Abstract:
An emitter ( 120 ) includes a flow path from a water intake path ( 221 ), which is for taking in irrigation liquid within a tube, to a recessed part ( 251 ). This flow path includes a recessed surface part ( 242 ) closed, without contact, by a film ( 300 ). A channel ( 243 ) that forms a reduced pressure flow path included in the above flow path is formed on the surface of the recessed surface part ( 242 ). If the film ( 300 ) is pressed by the pressure of the irrigation liquid in the tube ( 110 ) and adheres to the recessed surface part ( 242 ), the flow rate of the irrigation liquid inside the emitter ( 120 ) is controlled to an amount that can pass through the channel ( 243 ).

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to an emitter and a trickle irrigation tube including the emitter. 
       BACKGROUND ART 
       [0002]    A trickle irrigation method is known as a method for culturing plants. In the trickle irrigation method, for example, a trickle irrigation tube is disposed on the soil in which plants are planted, and irrigation liquid such as water and liquid fertilizer is slowly supplied from the trickle irrigation tube to the soil. The trickle irrigation method can minimize the consumption amount of the irrigation liquid, and has been increasingly attracting attention in recent years. 
         [0003]    The trickle irrigation tube typically has a tube and an emitter (also called “dripper”). The emitter typically supplies the soil with the irrigation liquid in the tube at a predetermined rate at which the irrigation liquid is dropped to the soil. Emitters which are pierced into the tube from the outside, and emitters joined to the inner wall surface of the tube are known. 
         [0004]    For example, the latter emitter has a channel including a pressure reduction channel for allowing the irrigation liquid having entered the emitter from the internal space of the tube toward the through hole of the tube while reducing the pressure of the liquid, and a diaphragm part configured to change the volume of a portion of the channel where the irrigation liquid having reduced pressure flows in accordance with the pressure of the liquid in the tube. The emitter is composed of a member which is joined to the inner wall surface of the tube, a member which is disposed on the member joined to the inner wall surface, and a diaphragm part which is disposed between the two members. The diaphragm part is composed of an elastic film such as a silicone rubber film (see, for example, PTL 1). 
         [0005]    The emitter can suppress variation of the discharge rate of the irrigation liquid regardless of change of the pressure of the irrigation liquid in the tube. Therefore, the emitter is advantageous from the viewpoint of uniformly growing multiple plants. 
       CITATION LIST 
     Patent Literature 
       [0006]    PTL 1 
         [0007]    Japanese Patent Application Laid-Open No. 2010-46094 
       SUMMARY OF INVENTION 
     Technical Problem 
       [0008]    The emitter is formed by assembling three components. In view of this, the emitter may cause assembling error. In particular, the assembling error of the diaphragm part may cause variation of the operation of the diaphragm part, and variation of the discharge rate of the irrigation liquid. 
         [0009]    In addition, the emitter is typically a molded article of an inexpensive resin such as polyethylene and polypropylene, and the diaphragm part is composed of a more expensive elastic material such as a silicone rubber film. The use of components of different materials has a room for improvement in material cost reduction. 
         [0010]    Generally, in a trickle irrigation tube, hundreds of emitters are disposed in one tube in some cases. In a long trickle irrigation tube, the supply pressure of irrigation liquid to the tube is required to be increased, and consequently the discharge rate of the irrigation liquid of the emitter may not be stable. In view of this, control of the discharge rate of the irrigation liquid of the emitter in accordance with the pressure of the irrigation liquid in the tube is desired. 
         [0011]    Furthermore, from the viewpoint of reducing the material cost and the manufacturing cost of the emitter, an emitter which can be manufactured with a single inexpensive material and fewer number of components is desired. 
         [0012]    An object of the present invention is to provide an emitter which can stabilize the discharge rate of the irrigation liquid and can further reduce the manufacturing cost. In addition, another object of the present invention is to provide a trickle irrigation tube having the emitter. 
       Solution to Problem 
       [0013]    The present invention provides an emitter for quantitatively discharging irrigation liquid in a tube from a discharge port communicating between inside and outside of the tube, the emitter being configured to be joined to an inner wall surface of the tube at a position corresponding to the discharge port, the tube being configured to distribute the irrigation liquid, the emitter including: an intake part for receiving the irrigation liquid in the tube; a first channel for allowing the irrigation liquid received from the intake part to flow therethrough; a flow rate control part for controlling a flow rate of the irrigation liquid supplied from the first channel in accordance with a pressure of the irrigation liquid in the tube; and a discharge part to face the discharge port, the discharge part being configured to be supplied with the irrigation liquid whose flow rate is controlled by the flow rate control part; the flow rate control part including: a recessed surface part formed at a portion of a surface of the emitter where the surface of the emitter is not joined to the tube, a groove connecting the first channel and the discharge part and formed on a surface of the recessed surface part, and a film having flexibility and configured to seal the recessed surface part to block communication between inside of the tube and the recessed surface part. The intake part or the first channel reduces a pressure of the irrigation liquid, and, when the pressure of the irrigation liquid in the tube is equal to or higher than a predetermined value, the film makes close contact with the recessed surface part, and the groove and the film form a second channel for allowing the irrigation liquid to flow therethrough. 
         [0014]    In addition, the present invention provides a trickle irrigation tube including a tube; and at least one emitter, the emitter being the above-mentioned emitter disposed on the tube. 
       Advantageous Effects of Invention 
       [0015]    The emitter according to the present invention controls the discharge rate of the irrigation liquid in accordance with the pressure of the irrigation liquid in the trickle irrigation tube, and thus can stabilize the discharge rate of the irrigation liquid. In addition, since the emitter according to the present invention can be formed with one or two components by injection molding of a resin material, the manufacturing cost can be further reduced in comparison with conventional emitters composed of three parts. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0016]      FIG. 1  is a schematic sectional view of a trickle irrigation tube according to an embodiment of the present invention; 
           [0017]      FIG. 2A  illustrates a top surface, a front surface and a side surface of an emitter according to the embodiment, and  FIG. 2B  illustrates a bottom surface, a front surface and a side surface of the emitter; 
           [0018]      FIG. 3A  is a plan view of the emitter according to the embodiment,  FIG. 3B  is a back view of the emitter, and  FIG. 3C  is a side view of the emitter; 
           [0019]      FIG. 4A  is a sectional view of the emitter according to the embodiment taken along line A-A of  FIG. 3A , and  FIG. 4B  is a sectional view of the emitter taken along line B-B of  FIG. 3A ; 
           [0020]      FIG. 5A  is a bottom view of the emitter according to the embodiment, and  FIG. 5B  is a sectional view of the emitter taken along line A-A of  FIG. 5A ; 
           [0021]      FIG. 6A  illustrates a top surface, a front surface and a side surface of the emitter according to the embodiment in the state before a film is joined to an emitter main body, and  FIG. 6B  illustrates a bottom surface, a front surface and a side surface of the emitter; 
           [0022]      FIG. 7A  is a plan view of the emitter according to the embodiment in the state before a film is joined to the emitter main body,  FIG. 7B  is a rear view of the emitter, and  FIG. 7C  is a side view of the emitter; 
           [0023]      FIG. 8A  is a sectional view of the emitter according to the embodiment taken along line A-A of  FIG. 7A  in the state before the film is joined to emitter the main body, and  FIG. 8B  is a sectional view of the emitter taken along line B-B of  FIG. 7A ; 
           [0024]      FIG. 9A  is a bottom view of the emitter according to the embodiment in the state before the film is joined to an emitter main body, and  FIG. 9B  is a sectional view of the emitter taken along line A-A of  FIG. 9A ; and 
           [0025]      FIG. 10A  illustrates part A of  FIG. 4A  in an enlarged manner in the case where the pressure of the irrigation liquid in the tube is equal to or higher than a first pressure value and lower than a second pressure value,  FIG. 10B  illustrates part A of  FIG. 4A  in an enlarged manner in the case where the pressure of the irrigation liquid in the tube is equal to or higher than the second pressure value and lower than the third pressure value, and  FIG. 10C  illustrates part A of  FIG. 4A  in an enlarged manner in the case where the pressure of the irrigation liquid in the tube is equal to or higher than the third pressure value. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0026]    In the following, embodiments of the present invention will be described in detail with reference to the accompanying drawings. 
       Embodiment 1 
     Configuration 
       [0027]      FIG. 1  is a schematic sectional view of a trickle irrigation tube according to Embodiment  1  of the present invention. Trickle irrigation tube  100  is composed of tube  110  and emitter  120 . Tube  110  is made of, for example, polyethylene. Emitters  120  are disposed along the axis direction at a predetermined interval (for example, 200 to 500 mm) Each emitter  120  is joined on the inner wall surface of tube  110 . Emitter  120  disposed at a position where it covers discharge port  130  of tube  110 . Discharge port  130  is a hole extending through the pipe wall of tube  110 . Discharge port  130  has a hole diameter of, for example, 1.5 mm. It is to be noted that arrow F indicates the flow direction of the irrigation liquid in tube  110 . 
         [0028]      FIG. 2A  illustrates a top surface, a front surface and a side surface of emitter  120 , and  FIG. 2B  illustrates a bottom surface, a front surface and a side surface of emitter  120 . In addition,  FIG. 3A  is a plan view of emitter  120 ,  FIG. 3B  is a rear view of emitter  120 , and  FIG. 3C  is a side view of emitter  120 . In addition,  FIG. 4A  is a sectional view of emitter  120  taken along line A-A of  FIG. 3A ,  FIG. 4B  is a sectional view of emitter  120  taken along line B-B of  FIG. 3A ,  FIG. 5A  is a bottom view of emitter  120 , and  FIG. 5B  is a sectional view of emitter  120  taken along line A-A of  FIG. 5A . It is to be noted that the X direction is the axial direction of tube  110  or the longitudinal direction of emitter  120 , the Y direction is the short (width) direction of emitter  120 , and the Z direction is the height direction of emitter  120 . 
         [0029]    As illustrated in  FIG. 2A  and  FIG. 2B , emitter  120  has a cuboid-like external shape. For example, the length of emitter  120  is 25 mm in the X direction, 10 mm in the Y direction, and 3 mm in the Z direction. Emitter  120  includes emitter main body  200  to be joined to the inner wall surface of tube  110 , and film  300  which is formed integrally with emitter main body  200 . 
         [0030]      FIG. 6A  illustrates a top surface, a front surface and a side surface of emitter  120  in the state before film  300  is joined to emitter main body  200 , and  FIG. 6B  illustrates a bottom surface, a front surface and a side surface of emitter  120 . In addition,  FIG. 7A  is a plan view of emitter  120  in the state before film  300  is joined to emitter main body  200 ,  FIG. 7B  is a rear view of the emitter  120 , and  FIG. 7C  is a side view of the emitter  120 . Further,  FIG. 8A  is a sectional view of emitter  120  taken along line A-A of  FIG. 7A  in the state before film  300  is joined to emitter main body  200 ,  FIG. 8B  is a sectional view of emitter  120  taken along line B-B of  FIG. 7A ,  FIG. 9A  is a bottom view of the emitter  120 , and  FIG. 9B  is a sectional view of the emitter  120  taken along line A-A of  FIG. 9A . 
         [0031]    As illustrated in  FIG. 3B  and  FIG. 3C , emitter main body  200  includes first surface  201  and second surface  202 . First surface  201  is one surface which is joined to film  300  in the Z direction. Second surface  202  is the other surface which is joined to the inner wall surface of tube  110  in the Z direction. 
         [0032]    As illustrated in  FIG. 6A ,  FIG. 6B ,  FIG. 7A  and  FIG. 8A , emitter main body  200  includes intake channel  221  extending through emitter main body  200  in the Z direction, a plurality of grooves  222  formed from the side edge of first surface  201  to the opening of intake channel  221 , and flow rate regulation valve  223  disposed in intake channel  221 . 
         [0033]    The shape of the opening of intake channel  221  at first surface  201  is a circular shape as illustrated in  FIG. 7A . The opening diameter of intake channel  221  is, for example, 5 mm. As illustrated in  FIG. 9A , the shape of the opening of intake channel  221  at second surface  202  is a shape (bell shape) which is formed with a semicircle of the above-mentioned circle and a rectangular which has a width of the diameter of the opening and extends in the Y direction from the diameter of the semicircle. 
         [0034]    As illustrated in  FIG. 7A , groove  222  is a linear groove formed along the Y direction on first surface  201  of emitter main body  200 . A plurality of grooves  222  are formed on both sides of intake channel  221  in the Y direction. Groove  222  has a depth of, for example, 0.5 mm. 
         [0035]    As illustrated in  FIG. 7A  and  FIG. 9A , flow rate regulation valve  223  is composed of four flexible opening-closing parts and closes intake channel  221 . As illustrated in  FIG. 8A , the opening-closing parts have a form in which a substantially hemisphere thin dome protruding from first surface  201  side toward second surface  202  side is divided with slits in a cross shape. The opening-closing part has a thickness of, for example, 0.5 mm, and, normally, the slit has a width of, for example, 0 mm. 
         [0036]    As illustrated in  FIG. 6B ,  FIG. 9A  and  FIG. 9B , emitter main body  200  further includes, on second surface  202 , three grooves  231 ,  232  and  233  and hole  234  communicating between groove  233  and the first surface  201  side. 
         [0037]    As illustrated in  FIG. 5A  and  FIG. 9A , groove  231  is connected with intake channel  221 . Groove  231  is a linear groove formed on second surface  202  and extending along the X direction. 
         [0038]    As illustrated in  FIG. 5A  and  FIG. 9A , groove  232  is connected with groove  231 . Groove  232  is a groove formed on second surface  202  and extending along the X direction. In plan view, groove  232  has a zigzag shape. In the zigzag shape, protrusions having a substantially triangular shape protruding from the side surface of groove  232  are alternately disposed along the extending direction (the X direction) of groove  232 . The protrusions are disposed such that the tip of each protrusion does not exceed the central axis line of groove  232  in plan view. Groove  232  has a depth of, for example, 0.5 mm, and groove  232  has a width (W1 in  FIG. 5 ) of, for example, 0.5 mm. 
         [0039]    As illustrated in  FIG. 5A  and  FIG. 9A , groove  233  is connected with groove  232 . Groove  233  is a linear groove formed on second surface  202  and extending along the X direction. 
         [0040]    As illustrated in  FIG. 5A  and  FIG. 9A , hole  234  opens at an end portion of groove  233 . The opening shape of hole  234  is a rectangular shape. As illustrated in  FIG. 5B  and  FIG. 9B , hole  234  opens at first surface  201 . Grooves  231  and  233  and hole  234  have a width (the length in the Y direction) of, for example, 1 mm. 
         [0041]    As illustrated in  FIG. 6A ,  FIG. 7A  and  FIG. 8A , emitter main body  200  further includes groove  241  formed on first surface  201 , recessed surface part  242  formed on first surface  201 , groove  243  formed on the bottom of recessed surface part  242  and extending toward intake channel  221 , and hole  244  communicated with second surface  202  side from an end of groove  243  on intake channel  221  side. 
         [0042]    As illustrated in  FIG. 7A , groove  241  is a linear groove formed along the Y direction on first surface  201 . In plan view, groove  241  has a rectangular shape. Hole  234  opens at an end portion of groove  241 . 
         [0043]    As illustrated in  FIG. 7A , recessed surface part  242  is a recess formed on first surface  201 . In plan view, recessed surface part  242  has a racetrack-like shape composed of a rectangular part and substantially semicircular parts connected with both ends of the rectangular part in the X direction. 
         [0044]    As illustrated in  FIG. 8B , the rectangular part is formed as a recessed curved surface which is curved with respect to the Z direction and is parallel to the X direction. That is, the valley bottom line of the recessed curved surface extends along the X direction. The curve of the rectangular part in the cross-section along the Y direction of emitter main body  200  ( FIG. 8B ) includes a curve which is defined by film  300  in the above-mentioned cross-section under a pressure of the irrigation liquid in tube  110  which is equal to or higher than a predetermined value. 
         [0045]    As illustrated in  FIG. 8A , in X direction, the substantially semicircular part is formed of an inclined surface which is inclined from first surface  201  toward the recessed curved surface. As illustrated in  FIG. 7A , groove  241  overlaps one end of recessed surface part  242  as viewed from the Z direction, and is thus directly connected with recessed surface part  242 . 
         [0046]    As illustrated in  FIG. 8A , recessed surface part  242  has a depth smaller than that of groove  241 . For example, groove  241  has a depth from first surface  201  of 1 mm, whereas recessed surface part  242  has a depth (height from first surface  201  to the valley bottom line (bottom) of recessed surface part  242 ) of 0.3 mm. It is to be noted that the length of recessed surface part  242  (the distance between vertexes of the substantially semicircular parts in the X direction) is, for example, 15 mm, and the width of recessed surface part  242  (the length of the rectangular part in the Y direction) is, for example, 6 mm. 
         [0047]    As illustrated in  FIG. 7A , groove  243  is connected with groove  241 . As illustrated in  FIG. 7A  and  FIG. 8A , groove  243  is a groove formed on recessed surface part  242  and extending along the valley bottom line of recessed surface part  242  (X direction) from groove  241  toward intake channel  221 . In plan view, groove  243  has a zigzag shape as illustrated in  FIG. 7A . In the zigzag shape, protrusions having a substantially triangular shape protruding from the side surface of groove  243  are alternately disposed along the extending direction (the X direction) of groove  243 . The protrusions are disposed such that the tip of each protrusion does not exceed the central axis line of groove  243  in plan view. The depth of groove  243  (the depth from the valley bottom line of recessed surface part  242 ) is, for example, 0.5 mm, and the width of groove  243  (W2 in  FIG. 7A ) is, for example, 0.5 mm. 
         [0048]    As illustrated in  FIG. 7A , hole  244  opens at an end portion of groove  243  on intake channel  221  side. The opening of hole  244  has a circular shape. As illustrated in  FIG. 8A , hole  244  also opens at second surface  202  side. The diameter of hole  244  is, for example, 1 mm. 
         [0049]    As illustrated in  FIG. 5A  and  FIG. 9A , emitter main body  200  further includes recess  251  which is formed on second surface  202  and at which hole  244  opens. 
         [0050]    As illustrated in  FIG. 9A , recess  251  is a recess formed on second surface  202 . In plan view, recess  251  has a rectangular shape, and hole  244  opens at one corner of the rectangular. In plan view, the corner is sectioned by bank  252  having an arc-like shape and provided with a cutout part at a center portion thereof. The top edge of bank  252  is flush with second surface  202 . Recess  251  has a depth of, for example, 1 mm. 
         [0051]    As illustrated in  FIG. 7A  and  FIG. 9A , film  300  is disposed integrally with emitter main body  200  through hinge part  301 . In plan view, film  300  has a rectangular shape as with first surface  201 . For example, the thickness of film  300  may be determined by a computer simulation or an experiment using a trial product or the like on the basis of the deformation amount under a pressure described later, and may be, for example, 0.15 mm. 
         [0052]    As illustrated in  FIG. 7A ,  FIG. 8B  and  FIG. 9A , hinge part  301  is disposed at an edge on first surface  201  side of emitter main body  200  in the Y direction. For example, hinge part  301  is a part which has a thickness identical to that of film  300  and a width of 0.5 mm and is molded integrally with emitter main body  200  and film  300 . 
         [0053]    Each of emitter main body  200  and film  300  is molded with one material having flexibility such as polypropylene, for example. Examples of the material include resin and rubber, and examples of the resin include polyethylene and silicone. The flexibility of emitter  120  and film  300  can be adjusted with use of elastic resin materials, and for example, can be adjusted by the type of an elastic resin, the mixing ratio of an elastic resin material to a hard resin material, and the like. Emitter  120  can be manufactured as an integrally molded member by injection molding, for example. 
       Operation 
       [0054]    Film  300  turns about hinge part  301 , and is closely joined on first surface  201  of emitter main body  200 . For example, the joining is performed by welding of a resin material of emitter main body  200  or film  300 , by bonding using an adhesive agent, by pressure bonding of film  300  to emitter main body  200  or the like. 
         [0055]    As illustrated in  FIG. 2A  and  FIG. 4A , by joining film  300  to first surface  201 , intake channel  221  is covered with film  300 , and groove  222  forms a plurality of channels opening at the side surface of emitter  120  and connected with intake channel  221 . Thus, when film  300  is joined to first surface  201 , intake channel  221  and groove  222  constitute an intake part for receiving the irrigation liquid in tube  110 . 
         [0056]    In addition, by joining film  300  to first surface  201 , groove  241  and recessed surface part  242  are covered with film  300  as illustrated in  FIG. 4A  and  FIG. 4B . The gap between recessed surface part  242  and film  300  serves as a channel for irrigation liquid. Further, when film  300  bends under the pressure of the irrigation liquid described later and makes close contact with recessed surface part  242 , groove  243  and film  300  constitute a second channel which communicates between groove  241  and hole  244 . The second channel formed by groove  243  and film  300  serves as a pressure reduction channel for allowing the irrigation liquid to flow therethrough while reducing the pressure of the irrigation liquid. Thus, when film  300  is joined to first surface  201 , grooves  241  and  243  and recessed surface part  242  serve as a flow rate controlling part for controlling the flow rate of the irrigation liquid supplied from a first pressure reduction channel described later in accordance with the pressure of the irrigation liquid in tube  110 . 
         [0057]    Second surface  202  is joined to the inner wall surface of tube  110 . This joining is performed by welding of the resin material of emitter main body  200  or tube  110 , by bonding using adhesive agent, by pressure bonding of emitter main body  200  to tube  110 , or the like. 
         [0058]    When second surface  202  is joined to the inner wall surface of tube  110 , second surface  202  makes close contact with tube  110 , and intake channel  221  and grooves  231  to  233  are covered with tube  110 . When grooves  231  to  233  are covered with tube  110 , grooves  231  to  233  and hole  234  serve as a channel through which the irrigation liquid received from the intake part flows. Grooves  231  to  233  and hole  234  constitute a first channel through which the irrigation liquid received from the intake part flows when grooves  231  to  233  are covered with tube  110 . In addition, groove  232  constitutes a pressure reduction channel for allowing the irrigation liquid to flow therethrough while reducing the pressure of the irrigation liquid. 
         [0059]    In addition, when second surface  202  is joined to the inner wall surface of tube  110 , recess  251  is covered with tube  110 . Discharge port  130  is disposed at a position where tube  110  covers recess  251 . In this manner, when second surface  202  is joined to tube  110 , recess  251  serves as a discharge part to which the irrigation liquid having a flow rate controlled by the flow rate controlling part is supplied and which is configured to face discharge port  130 . 
         [0060]    Normally, emitter  120  is joined to the inner periphery wall of tube  110  before discharge port  130  is formed, and thereafter, discharge port  130  is formed at a position corresponding to a discharge part (recess  251 ) of tube  110 . Alternatively, emitter  120  may be joined to the inner wall surface of tube  110  such that emitter  120  is located at the position of preliminarily provided discharge port  130 . 
         [0061]    Next, discharge of irrigation liquid by emitter  120  is described.  FIG. 10A  illustrates part A of  FIG. 4A  in an enlarged manner in the case where the pressure of the irrigation liquid in tube  110  is equal to or higher than a first pressure value and lower than a second pressure value.  FIG. 10B  illustrates part A of  FIG. 4A  in an enlarged manner in the case where the pressure of the irrigation liquid in tube  110  is equal to or higher than the second pressure value and lower than the third pressure value.  FIG. 10C  illustrates part A of  FIG. 4A  in an enlarged manner in the case where the pressure of the irrigation liquid in tube  110  is equal to or higher than the third pressure value. 
         [0062]    Supply of irrigation liquid to trickle irrigation tube  100  is performed in a range where the pressure of the irrigation liquid do not exceed 0.1 MPa for the purpose of preventing damaging of tube  110  and emitter  120 . When irrigation liquid is supplied into tube  110 , the irrigation liquid reaches intake channel  221  through a gap between film  300  and groove  222 . The gap prevents intrusion of floating materials in the irrigation liquid which have a size greater than the opening of the gap into intake channel  221 . Thus, film  300  and groove  222  function as a filter. 
         [0063]    When the pressure of the irrigation liquid in tube  110  is equal to or higher than the first pressure value (for example, 0.005 MPa), flow rate regulation valve  223  is pushed to second surface  202  side, and the slit of flow rate regulation valve  223  is expanded. In this manner, the irrigation liquid reaching intake channel  221  is received by emitter main body  200  from intake channel  221 . Flow rate regulation valve  223  suppresses inflow of the irrigation liquid to emitter main body  200  when the pressure of the irrigation liquid is lower than the first pressure value. Thus, high-pressure supply of the irrigation liquid to tube  110  can be achieved, and therefore the configuration in which emitter  120  has flow rate regulation valve  223  is favorable for forming trickle irrigation tube  100  having a greater length, for example. 
         [0064]    The irrigation liquid received from intake channel  221  is supplied to groove  232  (pressure reduction channel) through groove  231 . The pressure of the irrigation liquid flowing through groove  232  is reduced as a result of pressure loss caused by the shape (zigzag shape) in plan view of groove  232 . In addition, floating materials in the irrigation liquid are entangled in the turbulent flow generated between the protrusions of groove  232  and are retained in groove  232 . In this manner, the floating materials are further removed from the irrigation liquid by pressure reduction channel  230 . 
         [0065]    In addition, since the tip of the protrusion is disposed in such a manner that the tip does not exceed the center line of groove  232  in plan view, a space which is not blocked by the protrusion is formed at the center of groove  232  while the width of the space is small, and thus the irrigation liquid easily flow through groove  232 . Accordingly, in addition to the effect of reducing pressure and the effect of removing the floating material, groove  232  is favorable for allowing irrigation liquid to flow with a greater flow rate. 
         [0066]    The irrigation liquid having passed through groove  232  in which the pressure is reduced and the floating material is removed is supplied to recessed surface part  242  through groove  233 , hole  234 , and groove  241 . As illustrated in  FIG. 10A , the gap between film  300  and recessed surface part  242  and groove  243  formed on the bottom of recessed surface part  242  are filled with the irrigation liquid and the irrigation liquid is supplied to hole  244 . 
         [0067]    The irrigation liquid having passed through hole  244  reaches recess  251  and is then discharged out of tube  110  through discharge port  130  which faces recess  251  and opens at recess  252 . 
         [0068]    While foreign matters such as soil may intrude into recess  251  from discharge port  130 , intrusion of such foreign matters into hole  244  is blocked by bank  252  disposed in recess  251 . 
         [0069]    As the pressure of the irrigation liquid in tube  110  increases, the flow rate of the irrigation liquid received by emitter main body  200  from intake channel  221  increases, and the discharge rate of the irrigation liquid from discharge port  130  increases. 
         [0070]    When the pressure of the irrigation liquid in tube  110  is equal to or higher than the second pressure value (for example, 0.02 MPa), film  300  pushed by the irrigation liquid in tube  110  is bent as illustrated in  FIG. 10B . Consequently, the distance between film  300  and recessed surface part  242  at the flow rate control part is reduced. For example, the distance between recessed surface part  242  and film  300  is changed to 0.15 mm. Consequently, the amount of the irrigation liquid which passes between film  300  and recessed surface part  242  is reduced, and the increase of the discharge rate of the irrigation liquid from discharge port  130  is suppressed. 
         [0071]    When the pressure of the irrigation liquid in tube  110  is equal to or higher than the third pressure value (for example, 0.05 MPa), film  300  is pushed and further bent by the irrigation liquid in tube  110  and brought into close contact with recessed surface part  242  as illustrated in  FIG. 10C . In this manner, film  300  functions as a valve element for sealing a hole which is a channel of the irrigation liquid under high pressure, and recessed surface part  242  functions as a valve seat of the valve element. Meanwhile, since groove  243  is not sealed even when film  300  makes close contact with recessed surface part  242 , the irrigation liquid supplied to groove  241  is supplied to hole  244  through groove  243 . Consequently, the amount of the irrigation liquid which passes through the flow rate controlling part is restricted to a flow rate which can pass through groove  243 , and the discharge rate of the irrigation liquid from discharge port  130  becomes substantially constant. In this manner, emitter  120  quantitatively discharges the irrigation liquid from tube  110  supplied with the irrigation liquid. 
         [0072]    In addition, the pressure of the irrigation liquid flowing through groove  243  is reduced by the pressure drop caused by the shape of groove  243  in a plan view (zigzag shape), and the floating materials in the irrigation liquid are entangled in the turbulent flow generated between the protrusions and are retained in groove  243 . Further, since the tips of the protrusions are disposed such that the tips do not exceed the center line of groove  243  in plan view, the irrigation liquid easily flows through groove  243 . Therefore, in addition to the effects of pressure reduction and removal of floating materials, groove  243  is favorable for achieving flow of irrigation liquid at a greater flow rate. 
       Effect 
       [0073]    As described above, emitter  120  includes the intake part for receiving the irrigation liquid in tube  110 , the first channel for allowing the irrigation liquid received from the intake part to flow therethrough, the flow rate control part for controlling the flow rate of the irrigation liquid supplied from the first channel in accordance with the pressure of the irrigation liquid in tube  110 , and the discharge part to which the irrigation liquid having a flow rate controlled by the flow rate control part supplied, the discharge part facing the discharge port. In addition, the flow rate control part includes: recessed surface part  242  which is formed on first surface  201  at a portion which is not joined to tube  110  on the surface of emitter  120 ; groove  243  formed on the surface of recessed surface part  242  and configured to connect the first channel and the discharge part; and film  300  having flexibility which covers recessed surface part  242  to block the communication between the inside of tube  110  and recessed surface part  242 . When emitter  120  is disposed in tube  110  by joining to the inner wall surface of tube  110  at a position corresponding to discharge port  130  of tube  110 , trickle irrigation tube  100  is constituted. The first channel reduces the pressure of the irrigation liquid, and film  300  starts to bend when the pressure of the irrigation liquid in tube  110  is equal to or higher than the above-mentioned second pressure value, and film  300  makes close contact with recessed surface part  242  when the pressure is equal to or higher than the third pressure value. At this time, the second channel for irrigation liquid is constituted by groove  243  and film  300 . Therefore, emitter  120  discharges the irrigation liquid such that the amount of the liquid is limited to the amount which passes through groove  243  even when the pressure of the irrigation liquid in tube  110  increases. In this manner, emitter  120  quantitatively discharges the irrigation liquid in tube  110  from discharge port  130  in accordance with the pressure of the irrigation liquid in tube  110 , and thus can stabilize the discharge rate of the irrigation liquid. 
         [0074]    Further, since the above-described components of emitter  120  are composed of a groove, a recess and a hole formed on first surface  201  or second surface  202  of emitter main body  200 , emitter main body  200  can be integrally produced by injection molding. Therefore, emitter  120  can further reduce manufacturing cost in comparison with conventional emitters composed of three parts. 
         [0075]    In addition, the configuration in which one or both of the first channel and the second channel is a pressure reduction channel for allowing the irrigation liquid to flow therethrough while reducing the pressure of the irrigation liquid is effective from the viewpoint of ensuring a desired discharge rate of the irrigation liquid, and in addition, from the viewpoint of reducing the clogging of emitter  120  due to floating materials in irrigation liquid. In particular, the configuration in which both of the first channel and the second channel is the pressure reduction channel is effective from the above-mentioned the standpoint. Further, the configuration in which both the first channel and the second channel are the pressure reduction channel can reduce the pressure of the irrigation liquid through two processes in emitter  120 , and therefore the configuration is further effective also from the viewpoint of achieving supply of irrigation liquid to tube  110  at a higher pressure. 
         [0076]    In addition, with the configuration in which the valley bottom line of recessed surface part  242  extends in the X direction and groove  243  is formed along the valley bottom line, a sufficient space is formed between recessed surface part  242  and film  300  when the pressure is low (when film  300  is not in close contact with recessed surface part  242 ), and therefore the configuration is further effective from the viewpoint of suppressing the pressure loss (pressure drop) of the irrigation liquid flowing through recessed surface part  242  and groove  243  when the pressure is low. In addition, since groove  243  has the above-described planar shape and irrigation liquid flows through groove  243  even when the pressure is low, the configuration in which groove  243  is formed along the valley bottom line is further effective from the viewpoint of achieving the effect of removing the floating materials even when the pressure is low. 
         [0077]    In addition, with the configuration in which emitter  120  is molded with one material having flexibility and film  300  is integrally molded as a part of emitter  120  such that film  300  can close recessed surface part  242 , both of emitter main body  200  and film  300  can be molded as one component by injection molding, and consequently manufacturing error of the joining position of film  300  can be prevented, which is further favorable from the standpoint of further reducing manufacturing cost, for example. 
         [0078]    In addition, with the configuration in which the intake part further includes flow rate regulation valve  223  configured to expand the irrigation liquid channel at the intake part in accordance with the increase of the pressure of the irrigation liquid in tube  110 , the irrigation liquid can be supplied to tube  110  with a higher pressure, which is further favorable from the viewpoint of forming trickle irrigation tube  100  having a greater length. 
       Modification 
       [0079]    In trickle irrigation tube  100 , the above-described configurations may be partially changed, or other configurations may be additionally adopted as long as the above-described effect is achieved. 
         [0080]    For example, tube  110  may be a seamless tube, or a tube composed of slender sheet(s) joined together along the longitudinal direction. 
         [0081]    In addition, discharge port  130  may be a gap formed at the above-mentioned joining part of the sheets so as to communicate between the inside and the outside of tube  110 , or a pipe sandwiched by the sheets at the joining part. Further, the shape of the discharge port in an axial direction thereof may not be a straight line shape. Examples of the tube having the discharge port include a tube in which a depression having a desired shape and serving as a channel is formed on the surface of the above-mentioned sheet, and a discharge port composed of the channel is formed at the joining part when the sheets are joined together. 
         [0082]    While intake channel  221  of emitter  120  is located at a position on the upstream side in the flow direction of the irrigation liquid in tube  110 , intake channel  221  may be located at a position on the downstream side. In addition, the orientations of a plurality of emitters  120  in one tube  110  may be identical to one another or different from one another. 
         [0083]    In addition, the resin material of emitter main body  200  and the resin material of film  300  may be identical to each other or different from each other. 
         [0084]    While emitter main body  200  is integrally molded by injection molding of resin, emitter main body  200  may be composed of two components of a first surface  201  side component and a second surface  202  side component. In this case, the components on the first surface  201  side are molded integrally with film  300 . With the configuration in which emitter main body  200  is composed of the two components, the first channel can be disposed inside emitter main body  200 , for example. Further, the two components may be integrally molded through a hinge part. 
         [0085]    In addition, the first channel may be composed of a groove on first surface  201  which is covered with film  300  in emitter main body  200 . 
         [0086]    In addition, second surface  202  may be a curved surface along the inner wall of tube  110  (for example, a surface defined by the arc whose arc radius is the internal diameter of tube  110  in the YZ plane). 
         [0087]    Further, since it suffices to appropriately dispose flow rate regulation valve  223  in accordance with the pressure of the irrigation liquid supplied to tube  110 , emitter  120  may not be provided with flow rate regulation valve  223 . 
         [0088]    In addition, from the viewpoint of ensuring a desired discharge rate and suppressing clogging of floating materials in irrigation liquid, emitter  120  is preferably has a configuration in which one or both of the first channel and the second channel includes the pressure reduction channel; however, both the first channel and the second channel may not be provided with the pressure reduction channel. To be more specific, while film  300  bends toward recessed surface part  242  and makes close contact with recessed surface part  242  with the pressure difference between the pressure of the irrigation liquid in tube  110  and the pressure of the irrigation liquid in recessed surface part  242 , the first channel and the second channel may not be the above-described pressure reduction channel (for example, may be simple linear channels) as long as a sufficient pressure difference is obtained. For example, in the case where the intake part has a structure for receiving liquid irrigation into emitter  120  while reducing the pressure of the irrigation liquid such as a plurality of pores communicating between tube  110  and a channel in emitter  120 , each of the first channel and the second channel may be composed of a channel other than the pressure reduction channel 
         [0089]    While recessed surface part  242  is a recessed curved surface slightly recessed from first surface  201  in the present embodiment, other suitable configurations may also be adopted as long as close contact with film  300  around groove  243  is achieved. For example, recessed surface part  242  may be a planar part located at a position nearer to second surface  202  side than first surface  201 . 
         [0090]    This application is entitled to and claims the benefit of Japanese Patent Application No. 2013-259219 filed on Dec. 16, 2013, the disclosure of which including the specification, drawings and abstract is incorporated herein by reference in its entirety. 
       INDUSTRIAL APPLICABILITY 
       [0091]    According to the present invention, an emitter which can discharge liquid with an appropriate speed by the pressure of the liquid to be discharged can be easily provided. Accordingly, popularization of the above-mentioned emitter in technical fields of trickle irrigations, endurance tests and the like where long-term discharging is required, and further development of the technical fields can be expected. 
       REFERENCE SIGNS LIST 
       [0092]      100  Trickle irrigation tube 
         [0093]      110  Tube 
         [0094]      120  Emitter 
         [0095]      130  Discharge port 
         [0096]      200  Emitter main body 
         [0097]      201  First surface 
         [0098]      202  Second surface 
         [0099]      221  Intake channel 
         [0100]      222 ,  231 ,  232 ,  233 ,  241 ,  243  Groove 
         [0101]      223  Flow rate regulation valve 
         [0102]      234 ,  244  Hole 
         [0103]      242  Recessed surface part 
         [0104]      251  Recess 
         [0105]      252  Bank 
         [0106]      300  Film 
         [0107]      301  Hinge part