DE102019212862A1 - Charging device and method for operating a charging device - Google Patents

Abstract

The invention relates to a charging device (10) for inductively transmitting electrical energy from an electrical energy source to a receiving device (16). The charging device (10) comprises at least one charging coil (12) and a cover (14) delimiting the charging coil (12) from an outer region (26). The charging coil (12) is set up to receive a charging current (20) in order to transmit the energy from the energy source, whereby an alternating magnetic field (22) penetrating the outer area (26) at least in certain areas is generated. Temperature sensors (28) thermally coupled to the cover (14) are arranged on a surface of the cover (14) facing away from the outer region (26). A readout unit (30) is designed to read out an individual value from the temperature sensors (28), based on the individual values, to form a flat temperature distribution (36) along the cover (14), the temperature distribution (36) with a reference temperature distribution (38) to compare and when a permissible deviation (40) of the temperature distribution (36) from the reference temperature distribution (38) is exceeded, the reception of the charging current (20) is interrupted.

Description

The invention relates to a charging device for inductively transmitting electrical energy from an electrical energy source to a receiving device, for example to an electrical energy store of an at least partially electrically driven motor vehicle. The charging device has at least one charging coil or primary coil and a cover delimiting the charging coil from an outer area. The charging coil is set up to receive a charging current in order to transmit the energy from the energy source, whereby an alternating magnetic field penetrating at least in some areas of the outer area is generated. The invention also relates to a method for operating such a charging device.

For inductive transmission of electrical energy, in particular for inductive electrical charging of an electrical energy store of a receiving device, it is known to use coil arrangements which consist of a respective primary and a respective secondary coil. In such an arrangement, the primary coil is part of a charging device and is designed to receive an electrical current or charging current from an energy source, for example from a power grid. As a result, an electrical current flow is generated in the windings of the charging coil, which in turn causes a magnetic field. If the charging current is an alternating current, an alternating magnetic field is generated accordingly. In such an arrangement, the secondary coil is part of the receiving device and is positioned within this alternating magnetic field in order to transmit the electrical energy, so that a current flow is generated or induced in it by the alternating magnetic field. This electrical current flow is now preferably used to electrically charge the electrical energy store of the receiving device. In other words, electrical energy is transmitted from the energy source to the receiving device by means of the alternating magnetic field. The procedure described is used in connection with the contactless electrical charging of electrical energy stores or accumulators (batteries for short) and in particular in the field of inductive charging systems for the contactless electrical charging of electrical energy stores of at least partially electrically powered motor vehicles.

Inductive charging systems for charging electrical energy stores in at least partially electrically driven motor vehicles are preferably designed to transmit electrical power (amount of energy per unit of time) in the kilowatt range. A respective secondary coil is preferably arranged in the area of an underbody of such a motor vehicle. Due to the design, such a secondary coil has an area of less than 2 m ² , in particular 0.05 to 1 m ² . Because of this limited area that can be used for energy transmission, the electromagnetic field strengths required for the transmission of electrical power are very high. If there are electrically conductive objects, in particular metal objects, in the magnetic alternating field, the magnetic alternating field can induce a current flow, in particular an eddy current, in such an electrically conductive object. The current flow leads to heating or heat development of the object. A reliable detection of electrically conductive objects or a metal object detection is therefore essential for the safe operation of a described inductive charging system.

From the prior art it is known, for example, to detect a distortion of the magnetic alternating field caused by a respective metal object in order to identify metal objects. For example, the DE 10 2016 002 171 A1 a device for detecting a metallic object between a primary coil and a secondary coil of an inductive charging device. For this purpose, a measuring device measures a state variable of a magnetorheological fluid, which depends on the presence of the metallic object between the primary coil and the secondary coil.

In addition, arrangements are known by means of which a temperature or a temperature change of an area between the primary and secondary coils can be detected. The DE 10 2014 223 623 A1 provides optical sensors, in particular infrared sensors, for this purpose. The DE 10 2012 010 848 A1 provides a temperature-sensitive electrical resistor for this purpose, for example. The last two proposed solutions, disadvantageously, do not make it possible to localize a location of a detected temperature change in the area of the coil arrangement. Neither can a distinction be made between unproblematic heat development that normally occurs during operation of such a coil arrangement and unforeseen problematic heat development. Infrared sensors can also easily become dirty and thus become unusable.

The invention is based on the object of reliably detecting and localizing an unforeseen heat development or heat development in the area of a charging device of the type described above.

The object is achieved by the subjects of the independent claims. Advantageous further developments of the invention are described by the dependent claims, the following description and the figures.

The invention provides a charging device for inductively transmitting electrical energy from an electrical energy source to a receiving device. The charging device has at least one charging coil and a cover delimiting the charging coil from an outer area. A respective receiving device can, for example, comprise a secondary coil for charging an electrical energy store of an at least partially electrically driven motor vehicle. The charging device is preferably designed as a charging device which such a motor vehicle can drive on or drive over. In other words, the cover has stability or inherent rigidity and is designed to carry such a motor vehicle at least temporarily.

The charging coil or primary coil of the charging device is set up to receive a charging current in order to transmit the energy from the energy source, whereby an alternating magnetic field penetrating at least in certain areas of the outside is generated. As described above, the energy source can be a power grid, for example. In this way, electrical power in the range of several kilowatts can be transmitted to an electrical energy store of a motor vehicle described. During the inductive charging process, the varying magnetic flux density along the cover can result in heterogeneous heating or local temperature increases in the area of the cover. This temperature distribution or reference temperature distribution thus arises due to known construction-related fluctuations in the magnetic flux density along the cover.

According to the invention, a plurality of temperature sensors thermally coupled to the cover are arranged on a surface of the cover facing away from the outer region. In other words, the temperature sensors are arranged on a surface of the cover that is at the bottom in the position of use, so that they are not damaged when a motor vehicle is driven over. According to the invention, a readout unit or readout circuit is designed to read out an individual value from each of the temperature sensors. In other words, each of the temperature sensors can be read out individually. The readout unit is set up to form a surface temperature distribution along the cover based on the individual values. The surface temperature distribution can for example be calculated by the readout unit or extrapolated on the basis of the individual values and as a function of a known thermal conductivity of the cover. In other words, the readout unit is set up to derive a temperature value for each point of the cover from an individual value of a temperature sensor closest to the point.

The readout unit can combine the multitude of individual values and / or extrapolated or derived temperature values to form a temperature distribution along the cover or to form a temperature distribution map. The temperature distribution can be visualized as a map showing a topography of a land surface. According to this analogy, a mountain on this map would correspond to a high temperature value or a single value, while a valley would correspond to a low temperature value or a low single value.

According to the invention, the read-out unit is now set up to compare the surface temperature distribution thus formed along the cover with the mentioned reference temperature distribution. If a predetermined or permissible deviation of the temperature distribution from the reference temperature distribution is exceeded, the readout unit can interrupt the reception of the charging current. In other words, the readout unit is set up to interrupt or terminate a respective charging process if a deviation between the temperature distribution and the reference temperature distribution exceeds a predetermined or permissible limit value. A respective reference value is preferably assigned to a respective individual value. A separate reference value can therefore be assigned to each measuring location and thus to each temperature sensor. This advantageously results in that punctual differences between temperature distribution and reference temperature distribution can be detected. In addition, a normal local temperature increase during operation of the charging device can advantageously be taken into account. The comparison can be formed, for example, by simply subtracting the respectively recorded individual value and the reference value. If such a subtraction results in a value that exceeds a permissible deviation or is greater than a permissible difference, the readout unit or readout circuit can, for example, trigger a switching element and thus interrupt the reception of the charging current.

The invention also includes embodiments which result in additional advantages.

One embodiment provides that the readout unit is designed to read a current To assign charging current strength according to a predetermined assignment function to a respective maximum temperature value and to interrupt the reception of the charging current as a function of the maximum temperature value and the temperature distribution. The maximum temperature value is used to distinguish whether a hot spot identified on the basis of the individual values could have been caused by the magnetic field of the current charging current at all. Depending on the design, different magnetic flux densities are to be expected along the cover. If there is a metallic or otherwise electrically conductive object in the area of the cover, an eddy current is induced in the object by the alternating magnetic field, the strength of which depends on the magnetic flux density at the respective location or position of the cover where the object is located. depends. In other words, the object is heated to different degrees at different points on the cover. The maximum achievable temperature values therefore differ along the cover. The mentioned assignment function advantageously takes this relationship into account. A certain charging current intensity can be assigned to a maximum possible temperature value at a respective point of the cover by means of the assignment function. This advantageously avoids false triggering. If, for example, the permissible deviation between the temperature distribution and the reference temperature distribution is exceeded at a certain point on the cover due to partial heating, for example due to shaded solar radiation, this exceeding advantageously does not lead to an interruption of the reception of the charging current and thus not to a shutdown of the charging device if the current charging current is too low to be able to be based on the detected heat development at this point. This is recognized by comparing the individual values with the maximum temperature value.

A further embodiment provides that the cover has a plurality of mutually adjoining subsections or regions or zones, the deviation permissible within a respective subsection varying as a function of the position of the respective subsection along the cover. This embodiment is based on the consideration that when a charging device of the type described at the outset is in operation, due to a spatial distribution of magnetic flux densities, anticipated or normal local heating can occur. Such normal local heating should not lead to an interruption of the charging current. Therefore, in the embodiment described here, the permissible deviation is advantageously increased within areas or subsections of the cover that are known to heat up during normal operation. In other words, the tolerance defined by a respective permissible deviation is variable along the cover.

Another embodiment provides that a respective temperature sensor is designed as a temperature-sensitive electrical resistor and is connected to the read-out unit in an electrically conductive manner. A temperature-sensitive electrical resistor can be designed, for example, as a thermistor or a PTC thermistor. NTC thermistors are special electrical resistors that conduct electricity better at high temperatures than at low temperatures. NTC thermistors are also known under the English name "negative temperature coefficient thermistors (NTC)". PTC thermistors, on the other hand, conduct better at lower temperatures than at higher temperatures. PTC thermistors are also known as “positive temperature coefficient thermistors (PTC)”. Such an NTC resistor or PTC resistor can, for example, be calibrated during production so that a predetermined electrical resistance of the component (NTC or PTC) of, for example, 10 kOhm at 25 ° C. is set. According to the embodiment described here, the readout unit is designed to detect a change in an electrical conductivity of the respective electrical resistance as an individual value. The respective electrical resistance in an NTC or PTC is not measured directly, but rather derived from a current intensity or electrical voltage tapped at the respective NTC or PTC. Thus, by means of the electrical resistances, both an absolute temperature (if calibration has taken place) or a temperature change that has taken place compared to an initial value, for example within a predetermined time interval, can be recorded. If, for example, a change in temperature compared to an initial value is detected which comprises 5 percent within 2 minutes, this can be recognized by the readout unit as the permissible deviation being exceeded. This advantageously enables a particularly rapid diagnosis of an undesired temperature development. The NTCs or PTCs result in a cost-effective implementation option for the temperature sensors described.

Another embodiment provides that at least some of the temperature sensors are arranged at regular intervals along the cover, the cover having a location-dependent thermal conductivity distribution and the regular intervals corresponding to an inverse function of the thermal conductivity distribution. In other words, at least some of the temperature sensors are dependent on a respective thermal conductivity of the Covering material arranged spaced from each other. The temperature sensors are preferably arranged closer to one another, the lower the thermal conductivity of the cover material. Conversely, the greater the thermal conductivity of the material of the cover, the further away the temperature sensors are from one another. In other words, a smaller thermal conductivity means a higher number of temperature sensors per section of the cover and a higher thermal conductivity means a smaller number of temperature sensors per section. In this way, a number of temperature sensors and a geometric arrangement of the temperature sensors can advantageously be matched to a respective thermal conductivity distribution along the cover.

Another embodiment provides, with the same advantage, that the temperature sensors are arranged exclusively in those subsections of the cover which cover the charging coil and ferromagnetic guide cores of the charging device.

The temperature sensors are preferably arranged on a flexible printed circuit board or a flexible conductor grid or a circuit board. The circuit board can preferably be thermally coupled to the cover by means of a thermal paste. The electrical conductors which are led from the temperature sensors to the readout unit are preferably arranged in such a way that the conductors come to lie on top of one another. The conductors can also be arranged as a “twisted pair”. In both designs, the conductors advantageously do not offer any area for the magnetic field lines to flow through.

A preferred embodiment of the loading device provides that the loading device comprises a lifting mechanism for raising and lowering the loading device. The lifting mechanism can for example be designed as a hydraulic lifting platform. The lifting mechanism is preferably set up to reduce a region of the outer region penetrated by the alternating magnetic field by means of the lifting. The area described lies between the loading device and a horizontal reference plane which is provided for the arrangement of the receiving device. In the example of an at least partially electrically driven motor vehicle, the electrical energy store of which is to be charged inductively by means of the charging device, the area is thus between a surface of the cover and an underbody of the motor vehicle. If the loading device is now raised by means of the lifting mechanism, the area or the air gap between the loading device and the underbody of the motor vehicle is reduced and an area with a higher magnetic flux density is cut from the reference plane. In other words, by lifting the charging device relative to the charging device, a secondary coil of a respective receiving device is moved into an area with a greater magnetic flux density. Conversely, the lifting mechanism is designed to enlarge the area mentioned by means of the lowering and thus to reduce the magnetic flux density in the area of the reference plane. The primary coil and the secondary coil are therefore moved relative to one another by the lifting mechanism. The transmitted power can advantageously be varied in this way.

The read-out unit preferably has a low-pass filter for filtering out a frequency of the charging current from a respective sensor signal of the temperature sensors. The frequency of the charging current is preferably between 50 and 110 kHz, in particular 90 kHz. A respective sensor signal of a temperature sensor, on the other hand, preferably has a frequency between 5 and 20 kHz, in particular 10 kHz. The low-pass filter advantageously makes it possible for the read-out unit not to be provided with sensor signals that are falsified by a respective energy transfer frequency of the charging current itself.

The invention also relates to a method for operating a charging device, having at least one charging coil and a cover delimiting the charging coil from an outside area, the charging device inductively transmitting electrical energy from an electrical energy source to a receiving device. The charging coil or primary coil receives a charging current in order to transmit the energy from the energy source, whereby an alternating magnetic field is generated which penetrates the outer area at least in certain areas. A plurality of temperature sensors thermally coupled to the cover are provided on a surface of the cover facing away from the outer region. A readout unit or trigger circuit reads out a single value from the temperature sensors, forms a surface temperature distribution along the cover based on the individual values, compares the temperature distribution with a reference temperature distribution and interrupts the reception of the charging current if a permissible deviation of the temperature distribution from the reference temperature distribution is exceeded.

The invention also includes further developments of the method according to the invention which have features as they have already been described in connection with the further developments of the charging device according to the invention. For this reason, the corresponding training courses for method according to the invention is not described again here.

The invention also includes the combinations of the features of the described embodiments.

• 1 eine schematische seitliche Schnittansicht einer Ladevorrichtung und eines Kraftfahrzeugs;
• 2 eine schematische Darstellung von einer Temperaturverteilung in Abhängigkeit von einer Position eines Körpers oberhalb der Abdeckung, Referenztemperaturverteilung und zulässiger Abweichung;
• 3 eine schematische Darstellung einer möglichen Anordnung von T em peratursensoren;
• 4 eine schematische Darstellung des erfindungsgemäßen Verfahrens.

Exemplary embodiments of the invention are described below. This shows:

• 1 a schematic side sectional view of a charging device and a motor vehicle;
• 2 a schematic representation of a temperature distribution as a function of a position of a body above the cover, reference temperature distribution and permissible deviation;
• 3rd a schematic representation of a possible arrangement of temperature sensors;
• 4th a schematic representation of the method according to the invention.

The exemplary embodiments explained below are preferred embodiments of the invention. In the exemplary embodiments, the described components of the embodiments each represent individual features of the invention which are to be considered independently of one another and which also further develop the invention in each case independently of one another. Therefore, the disclosure is also intended to include combinations of the features of the embodiments other than those illustrated. Furthermore, the described embodiments can also be supplemented by further features of the invention already described.

In the figures, the same reference symbols denote functionally identical elements.

1 shows a schematic side sectional view of a loading device 10 with a charging coil 12th and one the charging coil 12th covering cover 14th . The loading device 10 is in the in 1 described embodiment as an inductive charging device 10 for inductively transmitting electrical energy from an electrical energy source to a receiving device 16 formed, the receiving device 16 in the in 1 The embodiment shown is a device for electrically charging an electrical energy store of an at least partially driven motor vehicle 18th is. The receiving device 16 accordingly has a further coil or secondary coil, which for the sake of clarity is shown in FIG 1 is not shown. The charging coil 12th or primary coil of the charger 10 is designed to provide a charging current 20th to receive from the energy source. The charging current flows through 20th the charging coil 12th so becomes an alternating magnetic field 22nd generated. The alternating magnetic field 22nd is in the 1 indicated by dashed magnetic field lines. The alternating magnetic field 22nd is made by means of ferromagnetic guide cores 24 guided. On the cover 14th or on one of an outdoor area 26th facing away from the surface of the cover 14th are several temperature sensors 28 arranged. In addition, the 1 on the cover 14th a readout unit 30th arranged. The readout unit 30th and the temperature sensors 28 are connected to one another in an electrically conductive manner. The readout unit 30th is in 1 only as an example directly on the cover 14th arranged, but can also be done elsewhere in the area of the loading device 10 be arranged. The 1 also shows a lifting mechanism 32 , by means of which the loading device 10 can be raised and lowered.

If there is a metallic or otherwise electrically conductive object during the charging process 34 in the outside area 26th which of the magnetic field lines of the alternating magnetic field 22nd is flowed through, so is in the object 34 an eddy current is induced. This eddy current leads to heating of the object 34 . This heating can be so strong, in particular several 100 ° C, that it spontaneously ignites or self-ignites of the object 34 can come. The heating of the object 34 is dependent on a thermal conductivity of the cover 14th thermally to the temperature sensors 28 directed. The temperature sensors 28 , which are preferably designed as temperature-sensitive electrical resistors, are now from the readout unit 30th individually read out so that the readout unit 30th a single value from each temperature sensor 28 is present. Reading out the temperature sensors 28 can take place at the same time, but it can also be provided that rows and / or columns (according to 3rd ) on temperature sensors 28 are read out one after the other.

2 shows now with reference to those in connection with 1 designated and described components exemplarily a course of a by the readout unit 30th formed surface temperature distribution 36 along the cover 14th . The readout unit 30th can the temperature distribution formed 36 with a reference temperature distribution 38 to compare. If a permissible deviation is exceeded 40 which along the cover 14th can vary, the readout unit 30th the receipt of the charging current 20th interrupt. In the in 2 The diagram shown exceeds the temperature distribution 36 in the area of the object 34 at point X1 of the cover 14th the permissible deviation 40 by an amount ΔT. In the in 2 The illustrated embodiment would therefore be an interruption in the reception of the charging current 20th through the readout unit 30th respectively. This would make the to the heating of the object 34 leading eddy currents are canceled and the heating is advantageously halted. In addition, the object 34 on the cover 14th exactly, namely at point X1.

3rd shows with reference to the in connection with the 1 and 2 designated and described components a schematic representation of a possible arrangement of temperature sensors 28 on an underside of the cover 14th . The distribution of the temperature sensors 28 this is followed by a heat distribution of the cover 14th inverse distribution function. In the 3rd Cover shown 14th has a homogeneous heat distribution along its entire surface. Hence the temperature sensors 28 in the in 3rd shown embodiment each at equal distances from one another or equidistant or arranged in a grid.

4th shows a schematic representation of a preferred embodiment of the method according to the invention. In one process step S1 receives a charging coil 12th a charging current for transmitting electrical energy from an energy source 20th . In one process step S2 becomes an outdoor area 26th at least partially penetrating alternating magnetic field 22nd generated. In one process step S3 will be on one of the outside areas 26th remote surface of a cover 14th a variety of thermal with the cover 14th coupled temperature sensors 28 provided. In one process step S4 reads a readout unit 30th from the temperature sensors 28 each select a single value. In one process step S5 forms the readout unit 30th a flat temperature distribution based on the individual values 36 along the cover 14th and compares the temperature distribution 36 with a reference temperature distribution 38 . In one process step S6 interrupts the readout unit 30th if a permissible deviation is exceeded 40 the temperature distribution 36 from the reference temperature distribution 38 the receipt of the charging current 20th .

Inductive charging systems or charging devices 10 for at least partially electrically driven motor vehicles usually transmit power in the kilowatt range. Due to the limited area that can be used for energy transmission, among other things, the electromagnetic field strengths that occur are relatively high. Are there any foreign bodies or objects 34 , for example metal objects or otherwise electrically conductive objects in an electromagnetic or magnetic alternating field 22nd , they can get very hot. Through the invention, any damage that may arise to the charging system, the motor vehicle and / or the environment can be avoided. In addition, the risk of burns from larger metal objects that only cool down slowly after a charging process can be reduced.

All inductive charging systems for motor vehicles require due to the problem described a metal object recognition, the electromagnetic field 22nd switches off or a charging current 20th interrupts as soon as there is a metal object in it.

Known metal object detection measures are complex since, disadvantageously, depending on the structure of the inductive charging system, relatively small metal parts such as paper clips or staples should be reliably detected. Metal objects can not only be directly on the surface of the charging system or the cover 14th , but also at a certain height (e.g. standing yoghurt pot). This makes recognition difficult. Metal objects not only have to be detected when they are inactive, but also during the charging process. The electromagnetic field 22nd the energy transfer usually has a negative impact on metal object detection. The motor vehicle itself, which represents a very inhomogeneous, metallic mass, is located in the immediate vicinity, not always directly above the charging plate or the charging device 10 is placed and can also change over the service life. If several vehicle types can be charged with one loading plate, this problem is exacerbated. Sensors for temperature detection on such a motor vehicle, such as, for example, infrared sensors, become heavily soiled during operation of the motor vehicle and thus become unusable. The environmental conditions under a motor vehicle are therefore an additional challenge for metal object detection, especially for long-term stability. This includes weather influences, different surfaces, dirt and driving over the base plate or cover 14th .

The many requirements disadvantageously usually lead to very complex and expensive systems. In addition, there is often a conflict between the reliable detection of problematic metal objects and the availability of the charging system.

So far, the transmitted power has been monitored as a simple way of detecting metal objects within the inductive charging system. Metal objects lead to higher electrical losses, which can basically be detected. However, since the power to be transmitted is relatively high, this method can only detect larger metal parts, which is not sufficient as a single measure.

Systems that use an array of coils on the loading plate for metal object detection offer good selectivity. Some of the coils are fed with high-frequency signals, while others are used as receiving coils. The electromagnetic field used usually works with a different frequency than the field for energy transmission and, above all, is not as energetic. If there is a metal object in the area above the loading plate on the bottom, the electromagnetic field is distorted, which can be detected via the receiving coils.

The major disadvantage of the systems mentioned for metal object recognition is their complexity. Detecting small metal objects requires a lot of effort. In addition, manufacturing tolerances and aging effects have a very negative effect due to the sensitivity.

There are other possible solutions, but what they all have in common is that they are either very complex and therefore expensive, cannot easily be used in the area under a vehicle, or are not sufficiently sensitive.

In a specific embodiment, the invention therefore provides directly under the cover 14th the bottom transmitter coil or charging coil 12th an array or grid of temperature sensors 28 to attach. In this way, heat sources can be identified quickly and robustly, as there is only a selective change in temperature or deviation 40 versus a reference temperature or reference temperature distribution 38 must be determined. The charging system or device 10 or a readout unit 30th can then start the charging process or receive the charging current 20th interrupt.

The system can also be used to determine the surface temperature of the charging system in error-free operation. This ensures that there are no impermissible contact temperatures.

The invention relates above all, but not exclusively, to inductive charging systems that work with an elevation of the base plate and a small distance between the base and receiving coil.

In connection with the invention, it is extremely advantageous that the undesired event, namely the development of heat, is recognized directly and not a possibly completely unproblematic change in the electromagnetic properties of the environment.

Reading out the temperature sensors 28 For example, when using NTC resistors, it is much easier and cheaper than the other previously known systems for metal object detection.

By using a resistor array, local heat developments can be seen very well. The system is hardly dependent on the current temperature of the overall system. Even normal, local temperature increases, as they occur with inductive charging systems, do not have a negative effect on the system, as the array of temperature sensors 28 can be built up in a sufficiently fine-grained manner.

In a further specific embodiment, an array of temperature sensors is provided on a loading plate on the bottom to detect local heat development 28 necessary. The exact number depends on the charging system. The system of temperature sensors 28 can be constructed in different ways, from a financial point of view, NTC resistors and a flexible circuit board or a conductor grid are ideal. These elements are extremely cheap to procure. Since, according to the specific embodiment, only changes in temperature are relevant, cheaper NTC resistors and the evaluation circuit or readout unit can also be used 30th just has to be relatively accurate.

The integration of the NTC array into an inductive charging system is possible without any mechanical problems. The use of a flexible printed circuit board causes deformations caused, for example, by driving over with the motor vehicle 18th do not have a negative impact on the system. Manufacturing tolerances are also less relevant. A certain amount of filtering in the range of the frequency that is used for energy transmission is preferably provided electrically. Since the temperature sensors are read out relatively slowly, such filtering is not a major challenge. The thermal conductivity of the top protective layer or cover 14th an inductive charging system is sufficient to quickly and selectively detect temperature increases. If necessary, the thermal connection or coupling can also be optimized. For example, by using a thermally conductive medium between the NTC resistor and the top cover of the base plate or by equipping the NTC resistors on the downward-facing side of the flexible circuit board and connecting it flatly to the cover 14th the base plate.

By raising the transmitter coil or charging coil 12th The lifting mechanism 32 ensures that there are no metal objects in the space but very far away from the transmitter coil (for example a yogurt cup). The distance between the transmitter and receiver coil and the surrounding material is preferably chosen so that Damage caused by the development of heat can be avoided. These points can advantageously be determined on a project-specific basis.

Overall, the examples show how the invention can reliably detect undesired heat development in the area of an inductive charging device.

QUOTES INCLUDED IN THE DESCRIPTION

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

Patent literature cited

• DE 102016002171 A1 [0004]
• DE 102014223623 A1 [0005]
• DE 102012010848 A1 [0005]

Claims (10)

Charging device (10) for inductively transmitting electrical energy from an electrical energy source to a receiving device (16), the charging device (10) having at least one charging coil (12) and a cover (14) delimiting the charging coil (12) from an outer area (26) ), wherein the charging coil (12) is set up to receive a charging current (20) in order to transmit the energy from the energy source, whereby an alternating magnetic field (22) penetrating at least regionally the outer region (26) is generated, characterized in that a plurality of temperature sensors (28) thermally coupled to the cover (14) is arranged on a surface of the cover (14) facing away from the outer region (26), a read-out unit (30) being designed to select from the temperature sensors (28) in each case read out an individual value, based on the individual values, to form a surface temperature distribution (36) along the cover (14), the tempera to compare tur distribution (36) with a reference temperature distribution (38) and to interrupt the reception of the charging current (20) when a permissible deviation (40) of the temperature distribution (36) from the reference temperature distribution (38) is exceeded. Loading device (10) after Claim 1 , wherein the read-out unit (30) is designed to assign a respective maximum temperature value to a current charging current intensity according to a predetermined assignment function and to interrupt the reception of the charging current (20) as a function of the maximum temperature value and the temperature distribution (36). Charging device (10) according to one of the preceding claims, wherein the cover (14) has a plurality of mutually adjoining subsections, the deviation (40) permissible within a respective subsection varying as a function of the position of the respective subsection along the cover (14) . Charging device (10) according to one of the preceding claims, wherein a respective temperature sensor (28) is designed as a temperature-sensitive electrical resistor and is electrically conductively connected to the readout unit (30), the readout unit (30) being designed to detect a change in electrical conductivity of the respective resistance as a single value. Charging device (10) according to one of the preceding claims, wherein at least some of the temperature sensors (28) are arranged at regular intervals along the cover (14) at regular intervals, the cover (14) having a location-dependent thermal conductivity distribution and the regular intervals having an inverse function correspond to the thermal conductivity distribution. Charging device (10) according to one of the preceding claims, wherein the temperature sensors (28) are arranged exclusively in those subsections of the cover (14) which cover the charging coil (12) and ferromagnetic guide cores (24) of the charging device (10). Charging device (10) according to one of the preceding claims, wherein the temperature sensors (28) are arranged on a flexible printed circuit board or a flexible conductor grid. Loading device (10) according to one of the preceding claims, comprising a lifting mechanism (32) for lifting and lowering the loading device (10), wherein the lifting mechanism (32) is designed to use the lifting to create a region of the To reduce the outer area (26), the area between the charging device (10) and a horizontal reference plane, which is provided for the arrangement of the receiving device (16), is arranged, whereby a magnetic flux density increases in the area, and the area by means of the Lowering to increase, whereby the magnetic flux density in the area decreases. Charging device (10) according to one of the preceding claims, wherein the read-out unit (30) has a low-pass filter for filtering out a frequency of the charging current (20) from a respective sensor signal of the temperature sensors (28). Method for operating a charging device (10) according to one of the preceding claims, comprising at least one charging coil (12) and a cover (14) delimiting the charging coil (12) from an outer region (26), the charging device (10) having an electrical energy of inductively transmits an electrical energy source to a receiving device (16), the charging coil (12) receiving a charging current (20) for transmitting the energy from the energy source, whereby an alternating magnetic field (22) penetrating at least in certain areas of the outer area (26) is generated, and a plurality of temperature sensors (28) thermally coupled to the cover (14) being provided on a surface of the cover (14) facing away from the outer region (26), a readout unit (30) each having a single value from the temperature sensors (28) reads out, based on the individual values, forms a surface temperature distribution (36) along the cover (14), the temperature curve division (36) with a reference temperature distribution (38) compares and at Exceeding a permissible deviation (40) of the temperature distribution (36) from the reference temperature distribution (38) interrupts the reception of the charging current (20).

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