JPH033900B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a detector. More specifically, the present invention relates to a detector that has good gas-sensitive characteristics, good temperature-sensitive characteristics, responsiveness, and durability. Gas-sensitive detectors and heat-sensitive detectors play an important role as devices that control the appropriate supply of fuel and the generation of harmful fuel waste gas in industrial and household fuel equipment and automobile engines. ,
Recently, it has become widely used. For example, if the detector is for exhaust gas from an automobile engine, it is important that the heat-sensitive element follows the exhaust gas temperature as quickly as possible and indicates a value close to the true gas temperature. Also, in the case of gas-sensitive elements,
After the engine starts, the faster the engine warms up with exhaust gas and reaches its activation temperature, the sooner it will operate and show the correct value. In other words, this means that when performing feedback control on the exhaust gas composition, the exhaust gas purification catalyst can be operated effectively to prevent harmful exhaust gas from being discharged by being activated quickly. On the other hand, gas-sensitive and heat-sensitive detectors are exposed to the high-temperature gas atmosphere immediately after being discharged from combustion equipment, so they have excellent responsiveness under the harsh conditions mentioned above. However, at present, there is no material that satisfies both requirements. In view of the above-mentioned circumstances, the present invention aims to provide a heat-sensitive and gas-sensitive detector that is highly durable and has not only heat-sensitive and gas-sensitive characteristics in a steady state, but also improved response characteristics in an emergency, for example, immediately after starting an engine. As a result of our studies, we found that by selecting specific materials for the gas- and heat-sensitive elements and the electrode wires included therein, and by selecting a specific material for the ceramic insulator tube through which the electrode wires pass, we found that not only the responsiveness but also the responsiveness could be improved. First, we have found a detector that is also satisfactory in terms of durability. That is, the present invention provides a detector comprising a gas-sensitive element or a heat-sensitive element and a ceramic insulator tube through which electrode wires connected to the element are passed, wherein the ceramic insulator tube is made of a material selected from zirconia, forsterite, and steatite. , the electrode wire is made of a material selected from nickel, nickel alloy, and stainless steel, and the detector is constructed by bonding the electrode wire and a ceramic insulator tube with a heat-resistant adhesive. . Hereinafter, the present invention will be explained based on the drawings. FIGS. 1A and 1B are a partially sectional side view and a sectional view at right angles to the longitudinal direction of an example of a heat-sensitive detector equipped with a thermoelectric element according to the present invention. Reference numeral 1 denotes a ceramic insulator tube with a through hole through which two electrode wires 22 pass. Electrode wire 2
A heat-resistant adhesive 3 is placed between 2 and the ceramic insulator 1.
The electrode wires 22 are respectively fixed in the through holes. 4, for example, depending on the thermal atmosphere detected by the thermocouple element provided at the tip of the electrode wire 22.
From PR thermocouple elements, CC thermocouple elements, CRC thermocouple elements, C ₀ O−Al ₂ O ₃ thermocouple elements, thermistors such as ZrO ₂ , CA thermocouple elements, IC thermocouple elements, and other known items. The selected item will be installed.
Reference numeral 5 denotes a metal fixture for fixing to a combustion exhaust gas exhaust pipe or the like in a hot atmosphere. In the above, the ceramic insulator 1 is required to be made of a material with a certain degree of low thermal conductivity in order to prevent the transfer of heat from the atmosphere to the heat-sensitive or gas-sensitive element when exposed to a hot atmosphere. , for the purpose of improving ease of handling and durability.
A strength of 1000 kg/cm ² or more is required. However, in order to bond with the electrode wire made of the material described later, it is necessary to minimize the thermal stress that acts between the two due to thermal strain, so the coefficient of thermal expansion is 85 × 10 ^-7 .
Materials with a rating of C ^-1 or higher are preferred; zirconia, forster liner,
Steatite is suitable, and among these, forsterite is the most excellent material for ceramic insulators in terms of cost and performance. Examples of the material for the electrode wire 22 include nickel and nickel alloy stainless wire, which have heat resistance to withstand a hot atmosphere. Among these, stainless steel wire is the most advantageous in terms of cost. Heat resistant adhesive 3
In addition to the commonly used glass sealants (water glass cement) and ceramic cement, it is also possible to use nickel or copper plating on the electrode wire and use the oxide film as a lubricating layer.
By providing the heat-resistant adhesive 3, it is possible to securely hold and fix the electrode wire 22 to the ceramic insulator tube 1, eliminate the gap between the two, and obtain a detector with good airtightness. When using the detector below, it is possible to prevent the electrode from swinging and mechanical damage to the element. Furthermore,
This serves to prevent the metal electrode itself from being attacked by the gas it absorbs. Figures 2A and 2B show an example of a gas-sensitive element detector equipped with a gas-sensitive element according to the present invention, and show a partially sectional side view and a side view of the gas-sensitive element attached to the tip of the detector. be. In the figures, the same numbers as in FIG. 1 have the same meanings as in the same figure.
Reference numeral 7 denotes a gas-sensitive element, to which a metal oxide semiconductor whose electrical resistance changes depending on the components of the exhaust gas to be detected is applied. For example, ceramic sintered bodies mainly made of titanium oxide and cobalt oxide are used to detect oxygen in automobile exhaust gas or exhaust gas from combustion equipment in factories, and oxidized bodies are used to detect hydrocarbon gases and monodispersed carbon in the gas. A ceramic sintered body mainly composed of tin and zinc oxide with a platinum electrode 8 embedded therein is used, and is welded to an electrode wire 22 and attached to the ceramic insulator tube 1. Note that 6 is a protector provided with atmospheric gas inlet/outlet holes 6a for protecting the ceramic insulator tube 1 and the gas-sensitive element 7.
In other respects, the materials of the ceramic insulator tube 1 and the electrode wires 2 are the same as those of the heat-sensitive detector shown in FIG. As described above, the present invention provides a heat-sensitive or gas-sensitive element in a ceramic insulator tube made of a specific material range with good output response and low thermal stress, and in the insulator tube,
Equipped with an electrode wire made of a specific material range that synergistically exhibits durability when combined with a ceramic insulator tube, and a heat-resistant adhesive between the ceramic insulator tube and the electrode wire that acts to enhance the durability. This is a detector that fixes electrode wires to a ceramic insulator tube by filling it with a chemical agent, and it is far superior to conventionally known detectors in terms of response and durability.
Its industrial utility value is great. Next, the present invention will be explained using Examples, but the present invention is not limited to the following Examples unless the gist of the invention is exceeded. Example 1 Using the materials listed in Table 1 below, a cylindrical ceramic insulator tube material with a diameter of 5φ with two through holes of 0.8φ was molded, and then fired at the temperature shown in Table 1.
A ceramic insulator 1 as shown in the figure was obtained. Insert a CA thermocouple into each through hole of this ceramic insulator,
The electrode nickel wire 1 to be connected is fixed in the through hole with water glass cement as a heat-resistant adhesive 3, and a CA thermocouple element 4 is attached to the tip of the wire.
The base is fixed to a metal fixture 5 with water glass cement, and is tightened and fixed in a gas combustion cylinder (not shown) in a combustion device via the metal fixture 5,
It was exposed to the exhaust gas atmosphere and the temperature was detected. Temperature measurement was performed based on a temperature of 320°C when measured by a detector that did not use a ceramic insulator tube. We also compared the time required to reach 200°C during exhaust gas temperature measurement. The results are shown in Table 1.

【table】

[Table] As is clear from the above results, it can be seen that the products of the present invention have faster response to temperature than those of the comparative examples. Example 2 A titania material with a diameter of 0.3φ and a length of 8 mm was added to a titania raw material made by mixing titanium oxide with a particle size of 1μ with 5% by weight of platinum black.
A 13% PR electrode 8 was buried therein, formed into a shape of 2×4×1 ^t as shown in FIG. 2, and fired at 1200° C. for 1 hour to obtain the gas-sensitive element 7 shown in the figure. the above
A nickel wire 2 with a length of 80 mm and a diameter of 0.6φ is dissolved at the end of the PR electrode, passed through the through hole of a ceramic insulator tube 1 made of various materials similar to those in Example 1, and a ceramic wire is used as a heat-resistant adhesive 3. Fixed with acid cement. Then, the base was fixed to the metal fixture 15 with ceramic phosphate cement, and the protector 6 was further bonded to cover the ceramic insulator tube and the gas-sensitive element, thereby creating a gas-sensitive detector as shown in FIG. 3. This was fastened and fixed in a gas combustion tube (not shown) in a combustion device via a metal fixture 5, and exposed to an exhaust gas atmosphere having a temperature of 320° C. and a CO content of 0.5%. At this time, the output was measured using the electric circuit shown in FIG. 3B, and the relationship between this and the response time was investigated. The results are shown in the graph of FIG. Incidentally, in the figure, the numbers refer to the above-mentioned Example 1.
means the same numbers as in Table 1. As is clear from these results, the product of the present invention has a comparatively superior response to output. Example 3 Using the same gas-sensitive element as in Example 2, the following second
A gas-sensitive detector of the same type as in Example 2 was prepared using the various electrode wires shown in the table and a ceramic insulator made of ceramic material. The gas-sensitive element part of this detector is heated to 850℃ with a burner, then cooled to 200℃ with compressed air, and this is repeated every 5 minutes. The number of cycles until the cutoff occurred was counted.
The results are shown in Table 2.

[Table] As is clear from the above results, the detector made of the combination of the ceramic insulator tube and electrode wire of the present invention has less thermal distortion than the comparative example, and therefore has excellent durability with less occurrence of wire breakage. I can see that

[Brief explanation of drawings]

Figure 1A is a side view of an example of the heat-sensitive detector of the present invention, partially shown in cross section, Figure B is a sectional view taken along line A-A' in Figure A, and Figure 2A is partially shown in cross section. Figure 3 is a side view of an example of the gas-sensitive detector of the present invention; FIG. 4 is a graph showing the relationship between response and responsiveness, and FIG. 4 is an electrical circuit diagram at that time. 1... Ceramic insulator tube, 2... Electrode wire, 3...
Heat-resistant adhesive, 4... thermocouple element, 5... metal fixture, 6... protector, 7... gas sensitive element,
8...Platinum electrode.

Claims (1)

[Scope of Claims] 1. A detector comprising a gas-sensitive element or a heat-sensitive element and a ceramic insulator tube through which an electrode wire connected to the element is passed, wherein the ceramic insulator tube is selected from zirconia, forsterite, and steatite. the electrode wire is made of a material selected from nickel, nickel alloy, and stainless steel;
Furthermore, the detector is characterized in that it has a structure in which an electrode wire and a ceramic insulator are bonded together using a heat-resistant adhesive. 2. The detector according to claim 1, wherein the gas-sensitive element is made of a metal oxide semiconductor whose electrical resistance changes depending on the type of gas to be detected. 3. The detector according to claim 1, wherein the heat-sensitive element is a thermistor whose electrical resistance changes depending on the ambient temperature to be detected.