DE102024108915A1 - Method for producing a temperature sensor and temperature sensor - Google Patents

Abstract

A method is provided for producing a temperature sensor (100) with a measuring point (14, 24, 124) arranged in the interior of a tubular metal casing (10, 20, 121) and embedded in electrically insulating material (11, 21, 122), in which the tubular metal casing (10, 20, 121) with the electrically insulating material (11, 21, 122) arranged therein is compacted before the measuring point (14, 24, 124) is introduced into the interior of the tubular metal casing (10, 20, 121), that a receptacle (13, 23, 123) for the measuring point (14, 24, 124) is subsequently incorporated into the compacted electrically insulating material (11, 21, 122), and that the measuring point (14, 24, 124) is introduced into this receptacle (13, 23, 123). and is preferably fixed, and a temperature sensor (100) with a measuring point (14, 24, 124) which is arranged in a receptacle (13, 23, 123) which is introduced into compressed electrically insulating material (11, 21, 122) which is arranged in the interior of a metal casing (10, 20, 121).

Description

The invention relates to a method for producing a temperature sensor and a temperature sensor.

When using temperature sensors to measure the temperature at a defined position of a heated component and especially when used as an immersion temperature sensor, as described in CH 689 875 A5 , the DE 20 2011 004 481 U1 or the DE 10 2013 100 892 A1 As is known, critical factors for reproducible and reliable measurements are, on the one hand, the best possible thermal contact between the measuring point of the temperature sensor, which can be formed, for example, by a contact area between the thermocouple legs, but in principle also by an NTC or PT100 sensor element and its leads, and the component, and, on the other hand, a high level of positioning accuracy, so that it is ensured that the measuring point is arranged in the same way relative to the position at which the measurement is to be taken. In this context, it should also be explicitly pointed out that in this disclosure, the term “thermocouple” includes not only the measuring point itself, but also the leads to the measuring point, and that a temperature sensor is used for an arrangement that typically has other components in addition to the measuring point and its leads.

Since the measuring point must be protected from direct environmental influences in many applications, they are usually enclosed in a metal sheath, as is the case with sheathed thermocouples, for example. The space between the metal sheath and the measuring point is then usually filled with an electrically insulating but highly thermally conductive material, such as magnesium oxide, so that the measuring point is embedded in this material. Materials with a thermal conductivity of at least 1.5 W/m*K are considered to be highly thermally conductive within the meaning of this disclosure; materials with a thermal conductivity of 4 W/m*K or better are particularly preferred.

To ensure good thermal contact with the component at the location of the heated component, close surface contact between the contact surface of the metal jacket and the component must be ensured. This means, in particular, that the shape of the contact surface must be precisely adapted to the component. At the same time, the heat transfer between the metal jacket and the measuring point should be as good as possible to enable the most precise and rapid temperature measurement possible.

Of the temperature sensors known from the prior art already mentioned above, it is already known in particular that the heat transfer between the metal sheath and the measuring point can be optimized by compressing the metal sheath with the measuring point arranged therein, embedded in electrically insulating but highly thermally conductive material.

However, the production of these temperature sensors using this approach involves considerable effort and is not easy to automate.

It also shows that the pressures required for optimal compaction are so high that the metal shell deforms, which on the one hand means that the contact surface for the component is deformed after compaction and on the other hand can lead to a change in the position of the measuring point in the metal shell.

The object of the invention is therefore to provide an improved method for producing a temperature sensor and a temperature sensor which is simpler and more cost-effective to implement and in which, preferably, good heat conduction between the metal sheath and the measuring point is achieved without significant subsequent deformation of the metal sheath.

This object is achieved by a method having the features of patent claim 1 and by a temperature sensor having the features of patent claim 9. Advantageous developments of the invention are the subject of the dependent claims.

The inventive method for producing a temperature sensor with a measuring point arranged in the interior of a tubular metal casing and embedded in electrically insulating material is characterized in that the tubular metal casing is compacted with the electrically insulating material before the measuring point is introduced into the interior of the tubular metal casing. Only then is a receptacle for the measuring point machined into the compacted electrically insulating material, the measuring point is inserted into this receptacle, and preferably fixed.

Unlike previously, the measuring point is placed in already compacted electrically insulating material and is no longer embedded in the electrically insulating material and compacted together with it. This means that even if the decision is made to fix it by pressing, the measuring point no longer needs to be subjected to the high pressures required to compact the electrically insulating material. material to ensure good heat conduction through this material.

Preferably, after compacting the tubular metal casing with the electrically insulating material, post-processing is carried out, which at least consists in separating at least one section of the tubular metal casing, including the compacted electrically insulating material contained therein. In this way, inhomogeneities that arise in the end sections of the tubular metal casing can be removed.

Optionally, if the tubular metal shell also has a base, this can be reworked from the outside to restore a defined outer contour.

However, such an effort can also be avoided in a simple manner if the tubular metal casing with the compacted electrically insulating material arranged therein is obtained by cutting off sections from a rod material which is produced by compacting a long tube filled with electrically insulating material, because this cutting off easily leads to flat end surfaces.

Preferably, the receptacle is created by drilling or machining into the compacted, electrically insulating material. In addition to the traditional use of mechanical drilling or machining tools, ultrasonic-based techniques such as ultrasonic drilling or ultrasonic milling can also be used.

The electrically insulating material is preferably introduced into the metal casing before compaction as a powder, granulate, crushable tube, or molded part. Magnesium oxide is particularly preferred, especially impregnated magnesium oxide. However, other materials, especially ceramic materials, can also be used.

In this process, a receptacle is preferably formed into the compacted electrically insulating material, which also accommodates sections of thermocouples or supply lines to the measuring point of the temperature sensor, which are surrounded by an insulating sheath. This allows for optimal strain relief.

Preferably, the sections of the temperature sensor housed in the receptacle are secured by compression. Lower pressures than those required for compression can be used for this purpose.

Preferably, pressing takes place after the metal jacket has been inserted into the interior of another metal jacket and preferably brought into contact with a base of the other metal jacket. This creates intimate thermal contact between the outer surface of the metal jacket and the inner surface of the other metal jacket.

Preferably, the temperature sensor is designed as an immersion temperature sensor in that sections of thermocouples or supply lines to the measuring point of the temperature sensor are pushed through a channel arranged in a contact plate and preferably the further metal sheath is connected to a contact surface of the contact plate so that it extends perpendicularly therefrom.

The temperature sensor according to the invention is characterized by a measuring point arranged in a receptacle embedded in a compacted electrically insulating material arranged inside a metal casing. It is particularly preferred if the electrically insulating material is impregnated magnesium oxide.

Preferably, sections of thermocouples or supply lines to the measuring point of the temperature sensor, which are surrounded by an insulating sheath, are also accommodated in the receptacle, whereby strain relief can be achieved.

It is particularly preferred if the metal jacket is arranged inside a further metal jacket in such a way that its outer walls are in direct contact with the inner walls of the further metal jacket and preferably additionally there is at least partial direct contact with a bottom of the further metal jacket.

Particularly preferably, the temperature sensor is an immersion temperature sensor having a contact plate and in which sections of thermocouple legs or supply lines to the measuring point of the temperature sensor run through a channel arranged in the contact plate. Preferably, the additional metal casing is connected to the contact plate, extending substantially perpendicular to the contact surface of the contact plate.

It is also advantageous if the contact plate has a tubular extension and if an anti-kink spring is pushed onto the outside of the tubular extension in the transition area between the tubular extension and a freely running section of the thermocouple.

• 1a: Ein erstes Zwischenstadium eines ersten Verfahrens zur Herstellung eines Temperatursensors,
• 1b: ein zweites Zwischenstadium des ersten Verfahrens zur Herstellung eines Temperatursensors,
• 1c: ein drittes Zwischenstadium des ersten Verfahrens zur Herstellung eines Temperatursensors,
• 1d: ein viertes Zwischenstadium des ersten Verfahrens zur Herstellung eines Temperatursensors,
• 1e: einen optionalen weiteren Schritt des ersten Verfahrens zur Herstellung eines Temperatursensors,
• 2a: ein erstes Zwischenstadium eines zweiten Verfahrens zur Herstellung eines Temperatursensors,
• 2b: ein zweites Zwischenstadium des zweiten Verfahrens zur Herstellung eines Temperatursensors,
• 2c: ein drittes Zwischenstadium des zweiten Verfahrens zur Herstellung eines Temperatursensors,
• 2d: ein viertes Zwischenstadium des zweiten Verfahrens zur Herstellung eines Temperatursensors,
• 2e: einen optionalen weiteren Schritt des zweiten Verfahrens zur Herstellung eines Temperatursensors,
• 3a: einen als Eintauch-Temperatursensor konfigurierten Temperatursensor, und
• 3b: einen Querschnitt durch den Eintauch-Temperatursensor aus 3a.

The invention is explained in more detail below with reference to figures showing exemplary embodiments of the invention. It shows:

• 1a : A first intermediate stage of a first method for producing a temperature sensor,
• 1b : a second intermediate stage of the first method for producing a temperature sensor,
• 1c : a third intermediate stage of the first method for producing a temperature sensor,
• 1d : a fourth intermediate stage of the first method for producing a temperature sensor,
• 1e : an optional further step of the first method for producing a temperature sensor,
• 2a : a first intermediate stage of a second method for producing a temperature sensor,
• 2b : a second intermediate stage of the second method for producing a temperature sensor,
• 2c : a third intermediate stage of the second method for producing a temperature sensor,
• 2d : a fourth intermediate stage of the second method for producing a temperature sensor,
• 2e : an optional further step of the second method for producing a temperature sensor,
• 3a : a temperature sensor configured as an immersion temperature sensor, and
• 3b : a cross-section through the immersion temperature sensor 3a .

The 1a The intermediate stage of a first manufacturing process for a temperature sensor shown shows a metal casing 10, which here is cup-shaped with a hemispherical base. The interior of the metal casing 10 is filled with an electrically insulating, highly thermally conductive material 11, which can be introduced into the interior, for example, as a powder or granulate, a ceramic breakable tube, or as a molded body. A particularly preferred material is magnesium oxide, preferably impregnated magnesium oxide. The open end of the metal casing 10, which is cup-shaped with a hemispherical base, is optionally closed with a plug 12.

The 1a The intermediate stage shown is then subjected to a diameter reduction for compaction, which can be done, for example, by hammering or rolling, which leads to the 1b shown intermediate stage with metal jacket 10, electrically insulating, heat-conducting material 11 and plug 12. As can be seen from the comparison of the 1a and 1b immediately recognizes, the compaction has led to a change in the length of the metal shell 10. Because deviations from the desired shape of a possibly provided frontal contact surface in the intermediate stage according to 1b can be easily reworked if necessary (which would be considerably more complex if the measuring point were already arranged in the metal sheath 10 at this point in time) and because there is no risk of any damage to the measuring point during the diameter reduction because it is not yet arranged in the metal sheath, the diameter reduction can be designed in such a way that optimal heat conduction through the electrically insulating, highly heat-conducting material is ensured.

To reach the intermediate stage according to 1b into the intermediate stage according to 1c To transfer the thermocouple 10, the tubular metal casing 10, together with the compacted, electrically insulating material 11 arranged therein, is tapped off with a first tool 1 on the side opposite the base, whereby the plug 12 is also removed at the same time. In addition, a second tool 2, which is shown here as a drill but can also be a different tool, is used to cut a receptacle 13 for the measuring point 14, which is adapted in particular to its outer contour, into the electrically insulating, heat-conducting material 12 that has been compacted by the diameter reduction. Optionally, as is the case in the example shown here, this receptacle 13 can also accommodate a section 15 of the thermocouple that adjoins the measuring point 14. It is possible to cut the receptacle 13 into the compacted, electrically insulating, heat-conducting material 12 before or after the tapping; however, the first variant can be particularly advantageous from a manufacturing perspective.

In the recording 13 can be subsequently, as in 1d shown intermediate stage, the measuring point 14, which is in 1d by bringing into contact, optionally twisted and/or welded thermocouple legs 16a, 16b of a thermocouple 16, are inserted and fixed. Here it is also clear once again that during the entire preceding manufacturing process, only the compact and essentially rigid assembly consisting of the tubular metal jacket 10 with the electrically insulating, highly heat-conducting material contained therein 12 must be handled, so that automated production on relatively simple machines is possible, which brings significant cost advantages.

In particular, as in the optional step according to 1e As shown, this fixation is achieved by a further external compression, which can be round, oval, with a bead, or with a hexagon, at the appropriate pressure. After fixation, the temperature sensor is essentially complete; however, it can also be supplemented with additional components to be used as an immersion temperature sensor, which will be explained in more detail below.

The 2a to 2e show intermediate stages or steps of a second method for producing a temperature sensor.

The 2a The intermediate stage of this second manufacturing process for a temperature sensor shown differs from the intermediate stage of the 1a This is due to the fact that the metal casing 20 is designed as a tube, which can, for example, have a length of 1 m or more. In this process, the interior of the metal casing 20, designed as a tube, is also filled with an electrically insulating, highly thermally conductive material 21, which can be introduced into the interior, for example, as a powder or granulate, a ceramic crushable tube, or as a molded body. A particularly preferred material here is again magnesium oxide, preferably impregnated magnesium oxide.

The 2a The intermediate stage shown is again subjected to a reduction in diameter, for example by hammering or rolling, for compaction, which leads to the 2b This leads to the intermediate stage shown with a metal jacket 20 and an electrically insulating, heat-conducting material 21. The metal jacket 21 thus obtained is a long, reduced-diameter tube, in whose interior the electrically insulating, heat-conducting material 21 is optimally compacted as a blank. The compaction at the tube mouths may exhibit inhomogeneities, which is why it is advantageous not to use these end sections in the further manufacturing process.

To reach the intermediate stage according to 2b into the intermediate stage according to 2c To transfer the heat transfer medium, an end section of the tubular metal casing 20 is cut off with the first tool 1, and a receptacle 23 for the measuring point 24, which is particularly adapted to its outer contour, is introduced into the compacted, electrically insulating, highly thermally conductive material 22 using the second tool 2, which is again shown as a drill but can also be a different tool. Optionally, as is the case in the example shown here, this receptacle 23 can also accommodate a section 25 of the thermocouple that is connected to the measuring point 24.

In this way, the tube is divided into a plurality of sleeves, which are filled with optimally compacted, electrically insulating, heat-conducting material 22 and each form the metal casing 21 for a temperature sensor. The measuring point 24 of the latter, which is 2d again formed by thermocouple legs 26a, 26b of a thermocouple 26 which are brought into contact with one another and optionally twisted and/or welded together, is then inserted into the receptacle 23 and fixed there.

In particular, as in the optional step according to 2e As shown, this fixation can be achieved by a further pressing from the outside, which can be round, oval, with a bead or with a hexagon, at suitable pressure.

A particular advantage of temperature sensors manufactured in this way is, on the one hand, that the production of a large number of metal casings with compacted, electrically insulating, heat-conducting material arranged therein from a compacted bar stock is particularly quick and cost-effective. A further advantage of this procedure is that a precisely defined, flat end face is created by cutting off the respective sleeve without any further post-processing. The lack of a bottom surface of the metal casing 21 is manageable, particularly when using impregnated, electrically insulating, heat-conducting material. This is especially true when they are used as immersion temperature sensors and are therefore placed inside another metal casing.

The 3a and 3b show a temperature sensor 100 according to the invention in a configuration as an immersion temperature sensor as an external view or as a cross-section through the immersion temperature sensor.

The temperature sensor 100, configured as an immersion temperature sensor, has a contact plate 110 with a fixing opening 111, a contact surface 112, and a tubular extension 113 extending parallel to the contact surface 112. A second metal casing 114, designed as a sleeve with a bottom, extends perpendicular to the contact surface 112 for immersion into an opening arranged in the object whose temperature is to be monitored with the immersion temperature sensor. The interior space 115 of the second metal casing 114 opens into a channel arranged in the contact plate 110. 116, which extends to the front side of the tubular extension 113.

The temperature measurement is carried out by means of a thermocouple 120, which has two thermocouple legs 125, 126, which are brought into electrical contact with one another in the region of the measuring point 124 and are preferably twisted or welded together. Outside the area surrounding the measuring point 124, they are each surrounded by an insulating sleeve 125a, 126a to electrically insulate them from one another. In the area in front of the contact plate 110, the thermocouple legs 125, 126 are held together by a wire mesh hose 127; in the area where the thermocouple 120 runs in the channel 116, they are held together by a glass fiber hose 128. The transition area between the tubular extension 113 and the freely extending section of the thermocouple 120 is secured by an anti-kink spring 117, which is pushed onto the outside of the tubular extension 113.

The thermocouple 120 is inserted through the channel 116 into the interior of the second metal sheath 114, so that its measuring point 124, which is formed from its weld-contacted thermocouple legs 125, 126, is positioned in the end region of the tubular extension 113.

The measuring point 124 of the thermocouple 120 is housed in a receptacle 123 machined into a compacted, electrically insulating, highly thermally conductive material 122, in this example impregnated magnesium oxide, which was previously compacted inside a sleeve-shaped metal casing 121 together with the sleeve-shaped metal casing 121. The outer surfaces of this casing are in contact with the inside of the second metal casing 114 and can be fixed there, which can be achieved, for example, by pressing the second metal casing 114 onto the metal casing 121 of the thermocouple, which is designed as a sleeve. Optionally, any empty volumes still present in the second metal casing 114 can also be filled with a highly thermally conductive material, which does not necessarily have to be electrically insulating, for example, with copper powder.

List of reference symbols

1

first tool

2

second tool

10.20

metal jacket

11.21

electrically insulating material

12

Plug

13.23

Recording

14.24

Measuring point

15.25

Section

16.26

thermocouple

16a,16b,26a,26b

Thermo leg

100

Temperature sensor

110

contact plate

111

Fixing opening

113

tubular process

114

second metal jacket

115

Interior

116

channel

117

Anti-kink spring

120

thermocouple

121

metal jacket

122

electrically insulating material

123

Recording

124

Measuring point

125,126

Thermo leg

125a,126a

Insulating cover

127

Wire braided hose

128

glass silk hose

QUOTES CONTAINED IN THE DESCRIPTION

This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• CH 689 875 A5 [0002]
• DE 20 2011 004 481 U1 [0002]
• DE 10 2013 100 892 A1 [0002]

Claims (18)

Method for producing a temperature sensor (100) with a measuring point (14, 24, 124) arranged in the interior of a tubular metal casing (10, 20, 121) and embedded in electrically insulating material (11, 21, 122), characterized in that the tubular metal casing (10, 20, 121) with the electrically insulating material (11, 21, 122) arranged therein is compacted before the measuring point (14, 24, 124) is introduced into the interior of the tubular metal casing (10, 20, 121), that a receptacle (13, 23, 123) for the measuring point (14, 24, 124) is subsequently incorporated into the compacted electrically insulating material (11, 21, 122), and that the measuring point (14, 24, 124) is introduced into this receptacle (13, 23, 123) and preferably fixed becomes. Procedure according to Claim 1 , characterized in that after the tubular metal casing (10,20,121) has been compacted with the electrically insulating material (11,21,122), at least a section of the tubular metal casing (10,20,121) is separated. Procedure according to Claim 2 , characterized in that the tubular metal casing (10,20,121) with the compacted electrically insulating material (11,21,122) arranged therein is obtained by cutting off a section of a compacted rod material. Method according to one of the Claims 1 until 3 , characterized in that the receptacle (13,23,123) is introduced into the electrically insulating material (11,21,122) by drilling or machining, wherein the drilling or machining is carried out with a tool (2) and/or with ultrasound. Method according to one of the Claims 1 until 4 , characterized in that the electrically insulating material (11,21,122), preferably impregnated magnesium oxide, is introduced into the metal casing (10,20,121) as a powder, granulate, crushable tube or shaped part before compaction. Method according to one of the Claims 1 until 5 , characterized in that a receptacle (13,23,123) is introduced into the compacted electrically insulating material (11,21,122), which also receives sections of thermolegs (125,126) or leads to the measuring point (14,24,124) of the temperature sensor (100), which are surrounded by an insulating sheath (125a,126a). Method according to one of the Claims 1 until 6 , characterized in that the sections of the thermocouple (120) accommodated in the receptacle (13,23,123) are fixed by pressing. Method according to claim one of the Claims 1 until 7 , characterized in that pressing takes place after the metal jacket (10, 20, 121) has been pushed into the interior (115) of a second metal jacket (114) and has preferably been brought into contact with a bottom of the further metal jacket (114), wherein preferably before pressing any empty volumes still present in the second metal jacket (114) are filled with a material with good heat conduction, for example magnesium oxide or copper powder. Method according to one of the Claims 1 until 8 , characterized in that sections of thermolegs (125,126) or supply lines to the measuring point (14,24,124) of the temperature sensor (100) are pushed through a channel (116) arranged in a contact plate (110). Procedure according to Claim 8 and 9 , characterized in that the further metal casing (114) is connected to a contact surface of the contact plate (110). Temperature sensor (100) with a measuring point (14, 24, 124) which is arranged in a receptacle (13, 23, 123) which is introduced into compressed electrically insulating material (11, 21, 122) which is arranged in the interior of a metal casing (10, 20, 121). Temperature sensor (100) after Claim 11 , characterized in that the electrically insulating material (11,21,121) is impregnated magnesium oxide. Temperature sensor (100) after Claim 11 or 12 , characterized in that sections of thermolegs (125,126) or supply lines to the measuring point (14,24,124) of the temperature sensor (100), which are surrounded by an insulating sleeve (125a,126a), are also accommodated in the receptacle (13,23,123). Temperature sensor (100) according to one of the Claims 11 until 13 , characterized in that the metal jacket (10, 20, 121) is arranged in the interior of a further metal jacket (114) in such a way that its outer walls are in direct contact with the inner walls of the further metal jacket (114) and preferably additionally there is at least partial direct contact with a bottom of the further metal jacket (114). Temperature sensor (100) after Claim 14 , characterized in that in the interior of the further metal casing (114) remaining empty lumina are filled with good heat-conducting material, such as magnesium oxide or copper powder. Temperature sensor (100) according to one of the Claims 11 until 15 , characterized in that the temperature sensor (100) has a contact plate (110) and that sections of thermolegs (125,126) or supply lines to the measuring point (14,24,124) of the temperature sensor (100) run through a channel (116) arranged in the contact plate (110). Temperature sensor (100) according to one of the Claims 14 until 16 , characterized in that the further metal casing (114) is connected to the contact surface of the contact plate (110) in a manner substantially perpendicular to the latter. Temperature sensor (100) according to one of the Claims 14 until 17 , characterized in that the contact plate (110) has a tubular extension (113) and that in the transition region between the tubular extension (113) and a freely extending section of the thermocouple (120) an anti-kink spring (117) is pushed onto the outside of the tubular extension (113).