DE102021127942B4 - Temperature sensor and flow meter - Google Patents

Abstract

Temperature sensor for determining the temperature of a medium, having a housing body (2) and a housing head (3) in which a temperature sensor (10) is arranged, the interior of the housing body (2) being designed as a bore (4) which extends to extends into the housing head (3), and wherein the temperature sensor (10) is connected to at least two strands (11) for electrical contact and the strands (11) pass through the bore (4) from the housing head (3) through the housing body (2) are guided, with an elongate plastic support (20) being introduced into the bore (4), through which the strands (11) are guided and on the end of which facing the housing head (3) the temperature sensor (10) is arranged, the plastic support ( 20) is connected to the housing body (2) at the end opposite the housing head (3) and generates a defined preload on the temperature sensor (10) and the plastic carrier (20) has a shoulder-like widening (21) and the housing wall of the temperature sensor ( 1) has two opposite slit-like recesses (5), the shoulder-like widening (21) of the plastic carrier (20) engaging in each case in the slit-like recesses (5).

Description

The invention relates to a temperature sensor according to the preamble of claim 1 and a flow meter according to the preamble of claim 3.

Process measurement technology measuring devices are used in automation technology to monitor the properties of a fluid, for example with regard to pressure, temperature, flow rate and fill level. Magnetic-inductive flow measuring devices have been known for many years for measuring the flow. The functionality of these measuring devices is based on the principle of magnetic induction. Here, the flow rate of the medium is determined through a measuring tube with the help of a magnetic field and two measuring electrodes. During the measurement, the magnetic field penetrates the measuring tube and at the same time the medium flowing through the measuring tube. If an electrically conductive medium is penetrated by a magnetic field perpendicular to its flow direction, the charge carriers in the magnetic field are deflected perpendicular to the flow direction and perpendicular to the magnetic field. In this case, an induced voltage is induced between the two measuring electrodes. If this induced voltage is picked up via the measuring electrodes, it can be used as a measure of the flow rate for further evaluation.

In addition to measuring the flow, it may also be necessary to record the temperature of the medium flowing through in order to compensate for temperature influences. It is well known that the temperature sometimes has a considerable influence on the physico-chemical properties of the medium, which in turn can have an influence on the measurement result. If the temperature of the medium is known, corresponding correction factors can be determined, which make the measurement results comparable with different temperature conditions.

From the German patent DE 10 2010 001 993 B4 For example, a magneto-inductive flow meter with a temperature measuring device is known, wherein a measurement of a minimum conductivity is also possible in addition to the temperature measurement.

Furthermore, from the DE 10 2012 109 312 A1 a temperature sensor and a magnetic-inductive flowmeter with such a temperature sensor are known. The temperature sensor essentially consists of a housing body and a housing head, in which a temperature sensor or temperature element is arranged. The housing has a bore that extends through the entire housing of the temperature sensor up to the housing head. The disadvantage here is the installation of the temperature sensor within this hole. On the one hand, it must be ensured that the temperature sensor rests completely and directly on the inside of the housing head in order to ensure largely loss-free thermal coupling. On the other hand, threading in the temperature sensor and the two connected strands is very cumbersome, especially since the diameter of the entire temperature sensor is typically only a few millimeters.

From the DE 39 43 437 A1 a heat transfer measuring device is known in which a good thermal coupling of the temperature sensor to the bottom of the measuring device housing was achieved by clamping an elongate plastic carrier axially between the bottom of the measuring device housing and an abutment attached to the open end of the measuring device housing and thereby clamping it between the end of the plastic carrier and the bottom of the measuring device housing arranged temperature sensor is pressed against the ground.

Furthermore, temperature sensors are usually soldered or glued into the housing of the temperature sensor for thermal connection. For this purpose, a comparatively expensive metallization of the temperature element and a copper coating of the inside of the temperature sensor housing are required during soldering. Gluing is also very time-consuming, especially with the small designs mentioned.

The object of the invention is to propose a temperature sensor that can be produced easily and inexpensively and in which the temperature sensor is thermally coupled securely and permanently to the sensor housing even with small housing shapes.

The object is achieved according to the invention by a temperature sensor having the features of claim 1 and by a flow meter having the features of claim 3. Advantageous refinements of the invention are specified in the dependent claims.

As is known from the prior art, an elongate plastic carrier is first inserted into the bore, through which the strands are guided and the temperature sensor is arranged on the end of which facing the housing head, the plastic carrier being connected to the housing body at the end opposite the housing head and is fixed. Advantageously, this connection is such that the plastic support is introduced into the bore under pretension, preferably by means of a nut screwed onto the housing body.

• - der Kunststoffträger fungiert als Halteelement für die Litzen, so dass diese geführt und fixiert sind und sich dadurch auch eine Zugentlastung realisieren lässt;
• - der Kunststoffträger stellt eine Einführhilfe dar, so dass das Einführen der Litzen zusammen mit dem Temperaturfühler vor allem bei sehr kleinen Bohrungen von bspw. 1,5 - 2,5 mm erheblich erleichtert wird;
• - der Kunststoffträger wirkt als Niederhalter, da er durch eine gewisse Elastizität des Kunststoffmaterials und durch die Verschraubung eine dauerhafte Vorspannung auf das Temperaturelement erzeugt und somit garantiert wird, dass das Temperaturelement auch über Temperaturwechsel auf den Boden der Bohrung im Gehäusekopf drückt und eine dauerhafte thermische Kopplung sichergestellt ist.

This fulfills the following three advantageous functions:

• - the plastic support acts as a holding element for the strands, so that they are guided and fixed and strain relief can also be implemented as a result;
• - The plastic carrier represents an insertion aid, so that the insertion of the strands together with the temperature sensor is made considerably easier, especially in the case of very small bores of, for example, 1.5 - 2.5 mm;
• - The plastic carrier acts as a hold-down device, since it creates a permanent preload on the temperature element due to a certain elasticity of the plastic material and the screw connection, thus guaranteeing that the temperature element also presses against the bottom of the bore in the housing head due to temperature changes and permanent thermal coupling is ensured.

The plastic carrier is advantageously made from a high-temperature plastic and is produced as an injection molded part. Possible concrete materials would be, for example, PEEK, PPS, PA6T or PPSU.

According to the invention, the plastic carrier has a shoulder-like widening and, at the same time, the housing wall of the temperature sensor has two opposite slot-like recesses. In this way, a defined alignment and an anti-twist protection for the plastic carrier can be implemented in a simple manner, and on the other hand, the widening serves as a shoulder for the contact pressure of the nut.

Furthermore, in the area of the slit-like recesses, the plastic carrier advantageously has a further broadening that lies somewhat above the outer diameter of the housing body. When screwing on, the nut then digs into this further widening of the plastic carrier, which means that a thread lock is implemented for reliable operation under shock and vibration.

An advantageous application of the temperature sensor according to the invention is to use it as an electrode in a magneto-inductive flowmeter. The housing of the temperature sensor then forms the measuring electrodes required for flow measurement, via which the voltage induced in the magnetic field by the flow of the medium is tapped.

The invention is explained in more detail below using exemplary embodiments with reference to the drawings.

• 1 einen erfindungsgemäßen Temperatursensor;
• 2a ein erstes Schnittbild eines erfindungsgemäßen Temperatursensors;
• 2b ein zweites Schnittbild eines erfindungsgemäßen Temperatursensors;
• 3 einen erfindungsgemäßen Temperatursensor in Explosionsdarstellung;
• 4 eine vorteilhafte Ausführungsform des erfindungsgemäßen Temperatursensors.

They show schematically:

• 1 a temperature sensor according to the invention;
• 2a a first sectional view of a temperature sensor according to the invention;
• 2 B a second sectional image of a temperature sensor according to the invention;
• 3 an exploded view of a temperature sensor according to the invention;
• 4 an advantageous embodiment of the temperature sensor according to the invention.

In the following description of the preferred embodiments, the same reference symbols designate the same or comparable components.

1 shows the temperature sensor 1 according to the invention in the form of an electrode for a magneto-inductive flowmeter for tapping a flow-related induced voltage. Electromagnetic flowmeters measure the flow of a flowing, conductive medium in a measuring tube made of a non-conductive material. A magnetic field that penetrates the measuring tube perpendicularly to the longitudinal axis of the measuring tube is generated with a magnetic field generating device, and a measuring voltage induced in the flowing medium is tapped off with two measuring electrodes. The measuring electrodes are arranged along a connecting line running perpendicularly to the longitudinal axis of the measuring tube and perpendicularly to the direction of the magnetic field.

The temperature sensor 1 consists essentially of a metallic housing, which is divided into a housing body 2 and a housing head 3, and a plastic carrier 20 located in the housing body 2, which is fixed in the housing body 2 by means of a nut 6. When using the temperature sensor in a magneto-inductive flow meter, the housing body 2 is then at least partially in the wall of the flow meter and the housing head 3 is galvanically coupled to the medium to be measured.

Two stranded wires 11 lead out of the plastic carrier 20 and make electrical contact with a temperature sensor 10 located inside the temperature sensor 1 .

The 2a and 2 B each show a sectional view of the temperature sensor 1 according to the invention from two views rotated by 90°.

The interior of the housing body 2 is formed by a bore 4, which has a diameter of only 2.4 mm in the present embodiment. In this bore there is a plastic carrier 20, at the end of which facing the housing head 3 a temperature element 10 is arranged. In addition, the strands 11 are guided through the plastic carrier 20 . The temperature element 10 is typically made of ceramic.

The plastic support 20 is firmly connected to the housing body 2 at the end opposite the housing head 3 in such a way that the plastic support 20 is clamped in the bore in an axially immovable manner and thereby presses the temperature element 10 onto the bottom of the bore 4 in the housing head 3 and thus also over temperature changes ensures permanent thermal coupling. The plastic carrier 10 thus acts as a hold-down device. Advantageously, this connection is such that the plastic carrier 10 is introduced into the bore under pretension, preferably as in FIGS 2a and 2 B shown by means of a nut 6 screwed onto the housing body 3. The nut 6 is advantageously tightened with a defined torque.

The geometry of the plastic carrier 20 guarantees a plane-parallel alignment of the temperature sensor 10 on the bottom of the bore 4 in the housing head 3 . Angular deviations of the temperature sensor 10 during the pre-assembly in the plastic carrier 20 are compensated for by the joining process as in the case of a joint. By screwing on the nut 6, the preload on the temperature sensor 10 is generated.

In addition, the nut 6 digs into the plastic support 20 during the last few turns, which represents a thread lock for the nut 6 for reliable operation under shock and vibration. For this purpose, the plastic carrier 20, as shown 2 B As can be seen, in the area of the slot-like recesses 5 there is a further widening which lies somewhat above the outer diameter of the housing body 2 and into which the nut 6 then engages.

The special T-shape of the plastic carrier 20 in the form of a shoulder-like widening 21 is used for the contact pressure of the nut 6. The wall of the housing body 2 has two opposite slot-like recesses 5 (see 1 and 3 ), into which the switch-like widening 21 of the plastic carrier 20 engages in each case. As a result, an anti-twist device can also be implemented in the housing body 2 .

In 2 B it can also be seen that the shoulder-like widening 21 does not rest on the housing body 2, but is at a minimal distance. This distance is necessary for tolerance compensation.

3 shows again all the individual elements of the temperature sensor 1, ie the housing body 2 with the housing head 3, the temperature sensor 10 with the strands 11, the plastic carrier 20 and the nut 6 in an exploded view.

In 4 An advantageous embodiment of the temperature sensor 1 according to the invention is shown, in which the temperature sensor 10 is rotated upwards by 90° compared to the embodiment according to the previous figures. As a result, the bore 4 and thus also the temperature sensor 1 itself can be made even narrower.

reference list

1

temperature sensor

2

case body

3

housing head

4

drilling

5

slot-like recess

6

Mother

10

temperature sensor

11

strand

20

plastic carrier

21

shoulder-like widening

Claims (3)

Temperature sensor for determining the temperature of a medium, having a housing body (2) and a housing head (3) in which a temperature sensor (10) is arranged, the interior of the housing body (2) being designed as a bore (4) which extends to extends into the housing head (3), and wherein the temperature sensor (10) is connected to at least two strands (11) for electrical contact and the strands (11) pass through the bore (4) from the housing head (3) through the housing body (2) are guided, an elongate plastic support (20) being inserted into the bore (4), through which the strands (11) are guided and on the end of which facing the housing head (3) the temperature sensor (10) is arranged, the plastic support ( 20) is connected to the housing body (2) at the end opposite the housing head (3) and generates a defined preload on the temperature sensor (10). and wherein the plastic carrier (20) has a shoulder-like widening (21) and the housing wall of the temperature sensor (1) has two opposite slot-like recesses (5), the shoulder-like widening (21) of the plastic carrier (20) fitting into the slot-like recesses (5 ) intervenes. temperature sensor claim 1 , characterized in that the connection between the plastic carrier (20) and the housing body (2) is realized via a screwed-on nut (6). Flow meter with a measuring tube and a device for determining the flow rate and / or the volume flow of a medium in the measuring tube, characterized in that the flow meter according to a temperature sensor claim 1 having.

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