Patent Publication Number: US-2015059749-A1

Title: Pump unit and respiratory assistance device

Description:
TECHNICAL FIELD 
     The present invention relates to a pump unit for transporting a fluid by means of a micro pump and a respiratory assistance device employing the same. 
     BACKGROUND ART 
     In medical practice, respiratory assistance devices such as artificial respirators are employed. Types of such a respiratory assistance device employ: a controlled ventilation (Controlled Ventilation) method employed for a patient in the absence of spontaneous breathing (a patient under general anesthesia, during cardiopulmonary resuscitation, or in a critical condition); an assisted ventilation (Assisted Ventilation) method in which a positive pressure is created in an air passage in synchronization with the spontaneous breathing of a patient; a partial assisted (Assist/Control) method employing the assisted ventilation and the controlled ventilation in combination; a high frequency oscillation ventilation (high frequency oscillation) with which a very small amount of a single ventilation, 1 to 2 ml/kg, can be achieved by causing a gas supplied by an air passage to oscillate at a frequency of 5 to 40 Hz, etc. 
     Such a respiratory assistance device is employed also for a patient suffering from a respiratory disorder during sleep. This respiratory disorder is caused by the blockage of an air passage as a result of relaxation of the muscle of the air passage during sleep and the resultant retraction of the posterior part of a tongue or a soft palate. Applying a positive pressure to the air passage of the patient suffering from this type of respiratory disorder can alleviate its symptoms. 
     Any of these respiratory assistance devices requires a pump unit for creating a positive pressure in an air passage. A blower for transporting a gas by rotating a fan, a cylinder pump for transporting a gas by causing a piston to reciprocate, or the like is employed as a power source for this pump unit. 
     SUMMARY OF INVENTION 
     Technical Problem 
     In the conventional respiratory assistance device, however, the pump unit is housed in a box-shaped housing and is placed beside a user when used due to a relatively large size thereof. Thus, there is a problem in that the downsizing of the respiratory assistance device is difficult to achieve. 
     Moreover, according to the pump unit employed in the respiratory assistance device, during an inspiratory operation, a pressure is initially increased (a positive pressure is created) rapidly at a high flow rate and then a constant flow rate is maintained while assisting inspiration by further increasing the pressure as shown in  FIG. 26 , for example. During an expiratory operation, a pressure is decreased (a negative pressure is created) rapidly at a high flow rate. Once the pressure is lowered, the flow rate is controlled so as to be gradually decreased in order to avoid a burden on a lung. Such control is merely an example and various control modes are required in practice. In order to perform fine control of this type, however, a relatively large blower or cylinder pump needs to be employed and its pressure and its flow rate should be capable of being changed as desired. Thus, there is a problem in that the downsizing of the pump unit is further complicated. 
     The present invention has been made in view of the aforementioned problems and it is an object of the present invention to provide a pump unit capable of achieving significant downsizing while maintaining an ability to control its pressure and its flow rate as desired and a respiratory assistance device employing the same. 
     Solution to Problem 
     As a result of intensive studies made by the present inventor, the aforementioned object is achieved by the following means. 
     More specifically, a pump unit achieving the aforementioned object includes: a body provided with an inlet and an outlet for a fluid; and a pump group composed of a plurality of micro pumps arranged in the body, for allowing a fluid entering through the inlet to exit from the outlet. The pump group includes: a micro pump positioned in most upstream in a serial state; a micro pump positioned in most downstream in the serial state; and a micro pump positioned in middle in the serial state. The body includes: an inlet direct-connecting flow passage directly connecting a suction port of the micro pump positioned in the most upstream with the inlet; an outlet direct-connecting flow passage directly connecting a discharge port of the micro pump positioned in the most downstream with the outlet; and a flow passage forming mechanism that connects the micro pumps constituting the pump group. The flow passage forming mechanism is switchable between the serial state in which the micro pump positioned in the most upstream, the micro pump positioned in the middle, and the micro pump positioned in the most downstream are connected in this order and a parallel state in which a branched passage connecting between a suction port of the micro pump positioned in the middle or in the most downstream and the inlet is formed and a confluent passage connecting between a discharge port of the micro pump positioned in the most upstream or in the middle and the outlet is formed. 
     Preferably, a flow passage forming control part for controlling the flow passage forming mechanism is provided. Moreover, the flow passage forming mechanism preferably includes: first flow passage forming means that allows the suction ports of the micro pumps positioned in the middle and in the most downstream and the inlet of the body to be communicated with or closed off from each other; second flow passage forming means that allows the discharge port of the micro pump on an upstream side and the suction port of the micro pump on a downstream side to be communicated with or closed off from each other in the micro pumps connected in the order of the most upstream, the middle, and the most downstream; and third flow passage forming means that allows the discharge ports of the micro pumps positioned in the most upstream and in the middle and the outlet of the body to be communicated with or closed off from each other. 
     The micro pumps constituting the pump group may be arranged so as to be stacked one another or may be arranged in a lattice pattern. Moreover, a row bypass flow passage that connects suction ports of a plurality of the micro pumps arranged in a row direction and connects discharge ports of the plurality of the micro pumps arranged in the row direction and a row bypass flow passage opening and closing device for opening and closing the row bypass flow passage are preferably provided. Furthermore, a column bypass flow passage that connects suction ports of a plurality of the micro pumps arranged in a column direction and connects discharge ports of the plurality of the micro pumps arranged in the column direction and a column bypass flow passage opening and closing device for opening and closing the column bypass flow passage are preferably provided. 
     The flow passage forming control part preferably includes: a failure detecting part for detecting a failure of the micro pump; a pump substitution control part for determining whether or not there is a micro pump which can be substituted for a broken micro pump; and a bypass control part for controlling, when it is determined that there is the substitution micro pump, the row bypass flow passage opening and closing device or the column bypass flow passage opening and closing device so that the fluid flowing toward the micro pump specified by a failure signal is sent to the substitution micro pump and the fluid exiting from the substitution micro pump is sent to the micro pump subsequent to the micro pump specified by the failure signal. 
     Preferably, a warning device capable of issuing a warning is provided and the flow passage forming control part includes a warning notification part for giving a warning by means of the warning device when it is determined that the substitution micro pump does not exist. 
     Preferably, the body is provided with a depressed portion for housing the micro pump. Moreover, the micro pump preferably includes a power-feeding terminal for feeding power to a pump device contained therein, and the depressed portion is preferably provided with a line electrically connecting to the power-feeding terminal of the micro pump housed in the depressed portion. 
     Preferably, the body includes an inlet package having the inlet and an outlet package having the outlet, the first flow passage forming means is provided in the inlet package, and the third flow passage forming means is provided in the outlet package. 
     A respiratory assistance device achieving the aforementioned object includes: a flow passage through which an expiratory or inspiratory gas passes; a nozzle disposed in the flow passage, for jetting an acceleration gas in an expiratory or inspiratory direction; and the above-described pump unit fixed around the flow passage, for supplying the acceleration gas to the nozzle. 
     Advantageous Effects of Invention 
     The present invention achieves an excellent effect such that the pump unit can be significantly downsized while maintaining an ability to control a pressure and a flow rate as desired. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view illustrating an outline of a pump unit. 
         FIG. 2  is a perspective view illustrating the outline of the pump unit. 
         FIG. 3  is an exploded perspective view illustrating the outline of the pump unit. 
         FIG. 4  is a perspective view illustrating an outline of a micro pump. 
         FIG. 5  is a cross-sectional view illustrating the outline of the micro pump. 
         FIG. 6  is a graph showing pressure-flow rate lines for the micro pump. 
         FIG. 7  is a plan view illustrating an outline of micro pumps arranged in a lattice pattern on an upper surface of an inlet-side housing plate. 
         FIG. 8  is a connection diagram of micro pumps contained in the pump unit. 
         FIG. 9  is a cross-sectional view of the pump unit. 
         FIG. 10  is a configuration diagram illustrating an outline of a controller. 
         FIG. 11  is a functional block diagram illustrating the outline of the controller. 
         FIG. 12  is a connection diagram illustrating an outline of a pump unit in a pressure preferential transporting state. 
         FIG. 13  is a connection diagram illustrating an outline of the pump unit in a flow rate preferential transporting state. 
         FIG. 14  is a connection diagram illustrating an outline of a pump unit including spare micro pumps. 
         FIG. 15  is a connection diagram illustrating an outline of a pump unit in a state where a flow passage has been switched so that a fluid is allowed to flow to a spare micro pump instead of a micro pump in a failure state. 
         FIG. 16  is a connection diagram illustrating an outline of a pump unit in a state where a flow passage has been switched so that a fluid is allowed to flow to a spare micro pump instead of a micro pump in a failure state. 
         FIG. 17  is a perspective view illustrating an outline of a pump unit. 
         FIG. 18  is a cross-sectional view illustrating the outline of the pump unit. 
         FIG. 19  is a cross-sectional view illustrating the outline of the pump unit. 
         FIG. 20  is a perspective view illustrating an outline of a plurality of micro pumps housed in a housing of the pump unit and a flow passage block disposed between the plurality of micro pumps. 
         FIG. 21  is a perspective view illustrating an outline of a pump unit. 
         FIG. 22A  is a cross-sectional view illustrating an outline of a respiratory assistance device. 
         FIG. 22B  is a cross-sectional view as viewed along arrows B-B in  FIG. 22A . 
         FIG. 23A  is a cross-sectional view illustrating a control example of the respiratory assistance device. 
         FIG. 23B  is a cross-sectional view illustrating a control example of the respiratory assistance device. 
         FIG. 24  is a cross-sectional view illustrating an outline of another respiratory assistance device. 
         FIG. 25  is a cross-sectional view illustrating an outline of another respiratory assistance device. 
         FIG. 26  shows graphs illustrating a control example of a pressure and a flow rate in a typical respiratory assistance device. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Embodiments of the present invention will now be described below with reference to the accompanying drawings. 
     As shown in  FIGS. 1 to 2 , a pump unit  10  includes: a plate-like housing  13  having an inlet  11  and an outlet  12 ; micro pumps  15  (see  FIG. 3 ) housed in the housing  13 ; and a light-emitting diode  18 . The pump unit  10  sucks a fluid in from the inlet  11  and lets the sucked fluid out from the outlet  12  by means of the micro pumps  15  (see  FIG. 3 ). 
     As shown in  FIG. 3 , the housing  13  has an inlet-side housing plate  13 A and an outlet-side housing plate  13 B. Depressed portions  13 K to which the micro pumps  15  are attached are formed on a surface  13 AS of the inlet-side housing plate  13 A. On the surface  13 AS, the depressed portions  13 K are arranged in a lattice pattern. Although the diagrammatic illustration thereof is omitted, depressed portions to which the micro pumps  15  are attached are formed also on a surface  13 BS of the outlet-side housing plate  13 B. The depressed portions on the surface  13 BS are provided at positions directly facing the depressed portions  13 K when the housing plates  13 A and  13 B are overlapped with each other with the surfaces  13 AS and  13 BS facing each other. When the housing plates  13 A and  13 B are overlapped with each other with the surfaces  13 AS and  13 BS facing each other, housing spaces for the micro pumps  15  are formed by the depressed portions  13 K on the inlet-side housing plate  13 A and the depressed portions on the outlet-side housing plate  13 B. Therefore, by placing the micro pumps  15  on the depressed portions provided on any one of the housing plates  13 A and  13 B, the micro pumps  15  are arranged in a lattice pattern of m rows×n columns (4 rows×4 columns, for example). Thereafter, by overlapping the housing plates  13 A and  13 B with each other with the surfaces  13 AS and  13 BS facing each other, the micro pumps  15  are contained in the housing  13  while keeping the lattice arrangement. 
     The plurality of micro pumps  15  (pump group) contained in the housing  13  form: a most upstream row group  21  composed of the micro pumps  15  arranged in the most upstream row (the row m1 in the figure); a most downstream row group  24  composed of the micro pumps  15  arranged in the most downstream row (the row m4 in the figure); and middle row groups  22  and  23  each composed of the micro pumps arranged in the row direction (the row m2 and the row m3 in the figure) between the most upstream row group  21  and the most downstream row group  24 . 
     A flow passage for a fluid is formed in the housing  13 . The flow passage is formed so as to connect between suction ports and discharge ports of the micro pumps  15  contained in the housing  13  and so that the fluid is transported in the housing  13  from the inlet  11  to the outlet  12 . The flow passage will be described later. 
     A micro pump proposed in Patent Literature WO 2008/069266, for example, can be employed as the micro pump  15 . As shown in  FIGS. 4 and 5 , the micro pump  15  includes: a case  31  having a suction port  31 A and a discharge port  31 B; a pump device  32  contained in the case  31 , for transporting a gas from the suction port  31 A to the discharge port  31 B; and a power-feeding terminal  33  exposed to the outside of the case  31 . 
     As shown in  FIG. 5 , the pump device  32  is electrically connected to the power-feeding terminal  33 . The pump device  32  includes: a piezoelectric element  32 A deformable when a voltage is applied; and a deformable box  32 B deformable by the actuation of the piezoelectric element. The deformable box  32 B includes a diaphragm  32 BA and an oscillation wall  32 BB. The diaphragm  32 BA is provided in a portion of the deformable box  32 B facing the suction port  31 A. The oscillation wall  32 BB is provided in a portion of the deformable box  32 B facing the discharge port  31 B. A primary blower chamber  32 K is formed between the diaphragm  32 BA and the oscillation wall  32 BB. The piezoelectric element  32 A is attached to a surface of the diaphragm  32 BA facing the suction port  31 A. Furthermore, in the oscillation wall  32 BB, an opening  32 BD through which the fluid is moved between the inside and outside of the primary blower chamber  32 K is formed at a position directly facing the discharge port  31 B. 
     When the diaphragm  32 BA is oscillated by the piezoelectric element  32 A, the fluid is moved between a secondary blower chamber  32 L formed by the case  31  and the pump device  32  and the primary blower chamber  32 K. Such a fluid movement causes the oscillation wall  32 BB to resonate. The oscillation of the diaphragm  32 BA and the oscillation wall  32 BB causes the fluid to be sucked in from the suction port  31 A. The fluid sucked in from the suction port  31 A is passed through the secondary blower chamber  32 L and emitted from the discharge port  31 B. The micro pump  15  is suitable for use as a blower for transporting a fluid. The micro pump  15  can transport a fluid without the use of a check valve. 
     A frequency of the diaphragm  32 BA is greater than ox equal to 1 kHz, for example, and preferably in a range between 18 kHz and 27 kHz. Moreover, the frequency of the diaphragm  32 BA is preferably in an inaudible range. Consequently, when a patient is equipped with a device including the pump device  32  (for example, a respiratory assistance device), the patient cannot hear the operation noise of the pump device  32 . Thus, this keeps the patient free from suffering discomfort caused by the operation noise. 
     The micro pump  15  further includes a sensor unit  36  for detecting a failure of the pump device  32 . The sensor unit  36  includes: a pressure sensor for detecting a static pressure P of a fluid at the discharge port  31 B; and a flow sensor for detecting a flow rate Q of the fluid at the discharge port  31 B. 
     The micro pump  15  is formed in a plate shape and extremely small (about 20 mm in length×20 mm in width×2 mm in thickness, for example). The micro pump  15  can still transport a fluid of about 1 L/min at maximum when the input sine wave is set at 26 kHz under 15 Vpp (Volt peak to peak) and can obtain a static pressure of 2 kPa at maximum (see  FIG. 6 ). 
     The micro pump  15  transports a fluid by means of the oscillation of the diaphragm  32 BA caused by the piezoelectric element  32 A. Thus, there is naturally a limit in the volume of a fluid the micro pump  15  can transport. The static pressure-vs-flow rate characteristics thereof also show a trend as shown in  FIG. 6  (for example, a linear function with a negative proportionality multiplier or something similar). In order to obtain a static pressure of about 1 kPa, for example, the required flow rate Q is 0.5 L/min. Setting the input sine wave at 10 Vpp or 20 Vpp causes the amplitude of the piezoelectric element  32 A to change. Thus, the flow rate Q and the static pressure P according to the input sine wave can be obtained. More specifically, if the Vpp of the input sine wave is smoothly changed, the flow rate Q and the static pressure P can be smoothly changed. Alternatively, if the frequency of the input sine wave is changed, the flow rate Q and the static pressure P can be changed. More specifically, if the frequency of the input sine wave is smoothly changed, the flow rate Q and the static pressure P can be smoothly changed. Note, however, that the flow rate Q and the static pressure P each have an upper limit according to the capacity of the piezoelectric element  32 A and the strength or durability of components of the micro pump  15 . The micro pump  15  is normally used at a rated Vpp and a rated frequency. 
     Note that the micro pump  15  may have a monomorph (unimorph) structure as described above in which the single piezoelectric element  32 A is attached to the diaphragm  32 BA or a bimorph structure in which two piezoelectric elements  32 A are attached together in order to increase the amount of oscillation. An appropriate structure of the micro pump  15  can be adopted in accordance with its purpose such as the transportation of a fluid. While the micro pump  15  can transport a gas without employing a check valve, the micro pump  15  may be replaced by a micro pump including a check valve at the suction port or the discharge port. 
     As shown in  FIGS. 3 and 7 , the housing  13  includes: an external power-supply terminal  37 ; a controller  38 ; and a line  39 . The external power-supply terminal  37  is provided so as to be exposed on the housing  13 . The controller  38  and the line  39  are provided in the inlet-side housing plate  13 A. The line  39  electrically connects between the external power-supply terminal  37  and the controller  38 . A bus  85 H electrically connects the controller  38 , the light-emitting diode  18 , and the power-feeding terminals  33  provided in the respective micro pumps  15 . The detail of the controller  38  will be described later. 
     The housing  13  has an inlet direct-connecting mechanism, an outlet direct-connecting mechanism, and a flow passage forming mechanism connecting between the inlet direct-connecting mechanism and the outlet direct-connecting mechanism. 
     As shown in  FIGS. 8 to 9 , the inlet direct-connecting mechanism is an inlet direct-connecting flow passage  41  directly connecting the suction ports  31 A of all the micro pumps  15  that belong to the most upstream row group  21  (the row m1 in the figure) with the inlet  11 . The inlet direct-connecting flow passage  41  is formed in the inlet-side housing plate  13 A. The inlet direct-connecting flow passage  41  is provided with a switching valve  41 Z. The switching valve  41 Z is switchable between a parallel state in which the suction ports  31 A of a plurality of micro pumps  15  that belong to the most upstream row group  21  (the row m1 in the figure) are communicated with the inlet  11  and a serial state in which the suction port  31 A of any one of the micro pumps  15  that belong to the most upstream row group  21  (the row m1 in the figure) is communicated with the inlet  11 . Note that when the switching valve  41 Z is in the parallel state, the suction ports  31 A of all the micro pumps  15  that belong to the most upstream row group  21  (the row m1 in the figure) may be communicated with the inlet  11  or the suction ports  31 A for a part of the micro pumps  15  that belong to the most upstream row group  21  (the row m1 in the figure) may be communicated with the inlet  11  while the suction ports  31 A for the remaining micro pumps  15  may not be communicated with the inlet  11 . 
     The outlet direct-connecting mechanism is an outlet direct-connecting flow passage  42  directly connecting the discharge ports  31 B in the most downstream row group  24  (the row m4 in the figure) with the outlet  12 . The outlet direct-connecting flow passage  42  is formed in the outlet-side housing plate  13 B. 
     Moreover, the flow passage forming mechanism is formed in the inlet-side housing plate  13 A and the outlet-side housing plate  13 B. The flow passage forming mechanism includes: the aforementioned switching valve  41 Z; a middle flow passage  43 ; and an opening and closing mechanism provided in the middle flow passage  43 . The middle flow passage  43  includes: a most upstream discharge port flow passage  51 B; a middle suction port flow passage  52 A; a middle discharge port flow passage  52 B; a middle suction port flow passage  53 A; a middle discharge port flow passage  53 B; a most downstream suction port flow passage  54 A; serial flow passages  61  to  63 ; and column bypass flow passages  71  to  73 . 
     The most upstream discharge port flow passage  51 B connects the discharge ports  31 B of all the micro pumps  15  that belong to the most upstream row group  21  (the row m1 in the figure) with one another. The middle suction port flow passage  52 A connects the suction ports  31 A of all the micro pumps  15  that belong to the middle row group  22  (the row m2 in the figure) with one another. The middle discharge port flow passage  52 B connects the discharge ports  31 B of all the micro pumps  15  that belong to the middle row group  22  (the row m2 in the figure) with one another. Similarly, the middle suction port flow passage  53 A connects the suction ports  31 A of all the micro pumps  15  that belong to the middle row group  23  (the row m3 in the figure) with one another. The middle discharge port flow passage  53 B connects the discharge ports  31 B of all the micro pumps  15  that belong to the middle row group  23  (the row m3 in the figure) with one another. The most downstream suction port flow passage  54 A connects the suction ports  31 A of all the micro pumps  15  that belong to the most downstream row group  24  (the row m4 in the figure) with one another. 
     Moreover, the suction port flow passages  52 A to  54 A are connected to the inlet  11  via the switching valve  41 Z and the inlet direct-connecting flow passage  41 . The discharge port flow passages  51 B to  53 B are connected to the outlet  12  via the outlet direct-connecting flow passage  42 . Note that the suction port flow passages  52 A to  54 A may be communicated with the inlet  11  regardless of the state of the switching valve  41 Z or may be communicated with the inlet  11  when the switching valve  41 Z is in the parallel state and may be closed off from the inlet  11  when the switching valve  41 Z is in the serial state. For example, the suction port flow passage  52 A and the suction port flow passage  53 A are connected to the inlet direct-connecting flow passage  41  at a position P 52A  (see  FIG. 9 ) and at a position P 53A  (see  FIG. 9 ), respectively. The suction port flow passage  54 A is connected to the flow passage  53 A at the position P 53A . Similarly, the discharge port flow passage  53 B and the discharge port flow passage  52 B are communicated with the outlet direct-connecting flow passage  42  at a position P 53B  (see  FIG. 9 ) and at a position P 52B  (see  FIG. 9 ), respectively. The discharge port flow passage  51 B is communicated with the flow passage  52 B at the position P 52B  (see  FIG. 9 ). 
     The serial flow passage  61  connects between the discharge port flow passage  51 B and the suction port flow passage  52 A. Similarly, the serial flow passage  62  connects between the discharge port flow passage  52 B and the suction port flow passage  53 A. The serial flow passage  63  connects between the discharge port flow passage  53 B and the suction port flow passage  54 A. 
     A valve  51 Y is provided at a connecting position between the discharge port flow passage  51 B and the serial flow passage  61 . The valve  51 Y can be transitioned between a parallel state in which the serial flow passage  61  is closed while opening the discharge port flow passage  51 B positioned downstream (the outlet  12  side) of the valve  51 Y and a serial state in which the serial flow passage  61  is opened while closing the discharge port flow passage  51 B positioned downstream (the outlet  12  side) of the valve  51 Y. Note that the discharge port flow passage  51 B positioned upstream (the discharge port  31 B side) of the valve  51 Y is kept opened in either of the parallel state and the serial state. 
     Similarly, a valve  52 Y is provided at a connecting position between the discharge port flow passage  52 B and the flow passage  62  and a valve  53 Y is provided at a connecting position between the discharge port flow passage  53 B and the serial flow passage  63 . The valve  52 Y can be transitioned between a parallel state in which the serial flow passage  62  is closed while opening the discharge port flow passage  52 B positioned downstream (the outlet  12  side) of the valve  52 Y and a serial state in which the serial flow passage  62  is opened while closing the discharge port flow passage  52 B positioned downstream (the outlet  12  side) of the valve  52 Y. Note that the discharge port flow passage  52 B positioned upstream (the discharge port  31 B side) of the valve  52 Y is kept opened in either of the parallel state and the serial state. Similarly, the valve  53 Y can be transitioned between a parallel state in which the serial flow passage  63  is closed while opening the discharge port flow passage  53 B positioned downstream (the outlet  12  side) of the valve  53 Y and a serial state in which the serial flow passage  63  is opened while closing the discharge port flow passage  53 B positioned downstream (the outlet  12  side) of the valve  53 Y. Note that the discharge port flow passage  53 B positioned upstream (the discharge port  31 B side) of the valve  53 Y is kept opened in either of the parallel state and the serial state. 
     A valve  52 X is provided at a connecting position between the suction port flow passage  52 A and the serial flow passage  61 . The valve  52 X can be transitioned among a parallel state in which the serial flow passage  61  is closed while the other flow passages are opened, a serial state in which the suction port flow passage  52 A positioned upstream (the inlet  11  side) of the valve  52 X is closed while the other flow passages are opened, and a bypass state in which the suction port flow passage  52 A positioned downstream of the valve  52 X is closed while the other flow passages are opened. Similarly, a valve  53 X is provided at a connecting position between the suction port flow passage  53 A and the serial flow passage  62  and a valve  54 X is provided at a connecting position between the suction port flow passage  54 A and the serial flow passage  63 . The valve  53 X can be transitioned among a parallel state in which the serial flow passage  62  is closed while the other flow passages are opened, a serial state in which the suction port flow passage  53 A positioned upstream (the inlet  11  side) of the valve  53 X is closed while the other flow passages are opened, and a bypass state in which the suction port flow passage  53 A positioned downstream of the valve  53 X is closed while the other flow passages are opened. The valve  54 X can be transitioned among a parallel state in which the serial flow passage  63  is closed while the other flow passages are opened, a serial state in which the suction port flow passage  54 A positioned upstream (the inlet  11  side) of the valve  54 X is closed while the other flow passages are opened, and a bypass state in which the suction port flow passage  54 A positioned downstream of the valve  54 X is closed while the other flow passages are opened. 
     A valve  81  is provided in the inlet direct-connecting flow passage  41  positioned downstream of the position P 52A . Similarly, a valve  82  is provided in the suction port flow passage  52 A positioned downstream of the valve  52 X. A valve  83  is provided in the suction port flow passage  53 A positioned downstream of the valve  53 X. 
     The column bypass flow passage  71  connects between the valve  81  and the suction port flow passage  52 A positioned between the valve  82  and the valve  52 X. Similarly, the column bypass flow passage  72  connects between the valve  82  and the suction port flow passage  53 A positioned between the valve  83  and the valve  53 X. The column bypass flow passage  73  connects between the valve  83  and the suction port flow passage  54 A positioned between the micro pump  15  and the valve  54 X. 
     The valve  81  can be transitioned among a normal state in which the column bypass flow passage  71  is closed while the other flow passages are opened, a bypass state in which the inlet direct-connecting flow passage  41  positioned downstream of the valve  81  is closed while the other flow passages are opened, and a closed-off state in which the inlet direct-connecting flow passage  41  positioned upstream of the valve  81  is closed while the other flow passages are opened. The valve  82  can be transitioned among a normal state in which the column bypass flow passage  72  is closed while the other flow passages are opened, a bypass state in which the suction port flow passage  52 A positioned downstream of the valve  82  is closed while the other flow passages are opened, and a closed-off state in which the suction port flow passage  52 A positioned upstream of the valve  82  is closed while the other flow passages are opened. The valve  83  can be transitioned among a normal state in which the column bypass flow passage  73  is closed while the other flow passages are opened, a bypass state in which the suction port flow passage  53 A positioned downstream of the valve  83  is closed while the other flow passages are opened, and a closed-off state in which the suction port flow passage- 53 A positioned upstream of the valve  83  is closed while the other flow passages are opened. 
     Note that the opening and closing mechanism is configured by the valves  52 X to  54 X,  51 Y to  53 Y, and  81  to  83 . Moreover, a first flow passage forming part is configured by the suction port flow passages  52 A to  54 A and the valves  52 X to  54 X. A second flow passage forming part is configured by the serial flow passages  61  to  63  and the valves  51 Y to  53 Y. A third flow passage forming part is configured by the discharge port flow passages  51 B to  53 B and the valves  51 Y to  53 Y. Furthermore, a row bypass flow passage is configured by the suction port flow passages  52 A to  54 A. 
     As shown in  FIG. 9 , a sensor unit  45  is provided in the vicinity of the outlet  12  in the outlet direct-connecting flow passage  42 . The sensor unit  45  includes: a pressure sensor  45 P for detecting the static pressure P of a fluid in the vicinity of the outlet  12  in the outlet direct-connecting flow passage  42 ; and a flow rate sensor  45 Q for detecting the flow rate Q of a fluid in the vicinity of the outlet  12  in the outlet direct-connecting flow passage  42 . 
     The controller  38  includes, as a hardware configuration, a CPU  85 A, a first memory medium  85 B, a second memory medium  85 C, a third memory medium  85 D, an input device  85 E, a display device  85 F, an input and output interface  85 G, and the bus  85 H (see  FIG. 10 ). The CPU  85 A is what is called a central processing unit and executes various programs to obtain various functions of the controller  38 . The first memory medium  85 B is what is called a RAM (Random Access Memory) and is a memory used as a work area for the CPU  85 A. The second memory medium  85 C is what is called a ROM (Read Only Memory) and is a memory for storing a basic operating system (OS) executed by the CPU  85 A. The third memory medium  85 D is configured by a hard disk device incorporating a magnetic disk, a disk device accommodating a CD, a DVD, or a BD, a non-volatile semiconductor flash memory device, and the like. The third memory medium  85 D saves various programs to be executed by the CPU  85 A, sensing data from the sensors, etc. The input device  85 E is an input key, a keyboard, a mouse, or the like and is a device used for inputting a variety of information. The display device  85 F is a display and displays various operating states. The input and output interface  85 G supplies predetermined power to the valves  52 X to  54 X,  51 Y to  53 Y, and  81  to  83 , the switching valve  41 Z, the respective micro pumps  15  (see  FIG. 8 ), and the respective sensor units  36  and  45  (see  FIGS. 5 and 9 ). The input and output interface  85 G also inputs and outputs predetermined control signals to and from the valves  52 X to  54 X,  51 Y to  53 Y, and  81  to  83 , the switching valve  41 Z, the respective sensor units  36  and  45 , and the respective micro pumps  15 . Furthermore, the input and output interface  85 G can also obtain data such as a program from an external personal computer or output measurement results to such a personal computer. The bus  85 H is a line used for integrally connecting the CPU  85 A, the first memory medium  85 B, the second memory medium  85 C, the third memory medium  85 D, the input device  85 E, the display device  85 F, the input and output interface  85 G, and the like to achieve communication thereamong. 
     It is preferable that the line  85 H be formed so as to be exposed to the depressed portion  13 K (see  FIG. 3 ) provided on the inlet-side housing plate  13 K (see  FIG. 9 ). As a result of this, when the micro pump  15  is housed in the depressed portion  13 K, the external power-supply terminal  37  of the micro pump  15  housed in the depressed portion  13 K is electrically connected to the line  85 H. In this manner, the housing of the micro pump  15  in the depressed portion  13 K achieves the wiring to the micro pump  15 . Note that it is only necessary that the line  85 H is formed so as to be exposed to the depressed portion on at least one of the inlet-side housing plate  13 A and the outlet-side housing plate  13 B. In the depressed portion on the other one of the inlet-side housing plate  13 A and the outlet-side housing plate  13 B, a biasing member (a plate spring, a coil spring, or the like)  85 J for biasing the external power-supply terminal  37  of the micro pumps  15  housed in the depressed portion toward the one of the depressed portions may be provided. If the biasing member is conductive, the biasing member and the line  85 H may be electrically connected to each other. 
     When a control program stored in the controller  38  is executed by the CPU  85 A, the controller  38  functions as a pump power feed control part  94 , a failure detecting part  95 , a pump substitution control part  96 , a flow passage forming control part  97 , and a warning notification part  98  as shown in  FIG. 11 . 
     The pump power feed control part  94  feeds power to the pump device  32  of a predetermined micro pump  15  according to operating conditions set in advance by an operation of the input device  85 E or the like. The operating conditions refer to conditions under which a fluid with a desired static pressure P and a desired flow rate Q is outputted from the outlet  12  (see  FIG. 5 ) of the pump unit  10 , for example. 
     The failure detecting part  95  reads sensing signals from the respective sensors of the sensor unit  36  provided in the micro pump  15  and determines whether or not a measured value indicated by the sensing signal exceeds an acceptable range. Herein, the acceptable range refers to values between the upper limit value and the lower limit value set by an operation of the input device  85 E or the like. The upper limit value and the lower limit value are set so that the static pressure P and the flow rate Q of a fluid exiting from the micro pump  15  failing to exert the expected capability due to the deterioration or failure of the pump device  32  each fall outside the acceptable range. Moreover, if all the measured values from the respective sensors fall within the acceptable range, the failure detecting part  95  determines that the micro pump  15  in which those measured values are obtained is in a normal state. If at least one of the measured values from the respective sensors exceeds the acceptable range, the failure detecting part  95  determines that the micro pump  15  in which such a measured value is obtained is in a failure state. Furthermore, the failure detecting part  95  outputs a failure signal. The failure signal contains information about an identifier of the micro pump  15  determined as failure (for example, the micro pump arranged in the i-th row×the j-th row). 
     The pump substitution control part  96  determines whether or not the failure signal is outputted from the failure detecting part  95 . Also, the pump substitution control part  96  can receive the failure signal. Moreover, the pump substitution control part  96  can load power feed list information about the micro pumps  15  fed by the pump power feed control part  94  from the pump power feed control part  94 . Furthermore, the pump substitution control part  96  determines if the micro pump  15  in a standby state is present or not. Herein, the standby state refers to a state in which determination as failure has not been made (normal state) and power supply is being stopped (power-feeding stopped state). 
     With reference to the sensing signals from the sensor units  36  and  45 , the flow passage forming control part  97  performs opening and closing operations of the opening and closing mechanism, i.e., the valves  52 X to  54 X,  51 Y to  53 Y, and  81  to  83 , so that the flow rate Q and the static pressure P at the outlet  12  are equal to or close to predetermined values. 
     The warning notification part  98  controls the turning ON and OFF of the light-emitting diode  18 . Note that a buzzer or the like may be used as a warning device without being limited to the light-emitting diode  18 . 
     Next, control examples of the pump unit  10  performed by the controller  38  will be described. The pump power feed control part  94  turns all the micro pumps  15  to an operating state. If the flow passage forming control part  97  sets the valves  81  to  83  to the normal state and sets the valves  52 X to  54 X and  51 Y to  53 Y to the serial state, a fluid entering through the inlet  11  then goes through the micro pumps  15  arranged in the column direction and exits from the outlet  12  (see  FIG. 12 ). As the number of the micro pumps  15  the fluid passed through is increased in this manner, the static pressure P of the fluid exiting from the outlet  12  is increased in preference to the flow rate Q. Thus, the pump unit  10  is in a state in which the static pressure P of the fluid exiting from the outlet  12  is increased in preference to the flow rate Q (pressure preferential transporting state). 
     If the flow passage forming control part  97  sets the switching valve  41 Z to the parallel state, the valves  81  to  83  to the normal state, and the valves  52 X to  54 X and  51 Y to  53 Y to the parallel state, a fluid entering through the inlet  11  then branches at each of the suction ports of the micro pumps  15  and enters into the micro pumps  15 . The fluids exited from the discharge ports of the micro pumps  15  join together again and exit from the outlet  12  (see  FIG. 13 ). As a result of this, the pump unit  10  is in a state in which the flow rate Q of the fluid exiting from the outlet  12  is increased in preference to the static pressure P (flow rate preferential transporting state). 
     If the flow passage forming control part  97  sets the switching valve  41 Z to the parallel state, the valves  81  to  83  to the normal state, the valves  52 X to  54 X and  51 Y to  52 Y to the serial state, and the valve  53 Y to the parallel state, the flow rate Q and the static pressure P of the fluid exiting from the outlet  12  each take a value between the aforementioned two examples. 
     Controlling the valves  52 X to  54 X and  51 Y to  52 Y separately in this manner allows the fluid exiting from the outlet  12  to have a desired flow rate Q and a desired static pressure P. 
     Here, if the micro pumps  15  fed by the pump power feed control part  94  include the micro pump  15  in a state in which the pump device  32  is not operating normally (hereinafter referred to as a failure state), the flow rate Q and the static pressure P of the fluid exiting from the outlet  12  cannot be controlled with high accuracy. 
     Therefore, it is preferable that a spare micro pump  15  substitutable for the micro pump  15  in the failure state be provided in the pump unit  10  in advance. 
     For example, as shown in  FIG. 14 , if the micro pumps  15  are arranged in a lattice pattern (4 rows×4 columns), all the micro pumps  15  positioned in the fourth column and the fourth row are used as the spare micro pumps  15 . 
     First, the pump power feed control part  94  feeds power only to the micro pumps  15  in the first to third rows×the first to third columns. The micro pumps  15  in the first to third rows×the first to third columns are therefore in the operating state while the spare micro pumps  15  are in the power-feeding stopped state. The flow passage forming control part  97  sets the switching valve  41 Z to the parallel state, the valves  81  to  83  in the first to third columns to the normal state, the valves  81  to  83  in the fourth column to the closed-off state, the valves  51 Y to  52 Y in the first to third columns to the serial state, the valves  53 Y in the first to third columns to the parallel state, and the valves  52 X to  54 X in the first to third columns to the serial state. In addition, the valves  54 X in the first to third columns and the valves  52 X to  54 X and the valves  51 Y to  53 Y in the fourth column may be set to the serial state. As a result of this, the pump unit  10  is in the state in which the static pressure P of the fluid exiting from the outlet  12  is increased in preference to the flow rate Q. 
     Here, the controller  38  performs the following control. The failure detecting part  95  reads the sensing signals from the respective sensor units  36 . The timing at which the sensing signals are read may occur periodically or continuously. The failure detecting part  95  determines whether or not the measured values indicated by the read sensing signals fall outside the acceptable range. If the measured values each fall within the acceptable range, the failure detecting part  95  determines that the micro pump  15  from which the sensing signals are read is in the normal state. If the measured values each fall outside the acceptable range, on the other hand, the failure detecting part  95  determines that the micro pump  15  from which the sensing signals are read is in the failure state. If it is determined that there is the micro pump  15  in the failure state, the failure detecting part  95  then outputs the failure signal. 
     The pump substitution control part  96  determines whether or not the failure signal is outputted from the failure detecting part  95 . If the pump substitution control part  96  determines that “the failure signal has been outputted from the failure detecting part  95 ,” the pump substitution control part  96  then determines “whether or not there is the micro pump  15  in the standby state among the micro pumps  15  contained in the pump unit  10 .” If the pump substitution control part  96  determines that there is the micro pump  15  in the standby state, the pump power feed control part  94  then starts feeding power to the micro pump  15  selected from the micro pumps  15  in the standby state (hereinafter referred to as a selected micro pump  15 ). Note that the pump power feed control part  94  preferably stops feeding power to the micro pump  15  determined as being in the failure state. Next, the flow passage forming control part  97  performs the opening and closing operations of the valves  51 Y to  53 Y,  52 X to  54 X, and  81  to  83  so that the fluid flows through the selected micro pump  15  instead of the micro pump  15  determined as failure. This allows the fluid with a desired static pressure P and a desired flow rate Q to be outputted from the outlet  12  of the pump unit  10  even when the micro pump  15  in the failure state is present in the pump unit  10 . 
     Control contents performed by the flow passage forming control part  97  for allowing the spare micro pump  15  to be used instead of the micro pump  15  in the failure state will be described next. 
     First, if it is determined that the micro pump  15  in the second row×the third column is in the failure state, the flow passage forming control part  97  selects any micro pump  15  from among the spare micro pumps  15  in the standby state. 
     Here, if the micro pump  15  in the second row×the fourth column is selected as the substitution micro pump  15 , the flow passage forming control part  97  sets the valve  52 X in the third column and the valve  53 X in the fourth column to the bypass state, the valve  52 X in the fourth column and the valve  53 X in the third column to the parallel state, the valve  52 Y in the fourth column to the serial state, and the valve  82  in the fourth column to the normal state. As a result of this, the fluid having passed through the micro pump  15  in the first row×the third column passes through the micro pump  15  in the second row×the fourth column instead of the micro pump  15  in the second row×the third column. Thereafter, the fluid passes through the micro pump  15  in the third row×the third column (see  FIG. 15 ). Thus, the fluid with the expected flow rate Q and the expected static pressure P can be outputted from the outlet  12 . 
     If the micro pump  15  in the fourth row×the third column is selected as the substitution micro pump  15 , the flow passage forming control part  97  sets the valve  82  in the third column to the bypass state, the valve  83  in the third column to the normal state, and the valves  53 Y and  54 X in the third column to the serial state. Note that it is preferable that the valve  53 X in the third column be in the serial state. As a result of this, the fluid having passed through the micro pump  15  in the first row×the third column passes through the micro pump  15  in the third, row×the third column without passing through the micro pump  15  in the second row×the third column. Thereafter, the fluid passes through the micro pump  15  in the fourth row×the third column (see  FIG. 16 ). Thus, the fluid with the expected flow rate Q and the expected static pressure P can be outputted from the outlet  12 . 
     If the pump substitution control part  96  determines that there is no micro pump  15  in the stopped state, on the other hand, the warning notification part  98  can give a notification of an abnormal state in the pump unit  10  by controlling the turning ON and OFF of the light-emitting diode  18 . As a result of this, the use of the pump unit  10  which cannot output the fluid with the desired static pressure P and the desired flow rate Q can be avoided. 
     As described above, according to the pump unit  10 , the micro pumps  15  are arranged in a lattice pattern and by means of the flow passage forming mechanism, i.e., the middle flow passage  43  and the opening and closing mechanism (the valves) provided in the middle flow passage  43 , rational combinations about the serial connection and parallel connection of the micro pumps  15  can be controlled. Consequently, even for an application in which a single micro pump  15  fails to achieve a sufficient flow rate and a sufficient static pressure, a plurality of micro pumps  15  can be used in combination. Therefore, such micro pumps  15  can be used in a similar manner to the conventional blowers or syringe pumps. Moreover, due to the small size of the micro pump  15 , even when a plurality of such micro pumps  15  are arranged, they can be configured to be smaller and lighter than the conventional blowers or the like. In particular, various variations about a combination of the number of parallel connections and the number of serial connections can be digitally controlled by the turning ON and OFF of the micro pumps  15  or the control of the opening and closing mechanism (valves). Thus, the control configuration thereof can be extremely simplified. Furthermore, in the case of the conventional blowers or syringe pumps, if one of them is broken down, the entire fluid transportation is disrupted. According to the above-described pump unit  10 , however, even if an individual micro pump  15  is broken down, the other micro pumps  15  can make up for the broken micro pump  15 . Thus, reliability or safety can be also enhanced. 
     Particularly in the pump unit  10 , the number of the micro pumps  15  that belong to the upstream row is equal to or smaller than the number of the micro pumps  15  that belong to the downstream row in the pressure preferential transporting state in which the micro pumps  15  are connected in series. Consequently, the unnecessary operation of the micro pumps  15  can be suppressed, thereby making it possible to reduce power consumption. This is especially suitable for a battery-driven application, for example. 
     Furthermore, the pump unit  10  collectively switches the connection relationship of the entire micro pumps  15  arranged at each row. Consequently, the configuration of the valves is simplified, thereby improving the maintainability thereof. 
     Note that a single or a plurality of inlets  11  may be provided in the pump unit  10 . The plurality of inlets  11  may be connected to the inlet direct-connecting flow passage  41  or directly connected to the micro pumps  15  that belong to the most upstream row group  21 . Moreover, a single or three or more middle row groups may be provided. 
     In the above-described embodiment, the most upstream row group  21 , the middle row groups  22  and  23 , and the most downstream row group  24  are arranged in this order in the housing  13 . However, the present invention is not limited thereto. For example, the order of the most upstream row group  21 , the most downstream row group  24 , and the middle row groups  22  and  23 , the order of the most downstream row group  24 , the middle row groups  22  and  23 , and the most upstream row group  21 , or the like is possible. 
     While the micro pumps  15  are arranged in a lattice pattern in the housing  13  in the above-described embodiment, the present invention is not limited thereto. The micro pumps  15  may be arranged to form a single row or a single column. 
     Moreover, while the micro pumps  15  are fitted into the housing  13  in the above-described embodiment, the present invention is not limited thereto. The micro pumps  15  and the housing  13  may be integrally formed. 
     While the micro pumps  15  are arranged on a plane in a lattice pattern in the above-described embodiment, the present invention is not limited thereto. A plurality of micro pumps  15  may be arranged so as to overlap one another. For example, the micro pumps  15  may be stacked in such a manner that the inlet  11  of the second micro pump  15  is positioned above the outlet  12  of the first micro pump  15  (see  FIGS. 17 to 20 ). 
     The pump unit  10  shown in  FIGS. 17 to 18  includes: the housing  13  with the inlet  11  and the outlet  12 ; and a pump unit  15  housed in the housing  13 . The housing  13  having a pump unit housing hole  13 X for housing the pump unit  15  is configured by a first housing forming block  13 L and a second housing forming block  13 R. A predetermined depressed part is formed in each of the first housing forming block  13 L and the second housing forming block  13 R. The first housing forming block  13 L and the second housing forming block  13 R are fitted together in such a manner that the depressed parts face each other to form the pump unit housing hole  13 X. 
     As shown in  FIGS. 18 to 19 , micro pumps  15 A,  15 B, and  15 C arranged in this order from the inlet  11  toward the outlet  12  in the housing  13 , a flow passage block  13 SA disposed between the micro pump  15 A and the micro pump  15 B, and a flow passage block  13 SB disposed between the micro pump  15 B and the micro pump  15 C are arranged in the housing  13 . 
     Moreover, in the housing  13 , the inlet direct-connecting flow passage  41  connecting between the suction port  31 A of the micro pump  15 A and the inlet  11  and the outlet direct-connecting flow passage  42  connecting between the discharge port  31 B of the micro pump  15 C and the outlet  12  are formed. The inlet direct-connecting flow passage  41  includes: a direct-connecting passage  41 A directly connecting the suction port  31 A of the micro pump  15 A with the inlet  11 ; and a branched passage  41 B branched from the direct-connecting passage  41 A. The branched passage  41 B extends to the vicinity of the suction port  31 A of the micro pump  15 C along the micro pumps  15 A,  15 B, and  15 C. The outlet direct-connecting flow passage  42  includes: a direct-connecting passage  42 A directly connecting the discharge port  31 B of the micro pump  15 C with the outlet  12 ; and a branched passage  42 B branched from the direct-connecting passage  42 A. The branched passage  42 B extends to the vicinity of the discharge port  31 B of the micro pump  15 A along the micro pumps  15 C,  15 B, and  15 A. 
     As shown in  FIGS. 18 and 20 , the flow passage block  13 SA is formed in the shape of a rectangular parallelepiped. In the flow passage block  13 SA, a serial flow passage  90 A directly connecting the discharge port  31 B of the micro pump  15 A with the suction port  31 A of the micro pump  15 B; a serial valve  90 AB for opening and closing the serial flow passage  90 A; a discharge-side parallel flow passage  92 A directly connecting the serial flow passage  90 A closer to the discharge port  31 B than the serial valve  90 AB with the branched passage  42 B; a discharge-side parallel valve  92 AB for opening and closing the discharge-side parallel flow passage  92 A; a suction-side parallel flow passage  91 A directly connecting the serial flow passage  90 A closer to the suction port  31 A than the serial valve  90 AB with the branched passage  41 B; and a suction-side parallel valve  91 AB for opening and closing the suction-side parallel flow passage  91 A are formed. Note that the diagrammatic illustration of the valves  90 AB,  91 AB, and  92 AB is omitted in  FIG. 20  in order to avoid being complicated. The flow passage block  13 SB is similar to the flow passage block  13 SA. More specifically, the flow passage block  13 SB is formed in the shape of a rectangular parallelepiped, and a serial flow passage  90 B directly connecting the discharge port  31 B of the micro pump  15 B with the suction port  31 A of the micro pump  15 C; a serial valve  90 BB for opening and closing the serial flow passage  90 B; a discharge-side parallel flow passage  92 B directly connecting the serial flow passage  90 B closer to the discharge port  31 B than the serial valve  90 BB with the branched passage  42 B; a discharge-side parallel valve  92 BB for opening and closing the discharge-side parallel flow passage  92 B; a suction-side parallel flow passage  91 B directly connecting the serial flow passage  90 B closer to the suction port  31 A than the serial valve  90 BB with the branched passage  41 B; and a suction-side parallel valve  91 BB for opening and closing the suction-side parallel flow passage  91 B are formed. 
     The serial flow passage  90 A is formed so as to run through from a discharge port side surface  13 AL of the flow passage block  13 SA facing the discharge port  31 B of the micro pump  15 A to a suction port side surface  13 AU of the flow passage block  13 SA facing the suction port  31 A of the micro pump  15 B. Since the housing of the micro pump  15 A is in contact with the discharge port side surface  13 AL in the housing  13 , a groove  13 LM formed on the discharge port side surface  13 AL and the micro pump  15 A together form the discharge-side parallel flow passage  92 A. Since the housing of the micro pump  15 B is in contact with the suction port side surface  13 AU in the housing  13 , a groove  13 UM formed on the suction port side surface  13 AU and the micro pump  15 B together form the suction-side parallel flow passage  91 A. Similarly, the serial flow passage  90 B is formed so as to run through from a discharge port side surface  13 BL of the flow passage block  13 SB facing the discharge port  31 B of the micro pump  15 B to a suction port side surface  13 BU of the flow passage block  13 SB facing the suction port  31 A of the micro pump  15 C. Since the housing of the micro pump  15 B is in contact with the discharge port side surface  13 BL in the housing  13 , a groove formed on the discharge port side surface  13 BL and the micro pump  15 B together form the discharge-side parallel flow passage  92 B. Since the housing of the micro pump  15 C is in contact with the suction port side surface  13 BU in the housing  13 , a groove formed on the suction port side surface  13 BU and the micro pump  15 C together form the suction-side parallel flow passage  91 B. 
     The opening and closing operations of the switching valve  41 Z, the serial valves  90 AB and  90 BB, the suction-side parallel valves  91 AB and  91 BB, and the discharge-side parallel valves  92 AB and  92 BB are performed by the controller  38  (see  FIG. 7 ). 
     Functions of the pump unit  10  shown in  FIGS. 17 to 20  will be described next. 
     The switching valve  41 Z is set to the parallel state, the serial valves  90 AB and  90 BB are set to a closed state, and the suction-side parallel valves  91 AB and  91 BB and the discharge-side parallel valves  92 AB and  92 BB are set to an open state (see  FIG. 19 ). A fluid entering through the inlet  11  is distributed through the inlet direct-connecting flow passage  41 , the suction-side parallel flow passage  91 A, and the suction-side parallel flow passage  91 B. The distributed fluids are sucked into the suction ports  31 A of the micro pumps  15 A to  15 C, respectively. In each of the micro pumps  15 A to  15 C, the pump device  32  (see  FIG. 5 ) compresses the fluid sucked in from the suction port  31 A. The fluids compressed in the micro pumps  15 A to  15 C exit from the discharge ports  31 B, join together through the discharge-side parallel flow passage  92 A, the discharge-side parallel flow passage  92 B, and the outlet direct-connecting flow passage  42 , and then exit from the outlet  12 . 
     The switching valve  41 Z is set to the serial state, the serial valves  90 AB and  90 BB are set to the open state, and the suction-side parallel valves  91 AB and  91 BB and the discharge-side parallel valves  92 AB and  92 BB are set to the closed state (see  FIG. 18 ). A fluid entering through the inlet  11  is sucked into the suction port  31 A of the micro pump  15 A through the inlet direct-connecting flow passage  41 . In the micro pump  15 A, the pump device  32  (see  FIG. 5 ) compresses the fluid sucked in from the suction port  31 A. The fluid compressed in the micro pump  15 A exits from the discharge port  31 B and is sucked into the suction port  31 A of the micro pump  15 B through the serial flow passage  90 A. The fluid sucked in from the suction port  31 A of the micro pump  15 B is compressed by the pump device  32  (see  FIG. 5 ) and then sucked into the suction port  31 A of the micro pump  15 C through the discharge port  31 B and the serial flow passage  90 B. Similarly, the fluid sucked in from the suction port  31 A of the micro pump  15 C is compressed by the pump device  32  (see  FIG. 5 ) and then exits from the outlet  12  through the discharge port  31 B and the outlet direct-connecting flow passage  42 . 
     According to the pump unit  10 , the static pressure P and the flow rate Q of the fluid exiting from the outlet  12  can be appropriately controlled by means of the opening and closing operations of the switching valve  41 Z, the serial valves  90 AB and  90 BB, the suction-side parallel valves  91 AB and  91 BB, and the discharge-side parallel valves  92 AB and  92 BB. 
     Moreover, since the groove  13 LM formed on the discharge port side surface  13 AL and the micro pump  15 A together form the discharge-side parallel flow passage  92 A, time and effort required to form the discharge-side parallel flow passage  92 A can be saved. Similarly, since the groove  13 UM formed on the suction port side surface  13 AU and the micro pump  15 B together form the suction-side parallel flow passage  91 A, time and effort required to form the suction-side parallel flow passage  91 A can be saved. 
     This applies also to the housing  13  shown in  FIG. 9 . It is preferable that the inlet-side housing plate  13 A be formed by flow passage forming plates  13 AA to  13 AD. Each of the flow passage forming plates  13 AA to  13 AD has a through hole formed in a thickness direction thereof at a predetermined position. Moreover, each of the flow passage forming plates  13 AA to  13 AD has a groove at a predetermined position on a surface facing another flow passage forming plate. When the flow passage forming plates  13 AA to  13 AD are fitted together in a stacked manner, the through holes and the grooves formed in the flow passage forming plates  13 AA to  13 AD form the respective flow passages  41 ,  52 A to  54 A, and  71  to  73  and upstream portions of the respective flow passages  61  to  63 . Similarly, it is preferable that the outlet-side housing plate  13 B be formed by flow passage forming plates  13 BA to  13 BB. Each of the flow passage forming plates  13 BA to  13 BB has a through hole formed in a thickness direction thereof and a groove formed on a surface facing another flow passage forming plate at predetermined positions. When the flow passage forming plates  13 BA to  13 BB are fitted together in a stacked manner, the through holes and the grooves formed in the flow passage forming plates  13 BA to  13 BB form the respective flow passages  42  and  51 B to  53 B and downstream portions of the respective flow passages  61  to  63 . 
     While the outlet  12  of the first micro pump  15  and the inlet  11  of the second micro pump  15  are arranged so as to directly face each other in the above-described embodiment, the present invention is not limited thereto. For example, as shown in  FIG. 21 , a plurality of micro pumps  15  may be stacked one another in an oblique direction. The pump unit  10  configured by the plurality of micro pumps  15  stacked one another in an oblique direction can be placed in a small space such as an interspace between objects. 
     An example in which the pump unit  10  is applied to a respiratory assistance device  700  for medical use is shown in  FIGS. 22A and 22B . The respiratory assistance device  700  is configured by including: a flow passage  702  through which air for respiration passes; an expiratory nozzle  704  and an inspiratory nozzle  706  disposed in the flow passage  702  and capable of emitting an acceleration air in an expiratory direction and in an inspiratory direction, respectively; the pump unit  10  disposed on an outer surface of the flow passage  702  in a circumferential direction thereof; and a battery  710  for driving the pump unit  10 . Venturi walls  720  are disposed in the vicinity of the expiratory and inspiratory nozzles  704  and  706  disposed in the flow passage  702 . Note that the battery  710  may be disposed at a remote location or may be omitted by connecting a power supply line. 
     Furthermore, an expiration and inspiration switching valve  725  is disposed at the outlet  12  (see  FIG. 1 , hereinafter referred to as an integrated discharge port) of the pump unit  10 . The expiration and inspiration switching valve  725  switches between a case where air to be discharged from the integrated discharge port is emitted from the expiratory nozzle  704  and a case where such air is emitted from the inspiratory nozzle  706 . When air is emitted from the expiratory nozzle  704  as shown in  FIG. 23A , such air is spread out by the Venturi wall  720 , thereby setting the expiratory side to a negative pressure state. Thus, carbon dioxide discharged from the inspiratory side (lung side) is drawn into the air and such air is caused to flow in the expiratory direction. Consequently, an expiratory action can be assisted. When air is emitted from the inspiratory nozzle  706  as shown in  FIG. 23B , on the other hand, such air is spread out by the Venturi wall  720 , thereby setting the inspiratory side to the negative pressure state. Thus, oxygen supplied from the inspiratory side is absorbed in the air and such air is caused to flow in the inspiratory direction (lung side). Consequently, an inspiratory action can be assisted. 
     According to the respiratory assistance device  700 , the downsized pump unit  10  is directly fixed to a pipe itself that forms the flow passage  702 . Thus, the respiratory assistance device  700  can be configured in an extremely compact manner. Furthermore, due to the integral formation of the flow passage  702  and the pump unit  10 , even when the flow passage  702  is moved along with a user&#39;s body movement, the flow passage  702  and the pump unit  10  move together. Thus, the connection between the expiratory and inspiratory nozzles  704  and  706  and the pump unit  10  is prevented from being cut off. Therefore, stability in the breathing assisting operation is enhanced and a user can also move his or her body more freely. 
     Furthermore, due to a reduced distance between the pump unit  10  and the expiratory and inspiratory nozzles  704  and  706 , responsiveness of the breathing assisting operation can be enhanced. 
     The respiratory assistance device  700  can be used continuously with an intubation tube inserted toward a windpipe through a mouth of a user. However, the respiratory assistance device  700  can alternatively be used with the flow passage  702  being connected to a nose mask  830  as shown in  FIG. 24 , for example. Furthermore, when applied to a nose mask, it is preferable that the pump unit  10  be directly fixed to an outer peripheral surface of the nose mask  830  as in a respiratory assistance device  800  shown in  FIG. 25 , for example. Such an arrangement enhances the overall stability. While the case where air is supplied to the expiratory nozzle or the inspiratory nozzle by switching a single pump unit  10  by means of the expiration and inspiration switching valve  725  has been illustrated here, two pump units  10  may be provided and connected to the expiratory nozzle and the inspiratory nozzle, respectively. 
     It is apparent that the pump unit and the respiratory assistance device according to the present invention are not limited to the above-described embodiments and various modifications can be made thereto without departing from the scope of the present invention. 
     INDUSTRIAL APPLICABILITY 
     The pump unit according to the present invention can be used in various applications other than the respiratory assistance device. Moreover, the respiratory assistance device according to the present invention can be utilized in order to assist the breathing of various creatures.