WO2009014224A1

WO2009014224A1 - Ink container, ink supplying system, and ink jet recording apparatus

Info

Publication number: WO2009014224A1
Application number: PCT/JP2008/063456
Authority: WO
Inventors: Soji Kondo; Kenta Udagawa
Original assignee: Canon Kabushiki
Priority date: 2007-07-20
Filing date: 2008-07-18
Publication date: 2009-01-29
Also published as: JP2009023251A

Abstract

In an ink jet recording apparatus, an air-liquid separation film is provided to a sub-container. An operation of reducing pressure in the sub-container through the air-liquid separation film to discharge air from an inside of the sub-container. This operation can be performed independently of an ink supplying operation and an ink discharging operation.

Description

DESCRIPTION

INK CONTAINER, INK SUPPLYING SYSTEM, AND

INK JET RECORDING APPARATUS

[TECHNICAL FIELD]

The present invention relates to an ink container disposed between an ink jet recording head and a main container, an ink supply system provided with the ink container, and an ink jet recording apparatus provided with an ink supplying system.

[BACKGROUND ART]

As one of ink jet recording apparatus, a so-called serial type ink jet recording apparatus in which an image is formed by reciprocal scanning of a recording head with respect to a recording material (medium) in a predetermined direction and by conveyance of the recording material in a direction perpendicular to the predetermined direction is known. As one of ink supplying methods applicable to such an ink jet recording apparatus, there is a method called an on-carriage method in which an ink container is integrally and inseparably or separably mounted to a recording head, which is mounted on a carriage or the like and subjected to reciprocal movement (main scanning) , so as to supply ink. In recent years, the ink jet recording apparatus (hereinafter also simply referred to as a "printer") is required to be downsized and is strongly required to produce a performance such that a high-quality image is recorded at high speed. In order to realize these requirements, the carriage is required to be moved stably at high speed. For this purpose, it is advantageous that the carriage or an ink container or the like to be mounted on the carriage is small and light weight. However, when downsizing and weight reduction of the ink container are improved, a volume of ink retained in the ink container has to be decreased, so that a user is forced to frequently replace the ink container with a new ink container.

Lately, the merits of employing such an off-carriage method that a main ink container (main container) is separately provided from a recording head mounted on a carriage and is fixedly mounted on a portion other than the carriage and then is connected to the recording head through a tube or the like to supply ink have been recognized once again. Of these, there is a method in which an ink container as a retaining portion for temporarily retaining a relatively small amount of ink (hereinafter referred to as a "sub-container") is provided to a recording head or a carriage and ink is supplied intermittently from the main ink container to the sub-container with appropriate timing. For example, as disclosed in Japanese Laid-Open Patent Application (JP-A) 2000-334982, such a constitution that a sub-container and a main container which is fixed to a main assembly of an ink jet recording apparatus are connected to and disconnected from each other as needed in a predetermined position in a scanning range of a carriage does not require piping or the like following movement of the carriage. For that reason, this constitution is advantageous for realizing downsizing of a printer and stable movement of the carriage.

The sub-container is required to keep negative pressure for properly supplying ink to the recording head and to ensure a substantial ink retention amount (ink net amount) for covering ink flow consumed by the recording head. In the sub-container disclosed in JP-A 2000-334982, an absorbing material as a negative pressure producing source is contained but the presence of the absorbing material leads to a decrease in ink retention amount with respect to a volume of the sub-container.

Therefore, as an constitutional example capable of effectively utilizing the volume of the sub-container, e.g., JP-A 2003-237108 proposes such a constitution that a sub-container includes a case one of side surfaces of which is opened, a flexible film for covering the opened portion of the case, and an internally provided spring as a negative pressure (producing) source for generating an urging force for pressing the flexible film outwardly. To the case of the sub-container, air bent for opening the air in the sub-container to ambient air and an ink injection port for receiving the ink supplied from the main container are provided. At each of the bent and the port, a valve for controlling an open state and a close state is disposed and by adjusting opening/closing of the valve, an ink filling operation or the like is performed.

In the thus-constituted sub-container, the air can be introduced, e.g., due to external gas permeation fluid connection between the main container and the sub-container, main container mounting, and the like. The introduction of the air causes a lowering in ink net amount in the sub-container and dripping of the ink from the recording head by expanded air in the case where ambient temperature or pressure is changed.

For that reason, a method in which an amount at air to be introduced in the sub-container is estimated and a corresponding air buffer is provided is proposed. However, this method leads to a large-size sub-container, thus resulting in loss of original advantages of the sub-container. Further, when the air in the sub-container reaches the recording head, print failure can be caused to occur, so that such a proposal that an air-removing operation (such as a refreshing operation) is incorporated in a control operation was made. However, when this operation was performed, a certain amount of ink was discharged from the sub-container, thus resulting in an occurrence of a large amount of wasted ink.

JP-A 2004-255862 proposes a constitution for reducing an amount of ink discharged by the air-removing operation. However, the amount of the discharged ink is reduced but the amount of wasted ink is not completely reduced.

JP-A 2003-237108 discloses a constitution in which ink is pressurized and supplied from a main container to a sub-container in a state in which an air vent is opened to discharge the air in the sub-container from the air vent. Further, a constitution in which the air is discharged from the air vent by changing a volume of the sub-container by an externally provided structure is also disclosed. In these constitutions, however, the discharge of the air depends on timing of the ink supply or requires the external structure for permitting the air discharge, thus leading to regulation of timing or a large-size structure.

Japanese Patent (JP-B) No. 3606282 discloses a constitution in which the air in a sub-container is removed by dissolving the air in degassed ink but the air which cannot be completely removed is to be discharged together with the ink after all. JP-A 2006-199040 proposes a printing system in which a sub-container and a main container are connected to each other with two tubes and ink is circulated through the tubes to supply and vent the ink. In this constitution, negative pressure is generated by the sub-container, during supply of the ink, first, the ink in the sub-container is returned to the main container to empty the sub-container and thereafter ink flow paths are pressurized to supply certain amount of the ink to the sub-container. The air generated in the sub-container can be removed by circulating the ink without generating waste ink. However, a valve is required for each of the ink flow paths, so that it is necessary to control these valves. Further, in order to supply a proper amount of ink to the sub-container, an air/ink sensor was required, thus resulting in a complicated apparatus. Further, the ink was required to reciprocate between the main container and the sub-container, so that it taken a long time to effect maintenance. In addition, a time in which the ink contacted the air was increased, so that an ink concentration was changed by evaporation to adversely affect a print quality. In any of the above-described conventional constitution, there is no proposal such that downsizing of a peripheral structure including a sub-container and prevention of wasteful discharge of ink by an air-removing operation can be realized compatibly.

Further, on removal of the air from a spring bladder type sub-container, a sufficient study of a constitution of the sub-container required to the air removal with reliability is not made.

Further, a study on a constitution of an ink supplying system suitable for air removal from a plurality of sub-containers is also not made sufficiently.

[DISCLOSURE OF THE INVENTION]

A principal object of the present invention is to solve the above described problems by carrying out a study on a structure which has not been studied sufficiently.

Another object of the present invention is to provide an ink container having solved the above-described problems.

A further object of the present invention is to provide an ink jet recording apparatus including the ink container.

According to an aspect of the present invention, there is provided an ink jet recording apparatus comprising: a carriage for mounting a recording head; a main container mounted to a main assembly of the ink jet recording apparatus; a sub-container, mounted on the carriage together with the recording head and provided with a mechanism for generating pressure for providing negative pressure in the recording head, for temporarily retaining liquid between the main container and the recording head; wherein the sub-container comprises: a container case, which comprises a flexible film, having an inner space for retaining ink; an opening provided in the container case; an air-liquid separation member, disposed in the opening, for permitting passing of the air but limiting passing of the liquid; and an urging member for urging the flexible film toward an outside of the container case; and a pressure-reducing mechanism, provided in the main assembly of the ink jet recording apparatus, for reducing pressure in the sub-container to remove air in the sub-container through the air-liquid separation member. In the ink jet recording apparatus, the air can be discharged from the inside of the sub-container by appropriately actuating the pressure-reducing mechanism.

According to another aspect of the present invention, there is provided an ink container for supplying ink to an ink jet recording head, comprising: a container casing having an opened surface; a flexible member which covers the opened surface of aid container casing to constitute a space between the flexible member and the container casing as an ink retaining portion and is disposed depending on an amount of ink accommodation; a spring member, disposed between the flexible member and the container casing, for urging the flexible member toward a direction in which the flexible member is moved apart from the container casing; and an air-liquid separation member, disposed to cover an opening provided to the container casing, for permitting passing of gas but limiting passing of liquid.

According to the present invention, it is possible to independently remove the air from the inside of the sub-container as needed with appropriate timing without the need to synchronize the timing with timing of ink supply or head refreshing. For that reason, a structure such as an air buffer for storing the air in the sub-container becomes unnecessary, so that it is possible to make a peripheral constitution of the sub-container compact without complicating and upsizing the constitution.

Further, it is possible to simply constitute a structure for removing the air generated and stagnated in the sub-container.

Therefore, with respect to air discharge from the sub-container, it is possible to realize an off-carriage type ink jet recording apparatus which is a small size and less lowering in print quality with no occurrence of wasted ink.

These and other objects, features and advantages of the present invention will become more apparent upon a consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings .

[BRIEF DESCRIPTION OF THE DRAWINGS] Figure l(a) is a schematic view showing a fundamental structure of an ink supplying system of a continuous ink supply type and Figure 1 (b) is a schematic view showing an ink supplying system of an intermittent ink supply type. Figure 2 (a) is a perspective view of a carriage in an Embodiment of the present invention and Figure 2 (b) is a schematic view showing an internal portion of a sub-container box mounted in a carriage.

Figure 3 (a) is a perspective view of a sub-container and Figures 3(b) and 3(c) are perspective views each showing an internal structure of the sub-container.

Figure 4 is a perspective view showing another configurational example of the sub-container.

Figure 5 is a perspective view showing an ink valve as a constituent of the sub-container. Figures 6 (a), 6 (b) and 6(c) are schematic views for illustrating a motion of the ink valve.

Figures 7 (a) , 7 (b) and 7 (c) are perspective views for illustrating a structure of an air chamber.

Figure 8 (a) is a schematic vie for illustrating a positional relationship between an air-liquid separation film and a spring member and Figures 8 (b) and 8 (c) are sectional views each showing the positional relationship.

Figure 9 is a schematic diagram showing a fundamental structure of an ink supplying system for supplying ink under reduced pressure.

Figure 10 is a schematic diagram showing a fundamental structure of an ink supplying system for supplying ink under application of pressure.

[BEST MODE FOR CARRYING OUT THE INVENTION]

Hereinbelow, Embodiments of the present invention will be described with reference to the drawings .

Figure 1 schematically shows a fundamental structure of an ink supplying system according to the present invention including an ink container (sub-container) and a main container.

An ink container (sub-container) 14 constitutes an ink accommodating space (hereinafter also referred to as a "pressure chamber") by attaching a flexible film 15 to a casing (a sub-container case, hereinafter also referred simply to as a "case") 22 having an opened side surface. Inside the sub-container 14, an elastic member (spring member) is disposed to outwardly urge the flexible film 15 to produce (generate) pressure for providing negative pressure in an ink jet recording head 4 connected to the sub-container 14 through an ink supply port 16 of the sub-container 14.

Further, at a portion of the casing 22 constituting the ink accommodating space 6, an air-liquid separation member 7 is disposed. The air-liquid separation member 7 is a member having such a characteristic that gas passes through the member but liquid does not pass through the member and is a sheet-like member in the present invention.

The sub-container 14 includes an air chamber 8 disposed opposite from the ink accommodating space 6 with respect to a side surface of the casing 22 at which the air-liquid separation member 7 is disposed. At a portion of the air chamber 8, an air discharge opening 31 (hereinafter also referred to as an "air opening") is provided and an air valve 9 is provided in the air opening 31. To the air opening 31, an air flow path 10 provided to a printer is connected and is constituted so as to be communicatable with a pressure-reducing pump 11. In Figure l(a), a schematic structure of a continuous ink supplying system in which the air opening 31 and the air flow path 10 is always connected to each other and an ink introducing port 17 and an ink flow path 2 are always connected to each other.

In the case of such a constitution that the air opening 31 and the air flow path 10 are always connected to each other, the air valve 9 is constituted so as to be switched as needed between a connecting state of the air opening 31 with the pump 11 and a closing state of the air opening 31.

Further, a main container 1 is disposed in a main assembly of a printer and is connected to the ink accommodating space 6 via an ink introducing port 16 of the sub-container 14 through a tube constituting the ink supply port 2. Ink in the main container 1 is supplied to the ink jet recording head 4 through the ink accommodating space 6. At the ink introducing port 17 which is a connecting portion between the ink accommodating space 6 and the ink supply path 2, an ink valve 3 is provided. A structure and a function of the ink valve 3 will be described later but is constituted in the continuous ink supplying system so that when ink in the sub-container 14 is decreased to increase negative pressure in the sub-container 14, the ink valve 3 is opened by a change in pressure in the sub-container 14. By this, the ink is supplied from the main container 1 to the sub-container 14. On the other hand, when a value of the negative pressure restored to a particular value by the ink supply, the ink valve 3 is closed to stop the ink supply.

Figure 1 (b) shows an example of a structure of an ink supplying system in which the air opening 31 and the air flow path 10 are connected to and separated from each other as needed and the ink introducing port 17 and the ink supply port 2 are connected to and separated from each other as needed.

In this structure, as a constitution of the sub-container side, a joint portion 311 is provided so that the air flow path 10 is capable of being connected to and separated from the joint portion 311. Further, a joint 117 is provided so that the ink flow path 2 is capable of being connected to and separated from the joint 117. Particularly, the joint 117 is provided with a valve mechanism 18 capable of closing and opening a path leading to the ink valve 3 in a state in which the ink flow path 2 is separated from the joint 117.

In a state in which the joint portion 311 and the air flow path 10 are connected, the air valve 9 is in a communicatable open state. In the separation state, the air valve 9 is closed to place the air chamber 8 in a sealed space state. On the other hand, in a state in which the joint 117 and the ink supply port 2 are connected, the valve mechanism 18 is in an open state. In the separation state, the valve mechanism 18 is in a close state. As described later, the ink valve 3 employs such a valve constitution that the open/close state is changed depending on an amount of ink in the sub-container 14. Particularly, a state in which printing is performed to consume the ink is the state in which the ink flow path 2 is separated from the joint 117, so that when the ink valve 3 is opened, ambient air is to be taken into the sub-container 14. For this reason, the valve mechanism 18 for preventing this and controlling the ink so as to be supplied to the sub-container 14 only when the ink supply path 2 is connected to the joint 117.

The state shown in Figure 1 (a) is such a state that the ink is sufficiently present in the ink accommodating space 6.

The flexible film 15 of the sub-container 14 is exposed to ambient air, so that when the ink is consumed, the flexible film 15 is displaced toward a direction_. in which a volume of the ink accommodating space 6 is decreased. By this displacement, the spring member 19 is also compression-deformed. A deforming stress of the spring member 19 functions as a negative pressure source with respect to the recording head 4, so that the ink accommodating space 6 is also called the pressure chamber 6.

In order to remove the air (bubble) generated in the ink accommodating space 6, the air flow path 10 and the air discharge opening 31 are connected and in a state in which the air valve 9 is opened, the pressure-reducing pump 11 is actuated. By the negative pressure acting on the ink accommodating space 6, the air is sucked from the ink accommodating space 6 through the air-liquid separation member 7 and the air chamber 8. By the action of the air-liquid separation member 7, only the air can pass through the air-liquid separation member 7 and is discharged from the air accommodating space 6, so that movement of the ink toward the outside is regulated to prevent the ink from being discharged to the outside.

When the recording is carried out, the air valve 9 is closed to shut the air chamber 8 from ambient air, thus constituting a substantially closed space. For this reason, it is possible to suppress unnecessary evaporation of the ink through the air-liquid separation member 7. A specific structure of the sub-container 14 and details of air removal will be described later.

Figures 2 (a) and 2 (b) are schematic views showing an Embodiment of a structure of an ink jet recording apparatus which employs an ink supplying system constituted by including four sub-containers each shown in Figure l(a) or 1 (b) , particularly shown in Figure l(b) in which each of the air flow path 10 and the ink supply path 2 is intermittently connected to and separated from an associated joint (portion). Figure 2 (a) shows an outer appearance of a carriage 5 provided with a recording head 4 and a sub-container box 13 in which four sub-containers 14 are accommodated. Figure 2 (b) shows an internal portion of the carriage 5 by removing a side surface of the carriage 5.

The carriage 5 is movably supported along a shaft 12 fixedly provided to the printing main assembly. A movement direction of the carriage 5 is perpendicular to a conveyance direction of a recording sheet facing an ink ejection portion of the recording head 4.

As described above, the sub-containers 14 are accommodated and disposed in the sub-container box 13 correspondingly to the number of colors for the recording head 4.

In the Embodiment shown in Figures 2 (a) and 2 (b) , the number of colors is four, i.e., yellow (Y), magenta (M) , cyan (C) and black (Bk) . Each of the sub-containers 14 is disposed in the sub-container box 13 so that a surface at which the flexible film 15 is provided is located downwardly with respect to a direction of gravitational force. That is, a largest surface of surfaces constituting the sub-container 14 is substantially parallel to the direction of gravitational force. In a side surface of the sub-container box 13, an air vent 312 for accommodating the inside of the sub-container box 13 and ambient air with each other is provided. Further, in the side surface of the sub-container box 13, connecting portions 117Y, 117M, 117C and 117Bk are provided so as to communicate with internally accommodated ink introducing ports 17 (Figure l(a) or 1 (b) ) for the four colors, respectively. The ink introducing ports 17 of the respective color sub-containers 14 and the connecting portions 117Y, 117M, 117C and 117Bk are individually connected to each other with an unshown associated communicating path. Each communicating path is provided with a valve as shown in Figure l(b). In the side surface of the sub-container box 13, a first suction opening 311 through which an air flow path for discharging the air from the sub-container 14 is to be connected is disposed. The first suction opening 311 is connected to each of air discharge openings 31 of the respective color sub-containers 14 by unshown communicating paths.

In the Embodiment shown in Figures 2 (a) and 2 (b) , such a constitution that the valve is disposed in the first suction opening 311 can be employed so as to common to all the sub-containers. Therefore, in the constitution shown in Figure 1 (b) , the air valve 9 is provided in the air discharge opening 31 of the sub-container 14 but in the constitution shown in Figures 2 (a) and 2 (b) , it is possible to obviate individual arrangement of the air valves 9 for the four sub-containers 14. It is also possible to employ such a constitution that the air valves 9 are provided in the air discharge openings 31 of all the sub-containers 14 and no valve is provided in the first suction opening 311 shown in Figures 2 (a) and 2(b) .

In a state in which the air flow path 10 is not connected, an unshown valve is in a closed state. Next, the specific constitution of the sub-container will be described with reference to the drawings. Figures 3 (a) , 3 (b) and 3 (c) are perspective views each showing the sub-container 14 for carrying out the present invention.

As shown in Figure 3 (a) , a surface of an outer shell of the ink container 14 is constituted by a molded flexible film 15 which constitutes a part of a pressure chamber 6 described later in detail. The flexible film 15 may also have an elliptical shape as shown in Figure 4. In a casing of the sub-container 14 (sub-container case 22), an ink introducing port 17 and an ink supply port 16 are formed to communicate with an ink accommodating space (pressure chamber) 6. The ink flowing from the main container 1 through the ink supply port 2 enters the pressure chamber 6 and is supplied from the ink supply port 16 to the recording head 4.

Figure 3 (b) shows the sub-container 14 from which the flexible film 15 is removed. In the pressure chamber 6 of the sub-container 14, a negative pressure spring (elastic member) 19 and a pressure plate 21 are disposed. The negative pressure spring 19 urges the flexible film 15 outwardly through the pressure plate 21 to generate negative pressure in the pressure chamber 6. In the pressure chamber 6, an ink valve 3 and a valve spring 20 are disposed. The ink valve 3 is urged against a wall surface of the pressure chamber 6 by the valve spring 6.

Figure 5 shows a perspective view of the ink valve 3. The ink valve 3 includes an elastic member 28 for closing the ink introducing port 17 and a lever portion 29 for moving the elastic member 28. The elastic member 28 is formed of an elastomer or the like and disposed correspondingly to a portion of the wall surface in the pressure chamber 6 where the ink introducing port 17 is formed. The elastic member 28 is urged against the wall surface in the pressure chamber 6 by the valve spring 20 to close the ink introducing port 17. The lever portion 29 is provided rotatably about a rotational shaft 27 in the pressure chamber 6, and the elastic member 28 is moved to open and close the ink introducing port 17 in interrelation with the rotation of the lever portion 29.

Figure 3(c) is a perspective view showing the sub-container case 22 as the outer shell of the sub-container 14. An internal portion of the sub-container case 22 corresponds to the pressure chamber 6 shown in Figure 1 and in at least one surface of the sub-container case 22, an opening 23 is formed. At the opening 23, a air-liquid separation film (air-liquid separation member) 7 is disposed. Such a surface side of the sub-container case 22 corresponds to a ceiling of the pressure chamber 6 in a state in which the sub-container 14 is incorporated and operated in the ink jet recording apparatus. To the ceiling, in order to efficiently collect the air to the air-liquid separation film 7, an inclined structure 24 with the opening 23 as a crest (apex) is provided.

Further, the inclined structure 24 is provided with grooves extended from one or more corner 25 of the opening 25 toward the outside of the opening 25. By this, in the case where the air comes near to the opening 25, the ink in the opening 23 flows out along the grooves 26, thus easily bringing the air near to the air-liquid separation film 7.

Next, with reference to Figures 6 (a) , 6 (b) and 6(c), a motion of the ink valve 3 will be described. In the following, a surface where the flexible film 15 of the sub-container 14 is provided is referred to as a "lower surface" and a surface opposite from the surface where the flexible film 15 is provided is referred to as an "upper surface". Figure 6 (a) is a schematic view of the ink valve 3 as seen from the lower surface side. Figures 6 (b) and 6(c) are schematic views showing an open state of the ink valve 3 and a close state of the ink valve 3, respectively, at an A-A cross section of Figure 6 (a). In these figures, the flexible film 15 is omitted in order to facilitate understanding of the motion of the ink valve 3. In the state shown in Figure 6 (b) , the ink is sufficiently contained in the pressure chamber 6 and substantially no pressure is applied to the lever portion 29 even when the lever portion 29 and the pressure plate 21 are in non-contact or contact with each other, so that the ink introducing port 17 is closed.

When the ink in the pressure chamber 6 is decreased, the flexible film 15 collapses to press the lever portion 29 of the ink valve 3 through the pressure plate 21. When the lever portion 29 is pressed, the lever portion 29 is rotated about the rotational shaft (Figure 5) to open the ink introducing port 17 as shown in Figure 6. The ink introducing port 17 is always connected to the main container 1, e.g., in the case of the constitution shown in Figure 1 (a) , so that when the ink introducing port 17 is opened, the pressure chamber 6 as the ink accommodating space constituted by the flexible film 15 is displaced in an expansion direction of the pressure chamber 6 to cause the ink to flow from the main container 1 into the pressure chamber 6 of the sub-container 14. When the flexible film 15 is expanded toward the outside of the sub-container 14 by the flowing of the ink into the pressure chamber 6, the lever 29 is rotated by the expansion. When a predetermined amount of the ink is supplied, the ink introducing port 17 is closed again.

The supply of the ink is performed by- repeating this operation. Spring constants of the negative pressure spring 19 and the valve spring 20 are set so as to enable.

On the other hand, in the case of the constitution shown in Figure 1 (b) , the main container 1 is connected as needed. Therefore, even when the ink introducing port 17 is opened by actuating the ink valve 3 through the consumption of the ink, the sub-container 14 is kept in the closed state by the valve 18 disposed outside the ink valve 3. For this reason, the spring 19 is displaced without introducing the air from the outside, so that the flexible film (member) 15 is kept in the collapsed state. .When the ink communicating path 2 is connected, the closed valve 18 is opened, so that the ink is replenished from the main container 1 to the sub-container 14. Next, air removal from the inside of the sub-container 14 will be described with reference to Figures 7 (a) , 7 (b) and 7 (c) .

Figures 7 (a) , 7 (b) and 7 (c) are perspective views showing the upper surface of the sub-container 14. As shown in Figure 7 (c) , at the surface of the sub-container case 22 where the opening 23 is formed, a recessed portion 321 constituting the air chamber 32 is formed. At the opening 23, the air-liquid separation film 7 is disposed as shown in Figure 7 (b) . Then, as shown in Figure 7 (a) , onto the surface of the sub-container case 22, a flow path film 30 is applied so as to seal the recessed portion 321 to form the air chamber 32. This air chamber 32 is connected to the pressure chamber 6 of the sub-container case 22 through the air-liquid separation film 7. By the action of the air-liquid separation film 7, only the air is allowed to pass from the pressure chamber 6 to the air chamber 32 while the passing of the ink is limited. The air chamber 32 corresponds to the air chamber 8 in Figures l(a) and l(b) .

The air chamber 32 is connected from the air discharge opening 31 to the pressure-reducing pump 11 through the tube constituting the air flow path 10 (Figure l(a)) . Between the air chamber 32 and the pressure-reducing pump 11, the air valve 9 is provided and closed during a period other than the time of performing the air removal. When the air removal is performed, the air valve 9 is opened to cause the air chamber 32 and the pressure-reducing pump 11 to communicate with each other. By the pressure-reducing pump 11, the air chamber 32 is reduced in pressure, so that the air is removed from the inside of the pressure chamber 6. After the air removal, the air valve 9 is closed. This operation is similarly performed also in the case of the constitution shown in Figure l(b) . In the state in which the air flow path 10 is connected, the air removal is performed. By the thus performed air removal using the air-liquid separation film 7, it is possible to discharge only the air without discharging the ink. The waste ink is not generated by the air removal, so that it is possible to perform the air removal diligently. As a result, a volume of the air buffer of the sub-container can be reduced to permit downsizing of the sub-container.

By employing the above described constitution, it is possible to realize an ink jet recording apparatus, of the off-carriage type, which is small in size with a simple constitution and causes no waste ink during bubble (air) removal.

The internal structure of the sub-container will be further described with reference to Figures 8 (a) , 8 (b) and 8 (c) . Figures 8 (a) , 8 (b) and 8(c) show a positional relationship between the air-liquid separation film 7 and the negative pressure spring 19 in the sub-container. The positional relationship between the air-liquid separation film 7 and the negative pressure spring 19 is not particularly limited but those shown in Figures 8 (a) and 8 (c) may be selected as a preferable constitution. Figures 8 (b) and 8 (c) are schematic views, so that the ceiling of the pressure chamber 6 of the sub-container is illustrated as a flat portion. The constitution of the ceiling of the pressure chamber 6 described with reference to Figures 3 (a) , 3 (b) and 3 (c) is explained such that the inclined structure 24 with the opening as the crest (apex) is provided for efficiently collecting the air to the air-liquid separation film 7 but in Figures 8 (b) and 8 (c) , the inclined structure 24 is omitted from illustration.

The negative pressure spring 19 used in this constitution is coil spring.

As shown in Figure 8 (b) , such a constitution that the air-liquid separation member 7 is disposed out of a negative pressure spring area in which the negative pressure spring 19 is disposed will be considered.

In this constitution, first air (Air 1) located out of the negative pressure spring area and second air (Air 2) located within the negative pressure spring area can be present. In order to discharge the air in the sub-container 14, when the inside of the air chamber 6 is reduced in pressure through the air discharge opening 31, the first air (Air 1) located outside the negative pressure spring

19 can be discharged through the air-liquid separation member 7. However, the second air (Air 2) located within the negative pressure spring area is hindered by the negative pressure spring 19, thus failing to move to the outside of the negative pressure spring 19, with the result that the second air cannot be discharged to the outside of the air chamber 6.

On the other hand, when a part of the negative pressure spring 19 overlaps with the air-liquid separation member 7 as shown in Figure 8 (c) , both of an area outside the negative pressure spring 19 and an area inside the negative pressure spring 18 communicate with the air-liquid separation member 7. Therefore, both of the first air (Air 1) located out of the negative pressure spring area and the second air (Air 2) located within the negative pressure spring area can communicate with the air-liquid separation member 7 with no obstructing material, so that it is possible to both of the first air and the second air with reliability by the air discharging operation. In addition, in the case where the ceiling of the sub-container is provided with the inclined structure toward the air-liquid separation member 7 as described above, the air is guided to a position in which the air can contact the air-liquid separation member 7 along the inclined structure of the ceiling, thus being further easily discharged.

In the case where the negative pressure spring 19 is the coil spring, the constitution shown in Figure 8 (c) is suitable but in the case of other spring structures, the suitable constitution is not limited to the constitution shown in Figure 8 (c) . The above description is to the effect that in the case where the air is prevented from reaching the air-liquid separation member 7 by a structure of the spring member resulting in the obstructing material, such a positional relationship between the air-liquid separation member 7 and the negative pressure spring 19 that the negative pressure spring 19 used does not constitute the obstructing material may be employed. Further, in order to increase a supply speed of the ink to the sub-container 14, the ink jet recording apparatus may desirably include an ink supply speed accelerating mechanism. This is because the ink supply speed accelerating mechanism is effective in the case where the ink in the pressure chamber 6 is consumed, for solid image printing or the like, in a large amount by the recording head 4. An example of the ink supply speed accelerating mechanism will be described with reference to the drawings.

As shown in Figure 9, the sub-container box 13 is formed to be hermetically sealed, and a supply pressure-reducing pump (second pressure-reducing mechanism) 34 is provided in the printer main assembly and is connected to an internal portion of the sub-container box 13 through a tube 33. An internal pressure of the sub-container box 13 is reduced to be lower than that of the pressure chamber 6 by the supply pressure-reducing pump 34, so that an ink supply speed from the main container 1 to the pressure chamber 6 can be increased. The supply pressure-reducing pump 34 can also function as at least one of the pressure-reducing pump 11 and a pump for effecting suction refreshing of the recording head 4.

Instead of the above-described type in which the sub-container is reduced in pressure to accelerate the ink supply speed, it is also possible to employ- such a type that the main container is pressurized by the air. In Figure 10, the main container is constituted by an ink pack 38 constituted by a flexible material filled with ink and an outer shell case 36 formed in a hermetically sealed state so as to surround the ink pack 38 through a space 35. By pressurizing the space 35 formed between the ink pack 38 and the outer shell case 36 by a supply pressurizing pump 39, the inside of the ink pack 38 is pressurized to increase the speed of the ink supplied to the pressure chamber 6.

[INDUSTRIAL APPLICABILITY]

According to the ink jet recording apparatus of the present invention, it is possible to independently remove the air from the inside of the sub-container as needed with appropriate timing without the need to synchronize the timing with timing of ink supply or head refreshing. For that reason, a structure such as an air buffer for storing the air in the sub-container becomes unnecessary, so that it is possible to make a peripheral constitution of the sub-container compact without complicating and upsizing the constitution.

Further, in the ink jet recording apparatus of the present invention, it is possible to simply constitute a structure for removing the air generated and stagnated in the sub-container. Therefore, with respect to air discharge from the sub-container, it is possible to realize an off-carriage type ink jet recording apparatus which is a small size and less lowering in print quality with no occurrence of wasted ink. While the invention has been described with reference to the structures disclosed herein, it is not confined to the details set forth and this application is intended to cover such modifications or changes as may come within the purpose of the improvements or the scope of the following claims.

Claims

1. An ink jet recording apparatus comprising: a carriage for mounting a recording head; a main container mounted to a main assembly of said ink jet recording apparatus; a sub-container, mounted on said carriage together with the recording head and provided with a mechanism for generating pressure for providing negative pressure in the recording head, for temporarily retaining liquid between said main container and the recording head; wherein said sub-container comprises: a container case, which comprises a flexible film, having an inner space forretaining ink; an opening provided in the container case; an air-liquid separation member, disposed in the opening, for permitting passing of the air but limiting passing of the liquid; and an urging member for urging the flexible film toward an outside of the container case; and a pressure-reducing mechanism, provided in the main assembly of said ink jet recording apparatus, for reducing pressure in said sub-container to remove air in said sub-container through the air-liquid separation member.

2. An apparatus according to Claim 1, wherein said sub-container has a flat outer shape and is disposed with respect to said ink jet recording apparatus so that the container case has a horizontal surface having a largest area.

3. An apparatus according to Claim 1, wherein said opening is disposed in an upper surface of the container case of said sub-container disposed in said ink jet recording apparatus.

4. An apparatus according to Claim 3, wherein the container case is provided with an inclined structure with the opening as an apex.

5. An apparatus according to Claim 1, wherein said ink jet recording apparatus further comprises a sub-container box, provided to said carriage, which accommodates a plurality of sub-containers and has a communicating hole for communicating an inside of each sub-container with ambient air.

6. An apparatus according to Claim 1, wherein said main container and said pressure-reducing mechanism are always connected to said sub-container.

7. An apparatus according to Claim 1, wherein said main container and said pressure-reducing mechanism are intermittently connected to said sub-container .

8. An apparatus according to Claim 1, wherein said sub-container is provided with a valve mechanism for regulating supply of ink from said main container to said sub-container in interrelation with displacement of the flexible film.

9. An apparatus according to Claim 1, wherein said ink jet recording apparatus further comprises pressing means for pressing said main container.

10. An apparatus according to Claim I₁ wherein said ink jet recording apparatus further comprises a pressure-reducing mechanism for reducing pressure in said sub-container to assist supply of ink from said main container.

11. An ink container for supplying ink to an ink jet recording head, comprising: a container casing having an opened surface; a flexible member which covers the opened surface of aid container casing to constitute a space between said flexible member and said container casing as an ink retaining portion and is disposed depending on an amount of ink accommodation; a spring member, disposed between said flexible member and said container casing, for urging said flexible member toward a direction in which said flexible member is moved apart from said container casing; and an air-liquid separation member, disposed to cover an opening provided to said container casing, for permitting passing of gas but limiting passing of liquid.

12. An container according to Claim 11, wherein said spring member is disposed so as not to hinder a path for communicating said air-liquid separation member and the ink retaining portion with each other.

13. An container according to Claim 11, wherein said ink container is provided with a liquid introducing port for receiving ink from an outside and is provided with a valve for opening and closing the liquid introducing port in interrelation with movement of said flexible member.