JPH04348237A - Temperature detection element - Google Patents

Abstract

PURPOSE:To obtain a temperature detection element which is superb in temperature characteristics and response characteristics. CONSTITUTION:A title item is a temperature-detection element which is formed by installing one to a plurality of silicon carbide fiber filaments with a fiber diameter of 3-200mum between terminals (electrodes) 2a and 2b. Since the silicon carbide fiber has an extremely superb heat resistance and then a proper inherent resistance and a thermistor constant and is further in a thin fiber shape, its thermal capacity is small and it can be balanced to an atmosphere temperature in a short time for improved characteristics.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is applicable to
The present invention relates to a temperature detection element with excellent heat resistance and responsiveness that can be used regularly at temperatures as high as 0°C.

0002

[Prior Art] Conventionally, resistance temperature detectors, thermocouples, ceramic thermistors, etc. have been used for many purposes as temperature detection elements for detecting temperature. Many of them are low.

Therefore, many thermocouples using platinum-rhodium alloys, thermocouples using tungsten-rhenium alloys, etc., which are commonly used at relatively high temperatures, have been provided and put into practical use. Furnace Handbook (edited by Japan Industrial Furnace Association, 1978 edition) P. 583 etc.].

0004

[Problems to be Solved by the Invention] However, the above-mentioned well-known thermocouples etc. using platinum-rhodium alloy or tungsten-rhenium alloy are
At temperatures of about 0 to 1500°C, there are the following problems.

■ Sensitivity decreases. ■ Sufficient response speed cannot be obtained. ■ Continuous use time is inevitably limited depending on the environment in which it is used, such as heat resistance. ■ The cost is high because it uses expensive materials.

[0006] In recent years, there has been a demand for the provision of temperature detection elements that can solve the above-mentioned problems, especially in high-temperature gas temperature measurement such as combustion gas of internal combustion engines such as vehicles, temperature measurement in high-temperature furnaces, continuous temperature measurement at various gas flow points, etc. is significantly high. The present invention
It is an object of the present invention to provide a temperature detection element that can solve these problems and meet the above requirements.

[0007]

[Means for Solving the Problems] The present invention provides a terminal (electrode)
This temperature sensing element is characterized in that one or more silicon carbide fiber filaments having a fiber diameter of 3 to 200 μm are arranged in between.

The silicon carbide fiber used in the present invention is made mainly of β-SiC, which is obtained by melt-spinning an organic silicon polymer compound such as polycarbosilane or polytitanocarbosilane, and then making it infusible and firing it. Continuous long fibers are preferably used.

The firing temperature must be at least 1000°C, and if the temperature detection element requires a commonly used temperature of 1000°C to 1500°C, it is necessary to perform the firing up to the commonly used temperature. When the firing temperature exceeds 1500℃,
This is not preferable because it causes deterioration of the filament.

[0010] The specific resistance of this silicon carbide fiber at room temperature is 108
~102 Ω・cm, thermistor constant B is 1000~
3000K, which is sufficient to electrically detect temperature changes using conventional methods.

[0011] Furthermore, the terminals (electrodes) for fixing these silicon carbide fiber filaments may be of any type as long as they have a lower specific resistance than the fibers and have sufficient heat resistance to the temperatures at which they are commonly used. An appropriate metal material or carbon material may be selected and used.

[0012] It is sufficient to fix 1 to 500 silicon carbide fiber filaments between the terminals, and the distance between the terminals is 0.1 m.
m or more, preferably 0.5 to 100 mm. If the distance between the terminals is less than 0.1 mm, it is undesirable because the device configuration means for temperature detection becomes complicated. Also this is 100mm
Exceeding this is also undesirable since the resistance between the terminals increases and the electrical detection characteristics deteriorate.

Next, sufficient detection is possible if the diameter of the silicon carbide fiber filament is 200 μm or less;
Particularly preferably, the thickness is 30 μm or less, and the response speed (thermal time constant: τ) can be at least 50 msec or less.

[0014]

[Function] In the temperature detection element of this invention, 3 to 20
One or more silicon carbide fiber filaments with a diameter of 0 μm are arranged, and the silicon carbide fiber has extremely excellent heat resistance, has appropriate specific resistance and thermistor constant, and is thin fibrous, so its heat capacity is high. is small, the temperature reaches equilibrium with the ambient temperature in a short period of time, and the effect exhibits the above-mentioned characteristics.

[0015]

[Examples] The present invention will be specifically explained below with reference to Examples. Examples 1 to 5 Polycarbosilane was melt-spun with different drawing ratios to obtain spun filaments with different diameters. This was subjected to infusibility treatment at 200°C for 50 minutes, and then fired at 1200 to 1400°C for 30 to 60 minutes to form a silicon carbide fiber filament with the characteristics shown in Table 1 (composition: Si: 56 wt%, C: 28 wt%).
, O: 11 wt%, balance such as H: 5 wt%).

The obtained fiber filament 1 was cut into 50 mm pieces, and 50 pieces each were connected and fixed between platinum electrodes 2a and 2b supported by an alumina insulating stand 3 (distance between the electrodes: 2 mm) to obtain the temperature sensing element of the present invention. In FIG. 1, 4a and 4b are electrode pins made of carbon or graphite.

Next, this was placed in an electric furnace and heated to 1200°C.
While keeping the temperature at the same temperature, arc light is passed through the peephole of the electric furnace from the outside at a shutter speed of 5 x 10-5.
sec and the thermal time constant (the time required for the voltage to change to 63% of the equilibrium value) was measured. The results are shown in Table 1.

[0018]

[Table 1]

According to the results shown in Table 1 above, it was clear that the examples exhibited excellent characteristics, particularly in response speed and the like. Furthermore, using the same electric furnace, the temperature was repeatedly raised and lowered to 1200° C., and the state of deterioration of the detection element was measured while detecting the temperature by resistance change. As a result, even when the temperature was raised 100 times, there was no abnormality in the detection performance and no deterioration of the element.

Comparative Example Commercially available platinum-platinum rhodium thermocouple (wire diameter 100 μm)
The thermal time constant was measured in the same manner as in Examples 1 to 5 without providing a protective tube to reduce the thermal time constant, and the result was 230 [msec]. In addition, the detection performance and deterioration of the thermocouple were measured in the same manner as in Examples 1 to 5, and as a result, it became abnormal after seven repeated temperature rises and became unusable.

[0021]

Effect of the invention: The temperature detection element of this invention has a temperature of 3 to 200
one to a plurality of silicon carbide fiber filaments having a diameter of μm are arranged, and the silicon carbide fiber has extremely excellent heat resistance and has an appropriate specific resistance and thermistor constant;
In addition, since it is thin fibrous, its heat capacity is small, and it reaches equilibrium with the ambient temperature in a short period of time.As a result, the above-mentioned temperature characteristics and response characteristics can be significantly improved, and its industrial use effect is extremely high. big.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of one embodiment of the temperature detection element of the present invention.

[Explanation of symbols]

1 Silicon carbide filament 2 Electrode

Claims (1)

[Claims] [Claim 1] Between terminals (electrodes), fiber diameter 3 to 20
A temperature detection element characterized by having one or more silicon carbide fiber filaments of 0 μm arranged in an array.