JPH08101079A - Temperature measuring method for traveling object - Google Patents

Abstract

PURPOSE: To accurately measure the temperature of a traveling object of which temperature is relatively low without causing any disturbance in the operation by bringing a temperature measuring element into contact with the object for a short time and measuring the temperature thereof. CONSTITUTION: A temperature detection head comprising a temperature measuring element 1 and a lining member 2 having thermal capacity higher than of the element 1 is brought into contact with a traveling object 3 while following up the traveling object 3. The temperature θ1 (t) of the measuring element 1, the initial value T0 thereof, and predetermined coefficient K and α satisfy a following relationship; T=T0 +(1/K)[θ1 (t)-T0 ]/[1-exp(αt)]. The temperature T of the object 3 is determined using the expression. t represents the time elapsed after starting a measurement.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring the temperature of a running object such as a metal belt while running.

[0002]

2. Description of the Related Art There are the following methods for measuring the temperature of a moving object.

(1) Radiation temperature measurement method (prior art) Radiant heat (mainly electromagnetic waves in the infrared region) radiated by a moving object is measured, and data processing such as emissivity correction is performed to measure the temperature of the object. To do. This method is characterized in that the temperature of an object can be measured without contact.

(2) Contact temperature measuring method (prior art) A temperature measuring resistor or a thermocouple is brought into contact with a moving object to directly measure the temperature of the object. This method is relatively simple and enables highly accurate temperature measurement depending on the measurement target.

[0005]

However, the prior art has the following problems. First, there is a problem that the emissivity changes depending on the state of the surface of the object, which makes it difficult to correct the temperature.

Next, the disturbance due to the background light, that is, the error in the temperature measurement due to the light incident on the thermometer from the background portion of the object cannot be ignored. Further, the disturbance due to the reflected light on the object surface also causes a measurement error. As a countermeasure against these, it is necessary to sufficiently shield the surroundings of the object, but this may be difficult in terms of equipment.

Further, there is a problem that the detection sensitivity is poor for an object having a relatively low temperature because the radiation heat itself is weak.

In the prior art, the simplest method is to temporarily stop the traveling of the object and bring it into contact with the temperature sensor, but this may impair the stability of the operation or reduce the efficiency. Further, by stopping, there is a possibility that a temperature different from the running state may be measured.

In order to prevent this, it is possible to use a mechanism in which the temperature sensor follows an object and measure the temperature in a contact state for a certain period of time. However, the response speed of the temperature sensor generally takes about several seconds until it shows a temperature almost close to the temperature of the measurement target. In a normal production line where the moving speed of goods is a few m / s, the temperature sensor needs to follow a considerably long distance, which is not practical as it is.

Further, when the shape of the object is a continuous object such as a band or a strip, the temperature can be continuously measured by bringing the sensor into contact with the object while traveling. However, in this case, there is a risk of causing surface defects such as scratches due to friction with the surface of the object. Wear is unavoidable for the sensor as well, and the sensor may be damaged due to a defective shape of the steel plate.

The present invention solves these problems and provides a method capable of accurately measuring the temperature of a running object without disturbing operation even at a relatively low temperature.

[0012]

According to a first aspect of the present invention, a temperature measuring head having a temperature measuring element and a backing material having a larger heat capacity than the temperature measuring head is brought into contact with a running measurement object to make contact with the temperature measuring element. Temperature θ ₁ (t) and its initial value T ₀ ,
In addition, a temperature measuring method for a moving object is characterized in that the temperature T of a measurement target is estimated and calculated using the following equations represented by the coefficients K and α which are obtained in advance.

T = T ₀ + (1 / K) [θ ₁ (t) -T ₀ ] / [1-exp (αt)] In the invention of claim 2, the temperature of the object to be measured is estimated as follows. Using the initial value T ₀ of the temperature of the measuring element, the values T ₁ , T ₂ , and T ₃ sampled sequentially at equal time intervals, and the following equation represented by the coefficient K obtained in advance, The method for measuring the temperature of a moving object according to claim 1, wherein T is estimated and calculated. T = T ₀ + (1 / K) [(T ₂ ² -T ₁ T ₃ ) / (2T ₂ -T ₁ -T ₃ ) -T ₀ ]

[0014]

FIG. 1 is a schematic diagram (a) of a temperature detecting head and a block diagram (b) showing the mechanism of heat transfer. Figure 1a
In the above, 1 is a temperature measuring element, 2 is a backing material, and 3 is an object to be measured. In FIG. 1b, T is the temperature of the object 3 to be measured, t is time, θ ₁ , c ₁ and h ₁ are the temperature and heat capacity of the temperature measuring element 1, the heat transfer coefficient with the object to be measured, θ ₂ , c ₂ and h.
₂ indicates the temperature and heat capacity of the backing material 2, the heat transfer coefficient with the object to be measured, and h indicates the heat transfer coefficient between the temperature measuring element 1 and the backing material 2, respectively.

The behavior of these temperatures is described by the following differential equation. c ₁・ d θ ₁ / dt = -h ₁ (θ ₁ -T) -h (θ ₁ -θ ₂ ) (1) c ₂・ d θ ₂ / dt = -h ₂ (θ ₂ -T) -h (θ ₂ -θ ₁ ) (2) Solve this using the Laplace transform. The above formula is expressed as follows (operator: s).

(C ₁ s + h ₁ + h) (θ ₁ -T) = h (θ ₂ -T) (3) (c ₂ s + h ₂ + h) (θ ₂ -T) = h (θ ₁ -T) (4) Eliminating (θ ₂ -T) from these equations, [(c ₂ s + h ₂ + h) (c ₁ s + h ₁ + h) -h ² ] (θ _1- T) = 0 (5). If the initial conditions are θ ₁ (0) = T ₀ and θ ₂ (0) = T ₀ , the solution of Equation (5) is θ ₁ (t) -T = (T ₀ -T) [K exp ( αt) + (1-K) exp (βt)] (6) is obtained. However, K is a coefficient and α and β are the roots of the characteristic equation (variable s) shown below. At the start of measurement
Let t = 0.

(C ₂ s + h ₂ + h) (c ₁ s + h ₁ + h) -h ² = 0 (7) Here, the sizes of α and β are estimated. The heat transfer coefficient h between the temperature measuring element and the backing material is smaller than the heat transfer coefficients h ₁ and h ₂ between the measurement target and the temperature measuring element or the backing material, so if neglected, the term h ^{2 in} Eq. (7) can be ignored. Can be ignored, so α, β
Becomes-(h ₁ + h) / c ₁ and-(h ₂ + h) / c ₂ . Here, α =-(h ₁ + h) / c ₁ and β =-(h ₂ + h) / c ₂ .

The heat capacity c ₁ of the temperature measuring element is much smaller than the heat capacity c _{2 of the} backing material, and the heat transfer coefficient h ₁ of the measuring object and the temperature measuring element is much larger than the heat transfer coefficient h ₂ of the measuring object and the backing material. Since α is larger than β, the absolute value of α is much larger than β, which is expressed as | α | >> | β |.

Next, by transposing T in equation (6) and transforming the right side, equation (6) yields θ ₁ (t) = T ₀ + (TT ₀ ) × [K (1-exp (αt)) + (1-K) (1-exp (βt))] (8). Looking at this equation, the response characteristic of the temperature θ ₁ (t) of the temperature measuring element is a composite system consisting of two first-order lag systems with a short time constant −1 / α and a long time constant −1 / β. You can see that

In the equation (8), the absolute value of βt becomes much smaller than 1 in the region where the absolute value of αt is small (around 1 or less), and exp (βt) becomes almost equal to 1. Therefore,
The second term in [] on the right-hand side of Eq. (8) is almost 0, so if we neglect this, Eq. (8) approximates θ ₁ (t) = T ₀ + in the region where the absolute value of αt is small. It can be expressed as (TT ₀ ) K [1-exp (αt)] (9). This formula is a formula in which the indicated temperature of the temperature measuring element is approximated by an exponential function.

From the equation (9), the temperature T of the object to be measured is expressed as follows by the indicated temperature θ ₁ (t) of the temperature measuring element. T = T ₀ + (1 / K) [θ ₁ (t) -T ₀ ] / [1-exp (αt)] (10) The temperature T of the measurement object can be calculated by this formula. Here, the values of the coefficients K and α are obtained by multiple regression analysis or the like by an experiment.

Further, since it is troublesome to actually obtain the value of α in this equation, as a result of various studies, it has been found that it is not necessary to obtain the value of α by the following. To do this, at constant sampling intervals, θ at times t ₁ , t ₂ , and t ₃
Measure the value of ₁ (t). Given that these values are T ₁ , T ₂ and T ₃ , it was found that there is the following relationship between these values and the temperature T of the measurement object.

First, since the times t ₁ , t ₂ and t ₃ are evenly spaced, exp [α (t ₃ -t ₂ )] = exp [α (t ₂ -t ₁ )]. If we write this in fractions, we get exp (αt ₃ ) / exp (αt ₂ ) = exp (αt ₂ ) / exp (αt ₁ ), and if we transpose, exp (αt ₂ ) ² = exp (αt ₁ ) exp (αt ₃ ) It becomes (11).

Next, the equation (10) is transformed into exp (αt) = 1- [θ ₁ (t) -T ₀ ] / [(TT ₀ ) K] (10 '). Substituting the value of θ ₁ (t) in equation (10 ′) with the values T ₁ , T ₂ , and T ₃ at times t ₁ , t ₂ , and t ₃ and substituting into equation (11), equation (11) Is [1- (T ₂ -T ₀ ) / K (TT ₀ )] ² = [1- (T ₁ -T ₀ ) / K (TT ₀ )] × [1- (T ₃ -T ₀ ) / K (TT ₀ )] becomes (11 '). Expanding the equation and multiplying both sides by K (TT ₀ ) ² and rearranging, 2K (TT ₀ ) (T ₂ -T ₀ ) + (T ₂ -T ₀ ) ² = K (TT ₀ ) [(T ₁ If _{-T 0) + (T 3 -T} 0)] + (T 1 -T 0) (T 3 -T 0) transposed to solve for K (TT _{0) to, K (TT 0) = [} (T 2 -T ₀ ) ^2- (T ₁ -T ₀ ) (T ₃ -T ₀ )] / [2 (T ₂ -T ₀ )-(T ₁ -T ₀ )-(T ₃ -T ₀ )] = [ T ₂ ² -T ₁ T ₃ -2T ₂ T ₀ + (T ₁ + T ₃ ) T ₀ ] / [2T ₂ -T ₁ -T ₃ ] = [T ₂ ² -T ₁ T ₃ ] / [2T ₂ -T ₁ -T ₃ ] -T ₀ Furthermore, by transposing and collecting T and T ₀ on the left side, K (TT ₀ ) + T ₀ = (T ₂ ² -T ₁ T ₃ ) / (2T ₂ -T ₁ -T ₃ ) (12). The temperature T to be measured is expressed as follows by solving the equation (12) for T. T = T ₀ + (1 / K) [(T ₂ ² -T ₁ T ₃ ) / (2T ₂ -T ₁ -T ₃ ) -T ₀ ] (13) From this, the initial value of the temperature of the measuring device T If the values of ₀ and K are known, the temperature T of the measurement target can be obtained from the sampling values T ₁ , T ₂ , and T ₃ . Here, the value of K may be obtained by calculation, but in general, it may be determined so as to match the measured value of the temperature of the measurement target for the actual machine.

[0025]

FIG. 2 shows an example of a temperature detecting device. In the figure, 1
Is a thermistor element used as a temperature measuring element, 2 is a backing material, 11 is a lead wire, 24 is a holder, 25 is a weight, 10
Is a temperature detection head, 20 is a temperature detector, and 30 is an arithmetic unit. Here, the weight 25 is used to secure a stable contact pressure with the running plate.
Various cylinders and the like can be appropriately used. The arithmetic unit is composed of an ordinary personal computer and an interface.

The temperature output detected by the thermistor element 1 is converted into a temperature by the temperature detector 20 and becomes a temperature signal, which is sent to the arithmetic unit 30. In the arithmetic unit 30, first, the temperature signal is sampled at a predetermined time interval and used as temperature measurement data. When a series of sampling is completed, the arithmetic unit 30 calculates and obtains the temperature of the object from the data sampled by the equation (12).

FIG. 3 is a temperature measurement recording chart showing the result of measuring the temperature of the color steel sheet using this temperature detecting device. From the figure, when the temperature detection head contacts the color steel plate, the temperature rises rapidly within 2 to 3 seconds after the temperature output contact. When this part is analyzed, the characteristic of the first-order lag of about 0.7 seconds is dominant. After that, it rises fairly slowly, but this is an asymptotic approach to the temperature to be measured with an extremely long time constant.

After contacting the temperature detecting head with the color steel sheet,
1 second 0.2 seconds 0.3 seconds sampled, calculated by equation (12), and compared with the measured value of the temperature of the color steel plate, equation (12)
When the coefficient K in the table was set to 0.77, good agreement with the measured value was found. As described above, according to the method of the present invention, the temperature of the steel sheet during traveling at a relatively low temperature can be accurately measured without causing any disturbance to the operation by simply bringing the steel sheets into contact with each other for a short time of about 0.5 seconds.

If the heat transfer coefficient h between the temperature measuring element and the backing material is almost 0, the influence of the backing material on the indicated temperature θ ₁ disappears. In this case, the indicated temperature is determined only by heat transfer with the measurement target, so the coefficient K in equation (11) is 1. Then, the temperature T of the measurement target is expressed by the following equation. T = (T ₂ ² -T ₁ T ₃ ) / (2T ₂ -T ₁ -T ₃ ) (12) This formula has an advantage that it can be estimated and calculated regardless of the device constant.

[0030]

According to the present invention, it is possible to measure the temperature of a traveling object having a relatively low temperature with high accuracy without disturbing the operation because the temperature measuring element can be measured only by bringing the temperature measuring element into contact with the object for a short time. .

[Brief description of drawings]

1A is a schematic diagram of a temperature detection head, and FIG. 1B is a block diagram showing a heat transfer mechanism.

FIG. 2 is a diagram showing an embodiment of a temperature detecting device.

FIG. 3 is a temperature measurement recording diagram showing a result of using the temperature detection device of the embodiment.

[Explanation of symbols]

1 temperature measurement element 2 backing material 3 measurement target 10 temperature detection head T temperature of measurement target θ ₁ temperature of temperature measurement element T ₀ initial value of temperature of temperature measurement element T ₁ , T ₂ , T _{3 of} temperature of temperature measurement element Sampling value

Claims (2)

[Claims] 1. A temperature detection head having a temperature measurement element and a backing material having a larger heat capacity than that of the temperature measurement head is brought into contact with a running measurement target to make contact with the temperature measurement element temperature θ ₁ (t) and its initial value. The temperature of the object to be measured is calculated using the following equation expressed by T ₀ and the coefficients K and α obtained in advance.
A method for measuring the temperature of a moving object, characterized by estimating and calculating T. T = T ₀ + (1 / K) [θ ₁ (t) -T ₀ ] / [1-exp (αt)] where t is the time from the start of measurement. 2. Regarding the estimation calculation of the temperature of the measurement target,
The initial value T ₀ of the temperature of the temperature measuring element and the values T ₁ , T ₂ , T ₃ sequentially sampled at equal time intervals, and the following equation represented by the coefficient K obtained in advance are used to measure the The temperature measuring method for a traveling object according to claim 1, wherein the temperature T is estimated and calculated. T = T ₀ + (1 / K) [(T ₂ ² -T ₁ T ₃ ) / (2T ₂ -T ₁ -T ₃ ) -T ₀ ]