JP3667099B2 - High temperature thermistor element, manufacturing method thereof, and temperature sensor for high temperature using the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a high temperature thermistor element excellent in heat resistance and thermal shock resistance used for, for example, a temperature sensor for gas combustion control and an exhaust temperature sensor for automobiles, a manufacturing method thereof, and a high temperature sensor using the same. is there.
[0002]
[Prior art]
As shown in FIGS. 11 and 12, the conventional high temperature thermistor element is electrically connected to the thermistor layer 81 formed by printing or the like on the ceramic substrate 82 formed of alumina or the like, and the thermistor layer 81. Electrodes 84 and 85 were formed, and a ceramic substrate 83 was provided thereon. In addition, a lead wire is connected to the high temperature thermistor element and used as a temperature sensor.
[0003]
[Problems to be solved by the invention]
According to the above configuration, due to the difference in thermal expansion coefficient between the ceramic substrates 82 and 83 and the thermistor layer 81, the thermistor layer 81 cracks or peels off during repeated heating and cooling, and cannot withstand thermal shock. Had problems.
[0004]
Accordingly, an object of the present invention is to provide a high-temperature thermistor element having stable resistance temperature characteristics at high temperatures and excellent in heat resistance and thermal shock resistance, a manufacturing method thereof, and a high-temperature sensor using the same. It is.
[0005]
[Means for Solving the Problems]
In order to achieve this object, a high temperature thermistor element of the present invention has a ceramic plate made of a long plate-like thermistor material and an electrode provided in the longitudinal direction of the surface of the ceramic plate, and the electrode is the ceramic plate. The ceramic plate made of the thermistor material is Mg (Al, Cr, Fe) ₂ O ₄ series, Mg (Al, Cr) ₂ O ₄ series, Mg (Al, Cr, Mn) ₂ O ₄ type, (Zn, Mg) (Al, Cr, Fe) ₂ O ₄ type, and (Al, Cr, Fe) ₂ O ₃ type selected from one type or more. There, possess two functions thermistor functions and support functions, which is characterized in that the unnecessary substrate supporting the thermistor layer, the two functions of the thermistor functions and support functions in a single ceramic plate Thermis as before The ceramic substrate that supports the data layer becomes unnecessary, and the problem that the thermistor layer cracks or peels off due to the difference in the thermal expansion coefficient between the ceramic plate and the thermistor layer does not cause the problem of being unable to withstand thermal shock, The above object can be achieved.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
The invention according to claim 1 of the present invention includes a ceramic plate made of a long plate-like thermistor material and an electrode provided in the longitudinal direction of the surface of the ceramic plate, and the electrode is provided at an end of the ceramic plate. The ceramic plates made of the thermistor material in a non-contact state are Mg (Al, Cr, Fe) ₂ O ₄ , Mg (Al, Cr) ₂ O ₄ , Mg (Al, Cr, Mn) ₂ O. Thermistor function is formed by using one or more kinds selected from among ₄ series, (Zn, Mg) (Al, Cr, Fe) ₂ O ₄ series, and (Al, Cr, Fe) ₂ O ₃ series. and have a two functions of supporting function, a high-temperature thermistor element characterized in that the unnecessary substrate supporting the thermistor layer, since it has two functions of the thermistor functions and support functions in a single ceramic plate Support the thermistor layer as before The ceramic substrate to be held is no longer necessary, and the problem that the thermistor layer cracks or peels off due to the difference in the thermal expansion coefficient between the ceramic plate and the thermistor layer does not cause the problem of being unable to withstand thermal shock. It has stable resistance-temperature characteristics and is excellent in heat resistance and thermal shock resistance.
[0007]
The invention according to claim 2 is the high temperature thermistor element according to claim 1, wherein an insulator having the same crystal structure as the ceramic plate made of the thermistor material is provided on the electrode so that a part of the insulating electrode is exposed. In addition to protecting electrodes exposed to high temperatures, the ceramic plate and insulator have the same crystal structure, that is, approximately the same thermal expansion coefficient, so they have stable resistance temperature characteristics at high temperatures and excellent heat resistance and thermal shock resistance It is a thing.
[0008]
The invention according to claim 3 is the high temperature thermistor element according to claim 1, characterized in that it has a protective layer formed on the electrode using the same material as the ceramic plate made of the thermistor material. Since the ceramic plate and the protective layer have the same thermal expansion coefficient, the ceramic plate and the protective layer have stable resistance-temperature characteristics at high temperatures and are excellent in heat resistance and thermal shock resistance.
[0009]
Invention of Claim 4 is the high temperature thermistor element as described in any one of Claims 1-3 which electrically connected the metal plate or the metal wire to the exposed electrode, The electrical connection strength can be secured.
[0010]
The invention according to claim 5 is a first step of forming an electrode on the ceramic green sheet in a non-contact state at an end of the ceramic green sheet, and then a second step of firing the ceramic green sheet. with the door, said with firing by shrinkage between the ceramic green sheet and the electrode used almost as the same or is larger of the ceramic green sheet, the ceramic plate was fired the ceramic green sheet, Mg (Al, Cr, Fe) ₂ O ₄ system, Mg (Al, Cr) ₂ O ₄ system, Mg (Al, Cr, Mn) ₂ O ₄ system, (Zn, Mg) (Al, Cr, Fe) ₂ O ₄ system, (Al, Cr, Fe) ₂ O ₃ is formed so as to contain at least one selected from the system, and has two functions, a thermistor function and a support function. A method for manufacturing a high temperature thermistor element that eliminates the need for a substrate that supports a layer. A high temperature thermistor that has stable resistance-temperature characteristics at high temperatures and has excellent heat resistance and thermal shock resistance at low cost and high yield. Can be manufactured.
[0011]
According to a sixth aspect of the present invention, a sheet that has the same crystal structure as the ceramic green sheet after firing on the electrode and is an insulator on the electrode before the second step after the first step is a part of the electrode. It is a manufacturing method of the high temperature thermistor element of Claim 5 which provided the process of laminating | stacking so that it may expose, and it can prevent that an electrode deteriorates by baking.
[0012]
The invention according to claim 7 is characterized in that the ceramic green sheet and the ceramic green sheet have the same crystal structure and the particle diameters of the raw material powder forming the sheet serving as an insulator are substantially the same. It is a manufacturing method of the high temperature thermistor element of Claim 6 , Comprising: The difference of the shrinkage rate at the time of baking can further be reduced.
[0013]
The invention according to claim 8 is the high temperature thermistor element according to any one of claims 1 to 4 , a lead wire electrically connected to an electrode of the high temperature thermistor element, and the high temperature thermistor element. It is a high temperature sensor having a mounting support provided at the end on the side where the lead wire is connected, and has high reliability.
[0014]
Invention of Claim 9 is the temperature sensor for high temperature of Claim 8 which accommodated the thermistor element in the heat-resistant metal, and is a thing with high reliability which can interrupt | block the influence on the high temperature thermistor element of external atmosphere. .
[0015]
Embodiments of the present invention will be described below with reference to the drawings.
[0016]
(Embodiment 1)
FIG. 1 is an exploded perspective view of a high temperature thermistor element in the present embodiment, FIG. 2 is a perspective view thereof, 11 is a ceramic plate made of a thermistor material, 13 and 14 are two electrodes provided on the ceramic plate 11, Reference numeral 12 denotes a ceramic plate formed of a thermistor material provided so as to expose one end portions of the electrodes 13 and 14. The electrodes 13 and 14 are not in contact with the end of the ceramic plate 11.
[0017]
3 is a perspective view of a temperature sensor using the high temperature thermistor element shown in FIG. 1. 31 is a high temperature thermistor element, 32 is a mounting support, and 33 is electrically connected to the electrodes 13 and 14 of the high temperature thermistor element 31. Lead wire.
[0018]
Next, a method for manufacturing this high temperature thermistor element will be described.
[0019]
First, Al ₂ O ₃ , Cr ₂ O ₃ and Fe ₂ O ₃ as starting materials are blended in predetermined amounts, put in a pot, and wet mixed by a ball mill. Next, this mixed dry powder is calcined at 1200 ° C. and wet-pulverized again with a ball mill to obtain (Al, Cr, Fe) ₂ O ₃ type thermistor material powder. Next, an organic vehicle is added to the thermistor material powder to form a slurry. From this, a green sheet having a thickness of 100 μm is produced by a doctor blade method, and 10 layers thereof are laminated to obtain a laminated body having a thickness of 1 mm. The laminate is cut into 10 mm length, 70 mm width, 10 mm length, and 60 mm width to obtain green sheets to be the ceramic plates 11 and 12.
[0020]
Next, as shown in FIG. 1, when using a Pt paste on the longitudinal direction of the green sheet of 10 mm length and 70 mm width, the green sheet is 5 mm away from both longitudinal ends and 1 to 2 mm away from the lateral edges. Two electrodes 13 and 14 having a width of 2 mm, a length of 60 mm, and a thickness of 10 μm are printed. The two electrodes have the same shape and are symmetrically formed on the green sheet. A green sheet having a length of 10 mm and a width of 60 mm is bonded by heating and pressing so that one end of the electrodes 13 and 14 to be connected to the outside is exposed on the upper surface, and then fired at a maximum temperature of 1600 ° C. for 5 hours. 2 is obtained.
[0021]
Next, as shown in FIG. 3, a lead wire 33 electrically connected to the attachment support portion 32 and the electrodes 13 and 14 is provided for the high temperature thermistor element 31 to serve as a temperature sensor. The attachment support portion 32 is provided at the end of the high temperature thermistor element 31 on the side where the lead wire 33 is connected.
[0022]
The resistance temperature characteristic of this temperature sensor is shown in FIG. 4, and it can be seen that it has a resistance temperature characteristic suitable for measurement.
[0023]
(Embodiment 2)
5 is an exploded perspective view of the high temperature thermistor element according to the present embodiment, FIG. 6 is a perspective view thereof, 51 is a ceramic plate made of the thermistor material, 54 is an electrode provided on the upper surface of the ceramic plate 51 (the same applies to the lower surface). , 52 and 53 are ceramic plates formed of a thermistor material provided so that one end of the electrode 54 is exposed.
[0024]
7 is a temperature sensor formed by using the high temperature thermistor element shown in FIG. 5. 71 is a high temperature thermistor element, 72 is a mounting support portion, and 73 is a lead wire electrically connected to the electrode 54 of the high temperature thermistor element 71. It is. The attachment support 72 is provided at the end of the high temperature thermistor element 71 on the side where the lead wire 73 is connected.
[0025]
First, a green sheet of (Al, Cr, Fe) ₂ O ₃ based thermistor material is produced in the same manner as in the first embodiment, and 10 layers are laminated to obtain a laminate having a thickness of 1 mm. The laminate is cut into 10 mm length, 70 mm width, 10 mm length, and 60 mm width to obtain green sheets to be the ceramic plates 51, 52, 53. Next, as shown in FIG. 5, the electrodes 54 are printed on each of the upper and lower surfaces of the 10 mm long and 70 mm wide green sheets by using Pt paste to form a pair of electrodes. Next, a green sheet having a length of 10 mm and a width of 60 mm is bonded by heating and pressing so that one end of the electrode 54 is exposed on the lower surface, and then fired to obtain a high temperature thermistor element shown in FIG. Using this high temperature thermistor element, the high temperature temperature sensor shown in FIG. 7 was produced in the same manner as in the first embodiment. Similar to the temperature sensor described in the first embodiment, this temperature sensor also has a resistance temperature characteristic suitable for measurement.
[0026]
(Comparative Example 1)
For comparison, a thermistor having a structure in which a thermistor layer made of an (Al, Cr, Fe) ₂ O ₃ based thermistor material is printed on a ceramic sheet green sheet made of a partially stabilized zirconia of a high temperature heat resistant material. An element was produced. As shown in FIG. 11, a thermistor layer 81 made of (Al, Cr, Fe) ₂ O ₃ based thermistor material is formed on a green sheet to be an insulating structural material ceramic plate 82 by printing, and two electrodes are formed thereon. After applying 84 and 85, after bonding the green sheet to be the insulating structure material ceramic plate 83 of the same material by heat pressure bonding so that one end portion of the electrodes 84 and 85 to be the connection portion is exposed on the upper surface, The high temperature thermistor element shown in FIG. 12 was obtained by firing. Using this high temperature thermistor element, a temperature sensor was fabricated in the same manner as in the first embodiment.
[0027]
The manufactured temperature sensor and the temperature sensor of Embodiments 1 and 2 were subjected to 1000 cycles of a thermal shock test at 1000 ° C. for 5 minutes and then at room temperature for 5 minutes and evaluated. Although there was no abnormality in the temperature sensor of Embodiment 2, the temperature of Comparative Example 1 using a thermistor element in which an (Al, Cr, Fe) ₂ O ₃ thermistor material was applied on the insulating structural material ceramic plate 82 by printing. The sensor was disconnected.
[0028]
From this result, it can be seen that the temperature sensor of the present invention provides a high-temperature sensor having high thermal shock resistance. In addition, since the (Al, Cr, Fe) ₂ O ₃ type thermistor material has sufficient thermal shock resistance, this difference is the thermal expansion between the insulating structural material ceramic plate 82 and the thermistor layer 81 as the substrate. This is probably because cracks occurred in the thermistor layer 81 due to the difference in coefficients.
[0029]
As described above, the high temperature thermistor element according to the present invention having the ceramic plate made of the thermistor material having high mechanical strength and the electrode provided on the surface thereof is not formed by forming the thermistor layer on the insulating structure material ceramic plate serving as the substrate. In addition, the ceramic plate itself plays the two roles of the substrate and thermistor function, so the thermistor element is not damaged even if heating and cooling are repeated, and it has stable resistance-temperature characteristics at high temperature, as well as heat resistance and heat resistance. It is possible to provide a high-temperature sensor having excellent impact properties.
[0030]
(Embodiment 3)
8 is an exploded perspective view of the high temperature thermistor element according to the present embodiment, FIG. 9 is a perspective view thereof, 101 is a ceramic plate made of the thermistor material, 103 and 104 are two electrodes provided on the ceramic plate 101, Reference numeral 102 denotes a ceramic plate formed of a thermistor material provided so as to expose one end of the electrodes 103 and 104, and 105 and 106 denote metal wires electrically connected to the exposed one end of the electrodes 103 and 104.
[0031]
The high temperature thermistor element is different from that shown in the first embodiment in that the metal wires 105 and 106 are electrically connected to the electrodes 103 and 104.
[0032]
The high temperature thermistor element is manufactured in substantially the same manner as in the first embodiment, but the metal wires 105 and 106 are printed with two electrodes 103 and 104 using a Pt paste on a green sheet having a length of 10 mm and a width of 70 mm. Thereafter, one end side is placed on one end portion of the electrode, and the other end side is drawn out to the outside of the green sheet, and then a green sheet having a length of 10 mm and a width of 60 mm is heated and pressed to be bonded. At this time, one end side of the metal wires 105 and 106 is covered with a green sheet having a length of 10 mm and a width of 60 mm.
[0033]
According to this configuration, there is no deterioration of the exposed portion of the electrode during firing. Further, the electrodes 103 and 104 and the metal wires 105 and 106 can be reliably connected.
[0034]
(Embodiment 4)
FIG. 10 is a cross-sectional view of a temperature sensor formed using the high temperature thermistor element shown in FIG. 9. After the thermistor element 121 is housed in a bottomed heat resistant metal case 122, The inorganic filler 123 is filled and fixed, and then the metal wires 105 and 106 of the thermistor element 121 and the lead wires 126 are electrically connected by welding with the connector 124 and mechanically fixed by the collar 125. Yes. By housing the thermistor element 121 in the refractory metal case 122, the influence of the external atmosphere can be blocked and a highly reliable temperature sensor for high temperature can be obtained.
[0035]
In addition, it describes below about becoming a point in each said embodiment.
[0036]
(1) The thermistor material has been described only for the (Al, Cr, Fe) ₂ O ₃ system, but the Mg (Al, Cr, Fe) ₂ O ₄ system, Mg (Al, Cr) ₂ O ₄ system, Mg ( Using one or more selected from Al, Cr, Mn) ₂ O ₄ system, (Zn, Mg) (Al, Cr, Fe) ₂ O ₄ system, and (Al, Cr, Fe) ₂ O ₃ system The same effect can be obtained if it forms a ceramic plate. These materials can provide a ceramic plate having high mechanical strength and high temperature stability.
[0037]
(2) The thermistor material shown in (1) varies depending on its composition, but is preferably fired at a maximum temperature of 1300 ° C to 1700 ° C. If it is less than 1300 ° C., the sintering is insufficient, which may cause problems in strength and durability. On the other hand, if the temperature exceeds 1700 ° C., there is a problem in characteristics due to abnormal grain growth and the characteristics as a temperature sensor for high temperature may be impaired, which is not preferable.
[0038]
(3) Further, since the thermistor material shown in (1) has a very high firing temperature, it is necessary to use a refractory metal such as platinum for the electrode and the metal wire to be fired simultaneously.
[0039]
(4) Although the ceramic plates 12, 52, 53, 102 were made using the same raw material as the ceramic plates 11, 51, 101, the same crystal structure as that of the ceramic plates 11, 51, 82, that is, when firing, is not the same raw material. May be formed using a raw material having substantially the same shrinkage rate.
[0040]
When the same raw material is not used, the difference in shrinkage during firing can be further reduced by setting the average particle size of the raw materials to be the same or substantially the same.
[0041]
(5) Instead of the metal wires 105 and 106 used in the third embodiment, a metal plate may be used.
[0042]
(6) Although the ceramic plates 11, 12, 51, 52, 53, 101, 102 are formed using green sheets, they may be formed using a thermistor molding obtained by dry molding instead.
[0043]
(7) The ceramic green sheet is formed by the doctor blade method or the like, but may be formed by extrusion molding or powder molding.
[0044]
【The invention's effect】
As described above, according to the present invention, since a single ceramic plate has two functions of a thermistor function and a support function, the conventional ceramic substrate for supporting the thermistor layer is not required, and the thermal expansion coefficient of the ceramic plate and the thermistor layer is not required. The thermistor layer cracks or peels due to the difference and does not withstand the problem of thermal shock. Thermistor has a stable resistance-temperature characteristic at high temperatures and excellent heat resistance and thermal shock resistance. An element can be provided.
[Brief description of the drawings]
1 is an exploded perspective view of a high temperature thermistor element in Embodiment 1 of the present invention. FIG. 2 is a perspective view of the high temperature thermistor element shown in FIG. 1. FIG. 3 is a perspective view of a temperature sensor using the high temperature thermistor element shown in FIG. FIG. 4 is a characteristic curve diagram showing temperature dependence of the resistance value of the high temperature thermistor element shown in the first embodiment of the present invention. FIG. 5 is an exploded perspective view of the high temperature thermistor element in the second embodiment of the present invention. 6 is a perspective view of a high temperature thermistor element shown in FIG. 5. FIG. 7 is a perspective view of a temperature sensor using the high temperature thermistor element shown in FIG. 5. FIG. 8 is an exploded perspective view of the high temperature thermistor element in Embodiment 3 of the present invention. FIG. 9 is a perspective view of the high temperature thermistor element shown in FIG. 8. FIG. 10 is a cross-sectional view of a temperature sensor using the high temperature thermistor element shown in FIG. Figure 1 Perspective view of a high-temperature thermistor element shown in [Description of symbols]
DESCRIPTION OF SYMBOLS 11 Ceramic plate 12 Ceramic plate 13 Electrode 14 Electrode 31 Thermistor element 32 Mounting support 33 Lead wire 51 Ceramic plate 52 Ceramic plate 53 Ceramic plate 54 Electrode 71 Thermistor element 72 Mounting support 73 Lead wire 81 Thermistor layer 82 Ceramic substrate 83 Ceramic substrate 84 Electrode 85 Electrode 101 Ceramic plate 102 Ceramic plate 103 Electrode 104 Electrode 105 Metal wire 106 Metal wire 121 Thermistor element 122 Heat-resistant metal case 123 Inorganic filler 124 Connector 125 Color 126 Lead wire

Claims (9)

It has a ceramic plate made of a long plate-like thermistor material and an electrode provided in the longitudinal direction of the surface of the ceramic plate, and the electrode is in a non-contact state with the end of the ceramic plate and made of the thermistor material The ceramic plate is made of Mg (Al, Cr, Fe) ₂ O ₄ system, Mg (Al, Cr) ₂ O ₄ system, Mg (Al, Cr, Mn) ₂ O ₄ system, (Zn, Mg) (Al, Cr , Fe) ₂ O ₄ system, (Al, Cr, are those formed using the one or more selected from among Fe) ₂ O ₃ system, have a dual function of the thermistor functions and support functions, thermistor A high temperature thermistor element characterized in that a substrate for supporting a layer is unnecessary .   2. The high temperature thermistor element according to claim 1, wherein an insulator having the same crystal structure as a ceramic plate made of a thermistor material is provided on the electrode so that a part of the electrode is exposed.   2. The high temperature thermistor element according to claim 1, further comprising a protective layer formed on the electrode using the same material as the ceramic plate made of the thermistor material.   The high temperature thermistor element according to any one of claims 1 to 3, wherein a metal plate or a metal wire is electrically connected to the exposed electrode. Comprising a first step of forming an electrode on a non-contact state on the ceramic green sheet to an end portion of the ceramic green sheet, then a second step of firing the ceramic green sheet, and the ceramic green sheet While using a ceramic green sheet having a contraction rate substantially the same as that of the electrode or larger than the ceramic green sheet, the ceramic plate obtained by firing the ceramic green sheet is Mg (Al, Cr, Fe) ₂ O ₄ system, Mg (Al, Cr) ₂ O ₄ system, Mg (Al, Cr, Mn) ₂ O ₄ system, (Zn, Mg) (Al, Cr, Fe) ₂ O ₄ system, (Al, Cr, Fe) ₂ O It is formed so as to contain one or more types selected from the _three systems, and has two functions of a thermistor function and a support function, eliminating the need for a substrate that supports the thermistor layer. A method for manufacturing a high temperature thermistor element, characterized in that:   After the first step and before the second step, there is provided a step of laminating a sheet to be an insulator on the electrode so as to have the same crystal structure as the ceramic green sheet after firing so that a part of the electrode is exposed A method for manufacturing a high temperature thermistor element according to claim 5.   7. The high temperature thermistor element according to claim 6, wherein the ceramic green sheet and the ceramic green sheet have the same crystal structure and have substantially the same grain size as the raw material powder forming the insulating sheet. Manufacturing method.   The high temperature thermistor element according to any one of claims 1 to 4, a lead wire electrically connected to an electrode of the high temperature thermistor element, and an end of the high temperature thermistor element on the side where the lead wire is connected. The temperature sensor for high temperature which has the attachment support part provided in the part.   The temperature sensor for high temperature according to claim 8, wherein the thermistor element is housed in a heat-resistant metal.

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