JPS587921B2 - Koubaikanchisouchi - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates generally to sensing devices that provide conditions representative of temperature or strain gradient profiles of objects, and more particularly to sensing devices that provide conditions representative of temperature or strain gradient profiles of objects, and more particularly to focusing devices that serve as temperature or strain sensitive elements of such sensing devices. It belongs to the use of polarized electrets that have both electrical and piezoelectric properties.

It is well known that temperature fluctuations at the outer surface of an object can be indicative of the adverse behavior of the object existing or expanding there.

For example, a motor defect may be indicated by abnormal localized heating of the motor enclosure near the defect.

Cancerous tissue in the human body is also indicated by a higher temperature than that of normal healthy tissue.

One existing technique for detecting such temperature changes and obtaining a temperature profile is disclosed in US Pat. No. 3,114,836 by Ferguson et al.
Published in the issue.

The sensing device of Ferguson et al. uses a liquid crystal temperature sensitive material that selectively scatters light and shows in color the temperature profile of the object it touches.

However, the resulting figure is not a residual figure, and when the Ferguson et al. sensing device is removed from the object, the color of the sensing device disappears as the sensing device returns to ambient temperature.

Several types of strain sensing devices are known in the art, and the use of piezoelectric materials in strain sensing devices is not new, as shown in U.S. Pat. No. 3,750,127 to Ayers et al.

The Ayers et al. patent discloses a coaxial strain sensing device that includes an inner conductor, an outer conductor that virtually surrounds the inner conductor, and a piezoelectric strainer between and firmly adhered to both conductors. and a sensing medium.

A sensing circuit of the electronic device is connected to the piezoelectric sensing medium and senses the charge generated by the medium as a result of subjecting the sensing device to mechanical deformation or strain.

The present invention proposes a sensing device that electrostatically creates a surface pattern of temperature or strain gradients in an object.

The device has a polarized electret layer and a thermally and electrically conductive layer attached to one side of such layer.

The sensing device is adapted to be attached to the outer surface of an object, and the electret layer creates electrostatic charges on both planar surfaces of opposite polarity according to the temperature or strain gradient of the object.

In a preferred embodiment, the electret layer is made of a single sheet of polymeric material, which makes the sensing device relatively thin.

This means that the sensing device conforms closely to the surface of the object on which it is placed, without acting as a heat sink and appreciably changing the temperature of the object.
This makes it possible to obtain temperature or strain gradients in such objects.

In order to ensure high accuracy and a precise gradient profile, the electret layer can be formed by two thin plates held together in face-to-face contact with each other by means of a bonding layer.

A preferred embodiment of the invention will now be described in conjunction with the following figures.

A preferred embodiment of the two-dimensional sensing device of the present invention is shown at 1 in FIG.

The sensing device 1 is made of a relatively thin plate 2 of uniformly polarized electret material, to which a thin electrically conductive layer 3 is applied on one side.

The thin plate 2 is preferably made of a material that is both pyroelectric and piezoelectric, such as polyvinylidine fluoride or other such polymeric materials.

A polarized piezoelectric material is unique in that when subjected to some type of mechanical deformation or strain, it develops an electrostatic charge on its flat surface, and the charge on one side is opposite in polarity to the charge on the opposite side. It has properties.

Polarized pyroelectric materials exhibit similar charge generation when subjected to changes in ambient temperature.

In order to be used as a strain sensing device, the sensing device 1 is used in such a manner that the conductive layer 3 is temporarily fixed face-to-face on the flat surface of the object to be strained. .

For example, in FIG. 2, sensing device 1 is shown attached to a portion of the outer surface of flat rectangular plate 6. As shown in FIG.

The sensing device 1 can be mounted on the plate 6 by adhesive or other such temporary attachment means.

Once the sensing device 1 is securely attached to the plate 6, pressure is applied to the plate 6, placing the plate 6 under distorting conditions, changing the dimensions of the plate 6, or effecting a deformation.

Due to the face-to-face bond between the conductive layer 3 of the sensing device 1 and the outer surface of the plate 6, the lamina 2 has a dimensional change in the shape of the surface of the portion of the plate 6 on which the sensing device 1 is attached. Transforms to match.

The elastic constants of the sensing device 1 are selected so that even when the sensing device 1 is attached to the plate 6, there is little influence on changes in dimensions or deformation of the plate 6.

On the contrary, the sensing device 1 changes in accordance with the shape of the surface of the plate 60 and is distorted in exactly the same way as the plate 6 is distorted.

Such distortions of the sensing device 1 create electrostatic charges of opposite polarity on the surfaces of the thin plate 2 covered and uncovered by the conductive layer.

For example, when the plate 6 is bent, the surface of the thin plate 2 stretches, and electrostatic charges of opposite polarity accumulate on the surface of the thin plate 2 covered by the conductive layer and the surface not covered by the conductive layer.

Such an electrostatic charge is created in direct proportion to the degree of bending of the plate 6.

In this way, the shape of the strain on the plate 6 is represented by the change in the amount of electrostatic charge generated on the surface of the thin plate 2.

Since the lamina 2 is electrically non-conductive, the charge accumulated on the surface of the lamina 2 that is not covered by the conductive layer will accurately trace the strain gradient in the part of the plate 60 that the sensing device 1 is in contact with. Creates an electrostatic latent image.

If desired, the latent image on plate 2 can be developed without relaxing plate 6.

Development at this point involves neutralizing the conductive layer-covered surface of the thin plate 2 by electrically grounding the conductive layer 3;
electrostatic charge patterns on surfaces not covered by a conductive layer using an electrostatic field voltmeter connected to a two-dimensional visual reader such as an XY recorder, or using toner powder technology to develop an ordinary electrostatic charge image. It can be done.

In many cases, however, it may be difficult or inconvenient to develop the latent image on the piezoelectric sensing device 1 while the plate 6 remains in a distorted state.

However, a problem arises if the strain on the plate is relaxed at this point.

This is because the distorted graphic image is not permanent, and as soon as the pressure on the plate 6 is removed, the distorted graphic image becomes invisible.

It is therefore desirable to neutralize both sides of the plate 2 to remove any static charge thereon before releasing the pressure on the plate 6.

The electrostatic charge on the surface of layer 2 electrically grounds layer 3 and
Charges on surfaces not covered by a conductive layer can be removed by wiping such surfaces with a grounded pluton brush, or by using a grounded alpha particle static charge eliminator.
It can be neutralized.

Neutralizing the surface of the sheet 2 in this manner places the sheet 2 in the same electrostatic state as it was before the sheet 6 was placed under the strain conditions.

Therefore, there is no static charge on the surface of the thin plate 2, and the thin plate 2
The strain gradient corresponds to the strain gradient in the part of the plate 6 that the sensing device 1 is in contact with.

It follows from this that once the stress in the plate 6 is relieved, the plate 6 and the sensing device 1 return to their normal shape, with the result that an electrostatic charge on the surface of the lamina 2 accumulates due to such recovery.

An electrostatic latent image of the distortion pattern of the plate 6 of opposite polarity to the previous image will thus be formed on the surface of the thin plate 2 not covered by the conductive layer.

Subsequently, such latent image can be developed as previously discussed to provide a permanent image that can be transferred to a blank sheet of paper.

The sheet 2 can then be neutralized once more and reused.

In this way, the invention proposes a reusable strain sensing device.

Although this sensing device is relatively simple in its construction and operation, it provides a quick means of obtaining strain gradient profiles for objects of various shapes.

When applied to strain sensing, the sensing device 1 is not limited to being used for objects with only regular surfaces, but on the contrary, it can be used for multiple types of irregular surfaces.

However, in order to obtain an accurate and precise strain profile of an object with an irregular surface, it is necessary to obtain an accurate and precise strain pattern as a result of the strain when the sensing device 1 is not yet attached to the object or when it is removed from the object. The lamina 2 must be constructed in such a way that it virtually compensates for the electrostatic charge created by the piezoelectric effect.

The charge created by such a piezoelectric effect can be reduced by making the sensing medium of the sensing device 1 with a relatively stiff central portion and subjecting it to bending forces when the sensing medium is not attached to an object. By bending around such a central portion, it can be significantly reduced.

Such bending motion follows the general principle that when bending a laminated body having a relatively stiff central layer and two outer layers with the same modulus, it occurs around the stiffest central portion of the laminated body.

Now, referring to FIG. 4, it is easy to see that the two electret thin plates 2 are bonded together face-to-face with a bonding layer 10 which is preferably made of, for example, epoxy or a similar material. It can be manufactured and performs such bending operations.

Bond layer 10 serves as a relatively rigid central part around which the two sheets 2 bend when layer 9 is subjected to bending stresses.

As shown in FIG. 5, such bending causes compression of the upper plate 2 and extension of the lower plate 2, but the dimensions of the central plane of the central portion 10 remain virtually unchanged.

In the upper and lower plates 2, the electret plates 2 are polarized in the same direction, as further indicated by arrows 11 and 12, respectively.

In this way, compression of the upper plate 2 creates positive and negative charges on the upper and lower surfaces of the upper plate 2, respectively, and expansion of the lower plate 2 creates negative and positive charges on the upper and lower surfaces of the lower plate 2, respectively.

The amount of positive charge on the upper surface of the upper plate 2 is approximately the same magnitude as the positive charge on the lower surface of the lower plate 2.

There is therefore virtually no potential difference between the upper and lower surfaces of layer 9.

This means that the piezoelectrically created charges generated by dimensional changes or deformations when the sensing device 1 is not attached to an object have virtually no effect on creating an image of the strain gradient when the object is distorted. do not have.

As a result, substituting a layer 10 for the sensing device of a single lamina 2 results in a sensing device that obtains highly accurate profiles of strain gradients even for irregular objects.

In order to be used as a temperature sensing device, the sensing device 1 is constructed by temporarily applying a conductive layer 3 to the flat surface of an object having a temperature gradient to be sensed and imaged, such as the plate 6 shown in FIG. It is designed to be used by attaching the two sides together.

The sensing device 1 is highly flexible and can be easily attached to regularly or irregularly shaped objects.

The thin plate 2 and the conductive layer 3 are made thin compared to the dimensions of the plate 6 so that the ambient temperature of the thin plate 2 and the layer 3 acts as a heat sink and sufficiently affects the temperature of the plate 6. There is no such thing.

Conversely, due to the surface-to-surface contact between the conductive layer 3 and the plate 6, a situation arises in which the temperature of the laminate 2 is varied according to the temperature gradient of the part of the plate 6 that the sensing device 1 contacts.

Due to the temperature change of the lamella 2, electrostatic charges of opposite polarity are created on the surface of the lamella 2 covered by the conductive layer and on the surface not covered with the conductive layer.

Such an electrostatic charge is created in proportion to the pyroelectric constant of the plate 2 and in proportion to the degree to which the temperature of the plate 2 is changed by the temperature gradient of the plate 6.

In this way, temperature gradients in the plate 6 are indicated by changes in the formation of electrostatic charges on the flat surface of the plate 2.

Since the thin plate 2 is electrically non-conductive, the charge accumulated on the uncovered surface of the plate 2 forms a latent electrostatic charge image that accurately reflects the temperature gradient of the part of the plate 6 in contact with the sensing device 1. do.

If desired, the latent image on the pyroelectric layer can be developed without removing the sensing device 1 from the plate 6.

The dust image is created by electrically grounding the conductive layer 3, neutralizing the layer covered with the conductive layer of the thin plate 2, and detecting the electrostatic charge pattern remaining on the surface of the thin plate 2 not covered with the conductive layer. It can be accomplished by doing so.

Such a charge pattern can be detected as described above.

However, in many cases it is difficult or disadvantageous to develop the latent image on the sensing device 1 while the sensing device is attached to the plate 6.

However, if the sensing device 1 is removed from the plate 6 at this point, a problem arises.

This is because the sensing device 1 will soon return to its original ambient temperature and the electrostatic latent image will no longer be visible.

Therefore, before separating the sensing device 1 from the plate 6, it is desirable to remove the static charge on it and to completely neutralize both sides of the thin plate 2.

Neutralizing the surface of the lamella 2 places the lamina 2 in the same state of electrostatic charge as it was before it was changed from its original ambient temperature by contact with the plate 6.

At this point there is no electrostatic charge on the surface of the plate 2, and the temperature gradient of the plate 2 corresponds to the temperature gradient of the part of the plate 6 that the sensing device 1 is in contact with.

Once the sensing device 1 is removed from the plate 6, the thin plate 2
The temperature of the thin plate 2 returns to the original ambient temperature, and an electrostatic charge is generated on the surface of the thin plate 2 due to such temperature change.

An electrostatic latent image of the temperature gradient of the plate 6 with a polarity opposite to the previous image is thus formed on the surface of the thin plate 20.

Such a latent image can subsequently be developed as previously discussed to yield a permanent scum that can be easily transferred to a blank sheet of paper.

Both surfaces of the sheet 2 are then neutralized once more and prepared for reuse.

Thus, the present invention proposes a reusable temperature gradient sensing device.

Although this sensing device is relatively simple in structure and operation,
It provides a quick means of illustrating temperature gradients in various types of objects.

The sensing device 1 is not limited to use on objects with flat surfaces, but on the contrary can also be used on a wide variety of irregular surfaces.

However, in order to use the sensing device 1 to obtain highly accurate and precise temperature gradient profiles of objects with irregular surfaces, the pyroelectric thin plate 2 is, as previously described, made of two The use of sheets 2 bonded together should be made to compensate for electrostatic charges created by piezoelectric effects due to bending.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of the sensing device of the present invention having a thin electret layer whose lower surface is covered with a conductive layer, and FIG. 2 shows the sensing device of FIG. 1 mounted on a part of the outer surface of a rectangular plate. 3 is a side view showing the sensing device in FIG. 2 and the plate in a bent state; FIG. 4 is a side view of the sensing device shown in FIG. FIG. 5 is a perspective view of the layer; FIG. 5 is a side view of the layer of FIG. 4 in a bent state; 1, 9...sensing device, 2...electret layer, 3...
Conductive layer, 10...layer of bond.

Claims (1)

[Claims] 1. A gradient sensing device attached face-to-face to an object for detecting the temperature and strain gradient of the object,
a layer of polarized electret material and an electrically and thermally conductive layer mounted on a planar surface of one of said layers and adapted to rest face-to-face on at least a portion of said object. and wherein the electret layer creates on its surface an electrostatic charge pattern that varies according to the temperature or strain gradient present in the part of the object in contact with the conductive layer.