JP2010008314A - Temperature sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high-precision temperature sensor capable of measuring a temperature in a corrosive fluid or corrosive atmosphere without being affected by the variation of ambient electric field. <P>SOLUTION: The high-precision temperature sensor includes a temperature measurement element 100, a protective tube 12 made of metal protecting the temperature measurement element 100, a signal line 13 having one end connected to the temperature measurement element 100, a shield line 14 shielding the periphery of the signal line, and an exterior member 15 consisting of an insulating protective member covering the protective tube 12. The temperature sensor measures the temperature in the corrosive fluid or corrosive atmosphere without being affected by the variation of ambient electric field by means of the continuity between the shield line 14 and the protective tube 12. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a temperature sensor that is excellent in measuring minute temperature changes and can be suitably used for temperature control of processes such as chemicals, foods, plating, and semiconductor devices.

  Conventionally, temperature sensors using platinum (Pt) resistance temperature detectors have been widely used in various processes that require delicate temperature control (see, for example, Patent Document 1). The temperature sensor described in Patent Document 1 includes a ceramic substrate such as alumina and a metal foil resistor such as platinum (Pt) formed on the surface of the ceramic substrate, and the temperature measuring element is a flexible printed wiring. The plate and hermetic parts are connected, and these are hermetically accommodated in a protective tube.

  The protective tube is made of, for example, stainless steel, which is a corrosion-resistant metal such as SUS304 or SUS316, and has a long and narrow small diameter pipe whose base end is open and whose front end is closed, and a large joint joined to the base end of the small diameter pipe It consists of a diameter pipe. The temperature measuring element is hermetically housed in a metal small-diameter pipe on the tip side.

  Since the temperature measuring element is formed by patterning a platinum foil having a line width of about 10 μm on the ceramic substrate, its resistance value is 1000Ω, which is considerably larger than the conventional temperature measuring element described above. By using this new temperature measuring element, the current flowing through the metal foil resistor can be about 0.1 mA. Therefore, the power W2 of the temperature measuring element = 1000 (Ω) × 0.0001 (A) × 0.0001 (A) = 0.00001 (W) = 0.01 (mW), which is 1/10 of the self-heating of the conventional temperature measuring element. Therefore, in a process that requires delicate temperature control, for example, when strict temperature measurement is required with an accuracy of about 0.001 ° C., the influence of self-heating of the temperature measuring element can be minimized, This new temperature sensor can be suitably used in such a technical field.

  FIG. 4 is a cross-sectional view taken along the central axis of the temperature sensor in the longitudinal direction, showing the temperature sensor 5 attached to a metal side wall 81 that is an attachment target. As apparent from FIG. 4, the temperature measuring element 51 schematically shown in FIG. 4 is housed inside a metal protective tube 52 via a potting material 55. Further, one end portion of the signal line 53 is connected to the temperature measuring element 51, and a portion of the signal line 53 led out from the protective tube 52 is covered with a shield wire 54. The signal line 53 is actually composed of 2 to 4 signal lines. A male screw 52a is formed on the outer peripheral portion of the base end side of the metal protective tube 52, and the protective tube 52 is screwed into the female screw 81a of the mounting hole of the metal side wall 81 via the male screw 52a. As a result, the front end side of the protective tube 52 protrudes from the side wall 81 to the left side in the drawing, that is, the side where the medium whose temperature is to be measured exists.

  On the other hand, a step portion 52 c is formed around the proximal end side opening 52 b of the protective tube 52, and the step portion 52 c is in contact with one wall surface of the side wall 81 with the O-ring 61 interposed therebetween. When the male screw 52a is a taper screw, it is not necessary to provide the O-ring 61, and the stepped portion 52c does not contact the side wall 81. Further, a housing 82 of the temperature sensor 5 is coupled to the proximal end side of the protective tube 52. The metal protective tube 52 is conductively connected to the metal side wall 81, and the side wall 81 is grounded, and the shield wire 54 covering the periphery of the signal line 53 led out from the protective tube 52 is grounded. As a result, in the signal line 53 of the temperature measuring element 51, noise generated by a change in the electric field around the temperature sensor is not superimposed on the output signal.

Normally, the side wall 81 and the shield wire 54 are not connected because their ground potentials are different. This is because a large current flows through the shield line 54 when the ground potentials are different from each other, which causes noise in the signal line 53 and causes a measurement error.
JP 2002-286555 A

  In recent years, high-accuracy temperature sensors as described above have been installed in production lines for chemicals, foods, plating, semiconductor devices, and the like. However, in such a manufacturing process, the corrosion resistance of the temperature sensor is required, and therefore the type of temperature sensor covered with the above-described conventional metal tube may not be used.

  Therefore, a temperature sensor is used in which the periphery of the metal protective tube is covered with an exterior material made of Teflon (registered trademark) having excellent corrosion resistance. Since such a temperature sensor detects the temperature of the measurement object outside the temperature sensor through an exterior material made of an insulating material such as Teflon (registered trademark) and a metal case, the detection response is slightly inferior, However, since a highly accurate temperature measuring element is used, sufficiently accurate temperature measurement can be performed.

  However, since the exterior material made of an insulating member is interposed between the grounded side wall that is the object to be attached to the temperature sensor and the metal protective tube, the internal metal protective tube is grounded to the side wall. For example, a change in the electric field around the temperature sensor due to a conductive wire near the temperature sensor or a radio wave is transmitted to the metal protective tube equivalently, for example, to a temperature measuring element or this signal line that is less than 1 mm away from the inner periphery of the metal protective tube. Influences the change of electric field. As a result, noise may be superimposed on the output signal of the temperature sensor, and it may be difficult to measure the temperature with high accuracy.

  An object of the present invention is to provide a highly accurate temperature sensor that can measure the temperature in a corrosive fluid or a corrosive atmosphere without being affected by changes in the surrounding electric field.

In order to solve the above-described problem, a temperature sensor according to claim 1 of the present invention provides:
A temperature sensor,
A metal protective tube for protecting the temperature measuring element;
A signal line having one end connected to the temperature measuring element;
A shield wire for shielding the periphery of the signal line;
An exterior member made of an insulating protective material covering the metal protective tube,
The shield wire and the protective tube are electrically connected.

  Since the temperature sensor according to the present invention has such a configuration, it is possible to prevent the noise accompanying the change in the electric field around the temperature sensor from being superimposed on the output signal of the temperature measuring element. As a result, the temperature in the corrosive fluid or corrosive atmosphere can always be accurately measured.

Moreover, the temperature sensor which concerns on Claim 2 of this invention is the temperature sensor of Claim 1,
The temperature measuring element includes a printed wiring board and a substrate that is bonded to the printed wiring board and on which at least one surface is formed a metal film for temperature measurement that is electrically connected to a wiring pattern of the printed wiring board. It is said.

  The temperature measuring element has a structure comprising a printed wiring board and a substrate on which a metal film for temperature measurement, which is bonded to the printed wiring board and is electrically connected to the wiring pattern of the printed wiring board, is formed on at least one surface. If this is the case, the temperature detection accuracy will be high, and noise will be easily superimposed on the output signal due to the influence of the change in the electric field around the temperature sensor. However, as in the present invention, the protective tube is grounded via the protective tube and the shield wire Therefore, the superposition of such noise can be reduced, and the temperature in the corrosive fluid or the corrosive atmosphere can always be detected accurately.

A temperature sensor according to claim 3 of the present invention is the temperature sensor according to claim 1 or 2,
The shield wire is connected to the protective tube with a metal tape.

  The shield wire is usually made of knitted wire. The method of ensuring the conduction by spreading the knitted wire and covering the protective tube and winding the adhesive portion with a conductive metal foil tape is simple and has good workability.

  According to the present invention, it is possible to provide a highly accurate temperature sensor that can measure the temperature in a corrosive fluid or a corrosive atmosphere without being affected by changes in the surrounding electric field.

  Hereinafter, a temperature sensor according to an embodiment of the present invention will be described with reference to the drawings. As shown in FIG. 1, the temperature sensor 1 according to an embodiment of the present invention includes a temperature measuring element 100 schematically shown, a metal protective tube 12 that protects the temperature measuring element 100, and the temperature measuring element 100. The signal line 13 to which one end is connected, the shield line 14 that shields the periphery of the signal line 13, and the exterior member 15 made of an insulating protective material that covers the protective tube 12, and protects the shield line 14 The tube 12 is electrically connected to the tube 12 through the conductive wire 16. Hereinafter, each of these components will be described in detail.

  In the following description, the side where the temperature measuring element 100 is accommodated in the longitudinal direction of the temperature sensor 1 is the front end side, the signal line 13 led out from the temperature measuring element 100 and the shield wire 14 covering the signal line 13. The side on which is extended is the base end side.

  A temperature measuring element 100 schematically shown in FIG. 1 includes an elongated ceramic substrate 110 having a resistor 101 made of platinum (Pt) foil on the upper surface as shown in FIG. A printed wiring board 120 having a length longer than that of the temperature measuring element 100 is bonded to the lower surface of the ceramic substrate 110 via an adhesive. The resistance element of the temperature measuring element 100 is formed by patterning a line width of about 10 μm with a platinum foil having a thickness of about 3 μm, for example, and its resistance value is 1000Ω. And the temperature measuring element which concerns on this embodiment is a highly accurate temperature sensor which measures 0.001 degreeC-0.01 degreeC.

  By using this new temperature measuring element, the current flowing through the metal foil resistor can be about 0.1 mA. Therefore, the power W2 of the temperature measuring element = 1000 (Ω) × 0.0001 (A) × 0.0001 (A) = 0.00001 (W) = 0.01 (mW), which is 1/10 of the self-heating of the 100Ω temperature measuring element defined by the conventional JIS. Therefore, in a process that requires delicate temperature control, for example, when strict temperature measurement is required with an accuracy of about 0.001 ° C., the influence of self-heating of the temperature measuring element can be minimized. It has become.

  In the case of the present embodiment, the printed wiring board 120 is a flexible printed wiring board that is extremely thin with a thickness of 0.2 mm or less and has sufficient flexibility. Although not shown in detail here, the two conductor portions extending to the lower layer of the printed wiring board are electrically connected to the upper-layer detection element tip-side connection electrodes through the through holes at the tips, respectively. . The conductor portion forms a cable connection side electrode in a state in which the lower layer and the upper layer are connected via a through hole while being separated by a predetermined interval on the proximal end side in the longitudinal direction.

  In addition, a detection element base end side connection electrode and a detection element base end side connection electrode that are spaced apart from each other in accordance with the length of the temperature measuring element are formed on the upper layer of the printed wiring board 120. The conductor portion extends almost in parallel toward the base end side end portion of the printed wiring board 120, and the lower layer and the upper layer are connected to each other at a base end side end portion of the printed wiring board through a through hole while being spaced apart from each other. The cable connection side electrode is formed in the state. These configurations are described in detail in, for example, Japanese Patent Application Laid-Open No. 2007-93379.

  The temperature measuring element 100 is a ceramic made of elongated alumina having a width of 0.8 mm, a length of 8 mm, and a thickness of about 0.25 mm, for example, having a resistor made of platinum (Pt) foil on the upper surface as described above. The manufacturing process is as follows.

  First, a platinum foil is bonded to a ceramic substrate, the foil is subjected to surface treatment, a resist for resist is applied, a resist resist pattern is created, a resist pattern is created (etched), and the resist resist is peeled off. Then, an electrode resist is applied, an electrode resist pattern is created, electrode (gold) plating is performed, and the electrode resist is peeled off. Then, a resist for pattern protection is applied, and resist etching for pattern protection is performed to expose only the electrode portion.

  The protective tube 12 made of metal is made of a metal having excellent corrosion resistance such as SUS304 or SUS316, has a cylindrical shape, and has a shape in which a distal end portion is closed and a proximal end portion is opened. The distance between the metal protective tube 12 and the temperature measuring element is 1 mm or less.

  One end of the signal line 13 is connected to the cable connection side end of the printed wiring board 120 that forms part of the temperature measuring element 100, and the signal line 13 extends from the opening at the base end side end of the protective tube 12. Derived.

  One end side of the temperature measuring element 100 in the protective tube and the signal line 13 connected to the temperature measuring device 100 is surrounded by the potting material 19 by filling the protective tube with a potting material 19 made of resin, and is protected from the surrounding environment. .

  The shield line 14 covers the periphery of the signal line 13 and the proximal end of the shield line 14 is grounded so that noise is not superimposed on the signal line 13 due to the influence of the electric field change outside the temperature sensor.

  More specifically, the signal line 13 is composed of a plurality of signal lines as shown in FIG. 3, the shield line 14 covers the periphery, and the outer surface of the shield line 14 is covered with the insulator covering portion 21.

  One end of the conducting wire 16 is connected to a part of the proximal end side of the protective tube 12, and the other end of the conducting wire 16 is connected to the vicinity of the distal end side of the shield wire 14 to electrically connect the protective tube 12 and the shield wire 14. Conducted. One end of the conducting wire 16 is firmly attached to the protective tube 12 by a copper foil tape 17 wound around the protective tube 12. Here, as the copper foil tape 17, it is more preferable to use a conductive tape containing a metal filler in its adhesive layer. The conductive wire 16 may be fixed to the protective tube 12 by soldering or the like with a solder or the like, or a conductive adhesive.

  The exterior member 15 is made of an insulating material excellent in corrosion resistance such as Teflon (registered trademark), has a sufficient inner diameter to cover the periphery of the protective tube 12, has a closed end, and an open base end. have. A temperature sensor mounting step 15b is formed around the base end side opening, and a temperature sensor mounting male screw portion 15a is formed adjacent to the temperature sensor mounting step 15b. And the base end side of the exterior member 15 is couple | bonded with the front end side of the housing 92 of the temperature sensor 1 shown with the dashed-two dotted line in FIG.

  In the case of the present embodiment, the exterior member 15 has the male screw portion 15a screwed into the female screw portion 91a formed on the side wall 91 that constitutes the attachment target, and the temperature sensor mounting step portion 15b is connected to the side wall 91. An O-ring 71 is sandwiched between the two to seal them. That is, here, the front end side of the exterior member 15 is projected to the inner side of the side wall 91 (left side in FIG. 1) in a state of being sealed by the O-ring 71. Thus, the temperature of the corrosive fluid accumulated inside the side wall and the temperature of the corrosive gas filled in the side wall 91 can be accurately measured. Note that a potting material 18 is filled between the exterior member 15 and the metal protective tube 12 until the lead wire 16 is completely buried on the base end side.

  Since the temperature sensor 1 according to the present embodiment has such a configuration, it is possible to prevent noise accompanying the change in the electric field around the temperature sensor from being superimposed on the output signal of the temperature measuring element 100. As a result, the temperature sensor 1 can always detect an accurate temperature.

  Specifically, if the protective tube 12 and the shield wire 14 are not electrically connected by a conductive wire, the protective tube 12 is electrically separated in the temperature sensor. This change is transmitted to the protective tube 12 unambiguously, and noise is superimposed on the output signals of the temperature measuring element 100 and the signal line 13 in the protective tube portion that is only 1 mm or less away from the inner peripheral surface of the protective tube 12.

  However, in the case of the temperature sensor 1 according to this embodiment, since the protective tube 12 and the shield wire 14 are electrically connected via the lead wire 16, it is possible to prevent such a problem from occurring. .

  In particular, in the case of this embodiment, the temperature measuring element is bonded to the printed wiring board 120 and the printed wiring board 120 as shown in FIG. 2, and the temperature measurement is conducted to the wiring pattern of the printed wiring board 120 on at least one surface. And a ceramic substrate 110 on which a resistor 101 made of a platinum metal film is formed.

  Since the temperature measuring element 100 of the temperature sensor 1 has such a structure, it is a highly accurate temperature sensor that measures 0.001 ° C. to 0.01 ° C. When the measurement temperature changes by 1 ° C., the resistance value changes by 4Ω. That is, it changes by 0.004Ω with respect to a temperature change of 0.001 ° C.

  Further, since the current value is 0.1 mA, the signal output value changes only by 0.4 μV with respect to a temperature change of 0.001 ° C. For this reason, noise due to changes in the surrounding electric field as described above can be easily superimposed on the output signal at a relatively large rate. However, according to the present invention, such noise can be effectively prevented from being superimposed.

  That is, since the element is formed of a thin film, it is possible to reduce the size and to be hardly affected by noise such as an electric field, and in the central portion of the protective tube 12 by the printed wiring board as compared with the case where only the lead wire is arranged. It can be arranged without moving away. More preferably, in the present invention, instead of connecting the shield wire 14 and the protective tube 12 via the conducting wire 16 shown in FIG. It is good to cover the opening. As a result, the entire opening of the protective tube 12 can be shielded, and is resistant to noise, and the influence of noise can be reduced.

  In this case, as shown in FIG. 2, it is preferable that the portion of the shield wire 14 covering the opening of the protective tube 12 is firmly attached to the protective tube 12 by the copper foil tape 17. Here, as the copper foil tape 17, it is more preferable to use a conductive tape containing a metal filler in its adhesive layer. The shield wire 14 may be fixed with an insulating tape so as to be in close contact with the protective tube 12. Further, the shield wire 14 may be fixed by brazing with a solder or the like, or a conductive adhesive.

  In addition, although the ceramic substrate was used in this embodiment and its modification as the board | substrate which comprises a temperature measuring element, the ceramic board | substrate in this case may be made from any materials, such as an alumina and a zirconia. Further, instead of a ceramic substrate, a substrate made of an inorganic material such as an insulating glass substrate may be used.

  In addition, although the platinum (Pt) foil is patterned on the upper surface of the ceramic substrate in the temperature sensor of the temperature sensor according to the above-described embodiment and its modification, the platinum thin film is not necessarily limited to this, and a platinum thin film is measured by a known etching technique. Patterning may be performed on the upper surface of the temperature element. Also, nickel (Ni) foil or thin film may be patterned on the upper surface of the ceramic substrate instead of platinum.

  In addition, the exterior member made of an insulating protective material covering the metal protective tube is made of Teflon (registered trademark) in the above-described embodiment, but is not necessarily limited to such a material, and is resistant to corrosion. It goes without saying that any material can be used as long as it is an excellent insulating material.

  The material of the internal metal protective tube is not limited to stainless steel, and may be a metal such as copper, brass, or aluminum.

It is side sectional drawing cut | disconnected along the longitudinal direction center axis line in the state which attached the temperature sensor which concerns on one Embodiment of this invention to the side wall which is a to-be-attached object. It is explanatory drawing which shows the structure of the temperature measuring element of the temperature sensor which concerns on one Embodiment of this invention, and a printed wiring board. It is a perspective view which shows the insulation coating part which covers a signal wire | line, a shield wire, and a shield wire. It is the sectional side view cut | disconnected along the longitudinal direction center axis line in the state which attached the conventional temperature sensor to the side wall which is a to-be-attached object.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,5 Temperature sensor 12 Protective tube 13 Signal line 14 Shield wire 15 Exterior member 15a Male screw part 15a for temperature sensor attachment 15b Step part for temperature sensor attachment 16 Conductor 17 Tape 18 Potting material 19 Potting material 21 Insulator covering part 51 Temperature measurement Element 52 Protective tube 52a Male screw 52b Base end side opening 52c Stepped portion 53 Signal line 54 Shield wire 55 Potting material 61, 71 O-ring 81 Side wall 81a Female screw 82 Housing 91 Side wall
91a Female thread portion 92 Housing 100 Temperature measuring element 101 Resistor 110 Ceramic substrate 120 Printed wiring board

Claims (3)

A temperature sensor,
A metal protective tube for protecting the temperature measuring element;
A signal line having one end connected to the temperature measuring element;
A shield wire for shielding the periphery of the signal line;
An exterior member made of an insulating protective material covering the protective tube,
The temperature sensor, wherein the shield wire and the protective tube are electrically connected.   The temperature measuring element includes a printed wiring board and a substrate that is bonded to the printed wiring board and on which at least one surface is formed a metal film for temperature measurement that is electrically connected to a wiring pattern of the printed wiring board. The temperature sensor according to claim 1. The temperature sensor according to claim 1, wherein the shield wire is connected to the protective tube with a metal tape.

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