Abstract:
To provide an oxygen concentrator that can reduce pressure loss when suctioning raw air and that can increase the amount of suctioned raw air by an amount of reduction in pressure loss, and moreover that can reduce noise without significantly changing a basic structure of a compressor. The oxygen concentrator includes: a compressor that has a plurality of suction ports suctioning raw air and that generates compressed air by compressing suctioned raw air; a conduit through which the compressed air is sent; a silencer that has a suction side end introducing the raw air and a discharge side end discharging the raw air, with the silencer being connected with the conduit; and a plurality of connection conduits directly connecting the discharge side end of the silencer and the respective suction ports of the compressor.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to an oxygen concentrator, and more particularly to a medical oxygen concentrator that is capable of supplying oxygen by compressing suctioned raw air and supplying the compressed air to an adsorbent. 
       BACKGROUND 
       [0002]    An oxygen concentrator is configured to acquire oxygen by using a pressure swing adsorbing method that generates oxygen by using zeolite selectively adsorbing nitrogen by transmitting oxygen in raw air, as an adsorbent. 
         [0003]    According to the oxygen concentrator using the method, introduced raw air is compressed by a compressor to generate compressed air and the compressed air is supplied to an adsorption column containing the adsorbent to separate oxygen by adsorbing nitrogen to the adsorbent. While the generated oxygen is stored in a tank, a predetermined flow of oxygen can be supplied from the tank through a pressure reducing valve or a flow setter to allow a patient to inhale oxygen by using a mechanism such as a nasal cannula, and the like. 
         [0004]    When the oxygen concentrator is installed at a place where an AC power supply (utility AC power supply) can be used, for example, a domiciliary oxygen therapy patient having a deteriorated lung function can safely inhale oxygen even while sleeping to have a good sleep. In particular, when the domiciliary oxygen therapy patient uses the oxygen concentrator even while sleeping, the oxygen concentrator preferably operates very quietly. For example, noise of the oxygen concentrator is preferably equal to or less than a noise level generated from an indoor air-conditioning facility. 
         [0005]    The oxygen concentrator used for a long-term oxygen inhalation therapy which is effective as a therapeutic method for a patient who suffers from respiratory disease, such as chronic bronchitis and the like, is generally not transportable and is not configured for the patient to take with them to go outside. 
         [0006]    When the patient is forced to go outside, for example, the patient inhales concentrated oxygen from an oxygen bomb while pushing a cart mounted with the oxygen bomb in which oxygen is charged in a predetermined receiving reservoir. Oxygen needs to be charged in the oxygen bomb by using an exclusive facility. Therefore, a transportable or movable oxygen concentrator is proposed, and the transportable or movable oxygen concentrator includes a compressor that introduces raw air to generate compressed air and decompressed air (see Patent Literature 1). 
       CITATION LIST  
     Patent Literature 
       [0007]    Patent Literature 1: Japanese Patent Application Laid-Open No. 2005-111016 
       SUMMARY OF INVENTION 
     Technical Problem 
       [0008]    However, in a conventional oxygen concentrator, as illustrated in  FIG. 6 , one conduit  401 , and a branch conduit  404  and a branch conduit  405  formed by branching the midstream of the conduit  401  are placed around a compressor  400 . The branch conduits  404  and  405  are connected to two intake ports  402  for raw air of the compressor  400 , respectively. A silencer  403  is set to reduce noise at midstream of the conduit  401 . The raw air is supplied to two intake ports  402  of the compressor  400  through the conduit  401 , the silencer  403 , and the branch conduits  404  and  405  of the conduit  401 . 
         [0009]    However, when the raw air is transported from the conduit  401  to the branch conduits  404  and  405  in order to increase the amount of suctioned raw air, pressure loss is increased, and as a result, the actual amount of suctioned raw air is decreased. 
         [0010]    Accordingly, an object of the present invention is to provide an oxygen concentrator that can reduce pressure loss when suctioning raw air and increase an amount of suctioned raw air by an amount of reduction in the pressure loss without significantly changing a basic structure of a compressor. 
       Solution to Problem 
       [0011]    An oxygen concentrator according to the present invention includes: a compressor that has a plurality of suction ports suctioning raw air and that generates compressed air by compressing the suctioned raw air; and a silencer installed at a stage preceding the compressor to reduce noise from the suction ports, in which the plurality of suction ports of the compressor are individually connected with the silencer. 
         [0012]    According to the configuration, by directly connecting the plurality of raw air suction ports of the compressor to the silencer by using respective connection conduits, the amount of sent raw air per one connection conduit can be reduced and the raw air can be introduced into the compressor without loss by reducing pressure loss. 
         [0013]    In the oxygen concentrator of the present invention, the compressor may include a first pump unit and a second pump unit that respectively generate the compressed air by compressing the raw air by reciprocatively moving a piston in a sleeve, and the suction ports may be formed in the first pump and the second pump unit, respectively. 
         [0014]    According to the configuration, since a raw air suction port of the first pump unit and the raw air suction port of the second pump can be directly connected by using the respective connection conduits, the influence of the pressure loss can be reduced by reducing the amount of sent raw air per one connection conduit. 
         [0015]    In the oxygen concentrator of the present invention, the silencer may have a filter removing dust in the compressed air. 
         [0016]    According to the configuration, after the filter removes the dust in the compressed air, the compressed air can be sent to the plurality of connection conduits and the influence of the pressure loss can be reduced by reducing the amount of sent raw air per one connection conduit. 
       Advantageous Effects of Invention 
       [0017]    According to the present invention, it is possible to provide an oxygen concentrator that can reduce pressure loss when suctioning raw air and increase an amount of suctioned raw air by an amount of reduction in the pressure loss without significantly changing a basic structure of a compressor. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]      FIG. 1  is a perspective view viewed from the front side, which illustrates an exterior of an embodiment of an oxygen concentrator with a compressor of the present invention. 
           [0019]      FIG. 2  is a bottom view of the exterior of the oxygen concentrator of  FIG. 1 . 
           [0020]      FIG. 3  is a perspective view diagonally viewed from the rear side, which illustrates an internal structure example of the oxygen concentrator illustrated in  FIGS. 1 and 2 . 
           [0021]      FIG. 4  is a diagram illustrating a compressor, a first connection conduit and a second connection conduit connected to the compressor, and a noise buffer also serving as an intake filter. 
           [0022]      FIG. 5  is a diagram illustrating a system configuration example of the oxygen concentrator. 
           [0023]      FIG. 6  is a diagram illustrating connection of a compressor and conduits in the related art. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0024]    Hereinafter, an exemplary embodiment of the present invention will be described in detail with reference to the accompanying drawings. 
         [0025]      FIG. 1  is a front perspective view illustrating an exterior of an embodiment of an oxygen concentrator with a compressor of the present invention.  FIG. 2  is a bottom view of the exterior of the oxygen concentrator of  FIG. 1 . 
         [0026]    The oxygen concentrator  1  illustrated in  FIGS. 1 and 2  is preferably a portable (also called transportable or movable) oxygen concentrator. The oxygen concentrator  1  illustrated in  FIG. 1  uses for example, compressed air pressure swing adsorption (PSA) by compressed air as an oxygen generation principle. 
         [0027]    The oxygen concentrator  1  illustrated in  FIGS. 1 and 2 , which is an oxygen concentrator having an oxygen flow of maximum 5 L class as one example, has a height of approximately 630 mm, a width of approximately 350 mm, an inner length of approximately 300 mm, and a weight of 21 to 23 kg, and a setting unit of the oxygen flow is set to be in the range of for example, 0.25 to 5 L. The oxygen concentrator  1  includes a substantially rectangular parallelepiped main case  2 , a display unit  128  capable of setting a flow, a humidifier G, a cannular rack  2 K, and casters  2 T positioned at four edges. 
         [0028]    The main case  2  includes a front panel  2 F, left and right side panels  2 S, and a rear panel  2 R, a top  2 D, and a bottom  2 B. In an inner surface of the main case  2 , as a soundproof material, a non-woven fabric, which consists of a polyolefin based fiber (preferably, a polypropylene fiber) having a fiber diameter in the range of 1 to 4 μm and a polyolefin based fiber (preferably, a polypropylene fiber) having a fiber diameter in the range of 20 to 30 μm, may be used. By using the non-woven fabric, a light weight and a soundproof effect are achieved. As illustrated in  FIG. 1 , the display unit  128 , an oxygen outlet  100 , a power switch  101 , and an oxygen flow setting button  102  are placed on the top  2 D. A placement section  2 G of the humidifier G is installed in an upper part of the front panel  2 F. The casters  2 T are placed at four edges of the bottom  2 B and the oxygen concentrator  1  is movable by using the casters  2 . 
         [0029]    Referring to  FIG. 2 , in the rear panel  2 R, an air introduction port  5  for introducing outdoor air into the main case  2  is formed at a central position of an upper part of the rear panel  2 R and an exhaust port  6  for discharging warmed air in the main case  2  to the outside is formed at a lower right part of the rear panel  2 R. An air introduction port filter  7  is removably mounted on an inner surface of the air introduction port  5 . In addition, the left and right side panels  2 B have handles  8  and the bottom  2 B has a retractable power cord  9 . 
         [0030]      FIG. 3  is a perspective view illustrating an internal structure example of the oxygen concentrator  1  illustrated in  FIGS. 1 and 2 , which is diagonally viewed from the rear side.  FIG. 4  is a diagram illustrating a horizontally-opposed compressor  10 , a first connection conduit  40  and a second connection conduit  41  connected to the compressor  10 , and a noise buffer  38  also serving as an intake filter. The first connection conduit  40  and the second connection conduit  41  are made of a thermoplastic resin, for example, polyurethane for easy handling at the time of installation and have an inner diameter in the range of 4 to 6 mm, an outer diameter in the range of 7 to 9 mm, and a wall thickness in the range of 1.3 to 2.0 mm, and preferably, have an inner diameter of 5 mm, an outer diameter of 8 mm, and a wall thickness of 1.5 mm. When the outer diameter is larger than 9 mm, a warpage radius is increased while handling, when the inner diameter is smaller than 4 mm, pressure loss is increased, and when the wall thickness is smaller than 1.3 mm, bending (kink) becomes easy while handling. As illustrated in  FIG. 3 , the compressor  10  is set on the bottom  2 B and the compressor  10  is placed in a rectangular parallelepiped compressor case  4  for sound proofing. In an inner surface of the compressor case  4 , as the soundproof material, a non-woven fabric, which consists of a polyolefin based fiber (preferably, a polypropylene fiber) having a fiber diameter in the range of 1 to 4 μm and a polyolefin based fiber (preferably, a polypropylene fiber) having a fiber diameter in the range of 20 to 30 μm, maybe used. By using the non-woven fabric, a light weight and a soundproof effect are achieved. On a bottom surface of the compressor case  4 , a first adsorption column body  31  and a second adsorption column body  32  are fixed while standing at an interval in an X direction and in parallel in a Z direction (vertical direction). 
         [0031]    As illustrated in  FIG. 3 , a sleeve  12  of the compressor  10  is connected to a conduit  15  and a cooling radiator  13  and 3-way switching valves  14 B and  14 C are connected to the midstream of the conduit  15 . A first fan  34  is mounted inside the first adsorption column body  31  and a second fan  36  is mounted inside the second adsorption column body  32 . 
         [0032]    As illustrated in  FIG. 3 , as the first fan  34  and the second fan  36  that have the same shape, for example, a sirocco fan is used and the first and second fans  34  and  36  are positioned to face each other, but the first and second fans  34  and  36  are fixed such that the first and second fans  34  and  36  are mounted in vertically opposite directions to each other and face each other. 
         [0033]    As illustrated in  FIG. 3 , the cooling radiator  13  is placed below the first fan  34  and the second fan  36 , between the first adsorption column body  31  and the second adsorption column body  32 . A power control circuit  39  is placed on the bottom  2 B. 
         [0034]      FIG. 4  is a diagram illustrating a structure example of the compressor  10  and the compressor  10  includes a first pump unit  51  and a second pump unit  52 . The first pump unit  51  includes a cylindrical sleeve  11 , a piston  11 P placed in the sleeve  11 , a head cover  11 H, a con rod  11 C, and a case section  11 F. Similarly, the second pump unit  52  includes a cylindrical sleeve  12 , a piston  12 P placed in the sleeve  12 , a head cover  12 H, a con rod  12 C, and a case section  12 F. 
         [0035]    As illustrated in  FIG. 4 , the sleeves  11  and  12  are also called piston cylinders. A driving motor  53 , which is for example, asynchronous motor, has an output shaft  54 . Con rods  11 C and  12 C are rotatably supported on both ends of the output shaft  54 . 
         [0036]    As illustrated in  FIG. 4 , the noise buffer (silencer)  38  also serving as the intake filter is placed among the conduit  37 , and the first connection conduit  40  and the second connection conduit  41 . The first connection conduit  40  and the second connection conduit  41  are made of a thermoplastic resin, for example, polyurethane for easy handling at the time of installation and have an inner diameter in the range of 4 to 6 mm, an outer diameter in the range of 7 to 9 mm, and a wall thickness in the range of 1.3 to 2.0 mm, and preferably, have an inner diameter of 5 mm, an outer diameter of 8 mm, and a wall thickness of 1.5 mm. When the outer diameter is larger than 9 mm, the warpage radius is increased while handling, when the inner diameter is smaller than 4 mm, the pressure loss is increased, and when the wall thickness is smaller than 1.3 mm, the bending (kink) becomes easy while handling. 
         [0037]    An end  37 B of the conduit  37  is connected to a suction side end  38 A of the noise buffer  38  also serving as the intake filter, and a first end  40 A of the first connection conduit  40  and a first end  41 A of the second connection conduit  41  are connected to a discharge side end  38 B of the noise buffer  38  also serving as the intake filter. A second end  40 B of the first connection conduit  40  is connected to a suction port  11 P of the case section  11 F and a second end  41 B of the second connection conduit  41  is connected to a suction port  12 P of the case section  12 F. 
         [0038]    An introduction path of the raw air between the noise buffer  38  also serving as the intake filter and the compressor  10  is divided into a plurality of paths, and the first connection conduit  40  and the second connection conduit  41  are connected in parallel between the noise buffer  38  also serving as the intake filter and the compressor  10 . In other words, the first connection conduit  40  and the second connection conduit  41  directly connect the suction ports  11 P and  12 P of the noise buffer  38  also serving as the intake filter and the compressor  10 . 
         [0039]    As a result, as the raw air introduced from the conduit  37  into the noise buffer  38  also serving as the intake filter passes through the noise buffer  38  also serving as the intake filter, dust is removed by the intake filter, and after noise is reduced, the raw air flows dividedly into the first connection conduit  40  and the second connection conduit  41  and may be introduced into the case section  11 F through the suction port  11 P of the case section  11 F and further, may be introduced into the case section  12 F through the suction port  12 P of the case section  12 F. 
         [0040]    The head covers  11 H and  12 H are commonly connected to the conduit  15  and the generated compressed air is sent through the conduit  15 . A heat-dissipating radiator  13  is placed at midstream of the conduit  15 . 
         [0041]    Herein, as the connection conduits, two conduits, that is, the first connection conduit  40  and the second connection conduit  41 , are installed in the embodiment, but the connection conduits are installed as many as sleeves (cylinders) and when the number of the sleeves increases, individually connected connection conduits are also correspondingly increased as many. 
         [0042]    Herein, referring to  FIG. 5 , a system configuration example of the oxygen concentrator  1  as described above will be described. 
         [0043]      FIG. 5  is a diagram illustrating the system configuration example of the oxygen concentrator  1 . 
         [0044]    A double line illustrated in  FIG. 5  represents a conduit serving as a path for the raw air, oxygen gas, and nitrogen gas. A thin solid line represents a wire for power supplying or an electrical signal. The main case  2  of the oxygen concentrator  1  illustrated in  FIG. 5  is represented by a dashed line and the main case  2  is an airtight container that hermetically seals components placed therein. 
         [0045]    As illustrated in  FIG. 5 , the main case  2  includes the air introduction port  5  for introducing raw air as outdoor air, the air introduction port filter  7  and the exhaust port  6  for exhausting raw air. The air introduction port filter  7  for removing impurities such as dust, and the like in the air is replaceably placed at the air introduction port  5 . When the compressor  10  operates, the raw air is introduced into the compressor  10  through the internal conduit  37 , the noise buffer  38  also serving as the intake filter, and the first connection conduit  40  and the second connection conduit  41  connected to the noise buffer  38  also serving as the intake filter in parallel via the air introduction port filter  7 . 
         [0046]    As such, the raw air is introduced into the compressor  10  to become the compressed air, but heat is generated when the raw air is compressed. As a result, the compressor  10 , in particular, the sleeves  11  and  12  are cooled by blowing from the first fan  34  and the second fan  36  for cooling. The compressed air sent from the compressor  10  through the conduit  15  is cooled by the radiator  13 . 
         [0047]    By cooling the compressed air, the temperature of zeolite as an adsorbent of which a function deteriorates at high temperature may be prevented from being increased. As a result, zeolite may sufficiently serve as the adsorbent for generating oxygen by adsorption of nitrogen and oxygen may be concentrated up to approximately 90% or more. 
         [0048]    The first adsorption column body  31  and the second adsorption column body  32  as examples of adsorption members placed in line are placed in parallel vertically. The 3-way switching valves  14 B and  14 C are connected to the first adsorption column body  31  and the second adsorption column body  32 , respectively. One end of one 3-way switching valve  14 B is connected to the conduit  15 . One 3-way switching valve  14 B and the other 3-way switching valve  14 C are connected to each other and one end of the other 3-way switching valve  14 C is connected to a conduit  15 R. An end of the conduit  15 R reaches the exhaust port  6 . 
         [0049]    The 3-way switching valves  14 B and  14 C are connected to correspond to the first adsorption column body  31  and the second adsorption column body  32 , respectively. The compressed air generated from the compressor  10  are alternately supplied to the first adsorption column body  31  and the second adsorption column body  32  through the conduit  15 , and the 3-way switching valves  14 B and  14 C. 
         [0050]    Zeolite as a catalyst adsorbent is stored in each of the first adsorption column body  31  and the second adsorption column body  32 . The zeolite is X-type zeolite in which for example, a ratio of Si 2 O 3 /Al 2 O 3  is in the range of 2.0 to 3.0, and zeolite in which at least 88% of a tetrahedral unit of Al 2 O 3  is combined with lithium cation is used to increase an adsorption amount of nitrogen per unit weight. The zeolite has particularly, a granule measurement value which is less than 1 mm and at least 88% of the tetrahedral unit is preferably fused with lithium cation. By using zeolite, the amount of used raw air required to separate oxygen may be reduced as compared with a case of using other adsorbent. As a result, the compressor  10  for generating the compressed air may be further miniaturized and low noise of the compressor  10  may be achieved. 
         [0051]    As illustrated in  FIG. 5 , a uniform-pressure valve  107  constituted by a check valve, a diaphragm valve, and an opening/closing valve is connected to outlets of the first adsorption column body  31  and the second adsorption column body  32 . A joined conduit  60  is connected to a downstream side of the uniform-pressure valve  107  and a buffer  61  is connected to the conduit  60 . The buffer  61  is an oxygen storing container for storing oxygen having a concentration of approximately 90% or more which is separately generated from the first adsorption column body  31  and the second adsorption column body  32 . 
         [0052]    As illustrated in  FIG. 5 , a pressure adjuster  62  is connected to a downstream side of the buffer  61  and the pressure adjuster  62  is a regulator that automatically adjusts the pressure of oxygen at an outlet of the buffer  61  to be uniform. A zirconia or ultrasonic oxygen concentration sensor  64  is connected to a downstream side of the pressure adjuster  62  through a filter  63  and the oxygen concentration sensor  64  detects the concentration of oxygen intermittently (every 10 to 30 minutes) or continuously. 
         [0053]    As illustrated in  FIG. 5 , a proportional opening rate valve  65  is connected to the buffer  61 . The proportional opening rate valve  65  is opened/closed in link with setting button operation of the oxygen flow setting button  102  by a signal from a flow control unit  202  according to a command of a central control unit  200 . An oxygen flow sensor  66  is connected to the proportional opening rate valve  65 . The humidifier G and an oxygen flow sensor  67  are connected to the oxygen flow sensor  66 . The oxygen outlet  100  is connected to a stage subsequent to the oxygen flow sensor  67 . 
         [0054]    A coupler socket  71  of a nasal cannula  70  is removably connected to the oxygen outlet  100 . The coupler socket  71  is connected to the nasal cannula  70  through a tube  72 . A patient may inhale for example, oxygen having a flow corresponding to a maximum flow of 5 L/min. and concentrated at approximately 90% or more, through the nasal cannula  70 . 
         [0055]    Subsequently, a power system will be described with reference to  FIG. 5 . 
         [0056]    A connector  203  of an AC (utility AC) power supply illustrated in  FIG. 5  is electrically connected to the power control circuit  39  and the power control circuit  39  rectifies AC voltage of the utility AC power supply into predetermined DC voltage. A built-in battery  204  is built in the main case  2 . The built-in battery  204  is a secondary battery which is repeatedly rechargeable and the built-in battery  204  may be recharged by receiving power supplied from the power control circuit  39 . 
         [0057]    As a result, the central control unit  200  of  FIG. 1  controls the power control circuit  39 , such that the power control circuit  39  may be, for example, used while being automatically switched to any one supply state of a first power supply state in which the power control circuit  39  operates by receiving power supplied from an AC adapter  203  and a second power supply state in which the power control circuit  39  operates by receiving power supplied from the built-in battery  204 . As the built-in battery  204 , a lithium ion secondary battery and a lithium hydrogen ion secondary battery, which are low in memory effect while charging and are fully charged even while recharging, may be used, but a nickel cadmium battery or a nickel hydrogen battery in the related art may be used. 
         [0058]    The central control unit  200  of  FIG. 5  is electrically connected to a motor driver  210  and a fan motor driver  211 . The central control unit  200  stores a program to switch an operation mode to an optimal operation mode depending on the amount of separated oxygen. The motor driver  210  and the fan motor driver  211  control to automatically drive the compressor  10 , and the first fan  34  and the second fan  36  at a high speed when a large amount of oxygen is generated and to rotatably drive the compressor  10 , and the first fan  34  and the second fan  36  at a low speed when a small amount of oxygen is generated, according to the command of the central control unit  200 . 
         [0059]    A read only memory (ROM) storing a predetermined operation program is built in the central control unit  200  and a circuit constituted by an external storage device, a volatile memory, a temporary storage device, and a real-time clock is electrically connected to the central control unit  200 . The central control unit  200  is accessible by connecting with an external communication line, and the like through a communication connector  205 . 
         [0060]    By on/off-controlling the 3-way switching valves  14 B and  14 C and the uniform-pressure valve  107  illustrated in  FIG. 5 , a control circuit (not illustrated) that controls unnecessary gas in the first adsorption column body  31  and the second adsorption column body  32  to be desorbed, the pressure adjuster  62 , the flow control unit  202 , and the oxygen concentration sensor  64  are electrically connected to the central control unit  200 . The flow control unit  202  controls the proportional opening rate valve  65 , and oxygen flow values of the oxygen flow sensor  66  and the oxygen flow sensor  67  are sent to the central control unit  200 . The oxygen flow setting button  102 , the display unit  128 , and the power switch  101  are electrically connected to the central control unit  200  illustrated in  FIG. 5 . 
         [0061]    The oxygen flow setting button  102  may set the flow of oxygen whenever for example, operating oxygen concentrated at approximately 90% or more from 0.25 L (liter) to the maximum 5 L by 0.25 L per minute. As the display unit  128 , for example, a display device such as a liquid crystal monitor displaying 7 segments, and the like is used. For example, display items including the oxygen flow, an oxygen lamp, warning icons (tube bending, separation of the humidifier, decrease in oxygen concentration, stoppage of power supplying, a residual quantity of the battery, battery in operation, and a charging lamp), an accumulation time, and the like may be displayed in the display unit  128 . 
         [0062]    The compressor  10  illustrated in  FIG. 5  generates only the compressed air to send the compressed air to the first adsorption column body  31  and the second adsorption column body  32  by static pressure swing adsorption (PSA) and adsorbs nitrogen in the compressed air by the adsorbent in the first adsorption column body  31  and the second adsorption column body  32 , as already described. Although the driving motor  53  of the compressor  10  is the synchronous motor, the driving motor  53  may be other motors, for example, a single phase AC induction motor or a single phase 4-pole AC synchronous motor and is not particularly limited to a specific type. 
         [0063]    Subsequently, an operation example of the oxygen concentrator  1  will be described. 
         [0064]    The central control unit  200  illustrated in  FIG. 5  gives a command to the motor driver  210  to allow the motor driver  210  to start the driving motor  53  of the compressor  10 , thus consecutively rotating the output shaft  54  of the driving motor  53  illustrated in  FIG. 7 . As a result, a piston  11 P of a first head section  51  and a piston  12 P of a second head section  52  illustrated in  FIG. 7  move reciprocatively. 
         [0065]    When the compressor  10  operates, the raw air is introduced from the air introduction port  5  illustrated in  FIG. 5  and the impurities such as dust are removed by the filter  7 . Thereafter, the raw air is introduced into the sleeves  11  and  12  via the suction ports  11 P and  12 P of the compressor  10 , through the internal conduit  37 , the noise buffer  38  also serving as the intake filter, and the first connection conduit  40  and the second connection conduit  41  connected in parallel. As such, as the raw air introduced from the conduit  37  illustrated in  FIG. 4  into the noise buffer  38  also serving as the intake filter passes through the noise buffer  38  also serving as the intake filter, dust and the like is removed, and after noise is reduced, the raw air flows dividedly into the first connection conduit  40  and the second connection conduit  41  connected in parallel and may be introduced into the case section  11 F through the suction port  11 P of the case section  11 F and further, may be introduced into the case section  12 F through the suction port  12 P of the case section  12 F. When the piston  11 P and the piston  12 P of  FIG. 4  are positioned at top dead points, the raw air in the sleeve  11  and the sleeve  12  is compressed. On the contrary, when the piston  11 P and the piston  12 P are positioned at bottom dead points, the raw air is suctioned into the sleeve  11  and the sleeve  12 . 
         [0066]    The first connection conduit  40  and the second connection conduit  41  divide an introduction path of the raw air between the noise buffer  38  also serving as the intake filter and the compressor  10  into a plurality of systems to be parallel and directly connect the noise buffer  38  also serving as the intake filter and the suction ports  11 P and  12 P of the compressor  10  to each other. As a result, the amount of raw air which should be sent per one of the first connection conduit  40  and the second connection conduit  41  maybe reduced. In other words, although the diameters of the first conduit  40  and the second conduit  41  are set to be small, the pressure loss is not increased. 
         [0067]    The compressed air generated by the compressor  10  illustrated in  FIG. 5  may be supplied to the first adsorption column body  13  and the second adsorption column body  32  through the conduit  15 . 
         [0068]    Meanwhile, the central control unit  200  illustrated in  FIG. 5  gives a command to the motor driver  211  to rotate the first fan  34  and the second fan  36 . When the compressor  10  compresses the raw air to generate the compressed air, the sleeves  11  and  12  of the compressor  10  are cooled by blowing from the first fan  34  and the second fan  36 , respectively and the compressed air that passes through the conduit  15  is cooled by passing through the radiator  13 . The compressed air adsorbs nitrogen by passing through the adsorbent in the first adsorption column body  31  and the second adsorption column body  32  through the conduit  15  and the 3-way switching valves  14 B and  14 C, such that oxygen is separated and generated from the compressed air. The buffer  61  may store oxygen having a concentration of approximately 90% or more which is separated and generated. 
         [0069]    The oxygen concentration sensor  66  of  FIG. 5  detects the concentration of oxygen from the buffer  61 . The proportional opening rate valve  65  is opened/closed in link with the oxygen flow setting button  102 . Oxygen is supplied to the nasal cannula  70  through the oxygen outlet  100 . As a result, the patient may inhale oxygen concentrated at approximately 90% or more at the maximum flow of, for example, 5 L/min through the nasal cannula  70 . 
         [0070]    In a connection structure of branch conduits  404  and  405  of the compressor  400  in the related art, which is illustrated in  FIG. 6 , when the output shaft of the driving motor is rotated at 2,200 rpm, compressed air of 61 L may be generated and electric energy used at that time is 231 Wh. On the other hand, in the embodiment of the oxygen concentrator of the present invention described above, when the driving motor  53  of the compressor  10  is rotated at 2,100 rpm, the compressed air of 61 L may be generated similarly and the electric energy used at that time is 222 Wh. That is, in order to generate the compressed air in the same quantity, 61 L, the number of rotations in the embodiment of the present invention may be decreased as compared with the related art by 100 rpm (2,200 rpm-2,100 rpm) and power consumption may also be decreased by 9 Wh (231-222). Therefore, the number of used rotations of the compressor  10  is reduced and power consumption is reduced. In other words, in the embodiment of the present invention, when the same number of rotations is maintained, more compressed air may be generated than the related art. 
         [0071]    However, the present invention is not limited to the embodiment and various modifications and changes of the present invention can be made and various transformations can be made within the scope of the appended claims. 
         [0072]    The illustrated compressor  10  includes the first pump unit  51  and the second pump unit  52 , but is not limited thereto and may include one pump unit or three or more pump units. Fans that cool the compressor  10  may be placed such that the number of fans corresponds to the number of pumps. The driving motor of the illustrated compressor  10  is for example, the 5 L-class motor, but is not limited thereto and may adopt for example, a motor suitable for 3 L class and the like. The type of the compressor is not particularly limited and may adopt a predetermined type. 
       REFERENCE SIGNS LIST 
       [0073]      1 : Oxygen concentrator 
         [0074]      2 : Main case 
         [0075]      2 F: Front panel 
         [0076]      2 S: Side panel 
         [0077]      2 R: Rear panel 
         [0078]      2 D: Top 
         [0079]      2 B: Bottom 
         [0080]      5 : Air introduction port 
         [0081]      6 : Exhaust port 
         [0082]      10 : Compressor 
         [0083]      11 : One sleeve 
         [0084]      12 : The other sleeve 
         [0085]      11 P,  12 P: Piston 
         [0086]      13 : Radiator 
         [0087]      15 : conduit 
         [0088]      31 : First adsorption column body 
         [0089]      32 : Second adsorption column body 
         [0090]      34 : First fan 
         [0091]      36 : Second fan 
         [0092]      38 : Noise buffer (silencer) also serving as intake filter 
         [0093]      40 : First connection conduit 
         [0094]      42 : Second connection conduit 
         [0095]      51 : First pump unit 
         [0096]      52 : Second pump unit