JP2010032237A - Temperature sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a temperature sensor having excellent durability, electrical insulation property and temperature measurement responsiveness. <P>SOLUTION: A temperature sensor 5 is configured so that a thermocouple 20 is installed in a protective tube 11 made of ceramic such as alumina. The ceramic protective tube 11 that is formed by injection molding includes: a base part 12 with a constant thickness; a tapered portion 13 that is continuous to the base part 12 and becomes gradually thinner toward a distal end; the distal end 14 that is continuous to the tapered portion 13 and is the thinnest portion; and a flange part 15 provided near the boundary between the base part 12 and the tapered portion 13. The thermocouple 20 includes: copper-constantan wires 21, 21; a glass bead 22 for coating the junction of these wires 21, 21; and a connector 23. The glass bead 22 is pushed and fixed in the distal end 14 of the ceramic protective tube 11 with a filler 24 mainly made of silicone resin (SiO<SB>2</SB>). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a temperature sensor incorporated in a water heater or a motor.

  A conventional temperature sensor houses a metal element wire constituting a thermocouple or a thermistor chip and dumet wire constituting a thermistor in a protective tube (sheath) made of stainless steel. However, the stainless steel protective tube is inferior in corrosion resistance, and when exposed to high temperatures, the stainless steel protective tube deteriorates, and further the electrical instability and insulation of the thermocouple or thermistor occur, resulting in the function as a temperature sensor. Can't be done. Therefore, a temperature sensor using a ceramic protective tube disclosed in Patent Documents 1 to 3 has been proposed.

In Patent Document 1, a mixture or a compound of molybdenum and zirconium boride is coated as an underlayer on the outer surface of a protective tube made of silicon nitride (Si ₃ N ₄ ) or sialon (SIALON), and an outer layer is formed as an intermediate layer. A temperature sensor is disclosed in which a mixture or compound of molybdenum, zirconium boride, and zirconia is coated, and zirconia is coated as an outermost layer on the outer side of the intermediate layer.

  In Patent Document 2, a protective tube is formed of high-purity alumina, and the protective tube is surrounded by a cooling cylinder through which a cooling medium flows, and a flange for fixing the protective tube to the cooling cylinder is formed in the protective tube. A temperature sensor is disclosed.

In the temperature sensor disclosed in Patent Document 3, a protective tube is made of silicon nitride (Si ₃ N ₄ ), sialon (SIALON), or silicon carbide (SiC), and the tip of the protective tube is thin (0.5 mm). ) To reduce the heat capacity and improve the temperature measurement responsiveness, and in the tip of the protective tube, a filler made of silicon nitride (Si ₃ N ₄ ) -based reaction sintered ceramic is put into a thermocouple. And a structure in which a filler made of SiC whiskers is disposed in the rear portion of the protective tube.

  The temperature sensor using the ceramic protective tube is mainly a thermocouple temperature sensor having a high operating temperature environment, and there is no prior art as a thermistor temperature sensor having a low temperature use range of 300 ° C. or less.

JP 2003-004538 A JP 2004-125643 A Japanese Patent Laid-Open No. 10-030967

  As disclosed in Patent Document 1, when the base layer, the intermediate layer, and the outermost surface layer are coated on the outside of the protective tube, the thickness of the tip of the protective tube increases and the temperature measurement responsiveness deteriorates.

In addition, when a flange is provided as disclosed in Patent Document 2, the material cannot go around by injection molding, and thus a large flange portion as shown in the drawing of Patent Document 2 cannot be formed.

Furthermore, as disclosed in Patent Document 3, if the tip of the protective tube is made thin, the response will be improved. However, if alumina is used as the ceramic material, the thickness of the tip will be 0.5 mm. It is insufficient.
In Patent Document 3, a silicon nitride (Si ₃ N ₄ ) -based reaction sintered ceramic is used as a filler, but when subjected to repeated high and low temperatures and external impact, the inner surface of the protective tube and the filler A gap is formed between them and the response is deteriorated.

  In order to solve the above-mentioned problems, a temperature sensor according to the present invention has a protective tube made of ceramics, the tip of the ceramic protective tube is formed thinner than other parts, and a thermocouple is formed inside the tip. Or the glass ball which coat | covers the part which comprises a thermistor was accommodated, and this glass bulb | ball was set as the structure hold | maintained with the resin filler which is excellent in heat conductivity and has a softness | flexibility.

  In the second aspect of the invention, the protective tube is made of ceramic, and the tip of the ceramic protective tube is formed thinner than the other parts, and the portion constituting the thermocouple or thermistor is insulated inside the tip. The portion covered with the coat and housed, and further the portion constituting the thermocouple or thermistor is held by a resin filler having excellent heat conductivity and flexibility.

The protective tube made of ceramic is preferably made of alumina, the tip portion has a thickness of 0.3 mm or less, and the resin having excellent heat conductivity and flexibility is mainly composed of silicone resin (SiO ₂ ). .

  If it is difficult to form a flange part with the required thickness and diameter when integrally forming a protective tube by injection molding, an annular protrusion is formed on the outer periphery of the ceramic protective tube during injection molding. And a metal flange can be press-fitted outside the annular convex portion.

  According to the temperature sensor of the present invention, since the heat sensitive part at the tip is thinned to, for example, 0.3 mm or less, sufficient response can be obtained even if alumina having inferior heat conductivity is used as the ceramic material. Is obtained.

  Also, as a filler for fixing the thermocouple or thermistor in the tip of the protective tube, a resin having excellent heat conductivity and flexibility, such as silicone resin, epoxy resin, or urethane resin, is used as an external material. Durability against impact and thermal shock is improved.

When a ceramic protective tube is used, the electrical insulation between the sensor sensing part, the sensor wetted part, and the mounting body can be reliably ensured, and the electrical performance is much higher than when a metal protective tube is used. Safety. For example, even in the case of a 0.1 mm thick alumina ceramic, it has been experimentally confirmed that a dielectric breakdown voltage of AC 3 KV for 1 minute can be secured.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. 1 (a) and 1 (b) are water heaters incorporating a temperature sensor according to the present invention. (A) is a gas water heater, (b) is a schematic diagram of an electric water heater, and FIG. 2 is a pipe of the temperature sensor. FIG. 3 is an enlarged cross-sectional view of the tip portion of the temperature sensor.

  The gas water heater shown in (a) has a burner 2, a pipe 3, and a heat transfer fin 4 arranged in the main body cover 1, water is supplied from one end of the pipe 3, and hot water is taken out from the other end of the pipe 3. A temperature sensor 5 according to the present invention is attached to a part of the pipe 3 on the downstream side of the burner 2. The electric water heater shown in (b) has a 220 V heater 2 a disposed in the main body cover 1. The temperature sensor according to the present invention can be applied not only to a water heater but also to temperature detection of a motor of an electric vehicle, a hybrid vehicle, and the like, taking advantage of its excellent corrosion resistance and excellent electrical insulation.

  An opening 6 is formed in the pipe 3 as shown in FIG. 2, and a metal block 7 is welded to the outer surface of the opening 6. The metal block 7 is formed with the opening 6 and a two-stage opening 8. The temperature sensor 5 is inserted into and fixed to the pipe 3 through the openings 6 and 8 and through the O-ring 9 and the mounting plate 10.

  The temperature sensor 5 is configured by mounting a thermocouple 20 in a protective tube 11 made of ceramics such as alumina. The ceramic protective tube 11 is formed by injection molding, and has a base portion 12 having a constant thickness (T1 = 0.45 mm), and a tapered portion 13 that is continuous with the base portion 12 and gradually decreases in thickness toward the tip. The tip portion 14 is continuous with the tapered portion 13 and has the thinnest thickness (T2 = 0.3 mm), and the flange portion 15 is provided near the boundary between the base portion 12 and the tapered portion 13.

  The thermocouple 20 includes copper-constantan strands 21, 21, glass balls 22 that cover the joints of the strands 21, 21, and a connector 23.

The glass ball 22 is fixed by being pushed into the distal end portion 14 of the ceramic protective tube 11 with a filler 24 mainly composed of silicone resin (SiO ₂ ). Here, since the filler 24 mainly composed of silicone resin (SiO ₂ ) has flexibility, no gap is formed between the inner surface of the distal end portion 14 and the air inside the distal end portion 14 of the protective tube when being pushed. Will not bite. Further, no gap is formed even when a thermal / external impact is applied. In addition, in order to improve heat conductivity, it is possible to add metal powder etc. to the filler 24.

  The rear part of the ceramic protective tube 11 is sealed with a filler 25 mainly composed of urethane.

  4 to 8 are sectional views of a temperature sensor according to another embodiment. Of these, the temperature sensor shown in FIGS. 4A and 4B has electrode portions on the left and right sides of one surface of the thin film thermistor 28 having a plate shape. And the tip of the dumet wire 18 is coupled to these electrode portions. The tip of this temperature sensor has a shape that is almost flat to match the shape of the thermistor 28, the outer diameter of the wide portion is 1.3 mm, and the outer diameter of the narrow portion is 1.1 mm. .

  Further, another embodiment shown in FIG. 5 does not integrally form the flange portion, but integrally forms an annular convex portion 26 having a lower height than the required flange portion, and a metal flange on the outside of the annular convex portion 26. The member 27 is press-fitted.

In another embodiment shown in FIG. 6, the protective tube 31 made of ceramic has a base 32 having a constant thickness (T1 = 0.45 mm) and a base 12 that is continuous with the base 12 and a reduced thickness (T2 = 0.15 mm). It consists of a leading end 33 and a flange 34.
The shape of the ceramic protective tube is not limited to the above, and the tip may be thin, for example, 0.3 mm or less. The shape of the tip is not limited to a spherical surface.

In another embodiment shown in FIG. 7, a thin insulating coat 29 is applied to the surface of a thin film thermistor 28 to which a dumet wire 18 is attached instead of the glass ball 22 of the above embodiment. According to this embodiment, the size of the tip portion 14 of the ceramic protective tube can be further reduced to a width of 1.0 mm and a height of 0.8 mm. In the present invention, since the protective tube 31 is made of ceramics such as alumina having excellent insulating properties, the size of the tip portion is made small so as not to cause a short circuit.
An example of the material of the insulating coat 29 is polysilazane. As a method for forming the insulating coat 29, spraying, hand coating, dipping, and the like are conceivable.

  The other embodiment shown in FIG. 8 does not use the glass ball 22 like the embodiment shown in FIG. In this embodiment, dumet wires 18 are connected to the upper and lower surfaces of the chip thermistor 19 and covered with an insulating coat 29 in this state. In the case of this embodiment as well, the dimensions of the tip 14 of the ceramic protective tube can be reduced to a width of 1.0 mm and a height of 0.8 mm.

(A) And (b) is the schematic of the water heater incorporating the temperature sensor which concerns on this invention Sectional drawing which shows the attachment state to piping of the same temperature sensor Enlarged sectional view of the tip of the temperature sensor (A) is an expanded sectional view of the front-end | tip part of the temperature sensor which concerns on another Example, (b) is a B direction arrow directional view of (a). Sectional drawing of the temperature sensor which concerns on another Example Sectional drawing of the temperature sensor which concerns on another Example (A) And (b) is a figure similar to FIG. 4 (a) and (b) which shows another Example. (A) And (b) is a figure similar to FIG. 4 (a) and (b) which shows another Example.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Body cover of water heater, 2 ... Burner, 2a ... Heater, 3 ... Piping, 4 ... Heat transfer fin, 5 ... Temperature sensor, 6 ... Opening, 7 ... Metal block, 8 ... Opening, 9 ... O-ring, DESCRIPTION OF SYMBOLS 10 ... Mounting plate, 11, 31 ... Ceramic protective pipe, 12, 32 ... Base part of ceramic protective pipe, 13 ... Tapered part of ceramic protective pipe, 14, 33 ... Tip part of ceramic protective pipe, 15, 34 DESCRIPTION OF SYMBOLS ... Flange part, 18 ... Dumet wire, 19 ... Chip thermistor, 20 ... Thermocouple, 21 ... Thermocouple strand, 22 ... Glass ball, 23 ... Connector, 24, 25 ... Filler, 26 ... Annular convex part, 27 ... Metal flange member, 28 ... Thin film thermistor, 29 ... Insulation coat.

Claims (5)

In the temperature sensor formed by holding a portion constituting a thermocouple or thermistor in a ceramic protective tube, the tip of the ceramic protective tube is formed thinner than the other parts, A temperature sensor characterized in that a glass ball covering a portion constituting a thermocouple or a thermistor is housed, and the glass ball is held by a resin filler having excellent heat conductivity and flexibility. In the temperature sensor formed by holding a portion constituting a thermocouple or thermistor in a ceramic protective tube, the tip of the ceramic protective tube is formed thinner than the other parts, A portion constituting the thermocouple or thermistor is covered with an insulating coat and stored, and further, the portion constituting the thermocouple or thermistor is held by a resin filler having excellent heat conductivity and flexibility. Temperature sensor. 3. The temperature sensor according to claim 1, wherein the ceramic protective tube is made of alumina, a tip portion has a thickness of 0.3 mm or less, and the resin filler is mainly a silicone resin, an epoxy resin, or a urethane resin. A temperature sensor characterized by the above. 3. The temperature sensor according to claim 1, wherein an annular convex portion that becomes a flange portion at the time of injection molding is formed on an outer periphery of the ceramic protective tube. 3. The temperature sensor according to claim 1, wherein an annular convex portion is formed on the outer periphery of the ceramic protective tube during injection molding, and a metal flange is press-fitted outside the annular convex portion. A characteristic temperature sensor.