JP5326600B2 - Temperature sensor and manufacturing method thereof - Google Patents

Description

  The present invention relates to a temperature sensor that is disposed so as to protrude into a flow path through which a fluid to be measured such as automobile exhaust gas flows, and a method for manufacturing the same.

  An exhaust gas recirculation system (hereinafter referred to as an EGR system) that suppresses the generation of NOx and an exhaust gas treatment system that uses a catalyst or the like are widely used in order to comply with exhaust gas regulations for automobile engines. In these systems, exhaust emission is reduced by providing a temperature sensor in the EGR gas or exhaust gas flow path and performing optimum control based on the EGR gas or exhaust gas temperature. As a temperature sensor used for such an application, a temperature sensor having a high response and a wide detection temperature range is required, and a temperature sensor using a temperature-sensitive element whose resistance changes with temperature is used.

  In general, a temperature sensor using a temperature-sensitive element whose resistance varies with temperature is generally a thermistor element in which a pair of electrodes are joined, a pair of electrode wires joined to the electrodes of the thermistor element, and the pair A pair of signal lines connected to the respective electrode lines, an insulator tube incorporating the signal lines, and a cover disposed at the tip so as to cover the thermistor element.

The bonding of the electrode wire to the thermistor element is performed, for example, by applying a Pt paste (platinum paste) on the surface of the thermistor element and attaching the electrode wire, followed by baking. 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 using a temperature sensing element having a structure in which a temperature sensing element is sealed with glass including a joint with an electrode wire (see Patent Documents 1 and 2). The temperature sensing element having such a structure can secure a stable conduction characteristic between the temperature sensing element and the electrode wire by the fixing force of the glass.

Although the temperature sensing element having a structure in which the temperature sensing element is glass-sealed can secure stable conduction characteristics as described above, the temperature sensing element is bonded to the glass in which the temperature sensing element and the electrode wire are sealed and fixed. When a crack reaching the element occurs, there is a problem that the electrical characteristics with respect to the temperature of the temperature-sensitive element change, causing a resistance abnormality and leading to a temperature detection error.
Conventionally, with respect to such a problem, the gap between the metal cover and the temperature sensitive body has been enlarged to suppress the occurrence of glass cracks by suppressing the vibration caused by the filler and lowering the operating temperature range (Patent Document 3).

  Patent Document 4 discloses that a metal case is expanded or contracted due to temperature detection by providing a coating material between the filler and the detection element or between the filler and the inner surface of the metal case. A temperature detection device is described that can prevent damage to the temperature detection element by being transmitted to the temperature detection element through the filler as it is. And it is described that a coating material does not need to be used when a filler containing an alkaline solvent is used.

Japanese Patent Laid-Open No. 3-92735 JP 2002-350241 A JP 7-43220 A JP 7-159250 A

However, these techniques are insufficient in preventing the occurrence of glass cracks.
As a result of extensive research, glass cracks are found on the glass surface at the start of use, and after the start of use, stresses such as internal stress of glass, external stress such as vibration, and thermal stress are observed on the glass surface. It was found that the microcracks were generated by concentrating on the microcracks that existed in the surface and progressing and expanding.

Moreover, it discovered that the crack which exists in the said glass surface was formed at the time of preparation of the said temperature sensor. Specifically, the temperature sensing element is generally placed in the metal cover by inserting the slurry into the metal cover in which the slurry constituting the filler is previously disposed and drying the slurry. The Then, moisture generated when the slurry is dried reacts with SiO _{2 of} the glass, and SiO ₂ is replaced with SiOH, resulting in a decrease in bonding force and generation of minute cracks on the glass surface. .

  Further, the internal stress of the glass is inevitably generated when the glass itself is distorted when it is hardened from the molten state, so that it is difficult to prevent the generation of the internal stress. Further, the external stress, thermal stress and the like during use cannot be eliminated. Therefore, once a microcrack is generated, it is difficult to reliably suppress the progress (expansion) particularly at high temperatures.

  In addition, even before the use (before vehicle mounting), even if a micro crack exists, the resistance value characteristic of the temperature sensing element is not affected. However, the micro cracks may later develop and expand, causing a resistance abnormality. For this reason, conventionally, a temperature detecting element in which the presence of a microcrack has been confirmed has to be discarded, and there is a problem that reliability is low, productivity is low, and production cost is high.

  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 heat resistance and high in reliability, and a method for manufacturing the same.

According to a first aspect of the present invention, a pair of electrode wires are joined to the temperature sensitive element, a protective layer made of glass that seals both the temperature sensitive element and a part of the pair of electrode wires is formed, A temperature detection element manufacturing step for obtaining a temperature detection element by forming a coating layer covering part or all of the surface;
An arrangement step of inserting and arranging the temperature detection element in a metal cover previously filled with slurry for filler,
A drying step for drying the slurry for filler,
In the temperature detection element manufacturing step, the covering layer is formed on a portion of the surface of the protective layer at least on the tip side from a position corresponding to the rear end portion of the temperature sensitive element,
And the said coating layer has water repellency and heat resistance which a main component consists of a silicone resin ,
The filler slurry is a slurry that hardens by dehydration condensation. (Claim 1)

According to a second aspect of the present invention, there is provided a temperature sensing element, a pair of electrode wires connected to the temperature sensing element, and a protective layer made of glass that seals both the temperature sensing element and a part of the pair of electrode wires. A temperature detection element having a coating layer covering part or all of the surface of the protective layer;
A pair of signal lines connected to the pair of electrode lines;
An insulator tube containing the signal line;
A metal cover disposed at the tip so as to cover the temperature detecting element and the insulator tube;
A filler interposed between the metal cover and the temperature detecting element or the insulator tube,
The coating layer is formed on the surface of the protective layer at least on the tip side from a position corresponding to the rear end portion of the temperature sensitive element, and the water repellent and heat resistant main component is a silicone resin. It is in the temperature sensor characterized by having the property ( Claim 3 ).

  As described above, when microcracks are present on the surface of the protective layer, stresses such as internal stress of glass, external stress such as vibration, and thermal stress are concentrated on the microcracks existing on the glass surface. Since progress and expansion are likely to occur, it is difficult to reliably suppress the progress and expansion of the microcrack once generated.

  And the manufacturing method of the temperature sensor of 1st invention pays attention to prevention of generation | occurrence | production of the micro crack in the surface of a protective layer. The most notable point in the present invention is that the coating layer having a specific property is provided in advance on a specific portion of the surface of the protective layer in the temperature detection element manufacturing step. This suppresses the occurrence of microcracks in specific parts on the protective layer in the process of manufacturing the temperature sensor, prevents the occurrence of glass cracks that cause abnormal resistance of the temperature sensitive element, and is excellent in high temperature heat resistance. A highly reliable temperature sensor can be obtained.

In the temperature sensor, the temperature detection element is accommodated in a metal cover in a state of being airtight with the outside via a filler. That is, the temperature detecting element hardly comes into contact with moisture after the filler slurry is dried. For this reason, it is unlikely that the moisture reacts with the glass of the protective layer during use (during vehicle mounting) and microcracks are generated.
Therefore, if the generation of microcracks can be prevented in the temperature sensor manufacturing process, internal stress of glass, external stress such as vibration, and stress such as thermal stress are locally concentrated during use (during vehicle mounting). It is considered that the occurrence of cracks that cause resistance abnormalities can be effectively suppressed.

In the present invention, as described above, the temperature detecting element is inserted and disposed in a metal cover in which the filler slurry is previously disposed, and then the filler slurry is dried.
And the said slurry for fillers is a slurry hardened | cured by dehydration condensation.
Therefore, in the drying step, moisture is generated by dehydration condensation of the filler slurry. The generated moisture is excluded in the drying process, but the temperature detecting element is exposed to water vapor during the process.

  However, in this invention, the said coating layer which covers the specific site | part on the surface of the protective layer which consists of said glass is provided previously. Thereby, in the said drying process, it can prevent that the part of protective layer covered with the said coating layer is exposed to a water | moisture content. Then, by blocking the contact with moisture and suppressing the reaction between the moisture and the glass constituting the protective layer, it is possible to suppress the occurrence of microcracks in the specific part in the temperature sensor manufacturing process. . Therefore, even when external stress such as internal stress of glass, vibration, or thermal stress is applied during use (mounted on the vehicle), it prevents local concentration of the stress and causes abnormal resistance. Generation of cracks can be suppressed.

  The covering layer not only prevents contact between the protective layer and moisture, but also has an effect of preventing the protective layer from being damaged due to contact with other substances in the temperature sensor manufacturing process.

The coating layer has water repellency and heat resistance.
The coating layer has water repellency that does not allow water to permeate and heat resistance that is resistant to the temperature conditions at which water evaporates, so that in the drying step, the moisture and the protective layer are brought into contact with each other at the coating layer forming portion. Can be blocked. The heat resistance needs to be 100 ° C. or higher, which is a moisture drying condition.

Moreover, the said coating layer is formed in the part of the front end side rather than the position corresponding to the rear-end part of the said thermosensitive element among the surfaces of the said protective layer. In other words, the protective layer in the front end surface and the side surface direction of the temperature sensitive element is covered with the coating layer.
Since a resistance abnormality occurs due to a crack in the vicinity of the temperature sensitive element, if a covering layer is formed so as to cover at least the range corresponding to the rear end of the temperature sensitive element on the surface of the protective layer, the covering layer is covered. Even if a microcrack occurs in the non-covered portion of the coating layer, the generation of a crack that causes resistance abnormality can be suppressed.
Here, the front end side is the front end side in the axial direction of the temperature sensor.

As described above, according to the present invention, even if a slurry that is cured by dehydration condensation is used by forming the coating layer in advance on a necessary portion of the protective layer, microcracks in the coating layer forming portion can be prevented. Occurrence can be prevented.
In this way, by preventing the occurrence of microcracks that cause the occurrence of cracks that cause resistance abnormalities, the reliability can be significantly improved as compared with the prior art. Moreover, even if it is the use at high temperature, the suppression effect of crack generation can be acquired and it can have high temperature heat resistance.

  Moreover, the manufacturing method of this invention suppresses generation | occurrence | production of the crack which causes resistance abnormality by restrict | limiting the formation area of the said coating layer, and the constituent material of the said coating layer. Therefore, there are no particular limitations on the material of the glass forming the protective layer, the material of the filler slurry, etc., and various known materials can be used.

  In recent years, regulations on exhaust gas from automobile engines tend to be strengthened, and a significant reduction in the amount of NOx generated is required. In addition, as the accuracy of the EGR system is increased and the control temperature range is expanded, demands for high responsiveness and high temperature heat resistance are increasing. And, due to the demand for high responsiveness, it is necessary to reduce the diameter of the metal cover, not only reducing the diameter of the metal cover, but also reducing the diameter of the temperature sensor and reducing the gap between the metal cover and the temperature sensor. Yes.

  The high temperature heat resistance obtained by the production method of the present invention, the effect of reliability, even when reducing the diameter of the metal cover, reducing the diameter of the temperature sensor, and reducing the gap between the metal cover and the temperature sensor, It can be obtained similarly. Therefore, when adopting the manufacturing method of the present invention to reduce the diameter of the metal cover, reduce the diameter of the temperature sensing element, and reduce the gap between the metal cover and the temperature sensing element, it is excellent in high temperature heat resistance and reliable. A temperature sensor having not only high but also high responsiveness can be manufactured.

  Thus, according to this invention, it turns out that it is excellent in high temperature heat resistance, and can provide the manufacturing method of a reliable temperature sensor.

  In the temperature sensor of the second invention, a coating layer is formed on a specific portion of the surface of the protective layer. Therefore, in the process of manufacturing the temperature sensor, the protective layer in the coating layer forming part is not exposed to moisture, and the reaction with moisture is prevented. Is hard to think. And the temperature sensor in which the micro crack does not exist in the coating layer forming part locally stresses such as internal stress of glass, external stress such as vibration, and thermal stress during use (during vehicle mounting). This can be prevented and the occurrence of cracks that cause abnormal resistance of the temperature sensitive element can be suppressed. Therefore, according to this invention, it turns out that it is excellent in high temperature heat resistance and can provide a reliable temperature sensor.

Explanatory drawing which shows the manufacturing method of the temperature sensor in Example 1. FIG. FIG. 3 is an explanatory diagram showing a temperature sensor in the first embodiment. Explanatory drawing which shows the temperature sensor in the comparative example 1. FIG. The graph figure which shows the result of the thermal endurance test in Experimental example 1. FIG.

As described above, the method for manufacturing a temperature sensor according to the first aspect of the present invention includes a temperature detection element manufacturing step, an arrangement step, and a drying step.
In the temperature detection element manufacturing step, a pair of electrode wires are joined to the temperature sensing element, a protective layer made of glass that seals both the temperature sensing element and a part of the pair of electrode wires is formed, and the protection is performed. A temperature detection element is obtained by forming a coating layer covering part or all of the surface of the layer.
As the temperature sensitive element, a thermistor element is preferably used.

Moreover, as said electrode wire, a dumet wire (copper covering nickel steel wire) and a platinum wire can be used, and it is preferable to use a dumet wire. Dumet wire is to coat the Cu intermediate layer on the surface of the wire made of Fe-Ni alloy, baked further Cu ₂ O layer, or Cu ₂ O borax on the layer _{(Na 2 B 4 O 7)} .

  Moreover, as glass which forms the said protective layer, the various glass conventionally used for the coating of a temperature sensitive element can be used, for example, lead system glass, the bismuth system glass which does not contain lead, etc. are used. Is preferred.

Moreover, as a material which comprises the said coating layer, it is necessary to use what has water repellency and heat resistance. And as for the said coating layer, a main component consists of a silicone resin .
Silicone resin is particularly preferable as a material for forming the coating layer because it is excellent in heat resistance and water repellency. Silicone resins are extremely excellent in heat resistance because they have a large bond energy of siloxane bonds that form the main skeleton of the molecular structure and a high thermal decomposition temperature. Further, the surface of the cured product can have an excellent water repellent effect due to the orientation of methyl groups in the molecule. As the silicone resin, methyl silicone resin, methylphenyl silicone resin, and the like can be used.

Moreover, the said arrangement | positioning process inserts and arrange | positions the said temperature detection element in the metal cover which filled the slurry for fillers inside.
The metal cover is preferably made of stainless steel or Ni-base heat-resistant alloy.

The filler slurry is a slurry filler that is cured by dehydration condensation.
From the viewpoint of curability and productivity, it is optimal to use a slurry for filler that cures by a dehydration condensation reaction.
And as a slurry-like filler that cures by dehydration condensation, for example, Al ₂ O ₃ , SiO ₂ as the main component, a slurry containing Li ₂ O, Al ₂ O ₃ , SiO ₂ as the main component, A slurry containing MgO or Zr ₂ O can be used.

  Moreover, generally, the filler slurry showing alkalinity is said to have poor compatibility with glass and has not been used in the past, but by providing the coating layer, the contact is blocked. Therefore, even when a filler slurry exhibiting alkalinity is applied, it is possible to obtain an effect that generation of microcracks on the surface of the protective layer can be prevented. The degree of alkalinity is preferably about pH 10-12.

  In the case of using a slurry for a filler that cures by a reaction other than dehydration condensation, for example, a slurry that cures by a hydrocondensation reaction (metal alkoxide reaction) (a slurry in which the solvent is an alcohol), moisture in the air (humidity) and In order to cure by reacting, there is a problem that the contact area with air is small and drying for a long time is necessary, and there is a problem that curing around the element at the tip of the tube becomes unstable.

When inserting the temperature detection element into the metal cover, generally, a pair of electrode wires in the temperature detection element is connected to a pair of signal lines, and Al ₂ O ₃ or the like is mainly used. As a component, the pair of signal lines are inserted and fixed in the two holes of the insulator tube having two holes.
As the signal line, for example, one made of stainless steel or Ni-base heat resistant alloy can be used.
Moreover, the said insulator tube ensures the insulation of a pair of electrode wire of a temperature detection element. For example, as described above, an insulator tube having two holes for arranging the signal lines and mainly composed of Al ₂ O ₃ can be used.

In the drying step, the filler slurry is dried.
Examples of the method for drying the filler slurry include a method of air-drying at room temperature for 15 to 20 minutes or more and then holding at 100 to 150 ° C. for 30 minutes or more.

Further, in the temperature detection element manufacturing step, the covering layer is formed at least on the front end side of the surface of the protective layer with respect to the position corresponding to the rear end of the temperature sensitive element.
If the coating layer is not formed in the portion on the tip side of the position corresponding to the rear end portion of the temperature sensitive element, there is a possibility that microcracks may be generated in the portion where the coating layer is not formed in the drying step. Then, the microcracks may develop and expand later, causing cracks that cause abnormal resistance of the temperature sensitive element, leading to a decrease in reliability.
The covering layer may cover the entire surface of the protective layer as long as it covers even the portion on the tip side from the position corresponding to the rear end of the temperature sensitive element. A part of the surface may be exposed. The covering layer is most preferably formed on the entire surface of the protective layer.

Moreover, it is preferable that the said coating layer is 2 micrometers or more in thickness ( Claim 2 ).
In this case, it is possible to reliably prevent contact between the protective layer and moisture in the portion where the coating layer is provided.
When the thickness of the coating layer is less than 2 μm, it is possible to sufficiently prevent the moisture generated when the filler slurry is dried and the glass constituting the protective layer in the drying step. It may not be possible.

  An efficient method for forming the coating layer is a method in which the protective layer is dipped in a liquid state, dried, and heated. And although the thickness of a coating layer changes with the viscosity of the liquid before a process, etc., the coating layer about 20 micrometers at maximum is formed by one dipping. Although installation with an excessive thickness of the coating layer is not economical, it is preferable to carry out dipping treatment twice for reliable installation of the coating layer, and the coating layer is preferably 40 μm or less.

As described above, the temperature sensor of the second invention has a temperature detection element, a signal line, an insulator tube, a metal cover, and a filler. The temperature detection element includes a temperature sensing element, A pair of electrode wires connected to the temperature sensitive element, a protective layer made of glass that seals both the temperature sensitive element and a part of the pair of electrode wires, and a part or all of the surface of the protective layer. And a covering layer arranged to cover.
Preferred materials constituting these are as described above.

And the temperature sensor of this invention can be obtained reliably by performing the manufacturing method of the temperature sensor of the said 1st invention.
Further, when the temperature sensor is disposed in a flow path through which a fluid to be measured such as automobile exhaust gas flows, the temperature detection element accommodated in the metal cover via the filler is projected into the flow path. Be placed.

Example 1
In this example, a method for manufacturing a temperature sensor according to an example of the present invention will be described with reference to FIGS.
The manufacturing method of the temperature sensor of this example includes a temperature detection element manufacturing process, an arrangement process, and a drying process.
This will be described in detail below.

  As shown in FIG. 1, in performing the manufacturing method of the temperature sensor 1, first, a thermistor element was prepared as the temperature sensitive element 2. The temperature sensitive element 2 has a substantially rectangular parallelepiped shape, and a pair of electrodes mainly composed of Au or Pt is formed on a pair of parallel surfaces.

Further, a jumet wire having a diameter of 0.3 mm was prepared as the electrode wire 3.
Moreover, lead glass was prepared as the glass for forming the protective layer 4.
Moreover, Shin-Etsu Chemical Co., Ltd. silicone coating material KR-251 was prepared as a material for forming the coating layer 5. This material has water repellency and heat resistance.
Moreover, Asahi Chemical Industry Co., Ltd. Sumiceram S-30A-3 which is the water-system filler shown in Table 1 was prepared as the slurry 71 for fillers. The filler slurry 71 is cured by dehydration condensation.
Moreover, as a cement for fixing the insulator 82 and the signal line 81 to be described later, ThreeBond 3732 manufactured by ThreeBond Co., Ltd., which is an alcohol-based filler shown in Table 1, was prepared. This cement is hardened by a water condensation reaction (metal alkoxide reaction).

Then, as shown in FIG. 1A, a pair of electrode wires 3 were joined to the temperature sensitive element 2 in the temperature detecting element manufacturing step.
Specifically, a paste containing Au as a main component is applied to the electrode surface of the temperature sensing element 2, the electrode wire 3 is pasted, and baked at 750 ° C., thereby the temperature sensing element 2 and the electrode wire 3. And joined.

Next, as shown in FIG. 1B, a protective layer 4 made of glass for sealing both the temperature sensitive element 2 and a part of the pair of electrode wires 3 was formed.
Specifically, the temperature-sensitive element 2 to which the electrode wire 3 was bonded was placed in a glass tube, and the protective layer 4 was formed by heat treatment at about 900 ° C., which is the glass melting temperature.

Then, as shown in FIG.1 (c), the coating layer 5 which covers a part of surface of the said protective layer 4 was formed, and the temperature detection element 6 was obtained.
Specifically, the material for forming the coating layer was applied to the protective layer 4 by dipping and dried to form the coating layer 5.
The thickness of the coating layer 5 was 10 μm.

Further, in this example, the covering layer 5 is formed in a range including at least a portion on the front end side of the surface of the protective layer 4 with respect to the position corresponding to the rear end portion 21 of the temperature sensitive element 2.
The formation of the covering layer 5 may be performed immediately after the formation of the protective layer 4 as in the present case, or may be performed after the electrode insulation ensuring step described later.
In the present example, the covering layer 5 is formed on a part of the surface of the protective layer 4 including the specific portion, but may be formed on the entire surface of the protective layer 4.

And as shown to FIG.1 (d)-(h), the electrode wire insulation ensuring process was given to the obtained temperature detection element 6. FIG.
Specifically, as shown in FIG. 1 (d), a pair of electrode wires 3 of the temperature detecting element 6 and two signal wires 81 made of stainless steel or Ni-base heat-resistant alloy were welded.
Further, as shown in FIG. 1E, the pair of electrode wires 3 of the temperature detection element 6 and the signal line 81 are inserted into an insulator tube 82 having a pair of holes (two holes 821) to ensure insulation. did.
The insulator tube 82 has two holes 821 and has a cylindrical shape. And the said signal wire | line 81 was inserted in the said 2 hole part 821, and it fixed with the said cement. The signal line 81 is exposed to the rear end side from the two holes 821 of the insulator tube 82.

Further, as shown in FIGS. 1F and 1G, the rear end of the signal line 81 was connected to the external lead wire 83 by caulking and welding.
Then, as shown in FIG. 1 (h), the connection portion between the signal line 81 and the external lead wire 83 was covered with a Teflon (registered trademark) tube 86. Further, the lead wire 83 was inserted into the bush 85, and the bush 85 was inserted into the tube holder 84.
The tube holder 84 is made of glass fiber coated with a silicone varnish.
The bush 85 is made of fluoro rubber.
Moreover, as shown in FIG.1 (h), the metal cover 7 which filled the slurry 71 for fillers inside was prepared. On the outer periphery of the metal cover 7, a screw portion 73 for attachment to the internal combustion engine is disposed. The metal cover 7 is inserted into the screw portion 73. The screw part 73 is made of Ni plating material of stainless steel or Fe.

Then, in the arranging step, as shown in FIG. 1 (i), the temperature detecting element 6 is inserted and arranged in the metal cover 7 filled with the filler slurry 71 therein.
Thereafter, in the drying step, the filler slurry 71 was dried by heating at 80 ° C. for 1.0 hour and at 150 ° C. for 1.5 hours.

  Finally, the temperature sensor 1 was obtained by caulking and fixing the metal cover 7, the tube holder 84, the bush 85, and the external lead wire 83 integrally from the outside.

  The temperature sensor 1 obtained in this example includes a temperature sensing element 2, a pair of electrode wires 3 connected to the temperature sensing element 2, and the temperature sensing element 2 and a part of the pair of electrode wires 3. A pair of signals connected to the pair of electrode wires 3 and a temperature detecting element 6 having a protective layer 4 made of glass that is sealed together, and a covering layer 5 that covers part or all of the surface of the protective layer 4. A wire 81, an insulator tube 82 containing the signal line 81, a metal cover 7 disposed at the tip so as to cover the temperature detection element 6, the metal cover 7 and the temperature detection element 6, or the insulator And a filler 72 interposed between the pipe 82. The covering layer 5 is formed on the surface of the protective layer 4 at least on the front end side from the position corresponding to the rear end portion 21 of the temperature sensitive element 2. Has heat resistance.

  Moreover, in the manufacturing method of the temperature sensor 1 of this example, the coating layer 5 having a specific property was previously provided in a specific part of the surface of the protective layer 4 in the temperature detection element manufacturing step. Thereby, it is possible to suppress the occurrence of microcracks in a specific portion on the protective layer 4 in the manufacturing process of the temperature sensor 1, and to prevent the occurrence of glass cracks that cause abnormal resistance of the temperature sensitive element 2. A highly reliable temperature sensor 1 having excellent heat resistance can be obtained.

By providing the coating layer 5 in advance so as to cover a specific portion on the surface of the protective layer 4 made of glass, the protective layer 4 covered with the coating layer 5 is exposed to moisture in the drying step. It can be prevented from being exposed. And it can suppress that a microcrack generate | occur | produces in the said specific site | part by interrupting | blocking a contact with a water | moisture content and suppressing reaction with water | moisture content and the glass which forms the protective layer 4. FIG. Therefore, it is possible to prevent local stresses such as internal stress of glass, external stress such as vibration, and thermal stress from being concentrated locally during use (in-vehicle mounting), and to suppress the occurrence of cracks that cause resistance abnormalities. .
The covering layer 5 not only prevents contact between the protective layer 4 and moisture, but also prevents the protective layer 4 from being damaged due to contact with other substances in the manufacturing process of the temperature sensor 1. It also has an effect.

The covering layer 5 has water repellency and heat resistance.
The coating layer 5 has water repellency that does not allow water to permeate and heat resistance that is resistant to the temperature conditions at which water evaporates, thereby preventing contact between the glass constituting the protective layer 4 and moisture in the drying step. be able to.

Further, the covering layer 5 is formed on the surface of the protective layer 4 at least on the tip side of the position corresponding to the rear end portion 21 of the temperature sensitive element 2. That is, at least the tip surface of the temperature sensing element 2 and the protective layer 4 in the side surface direction are covered with the coating layer 5.
Since the resistance abnormality occurs due to a crack in the vicinity of the temperature sensing element 2, the covering layer 5 is provided so as to cover at least the range corresponding to the rear end portion 21 of the temperature sensing element 2 on the surface of the protective layer 4. If formed, even if a microcrack occurs in the uncovered portion of the coating layer 5, the occurrence of a crack that causes a resistance abnormality can be suppressed.

In the present invention, as described above, the drying step is performed even when the filler slurry 71 that is cured by dehydration condensation is formed by forming the coating layer 5 in advance on the necessary portion of the protective layer 4. In this case, it is possible to prevent the occurrence of microcracks in specific portions of the protective layer 4.
Thus, since the generation | occurrence | production of the micro crack used as the generation | occurrence | production of the crack which causes resistance abnormality is prevented, reliability can be improved significantly compared with the past. Moreover, even if it is the use at high temperature, the suppression effect of crack generation can be acquired and it can have high temperature heat resistance.

(Comparative Example 1)
In this example, for comparison, as shown in FIG. 3, a temperature sensor 9 having a temperature detection element 906 that does not form the coating layer 5 in the temperature sensor 1 manufactured in Example 1 is manufactured.
This example was performed in the same manner as in Example 1 except that the coating layer was not formed.

(Experimental example 1)
In this example, a thermal endurance test was performed on the temperature sensors manufactured in Example 1 and Comparative Example 1.
<Cooling durability test>
In the cold endurance test, four temperature sensors obtained in Example 1 and Comparative Example 1 were prepared, and for each of the temperature sensor 1 (sample E1 to sample E4) and the temperature sensor 9 (sample C1 to sample C4), The heating time was 2 minutes and heating was performed to achieve a maximum temperature of 500 ° C., and the cooling time was set to 2 minutes and cooling was performed to achieve a minimum temperature of 50 ° C., which was performed as 1000 cycles. And the resistance value change after a cold-heat endurance test was measured.

  The measurement results are shown in Table 2 and FIG. FIG. 4 is a plot of the measurement results, with the horizontal axis representing the number of cycles (cycles) and the vertical axis representing the temperature error (° C.). In FIG. 4, curve E1 shows the result of sample E1, curve E2 shows the result of sample E2, curve E3 shows the result of sample E3, curve E4 shows the result of sample E4, and curve C1 shows the result of sample C1. , Curve C2 shows the result of sample C2, curve C3 shows the result of sample C3, and curve C4 shows the result of sample C4.

  In the evaluation, a case where the temperature error after the thermal endurance test (after 1000 cycles) is within ± 5 ° C. with respect to the initial temperature is acceptable, and the temperature error after the thermal endurance test (after 1000 cycles) is the initial The case where it was out of the range of ± 5 ° C. with respect to the temperature was regarded as rejected.

As can be seen from Table 2 and FIG. 4, the temperature sensor 1 (sample E1 to sample E4) as an example has a small temperature error, good results, excellent high temperature heat resistance, It turns out that the reliability is high.
In addition, among the temperature sensors 9 (sample C1 to sample C4) as comparative examples, the sample C3 and the sample C4 showed good results, but the sample C1 and the sample C2 have a large temperature error and fail. It can be seen that a resistance abnormality of the temperature element has occurred. That is, the reliability is low.

  Thus, according to this invention, it turns out that it is excellent in high temperature heat resistance, can provide a highly reliable temperature sensor, and its manufacturing method.

(Experimental example 2)
In this example, an experiment was conducted to compare the curability of a slurry filler that is cured by dehydration condensation and a slurry that is cured by a hydrocondensation reaction (metal alkoxide reaction).
As the slurry-like filler that hardens by dehydration condensation, the aqueous filler shown in Table 1 used in Example 1 was prepared.
Moreover, as a slurry cured by a hydrolysis condensation reaction (metal alkoxide reaction), alcohol-based fillers shown in Table 1 used in Example 1 were prepared.

  As for the water-based filler, the water-based filler is disposed in a metal cover similar to the metal cover in the first embodiment, and the temperature detection element is inserted and disposed in the metal cover in the same manner as in the first embodiment. Then, the curing conditions were set to 80 ° C. for 1 hour or longer and 150 ° C. for 1.5 hours or longer to cure the filler.

  As for the alcohol-based filler, the alcohol-based filler is disposed on a metal cover similar to the metal cover in the first embodiment, and the temperature detection element is inserted into the metal cover in the same manner as in the first embodiment. After placement, the filler was cured by setting the curing conditions at room temperature for 20 hours or more, and at 50 ° C. and 80% RH for 100 hours or more.

As a result, the aqueous filler cured by dehydration condensation was cured evenly by drying, showed no curability, and exhibited excellent curability.
On the other hand, the alcohol-based filler is cured by reacting with moisture (humidity) in the air. In this experimental example, since the metal tube closed at one end is filled, the contact area with the air is small, and drying for a long time is required. Inferior.

DESCRIPTION OF SYMBOLS 1 Temperature sensor 2 Temperature sensing element 21 Rear end part 3 Electrode wire 4 Protective layer 5 Covering layer 6 Temperature detection element 7 Metal cover 71 Slurry for filler 72 Filler

Claims (3)

A pair of electrode wires are joined to the temperature sensitive element, a protective layer made of glass that seals both the temperature sensitive element and a part of the pair of electrode wires is formed, and part or all of the surface of the protective layer Forming a temperature detection element by forming a coating layer covering the temperature detection element;
An arrangement step of inserting and arranging the temperature detection element in a metal cover previously filled with slurry for filler,
A drying step for drying the slurry for filler,
In the temperature detection element manufacturing step, the covering layer is formed on a portion of the surface of the protective layer at least on the tip side from a position corresponding to the rear end portion of the temperature sensitive element,
And the said coating layer has water repellency and heat resistance which a main component consists of a silicone resin ,
The method for manufacturing a temperature sensor, wherein the filler slurry is a slurry that is cured by dehydration condensation.   The method for manufacturing a temperature sensor according to claim 1, wherein the coating layer has a thickness of 2 μm or more.   A temperature-sensitive element; a pair of electrode wires connected to the temperature-sensitive element; a protective layer made of glass that seals both the temperature-sensitive element and a part of the pair of electrode wires; and a surface of the protective layer A temperature detecting element having a coating layer covering part or all of
  A pair of signal lines connected to the pair of electrode lines;
  An insulator tube containing the signal line;
  A metal cover disposed at the tip so as to cover the temperature detecting element and the insulator tube;
  A filler interposed between the metal cover and the temperature detecting element or the insulator tube,
  The coating layer is formed on the surface of the protective layer at least on the tip side from a position corresponding to the rear end portion of the temperature sensitive element, and the water repellent and heat resistant main component is a silicone resin. A temperature sensor characterized by having a property.

Images