Temperature measurement device

Abstract

To provide a temperature measuring device that reduces an influence of ambient temperature while maintaining mechanical strength, and is fitted closely to kneading facilities.SOLUTION: A temperature measuring device comprises a protection pipe formed in a cylindrical shape, and a thermocouple having a temperature sensing part at a tip and inserted into the protection pipe, wherein the temperature sensing part of the thermocouple is fixed to the tip part of the protection pipe, a recessed groove is formed over an outer peripheral surface of the protection pipe, and a low heat-conductive part made of a low heat-conductive material lower in heat conductivity than the protection pipe is provided in the recessed groove.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a temperature measuring device, and more particularly to a temperature measuring device that is preferably installed in a kneading device to measure the temperature of a kneaded material.

Background Art

[0002] As a temperature measuring device for this type of kneading device, in order to withstand the stress (impact and bending forces) received from a viscous kneaded material, a metal protective tube having durability is attached with a part of its tip protruding into the kneading chamber, and a sheath thermocouple is inserted therein. This has been conventionally proposed (see, for example, Patent Document 1).

[0003] By the way, when kneading a highly viscous kneaded material in a kneading device, if the set temperature is exceeded, the kneaded material will burn and become defective. Therefore, the responsiveness of the temperature measuring device installed in the kneading device is very important. However, the conventional protective tubes are made of the same material, and their responsiveness is determined by their shape, the thermal conductivity of the material, etc., and improvement in responsiveness has not been expected.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] An object of the present invention is to provide a temperature measuring device that has durability and is easily improved in responsiveness.

Means for Solving the Problems

[0006] In view of such a situation, the present inventor has conducted intensive studies and, as a result, considers that one of the reasons for the decrease in responsiveness is that heat escapes from the proximal end side through the protective tube, particularly from the attachment portion to the equipment side. The inventor conceived of preventing heat escape by thinning the thickness of the proximal end side of the protective tube, and further provided a low heat conduction portion made of a low heat conduction material having a lower heat conductivity than the protective tube at the thinned portion. As a result, it was found that the mechanical strength against the impact and bending force received from the measurement object can be maintained, and the present invention has been completed.

[0007] That is, the temperature measuring device according to the present invention includes a protective tube formed in a cylindrical shape, and a thermocouple having a temperature sensing portion at its tip and inserted into the protective tube. The temperature sensing portion of the thermocouple is fixed to the tip of the protective tube, at least one concave groove is provided on the outer peripheral surface of the protective tube, and a low heat conduction portion made of a low heat conduction material having a lower heat conductivity than the protective tube is provided in the concave groove.

[0008] According to this configuration, heat energy is conducted from the measurement object to the tip of the protective tube and the temperature sensing portion fixed to the tip, and heat is transferred toward the proximal end. The heat transfer of the protective tube in the proximal end direction is suppressed by the low heat conduction portion made of a low heat conduction material, and heat energy is likely to concentrate on the temperature sensing portion. Therefore, the time for the measured temperature to reach the temperature of the measurement object is shortened. Furthermore, since the low heat conduction portion is provided in the concave groove, the mechanical strength of the thinned protective tube is reinforced.

[0009] Also, it is preferable that the concave groove is provided over the entire outer peripheral surface of the protective tube.

[0010] According to this configuration, the heat transfer from the tip of the protective tube is significantly suppressed by the concave groove provided over the entire circumference and the low heat conduction portion provided in the concave groove. Heat energy is more concentrated on the temperature sensing portion, and the installation area of the low heat conduction portion is reduced, thereby reducing the material cost.

[0011] Also, it is preferable that the outer peripheral surface of the low heat conduction portion is configured to be substantially flush with the outer peripheral surface of the protective tube or recessed from the outer peripheral surface of the protective tube.

[0012] According to this configuration, the low heat conduction part is provided in the concave groove, not only reinforcing the mechanical strength of the thin-walled protective tube, but also making the outer peripheral surface of the low heat conduction part and the outer peripheral surface of the protective tube substantially flush, or the outer peripheral surface of the low heat conduction part is recessed from the outer peripheral surface of the protective tube. Therefore, when attaching to equipment that requires temperature measurement, by opening a hole that matches the outer shape of the protective tube, the contact between the low heat conduction part and the inner wall of the hole is reduced, and it can be attached easily and smoothly.

[0013] Further, it is preferable that the low heat conduction part is formed using a ceramic material containing zirconia or zirconium dioxide.

[0014] According to this configuration, the ceramic material containing zirconia or zirconium dioxide has a lower thermal conductivity than the metal material often used as a protective tube, and can suppress the transfer of thermal energy to the base end. Also, the mechanical strength of the thin-walled protective tube provided in the concave groove is reinforced.

[0015] Further, it is preferable that an attachment surface is provided between the tip of the protective tube and the low heat conduction part, and the attachment surface is part of the outer peripheral surface of the protective tube.

[0016] According to this configuration, when attaching to equipment that requires temperature measurement, the attachment surface is used to facilitate the attachment of the temperature measurement device. In particular, when attaching to a hole or the like that is opened according to the outer shape of the protective tube, it can be in close contact with the inner wall of the hole without a gap.

[0017] Further, it is preferable that the tip is tapered.

[0018] According to this configuration, the volume of the tip of the protective tube becomes small, the heat capacity is reduced, and the thermal energy is more likely to be concentrated by the tip, and the time for the measured temperature to reach the temperature of the measurement object is further shortened.

[0019] Further, it is preferable that the tip is subjected to a surface treatment for improving wear resistance.

[0020] According to this configuration, since the wear resistance is improved, the tip protruding into the kneading chamber is less likely to be damaged.

Effects of the Invention

[0021] A temperature measuring device having such a configuration can easily improve the responsiveness while enhancing the strength of the thermocouple.

Brief Description of the Drawings

[0022]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Modes for Carrying Out the Invention

[0023] Hereinafter, embodiments according to the present invention will be described with reference to the drawings. In each figure, components denoted by the same reference numerals are the same components, and the description thereof will be omitted.

[0024] FIG. 1 is a perspective view showing a temperature measuring device according to an embodiment of the present invention. FIG. 2 is a cross-sectional view showing the configuration of a temperature measuring device according to an embodiment of the present invention. The temperature measuring device 1 shown in FIG. 2 includes a sheathed thermocouple 20 and a protective tube 40.

[0025] The sheath thermocouple 20 is a grounded sheath thermocouple having a sheath 21, compensating leads 23, and a sleeve 22 connecting the sheath 21 and the compensating leads 23. Among them, the sheath 21 has a pair of thermocouple element wires (not shown) provided therein, and a temperature sensing portion 211 which is a temperature measuring contact where a pair of thermocouple element wires are directly welded to the tip of the sheath 21 is provided.

[0026] The protective tube 40 is provided with a tapered tip portion 401, and a concave groove 41 is provided on the outer peripheral surface over the entire circumference. The other parts are cylindrical metal protective tubes having the same outer diameter.

[0027] The tip portion 401 is formed in a tapered shape both inside and outside, and a certain wall thickness is ensured. Note that the tip portion 401 is preferably tapered, but this is not limiting. Also, in order to improve the wear resistance on the surface of the tip portion 401, a surface treatment such as DLC (diamond-like carbon) treatment may be performed.

[0028] The concave groove 41 is provided on the outer peripheral surface of the protective tube 40 with the same depth. Preferably, it is provided on the outer peripheral surface of the protective tube 40 on the side of the tip portion 401, but this is not limiting. Also, the concave groove 41 is provided with a low heat conduction portion 42 having a lower thermal conductivity than the protective tube 40.

[0029] The protective tube 40 is interposed between the base end of the tip portion 401 and the low heat conduction portion 42, and a mounting surface 43 which is a part of the outer peripheral surface of the protective tube 40 is provided. Note that the mounting surface 43 does not necessarily have to be interposed between the base end of the tip portion 401 and the low heat conduction portion 42. Further, the mounting surface 43 may not be provided on the outer peripheral surface of the protective tube 40, and a mounting surface 43' may be provided at the low heat conduction portion 42.

[0030] The temperature sensing portion 211 is fixed to the apex of the tip portion 401 by welding. Note that this is not limiting as long as the temperature sensing portion 211 is fixed at a location where it can easily measure the temperature of the measurement target.

[0031] The outer peripheral surface of the low heat conduction part 42 is configured to be substantially flush with the outer peripheral surface of the protective tube 40. Note that the outer peripheral surface of the low heat conduction part 42 may be configured to be slightly recessed from the outer peripheral surface of the protective tube 40, but this is not limiting.

[0032] The protective tube 40 has a total length of 200 mm, an outer diameter of 19.9 mm, and is made of Inconel 625. It is provided with a tip part 401 having a length of 25 mm from the tip, a low heat conduction part 42 having a length of 34 mm and a thickness of 2 mm extending from a position 33 mm from the tip toward the rear end side, and a mounting surface 43 having a length of 8 mm intervening from the base end of the tip part 401 to the low heat conduction part 42.

[0033] The low heat conduction part 42 is configured by spraying zirconia, which has a lower thermal conductivity than the Inconel 625 used for the protective tube 40, into the concave groove 41.

[0034] Note that the low heat conduction part 42 may be made of a material having a lower thermal conductivity than the material used for the protective tube 40, but this is not limiting. Also, the concave groove 41 and the low heat conduction part 42 provided in the concave groove 41 are provided over the entire outer peripheral surface of the protective tube 40, but this is not limiting as long as the mechanical strength is not impaired and heat energy can be retained.

[0035] FIG. 3 is a schematic diagram showing a state in which the temperature measuring device according to an embodiment of the present invention is attached to a kneader. The temperature measuring device 1 shown in FIG. 3 is fitted and attached to the attachment hole 91 of the kneader 90.

[0036] Since the structure of the kneader 90 is well-known, its description is omitted. The attachment hole 91 is opened in accordance with the outer diameter of the protective tube 40 so that no gap is generated between the protective tube 40 when the temperature measuring device 1 is attached.

[0037] When the outer peripheral surface of the low heat conduction part 42 is formed by spraying, it is formed to be substantially flush with the outer peripheral surface of the protective tube 40, and the temperature measuring device 1 can be fitted without being caught by the attachment hole 91.

[0038] FIG. 4 is a partial enlarged view showing a portion where the temperature measuring device according to an embodiment of the present invention is in contact with the kneader. The temperature measuring device 1 shown in FIG. 4 is fitted into a mounting hole 91 that is opened according to the outer diameter of the protective tube 40, and a mounting surface 43 interposed between the base end of the tip portion 401 and the low heat conduction portion 42 is in close contact with the inner wall 911 of the mounting hole 91.

[0039] The low heat conduction portion 42 is formed in the concave groove 41 by a process such as spraying on the outer peripheral surface of the protective tube 40 formed by metal processing. That is, in terms of the manufacturing process, the processing accuracy of the low heat conduction portion 42 is lower than that of the outer peripheral surface of the protective tube 40 formed by metal processing. For this reason, even if an attempt is made to form the low heat conduction portion 42 flush with the protective tube 40, variations will occur in the manufacturing process, and there is a risk that it may bulge or dent compared to the outer peripheral surface of the protective tube 40.

[0040] If the outer peripheral surface of the low heat conduction portion 42 is formed to coincide with the outer peripheral surface of the protective tube 40, the formation of the protective tube becomes complicated, which is not preferable in terms of cost.

[0041] On the other hand, if the outer peripheral surface of the low heat conduction portion 42 is formed to bulge from the outer peripheral surface of the protective tube 40, it will come into contact with the opening of the mounting hole 91 opened according to the outer diameter of the protective tube 40, making it difficult to fit.

[0042] Even if the mounting hole 91 is opened according to the outer diameter of the low heat conduction portion 42 formed to bulge from the outer peripheral surface of the protective tube 40, when the temperature measuring device 1 is mounted, it will be supported by the low heat conduction portion 42 on the rear end side from the tip portion 401 of the protective tube, and there is a risk that the strength of the temperature measuring device 1 will be weakened.

[0043] For this reason, it is conceivable to make a slight recess in advance so that the low heat conduction portion 42 does not protrude from the outer peripheral surface of the protective tube 40 in consideration of variations during manufacturing. In this case, as shown in FIG. 4, it is preferable to configure the low heat conduction portion 42 to be slightly recessed from the outer peripheral 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 heat conduction portion 42 is in close contact with the inner wall 911 of the mounting hole 91.

[0044] In addition, a plurality of concave grooves 41 and low thermal conductivity portions 42 provided in the concave grooves 41 can be provided at intervals in the axial direction of the protective tube 40, or can be spaced apart in the entire circumferential direction of the protective tube 40. FIGS. 5 and 6 are partial enlarged views showing a portion where the temperature measuring device according to a modification of an embodiment of the present invention is in contact with the kneading equipment.

[0045] As shown in FIG. 5, the low thermal conductivity portions 42 having a small axial width are divided at intervals, or as shown in FIG. 6, the concave grooves 41 are provided in a serrated shape by knurling and the low thermal conductivity portions 42 are provided in the concave grooves 41. As a result, although the total installation area of the low thermal conductivity portions 42 becomes smaller than that in the above-described embodiment, the material cost can be reduced. Further, in FIG. 5, the spaces between the low thermal conductivity portions 42 function as the mounting surface 43, and in FIG. 6, not only is the mounting surface 43 provided between the tip portion and the concave grooves 41 and the low thermal conductivity portions 42 provided in the concave grooves 41, but also the serrated convex portions flush with the outer peripheral surface of the protective tube also serve as the mounting surface 43 (not shown), so that the holding posture in the kneader becomes more stable.

Example

[0046] Next, a comparative example a which is a temperature measuring device including a grounded sheath thermocouple and a cylindrical metal protective tube made of Inconel 625 and provided with a tapered tip portion, and a comparative example b which is a temperature measuring device having the same specifications as the comparative example a except that SUS304 is used instead of Inconel 625 will be described with respect to the results of measuring the time constant under the same test conditions. Note that neither the comparative example a nor the comparative example b includes the concave grooves and the low thermal conductivity portions as in the present embodiment.

[0047] In the test, each temperature measuring device is inserted 150 mm into the oil bath, and the temperature of the oil bath is heated from the room temperature at the time of measurement to 150°C to measure the time constant, which is performed in 5 steps (N = 1 to 5). The humidity at the time of measurement is maintained at the same humidity, and the results are as shown in Table 1.

[0048]

Table 1

[0049] As shown in Table 1, it can be seen that Comparative Example a using Inconel 625 has a larger time constant for temperature rise than Comparative Example b using SUS304. Due to the material, it can be seen that SUS304 has better thermal conductivity than Inconel 625 and faster temperature responsiveness.

[0050] Therefore, a new Example a1 using the same Inconel 625 as Comparative Example a was prepared.

[0051] Example a1 is a temperature measuring device including, similar to this embodiment, a grounded sheath thermocouple and a cylindrical metal protection tube provided with a tapered tip portion, a concave groove on the rear end side from the tip portion, and a low thermal conductivity portion provided inside the concave groove. Further, the low thermal conductivity portion according to Example a1 is made of zirconia having a lower thermal conductivity than Inconel 625 as the material, and is provided inside the protection tube by thermal spraying.

[0052] When the time constant was measured again for this Example a1 and Comparative Example b, which had a fast temperature responsiveness in the previous test, under the same test conditions as the above-described experiment, the results were as shown in Table 2.

[0053]

Table 2

[0054] As can be seen from the results in this Table 2, it can be seen that Example a1 in which zirconia having a lower thermal conductivity than Inconel 625 was provided at the tip portion of the metal protection tube using Inconel 625 had a faster temperature responsiveness than Comparative Example b.

[0055] Due to the material, a metal protection tube using Inconel 625, which is inferior to a metal protection tube using SUS304 in terms of thermal conductivity, will not have a faster temperature responsiveness than SUS304 under the same conditions.

[0056] However, by providing a concave groove on the rear end side from the tip of the metal protection tube and internally installing a low heat conduction part made of a material with a lower thermal conductivity than the metal protection tube in the concave groove, it was confirmed that under the same test conditions, the metal protection tube with inferior material responsiveness had a faster temperature responsiveness than the metal protection tube with superior material responsiveness.

[0057] That is, it can be inferred that by internally installing a low heat conduction part made of a material with a lower thermal conductivity than the protection tube in the concave groove recessed on the protection tube, the responsiveness is improved compared to the protection tube formed of only a single material.

Explanation of Signs

[0058] 1 Temperature measuring device 20 Sheathed thermocouple 21 Sheath 211 Temperature sensing part 40 Protection tube 401 Tip 41 Concave groove 42 Low heat conduction part 43 Mounting surface 90 Kneader 91 Mounting hole 911 Inner wall

Claims

1. A protective tube formed in a cylindrical shape, a thermocouple having a temperature-sensitive part at the tip and inserted into the protective tube, comprising: the temperature-sensitive part of the thermocouple is fixed to the tip of the protective tube, at least one concave groove is provided on the outer peripheral surface of the protective tube, a low heat conduction part made of a low heat conduction material having a lower heat conductivity than the protective tube is provided in the concave groove, the concave groove is provided over the entire outer peripheral surface of the protective tube, a temperature measuring device.

2. The temperature measuring device according to claim 1, wherein the outer peripheral surface of the low heat conduction part is configured to be substantially flush with the outer peripheral surface of the protective tube or recessed from the outer peripheral surface of the protective tube.

3. The temperature measuring device according to claim 1 or 2, wherein the low heat conduction part is made of a ceramic material containing zirconia or zirconium dioxide.

4. The temperature measuring device according to any one of claims 1 to 3, wherein the protective tube has an attachment surface interposed between the tip of the protective tube and the low heat conduction part and formed of a part of the outer peripheral surface of the protective tube.

5. The temperature measuring device according to any one of claims 1 to 4, wherein the tip is tapered.

6. The temperature measuring device according to any one of claims 1 to 5, wherein the tip is subjected to a surface treatment for improving wear resistance.

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