JP3291781B2 - Method and apparatus for measuring temperature of steel sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for measuring the emissivity and temperature of a steel sheet to be measured simultaneously without contact.

[0002]

2. Description of the Related Art In general, a radiation thermometer is used to measure the surface temperature of a steel sheet in a non-contact manner. This radiation thermometer detects radiant energy radiated from an object to be measured and converts the radiant energy into a temperature. In the conversion, it is necessary to set an emissivity correctly. Therefore, when measuring the temperature of a steel sheet with a radiation thermometer, it is extremely important to determine the emissivity of the steel sheet surface. Conventionally, as a radiation thermometer considering the emissivity, for example, Japanese Patent Laid-Open No. 62-28
No. 7124, for example.

[0003] This radiation thermometer emits light radiation energy from a radiation source to a measurement object in three different states (shutter fully open, half open, fully closed).
The radiant energy from the measurement target and the radiant energy from the radiation source are reflected by the measurement target, and the sum of the energies is measured. Then, the difference between the contribution ratios of the radiation sources is calculated from the two outputs, and the ratio of the contribution ratio is calculated from the difference between the contribution ratios based on the relationship between the difference between the contribution ratios and the ratio obtained in advance. The reflectance of the measurement object in consideration of the diffuse reflection is determined from the ratio of the rates, the emissivity is determined from the reflectance, and the temperature of the measurement object is determined using this.

[0004]

However, this radiation thermometer has the following disadvantages.

First, in this radiation thermometer, in order to accurately determine the temperature of a measurement object whose emissivity is unknown, the radiation energy from the auxiliary heat source diffusely reflects on the surface of the measurement object when measuring the emissivity of the measurement object. The state of the diffuse reflection is changed in two steps of the area of the heat source, and the ratio of the contribution ratio of the radiant energy is obtained from the change of the output of the radiation thermometer at that time,
The ratio of the contribution ratio is determined from the relationship between the difference and the ratio of the contribution ratio determined in advance, and the reflectance of the measurement object is determined from the ratio of the contribution ratios. At this time, it is assumed that the relationship between the difference between the contribution ratios and the ratio is established in advance in the offline measurement of actual use, but the surface properties are not necessarily the same because the online and offline environments are different. There is no guarantee that it will. Therefore, in such a conventional radiation thermometer, it is premised that the above-mentioned relationship is established, and if this relationship is not established, it cannot be applied.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and its object is to control the temperature of a steel sheet without being affected by changes in the surface properties of the steel sheet, ie, the emissivity of the steel sheet and the diffuse reflection state. It is an object of the present invention to provide a method and an apparatus for measuring the temperature of a steel plate that can be measured with high accuracy.

[0007]

In order to achieve the above object, the present invention radiates radiant energy from a radiant heat source having a known emissivity and temperature to a range including a plurality of points on the surface of a steel plate to be measured. The radiant energy reflected from the steel plate surface and the radiant energy from the steel plate to be measured are measured at a plurality of points on the surface while scanning the detection surface thereof at a predetermined angle with respect to the steel plate surface by a scanning radiation thermometer. The reflected energy obtained from the difference between the radiant energy measured by the scanning radiation thermometer and the radiant energy from the steel plate to be measured and the radiation heat source, the scanning radiation thermometer and the positional relationship of the measurement object on the steel sheet surface The diffuse reflection state of the radiant energy is obtained, and the angle component of the diffuse reflection is obtained from the diffuse reflection state and the radiant energy of the radiant heat source obtained from the emissivity and temperature of the radiant heat source. Together determine the reflectivity of the including steel sheet surface, determine the emissivity of the measured steel plate of this reflectance based, and requests the temperature of the measured steel plate from the emissivity.

[0008] Further, it is installed at a predetermined height position above the steel plate to be measured, and is located on the surface of the steel plate to be measured .
A radiant heat source of a known emissivity and temperature that radiates radiant energy to a range including a plurality of points, and a detection surface can scan a predetermined angle with respect to the steel sheet surface at a preset height position above the steel sheet to be measured. The radiant energy from the steel plate to be measured and the radiant energy from the radiant heat source reflected on the steel plate surface according to the scanning angle are copied to the inspection surface.
A scanning radiation thermometer for measuring a number of points, an output signal measured by the scanning radiation thermometer is input, and the radiation energy measured by the scanning radiation thermometer and the radiation energy from the steel plate to be measured are input. A first calculating means for obtaining a diffuse reflection state of radiant energy on the surface of the steel sheet from the reflected energy obtained from the difference from the radiant heat source, the scanning radiation thermometer, and the positional relationship of the steel plate to be measured; and From the radiant energy of the radiant heat source obtained from the emissivity and the temperature and the diffuse reflection state obtained by the first calculating means, the reflectivity of the steel sheet surface including the angle component of the diffuse reflection is obtained. Second estimating means for obtaining the emissivity of the steel plate to be measured based on the above, and obtaining the temperature of the steel plate to be measured from the emissivity.

[0009]

In such a method and apparatus for measuring the temperature of a steel sheet, the pattern of the radiant energy from the radiant heat source installed above the steel sheet to be measured and the pattern of the radiant energy from the steel sheet to be measured are measured above the steel sheet to be measured. The measurement is performed while scanning the detection surface at a predetermined angle by the installed scanning radiation thermometer, and the reflected energy and the radiation heat source obtained from the difference between the measured value and the radiation energy from the steel plate to be measured, the scanning radiation thermometer, The diffuse reflection state of the radiant energy on the steel sheet surface is determined from the positional relationship of the steel sheet to be measured, and the reflectance of the steel sheet surface including the angular component of the diffuse reflection is further determined. Since the emissivity is determined, it is possible to accurately measure the surface temperature of the steel sheet to be measured without being affected by changes in the emissivity of the steel sheet surface and changes in the diffusion state by using this emissivity. That.

[0010]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows an example of a configuration of a steel sheet temperature measuring apparatus according to the present invention. In FIG. 1, 1 is a steel plate to be measured, 2 is a scanning radiation thermometer (one-dimensional scanning radiation detector) installed at a set position above the steel plate 1, 3
Is a radiant heat source having a known emissivity installed on a scanning surface of the scanning radiation thermometer 2 and at a set position above the steel plate 1. Reference numeral 4 denotes a shutter device provided in front of the radiant heat source 3, and 5 denotes a temperature control device having a temperature measuring function for measuring the temperature of the radiant heat source 3 and keeping the radiant heat source 3 at an arbitrary constant temperature. is there.

On the other hand, reference numeral 6 denotes a heat source emissivity ε, and a scan output waveform (measured luminance output) E from the scanning radiation thermometer 2, a temperature T of the radiation heat source 3, and a shutter opening / closing signal S of the shutter device 4 are provided. The arithmetic unit 6 receives the scan output waveform E, the heat source temperature T,
Emissivity ε and steel plate 1, radiant heat source 3, scanning radiation thermometer 2
, The diffuse reflection state, reflectance, emissivity, and temperature of the radiant energy on the surface of the steel sheet are calculated from the positional relationship. Next, the operation of the steel sheet temperature measuring device configured as described above will be described.

Now, assuming that radiant energy is radiated from the radiant heat source 3 onto the steel plate 1 and that the detection surface of the scanning radiation thermometer 2 is scanned at a predetermined angle with respect to the surface of the steel plate 1, this scanning is performed. Radiant energy from the steel plate 1 at that time by the radiant thermometer 2 and a radiant heat source 3 reflected on the steel plate surface
The energy of the sum of the radiant energies from the above is measured, and the scan output waveform is input to the arithmetic unit 6.

In order to obtain the reflected energy from the sum energy, the arithmetic unit 6 determines the difference between the measured values when the shutter device 4 provided in front of the radiant heat source 3 is opened and closed. In this case, as the radiant energy from the radiant heat source 3, the specular reflection direction and the reflection (diffuse reflection) energy deviating from the specular reflection direction are measured by the scanning angle (measurement angle) of the scanning radiation thermometer 2. Since the reflected energy becomes very small and the measured value at the scanning end that can be ignored is only the light emitted from the steel plate, this radiant energy may be subtracted from the measured value.

Next, in the arithmetic unit 6, based on the reflected energy and the scanning angle of the scanning radiation thermometer 2, the scanning angle is determined from the positional relationship among the radiation heat source 3, the scanning radiation thermometer 2, and the steel plate 1. The diffusion angle of the reflected energy is determined, and the diffuse reflection state of the reflected energy is determined from the diffusion angle and the reflected energy as follows.

That is, focusing on the property of diffuse reflection, of the radiant energy incident on the scanning radiation thermometer 2 that scans the steel plate, the diffuse reflection component of the radiation emitted from the radiation heat source 3 is
As shown in FIG. 2, an angle component of diffuse reflection is obtained by scanning the detection surface of the scanning radiation thermometer 2 at a predetermined angle with respect to the steel plate surface. Since the specular component is obtained at the position of the maximum value of the output of the scanning radiation thermometer 2, the scanning thermometer 2 is scanned from the point toward the scanning end to obtain the diffuse reflection. Can be measured. When the relationship between the scanning angle and the radiant energy is obtained by the arithmetic unit 6 in this manner, the two-dimensional diffusion as shown in FIG. Find the reflection state. Furthermore, the three-dimensional diffuse reflection state can be obtained by rotating the two-dimensional diffuse reflection state by 360 ° about the specular reflection axis, that is, by integrating the circumference.

The scanning thermometer 2 is thus operated by the arithmetic unit 6.
When the diffuse reflection components diffused in all three-dimensional directions are comprehensively determined from the output of the radiant heat source 3, the arithmetic unit 6 determines the radiant energy from the radiant heat source 3 from the emissivity ε of the radiant heat source 3 and the temperature T. The reflectance of the steel sheet 1 is obtained by dividing the above-mentioned reflection energy in the diffuse reflection state by the radiation energy of No. 3. Then, based on the reflectance of the steel sheet 1,
According to Kirchhoff's law, {emissivity} = 1− {reflectance}

The temperature of the steel sheet can be accurately obtained from the emissivity and the radiation energy of the steel sheet 1 when the radiation energy of the radiation heat source 3 is cut off by the shutter device 4 installed in front of the radiation heat source.

As described above, in the present embodiment, the radiant energy is radiated from the radiant heat source 3 having the known emissivity and temperature to the steel sheet,
The radiant energy reflected on the surface of the steel plate is measured together with the radiant energy from the steel plate by scanning the detection surface by a scanning radiation thermometer 2 at a predetermined angle, and the measurement signal is input to the arithmetic unit 6 and diffused in all directions. By comprehensively calculating the diffuse reflection component, the reflectivity of the steel sheet is obtained from the radiant energy from the radiant heat source 3 and the radiant energy reflected on the surface of the steel sheet, and the emissivity is obtained from the reflectivity. The temperature of the steel sheet surface can be accurately measured without being affected by the change in the emissivity and the change in the diffusion state. In particular, the alloying temperature control of an alloyed hot-dip galvanizing line in which alloying is performed by heating after hot-dip galvanizing (because the emissivity and diffusion state of the surface change significantly during alloying, accurate temperature measurement is not possible with the conventional temperature measurement method. Measurement cannot be performed), and a great effect can be obtained for improvement of product quality. Here, a result of an off-line test using the steel sheet temperature measuring device according to the present embodiment will be described.

As shown in FIG. 4, a spherical heat source was used as the heat source 3, which was installed at a position of 200 mm from the steel plate 1, the temperature was controlled to be constant, the temperature was actually measured, and used for calculating the radiation amount. The scanning thermometer 2 used had a scanning angle of 50 ° and was installed at a position of 600 mm from the steel plate 1 so that the measured regular reflection component was incident on the steel plate 1 at an angle of 20 °. Further, the steel sheet 1 was heated to 200 ° C to 300 ° C by a heater. On the other hand, the reflected energy was defined as the reflected energy by taking the difference between the measurement pattern when the heat source was installed and the measurement pattern when the heat source was removed.

Under these conditions, the measured values of the reflectance of aluminum, CGL and tinplate and the true reflectance of the steel sheet 1 are shown in a graph, and the results shown in FIG. 5 are obtained. . The above graph shows the integrated value of reflected light measured by the device of the present embodiment / radiated light from the heat source.

The values and the true reflectance of aluminum (diffuse reflectivity), CGL (strong diffusivity), and tinplate (weak diffusivity) are normalized to 1 at the time of aluminum (calculation of the ratio).
And compared. It can be said that the fact that the values become equal by the operation of normalization can be actually measured by calibration using a calibration plate with a known reflectance.

[0023]

As described above, according to the present invention, the reflectivity of the steel sheet including the angle component of the diffuse reflection is obtained, and the emissivity is obtained from the reflectivity. It is possible to provide a method and an apparatus for measuring the temperature of a steel sheet which can measure the temperature of the steel sheet with high accuracy without being influenced by the change of the temperature and the change of the diffusion state.

[Brief description of the drawings]

FIG. 1 is a structural explanatory view showing one embodiment of a steel sheet temperature measuring apparatus according to the present invention.

FIG. 2 is an explanatory diagram of a method for measuring an angle component of diffuse reflection by scanning with a scanning radiation thermometer in the embodiment.

FIG. 3 is a conceptual diagram for explaining a state of diffuse reflection on a steel sheet surface in the embodiment.

FIG. 4 is a diagram showing an outline when the present invention is tested using a test apparatus.

FIG. 5 is a diagram showing a test result by the test apparatus as a graph.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Steel plate, 2 ... Scanning radiation thermometer, 3 ... Radiant heat source, 4 ... Shutter device, 5 ... Heat source temperature control device, 6
…… A computing device.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01J 5/00-5/62

Claims (5)

(57) [Claims] 1. A radiant heat source having a known emissivity and temperature emits radiant energy to a range including a plurality of points on the surface of a steel sheet to be measured, and the radiant energy reflected on the steel sheet surface and the radiant energy from the steel sheet to be measured. The radiant energy is measured at a plurality of points on the inspection surface by scanning the detection surface with a scanning radiation thermometer at a predetermined angle with respect to the steel plate surface, and the radiant energy measured by the scanning radiation thermometer and the radiation intensity are measured. Determine the diffuse reflection state of the radiant energy on the steel sheet surface from the reflected energy and the radiant heat source obtained from the difference with the radiant energy from the measurement steel sheet, and the positional relationship of the scanning radiation thermometer and the measurement target. From the emissivity of the radiant heat source and the radiant energy of the radiant heat source obtained from the temperature, the reflectivity of the steel sheet surface including the angle component of diffuse reflection is obtained. A method for measuring the temperature of a steel sheet, wherein the emissivity of the steel sheet to be measured is obtained based on the emissivity, and the temperature of the steel sheet to be measured is obtained from the emissivity. 2. A first step of radiating radiant energy from a radiant heat source to a range including a plurality of points on a surface of the steel plate to be measured, and a plurality of points on the surface of the steel plate to be measured are scanned by a scanning radiation thermometer. A second step of measuring while scanning; a measurement result in the second step; each scanning angle of the scanning radiation thermometer; and positions of the radiation heat source, the scanning radiation thermometer, and the steel plate to be measured. Based on the relationship
A third step of obtaining a diffuse reflection state on the steel sheet surface; and, based on radiant energy from the radiant heat source and the diffuse reflection state, the measured steel sheet corresponding to the reflectance of the steel sheet surface including diffuse reflection. A method for measuring the temperature of a steel sheet, comprising: a fourth step of determining a reflectance; and a fifth step of determining a temperature of the measured steel sheet based on the reflectance of the measured steel sheet. 3. The steel plate according to claim 1, wherein the measurement by the scanning radiation thermometer is performed when a shutter device provided in front of the radiation heat source is opened and closed. Temperature measurement method. 4. A radiant heat source having a known emissivity and temperature installed at a predetermined height position above a steel plate to be measured and radiating radiant energy to a range including a plurality of points on the surface of the steel plate to be measured. A detection surface is installed at a predetermined height position above the steel plate to be measured so as to scan the steel plate surface at a predetermined angle, and radiant energy from the steel plate to be measured and a steel plate surface according to a scanning angle. A scanning radiation thermometer for measuring radiant energy from the radiation heat source reflected at a plurality of points on the scanning surface, and an output signal measured by the scanning radiation thermometer; The reflected energy obtained from the difference between the radiant energy measured by the thermometer and the radiant energy from the steel plate to be measured and the radiant heat source, the scanning radiation thermometer, the positional relationship between the steel plate to be measured and the steel First calculating means for obtaining a diffuse reflection state of radiant energy on the plate surface; radiant energy of the radiant heat source obtained from the emissivity and temperature of the radiant heat source; and diffuse reflection obtained by the first calculating means. From the state and the reflectance of the steel sheet surface including the angle component of the diffuse reflection is determined, the emissivity of the measured steel sheet is determined based on the reflectance, and the temperature of the measured steel sheet is determined from the emissivity. 2
A temperature measuring device for a steel sheet, comprising: 5. A radiant heat source that radiates radiant energy to a range including a plurality of points on a surface of a steel sheet to be measured, a scanning radiation thermometer that measures while scanning a plurality of points on the surface of the steel sheet to be measured. The measurement results of the scanning radiation thermometer, the respective scanning angles of the scanning radiation thermometer, the positional relationship between the radiation heat source, the scanning radiation thermometer and the steel plate to be measured, and the radiation from the radiation heat source Calculating means for calculating the temperature of the steel sheet to be measured in consideration of the reflectance of the steel sheet surface including the diffuse reflection based on the energy, and a calculating means for calculating the temperature of the steel sheet.