JP2001305241A - Rainfall sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rainfall sensor mountable on a mobile body, capable of measuring constantly-varying rainfall. SOLUTION: This rainfall sensor has a nearly circular piezoelectric element film; a pair of electrode terminals respectively contacting with the upper face side and the lower face side of the piezoelectric element film; and a bottom cover protecting the piezoelectric element film from the lower face side of the piezoelectric element film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a rainfall sensor, and more particularly, to a rainfall sensor that measures rainfall based on kinetic energy and kinetic energy when a raindrop collides with a piezoelectric element.

[0002]

2. Description of the Related Art Conventionally, as a rain gauge, a device for measuring rainfall by storing rainwater in a certain amount of cells and measuring the number of times that a filled cell is overturned and drained by the weight of rainwater. Was used. This device has been used for a long time in places such as weather observation, but has the following problems in relation to the use environment.

[0003] In other words, the mechanism of the apparatus that measures the number of times a filled trout falls over and drains water is not suitable for measuring the temporal change of precipitation that changes every moment. Changes in precipitation until full were impossible to measure.

When a rain gauge is mounted on a meteorological observation boat to measure the amount of precipitation in the ocean, the mass falls over before the vessel becomes full due to the shaking of the ship. It was difficult. Or, the water stored in the trout spilled out due to the shaking of the ship, making measurement impossible. Furthermore, when a conventional water storage type rain gauge is mounted on a land vehicle or aircraft other than a ship, the fluctuation of the liquid level is more remarkable,
It was not possible to make an accurate measurement.

[0005]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems of a conventional rain gauge, and can be installed on a moving object such as a small-sized vehicle. It is an object of the present invention to provide a rainfall sensor capable of measuring not only rainfall but also rainfall incident on an arbitrary inclined surface.

[0006]

SUMMARY OF THE INVENTION The present invention relates to a piezoelectric element film having a substantially circular shape, conductive wires connected to upper and lower sides of a peripheral portion of the piezoelectric element film, and a lower surface of the piezoelectric element film. The problem is solved by a rainfall sensor having a bottom cover that supports the piezoelectric element film from the side.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure, operation principle, application form and manufacturing method of a rainfall sensor according to the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is an exploded perspective view showing a preferred embodiment of a rainfall sensor according to the present invention. In the case of the embodiment shown in the figure, an upwardly convex piezoelectric element film 3 made of a piezoelectric element
A pair of electrode terminals 4 and a shield wire 5 connected to the electrode terminals are connected to the upper and lower surfaces of the piezoelectric element, so that an electromotive force generated between the upper and lower surfaces of the piezoelectric element film can be measured by a measuring instrument (not shown). It is configured.

As a material of the piezoelectric element, for example, a polymer piezo film such as vinylidene fluoride or a copolymer thereof is suitably used.

[0010] As shown in FIG.
The upper and lower surfaces are respectively covered with a protective layer composed of resin layers 2 and 6 of epoxy or the like, and the epoxy resin layer for protecting the upper surface of the piezoelectric element film 3 is further covered on its upper surface with a resin or metal top cover. I have. There is no gap between the top cover 1, the resin layer 2 and the piezoelectric element film 3,
The structures are in close contact with each other.

A part of the lower surface of the resin layer 6 provided on the lower surface of the piezoelectric element film 3 is in contact with a vibration-proof rubber, and the vibration-proof rubber is made of a bottom cover made of a metal having a higher rigidity, such as metal or hard plastic. The lower surface is covered by.

The top cover not only covers the upper surface of the resin layer 2 as described above, but also covers the resin layer 2, the piezoelectric element film,
Electrode terminal 4, shield wire 5, resin layer 6, and vibration-proof rubber 7
And protect them from direct exposure to raindrops.

FIG. 2 is a perspective view showing the assembled state of the embodiment of the sensor according to the present invention shown in FIG. 1 with the top cover 1 and a part of the resin layer 2 removed.

Although it is not essential, it is desirable that the resin layer 2 and the top cover that cover the upper surface of the piezoelectric element film 3 also have an upward convex like the piezoelectric element film 3 having an upward convex. Also, a pair of electrode terminals 4 for connecting the piezoelectric element film 3 and a measuring device (not shown).
It is desirable that the portion where the shield wire 5 penetrates the top cover 1 or the bottom cover 8 has a liquid-tight structure so that raindrops do not enter inside.

FIG. 3 is a partially enlarged view showing a connection state between the upper and lower surfaces of the piezoelectric element 3 shown in FIG.

Next, the operation principle of the rainfall sensor according to the present invention will be described. A piezoelectric element has a property of generating a potential difference between both surfaces when deformation or stress is generated by an external force. When a raindrop collides with the sensor having the above structure from above, the external force due to the raindrop partially generates a stress on the piezoelectric element, and this stress generates an electromotive force between the front surface and the back surface of the film. Can be taken out from the electrode terminal 4 and the shield wire 5 and used as an electric signal. The upper surface of the piezoelectric element 3 is covered with the resin 2 and the top cover 1 as shown in FIGS. 1 and 2, but if there is no gap between them, the resin 2 and the top cover 1 As long as the material No. 1 is not extremely high in rigidity, a weak vibration reaches the piezoelectric element film 3 due to the impact of raindrops, and this weak vibration is sufficient to measure the electromotive force.

Since the magnitude of the generated electromotive force is a function of the kinetic energy (or momentum) of the raindrop, it is possible to calculate the kinetic energy (or momentum) of the raindrop based on the measured magnitude of the electromotive force. It is. The kinetic energy (or momentum) of a raindrop is the product of the square of the mass and velocity of the raindrop (or the product of mass and velocity), while the falling velocity of the raindrop has a good correlation with the mass of the raindrop Is known by observation. Therefore, by using this relationship, it is possible to calculate the mass of the raindrop from the kinetic energy (or momentum) of the raindrop, and finally, when the raindrop collides with the top cover, the piezoelectric element film 3
It is possible to calculate the mass of the raindrop by measuring the electromotive force generated in the raindrop.

The rainfall sensor according to the present invention uses a piezoelectric element film to convert the kinetic energy (or momentum) of the raindrop into a current, and based on this current, the mass of the raindrop is determined by an electric circuit configuration known to those skilled in the art. Is calculated and further integrated to obtain the rainfall. In the situation where a crosswind is blowing, the speed of the raindrop is the vector sum of the vertical speed vector and the horizontal speed vector due to the crosswind, but when the piezoelectric film of the rainfall sensor is installed in the horizontal direction, the raindrop Among the collision energies at the time of the collision, the contribution of the velocity component in the horizontal direction is almost zero. That is, only the kinetic energy of the raindrop in the falling direction is measured by the rainfall sensor, and the measurement value by the rainfall sensor of the present invention is not affected by the crosswind.

It is desirable that the piezoelectric element film has a convex or concave shape in order to operate well, but by making the piezoelectric element film and the top cover convex upward,
It is possible to prevent raindrops from accumulating on the piezoelectric element film and lowering the measurement sensitivity. However, since the piezoelectric element measures the kinetic energy (or momentum) of the raindrop, even if a liquid film is formed on the upper surface of the piezoelectric element, a decrease in measurement accuracy is negligibly small.

The area of the piezoelectric element film is not particularly limited.
Sufficient measurement accuracy can be obtained with a size of 00 square centimeters or less. For this area, even if the amount of precipitation per hour is very large, there is a possibility that raindrops will simultaneously strike the piezoelectric element film. Is negligibly small. Furthermore, since the pulse of the electromotive force observed when the raindrop collides with the piezoelectric element film abruptly attenuates, interference with the next raindrop collision does not pose any problem.

In the above embodiment, the upper surface of the piezoelectric element film is covered with the resin layer and the top cover. However, these are not necessarily essential. Only the resin layer, only the top cover, or neither of them has the upper surface of the piezoelectric element film. May be exposed. When the top surface of the piezoelectric element curtain is covered only by the top cover without the resin layer, it is necessary to pay particular attention to the fact that both are in close contact with each other. In addition, the planar shape of the piezoelectric element film is illustrated as a circular shape, but other than the circular shape, for example,
The shape may be an ellipse, a square, or the like.

Since the rainfall sensor according to the present invention measures the collision of raindrops without storing water, it is suitable for the measurement of rainfall that changes every moment, and follows a rapid change in precipitation. It is easy. Furthermore, since there is no problem of liquid level fluctuation, it can be mounted on a ship or a vehicle to measure rainfall.

Further, a rainfall sensor according to the present invention
An embodiment used for measuring the amount of rain colliding with a vehicle will be described. In this embodiment, the rainfall sensor according to the present invention is installed near a front window shield of a vehicle such as an automobile or a train. By providing the piezoelectric element film of the rainfall sensor so as to be inclined in parallel with the window shield, it is possible to more accurately measure the rainfall colliding with the window shield. Based on the rainfall measured by the rainfall sensor, i.e. the rainfall hitting the front window shield, the movement of the vehicle wiper can be controlled through an electric circuit which can be easily designed by those skilled in the art. The movement of the wiper is, for example, to automatically activate the wiper when it is observed that a certain amount of raindrops is hitting the window shield, and gradually increase the movement speed of the wiper in proportion to the rainfall. . The activation of the wiper itself is performed by a driver's manual switch, and the exercise speed, including the intermittent drive of the wiper, may be controlled by the rainfall measured by the sensor.

Next, a method of manufacturing a rainfall sensor according to the present invention will be briefly described. Furthermore, the above-mentioned rainfall sensor has no tendency to adsorb moisture, dust, etc., and can withstand use in a severe use environment, and exhibits stable performance even for long-term use.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing an embodiment of a rainfall sensor according to the present invention.

FIG. 2 is a perspective view showing a part of the embodiment of the rainfall sensor according to the present invention shown in FIG. 1 in an open state.

FIG. 3 is a partially enlarged view of the embodiment shown in FIGS. 1 and 2 of the rainfall sensor according to the present invention.

FIG. 4 is a longitudinal sectional view of the embodiment shown in FIG. 1 of the rainfall sensor according to the present invention.

FIG. 5 is a plan view of the embodiment shown in FIG. 1 of the rainfall sensor according to the present invention.

Claims (14)

[Claims] 1. A substantially circular piezoelectric element film, a pair of electrode terminals contacting an upper surface and a lower surface of the piezoelectric element film, respectively, and a bottom cover for protecting the piezoelectric element film from the lower surface of the piezoelectric element film. Rainfall sensor. 2. The rainfall sensor according to claim 1, wherein the piezoelectric element film is made of a polymer piezo film. 3. The rainfall sensor according to claim 1, wherein the piezoelectric element film is made of vinylidene fluoride or a copolymer thereof. 4. The rainfall sensor according to claim 1, wherein the piezoelectric element film is convex upward. 5. The rainfall sensor according to claim 1, wherein a filling material is filled in a lower portion of the piezoelectric element film. 6. The rainfall sensor according to claim 1, wherein the filler is an epoxy polymer resin. 7. The semiconductor device according to claim 1, further comprising a top cover for covering an upper surface of the piezoelectric element film, and a resin filled in a gap between the top cover and the piezoelectric element film. The rainfall sensor described. 8. The rainfall sensor according to claim 1, wherein a part of the top cover and the bottom cover is covered with an anti-vibration rubber. 9. The rainfall sensor according to claim 1, wherein a lower surface of the piezoelectric element film is covered with a resin. 10. The rainfall sensor according to claim 9, wherein the resin that fills the gap between the top cover and the piezoelectric element film and the resin that covers the lower surface side of the piezoelectric element film are epoxy resins. . 11. The rainfall sensor according to claim 1, which is mounted on a vehicle. 12. The rainfall sensor according to claim 1, wherein the rainfall sensor is mounted on a vehicle and used together with control means for controlling driving of a wiper of the vehicle based on the measured rainfall amount. 13. A wiper control device, comprising: the rainfall sensor according to claim 1; and control means for controlling a driving state of the wiper in accordance with the rainfall measured by the rainfall sensor. 14. A rainfall sensor comprising: a step of forming a flat piezoelectric element film into a substantially circular and convex piezoelectric element film by embossing; and a step of attaching conductive wires to the convex and concave sides of the piezoelectric element film. Production method.