Patent Publication Number: US-9409404-B2

Title: Liquid ejection head and liquid ejection apparatus

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a liquid ejection head and a liquid ejection apparatus which are widely applicable, for example, as an ink jet print head that enables ink to be ejected and an ink jet printing apparatus including the ink jet print head. 
     2. Description of the Related Art 
     A liquid ejection head of this type generally includes liquid channels extending from an upstream side in a direction in which a liquid is fed toward ejection ports. Each of the liquid channels provides an ejection energy generating element such as an electrothermal converter (heater) or piezo element. When the liquid channel provides an electrothermal converter, heat generated by the electrothermal converter bubbles a liquid in the liquid channel, and the resulting bubbling energy can be utilized to eject the liquid through the ejection port. 
     Such a liquid ejection head is internally maintained at a constant negative pressure for ejecting liquid stably from the ejection port. Japanese Patent Laid-Open No. 2009-40062 describes a configuration in which a liquid is fed from a liquid tank, with a negative pressure applied to the liquid by a negative pressure generating section provided in an ink cartridge. 
     In the configuration described in Japanese Patent Laid-Open No. 2009-40062, the ink cartridge includes the negative pressure generating section, and the pressure (negative pressure) is applied to the inside of the liquid ejection head only by the negative pressure generating section. This precludes the pressure inside the liquid ejection head from being adjusted. 
     SUMMARY OF THE INVENTION 
     The present invention provides a liquid ejection head and a liquid ejection apparatus which allows the pressure inside a print head to be adjusted. 
     In the first aspect of the present invention, there is provided a liquid ejection head capable of ejecting a liquid through an ejection port, the liquid being supplied from a liquid container with a negative pressure generating section, the liquid ejection head comprising: 
     a liquid chamber configured to contain the liquid; 
     a liquid supply section configured to allow the liquid to be supplied from the liquid container to the liquid chamber; and 
     an opening configured to communicate with the liquid chamber and to enable the liquid and/or a gas to flow into the liquid chamber through the opening. 
     In the second aspect of the present invention, there is provided a liquid ejection apparatus configured to use a liquid ejection head configured to enable a liquid to be ejected to apply the liquid ejected from the ejection head to a print medium, 
     wherein the liquid ejection head according to the first aspect of the present invention is used as the liquid ejection head, and 
     the apparatus comprises a transfer section configured to transfer the liquid or a gas to the opening in the liquid ejection head which communicates with the liquid chamber. 
     The present invention includes, besides the liquid supply section feeding the liquid into the liquid ejection head, the opening enabling the liquid and/or gas inside the liquid chamber to flow out through the opening. This allows the pressure inside the liquid ejection head to be adjusted. 
     Further features of the present invention will become apparent from the following description of exemplary embodiments (with reference to the attached drawings). 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a schematic diagram of a configuration of a printing apparatus including a print head serving as a liquid ejection head according to a first embodiment of the present invention, and  FIG. 1B  is a block diagram of a control system for the printing apparatus in  FIG. 1A ; 
         FIG. 2  is a schematic diagram of a configuration of an ink supply system in the printing apparatus in  FIG. 1A ; 
         FIG. 3  is a cross-sectional view of an ink tank in  FIG. 2 ; 
         FIG. 4  is a cross-sectional view of the print head in  FIG. 2 ; 
         FIG. 5A  is a perspective view of an ink holding member in  FIG. 4 , and  FIG. 5B  is a cross-sectional view taken along line VB-VB in  FIG. 5A ; 
         FIG. 6A  is a diagram illustrating the state of the ink supply system observed when ink is stationary, and  FIG. 6B  is an enlarged cross-sectional view of the ink holding member in  FIG. 6A ; 
         FIG. 7A ,  FIG. 7B , and  FIG. 7C  are each a diagram illustrating the state of the ink supply system during printing; 
         FIG. 8A ,  FIG. 8B , and  FIG. 8C  are each a diagram illustrating the state of the ink supply system during cleaning of the print head; 
         FIG. 9A ,  FIG. 9B , and  FIG. 9C  are each a diagram illustrating the state of the ink supply system during cleaning of the print head; 
         FIG. 10A , and  FIG. 10B  are each a diagram illustrating the state of the ink supply system during cleaning of the print head; 
         FIG. 11A ,  FIG. 11B , and  FIG. 11C  are each a diagram illustrating the state of the ink supply system during stirring of ink; 
         FIG. 12A  and  FIG. 12B  are each a diagram illustrating a part of another example of the ink stirring operation; and 
         FIG. 13A  and  FIG. 13B  are each a diagram illustrating another part of the example of the ink stirring operation in  FIG. 12A  and  FIG. 12B . 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     An embodiment of the present invention will be described below with reference to the drawings. 
       FIG. 1A  is a perspective view of an important part of an ink jet printing apparatus (liquid ejection apparatus)  100  to which the present invention can be applied.  FIG. 1B  is a block diagram of a control system for the printing apparatus  100 . The printing apparatus  100  includes an ink jet print head  20  provided in a replaceable manner and configured to eject ink (liquid), as an embodiment of a liquid ejection head according to the present invention. 
     The printing apparatus  100  in the present example is what is called a full-line printing apparatus. The printing apparatus  100  can print an image on a print medium P by ejecting ink from the print head  20  while a conveying system (conveying mechanism)  110  is continuously conveying the print medium P in a direction of arrow A. The conveying system  110  in the present example conveys the print medium P using a conveying belt  110 A. However, the configuration of the conveying system  110  is not limited, and a conveying roller or the like may be used to convey the print medium P. Furthermore, in the present example, the print head  20  includes print heads  20 Y,  20 M,  20 C, and  20 Bk that eject a yellow (Y) ink, a magenta (M) ink, a cyan (C) ink, and a black (Bk) ink, respectively, which are all supplied by an ink supply system (ink supply mechanism)  120  described below. This allows color images to be printed. 
     The printing apparatus  100  includes a recovery operation system  130  used for a recovery operation for keeping an ink ejection state of the print head  20  appropriate. The recovery operation may include a preliminary ejecting operation of ejecting ink making no contribution to image printing into a cap through ejection ports and a pressure-based recovery operation of pressurizing ink in the print head and forcibly discharging the pressurized ink into the cap through the ejection ports. The recovery operation may further include a suction-based recovery operation of sucking and discharging ink into the cap through the ejection ports and a wiping operation of wiping an ejection port surface of the print head in which the ejection ports are formed. 
     A CPU (control section)  101  in the printing apparatus  100  carries out processing for controlling operations of the printing apparatus, data processing, and the like. Programs for procedures for the above-described processing and the like are stored in ROM  102 . RAM  103  is used, for example, as a work area in which the processing is carried out. The CPU  101  controls the print head  20 , the conveying system  110 , the ink supply system  120 , and the recovery operation system  130  via corresponding drivers  20 A,  110 A,  120 A, and  130 A. The CPU  101  allows an image to be printed on the print medium P by ejecting ink from the print head  20  based on image data input via a host apparatus  200  such as a host computer. The CPU  101  operates the print head  20 , the conveying system  110 , the ink supply system  120 , and the recovery operation system  130  to perform control “during cleaning of the print head”, control “during stirring of ink”, and control “at the start of ink supply”. 
       FIG. 2  is a diagram illustrating the ink supply system  120  and the recovery operation system  130 .  FIG. 3  is an enlarged cross-sectional view of an ink tank  30  in  FIG. 2 .  FIG. 4  is an enlarged cross-sectional view of the print head  20  in  FIG. 2 . 
     An ink chamber (liquid chamber)  31  in which ink is contained is formed inside the ink tank  30 , which serves as a liquid container. The ink chamber  31  forms a closed space that can communicate with the outside only at a joint portion  32 . The ink tank  30  is configured to be able to be installed in and removed from the print head  20 . Furthermore, the ink tank  30  is provided above the print head  20 . The ink chamber  31  is formed of a flexible member, and a pressure plate  33 - 2  connected to a spring  33 - 1  for negative pressure generation is incorporated in the ink chamber  31 . The spring  33 - 1  biases the inside of the ink chamber  31  toward the outside so as to enlarge an internal space in the ink chamber  31  via the pressure plate  33 - 2 . Thus, the spring  33 - 1  generates a predetermined negative pressure inside the ink chamber  31 . The spring  33 - 1 , the pressure plate  33 - 2 , and the ink chamber  31  provide a negative pressure generating section. The joint portion  32  is provided with a filter  34  of a nonwoven cloth. 
     The print head  20  includes an ejection energy generating element (not shown in the drawings) for ejecting ink I in an ink chamber  21  (a liquid in the liquid chamber) through ejection ports  20 A. The ejection energy generating element may be an electrothermal converter (heater), a piezo element, or the like. With an electrothermal converter, heat generated by the electrothermal converter bubble the ink, and the resulting bubbling energy can be utilized to eject the ink through the ejection port  20 A. Air (gas), as well as the ink I, is preset in the ink chamber  21 . Thus, the ink chamber  21  includes an ink containing section (liquid containing section) formed therein and containing the ink and an air containing section (gas containing section) also formed therein and containing air (gas). 
     An ink supply section (liquid supply section)  22  for communication with the ink tank (liquid tank)  30  is provided above the ink chamber  21 . A filter member  23  is provided on an opening of the supply section  22 . In the present example, the filter member  23  is formed of an SUS mesh. The mesh is configured by inweaving metal fiber, and the supply section  22  has an average width of about 10 mm. The filter member  23  is finely woven and thus prevents external dust and dirt from entering the print head. A bottom surface of the filter member  23  is pressed against an ink holding member (liquid holding member)  24  capable of holding the ink. As shown in  FIG. 5A  and  FIG. 5B , a plurality of channels  24 A each with a circular cross section is formed inside the ink holding member  24 . Each of the channels  24 A has a diameter of about 1.0 mm. 
     Furthermore, the ink chamber  21  includes an opening  25  provided in an upper portion of the ink chamber  21  and which can be connected to a transfer section  51  serving as an external channel to transfer the gas and/or liquid. The opening  25  is provided with a filter  26 . The opening  25  is configured to enable the liquid (ink) or gas in the ink chamber  21  to flow out to the outside through the opening  25 . The opening  25  also enables both the liquid (ink) and gas in the ink chamber  21  to flow out through the opening  25 . Additionally, the opening  25  is configured to enable the liquid (ink) or gas outside the print head  20  to flow into the opening  25 . Moreover, the opening  25  is configured to enable both the liquid (ink) and gas outside the print head  20  to flow into the opening  25 . 
     The print head  20  and the ink tank  30  are coupled together as shown in  FIG. 2 . That is, the supply section  22  of the print head  20  and the joint portion  32  of the ink tank  30  are coupled together so the filter member  23  on the print head  20  side and the filter  34  on the ink tank  30  side are compressed against each other in the vertical direction. Such a coupled portion between the print head  20  and the ink tank  30  is kept closed by being circumferentially surrounded by an elastic cap member  50  formed of rubber. In the present example, the print head  20  and the ink tank  30  are directly connected together, and thus, an ink supply path (liquid supply path) between the print head  20  and the ink tank  30  is very short. 
     The transfer section  51  connected to the opening  25  of the print head  20  is divided into two branches. One of the branches is in communication with the outside air via an openable and closable valve  52 . The other branch is in communication with a buffer chamber  54  via an openable and closable valve  53 . A space of about 10 mL is formed in the buffer chamber  54  and is in communication with a waste ink tank  56  through a pump  55 . The pump  55  is a transfer section which serves as means for transferring the liquid (ink) and/or gas (air) and which pumps the liquid (ink) and/or gas (air) into and out from the print head  20 . In the present example, a tube pump capable of forward and reverse rotations is used as the pump  55 . 
     A cap  60  is connected to the buffer chamber  54  via an openable and closable valve  61 . The cap  60  can come into tight contact with a surface (ejection port formation surface) of the print head  20  in which the ejection ports  20 A are formed. When the cap  60  is internally sucked using the pump  55  with the ejection ports  20 A capped by the cap  55 , the ink can be sucked and discharged into the cap  60  through the ejection ports  20 A (suction-based recovery operation). Furthermore, the following are possible: a preliminary ejection operation of ejecting ink making no contribution to image printing into the cap  60  through the ejection ports  20 A and a pressure-based recovery operation of pressurizing the ink in the print head  20  to forcibly discharge the ink into the cap  60  through the ejection ports  20 A. During the pressuring recovery operation, a pressurizing force generated using the pump  55  can be exerted into the print head  20  through the buffer chamber  54  and the valve  53 . The ink contained in the cap  60  as result of the recovery operation can be discharged into the waste ink tank  56  (see  FIG. 2 ) by a suction force generated using the pump  55 . 
     Now, description will be provided which relates to the state of the printing apparatus while the ink is stationary, during a printing operation, during cleaning of the print head, during stirring of the ink, and at the start of ink supply. 
     (While the Ink is Stationary) 
     While the ink is stationary, for example, while the printing apparatus is stopped, the valves  52  and  53  are closed as shown in  FIG. 6A . Ink is filled in the channels  24 A of the ink holding member  24 . The ink chamber  21  in the print head  20  is internally at a predetermined negative pressure. Ink meniscuses formed in the ejection ports  20 A are maintained. Ink meniscuses are formed in the channels  24 A of the ink holding member  24  as shown in  FIG. 6B . Forces Pt, Ph, Pk, and Pg act on the meniscuses in the channels  24 A of the ink holding member  24 . The force Pt results from the negative pressure in the ink tank  30  to draw in the meniscuses toward the ink tank side. The force Ph results from the negative pressure in the print head  20  to draw the meniscuses into the print head. The force Pk is a meniscus force resulting from the surface tension of the ink to draw in the ink toward the ink tank side. The force Pg results from the weight of the ink to move the ink downward. The forces are balanced to maintain the meniscuses formed in the ink holding member  24 , keeping the ink in the print head  20  stationary. 
     (During a Printing Operation) 
     During a printing operation by the printing apparatus, the valves  52  and  53  are closed as shown in  FIG. 7A ,  FIG. 7B , and  FIG. 7C . When the ink is ejected through the ejection ports  20 A as shown in  FIG. 7A , the ink I in the ink chamber  21  is consumed to further reduce the pressure in the ink chamber  21  as shown in  FIG. 7B . The thus increasing negative pressure in the ink chamber  21  acts as a force in a direction in which the ink in the channels  24 A in the ink holding member  24  is drawn into the ink tank  30 . When the negative pressure in the ink chamber  21  increases to a predetermined negative pressure or higher, the ink meniscuses formed in the channels  24 A of the ink holding member  24  are broken to allow the ink in the ink tank  30  to be supplied to the print head  20  as shown in  FIG. 7C . The supply of the ink reduces the negative pressure in the ink chamber  21  to form meniscuses again in the channels  24 A of the ink holding member  24  as shown in  FIG. 7A . The supply of the ink is then stopped. Thus, the ink is fed from the ink tank  30  into the ink chamber  21  in the print head  20  according to ink consumption. 
     The meniscus force Pk of the meniscus formed in each of the channels  24 A of the ink holding member  24  acts as a force against the flow of the ink fed from the ink tank  30  to the print head  20 . Thus, when the meniscus force Pk is excessively strong, the ink supply is hindered to degrade ink supply performance. The meniscus force P of the meniscus of the liquid formed in the opening of the liquid channel can be expressed by Formula 1 when the surface tension is denoted by γ, the radius of the opening is denoted by r, and the contact angle of the ink in the liquid channel is denoted by θ. 
     
       
         
           
             
               
                 
                   P 
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                         2 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         γ 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         cos 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         θ 
                       
                     
                     r 
                   
                 
               
               
                 
                   ( 
                   
                     Formula 
                     ⁢ 
                     
                         
                     
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                     1 
                   
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     Furthermore, when the opening of the channel is not circular, the meniscus force P in the opening has a relation with a circumferential length L and an opening area S which is expressed by Formula 2 (the meniscus force P is proportional to L/S). Even if the opening is not truly circular, the theoretical formula in Formula 1 is applicable regardless of the shape of the opening when the opening is assumed to be a circular tube having an area as that of the opening and a radius r.
 
P∝L/S  (Formula 2)
 
     Thus, the meniscus force P decreases with increasing radius r of the opening of the liquid channel. 
     The plurality of channels  24 A each with an inner diameter of about 1 mm is formed in the ink holding member  24  according to the present embodiment in a penetrating manner. The inner diameter of the channel  24 A is set such that the meniscus force of the ink in the channel  24 A is weaker than the meniscus force of the ink in the filter members  23  and  34 . When the ink is supplied in association with a printing operation, no ink meniscus is formed in the filter members  23  and  24 . This allows the ink supply performance to be improved so as to enable high-speed printing. 
     If the ink holding member  24  is not provided, meniscuses are formed in the filter member  23  or  34 , degrading the ink supply performance. Specifically, the inner diameter of each of the ink channels formed in the filter members  23  and  34  is about one-thousandth of the inner diameter of the channel  24 A of the ink holding member  24 , and thus, the meniscus force in the ink channels in the filter members  23  and  34  is about 1,000 times as strong as the meniscus force in the channel  24 A. Thus, without the ink holding member  24 , the ink supply performance is significantly degraded. 
     (During Cleaning of the Print Head) 
     When the ejection port formation surface of the print head  20  is wiped and cleaned, the print head  20  is internally pressurized to push the ink I in the ink chamber  21  out through the ejection ports  20 A to improve the lubricity of the ejection port formation surface. 
     First, as shown in  FIG. 8A , the valve  52  is opened to admit the outside air into the print head  20 , thus releasing the negative pressure in the ink chamber  21 . Then, as shown in  FIG. 8B , the pump  55  is rotated in one direction with the valves  52  and  53  closed to feed air into the buffer chamber  54 , thus pressurizing the buffer chamber  54 . Then, as shown in  FIG. 8C , the valve  53  is opened to admit the pressurized air in the buffer chamber  54  into the print head  20 , thus pressuring the inside of the ink chamber  21 . At this time, if, for example, the liquid (ink) is mixed in the buffer chamber  54  or the transfer section  51 , the liquid (ink) and/or gas (air) flows into the print head  20 . 
     The internal pressurization of the ink chamber  21  moves the ink in the channels  24 A of the ink holding member  24  and the ink in the ink chamber  21  as shown in  FIG. 9A  and  FIG. 9B . 
     A relation shown below is set for the inner diameter Df of each ink channel formed in the filter member  23  on the print head side, the inner diameter Dk of each channel  24 A in the ink holding member  24 , and the inner diameter Dn of each ejection port  20 A.
 
Df&lt;Dn&lt;Dk
 
     Thus, a relation shown below is set for the meniscus force Pf in the filter member  23  on the print head side, the meniscus force Pk in the channel  24 A of the ink holding member  24 , and the meniscus force Pn in the ejection port  20 A.
 
Pf&gt;Pn&gt;Pk
 
     If the ink chamber  21  is internally pressurized, then as shown in  FIG. 9A , the meniscuses in the channels  24 A of the ink holding member  24  move backward, that is, upward in  FIG. 9A . The meniscuses reach the filter member  23 , and then, the ink is pushed out through the ejection ports  20 A as shown in FIG.  9 B. More specifically, first, the meniscuses in the ink holding member  24 , which exert the weak meniscus force Pk, move backward to allow the ink in the channels  24 A to flow backward into the ink tank  30  as shown in  FIG. 10A . As shown in  FIG. 10B , all of the ink in the channels  24 A is returned into the ink tank  30  to form meniscuses in the filter member  23 . The meniscus force Pn in the ejection ports  20 A is weaker than the meniscus force Pf in the filter member  23 , and thus, the ink in the ink chamber  21  is pushed out through the ejection ports  20 A as shown in  FIG. 10B . 
     The ink chamber  21  is internally pressurized to a pressure Pc. When the pressure Pc is higher than the meniscus force Pk, the meniscuses in the ink holding member  24  are moved toward the ink tank  30  side, and the ink is pushed out through the ejection ports  20 A without moving the meniscuses in the filter member  23 , which have the meniscus force Pf. Thus, the ink can be pushed out through the ejection ports  20 A without moving the meniscuses in the filter member  23 , in other words, without pushing the air in the print head into the ink tank. 
     After the ejection port formation surface is sufficiently wetted with the ink pushed out as described above or while the ink is being pushed out through the ejection ports  20 A, the ejection port formation surface is wiped by a plate-like cleaning member  57  as shown in  FIG. 9C . This allows the capability of cleaning the ejection port formation surface to be improved. The cleaning member  57  is, for example, formed of urethane rubber and moves in a lateral direction in  FIG. 9C  while keeping in contact with the ejection port formation surface. Such movement may involve movement of at least either the cleaning member  57  or the print head  20 . 
     After the wiping operation by the cleaning member  57 , the pump  55  is reversely rotated to introduce a negative pressure into the print head  20 . Thus, the liquid (ink) and/or gas (air) flows out from the print head  20 , enabling such a state as shown in  FIG. 6A  and  FIG. 6B  to be recovered. 
     (During Stirring of Ink) 
     When the ink tank  30  is left untouched for a long period of time, the components of the ink inside the ink tank  30  may become nonuniform. In particular, if the ink in the ink tank  30  is pigment ink, a color material precipitates in a lower portion of the ink tank  30 , leading to the risk of changing the density of a printed image. According to the present embodiment, the ink in the channels  24 A of the ink holding member  24  is drawn into and out from the ink tank  30  in order to make the components of the ink in the ink tank  30  uniform. 
     First, as shown in  FIG. 11A , the valve  52  is opened to open the ink chamber  21  in the print head  20  to the atmosphere. Then, as shown in  FIG. 11B , the valve  52  is closed and the valve  53  is opened, and then, the pump  55  is rotated in one direction to pressurize the inside of the ink chamber  21 . The ink chamber  21  is pressurized up to a pressure Ps. The pressure Ps has a magnitude sufficient to move the meniscuses in the ink holding member  24 , which have the meniscus force Pk, without pushing the ink out through the ejection ports  20 A or moving the meniscuses in the filter member  23 , which have the meniscus force Pf. Such a pressure Ps returns the ink in the channels  24 A of the ink holding member  24  to the ink tank  30  as shown in  FIG. 11B . The returned ink disturbs the ink components precipitated in a lower layer in the ink tank  30 . As a result, the ink in the ink tank  301  can be stirred. 
     Thereafter, the pump  55  is reversely rotated to reduce the pressure in the print head  20 , thus drawing the ink in the ink tank  30  into the channels  24 A of the ink holding member  24  again, as shown in  FIG. 11C . Thus, the ink positioned in an upper layer in the ink tank  30  can be drawn downward to stir the ink in the ink tank  30 . 
     Such pressurization and pressure reduction in the print head  20  are repeated to draw the ink in the channels  24 A of the ink holding member  24  into and out from the ink tank  30  a desired number of times. Then, the ink in the ink tank  30  can be sufficiently stirred to make the ink components uniform. 
     Furthermore, ink may be fed from the ink tank  30  into the ink chamber  21  until the level of the ink I in the ink chamber  21  becomes higher than a bottom surface of the ink holding member  24 . Then, the ink I in the ink chamber  21  may be fed back to the ink tank  30  through the channels  24 A of the ink holding member  24 . This enables an increase in the amount of ink fed into and from the ink tank  30  to allow the ink in the ink tank to be effectively stirred. A specific example of such an ink stirring operation will be described using  FIG. 12A ,  FIG. 12B ,  FIG. 13A , and  FIG. 13B . 
     First, as shown in  FIG. 12A , the pump  55  is reversely rotated with the valve  52  closed and the valve  53  open to discharge the gas in the ink chamber  21 , thus reducing the pressure in the ink chamber  21  to generate a negative pressure. Consequently, ink is fed from the ink tank  30  into the ink chamber  21 . Then, ink is fed from the ink tank  30  into the ink chamber  21  until an ink amount sensor (not shown in the drawings) which detects the amount of the ink I in the ink chamber  21  detects that the level of the ink I in the ink chamber  21  is higher than the bottom surface of the ink holding member  24 . The ink amount sensor may be, for example, a level sensor including a plurality of electrodes in the ink chamber  21 . The level sensor is configured to detect the level of ink by allowing the electrodes to be made electrically continuous or discontinuous by the ink when the surface of the ink reaches a predetermined position. Additionally, the ink amount sensor may be able to detect the amount of the ink I in the ink chamber  21 , and is not limited to a configuration that detects the level of ink. 
     After ink is supplied until the level of the ink I becomes higher than the bottom surface of the ink holding member  24 , the pump  55  is rotated in one direction to introduce the gas into the ink chamber  21  to pressurize the inside of the ink chamber  21  as shown in  FIG. 12B . Thus, the ink in the ink chamber  21  is fed back to the ink tank  30  through the channels  24 A of the ink holding member  24 . Subsequently, as shown  FIG. 13A , the surface of the ink I in the ink chamber  21  leaves the bottom surface of the ink holding member  24 . Then, as shown in  FIG. 13B , the ink in the channels  24 A of the ink holding member  24  is fed back to the ink tank  30 . 
     As described above, the operation of stirring ink by feeding the ink into and from the ink tank  30  may be repeated a predetermined number of times. Furthermore, such an ink stirring operation enables an increase in the amount of ink fed into and from the ink tank  30  during one stirring operation compared to the operation in  FIG. 11A ,  FIG. 11B , and  FIG. 11C  in which the ink in the channels  24 A of the ink holding member  24  is fed into and from the ink tank  30 . As a result, the ink in the ink tank  30  can be more effectively stirred. 
     Furthermore, when the ink I in the ink chamber  21  is fed back to the ink tank  30  using the pump  55 , the inside of the ink chamber  21  may be intermittently pressurized or the pressure in the ink chamber  21  may be changed (increased or reduced). Moreover, the amount of ink fed into and from the ink tank  30  may be changed in accordance with the length of the period for which the ink tank  30  is left uncontrolled. For example, the amount of ink fed from the ink tank  30  into the ink chamber  21  may be increased consistently with the length of the period for which the ink tank  30  is left uncontrolled. Subsequently, the amount of ink fed back from the ink chamber  21  to the ink tank may be increased. Furthermore, such an ink stirring operation as shown in  FIG. 11A ,  FIG. 11B , and  FIG. 11C  and such an ink stirring operation as shown in  FIG. 12A ,  FIG. 12B ,  FIG. 13A , and  FIG. 13B  may be performed in a switchable manner in accordance with the length of the period for which the ink tank  30  is left uncontrolled. Furthermore, the amount of ink fed into and from the ink tank  30  may be changed not only during one stirring operation but also in accordance with the number of times the stirring operation has been performed. 
     (At the Start of Ink Supply) 
     When the ink tank  30  is connected to the print head  20  with no ink present therein, a capping state is established in which the cap  60  is in tight contact with the ejection port formation surface of the print head  20 . Then, the cap  60  is internally sucked using the pump  55 . Thus, as shown in  FIG. 6A , the ink in the ink tank  30  can be supplied to the print head  20 . Furthermore, the ink in the ink tank  30  can be supplied to the print head  20  by generating a negative pressure using the pump  55  so that the negative pressure acts in the ink chamber  21  through the buffer chamber  54 , the valve  53 , and the opening  25 . When the cap  60  is used for the suction as in the above-described former case, ink making no contribution to image printing is discharged into the cap  60  as is the case with the suction-based recovery operation. On the other hand, when the suction is carried out through the opening  25  as in the above-described latter case, the ink can be fed into the print head  20  without discharging the ink, making no contribution to image printing, thus suppressing ink consumption. 
     The amount of ink fed into the print head  20  can be adjusted to an optimum amount using an ink amount sensor (a fluid level sensor for ink; not shown in the drawings) that detects the amount of ink in the ink chamber  21 . Ink meniscuses can be formed in the ejection ports  20 A by performing the suction-based recovery operation of internally sucking the cap  60  in the capping state using the pump  55 . 
     Furthermore, if the ink in the ink tank  30  connected to the print head  20  is exhausted to reduce the amount of ink in the print head  20 , when a new ink tank  30  is connected to the print head  20 , the amount of ink in the print head  20  needs to be increased to the optimum value. In this case, the ink in the newly connected ink tank  30  can be fed into the print head  20  by introducing, through the opening  25 , a negative pressure generated using the pump  55 . Furthermore, when the amount of ink in the print head  20  decreases to the degree that the ink amount sensor fails to detect the amount, the ink in the ink tank  30  can be fed into the print head  20  by introducing a negative pressure into the print head  20  through the opening  25 . 
     As described above, the ink can be fed into the print head  20  without wasteful ink consumption by introducing a negative pressure (a suction force used to reduce the pressure in the print head  20 ) into the print head  20 . During such ink supply, the cap may be in the capping state. 
     According to the above-described embodiment, the ink holding member  24  is provided on the print head  20  side. However, the ink holding member  24  may be provided on the ink tank  30  side or in a print head installation portion on the printing apparatus side on which the print head  20  is installed. Similarly, the filter member  23  may be provided on the ink tank  30  side or in the print head installation portion on the printing apparatus side on which the print head  20  is installed. 
     Furthermore, the pressure in the print head  20  may be controlled through the opening  25  in order to reduce a variation in the negative pressure in the print head  20  during a printing operation. When a pressure is applied to the inside of the print head  20 , the opening  25  functions as an applied pressure introducing section that allows an applied pressure to be introduced into the print head  20  by introducing the gas and/or liquid through the opening  25 . The transfer section  51  functions as an applied pressure supply path that enables the supply of an applied pressure. Additionally, when a suction (pressure reduction) force is applied to the inside of the print head  20 , the opening  25  functions as a suction force introducing section that allows a suction force to be introduced into the print head  20  by discharging the gas and/or liquid through the opening  25 . The transfer section  51  functions as a suction force supply path that enables the supply of a suction force. The opening  25  may be divided into an introduction section for pressurization and a discharge section for suction. In addition, the applied pressure and the suction force may be a pressure that applies a force to the inside of the print head  20  and a pressure that serves to reduce the pressure in the print head  20 , respectively, and are not necessarily limited to a positive pressure and a negative pressure based on the atmospheric pressure. 
     The present invention can be applied to, besides the full-line printing apparatus, various other printing apparatuses based on the respective printing schemes such as a serial scan printing apparatus that prints an image by moving the print head and performing an operation of conveying the print medium. 
     Furthermore, the liquid ejection head according to the present invention is not only applicable as an ink jet print head capable of ejecting ink but also widely applicable as a head for ejecting any of various liquids. For example, the liquid ejection head according to the present invention can be used as a head for ejecting any of various process liquids or drugs supplied to a liquid channel. Additionally, the liquid ejection apparatus according to the present invention is not only applicable as an ink jet printing apparatus using an ink jet print head but also widely applicable as an apparatus that applies any of various process liquids or drugs to a processing target member. 
     While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions. 
     This application claims the benefit of Japanese Patent Application Nos. 2013-060517, filed Mar. 22, 2013 and 2014-005229, filed Jan. 15, 2014 which are hereby incorporated by reference herein in their entirety.