation of the atmospheric pressure is within 0.15 atm, and the fluctuation of the temperature is 25 ° C to 70 ° C.
And Further, the volume of the main ink chamber 4 is X,
Let Y be the volume of the absorbing member 9 inside.

It is assumed that the static pressure in the initial state is 50 mmH ₂ O in the ink jet head 1. Also, 1
Pressure = 10332mmH a ₂ O. If an ink leak occurs when the static pressure of the inkjet head 1 becomes negative, the change in the atmospheric pressure until the ink leak occurs is used for relaxing the initial negative pressure. Is 0.15-0.005 = 0.145 (atmospheric pressure). Subsequent changes can be considered constant volume changes, PV = nRT = const. (However,
It is assumed that P is atmospheric pressure, V is volume, R is gas constant, and T is absolute temperature), and the amount of ink leak is considered to correspond to this volume change. Here, assuming that the changed volume is V ′ and the change is ΔV ′, V ′ = 1.145V ΔV ′ = 0.145V

The temperature change (from 25 ° C. (T) to 70 ° C.)
° C (T ')) also contributes to volume expansion. If the volume after the change is V "and the change is ΔV", V "= (T' / T) V = (343/298) V = 1.1
5V ΔV ″ = 0.15 V. Here, the change in the vapor pressure of the ink also contributes to the volume expansion. Therefore, the changed volume is V ′ ″, and the change is △.
Assuming that V ″ ″, ΔV ′ ″ = (0.31-0.03) V = 0.28V.

Assuming that the change in volume when considering the effects of changes in air pressure, temperature, and vapor pressure is ΔV ″ ″, ΔV ″ ″ = ΔV ′ + ΔV ″ + ΔV ′ ″ = 0 .145V
+ 0.15V + 0.28V = 0.575V. From this, the volume expansion is 0.575 · X.

If the total volume of the main ink chamber 4 and the absorbing member 9 is 1, X + Y = 1. Assuming that the actual use efficiency of the absorbing member 9 is 56%,
In order to absorb the volume expansion, the following two relationships must be established. 0.56Y ≧ 0.575X Y ≧ 1.03X (approximately, = X) When this relational expression is almost satisfied and the volume X of the main ink chamber 4 is increased as much as possible, the volume ratio of the main ink chamber 4 and the absorbing member 9 becomes , Almost 50%: 50%. At this time, the ink water retention efficiency H, the use efficiency S, and the real use efficiency J are as follows: H = 50 + 50 × 0.8 = 90 (%) S = 50 + 50 × 0.7 = 85 (%) J = S × H = 0. 9 × 0.85 = 77 (%)

In the above calculation, the allowable pressure fluctuation is 0.15 atm and the temperature fluctuation is from 25 ° C. to 70 ° C. When these allowable values are changed, the main ink chamber 4 and the absorbing member are changed. The volume ratio of 9 changes. In the above calculation, various conditions such as the water retention capacity of the absorbing member 9, the static pressure in the ink jet head 1, and the ink vapor pressure are assumed. Therefore, the main ink chamber is determined based on these conditions. What is necessary is just to determine the volume ratio between 4 and the absorbing member 9.

FIG. 11 is a sectional view showing another embodiment of the ink supply device of the present invention. In the figure, the same parts as those in FIG. 14 is a filter,
15 is a buffer member. This embodiment is almost the same as the embodiment shown in FIG. 1, except that a filter 14 and a buffer member 15 are inserted between the main ink chamber 4 and the supply path 12. The filter 14 is arranged below the buffer member 20. This enables filtration at the end of the supply path 12 leading to the inkjet head 1, so that dust and foreign matter can be reliably removed. The filter 14 is securely adhered to the upper portion of the supply path 12 by ultrasonic fusion or heat fusion. As a material of the filter 14,
A mesh having a filtration particle size of 5 μm to 50 μm,
Alternatively, a filter or the like using a SUS fine wire in a felt shape and further compression-sintering the base material can be used. The filtration particle size is determined so as to trap foreign matter larger than the ink flow path diameter in the inkjet head.

The relationship between the meniscus forming section 10 and the filtering accuracy of the filter 14 is determined so that the meniscus forming section 10 is rougher. For example, the filtering accuracy of the meniscus forming unit 10 is set to 70 μm, and the filtering accuracy of the filter 14 is set to 20 μm.
μm. This may be because when the ink supply device is left sideways or the like, the ink does not come into contact with the meniscus forming unit 10 and the filter 14 if the remaining amount of ink is small. In this state, the outside temperature rises,
Alternatively, when the outside air pressure decreases and the negative pressure in the main ink chamber becomes relatively small, the ink does not move to the absorbing member 9 and the internal pressure of the main ink chamber becomes considerably high. Here, the capillary force at which the meniscus is generated in the meniscus forming unit 10 is higher than that of the filter 14,
Alternatively, by making the capillary force smaller than the capillary force generated by the meniscus formed in the nozzle of the inkjet head 1, the expanded air destroys the meniscus of the meniscus forming section 10 and the air moves to the sub ink chamber 6. ,
No ink leaks from the recording head nozzles. The filter 14 also has a part of an effect of preventing the ink jet head 1 from excessively fluctuating in pressure due to vibration, impact, and acceleration.

The cushioning member 15 is made of, for example, a batting material in which the same polyester fibers as the absorbing member 9 are bundled in one direction. The buffer member 15 is desirably disposed immediately before the mouth of the supply path 12 to prevent vibration and impact, pressure fluctuation due to acceleration, and air bubbles from the nozzle side of the inkjet head 1.

FIG. 12 is a schematic configuration diagram of an ink jet recording unit using the ink supply device of the present invention. In the figure, 21 is an ink jet recording unit, 22 is an ink tank, 23 is a heat sink, 24 is a flow path forming member, 25 is a substrate, 26 is an ink jet head, 27 is a wiring pad,
28 is a sub ink chamber, 29 is an air communication hole, 30 is an absorbing member, 31 is an ink guide section, 32 is a main ink chamber, and 33 is a meniscus forming section.

The ink jet recording unit 21 includes an ink tank 22, a heat sink 23, a flow path forming member 24,
5, an ink jet head 26, a wiring pad 27 and the like. The ink tank 22 includes a sub ink chamber 28, an air communication hole 29, an absorbing member 30, an ink guide section 31, a main ink chamber 32, and a meniscus forming section 33. The ink jet head 26 and the substrate 2 on the heat sink 23
5 and electrical connection is made by wire bonding or the like. Receiving an electric signal from a recording apparatus main body (not shown) is performed via a wiring pad 27 on the substrate 25. A drive circuit and the like are arranged on the substrate 25, and control a heating element provided in the ink jet head 26 to discharge ink from nozzles. On the other hand, the supply of ink from the ink tank 22 is as described above.
The ink supplied from the ink tank 22 is sent to the inkjet head 26 via an ink supply path formed by the flow path forming member 24, and is ejected from a nozzle to perform printing.

The ink jet recording unit 21 shown in FIG. 12 has an ink tank and an ink jet head integrally formed, and by using the ink supply device of the present invention, a compact recording unit having a good ink utilization rate is formed. It is possible to do. In such a configuration, the inkjet recording unit 21 is configured to be detachable from the recording apparatus main body. Therefore, the ink jet head must be replaced when the ink runs out.However, the amount of ink that can be used can be made larger than before, so that the interval between replacements can be lengthened, reducing costs and reducing waste. Can be planned. Of course, the ink tank unit may be configured to be replaceable as a separate unit.

[0063]

As is apparent from the above description, according to the present invention, there is provided a main ink chamber for storing ink in an ink tank, a sub ink chamber containing an absorbing member, and
By having a meniscus forming section and an ink guiding section, air is introduced into the main ink chamber in accordance with a pressure drop in the ink chamber caused by consumption of ink for printing,
The fluctuation of the ink pressure acting on the ink jet head is kept within a proper value range, and good image quality can always be obtained. In addition, the ink in the sub ink chamber can be used up, and even when the ink in the main ink chamber becomes small, printing can be performed without causing pressure fluctuation in the main ink chamber. Efficiency can be improved. Further, even if there is a pressure change in the main ink chamber caused by a change in the surrounding environment, there is no ink leakage and an appropriate pressure can be maintained, so that there is an effect that good printing can be performed.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of an ink supply device of the present invention.

FIG. 2 is an enlarged view of a lower portion of a sub ink chamber.

FIG. 3 is an explanatory diagram of an example of a mesh body that can be used for the meniscus forming section 10;

FIG. 4 is an explanatory diagram of characteristics of a tatami twill wire mesh.

FIG. 5 is an explanatory diagram of a process of ink consumption.

FIG. 6 is an explanatory diagram of a process of generating bubbles in a tatami twill wire mesh.

FIG. 7 is an explanatory diagram of a relationship between an ink amount and an ink pressure in an inkjet head.

FIG. 8 is an explanatory diagram of a state inside the ink tank due to a change in the surrounding environment.

FIG. 9 is an explanatory diagram of a state inside the ink tank due to another change in the surrounding environment.

FIG. 10 is a diagram illustrating the relationship between the atmospheric pressure and the ink static pressure.

FIG. 11 is a cross-sectional view showing another embodiment of the ink supply device of the present invention.

FIG. 12 is a schematic configuration diagram of an ink jet recording unit using the ink supply device of the present invention.

[Explanation of symbols]

1 ink jet head, 2 ink tanks, 3 inks, 4 main ink chambers, 5 communicating paths, 6 sub ink chambers,
7 communication hole, 8 atmosphere communication hole, 9 absorbing member, 10 meniscus forming section, 11 ink guiding section, 12 supply path,
13 air layer, 14 filter, 15 cushioning member, 21
Inkjet recording unit, 22 ink tanks, 2
3 heat sink, 24 flow path forming member, 25 substrate, 26
Inkjet head, 27 wiring pad, 28 sub ink chamber, 29 atmosphere communication hole, 30 absorbing member, 31 ink guiding section, 32 main ink chamber, 33 meniscus forming section.

────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Yoshihiko Fujimura 2274 Hongo, Ebina-shi, Kanagawa Fuji Xerox Co., Ltd. (56) References JP-A-6-238908 (JP, A) JP-A-6-286160 ( JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) B41J 2/175

Claims (7)

(57) [Claims] 1. An ink supply device that is connected to an ink jet head and supplies ink to the ink jet head, wherein a main ink storage chamber that communicates with the ink jet head and stores ink is adjacent to a side of the main ink storage chamber. A sub-ink storage chamber that is disposed in communication with the main ink storage chamber through a communication hole in a lower space, and has an air communication port opened in an upper side; Has an ink absorbing member arranged to be in close contact with the inner wall of the sub-ink storage chamber, and a meniscus formation section provided to cover the communication hole of the sub-ink storage chamber, forming a meniscus and generating bubbles. An ink supply device characterized by the above-mentioned. 2. An ink supply device, which is connected to an ink jet head and supplies ink to the ink jet head, wherein: a main ink storage chamber, which communicates with the ink jet head and stores ink, is adjacent to a side of the main ink storage chamber. A sub-ink storage chamber that is disposed in communication with the main ink storage chamber through a communication hole in a lower space, and has an air communication port opened in an upper side; An ink absorbing member disposed so as to be in intimate contact with the inner wall of the sub ink storage chamber, a meniscus forming portion provided to cover a communication hole of the sub ink storage chamber, and a main surface contacting the lower surface of the meniscus forming portion. An ink supply device comprising: an ink guide portion extending in a lower space communicating with an ink storage chamber. 3. The ink guide section according to claim 2, wherein one end of the ink guide section contacts the meniscus forming section, and the other end contacts a bottom of a lower space communicating with the main ink storage chamber. The ink supply device according to claim 1. 4. The ink according to claim 2, wherein the ink guide section is formed to have a smaller cross section than the communication hole, and forms a non-contact area with the ink guide section in the meniscus forming section. Feeding device. 5. The ink supply device according to claim 1, wherein the meniscus forming section is formed of a mesh. 6. The ink supply device according to claim 1, wherein the meniscus forming section is formed of a porous body. 7. The ink according to claim 1, wherein a filter having higher filtration accuracy than the meniscus forming portion is disposed between the main ink storage chamber and the inkjet head. Feeding device.