JPH0663850B2 - Method for measuring temperature in furnace of hot isostatic press - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a measuring method for measuring the temperature in a furnace of a hot isostatic press (hereinafter abbreviated as HIP) apparatus, particularly a closed end tube tip. HFP with improved temperature measuring optics for focusing the thermal radiation of
The present invention relates to a method for measuring a temperature inside a furnace of an apparatus.

(Prior Art) A HIP device is a device that utilizes the synergistic effect of high temperature and high pressure to perform pressure sintering of powder, defect removal of a sintered product or forged product, or diffusion bonding. Its industrial use has been attracting attention, but recently its application has spread to the high temperature range of 1700 ° C to 2100 ° C for engineering ceramics.

However, in such a device, the temperature control in the high temperature and high pressure furnace is extremely important for the treatment effect, and therefore various temperature measuring means for detecting the temperature in the furnace are provided, and at present, the closed end pipe is The adoption of the radiation temperature measuring method used is being discussed.

10 and 13 show examples of known HIP devices provided with such temperature measuring means in the furnace.

That is, FIG. 10 shows that a closed end tube (15) and an optical fiber (16) are used, and the closed end tube (15) includes a heat insulating layer (12).
1) Installed so that the tip is located at the temperature measurement site in the furnace chamber defined by the heat insulation layer (12) of the HIP device where the sample table (14) is installed on the lower lid (13) Then, heat radiation from the closed end tube is guided to the outside of the furnace by an optical fiber (16) located at the lower part of the closed end tube, and connected to a measurement system consisting of a radiation thermometer (17) (JP-A-60-133327). In order to take in the radiated light from the closed end tube to the optical fiber (16), the method of making it enter the optical fiber (16) directly as shown in FIG. 11 or the lens (19) as shown in FIG. 12 is used. The collimator (20) was used to focus light on the optical fiber (16).
Fig. 13 shows the furnace chamber of the HIP device, that is, the long and narrow slender circular tubes (30) and (31) whose upper end is closed in the processing chamber (A), the upper end of which is opened in the processing chamber (A) and opened. The other end is located outside the processing chamber, and the measurement terminals (32) and (33) of the radiation thermometer are adjusted at the opening end to focus on the upper ends of the elongated circular tubes (30) and (31). Then attach the measuring terminal (32),
The signal detected by (33) is the optical signal cable (34),
It is led to the temperature conversion device (36) in the HIP device through (35), and the output corresponding to the temperature is taken out to the outside by the lead wire (37) penetrating the high pressure vessel, and the processing chamber temperature automatic control device (38), A thyristor control device (39) or the like controls both upper and lower heaters (40) and (41) (see Japanese Patent Laid-Open No. 60-144627).

However, in the HIP device, the place where the optical system is placed is usually about 300 ° C. and 2000 ° C. atmospheric pressure, and the density of a gas such as _Ar or N ₂ forming the atmosphere is normal temperature and normal pressure. It is remarkably different from and has a high density. In particular, in the device shown in FIG. 10, the portion where the collimator (see FIG. 12) is installed has a relatively low temperature, so that the density becomes higher.

As a result, the refractive index of the gas increases with the increase of the density, and increases from the value at room temperature and pressure, and the optical characteristics of the lens designed for the air at room temperature and pressure, such as the lens focal length, The numerical aperture of the optical fiber changes, which affects the characteristics of the thermometer.

More specifically, the focal length of the lens is usually expressed by the following equation.

Where: r ₁ , r ₂ : radius of curvature on both sides of the lens However, n _{L is} the absolute refractive index of the lens material, _{ng is} the absolute refractive index of the lens surrounding medium, and n ₉ is almost equal to 1 in the case of a gas at normal temperature and normal pressure, and the lens is designed under the conditions.

However, as shown in the following table, the absolute refractive index of the gas changes depending on the pressure, and the focal length changes from the above equation.
(Refer to High-pressure experimental technology and its application, page 441) Of course, since the inside of the HIP device is at a high temperature and a high temperature at the same time, the number of close meetings tends to decrease, and the refractive index change rate is smaller than in the case of the above table, but there is no change in the state of the temperature measuring optical system.

Under such conditions, the conventional temperature measuring means
It does not respond well to changes in the refractive index of the medium gas due to the operating conditions of the HIP device, and has not yet achieved a sufficient stable temperature measurement.

(Problems to be Solved by the Invention) The present invention solves the above-mentioned defects by coping with the actual situation as described above and finding a means for effectively focusing the thermal radiation energy from the measurement target point on the light receiving part. The purpose is to respond to changes in the atmosphere in the furnace such as changes in the refractive index of the medium to enable stable temperature measurement.

(Means for Solving Problems) That is, the feature of the present invention that meets the above purpose and achieves a desired effect is to install a closed end tube in the high pressure furnace of the HIP device as described above. When the thermal radiation energy at the tip of the closed-end tube is focused on the light receiving section by the temperature measuring optical system and is guided to the detecting section to measure the temperature inside the furnace, the incident surface is used as the optical system to measure the temperature. A sphere centered around a point, the exit surface is a flat surface, and the optical system composed of a solid lens that emits a light beam on the exit surface side into parallel rays and perpendicular to the surface is used to focus the radiant energy. is there.

Here, the temperature-measuring optical system usually refers to what is called a collimator optical system, and the temperature-measuring target point is a closed-end tube tip,
The condensing point corresponds to, for example, the opening of the optical fiber of the light receiving portion or the light receiving element itself.

Further, the detector is composed of a photoelectric converter, an amplifier, an emissivity correction circuit, a linearizer, etc., as is known, and displays the temperature.

In addition, the incident surface in the optical system is a spherical surface centering on the temperature measurement target point, the exit surface is a flat surface, and the light flux on the exit surface side is a parallel light beam and a solid lens that emits perpendicularly to the surface focuses the incident light. It is necessary to satisfy the conditions of the function to output light as a parallel light beam and the condition that the light beam is emitted as a parallel light beam. Therefore, the element of the optical system needs both an element that focuses the incident light and an element that makes the focused light beam a parallel light beam. To be done.

That is, specifically, FIGS. 1 and 2 show the basic mode, but a convex lens (1) that acts on focusing and a concave lens (2) or a convex lens (1) ′ that acts on parallel rays.
And consists of.

Therefore, the solid lens includes this configuration, and a shape and a configuration satisfying both of the above requirements are required. From the above both requirements, the shape of the solid lens of the optical system is the entrance surface-concave surface, the exit surface-plane. Therefore, as long as it has a concave lens shape and the inside has a uniform refractive index, it cannot have the functions of focusing and collimating rays as shown in FIGS. 1 and 2. Therefore, it is necessary to provide the above function by providing a portion having a different refractive index in the solid lens of the optical system.

This is specifically possible by making the interface have a focusing or diverging action by selecting the shape of the interface having a different refractive index and the refractive index ratio before and after. Various combinations to achieve are realized.

(Operation) When the solid lens as described above is used for the optical system to measure the temperature inside the furnace of the HIP device, since the incident surface of the optical system is a spherical surface centering on the temperature measurement target surface, the temperature measurement target surface Rays entering the optical system from are incident perpendicularly to the incident surface, and refraction does not occur at the incident surface. Further, since the exit surface is a plane and the outgoing light flux is a parallel light beam and is perpendicular to the surface, refraction does not occur even on the exit surface. Therefore, even if the refractive index of the medium outside the lens changes due to changes in temperature and pressure, the state of the light beam does not change without being affected thereby. Moreover, since the emitted light beam is a parallel light beam as described above, the size of the light beam does not change in the optical axis direction, and even if the light receiving unit moves in the optical axis direction, the received light amount does not change, and an extremely appropriate temperature measurement can be performed. It will be possible.

(Examples) Specific embodiments of the temperature measuring method according to the present invention will be described below with reference to the accompanying drawings.

FIGS. 3 to 9 are each an example of an optical system forming an essential part of the temperature measuring method of the present invention. Although the HIP device is omitted in the drawings, the collimator of the HIP device shown in FIG. Applied to optical system.

Thus, in each of the above figures, (3) shows the solid lens of the optical system, (4) shows the temperature measurement target point, (5) shows the light receiving part, and
In FIGS. 4 and 5, the entrance surface of the lens (3) is a spherical surface with a radius _r centered on the temperature measurement target point (4), while
The emission surface is flat.

In the case of FIG. 3, the lens (3) is provided with a high refractive index portion (6) in the shape of a convex lens, which is higher than the refractive index n _{1 of} the incident portion and the refractive index n _{3 of the} outgoing portion. The refractive index is n _2, and the condition of converging the incident light and the condition of emitting it as a parallel light beam are satisfied. That is, n ₁ <n
The optical system of the present invention has a refractive index of ₂ , n ₂ > n ₃ .

On the other hand, in the example of FIG. 4, a convex lens-shaped portion having a high refractive index, that is, a portion (7) having a refractive index n ₅ and a portion (8) having a refractive index n ₇ are provided in the optical system lens (3). The condition is satisfied.

That is, n ₄ and n ₆ are the refractive indices of the concave lens portion, and n ₄ <
The optical system according to the present invention is constituted by the relationship of n ₅ , n ₅ > n ₆ , n ₆ <n ₇ .

In each of the above examples, as means for providing the lens-shaped portions (6), (7), (8) having a high refractive index in the lens (3), specifically, a plurality of lenses having different refractive indexes are used. It is possible by combining them.

In this case, the surfaces of the lenses to be combined must be sufficiently close to each other so that the influence of the medium refractive index in the space formed by the lens gap can be ignored.

Next, considering the case where the temperature measurement target point (4) is a sufficiently long distance, or conversely, the temperature measurement target point (4) is in close proximity and is in contact with the incident surface, in these cases, the incident surface is the fifth surface. As shown in FIG. 6 and FIG. 6, it becomes a substantially flat surface.

However, even in such a case, the above-mentioned purpose, that is,
The fact that refraction does not occur on the entrance surface and the exit surface and the state of the light beam does not change is the same, and is included in the gist of the present invention.

Further, although the above embodiments have been described as being based on a combination lens, the refractive index is gradually changed from the optical axis portion to the peripheral portion within a single lens like a gradient index lens. Those having a distribution and a convex lens action can also be used.

Of course, in this case as well, it is needless to say that the shapes of the entrance surface and the exit surface satisfy the required conditions, respectively, as described above.

The optical system (3) of FIG. 7 shows such an embodiment comprising lenses (3) ′ and (3) ″ having a refractive index distribution.

In addition to the above, a system including a reflecting surface in the above optical system is also possible, and the reflecting surface may have a function in the basic mode of the lens element shown in FIGS. 1 and 2. FIG. 8 shows an example including the former reflecting surface (9). Further, FIG. 9 shows a concave lens surface (10) having a convex lens function,
This can also be used in the optical system of the present invention by satisfying the conditions required for the shapes of the entrance surface and the exit surface.

It is needless to say that the above examples are not all of the optical system according to the present invention, and accordingly various modifications can be made without departing from the spirit of the invention.

Thus, the radiant energy focused by the optical system constituted by the lens as described above is transmitted to the detection portion by the optical fiber or the like, and is used for temperature display and, if necessary, heater control.

(Effect of the invention) As described above, in the measurement of the temperature in the furnace of the HIP device, the present invention improves the configuration of the optical system so that the entrance surface is a spherical surface centered on the temperature measurement target surface and the exit surface is a flat surface. , A method in which the radiant energy is focused by using an optical system composed of a solid lens in which the light beam on the exit surface side is a parallel light beam and exits perpendicularly to the surface. Does not sufficiently respond to changes in the refractive index of the medium gas due to
The characteristics of the thermometer optical system change due to the fluctuation of the refractive index, and stable measurement cannot be performed.However, in the method of the present invention, the temperature is measured because the incident surface of the optical system is a spherical surface centered on the temperature measurement target point as described above. Light rays entering the optical system from the target point are incident perpendicularly to the incident surface, refraction does not occur on the incident surface, and since the light flux emitted at the exit surface is a flat light ray and perpendicular to the surface, refraction at the exit surface is also Even if the refractive index of the medium does not change, the state of the light beam does not change at all, and it is possible to measure the temperature in the HIP process without depending on the ambient temperature and pressure. Moreover, in the temperature measuring method of the present invention, since the light beam on the emission side is a parallel light beam, the size of the light beam does not change in the optical axis direction. Of the HIP
The temperature measurement accuracy of the device is remarkably enhanced, and a remarkable effect of promoting industrialization of the device is achieved.

[Brief description of drawings]

FIGS. 1 and 2 are explanatory views showing a basic mode of the temperature measuring method of the present invention, and FIGS. 3 to 9 are schematic views showing respective embodiments of an optical system forming a main part of the temperature measuring method of the present invention. FIG. 10 is a schematic sectional view showing an example of a HIP device to which the method of the present invention is applied, FIGS. 11 and 12 are schematic diagrams of respective optical systems used in the device shown in FIG. 10, and FIG. It is a schematic diagram showing an example of an existing temperature measurement system of another HIP device example to which the method of the present invention is applied. (1), (1) '... Convex lens, (2) ... Concave lens, (3) ... Optical system, (4) ... Temperature measurement target point, (5) ... Light receiving part, (6), ( 7), (8) ... High refractive index part (9) ... Reflecting surface, (10) ... Concave reflecting surface.

Claims (4)

[Claims] 1. A closed-end tube is installed in a high-pressure furnace of a hot isostatic pressurizer, and heat radiation at the tip of the closed-end tube is focused by an optical system, which is guided to a detection part and the temperature in the furnace is increased. When measuring
In the optical system, the incident surface is a spherical surface centering on the temperature measurement target point, the exit surface is a flat surface, and the light flux on the exit surface side is a parallel light beam,
A method for measuring an in-furnace temperature of a hot isostatic pressurizing device, characterized in that radiant energy from a temperature measurement target point is focused by using an optical system configured by a solid lens that emits perpendicularly to a surface. 2. The method for measuring the temperature inside a furnace of a hot isostatic pressurizer according to claim 1, wherein the solid lens has a convex lens-shaped portion having a high refractive index therein. 3. The hot isostatic pressing device according to claim 2, wherein the solid lens having a convex lens-shaped portion having a high refractive index therein is a combination of a plurality of lenses having different refractive indexes. Method for measuring furnace temperature. 4. The method for measuring the temperature inside a furnace of a hot isostatic pressurizer according to claim 1, 2, or 3, wherein the solid lens has a reflecting surface.