JPH06123656A - Contactless measuring method of temperature of tunnel kiln - Google Patents

Abstract

PURPOSE:To measure the temperature of a baked object or the like accurately by processing a black body to the side wall of a sheath, detecting the luminance by a slit CCD camera, combining thermal images obtained through the slit and obtaining the total image of the baked object. CONSTITUTION:A CCD camera 6 is set to the outer face of a slit 5 of a narrow width formed in a kiln wall 1. The luminance and thermal images of a sheath 4 transferring a baked object 3 are continuously caught and detected. The temperature of the baked object 3 is measured by correcting the influences of the other reflecting light on the basis of the temperature data obtained from the CCD luminance of a point of a black body preliminarily processed at the side wall of the sheath 4. The shape and temperature distribution of the baked object 3 are measured in a manner whereby the strips of thermal images obtained through the slit 5 are combined in conformity with the moving speed of the sheath 4 and displayed in pseudo colors as a total image onto an ITV monitor. Therefore, if the temperature measuring mechanism is installed at each of a plurality of points in the longitudinal direction of a tunnel kiln, a highly reliable heat pattern within the furnace can be formed from the obtained temperature data.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-contact temperature measuring method for a tunnel furnace which is capable of accurately measuring the temperature and temperature distribution of an object moving in the tunnel furnace in a non-contact state.

[0002]

2. Description of the Related Art When performing a firing process using a tunnel furnace, the material to be fired is usually placed on a firing dish called a pod, and the pods are slowly stacked in a stack in a plurality of stages. A method of heating while being transported to the container is adopted. Each tunnel furnace has a heat pattern that shows the temperature distribution from the inlet to the outlet, and the quality of the fired product depends largely on how close this heating program can be to the operation. In addition, since the temperature inside the furnace tends to be different between the upper and lower stages of the sheath, the firing quality often changes.

In order to control these inconvenient factors,
It is necessary to properly adjust the transport speed in the furnace and the temperature setting of the heating element, but the temperature cannot be directly measured because the burned material is moving in a long closed tunnel furnace. . Therefore, based on the temperature of the atmosphere inside the furnace measured by a thermocouple inserted through the furnace wall and the temperature of the fired product after leaving the furnace, it has been considered that the heat that has been considered optimal from many years of experience. The pattern was set speculatively. However, recently, as the number of cases in which a tunnel furnace is used for the purpose of baking a precision component such as a semiconductor substrate increases, a heat pattern is estimated based on an in-furnace ambient temperature indirectly measured by a thermocouple. It is becoming difficult to obtain sufficient reliability and stable firing characteristics by the method.

As a non-contact type in-furnace temperature measuring method instead of this, there is a method using a radiation thermometer or a CCD camera. It is impossible to expect warmth.

[0005]

SUMMARY OF THE INVENTION The present invention was developed in view of such circumstances, and an object thereof is to control the temperature state of an object to be fired moving through a slit provided in a furnace wall to the brightness and the heat. It is an object of the present invention to provide a non-contact temperature measuring method for a tunnel furnace, which can accurately measure the temperature and temperature distribution of the object by capturing it as an image and thus improve the reliability of condition control in the furnace operation.

[0006]

A non-contact temperature measuring method for a tunnel furnace according to the present invention for achieving the above object is to perform a blackbody process on a side wall portion of a sheath for carrying an object to be fired, The temperature of the burned material is measured by detecting the brightness with a CCD camera from the slit formed in the furnace wall of the tunnel furnace corresponding to the side wall part, correcting and removing the influence of the reflected light in the furnace entering the measurement point, and converting the temperature. Then, a strip-shaped temperature image obtained from the slit is synthesized according to the moving speed of the sheath to be displayed on the ITV monitor as a whole image of the fired product, and the temperature distribution of the fired product is measured. And

[0007]

The non-contact temperature measuring method according to the present invention uses the CCD camera to remove the influence of reflected light from the brightness of the sheath for transporting the object to be burned and convert it to the temperature of the object to be burned. It is characterized in that the obtained thermal images are combined to detect the temperature distribution. Generally, in order to know the condition inside the tunnel furnace, it is necessary to open as small a hole as possible in order to avoid temperature fluctuations, but when the firing temperature is high, the synchrotron radiation is intense and the inside can be seen with the naked eye. Is almost impossible to observe. According to the present invention, the CCD camera is installed on the outer surface of the narrow slit formed in the furnace wall, and the brightness and thermal image of the moving sheath are continuously captured and detected by the CCD camera.

The temperature of the fired product is measured by correcting the influence of other reflected light on the basis of the temperature data obtained from the CCD brightness of the black body processing point previously formed on the side wall of the sheath. The shape and the temperature distribution of are measured by a method in which a thermal image obtained through the slit is combined according to the transport speed and is displayed as a whole image. Since the entire image at this time can be displayed in pseudo color by ITV, it can be reproduced in the same way as when directly observing with the outer wall of the furnace removed.

Therefore, by installing the temperature measuring mechanism of the present invention at a plurality of points in the length direction of the tunnel furnace,
Accurate temperature measurement of the fired product is possible, and a highly reliable heat pattern in the furnace can be created from the obtained temperature data.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below based on the illustrated embodiments.

FIG. 1 is a schematic cross-sectional view showing an embodiment of a non-contact temperature measuring method for a tunnel furnace according to the present invention. 1 is a furnace wall of the tunnel furnace, 2 is a heating element installed at a vertical position in the furnace, 4 Is a sheath with a two-stage structure for placing the material to be fired 3 and transporting it inside the furnace, 5 is a slit formed in the furnace wall of the tunnel furnace corresponding to the side wall of the sheath 4, and 6 is a neutral density filter 7 It is a CCD camera set outside the front furnace of the slit 5 via. The memory of the image device connected to the CCD camera 6 has a built-in brightness-temperature conversion mechanism produced by associating the reference blackbody furnace temperature with CCD brightness data obtained from the reflected light.

In the heating state as shown in FIG. 1, the following equation (1) is established at one point on the sheath. P (T) = εP (Ts) + (1-ε) P (Tw) (1) where P (T) is the radiant energy of the blackbody in TK,
ε is the emissivity of the sheath, T is the temperature of the sheath (apparent temperature), T
s is the true temperature of the sheath, and Tw is the temperature in which the external light incident on the measurement point is represented by one point.

The temperature of the CCD camera 6 is an accurate measured value when a perfect blackbody is the object of measurement, but since the object to be fired is not a perfect blackbody, it is affected by various reflected lights. The reflected light includes stray light of complex elements such as direct light from the heating element as shown by the arrow in FIG. 1, reflected light on the wall surface, reflected light from the sheath other than the measurement point (the largest cause of stray light). Be done. However, as mentioned above, C
Since the accurate temperature can be obtained from the CD brightness, the temperature can be measured from the brightness by making the measurement portion the same as that of a black body. In the present invention, the correction for removing the influence of other reflected light is performed based on the temperature data at this time.

That is, as shown in FIG. 2, a black body is preliminarily applied to the side wall portion (hatched portion including point A) of the sheath 4. The black body processing is performed by means of coating and forming silicon carbide, for example. Since the emissivity of silicon carbide is 0.8 to 0.9, it cannot be said to be a perfect black body, but there is no problem because the error caused by this emissivity difference is within the allowable range. During operation, the sheath 4 moves (leftward) in the furnace at a slow speed. In this process, the CCD camera sequentially detects the brightness of the wall portion W between the sheaths, the black body processing point A on the side wall of the sheath, and the side walls B and C other than the black body processing point on the sheath.
An accurate temperature can be obtained from the brightness at the blackbody processing point A, but the brightness data including the influence of various stray light is obtained at points B and C where the blackbody processing is not performed.

In the above equation (1), if the luminance data at each point of W, A and B are TW, TA and TB, respectively,
The emissivity (ε) of the sheath is obtained by the following equation (2). At this time, ε is the emissivity when it is considered that all the stray light is emitted from the point W and A and B are the same point. This value is valid on the same sheath, and the brightness of any point C is TC
Then, the temperature TCS has a relation of the equation (3).

When the sheath 4 passes, the calculation operation up to that point is initialized, and when the next sheath is conveyed, the same calculation is repeated again. As a result of repeating the correction calculation for each sheath in this way, it becomes possible to correct in real time the latest influence of external light that accompanies fluctuations in the setting of the conveyance speed and the temperature of the heating element.

On the other hand, the temperature image captured by the CCD camera 6 is a strip-shaped image along the slit width, but by combining the images in accordance with the moving speed of the sheath 4, IT
The V monitor can be made to appear as an overall image of the fired product. FIG. 3 is a schematic diagram showing an example of combining sheath images.
First, the side wall of the sheath 4 that conveys the inside of the tunnel furnace 8 is CC
The first image 9 corresponding to the slit width is obtained by projecting on the D camera. In this case, the captured image area is specified to be narrower than the slit width in order to avoid irregular light at the slit edge. When the image of the next slit width appears completely due to the movement of the sheath 4, the image is captured. By thus combining the respective images, the entire image of the fired product can be displayed on the ITV monitor, and by repeating this, the state inside the furnace can be reproduced outside the system. Therefore, it is possible to continuously check the shape and temperature distribution of the fired product.

The radiation at each point is converted into a voltage by a CCD camera, taken into an image device and converted into an 8-bit digital value, and then converted into temperature data by a brightness-temperature conversion formula. This calculation operation is performed at each point of W, A and B in FIG. 2 in the following order. When there is a wall at the measurement position, the brightness at that point is taken to obtain the temperature at point W. At this time, the sampling position of the wall is determined in advance by experiments so that stray light can be represented. The sheath is transported and its temperature is calculated at the position of point A. When the point B is reached, the temperature is calculated. At this point, the temperatures at W, A, and B points are obtained, and these temperature data are substituted into the equation (2) as radiant energy to obtain the sheath emissivity (ε).

Measurement is started from this. The above
Since P (Tw) and ε of the data obtained in step 1 are valid on the same sheath, they can be regarded as constants. Therefore,
Equation (3) is transformed into equation (4) below. P (Tcs) = f [P (Tc)] (4) After B point, the apparent temperature of each point such as C point on the right side is taken in every designated time, and it is substituted into the equation (4) and corrected temperature. Obtained as. This temperature data is transferred from the imager to the computer and displayed as a time-temperature plot graph or a camera position (circuit) -temperature heat pattern. In the latter case, the deviation from the target heat pattern is detected at the same time, and the heater is controlled and the conveyance speed is adjusted. When the entire sheath has passed and the wall is visible, return to the next stage. Since it is not possible to measure from to, the temperature data at the time of returning to will be displayed.

FIG. 4 is a block diagram showing a case where a tunnel furnace is continuously operated using the present invention. A plurality of slits are formed in the side wall of the tunnel furnace 8, and the CCD camera 6 is set in front of each slit. Each CCD camera 6 is connected to the image processing device 10, and the image processing device 10
Is connected to ITV monitor 11 and computer (CRT). At the time of operation, the image information detected by the image processing device 10 and synthesized based on the image is displayed on the ITV monitor 11, and the data obtained as the brightness is converted into the temperature. At the same time, the signal from the image processing device 10 enters the heating element control device 13 and the transfer control device 14, and the processing conditions in the furnace are adjusted. If this mechanism is designed so that an alarm is issued when the set conditions are abnormal, the operator can check defective firing and examine the heat pattern.

[0021]

As described above, according to the present invention, the temperature condition in the tunnel furnace is accurately detected in a non-contact state by capturing the brightness and thermal image of the sheath moving in the furnace with the CCD camera through the slit. Therefore, the reliability of the furnace operating conditions can be significantly improved. Moreover, since the delicate temperature distribution of the fired product can be visually reproduced by the thermal image display, the abnormality can be immediately determined. Therefore, it is extremely useful for the purpose of firing the precision member using a tunnel furnace.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing a non-contact temperature measurement state of a tunnel furnace according to the present invention.

FIG. 2 is a perspective explanatory view of a sheath subjected to black body processing.

FIG. 3 is a schematic diagram showing an example of combining sheath images.

FIG. 4 is a configuration diagram when a tunnel furnace is continuously operated using the present invention.

[Explanation of symbols]

 1 Tunnel Wall of Tunnel Furnace 2 Heating Element 3 Burned Object 4 Sheath 5 Slit 6 CCD Camera 7 Dimming Filter 8 Tunnel Furnace 9 Image 10 Image Processing Device 11 ITV Monitor 12 Computer 13 Heating Element Control Device 14 Transfer Control Device

Claims (1)

[Claims] 1. A black body is applied to a side wall portion of a sheath that conveys a material to be fired, and a brightness is detected by a CCD camera from a slit formed in a furnace wall of a tunnel furnace corresponding to the side wall portion of the sheath. The temperature of the fired product is measured by correcting and removing the effect of the reflected light in the furnace incident on the ITV, and the strip-shaped temperature image obtained from the slit is synthesized according to the moving speed of the sheath to produce the ITV. A non-contact temperature measurement method for a tunnel furnace, which is characterized by displaying the entire image of the fired product on a monitor and measuring the temperature distribution of the fired product.