Patent Publication Number: US-10786993-B2

Title: Liquid ejecting apparatus

Description:
BACKGROUND 
     1. Technical Field 
     The present invention relates to a liquid ejecting apparatus including a liquid ejecting portion capable of ejecting a liquid from a nozzle. 
     2. Related Art 
     In the related art, there is known a liquid ejecting apparatus including a liquid ejecting portion having a nozzle capable of ejecting a liquid and a cap capable of forming a closed space in which the nozzle of the liquid ejecting portion is opened by bringing the cap into contact with the liquid ejecting portion. In such a liquid ejecting apparatus, a negative pressure generated by a negative pressure generator such as a tube pump is accumulated in a pressure chamber of a constant volume, and the accumulated negative pressure is applied to the closed space formed between the cap and the liquid ejecting portion so as to perform cleaning of discharging a liquid from the liquid ejecting portion to an outside via the nozzle (for example, refer to JP-A-2012-35424). 
     However, when the volume of the pressure chamber that accumulates the negative pressure is constant as in the above liquid ejecting apparatus, it is not possible to change the magnitude of the negative pressure which is applied to the closed space when executing a cleaning. 
     SUMMARY 
     An advantage of some aspects of the invention is to provide a liquid ejecting apparatus capable of executing a cleaning in which the magnitude of a negative pressure applied on a closed space is different. 
     According to an aspect of the invention, there is provided a liquid ejecting apparatus including: a liquid ejecting portion configured to eject a liquid from a nozzle; a cap configured to be relatively move with respect to the liquid ejecting portion and configured to form a closed space in which the nozzle is open between the cap and the liquid ejecting portion; a negative pressure generation mechanism configured to generate a negative pressure; a pressure chamber configured to accumulate the negative pressure by driving the negative pressure generation mechanism; a discharge flow path that communicates with the cap and the pressure chamber; a discharge flow path opening/closing mechanism configured to open and close the discharge flow path; a volume variable mechanism configured to change a volume of the pressure chamber; and a controller that controls the negative pressure generation mechanism, the discharge flow path opening/closing mechanism, and the volume variable mechanism. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be described with reference to the accompanying drawings, wherein like numbers reference like elements. 
         FIG. 1  is a schematic diagram schematically showing an overall configuration of a liquid ejecting apparatus according to a first embodiment. 
         FIG. 2  is a block diagram of a control configuration in the liquid ejecting apparatus. 
         FIG. 3  is a schematic diagram schematically showing an overall configuration of a liquid ejecting apparatus according to a second embodiment. 
         FIG. 4  is a schematic diagram schematically showing a part of a liquid ejecting apparatus according to a modification example. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     First Embodiment 
     Hereinafter, a liquid ejecting apparatus according to a first embodiment will be described with reference to the drawings. 
     As shown in  FIG. 1 , the liquid ejecting apparatus  11  of the present embodiment includes a liquid ejecting portion  12  that ejects a liquid, a liquid supply unit  13  that supplies the liquid to the liquid ejecting portion  12 , and a maintenance device  14  for performing maintenance of the liquid ejecting portion  12 . The liquid ejecting portion  12  has an opening surface  16  in which one or a plurality of nozzles  15  is opened, and is configured so that a liquid such as ink can be ejected from the nozzle  15  to a medium  17  such as a paper. 
     The liquid supply unit  13  includes a liquid storage portion  18  which is a container in which the liquid to be supplied to the liquid ejecting portion  12  is contained, a holder portion  19  which makes the liquid storage portion  18  attachable/detachable, and a supply flow path  20  disposed so as to supply the liquid from the liquid storage portion  18  attached to the holder portion  19  to the liquid ejecting portion  12 . In the liquid storage portion  18 , for example, a plurality of liquid storage portions  18  corresponding to each of a plurality of colors of liquid is attached to the holder portion  19  in an attachable/detachable manner. The supply flow path  20  is configured with a plurality of flexible tubes or the like corresponding to each of the plurality of liquid storage portions  18 . The liquid storage portion  18  may be, for example, a cartridge attached to the liquid ejecting apparatus  11  in an attachable/detachable manner, or a tank that can supply liquid by filling. 
     The maintenance device  14  includes a cap  21 , a container  22  having a space inside, and a waste liquid storage portion  23 . The cap  21  is provided so as to be relatively movable with respect to the liquid ejecting portion  12 . That is as shown in  FIG. 1 , the cap  21  is movable in a vertical direction between a separated position that is separated downward from the liquid ejecting portion  12  and a contact position that contacts the opening surface  16  which is a lower surface of the liquid ejecting portion  12  so as to surround the nozzle  15  by an elevating mechanism (not shown). When the cap  21  moves to the contact position and comes into contact with the liquid ejecting portion  12 , a closed space, in which the nozzle  15  is open to a space between the cap  21  and the liquid ejecting portion  12 , can be formed. 
     Between the cap  21  and the container  22 , a discharge flow path  24  configured with a tube or the like that allows the inside of the cap  21  and the inside of the container  22  communicate with each other, is disposed. When the cap  21  moves to the contact position to form the closed space between the cap  21  and the liquid ejecting portion  12 , the discharge flow path  24  allows the closed space and the upstream end of the discharge flow path  24  communicate with each other. A pressure opening/closing valve  25 , which is an example of a discharge flow path opening/closing mechanism capable of opening/closing the discharge flow path  24 , is provided in the middle of the discharge flow path  24 . The cap  21  is provided with an atmosphere opening valve  26  capable of opening the closed space in the cap  21  to the atmosphere in a state where the closed space is formed between the cap  21  and the liquid ejecting portion  12 . 
     Between the container  22  and the waste liquid storage portion  23 , a recovery flow path  27  configured with a tube or the like that allows the inside of the container  22  and the inside of the waste liquid storage portion  23  communicate each other, is disposed. A check valve  28 , which is a one way valve that allows the flow of a liquid to a downstream which is on the side of the waste liquid storage portion  23  from the position of the check valve  28  while the flow of a liquid to an upstream which is on the side of the container  22  from the position of the check valve  28  is suppressed, is provided in the middle of the recovery flow path  27 . In the recovery flow path  27 , a suction pump  29  such as a tube pump or the like is provided at a position between the check valve  28  and the waste liquid storage portion  23 . 
     As shown in  FIG. 1 , a space inside the container  22  is partitioned into a plurality (three in the present embodiment) of chambers  31 ,  32  and  33  which constitute the pressure chamber by at least one partition wall  30  (two in the present embodiment). Among the plurality of chambers  31 ,  32  and  33 , the downstream end of the discharge flow path  24  and the upstream end of the recovery flow path  27  are connected to a first chamber  31  having the largest volume and positioned at the right end in  FIG. 1 . In the container  22 , a second chamber  32  and a third chamber  33  partitioned as a chamber different from the first chamber  31  by the partition wall  30  are configured to have the same volume and the total volume thereof is smaller than that of the first chamber  31 . 
     In the container  22 , a space between the first chamber  31  and the second chamber  32 , a space between the first chamber  31  and the third chamber  33 , and a space between the second chamber  32  and the third chamber  33  are connected by a communication flow path  34  configured with a tube or the like. In the communication flow path  34 , a first flow path opening/closing valve  35  is provided in the middle of a part of the flow path connecting the first chamber  31  and the second chamber  32 , and the first chamber  31  and the third chamber  33 . The first flow path opening/closing valve  35  is an example of a communication flow path opening/closing mechanism capable of opening/closing the part of the flow path. In the communication flow path  34 , a second flow path opening/closing valve  36  is provided in the middle of a part of the flow path connecting the third chamber  33  and the second chamber  32 , and the third chamber  33  and the first chamber  31 . The second flow path opening/closing valve  36  is an example of a communication flow path opening/closing mechanism capable of opening/closing the part of the flow path. 
     A negative pressure generation mechanism  37  configured with a diaphragm pump or the like is connected to the first chamber  31  via a suction flow path  38 . When the pressure opening/closing valve  25  of the discharge flow path  24  is a closed state, the first chamber  31  is in a state of being isolated from the outside. Therefore, when the negative pressure generation mechanism  37  is driven in the state of being isolated from the outside, negative pressure is accumulated inside the first chamber  31 . Note that, although not shown, in the suction flow path  38 , it is preferable to provide an opening/closing valve capable of opening/closing the suction flow path  38  in a part of the flow path which is on the side of the first chamber  31  from the negative pressure generation mechanism  37 , and open the opening/closing valve in a case where the negative pressure generation mechanism  37  is driven to accumulate the negative pressure to the first chamber  31  and close the opening/closing valve in a case where the accumulated negative pressure is applied to perform a cleaning. As shown in  FIG. 1 , the container  22  is provided with a pressure sensor  39  capable of detecting the magnitude of the pressure in the first chamber  31  and a release valve  40  capable of communicating the first chamber  31  with the atmosphere by opening the release valve  40 . 
     Next, the electrical configuration of the liquid ejecting apparatus  11  will be described. 
     As shown in  FIG. 2 , the liquid ejecting apparatus  11  includes a control device  41  configured with a microprocessor or the like as an example of a controller. The control device  41  includes a CPU  42  as a central processing device that performs overall control of the liquid ejecting apparatus  11  and a storage unit  43  configured with a nonvolatile memory or the like for storing a program or the like performed by the CPU  42  at the time of the maintenance of the liquid ejecting portion  12  by the maintenance device  14  or the like. In addition to the above-described pressure sensor  39 , an operation unit  44 , a measurement unit  45 , and a discharge failure detection unit  46  are connected to the input side interface (not shown) of the control device  41 . 
     The pressure sensor  39  periodically detects the pressure in the first chamber  31  and transmits a detection signal indicating the detection result to the control device  41 . The operation unit  44  is configured with a touch panel or the like provided on an upper part of a front surface of a housing (not shown) which contains various mechanisms such as the liquid ejecting portion  12  inside in the liquid ejecting apparatus  11 . On the surface of the operation unit  44 , in addition to displaying an operational state of the liquid ejecting apparatus  11 , a power button or various operation buttons operated by a user or the like are displayed. As the operation buttons, there are a cleaning command button or the like to which an operation command is inputted by a user, for example, when executing a cleaning which is one of the maintenance operations of the liquid ejecting portion  12 . 
     Note that, the cleaning is a maintenance operation for discharging foreign materials such as air bubbles contained in the liquid inside the liquid ejecting portion  12  or inside the supply flow path  20  by forcibly discharging the liquid from the nozzle  15  of the liquid ejecting portion  12 . Cleaning is roughly classified into a pressurized cleaning and a suction cleaning depending on a difference in a method of applying pressure to the nozzle  15  of the liquid ejecting portion  12 . The pressurized cleaning is a cleaning where a positive pressure is applied to a liquid, which is on the upstream side from the nozzle  15  in the liquid ejecting portion  12 , from the upstream side of the supply flow path  20  toward the nozzle  15  on the downstream side to discharge the liquid from the nozzle  15 . 
     On the other hand, the suction cleaning is a cleaning where a negative pressure accumulated in the pressure chamber which has a predetermined volume including the first chamber  31  is applied to the closed space formed by the cap  21  contacting the liquid ejecting portion  12  based on the driving of the suction pump  29  or the negative pressure generation mechanism  37 , and the liquid is discharged from the nozzle  15  which opens into the closed space. In the present embodiment, the maintenance device  14  performs the suction cleaning instead of the pressurized cleaning. 
     The measurement unit  45  is configured with a counting circuit which counts pulse signals outputted at a constant period, for example, and outputs the count value as measurement signals. In the present embodiment, in the maintenance device  14 , the measurement unit  45  transmits a measurement signal indicating an elapsed time from the execution of the previous cleaning to the control device  41 . The control device  41  determines whether or not the elapsed time from the execution of the previous cleaning exceeds a predetermined time based on the measurement signal transmitted from the measurement unit  45 . Note that, the predetermined time can be set any. 
     The discharge failure detection unit  46  is configured with a detection circuit for detecting residual vibration of a cavity (not shown) temporarily storing a liquid for discharging from the nozzle  15  inside the liquid ejecting portion  12 , for example. That is when the liquid is ejected from the nozzle  15  of the liquid ejecting portion  12  at the time of printing or the like, a piezoelectric element (not shown) provided in the cavity corresponding to each nozzle  15  is driven. And the nozzle  15  having a discharge failure is detected by detecting the residual vibration after vibrating the inside of the cavity by the driving of the piezoelectric element with the piezoelectric element. 
     For example, as the viscosity of the liquid in the cavity increases, the residual vibration tends to attenuate and the cycle of the residual vibration becomes shorter. On the other hand, if air bubbles are mixed in the cavity, the residual vibration hardly attenuates and the period of the residual vibration becomes longer. When the cycle of the residual vibration in the cavity detected by the piezoelectric element becomes shorter than a predetermined lower limit cycle or becomes longer than a predetermined upper limit cycle, the discharge failure detection unit  46  detects the nozzle  15  corresponding to the cavity and the piezoelectric element as an nozzle  15  having a discharge failure and transmits detection signals indicating the detection result to the control device  41 . 
     As shown in  FIG. 2 , a plurality kinds of drive circuits is connected to the output side interface (not shown) of the control device  41 . The piezoelectric element driving circuit  47  drives the piezoelectric element provided in the cavity of the liquid ejecting portion  12  to eject the liquid from the nozzle  15  corresponding to the piezoelectric element. As described above, the piezoelectric element driving circuit  47  also drives the piezoelectric element when detecting the residual vibration of the cavity of the liquid ejecting portion  12  in order to detect the nozzle  15  having a discharge failure. The cap driving circuit  48  drives an elevating mechanism (not shown) that makes the cap  21  vertically move between the contact position and the separated position in order to relatively move the cap  21  with respect to the liquid ejecting portion  12 . The negative pressure generation mechanism driving circuit  49  drives the negative pressure generation mechanism  37  configured with a diaphragm pump or the like when setting the pressure chamber in the container  22  including at least the first chamber  31  to a negative pressure. 
     The suction pump driving circuit  50  drives the suction pump  29  configured with a tube pump or the like when sucking the liquid which becomes a waste liquid from the pressure chamber of the container  22  including at least the first chamber  31  and causing the waste liquid storage portion  23  to recover the liquid. The pressure opening/closing valve driving circuit  51  drives the pressure opening/closing valve  25  so as to open or close the valve which is in the middle of the discharge flow path  24  when a state between the cap  21  and the first chamber  31 , which are connected to each other via the discharge flow path  24 , is switched between the communication state and the isolated state. 
     The flow path opening/closing valve driving circuit  52  drives at least one of the first flow path opening/closing valve  35  and the second flow path opening/closing valve  36  provided in the communication flow path  34 . When both of the first flow path opening/closing valve  35  and the second flow path opening/closing valve  36  are opened, the volume of the pressure chamber which becomes a state of communicating with the cap  21  via the discharge flow path  24  is the sum of the volumes of the three chambers of the first chamber  31 , the second chamber  32 , and the third chamber  33 . When the first flow path opening/closing valve  35  is opened and the second flow path opening/closing valve  36  is closed, the volume of the pressure chamber which becomes a state of communicating with the cap  21  via the discharge flow path  24  is the sum of the volumes of the two chambers of the first chamber  31 , and the second chamber  32 . Regardless of the opening/closing state of the second flow path opening/closing valve  36 , when the first flow path opening/closing valve  35  is closed, the volume of the pressure chamber which becomes a state of communicating with the cap  21  via the discharge flow path  24  is only the volume of one chamber which is the first chamber  31 . 
     Further, in a case where the atmosphere opening valve driving circuit  53  is in a state in which the closed space is formed between the cap  21  and the liquid ejecting portion  12  at the contact position where the cap  21  is in contact with the liquid ejecting portion  12 , the atmosphere opening valve driving circuit  53  opens the atmosphere opening valve  26  when opening the closed space to the atmosphere. Then, the release valve driving circuit  54  opens the release valve  40  when the interior of the first chamber  31  communicates with the atmosphere. Each of the driving circuits described above drives each corresponding driving target based on control signals appropriately transmitted from the control device  41 . 
     Next, the action of the liquid ejecting apparatus  11  configured as described above will be described focusing on the action in a case where the maintenance device  14  performs a suction cleaning, which is one of the maintenance operations for the liquid ejecting portion  12 . 
     When the suction cleaning is to be performed in the liquid ejecting apparatus  11 , first, the elevating mechanism of the cap  21  is driven by the cap driving circuit  48 . Then, the cap  21  ascends from the separated position separated downward from the liquid ejecting portion  12  to the contact position in contact with the upward of the liquid ejecting portion  12 , and a closed space, in which the nozzle  15  is open to a space between the opening surface  16  of the liquid ejecting portion  12  and the inner surface of the cap  21 , is formed. In this case, it is assumed that the atmosphere opening valve  26  of the cap  21 , the release valve  40  of the first chamber  31 , the first flow path opening/closing valve  35  and the second flow path opening/closing valve  36  of the communication flow path  34  are in a closed state respectively. 
     Then, from this state, the pressure opening/closing valve  25  of the discharge flow path  24  is set in a closed state by the pressure opening/closing valve driving circuit  51 , subsequently, the negative pressure generation mechanism  37  is driven in a state in which the opening/closing valve of the suction flow path  38  is opened by the negative pressure generation mechanism driving circuit  49 . Then, as the negative pressure generation mechanism  37  is driven, a negative pressure is accumulated in the first chamber  31 . When it is determined that a value of the negative pressure accumulated in the first chamber  31  reaches a preset threshold value at a normal time based on detection signals from the pressure sensor  39 , the driving of the negative pressure generation mechanism  37  is stopped by the negative pressure generation mechanism driving circuit  49  and the opening/closing valve of the suction flow path  38  is closed. 
     When accumulating the negative pressure in the first chamber  31 , the suction pump  29  may be driven by a suction pump driving circuit  50  instead of the negative pressure generation mechanism  37  or together with the negative pressure generation mechanism  37 . In this case, the suction pump  29  functions as a negative pressure generation mechanism. In a case where the suction pump  29  is driven together with the negative pressure generation mechanism  37 , since the negative pressure can be accumulated in the first chamber  31  in a shorter time than when only the negative pressure generation mechanism  37  is driven, it can contribute to improvement in cleaning efficiency. 
     Next, from this state, the pressure opening/closing valve  25  of the discharge flow path  24  is opened by the pressure opening/closing valve driving circuit  51 . Then, the negative pressure accumulated in the first chamber  31  is applied to the closed space between the cap  21  and the liquid ejecting portion  12  via the discharge flow path  24 . As a result, a suction cleaning, in which the liquid is discharged from the nozzle  15  of the liquid ejecting portion  12  by the negative pressure, is performed. That is a liquid is discharged from the nozzle  15  of the liquid ejecting portion  12  to the closed space with the suction force by the negative pressure, and the discharged liquid passes through the discharge flow path  24  and is temporarily storage stored in the first chamber  31 . 
     Next, from this state, the suction pump  29  of the recovery flow path  27  is driven by the suction pump driving circuit  50 , in a state in which the pressure opening/closing valve  25  of the discharge flow path  24  is closed again by the pressure opening/closing valve driving circuit  51  and also in a state in which the release valve  40  is by the release valve driving circuit  54 . Then, the liquid temporarily storage stored in the first chamber  31  is sucked into the recovery flow path  27  by the suction pump  29 , and then recovered in the waste liquid storage portion  23  at the downstream end of the recovery flow path  27 . The cleaning performed by applying the negative pressure accumulated in the first chamber  31  to the closed space as described above is hereinafter referred to as a normal cleaning. 
     Generally, the cleaning operation is performed in order to suppress introducing a printing failure due to clogging of the nozzle  15  or the like when foreign materials such as air bubbles or dust are mixed in the liquid on the upstream side of the nozzle  15  of the liquid ejecting portion  12  to be cleaned and when a liquid is thickened, dried, and solidified in the liquid ejecting portion  12 . However, depending on the thickening degree, the drying condition, and the mixing condition of air bubbles and foreign materials, there is a possibility that clogging of the nozzle  15  or the like can not be removed by performing the normal cleaning only once. 
     In such a case, it may be possible to repeat the same normal cleaning twice, three times, but then it takes too much time for cleaning. Therefore, in such a case, a so-called intensive cleaning is performed in which the magnitude of the negative pressure applied to the closed space is larger than the normal cleaning. 
     When the volume of the pressure chamber in which a negative pressure is accumulated is V, a pressure in the pressure chamber is P, the volume of the closed space is V′, the volume of a total space of the pressure chamber and the closed space is (V+V′), and a pressure in the total space is P′, the magnitude of a negative pressure applied to the closed space in which the nozzle  15  is open as the pressure opening/closing valve  25  is opened after the negative pressure is accumulated in the pressure chamber at the time of cleaning, is expressed by the following expressions. Note that, the volume of a part of the flow path such as the discharge flow path  24  is smaller than the volume of the pressure chamber or the closed space, and has little influence on the magnitude of the negative pressure applied to the closed space. Therefore, for convenience, the volume of the part of the flow path is ignored. 
     The magnitude of the negative pressure accumulated in the pressure chamber is shown on the left side and the magnitude of the negative pressure applied to the closed space after opening the pressure opening/closing valve  25  is shown on the right side, then the expression PV=P′(V+V′) is established, which can be converted to the expression P′=PV/(V+V′). From the converted expression, it can be seen that the larger the volume V of the pressure chamber in which the negative pressure is accumulated, the larger the negative pressure applied to the nozzle  15  in the closed space when cleaning. 
     In other words, in suction cleaning, it can be assumed that the magnitude of the negative pressure applied to the closed space is determined by the volume of the pressure chamber in which the negative pressure is accumulated. Therefore, in the liquid ejecting apparatus  11  of the present embodiment, in a case where the suction cleaning is performed for the liquid ejecting portion  12 , the volume of the pressure chamber in which the negative pressure is accumulated is increased by the driving of the negative pressure generation mechanism  37  when executing an intense cleaning in which the magnitude of the negative pressure applied to the closed space is larger than that of the normal cleaning. In addition, it is possible to increase the amount of liquid discharged by performing the intensive cleaning. 
     The normal cleaning is used at the time of cleaning which is called a manual cleaning in which the cleaning is performed when a user arbitrarily presses a cleaning command button of the operation unit  44 , in addition to cleaning which is called a periodic cleaning in which the cleaning is performed periodically at a preset cycle based on the control of the control device  41 . The manual cleaning is performed by a user to press the cleaning command button of the operation unit  44  in a case where the user visually recognizes display content indicating that there is a discharge failure in the nozzle  15  on the display screen of the operation unit  44  based on the detection result of the discharge failure detection unit  46 , in addition to a case where the user actually visually recognizes and determines that there is a printing failure in a printed image on the printed medium  17 . 
     Suppose that the user watches the displayed content of the operation unit  44  indicating that there is a printing failure on the printed medium  17  or a discharge failure in the nozzle  15  and presses the cleaning command button of the operation unit  44  in order to perform the manual cleaning. In this case, normally, the above-described normal cleaning is performed and in a case described below, the above-described intensive cleaning is performed. 
     First, in a case where the control device  41  determines that an elapsed time since the previous cleaning, which is one time before this time, has exceeded the preset predetermined time based on the measurement signals from the measurement unit  45 , the intensive cleaning is performed instead of normal cleaning since there is a high possibility that the liquid is thickened or solidified due to drying. That is in this case, at least the first flow path opening/closing valve  35  of the first flow path opening/closing valve  35  and the second flow path opening/closing valve  36  is opened by the flow path opening/closing valve driving circuit  52 , at least the second chamber  32  of the second chamber  32  and the third chamber  33  communicates with the first chamber  31 . 
     Then, the volume of the pressure chamber in which the negative pressure is accumulated as the negative pressure generation mechanism  37  is driven becomes a total volume in which the volume of the first chamber  31  and the volume of at least the second chamber  32  of the second chamber  32  and the third chamber  33  are summed. Accordingly, the volume of the pressure chamber is larger than the single volume of only the first chamber  31  when executing the normal cleaning. As a result, by applying a negative pressure accumulated in a large volume of the pressure chamber in which the plurality of chambers communicate and the volume is increased, to the closed space between the cap  21  and the liquid ejecting portion  12 , the intensive cleaning is performed. 
     In the present embodiment, as described above, the flow path opening/closing valve driving circuit  52  opens at least the first flow path opening/closing valve  35  of the first flow path opening/closing valve  35  and the second flow path opening/closing valve  36  provided in the communication flow path  34  to increase the volume of the pressure chamber in which the negative pressure is accumulated. In this respect, in the present embodiment, the volume variable mechanism that is capable of changing the volume of the pressure chamber in which the negative pressure is accumulated is configured to include the communication flow path  34 , at least one of the first flow path opening/closing valve  35  and the second flow path opening/closing valve  36 , and the flow path opening/closing valve driving circuit  52 . 
     Note that, in a case where the manual cleaning is performed by user&#39;s operation, even if it can be determined that the elapsed time from the previous cleaning has not exceeded the predetermined time based on the measurement signals from the measurement unit  45 , the intensive cleaning is performed instead of normal cleaning in the following cases. That is in a case of manual cleaning by a user pressing the cleaning command button in the previous time and this time and when the number of times of cleaning performed by the operation command by the user within the predetermined time is larger than the predetermined number of times previously set, it is determined that clogging or the like of the nozzle  15  can not be eliminated by the magnitude of the negative pressure that accumulates the negative pressure in a single volume chamber of only the first chamber  31  and applied to the closed space as in the previous normal cleaning, therefore, as described above, the intensive cleaning where the volume of the pressure chamber in which the negative pressure is accumulated is large, is performed. Note that, the predetermined number of times of cleaning performed by an operation command by the user within the preset predetermined time can be arbitrarily set. 
     Next, in a case where it is determined that there is a nozzle  15  having a discharge failure by the detection result of the discharge failure detection unit  46 , the normal cleaning is performed when the number of the nozzles  15  having a discharge failure is equal to or less than the preset predetermined number, and the intensive cleaning is performed when the number of the nozzles  15  having a discharge failure is larger than the preset predetermined number. It is desirable that the negative pressure applied to the ejection ports  15  having such discharge failure is larger in the case where the number of the ejection ports  15  having a discharge failure is larger than the predetermined number as compared with the case where the ejection number of the nozzles  15  having a discharge failure is equal to or less than the predetermined number, therefore, as described above, the intensive cleaning where the volume of the pressure chamber in which the negative pressure is accumulated is large, is performed. A cleaning based on the detection result of the nozzle  15  having a discharge failure by the discharge failure detection unit  46  may be a cleaning which is automatically performed under the control of the control device  41  based on the detection signals from the discharge failure detection unit  46 , in addition to the manual cleaning by a user who checked such detection result. Note that, the preset predetermined number of the nozzles having a discharge failure can be arbitrarily set. 
     In a case where it is again detected that a nozzle  15  having a discharge failure still exists by the discharge failure detection unit  46  after executing the intense cleaning due to the fact that the number of the nozzles  15  having such discharge failure is larger than the predetermined number, the intensive cleaning in which the negative pressure that is even larger than the previous intensive cleaning is applied to the closed space is performed. For example, in a case where only the second chamber  32  is communicated with the first chamber  31  at the previous intensive cleaning, the flow path opening/closing valve driving circuit  52  opens the second flow path opening/closing valve  36  in addition to the first flow path opening/closing valve  35  and not only the second chamber  32  but also the third chamber  33  is communicated with the first chamber  31 . 
     Then, the volume of the pressure chamber in which the negative pressure is accumulated as the negative pressure generation mechanism  37  is driven becomes an even larger total volume in which the volume of the first chamber  31 , the volume of the second chamber  32 , and the volume of the third chamber  33  are summed. As a result, as more chambers communicate with each other than the previous intensive cleaning, the negative pressure is accumulated in a large volume of the pressure chamber in which the volume is increased, and it is possible to discharge the liquid from the nozzle  15  which still has a discharge failure by applying the negative pressure larger than the previous cleaning to the closed space between the cap  21  and the liquid ejecting portion  12 . 
     Even when the number of the nozzles  15  having a discharge failure is determined to be equal to or less than the predetermined number by the detection result of the discharge failure detection unit  46 , the intensive cleaning is performed instead of the normal cleaning in the following cases. In other words, in a case where the elapsed time from the execution of the previous cleaning, which is one time before the normal cleaning scheduled to be performed this time based on the detection of a discharge failure, exceeds the predetermined time set in advance, the above-described intensive cleaning is performed instead of normal cleaning since there is a high possibility that the liquid is thickened or solidified due to drying. 
     Next, for example, when the cartridge-type liquid storage portion  18  is attached to and detached from the holder portion  19  and the new/old liquid storage portion  18  is exchanged, it is considered that there is a high possibility that air bubbles are mixed in the liquid inside the liquid ejecting portion  12  via the supply flow path  20 . Therefore, the amount of liquid discharged from the nozzle  15  required when the cleaning performed after the exchange of the liquid storage portion  18  is increased. When such a liquid storage portion  18  is exchanged, the above-described intensive cleaning which is also called an exchange cleaning is performed. 
     Note that, in a case where the normal cleaning is scheduled to be performed this time and the volume of the pressure chamber at that time is, for example, a large volume in which the first chamber  31  and the second chamber communicate with each other, it takes too much time to accumulate the negative pressure in such a large volume of the pressure chamber until it reaches a desired pressure value. Therefore, in such a case, the control device  41  drives the flow path opening/closing valve driving circuit  52  to switch the first flow path opening/closing valve  35  of the communication flow path  34  from the open state to the closed state. Then, the communication between the first chamber  31  and the second chamber  32  is isolated inside the container  22 , and only the first chamber  31  becomes the pressure chamber in which negative pressure is accumulated. Accordingly, it is possible to shorten the time for accumulating the negative pressure until the desired pressure value is reached since the negative pressure is accumulated in the pressure chamber having a small volume necessary and sufficient in the normal cleaning to be performed this time. 
     According to the above-described first embodiment, the following effects can be obtained. 
     (1) It is possible to perform a cleaning in which the magnitude of the negative pressure applied to the closed space is different since the magnitude of the negative pressure applied to the closed space can be changed by changing the volume of the pressure chamber. 
     (2) It is possible to efficiently perform a cleaning for discharging the liquid from the liquid ejecting portion  12  since the amount of liquid discharged from the liquid ejecting portion  12  via the nozzle  15  and the time for accumulating the negative pressure in the pressure chamber can be optimized by changing the volume of the pressure chamber. 
     (3) When the elapsed time from the execution of the previous cleaning is long enough to exceed the predetermined time, it is desirable that the negative pressure applied to the closed space is large since there is a high possibility that the liquid is thickened or solidified due to drying. In this regard, according to the present embodiment, when the elapsed time after execution of the previous cleaning exceeds the predetermined time, the negative pressure applied to the closed space can be increased by increasing the volume of the pressure chamber. Therefore, it is possible to perform a cleaning in which the magnitude of the negative pressure applied to the closed space is different in accordance with the elapsed time from the previous cleaning. 
     (4) When an attachable/detachable exchange of the liquid storage portion  18  is performed, the amount of liquid discharged from the nozzle  15  required for the cleaning performed after the exchange is increased due to air bubbles tend to be mixed into the flow path from the liquid storage portion  18  to the liquid ejecting portion  12 . In this regard, according to the present embodiment, the amount of liquid discharged from the nozzle  15  can be increased by increasing the volume of the pressure chamber after the liquid storage portion  18  is exchanged. Therefore, it is possible to perform a cleaning in which the magnitude of the negative pressure applied to the closed space is different in accordance with the attachable/detachable exchange of the liquid storage portion  18 . 
     (5) When the number of the nozzles  15  having a discharge failure is larger than the predetermined number, it is possible to increase the negative pressure applied to the closed space by making the volume of the pressure chamber larger than when the number of the nozzles  15  having a discharge failure is equal to or less than the predetermined number. Furthermore, when the number of the nozzles  15  having a discharge failure is equal to or less than the predetermined number, the volume of the pressure chamber may be small, so that the amount of liquid discharged from the nozzle  15  is reduced, and it is possible to reduce the waste of liquid. Therefore, it is possible to perform a cleaning in which the magnitude of the negative pressure applied to the closed space is different in accordance with the number of the nozzles  15  having a discharge failure. 
     (6) It is possible to achieve a recovery by applying further larger negative pressure to the closed space with respect to the nozzle  15  in which a discharge failure cannot be recovered in the previous cleaning. 
     (7) When the number of the operation commands is larger than the predetermined number, it can be determined that the negative pressure applied to the closed space is insufficient in the cleaning based on the previous operation command, so that it is possible to increase the negative pressure applied to the closed space by making the volume of the pressure chamber larger than when the number of the operation commands is equal to or less than the predetermined number. Therefore, it is possible to perform a cleaning in which the magnitude of the negative pressure applied to the closed space is different in accordance with the number of the operation commands. 
     (8) When the number of the liquid ejecting portions  12  on which the cleaning is performed is large, the magnitude of the negative pressure applied to the closed space becomes larger than when the number of the liquid ejecting portions  12  on which the cleaning is performed is small. In this regard, according to the present embodiment, even when the cleaning is performed where the number of the liquid ejecting portions  12  on which the cleaning is performed is large, it is possible to suppress a decrease in the magnitude of the negative pressure applied to the closed space since the volume of the pressure chamber can be increased. Further, when the number of the liquid ejecting portions  12  on which the cleaning is performed is small, it is possible to shorten the time taken to accumulate the negative pressure with respect to the pressure chamber since the volume of the pressure chamber may be smaller than when the number of the liquid ejecting portions  12  on which the cleaning is performed is large. 
     (9) The volume of the pressure chamber may be small when the number of the liquid ejecting portions  12  that need to be cleaned is small since the number of the nozzles  15  having a discharge failure is larger than the predetermined number and the volume of the pressure chamber can be changed in accordance with the number of the caps  21  corresponding to the liquid ejecting portions  12  that need to be cleaned. Therefore, it is possible to shorten the time taken to accumulate the negative pressure with respect to the pressure chamber. In addition, it is possible to suppress wasteful liquid ejection from the nozzle  15  since only the liquid ejecting portion  12  that needs to be cleaned is cleaned. 
     (10) As an example, the volume of the pressure chamber can be easily changed based on driving of the communication flow path opening/closing mechanism configured with at least one of the first flow path opening/closing valve  35  and the second flow path opening/closing valve  36 . 
     Second Embodiment 
     Next, a second embodiment of the liquid ejecting apparatus  11  will be described. 
     In the second embodiment, the same reference numerals as those in the first embodiment denote the same configurations as those of the first embodiment, and the description thereof will be omitted. In the following description, differences from the first embodiment will be mainly described. 
     As shown in  FIG. 3 , a space inside a container  22  is divided into a plurality (two in the present embodiment) of chambers  61  and  61  by a moving member  60  which is a movable partition wall provided so as to be reciprocally movable within the container  22 . Among the plurality of chambers  61  and  62 , the downstream end of the discharge flow path  24  and the upstream end of the recovery flow path  27  are connected to the chamber  61  positioned on the right side of the moving member  60  in  FIG. 3 . That is in a case where a pressure opening/closing valve  25  is opened, the chamber  61  positioned on the right side of the moving member  60  in  FIG. 3  is communicated via a discharge flow path  24  with a closed space between a cap  21  that is ascended to a contact position and a liquid ejecting portion  12 . A pressure sensor  39  and a release valve  40  are provided in the right side chamber  61 . 
     On the other hand, in a part of a partition wall of the chamber  62  positioned on the left side of the moving member  60  in  FIG. 3 , an atmosphere opening port  63  for opening the internal space of the chamber  62  to the outside atmosphere is formed. Therefore, in either case of a state in which the right side chamber  61  communicates with the atmosphere due to opening of the release valve  40  or the like and a state of non-communication state, the moving member  60  can be moved in a first direction D 1  and a second direction D 2  indicated by an arrow in  FIG. 3 . 
     That is in a state in which the right side chamber  61  connected to the downstream end of a discharge flow path  24  is in communication with the atmosphere, the moving member  60  is movable in the first direction D 1  for decreasing the volume of the right side chamber  61 . After the movement, in a state in which the pressure opening/closing valve  25  of the discharge flow path  24  is closed and a state in which the chamber  61  on the right side is isolated from the atmosphere, the moving member  60  is movable in the second direction D 2  at this time for increasing the volume of the right side chamber  61 . 
     In this case, in the right side chamber  61  in the container  22  after the moving member  60  once moved in the first direction D 1 , it becomes possible to accumulate a negative pressure in the right side chamber  61  when moving in the second direction D 2 . Then, the negative pressure accumulated in the right side chamber  61  applied to the closed space between the cap  21  and the liquid ejecting portion  12  by opening the pressure opening/closing valve  25  of the discharge flow path  24 . In this regard, in a case of the present embodiment, among the plurality of chambers  61  and  62  partitioned by the moving member  60  in the container  22 , the right side chamber  61  becomes a pressure chamber in which the negative pressure is accumulated. Then, a negative pressure generation mechanism  70  and a volume variable mechanism are configured including the container  22  and the moving member  60  capable of reciprocating within the container  22 . The volume variable mechanism makes it possible to change the volume of the chamber  61  functioning as a pressure chamber by moving the moving member  60  in the first direction D 1  and the second direction D 2 . 
     As shown in  FIG. 3 , a connection portion between the right side chamber  61  and the discharge flow path  24 , a connection portion between the right side chamber  61  and the recovery flow path  27 , a connection portion between the right side chamber  61  and the flow path communicating with the release valve  40 , and a connection portion between the right side chamber  61  and the pressure sensor  39  are provided so as not to protrude to the side wall of the right side chamber  61 , in other words, to the wall portion of the right side chamber  61  on the side in the first direction D 1 . With such a configuration, the moving member  60  can move so that the volume of the right side chamber  61  becomes zero. Accordingly, it is possible to increase the magnitude of the negative pressure that can be accumulated in the right side chamber  61 . 
     In the liquid ejecting apparatus  11  of the second embodiment configured as described above, the normal cleaning and the intensive cleaning described above are selectively used as in the case of the first embodiment when a maintenance device  14  performs a suction cleaning for the liquid ejecting portion  12 . That is, the intensive cleaning in which the volume of the pressure chamber is increased and the negative pressure is increased is performed in the following cases. When the elapsed time from the previous cleaning is performed exceeds the predetermined time, the number of times of cleaning by the operation command by a user within the predetermined time is larger than the predetermined number of times, the number of the nozzles  15  having a discharge failure is larger than the predetermined number, the liquid storage portion  18  is exchanged, or the like. In this case, instead of opening/closing the flow path opening/closing valves  35 ,  36  of the communication flow path  34  communicating the plurality of chambers  31 ,  32 , and  33  as in the first embodiment, the volume of the pressure chamber in which the negative pressure is accumulated is changed by moving the moving member  60  that defines the chamber  61  which becomes a pressure chamber in the container  22 . 
     More specifically, the volume variable mechanism at the time of performing the intensive cleaning performs at least either one of an operation of moving the movement amount of the moving member  60  in the first direction D 1  so as to be larger than that in the case of the normal cleaning in a state in which the right side chamber  61  in the container  22  is in communication with the atmosphere and an operation of moving the movement amount of the moving member  60  in the second direction D 2  so as to be larger than that in the case of the normal cleaning in a state in which the right side chamber  61  in the container  22  is isolated from the atmosphere. 
     According to the second embodiment, in addition to the effects (1) and (2) of the first embodiment, the following effects can be obtained. 
     (11) The number of parts can be reduced by integrating the volume variable mechanism and the negative pressure generation mechanism  70 . 
     Note that, the above-described embodiment may be modified as in the following modification examples. In addition, the configurations included in these embodiments and the configurations included in the following modification examples may be arbitrarily combined, or the configurations included in the following modification examples may be arbitrarily combined with each other. 
     As shown in  FIG. 4 , it may be configured to provide a plurality of liquid ejecting portions  112 ,  212 ,  312 , and  412 , and a plurality of caps  121 ,  221 ,  321 , and  421  corresponding to the plurality of liquid ejecting portions, and include branch flow path portions  124 ,  224 ,  324 , and  424  branching to be capable of communicating with the plurality of caps on the side opposite to the side communicating with the pressure chamber in the length direction of the discharge flow path  24 . Branch flow path opening/closing valves  125 ,  225 ,  325 , and  425  may be provided in the branch flow path portions  124 ,  224 ,  324 , and  424 , respectively. The branch flow path opening/closing valves  125 ,  225 ,  325 , and  425  are valves capable of opening/closing the branch flow path portions  124 ,  224 ,  324 , and  424 , respectively. With such a configuration, only the cap corresponding to the liquid ejecting portion of a cleaning target on which the cleaning is performed can be communicated with the pressure chamber. 
     In a case where the cleaning is performed for a plurality of liquid ejecting portions, the volume V′ of the closed space increases according to the above expression, so that the pressure P′ inside the total space of the pressure chamber and the closed space becomes small. That is when the volume of the pressure chamber is the same, the magnitude of the negative pressure applied to the closed space decreases as the number of the caps increases. Therefore, when cleaning is performed for the plurality of liquid ejecting portions, for example, as described above, it is necessary to increase the volume V of the pressure chamber in order to perform a cleaning with the same intensity as the magnitude of the negative pressure applied to the closed space by the cleaning performed for one liquid ejecting portion. 
     In this regard, with the configuration as shown in the modification example shown in  FIG. 4 , the volume variable mechanism enabling the volume of the pressure chamber to be changed can change the volume of the pressure chamber in accordance with the number of the liquid ejecting portions of a cleaning target on which the cleaning is performed. In other words, when the number of the liquid ejecting portions of a cleaning target on which the cleaning is performed is large, it is possible to suppress a decrease in the magnitude of the negative pressure applied to the closed space by making the volume of the pressure chamber larger than when the number of the liquid ejecting portions of a cleaning target on which the cleaning is performed is small. Further, when the number of the liquid ejecting portions on which the cleaning is performed is small, it is possible to shorten the time taken to accumulate the negative pressure with respect to the pressure chamber since the volume of the pressure chamber may be small. In addition, each of the plurality of liquid ejecting portions, the number of the caps, the number of branches of the branch flow path portion, and the branch flow path opening/closing valves may be plural other than the four shown in  FIG. 4 . 
     In the modification example shown in  FIG. 4 , it may be configured that a discharge failure detection unit  46  capable of detecting a discharge failure of the nozzles  15  of the plurality of liquid ejecting portions is provided and the cleaning is performed with respect to the liquid ejecting portion in which the number of the nozzles  15  having a discharge failure is larger than the predetermined number. According to the configuration, since the number of the nozzles  15  having a discharge failure is larger than the predetermined number and the volume of the pressure chamber can be changed in accordance with the number of the liquid ejecting portions that need to be cleaned, the volume of the pressure chamber may be small when the number of the liquid ejecting portions that need to be cleaned is small. Therefore, it is possible to shorten the time taken to accumulate the negative pressure with respect to the pressure chamber. In addition, since only the liquid ejecting portion that needs to be cleaned is cleaned, it is possible to suppress wasteful liquid ejection from the nozzle  15 . 
     In the modification example shown in  FIG. 4 , when cleaning is required for the plurality of liquid ejecting portions, cleaning may be performed by dividing the cleaning into a plurality of times. That is when it is necessary to perform a cleaning for a plurality of liquid ejecting portions, for example, a plurality of liquid ejecting portions such as eight, the cleaning may be performed twice by setting the liquid ejecting portions of a cleaning target on which the cleaning is performed to four by controlling the opening/closing of the branch flow path opening/closing valve. By decreasing the number of the liquid ejecting portions on which the cleaning is performed at a time, it is possible to apply the negative pressure uniformly to the closed space as compared with a case where the number of the liquid ejecting portions on which the cleaning is performed at a time is large. Further, when the number of the liquid ejecting portions on which the cleaning is performed is small by changing the volume of the pressure chamber corresponding to the number of the liquid ejecting portions of a cleaning target on which the cleaning is performed at a time, it is possible to shorten the time for accumulating the negative pressure in the pressure chamber as compared with the case where the number of the liquid ejecting portions on which the cleaning is performed is large. 
     The moving member  60  in the second embodiment may be configured to a member having flexibility and capable of being flexibly deformed, and may be configured to be able to change the volume of the pressure chamber by deforming the part of the area facing the right side chamber  61  functioning as a pressure chamber in the moving member  60  so as to reciprocate with deflection in the first direction D 1  and the second direction D 2 . 
     In the discharge flow path  24 , when at least a part of the flow path where the discharge flow path opening/closing mechanism is provided is configured to a tube having a flexibility or the like, the discharge flow path opening/closing mechanism capable of opening/closing the discharge flow path  24  may be configured to a clip member that sandwiches or opens the part of the flow path having a flexibility. 
     In the communication flow path  34 , when at least a part of the flow path where the communication flow path opening/closing mechanism is provided is configured to a tube having a flexibility or the like, the communication flow path opening/closing mechanism capable of opening/closing the communication flow path  34  may be configured to a clip member that sandwiches or opens the part of the flow path having a flexibility. 
     In the first embodiment, the number of the chambers  31 ,  32 , and  33  partitioned by the partition walls  30  in the container  22  may be a plurality of numbers other than three. The pressure chamber may be configured that a plurality of pressure chambers individually provided in each of the plurality of containers  22  are communicated with each other or blocked, other than being partitioned into a plurality of chambers by the partition walls  30  in one container  22 . 
     In the first embodiment, the communication flow path  34  may be configured with a first communication flow path that allows the first chamber  31  and the second chamber  32  communicate each other, and a second communication flow path that allows the first chamber  31  and the third chamber  33  communicate each other. Also in the communication flow path  34 , the first flow path opening/closing valve  35  may be provided in the first communication flow path and the second flow path opening/closing valve  36  may be provided in the second communication flow path. 
     A cleaning, in which the negative pressure is accumulated in the pressure chamber by driving the negative pressure generation mechanism  37  and the negative pressure generation mechanism  37  is continuously driven even after opening the pressure opening/closing valve  25  in order to apply the negative pressure to the closed space, may be performed. With such a configuration, it is possible to maintain a state where the negative pressure applied to the closed space is large for a long time as compared with a case where the negative pressure generation mechanism  37  is not driven after the pressure opening/closing valve  25  is opened. 
     When the nozzle  15  having a discharge failure is detected again after executing the intensive cleaning based on the result that the discharge failure detection unit  46  detected the number of the nozzles  15  having a discharge failure more than the predetermined number, a negative pressure accumulated in the pressure chamber having the same volume as that of the previous intensive cleaning may be applied to the closed space and the intensive cleaning may be performed again without further increasing the volume of the pressure chamber. 
     The suction cleaning performed immediately after the attachable/detachable exchange of the liquid storage portion  18  may be the normal cleaning in which the volume of the pressure chamber is the same as usual, instead of the intensive cleaning in which the volume of the pressure chamber is increased. 
     A threshold value for determining whether or not the elapsed time since the execution of the previous cleaning has exceeded the predetermined time can be set to any value. 
     When a range in which the suction pump  29  is pressed by a rollers in a tube disposed along the inner wall surface of a pump case is 360 degrees or more and the arrangement shape of the tube is a so-called a character shape tube pump formed into a spiral shape, the check valve  28  on the upstream side from the suction pump  29  of the recovery flow path  27  may be omitted as the tube pump functions as a one-way valve. 
     The idea of the cleaning in which the negative pressure accumulated in the pressure chamber is changed by changing the volume of the pressure chamber and the changed negative pressure is applied to the closed space can be applied to so-called flushing in which a liquid is discharged by driving a piezoelectric element based on command information irrelevant to printing from the liquid ejecting portion  12 . That is the liquid discharged into the cap  21  by the flushing may be sucked by using the negative pressure accumulated in the pressure chamber. 
     According to the configuration, suction performance improves since the suction force due to the negative pressure is applied and the flow rate becomes fast as compared with a case where the liquid is sucked from the cap  21  by suction driving of the suction pump  29 . It is preferable to reduce the driving time of the negative pressure generation mechanism for accumulating the negative pressure by reducing the volume of the pressure chamber, since the amount of liquid discharged into the cap  21  by the flushing is smaller than the amount of liquid discharged from the nozzle  15  by the cleaning. 
     When the liquid ejecting apparatus  11  of the embodiment is used in a low altitude high land or the like, the time for accumulating the negative pressure to the target relative pressure can be shortened by reducing the volume of the pressure chamber. 
     In the liquid ejecting apparatus  11  may be a so-called line head printer in which a liquid ejecting portion  12  having a group of nozzles  15  covering the entire width direction intersecting the transport direction of a medium  17  is fixedly disposed and printing is performed by ejecting a liquid from the group of the nozzles  15  of the liquid ejecting portion  12  to the medium  17  transported at a position facing the opening surface  16  of the liquid ejecting portion  12 . 
     Technical ideas and the working effects grasped from the above-described embodiments and modifications are described below. 
     Idea 1 
     A liquid ejecting apparatus including: a liquid ejecting portion configured to eject a liquid from a nozzle; a cap configured to be relatively move with respect to the liquid ejecting portion and configured to form a closed space in which the nozzle is open between the cap and the liquid ejecting portion; a negative pressure generation mechanism configured to generate a negative pressure; a pressure chamber configured to accumulate the negative pressure by driving the negative pressure generation mechanism; a discharge flow path that communicates with the cap and the pressure chamber; a discharge flow path opening/closing mechanism configured to open and close the discharge flow path; a volume variable mechanism configured to change a volume of the pressure chamber; and a controller that controls the negative pressure generation mechanism, the discharge flow path opening/closing mechanism, and the volume variable mechanism. 
     According to the configuration, it is possible to perform a cleaning in which the magnitude of the negative pressure applied to the closed space is different since the magnitude of the negative pressure applied to the closed space can be changed by changing the volume of the pressure chamber. 
     Idea 2 
     The liquid ejecting apparatus according to “Idea 1”, in which the controller drives the negative pressure generation mechanism to accumulate the negative pressure in the pressure chamber in a state that the discharge flow path is closed, then by opening the discharge flow path, the negative pressure accumulated in the pressure chamber is applied to the closed space to perform a cleaning that the liquid is discharged from the nozzle. 
     According to the configuration, it is possible to efficiently perform a cleaning in which the liquid is discharged from the liquid ejecting portion since the amount of the liquid discharged from the liquid ejecting portion via the nozzle and the time for accumulating the negative pressure in the pressure chamber can be optimized by changing the volume of the pressure chamber. 
     Idea 3 
     The liquid ejecting apparatus according to “Idea 2”, further including: a measurement unit measuring an elapsed time from a performance of the cleaning last time, in which when the elapsed time measured by the measurement unit exceeds a predetermined time, the controller controls the volume variable mechanism so as to make the volume of the pressure chamber larger than the volume of the pressure chamber when the elapsed time does not exceed the predetermined time, and then performs the cleaning. 
     When the elapsed time from the performance of the previous cleaning is long enough to exceed the predetermined time, it is desirable that the negative pressure applied to the closed space is large since there is a high possibility that the liquid is thickened or solidified due to drying. In this regard, according to the above-described configuration, when the elapsed time after the performance of the previous cleaning exceeds the predetermined time, the negative pressure applied to the closed space can be increased by increasing the volume of the pressure chamber. Therefore, it is possible to perform a cleaning in which the magnitude of the negative pressure applied to the closed space is different in accordance with the elapsed time from the previous cleaning. 
     Idea 4 
     The liquid ejecting apparatus according to “Idea 2 or 3”, further including: a liquid storage portion configured to be attached to the liquid ejecting apparatus in an attachable/detachable manner and stored a liquid to be supplied to the liquid ejecting portion, in which when an exchange of the liquid storage portion is performed, the controller controls the volume variable mechanism so as to make the volume of the pressure chamber larger than the volume of the pressure chamber before the exchange of the liquid storage portion is performed, and then performs the cleaning. 
     When the attachable/detachable exchange of the liquid storage portion is performed, the amount of liquid discharged from the nozzle required for the cleaning performed after the exchange is increased due to air bubbles tend to be mixed into the flow path from the liquid storage portion to the liquid ejecting portion. In this regard, according to the above-described configuration, the amount of liquid discharged from the nozzle can be increased by increasing the volume of the pressure chamber after the liquid storage portion is exchanged. Therefore, it is possible to perform a cleaning in which the magnitude of the negative pressure applied to the closed space is different in accordance with the attachable/detachable exchange of the liquid storage portion. 
     Idea 5 
     The liquid ejecting apparatus according to “any one of Ideas 2 to 4”, further including: a discharge failure detection unit that detects a discharge failure of the nozzle, in which when the number of the nozzles having a discharge failure detected by the discharge failure detection unit is larger than a predetermined number, the controller controls the volume variable mechanism so as to make the volume of the pressure chamber larger than the volume of the pressure chamber when the number of the nozzles having a discharge failure is equal to or less than the predetermined number, and then performs the cleaning. 
     According to the configuration, when the number of the nozzles having a discharge failure is larger than the predetermined number, it is possible to increase the negative pressure applied to the closed space by making the volume of the pressure chamber larger than the volume of the pressure chamber when the number of the nozzles having a discharge failure is equal to or less than the predetermined number. Furthermore, when the number of the nozzles having a discharge failure is equal to or less than the predetermined number, the volume of the pressure chamber may be small, so that the amount of liquid discharged from the nozzle is reduced, and it is possible to reduce the waste of liquid. Therefore, it is possible to perform a cleaning in which the magnitude of the negative pressure applied to the closed space is different in accordance with the number of the nozzles having a discharge failure. 
     Idea 6 
     The liquid ejecting apparatus according to “Idea 5”, in which when a discharge failure of the nozzle is detected by the discharge failure detection unit after the cleaning is performed by changing the volume of the pressure chamber in accordance with the number of the nozzles having a discharge failure detected by the discharge failure detection unit, the controller controls the volume variable mechanism so as to make the volume of the pressure chamber larger than the volume of the pressure chamber when the cleaning last time is performed, and then performs the cleaning. 
     According to the configuration, it is possible to achieve a recovery by applying further larger negative pressure to the closed space with respect to the nozzle in which a discharge failure cannot be recovered in the previous cleaning. 
     Idea 7 
     The liquid ejecting apparatus according to “any one of Ideas 2 to 6”, in which when the number of times of an operation command of the cleaning performed based on the operation command from an outside is larger than predetermined number of times, the controller controls the volume variable mechanism so as to make the volume of the pressure chamber larger than the volume of the pressure chamber when the number of times of the operation command of the cleaning is equal to or less than the predetermined number of times, and then performs the cleaning. 
     According to the configuration, when the number of the operation commands is larger than the predetermined number, it can be determined that the negative pressure applied to the closed space is insufficient in the cleaning based on the previous operation command, so that it is possible to increase the negative pressure applied to the closed space by making the volume of the pressure chamber larger than the volume of the pressure chamber when the number of the operation commands is equal to or less than the predetermined number. Therefore, it is possible to perform a cleaning different in the magnitude of the negative pressure applied to the closed space according to the number of the operation commands. 
     Idea 8 
     The liquid ejecting apparatus according to “Idea 2”, in which a plurality of the liquid ejecting portions are provided, in which a plurality of the caps are provided respectively corresponding to the plurality of the liquid ejecting portions, and closed spaces corresponding to each of the plurality of the liquid ejecting portions can be formed, in which the discharge flow path has a branch flow path portion that branches so as to communicate with the plurality of the caps, and in which when the number of the caps corresponding to the liquid ejecting portions of a cleaning target on which the cleaning is performed is larger than a prescribed number, the controller controls the volume variable mechanism so as to make the volume of the pressure chamber larger than the volume of the pressure chamber when the number of the caps corresponding to the liquid ejecting portions of a cleaning target on which the cleaning is performed is equal to or less than the prescribed number, and then performs the cleaning. 
     When the number of the liquid ejecting portions on which the cleaning is performed is larger than the prescribed number, the magnitude of the negative pressure applied to the closed space becomes larger than the magnitude of the negative pressure applied to the closed space when the number of the liquid ejecting portions on which the cleaning is performed is equal to or less than the prescribed number. In this regard, according to the above-described configuration, even when the cleaning is performed where the number of the liquid ejecting portions on which the cleaning is performed is larger than the prescribed number, it is possible to suppress a decrease in the magnitude of the negative pressure applied to the closed space since the volume of the pressure chamber can be increased. Further, when the number of the liquid ejecting portions on which the cleaning is performed is equal to or less than the prescribed number, it is possible to shorten the time taken to accumulate the negative pressure with respect to the pressure chamber since the volume of the pressure chamber may be smaller than the volume of the pressure chamber when the number of the liquid ejecting portions on which the cleaning is performed is larger than the prescribed number. 
     Idea 9 
     The liquid ejecting apparatus according to “Idea 8”, further including: a discharge failure detection unit that detects a discharge failure of the nozzles of the plurality of the liquid ejecting portions, in which the controller performs the cleaning for the caps corresponding to the liquid ejecting portions in which the number of the nozzles having a discharge failure detected by the discharge failure detection unit is larger than a predetermined number. 
     According to the configuration, the volume of the pressure chamber may be small when the number of the liquid ejecting portions that need to be cleaned is small since the number of the nozzles having a discharge failure is larger than the predetermined number and the volume of the pressure chamber can be changed in accordance with the number of the caps corresponding to the liquid ejecting portions that need to be cleaned. Therefore, it is possible to shorten the time taken to accumulate the negative pressure with respect to the pressure chamber. In addition, it is possible to suppress wasteful liquid ejection from the nozzle since only the liquid ejecting portion that needs to be cleaned is cleaned. 
     Idea 10 
     The liquid ejecting apparatus according to “any one of Ideas 1 to 9”, in which the pressure chamber is configured to include one chamber communicated with the discharge flow path and at least one other chamber communicable with the one chamber via a communication flow path, and the volume variable mechanism is configured to be provided in the middle of the communication flow path and include a communication flow path opening/closing mechanism configured to open and close the communication flow path. 
     According to this configuration, the volume of the pressure chamber can be easily changed based on driving of the communication flow path opening/closing mechanism. 
     Idea 11 
     The liquid ejecting apparatus according to “Idea 1”, in which the negative pressure generation mechanism and the volume variable mechanism are configured to include a common container and a common moving member capable of reciprocating within the container, in which the pressure chamber is partitioned into the container by the moving member and communicates with the closed space via the discharge flow path, in which the volume variable mechanism makes the volume of the pressure chamber changeable by moving the moving member, and in which the controller causes the volume variable mechanism to move the moving member in a direction to decrease the volume of the pressure chamber in a state where the pressure chamber communicates with the atmosphere, then causes the volume variable mechanism to move the moving member in a direction to increase the volume of the pressure chamber so as to accumulate the negative pressure in the pressure chamber in a state in which the discharge flow path is closed and the pressure chamber is isolated from the atmosphere, after that, by opening the discharge flow path, the negative pressure accumulated in the pressure chamber is applied to the closed space to perform a cleaning in which the liquid is discharged from the nozzle. 
     According to this configuration, the same effects as Ideas 1 and 2 can be obtained while reducing the number of the parts by integrating the volume variable mechanism and the negative pressure generation mechanism. 
     The entire disclosure of Japanese Patent Application No. 2018-052139, filed Mar. 20, 2018 is expressly incorporated by reference herein.