JP4990256B2 - Temperature sensor and manufacturing method thereof - Google Patents

Description

  The present invention relates to a temperature sensor including a temperature-sensitive element whose electrical characteristics change with temperature, and a method for manufacturing the same.

As a temperature sensor for measuring the temperature of an automobile exhaust gas or the like, there is a temperature sensor using a thermistor element whose resistance value varies with temperature.
The temperature sensor has a thermistor element provided with a pair of electrodes, a sheath pin containing a pair of signal lines respectively connected to a pair of electrode wires respectively joined to the pair of electrodes, and a tip so as to cover the thermistor element And a cover disposed on the portion.

In joining the electrode wire to the thermistor element, for example, a Pt paste (platinum paste) is applied to the surface of the thermistor element, the electrode wire is attached, and then baked. However, when a temperature sensor is installed near the engine, large vibrations are transmitted to the temperature sensor, the thermistor element vibrates, and the junction between the thermistor element and the electrode wire may be disconnected. Further, the thermistor element may be altered by the reducing gas in the cover, and the resistance characteristic may be changed.
Therefore, there is a temperature sensor in which a thermistor element is sealed with glass including a joint portion with an electrode wire (see Patent Documents 1 and 2).

Japanese Patent Laid-Open No. 3-92735 JP 2002-350241 A

However, since the glass comes into contact with both the thermistor element and the electrode wire, the following problems may occur. That is, since there is a difference in thermal expansion coefficient between the thermistor element and the electrode wire, the thermal expansion coefficient of glass cannot be matched with the thermal expansion coefficient of both the thermistor element and the electrode wire. Therefore, for example, in a temperature sensor with a temperature change from room temperature to 1000 ° C. or more, thermal stress may occur between the glass and the thermistor element or between the glass and the electrode wire.
Specifically, if there is a difference in coefficient of thermal expansion between the glass and the thermistor element, stress is generated in the thermistor element, and the electrical characteristics of the thermistor element with respect to temperature change, making accurate temperature measurement difficult. There is a risk.

  Further, if there is a difference in thermal expansion coefficient between the glass and the electrode wire, a gap is generated between the electrode wire and the glass, and the reducing gas in the cover may enter through this gap and reach the thermistor element. That is, particularly in a temperature sensor placed in a high temperature environment of, for example, 1000 ° C. or higher, the air enclosed in the cover may become a reducing gas having a low oxygen concentration by oxidizing the inner wall surface of the cover. The thermistor element is made of an oxide semiconductor, and the resistance value changes when oxygen defects are formed in the lattice. Therefore, when the reducing gas reaches the thermistor element, the thermistor element is reduced and oxygen lattice defects are generated, which may change the electrical characteristics.

The present invention has been made in view of such conventional problems, and an object of the present invention is to provide a temperature sensor excellent in high temperature durability used in a high temperature environment of 1000 ° C. or higher and a manufacturing method thereof.

According to a first aspect of the present invention, there is provided a temperature sensing element having a temperature sensing element whose electrical characteristics change with temperature,
A sheath pin built in a state in which a pair of signal lines respectively connected to a pair of electrode wires of the temperature sensing element is exposed to the tip side;
A cover disposed at the tip so as to cover the temperature sensing element,
The temperature sensing element has the temperature sensing element and an inner protective layer and an outer protective layer that seal the temperature sensing element together with a part of the electrode wire,
When the thermal expansion coefficient of the thermosensitive element is k1, the thermal expansion coefficient of the electrode wire is k2, the thermal expansion coefficient of the inner protective layer is k3, and the thermal expansion coefficient of the outer protective layer is k4,
| K1-k3 | <| k1-k2 |, | k2-k4 | <| k2-k3 |
Chi is made standing,
And the material which comprises the said inner side protective layer adds 40 weight% or more of the thermistor material which comprises the said thermosensitive element to crystallized glass,
On the other hand, the material constituting the outer protective layer is a temperature sensor characterized in that 30% by weight or less of yttrium oxide is added to crystallized glass .

Next, the effects of the present invention will be described.
The temperature sensing element in the temperature sensor includes an inner protective layer and an outer protective layer that seal the temperature sensitive element together with a part of the electrode wire. Then, the thermal expansion coefficients k3 and k4 of the inner protective layer and the outer protective layer are set to | k1−k3 | <| k1−k2 |, | k2− with respect to the thermal expansion coefficients k1 and k2 of the temperature sensitive element and the electrode wires. k4 | <| k2-k3 | is set to hold. That is, the thermal expansion coefficient k3 of the inner protective layer is brought closer to the thermal expansion coefficient k1 of the thermosensitive element, and the thermal expansion coefficient k4 of the outer protective layer is brought closer to the thermal expansion coefficient k2 of the electrode wire. Therefore, it is possible to suppress the thermal stress generated between the inner protective layer that directly covers the temperature sensing element and the temperature sensing element. Moreover, it can suppress that a clearance gap produces between the outer side protective layer which covers an inner side protective layer, and is closely_contact | adhered to the outer periphery of an electrode wire, and an electrode wire.

Thereby, the action of the thermal stress in the temperature sensing element accompanied by a large temperature change can be suppressed, and the change in the electrical characteristics of the temperature sensing element can be prevented. In addition, by suppressing the generation of gaps between the electrode wires and the outer protective layer, it is possible to prevent the reducing gas in the cover from entering the temperature sensing element and to change the electrical characteristics of the temperature sensing element. Can be prevented.
Therefore, in the temperature sensor accompanied by a large temperature change from room temperature to high temperature, the durability of the temperature sensitive element can be ensured.
In particular, in the present invention, the material constituting the inner protective layer is formed by adding 40% by weight or more of the thermistor constituting the temperature sensitive element to crystallized glass, so that the stress applied to the temperature sensitive element is less than 10 MPa. As a result, the resistance value change rate can be suppressed to less than 20% (see FIGS. 6A to 6C).
Moreover, since the material which comprises the said outer side protective layer as mentioned above adds 30 weight% or less of yttrium oxide to crystallized glass, it can suppress a resistance value change rate to 20% or less (FIG. 7 ( a) to (c)).

As described above, according to the present invention, it is possible to provide a temperature sensor that is used in a high temperature environment of 1000 ° C. or more and excellent in high temperature durability.

A second invention is a method of manufacturing the temperature sensor according to the first invention,
Join the temperature sensor to the tip of the seaspin,
Next, with the cover heated to 300 ° C. or higher, the temperature sensing element is inserted inside the cover,
Then the cover is cooled to room temperature,
Then, there is the cover to the method of manufacturing a temperature sensor, characterized in that welded to the side surface of the sheath pin (claim 14).

  In this manufacturing method, the temperature sensing element is inserted inside the cover while the cover is heated to 300 ° C. or higher. Therefore, the temperature sensing element can be easily inserted inside the cover with the cover sufficiently expanded. Then, by cooling the cover to room temperature after that, the temperature sensing body can be brought into contact with the inner surface of the cover. The temperature sensitive body can be held in the cover by so-called shrink fitting.

  For this reason, in the obtained temperature sensor, even if there is a large temperature change, the cover can squeeze the temperature sensor with an appropriate pressing force, and heat transfer between the cover and the temperature sensor is possible. As a result, heat transferability between the outside and the temperature sensitive element can be improved. Thereby, the measurement accuracy of the temperature sensor can be improved. Further, in the cover, it is possible to prevent the temperature sensing element from vibrating relative to the cover and to prevent the temperature sensing element from being damaged.

  As described above, according to the present invention, it is possible to provide a method for manufacturing a temperature sensor excellent in high temperature durability.

A third invention is a method of manufacturing the temperature sensor according to the first invention,
Join the temperature sensor to the tip of the seaspin,
Next, in a state where the inside of the cover is filled with a slurry-like filler, the temperature sensing element is inserted inside the cover,
Next, the filler inside the cover is dried,
Next, the cover is welded to the side surface of the sheath pin, and the filler is then heat-cured. The method of manufacturing a temperature sensor according to claim 15 .

  In this manufacturing method, the temperature sensing element is inserted inside the cover in a state where the cover is filled with a slurry-like filler. Thereby, in the obtained temperature sensor, it can be set as the state which interposed the filler between the temperature sensing body and the cover. As a result, the heat transferability between the cover and the temperature sensing element can be improved, and as a result, the heat transferability between the outside and the temperature sensing element can be improved. Therefore, the measurement accuracy of the temperature sensor can be improved. Further, in the cover, it is possible to prevent the temperature sensing element from vibrating relative to the cover and to prevent the temperature sensing element from being damaged.

  As described above, according to the present invention, it is possible to provide a method for manufacturing a temperature sensor excellent in high temperature durability.

In the first invention (invention 1), the thermal expansion coefficient is, for example, a thermal expansion coefficient at a temperature of room temperature to 1000 ° C.
Next, the composition of the crystallized glass used for the inner protective layer and the outer protective layer is as follows : SiO ₂ : 30 to 60% by weight, CaO: 10 to 30% by weight, MgO: 5 to 25% by weight, Al ₂ O ₃ : It is preferable that it is 0 to 15 weight% (Claim 2).
In this case, the bondability between the inner protective layer and the outer protective layer is good, and the occurrence of peeling and cracking between them can be prevented.
The thermal expansion coefficients k1, k2, k3, and k4 preferably satisfy | k1-k3 | ≦ 5 × 10 ⁻⁷ / ° C. and | k2−k4 | ≦ 4 × 10 ⁻⁷ / ° C. 3 ).
In this case, the thermal expansion coefficient k3 of the inner protective layer can be sufficiently close to the thermal expansion coefficient k1 of the thermosensitive element, and the thermal expansion coefficient k4 of the outer protective layer can be sufficiently close to the thermal expansion coefficient k2 of the electrode wire. . Therefore, the thermal stress generated between the inner protective layer that directly covers the temperature sensing element and the temperature sensing element can be effectively suppressed. Moreover, it can suppress effectively that a clearance gap generate | occur | produces between the outer side protective layer closely_contact | adhered to the outer periphery of an electrode wire, and an electrode wire. As a result, a temperature sensor excellent in durability can be obtained by further suppressing changes in the electrical characteristics of the temperature sensitive element.

The outer protective layer is preferably always in contact with the inner surface of the cover in a temperature range from room temperature to 850 ° C. (Claim 4 ).
In this case, the cover can be kept in contact with the cover even if thermal expansion of the cover occurs due to a temperature change in a temperature range of at least room temperature to 850 ° C. Excellent heat transfer between the two can be ensured. As a result, a temperature sensor excellent in measurement accuracy can be obtained. Further, in this case, the outer protective layer can be prevented from vibrating relative to the cover, and an impact can be prevented from being applied to the temperature sensing element, and a change in its electrical characteristics can be suppressed.

More preferably, the outer protective layer is always in contact with the inner surface of the cover in a temperature range from room temperature to 1000 ° C. (Claim 5 ).
In this case, the cover can be kept in contact with the cover even if thermal expansion of the cover occurs due to temperature change in a temperature range of at least room temperature to 1000 ° C. Excellent heat transfer between the two can be ensured. As a result, a temperature sensor with further excellent measurement accuracy and durability can be obtained.

The outer protective layer preferably does not cause a chemical reaction with the cover in a temperature range from room temperature to 850 ° C. (Claim 6 ).
In this case, even when the outer protective layer is in close contact with the cover, it is possible to prevent the outer protective layer from being altered at least in the temperature range of room temperature to 850 ° C. Therefore, a temperature sensor having excellent durability can be obtained.

More preferably, the outer protective layer does not cause a chemical reaction with the cover in a temperature range from room temperature to 1000 ° C. (Claim 7 ).
In this case, even when the outer protective layer is in close contact with the cover, the outer protective layer can be prevented from being altered at least in the temperature range of room temperature to 1000 ° C. Therefore, a temperature sensor having excellent durability can be obtained.

Moreover, it is preferable that the said electrode wire is joined to the outer surface of the said thermosensitive element (Claim 8 ).
In this case, the electrode wire can be easily joined to the temperature sensitive element, and an easily manufactured temperature sensor can be obtained. In this case, the fixing force between the temperature sensing element and the electrode wire generally tends to decrease, but the temperature sensor of the present invention has an inner protective layer and an outer protective layer, so that the joint can be reinforced. it can. And the temperature sensor excellent in durability can be obtained by adjusting the thermal expansion coefficient of this inner side protective layer and an outer side protective layer as mentioned above.

Further, a filler may be interposed between the cover and the outer protective layer (Claim 9 ).
In this case, the outer protective layer and the cover are brought into contact with each other via the filler, and excellent heat transfer between the outside of the temperature sensor and the temperature sensing element can be ensured. Further, relative vibration of the temperature sensing element in the cover can be prevented, and damage to the temperature sensing element can be prevented.

Further, in the temperature range of 850 ° C. from room temperature the outer protective layer with being always in contact with the filler, the filler is preferably being in constant contact with the cover (claim 10).
In this case, the outer protective layer is kept in contact with the cover via the filler even if the cover and the filler are thermally expanded due to a temperature change in the temperature range of at least room temperature to 850 ° C. It is possible to ensure excellent heat transfer between the cover and the temperature sensitive body. As a result, a temperature sensor excellent in measurement accuracy can be obtained. Further, in this case, it is possible to prevent the outer protective layer from vibrating relative to the cover, and it is possible to prevent an impact from being applied to the temperature sensitive element and to suppress a change in its electrical characteristics.

Further, in the temperature range of 1000 ° C. from room temperature, the outer protective layer with being always in contact with the filler, the filler is more preferable that the constant contact with the cover (claim 11).
In this case, the outer protective layer keeps the cover in contact with the cover via the filler even if the cover or the filler expands due to a temperature change in the temperature range of at least room temperature to 1000 ° C. It is possible to ensure excellent heat transfer between the cover and the temperature sensitive element. As a result, a temperature sensor excellent in measurement accuracy can be obtained. Further, in this case, it is possible to prevent the outer protective layer from vibrating relative to the cover, and it is possible to prevent an impact from being applied to the temperature sensitive element and to suppress a change in its electrical characteristics.

Moreover, it is preferable that the said outer side protective layer does not produce a chemical reaction with the said filler in the temperature range of room temperature to 850 degreeC (Claim 12 ).
In this case, even if the outer protective layer is in close contact with the filler, it is possible to prevent the outer protective layer from being altered in the temperature range from room temperature to 850 ° C. Therefore, a temperature sensor having excellent durability can be obtained.

Further, it is more preferable that the outer protective layer does not cause a chemical reaction with the filler in a temperature range from room temperature to 1000 ° C. (claim 13 ).
In this case, even if the outer protective layer is in close contact with the filler, it is possible to prevent the outer protective layer from being altered in the temperature range of room temperature to 1000 ° C. Therefore, a temperature sensor having excellent durability can be obtained.

Example 1
A temperature sensor and a manufacturing method thereof according to an embodiment of the present invention will be described with reference to FIGS.
As shown in FIGS. 1 to 3, the temperature sensor 1 of this example includes a temperature sensing element 14 having a temperature sensing element 2 whose electrical characteristics change according to temperature, and a pair of electrode wires 21 of the temperature sensing element 14. A sheath pin 3 that houses a pair of signal lines 31 that are exposed at the tip end side, and a cover 4 that is disposed at the tip end so as to cover the temperature sensitive body 14. The temperature sensing element 14 includes a temperature sensing element 2 and an inner protective layer 51 and an outer protective layer 52 that seal the temperature sensing element 2 together with a part of the electrode wire 21.

Here, the thermal expansion coefficient of the thermosensitive element 2 is k1, the thermal expansion coefficient of the electrode wire 21 is k2, the thermal expansion coefficient of the inner protective layer 51 is k3, and the thermal expansion coefficient of the outer protective layer 52 is k4. At this time,
| K1-k3 | <| k1-k2 |, | k2-k4 | <| k2-k3 |
Holds.

The thermal expansion coefficients k1, k2, k3, and k4 satisfy | k1-k3 | ≦ 5 × 10 ⁻⁷ / ° C. and | k2−k4 | ≦ 4 × 10 ⁻⁷ / ° C.
In this example, the temperature sensitive element 2 is made of a thermistor material, and the electrode wire 21 is made of platinum or a platinum alloy. The inner protective layer 51 is made of a material having an effect of protecting the temperature sensitive element 2 at a high temperature of 1000 ° C. or higher. Examples of the material include inorganic materials, amorphous glass, and crystallized glass. Each of them may be used alone if it has a desired range of thermal expansion coefficient, but it is a mixture of amorphous glass and crystallized glass so as to have the desired thermal expansion coefficient. You may comprise using what added the powder. Examples of the inorganic material powder added to the glass include aluminum oxide (Al ₂ O ₃ ), magnesium oxide (MgO), yttrium oxide (Y ₂ O ₃ ), chromium oxide (Cr ₂ O ₃ ), zirconium oxide (ZrO ₂ ), The thermistor material etc. which comprise the temperature sensitive element 2 are mentioned. As the material constituting the inner protective layer 51, a material obtained by adjusting the thermal expansion coefficient by adding 40% by weight or more of the thermistor material constituting the thermosensitive element 2 to a high-temperature stable crystallized glass is more preferable.
The outer protective layer 52 is made of a material that has an effect of protecting the temperature sensitive element 2 at a high temperature of 1000 ° C. or higher, like the inner protective layer 51. Examples of the material include inorganic materials, amorphous glass, and crystallized glass. When each has a thermal expansion coefficient in the above desired range, it is preferable to use it alone, but a mixture of amorphous glass and crystallized glass so as to have a desired thermal expansion coefficient, You may comprise using what added the inorganic material powder. Examples of the inorganic material powder added to the glass include aluminum oxide (Al ₂ O ₃ ), magnesium oxide (MgO), yttrium oxide (Y ₂ O ₃ ), chromium oxide (Cr ₂ O ₃ ), zirconium oxide (ZrO ₂ ), The thermistor material etc. which comprise the temperature sensitive element 2 are mentioned. As the material constituting the outer protective layer 52, a material obtained by adding 30% by weight or less of yttrium oxide to a crystallized glass which is stable at a high temperature is more preferable.

Here, the composition of the crystallized glass, oxidation silicon, calcium oxide, manganese oxide, Ru is composed of aluminum oxide. Then, the crystallized _glass, SiO 2: 30 to 60 wt%, CaO: 10 to 30 wt%, MgO: 5 to 25 wt%, Al ₂ O _3: that having a composition of 0-15 wt%.
When the main component of the material forming the inner protective layer 51 and the main component of the material forming the outer protective layer 52 are the same material, the bonding properties between the inner protective layer 51 and the outer protective layer 52 are the same. Can be prevented, and peeling and cracking between the inner and outer protective layers can be prevented.

  In the temperature sensor 1 of this example, as shown in FIG. 2, a guard tube 11 is provided on the rear end side of the cover 4 so as to cover the outer periphery of the sheath pin 3. The guard tube 11 is fixed to the rear end portion 302 of the sheath pin 3 at the rear end portion 112. The rear end portion 112 of the guard tube 11 and the rear end portion 302 of the sheath pin 3 are welded all around. The tip 111 of the guard tube 11 is not fixed to the seaspin 3 but is formed so as to interfere with the side surface of the seaspin 3 with little clearance between the side surfaces of the seaspin 3.

The guard tube 11 is obtained by reducing the diameter of the front end portion 111 and the rear end portion 112 from the portion between them, and in the portions other than the front end portion 111 and the rear end portion 112, A clearance is formed with the seaspin 3.
A rib 12 is disposed on the outer periphery of the guard tube 11. The rib 12 holds the sheath pin 3 through the guard tube 11.

The rib 12 includes an abutting portion 121 that abuts against the front end surface of the inner wall of the mounting boss for the internal combustion engine, a first extending portion 122 that extends rearward and has a smaller outer diameter than the abutting portion 121, The second extending portion 123 extends further rearward than the first extending portion 122 and has a smaller outer diameter. The guard tube 11 is inserted inside the abutting portion 121, the first extending portion 122, and the second extending portion 123.
In addition, one end of a protective tube 13 that protects a part of the sheath pin 3, the guard tube 11, and the external lead 17 is fixed to the outer periphery of the first extending portion 122 by welding.
Further, the rib 12 is welded to the guard tube 11 all around the second extending portion 123.

Further, the cover 4 is welded all around the outer periphery of the tip 301 of the sheath pin 3.
The guard tube 11, the sheath pin 3, and the cover 4 are made of stainless steel or Ni-base heat resistant alloy. Further, the rib 12 and the protective tube 13 are also made of stainless steel or Ni-base heat resistant alloy.
Further, the thickness of the guard tube 11 is larger than the thickness of the outer tube portion 34 of the sheath pin 3, and the guard tube 11 has higher rigidity than the outer tube portion 34 of the sheath pin 3.

  As shown in FIG. 2, the sheath pin 3 includes two signal lines 31 made of stainless steel or a Ni-base heat-resistant alloy, and an insulating portion 33 made of an insulating powder such as magnesia disposed around the signal line 31. And an outer pipe portion 34 made of stainless steel covering the outer periphery of the insulating portion 33. The sheath pin 3 has a cylindrical shape, and the outer tube portion 34 has a cylindrical shape. The signal line 31 is exposed from the insulating portion 33 and the outer tube portion 34 to the front end side and the rear end side. The front end of the signal line 31 is welded to the electrode 21 of the temperature sensing body 14, and the rear end of the signal line 31 is connected to the external lead wire 17.

The outer protective layer 52 is always in contact with the inner surface of the cover 4 in the temperature range from room temperature to 850 ° C. More preferably, the outer protective layer 52 is always in contact with the inner surface of the cover 4 in a temperature range from room temperature to 1000 ° C.
Further, the outer protective layer 52 does not chemically react with the cover 4 in the temperature range from room temperature to 850 ° C. More preferably, the outer protective layer 52 does not chemically react with the cover 4 in a temperature range from room temperature to 1000 ° C.

  The electrode wire 21 is bonded to the outer surface of the temperature sensitive element 2. That is, the temperature sensing element 2 has a substantially rectangular parallelepiped shape, and a pair of electrodes are formed on a pair of surfaces parallel to each other, and an electrode wire 21 is joined to each of these electrodes.

Next, an example of a manufacturing method of the temperature sensor 1 of this example will be described.
First, the temperature sensitive element 2 is manufactured as follows.
That is, yttrium oxide: 75 to 85 mol%, chromium oxide: 3 to 8 mol%, manganese oxide: 5 to 15 mol%, calcium oxide: 0.5 to 1.0 mol% are weighed and mixed in a ball mill. Next, the mixed raw materials are calcined at 1100 ° C. A binder and a plasticizer are added to the calcined powder and kneaded with a kneader. An extruded sheet having a thickness of 1 mm is produced by extruding the kneaded material with a vacuum extruder.

Next, the extruded sheet is cut into a 80 mm square fixed size sheet.
And a fixed-size sheet | seat is baked at 1600 degreeC, and as shown to Fig.4 (a), the plate-shaped thermistor sintered compact 20 is obtained.
The distortion of the thermistor sintered body 20 is removed by annealing after firing.
Next, the both sides of the thermistor sintered body 20 are lapped so as to be ground to a plate thickness of 0.35 mm.

  Next, a Pt paste is printed on both surfaces of the thermistor sintered body 20 to a thickness of about 10 μm and baked at 1300 ° C. to form electrodes. Pt paste is commercially available and has a Pt particle size of about 0.8 μm. In order to increase the bonding strength, an inorganic powder may be added to the Pt paste.

Next, as shown in FIG. 4B, the thermistor sintered body 20 having electrodes baked on both sides is cut into a 0.5 mm square by a dicing machine.
A Pt paste similar to the above is applied to a pair of electrode surfaces of the cut chip-shaped temperature sensitive element (thermistor element) 2 and an electrode wire 21 made of Pt having a diameter of 0.25 mm is pasted and baked at 1250 ° C. . Thereby, as shown in FIG.4 (c), the temperature sensing element 2 and the electrode wire 21 are joined.

Next, for example, crystallized glass powder composed of SiO ₂ : 30 to 60% by weight, CaO: 10 to 30% by weight, MgO: 5 to 25% by weight, Al ₂ O ₃ : 0 to 15% by weight is mixed with a solvent. Then, the temperature sensitive element 2 to which the electrode wire 21 is bonded is dipped into the paste, and a predetermined amount of glass paste is adhered. After drying, the glass is crystallized and baked simultaneously by heat treatment at 1200 ° C. to form the inner protective layer 51 as shown in FIG.
The glass paste is made into a paste by adding the same powder as the thermistor material in order to match the linear expansion coefficient to the temperature sensitive element 2.

Further, the temperature sensitive element 2 covered with the inner protective layer 51 is dipped in the same glass paste as described above, and a predetermined amount of glass paste is adhered on the inner protective layer 51. This is baked by heat treatment at 1200 ° C. after drying to form an outer protective layer 52 as shown in FIG.
This glass paste is made into a paste by adding yttrium oxide powder, which is a component of the thermistor material, in order to bring the coefficient of linear expansion close to that of the temperature sensitive element 2.

Next, the temperature sensing element 14 that covers the temperature sensing element 2 with the inner protective layer 51 and the outer protective layer 52 as described above is bonded to the tip of the sheath pin 3.
Next, with the cover 4 heated to 300 ° C. or higher, the temperature sensing element 14 is inserted inside the cover 4.
Next, the cover 4 is cooled to room temperature.
Next, the cover 4 is welded to the side surface of the sheath pin 3.
Thus, the temperature sensor 1 is obtained.

Next, the function and effect of this example will be described.
The temperature sensing element 14 in the temperature sensor 1 includes an inner protective layer 51 and an outer protective layer 52 that seal the temperature sensitive element 2 together with a part of the electrode wire 21. Then, the thermal expansion coefficients k3 and k4 of the inner protective layer 51 and the outer protective layer 52 are set to | k1-k3 | <| k1-k2 | with respect to the thermal expansion coefficients k1 and k2 of the thermosensitive element 2 and the electrode wire 21. , | K2−k4 | <| k2−k3 |. That is, the thermal expansion coefficient k3 of the inner protective layer 51 is brought closer to the thermal expansion coefficient k1 of the thermosensitive element 2, and the thermal expansion coefficient k4 of the outer protective layer 52 is brought closer to the thermal expansion coefficient k3 of the electrode wire 21. Therefore, it is possible to suppress the thermal stress generated between the inner protective layer 51 and the temperature sensitive element 2 that directly covers the temperature sensitive element 2. Further, it is possible to suppress the generation of a gap between the outer protective layer 52 that covers the inner protective layer 51 and is in close contact with the outer periphery of the electrode wire 21 and the electrode wire 21.

Thereby, the effect of the thermal stress in the temperature sensing element 2 accompanied by a large temperature change can be suppressed, and the change in the electrical characteristics of the temperature sensing element 2 can be prevented. Further, the generation of a gap between the electrode wire 21 and the outer protective layer 52 is suppressed, so that the reducing gas in the cover 4 is prevented from entering the temperature sensing element 2, and the temperature sensing element 2. A change in electrical characteristics can be prevented.
Therefore, in the temperature sensor 1 accompanied by a large temperature change from room temperature to high temperature, the durability of the temperature sensitive element 2 can be ensured.

The thermal expansion coefficients k1, k2, k3, and k4 satisfy | k1-k3 | ≦ 5 × 10 ⁻⁷ / ° C. and | k2−k4 | ≦ 4 × 10 ⁻⁷ / ° C. For this reason, the thermal expansion coefficient k3 of the inner protective layer 51 is sufficiently close to the thermal expansion coefficient k1 of the thermosensitive element 2, and the thermal expansion coefficient k4 of the outer protective layer 52 is sufficiently close to the thermal expansion coefficient k2 of the electrode wire 21. it can. Therefore, the thermal stress generated between the inner protective layer 51 and the temperature sensitive element 2 that directly covers the temperature sensitive element 2 can be effectively suppressed. Moreover, it can suppress effectively that a clearance gap produces between the outer side protective layer 52 closely_contact | adhered to the outer periphery of the electrode wire 21, and the electrode wire 21. FIG. As a result, the temperature sensor 1 having excellent durability can be obtained by further suppressing the change in the electrical characteristics of the temperature sensitive element 2.

  The outer protective layer 52 is always in contact with the inner surface of the cover 4 in the temperature range from room temperature to 850 ° C., preferably 1000 ° C. Therefore, the outer protective layer 52 can be kept in contact with the cover 4 even if thermal expansion of the cover 4 occurs due to a temperature change in a temperature range of at least room temperature to 850 ° C. (preferably 1000 ° C.). Excellent heat transfer between the cover 4 and the temperature sensitive element 2 can be ensured. As a result, the temperature sensor 1 with excellent measurement accuracy can be obtained. Further, in this case, the outer protective layer 52 can be prevented from vibrating relative to the cover 4, and an impact is prevented from being applied to the temperature sensitive element 2, thereby suppressing changes in its electrical characteristics. Can do.

  Further, the outer protective layer 52 does not cause a chemical reaction with the cover 4 in a temperature range from room temperature to 850 ° C. (preferably 1000 ° C.). Thereby, even if the outer protective layer 52 is in close contact with the cover 4, it is possible to prevent the outer protective layer 52 from being altered in the temperature range from room temperature to 850 ° C. (preferably 1000 ° C.). Therefore, the temperature sensor 1 excellent in durability can be obtained.

Further, the outer protective layer 52 does not cause a chemical reaction with the cover 4 in a temperature range from room temperature to 850 ° C. (preferably 1000 ° C.). Thereby, even if the outer protective layer 52 is in close contact with the cover 4, it is possible to prevent the outer protective layer 52 from being altered in the temperature range from room temperature to 850 ° C. (preferably 1000 ° C.). Therefore, the temperature sensor 1 excellent in durability can be obtained.
The chemical reaction does not occur when, for example, when the temperature sensitive element 2 is in contact with the cover 4 and exposed to a temperature atmosphere of 1000 ° C. for 100 hours, the cover component extends from the outer surface of the outer protective layer 52 to the inside. This can be confirmed by not entering.
Moreover, the material of the cover 4 is made of a Ni—Cr—Fe based, high heat resistant metal. For this reason, an oxidation protective film is formed at 1000 ° C., and the metal component is not liberated alone. Accordingly, diffusion and reaction to the outer protective layer 52 are suppressed. In addition to the Ni—Cr—Fe system, the same effect can be obtained by using a refractory metal such as a Ni—Fe system.

  Further, since the electrode wire 21 is bonded to the outer surface of the temperature sensing element 2, the electrode wire 21 can be easily joined to the temperature sensing element 2, and the temperature sensor 1 that is easy to manufacture is obtained. Can do. In this case, in general, the fixing force between the temperature sensitive element 2 and the electrode wire 21 is likely to be reduced, but the temperature sensor 1 of the present invention includes the inner protective layer 51 and the outer protective layer 52, so Can be reinforced. And the temperature sensor 1 excellent in durability can be obtained by adjusting the thermal expansion coefficient of this inner side protective layer 51 and the outer side protective layer 52 as mentioned above.

  In the method for manufacturing the temperature sensor 1, the temperature sensing element 14 is inserted inside the cover 4 in a state where the cover 4 is heated to 300 ° C. or more. Therefore, the temperature sensing element 14 can be easily inserted inside the cover 4 in a state where the cover 4 is sufficiently thermally expanded. Then, by cooling the cover 4 to room temperature, the temperature sensitive element 2 can be brought into contact with the inner surface of the cover 4. The temperature sensitive body 14 can be held in the cover 4 by so-called shrink fitting.

  Therefore, in the obtained temperature sensor 1, even if there is a large temperature change, the cover 4 temperature sensor 14 can be caulked with an appropriate pressing force, and between the cover 4 and the temperature sensor 14. The heat transferability between the outside and the temperature sensitive element 2 can be improved. Thereby, the measurement accuracy of the temperature sensor 1 can be improved. Further, in the cover 4, the temperature sensing body 14 can be prevented from vibrating relatively with respect to the cover 4, and damage to the temperature sensing body 14 can be prevented.

  As described above, according to this example, it is possible to provide a temperature sensor excellent in high-temperature durability and a manufacturing method thereof.

(Example 2)
This example is an example of the temperature sensor 1 in which the filler 15 is interposed between the cover 4 and the outer protective layer 52 as shown in FIG.
In the temperature range from room temperature to 850 ° C. (preferably 1000 ° C.), the outer protective layer 52 is always in contact with the filler 15 and the filler 15 is always in contact with the cover 4.
Further, the outer protective layer 52 does not cause a chemical reaction with the filler 15 in a temperature range from room temperature to 850 ° C. (preferably 1000 ° C.).
As the filler 15, for example, cement, alumina powder or the like can be used.

In manufacturing the temperature sensor 1 of this example, the temperature sensing element 2, the inner protective layer 51, and the outer protective layer 52 are joined to the tip of the sheath pin 3 in the same manner as in the first embodiment, and the temperature sensing element 14 is attached. Form.
Next, the temperature sensing element 14 is inserted into the cover 4 in a state where the slurry 4 is filled in the cover 4.
Next, the filler 15 inside the cover 4 is dried.
Next, the cover 4 is welded to the side surface of the sheath pin 3, and then the filler 15 is heated and cured.
Others are the same as in the first embodiment.

  In the case of this example, the outer protective layer 52 and the cover 4 are brought into contact with each other through the filler 15, and excellent heat transfer properties between the outside of the temperature sensor 1 and the temperature sensitive element 2 are ensured. be able to. Further, relative vibration of the temperature sensing element 2 in the cover 4 can be prevented, and damage to the temperature sensing element 2 can be prevented.

  In the temperature range from room temperature to 850 ° C. (preferably 1000 ° C.), the outer protective layer 52 is always in contact with the filler 15 and the filler 15 is always in contact with the cover 4. Therefore, even if thermal expansion of the cover 4 or the filler 15 occurs with a temperature change in a temperature range of at least room temperature to 850 ° C. (preferably 1000 ° C.), the outer protective layer 52 is applied to the cover 4 via the filler 15. It is possible to maintain the contacted state, and to ensure excellent heat transfer between the cover 4 and the temperature sensitive element 2. As a result, the temperature sensor 1 with excellent measurement accuracy can be obtained. Further, in this case, the outer protective layer 52 can be prevented from vibrating relative to the cover 4, and an impact is prevented from being applied to the temperature sensitive element 2, thereby suppressing changes in its electrical characteristics. Can do.

Further, the outer protective layer 52 does not cause a chemical reaction with the filler 15 in a temperature range from room temperature to 850 ° C. (preferably 1000 ° C.). Therefore, even when the outer protective layer 52 is in close contact with the filler 15, it is possible to prevent the outer protective layer 52 from being altered in the temperature range from room temperature to 850 ° C. (preferably 1000 ° C.). Therefore, the temperature sensor 1 excellent in durability can be obtained.
In addition, the same effects as those of the first embodiment are obtained.

Further, the outer protective layer 52 does not cause a chemical reaction with the filler 15 in a temperature range from room temperature to 850 ° C. (preferably 1000 ° C.). Therefore, even when the outer protective layer 52 is in close contact with the filler 15, the outer protective layer 52 can be prevented from being altered in the temperature range from room temperature to 850 ° C. (preferably 1000 ° C.), and has excellent durability. Temperature sensor 1 can be obtained.
The chemical reaction does not occur, for example, when the temperature sensitive element 2 is in contact with the filler 15 and exposed to a temperature atmosphere of 1000 ° C. for 100 hours from the outer surface of the outer protective layer 52. Can be confirmed by not penetrating into the interior.
The filler 15 is made of a stable inorganic material that is not decomposed at 1000 ° C. mixed with aluminum oxide, magnesium oxide, yttrium oxide, silicon oxide, zirconium oxide, or the like. Thereby, metal vapor | steam etc. do not generate | occur | produce, but the diffusion and reaction in the external protective layer 52 can be suppressed.
In addition, the same effects as those of the first embodiment are obtained.

(Example 3)
In this example, as shown in FIGS. 6 and 7, the amount of additive added to the crystallized glass in the inner protective layer and the outer protective layer, the change in the thermal expansion coefficient, the change in the thermal stress on the thermosensitive element, and It is the example which investigated the relationship with the resistance value change rate of a temperature sensing element.

First, the inner protective layer is constructed by the crystallized glass, the addition of a thermistor material as additive.
The composition of the crystallized glass was SiO ₂ : 30 to 60% by weight, CaO: 10 to 30% by weight, MgO: 5 to 25% by weight, and Al ₂ O ₃ : 0 to 15% by weight. The composition of the thermistor material added to the inner protective layer is yttrium oxide: 75 to 85 mol%, chromium oxide: 3 to 8 mol%, manganese oxide: 5 to 15 mol%, calcium oxide: 0.5 to 1.0 mol%. did. And the additive which consists of the said thermistor material was added to the said crystallized glass, and the thing which changed the addition amount between 0 to 100 weight% was used as the inner side protective layer. In addition, the outer side protective layer in the temperature sensor used here adds 20 weight% of yttria materials mentioned later to crystallized glass.

First, the thermal expansion coefficient of each of a plurality of types of inner protective layers having different additive amounts was analyzed. The results are shown in the solid line graph in FIG. The broken line in the figure shows the thermal expansion coefficient (85 × 10 ⁻⁷ / ° C.) of the temperature sensitive element.

  In addition, the stress generated between the inner protective layer and the temperature-sensitive element when a temperature sensor was formed using a plurality of types of inner protective layers with different additive amounts was analyzed. This generated stress is a stress generated when the temperature of the temperature sensing element is 1000 ° C. The result is shown in FIG.

  In addition, the rate of change in resistance value of the temperature-sensitive element was analyzed when a temperature sensor was formed using a plurality of types of inner protective layers with different additive amounts. This resistance value change rate is a value determined by how much the resistance value of the thermosensitive element has changed with respect to the initial value after performing a cooling test between room temperature and 1000 ° C. for 12000 cycles. The result is shown in FIG.

As can be seen from FIGS. 6 (a) to 6 (c), by setting the addition amount of the additive to 40% by weight or more, the stress applied to the temperature sensitive element is less than 10 MPa, and the resistance value change rate is suppressed to less than 20%. be able to. And the thermal expansion coefficient of the inner side protective layer at this time is 85-90 * 10 < ^-7 > / degreeC, and the difference with the thermal expansion coefficient of a thermosensitive element is 5 * 10 < ^-7 > / degreeC or less. That is, by making the difference between the thermal expansion coefficient of the temperature sensitive element and the thermal expansion coefficient of the inner protective layer 5 × 10 ⁻⁷ / ° C. or less, the rate of change in resistance value of the temperature sensitive element can be suppressed. That is, the durability of the temperature sensor can be ensured. As can be seen from the above results, the inner protective layer may be composed of only the additive material, that is, the thermistor material.

Next, the outer protective layer is constructed by the crystallized glass, the addition of yttria material as additive.
The composition of the crystallized glass is the same as that of the crystallized glass used for the inner protective layer. And the additive which consists of the said yttria material was added to the said crystallized glass, and it was set as the outer side protective layer using what was changed between the addition amount of 0-30 weight%. The inner protective layer in the temperature sensor used here is obtained by adding 80% by weight of the thermistor material to crystallized glass.

First, the thermal expansion coefficient of each of a plurality of types of outer protective layers having different additive amounts was analyzed. The results are shown in the solid line graph in FIG. The broken line in the figure shows the thermal expansion coefficient (94 × 10 ⁻⁷ / ° C.) of the electrode wire.

  In addition, the stress generated between the outer protective layer and the electrode wire when a temperature sensor was formed using a plurality of types of inner protective layers having different additive amounts was analyzed. This generated stress is a stress generated when the temperature of the temperature sensing element is 1000 ° C. The result is shown in FIG.

  Moreover, the resistance value change rate of the temperature sensing element was analyzed when a plurality of types of outer protective layers having different additive amounts were employed. The rate of change in the resistance value is the degree to which the resistance value of the temperature sensing element changed from the initial value after leaving the temperature sensing element for 10 hours in a reducing atmosphere of 1000 ° C. (5% hydrogen, 95% nitrogen). It was measured by. The result is shown in FIG. The reducing atmosphere is an atmosphere created under stricter conditions than the atmosphere in the cover when the actual temperature sensor is used.

As can be seen from FIGS. 7A to 7C, for the outer protective layer, the rate of change in resistance value can be suppressed to 20% or less by making the amount of yttria added as an additive 30% by weight or less. it can. At this time, the outer protective layer has a thermal expansion coefficient of 90 to 98 × 10 ⁻⁷ / ° C., and the difference from the thermal expansion coefficient of the electrode wire is 4 × 10 ⁻⁷ / ° C. or less. That is, by making the difference between the thermal expansion coefficient of the electrode wire and the thermal expansion coefficient of the outer protective layer 4 × 10 ⁻⁷ / ° C. or less, the rate of change in resistance value of the temperature sensitive element can be suppressed. That is, the durability of the temperature sensor can be ensured.
More preferably, the rate of change in the resistance value of the temperature sensitive element can be further reduced by setting the additive amount to 10 to 20% by weight.

Further, in order to prevent a large thermal stress from being generated between the inner protective layer and the outer protective layer, for example, the difference in thermal expansion coefficient between the inner protective layer and the outer protective layer is set to 5-9 × 10 ^{− 7} / ° C is desirable.

Sectional drawing of the temperature sensor vicinity of the temperature sensor in Example 1. FIG. FIG. 3 is a cross-sectional view of the temperature sensor in the first embodiment. FIG. 3 is a cross-sectional view of the tip portion of the temperature sensor in the first embodiment. Explanatory drawing of the manufacturing method of the temperature sensing body in Example 1. FIG. Sectional drawing of the front-end | tip part of the temperature sensor in Example 2. FIG. The diagram which shows the test result about the inner side protective layer in Example 3. FIG. The diagram which shows the test result about the outer side protective layer in Example 3. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Temperature sensor 14 Temperature sensing body 2 Temperature sensing element 21 Electrode wire 3 Seaspin
31 signal line 4 cover 51 inner protective layer 52 outer protective layer

Claims (15)

A temperature sensing element having a temperature sensing element whose electrical characteristics change with temperature;
A sheath pin built in a state in which a pair of signal lines respectively connected to a pair of electrode wires of the temperature sensing element is exposed to the tip side;
A cover disposed at the tip so as to cover the temperature sensing element,
The temperature sensing element has the temperature sensing element and an inner protective layer and an outer protective layer that seal the temperature sensing element together with a part of the electrode wire,
When the thermal expansion coefficient of the thermosensitive element is k1, the thermal expansion coefficient of the electrode wire is k2, the thermal expansion coefficient of the inner protective layer is k3, and the thermal expansion coefficient of the outer protective layer is k4,
| K1-k3 | <| k1-k2 |, | k2-k4 | <| k2-k3 |
Chi is made standing,
And the material which comprises the said inner side protective layer adds 40 weight% or more of the thermistor material which comprises the said thermosensitive element to crystallized glass,
On the other hand, the material constituting the outer protective layer is obtained by adding 30% by weight or less of yttrium oxide to crystallized glass .   In Claim 1, the composition of the crystallized glass used for the inner protective layer and the outer protective layer is SiO. ₂ : 30-60% by weight, CaO: 10-30% by weight, MgO: 5-25% by weight, Al ₂ O ₃ : 0-15 wt% temperature sensor. 3. The thermal expansion coefficient k1, k2, k3, k4 according to claim 1 or 2 , satisfying | k1-k3 | ≦ 5 × 10 ⁻⁷ / ° C. and | k2−k4 | ≦ 4 × 10 ⁻⁷ / ° C. Temperature sensor. 4. The temperature sensor according to claim 1, wherein the outer protective layer is always in contact with the inner surface of the cover in a temperature range of room temperature to 850 ° C. 5. 4. The temperature sensor according to claim 1, wherein the outer protective layer is always in contact with the inner surface of the cover in a temperature range of room temperature to 1000 ° C. 5. In any one of claims 1 to 5, wherein the outer protective layer, the temperature sensor, characterized in that does not cause the cover and chemical reaction in the temperature range of 850 ° C. from room temperature. In any one of claims 1 to 5, wherein the outer protective layer, the temperature sensor, characterized in that does not cause the cover and chemical reaction in the temperature range of 1000 ° C. from room temperature. In any one of claims 1 to 7, wherein the electrode line is a temperature sensor, characterized in that it is joined to the outer surface of the temperature sensitive device. The temperature sensor according to any one of claims 1 to 8 , wherein a filler is interposed between the cover and the outer protective layer. 10. The temperature sensor according to claim 9, wherein, in the temperature range from room temperature to 850 ° C., the outer protective layer is always in contact with the filler, and the filler is always in contact with the cover. 10. The temperature sensor according to claim 9 , wherein the outer protective layer is always in contact with the filler and the filler is always in contact with the cover in a temperature range from room temperature to 1000 ° C. The temperature sensor according to any one of claims 9 to 11 , wherein the outer protective layer does not cause a chemical reaction with the filler in a temperature range of room temperature to 850 ° C. The temperature sensor according to any one of claims 9 to 11 , wherein the outer protective layer does not cause a chemical reaction with the filler in a temperature range of room temperature to 1000 ° C. A method for manufacturing the temperature sensor according to any one of claims 1 to 13 ,
Join the temperature sensor to the tip of the seaspin,
Next, with the cover heated to 300 ° C. or higher, the temperature sensing element is inserted inside the cover,
Then the cover is cooled to room temperature,
Next, the temperature sensor manufacturing method, wherein the cover is welded to the side surface of the sheath pin. A method for manufacturing the temperature sensor according to any one of claims 9 to 13 ,
Join the temperature sensor to the tip of the seaspin,
Next, in a state where the inside of the cover is filled with a slurry-like filler, the temperature sensing element is inserted inside the cover,
Next, the filler inside the cover is dried,
Next, the cover is welded to the side surface of the sheath pin,
Next, a method for manufacturing a temperature sensor, wherein the filler is cured by heating.

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