Airtight temperature probe and processing method thereof

Abstract

The invention belongs to the field of temperature sensor design, and particularly relates to an airtight temperature probe and a processing method thereof. The temperature probe is in urgent need of improving the welding reliability and the overall air tightness of the platinum resistor and the wire, and the reliability and the stability of the product are improved. The device comprises a sintering tube base and a shell which are fixed together through laser welding, the sintering tube base is provided with a first lead and a second lead which penetrate through the sintering tube base and are sintered at high temperature through glass, an insulating bush is arranged in the shell and is of a semi-cylinder structure, and the inner side of the insulating bush is provided with an axial isolation plate and a groove; the first lead and the second lead are separated by the isolation plate, the platinum resistor is placed in the groove, the platinum resistor is welded through precision resistance welding, and high-temperature curing is conducted in the shell through the high-temperature structural adhesive. The completely sealed temperature probe is formed, the platinum resistor is prevented from being damaged by external tension, the influence of moisture absorption of the filler on heat conduction and insulation is avoided, and the sealing performance, the reliability and the stability of the temperature probe are greatly improved.

Description

Technical Field

[0001] The invention belongs to the field of temperature sensor design, and in particular relates to an airtight temperature probe and a processing method thereof. Background Art

[0002] For platinum resistance temperature sensors, the solder joints of traditional temperature probe components are isolated from the outside world only by glues such as resin glue and silicone rubber, which cannot be completely airtight. Because when the glue isolation is subjected to external tension, the solder joints will be directly damaged by the force, causing the isolation glue to break and the thermal conductive glue to absorb moisture and reduce insulation. In particular, one of the bottlenecks in the development of high-temperature platinum resistance temperature sensors above 300°C is that the filler high-temperature thermal conductive glue or magnesium oxide powder cannot be isolated from the outside world for a long time and stably, resulting in moisture absorption of the filler during long-term use and reduced insulation performance.

[0003] The temperature probe urgently needs to make improvements in the reliability and overall air tightness of the welding between the platinum resistor and the wire to enhance the reliability and stability of the product. Summary of the invention

[0004] In order to solve the isolation problem between the inside and the outside of the product without affecting the functional performance of the product, the present invention designs a sintered tube shell to connect the internal and external electrical connections, uses resistance welding instead of soldering, and improves the welding quality of the product; the packaging tube shell is welded to the product shell by laser welding, and laser welding is used to make it airtight, thereby achieving the purpose of improving the sealing, reliability and stability of the product.

[0005] In one aspect, the present invention provides an airtight temperature probe, which comprises a sintered tube base and a shell fixed together by laser welding, wherein the sintered tube base has a first lead and a second lead which penetrate through and are sintered at a high temperature using glass, and an insulating bushing is provided in the shell, wherein the insulating bushing is a semi-cylindrical structure, and an axial isolation plate and a groove are provided on the inner side thereof, the first lead and the second lead are separated by the isolation plate, a platinum resistor is placed in the groove, the platinum resistor is welded to the first lead and the second lead by precision resistance welding, and the sintered tube base, the first lead, the second lead, the insulating bushing and the platinum resistor are cured at a high temperature in the shell by high-temperature structural adhesive.

[0006] Advantageously, lead placement grooves are processed at the bottom of both sides of the isolation plate, which are countersunk holes larger than a semicircle.

[0007] Advantageously, a waist-shaped hole is provided at the bottom of the groove.

[0008] Advantageously, a through hole is provided at the bottom of the insulating bushing.

[0009] Advantageously, before high-temperature curing, the fluidity of the high-temperature structural adhesive is increased at 80° C. and vacuum is applied for 1 hour to remove bubbles in the adhesive.

[0010] Advantageously, the groove is close to the lower end of the insulating bushing.

[0011] Advantageously, the sintered tube seat has an annular protrusion in the middle, and the size of the annular protrusion satisfies the installation relationship with the shell.

[0012] In another aspect, the present invention further provides a method for processing an airtight temperature probe, which is used to process the airtight temperature probe. The method comprises the following steps:

[0013] S1. Weld the platinum resistor to the first lead and the second lead inside the sintered tube holder by using precision resistance welding;

[0014] S2. Place the platinum resistor into the groove of the insulating bushing, and place the first lead and the second lead on both sides of the isolation plate;

[0015] S3, placing the whole into a casing filled with high-temperature structural adhesive, and sending it into a high-temperature oven;

[0016] S4, using 80°C to increase the fluidity of the high temperature structural adhesive and evacuating for 1 hour to remove bubbles in the adhesive, and then raising the temperature to 150°C for high temperature curing for 2 hours;

[0017] S5. Within 1 hour after high-temperature curing is completed, continuous laser welding is used to seal the shell and the sintered base.

[0018] Beneficial effects: Compared with the traditional manual soldering method, the present invention utilizes precision resistance welding to weld the platinum resistor leads, which has high welding efficiency, good solder joint consistency, high yield rate and simple operation; the glass encapsulation leads of the sintered base and continuous laser welding sealing welding are utilized to form a completely sealed temperature probe, thereby avoiding damage to the platinum resistor caused by external tension and avoiding the influence of moisture absorption of the filler on thermal conductivity and insulation, thereby greatly improving the sealing, reliability and stability of the temperature probe.

[0019] The features, functions, and advantages that have been discussed can be achieved independently in various examples or may be combined in yet other examples. Further details of the examples can be seen with reference to the following description and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Examples, as well as preferred modes of use, other objects and description thereof, will be best understood by reference to the following detailed description of examples of the invention when read in conjunction with the accompanying drawings, in which:

[0021] Figure 1 This is an oblique view of the airtight temperature probe;

[0022] Figure 2 It is a schematic diagram of the internal structure of the airtight temperature probe;

[0023] Figure 3 is a schematic diagram of an insulating bushing;

[0024] Figure 4 It is a schematic diagram of the sintered tube socket.

[0025] 1-sintered tube base, 2-housing, 3-first lead, 4-second lead, 5-insulating bushing, 6-platinum resistor, 7-isolation plate, 8-groove DETAILED DESCRIPTION

[0026] The disclosed examples will be more fully described with reference to the accompanying drawings, in which some (but not all) of the disclosed examples are shown. In fact, many different examples may be described and these examples should not be construed as limited to the examples set forth herein. Instead, these examples are described so that this disclosure will be thorough and complete and will fully convey the scope of the disclosure to those skilled in the art.

[0027] The present invention is described in further detail below.

[0028] First, use precision resistance welding to weld the platinum resistor 6 to the first lead 3 and the second lead 4 on the inner side of the sintered tube seat 1 to ensure that the welding point is firm and reliable. Then, assemble the insulating bushing 5 with the above components and put the whole into the shell 2 filled with high-temperature structural glue, and send the whole into a high-temperature oven. Use 80°C temperature to increase the fluidity of the high-temperature structural glue and evacuate for 1 hour to remove bubbles in the glue, then heat it to 150°C for high-temperature curing for 2 hours. Within 1 hour after the high-temperature structural glue curing step is completed, use continuous laser welding to seal the shell 2 and the sintered base 1.

[0029] Since precision resistance welding releases low heat during welding, it can avoid damage to the platinum resistor 6 due to high welding temperature. The filler-free method can achieve molecular connection between the parent materials, and it has high welding efficiency, good solder joint consistency, high yield rate, and simple operation. It replaces the common manual soldering in the industry and avoids the common problems of manual soldering of platinum resistors, such as easy breakage and desoldering of solder joints, and scrapping of platinum resistors due to high welding temperature.

[0030] The sintered tube holder 1 adopts a stainless steel shell made of OCr18Ni9. The first lead 3 and the second lead 4 are made of copper and are made using a glass high-temperature sintering method. The performance meets the requirements of withstanding an air pressure of 2MPa. The resistance between the sintered tube holder 1 and the lead is ≥20MΩ at 400°C. The shell 2 is made of the same material as the shell of the sintered tube holder 1, which is convenient for welding. Other high-temperature resistant, weldable metal materials that can be used with the glass sintering process can also be replaced.

[0031] The insulating bushing 5 is a semi-cylindrical structure with an axial isolation plate 7 and a groove 8 on the inner side. The isolation plate 7 isolates the first lead 3 and the second lead 4 to prevent the leads from moving around and affecting the insulation. In another embodiment, lead placement grooves are also processed at the bottom of both sides of the isolation plate 7, which are countersunk holes larger than a semicircle to reduce the possibility of lead slippage. The platinum resistor 6 is placed in the groove 8 to prevent the platinum resistor 6 from bending due to the resistance of the glue when the whole is placed in the shell 2 that has been filled with high-temperature structural glue. A waist-shaped hole is also opened at the bottom of the groove 8 to ensure that the platinum resistor 6 is in full contact with the high-temperature structural glue as much as possible. The material of the insulating bushing 4 is zirconium oxide, which has the characteristics of high temperature resistance, good insulation performance, fast temperature transfer speed, and no moisture absorption. Due to the small size and complex structure of the insulating bushing, the parts are manufactured by 3D printing technology.

[0032] When pouring high-temperature structural glue 5 into the housing 2, an appropriate amount should be used. If too little is poured, a large number of bubbles will be easily formed in the lower part of the insulating bushing when replenishing the glue, and it cannot be completely discharged. If too much is poured, it will easily cause the glue to be squeezed out of the inner cavity of the housing when the platinum resistor and the insulating bushing are installed, and then contact the welding part. The glue is not easy to clean, which will affect the subsequent welding. After the platinum resistor 1 and the insulating bushing 4 are combined, they should be slowly pushed into the glue in the housing 2 to prevent a large number of bubbles from forming inside the glue.

[0033] Before curing, the high-temperature structural adhesive 5 needs to be placed in an 80°C environment to increase fluidity and be vacuumed for 1 hour to expel internal bubbles to avoid affecting thermal conductivity; after completion, the vacuuming is stopped, the temperature is raised to 150°C, and maintained for 2 hours to complete the curing of the adhesive; the continuous laser welding of the sealing welding must be completed within 1 hour after the curing is completed to prevent the adhesive from absorbing moisture.

[0034] Descriptions of different advantageous arrangements have been presented for purposes of illustration and description, but the description is not intended to be exclusive or limited to examples of the disclosed form. Many modifications and variations will be apparent to those of ordinary skill in the art. Additionally, different advantageous examples may be described as having different advantages over other advantageous examples. The selected example or examples are selected and described in order to best illustrate the principles of the examples, practical applications, and to enable those of ordinary skill in the art to understand the disclosure as having various examples with various modifications suitable for the particular use contemplated.

Claims

1. An airtight temperature probe, characterized in that: The probe comprises a sintered tube seat (1) and a shell (2) fixed together by laser welding. The sintered tube seat (1) has a first lead (3) and a second lead (4) which penetrate through and are sintered at high temperature using glass. An insulating bushing (5) is provided in the shell (2). The insulating bushing (5) is a semi-cylindrical structure with an axial isolation plate (7) and a groove (8) on its inner side. The first lead (3) and the second lead (4) are separated by the isolation plate (7). A platinum resistor (6) is placed in the groove (8). The platinum resistor (6) is welded to the first lead (3) and the second lead (4) by precision resistance welding. The sintered tube seat (1), the first lead (3), the second lead (4), the insulating bushing (5) and the platinum resistor (6) are cured at high temperature in the shell (2) by high-temperature structural adhesive.

2. The airtight temperature probe according to claim 1, characterized in that: Lead placement grooves are also processed on the bottoms of both sides of the isolation plate (7), which are countersunk holes larger than a semicircle.

3. The airtight temperature probe according to claim 1, characterized in that: A waist-shaped hole is provided at the bottom of the groove (8).

4. The airtight temperature probe according to claim 3, characterized in that: A through hole is provided at the bottom of the insulating bushing (5).

5. The airtight temperature probe according to claim 1, characterized in that: Before high-temperature curing, the fluidity of the high-temperature structural adhesive needs to be increased at 80°C and vacuumed for 1 hour to remove bubbles in the adhesive.

6. The airtight temperature probe according to claim 1, characterized in that: The groove (8) is close to the lower end of the insulating bushing (5).

7. The airtight temperature probe according to claim 1, characterized in that: The sintered tube seat (1) has an annular protrusion in the middle, and the size of the annular protrusion satisfies the installation relationship with the outer shell (2).

8. A method for processing an airtight temperature probe, used for processing the airtight temperature probe as claimed in any one of claims 1 to 7, characterized in that: The method comprises the following steps: S1. Using precision resistance welding, weld the platinum resistor (6) to the first lead wire (3) and the second lead wire (4) inside the sintered tube holder (1); S2, placing the platinum resistor (6) into the groove of the insulating bushing (5), and placing the first lead wire (3) and the second lead wire (4) on both sides of the isolation plate (7); S3, placing the whole into the housing (2) filled with high-temperature structural adhesive, and sending it into a high-temperature oven; S4, using 80°C to increase the fluidity of the high temperature structural adhesive and evacuating for 1 hour to remove bubbles in the adhesive, and then raising the temperature to 150°C for high temperature curing for 2 hours; S5. Within 1 hour after the high-temperature curing is completed, the housing (2) and the sintered base (1) are sealed and welded using continuous laser welding.

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