JPS6221953Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for measuring the temperature of an object, particularly an object moving in an industrial furnace.

In order to measure the surface temperature of a heated object that is stationary or running in an industrial furnace, a radiation thermometer or radiometer that can be measured without contact is convenient.
It is actually used in many fields. However, the methods commonly used in the past cannot necessarily be said to be appropriate methods. Therefore, one of the inventors of the present invention invented a method and apparatus for accurately measuring the surface temperature of an object by using a radiation thermometer and a reflecting mirror (Japanese Patent Application No. 55-94594). Although this method is very effective as a temperature measurement method, there are other problems in practical use. In other words, the atmosphere inside an industrial furnace is often contaminated with dust, etc., and this dust adheres to the transmission window installed on the furnace wall and changes the transmittance, causing measurement errors. In order to maintain the transmittance of the transmission window constant, the transmission window is purged with clean gas.
At this time, if the area of the transmission window is large, there is a possibility that purging may not be completed completely.

This invention attempts to solve this problem,
A radiation thermometer that receives radiant energy emitted from a temperature-measuring object, energy emitted from the temperature-measuring object, reflected by a concave mirror, and further reflected by the temperature-measuring object, and an opening/closing device provided on the concave mirror and its front surface. This radiation temperature measurement device is characterized in that the radiation thermometer and the concave mirror are provided in mirror-symmetrical positions with respect to the normal to the surface of the object to be measured. That is, the present invention attempts to narrow the optical path between the object to be measured and the reflecting mirror by using a concave mirror as the reflecting mirror in the prior invention, thereby reducing the area of the transmission window. The present invention will be explained below with reference to the drawings.

FIG. 1 shows the principle of the present invention, in which 10 is an object to be measured, 12 is a reflecting mirror, 14 is a rotating sector used as an opening/closing mechanism, and 16 is a radiometer. The temperature-measuring object 10 is, for example, a heating strip running in a furnace. In this case the reflector 12 and the rotating sector 14 are placed outside the furnace and the object 10 can be seen through the window 18.
I will take a look at it. The radiometer 16 may be placed either inside the furnace or outside the furnace. The reflecting mirror 12 and the radiometer 16 are arranged at the same angle θ on both sides of the normal line N-O to the object surface, and the reflecting mirror 12 is a plane mirror and is connected to a straight line connecting the point O and the reflecting mirror as shown in the figure. perpendicular to Therefore, there are the following radiant energy paths. That is,
The object 10 at temperature T emits radiation energy of εθ·Eb(T) in almost all directions, with emissivity in the θ direction being εθ. However, Eb(T) is the blackbody radiant energy at temperature T. Of this, the radiant energy directed towards the radiometer 16 enters the radiometer as it is,
Further, the radiant energy directed toward the reflecting mirror 12 is reflected by the reflecting mirror, specularly reflected at point O, and enters the radiometer 16. There is a rotating sector on the front side of the reflecting mirror 12, that is, on the object 10 side, and this rotating sector has a blade portion 14a whose surface is an absorbing surface as shown in FIG. 2a.
and a space 14b between them, or an absorbing surface 14a and a reflective surface 14c as shown in FIG. 2b,
Since it is rotated by a motor (not shown), when the blade portion 14a intersects the straight line 12-0, it absorbs the radiant energy from the object 10 and also blocks the radiant energy from the reflecting mirror 12. Furthermore, this reflector 1
2. Also, since the rotating sector 14 is kept sufficiently cold relative to the temperature of the object 10, the radiant energy emitted from it is negligible. When the sector 14 absorbs or blocks radiant energy, the only radiant energy that enters the radiometer 16 is that emitted by the object 10. In other words, there is a possibility that radiation from the reactor wall or the like is reflected by the object surface and enters the radiometer 16, but the possible specular reflection path is the sector 14.
Since the backlight noise is shielded by the radiometer 16,
It never enters. This point is an advantage of the radiation temperature measurement method that uses specular reflection. Note that this specular reflection becomes stronger as the angle θ becomes larger. Since the radiant energy entering the radiometer 16 is as described above, the following formula holds true.

E ₁ = τ・εθ・E _b (T) ...(1) E ₂ = τ・[εθ・E _b (T)+r _a・τ ²・εθ (1−εθ) (1−p) E _b
(T) ...(2) Here, E ₁ and E ₂ are the energy incident on the radiometer 16 with and without shielding with the sector 14, and τ is the radiation transmission through the window 18 provided in the filter wall in this example. r _a is the effective reflectance of the reflecting mirror 12, and p is the diffuse reflection coefficient of the object surface. From (1) and (2), E ₂ /E ₁ =1+ _ra・τ ² (1−εθ)(1−p) ∴εθ=1−1/ _ra τ ² (1−p)(E ₂ /E ₁
-1)...(3) ≡1-K(G-1)...(4) Also, from equation (1), E _b (T)=E ₁ /τ・εθ...(5) These (3) Or, from equations (4) and (5), the emissivity ε of the object
θ and temperature T are determined. In addition, in this temperature measurement, G=E ₂ /E ₁ was actually measured, and K=1/ _ra・τ ² (1-p
) is treated as a constant. r _a and τ can be maintained at constant values with sufficient maintenance and management. Since p is the diffuse reflection coefficient of the steel plate to be measured, it is troublesome to actually measure it each time, so a value determined by measurement in advance is used. Therefore, the condition for performing this temperature measurement method with few errors is that the actual value does not deviate greatly from the predicted value. If K is constant, εθ is the third
The relationship becomes a straight line as shown in the figure. In equation (2), the second term on the right side is a signal component that is detected by the radiometer when the radiant energy reflected by the reflecting mirror is reflected again on the surface of the temperature measuring object. In equation (3), the ratio of this signal component to the direct radiant energy from the temperature measuring object (E ₂ /E ₁
-1) to find the emissivity, and then use this emissivity to find the temperature using equation (5). That is, the second term on the right side of equation (2) is an important signal component for determining emissivity and temperature. In order to make this signal component a signal with a significant magnitude, it is necessary to reduce the diffuse reflection coefficient p, as seen from equation (2). The diffuse reflection coefficient is related to the solid angle at which the measuring point of the temperature measuring object looks into the reflecting mirror, and in order to reduce the diffuse reflection coefficient, it is necessary to increase the solid angle. Fig. 4 a, b shows the case where a plane mirror is used as a reflecting mirror, Fig. 5 a, b,
c is when a concave mirror is used as a reflecting mirror (this invention)
18 is a transparent window, 21 is a protective tube installed inside the transparent window, and 22 is a gas ejection hole provided in the protective tube. .

The present invention uses a concave mirror 1 as a reflecting mirror as described above.
2', as shown in Figure 5a,
Compared to the case of the plane mirror shown in FIG. 4a, the optical path for obtaining reflected energy of the same solid angle can be made smaller.

As mentioned above, the atmosphere inside general industrial furnaces is often contaminated to some extent. For example, when measuring the surface temperature of a steel plate in a continuous annealing furnace in the steel industry, radiant energy is transmitted as described above. Since the transmission window becomes contaminated, gas is blown onto the transmission window to remove the attached dust and other particles.In this case, in this case, the present invention uses a concave mirror to make the optical path small, making it easy to purge the transmission window with gas. The transmittance can always be maintained within a certain range, and temperature measurement can be performed accurately.

FIG. 5c shows a case in which dust prevention fins 23 are provided inside the protective tube 21, and in this case as well, the fins can be made large and gas purge can be omitted depending on the conditions.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the measurement principle of the present invention, Fig. 2 a and b are explanatory diagrams of the rotating sector, and Fig. 3 is an illustration of G and ε _p
4a, b and 5a, b, c are explanatory diagrams showing the optical path and the transmission window protection tube when a plane mirror is used as a reflecting mirror and when a concave mirror is used, and It is an explanatory view showing other examples of the present invention. In the drawing, 10 is the temperature measured object, 12' is a concave mirror, 1
4 is a rotating sector, 16 is a radiometer, and O-N is a normal line.

Claims (1)

[Scope of utility model registration request] Radiant energy emitted from the object to be measured,
The radiometer comprises a radiometer that receives energy emitted from the object to be measured, reflected by a concave mirror, and further reflected by the object to be measured, and an opening/closing mechanism provided on the concave mirror and the front surface thereof and the rear surface of the transmission window, and the radiometer and A radiation temperature measuring device characterized in that a concave mirror is provided at a mirror-symmetrical position with respect to the normal to the surface of an object to be temperature measured.