JP2008017655A - Water level sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a water level sensor capable of detecting a water level and the fluctuation of the water level, and acquiring power for transmitting water level information by radio transmission in the detection of water level. <P>SOLUTION: The water level sensor 50 has a structure in which an air hole 21 is formed at the upper part, a water permeating hole 22 is formed at the lower part of a cylindrical member 11, and they are formed in a vertical posture; and a plurality of power generation units 16 are provided at predetermined interval in a vertical direction in its inside. The sensor 50 causes the power generation units to generate power in response to a change in a water level in the cylindrical member 11, and a signal transmitter 14 to transmit a voltage signal in the power generation while utilizing the power. The power generation units 16 have bending displaceable piezoelectric elements 31, springs 32 for bending the piezoelectric elements 31, permanent magnets 33 attached on the piezoelectric elements 31, water-proof cases 34 for housing these component, floats 27 provided outside the cases 34, and weights 28 provided outside the cases to the permanent magnet 33 so as to be closable to and separable from the magnet. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a water level detection device for detecting a change in water level due to a flood or the like and transmitting the water level information to a management facility such as a disaster prevention center.

  When a flood is likely to occur due to heavy rain or a tsunami, local disaster monitors, etc. monitor changes in the water level in residential areas, notify relevant parties as necessary, and supply personnel. The sandbags are piled up and residents are evacuated. However, it is difficult to uniformly monitor a wide area by such a manual monitoring. Thus, it is desired to develop a system that measures such water level detection in a wide range in real time and is useful for disaster prevention as infrastructure.

  However, the conventional water level sensor whose detection water level reaches as high as a meter is expensive, and enormous investment is required to install it in a wide range. In addition, since a battery is used as a power source for transmitting the water level information of the installed water level sensor to the disaster prevention center, etc. by radio waves, etc., periodic maintenance is necessary. There is also a risk of not.

  For such a water level sensor, there is a system for raising and lowering a float according to a change in the water level, generating a piezoelectric element using the movement of the float at this time, and monitoring the change in the water level with the electric power. It is known (see, for example, Patent Document 1).

However, the monitoring device disclosed in Patent Document 1 cannot detect the water level even if it is known that the water level has changed. That is, the signal (voltage waveform) transmitted by the piezoelectric element is the same whether the float is rising or falling, for example, when the float is raised by 5 steps and further raised by 5 steps. Since the same signal is obtained in the case of 5 steps up and 5 steps down, the water level itself cannot be detected. Further, in the monitoring device disclosed in Patent Document 1, it is difficult to take a waterproof measure on the portion from the operating body that operates by raising and lowering the float to the piezoelectric element due to its structure.
Japanese Unexamined Patent Publication No. 2004-320975 (see FIG. 6, [Example 3], etc.)

  The present invention has been made in view of such circumstances, and can detect water level and water level fluctuation, obtain electric power for transmitting water level information by wireless transmission or the like when detecting the water level, and has a waterproof measure. An object is to provide a water level detection device that is easy.

  Both of the water level detection devices according to the first and second aspects of the present invention form an air hole in the upper part of the cylindrical member and a water immersion hole into which water can enter, and install it in a vertical posture. Inside the cylindrical member, a weight made of a ferromagnetic material and a float as a float attached to the weight are arranged so as to move up and down according to the water level inside the cylindrical member, and further, a predetermined vertical direction is provided outside the cylindrical member. A plurality of power generation units are installed at intervals, and the power generation unit at the float height is generated by using the rise and fall of the float accompanying the water level change in the cylinder member, and the water level information is obtained using the power obtained by this power generation. For example, the information is transmitted to a facility such as a disaster prevention management center by the signal transmission device.

  In the water level detection device according to the first aspect, each of the plurality of power generation units has a bending displacement type piezoelectric element, a spring for bending the piezoelectric element, and a permanent magnet attached to the piezoelectric element. By arranging the permanent magnet on the cylindrical member side and changing the attractive force acting between the weight and the permanent magnet by raising and lowering the float, the bending state of the piezoelectric element is changed, and the piezoelectric element is caused to generate electric power. At the time of information transmission, the signal transmission device transmits a signal to which ID information for specifying which power generation unit of the plurality of power generation units generates the voltage is added.

  Further, in the water level detection device according to the second aspect of the present invention, each of the plurality of power generation units has piezoelectric elements having different voltage values when power is generated by bending displacement, and springs that bend each piezoelectric element. And a permanent magnet attached to each piezoelectric element, and by changing the attractive force acting between the weight and the permanent magnet by raising and lowering the float by arranging the permanent magnet on the cylindrical member side. The bending state of the piezoelectric element is changed to generate electricity. At the time of information transmission, the signal transmission device specifies which power generation unit of the plurality of power generation units generates the voltage based on the generated voltage value, and adds the ID information of the power generation unit. Send.

  The water level detection device according to the third aspect of the present invention is formed by forming an air hole in the upper part of the cylindrical member and a water immersion hole in which water can enter in the lower part thereof, and installing it in a vertical posture. Has a structure in which a plurality of power generation units are provided at a predetermined interval, and the power generation unit is caused to generate power in accordance with a change in the water level in the cylindrical member, and the voltage signal at that time is generated by the signal transmission device using the power Send. Therefore, the power generation unit includes a bending displacement type piezoelectric element, a spring for bending the piezoelectric element, a permanent magnet attached to the piezoelectric element, a case for waterproofly housing the piezoelectric element, the spring, and the permanent magnet, and an outside of the case. It has a structure that has a float that is provided and a weight made of a ferromagnetic material that is provided on the outside of the case so as to be close to and away from the permanent magnet. Due to the balance with the acting gravity, the attractive force acting between the weight and the permanent magnet changes, thereby causing the piezoelectric element to generate electricity.

  According to the present invention, it is possible to detect water level and water level fluctuation. Further, it is possible to detect a water level using a piezoelectric element, and to transmit a voltage signal with the power using the power generation of the piezoelectric element at the time of detecting the water level. This eliminates the need for a battery for signal transmission and eliminates maintenance such as battery replacement. In addition, the configuration of the power generation unit is simple, measures for waterproofing are easy, and the entire apparatus can be configured at low cost.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a cross-sectional view showing a schematic structure of a water level detection device according to a first embodiment of the present invention. The water level detection device 10 includes a cylindrical member 11, a float 12 provided inside the cylindrical member 11, a plurality of power generation units 13 provided outside the cylindrical member 11, and a plurality of the power generation units 13. A signal transmission device 14 for transmitting a signal indicating that power generation has occurred in the predetermined power generation unit.

  The cylindrical member 11 is installed so that the length direction thereof is a vertical direction, and an air hole 21 is formed in the upper part thereof, and a water immersion hole 22 is formed in the lower part thereof. When water enters the inside of the cylindrical member 11 from the water immersion hole 22, the internal air is discharged from the air hole 21. Thus, the water level inside the cylinder member 11 is always the same as the water level outside the cylinder member 11. The cylinder member 11 may be a cylinder or a square cylinder.

  The float 12 includes a weight 25 made of a ferromagnetic material and a float 26 attached to the weight 25. The float 12 moves up and down according to the water level inside the cylindrical member 11. For this reason, the buoyancy of the float 26 is designed to be greater than the gravity of the weight 25 when the float 26 is floating on the water surface. The float 26 is, for example, a polystyrene foam ball or a hollow plastic ball. The weight 25 is, for example, an iron plate, and it is also preferable to apply a resin coat or the like on the surface in order to prevent the occurrence of rust.

  The outer peripheral shape of the weight 25 is similar to the cross section of the cylindrical member 11 (a cross section perpendicular to the length direction), and a fixed gap is formed between the outer periphery of the weight 25 and the inner wall of the cylindrical member 11 to float. It is preferable that 12 can move up and down smoothly as the water level in the cylindrical member 11 changes. This is because, as will be described later, it is preferable that the horizontal movement of the weight 25 in the cylindrical member 11 is small in order to generate an attractive force between the weight 25 and the permanent magnet 33 constituting the power generation unit 13. It is.

  The shape of the float 26 is not limited as long as it can move up and down smoothly in the cylindrical member 11, and is not limited to a sphere as shown in FIG. In addition, although the example which attached the float 26 to the upper side of the weight 25 as the float 12 was shown in FIG. 1, it is good also as a shape which provided the float 26 below the weight 25. FIG.

  The power generation units 13 are arranged at predetermined intervals in the length direction of the cylindrical member 11. Although the interval between the power generation units 13 may be changed, considering the convenience of water level management, it is preferable that the intervals be equal.

  FIG. 2 shows the structure and operation mode of the power generation unit 13. The power generation unit 13 includes a bending displacement type piezoelectric element 31, a spring 32 for bending the piezoelectric element 31, and a permanent magnet 33 attached to the piezoelectric element 31. The piezoelectric element 31, the spring 32, and the permanent magnet 33 are provided. Has a structure housed in a case 34 in a waterproof manner.

  Here, the piezoelectric element 31, the spring 32, and the permanent magnet 33 are shown as being connected via a connecting rod 35, but the spring 32 and the permanent magnet 33 are directly on the front and back surfaces of the piezoelectric element 31. It may be attached.

  Specifically, the bending displacement type piezoelectric element 31 is a bimorph element and a unimorph element. As is well known, a bimorph element has a structure in which a piezoelectric plate is attached to both sides of a rectangular reinforcing plate (metal thin plate (shim plate) or resin plate), and a unimorph element has a piezoelectric structure on one side of a rectangular reinforcing plate. It has a structure in which a plate is attached. Although the monomorph element which consists of a piezoelectric plate single-piece | unit can also be used as the piezoelectric element 31, it is inferior to a bimorph element or a unimorph element from a durable viewpoint.

  1 and 2, the main surface of the piezoelectric element 31 is perpendicular to the paper surface. Cylindrical support members 38 are attached to both ends of the piezoelectric element 31, and a holding member 39 having a hole for allowing the support member 38 to pass through is fixed inside the case 34. By using such a support member 38, it is difficult for refraction to occur at both ends of the piezoelectric element 31 when the piezoelectric element 31 is bent, and the life of the piezoelectric element 31 can be extended. Can be easily arranged.

  The power generation unit 13 is arranged so that the length direction of the piezoelectric element 31 coincides with the length direction of the cylindrical member 11. Thereby, when the piezoelectric element 31 is long and the cylindrical member 11 is thin, the entire water level detection device 10 can be configured to be thin and compact. In particular, when it is desired to increase the displacement amount of the piezoelectric element 31 in order to increase the power generation amount of the piezoelectric element 31, it is necessary to lengthen the piezoelectric element 31, and in this case, the length of the piezoelectric element 31 is increased. The configuration in which the vertical direction coincides with the length direction of the cylindrical member 11 is extremely advantageous for making the entire apparatus compact.

  The movement of the piezoelectric element 31 in the power generation unit 13 will be described. As shown in the left diagram of FIG. 2, when the float 12 is away from the power generation unit 13, the piezoelectric element 31 is bent so as to protrude toward the spring 32 due to the spring force (contraction force) of the spring 32. ing. At this time, the permanent magnet 33 is located away from the wall surface of the cylindrical member 11.

  When the float 12 approaches the power generation unit 13, the attractive force acting between the weight 25 and the permanent magnet 33 increases, and when the attractive force becomes larger than the spring force of the spring 32, as shown in the right diagram of FIG. 2, The permanent magnet 33 slides toward the cylindrical member 11 and the position of the permanent magnet 33 is held by the attractive force. When the permanent magnet 33 slides, the bending state of the piezoelectric element 31 is reversed, and the piezoelectric element 31 generates power. The bending displacement of the piezoelectric element 31 at this time is a so-called transition between bistable states, and a large voltage can be generated when the displacement occurs steeply.

  As shown in FIG. 2, the portion between the permanent magnet 33 and the weight 25 in the case 34 is preferably thin as long as the structural strength can be maintained, and thereby the displacement of the piezoelectric element 31 is reduced. The case 34 itself can be made thin while taking a large space. The case 34 is preferably made of a material that is not magnetized by a permanent magnet, such as resin or aluminum.

  Further, when the water level changes and the float 12 tries to move away from the power generation unit 13, the attractive force acting between the weight 25 and the permanent magnet 33 becomes weak, and the attractive force is smaller than the spring force (contracting force) of the spring 32. If it becomes, it will return to the state of the left figure of FIG. Also at this time, the bending state of the piezoelectric element 31 is reversed and a voltage is generated.

  Whether the electric power generation of the piezoelectric element 31 is due to the fact that the float 12 approaches the power generation unit 13 or the distance from the power generation unit 13 can be known by analyzing the waveform of the generated voltage.

  FIG. 3 shows an example of a voltage waveform generated in the piezoelectric element 31. In FIG. 3, when the voltage waveform having a peak on the + side is due to the fact that the float 12 approaches the power generation unit 13, the voltage waveform having a peak on the − side is due to the float 12 being separated from the power generation unit 13. . Such a difference is caused by the polarization direction of the piezoelectric plate constituting the piezoelectric element 31.

  The magnitude of the attractive force acting between the weight 25 and the permanent magnet 33 (that is, the magnitude of the magnetic force of the permanent magnet 33) and the magnitude of the spring force of the spring 32 are determined by bending of the piezoelectric element 31 shown in FIG. Set to change state. Here, although the ferromagnetic material is used for the weight 25, a reverse configuration, that is, a permanent magnet may be used for the float, and a ferromagnetic material may be used for the power generation unit. Further, permanent magnets may be used for both the float and the power generation unit. In this case, the two permanent magnets may be arranged so that the S pole and the N pole face each other.

  By the way, two permanent magnets can be arranged such that the S poles or the N poles face each other. That is, when the permanent magnets approach, the piezoelectric element 31 protrudes toward the spring due to repulsion, and when the permanent magnets move away, the piezoelectric element 31 protrudes toward the permanent magnet due to the extension force of the spring. Also good.

  The signal transmission device 14 transmits a signal related to the water level information to a management computer installed in the disaster prevention management center or the like using the electric power generated by the piezoelectric element 31 of the power generation unit 13. It is preferable that the signal transmission device 14 has a simple configuration that operates with as little power consumption as possible. The signal relating to the water level information is, for example, a signal added to the voltage signal that has generated ID information for identifying which power generation unit of the plurality of power generation units 13 has generated power.

  A schematic configuration of the signal transmission device 14 is shown in FIG. The voltage generated in the piezoelectric element 31 is rectified by the bridge rectifier circuit 45 and then sent to the smoothing circuit 46, where the pulsating current output from the bridge rectifier circuit 45 is smoothed to a state close to direct current. The DC voltage is adjusted to a voltage necessary for operating the determination circuit 44, the control circuit 48, and the RF circuit 49 by the DC-DC converter circuit 47, and is output to these voltages (Vout → Vin in FIG. 4).

  For example, in FIG. 1, among the plurality of power generation units 13, the lowermost one is in a state after power generation and the others are not in power generation, but the water level further rises from this state. Then, power generation occurs due to the separation of the float 12 in the lowermost power generation unit, and if the water level subsequently rises, the float 12 rises and power generation occurs in the second power generation unit from the bottom. When 12 is close to the power generation unit arranged at the lowest position again without being close to the second power generation unit, the power generation unit generates power.

  Therefore, the signal transmission device 14 includes a determination circuit 44 for specifying which power generation unit of the plurality of power generation units 13 generates the voltage. For example, the signal input gate to the determination circuit 44 is divided for each power generation unit 13 as shown in FIG. 4, and which power generation unit has generated power by determining which gate has received a voltage signal. Can be specified.

  The voltage signal input to the determination circuit 44 is converted into a digital signal and sent to the control circuit 48. In addition, the determination circuit 44 sends the identified power generation unit ID information to the control circuit 48. The control circuit 48 creates a signal obtained by adding ID information to these voltage signals, and the signal is modulated into a radio signal by the RF circuit 49 and transmitted. Note that the determination circuit 44 may create a signal obtained by adding ID information to the voltage signal.

  The management computer that has received this signal analyzes which waveform the voltage signal has as shown in FIG. 3, and determines whether the float 12 has reached or separated from the power generation unit that issued the voltage signal. Can know the water level and water level change.

  Next, a water level detection device according to a second embodiment of the present invention will be described. FIG. 5 is a schematic cross-sectional view of the water level detection device 10A.

  The difference between the water level detection device 10A and the water level detection device 10 is that the generated voltages of the piezoelectric elements 31 included in the plurality of power generation units 13 are different. For example, when the piezoelectric element 31 has substantially the same form (the same shape when there is no load), a power generation unit in which the displacement amount (bending state) of the piezoelectric element 31 is changed is configured as shown in FIG. In FIG. 5, among the three power generation units 13, the bending of the piezoelectric element in the central power generation unit is the largest, and the bending of the piezoelectric element in the upper power generation unit is the smallest.

  The bending state of the piezoelectric element 31 can be adjusted by the spring constant and length of the spring 32, and the magnetic force of the permanent magnet 33 is adjusted accordingly. That is, a permanent magnet having a strong magnetic force may be used for a piezoelectric element having a large bend. Since the generated voltage value of the piezoelectric element 31 increases when the displacement amount is large, it can be determined in which power generation unit the voltage is generated based on the peak voltage value.

  In addition, when the bending state of the piezoelectric element 31 is individually changed, since the generated voltage becomes small when the displacement amount is small, the bending state is set to a level at which a radio signal can be transmitted with at least the generated power. .

  Using this characteristic, the signal transmission device 14 constituting the water level detection device 10A can use a determination circuit that identifies one power generation unit that generates power from among the plurality of power generation units 13 from the generated voltage value. Of course, the above-described determination circuit 44 shown in FIG. 4 can also be used.

  When the piezoelectric element 31 is, for example, a unimorph element or a bimorph element instead of the method of making the curved state different in this way, the width and thickness of the piezoelectric plate are the same but the length is different, and the thickness and width of the reinforcing plate are different. The same method but using different power generation units depending on the length of the piezoelectric plate can be used. In this case, if the displacement amount of each piezoelectric element is the same, the shorter piezoelectric element is bent more greatly and the generated voltage becomes larger. Therefore, in which power generation unit the voltage is generated based on this generated voltage. Can be determined.

  Next, a water level detection device according to a third embodiment of the present invention will be described. FIG. 6 shows a schematic cross-sectional view of the water level detection device 50. The water level detection device 50 has a structure in which the power generation units 16 are arranged at predetermined intervals in the vertical direction inside the cylindrical member 11 (the same as that constituting the water level detection device 10). The generated voltage signal is transmitted by the signal transmission device 14.

  The power generation unit 16 waterproofly accommodates a bending displacement type piezoelectric element 31, a spring 32 that bends the piezoelectric element 31, a permanent magnet 33 attached to the piezoelectric element 31, and the piezoelectric element 31, the spring 32, and the permanent magnet 33. Case 34, a hinge 29 provided outside the case 34, a float 27 attached to the hinge 29, and a hinge 29 attached to the hinge 29 to rotate the hinge 29 using buoyancy acting on the float 27. Thus, a permanent magnet 33 and a weight 28 made of a ferromagnetic material that can be freely approached / separated are provided.

  The case 34 constituting the power generation unit 16 and the internal part of the case 34 are the same as the power generation unit 13 used in the water level detection device 10, and thus description of this part is omitted. In FIG. 6, the internal structure of the case 34 is shown in a simplified manner.

  FIG. 7 shows an operation mode of the power generation unit 16. As shown in the left diagram of FIG. 7, when the water level is lower than the float 27, the weight 28 is separated from the case 34 due to the gravity acting on the float 27 and the weight 28. When the water level rises, the float 27 rises due to the buoyancy, and the hinge 29 rotates along with this, and the weight 28 approaches the case 34. As shown in the right diagram of FIG. 7, when the attractive force acting between the weight 28 and the permanent magnet 33 increases as described above, the permanent magnet 33 is drawn toward the weight 28, and at this time, the bending state of the piezoelectric element 31 is changed. Inverted, the piezoelectric element 31 generates power. The voltage signal generated by the power generation unit 16 is also the same as that of the power generation unit 13.

  In the power generation unit 16, even if the water level further rises after the state shown in the right diagram of FIG. 7, the state is maintained. The state of the right diagram in FIG. 7 returns to the state of the left diagram in FIG. Only when it falls.

  Therefore, in principle, the signal transmission device 14 used for the water level detection device 50 does not need to have a function of identifying which of the plurality of power generation units 16 has generated power. Therefore, the determination circuit included in the signal transmission device 14 has only a function of converting the incoming voltage signal into a digital signal and sending it to the control circuit 48 without specifying which power generation unit has received the voltage signal. Things can be used.

  However, it cannot be said that there is no possibility that the water level is erroneously recognized because a power generation unit among the plurality of power generation units 16 has malfunctioned. Therefore, also in the water level detection device 50, the signal transmission device 14 of FIG. 4 used in the water level detection device 10 described above is preferably used.

  FIG. 8 shows an example of a signal transmitted from the water level detection device 50. In the signal shown in FIG. 8, a positive peak indicating a water level rise (referred to as peak A) and a negative peak indicating a water level drop (referred to as peak B) are peak A, peak A, peak A, peak B, Peak A and peak B appear in this order. Assuming that there is no failure in each power generation unit 16, this shows that the first three peaks A caused the water level to rise to the third power generation unit from the bottom, and then peak B appears. From this, it can be seen that the descent of the water level has begun. At this point, it can be seen that the water level is intermediate between the second power generation unit from the bottom and the third power generation unit from the bottom. Next, since peak A appears again, it can be seen that the water level has risen and the water level has risen again from the bottom to the third power generation unit, and since peak B has subsequently appeared, At that time, it can be seen that the water level is intermediate between the second power generation unit from the bottom and the third power generation unit from the bottom.

  A power generation unit that replaces the power generation unit 16 will be described. FIG. 9 shows a schematic structure and an operation mode of the power generation unit 16A.

  The case 34 and the internal structure of the power generation unit 16 </ b> A are the same as those of the power generation unit 16. In the power generation unit 16 </ b> A, the permanent magnet 33 is arranged in the cylindrical member 11 (not shown in FIG. 9) so that the permanent magnet 33 can slide in the vertical direction that is the direction of fluctuation of the water level. And the small cylinder member 52 in which the hole 51 is formed at an appropriate position is arranged on the upper side of the case 34 so that the length direction thereof is the vertical direction, and the float 12 (the water level detecting device described above) is disposed therein. The structure is the same as that of the float 12 used in the apparatus 10, and the size is adapted to accommodate the diameter of the small tube member 52).

  As shown in the left diagram of FIG. 9, when the water level is lower than the lower end of the small tubular member 52, the float 12 is lowered by gravity, and the piezoelectric element 31 is attracted by the attractive force between the weight 25 and the permanent magnet 33. Is in a state protruding toward the permanent magnet 33. When the water level rises, as shown in the right diagram of FIG. 9, when the buoyancy acting on the float 26 becomes larger than the attractive force acting between the weight 25 and the permanent magnet 33, the float 12 rises and the spring The bending state of the piezoelectric element 31 is reversed by the contraction force of 32, and power is generated. When the water level drops from this state, the float 12 starts to descend, and when the attractive force acting between the weight 25 and the permanent magnet 33 increases, the permanent magnet 33 moves to the weight 25 side, and the state shown in the left diagram of FIG. Return to. The water level can be detected by such movement.

  This power generation unit 16A is also maintained even if the water level rises after the state shown in the right figure of FIG. 9, and returns from the state shown in the right figure of FIG. 9 to the state shown in the left figure of FIG. Since this is only when the water level is lowered, it is not necessary to add ID information for identifying which of the plurality of power generation units 16A has generated power to the voltage signal.

  The power generation unit 16A may have a configuration in which the structure is reversed vertically (vertical direction).

  As mentioned above, although embodiment of this invention was described, this invention is not limited to such a form. For example, as the power generation unit, a coiled spring (a so-called string spring) is used as a spring for controlling the bending state of the piezoelectric element, but a plate spring may be used as the spring. A piezoelectric unit 16B shown in FIG. 10 is a modification of the piezoelectric unit 16A shown in FIG. 9, and uses a leaf spring as the spring 32 in place of the string-wound spring. By using a leaf spring, there is an advantage that the piezoelectric unit can be made thin.

  In addition, the number of piezoelectric elements provided in one power generation unit is not limited to one, and for example, a plurality of piezoelectric elements may be arranged in parallel with a certain gap in the thickness direction. By bending a plurality of piezoelectric elements, larger electric power can be obtained.

  The method of holding the piezoelectric element is not limited to a method of holding both ends of the piezoelectric element so as to be rotatable. For example, both ends of one or a plurality of piezoelectric elements may be fixed by bolting or the like. The state in which the piezoelectric element is held is not limited to the arc shape, and half of the length direction may be S-shaped. In this case, it is preferable that the electrode pattern is divided into two in the longitudinal direction in the region in the longitudinal direction half of the piezoelectric element (totally divided into four), so that the electric power generated when the piezoelectric element is displaced is reduced. It can be taken out with high efficiency.

Sectional drawing which shows schematic structure of the water level detection apparatus which concerns on the 1st Embodiment of this invention. The figure which shows the structure and operation | movement aspect of a power generation unit which comprise the water level detection apparatus of FIG. The voltage waveform example generate | occur | produced with the piezoelectric element which comprises the electric power generation unit of FIG. The figure which shows schematic structure of the signal transmission apparatus which comprises the water level detection apparatus of FIG. Sectional drawing which shows schematic structure of the water level detection apparatus which concerns on the 2nd Embodiment of this invention. Sectional drawing which shows schematic structure of the water level detection apparatus which concerns on the 3rd Embodiment of this invention. The figure which shows the operation | movement aspect of the electric power generation unit which comprises the water level detection apparatus of FIG. The signal example transmitted from the water level detection apparatus of FIG. Sectional drawing which shows schematic structure and the operation | movement aspect of a power generation unit replaced with the power generation unit of FIG. Sectional drawing which shows schematic structure and the operation | movement aspect of a power generation unit replaced with the power generation unit of FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 * 10A ... Water level detection apparatus, 11 ... Tube member, 12 ... Float, 13 ... Power generation unit, 14 ... Signal transmission device, 16 * 16A * 16B ... Power generation unit, 21 ... Air hole, 22 ... Submerged hole, 25 ... Weight , 26 ... float, 27 ... float, 28 ... weight, 29 ... hinge, 31 ... piezoelectric element, 32 ... spring, 33 ... permanent magnet, 34 ... case, 35 ... connecting rod, 38 ... support member, 39 ... holding member, 44 ... judgment circuit, 45 ... rectification circuit, 46 ... smoothing circuit, 47 ... DC-DC converter circuit, 48 ... control circuit, 49 ... RF circuit, 50 ... water level detection device, 51 ... hole, 52 ... small cylinder member.

Claims (5)

A cylindrical member having a cylindrical shape, installed vertically, with an air hole formed in the upper part thereof and a water immersion hole formed therein in which water can enter therein;
A float that is provided inside the cylindrical member, has a weight made of a ferromagnetic material, and a float attached to the weight, and floats up and down according to the water level inside the cylindrical member;
A plurality of bending displacement type piezoelectric elements, a spring that bends the piezoelectric elements, and a permanent magnet attached to the piezoelectric elements, each provided at a predetermined interval in the vertical direction outside the cylindrical member A power generation unit;
A signal transmission device that transmits a signal added with ID information for specifying which power generation unit of the plurality of power generation units generates a voltage using the power generated by the piezoelectric element;
The bending state of the piezoelectric element is changed by changing the attractive force acting between the weight and the permanent magnet by raising and lowering the float accompanying the water level change in the cylindrical member, and the piezoelectric element is caused to generate electric power. A water level detection device characterized by. A cylindrical member having a cylindrical shape, installed vertically, with an air hole formed in the upper part thereof and a water immersion hole formed therein in which water can enter therein;
A float that is provided inside the cylindrical member, has a weight made of a ferromagnetic material, and a float attached to the weight, and floats up and down according to the water level inside the cylindrical member;
Each of the piezoelectric elements has a different voltage value when power is generated by bending displacement, and each has a spring that bends each piezoelectric element and a permanent magnet attached to each piezoelectric element. A plurality of power generation units provided outside at predetermined intervals in the vertical direction;
The power generation unit of the plurality of power generation units is identified based on the generated voltage value, and a signal to which ID information of the identified power generation unit is added is used using the power generated by the piezoelectric element. A signal transmission device for transmission,
The bending state of the piezoelectric element is changed by changing the attractive force acting between the weight and the permanent magnet by raising and lowering the float accompanying the water level change in the cylindrical member, and the piezoelectric element is caused to generate electric power. A water level detection device characterized by. A cylindrical member having a cylindrical shape, installed vertically, with an air hole formed in the upper part thereof and a water immersion hole formed therein in which water can enter therein;
A bending displacement type piezoelectric element, a spring for bending the piezoelectric element, a permanent magnet attached to the piezoelectric element, a case for waterproofly housing the piezoelectric element, the spring, and the permanent magnet, and an outside of the case And a weight made of a ferromagnetic material provided outside the case so as to be able to approach / separate from the permanent magnet, and is provided at predetermined intervals in the vertical direction inside the cylindrical member. A plurality of power generation units,
A signal transmission device that transmits a voltage signal using the generated power of the piezoelectric element;
The piezoelectric element is generated by changing the attractive force acting between the weight and the permanent magnet according to the balance between the buoyancy change of the float associated with the water level change in the cylindrical member and the gravity acting on the weight. A water level detection device characterized in that The power generation unit includes a hinge-like member provided outside the case,
The water level detection device according to claim 3, wherein the float and the weight are attached to the hinge-like member.   The power generation unit further includes a small cylinder member attached to the outside of the case and having a hole formed at a predetermined position, and the float and the weight are connected to be accommodated in the small cylinder member. The water level detection device according to claim 3, wherein

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