JP7708356B2 - temperature measuring device - Google Patents

Description

The present invention relates to a temperature measuring device, and in particular to a temperature measuring device that is installed in a kneading device and is preferably used to measure the temperature of the material being kneaded.

As a temperature measuring device for this type of kneading device, a device has been proposed in the past in which a durable metal protective tube is attached with its tip protruding partially into the kneading chamber in order to withstand the stress (impact and bending force) exerted by the viscous material being kneaded, and a sheath-type thermocouple is inserted inside the tube (see, for example, Patent Document 1).

However, when mixing high-viscosity materials in a mixing device, if the set temperature is exceeded, the material will burn and become a defective product. Therefore, the responsiveness of the temperature measuring device installed in the mixing device is very important, but conventional protective tubes are made of the same material, and the responsiveness is determined by the shape and thermal conductivity of the material, so there is no hope for improving the responsiveness.

JP 2004-37381 A

The present invention aims to provide a temperature measuring device that is durable and easy to improve responsiveness.

In light of this current situation, the inventors conducted extensive research and concluded that one of the causes of the reduced responsiveness was the loss of heat through the protective tube to the base end, particularly from the attachment part to the equipment side. They came up with the idea of preventing heat loss by thinning the base end of the protective tube, and discovered that by providing a low thermal conductivity section made of a low thermal conductivity material with a lower thermal conductivity than the protective tube at the thinner section, it was possible to maintain mechanical strength against impacts and bending forces from the measurement object, which led to the completion of the present invention.

That is, the temperature measuring device according to the present invention comprises a protective tube formed in a cylindrical shape, and a thermocouple having a temperature sensing part at its tip and inserted into the protective tube, the temperature sensing part of the thermocouple is fixed to the tip of the protective tube, at least one groove is provided on the outer circumferential surface of the protective tube, and a low thermal conductivity part made of a low thermal conductivity material having a thermal conductivity lower than that of the protective tube is provided within the groove.

With this configuration, thermal energy is conducted from the object to be measured to the tip of the protective tube and the temperature-sensing part fixed to the tip, and the heat is transferred toward the base end of each. The low thermal conductivity part of the protective tube, which is made of a low thermal conductivity material, suppresses heat transfer toward the base end, making it easier for thermal energy to concentrate in the temperature-sensing part, thereby shortening the time it takes for the measurement temperature to reach the temperature of the object to be measured. Furthermore, the low thermal conductivity part is provided within the groove, reinforcing the mechanical strength of the thin-walled protective tube.

It is also preferable that the groove is provided around the entire outer periphery of the protective tube.

With this configuration, the grooves around the entire circumference and the low thermal conductivity section in the grooves significantly reduce heat transfer from the tip of the protective tube, concentrating heat energy more on the temperature-sensing section and reducing the installation area of the low thermal conductivity section, thereby reducing material costs.

It is also preferable that the outer circumferential surface of the low thermal conductivity portion is configured to be substantially flush with the outer circumferential surface of the protective tube or recessed from the outer circumferential surface of the protective tube.

With this configuration, the low thermal conductivity section is provided in a groove, which not only reinforces the mechanical strength of the thin-walled protective tube, but also makes the outer circumferential surface of the low thermal conductivity section approximately flush with the outer circumferential surface of the protective tube, or makes the outer circumferential surface of the low thermal conductivity section recessed from the outer circumferential surface of the protective tube. Therefore, when mounting on equipment requiring temperature measurement, by drilling a hole that matches the outer shape of the protective tube, contact of the low thermal conductivity section with the inner wall of the hole, etc. is reduced, allowing for easy and smooth mounting.

The low thermal conductivity portion is preferably made of a ceramic material containing zirconia or zirconium dioxide.

According to this configuration, the ceramic material containing zirconia or zirconium dioxide has a lower thermal conductivity than the metal materials that are often used for the protective tube, and can suppress the transfer of thermal energy to the base end. In addition, by being placed in the groove, the mechanical strength of the thin-walled protective tube is reinforced.

It is also preferable that the protective tube is provided with an attachment surface that is interposed between the tip of the protective tube and the low thermal conductivity portion and that is made up of a portion of the outer circumferential surface of the protective tube.

This configuration makes it easy to install the temperature measuring device when it is attached to equipment that requires temperature measurement, and in particular, when it is attached to a hole that is drilled to match the outer shape of the protective tube, it can fit tightly with the inner wall of the hole without any gaps.

It is also preferable that the tip is tapered.

With this configuration, the volume of the tip of the protective tube is reduced, the heat capacity is reduced, and heat energy is more easily concentrated at the tip, further shortening the time it takes for the measurement temperature to reach the temperature of the object being measured.

Furthermore, it is preferable that the tip portion is subjected to a surface treatment to improve abrasion resistance.

With this configuration, the wear resistance is improved, making the tip protruding into the kneading chamber less susceptible to damage.

A temperature measuring device with this configuration makes it easy to improve the strength of the thermocouple while also improving its responsiveness.

1 is a perspective view showing a temperature measuring device according to an embodiment of the present invention; 1 is a cross-sectional view showing a configuration of a temperature measuring device according to an embodiment of the present invention. 1 is a cross-sectional view showing a state in which a temperature measuring device according to an embodiment of the present invention is attached to a kneader. FIG. 2 is a local enlarged view showing a portion where a temperature measuring device according to an embodiment of the present invention contacts a kneading facility. FIG. 4 is a local enlarged view showing a portion where a temperature measuring device according to a first modified example of one embodiment of the present invention contacts a kneading facility. FIG. 11 is a local enlarged view showing a portion where a temperature measuring device according to a second modified example of one embodiment of the present invention contacts with a kneading facility.

The following describes an embodiment of the present invention with reference to the drawings. Note that components with the same reference numerals in each drawing are the same, and their description will be omitted.

Figure 1 is a perspective view showing a temperature measuring device according to one embodiment of the present invention. Figure 2 is a cross-sectional view showing the configuration of a temperature measuring device according to one embodiment of the present invention. The temperature measuring device 1 shown in Figure 2 includes a sheath thermocouple 20 and a protective tube 40.

The sheathed thermocouple 20 is a grounded sheathed thermocouple having a sheath 21, a compensation wire 23, and a sleeve 22 that connects the sheath 21 and the compensation wire 23. The sheath 21 has a pair of thermocouple wires (not shown) disposed therein, and the tip of the sheath 21 is provided with a temperature sensing part 211, which is a temperature measuring junction where the pair of thermocouple wires are directly welded.

The protective tube 40 has a tapered tip 401 and a groove 41 on its outer surface all around, and the rest of the protective tube is a cylindrical metal protective tube with the same outer diameter.

The tip 401 is tapered both inside and out to ensure a constant thickness. It is preferable that the tip 401 be tapered, but this is not a limitation. In addition, the surface of the tip 401 may be subjected to a surface treatment such as DLC (diamond-like carbon) treatment to improve wear resistance.

The grooves 41 are provided at the same depth on the outer circumferential surface of the protective tube 40. Preferably, they are provided on the outer circumferential surface of the protective tube 40 on the tip portion 401 side, but this is not limited thereto. The grooves 41 are also provided with a low thermal conductivity portion 42 that has a lower thermal conductivity than the protective tube 40.

The protective tube 40 is interposed between the base end of the tip portion 401 and the low thermal conductivity portion 42, and has an attachment surface 43 formed of a part of the outer circumferential surface of the protective tube 40. The attachment surface 43 does not have to be interposed between the base end of the tip portion 401 and the low thermal conductivity portion 42. Furthermore, the attachment surface 43 may not be provided on the outer circumferential surface of the protective tube 40, and the attachment surface 43' may be provided on the low thermal conductivity portion 42.

The temperature-sensing part 211 is fixed to the apex of the tip part 401 by welding. However, this is not limited as long as the temperature-sensing part 211 is fixed to a location where it is easy to measure the temperature of the measurement target.

The outer peripheral surface of the low thermal conductivity section 42 is configured to be approximately flush with the outer peripheral surface of the protective tube 40. Note that the outer peripheral surface of the low thermal conductivity section 42 may be configured to be slightly recessed from the outer peripheral surface of the protective tube 40, but is not limited to this.

The protective tube 40 has a total length of 200 mm and an outer diameter of 19.9 mm, is made of Inconel 625, and is provided with a tip portion 401 that is 25 mm long from the tip, a low thermal conductivity portion 42 that is 34 mm long and 2 mm thick from a position 33 mm from the tip toward the rear end, and an attachment surface 43 that is 8 mm long and extends from the base end of the tip portion 401 to the low thermal conductivity portion 42.

The low thermal conductivity section 42 is constructed by installing zirconia, which has a lower thermal conductivity than the Inconel 625 used in the protective tube 40, in the recessed groove 41 by thermal spraying.

The low thermal conductive portion 42 may be made of a material having a lower thermal conductivity than the material used for the protective tube 40, but is not limited to this. In addition, the groove 41 and the low thermal conductive portion 42 provided within the groove 41 are provided along the entire outer periphery of the protective tube 40, but this is not limited as long as the configuration is capable of retaining thermal energy without impairing mechanical strength.

Figure 3 is a schematic diagram showing a state in which a temperature measuring device according to one embodiment of the present invention is attached to a kneader. The temperature measuring device 1 shown in Figure 3 is fitted into the mounting hole 91 of the kneader 90.

The structure of the kneader 90 is well known, so a description thereof will be omitted. The mounting hole 91 is opened to match the outer diameter of the protective tube 40 so that no gap is created between the protective tube 40 and the temperature measuring device 1 when it is attached.

When the outer surface of the low thermal conductivity section 42 is formed by thermal spraying, it is formed to be approximately flush with the outer surface of the protective tube 40, so that the temperature measuring device 1 can be inserted without getting caught in the mounting hole 91.

Figure 4 is a localized enlarged view showing the portion of the temperature measuring device according to one embodiment of the present invention that contacts the kneader. The temperature measuring device 1 shown in Figure 4 is inserted into a mounting hole 91 that is opened to match the outer diameter of the protective tube 40, and the mounting surface 43 interposed between the base end of the tip portion 401 and the low thermal conductivity portion 42 is in close contact with the inner wall 911 of the mounting hole 91.

The low thermal conductivity portion 42 is formed in the groove 41 by processing such as thermal spraying on the outer circumferential surface of the protective tube 40, which is formed by metal processing. In other words, in the manufacturing process, the processing precision of the low thermal conductivity portion 42 is lower than that of the outer circumferential surface of the protective tube 40, which is formed by metal processing. For this reason, even if an attempt is made to form the low thermal conductivity portion 42 flush with the protective tube 40, there is a risk that manufacturing variations will occur and the low thermal conductivity portion 42 will be raised or recessed from the outer circumferential surface of the protective tube 40.

If the outer surface of the low thermal conductivity portion 42 is formed to match the outer surface of the protective tube 40, the formation of the protective tube becomes complicated, which is undesirable from a cost perspective.

In contrast, if the outer surface of the low thermal conductivity section 42 is formed higher than the outer surface of the protective tube 40, it will come into contact with the opening of the mounting hole 91, which is opened to match the outer diameter of the protective tube 40, making it difficult to fit it in.

Even if the mounting hole 91 is opened to match the outer diameter of the low thermal conductivity section 42 that is formed by protruding from the outer surface of the protective tube 40, when the temperature measuring device 1 is attached, it will be supported by the low thermal conductivity section 42 that is located rearward of the tip 401 of the protective tube, which may weaken the strength of the temperature measuring device 1.

For this reason, it is possible to consider variations during manufacturing and to make the low thermal conductive portion 42 slightly recessed in advance so that it does not protrude from the outer circumferential surface of the protective tube 40. In this case, as shown in FIG. 4, it is preferable to configure the low thermal conductive portion 42 to be slightly recessed from the outer circumferential surface of the protective tube 40 so that the mounting surface 43 interposed between the base end of the tip portion 401 and the low thermal conductive portion 42 is in close contact with the inner wall 911 of the mounting hole 91.

The groove 41 and the low thermal conductivity portion 42 provided within the groove 41 may be provided in a plurality of locations spaced apart in the axial direction of the protective tube 40, or may be spaced apart all around the circumference of the protective tube 40. Figures 5 and 6 are enlarged views of a portion of a temperature measuring device according to a modified embodiment of the present invention that contacts the kneading equipment.

As shown in FIG. 5, the low thermal conductive portion 42 having a small axial width is divided and configured at intervals, or as shown in FIG. 6, the groove 41 is knurled to form a twill pattern and the low thermal conductive portion 42 is provided in the groove 41, so that the total installation area of the low thermal conductive portion 42 is smaller than that of the above-mentioned embodiment, but the material cost can be reduced. In addition, in FIG. 5, the space between the low thermal conductive portions 42 functions as the mounting surface 43, and in FIG. 6, not only is the mounting surface 43 provided between the tip portion and the groove 41 and the low thermal conductive portion 42 provided in the groove 41, but the twill-patterned convex portion that is flush with the outer peripheral surface of the protective tube also serves as the mounting surface 43 (not shown), so that the holding position in the kneader is more stable.

Next, we will explain the results of measuring the time constant under the same test conditions for Comparative Example a, which is a temperature measuring device equipped with a grounded sheathed thermocouple and a cylindrical metal protective tube made of Inconel 625 and equipped with a tapered tip, and Comparative Example b, which is a temperature measuring device of the same specifications as Comparative Example a except that SUS304 is used instead of Inconel 625. Note that neither Comparative Example a nor Comparative Example b has a recessed groove or low thermal conductivity portion as in this embodiment.

The test was carried out five times (N = 1 to 5) by inserting each temperature measuring device 150 mm into an oil bath, heating the oil bath from room temperature at the time of measurement to 150°C, and measuring the time constant. The same humidity was maintained during each measurement, and the results are shown in Table 1.

As shown in Table 1, it can be seen that Comparative Example a, which uses Inconel 625, has a larger time constant for temperature rise than Comparative Example b, which uses SUS 304. In terms of material, it can be seen that SUS 304 has better thermal conductivity than Inconel 625 and has faster temperature response.

Therefore, we prepared a new example a1, which uses the same Inconel 625 as comparative example a.

Example a1, like this embodiment, is a temperature measuring device equipped with a grounded sheathed thermocouple and a cylindrical metal protective tube with a tapered tip, a groove on the rear end side of the tip, and a low thermal conductivity part installed within the groove. In addition, the low thermal conductivity part in Example a1 is made of zirconia, which has a lower thermal conductivity than Inconel 625, and is installed within the protective tube by thermal spraying.

The time constants of Example a1 and Comparative Example b, which had a fast temperature response in the previous test, were measured again under the same test conditions as in the above experiment, with the results shown in Table 2.

As can be seen from the results in Table 2, Example a1, in which zirconia, which has a lower thermal conductivity than Inconel 625, is attached to the tip of a metal protective tube made of Inconel 625, has a faster temperature response than Comparative Example b.

Due to its material, a metal protective tube made of Inconel 625 has a thermal conductivity that is inferior to that of a metal protective tube made of SUS304, so its temperature response will not be faster than that of SUS304 under the same conditions.

However, by providing a groove on the rear end side of the tip of the metal protective tube and placing a low thermal conductivity section made of a material with a lower thermal conductivity than the metal protective tube inside the groove, it was confirmed that under the same test conditions, the metal protective tube, which is inferior in terms of responsiveness and material properties, had a faster temperature response than the metal protective tube, which is superior in terms of responsiveness and material properties.

In other words, by providing a low thermal conductivity section made of a material with a lower thermal conductivity than the protective tube in a groove recessed in the protective tube, it can be inferred that the responsiveness can be improved compared to a protective tube made of only a single material.

REFERENCE SIGNS LIST 1 Temperature measuring device 20 Sheathed thermocouple 21 Sheath 211 Temperature sensing part 40 Protective tube 401 Tip part 41 Groove 42 Low thermal conductive part 43 Mounting surface 90 Kneader 91 Mounting hole 911 Inner wall

Claims (6)

A protective tube formed in a cylindrical shape;
a thermocouple having a temperature sensing portion at a tip and inserted into the protective tube;
A temperature sensing portion of the thermocouple is fixed to a tip portion of the protective tube,
At least one groove is provided on an outer circumferential surface of the protective tube,
a low thermal conductive portion made of a low thermal conductive material having a thermal conductivity lower than that of the protective tube is provided in the recessed groove;
The groove is provided around the entire outer circumferential surface of the protective tube . The temperature measuring device according to claim 1 , wherein an outer circumferential surface of the low thermal conductivity portion is configured to be substantially flush with an outer circumferential surface of the protective tube or to be recessed from the outer circumferential surface of the protective tube. 3. The temperature measuring device according to claim 1 , wherein the low thermal conductive portion is made of a ceramic material containing zirconia or zirconium dioxide. 4. The temperature measuring device according to claim 1 , wherein the protective tube is interposed between a tip of the protective tube and the low thermal conductivity portion, and an attachment surface is provided that is formed of a part of an outer peripheral surface of the protective tube. The temperature measuring device of claim 1 , wherein the tip is tapered. 6. The temperature measuring device according to claim 1 , wherein the tip portion is subjected to a surface treatment for improving abrasion resistance.