Patent Publication Number: US-10766271-B2

Title: Inkjet printing apparatus

Description:
This application is a continuation of U.S. patent application Ser. No. 16/019,076, filed Jun. 26, 2018, currently pending; and claims the benefit of priority under 35 U.S.C. § 119 of Japan Application No. 2017-133621, filed in Japan on Jul. 7, 2017; the contents of all of which are hereby incorporated by reference as if set forth herein in full. 
    
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to an inkjet printing apparatus including a print head which ejects ink to print an image. 
     Description of the Related Art 
     Japanese Patent Laid-Open No. 2011-240628 discloses a configuration of stably supplying ink to a print head irrespective of the frequency of ejection by disposing pumps in a path that supplies ink from a sub-tank to the print head and a path that collects ink from the print head to the sub-tank, respectively. 
     In a case of using an ink circulation system disclosed in Japanese Patent Laid-Open No. 2011-240628 for a color inkjet printing apparatus, pumps and circulation flow paths need to be prepared by each color. In this case, in terms of space saving and cost reduction, it is preferable that a pump of the same type that serves a common role for each color be used by each color. 
     Even if common circulation control is made by each color, a degree of ink concentration and degradation per unit time varies depending on the type of ink and the consumption amount of ink also varies depending on a printing mode. In addition, ink with less ejection frequency may possibly increase the viscosity of the entire circulating ink due to frequent circulation beyond necessity. Accordingly, in terms of the stability of an image and the reliability of an apparatus, it is preferable that the flow amount of ink to be circulated in the ink circulation system be appropriately adjusted by each ink. 
     However, in the conventional ink circulation system, it has been difficult to make appropriate circulation control per ink in a color inkjet printing apparatus without resulting in cost increase. 
     SUMMARY OF THE INVENTION 
     The present invention has been made to solve the above problem. Accordingly, an object of the present invention is to provide an inkjet printing apparatus capable of making appropriate circulation control for individual ink in a color inkjet printing apparatus employing an ink circulation system without resulting in cost increase. 
     According to a first aspect of the present invention, there is provided an inkjet printing apparatus comprising: a tank in which ink is contained; a print head for ejecting ink supplied from the tank; a supply flow path for supplying ink from the tank to the print head; a collection flow path for collecting ink from the print head to the tank; a first diaphragm pump which is provided in the collection flow path; and a second diaphragm pump which is provided in the supply flow path, ink being circulated among the tank, the supply flow path, the print head, and the collection flow path by the first diaphragm pump and the second diaphragm pump, wherein the first diaphragm pump includes a first volume change portion which allows volume changes and a first control member which controls a volume of the first volume change portion, the first diaphragm pump delivering ink in a first flow amount, and the second diaphragm pump includes a second volume change portion having the same volume as the first volume change portion and a second control member which is different from the first control member and controls a volume of the second volume change portion, the second diaphragm pump delivering ink in a second flow amount that is larger than the first flow amount. 
     According to a second aspect of the present invention, there is provided an inkjet printing apparatus comprising: a print head for ejecting a first ink and a second ink; a first tank in which the first ink is contained; a second tank in which the second ink is contained; a first supply flow path for supplying the first ink from the first tank to the print head; a second supply flow path for supplying the second ink from the second tank to the print head; a first collection flow path for collecting the first ink from the print head to the first tank; a second collection flow path for collecting the second ink from the print head to the second tank; a first pump for circulating the first ink among the first tank, the first supply flow path, the print head, and the first collection flow path; and a second pump for circulating the second ink among the second tank, the second supply flow path, the print head, and the second collection flow path, wherein the first pump and the second pump are driven by a common driving source, and the inkjet printing apparatus further comprises a switching unit for switching between a first mode for driving the first pump and the second pump and a second mode for driving the first pump and not driving the second pump. 
     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. 1  is a diagram of an internal configuration of an inkjet printing apparatus  1 ; 
         FIG. 2  is a control configuration diagram of the printing apparatus; 
         FIG. 3  is a diagram showing the printing apparatus in a printing state; 
         FIGS. 4A to 4C  are conveying path diagrams of a print medium fed from a first cassette; 
         FIGS. 5A to 5C  are conveying path diagrams of a print medium fed from a second cassette; 
         FIGS. 6A to 6D  are conveying path diagrams in the case of performing print operation for the back side of a print medium; 
         FIG. 7  is a diagram showing the printing apparatus in a maintenance state; 
         FIGS. 8A and 8B  are perspective views showing the configuration of a maintenance unit; 
         FIG. 9  is a diagram showing an ink supply system; 
         FIGS. 10A and 10B  are diagrams showing an ink flow in a printing element substrate  80   a;    
         FIG. 11  is a diagram illustrating a connection mechanism of collection pumps according to a first embodiment; 
         FIGS. 12A and 12B  are diagrams showing a structure of a diaphragm pump; 
         FIGS. 13A to 13D  are diagrams showing the relation between a control member and a diaphragm  602 ; 
         FIG. 14  is a diagram illustrating a connection mechanism of collection pumps according to a second embodiment; 
         FIGS. 15A and 15B  are diagrams of the relation between collection pump operation and ink circulation; and 
         FIG. 16  is a flowchart illustrating processes in a case where a print command is inputted. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
       FIG. 1  is an internal configuration diagram of an inkjet printing apparatus  1  (hereinafter “printing apparatus  1 ”) used in the present embodiment. In the drawings, an x-direction is a horizontal direction, a y-direction (a direction perpendicular to paper) is a direction in which ejection openings are arrayed in a print head  8  described later, and a z-direction is a vertical direction. 
     The printing apparatus  1  is a multifunction printer comprising a print unit  2  and a scanner unit  3 . The printing apparatus  1  can use the print unit  2  and the scanner unit  3  separately or in synchronization to perform various processes related to print operation and scan operation. The scanner unit  3  comprises an automatic document feeder (ADF) and a flatbed scanner (FBS) and is capable of scanning a document automatically fed by the ADF as well as scanning a document placed by a user on a document plate of the FBS. The present embodiment is directed to the multifunction printer comprising both the print unit  2  and the scanner unit  3 , but the scanner unit  3  may be omitted.  FIG. 1  shows the printing apparatus  1  in a standby state in which neither print operation nor scan operation is performed. 
     In the print unit  2 , a first cassette  5 A and a second cassette  5 B for housing a print medium (cut sheet) S are detachably provided at the bottom of a casing  4  in the vertical direction. A relatively small print medium of up to A4 size is placed flat and housed in the first cassette  5 A and a relatively large print medium of up to A3 size is placed flat and housed in the second cassette  5 B. A first feeding unit  6 A for sequentially feeding a housed print medium is provided near the first cassette  5 A. Similarly, a second feeding unit  6 B is provided near the second cassette  5 B. In print operation, a print medium S is selectively fed from either one of the cassettes. 
     Conveying rollers  7 , a discharging roller  12 , pinch rollers  7   a , spurs  7   b , a guide  18 , an inner guide  19 , and a flapper  11  are conveying mechanisms for guiding a print medium S in a predetermined direction. The conveying rollers  7  are drive rollers located upstream and downstream of the print head  8  and driven by a conveying motor (not shown). The pinch rollers  7   a  are follower rollers that are turned while nipping a print medium S together with the conveying rollers  7 . The discharging roller  12  is a drive roller located downstream of the conveying rollers  7  and driven by the conveying motor (not shown). The spurs  7   b  nip and convey a print medium S together with the conveying rollers  7  and discharging roller  12  located downstream of the print head  8 . 
     The guide  18  is provided in a conveying path of a print medium S to guide the print medium S in a predetermined direction. The inner guide  19  is a member extending in the y-direction. The inner guide  19  has a curved side surface and guides a print medium S along the side surface. The flapper  11  is a member for changing a direction in which a print medium S is conveyed in duplex print operation. A discharging tray  13  is a tray for placing and housing a print medium S that was subjected to print operation and discharged by the discharging roller  12 . 
     The print head  8  of the present embodiment is a full line type color inkjet print head. In the print head  8 , a plurality of ejection openings configured to eject ink based on print data are arrayed in the y-direction in  FIG. 1  so as to correspond to the width of a print medium S. However, the present invention is not limited to the full line type inkjet print head, and is also applicable to a serial type inkjet print head which performs printing by reciprocating for ejecting ink. In a case where the print head  8  is in a standby position, an ejection opening surface  8   a  of the print head  8  is oriented vertically downward and capped with a cap unit  10  as shown in  FIG. 1 . In print operation, the orientation of the print head  8  is changed by a print controller  202  described later such that the ejection opening surface  8   a  faces a platen  9 . The platen  9  includes a flat plate extending in the y-direction and supports, from the back side, a print medium S subjected to print operation by the print head  8 . The movement of the print head  8  from the standby position to a printing position will be described later in detail. 
     An ink tank unit  14  separately stores ink of four colors to be supplied to the print head  8 . An ink supply unit  15  is provided in the midstream of a flow path connecting the ink tank unit  14  to the print head  8  to adjust the pressure and flow amount of ink in the print head  8  within a suitable range. The present embodiment adopts a circulation type ink supply system, where the ink supply unit  15  adjusts the pressure of ink supplied to the print head  8  and the flow amount of ink collected from the print head  8  within a suitable range. 
     A maintenance unit  16  comprises the cap unit  10  and a wiping unit  17  and activates them at predetermined timings to perform maintenance operation for the print head  8 . The maintenance operation will be described later in detail. 
       FIG. 2  is a block diagram showing a control configuration in the printing apparatus  1 . The control configuration mainly includes a print engine unit  200  that exercises control over the print unit  2 , a scanner engine unit  300  that exercises control over the scanner unit  3 , and a controller unit  100  that exercises control over the entire printing apparatus  1 . A print controller  202  controls various mechanisms of the print engine unit  200  under instructions from a main controller  101  of the controller unit  100 . Various mechanisms of the scanner engine unit  300  are controlled by the main controller  101  of the controller unit  100 . The control configuration will be described below in detail. 
     In the controller unit  100 , the main controller  101  including a CPU controls the entire printing apparatus  1  using a RAM  106  as a work area in accordance with various parameters and programs stored in a ROM  107 . For example, when a print job is input from a host apparatus  400  via a host I/F  102  or a wireless I/F  103 , an image processing unit  108  executes predetermined image processing for received image data under instructions from the main controller  101 . The main controller  101  transmits the image data subjected to the image processing to the print engine unit  200  via a print engine I/F  105 . 
     The printing apparatus  1  may acquire image data from the host apparatus  400  via a wireless or wired communication or acquire image data from an external storage unit (such as a USB memory) connected to the printing apparatus  1 . A communication system used for the wireless or wired communication is not limited. For example, as a communication system for the wireless communication, Wi-Fi (Wireless Fidelity; registered trademark) and Bluetooth (registered trademark) can be used. As a communication system for the wired communication, a USB (Universal Serial Bus) and the like can be used. For example, when a scan command is input from the host apparatus  400 , the main controller  101  transmits the command to the scanner unit  3  via a scanner engine I/F  109 . 
     An operating panel  104  is a mechanism to allow a user to do input and output for the printing apparatus  1 . A user can give an instruction to perform operation such as copying and scanning, set a print mode, and recognize information about the printing apparatus  1  via the operating panel  104 . 
     In the print engine unit  200 , the print controller  202  including a CPU controls various mechanisms of the print unit  2  using a RAM  204  as a work area in accordance with various parameters and programs stored in a ROM  203 . Once various commands and image data are received via a controller I/F  201 , the print controller  202  temporarily stores them in the RAM  204 . The print controller  202  allows an image processing controller  205  to convert the stored image data into print data such that the print head  8  can use it for print operation. After the generation of the print data, the print controller  202  allows the print head  8  to perform print operation based on the print data via a head I/F  206 . At this time, the print controller  202  conveys a print medium S by driving the feeding units  6 A and  6 B, conveying rollers  7 , discharging roller  12 , and flapper  11  shown in  FIG. 1  via a conveyance control unit  207 . The print head  8  performs print operation in synchronization with the conveyance operation of the print medium S under instructions from the print controller  202 , thereby performing printing. 
     A head carriage control unit  208  changes the orientation and position of the print head  8  in accordance with an operating state of the printing apparatus  1  such as a maintenance state or a printing state. An ink supply control unit  209  controls the ink supply unit  15  such that the pressure of ink supplied to the print head  8  is within a suitable range. A maintenance control unit  210  controls the operation of the cap unit  10  and wiping unit  17  in the maintenance unit  16  when performing maintenance operation for the print head  8 . 
     In the scanner engine unit  300 , the main controller  101  controls hardware resources of the scanner controller  302  using the RAM  106  as a work area in accordance with various parameters and programs stored in the ROM  107 , thereby controlling various mechanisms of the scanner unit  3 . For example, the main controller  101  controls hardware resources in the scanner controller  302  via a controller I/F  301  to cause a conveyance control unit  304  to convey a document placed by a user on the ADF and cause a sensor  305  to scan the document. The scanner controller  302  stores scanned image data in a RAM  303 . The print controller  202  can convert the image data acquired as described above into print data to enable the print head  8  to perform print operation based on the image data scanned by the scanner controller  302 . 
       FIG. 3  shows the printing apparatus  1  in a printing state. As compared with the standby state shown in  FIG. 1 , the cap unit  10  is separated from the ejection opening surface  8   a  of the print head  8  and the ejection opening surface  8   a  faces the platen  9 . In the present embodiment, the plane of the platen  9  is inclined about 45° with respect to the horizontal plane. The ejection opening surface  8   a  of the print head  8  in a printing position is also inclined about 45° with respect to the horizontal plane so as to keep a constant distance from the platen  9 . 
     In the case of moving the print head  8  from the standby position shown in  FIG. 1  to the printing position shown in  FIG. 3 , the print controller  202  uses the maintenance control unit  210  to move the cap unit  10  down to an evacuation position shown in  FIG. 3 , thereby separating the cap member  10   a  from the ejection opening surface  8   a  of the print head  8 . The print controller  202  then uses the head carriage control unit  208  to turn the print head  8  45° while adjusting the vertical height of the print head  8  such that the ejection opening surface  8   a  faces the platen  9 . After the completion of print operation, the print controller  202  reverses the above procedure to move the print head  8  from the printing position to the standby position. 
     Next, a conveying path of a print medium S in the print unit  2  will be described. When a print command is input, the print controller  202  first uses the maintenance control unit  210  and the head carriage control unit  208  to move the print head  8  to the printing position shown in  FIG. 3 . The print controller  202  then uses the conveyance control unit  207  to drive either the first feeding unit  6 A or the second feeding unit  6 B in accordance with the print command and feed a print medium S. 
       FIGS. 4A to 4C  are diagrams showing a conveying path in the case of feeding an A4 size print medium S from the first cassette  5 A. A print medium S at the top of a print medium stack in the first cassette  5 A is separated from the rest of the stack by the first feeding unit  6 A and conveyed toward a print area P between the platen  9  and the print head  8  while being nipped between the conveying rollers  7  and the pinch rollers  7   a .  FIG. 4A  shows a conveying state where the front end of the print medium S is about to reach the print area P. The direction of movement of the print medium S is changed from the horizontal direction (x-direction) to a direction inclined about 45° with respect to the horizontal direction while being fed by the first feeding unit  6 A to reach the print area P. 
     In the print area P, a plurality of ejection openings provided in the print head  8  eject ink toward the print medium S. In an area where ink is applied to the print medium S, the back side of the print medium S is supported by the platen  9  so as to keep a constant distance between the ejection opening surface  8   a  and the print medium S. After ink is applied to the print medium S, the conveying rollers  7  and the spurs  7   b  guide the print medium S such that the print medium S passes on the left of the flapper  11  with its tip inclined to the right and is conveyed along the guide  18  in the vertically upward direction of the printing apparatus  1 .  FIG. 4B  shows a state where the front end of the print medium S has passed through the print area P and the print medium S is being conveyed vertically upward. The conveying rollers  7  and the spurs  7   b  change the direction of movement of the print medium S from the direction inclined about 45° with respect to the horizontal direction in the print area P to the vertically upward direction. 
     After being conveyed vertically upward, the print medium S is discharged into the discharging tray  13  by the discharging roller  12  and the spurs  7   b .  FIG. 4C  shows a state where the front end of the print medium S has passed through the discharging roller  12  and the print medium S is being discharged into the discharging tray  13 . The discharged print medium S is held in the discharging tray  13  with the side on which an image was printed by the print head  8  facing down. 
       FIGS. 5A to 5C  are diagrams showing a conveying path in the case of feeding an A3 size print medium S from the second cassette  5 B. A print medium S at the top of a print medium stack in the second cassette  5 B is separated from the rest of the stack by the second feeding unit  6 B and conveyed toward the print area P between the platen  9  and the print head  8  while being nipped between the conveying rollers  7  and the pinch rollers  7   a.    
       FIG. 5A  shows a conveying state where the front end of the print medium S is about to reach the print area P. In a part of the conveying path, through which the print medium S is fed by the second feeding unit  6 B toward the print area P, the plurality of conveying rollers  7 , the plurality of pinch rollers  7   a , and the inner guide  19  are provided such that the print medium S is conveyed to the platen  9  while being bent into an S-shape. 
     The rest of the conveying path is the same as that in the case of the A4 size print medium S shown in  FIGS. 4B and 4C .  FIG. 5B  shows a state where the front end of the print medium S has passed through the print area P and the print medium S is being conveyed vertically upward.  FIG. 5C  shows a state where the front end of the print medium S has passed through the discharging roller  12  and the print medium S is being discharged into the discharging tray  13 . 
       FIGS. 6A to 6D  show a conveying path in the case of performing print operation (duplex printing) for the back side (second side) of an A4 size print medium S. In the case of duplex printing, print operation is first performed for the first side (front side) and then performed for the second side (back side). A conveying procedure during print operation for the first side is the same as that shown in  FIGS. 4A to 4C  and therefore description will be omitted. A conveying procedure subsequent to  FIG. 4C  will be described below. 
     After the print head  8  finishes print operation for the first side and the back end of the print medium S passes by the flapper  11 , the print controller  202  turns the conveying rollers  7  reversely to convey the print medium S into the printing apparatus  1 . At this time, since the flapper  11  is controlled by an actuator (not shown) such that the tip of the flapper  11  is inclined to the left, the front end of the print medium S (corresponding to the back end during the print operation for the first side) passes on the right of the flapper  11  and is conveyed vertically downward.  FIG. 6A  shows a state where the front end of the print medium S (corresponding to the back end during the print operation for the first side) is passing on the right of the flapper  11 . 
     Then, the print medium S is conveyed along the curved outer surface of the inner guide  19  and then conveyed again to the print area P between the print head  8  and the platen  9 . At this time, the second side of the print medium S faces the ejection opening surface  8   a  of the print head  8 .  FIG. 6B  shows a conveying state where the front end of the print medium S is about to reach the print area P for print operation for the second side. 
     The rest of the conveying path is the same as that in the case of the print operation for the first side shown in  FIGS. 4B and 4C .  FIG. 6C  shows a state where the front end of the print medium S has passed through the print area P and the print medium S is being conveyed vertically upward. At this time, the flapper  11  is controlled by the actuator (not shown) such that the tip of the flapper  11  is inclined to the right.  FIG. 6D  shows a state where the front end of the print medium S has passed through the discharging roller  12  and the print medium S is being discharged into the discharging tray  13 . 
     Next, maintenance operation for the print head  8  will be described. As described with reference to  FIG. 1 , the maintenance unit  16  of the present embodiment comprises the cap unit  10  and the wiping unit  17  and activates them at predetermined timings to perform maintenance operation. 
       FIG. 7  is a diagram showing the printing apparatus  1  in a maintenance state. In the case of moving the print head  8  from the standby position shown in  FIG. 1  to a maintenance position shown in  FIG. 7 , the print controller  202  moves the print head  8  vertically upward and moves the cap unit  10  vertically downward. The print controller  202  then moves the wiping unit  17  from the evacuation position to the right in  FIG. 7 . After that, the print controller  202  moves the print head  8  vertically downward to the maintenance position where maintenance operation can be performed. 
     On the other hand, in the case of moving the print head  8  from the printing position shown in  FIG. 3  to the maintenance position shown in  FIG. 7 , the print controller  202  moves the print head  8  vertically upward while turning it 45°. The print controller  202  then moves the wiping unit  17  from the evacuation position to the right. Following that, the print controller  202  moves the print head  8  vertically downward to the maintenance position where maintenance operation can be performed by the maintenance unit  16 . 
       FIG. 8A  is a perspective view showing the maintenance unit  16  in a standby position.  FIG. 8B  is a perspective view showing the maintenance unit  16  in a maintenance position.  FIG. 8A  corresponds to  FIG. 1  and  FIG. 8B  corresponds to  FIG. 7 . When the print head  8  is in the standby position, the maintenance unit  16  is in the standby position shown in  FIG. 8A , the cap unit  10  has been moved vertically upward, and the wiping unit  17  is housed in the maintenance unit  16 . The cap unit  10  comprises a box-shaped cap member  10   a  extending in the y-direction. The cap member  10   a  can be brought into intimate contact with the ejection opening surface  8   a  of the print head  8  to prevent ink from evaporating from the ejection openings. The cap unit  10  also has the function of collecting ink ejected to the cap member  10   a  for preliminary ejection or the like and allowing a suction pump (not shown) to suck the collected ink. 
     On the other hand, in the maintenance position shown in  FIG. 8B , the cap unit  10  has been moved vertically downward and the wiping unit  17  has been drawn from the maintenance unit  16 . The wiping unit  17  comprises two wiper units (wiping members): a blade wiper unit  171  and a vacuum wiper unit  172 . 
     In the blade wiper unit  171 , blade wipers  171   a  for wiping the ejection opening surface  8   a  in the x-direction are provided in the y-direction by the length of an area where the ejection openings are arrayed. In the case of performing wiping operation by the use of the blade wiper unit  171 , the wiping unit  17  moves the blade wiper unit  171  in the x-direction while the print head  8  is positioned at a height at which the print head  8  can be in contact with the blade wipers  171   a . This movement enables the blade wipers  171   a  to wipe ink and the like adhering to the ejection opening surface  8   a.    
     The entrance of the maintenance unit  16  through which the blade wipers  171   a  are housed is equipped with a wet wiper cleaner  16   a  for removing ink adhering to the blade wipers  171   a  and applying a wetting liquid to the blade wipers  171   a . The wet wiper cleaner  16   a  removes substances adhering to the blade wipers  171   a  and applies the wetting liquid to the blade wipers  171   a  each time the blade wipers  171   a  are inserted into the maintenance unit  16 . The wetting liquid is transferred to the ejection opening surface  8   a  in the next wiping operation for the ejection opening surface  8   a , thereby facilitating sliding between the ejection opening surface  8   a  and the blade wipers  171   a.    
     The vacuum wiper unit  172  comprises a flat plate  172   a  having an opening extending in the y-direction, a carriage  172   b  movable in the y-direction within the opening, and a vacuum wiper  172   c  mounted on the carriage  172   b . The vacuum wiper  172   c  is provided to wipe the ejection opening surface  8   a  in the y-direction along with the movement of the carriage  172   b . The tip of the vacuum wiper  172   c  has a suction opening connected to the suction pump (not shown). Accordingly, if the carriage  172   b  is moved in the y-direction while operating the suction pump, ink and the like adhering to the ejection opening surface  8   a  of the print head  8  are wiped and gathered by the vacuum wiper  172   c  and sucked into the suction opening. At this time, the flat plate  172   a  and a dowel pin  172   d  provided at both ends of the opening are used to align the ejection opening surface  8   a  with the vacuum wiper  172   c.    
     In the present embodiment, it is possible to carry out a first wiping process in which the blade wiper unit  171  performs wiping operation and the vacuum wiper unit  172  does not perform wiping operation and a second wiping process in which both the wiper units sequentially perform wiping processes. In the case of the first wiping process, the print controller  202  first draws the wiping unit  17  from the maintenance unit  16  while the print head  8  is evacuated vertically above the maintenance position shown in  FIG. 7 . The print controller  202  moves the print head  8  vertically downward to a position where the print head  8  can be in contact with the blade wipers  171   a  and then moves the wiping unit  17  into the maintenance unit  16 . This movement enables the blade wipers  171   a  to wipe ink and the like adhering to the ejection opening surface  8   a . That is, the blade wipers  171   a  wipe the ejection opening surface  8   a  when moving from a position drawn from the maintenance unit  16  into the maintenance unit  16 . 
     After the blade wiper unit  171  is housed, the print controller  202  moves the cap unit  10  vertically upward and brings the cap member  10   a  into intimate contact with the ejection opening surface  8   a  of the print head  8 . In this state, the print controller  202  drives the print head  8  to perform preliminary ejection and allows the suction pump to suck ink collected in the cap member  10   a.    
     In the case of the second wiping process, the print controller  202  first slides the wiping unit  17  to draw it from the maintenance unit  16  while the print head  8  is evacuated vertically above the maintenance position shown in  FIG. 7 . The print controller  202  moves the print head  8  vertically downward to the position where the print head  8  can be in contact with the blade wipers  171   a  and then moves the wiping unit  17  into the maintenance unit  16 . This movement enables the blade wipers  171   a  to perform wiping operation for the ejection opening surface  8   a . Next, the print controller  202  slides the wiping unit  17  to draw it from the maintenance unit  16  to a predetermined position while the print head  8  is evacuated again vertically above the maintenance position shown in  FIG. 7 . Then, the print controller  202  uses the flat plate  172   a  and the dowel pins  172   d  to align the ejection opening surface  8   a  with the vacuum wiper unit  172  while moving the print head  8  down to a wiping position shown in  FIG. 7 . After that, the print controller  202  allows the vacuum wiper unit  172  to perform the wiping operation described above. After evacuating the print head  8  vertically upward and housing the wiping unit  17 , the print controller  202  allows the cap unit  10  to perform preliminary ejection into the cap member and suction operation of collected ink in the same manner as the first wiping process. 
       FIG. 9  is a diagram showing an ink supply system including the ink supply unit  15  adopted in the inkjet printing apparatus  1  of the present embodiment. With reference to  FIG. 9 , a flow path configuration of an ink circulation system of the present embodiment will be described. The ink supply unit  15  is a configuration of supplying ink from the ink tank unit  14  to the print head  8 . In the diagram, a configuration of one color ink is shown, but such a configuration is practically prepared for each color ink. The ink supply unit  15  is basically controlled by the ink supply control unit  209  shown in  FIG. 2 . Each configuration of the unit will be described below. 
     Ink is circulated mainly between a sub-tank  151  and the print head  8  (a head unit in  FIG. 9 ). In the head unit  8 , ink ejection operation is performed based on image data and ink that has not been ejected is collected and flows back to the sub-tank  151 . 
     The sub-tank  151  in which a certain amount of ink is contained is connected to a supply flow path C 2  for supplying ink to the head unit  8  and to a collection flow path C 4  for collecting ink from the head unit  8 . In other words, a circulation path for circulating ink is composed of the sub-tank  151 , the supply flow path C 2 , the head unit  8 , and the collection flow path C 4 . 
     In the sub-tank  151 , a liquid level detection unit  151   a  composed of a plurality of pins is provided. The ink supply control unit  209  detects presence/absence of a conducting current between those pins so as to grasp a height of an ink liquid level, that is, an amount of remaining ink inside the sub-tank  151 . A vacuum pump P 0  is a negative pressure generating source for reducing pressure inside the sub-tank  151 . An atmosphere release valve V 0  is a valve for switching between whether or not to make the inside of the sub-tank  151  communicate with atmosphere. 
     A main tank  141  is a tank that contains ink which is to be supplied to the sub-tank  151 . The main tank  141  is made of a flexible member, and the volume change of the flexible member allows filling the sub-tank  151  with ink. The main tank  141  has a configuration removable from the printing apparatus body. In the midstream of a tank connection flow path C 1  connecting the sub-tank  151  and the main tank  141 , a tank supply valve V 1  for switching connection between the sub-tank  151  and the main tank  141  is provided. 
     Under the above configuration, once the liquid level detection unit  151   a  detects that ink inside the sub-tank  151  is less than the certain amount, the ink supply control unit  209  closes the atmosphere release valve V 0 , a supply valve V 2 , a collection valve V 4 , and a head replacement valve V 5  and opens the tank supply valve V 1 . In this state, the ink supply control unit  209  causes the vacuum pump P 0  to operate. Then, the inside of the sub-tank  151  is to have a negative pressure and ink is supplied from the main tank  141  to the sub-tank  151 . If the liquid level detection unit  151   a  detects that the amount of ink inside the sub-tank  151  is more than the certain amount, the ink supply control unit  209  closes the tank supply valve V 1  to stop the vacuum pump P 0 . 
     The supply flow path C 2  is a flow path for supplying ink from the sub-tank  151  to the head unit  8 , and a supply pump P 1  and the supply valve V 2  are arranged in the midstream of the supply flow path C 2 . During print operation, driving the supply pump P 1  in the state of the supply valve V 2  being open allows ink circulation in the circulation path while supplying ink to the head unit  8 . The amount of ink to be ejected per unit time by the head unit  8  varies according to image data. A flow rate set for the supply pump P 1  is determined so as to be adaptable even in a case where the head unit  8  performs ejection operation in which ink consumption amount per unit time becomes maximum. 
     A relief flow path C 3  is a flow path which is located in the upstream of the supply valve V 2  and which connects between the upstream and downstream of the supply pump P 1 . In the midstream of the relief flow path C 3 , a relief valve V 3  which is a differential pressure valve is provided. In a case where an amount of ink supply from the supply pump P 1  per unit time is larger than the total value of an ejection amount of the head unit  8  per unit time and a flow amount (ink drawing amount) in a collection pump P 2  per unit time, the relief valve V 3  is released according to a pressure applied to its own. As a result, a cyclic flow path composed of a portion of the supply flow path C 2  and the relief flow path C 3  is formed. By providing the configuration of the above relief flow path C 3 , the amount of ink supply to the head unit  8  is adjusted according to the ink consumption amount by the head unit  8  so as to stabilize a pressure inside the circulation path irrespective of the image data. 
     The collection flow path C 4  is a flow path for collecting ink from the head unit  8  to the sub-tank  151 . In the midstream of the collection flow path C 4 , the collection pump P 2  and the collection valve V 4  are provided. At the time of ink circulation within the circulation path, the collection pump P 2  sucks ink from the head unit  8  by serving as a negative pressure generating source. By driving the collection pump P 2 , an appropriate differential pressure is generated between an IN flow path  80   b  and an OUT flow path  80   c  inside the head unit  8 , thereby causing ink to circulate from the IN flow path  80   b  to the OUT flow path  80   c . A flow path configuration inside the head unit  8  will be described later in detail. 
     The collection valve V 4  is a valve for preventing a backflow at the time of not performing print operation, that is, at the time of not circulating ink within the circulation path. In the circulation path of the present embodiment, the sub-tank  151  is disposed higher than the head unit  8  in a vertical direction (see  FIG. 1 ). For this reason, in a case where the supply pump P 1  and the collection pump P 2  are not driven, there may be a possibility that ink flows back from the sub-tank  151  to the head unit  8  due to a water head difference between the sub-tank  151  and the head unit  8 . In order to prevent such a backflow, the present embodiment provides the collection valve V 4  in the collection flow path C 4 . 
     Similarly, at the time of not performing print operation, that is, at the time of not circulating ink within the circulation path, the supply valve V 2  also functions as a valve for preventing ink supply from the sub-tank  151  to the head unit  8 . 
     A head replacement flow path C 5  is a flow path connecting the supply flow path C 2  and an air layer (a part in which ink is not contained) of the sub-tank  151 , and in its midstream, the head replacement valve V 5  is provided. One end of the head replacement flow path C 5  is connected to the upstream of the head unit  8  in the supply flow path C 2  and the other end is connected to the upper part of the sub-tank  151  and is communicated with the air layer inside the sub-tank  151 . The head replacement flow path C 5  is used in the case of collecting ink from the head unit  8  in use such as upon replacing the head unit  8  or transporting the printing apparatus  1 . The head replacement valve V 5  is controlled by the ink supply control unit  209  so as to be closed except for a case of initial ink filling in the printing apparatus  1  and a case of collecting ink from the head unit  8 . In addition, the above-described supply valve V 2  is provided, in the supply flow path C 2 , between a connection point to the head replacement flow path C 5  and a connection point to the relief flow path C 3 . 
     Next, a flow path configuration inside the head unit  8  will be described. Ink supplied from the supply flow path C 2  to the head unit  8  passes through a filter  83  and then is supplied to a first negative pressure control unit  81  and a second negative pressure control unit  82 . The first negative pressure control unit  81  is set to have a control pressure of a low negative pressure. The second negative pressure control unit  82  is set to have a control pressure of a high negative pressure. Pressures in those first negative pressure control unit  81  and second negative pressure control unit  82  are generated within a proper range by the driving of the collection pump P 2 . 
     In an ink ejection unit  80 , a printing element substrate  80   a  in which a plurality of ejection openings are arrayed is arranged in plural to form an elongate ejection opening array. A common supply flow path  80   b  (IN flow path) for guiding ink supplied from the first negative pressure control unit  81  and a common collection flow path  80   c  (OUT flow path) for guiding ink supplied from the second negative pressure control unit  82  also extend in an arranging direction of the printing element substrates  80   a . Furthermore, in the individual printing element substrates  80   a , individual supply flow paths connected to the common supply flow path  80   b  and individual collection flow paths connected to the common collection flow path  80   c  are formed. Accordingly, in each of the printing element substrates  80   a , an ink flow is generated such that ink flows in from the common supply flow path  80   b  which has relatively lower negative pressure and flows out to the common collection flow path  80   c  which has relatively higher negative pressure. In the midstream of a path between the individual supply flow path and the individual collection flow path, pressure chambers each of which is communicated with each ejection opening and filled with ink are provided. An ink flow is generated in the ejection opening and the pressure chamber even in a case where printing is not performed. Once the ejection operation is performed in the printing element substrate  80   a , a part of ink moving from the common supply flow path  80   b  to the common collection flow path  80   c  is ejected from the ejection openings and is consumed. Meanwhile, ink not having been ejected moves toward the collection flow path C 4  via the common collection flow path  80   c.    
     Under the above configuration, in performing print operation, the ink supply control unit  209  closes the tank supply valve V 1  and the head replacement valve V 5  and opens the atmosphere release valve V 0 , the supply valve V 2 , and the collection valve V 4  to drive the supply pump P 1  and the collection pump P 2 . As a result, the circulation path in the order of the sub-tank  151 , the supply flow path C 2 , the head unit  8 , the collection flow path C 4 , and the sub-tank  151  is established. In a case where an amount of ink supply from the supply pump P 1  per unit time is larger than the total value of an ejecting amount of the head unit  8  per unit time and a flow amount in the collection pump P 2  per unit time, ink flows from the supply flow path C 2  into the relief flow path C 3 . As a result, the flow amount of ink from the supply flow path C 2  to the head unit  8  is adjusted. 
     In the case of not performing print operation, the ink supply control unit  209  stops the supply pump P 1  and the collection pump P 2  and closes the atmosphere release valve V 0 , the supply valve V 2 , and the collection valve V 4 . As a result, the ink flow inside the head unit  8  stops and the backflow caused by the water head difference between the sub-tank  151  and the head unit  8  is suppressed. Further, by closing the atmosphere release valve V 0 , ink leakage and ink evaporation from the sub-tank  151  are suppressed. 
     In the case of collecting ink from the head unit  8 , the ink supply control unit  209  closes the tank supply valve V 1 , the supply valve V 2 , and the collection valve V 4  and opens the atmosphere release valve V 0  and the head replacement valve V 5  to drive the vacuum pump P 0 . As a result, the inside of the sub-tank  151  becomes in a negative pressure state, and ink inside the head unit  8  is collected to flow back to the sub-tank  151  via the head replacement flow path C 5 . As such, the head replacement valve V 5  is a valve being closed during normal print operation or at the time of standby and being open upon collecting ink from the head unit  8 . In addition, the head replacement valve V 5  is released even at the time of filling the head replacement flow path C 5  with ink for an initial ink filling to the head unit  8 . 
       FIGS. 10A and 10B  are diagrams illustrating an ink flow in a printing element substrate  80   a  of the head unit  8 .  FIG. 10A  is an enlarged plan view viewing a part of the printing element substrate  80   a  from the ejection opening surface  8   a  side, and  FIG. 10B  is a sectional schematic view of a cross section taken from line XB-XB of  FIG. 10A . 
     In the printing element substrate  80   a , a pressure chamber  2402  which is filled with ink and an ejection opening  2311  from which ink is ejected are provided. In the pressure chamber  2402 , an energy generation element  2323  is provided at a position facing the ejection opening  2311 . Further, in the printing element substrate  80   a , a plurality of ejection openings  2311  are formed, each of which is connected to an individual supply flow path  2321  which is connected to the common supply flow path  80   b  and an individual collection flow path  2322  which is connected to the common collection flow path  80   c.    
     According to the above configuration, in the printing element substrate  80   a , an ink flow is generated such that ink flows in from the common supply flow path  80   b  which has relatively lower negative pressure (high pressure) and flows out to the common collection flow path  80   c  which has relatively higher negative pressure (low pressure). To be more specific, ink flows in the order of the common supply flow path  80   b , the individual supply flow path  2321 , the pressure chamber  2402 , the individual collection flow path  2322 , and the common collection flow path  80   c . Once ink is ejected by the energy generation element  2323 , part of ink moving from the common supply flow path  80   b  to the common collection flow path  80   c  is ejected from the ejection opening  2311  to be discharged outside the head unit  8 . Meanwhile, ink not having been ejected from the ejection opening  2311  is collected and flows to the collection flow path C 4  via the common collection flow path  80   c.    
     As such, in the printing element substrate  80   a  under print operation, ink constantly flows irrespective of print data or frequency of ejection from individual ejection openings, and at the ejection opening  2311 , ink continuously supplied from the sub-tank  151  is exposed to atmosphere. Accordingly, there may be a concern that the entire circulating ink is concentrated compared to a configuration of not using an ink circulation system. 
     First Embodiment 
     The printing apparatus  1  of the present embodiment provides the ink circulation system described in  FIG. 9 ,  FIGS. 10A and 10B  for each of cyan, magenta, yellow, and black inks, and each of the systems includes the supply pump P 1  and the collection pump P 2 . The supply pumps P 1  for four colors have one common supply motor as a driving source and the collection pumps P 2  for the four colors have one common collection motor  500  as a driving source. 
       FIG. 11  is a diagram for illustrating a mechanism of driving the collection pumps P 2  for the four colors using the common collection motor  500 . A collection pump for black ink (P 2   k ), a collection pump for cyan ink (P 2   c ), a collection pump for magenta ink (P 2   m ), and a collection pump for yellow ink (P 2   y ) are coupled to the collection motor  500 . The collection pump for black ink (P 2   k ) is driven by the collection motor  500  via a first gear train  501 . The collection pump for cyan ink (P 2   c ), the collection pump for magenta ink (P 2   m ), and the collection pump for yellow ink (P 2   y ) are driven by the collection motor  500  via a second gear train  502 . These four collection pumps P 2   k , P 2   c , P 2   m , and P 2   y  basically include the same structure. Meanwhile, the supply pumps P 1  for the four colors are also composed of a supply pump for black ink (P 1   k ), a supply pump for cyan ink (P 1   c ), a supply pump for magenta ink (P 1   m ), and a supply pump for yellow ink (P 1   y ), all of which are coupled to the supply motor. 
       FIGS. 12A and 12B  are diagrams showing a structure of a diaphragm pump  600  which is used for both the supply pump P 1  and the collection pump P 2 .  FIG. 12A  is a perspective view of the diaphragm pump  600  and  FIG. 12B  is a side view thereof. Both show a state where a cover that is supposed to be mounted at the time of practical use is removed. The diaphragm pump  600  of the present embodiment is configured such that a control member  610  is mounted on a diaphragm unit (volume change portion) in which three diaphragms  602  are laid out on a supporting unit  601 . Further, once a driving force of the supply motor or the collection motor  500  is transferred to the control member  610 , the control member  610  rotates about an axis O that serves as a center and thus the three diaphragms  602  are pressed down in order by a pressing member  603  so as to generate an ink sucking force and an ink discharging force. 
     In the present embodiment, while using diaphragms  602  in the same type and with the same volume, the control member  610  to be mounted thereon for the supply pump P 1  is made to be different from that for the collection pump P 2  so that pump sucking forces applied onto the supply side and the collection side are adjusted to be different from each other. 
       FIGS. 13A to 13D  are diagrams each showing the relation between the control member  610  and the diaphragm  602 . The control member  610  is composed of the pressing member  603 , a working shaft  604 , and a strut  605 . The strut  605  has a columnar shape and rotates about a rotational axis O that serves as a center of the strut along with the driving of the supply motor or the collection motor  500 . One end of the rod-like working shaft  604  is inserted from the bottom face of the strut  605  with a predetermined angle θ with respect to the rotational axis O, and the other end is inserted into the center of the pressing member  603  extending in three directions. In such a structure, in the case where the strut  605  rotates along with the driving of the supply motor or the collection motor  500 , the working shaft  604  rotates around the rotational axis O while retaining the predetermined angle θ with respect to the rotational axis O. Then, each of the pressing members  603  extending in three directions from the working shaft  604  presses the three diaphragms  602  in order. 
     In the control member  610 , an angle θ of the working shaft  604  with respect to the rotational axis O and a length L of the pressing member  603  for the supply pump P 1  differ from those for the collection pump P 2 . Accordingly, pressing amounts of the diaphragms  602  are made to be different, and thus the sucking amount and discharging amount of the pumps are adjusted. The supply pump P 1   c  and collection pump P 2   c  for cyan ink will be described below as an example. 
       FIGS. 13A and 13B  are cross-sectional views of pumps in rotational positions in which the largest pressing amounts are respectively applied onto the diaphragms  602 . Specifically,  FIG. 13A  shows the collection pump P 2   c  for the cyan ink and  FIG. 13B  shows the supply pump P 1   c  for the cyan ink.  FIGS. 13C and 13D  are cross-sectional views of pumps in rotational positions in which the smallest pressing amounts are respectively applied onto the diaphragms  602 , which correspond to positions where the working axes  604  have been rotated by 180 degrees from the states shown in  FIGS. 13A and 13B . To be more specific,  FIG. 13C  shows the collection pump P 2   c  for the cyan ink and  FIG. 13D  shows the supply pump P 1   c  for the cyan ink. 
     Among members constituting the control member  610 , the same member is used for the diaphragms  602  and the working axes  604  for the supply pumps P 1  and the collection pumps P 2 . Meanwhile, the pressing member  603  for the supply pump P 1  is configured to have a length different from that for the collection pump P 2 , and the strut  605  for the supply pump P 1  is configured to have an angle θ for inserting the working shaft  604  different from that for the collection pump P 2 . As shown in  FIGS. 13A to 13D , in the collection pump P 2   c  for the cyan ink, an angle of the working shaft  604  with respect to the rotational axis O is denoted as θa and a length of the pressing member  603   a  is denoted as La. Meanwhile, in the supply pump P 1   c  for the cyan ink, an angle of the working shaft  604  with respect to the rotational axis O is denoted as θb and a length of the pressing member  603   b  is denoted as Lb. 
     In the present embodiment, it is designed that the supply pump P 1  has a larger angle θ of the working shaft  604  with respect to the rotational axis O (θa&lt;θb), and the collection pump P 2  has a larger length L of the pressing member  603  (La&gt;Lb). As a result, in the states shown in  FIGS. 13A and 13B , a larger pressing amount is applied onto the diaphragm  602  of the supply pump P 1   c  for the cyan ink than that of the collection pump P 2   c  for the cyan ink. Further, in the states shown in  FIGS. 13C and 13D , a smaller pressing amount is applied onto the diaphragm  602  of the supply pump P 1   c  for the cyan ink than that of the collection pump P 2   c  for the cyan ink. In other words, the diaphragm  602  of the supply pump P 1   c  for the cyan ink has a larger volume change per stroke than that of the collection pump P 2   c  for the cyan ink, and consequently has a larger delivering amount of ink to be circulated within the circulation system. 
     As described above, in the diaphragm pump  600  of the present embodiment, ink sucking amount and ink discharging amount can be adjusted by using different control members  610  to be mounted while using the same type of diaphragm  602 . As a result, the same type of parts can be used for the supply pump P 1  and the collection pump P 2  so as to reduce the cost. 
     As such, the example of setting different pump flow rates between the supply pump P 1  and the collection pump P 2  has been described, but the present invention may be applied to the supply pump P 1  and the collection pump P 2  having different flow rates by the respective ink colors. Further, one collection motor  500  is configured to drive the collection pumps P 2   k , P 2   c , P 2   m , and P 2   y  for the four colors of ink, but each of the pumps may be driven by a dedicated motor. The same applies to the supply side. 
     More specifically, according to the present embodiment, flow amounts in the ink circulation system may be appropriately adjusted depending on a location of the circulation flow path or by each ink color in a manner of providing different types of control members  610  to be mounted on the same type of diaphragm  602 . 
     Second Embodiment 
     As for a typical color inkjet printing apparatus, a monochrome mode which outputs black characters and line drawing and a color mode which outputs graphics and photos, for example, in full colors are prepared. In the color mode, all four color inks are used for printing. Meanwhile, in the monochrome mode, only a black ink is used and no color inks are used. 
     In a case of employing the above-described ink circulation system for such a color inkjet printing apparatus, there may be a possibility that circulating the color inks and the black ink simultaneously in the monochrome mode leads to further concentration of the color inks beyond necessity. As described above with reference to  FIGS. 10A and 10B , since ink continuously supplied from the sub-tank  151  in the ink circulation system is exposed to atmosphere at the time of passing by the ejection openings, the evaporation of the color inks that are not actually subjected to ejection operation is promoted beyond necessity. For this reason, in the inkjet printing apparatus employing the ink circulation system, only inks that are actually subjected to ejection operation should preferably be appropriately circulated during such print operation. In view of the above situation, according to the present embodiment, a circulation method of the ink circulation system depending on printing modes is to be further varied in addition to the feature of the first embodiment. 
       FIG. 14  is a diagram showing a state of coupling the collection pumps P 2  for four colors used in the present embodiment to the collection motor  500 . A mechanism of the collection pumps P 2   k , P 2   c , P 2   m , and P 2   y  corresponding to respective four color inks is identical to that of the first embodiment. 
     An aspect different from the case of  FIG. 11  is that a one-way gear  502   a  is disposed at the beginning of the second gear train  502  which connects the collection motor  500  and the collection pumps P 2   c , P 2   m , and P 2   y . The one-way gear  502   a  transfers a driving force of the collection motor  500  upon its forward rotation to the collection pumps P 2   c , P 2   m , and P 2   y , but does not transfer a driving force of the collection motor  500  upon its reverse rotation. Accordingly, the collection pumps P 2   c , P 2   m , and P 2   y  for the color inks are to be operated in the case where the collection motor  500  makes forward rotation, but are not to be operated in the case where the collection motor  500  makes reverse rotation. Meanwhile, the collection pump P 2   k  for the black ink which is connected to the collection motor  500  via the first gear train  501  is operated irrespective of whether the collection motor  500  makes forward rotation or reverse rotation. 
     In the ink supply system of the present embodiment, the coupling mechanism shown in  FIG. 14  is adopted for the collection pumps P 2  for the four color inks, whereas the coupling mechanism shown in  FIG. 11  is adopted for the supply pumps P 1 . 
       FIGS. 15A and 15B  show the states of ink circulation in the cases of operating/not operating the collection pump P 2  during the execution of print operation.  FIG. 15A  shows a state where the collection pump P 2  is in operation, and  FIG. 15B  shows a state where the collection pump P 2  is not in operation. It should be noted that, in the present embodiment, the one-way gear is not provided in the supply pump P 1  side, and thus, the supply pump P 1  is in operation for both cases shown in  FIGS. 15A and 15B . 
     As shown in  FIG. 15A , in the case where both the supply pump P 1  and the collection pump P 2  are in operation, ink contained in the sub-tank  151  flows through the supply flow path C 2 , the head unit  8 , and the collection flow path C 4  and returns to the sub-tank  151 . Meanwhile, as shown in  FIG. 15B , in the case where the supply pump P 1  is in operation but the collection pump P 2  is not in operation, the ink contained in the sub-tank  151  does not flow toward the head unit  8 , but circulates within a circuit flow path which is composed of a portion of the supply flow path C 2  and the relief flow path C 3 . A reason for this is that the stop of the collection pump P 2  causes decrease in negative pressure in the collection flow path C 4  side, thereby blocking the first negative pressure control unit  81  and the second negative pressure control unit  82 . 
     In the present embodiment, in the case where the color mode is set, the collection pumps P 2   k , P 2   c , P 2   m , and P 2   y  for all the colors are to be operated to achieve ink circulation as in  FIG. 15A . In contrast, in the case where the monochrome mode is set, ink circulation shown in  FIG. 15A  is to be made for the black ink, while ink circulation shown in  FIG. 15B  is to be made for the color inks by way of not operating the collection pumps P 2   c , P 2   m , and P 2   y.    
       FIG. 16  is a flowchart, in a case where a print command is inputted from the host apparatus  400 , for illustrating processes relating to ink circulation and print operation executed by the main controller  101  of the controller unit  100 . With reference to  FIGS. 15A and 15B , an explanation will be given below along with the flowchart of  FIG. 16 . 
     At the start of the processes, in Step S 1510 , the main controller  101  first makes initial setting for valves in the ink circulation system. To be more specific, as for the ink circulation system for all the colors, the ink supply control unit  209  closes the tank supply valve V 1  and the head replacement valve V 5  and opens the atmosphere release valve V 0 , the supply valve V 2 , and the collection valve V 4 . 
     In Step S 1502 , the main controller  101  determines whether a received print command specifies the monochrome mode or specifies the color mode. If the color mode is specified, the process advances to Step S 1503 , and if the monochrome mode is specified, the process advances to Step S 1504 . 
     In Step S 1503 , the main controller  101  causes the ink supply control unit  209  to control driving the supply motor for the supply pump P 1  and the collection motor  500  for the collection pump P 2  in forward rotation. Accordingly, in the ink circulation system for four colors, both the supply pump P 1  and collection pump P 2  are driven so as to generate ink flow shown in  FIG. 15A . 
     In Step S 1504 , the main controller  101  causes the ink supply control unit  209  to control driving the supply motor in normal rotation and driving the collection motor  500  in reverse rotation. Accordingly, the supply pump P 1  is operated in the ink circulation system for all the colors, but the collection pump P 2  is operated in the ink circulation system only for the black ink but is not operated in the ink circulation system for the color inks. Consequently, in the ink circulation system for the black ink, ink flow shown in  FIG. 15A  is generated, whereas in the ink circulation system for the color inks, ink flow shown in  FIG. 15B  is generated. 
     In Step S 1503  or Step S 1504 , in the case where ink circulation in accordance with the print mode is made, the process advances to Step S 1505  where the main controller  101  makes predetermined print operation. In other words, the print controller  202  is used to cause the print head  8  to execute print operation in accordance with print data generated based on a received print command. In this case, in a case where the received print command indicates the monochrome mode, only the black ink is ejected from the print head  8 . In a case where the received print command indicates the color mode, all of the four color inks are ejected from the print head  8 . 
     After the completion of the print operation in Step S 1505 , the process advances to Step S 1506  where the main controller  101  determines whether a new print job is received from the host apparatus  400 . In the case of receiving the new print job, the process returns to Step S 1502  where the main controller  101  starts a process for a next print command. Meanwhile, in the case where a new print command is not received, the process advances to Step S 1507  where the main controller  101  causes the ink supply control unit  209  to stop the motor  500  for the supply pump P 1  and the motor  500  for the collection pump P 2 . 
     The process further advances to Step S 1508  where the main controller  101  causes the ink supply control unit  209  to close the atmosphere release valve V 0 , the supply valve V 2 , and the collection valve V 4 . As such, these processes are finished. 
     According to the present embodiment as described above, by providing the one-way gear and by switching the motor between forward rotation and reverse rotation, the presence/absence of ink circulation within the print head  8  can be switched according to each print mode with a relatively simple configuration. In other words, a stable ejection performance can be maintained by making ink circulation for the ink to be subjected to ejection operation. On the other hand, further ink evaporation and progress in concentration beyond necessity can be suppressed by stopping the ink circulation for the ink that is not subjected to ejection operation. Further, based on the above, the control members  610  to be mounted on the same type of diaphragm  602  are to be varied, as in the first embodiment, so as to enable appropriate adjustment of flow amounts in the ink circulation system depending on a location of the circulation flow path or by each ink color. 
     Incidentally, the one-way gear is disposed only in the collection pump P 2  in the present embodiment, but the present invention is not limited to this. The one-way gear may be disposed in the supply pump P 1  as well. 
     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 No. 2017-133621, filed Jul. 7, 2017, which is hereby incorporated by reference wherein in its entirety.