JP2011043485A - Temperature sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a temperature sensor capable of further improving thermal response properties as a temperature sensor for measuring temperature of an EGR (Exhaust Gas Recirculation) gas, or the like. <P>SOLUTION: The temperature sensor includes: a closed-end cylindrical metal tube 2; a heat-sensitive element 4 which is installed on an inner surface of the bottom of the metal tube 2 and on which a pair of terminal electrodes is formed; and a pair of lead wires 5 connected to the pair of terminal electrodes. A through hole 2a is formed at the bottom of the metal tube 2 and the heat-sensitive element 4 is installed for blocking the through hole 2a, thus exposing one portion of the heat-sensitive element 4 via the through hole 2a for enabling contact with an atmosphere gas, such as an external exhaust gas, directly, and hence improving thermal response properties. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a temperature sensor suitable for temperature measurement of, for example, EGR (Exhaust Gas Recirculation) gas.

In automobiles equipped with diesel engines, exhaust gas recirculation (EGR) that reduces the emission of nitrogen oxides (NOx) by reducing the combustion temperature by sending exhaust gas with low O ₂ to the combustion process again. ) The system is adopted.
In this EGR system, a temperature sensor for detecting the temperature of EGR gas is attached to an intake port of an EGR valve (exhaust gas recirculation control valve), and optimal oxygen concentration control is performed.

Conventionally, as temperature sensors for temperature detection of ERG gas etc., for example, Patent Documents 1 and 2 propose a thermistor temperature sensor in which a conical glass type thermistor is inserted into a metal tube together with a filler such as cement or silicone oil. Has been.
Patent Document 3 proposes a technique in which a temperature sensitive resistor film is formed on a ceramic lead holding part and the ceramic lead holding part is bonded to the bottom of a metal tube with a solder or the like.

JP 7-43220 A JP 2003-234203 A Japanese Patent Application Laid-Open No. 60-215584

The following problems remain in the conventional technology.
That is, as in the techniques described in the conventional patent documents 1 and 2, when a filler such as cement or silicone oil is inserted in the metal tube, the heat capacity is increased, so that the thermal responsiveness is deteriorated, There is an inconvenience that it is not suitable when high-speed thermal response is required as in the temperature measurement of EGR gas. In addition, as in the technique described in Patent Document 3, when a plate-like element having a temperature-sensitive resistor film formed on the bottom of a metal tube is bonded, the responsiveness is improved, but the further thermal responsiveness is increased. There is a demand for higher speed.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a temperature sensor that can further improve thermal responsiveness for temperature measurement of EGR gas or the like.

  The present invention employs the following configuration in order to solve the above problems. That is, the temperature sensor of the present invention includes a bottomed cylindrical metal tube, a thermal element installed on the inner surface of the bottom of the metal tube, and a pair of terminal electrodes, and a pair of terminal electrodes connected to the pair of terminal electrodes. And a lead wire, wherein a through hole is formed in the bottom of the metal tube, and the thermal element is installed with the through hole closed.

  That is, in this temperature sensor, a through hole is formed at the bottom of the metal tube, and the thermal element is installed on the inner surface of the bottom of the metal tube with the through hole closed, so that a part of the thermal element has the through hole. Thus, the thermal responsiveness can be improved by being in an exposed state and being able to directly contact an ambient gas such as an external exhaust gas.

In the temperature sensor of the present invention, the thermosensitive element is a thin film thermistor element in which a thermistor thin film is formed on the surface of an insulating substrate, and the through hole is closed on the back surface of the insulating substrate. And
That is, in this temperature sensor, since the thermal element is a thin film thermistor element in which a thermistor thin film is formed on the surface of the insulating substrate, the thermal capacity of the thermal element itself is small, and the thermal responsiveness can be further improved. Furthermore, since the through hole is closed on the back surface of the insulating substrate, the ambient gas such as external exhaust gas does not directly touch the thermistor thin film formed on the surface, and the influence of deterioration of the thermistor thin film can be prevented. High reliability can be ensured.

The present invention has the following effects.
That is, according to the temperature sensor of the present invention, the through hole is formed in the bottom of the metal tube, and the thermal element is installed on the inner surface of the bottom of the metal tube with the through hole being closed. The part is exposed through the through hole, and can be directly brought into contact with an ambient gas such as an external exhaust gas, thereby improving the thermal response. Therefore, the temperature sensor of the present invention has high thermal responsiveness and is suitable for detecting the temperature of EGR gas.

It is sectional drawing which shows one Embodiment of the temperature sensor which concerns on this invention. It is sectional drawing to which the principal part was expanded in the temperature sensor of this embodiment. In the temperature sensor of this embodiment, it is a top view which shows a thermal element. In the temperature sensor of this embodiment, it is a figure which shows the state which installed the figure which shows the bottom inner surface of a metal tube, the AA sectional view at the time of forming an adhesive agent, and a thermal element.

  Hereinafter, an embodiment of a temperature sensor according to the present invention will be described with reference to FIGS. In each drawing used for the following description, the scale is appropriately changed in order to make each member recognizable or easily recognizable.

  As shown in FIGS. 1 and 2, the temperature sensor 1 of the present embodiment is a temperature sensor that is attached to an intake port of an EGR valve, for example, for detecting the temperature of EGR gas in a diesel engine. A tube 2, a thermal element 4 provided on the bottom inner surface of the metal tube 2 and having a pair of terminal electrodes 3 formed thereon, a pair of lead wires 5 connected to the pair of terminal electrodes 3, and an open end of the metal tube 2 And a connector 6 attached to the section.

The metal tube 2 is, for example, a bottomed cylindrical SUS (stainless steel) tube.
As shown in FIGS. 3 and 4, a through hole 2 a is formed at the bottom of the metal tube 2, and the thermal element 4 is installed with the through hole 2 a closed. That is, the circular through hole 2 a is formed at the center of the bottom of the metal tube 2. Further, an adhesive 7 such as wax is formed around the through-hole 2a on the inner surface of the bottom portion of the metal tube 2 so as to correspond to the outer shape of the thin plate-like and rectangular heat-sensitive element 4 in plan view. Is adhered to the inner surface of the bottom.

The thermal element 4 is a thin film thermistor element in which a thermistor thin film 9 is formed on an insulating substrate 8 which is a ceramic substrate such as alumina or aluminum nitride.
For example, as the thermal element 4, Mn—Co based composite metal oxide (for example, Mn ₃ O ₄ —Co ₃ O ₄ based composite metal oxide) or Mn—Co based composite metal oxide may be made of Ni, Fe, or Cu. A thermistor thin film 9 of a composite metal oxide film comprising a composite metal oxide containing at least one kind (for example, Mn ₃ O ₄ —Co ₃ O ₄ —Fe ₂ O ₃ composite metal oxide), and the composite metal oxide A thin film thermistor element including a pair of on-film electrodes (not shown) such as comb electrodes formed on the film and the terminal electrode 3 connected to these on-film electrodes is employed. The through-hole 2 a is blocked by the back surface of the insulating substrate 8 and is disposed immediately below the thermistor thin film 9. Further, by forming a protective film such as SiO ₂ , Si ₃ N ₄ , or HfO _{2 so as} to cover the thermistor thin film 9, it becomes possible to prevent the ingress of O ₂ from the outside air, and the electrical characteristics are stabilized.

  The connector 6 includes a screw portion 10 to which an opening end portion of the metal tube 2 is attached, and a main body portion 12 to which an end portion of a wiring 11 connected to a temperature detection circuit or the like is fixed. The lead wire 5 in the metal tube 2 is inserted through the screw portion 10 and connected to the wiring 11 in the main body portion 12. This connector 6 is produced by resin molding, for example.

In order to attach the thermal element 4 to the metal tube 2, first, a through hole 2 a is formed on the inner surface of the bottom of the metal tube 2 as shown in FIG. At this time, the through hole 2a is set to an area smaller than the area of the back surface side of the insulating substrate 8 of the thermal element 4 to be attached. The area of the hole diameter is set to 1/2 or less of the area of the back surface of the element in consideration of the strength of the adhesive surface, and to 1/3 or more of the area of the back surface of the element in consideration of thermal response.
Further, the lead wire 5 and the terminal electrode 3 of the thermal element 4 are bonded in advance. This joining is performed by laser welding or resistance welding.

  Next, as shown in FIG. 4B, an adhesive 7 such as wax is formed around the through hole 2a in accordance with the outer shape of the thermal element 4. Note that an adhesive 7 such as a wax may be formed on the back surface of the thermal element 4 in advance excluding a portion facing the through hole 2a. Further, as shown in FIG. 5 (c), the thermal element 4 is installed on the bottom inner surface of the metal tube 2 so as to block the through hole 2a with the back surface of the insulating substrate 8, and the back surface and bottom inner surface of the insulating substrate 8 are disposed. Are bonded by an adhesive 7. Note that the lead wire 5 and the terminal electrode 3 may be bonded after the thermal element 4 is bonded.

For the adhesive 7, when using a brazing material, an active silver brazing that does not require metallization is used. By applying a paste-like brazing material to the substrate in advance and holding at 780 to 800 ° C. for 5 minutes in an Ar atmosphere, the ceramic substrate and the stainless steel metal can be connected. It is also possible to pre-metallize the ceramic substrate (Mo—Mn, Mo—W, or Ti, Ni, Au plating) and use Ag brazing.
In addition, when a ceramic adhesive is used for an alumina substrate, the thermal expansion coefficient of alumina is 7.9 × 10 ⁻⁶ / K and the thermal expansion coefficient of stainless steel is 16.6 × 10 ⁻⁶ / K. A magnesia-based adhesive (12.6 × 10 ⁻⁶ / K) in which the coefficient of thermal expansion is located is optimal, and after being applied to a ceramic substrate, it is cured at 93 ° C. for 2 hours for adhesion. Alumina-based adhesives can also be used in environments where the temperature difference in the usage environment is relatively small.

  As described above, in the temperature sensor 1 of the present embodiment, the through hole 2a is formed at the bottom of the metal tube 2, and the thermal element 4 is installed on the inner surface of the bottom of the metal tube 2 with the through hole 2a closed. A part of the thermal element 4 is exposed through the through-hole 2a, and can directly contact an ambient gas such as an external exhaust gas, thereby improving the thermal responsiveness.

  Further, since the thermal element 4 is a thin film thermistor element in which the thermistor thin film 9 is formed on the surface of the insulating substrate 5, the thermal capacity of the thermal element 4 itself is small, and the thermal response can be further improved. Furthermore, since the through-hole 2a is closed on the back surface of the insulating substrate 5, the thermistor thin film 9 formed on the front surface is not directly contacted with an ambient gas such as an external exhaust gas, thereby preventing the influence of deterioration of the thermistor thin film 9 or the like. And high reliability can be ensured.

  The technical scope of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

For example, in the above embodiment, as described above, it is preferable to use a thin film thermistor element using a thermistor thin film as the heat sensitive element, but a chip thermistor heat sensitive element using a bulk thermistor element may be adopted.
In the above embodiment, when the thermal element is attached to the metal tube, the through hole is formed in advance on the inner surface of the bottom of the metal tube, but the thermal element is fixed to the inner surface of the bottom of the metal tube with an adhesive such as wax. Later, a through hole may be formed from the outer surface of the bottom of the metal tube.

  DESCRIPTION OF SYMBOLS 1 ... Temperature sensor, 2 ... Metal pipe, 2a ... Through-hole, 3 ... Terminal electrode, 4 ... Thermal element, 5 ... Lead wire, 7 ... Adhesive, 8 ... Insulating substrate, 9 ... Thermistor thin film

Claims (2)

A bottomed cylindrical metal tube,
A thermal element installed on the bottom inner surface of the metal tube and having a pair of terminal electrodes formed thereon;
A pair of lead wires connected to the pair of terminal electrodes,
A temperature sensor, wherein a through hole is formed in a bottom portion of the metal tube, and the thermal element is installed with the through hole closed. The temperature sensor according to claim 1,
The thermosensitive element is a thin film thermistor element in which a thermistor thin film is formed on the surface of an insulating substrate,
A temperature sensor characterized in that the through hole is closed on the back surface of the insulating substrate.

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