Patent Publication Number: US-2022225581-A1

Title: Plant Cultivation Device

Description:
TECHNICAL FIELD 
     The present invention relates to a plant cultivation device used in an artificial light-type plant factory. 
     BACKGROUND ART 
     Plant factories are attracting attention as a solution to problems such as food shortages due to global population growth and a decrease in agricultural production due to a decrease in rural population with aging in developed countries such as Japan. 
     Plant factories are roughly divided into two types: fully artificial light type and sunlight utilization type. In the fully artificial light type, the plants are cultivated using only an artificial light source without using sunlight in an isolated environment. In the sunlight utilization type, which is based on utilization of sunlight in an environment isolated to a greenhouse, the plants are cultivated using light supplement with artificial light or high temperature control technology in summer. 
     In a general fully artificial light type plant factory, a cultivation chamber including an artificial light source is arranged. The inside of the cultivation chamber is illuminated by the artificial light source, and air is circulated in a lateral direction by an air conditioner, and temperature and humidity are controlled to desired values, thereby increasing growth efficiency of plants (see Patent Document 1). 
     Patent Document 1: Japanese Unexamined Patent Application, Publication No. 2002-291349 
     DISCLOSURE OF THE INVENTION 
     Problems to be Solved by the Invention 
     However, when the growth efficiency of plants is increased, tipburn becomes a problem in leafy vegetables such as lettuce. Tipburn is a growth disorder of vegetables caused by calcium deficiency during rapid growth. Vegetables with tipburn have brown buds and wither, resulting in reduction of commercial value. 
     An object of the present invention is to provide a plant cultivation device capable of preventing occurrence of tipburn. 
     Means for Solving the Problems 
     In order to solve the above problems, the present invention provides a plant cultivation device that is an artificial light-type plant cultivation device, the plant cultivation device including a cultivation chamber having a closable inside, the cultivation chamber including therein: a cultivation room for cultivating plants; and an air circulation system that generates an air flow flowing from top to bottom in the cultivation room. 
     Preferably, the plant cultivation device further includes a lighting device that illuminates the cultivation room, wherein the air circulation system includes an exhaust fan that exhausts air from the cultivation room, an air supply fan that supplies the air to the cultivation room, and a plurality of air blowing pipes extending on an upper part of the cultivation room and provided with a plurality of air blowing holes for letting the air supplied from the air supply fan from an upper side toward a lower side of the cultivation room. 
     Preferably, the air circulation system includes a gas circulation room provided inside the cultivation chamber, the exhaust fan exhausts air from the cultivation room to the gas circulation room, and the air supply fan supplies air from the gas circulation room to the cultivation room. 
     Preferably, the air circulation system further includes an air conditioner that adjusts the air in the gas circulation room, and the exhaust fan, the air conditioner, and the air supply fan are arranged on one surface side of the cultivation room. 
     Preferably the lighting device and the air blowing pipes are arranged at the same height. 
     Preferably, the exhaust fan is provided above the lighting device and the air blowing pipes in the cultivation room. 
     Preferably, the cultivation room is provided with a cultivation plate having a plurality of plant cultivation holes, and the air blowing holes correspond to the plant cultivation holes, respectively, and are arranged above the plant cultivation holes. 
     Preferably, the cultivation room is provided with a cultivation container, and a load measuring device that measures a load of the cultivation container while the plants are cultivated. 
     Preferably, the plant cultivation device further includes a liquid circulation system that circulates a liquid supplied to the cultivation room, wherein the liquid circulation system includes a liquid supply path through which a liquid flows into the cultivation room, and a liquid collection path through which the liquid collected from the cultivation room is collected, and the liquid supply path and the liquid collection path are arranged on one surface side of the cultivation room. 
     Effects of the Invention 
     According to the present invention, it is possible to provide a plant cultivation device capable of preventing occurrence of tipburn. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a plant cultivation device  1  according to a first embodiment of the present invention in a state where an outer wall  5  is partially cut out. 
         FIG. 2  is a top view of the plant cultivation device  1  in a state where an upper surface  5 T of the outer wall  5  is removed. 
         FIG. 3  is a block diagram showing a configuration of the plant cultivation device  1 . 
         FIG. 4  is a schematic diagram of a nutrient solution circulation system  40 . 
         FIG. 5  is an exploded perspective view of a cultivation container  11 . 
         FIG. 6  is a partial perspective view of a portion of the plant cultivation device  1  related to an air circulation system  30 . 
         FIG. 7  is a perspective view showing a transport mechanism  80  and a load measuring device  70  of the plant cultivation device  1 . 
         FIG. 8  is a schematic diagram of a plant cultivation device  101  of a second embodiment of the present invention in a state where the outer wall  5  is removed, and 
         FIG. 9  is a schematic diagram of a plant cultivation device  201  of a third embodiment of the present invention in a state where the outer wall  5  is removed. 
     
    
    
     PREFERRED MODE FOR CARRYING OUT THE INVENTION 
     First Embodiment 
     (Plant Cultivation Device  1 ) 
     A plant cultivation device  1  of a first embodiment of the present invention will be described below.  FIG. 1  is a perspective view of the plant cultivation device  1  in a state where an outer wall  5  is partially cut out.  FIG. 2  is a top view of the plant cultivation device  1  in a state where an upper surface  5 T of the outer wall  5  is removed.  FIG. 3  is a block diagram showing a configuration of the plant cultivation device  1 . 
     The plant cultivation device  1  is used in an artificial light-type plant factory. The plant cultivation device  1  includes a frame body  2  as a framework, and has a rectangular parallelepiped shape as a whole. The plant cultivation device  1  is provided with a lower space  3  at a lower part and a cultivation chamber  4  surrounded by and outer wall  5  at an upper part. Hereinafter, a description will be given with reference to the drawings in which a side on which a nutrient solution circulation room  33 F to be described below is provided in the plant cultivation device  1  indicates a front, an opposite side thereof indicates a rear, a left side as viewed from the front indicates a left, and a right side as viewed from the front indicates a right. 
     (Cultivation Chamber  4 ) 
     The cultivation chamber  4  is closed such that an inside is openable and closable by the outer wall  5 , and is isolated from the outside. In other words, a temperature, an air flow, and brightness in the cultivation chamber  4  can be controlled independently of the outside, and thus a cultivation environment can be maintained independently of an environment of a work room in the plant factory in which the plant cultivation device  1  is arranged. 
     The closed state is a state of being isolated to the extent that air does not flow out or outside air does not flow in, and mixing of insects does not also occur when the cultivation chamber  4  is closed by the outer wall  5 . 
     As a material of the outer wall  5 , it is preferable to use a non-light transmissive heat insulating material so that the cultivation chamber  4  inside the outer wall is not easily affected by the external environment. 
     The cultivation chamber  4  of the plant cultivation device  1  of the embodiment has a single stage, but the plant cultivation device  1  may be provided a multi-stage cultivation chamber  4 , and may be provided with a plurality of cultivation chambers  4  in a single stage. In this case, the cultivation chambers  4  are isolated from each other, and the internal temperature, air flow, and brightness can be independently controlled. 
     A cultivation room  10  is provided inside the cultivation chamber  4  surrounded by the outer wall  5  to cultivate plants. In the embodiment, the cultivation room  10  is surrounded by six surfaces of a front wall  10 F, a right wall  10 R, a rear wall  10 B, a left surface  5 L of the outer wall  5 , a bottom surface  5 D of the outer wall  5 , and an upper surface  5 T of the outer wall  5 . 
     A space between a right surface  5 R of the outer wall  5  and a right wall  10 R of the cultivation room  10  is a gas circulation room  33 R. A space between a front surface  5 F of the outer wall  5  and a front wall  10 F of the cultivation room  10  is a nutrient solution circulation room  33 F. 
     The plant cultivation device  1  further includes a nutrient solution circulation system  40 , an air circulation system  30 , a control unit  60 , an operation unit  61 , a display unit  62 , a lighting device  20 , and a load measuring device  70 . 
     (Nutrient Solution Circulation System  40 ) 
       FIG. 4  is a schematic diagram of the nutrient solution circulation system  40 . The nutrient solution circulation system  40  is a device that circulates a nutrient solution that is a liquid necessary for growth of the plants. In the embodiment, the nutrient solution containing nutrients necessary for cultivation of the plants circulates, but another fluid, for example, water may be used without being limited the nutrient solution. 
     As shown in  FIGS. 1 and 2 , the nutrient solution circulation system  40  is arranged on one side, that is, a front side of the plant cultivation device  1 . 
     The nutrient solution circulation system  40  includes a nutrient solution storage tank  41  that stores the nutrient solution and a nutrient solution supply pipe  42 , as a nutrient solution supply path, in which one end is connected to a lower part of a side surface of the nutrient solution storage tank  41  and extends in a horizontal direction from the nutrient solution storage tank  41  and the other end is curved upward. 
     The nutrient solution circulation system  40  further includes a nutrient solution collection groove  46  as a nutrient solution collection path, a groove extending portion  47  extending vertically to a front side of the nutrient solution collection groove  46 , and a nutrient solution collection tank  49 . 
     The nutrient solution storage tank  41  is a bottomed container having a rectangular cross section. However, such a shape is not limited to the rectangular cross section, and may be other cross sections such as a circular cross section and the like as long as the bottomed container. 
     The nutrient solution contained in the nutrient solution storage tank  41  contains nutrients necessary for cultivation of the plants, and the nutrient solution includes a fertilizer containing, as components, calcium, a large amount of elements such as nitrogen, phosphorous, and potassium which are called three elements, and trace elements such as iron and magnesium, for example. 
     A water level sensor  41   a  is arranged in the nutrient solution storage tank  41 . The water level sensor  41   a  detects a position of a liquid level of the nutrient solution stored in the nutrient solution storage tank  41 , for example, a height H 3  from the bottom surface of the nutrient solution storage tank  41 , and may be any one of a float type level sensor, an ultrasonic type level sensor, a capacitance type level sensor, and a pressure type level sensor. In the following description, a height means the height from the bottom surface of the nutrient solution storage tank  41 . A measurement value of a water level measured by the water level sensor  41   a  is transmitted to the control unit  60 . 
     The liquid level of the nutrient solution may be kept constant by overflowing of the nutrient solution on the side surface of the nutrient solution storage tank  41  without using the water level sensor. The water drained by the overflowing may be returned to the nutrient solution collection tank  49 , or may be drained as it is. 
     The nutrient solution supply pipe  42  is a round pipe in the embodiment, but not limited thereto, and may have shapes other than the round shape. One end of the nutrient solution supply pipe  42  is coupled to a bottom side of the side surface of the nutrient solution storage tank  41 , but may be coupled to the bottom surface without being limited thereto. The nutrient solution supply pipe  42  includes a liquid distribution pipe  42   b  extending horizontally from the nutrient solution storage tank  41  and a rising portion  42   c  extending upward from the other end of the liquid distribution pipe  42   b  in a state of being bent by about 90 degrees with respect to the liquid distribution pipe  42   b . In the embodiment, the liquid distribution pipe  42   b  and the rising portion  42   c  are formed by bending one nutrient solution supply pipe, but may be formed by joining separate members without being limited thereto. 
     The rising portion  42   c  is a release portion in which an upper part is opened to release the internal nutrient solution toward an atmosphere. A height H 5  of an upper end of the rising portion  42   c  is higher than a height H 4  of an upper end of a wall of the nutrient solution storage tank  41 . In other words, the rising portion  42   c  extends higher than the nutrient solution storage tank  41 . 
     Since the nutrient solution overflows when the nutrient solution stored in the nutrient solution storage tank  41  exceeds the upper end of the nutrient solution storage tank  41 , the height H 3  of the liquid level in the nutrient solution storage tank  41  will not be higher than the height H 4  of the upper end of the nutrient solution storage tank  41 . 
     Therefore, the height H 2  of the liquid level of the nutrient solution in the rising portion  42   c  is equal to or lower (being equal to or slightly lower when there is pressure loss) than the height H 3  of the liquid level of the nutrient solution in the nutrient solution storage tank  41 , and thus the nutrient solution does not overflow from the upper end of the rising portion  42   c.    
     A plurality of discharge ports  44  are provided at the same height on a pipe wall of the liquid distribution pipe  42   b  at a position lower than the height H 3  of the liquid level of the nutrient solution in the nutrient solution storage tank  41 . In the embodiment, the plurality of discharge ports  44  are holes opened downward and having a predetermined diameter. A discharge pipe  44   a  having a smaller diameter than the liquid distribution pipe  42   b  is attached to each of the discharge ports  44  diagonally downward. The discharge pipe  44   a  may not be provided, and the nutrient solution may be directly discharged from the discharge port  44 . 
     Front sides of rectangular nutrient solution inflow plates  45  are arranged below the plurality of discharge ports  44  and the plurality of discharge pipes  44   a . A rear end of the nutrient solution inflow plate  45  is located above the front side of the cultivation container  11 , and is provided with a hole  45   a . The nutrient solution discharged from the discharge pipe  44   a  flows through the nutrient solution inflow plate  45 , and flows into the cultivation container  11  from the hole  45   a . The nutrient solution inflow plate  45  is detachably attached to the plant cultivation device  1  and can be removed and cleaned. In the embodiment, the nutrient solution inflow plate  45  is inclined such that a rear end is lower than a front end. 
     The nutrient solution inflow plate  45  may not be provided, and the nutrient solution may flow directly into the cultivation container  11  from the discharge pipe  44   a.    
     The nutrient solution collection groove  46  is a groove extending in a longitudinal direction below an elongated hole  13   e  of a lower tray  13  (which will be described below) of the cultivation container  11  on the front side of the cultivation room  10 . Both ends of the nutrient solution collection groove  46  in the longitudinal direction are closed. 
     The groove extending portion  47  is a groove extending forward from a right end that is a downstream side of the nutrient solution collection groove  46 , and guides the surplus nutrient solution flowing cut from the nutrient solution collection groove  46  forward to cause it to flow out to a nutrient solution collection tube  48  extending downward from a hole  47   a  which opens to a bottom of a front end. 
     The nutrient solution collection groove  46 , the groove extending portion  47 , and the nutrient solution collection tube  48  are detachably attached to the plant cultivation device  1 , and can be removed and cleaned. 
     The nutrient solution collection groove  46  and the groove extending portion  47  are preferably slightly inclined from the upstream side toward the downstream side, that is, a direction in which the nutrient solution flows. 
     Further, the nutrient solution collection groove  46 , the groove extending portion  47  and the like are covered with a lid or the like such that light is not incident from the lighting device  20 , and thus algae is prevented from growing. 
     The nutrient solution collection tank  49  is a bottomed container having a rectangular cross section. However, such a shape is not limited to the rectangular cross section, and may be other cross sections such as a circular cross section and the like. The nutrient solution collection tank  49  is arranged below of the nutrient solution collection tube  48 , and the nutrient solution flowing from the nutrient solution collection tube  48  flows into such a tank. 
     Since the nutrient solution collection tank  49  is arranged at a position lower than the nutrient solution storage tank  41 , the nutrient solution collection tank  49  is arranged in the lower space  3  below the plant cultivation device  1 , for example, as shown in  FIG. 1 . 
     A pump  50  is arranged between the nutrient solution collection tank  49  and the nutrient solution storage tank  41 , so that the nutrient solution in the nutrient solution collection tank  49  can be sent to the nutrient solution storage tank  41 . The pump  50  is a pump of a predetermined type such as a centrifugal pump or an axial-flow pump, pumps up the nutrient solution collected in the nutrient solution collection tank  49 , and sends the collected nutrient solution to the nutrient solution storage tank  41 , thereby circulating the nutrient solution. The control unit  60  controls the pump  50  to operate supplying the nutrient solution to the nutrient solution storage tank  41  such that the height H 3  of the liquid level of the nutrient solution in the nutrient solution storage tank  41  becomes a predetermined height. 
     (Cultivation Container  11 ) 
       FIG. 5  is an exploded perspective view of the cultivation container  11 . The cultivation container  11  includes an upper tray  12 , a lower tray  13 , two cultivation plates  14 , and two partition plate  15 . 
     The four cultivation containers  11  are horizontally arranged in the cultivation room  10  such that the cultivation plate  14  is fitted into the upper tray  12  in a state where the upper tray  12  attached with the partition plates  15  on both sides is stacked on the lower tray  13  and transverse directions thereof follow a left-right direction of the cultivation room  10  (see  FIG. 1 ). However, the number of cultivation containers is not limited to four. In the embodiment, the cultivation container  11  has a shape satisfying a condition of a length in the transverse direction: a length in the longitudinal direction=1:5, but is not limited thereto. 
     The lower tray  13  includes a rectangular bottom surface  13   a , and two side walls  13   b , a front wall  13   c , and a rear wall  13   d  which surround corners of the bottom surface  13   a . The front wall  13   c  is higher than the rear wall  13   d . The side wall  13   b  has a trapezoidal shape in which the front side is high and the rear side is low. An elongated hole  13   e  is provided on the front side of the bottom surface  13   a . When the cultivation container  11  is arranged in the cultivation room  10 , the bottom surface  13   a  becomes an inclined surface whose front side is gradually lower than the rear side at an angle θ (θ being 0.5 degrees to 1 degree). 
     A plurality of ribs  13   f  parallel to each other are erected on an upper surface of the bottom surface  13   a  in the longitudinal direction (front-rear direction) of the bottom surface  13   a . The ribs  13   f  are provided intermittently in the longitudinal direction of the bottom surface  13   a . When the nutrient solution flows from the rear side to the front side of the bottom surface  13   a  as will be described below, since the nutrient solution flows between the ribs  13   f  along the ribs  13   f , the nutrient solution flows uniformly without being accumulated in one side of the bottom surface  13   a  in the transverse direction. 
     A roller slide portion  13   g  having an L-shaped cross section and extending in the transverse direction is provided at a lower part of the lower tray  13 . 
     Similarly to the lower tray  13 , the upper tray  12  includes a rectangular bottom surface  12   a , and two side walls  12   b , a front wall  12   c , and a rear wall  12   d  which surround corners of the bottom surface  12   a . The upper tray  12  has an outer diameter substantially equal to that of the lower tray  13 , and when the walls of the upper tray  12  are placed on the walls of the lower tray  13 , a liquid flowing space is secured in the lower tray  13 . The front wall  12   c  is higher than the rear wall  12   d . The side wall  12   b  has a trapezoidal shape in which the front side is low and the rear side is high. 
     An elongated hole  12   e  is provided on the rear side of the bottom surface  12   a . When the cultivation container  11  is arranged in the cultivation room  10 , the bottom surface  12   a  becomes an inclined surface whose front side is gradually higher than the rear side at an angle θ (θ being 0.5 degrees to 1 degree). 
     Similarly to the bottom surface  13   a , a plurality of ribs  12   f  parallel to each other are erected on an upper surface of the bottom surface  12   a  in the longitudinal direction (front-rear direction) of the bottom surface  12   a . The ribs  12   f  are provided intermittently in the longitudinal direction of the bottom surface  13   a.    
     When the nutrient solution flows from the front side to the rear side of the bottom surface  12   a  as will be described below, since the nutrient solution flows between the ribs  12   f , the nutrient solution flows uniformly without being accumulated in one side of the bottom surface  12   a  in the transverse direction. 
     Further, partition plate holding grooves  12   g  extending up and down are provided in front of and behind an inner surface side of the side walls  12   b  on both sides. 
     The partition plates  15  are inserted and erected into the partition plate holding grooves  12   g  provided in front of and behind the inner surface side of the side walls  12   b  on both sides. A gap is provided between the partition plate  15  and the bottom surface  12   a  that do not contact with each other, and the nutrient solution can flow through the gap. The partition plate  15  prevents the grown plants from being contact with other members. 
     The cultivation plate  14  is made of foamed styrol or sponge, plant cultivation holes  14   a  are provided at predetermined intervals, and plants are planted in the plant cultivation holes  14   a . The two cultivation plates  14  are separated into two plates having a size to be arranged between the front and rear partition plates  15  when the partition plates  15  are attached to the partition plate holding grooves  12   g  of the upper tray  12 . However, the number of cultivation plates  14  arranged on one upper tray  12  may not be two or may be one, and the cultivation plate  14  may be divided in several. 
     (Air Circulation System  30 ) 
       FIG. 6  is a partial perspective view of a portion of the plant cultivation device  1  related to the air circulation system  30 . The gas circulation room  33 R is provided between the right wall  10 R and the right surface  5 R of the outer wall  5 . 
     A plurality of openings provided at regular intervals in the front-rear direction are formed on the right wall  10 R of the cultivation room  10 , and an exhaust fan  32 A is attached to each of the openings. Further, an air conditioner  34 , which is a Pelche type cooler, is attached to the right surface  5 R of the outer wall  5  in the embodiment. Further, an air supply fan  32 B is attached to a lower part from a front of the gas circulation room  33 R. 
     As described above, all of the exhaust fan  32 A, the air conditioner  34 , and the air supply fan  32 B in the air circulation system  30  are provided closer to the gas circulation room  33 R. Therefore, maintenance work and the like of such components of the air circulation system  30  can be performed only by removal of the right surface  5  of the outer wall  5 . 
     An air blowing duct  31  extends upward from the air supply fan  32 B. The air blowing duct  31  is bent by about 90° at upper part, penetrates the hole provided in the right wall  10 R, enters the cultivation room  10 , and extends to the left and right on the front upper part of the cultivation room  10 . A left end of the air blowing duct  31  is closed. 
     A plurality of air blowing pipes  31 A extend rearward from the air blowing duct  31 , and air is sent from the air blowing duct  31  to each of the air blowing pipes  31 A. Each of the air blowing pipes  31 A extends to a rear end of the cultivation room  10 , and the end thereof is closed. Each of the air blowing pipes  31 A corresponds to a row aligned in front of and behind the plant cultivation hole  14   a  provided in the cultivation plate  14 , and extends above the row. 
     Further, as shown in  FIG. 3 , air blowing holes  31 B are provided on a lower side of each of the air blowing pipes  31 A. The air blowing holes  31 B correspond to the positions of the plant cultivation holes  14   a , and one air blowing hole  31 B is provided above one plant cultivation hole  14   a  in the embodiment. 
     The air circulation system  30  is constructed by the exhaust fan  32 A, the gas circulation room  33 R, the air conditioner  34 , the air supply fan  32 B, the air blowing duct  31 , the air blowing pipe  31 A, and the air blowing hole  31 B described above. 
     Air is exhausted from the cultivation room  10  to the gas circulation room  33 R by the exhaust fan  32 A serving as a first air flow path by the air circulation system  30 , and the air exhausted to the gas circulation room  33 R is cooled by the air conditioner  34 . The cooled air is supplied to the air blowing duct  31  in the cultivation room  10  by the air supply fan  32 B. The air supplied to the air blowing duct  31  flows through the air blowing duct  31 , and is sent from the air blowing duct  31  to the air blowing pipe  31 A. The air sent to the air blowing pipe  31 A is jetted downward from the air blowing holes  31 B. The jetted air is blown from above to a plant V directly below. 
     In the embodiment, since the Pelche type cooler is used as the air conditioner  34 , the variation in cooling effect is small, and the air conditioner  34  is small. 
     (Lighting Device  20 ) 
     The lighting device  20  is an artificial light source arranged in the upper part of the cultivation room  10 . In the present embodiment, a plurality of lighting devices  20  are arranged in parallel with the air blowing pipe  31 A so as to extend from the front to the rear of the cultivation room  10 , and irradiate the plants planted in the cultivation room  10  with light. As the lighting device  20 , an LED (light emitting diode) is preferably used that has small power consumption and can be configured to be thin. Further, a fluorescent lamp may be used as an artificial light source. The lighting device  20  is controlled by the control unit  60 , and is turned ON/OFF by a switch provided in the operation unit  61 . 
     The lighting device  20  is located at the upper part of the cultivation room  10  and is arranged at the height substantially equal to that of the air blowing pipe  31 A, and in the embodiment, the lighting device  20  and the air blowing pipe  31 A are arranged parallel to each other and are arranged substantially alternately. 
     However, the present invention is not limited thereto, and the lighting device  20  and the air blowing pipe  31 A may be arranged so as to intersect with each other. 
     In the embodiment, the exhaust fan  32 A is attached above the air blowing pipe  31 A and the lighting device  20  on the right wall  10 R. However, the exhaust fan  32 A may be attached at the central part or the lower part other than the upper part of the right wall  10 R. 
     (Control Unit  60 ) 
     The operation of the plant cultivation device  1  is controlled by the control unit  60 . The control unit  60  is configured by, for example, a general-purpose personal computer, a computer for factory automation, or a programmable controller. 
     The operation unit  61  configured by buttons and a keyboard for setting the inside of the cultivation room  10  to be in a predetermined cultivation environment, and is arranged on the cuter wall  5  of the cultivation room  10 . 
     The display unit  62  is configured by a liquid crystal panel to display measurement results monitored by various sensors including a load measuring device  70  to be described below in the cultivation room  10  and the predetermined cultivation environment set by the operation unit  61 , and is arranged on the outer wall  5  of the cultivation room  10 . 
     The operation unit  61 , the control unit  60 , and the display unit  62  may be configured separately from the plant cultivation device  1  instead of being configured integrally with the plant cultivation device  1 . In this case, a control panel including an operation unit, a control unit, and a display unit are arranged at a predetermined position in the plant factory, and the cultivation environment in each of the plurality of cultivation chambers  4  of the plant cultivation device  1  may be centrally governed by such a control panel. 
     (Transport Mechanism  80 , Load Measuring Device  70 ) 
     The plant cultivation device  1  further includes a transport mechanism  80  for transporting the cultivation container  11  and a load measuring device  70  for measuring a load of the plant V being cultivated.  FIG. 7  is a perspective view showing the transport mechanism  80  and the load measuring device  70  of the plant cultivation device  1 , and is partially cut out such than the transport mechanism  80  can be seen. 
     The load measuring devices  70  such as load cells are provided at four places (only one place in the drawing) on the bottom surface  5 D of the cultivation room  10 . One rectangular plate member  71  is placed on the four load measuring devices  70 . The load measuring device  70  can measure a load of an object placed on the plate member  71 , and the measured information can be sent to the control unit  60  and can be displayed by the display unit  62 . Roller holding portions  81  extending to the left and right are attached to front and rear edges on the plate member  71 . A plurality of rollers  82  are arranged in a row on the roller holding portion  81 . An axis of rotation of each of the rollers  82  faces back and forth. The roller slide portion  13   g  of the lower tray  13  described above is placed on the row of the rollers  82 . 
     Thus, the lower tray  13  to which the roller slide portion  13   g  is fixed, that is, the cultivation container  11  can slide in the left-right direction in which the rollers  82  are lined up. Therefore, the left surface  5 L of the outer wall  5  shown in  FIG. 1  can be removed, and the grown plant V can be taken out together with the cultivation container  11  from the left side of the cultivation room  10 . 
     In addition, since the cultivation container  11  in which the plant V is cultivated is placed on the plate member  71  through the roller  82  and the roller holding portion  81 , the load of the plant V can be measured together with the cultivation container  11  by the load measuring device  70 . 
     The plant cultivation device  1  of the embodiment operates as follows. 
     (Lighting Device  20 ) 
     The control unit  60  controls the lighting device  20  to irradiate the plants with light such that a luminous flux, illuminance, distribution of wavelengths of the irradiating light are set to predetermined values. 
     (Nutrient Solution Circulation System  40 ) 
     The control unit  60  controls the pump  50  to supply the nutrient solution to the nutrient solution storage tank  41  such that the liquid level of the nutrient solution in the nutrient solution storage tank  41  is at a predetermined height, based on the signal indicating the height of the liquid level of the nutrient solution stored in the nutrient solution storage tank  41  and supplied from the water level sensor  41   a.    
     The nutrient solution stored in the nutrient solution storage tank  41  flows into the nutrient solution supply pipe  42  extending horizontally. 
     According to the embodiment, compared with the case of being pumped by the pump, the nutrient solution in the nutrient solution supply pipe  42  is small in pressure difference between the upstream side and the downstream side, and the height H 2  of the liquid level of the nutrient solution in the rising portion  42   c  being open to the atmosphere is substantially equal to the height H 3  of the liquid level of the nutrient solution in the nutrient solution storage tank  41 . 
     Since the pressure of the nutrient solution is substantially constant in the liquid distribution pipe  42   b , the nutrient solution can be discharged at the same pressure from each of the plurality of discharge ports  44  due to the difference in water level from the height H 3  of the nutrient solution in the nutrient solution storage tank  41 . Accordingly, the flow rate of the nutrient solution can be easily made substantially constant. 
     Further, when the nutrient solution flows into the nutrient solution supply pipe  42 , the air in the nutrient solution supply pipe  42  is driven out to the pipe end, but since the rising portion  42   c  is open to the atmosphere, the air in the nutrient solution supply pipe  42  does not be accumulated at the pipe end. 
     Therefore, the nutrient solution can flow into the nutrient solution supply pipe  42 , and the nutrient solution can uniformly flow out from each of the discharge ports  44  at the same time. 
     Since the pump  50  is used for pumping the nutrient solution and does not pump the nutrient solution into the nutrient solution supply pipe  42 , the nutrient solution can be supplied to the plant cultivation device  1  with less energy. 
     In addition, the control unit  60  can control of the operation timing of the pump  50  and adjust the height H 3  of the liquid level of the nutrient solution in the nutrient solution storage tank  41 . Then, when the height H 3  is adjusted, it is possible to change the amount of nutrient solution discharged from each of the discharge ports  44  per unit time. 
     It is possible to change the amount of nutrient solution to be discharged per unit time by change of the smaller diameter of the inner diameter of the discharge port  44  or the inner diameter of the discharge pipe  44   a.    
     The nutrient solution discharged from each of the discharge pipes  44   a  flows into the nutrient solution inflow plate  45 . Then, the nutrient solution discharged from one discharge pipe  44   a  flows through the nutrient solution inflow plate  45 , and flows into the cultivation container  11  from the hole  45   a.    
     The nutrient solution flowing into the cultivation container  11  absorbed by the plant V planted on the cultivation plate  14  while flowing from the front side to the rear side along the inclined bottom surface  12   a  of the upper tray  12 . At this time, since the nutrient solution flows between the ribs  12   f , the nutrient solution can uniformly flow without being accumulated on one side of the bottom surface  12   a  in the transverse direction. Therefore, the nutrient solution does not stagnate. 
     The surplus nutrient solution not absorbed by the plant V flows out from the elongated hole  12   e  of the upper tray  12  onto the lower tray  13 . The nutrient solution flowing into the lower tray  13  flows from the rear side to the front side along the inclined bottom surface  13   a  of the lower tray  13 . At this time, since the nutrient solution flows between the ribs  13   f  along the ribs  13   f , the nutrient solution can uniformly flow without being accumulated on one side of the bottom surface  13   a  in the transverse direction. 
     Then, the nutrient solution flows out from the elongated hole  13   e  of the lower tray  13  to the nutrient solution collection groove  46 . Therefore, the nutrient solution does not stagnate in the cultivation container  11 . 
     Further, since the partition plates  15  are erected on the front and rear of the cultivation container  11 , when the plant V grows and becomes large in size, the partition plate  15  prevents the grown plant from contacting with other members. 
     The surplus nutrient solution flowing out into the nutrient solution collection groove  46  flows forward through the corresponding groove extending portion  47 , and flows into the nutrient solution collection tube  48  below from the hole  47   a . Then, the nutrient solution flows through the nutrient solution collection tube  48 , flows out from the downstream side of the nutrient solution collection tube  48 , and is collected in the nutrient solution collection tank  49 . As for the nutrient solution collected the nutrient solution collection tank  49 , the concentration of the nutrient solution is measured by a sensor (not shown), and the concentration of the nutrient solution is adjusted to an appropriate optimum concentration by the control unit. 
     The nutrient solution collection tube  48  uses a U-shaped pipe to maintain closability of the cultivation chamber  4 , and thus outside air do not flow in from the nutrient solution collection tube  48 . 
     The height of the liquid level of the nutrient solution in the nutrient solution storage tank  41  is appropriately measured by the water level sensor  41   a . The control unit  60  controls the pump  50  to supply the nutrient solution to the nutrient solution storage tank  41  such that the height of the liquid level of the nutrient solution in the nutrient solution storage tank  41  is at the predetermined height, based on the signal indicating the height of the liquid level thereof. 
     The nutrient solution supplied to the nutrient solution storage tank  41  flows into the nutrient solution supply pipe  42  again to be circulated. 
     In the embodiment, the nutrient solution supply path  42  and the nutrient solution collection paths  46 ,  47 , and  48  are arranged on one surface side (the front surface side in the embodiment) of the cultivation room  10 . Therefore, maintenance work such as inspection of the flow of nutrient solution or inspection of the electric system can be performed only by removal of the outer wall  5  on the front side. 
     On the other hand, when a part of the pipe of the nutrient solution circulation system  40  is arranged not only on the front surface but also on the rear surface and the side surface of the plant cultivation device  1 , during the maintenance of the plant cultivation device  1 , it is necessary to remove the outer wall  5  in addition to the front surface and it also takes time for maintenance. 
     However, in the embodiment, the maintenance may be sufficiently performed only by the removal of the outer wall  5  on the front side. Accordingly, the maintenance is easy. 
     (Air Circulation System  30 ) 
     When the exhaust fan  32 A is operated by the control unit  60 , the air in the cultivation room  10  is exhausted to the gas circulation room  33 R by the exhaust fan  32 A serving as the first air flow path of the air circulation system  30 . 
     A temperature sensor and a humidity sensor, which are not shown, are attached to predetermined locations of the cultivation room  10  to monitor the temperature of the air in a fluid circulation room  33 . The control unit  60  controls the air conditioner  34  based on the temperature of the air around the plants, and appropriately adjusts the temperature of the air in the fluid circulation room  33 . 
     The air adjusted to the appropriate temperature is supplied to the air blowing duct  31  in the cultivation room  10  by the air supply fan  32 B, and is sent from the air blowing duct  31  to the air blowing pipe  31 A. The air sent to the air blowing pipe  31 A is blown out downward from the air blowing hole  31 B. The jetted air is blown out from above to the plant V directly below. 
     In the embodiment, the air circulation system  30  including the exhaust fan  32 A and the air supply fan  32 B is arranged in the gas circulation room  33 R on one surface side (the right surface side in the embodiment) of the cultivation room  10 . 
     Therefore, all maintenance work such as inspection of the flow of air and inspection of the electric system of the air circulation system  30  related to the air circulation system  30  can be performed only by removal of the right surface  5 R of the outer wall  5 , and thus the maintenance is easy. 
     Further, in a general plant cultivation device, unlike the present embodiment, an air flow in a lateral direction is generated in the cultivation room  10 , and the wind blows against the plant in the lateral direction. Then, the wind blows against outer leaves of the plants, transpiration of water from the outer leaves increases, the solution absorbed from the roots of the plants is sent to the outer leaves in large quantities, and thus calcium contained in the nutrient solution is also distributed to the outer leaves in large quantities. 
     However, in particular, spherical head vegetables, such as Chinese cabbage, cabbage, and lettuce, having leaves rolled up one by one or semi-head vegetables, such as leaf lettuce, having loosely rolled leaves and having semi-head leaves without complete head leaves have new leaves growing from the center, but these new leaves are covered with outer leaves. 
     Therefore, in a general plant growing device in which an air flow is generated in the lateral direction, the wind does not blow against the central leaves. Then, in the central new leaves compared with the outer leaves, the transpiration less occurs and calcium is lack due to the lack of supply of the nutrient solution, whereby cell necrosis may be caused to cause a tipburn and it is more likely to cause rot of a root. 
     In particular, in the plant cultivation device, the temperature and lighting in the cultivation room and the nutrient solution to be supplied are controlled to promote the growth of the plants. For this reason, in the plant cultivation device, the plants grow faster than in the natural state, and it is more likely that the central leaves are not sufficiently supplied with nutrients. 
     However, in the embodiment, air is blown out from directly above the plant V. Then, the wind can blow against the central new growing leaves, the transpiration from the growing leaves is promoted, and a large amount of nutrient solution is supplied. Thus, calcium is sufficiently supplied to the growing leaves. Therefore, calcium is supplied to tips of the growing leaves, and tipburn is less likely to occur. 
     In the embodiment, the exhaust fan  32 A is attached above the air blowing pipe  31 A and the lighting device  20  on the right wall  10 R. After the air sent downward from the air blowing hole  31 B of the air blowing pipe  31 A is blown onto the plant V, the air makes a turn upward, passes between the lighting devices  20 , rises above the lighting device  20 , and is exhausted by the exhaust fan  32 A. 
     The lighting device  20  generates heat during lighting, but since the air passes between the lighting device  20 , the lighting device  20  can be cooled. 
     Further, the lighting device  20  is arranged at the height substantially equal to that of the air blowing pipe  31 A, so that the lighting from the lighting device  20  is not blocked by the air blowing pipe  31 A. 
     In addition, the cooling of the lighting device  20  is performed by the air already blown no the plant V, and since the influence of the heating of the air blown from the air blowing pipe  31 A before being blown to the plant V due to the heat generated from the lighting device  20  is small, it is easy to control the temperature of the air blown to the plant V. 
     (Load Measuring Device  70 ) 
     Further, since the cultivation container  11  in which the plant V is cultivated is placed on the plate member  71  through the roller  82  and the roller holding portion  81 , the load of the plant V can be measured together with the cultivation container  11  by the load measuring device  70 . 
     Since the measurement result of the load measuring device  70  is sent to the control unit  60  and continuous load measurement is possible, the growth state of the plant V can be governed by the load, and an appropriate harvest time can be grasped. 
     Further, since the cultivation chamber  4  of the embodiment is closed to the outside, the temperature and humidity in the cultivation chamber  4  (cultivation room  10 ) can be governed without being affected by the temperature and humidity inside the plant factory. Therefore, the environment inside the cultivation chamber  4  can be set independently of the environment of the work room. Accordingly, it is not necessary for plants and humans to coexist unlike a work room in a conventional plant factory. Therefore, for example, the environment in the cultivation chamber  4  is not suitable for the human body, but can be set to the optimum cultivation conditions for the plants. 
     (Modification) 
     Although the preferred embodiment of the present invention has been described above, the present invention is not limited to the embodiment. 
     For example, in the embodiment, the nutrient solution storage tank  41  and the nutrient solution collection tank  49  are provided separately, but these tanks may be provided integrally. 
     The embodiment is configured in which the nutrient solution is circulated from the nutrient solution collection tank  49  to the nutrient solution storage tank  41  by the pump  50 , but the collected nutrient solution is drained without the nutrient solution collection tank, and only the nutrient solution storage tank may be provided. 
     For example, the cultivation container may be configured by one tray instead of the configuration in which the upper tray and the lower tray are provided. In this case, for example, the inside of one tray may be separated into two left and right parts in which one part is inclined such that the nutrient solution flows from the front side to the rear side and the other part is configured such that the nutrient solution flows from the rear side to the front side. Further, the tray may be partitioned into a central part and an end such that the nutrient solution flows reciprocatively through the tray in a T-shape. 
     Further, the embodiment has the configuration in which the tray is provided with an inclination to promote the flow of the nutrient solution, but the bottom surface of the tray may not be provided with an inclination. 
     In addition, the flow method of the nutrient solution storage tank does not matter as long as the liquid circulates between the nutrient solution storage tank and the cultivation container. The embodiment has the configuration in which the nutrient solution storage tank is open to the atmosphere and the nutrient solution flows at atmospheric pressure, but the invention is not limited thereto, and the nutrient solution may flow by a pump without opening to the atmosphere. 
     Second Embodiment 
       FIG. 8  is a schematic diagram of a plant cultivation device  101  of a second embodiment. The plant cultivation device  101  of the second embodiment includes, as an air circulation system, a second air flow path through which air flows in a cultivation room  10  in a lateral direction in addition to the first air flow path, through which the air flows to the plant V from above as described in the first embodiment. Since other configurations are the same as those in the first embodiment, such configurations will not be described and shown, and the common components are designated by the same reference numerals. 
     An air supply fan  32 B in the first air flow path may be arranged in a right gas circulation room  33 R as in the first embodiment, or may be arranged in a nutrient solution circulation room  33 F. 
     The second air flow path includes three circulation rooms, for example, a nutrient solution circulation room  33 F between a front wall  10 F of the cultivation room  10  and a front surface  5 F of an outer wall  5 , a right gas circulation room  33 R between a right wall  10 R of the cultivation room  10  and a right surface  5 R of the outer wall  5 , and an upper gas circulation room  33 T between an upper wall  10 T of the cultivation room  10  and an upper surface  5 T of the outer wall  5 . A plurality of exhaust fans  32 A are attached to the front wall  10 F of the cultivation room  10 . 
     The nutrient solution circulation room  33 F communicates with the right gas circulation room  33 R, and the right gas circulation room  33 R communicates with the upper gas circulation room  33 T. 
     The upper wall  10 T of the cultivation room  10  does not extend until contacting with the rear wall  10 B, and a gap S penetrating in an up-down direction is provided between the upper wall  10 T and the rear wall  10 B. The gap S is an air inflow port through which air flows into the cultivation room  10 . 
     Further, a second air conditioner  34 B is arranged in the right gas circulation room  33 R to govern the temperature, the humidity, and the amount of carbon dioxide or oxygen of the air around the plants. However, as in the first embodiment, only the air conditioner  34  may be provided to perform cooling without the second air conditioner  34 B. 
     When the exhaust fan  32 A is operated by the control unit  60 , the air in the cultivation room  10  flows out to the nutrient solution circulation room  33 F by the exhaust fan  32 A. The outflowed air flows to the right gas circulation room  33 R, and is sent to the upper gas circulation room  33 T after the temperature, the humidity, and the amount of carbon dioxide or oxygen of the air are adjusted by the air conditioner  34 B arranged in the right gas circulation room  33 R. The air sent to the upper gas circulation room  33 T flows into the cultivation room  10  through the gap S. The air flows in the cultivation room  10  in the lateral direction, and flows out to the nutrient solution circulation room  33 F by the exhaust fan  32 A to be circulated. 
     According to the second embodiment, the following effects can be obtained in addition to the effects of the first embodiment. 
     Since the second air flow path does not pass through the hole having a smaller diameter such as the air blowing hole  31 B as in the first embodiment, a large amount of air can be circulated compared with the first air and the air in the cultivation room  10  can be circulated faster. Therefore, control of the environment around the plants can be maintained in a desired state more quickly. Accordingly, it is possible to reduce changes in environment (changes in temperature and humidity) in the cultivation room  10 . As a result, the optimum and homogeneous cultivation environment for the growth of the plants can be maintained, and productivity of the plant factory can be improved. 
     Third Embodiment 
       FIG. 9  is a schematic diagram of a plant cultivation device  201  of a third embodiment. The third embodiment is similar to the second embodiment except that a direction of a second air flow path through which air flows in a cultivation room  10  in a lateral direction is different, and thus the same configurations will not be described and shown. 
     Unlike the second embodiment, the second air flow path does not include the right gas circulation room  33 R between the right wall  10 R of the cultivation room  10  and the right surface  5 R of the outer wall  5 , and includes two air circulation rooms, for example, a nutrient solution circulation room  33 F between the front wall  10 F and the front surface  5 F of the outer wall  5  and an upper gas circulation room  33 T between the upper wall  10 T of the cultivation room  10  and the upper surface  5 T of the outer wall  5 . Then, an exhaust fan  32 A is attached to the front wall  10 F of the cultivation room  10 . 
     The nutrient solution circulation room  33 F communicates with the upper gas circulation room  33 T. In addition, the upper wall  10 T of the cultivation room  10  does not extend up to the rear wall  10 B, and a gap S penetrating in an up-down direction is provided between the upper wall  10 T and the rear wall  10 B. The gap S is an air inflow port through which air flows into the cultivation room  10 . 
     (Air Flow in Second Air Flow Path) 
     When the exhaust fan  32 A is operated by the control unit  60 , the air in the cultivation room  10  flows out to the nutrient solution circulation room  33 F by the exhaust fan  32 . The air flowing out to the nutrient solution circulation room  33 F is sent to the upper gas circulation room  33 T after the temperature, the humidity, and the amount of carbon dioxide or oxygen of the air are adjusted by the air conditioner  34 B. 
     The air sent to the upper gas circulation room  33 T flows into the cultivation room  10  through the gap S. The air flows in the cultivation room  10  in the lateral direction, and flows out to the nutrient solution circulation room  33 F by the exhaust fan  32 A to be circulated. 
     Also in the third embodiment, since the second air flow path does not pass through the hole having a smaller diameter such as the air blowing hole  31 B as in the second embodiment, a large amount of air can be circulated compared with the first air and the air in the cultivation room  10  can be circulated faster. Therefore, control of the environment around the plants can be maintained in a desired state more accurately and more quickly. 
     EXPLANATION OF REFERENCE NUMERALS 
     
         
         V plant 
           1 ,  101 ,  201  plant cultivation device 
           4  cultivation chamber 
           5  outer wall 
           5 D bottom surface 
           5 F front surface 
           5 L left surface 
           5 R right surface 
           5 T upper surface 
           10  cultivation room 
           10 B rear wall 
           10 F front wall 
           10 R right wall 
           11  cultivation container 
           14  cultivation plate 
           14   a  plant cultivation hole 
           20  lighting device 
           30  air circulation system 
           31  air blowing duct 
           31 A air blowing pipe 
           31 B air blowing hole 
           32 A exhaust fan 
           32 B air supply fan 
           33 F nutrient solution circulation room 
           33 R gas circulation room 
           34  air conditioner 
           34 B second air conditioner 
           40  nutrient solution circulation system 
           41  nutrient solution storage tank 
           49  nutrient solution collection tank 
           50  pump 
           60  control unit 
           70  load measuring device 
           80  transport mechanism