WO2019214772A1 - Sensor line, use of a sensor line for detecting a temperature, and insulating material - Google Patents

Abstract

The invention relates to a sensor line for detecting the temperature and comprising a temperature-dependent dielectric for this purpose.

Description

 description

 Sensor The invention relates to a sensor line, the use of such a sensor line for detecting a temperature and an insulating material, in particular for electrical lines, especially for such a sensor line.

The sensor line generally has a conductor, which is surrounded by an insulating jacket, hereinafter also referred to as jacket for short. The insulating jacket forms a dielectric, which influences the transmission properties of a signal fed into the sensor line. By measuring the transit time of a signal fed in, conclusions can be drawn about the dielectric or, in general, the condition of the sensor line.

For example, TDR measurements (Time Domain Reflectometry) are known as measuring methods which are based on a transit time measurement of an injected signal. Another measuring method is for example from WO

2017/216061 A1. It is described here that a temperature measurement can take place by the use of a temperature-dependent dielectric. The dielectric constant of the insulation is thus dependent on the temperature. The dielectric constant significantly determines the transit time, so that when using a temperature-dependent dielectric from the running time, a conclusion about the prevailing temperature can be made.

The invention has for its object to enable an improved temperature measurement. The object is achieved according to the invention by a sensor line with a conductor, which is surrounded by an insulating jacket, which has a temperature-dependent dielectric and in particular from the temperature-dependent dielectric is formed, wherein the dielectric contains a pyroelectric material.

The insulating jacket consists of an insulating material extending along the

Conductor extends over its entire length (except for possibly stripped end region for contacts), wherein the insulating material typically has plastic up. The insulating jacket preferably has a constant thickness over the entire length of the conductor and / or has a homogeneous material over the entire length.

A pyroelectric material is generally understood to mean materials which have an electrical polarity, that is to say in particular an electric dipole. In particular, a pyroelectric material is understood to mean an at least partially crystalline material which has a preferably permanent electrical dipole. In particular, the material has (electrically) polar crystals. Such crystals are usually constructed of electrically polar unit cells, each having a dipole, wherein the totality of the individual dipoles to the total, permanent electric dipole composed.

This embodiment is based on the consideration and the recognition that the dielectric constant of insulators is a measure of the absorption and storage capacity of charges in the material and that this measure is significantly influenced by intrinsic material properties. Specifically, the factors of crystallinity and polarity play an important role in the material structure. Furthermore, the invention is based on the recognition that with increasing

Crystallinity and / or polarity, the dielectric constant reacts increasingly to temperature changes, ie changes more strongly with temperature. By integrating such pyroelectric materials into an insulating material and thus using such pyroelectric materials for the dielectric, it becomes generally more sensitive to changes in temperature. Due to the strong / increased temperature-dependent change in the dielectric constant is at a measurement a clear difference in transit time can be detected. This makes the sensor cable more sensitive to changes in temperature overall.

In a preferred embodiment, the pyroelectric material is a pyroelectric ceramic. Such one typically has a high crystallinity and a high polarity.

Examples of such pyroelectric materials are minerals of the tourmaline group, strontium barium niobate (SrBaNbO ₃ ), lead titanate (PbTiO ₃ ), barium titanate (BaTiO ₃ ), sodium nitrite (NaNO ₂ ), lithium niobate (LiNbO ₃ ). At least one or more of these aforementioned materials are therefore used for the dielectric.

Depending on the requirement profile and application, a specific selection of a suitable pyroelectric material takes place. For example, it avoids pyro- electric materials that are potentially harmful, such as RoHS or REACH substances (RoHS: Restriction of Hazardous Substances, EU Directive 2011/65 / EU; REACH: Registration, Evalua- tion, Authorization and Restriction of Chemicals, EC Regulation No. 1907/2006). Thus, for example, materials with a lead content are preferably avoided.

In a preferred embodiment, barium titanate is used as the pyroelectric material. In this case, tests have shown a good effect on the temperature dependence and, in addition, the use of barium titanate has also proven to be suitable for the production process of the sensor line, especially for a continuous extrusion process for applying the dielectric to the conductor as an insulating jacket.

In a preferred development, the dielectric, that is to say the material for the insulating jacket, is a compound made of a plastic and the pyroelectric material. The material for the insulating jacket is therefore a mixture of, for example, a conventional insulating plastic and the pyroelectric material. The plastic therefore forms a matrix in which the pyroelectric material is inserted. is bedding. The compound allows easy processing and the use of conventional manufacturing processes. Specifically, the dielectric forming the insulating jacket is applied to the conductor in an extrusion process.

The proportion of the pyroelectric material is preferably in the range between 30 vol.% And 80 vol.%. In particular, the proportion of the pyroelectric material is between 40 vol.% And 60 vol.%. This proportion, also referred to as degree of filling, also depends on the choice of the respective pyroelectric material. With the use of barium titanate, a degree of filling of 40 to 60% by volume, especially of 50% by volume, has proven suitable, which is preferably also set accordingly. The volume fraction is based on the total volume of the compound, that is based on the total volume formed by the plastic and the pyroelectric material.

The plastic used for the compound is preferably selected from one of the following plastics or a mixture of several of the following plastics:

 Polyurethane (PU), optionally a halogen-containing or a halogen-free polyurethane,

 Polyethylene (PE)

 polyvinyl chloride,

 thermoplastic elastomers, in particular thermoplastic polyester elastomers (TPE-E) or thermoplastic urethane (TPU) or else an olefin-based thermoplastic elastomer (TPO),

 Ethylene Vinyl Acetate (EVA), especially in an FRNC variant,

 Polyvinyl chloride PVC, especially halogen-free.

Depending on the application profile, FRNC materials (FRNC: Flame Retardant Non Corrosive, halogen-free, flame retardant material) or halogen-free materials are used. Plastics having a high crystallinity / crystallization degree and high (di) polarity are particularly preferably used. The plastics generally have a polarity (dipole moment in the plastic molecule) and a crystalline fraction. For polymers, crystallinity is generally understood to mean the degree of alignment of parallel aligned molecular chains. Specifically, ester-based TPU plastics have been found to be suitable and, for example, more suitable than ether-based TPU plastics.

Specifically, TPU and PVC, preferably each in a halogen-free variant, have proven to be suitable. Therefore, TPU or PVC is preferably used as the plastic matrix for the dielectric.

Investigations have shown that these plastics already show a temperature effect per se, that is, that even the pure plastic shows a Dielektr- rizitätszahl showing a relatively strong temperature dependence. In this respect, the use of a TPU and / or PVC, or generally a plastic with a high degree of crystallization in combination with one of the abovementioned pyroelectric materials, especially barium titanate, achieves a particularly strong temperature dependence of the dielectric.

As the TPU, a polyester-based TPU is preferably used. Examples include polyester-based plastics from BASF Polyurethanes GmbH, which are available under the brand name Elastollan. For example, the Elastollan with the designation 754 D HPM is suitable.

The pyroelectric material is preferably added to the compound as a powder. The particle size is preferably in the range between 0.1 pm and 30 pm, in particular the so-called d90 value in the stated range is between 0.1 pm and 30 pm. This means that for a powder with a given particle size distribution 90% of the particles fall within the specified size range. With regard to the production of the sensor line, the dielectric, especially the compound, is preferably extrudable, so that the dielectric, like conventional cladding materials, can be extruded and is also applied to the conductor by extrusion.

According to a first embodiment variant, the sensor line is designed as a coaxial line, in which the dielectric is arranged between the conductor designed as an inner conductor and an outer conductor. The outer conductor is usually a shield arranged concentrically with the inner conductor, for example a braided shield or also a foil shielding.

According to an alternative embodiment variant, the sensor line is a wire or it has at least one wire. A vein is generally formed by the conductor and a surrounding vein jacket, which forms the dielectric. The sensor line is formed, for example, overall by a pair of wires, in which at least one core, and preferably both cores, has / has the temperature-dependent dielectric.

Furthermore, the object is achieved according to the invention by the use of a sensor line for detecting a temperature, wherein the sensor line has a NEN conductor, which is surrounded by a temperature-dependent dielectric to give. The dielectric has a TPU, a PVC or a pyroelectric material. In particular, the TPU is a polyester-based TPU such as that marketed under the brand name Elastollan. Specifically, the temperature-dependent dielectric has a mixture of TPU or PVC in combination with the pyroelectric material. In particular, the temperature-dependent dielectric is finally formed by a compound of a TPU or PVC in conjunction with the pyroelectric material. The plastics used are generally polar plastics preferably having at least one crystalline fraction.

Basically, however, a dielectric purely of a plastic (ie, without pyroelectric material) is suitable, for example formed or at least containing a TPU and / or a PVC, as have already been described for the compound. In this respect, reference is made to the preceding statements. As already mentioned above, investigations have shown that these materials already show a good temperature dependence of the relative permittivity. These materials are therefore used for such a sensor line for detecting a temperature.

When the temperature is recorded, a test or measuring signal is fed into the sensor cable, specifically a measuring pulse, and its runtime is evaluated. From this, for example, by comparison with stored reference values or also by a suitable algorithm, with a known temperature dependence of the dielectric, a conclusion is drawn on the currently prevailing temperature. The sensor line and the temperature measurement are preferably used in a wide variety of applications. On the one hand, the temperature of the sensor line and / or a cable in which the sensor line is integrated is monitored. The cable is, for example, a charging cable, especially for charging a vehicle driven by an electric motor. In addition, the cable is a supply cable for the power and power supply of an electrical machine. In addition, for example, the sensor line is used to determine the temperature of the environment in which the sensor line runs. The object is further achieved according to the invention by an insulating material, in particular for electrical lines, which comprises a compound of a plastic and a pyroelectric material, especially the insulating material is formed by the compound. The embodiments mentioned above with regard to the sensor line in connection with the dielectric are to be transferred to the insulating material in the same way, ie valid for the insulating material.

An embodiment will be explained in more detail with reference to FIGS. These show in schematic, simplified representations: Fig. 1 shows a cross section through a sensor line and

 Fig. 2 is a block diagram of a measuring arrangement. In the figures, like-acting parts are given the same reference numerals.

The sensor line 2 shown in FIG. 1 extends in a longitudinal direction L.

The sensor line 2 is embodied in the exemplary embodiment as a coaxial line 4. For this purpose, the sensor line 2 has a conductor formed as an inner conductor 6 and an outer conductor 8. This is formed in the embodiment as a mesh. Between the inner conductor 6 and the outer conductor 8 is a dielectric kum 10, so an insulating material attached. This fills the intermediate space between the inner conductor 6 and the outer conductor 8. The dielectric 10 virtually forms an insulating jacket for the inner conductor 6. The signal line 2 furthermore has an outer jacket 12 made of a suitable insulating material.

The dielectric 10 is formed by a compound of a plastic 14 and a filler, wherein the filler is a pyroelectric material 16, in particular barium titanate. The pyroelectric material 16 is embedded in the plastic 14. The plastic 14 therefore virtually forms a matrix in which the pyroelectric material 16 is at least largely homogeneously distributed. The pyroelectric material 16 is in powder form, that is, has individual particles that are distributed within the plastic 14.

The particle size of the individual particles is preferably in the range between 0.1 pm and 30 pm (d90 value). The pyroelectric material 16 has a proportion of 40% by volume to 60% by volume, especially of 50% by volume, based on the total volume of the dielectric 10.

The sensor line 2 shown in FIG. 1 is used as a sensor line 2 for measuring the temperature, as will be explained in more detail below with reference to FIG. 2. It is exploited that the dielectric 10 a temperature-dependent dielectric value shows. This means that when the temperature changes, the dielectric value changes and thus also the impedance value of the sensor line 2 is changed, so that the propagation time of a signal fed in is influenced.

The sensor line 2 serves, for example, for monitoring the temperature of a cable 22, which is designed, for example, as a charging cable for an electrically driven motor vehicle. The sensor line 2 is integrated in the cable 22. In addition to the sensor line 2, the cable 22 typically also has further power cores and / or data lines.

FIG. 2 shows a measuring arrangement 20 for monitoring the temperature of the cable 22. In this case, the measuring arrangement 20 comprises the sensor line 2, a transmitting unit 24 and a receiving unit 26 and additionally an evaluation unit 28. The transmitting unit 24 is for feeding a measuring signal S _M and the receiving unit 26 is for receiving a response signal S _A and for transmitting the Response signal S _A to the evaluation unit 28 trained det. In the evaluation unit 28, the response signal S _{A is} evaluated. The evaluation unit 28 can also be integrated in the receiving unit 26.

The response signal S _A varies as a function of the dielectric value of the dielectric 10 and indeed a change in temperature leads to a change in the transit time of the applied measurement signal S _M. The fed measurement signal S _M is specifically a measurement pulse, which is reflected, for example, at one end of the line and is reflected back as the reflected response signal S _A in the direction of the receiving unit 26. Evaluation unit 28 evaluates the transit time between supply and reception and determines the temperature based on the measured transit time. The invention is not limited to the embodiment described above. Rather, other variants of the invention can be derived therefrom by the person skilled in the art without departing from the subject matter of the invention.

Claims

claims 1. sensor line with a conductor which is surrounded by a temperature-dependent dielectric, wherein the dielectric contains a pyroelectric material. 2. Sensor lead according to claim 1, wherein the pyroelectric material is a pyroelectric ceramic. 3. Sensor line according to claim 1 or 2, wherein it is in the  pyroelectric material is barium titanate. 4. Sensor line according to one of claims 1 to 3, wherein the dielectric a Compound is made of a plastic and the pyroelectric material. 5. Sensor line according to claim 4, wherein the proportion of the pyroelectric Mate- rials at 30 vol% to 80 vol.% And in particular in the range between  40Vol% and 65Vol% is. 6. Sensor line according to claim 4 or 5, wherein the plastic is selected from one of the following materials: PE, PU, PVC, TPU, TPO, TPE-E, in particular halogen-free TPU or halogen-free PVC. 7. Sensor line according to one of claims 1 to 6, wherein the pyroelectric material has a particle size in the range of 0.1 pm to 30pm. 8. Sensor lead according to one of claims 1 to 7, wherein the dielectric is extruded onto the conductor. 9. Sensor line according to one of claims 1 to 8, which is formed as a coaxial line, wherein the dielectric between the inner conductor ausgebil- The conductor and an outer conductor is arranged or which has at least one core, in which a wire jacket is formed by the dielectric. 10. Insulating material, in particular for electrical lines, which is a composite of a plastic and a pyroelectric material. 11. Use of a sensor line for detecting a temperature, wherein the sensor line has a conductor which is surrounded by a temperature-dependent dielectric, wherein the temperature-dependent dielectric TPU, PVC or contains a pyroelectric material. 12. Use according to claim 11, wherein the TPU is a polyester-based TPU.