JP7044675B2 - Manufacturing method of temperature sensor - Google Patents

Description

The present invention relates to a method for manufacturing a temperature sensor including a thermistor element, a Pt resistor element, a temperature sensitive element such as a thermoelectric pair.

As a temperature sensor that detects the temperature of exhaust gas of an automobile or the like, a thermometer, a Pt resistor, or the like that uses a resistor whose resistance value changes depending on the temperature is known.
As shown in FIG. 5, in such a temperature sensor, for example, the thermistor element 101 and the sheath member 105 are welded together and housed inside the temperature sensitive cover 104, and the gap in the temperature sensitive cover 104 is insulated with alumina or the like. It is configured by filling the member 107 (see Patent Document 1).
By the way, when the paste-like insulating member 107 is injected into the gap in the temperature-sensitive cover 104, if air bubbles are mixed in, holes are generated in the cured insulating member 107, and the thermistor element 101 is placed in the temperature-sensitive cover 104. It cannot be held well.
Therefore, Patent Document 1 describes that a rotational motion is applied to an intermediate forming body including a temperature-sensitive cover 104 in which an insulating member 107 is injected, and defoaming is performed by centrifugal force.

Japanese Unexamined Patent Publication No. 2008-286786

However, when defoaming is performed by centrifugal force, the components of the insulating member 107 are separated according to the specific gravity, and the hardness of the insulating member 107 varies depending on the position of the insulating member 107 in the temperature sensitive cover 104. There is a problem that the insulating member 107 on the tip end side becomes brittle and easily damaged.
In addition, a large amount of water having a light specific gravity increases on the rear end side of the temperature-sensitive cover 104, and this water evaporates during drying, and bubbles are likely to be generated.

Therefore, the present invention provides a method for manufacturing a temperature sensor that reduces the voids of the holding member arranged between the temperature sensitive element and the metal tube and suppresses the variation in the hardness of the holding member depending on the position in the metal tube. With the goal.

In order to solve the above problems, the method for manufacturing a temperature sensor of the present invention comprises a temperature-sensitive portion whose electrical characteristics change depending on the temperature, a temperature-sensitive element having a pair of element electrode wires extending from the temperature-sensitive portion, and the element. A metal having a sheath outer tube containing an electrode wire or a sheath core wire connected to the element electrode wire between insulating materials and a tubular shape having one end closed and extending in the axial direction, and at least accommodating the temperature-sensitive element. A method for manufacturing a temperature sensor including a tube and a holding member arranged in a space between the temperature-sensitive element and the metal tube, which is connected to the element electrode line or the element electrode line in advance. The insertion step of inserting the sheath core wire into the sheath outer tube and the material powder of the holding member are arranged at least between the temperature sensitive element and the sheath outer tube, and are smaller than the internal space of the metal tube. A pressing step of pressing the material powder so as to have external dimensions, a storage step of accommodating the material powder pressed in the pressing step together with the temperature-sensitive element and the sheath outer tube inside the metal tube, and the above-mentioned It is characterized by having a firing step of firing a material powder to form the holding member.

According to the manufacturing method of this temperature sensor, the material powder of the holding member is placed between the temperature sensitive element and the outer tube of the sheath in advance and pressed to reduce the gap of the material powder, and then the whole is inside the metal tube. By accommodating and firing, the voids of the holding member after firing can be reduced. Further, since centrifugation is not required to reduce the voids, it is possible to suppress the variation in the hardness of the holding member depending on the position in the metal tube and suppress the damage of the holding member.

In the method for manufacturing a temperature sensor of the present invention, a slurry or a paste containing the material powder may be previously coated on the inner surface of the metal tube in the accommodating step.
According to this method for manufacturing a temperature sensor, the gap between the material powder and the inner surface of the metal tube can be filled with slurry or paste, and the voids of the holding member after firing can be further reduced.

According to the present invention, it is possible to obtain a temperature sensor that reduces the voids of the holding member arranged between the temperature sensitive element and the metal tube and suppresses the variation in the hardness of the holding member depending on the position in the metal tube.

It is sectional drawing which cut the 1st temperature sensor manufactured by the manufacturing method of the temperature sensor which concerns on embodiment of this invention, along the axial direction. It is a process drawing which shows the manufacturing method of the temperature sensor which concerns on embodiment of this invention. It is a perspective view which shows the press die used in a press process. It is sectional drawing which cut the 1st temperature sensor manufactured by the manufacturing method of the temperature sensor which concerns on embodiment of this invention, along the axial direction. It is a partially enlarged view of the cross section of the conventional temperature sensor.

Hereinafter, embodiments of the present invention will be described.
FIG. 1 shows a cross-sectional structure in which a part of the first temperature sensor 1 manufactured by the method for manufacturing a temperature sensor according to the embodiment of the present invention is broken along the axis O direction. The first temperature sensor 1 is an embodiment in which the sheath member 20 is housed from the rear end side of the metal tube 30.
The temperature sensor 1 is inserted through and attached to an opening (not shown) on the side wall of the exhaust pipe of the internal combustion engine, and detects the temperature of the exhaust gas of the automobile.

The temperature sensor 1 includes a thermistor element (temperature sensitive element) 10, a sheath member 20 connected to the thermistor element 10, and a bottomed tubular metal member containing the thermistor element 10 and the sheath member 20 (in this embodiment, the temperature sensor 1 is a bottomed tubular metal member. (Use SUS310S) 30, a mounting portion 50 fitted to the outer periphery of the metal tube 30, a nut portion 60 loosely fitted to the outer periphery of the mounting portion 50, and a tubular metal mounted on the rear end side of the mounting portion 50. It is provided with an outer cylinder 70 made of heat-resistant rubber and an auxiliary ring 26 made of heat-resistant rubber attached to the rear end of the outer cylinder 70 to pull out the lead wire 24 to the outside.
In the temperature sensor 1 of the present invention, the metal tube 30 extends in the O-axis direction, and the bottom side of the metal tube 30 is referred to as the “tip” and the open end side of the metal tube 30 is referred to as the “rear end”.

The thermistor element (temperature sensitive element) 10 includes a thermistor sintered body (temperature sensitive portion) 11 for measuring temperature and a pair of element electrode wires 12 extending from one end (rear end side) of the thermistor sintered body 11. Have.
As the thermistor sintered body 11, a perovskite-type oxide having a base composition of (Sr, Y) (Al, Mn, Fe) O ₃ can be used, but is not limited thereto.
In the present embodiment, the thermistor sintered body 11 is a hexagonal columnar, and the column axis direction of the hexagonal column is perpendicular to the axis O direction of the temperature sensor 1 (metal tube 30), and six surfaces forming a hexagonal outer edge. Of these, one surface is arranged in the metal tube 30 with the tip facing surface. Since the electric resistance value of the thermistor sintered body 11 changes according to the temperature change, the change can be detected as a voltage change between the pair of element electrode wires 12. In addition to the thermistor described above, a resistor such as Pt can also be used as the temperature sensitive portion.

The sheath member 20 has a sheath core wire 21 connected to a pair of element electrode wires 12 of the thermista element 10 by a welded portion J, and a metal sheath outer tube 22 accommodating the sheath core wire 21. An insulating material made of SiO ₂ is filled between 21 and the inner surface of the sheath outer tube 22.
Since the element electrode wire 12 is usually an expensive Pt-Rh wire or the like, cost reduction is achieved by connecting it to an inexpensive sheath core wire 21 made of SUS or the like.

The mounting portion 50 has a substantially cylindrical shape in which a central hole for inserting the metal tube 30 opens in the axis O direction, and has a diameter smaller than that of the large diameter flange portion 51 and the flange portion 51 from the tip side of the temperature sensor 1. The tubular sheath portion 52, the first step portion 54 constituting the tip side of the sheath portion 52, and the second step portion 55 constituting the rear end side of the sheath portion 52 and having a diameter smaller than that of the first stage portion 54 are the same. It is formed in order. The tip surface of the flange portion 51 has a tapered seat surface 53, and when the nut portion 60 described later is screwed into the exhaust pipe, the seat surface 53 is pressed against a corner portion (not shown) of the side wall of the exhaust pipe. It is designed to be sealed.
The mounting portion 50 is press-fitted to the outer periphery of the rear end portion of the metal tube 30, and the second stage portion 55 and the metal tube 30 are laser-welded all around to fix them.
Further, the outer cylinder 70 is press-fitted to the outer periphery of the first step portion 54, and both are fixed by laser welding all around. The outer cylinder 70 accommodates and holds a connecting portion between the sheath core wire 21 and the lead wire 24 drawn out from the sheath member 20.

The nut portion 60 has a central hole having a diameter slightly larger than the outer circumference of the outer cylinder 70 in the axis O direction, and a screw portion 62 and a hexagon nut portion 61 having a diameter larger than that of the screw portion 62 are formed from the tip side. Then, with the front surface of the screw portion 62 in contact with the rear surface of the flange portion 51 of the mounting portion 50, the nut portion 60 is loosely fitted to the outer periphery of the mounting portion 50 (outer cylinder 70) and rotates in the axis O direction. It is free.
Then, the temperature sensor 1 is attached to the side wall of the exhaust pipe by screwing the screw portion 62 into a predetermined screw hole of the exhaust pipe.

Two sheath core wires 21 are pulled out from the rear end of the sheath outer tube 22 of the sheath member 20, the end of each sheath core wire 21 is connected to the crimping terminal 23, and the crimping terminal 23 is connected to the lead wire 24. There is. The sheath core wire 21 and the crimping terminal 23 are each insulated by an insulating tube 25.
Each lead wire 24 is pulled out to the outside through a lead wire insertion hole of an auxiliary ring 26 fitted inside the rear end of the outer cylinder 70, and is connected to an external circuit via a connector (not shown).
Further, the gap between the inner surface of the metal tube 30 and the thermistor element 10 and the sheath member 20 is filled with cement (holding member) 40 such as alumina and silica to hold the thermistor element 10 and the sheath member 20. The vibration is suppressed. As the cement 40, a material having high thermal conductivity, high heat resistance, and high insulating properties may be used.

Next, a method for manufacturing a temperature sensor according to an embodiment of the present invention will be described with reference to FIGS. 2 and 3. FIG. 2 is a process diagram showing a manufacturing method of a temperature sensor, and FIG. 3 is a perspective view showing press molds 91 and 92 used in the pressing process.
First, the sheath core wire 21 is connected to the element electrode wire 12 of the thermistor element 10 at the welded portion J in advance, and the sheath core wire 21 is inserted into the sheath outer tube 22 (FIG. 2A: insertion step).
Next, the material powder 40x of the holding member is placed between at least the thermistor element 10 and the sheath outer tube 22 in the press molds 91 and 92, and the material powder has an outer dimension smaller than the internal space of the metal tube 30. 40x is pressed (FIGS. 2 (b) and 2 (c): pressing process).

Here, as shown in FIG. 3, the press dies 91 and 92 are an upper die and a lower die, respectively, and the thermistor element 10 and the front end of the sheath outer tube 22 are sandwiched and included in the press dies 91 and 92 from above and below. It has become. Further, an introduction port 90h for charging the material powder 40x is opened on the tip side of the press molds 91 and 92. Then, after charging the material powder 40x from the introduction port 90h, the introduction port 90h is appropriately closed, and the press molds 91 and 92 are pressed from the outside (for example, hydrostatic pressure is applied) to press the material powder 40x.
As the press dies 91 and 92, rubber dies, metal dies and the like can be used.

Then, the material powder 40x pressed in the pressing process is accommodated inside the metal tube 30 together with the thermistor element 10 and the sheath outer tube 22 (FIG. 3 (d): accommodating step).
Here, in the present embodiment, the slurry or paste 40b containing the material powder is previously coated on the inner surface of the metal tube 30. The slurry or paste 40b contains an aggregate made of a constituent material (alumina powder or the like) of a holding member and a binder (water, solvent or the like).
Next, the material powder 40x is fired to form the holding member 40 (FIG. 3 (e): firing step). After that, various members are assembled to complete the temperature sensor 1.

In this way, the material powder 40x of the holding member is previously arranged between the thermistor element 10 and the sheath outer tube 22 and pressed to reduce the gap of the material powder 40x, and then the whole is housed inside the metal tube 30. By firing, the voids in the holding member 40 after firing can be reduced. Further, since centrifugation is not required to reduce the voids, it is possible to suppress the variation in the hardness of the holding member 40 depending on the position in the metal tube 30, and to suppress the damage of the holding member 40 and the like.
Further, in the present embodiment, after the slurry or paste 40b containing the material powder is previously coated on the inner surface of the metal tube 30, the pressed material powder 40x is placed inside the metal tube 30 together with the thermista element 10 and the sheath outer tube 22. Since it is accommodated, the gap between the material powder 40x and the inner surface of the metal tube 30 can be filled with the slurry or the paste 40b, and the voids of the holding member 40 after firing can be further reduced.

Next, with reference to FIG. 4, a second temperature sensor 1B manufactured by the method for manufacturing a temperature sensor according to the embodiment of the present invention will be described. FIG. 4 shows a cross-sectional structure in which the temperature sensor 1B is broken along the axis O direction.
In the temperature sensor 1B, the temperature-sensitive element 10B is a thermocouple, and the pair of thermocouple strands (element electrode wires) 12B from the temperature-sensitive element 10B are directly sheathed without using the sheath core wire 21. Since it is the same as the first temperature sensor 1 except that it is inserted into the inside of 22, the same parts as those of the temperature sensor 1 are designated by the same reference numerals and the description thereof will be omitted.

In the temperature sensor 1B, the temperature sensitive element (thermocouple) 10B includes a temperature measuring contact (temperature sensing unit) 11B for measuring the temperature and a pair of thermocouple strands extending from the temperature measuring contact 11B to the rear end side (the thermocouple). The element electrode wire) 12B and the like.
The thermocouple strands 12B are made of different metals. In this embodiment, one thermocouple wire 12B is made of an alloy containing nickel, chromium and silicon, and the other thermocouple wire 12B is made of an alloy containing nickel and silicon.
Then, the tips of the thermocouple strands 12B are joined to each other by welding or the like to form a temperature measuring contact 11B. Since a thermoelectromotive force is generated according to the temperature difference between the temperature measuring contact 11B and the reference contact, it can be detected as a voltage between the pair of thermocouple strands 12B.

Each thermocouple wire 12B is directly inserted into the sheath outer tube 22 without using the sheath core wire 21. An insulating material made of, for example, SiO ₂ is filled between the sheath outer tube 22 and each thermocouple wire 12B.
Each of the thermocouple strands 12B exposed on the rear end side of the sheath outer tube 22 is connected to the stranded wire 27f from which the tip of the corresponding compensating lead wire 27 is stripped by welding by a welded portion J. Each of the compensating conductors 27 is insulated by an insulating tube 25, and is led out to the outside through an insertion hole of a heat-resistant rubber grommet 26 fitted inside the rear end of the outer cylinder 70.

Also in the manufacture of the temperature sensor 1B, the material powder 40x (see FIG. 2) of the holding member is placed between the thermocouple 10B and the sheath outer tube 22 in advance and pressed, and then the whole is housed inside the metal tube 30. By firing, the voids in the holding member 40 after firing can be reduced. Further, since centrifugation is not required to reduce the voids, it is possible to suppress the variation in the hardness of the holding member 40 depending on the position in the metal tube 30, and to suppress the damage of the holding member 40 and the like.

It goes without saying that the present invention is not limited to the above embodiments and extends to various modifications and equivalents included in the idea and scope of the present invention. for example,
The overall shape of the thermistor sintered body is not particularly limited, and may be, for example, a quadrangular prism.

1,1B Temperature sensor 10,10B Temperature sensitive element 11,11B Temperature sensitive part 12,12B Element electrode wire 21 Sheath core wire 22 Sheath outer tube 30 Metal tube 40 Holding member 40x Holding member material powder 40b Slurry or paste containing material powder O axis

Claims (2)

A temperature-sensitive part whose electrical characteristics change depending on the temperature, and a temperature-sensitive element having a pair of element electrode wires extending from the temperature-sensitive part.
A sheath outer tube containing the element electrode wire or a sheath core wire connected to the element electrode wire between insulating materials, and a sheath outer tube.
A metal tube that has a cylindrical shape with one end closed and extends in the axial direction, and at least accommodates the temperature-sensitive element.
A method for manufacturing a temperature sensor including a holding member arranged in a space between the temperature sensing element and the metal tube.
The insertion step of inserting the element electrode wire or the sheath core wire connected to the element electrode wire into the sheath outer tube in advance.
A pressing step in which the material powder of the holding member is placed at least between the temperature sensing element and the sheath outer tube, and the material powder is pressed so as to have an outer dimension smaller than the internal space of the metal tube.
A storage step of accommodating the material powder pressed in the press step together with the temperature-sensitive element and the sheath outer tube inside the metal tube, and a storage step.
A method for manufacturing a temperature sensor, which comprises a firing step of firing the material powder to form the holding member. The method for manufacturing a temperature sensor according to claim 1, wherein in the accommodating step, a slurry or a paste containing the material powder is previously coated on the inner surface of the metal tube.

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