JP6234882B2 - Plant cultivation equipment - Google Patents

Description

  The present invention relates to a plant cultivation apparatus.

  As a conventional plant cultivation apparatus, for example, Patent Document 1 describes a plant factory for hydroponically cultivating a plant. In the plant factory described in Patent Document 1, when the nutrient solution is discharged from the plant cultivation shelf via the drainage line, the concentration of nitrate ions contained in the nutrient solution is detected by the sensor. And in the plant factory of patent document 1, a plant growth management apparatus controls the supply amount of the fertilizer to a nutrient solution tank based on the detection signal of nitrate ion concentration.

JP 2012-231721 A

  In the plant cultivation apparatus as described above, the ion concentration of the predetermined substance contained in the nutrient solution varies greatly depending on the cultivated species, the amount of cultivation, or the degree of plant growth. For this reason, in order to detect ion concentration with high accuracy, a wide dynamic range and high detection sensitivity are required.

  Here, Patent Document 1 does not specifically disclose a sensor that detects a nitrate ion concentration. Therefore, for example, when the concentration of nitrate ions is detected using an ultraviolet absorbance analysis method, when the nitrate ion concentration is high, the saturation of the absorbance is likely to occur, so that the dynamic range is narrow and the detection accuracy is also lowered.

  In the absorbance analysis method, if the optical path length (flow path width) of the measurement unit into which the nutrient solution is introduced is shortened, the saturation of the absorbance becomes difficult to occur, so the dynamic range is widened and the detection accuracy is improved. However, the measurement part is likely to be clogged with plant fragments, secretions, sand, etc., and light scattering due to mixing of these plant fragments into the optical path is likely to occur. It becomes difficult to detect with high accuracy.

  Then, an object of this invention is to provide the plant cultivation apparatus which has a wide dynamic range and high detection sensitivity, and can detect accurately the ion concentration of the predetermined substance contained in a nutrient solution.

  The plant cultivation apparatus of the present invention includes a cultivation tank in which a plant is cultivated with a nutrient solution, a flow path through which the nutrient solution flows, a measurement unit having a light transmission region in contact with the flow channel, and a light transmission region and a flow from the light transmission region side. A predetermined substance contained in the nutrient solution based on the light-absorbing intensity of the light-emitting part that emits light incident on the boundary surface with the path, the light-receiving part that receives the light reflected on the light transmission region side at the boundary surface, and the measurement part And a detector for detecting the ion concentration of

  In this plant cultivation device, the number of reflections at the boundary surface is reduced for a nutrient solution having a large absorption intensity per reflection at the boundary surface, and a nutrient solution with a low absorption intensity per reflection at the boundary surface is obtained. On the other hand, by increasing the number of reflections at the boundary surface, a wide dynamic range and high detection sensitivity can be realized in the detection of the ion concentration of the predetermined substance contained in the nutrient solution. Moreover, since the detection target is limited to the nutrient solution in the region where the evanescent light generated by the light reflection reaches, the width of the flow path can be expanded so as not to be clogged with plant fragments. Furthermore, light scattering and the like due to mixing of plant fragments into the optical path is difficult to occur. Corresponding to a large change in the ion concentration in the nutrient solution, the ion concentration can be accurately detected. Therefore, according to this plant cultivation apparatus, it has a wide dynamic range and high detection sensitivity, and can accurately detect the ion concentration of the predetermined substance contained in the nutrient solution.

  The plant cultivation apparatus of the present invention further includes a nutrient solution supply unit that supplies the nutrient solution to the cultivation tank, and the detection unit includes the nutrient solution supply unit based on the detected ion concentration so that the ion concentration becomes a predetermined concentration. You may control. According to this structure, the ion concentration of the predetermined substance contained in the nutrient solution can be adjusted to a desired ion concentration according to the cultivated species, the cultivation amount, or the degree of plant growth.

  The plant cultivation apparatus of the present invention includes a standard solution supply unit that supplies a standard solution to the measurement unit, a supply of nutrient solution from the cultivation tank to the measurement unit, and a supply of the standard solution from the standard solution supply unit to the measurement unit. A first switching unit for switching, and the detection unit controls the first switching unit to absorb light in the measurement unit when the standard solution is supplied from the standard solution supply unit to the measurement unit. The measuring unit may be calibrated based on the intensity. According to this configuration, since the calibration is performed by the detection unit, the plant cultivation apparatus can easily detect the ion concentration of the predetermined substance contained in the nutrient solution, although the secular change or environmental change of each unit is likely to occur. .

  The plant cultivation apparatus of the present invention further includes a cleaning liquid supply unit that supplies a cleaning liquid to the measurement unit, and the first switching unit supplies the nutrient solution from the cultivation tank to the measurement unit and the standard from the standard solution supply unit to the measurement unit. The detection unit controls the first switching unit to perform calibration after the cleaning solution is supplied from the cleaning solution supply unit to the measurement unit. You may go. According to this configuration, it is possible to improve the accuracy of calibration by the detection unit in a state in which dirt or the like attached to the measurement unit is removed.

  The plant cultivation apparatus of the present invention may further include a discharge unit from which the nutrient solution supplied from the cultivation tank to the measurement unit is discharged. According to this configuration, when the ion concentration of the predetermined substance contained in the nutrient solution is detected, if the ion concentration is not suitable for plant cultivation, the nutrient solution can be discharged to the discharge unit.

  The plant cultivation apparatus of the present invention may further include a second switching unit that switches between the circulation supply of the nutrient solution from the measurement unit to the cultivation tank and the discharge of the nutrient solution from the measurement unit to the discharge unit. According to this configuration, when the ion concentration of the predetermined substance contained in the nutrient solution is detected and the ion concentration is suitable for plant cultivation, the nutrient solution is re-supplied to the cultivation tank and reused. be able to.

  The plant cultivation apparatus of the present invention may further include an incident angle adjusting unit that adjusts an incident angle of the light incident on the boundary surface from the light transmission region side. According to this configuration, for a nutrient solution having a high absorption intensity per reflection at the boundary surface, the number of reflections at the boundary surface is reduced, and a nutrient solution having a low absorption intensity per reflection at the boundary surface is obtained. On the other hand, the dynamic range and detection sensitivity can be adjusted so as to increase the number of reflections at the boundary surface.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the plant cultivation apparatus which has a wide dynamic range and high detection sensitivity, and can detect accurately the ion concentration of the predetermined substance contained in a nutrient solution.

It is a block diagram of the plant cultivation apparatus of 1st Embodiment. It is sectional drawing of the measurement cell of the plant cultivation apparatus of FIG. It is a conceptual diagram which shows a mode that the frequency | count of reflection in a boundary surface is increased / decreased. It is an example figure of the structure of the incident angle adjustment part for increasing / decreasing the frequency | count of reflection in a boundary surface. It is a figure which shows the relationship between the absorption intensity acquired by the measurement unit of FIG. 4, and a measurement wavelength. It is a block diagram of the plant cultivation apparatus of 2nd Embodiment. It is a block diagram of the plant cultivation apparatus of 3rd Embodiment. It is sectional drawing of the 1st modification of a measurement cell. It is sectional drawing of the 2nd modification of a measurement cell. It is sectional drawing of the 3rd modification of a measurement cell.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the same or an equivalent part, and the overlapping description is abbreviate | omitted.

[First Embodiment]
As shown in FIG. 1, the plant cultivation device 1 </ b> A includes a plant cultivation unit 20, a measurement device 10, a nutrient solution supply unit 4, a standard solution supply unit 5, a cleaning solution supply unit 6, and a discharge unit 7. The plant cultivation unit 20 cultivates the plant P with the circulating nutrient solution N. The measuring apparatus 10 receives the supply of the nutrient solution N from the plant cultivation unit 20 and detects the ion concentration of the predetermined substance contained in the nutrient solution N. The nutrient solution supply unit 4 supplies the nutrient solution N to the plant cultivation unit 20. The standard solution supply unit 5 supplies the standard solution to the measuring apparatus 10. The cleaning liquid supply unit 6 supplies the cleaning liquid to the measuring device 10. The nutrient solution N supplied to the measuring device 10 is discharged to the discharge unit 7.

  The plant cultivation unit 20 includes a cultivation tank 21, an intermediate tank 22, a pipe 23 and a pipe 24. In the cultivation tank 21, a plant cultivation shelf 21a that supports the plant P in a state where the root of the plant P is immersed in the nutrient solution N is disposed. Thus, the plant P is cultivated with the nutrient solution N in the cultivation tank 21. The pipe 23 and the pipe 24 connect the cultivation tank 21 and the intermediate tank 22 to each other. The nutrient solution N is circulated and supplied from the intermediate tank 22 to the cultivation tank 21 by the pipe 23 and the pipe 24 and a pump (not shown).

  The measurement apparatus 10 includes a measurement unit 11 and a control unit (detection unit) 12. In the measurement unit 11, the measurement of the absorption intensity for detecting the ion concentration of the predetermined substance contained in the nutrient solution N is performed for the nutrient solution N supplied from the intermediate tank 22. In the control unit 12, the ion concentration of the predetermined substance contained in the nutrient solution N is detected for the nutrient solution N supplied from the intermediate tank 22.

  The nutrient solution supply unit 4 includes a tank 4 a and a pipe 4 b and supplies the nutrient solution N to the cultivation tank 21. The nutrient solution N is stored in the tank 4a. The nutrient solution N stored in the tank 4a is supplied to the intermediate tank 22 by a pipe 4b and a pump (not shown). When supplying the nutrient solution N to the intermediate tank 22, the nutrient solution supply unit 4 is controlled by the control unit 12 so that the ion concentration is suitable for cultivation of the plant P.

  The standard solution supply unit 5 includes a tank 5a and a pipe 5b, and supplies the standard solution to a measurement cell 16 of the measurement unit 11 described later. A standard solution is stored in the tank 5a. The cleaning liquid supply unit 6 includes a tank 6a and a pipe 6b, and supplies the cleaning liquid to a measurement cell 16 of the measurement unit 11 described later. A cleaning liquid is stored in the tank 6a. The downstream end of the pipe 5 b and the downstream end of the pipe 6 b are connected to the upstream end of the pipe 51. The downstream end of the pipe 51 and the downstream end of the pipe 52 are connected to the upstream end of the pipe 53. The upstream end of the pipe 52 is connected to the intermediate tank 22. The downstream end of the pipe 53 is connected to a measurement cell 16 of the measurement unit 11 described later.

  A first electromagnetic valve 54 is provided at a portion where the downstream end of the pipe 5 b and the downstream end of the pipe 6 b are connected to the upstream end of the pipe 51. A second solenoid valve 55 is provided at a portion where the downstream end of the pipe 51 and the downstream end of the pipe 52 are connected to the upstream end of the pipe 53. The first electromagnetic valve 54 and the second electromagnetic valve 55 switch the pipe connection under the control of the control unit 12. The first switching unit 50 is configured by the first electromagnetic valve 54 and the second electromagnetic valve 55. The first switching unit 50 supplies the nutrient solution N from the cultivation tank 21 to the measurement cell 16 of the measurement unit 11 described later, and the standard solution from the standard solution supply unit 5 to the measurement cell 16 of the measurement unit 11 described later. The supply and the supply of the cleaning liquid from the cleaning liquid supply unit 6 to the measurement cell 16 of the measurement unit 11 to be described later are switched.

  That is, when the connection between the pipe 52 and the pipe 53 is interrupted by the first switching unit 50, the supply of the nutrient solution N to the measurement unit 11 is stopped. On the other hand, when the pipe 51 is connected to the pipe 53 by the first switching unit 50, the standard solution or the cleaning liquid is supplied to the measurement unit 11. When the pipe 5 b is connected to the pipe 51, the standard solution is supplied to the measurement unit 11, and when the pipe 6 b is connected to the pipe 51, the cleaning liquid is supplied to the measurement unit 11.

  The discharge unit 7 has a discharge tank 7a, and the discharge unit 7 is fed from the plant cultivation unit 20, the standard solution supply unit 5, and the cleaning solution supply unit 6 to the measurement cell 16 of the measurement unit 11 described later. Liquid N, standard liquid, and cleaning liquid are discharged. The downstream end of the pipe 61 is connected to the upstream end of the pipe 62 and the upstream end of the pipe 63. The upstream end of the pipe 61 is connected to a measurement cell 16 of the measurement unit 11 described later. The downstream end of the pipe 62 is connected to the discharge tank 7a. The downstream end of the pipe 63 is connected to the intermediate tank 22.

  A third electromagnetic valve 64 is provided at a portion where the downstream end of the pipe 61 is connected to the upstream end of the pipe 62 and the upstream end of the pipe 63. The third solenoid valve 64 switches the pipe connection under the control of the control unit 12. A second switching unit 60 is configured by the third electromagnetic valve 64. The second switching unit 60 supplies the nutrient solution N from the measurement cell 16 of the measurement unit 11 to be described later to the plant cultivation unit 20, and the nutrient solution N and standard from the measurement cell 16 to the discharge unit 7 of the measurement unit 11 to be described later. Switch between discharging liquid and cleaning liquid.

  That is, when the pipe 61 is connected to the pipe 62 by the second switching unit 60, the nutrient solution N is discharged to the discharge tank 7a. When the pipe 61 is connected to the pipe 63, the nutrient solution N is returned to the intermediate tank 22 and used again for the nutrient solution cultivation of the plant P. The plant cultivation apparatus 1A constitutes a circulation type in which the nutrient solution N circulates.

  As shown in FIG. 2, the measurement unit 11 includes a measurement cell (measurement unit) 16, a light emitting unit 14, and a light receiving unit 15. The measurement cell 16 is formed in a rectangular cylinder shape by a material having light transmittance. A part of the measurement cell 16 is a light transmission region 17 that propagates the measurement light L. Inside the measurement cell 16 is a flow path 18 that connects the downstream end of the pipe 53 and the upstream end of the pipe 61 (see FIG. 1). As described above, the measurement cell 16 includes the flow path 18 through which the nutrient solution N flows and the light transmission region 17 in contact with the flow path 18. In FIG. 2, the measurement cell 16 is represented as a cross-sectional view perpendicular to the direction in which the nutrient solution N flows.

  The light emitting unit 14 emits measurement light L incident on the boundary surface A between the light transmission region 17 and the flow path 18 from the light transmission region 17 side via the incident surface 17 a of the light transmission region 17. The light emitting unit 14 includes, for example, a light source such as a deuterium lamp or a halogen lamp.

  The light receiving unit 15 receives the measurement light L reflected at least once on the light transmission region 17 side at the boundary surface A via the emission surface 17 b of the light transmission region 17. The light receiving unit 15 includes a light receiving element such as a small spectroscope.

  The light transmission region 17 is formed of a material having light transmission characteristics in a wavelength region for detecting the ion concentration of a predetermined substance contained in the nutrient solution N. Further, the light transmission region 17 is formed of a material having a higher refractive index than the nutrient solution N, the cleaning solution, and the standard solution so that total reflection occurs at the boundary surface A. As an example, the material of the light transmission region 17 is quartz or fluorite.

  The width of the flow path 18 is, for example, about 10 μm or more. The width of the flow path 18 is desirably about 100 μm or more, and more desirably about 1 mm or more. The boundary surface A may be subjected to a coating process or the like that makes it difficult to get dirt or the like. The shape of the measurement cell 16 is preferably a structure that can be easily removed and replaced, such as one having a screw shape at the upper and lower ends.

  The light transmission region 17 has an incident surface 17a, a reflecting surface 17c, and an exit surface 17b. The measurement light L emitted from the light emitting unit 14 and passed through the incident surface 17a is incident on the boundary surface A so as to cause total reflection at the boundary surface A. After the measurement light L undergoes total reflection at the boundary surface A, the measurement light L enters the reflection surface 17c so as to cause total reflection also at the reflection surface 17c facing the boundary surface A. The measurement light L that has undergone total reflection at the reflecting surface 17c is incident on the boundary surface A so as to cause total reflection at the boundary surface A again. The measurement light L that has undergone the second total reflection at the boundary surface A passes through the emission surface 17b and is received by the light receiving unit 15.

  On the boundary surface A, evanescent light that oozes out from the boundary surface A toward the nutrient solution N side is generated along with the total reflection of the measurement light L. When the evanescent light is absorbed by the nutrient solution N, the light intensity of the measurement light L that has undergone total reflection twice is attenuated. For this reason, by acquiring the absorption intensity of the measurement light L, the ion concentration of the predetermined substance contained in the nutrient solution N can be detected. The distance that evanescent light reaches within the nutrient solution N is about several tens to several hundreds of nanometers from the boundary surface A.

  In FIG. 2, the number of reflections of the measurement light L on the boundary surface A is two, but the number of reflections can be increased or decreased for accurate detection depending on the ion concentration of the predetermined substance contained in the nutrient solution N. it can. That is, when the ion concentration to be detected is high and the absorption intensity per reflection is large, for example, the number of reflections at the boundary surface A can be set to one. On the other hand, when the ion concentration to be detected is low and the absorption intensity per one reflection is small, for example, the number of reflections on the boundary surface A can be made a plurality of times.

  FIG. 3 is a conceptual diagram showing how the number of reflections on the boundary surface A is increased or decreased. As shown in FIG. 3, the number of reflections at the boundary surface A can be increased or decreased by adjusting the incident angle of the measurement light L with respect to the boundary surface A. In FIG. 3, the measurement light L has, for example, three incident angles θ1, θ2, and θ3 on the incident surface 17a. The incident angles θ1, θ2, and θ3 correspond to the optical paths R1, R2, and R3 of the measurement light L, respectively. The measurement light L that has passed through the optical paths R1, R2, and R3 undergoes total reflection once, twice, and three times on the boundary surface A, respectively. When the ion concentration to be detected is high, for example, the incident angle θ1 is selected, and the number of reflections at the boundary surface A is one. When the ion concentration is low, for example, the incident angle θ2 or θ3 is selected, and the number of reflections at the boundary surface A is two or three. The plant cultivation apparatus 1A can cope with the ion concentration of the predetermined substance contained in the nutrient solution N by selecting the incident angles θ1, θ2, and θ3. On the exit surface 17b, the measurement light L is emitted at the exit angles θ4, θ5, and θ6, corresponding to the incident angles θ1, θ2, and θ3, respectively.

  FIG. 4 is an example of a configuration of the incident angle adjustment unit 30 for increasing or decreasing the number of reflections on the boundary surface A. As shown in FIG. 4, the measurement unit 11 includes an incident angle adjustment unit 30 and an emission optical system 40. The incident angle adjusting unit 30 adjusts the incident angle of the measurement light L incident on the boundary surface A from the light transmitting region 17 side via the incident surface 17 a of the light transmitting region 17. More specifically, the incident angle adjusting unit 30 receives the measurement light L from the light emitting unit 14 and makes the measurement light L incident on the incident surface 17a of the light transmission region 17 while changing the incident angle on the incident surface 17a. Let The emission optical system 40 receives the measurement light L from the emission surface 17 b and guides the measurement light L to the light receiving unit 15.

  The incident angle adjustment unit 30 includes an incident lens system 31 and a scanning mirror system 34. The incident lens system 31 includes a condenser lens 32 and a condenser lens 33. The incident lens system 31 collects the measurement light L and makes it incident on the light transmission region 17. The scanning mirror system 34 includes a mirror control unit 35 and a scanning mirror 36. The mirror control unit 35 adjusts the deflection angle of the scanning mirror 36. The scanning mirror 36 has three deflection angles Φ1, Φ2, and Φ3 for the measurement light L. The deflection angles Φ1, Φ2, and Φ3 create the optical paths R1, R2, and R3 of the measurement light L, respectively. The optical paths R1, R2, and R3 are guided to the incident surface 17a at incident angles θ1, θ2, and θ3, respectively. The measurement light L incident on the light transmission region 17 at the incident angles θ1, θ2, and θ3 passes through the optical paths R1, R2, and R3 in the light transmission region 17, respectively. The measurement light L undergoes total reflection once, twice, and three times on the boundary surface A, respectively. The measurement light L that has passed through the light transmission region 17 is emitted from the emission surface 17b at the emission angles φ4, φ5, and φ6 corresponding to the incident angles φ1, φ2, and φ3. The measurement light L emitted from the emission surface 17 b is collected by the emission optical system 40 and then received by the light receiving unit 15. The emission optical system 40 includes a condenser lens 41 and a condenser lens 42. In the measurement unit 11, the deflection angles Φ1, Φ2, and Φ3 of the scanning mirror 36 correspond to the number of times of reflection once, twice, and three times on the boundary surface A, respectively.

  When the ion concentration of the predetermined substance contained in the nutrient solution N is detected using the measurement unit 11, an absorption spectrum S as shown in FIG. 5 is obtained. In the absorption spectrum S, the absorption intensity based on ions of a predetermined substance having absorption in the measurement wavelength region changes. In the measurement unit 11, when the deflection angle of the scanning mirror 36 is adjusted to be, for example, the deflection angle Φ1 to the deflection angles Φ2 and Φ3, the number of reflections at the boundary surface A is 1 to 2 and 3 respectively. Changed to times. When the number of reflections increases, the amount of evanescent light of the measurement light L absorbed by ions of the predetermined substance in the nutrient solution N increases, and the absorption intensity increases. As a result, the absorption spectrum S changes from S1 to S2 and S3.

  The control unit 12 detects the ion concentration of the predetermined substance contained in the nutrient solution N based on the absorption intensity of the totally reflected measurement light L, and the ion concentration becomes the predetermined concentration based on the detected ion concentration. The nutrient solution supply unit 4 is controlled.

  The standard liquid supply unit 5 and the cleaning liquid supply unit 6 will be described in detail using FIG. 1 again. For example, the switching of piping when the cleaning liquid and the standard liquid are supplied to the measurement cell 16 of the measurement unit 11 is performed as follows. When the measurement cell 16 is cleaned, first, the second electromagnetic valve 55 is operated to disconnect the connection between the measurement cell 16 and the pipe 52. Next, the first electromagnetic valve 54 is operated to connect the pipe 6 b to the pipe 51. Thereafter, the pipe 51 is connected to the pipe 53 via the second electromagnetic valve 55, and the cleaning liquid is supplied to the measurement cell 16.

  When the cleaning of the measurement cell 16 is completed, the first electromagnetic valve 54 is operated and the supply of the cleaning liquid is stopped. Next, the pipe 5 b is connected to the pipe 51 by the first electromagnetic valve 54. A standard solution is supplied to the measurement cell 16 and calibration using the standard solution is performed. That is, the control unit 12 controls the first switching unit 50 to adjust the absorption intensity of the measurement light L in the measurement cell 16 when the standard solution is supplied from the standard solution supply unit 5 to the measurement cell 16. Based on the calibration. In the first embodiment, for example, before the detection of the ion concentration of the nutrient solution N or at regular intervals, the control unit 12 controls the first switching unit 50 to supply the cleaning liquid from the cleaning liquid supply unit 6 to the measurement cell 16. Calibrate after it is done. For more rigorous calibration, after the standard solutions having a plurality of types of concentrations are sequentially supplied to the measurement cell 16, the absorption intensity of the standard solution may be acquired, and calibration using the plurality of data may be performed. .

  In the first embodiment, for example, the contamination of the measurement cell may be removed by the water flow of the standard solution, and the cleaning with the cleaning solution may be omitted. A cleaning solution that does not affect the absorption measurement of ions of the predetermined substance contained in the nutrient solution N may be mixed with the standard solution, and cleaning and calibration may be performed simultaneously. In addition, after the calibration is completed, the measurement cell may be washed again with the washing solution in order to wash away the standard solution. After the cleaning with the cleaning liquid is completed, the cleaning liquid may be discharged from the measurement cell 16 with, for example, water. After the ion concentration of the predetermined substance contained in the nutrient solution N is detected, the measurement cell 16 is cleaned and calibrated again. The cleaning and calibration are performed every time the ion concentration of the predetermined substance contained in the nutrient solution N is detected, or may be performed after a plurality of times of detection.

  In the hydroponic cultivation of the plant P, for example, a period of several tens of days to several months may be required for one cultivation, so the light source of the light emitting unit 14 may deteriorate, and the temperature The value of the absorption strength of the nutrient solution N may change due to environmental changes such as. Furthermore, dirt or the like may adhere to the boundary surface of the flow path 18 due to long-term use. In order to accurately obtain the absorption intensity of the nutrient solution N, cleaning of the measurement cell 16 and calibration using a standard solution are important.

  For the cleaning liquid, for example, a chlorine agent, hydrogen peroxide water, chlorine dioxide water or the like is used. In addition, for example, tap water that does not contain a special cleaning component is used as the cleaning liquid. Even tap water or the like can be cleaned by, for example, a water stream. The standard solution includes, for example, a liquid that does not contain ions of a predetermined substance that is the object of measurement, or a liquid that has a clear ion concentration even if it contains ions of a predetermined substance that is the object of measurement. Etc. are used. Even if the standard solution does not contain ions that are the object of measurement, a liquid containing ions whose spectral characteristics such as the absorption maximum wavelength have been clarified may be used.

  The effect obtained by the plant cultivation apparatus 1A of the first embodiment will be described. In this plant cultivation apparatus 1A, the number of reflections at the boundary surface A is reduced for the nutrient solution N having a large absorption intensity per reflection at the boundary surface A, and the absorption intensity per reflection at the boundary surface A is reduced. By increasing the number of reflections at the boundary surface A for a nutrient solution having a small value, a wide dynamic range and high detection sensitivity can be realized in the detection of the ion concentration of a predetermined substance contained in the nutrient solution N. In addition, since the detection target is limited to the nutrient solution N in the region where the evanescent light generated by the light reflection reaches, the width of the flow path 18 can be expanded so as not to be clogged with plant fragments or the like. it can. Furthermore, light scattering and the like due to mixing of plant fragments into the optical path is difficult to occur. Corresponding to a large change in the ion concentration in the nutrient solution N, the ion concentration can be detected with high accuracy. Therefore, according to this plant cultivation apparatus 1A, it has a wide dynamic range and high detection sensitivity, and can accurately detect the ion concentration of the predetermined substance contained in the nutrient solution N.

  Moreover, in the plant cultivation apparatus 1A, since clogging due to plant fragments and the like can be prevented, a large-scale filtration device for the flow path becomes unnecessary, and labor for replacing the filtration device when clogging occurs is reduced. The plant cultivation apparatus 1A is also easy to operate and maintain for a long time.

  Moreover, in the plant cultivation apparatus 1A, the ion concentration of the predetermined substance contained in the nutrient solution N can be adjusted to a desired ion concentration according to the cultivated species, the cultivation amount, or the degree of growth of the plant P. Moreover, since the calibration is performed by the control unit 12, the plant cultivation apparatus 1A can easily detect the ion concentration of the predetermined substance contained in the nutrient solution N although the aging or environmental change of each part is likely to occur. Moreover, in the plant cultivation apparatus 1A, the accuracy of calibration by the control unit 12 can be improved in a state in which dirt or the like attached to the measurement cell 16 is removed.

  Further, in the plant cultivation apparatus 1A, when the ion concentration of the predetermined substance contained in the nutrient solution N is detected, if the ion concentration is not suitable for the cultivation of the plant P, the nutrient solution N is discharged to the discharge unit 7 can do. As a result of detecting the ion concentration of the predetermined substance contained in the nutrient solution N, when the ion concentration is suitable for cultivation of the plant P, the nutrient solution N can be re-supplied to the cultivation tank 21 and reused. it can.

  Moreover, in the plant cultivation apparatus 1A, the number of reflections at the boundary surface A is reduced for the nutrient solution N having a large absorption intensity per reflection at the boundary surface A, and the absorption per reflection at the boundary surface A is reduced. For the nutrient solution N having a low strength, the dynamic range and detection sensitivity can be adjusted so that the number of reflections at the boundary surface A is increased.

  In the plant cultivation device 1A, by providing the intermediate tank 22, the ion concentration contained in the nutrient solution N of the cultivation tank 21 can be maintained at a suitable value. For example, when the cultivation tank 21 is separated from the intermediate tank 22 at the time of maintenance of the plant cultivation apparatus 1A, the nutrient solution N in the cultivation tank 21 is not affected by the maintenance, so that a suitable ion concentration is substantially maintained. On the other hand, since the intermediate tank 22 can supply and discharge the nutrient solution N to and from the nutrient solution supply unit 4 and the measurement cell 16, there is no problem in maintenance.

[Second Embodiment]
As FIG. 6 shows, the plant cultivation apparatus 1B of 2nd Embodiment is different from the plant cultivation apparatus 1A of 1st Embodiment by the point by which the 2nd switching part 60, the piping 61, and the piping 63 are not provided. ing. In the plant cultivation device 1 </ b> B, the nutrient solution N in which the ion concentration of the predetermined substance is detected by the measurement device 10 is discharged to the discharge unit 7. The plant cultivation device 1B is a flooded type different from the plant cultivation device 1A of the first embodiment. In the plant cultivation device 1B, while the nutrient solution N used for detection is discharged to the discharge unit 7, the nutrient solution N having a suitable ion concentration is supplied from the nutrient solution supply unit 4, so The ion concentration contained in the nutrient solution N maintains a value suitable for plant cultivation.

[Third Embodiment]
As shown in FIG. 7, the first embodiment is that the second switching unit 60, the pipe 61 and the pipe 63 are not provided, and further, the intermediate tank 22, the pipe 23 and the pipe 24 are not provided. This is different from the plant cultivation apparatus 1A. In the plant cultivation device 1 </ b> C, the nutrient solution N whose ion concentration is detected by the measurement device 10 is discharged to the discharge unit 7. The plant cultivation apparatus 1C is a flooded type different from the plant cultivation apparatus 1A according to the first embodiment. Since the intermediate tank 22 is not provided in the plant cultivation apparatus 1C, the plant cultivation apparatus 1C can supply the nutrient solution N directly from the nutrient solution supply unit 4 to the cultivation tank 21.

  As mentioned above, although the plant cultivation apparatus by this invention was demonstrated in detail, the plant cultivation apparatus by this invention is not restricted to embodiment mentioned above, Other various deformation | transformation are possible as follows.

[First Modification]
As shown in FIG. 8, in the first modification, the measurement cell 16 can include a trapezoidal light transmission region 17, for example. In FIG. 8, the measurement cell 16 is represented as a cross-sectional view along the direction in which the nutrient solution N flows. The light transmission region 17 has a higher refractive index than the region other than the light transmission region 17 in the measurement cell 16 due to total reflection. In the light transmission region 17, the measurement light L can be reflected as shown in FIG. The light transmission region 17 may have a shape such as a rectangular shape in addition to the trapezoidal shape. According to the first modification, the measurement light L can be totally reflected by the light transmission region 17 contained in the measurement cell 16 in a compact manner.

[Second Modification]
In the second modification, the measurement cell 16 includes a trapezoidal light transmission region 17 as shown in FIG. In FIG. 9, the measurement cell 16 is represented as a cross-sectional view perpendicular to the direction in which the nutrient solution N flows. In the second modification, the flow path 18 extends in the measurement cell 16 toward the light transmission region 17 and extends in a direction along the light transmission region 17 when contacting the light transmission region 17. Then, it extends along the direction away from the light transmission region 17 again. Even in the flow path 18 having such a configuration, the light transmission region 17 can detect the ion concentration with high accuracy.

[Third Modification]
As shown in FIG. 10, in the third modification, for example, the light transmission region 17 extends around the entire circumference of the measurement cell 16. The measurement cell 16 can take a shape such as an octagon. In FIG. 10, the measurement cell 16 is represented as a cross-sectional view perpendicular to the direction in which the nutrient solution N flows. In the third modified example shown in FIG. 10, the measurement light L that has passed through the incident surface 17a is reflected on the boundary surface A so as to cause total reflection at the boundary surface A from the incident surface that is adjusted to an optimum angle only at that portion. Incident. The measurement light L undergoes the sixth total reflection at the boundary surface A, and then passes through the emission surface 17b adjusted to an optimum angle in the same manner as the incident surface, and is extracted from the measurement cell 16. According to this configuration, when the ion concentration cannot be accurately detected with the number of reflections of six times on the boundary surface A, the three-dimensional shallow angle is set so that the measurement light L travels along the flow path. By making it incident, it is possible to increase the number of turns in the light transmission region 17. For this reason, in the third modification, a wide dynamic range and high detection sensitivity can be obtained, so that even when the ion concentration of the predetermined substance is very small, detection of the ion concentration with high accuracy is performed.

DESCRIPTION OF SYMBOLS 1A, 1B, 1C ... Plant cultivation apparatus, 4 ... Nutrient solution supply part, 5 ... Standard solution supply part, 6 ... Cleaning liquid supply part, 7 ... Discharge part, 10 ... Measuring apparatus, 11 ... Measurement unit, 12 ... Control part ( Detection unit), 14 ... Light emitting unit, 15 ... Light receiving unit, 16 ... Measurement cell (measurement unit), 17 ... Light transmission region, 18 ... Channel, 20 ... Plant cultivation unit, 21 ... Cultivation tank, 30 ... Incident angle adjustment Part, 50 ... first switching part, 60 ... second switching part, A ... boundary surface, L ... measurement light (light), N ... nutrient solution, P ... plant.

Claims (7)

A cultivation tank in which plants are cultivated with nutrient solution;
A measurement unit having a flow path through which the nutrient solution flows and a light transmission region in contact with the flow path;
A light emitting unit that emits light incident on a boundary surface between the light transmission region and the flow path from the light transmission region side;
A light receiving unit that receives the light reflected toward the light transmission region at the boundary surface;
A plant cultivation device comprising: a detection unit that detects an ion concentration of a predetermined substance contained in the nutrient solution based on the light absorption intensity of the measurement unit. Further comprising a nutrient solution supply unit for supplying the nutrient solution to the cultivation tank,
The plant cultivation device according to claim 1, wherein the detection unit controls the nutrient solution supply unit based on the detected ion concentration so that the ion concentration becomes a predetermined concentration. A standard solution supply unit for supplying a standard solution to the measurement unit;
A first switching unit for switching the supply of the nutrient solution from the cultivation tank to the measurement unit and the supply of the standard solution from the standard solution supply unit to the measurement unit;
The detection unit controls the first switching unit, and when the standard solution is being supplied from the standard solution supply unit to the measurement unit, based on the light absorption intensity in the measurement unit. The plant cultivation apparatus according to claim 1, wherein calibration is performed. A cleaning liquid supply unit for supplying a cleaning liquid to the measurement unit;
The first switching unit is configured to supply the nutrient solution from the cultivation tank to the measurement unit, supply the standard solution from the standard solution supply unit to the measurement unit, and supply the standard solution from the cleaning solution supply unit to the measurement unit. Switching between cleaning liquid supply and
The plant cultivation apparatus according to claim 3, wherein the detection unit controls the first switching unit, and performs the calibration after the cleaning liquid is supplied from the cleaning liquid supply unit to the measurement unit.   The plant cultivation apparatus as described in any one of Claims 1-4 further equipped with the discharge part from which the said nutrient solution supplied to the said measurement part from the said cultivation tank is discharged | emitted.   The plant cultivation device according to claim 5, further comprising a second switching unit that switches between supply of the nutrient solution from the measurement unit to the cultivation tank and discharge of the nutrient solution from the measurement unit to the discharge unit.   The plant cultivation apparatus according to any one of claims 1 to 6, further comprising an incident angle adjustment unit that adjusts an incident angle of the light incident on the boundary surface from the light transmission region side.

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