JPH01169330A - Optical fiber sensor - Google Patents

Abstract

PURPOSE:To make it possible to detect abnormal temperature in high voltage parts of electric equipment and the like, when the temperature of a material to be measured is increased, by changing a shape memory alloy member by its shape memory effect, and imparting mechanical deformation to optical fiber. CONSTITUTION:When the temperature of a material to be measured is increased and the temperature of a shape memory alloy material member 7 becomes higher than a specified temperature, the shape memory alloy member 7 becomes a coil shape formed by its shape memory effect. Therefore, a linking member 8 is moved away from a fixing member 4. The loop of optical fiber 2 in a case 5 becomes extremely small, and kink occurs. As a result, the transmission loss in the optical fiber transmission path 2 is extremely increased. Thus, the amount of the received light at a light receiving part 1b in a light detecting means 1 is decreased lower than the specified amount. Thus, the abnormal temperature increase in the material to be measured is readily detected.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an optical fiber sensor for detecting localized abnormal temperature rises in various electrical and mechanical equipment using optical fibers. be.

[Prior Art] and [Problems to be Solved by the Invention] Conventionally, in order to detect abnormal local temperature rises in various electrical and mechanical equipment, a large number of thermocouples have been installed at appropriate locations. However, when using a thermocouple, it is impossible to measure the temperature of the high voltage section.

Therefore, as a practical matter, the high-voltage parts of electrical equipment are not monitored, and it is only after an accident occurs that it becomes clear that there has been an abnormal temperature rise.

Another method is to detect abnormal temperature rises using optical fibers.

However, even with this method, in order to measure a large number of locations, a number of detection devices corresponding to the n1 fixed locations are required. In other words, since there is a one-to-one correspondence between the detection device and the sensor section, the equipment becomes large and the cost also increases.

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical fiber sensor that can detect localized abnormal temperature rises even in high-voltage parts of electrical equipment and is advantageous in terms of cost.

[Means for Solving the Problems] An optical fiber sensor according to the present invention includes a light detection means having a light emitting section and a light receiving section, an optical fiber transmission line, and a shape memory alloy member.

The optical fiber transmission line is arranged so as to pass over the object to be measured, and is configured to guide the optical signal emitted from the light emitting section of the photodetecting means to the light receiving section. In addition, the shape memory alloy member is placed in the middle of the optical fiber transmission line, and when the temperature of the wave measurement object rises above a predetermined temperature, the shape memory alloy member changes its shape due to the shape memory effect and causes mechanical deformation to the optical fiber. give.

[Function] When the temperature of the wave measurement object increases abnormally, the shape memory alloy member changes shape due to its shape memory effect, thereby imparting mechanical deformation to the optical fiber. Therefore, the transmission loss of the optical fiber transmission line increases, and the amount of light received by the light receiving section of the photodetecting means falls below a predetermined amount. In this way, an abnormal temperature rise of the wave measurement object can be detected based on a change in the amount of light received by the light receiving section.

[Embodiment] FIG. 1 schematically shows an embodiment of the present invention. The optical fiber sensor includes a light emitting section 1a and a light receiving section 1b.
The optical detecting means 1 has an optical fiber transmission line 2, and a plurality of sensor units 3a, 3b, . . . 3g arranged in series along the optical fiber transmission line 2.

The optical fiber transmission line 2 is arranged so as to pass over the object to be measured, and guides the optical signal emitted from the light emitting section 1a of the photodetecting means 1 to the light receiving section 1b. Each sensor section 3 is configured to mechanically deform the optical fiber 2 when the temperature of the wave measurement object rises above a predetermined temperature.

FIG. 2 is a diagram specifically showing the structure of one sensor section 3. As shown in FIG. The optical fiber 2 passes through a fixing member 4 fixed on a wave measurement object 9, and further draws a loop inside a case 5.

The fixing member 4 fixes the optical fiber 2 so that it does not shift. A shape memory alloy member 7 is located near the case 5.
is located. This shape memory alloy member 7 is held by a fixing member 6 whose one end is fixed onto the wave measurement object 9 . Further, the tip of the shape memory alloy member 7 and the optical fiber 2 are connected by a connecting member 8.

The shape memory alloy member 7 is adapted to return to its coiled form due to the shape memory effect when the temperature rises to exceed the transformation point. At room temperature, the shape memory alloy member 7 has a linear shape as shown in FIG.

When the wave measurement object 9 has a normal temperature, the shape memory alloy member 7 maintains a linear shape as shown in FIG. When the temperature of the wave measurement object rises abnormally and the temperature of the shape memory alloy member 7 becomes higher than a predetermined temperature, the shape memory alloy member 7 becomes coiled due to its shape memory effect, as shown in FIG. Becomes a form. Therefore, the connecting member 8 moves away from the fixed member 4, and the loop of the optical fiber 2 within the case 5 becomes extremely small, causing a kink. As a result, the transmission loss of the optical fiber transmission line 2 increases extremely. Depending on the conditions, the optical fiber 2 may break.

When the optical fiber is mechanically deformed in the sensor section 3 at the location described above and the transmission loss of the optical fiber transmission line 2 increases as a result, the light receiving section 1 of the photodetecting means 1
The amount of light received at point b becomes lower than the predetermined amount. In this way, an abnormal temperature rise of the wave measurement object is easily detected.

For example, in the system shown in FIG.
Suppose that the optical fiber 2 breaks at f. FIG. 4 shows the light emission and light reception levels in that case. When there is no abnormal temperature rise in the object to be measured, as shown by dotted line A,
A predetermined amount of received light is detected by the light receiving section 1b of the photodetecting means 1. However, if the optical fiber is broken at the sensor section 3f, the transmission level drops rapidly at that point, as shown by line B. Therefore, the light receiving section 1b of the light detecting means 1 does not detect light.

The light detection means 1 may include a sounding section that emits an alarm sound when the amount of light received by the light receiving section 1b falls below a predetermined amount.

As is clear from the above description, the shape memory alloy member is
The shape is such that it does not cause mechanical deformation to the optical fiber when the wave measurement target is normal, but it does not cause mechanical deformation to the optical fiber when the wave measurement target has an abnormal temperature rise. It becomes a shape. There are various possible ways of such a change in shape. Some examples are shown in FIGS. 5-9.

In the example shown in FIG. 5, the linear shape memory alloy member is deformed into a coil shape due to its shape memory effect. By utilizing such a shape change, tensile force can be applied to the optical fiber.

In the example shown in FIG. 6, the linear shape memory alloy member is deformed into a bent shape due to its shape memory effect. By utilizing such shape changes, bending force and tensile force can be applied to the optical fiber.

In the example shown in FIG. 7, the coiled shape memory alloy member is
Due to its shape memory effect, it changes into a linear shape. By utilizing such a shape change, tensile force can be applied to the optical fiber.

In the example shown in FIG. 8, the bent shape memory alloy member is deformed into a straight shape due to its shape memory effect. By utilizing this shape change, tensile force or bending force can be applied to the optical fiber.

In the example shown in FIG. 9, the coiled shape memory alloy member is
Due to its shape memory effect, it transforms into a coiled form with a shorter overall length. By utilizing such a shape change, tensile force can be applied to the optical fiber.

FIGS. 10 and 11 are diagrams showing other examples of structures that apply mechanical deformation to optical fibers. As shown in FIG. 10, the optical fiber 2 is arranged in a loop. The shape memory alloy member 7, which is linear at room temperature, has one end held by the fixing member 10.

The tip of the shape memory alloy member 7 is bent into a hook shape and engaged with the optical fiber 2. When the shape memory alloy member 7 rises above a predetermined temperature, it deforms into a coil shape due to the shape memory effect. The state is shown in FIG. Due to the shape change of the shape memory alloy member 7,
The loop of the optical fiber 2 approaches the fixing member 10 and becomes elongated, resulting in increased transmission loss.

The shape memory effect of the shape memory alloy member is expressed at a certain temperature. That is, when the shape memory alloy member is in direct contact with the wave measurement object, the shape memory alloy member deforms into a predetermined shape when the wave measurement object rises to the above-described certain temperature.

It is also possible to provide a difference between the detected temperature of the wave measurement object and the temperature at which the shape memory effect of the shape memory alloy member appears.

For example, a desired temperature difference can be obtained by interposing a thermal resistor between the shape memory alloy member and the object to be measured. Similarly, the shape memory alloy member may be wrapped with insulating tape, thereby increasing thermal resistance. Alternatively, instead of the insulating tape, a shape memory alloy member may be placed inside a metal vibrator or plastic pipe to increase the thermal resistance between the shape memory alloy member and the object to be measured.

[Effects of the Invention] As described above, according to the present invention, an abnormal temperature rise at a measurement point is detected using an optical fiber transmission line, and therefore it is also possible to detect an abnormal temperature at a high voltage section of electrical equipment. becomes. Also, as explained using Figure 1,
Since a large number of sensor units can be arranged in series along the optical fiber transmission path, the overall configuration of the device can be simplified.
Cost reduction can be achieved.

[Brief explanation of the drawing]

FIG. 1 is a diagram schematically showing an embodiment of the present invention. FIG. 2 is a diagram showing an example of a structure for applying mechanical deformation to an optical fiber. FIG. 3 is a diagram showing a state in which the shape memory alloy member shown in FIG. 2 is deformed due to the shape memory effect, thereby imparting mechanical deformation to the optical fiber. FIG. 4 is a diagram showing light emission and light reception levels. FIG. 5, FIG. 6, FIG. 7, FIG. 8, and FIG. 9 are diagrams showing examples of shape deformation due to the shape memory effect of the shape memory alloy member, respectively. FIG. 10 is a diagram showing another example of a structure for applying mechanical deformation to an optical fiber. Figure 11 shows the 10th
FIG. 3 is a diagram showing a state in which the shape memory alloy member 7 shown in the figure changes shape and thereby mechanically deforms the optical fiber. In the figure, 1 is a light detection means, 1a is a light emitting part, 1b is a light receiving part, 2 is an optical fiber transmission line, 3 is a sensor part, 7 is a shape memory alloy member, and 9 is a wave measurement object. Note that in each figure, the same reference numerals indicate the same or equivalent elements. Figure 4 Figure 6 □ → Yu〉

Claims (4)

[Claims] (1) A light detection means having a light emitting part and a light receiving part, and an optical fiber arranged to pass over the object to be measured and guiding the optical signal emitted from the light emitting part to the light receiving part. a transmission path, and a shape that is placed in the middle of the optical fiber transmission path and changes its shape due to a shape memory effect to mechanically deform the optical fiber when the temperature of the object to be measured rises above a predetermined temperature. An optical fiber sensor comprising: a memory alloy member; (2) between the shape memory alloy member and the wave measurement object;
The optical fiber sensor according to claim 1, wherein a thermal resistor is arranged. (3) The light detection means has a sounding section that emits an alarm sound when the amount of light received by the light receiving section falls below a predetermined amount.
An optical fiber sensor according to claim 1 or 2. (4) The optical fiber sensor according to any one of claims 1 to 3, wherein a plurality of the shape memory alloy members are arranged in series along the optical fiber transmission path.