Abstract:
Dripper comprises Substrate integrally formed of a resin material and that includes a channel for an irrigating liquid. The channel comprises Inflow control part for controlling flowing in of the irrigating liquid and/or Flow rate control part for controlling the flow rate of the irrigating liquid that has flowed in. Inflow control part opens the channel in association with an increase in the pressure of the liquid to flow therein, and Flow rate control part closes the channel in association with an increase in the pressure of the liquid that has flowed in Dripper. Dripper is able to stabilize the control of inflow and discharge of the irrigating liquid, regardless of whether the pressure of the irrigating liquid increases or decreases, and also is able to achieve a reduction in manufacturing costs and improvement in manufacturing efficiency.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a dripper for drip irrigation (hereinafter also referred to as an “dripper”) and a drip irrigation apparatus including the dripper, and particularly to a dripper and a drip irrigation apparatus including the dripper which are suitable for growing plants. 
       BACKGROUND ART 
       [0002]    Conventionally, drip irrigation systems have been employed to supply water or irrigation liquid such as liquid fertilizer to the plants to be grown on the soil in the agricultural land, plantation and the like. 
         [0003]    Such a drip irrigation system comprises for example a channel terminal and an elongated drip watering tube connected to the channel terminal, wherein the channel terminal comprises a filter, a fertigation apparatus (a chemigation apparatus if necessary), a back flow prevention apparatus, a main pipe, and the like connected in sequence on the downstream side of a pump that brings up water from a water source. The drip watering tube is laid on the soil on which plants may be grown. 
         [0004]    The drip watering tube has a plurality of ejection ports provided to an elongated tube main body at a predetermined interval between the adjacent ports along the longitudinal direction of the tube main body. The irrigation liquid in the tube main body is ejected at a predetermined ejection amount per unit time (or ejection speed) from the ejection ports. Thus, the irrigation liquid is slowly supplied to the soil outside of the drip watering tube (that is, drip irrigation is performed). 
         [0005]    The drip watering tube can save water and fertilizer. Further, the drip watering tube can supply water at a moderate supply speed, and oxygen for plant roots can be ensured in the soil. Accordingly, plants can be favorably managed for growing. 
         [0006]    In the above drip watering tube, a plurality of drippers, which correspond to the respective ejection ports, for controlling the amount of the irrigation liquid to be ejected from the respective ejection ports per unit time are provided. 
         [0007]    The dripper is configured, for example, such that water flowing in the tube main body flows into the dripper through an inlet of the dripper and flows through a pressure reduction channel, which is called labyrinth, in the dripper to reduce the pressure of the water, and is ejected from the ejection port communicated with the pressure reduction channel on the downstream side thereof. 
         [0008]    Further, there are known some conventional drippers provided with a so-called differential pressure control mechanism (pressure correction function). Such conventional drippers have, for example, a three-component structure in which an elastic film (for example, silicone rubber) such as a diaphragm is sandwiched by an inflow side member and an ejection side member, as disclosed in PTL 1. 
         [0009]    The dripper disclosed in PTL 1 controls the opening/closing of the entrance port of the dripper and the flow rate of water from the exit port of the dripper, by the movement of the diaphragm (film) in accordance with a water pressure outside of the dripper (in-pipe water pressure). 
         [0010]    Specifically, in the dripper disclosed in PTL 1, when the in-pipe water pressure outside of the dripper is increased to a certain level, the diaphragm that is originally so disposed as to shield the entrance is deflected by the in-pipe water pressure toward the outlet. Due to the deformation of the diaphragm, the entrance is opened. When the in-pipe water pressure is further increased, the amount of the deflection of the diaphragm toward the outlet is increased. In association with the deformation of the diaphragm, the sectional size of the channel at the outlet is reduced, and thus the ejection amount of water is regulated. 
         [0011]    As disclosed also in paragraph [0004] of PTL 1, the dripper disclosed in PTL 1 is designed such that the ejection speed from the dripper has substantially no relation with the fluctuation in pressure of the supplied liquid for irrigation to the dripper. 
         [0012]    Therefore, PTL 1 discloses that the disclosed dripper is favorable for limiting variation in the ejection amount of the irrigation liquid between the drippers disposed on the upstream side (high pressure side) and on the downstream side (low pressure side) in the tube main body, to thereby uniformize the growing of plants over the entire soil. 
       CITATION LIST 
     Patent Literature 
       [0000]    
       
         PTL 1 
         Japanese Patent Application Laid-Open No. 2010-46094 
       
     
       SUMMARY OF INVENTION 
     Technical Problem 
       [0015]    However, the dripper disclosed in PTL 1 has the following four problems. 
       (First Problem) 
       [0016]    The dripper disclosed in PTL 1 has a configuration of sandwiching the diaphragm (film) between other two members. Therefore, an increase in the size of the dripper (in particular, increase in the size in the height direction) is required. Accordingly, the area occupancy of the dripper in the tube main body with respect to the section of the channel becomes naturally larger. 
         [0017]    Thus, in the tube main body, the dripper on the upstream side serves as a large hindrance laid on the channel, and hinders the flow of the irrigation liquid that passes through the dripper on the upstream side to be supplied to the dripper on the downstream side. Therefore, the pressure drop in the tube main body is undesirably increased. 
         [0018]    Therefore, the dripper disclosed in PTL 1 may require a high pressure pump for long-distance watering utilizing a considerably long drip watering tube, and the ejection amount may also be unstable. 
       (Second Problem) 
       [0019]    In addition, the dripper disclosed in PTL 1 may have a problem of an error in the operations of the diaphragm that should control the opening/closing of the entrance port (flow rate of the irrigation liquid) when the three components are assembled together with low precision, causing the flow control of the irrigation liquid to be unstable. 
       (Third Problem) 
       [0020]    Further, the dripper disclosed in PTL 1 may have a problem of increased material costs when silicone rubber is used for the diaphragm. 
       (Fourth Problem) 
       [0021]    Furthermore, the dripper disclosed in PTL 1 requires that the above three components should be precisely assembled after the three components are separately manufactured, thus making it difficult to enhance manufacturing efficiency. 
         [0022]    The present invention has been achieved taking into consideration the above-mentioned problems. An object of the present invention is to provide a dripper and a drip irrigation apparatus including the dripper which can properly perform a long-distance irrigation even when the liquid pressure of irrigation liquid is low, can stabilize the inflow control of the irrigation liquid, and can achieve cost reduction and enhancement in manufacturing efficiency. 
       Solution to Problem 
       [0023]    To achieve the above-mentioned object, the present invention provides the following dripper and drip irrigation apparatus. 
         [0000]    [1] A dripper for controlling an amount of irrigation liquid ejected from an ejection port extending through a pipe wall of a flow pipe through which the irrigation liquid flows, the dripper configured to be disposed at a position corresponding to the ejection port on an inner peripheral surface of the flow pipe, the dripper including: a substrate including a resin material, to be joined to the inner peripheral surface of the flow pipe, and including a channel part for composing a channel in the dripper, wherein the channel part includes an inflow part that introduces the irrigation liquid in the flow pipe into the dripper, and satisfies one or both of the following items (A) and (B):
 
(A) the inflow part being an inflow control part that controls the inflow of the irrigation liquid based on a set value of a liquid pressure of the irrigation liquid in the flow pipe, the inflow control part having a plate-like body to be exposed to the irrigation liquid in the flow pipe and a first slit formed in the plate-like body, for introducing the irrigation liquid in the flow pipe thereinto, the first slit being formed so as to have an opening width of zero when the plate-like body is not exposed to the irrigation liquid having a liquid pressure equal to or more than the set value, and the plate-like body maintaining the opening width of the first slit at zero without deforming the first slit toward the inner peripheral surface side of the flow pipe so as to inhibit the inflow of the irrigation liquid through the first slit when the liquid pressure is less than the set value, and expanding the first slit such that the opening width of the first slit is more than zero by deforming the first slit toward the inner peripheral surface side of the flow pipe so as to allow the inflow of the irrigation liquid through the first slit when the liquid pressure is equal to or more than the set value; and (B) the channel part further including a flow rate control part formed at a position on a downstream side of the inflow part so as to face the inner peripheral surface of the flow pipe for controlling a flow rate of the irrigation liquid flowing from the inflow part to the ejection port, the flow rate control part having a plate-shaped valve element to be exposed to the introduced irrigation liquid and a second slit being formed in the valve element, for allowing the introduced irrigation liquid to flow toward the ejection port side, the second slit being formed so as to have a predetermined opening width when the valve element does not receive a liquid pressure equal to or more than a predetermined value, and the valve element being deformed toward the inner peripheral surface side from a side of the flow pipe opposite to the inner peripheral surface depending on the liquid pressure to decrease the opening width of the second slit with respect to the predetermined opening width as the liquid pressure is increased.
 
[2] The dripper according to [1], wherein the first slit is formed radially to divide the plate-like body into a plurality of segments.
 
[3] The dripper according to [2], wherein the plate-like body is formed so as to be protruded toward the inner peripheral surface side of the flow pipe.
 
[4] The dripper according to [3], wherein the plate-like body is formed such that a center portion of the plate-like body is protruded the most, and the first slit is formed radially around the center portion.
 
[5] The dripper according to [4], wherein the plate-like body is formed in a domed shape.
 
[6] The dripper according to [1], wherein the valve element is formed so as to be protruded toward a side of the flow pipe opposite to the inner peripheral surface, and the second slit is formed radially to divide the valve element into a plurality of valve segments.
 
[7] The dripper according to [6], wherein the valve element is formed such that a center portion of the valve element is protruded the most, and the second slit is formed radially around the center portion.
 
[8] The dripper according to [7], wherein the valve element is formed in a domed shape.
 
[9] The dripper according to any one of [1] to [8], wherein the flow rate control part is disposed at a position offset in a direction orthogonal to a thickness direction of the substrate with respect to the inflow control part.
 
[10] The dripper according to any one of [1] to [9], wherein the channel part further includes a guide channel part for composing, together with the inner peripheral surface of the flow pipe, a guide channel for guiding the introduced irrigation liquid toward the flow rate control part side, and a hollow part that is formed at a position on a downstream side of the guide channel part and on an upstream side of the flow rate control part and allows communication between the guide channel part and the second slit.
 
[11] The dripper according to any one of [1] to [10], wherein the channel part further includes a pressure reduction channel part for composing, together with the inner peripheral surface of the flow pipe, a pressure reduction channel that allows the irrigation liquid having passed through the flow rate control part or the inflow control part to flow toward the ejection port while reducing the pressure of the irrigation liquid.
 
[12] A drip irrigation apparatus including a flow pipe through which irrigation liquid flows, and the dripper according to any one of [1] to [11] for controlling an amount of the irrigation liquid ejected from an ejection port extending through a pipe wall of the flow pipe, the dripper being disposed at a position corresponding to the ejection port on an inner peripheral surface of the flow pipe.
 
       Advantageous Effects of Invention 
       [0024]    According to the present invention, even when the liquid pressure of irrigation liquid is low, long-distance watering can be properly performed, and the inflow control of the irrigation liquid can be stabilized. Further, cost reduction and enhancement in manufacturing efficiency can be achieved. 
         [0025]    With the invention according to [1], the channel part for composing the channel, of the dripper, including one or both of the inflow control part and the flow rate control part can be integrally formed with the substrate comprising a resin material. Therefore, the dripper can be precisely manufactured at lower cost and at fewer processes and in a smaller size (in particular, reduced thickness (lower height)). As a result, it is possible to achieve cost reduction for the dripper due to reduction in manufacturing cost and enhancement in manufacturing efficiency for the dripper without a high-precision assembly process being required. 
         [0026]    In a case where the above inflow part is the inflow control part, even when the liquid pressure (in other words, flow pressure) of the irrigation liquid is low, long-distance watering can be properly performed, and in addition the inflow control and thus the ejection control of the irrigation liquid can be stabilized. When the channel part includes the inflow part and the above flow rate control part, a dripper excellent in the control of the ejecting amount can be provided, thus enabling the ejecting amount of the irrigation liquid to be stabilized. When the channel part includes both the inflow control part and the flow rate control part, the flow rate of the irrigation liquid toward the ejection port can be limited by the flow rate control part, not only in the case of using the dripper under low liquid pressure but also in the case of using the dripper under high liquid pressure, and thus the ejection amount of the irrigation liquid can be properly controlled. 
         [0027]    With the invention according to [2], a plurality of segments are deformed toward the inner peripheral surface side of the flow pipe and radially relative to the center of the first slit (outwardly in the radial direction), and in accordance with this deformation the opening width of the first slit is increased. Therefore, it is possible to form the inflow control part in a simple shape suitable to expand the first slit depending on the liquid pressure of the irrigation liquid, thus enabling the inflow control to be further suitable and the costs to be further reduced. 
         [0028]    With the invention according to [3], the contact area between each segment and the irrigation liquid is increased, thereby increasing force in a direction to expand the first slit acting on each segment when each segment recieves the liquid pressure. Therefore, even when the liquid pressure of the irrigation liquid is low, each segment can be further surely deformed to allow the first slit to be properly expanded. 
         [0029]    With the invention according to [4], a suitable configuration can be selected for aligning the deforming movements of the valve segments by equalizing their size. Therefore, it becomes possible to further simplify the inflow control and further reduce the costs. 
         [0030]    With the invention according to [5], the plate-like body can be formed into a further simpler shape. Therefore, it becomes possible to further reduce the costs. 
         [0031]    With the invention according to [6], a plurality of valve segments are deformed toward the center of the radial slit while the height of the protrusion toward the side of the flow pipe opposite to the inner peripheral surface is reduced by the liquid pressure, thereby decreasing the opening width of the second slit. Therefore, the flow rate control part can be formed into a simple shape suitable to decrease the opening width of the second slit depending on the liquid pressure of the irrigation liquid, thus enabling the inflow control to be further suitable and the costs to be further reduced. 
         [0032]    With the invention according to [7], a suitable configuration can be selected for aligning the deforming movements of the valve segments by equalizing their size. Therefore, it becomes possible to further simplify the inflow control and further reduce the costs. 
         [0033]    With the invention according to [8], the valve element can be formed into a further simpler shape. Therefore, it becomes possible to further reduce the costs. 
         [0034]    With the invention according to [9], a further reduced thickness can be achieved. Therefore, it becomes possible to allow long-distance watering under low liquid pressure to be further suitable. 
         [0035]    With the invention according to [10], even when the flow rate control part is formed at a position offset in a direction orthogonal to the thickness direction from the inflow control part for the purpose of reduced thickness, a part of the channel from the inflow part (inflow control part) to the flow rate control part can be properly formed with a guide channel part and a hollow part formed in the substrate. 
         [0036]    With the invention according to [11], it becomes possible to allow the ejection speed to be further suitable by reducing the pressure of the irrigation liquid. 
         [0037]    With the invention according to [12], even when the liquid pressure of the irrigation liquid is low, long-distance watering can be properly performed. In addition, the flow control and thus the ejection control (ejection amount) of the irrigation liquid can be stabilized. Further, it is possible to provide a drip irrigation apparatus capable of achieving cost reduction due to the reduction in manufacturing cost and enhancement in manufacturing efficiency without a high-precision assembly process being required. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0038]      FIG. 1  is a transparent perspective birds-eye view of a dripper according to an embodiment of the present invention; 
           [0039]      FIG. 2  is a perspective birds-eye view of a substrate for the dripper; 
           [0040]      FIG. 3  is a plan view of the substrate; 
           [0041]      FIG. 4  is a bottom view of the substrate; 
           [0042]      FIG. 5  is a front view of the substrate; 
           [0043]      FIG. 6  is a right side view of the substrate; 
           [0044]      FIG. 7  is a sectional view of the substrate taken along line A-A in  FIG. 3 ; 
           [0045]      FIG. 8  is a sectional view of the substrate taken along line B-B in  FIG. 3 ; 
           [0046]      FIG. 9  is a sectional view of the substrate taken along line C-C in  FIG. 3 ; 
           [0047]      FIG. 10  is a sectional view schematically illustrating a drip irrigation apparatus according to an embodiment of the present invention; 
           [0048]      FIG. 11A  is an enlarged perspective birds-eye view illustrating an inflow control part in the present embodiment, and  FIG. 11B  is an enlarged perspective upward view illustrating the inflow control part; 
           [0049]      FIG. 12A  is a sectional view schematically illustrating the state in which the inflow control part is closed, and  FIG. 12B  is a sectional view schematically illustrating the state in which the inflow control part is opened; 
           [0050]      FIG. 13A  is an enlarged perspective birds-eye view illustrating a flow rate control part in the present embodiment, and  FIG. 13B  is an enlarged perspective upward view illustrating the flow rate control part; and 
           [0051]      FIG. 14A  is a sectional view schematically illustrating the flow rate control part in a full-open state,  FIG. 14B  is a sectional view schematically illustrating the flow rate control part in a semi-open state, and  FIG. 14C  is a sectional view schematically illustrating the flow rate control part in a full-close state. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0052]    In the following, a dripper according to the present invention and a drip irrigation apparatus including the dripper will be described with reference to  FIGS. 1 to 14 . 
         [0053]      FIG. 1  is a transparent perspective birds-eye view illustrating dripper  1  of the present embodiment.  FIG. 2  is a perspective bird&#39;s-eye view of substrate  11  in dripper  1 .  FIG. 3  is a plan view of substrate  11  in dripper  1 .  FIG. 4  is a bottom view of substrate  11  in dripper  1 .  FIG. 5  is a front view of substrate  11  in dripper  1 .  FIG. 6  is a right side view of substrate  11  in dripper  1 .  FIG. 7  is a sectional view of substrate  11  in dripper  1 , taken along line A-A in  FIG. 3 .  FIG. 8  is a sectional view of substrate  11  in dripper  1 , taken along line B-B in  FIG. 3 .  FIG. 9  is a sectional view of dripper  1  taken along line C-C in  FIG. 3 .  FIG. 10  is a schematic sectional view illustrating drip watering tube  2  as the drip irrigation apparatus in the present embodiment. 
         [0054]    As illustrated in  FIG. 10 , drip watering tube  2  includes elongated tube main body  3  serving as a flow pipe through which an irrigation liquid flows, and dripper  1  disposed in tube main body  3 . 
         [0055]    In addition, as illustrated in  FIG. 10 , dripper  1  is disposed on inner peripheral surface  31  of tube main body  3  at a position corresponding to ejection port  33  for ejecting the irrigation liquid, in such a manner as to cover ejection port  33 . Ejection port  33  opens through inner peripheral surface  31  and outer peripheral surface  32 , and extends through the pipe wall of tube main body  3 . Dripper  1  is configured to control the ejection amount per unit time of the irrigation liquid from the corresponding ejection port  33 . 
         [0056]    It is noted that, while  FIG. 10  illustrates one dripper  1  and one ejection port  33  for convenience, a plurality of drippers  1  and a plurality of ejection ports  33  are actually disposed along the longitudinal direction of tube main body  3  at a predetermined interval between the adjacent ports. 
         [0057]    In addition, in  FIG. 10 , the right and left sides of the channel in tube main body  3  correspond to the upstream side and the downstream side, respectively. 
         [0058]    Further, in the present embodiment, dripper  1  is integrally formed by resin molding using a metal mold. Examples of the resin material used for the resin molding include inexpensive materials such as polypropylene. The molding method may be injection molding. 
         [0059]    &lt;Outline of Substrate&gt; 
         [0060]    As illustrated in  FIGS. 1 to 10 , dripper (dripper main body)  1  has substrate  11  made of a resin material. A channel part for providing a channel for dripper  1  is formed in substrate  11 . The rough external shape of substrate  11  is composed of the respective planar surfaces of bottom end surface  11   a , top surface  11   b  at the side opposite to bottom end surface  11   a , left side surface  11   c , right side surface  11   d , front side surface  11   e , and rear side surface  11   f . The vertical and lateral positional relationship among the surfaces is as indicated by cross arrow in  FIG. 3 . As illustrated in  FIGS. 1 to 10 , top surface  11   b  and bottom end surface  11   a  are in parallel to each other, left side surface  11   c  and right side surface  11   d  are in parallel to each other, and front side surface  11   e  and rear side surface  11   f  are in parallel to each other. In addition, top surface  11   b  and bottom end surface  11   a  are perpendicular to left side surface  11   c , right side surface  11   d , front side surface  11   e , and rear side surface  11   f . Further, top surface  11   b  and bottom end surface  11   a  are elongated in the left-right direction. 
         [0061]    Substrate  11  is joined to inner peripheral surface  31  of tube main body  3  through bottom end surface  11   a . When tube main body  3  is formed by extrusion molding using a resin material (such as polyethylene) having a melting point equal to or lower than that of the material for dripper  1  (resin material), the above-mentioned joining may be performed by curing tube main body  3 , with ready-made dripper  1  being disposed on inner peripheral surface  31  of tube main body  3  to be cured. 
         [0062]    &lt;Specific Configuration of Inflow Control Part&gt; 
         [0063]    As illustrated in  FIGS. 3 ,  7  and  9 , dripper  1  has, at the right end portion of top surface  11   b , inflow control part  111 , which is a part of the channel part of substrate  11 , as an inflow part that introduces the irrigation liquid in tube main body  3  into (into the channel of) dripper  1 . Inflow control part  111  is configured to control the inflow of the irrigation liquid, at the lower limit value of the liquid pressure of the irrigation liquid to be introduced, i.e., the liquid pressure outside of the channel of dripper  1 , or the pressure of the liquid in tube main body  3  (hereinafter, also referred to as “external liquid pressure”). 
         [0064]    Specifically, as illustrated in  FIG. 11A , inflow control part  111  has plate-like body  1111  to receive the external liquid pressure, and first slit  1112  formed in plate-like body  1111 , for introducing the irrigation liquid in tube main body  3 . 
         [0065]    As illustrated in  FIG. 11A , plate-like body  1111  is formed into the shape of a thin dome. Plate-like body  1111  is disposed in a cavity formed of cylindrical first elevation surface  11   g  that generates an elevation difference from top surface  11   b , in such a manner that the center portion of plate-like body  1111  is protruded the most toward inner peripheral surface  31  side of tube main body  3  (downwardly). As illustrated in  FIG. 11A , first slit  1112  is formed radially (in  FIG. 11A , in a cross-shaped manner) and concentrically with plate-like body  1111 . Plate-like body  1111  is equally divided into a plurality of (in  FIG. 11A , four) segments  1111   a  by first slit  1112 . 
         [0066]    As illustrated in  FIG. 11A , first slit  1112  is formed such that the opening width W 1  is zero when plate-like body  1111  is not exposed to the irrigation liquid having an external liquid pressure equal to or more than the lower limit value in tube main body  3 . The lower limit value is a set lower limit value of the above external liquid pressure. The opening width W 1  is a width in a direction orthogonal to the longitudinal direction of the opening given by first slit  1112 . Inflow control part  111  may be configured by forming first slit  1112  as a cut line not having a substantial gap in plate-like body  1111 . 
         [0067]    Further, as illustrated in  FIG. 11A , plate-like body  1111  is configured such that the opening width W 1  of first slit  1112  is maintained at zero when the external liquid pressure is less than the set lower limit value. In inflow control part  111  in such closed state, the rigidity of plate-like body  1111  surpasses the external liquid pressure, and thus elastic deformation of plate-like body  1111  toward inner peripheral surface  31  side of tube main body  3  does not occur, to thereby maintain the closed inflow control part  111 . In this case, the inflow of the irrigation liquid through first slit  1112  is inhibited. It is noted that the lower limit value may be 0.005 MPa, for example. 
         [0068]    When the external liquid pressure is equal to or more than the above-mentioned lower limit value, plate-like body  1111  undergoes elastic deformation toward inner peripheral surface  31  side of tube main body  3  after yielding to the external liquid pressure. As illustrated in  FIG. 11B , that elastic deformation allows plate-like body  1111  to be expanded such that the opening width W 1  of first slit  1112  is more than zero. Thus, inflow control part  111  allows the inflow of the irrigation liquid through first slit  1112 . 
         [0069]      FIGS. 12A and 12B  illustrate the simulation results of the movement of inflow control part  111  made of polypropylene having a thickness of 0.2 mm, as a specific example of such movement of inflow control part  111 . 
         [0070]    When the external liquid pressure is less than 0.005 MPa as the lower limit value, as illustrated in  FIG. 12A , the opening width W 1  of first slit  1112  is maintained at zero, so that the inflow of the irrigation liquid into dripper  1  is inhibited. When the external liquid pressure is equal to or more than 0.005 MPa, as illustrated in  FIG. 12B , the opening width W 1  is more than zero, so that the inflow of the irrigation liquid into dripper  1  is allowed. 
         [0071]    &lt;Specific Configuration of Inflow Control Part&gt; 
         [0072]    As illustrated in  FIGS. 4 ,  9  and  10 , dripper  1  has flow rate control part  112  as a part of the channel part of substrate  11 . Flow rate control part  112  is disposed at left end portion of bottom end surface  11   a , being a position on the downstream side of inflow control part  111  (in other words, a position offset in a direction orthogonal to the thickness direction of substrate  11  with respect to inflow control part  111 ). Flow rate control part  112  is formed so as to face inner peripheral surface  31  of tube main body  3 . That is, flow rate control part  112  is disposed at a position, in substrate  11 , opposed to inner peripheral surface  31  of tube main body  3 . Flow rate control part  112  is configured to control the flow rate of the irrigation liquid (hereinafter, also referred to as “inflow liquid”) that flows into the channel in dripper  1  from inflow control part  111  and flows toward ejection port  33 . 
         [0073]    Specifically, as illustrated in  FIG. 13A , flow rate control part  112  has plate-shaped valve element  1121  to receive the pressure of the inflow liquid (hereinafter, also referred to as “internal liquid pressure”), and second slit  1122  formed in valve element  1121 , for allowing the inflow liquid to flow toward ejection port  33  side. 
         [0074]    As illustrated in  FIG. 13A , valve element  1121  is formed into the shape of a thin dome. Valve element  1121  is disposed in a cavity formed of cylindrical second elevation surface  11   h  (see  FIG. 9 ) that generates an elevation difference from bottom end surface  11   a , in such a manner that the center portion of valve element  1121  is protruded the most toward the side of tube main body  3  opposite to inner peripheral surface  31  (i.e., upwardly protruded). As illustrated in  FIG. 13A , second slit  1122  is formed radially (in  FIG. 13A , in a cross-shaped manner) around the center portion of valve element  1121 . Valve element  1121  is equally divided into a plurality of (in  FIG. 13A , four) valve segments  1121   a  by second slit  1122 . 
         [0075]    As illustrated in  FIG. 13A , second slit  1122  is formed such that the opening width W 2  is a predetermined opening width A more than zero when valve element  1121  does not receive an internal liquid pressure more than a set value. The opening width W 2  is a width in a direction orthogonal to the longitudinal direction of the opening given by second slit  1122 . 
         [0076]    When valve element  1121  receives an internal liquid pressure more than the set value of the inflow liquid having reached from the side of tube main body  3  opposite to inner peripheral surface  31 , valve element  1121  is deformed toward inner peripheral surface  31  side of tube main body  3  depending on the scale of the internal liquid pressure. As illustrated in  FIG. 13B , valve element  1121  allows the opening width W 2  of second slit  1122  to be decreased such that the amount of decrease relative to the predetermined opening width A becomes larger as the internal liquid pressure is increased. There may be a lower limit value of the internal liquid pressure at which the deformation of valve element  1121  is started. 
         [0077]      FIGS. 14A to 14C  illustrate the simulation results of the movement of flow rate control part  112  made of polypropylene. The thickness of valve element  1121  is 0.2 mm, and the opening width W 2 (A) of second slit  1122  when flow rate control part  112  does not receive the internal liquid pressure is 0.1 mm 
         [0078]    As illustrated in  FIG. 14A , for example when the internal liquid pressure is increased to 0.01 MPa, the deformation of valve element  1121  and the decrease in the opening width W 2  of second slit  1122  associated with that deformation are started. As illustrated in  FIG. 14B , for example when the internal liquid pressure is 0.05 MPa, the opening width W 2  of second slit  1122  is 0.05 mm, a half width of the original width A. As illustrated in  FIG. 14C , for example when the internal liquid pressure is 0.10 MPa, the opening width W 2  of second slit  1122  is 0 mm Thus, dripper  1  may be used under pressure lower than 0.10 MPa, for example. 
         [0079]    &lt;Specific Configuration of Guide Channel Part&gt; 
         [0080]    As illustrated in  FIGS. 4 to 9 , dripper  1  has, in bottom end surface  11   a , guide channel part  113  as a part of the channel part of substrate  11 . 
         [0081]    Guide channel part  113  is composed of a recess concaved from bottom end surface  11   a . Guide channel part  113  is formed in a predetermined area leftward from under inflow control part  111  such that the bottom surface of plate-like body  1111  is exposed downwardly. 
         [0082]    As illustrated in  FIG. 10 , guide channel part  113  composes guide channel  21  for guiding the inflow liquid toward flow rate control part  112  side together with inner peripheral surface  31  of tube main body  3 , which seals the bottom end opening of the above recess. 
         [0083]    &lt;Specific Configuration of Hollow Part&gt; 
         [0084]    As illustrated in  FIGS. 3 ,  4 ,  8  and  9 , dripper  1  has hollow part  114  as a part of the channel part of substrate  11 , at a position on the downstream side of guide channel part  113  and on the upstream side of flow rate control part  112 . Hollow part  114  is a cavity concaved from top surface  11   b . Hollow part  114  is formed such that the top surface of valve element  1121  is exposed upwardly and so as to be connected continuously to the terminal of guide channel part  113  (left end in  FIG. 4 ). 
         [0085]    As illustrated in  FIG. 9 , the upper opening of hollow part  114  is shielded from the outside of dripper  1  by plate-shaped first shielding wall part  23 . First shielding wall part  23  may be formed by bending a plate-shaped part having been molded integrally with substrate  11  using the same resin material as that of substrate  11  and being bendable so as to cover the opening of hollow part  114  afterward and then by heat-welding the plate-shaped part on the periphery of that opening (allowing the opening to be shielded). Alternatively, first shielding wall part  23  may be formed using another member (e.g., film sheet) having been manufactured in processes separated from those for substrate  11  and being joined so as to shield the upper opening of hollow part  114 . 
         [0086]    Hollow part  114  allows communication between guide channel part  113  and the channel in second slit  1122 . 
         [0087]    &lt;Specific Configuration of Pressure Reduction Channel Part&gt; 
         [0088]    As illustrated in  FIGS. 4 and 9 , dripper  1  has, on bottom end surface  11   a , pressure reduction channel part  115  as a part of the channel part of substrate  11 . 
         [0089]    As illustrated in  FIG. 4 , pressure reduction channel part  115  is a groove formed in bottom end surface  11   a . Pressure reduction channel part  115  is formed in an area from flow rate control part  112  side (left side) to ejection port  33  side (right side). The planar shape of pressure reduction channel part  115  is a serpentine shape (in other words, stream line shape or zig-zag shape) in the front-rear direction in  FIG. 4 . Pressure reduction channel part  115  is formed at a position on the front side relative to guide channel part  113  so as not to interfere with guide channel part  113 . 
         [0090]    As illustrated in  FIG. 10 , pressure reduction channel part  115  composes pressure reduction channel  22  together with inner peripheral surface  31 , which shields the bottom end opening of the groove, of tube main body  3 . Pressure reduction channel  22  allows the inflow liquid having passed through flow rate control part  112  to flow toward ejection port  33  while reducing the pressure of the inflow liquid. 
         [0091]    Pressure reduction channel  22  is allowed to communicate with the channel in second slit  1122  through a space surrounded by valve element  1121 , elevation surface  11   h  and inner peripheral surface  31  of tube main body  3 . 
         [0092]    &lt;Other Components&gt; 
         [0093]    As illustrated in  FIGS. 1 and 3 , in a predetermined area in the longitudinal direction on top surface  11   b , there is formed a recess having substantially the same width as the width of top surface  11   a . On the bottom of the recess, a plurality of plate-shaped convex parts  12  protruded upwardly and elongated in the front-rear direction are aligned at a predetermined interval between the adjacent parts in the longitudinal (left-right) direction of top surface  11   b . The length (length in the front-rear direction) of convex part  12  is shorter than the width of the recess, and there is a gap between each end of convex part  112  and the wall surface of the recess. A plurality of convex parts  12  function as a filter to prevent the inflow of relatively large foreign matter into the channel of dripper  1 . 
         [0094]    As illustrated in  FIGS. 1 to 3 , between convex part  12  in top surface  11   b  and inflow control part  111 , a plurality of groove parts  13  are aligned at a predetermined interval between the adjacent parts in the short-length (front-rear) direction of top surface  11   b . Groove part  13  is a strip of recess elongated in the left-right direction and recessed vertically downwardly. The right end surface of each of linear protrusions between a plurality of grooves  13  composes a part of first elevation surface  11   g , and the right end of each of a plurality of groove parts  13  is connected continuously to first elevation surface  11   g.    
         [0095]    Further, as illustrated in  FIGS. 1 and 9 , second shielding wall part  24  is formed at a position corresponding to groove part  13  on top surface  11   b  and inflow control part  111 . Second shielding wall part  24  shields both the upper opening of groove part  13  and the upper opening of first elevation surface  11   g . Between groove part  13  and second shielding wall part  24 , there is formed a channel for the irrigation liquid flowing toward inflow control part  111  from the recess. Second shielding wall part  24  may be formed in a method similar to that for first shielding wall part  23 . 
       Principal Operation and Effect of Present Embodiment 
       [0096]    According to the present embodiment, the irrigation liquid in tube main body  3  is deprived of relatively large foreign matter by convex part  12 , and then reaches inflow control part  111  through between groove part  13  and second shielding wall part  24 . 
         [0097]    When the external liquid pressure of the irrigation liquid having reached inflow control part  111  does not amount to the set lower limit value, the rigidity of plate-like body  1111  in inflow control part  111  surpasses the external liquid pressure. Accordingly, elastic deformation of plate-like body  1111  does not occur. Thus, the opening width W 1  in first slit  1112  is maintained at zero (i.e., equivalent to the state where the external liquid pressure has no influence), thereby inhibiting the inflow of the irrigation liquid. 
         [0098]    When the external liquid pressure of the irrigation liquid having reached inflow control part  111  amounts to the set lower limit value, the external liquid pressure surpasses the rigidity of plate-like body  1111 . Accordingly, plate-like body  1111  (each segment  1111   a ) undergoes elastic deformation toward inner peripheral surface  31  side of tube main body  3 . Thus, first slit  1112  is expanded such that the opening width W 1  is increased from zero to a value depending on the external liquid pressure, thereby allowing the inflow of the irrigation liquid. 
         [0099]    The inflow liquid having been flowed out of inflow control part  111  reaches flow rate control part  112  after going through guide channel  21  and hollow part  114  sequentially. 
         [0100]    Valve element  1121  of flow rate control part  112  undergoes elastic deformation toward inner peripheral surface  31  side of tube main body  3  depending on the internal liquid pressure of the inflow liquid having reached flow rate control part  112 . Due to the elastic deformation, the opening width W 2  of second slit  1122  is decreased relative to the opening width W 2  (=A) where the internal liquid pressure has no influence, such that the amount of decrease in the flow rate of the liquid passing through flow rate control part  112  becomes larger as the internal liquid pressure is increased. For example, when the internal liquid pressure of the inflow liquid is less than a first set value of the internal liquid pressure, the opening width W 2  is an initial value A; when the internal liquid pressure of the inflow liquid is equal to or more than that first set value, the opening width W 2  becomes smaller than the initial value A; and when the internal liquid pressure of the inflow liquid is further raised to be equal to or more than a second set value, the opening width W 2  is zero. It is noted that a suitable lower limit value may be set depending on the thickness of valve element  1121 , the width of slit  1122 , or the like, as a lower limit value of the internal liquid pressure at which valve element  1121  undergoes elastic deformation. 
         [0101]    Due to the decrease in the opening width W 2  associated with the elastic deformation of valve element  1121 , the flow rate of the inflow liquid passing through the channel in second slit  1122  (flow rate of that inflow liquid flowing toward ejection port  33  side all at once) is regulated. 
         [0102]    The inflow liquid, of which flow rate is regulated by flow rate control part  112 , undergoes pressure reduction due to a pressure loss caused by the shape of the channel of pressure reduction channel  22 , and then is ejected outside of drip watering tube  2  from ejection port  33 . 
         [0103]    It is noted that the liquid flowed out of pressure reduction channel  22  is guided by a baffle part of which planar shape is a circular arc (see  FIG. 4 ) so as to be diffused in a chamber in which ejection port  33  is formed. Further, since the above baffle part is disposed between the outlet of pressure reduction channel  22  and ejection port  33 , foreign matter having intruded into the above chamber from ejection port  33  are prevented from further intruding into pressure reduction channel  22 . 
         [0104]    Here, two drippers  1  disposed relatively on the upstream side and the downstream side will be discussed. 
         [0105]    In dripper  1  relatively on the upstream side, relatively high external liquid pressure causes the amount of the inflow liquid to be relatively large. At the same time, relatively higher internal liquid pressure also causes the flow rate limited by flow rate control part  112  to be relatively larger. Therefore, the amount of the inflow liquid to be ejected from ejection port  33  is not excessively large. 
         [0106]    In dripper  1  relatively on the downstream side, relatively low external liquid pressure causes the amount of the inflow liquid to be relatively small. At the same time, relatively lower internal liquid pressure also causes the flow rate limited by flow rate control part  112  to be relatively smaller. Therefore, the amount of the inflow liquid to be ejected from ejection port  33  is not excessively small. 
         [0107]    Accordingly, there is less variation in the amount of the inflow liquid to be ejected from ejection port  33  between ejection ports  33  on the upstream side and the downstream side (e.g., the variation may be limited to 5 to 10%). Thus, the amount of the inflow liquid to be ejected through individual ejection ports in drip watering tube  2  can be favorably controlled. The above-described effects can be surely achieved also in the case of performing long-distance watering using irrigation liquid with low liquid pressure, since dripper  1  is devised such that the pressure loss in tube main body  3  is alleviated, as described later. 
         [0108]    According to the present embodiment, the channel part, for composing the channel of dripper  1 , including inflow control part  111  is integrally formed into substrate  11  made of a resin material, and thus dripper  1  can be precisely manufactured at lower cost and at fewer processes and in a smaller size (in particular, reduced thickness). 
         [0109]    Alternatively, according to the present embodiment, the channel part for composing the channel including flow rate control part  112  is integrally formed into substrate  11  made of a resin material, thereby enabling such dripper  1  excellent in controlling the ejection amount of the irrigation liquid to be precisely manufactured at lower cost and at fewer processes and in a smaller size (in particular, reduced thickness). 
         [0110]    The smaller size (reduced thickness) of dripper  1  enables the area occupancy of dripper  1  with respect to a section of the channel in tube main body  3  to be reduced, and thus the pressure loss of the irrigation liquid in tube main body  3  can be limited. As a result, even when the liquid pressure (in other words, external liquid pressure) of the irrigation liquid to be supplied to drip watering tube  2  from the water source side is low, sufficient liquid pressure can be secured in an area up to the downstream side of tube main body  3 . Therefore, long-distance watering can be properly performed at a stable ejection amount. 
         [0111]    In addition, since inflow control part  111  is an integrally molded product with substrate  11 , a malfunction of inflow control part  111  caused by assembly error does not occur. Therefore, the inflow control and thus the ejection control of the irrigation liquid can be stabilized. 
         [0112]    In addition, since flow rate control part  112  is an integrally molded product with substrate  11 , a malfunction of flow rate control part  112  caused by assembly error does not occur. Therefore, the ejection amount of the inflow liquid can be further stabilized. 
         [0113]    Further, dripper  1  does not require an expensive material such as silicone rubber, and can be manufactured basically with a single inexpensive resin material. Therefore, the production cost can be reduced. In addition, the number of components and the number of manufacturing processes can also be surely reduced, compared to the dripper into which three components are assembled as disclosed in PTL 1. Thus, according to the present embodiment, cost reduction can be achieved. 
         [0114]    Furthermore, flow rate control part  112  is disposed at a position offset in a direction orthogonal to the thickness direction of substrate  11  with respect to inflow control part  111 . Therefore, it is further advantageous to make dripper  1  thinner. 
         [0115]    In addition, when each segment  1111   a  receives the external liquid pressure from above, plate-like body  1111  of inflow control part  111  deflects downwardly and outwardly utilizing the elasticity of a resin material, in such a manner that the tips of the respective segments  1111   a  are spaced apart from each other. Thus, segment  1111   a  is formed into a suitable shape to expand first slit  1112  upon receiving the external liquid pressure efficiently, and thus the inflow control can be performed more properly. 
         [0116]    In addition, when each valve segment  1121   a  receives the internal liquid pressure from above, valve element  1121  of flow rate control part  112  deflects downwardly and inwardly utilizing the elasticity of a resin material. As a result, the height of the upward protrusion of valve segment  1121   a  is decreased, and at the same time the tips of the respective valve elements  1121   a  come closer to each other. Thus, valve element  1121  is formed into a suitable shape to decrease the opening width W 2  of second slit  1122  upon receiving the internal liquid pressure efficiently, and thus the control of the flow rate toward ejection port  33  can be performed more properly. 
         [0117]    It is noted that the present invention is not limited to the above-described embodiments, and may be variously modified as long as the features of the present invention are not impaired. 
         [0118]    For example, plate-like body  1111  may have a shape other than the domed shape (e.g., pyramidal shape or flat shape) as necessary. 
         [0119]    For example, valve element  1121  may have a shape other than the domed shape (e.g., pyramidal shape) as necessary. 
         [0120]    For example, both plate-like body  1111  and valve element  1121  may be disposed so as to be protruded toward the center of tube main body  3 , or alternatively may be disposed so as to be protruded toward inner peripheral surface  31  of tube main body  3 . Further, plate-like body  1111  may be disposed so as to be protruded toward the center of tube main body  3 , with valve element  1121  being disposed so as to be protruded toward inner peripheral surface  31  of tube main body  3 . 
         [0121]    In addition, the inflow part does not need to be the inflow control part. For example, the inflow part may be mere a channel for liquid, such as a pore or a slit. In this case, the dripper has the flow rate control part, and achieves the effects obtained by the flow rate control part, among the above-described effects. 
         [0122]    In addition, the dripper does not need to have the flow rate control part when the dripper has the inflow control part. In this case, the dripper achieves the effects obtained by the inflow control part, among the above-described effects. 
         [0123]    All the contents disclosed in the specification, drawings and abstract of Japanese Patent Application No. 2012-216575 filed on Sep. 28, 2012 and Japanese Patent Application No. 2012-216576 filed on Sep. 28, 2012 are incorporated herein by reference. 
       INDUSTRIAL APPLICABILITY 
       [0124]    The dripper according to the present invention is capable of supplying a stable amount of liquid without depending on the pressure of liquid inside a tube. Therefore, it is expected that the dripper and drip irrigation apparatus according to the present invention are utilized not only in drip irrigation but also in various industries where stable dropwise addition of liquid is demanded. 
       REFERENCE SIGNS LIST 
       [0000]    
       
           1  Dripper 
           11  Substrate 
           111  Inflow control part 
           112  Flow rate control part 
           1111  Plate-like body 
           1112  First slit 
           1121  Valve element 
           1122  Second slit 
           2  Drip watering tube 
           3  Tube main body 
           31  Inner peripheral surface 
           32  Outer peripheral surface 
           33  Ejection port