Inductive charging device for an electrically powered motor vehicle and operating procedure for the charging device

Abstract

Inductive charging device (10) for an electrically powered motor vehicle, comprising - a ground unit (11) for placement in a ground (12) and for generating an alternating magnetic field for inductive charging operation, wherein: - along an edge (21) of the ground unit (11) distance sensors (19) are arranged for the respective detection of a distance to at least one object arranged above the ground and - a weight sensor arrangement (20) is provided for detecting a weight force acting on the ground unit (11) and - a control unit (15) for object monitoring is set up to activate the charging operation depending on a respective distance (17) signaled by the distance sensors (19) and depending on a weight signal (18) from the weight sensor arrangement (20), wherein the control unit (15) is configured, when a receiving unit of the motor vehicle is in the charging position (S11), to define the distances signaled by the distance sensors (19) as the respective reference distances (S10) and to generate an enable signal (16) to activate the charging operation, as long as each of the distance sensors (19) signals a distance (17) that corresponds to the respective reference distance, wherein the control unit (15) is configured so that if such an object is detected, the release signal (16) is interrupted or not generated.

Description

[0001] The invention relates to an inductive charging device for an electrically powered motor vehicle. The charging device has a base unit in which the primary coil for generating the magnetic field for inductive charging can be provided. The base unit can be embedded, for example, in a garage floor or in a street. The invention also includes an operating method for the inductive charging device.

[0002] An inductive charging device enables wireless charging of an electric traction battery in an electrically powered vehicle. Energy is transferred inductively, with a stationary ground unit on the ground interacting with a mobile unit on the vehicle. Since very high power can be transferred between the two units, a control unit must ensure safe shutdown in the event of penetration by, for example, living beings or electrically conductive objects. This is even more important if the charging process is to be automated.

[0003] An inductive charging device is known from DE 11 2012 006 354 T5.

[0004] DE 10 2009 012 317 A1 discloses a capacitive sensor comprising layers of protective panels and conductive panels arranged alternately in such a way that applying a weight force to the arrangement compresses the protective panels, thereby reducing the distance between the conductive panels, which leads to a change in the electrical capacitance of the arrangement. This change is detected by a control unit and used to determine a weight force value.

[0005] DE 601 12 595 T2 discloses a weight sensor that is arranged in the seat frame of a vehicle seat. The weight sensor can detect the weight force acting on the seat surface of the vehicle seat.

[0006] DE 10 2014 202 405 A1 discloses a method for detecting a foreign body in the area of ​​a primary coil of an inductive coupling system. The method comprises the following steps: determining a force acting due to weight in the area of ​​the primary coil, classifying the force, and detecting the foreign body based on the class.

[0007] DE 10 2012 105 615 A1 discloses a device for contactless energy transmission comprising a primary coil arrangement and a secondary coil arrangement that can be inductively coupled thereto. At least one detection device is assigned to the primary coil arrangement and / or the secondary coil arrangement, with which a gap between the primary coil arrangement and the secondary coil arrangement can be monitored. The at least one detection device has at least one sensor with which foreign bodies can be directly detected. For example, a foreign body can be detected by ultrasonic sensors, radar sensors, infrared sensors, or optical sensors if it is located in the beam path of the respective sensor.

[0008] DE 10 2012 015 262 A1 discloses a method for positioning a motor vehicle relative to a primary element of a charging device arranged on the side of a roadway of the motor vehicle for contactless charging of an electrical storage device of the motor vehicle. Reaching of the charging position by the secondary element is determined by means of at least one sensor and at least one positioning element having at least two different markings, by detecting the markings with the sensor. For example, one of the markings is raised relative to the other marking, and the sensor is used as a distance sensor.

[0009] DE 10 2009 033 236 A1 discloses a device for the inductive transmission of electrical energy from a stationary unit having at least one primary inductance to a vehicle parked adjacent thereto having at least one secondary inductance. The stationary unit or the vehicle has a device for detecting the presence of an object within a predetermined space, which includes at least the space between the primary inductance and the secondary inductance during the energy transmission. The sensor can be an ultrasonic, radar, or infrared sensor, or an electronic image sensor.

[0010] From CN 1 03 336 268 A a device is known for charging position alignment during inductive charging of a vehicle battery, which uses an ultrasonic sensor.

[0011] The invention is based on the object of monitoring the air gap or intermediate area between a base unit of an inductive charging device and a vehicle-side receiving unit for inductive charging operation to determine whether there is an object therein and whether charging operation must therefore be blocked.

[0012] The problem is solved by the subject matter of the independent patent claims. Advantageous developments of the invention are described by the dependent patent claims, the following description, and the figures.

[0013] The invention provides an inductive charging device for an electrically powered motor vehicle. The inductive charging device provides the primary side for an inductive charging process or inductive charging operation. In other words, the charging device has a base unit for placement in a floor. The base unit is designed to generate an alternating magnetic field for inductive charging operation. In other words, the base unit can have the so-called electrical primary coil for the inductive transmission of energy. The base unit can, for example, be integrated or embedded in a garage floor or the floor of a parking lot.

[0014] In order to ensure that no object is located between the ground unit and the motor vehicle during charging operation when charging is started automatically and / or during charging operation, the following features are provided. Distance sensors are arranged along an edge of the ground unit and are designed to detect a distance to at least one object arranged above the ground. Each distance sensor can therefore generate a sensor signal which is dependent on a distance of the object from the respective distance sensor. The distance sensors can be arranged along the edge still within the ground unit or can surround or encircle the ground unit on the outside. Furthermore, a weight sensor arrangement is provided which is designed to detect a force acting on the ground unit, namely the weight of an object standing on the ground unit or moving over the ground unit.The inductive charging device can therefore measure the distance of an object along the edge of the ground unit, as well as measure its weight or detect the weight force acting on the ground unit. A control unit of the charging device is configured to enable the charging operation of the charging device, i.e., the generation of the alternating magnetic field, depending on a respective distance signaled by the distance sensors and depending on a weight signal from the weight sensor arrangement. In other words, the control unit receives a respective distance from the distance sensors or a distance signal describing the distance, and a weight signal from the weight sensor arrangement that characterizes the weight force acting on the ground unit.The control unit only enables charging if the distances and the weight force meet a predetermined enabling condition.

[0015] The invention offers the advantage that a combination of distance measurement and weight measurement enables monitoring of the gap between the ground unit on the ground and the receiving unit on the vehicle. This allows the presence of such objects, such as animals, to be detected even if they can no longer be detected by one of the two sensor systems (distance sensors and weight sensor array) alone.

[0016] The invention also includes further developments which result in additional advantages.

[0017] A further development provides for the distance sensors to each comprise an ultrasonic sensor and / or a radar sensor and / or a combination of a light source and a photosensor / light sensor. An ultrasonic sensor has a detection range in an angular interval of 45° to 20° measured along a central axis. An ultrasonic sensor therefore has the advantage of scanning a relatively wide area. This allows the edge of the ground unit to be scanned completely or almost completely. This allows even narrow objects, such as a hand, to be reliably detected. A so-called short-range radar sensor (SSR) can be selected as the radar sensor. This allows the relatively short distance between the ground unit and the vehicle underbody to be scanned or monitored using a radar sensor. A short-range radar also has a relatively wide beam angle.This can be within a range of 50° to 70° in one axial direction and within a range of 5° to 20° in the axial direction perpendicular to it. Using the aforementioned combination of light source and photosensor, a light barrier grid can be created along the edge of the base unit, thus implementing a type of light barrier known as a reflex light sensor. This can trigger a switching operation if the light barrier grid is crossed by an object.

[0018] A further development provides that the weight sensor arrangement comprises at least one capacitive sensor arrangement and / or at least one pressure sensor and / or at least one force sensor. The capacitive sensor arrangement can be formed in the manner described from a layer arrangement comprising two layers, each with at least one electrically conductive element, and an elastic intermediate layer. By applying a force to the layer arrangement perpendicular to its layer plane, the elastic intermediate layer is compressed, thereby reducing the distance between the electrically conductive elements of the two surrounding layers, which leads to a change in capacitance depending on the magnitude of the force.Using a pressure sensor and / or a force sensor, it is possible to monitor the entire surface of the floor unit for an acting weight force, while providing a weight sensor arrangement whose surface or sensor area is smaller than the surface of the floor unit itself. Such a pressure sensor and / or a force sensor can be formed on the basis of an electrical circuit with strain gauges.

[0019] In order to be able to use a weight sensor arrangement whose sensor area or sensitive area is smaller than the total area of ​​the floor unit, the floor unit has a hinge and / or a rail system, each of which is designed to movably mount the floor unit relative to a floor area adjacent to the floor unit. This allows the floor unit to be subjected to a weight force at any contact point, resulting in a movement of the entire floor unit. This allows the weight force to be redirected from the contact point via the floor unit to the weight sensor arrangement.

[0020] Preferably, at least one spacer is provided which is configured to absorb a predetermined portion of the weight force instead of the weight sensor arrangement in the event that the weight force acting on the floor unit is greater than a predetermined maximum value. In other words, the floor unit rests on the spacer if the weight force exceeds or is greater than the maximum value. This results in the advantage that the weight sensor arrangement is protected against damage such as can be caused by a weight force greater than the maximum value. The at least one spacer can comprise or provide at least one stop bolt and / or at least one spring and / or at least one support element, for example a cube or block.A stop bolt and a support element each have the advantage of blocking or preventing further movement of the base unit as the weight force increases. A spring, on the other hand, has the advantage that further deflection of the base unit is possible with increasing weight force, even after the maximum force has been exceeded. This allows the weight sensor arrangement to continue to quantify the weight force, i.e., its value can be determined, as long as the spring is not fully compressed.

[0021] In order to enable or control charging operation by means of the charging device, the invention provides a method for operating the inductive charging device.

[0022] The control unit of the loading device assumes a free state in which it is assumed that the ground unit is free of any object. Such a free state can be managed using an object marker. It is then detected that all distance sensors along the edge of the ground unit signal a distance less than a predetermined distance threshold. This means that there is an object above the ground unit that is at least as large as the ground unit itself, as it extends into the detection range of all distance sensors along the edge. If the distance is detected as less than the distance threshold for all distance sensors, it is verified or detected in this case that the weight sensor arrangement has been signaling a weight value less than a predetermined weight threshold since the free state.In other words, it is verified that the object is located above the ground unit, but not resting on the ground unit. This is the typical situation that arises when a vehicle underbody is arranged or parked above the ground unit for charging, but no wheel of the vehicle is still on the ground unit. It can therefore be assumed that a vehicle has positioned itself or has been positioned above the ground unit for charging. In this case, a predetermined positioning routine is triggered by the control unit in order to position a receiving unit of the vehicle, i.e. the secondary coil for inductive charging, in a predetermined charging position defined with respect to the ground unit. Such a positioning routine is known from the prior art and is not itself part of the method according to the invention. It can, for example,consist of giving a driver of the motor vehicle instructions for driving maneuvers to position the vehicle-side receiving unit relative to the ground unit. It can also be control signals for an autopilot of the motor vehicle. The positioning routine can end with a signal that the charging position has been successfully assumed by the motor vehicle. Once the charging position has been assumed, the distances then signaled by the distance sensors are set as the respective reference distances. In other words, the motor vehicle is now above the ground unit and is ready for inductive charging. The distance sensors now permanently measure a distance less than infinity, since the vehicle underbody is above the ground unit.The resulting reference distances (respective distance between distance sensor and vehicle underbody) can be used to detect an object entering the air gap or space between the floor unit and the vehicle during charging. An enable signal is generated to enable charging, but only as long as each of the distance sensors signals a distance that corresponds at least to the respective reference distance. If a person tries to reach into the said space or an animal runs into the space, the detection range of one of the distance sensors is crossed, causing it to signal a distance smaller than the reference distance. This means that an object entering the space can also be detected during charging. The enable signal is then interrupted or terminated, i.e. charging is blocked or aborted.

[0023] The case distinction described here is multi-stage: Initially, all distance sensors signal a distance smaller than the distance threshold (vehicle parked above the ground unit). A weight value smaller than the predetermined weight threshold is signaled (no tire resting on the ground unit). The distances remain at least as large as the reference distances during charging. In all other cases, charging is blocked; the enable signal is either not generated at all, or it is aborted or interrupted.

[0024] The method, as described, assumes that the said free state has already been detected before the motor vehicle is positioned above the ground unit. In order to detect the free state while no motor vehicle is yet above the ground unit, an object marker is used according to a further development. This object marker is a stored value or parameter value. If no object has been detected on the ground unit, the object marker is deleted, i.e., it has the value 0, for example, or another predetermined signal value. If an object is detected on the ground unit, the object marker is set, i.e., it has a correspondingly predetermined signal value, e.g., 1.The free state is detected by detecting, based on a deleted object marker, that at least one of the distance sensors, but in particular not all of the distance sensors, signals a distance less than a predetermined second distance threshold, and by means of the weight sensor arrangement during and / or after this, a weight value greater than a predetermined increase threshold is detected. This means that a detection range of one or more of the distance sensors is crossed and during and / or after this, an increase in weight is detected. This sequence of events occurs if an object moves through the row or ring of distance sensors onto the ground unit. In this case, the object marker is set. However, the release state is only signaled if the object marker is deleted. A state has therefore now been reached in which the release state is no longer displayed.

[0025] It has previously been assumed that the object marker is cleared at the very beginning. This can be ensured during commissioning of the ground unit, for example, by maintenance personnel who start up the loading device and ensure that there is no object on the ground unit initially.

[0026] If the object marker is set because an object was detected on the ground unit in the manner described, a further development checks when the object leaves the ground unit again. If the object marker is set, it is detected that at least one of the distance sensors signals a distance less than the said second distance threshold, and the weight sensor arrangement detects a weight value less than a predetermined decrease threshold during and / or after this. In this case, the object marker is deleted if the distance sensors subsequently only signal distances greater than the second distance threshold. If, for example, an animal or another object moves down from the ground unit, it crosses the detection range of at least one distance sensor again, and during and / or after this, the weight force acting on the ground unit decreases again.

[0027] The inductive charging device according to the invention is therefore preferably designed to carry out an embodiment of the method according to the invention by means of its control unit.

[0028] Accordingly, the invention also includes further developments of the method according to the invention that have features as described in connection with the further developments of the charging device according to the invention. For this reason, the corresponding further developments of the method according to the invention are not described again here.

[0029] Exemplary embodiments of the invention are described below. Shown are: Fig. 1 a schematic representation of a first embodiment of the charging device according to the invention in a perspective view; Fig. 2 a schematic representation of a base unit of the loading device of Fig. 1 in a plan view; Fig. 3 a schematic representation of a capacitive weight sensor arrangement of the loading device of Fig. 1; Fig. 4 a schematic representation of a second embodiment of the charging device according to the invention; Fig. 5 is a schematic representation of a top view of the loading device of Fig. 4; Fig. 6 a schematic representation of a weight sensor arrangement for pressure and / or force of the loading device of Fig. 4; Fig. 7 is a flowchart of an embodiment of the method according to the invention; Fig. 8 a flow chart of an object monitoring of the process of Fig. 7.

[0030] The exemplary embodiment explained below is a preferred embodiment of the invention. In the exemplary embodiment, the described components of the embodiment each represent individual, independently considered features of the invention, which also further develop the invention independently of one another and are thus also to be considered as components of the invention, either individually or in a combination other than that shown. Furthermore, the described embodiment can also be supplemented by further features of the invention already described.

[0031] In the figures, functionally identical elements are provided with the same reference numerals.

[0032] Fig. 1 shows an inductive charging device 10, which may have a ground unit 11 that may be embedded or sunk into a ground 12, for example, a garage floor or a street. The ground unit 11 may have a primary coil (not shown in detail) for inductive charging operation in order to generate an alternating magnetic field above the ground unit 11, which can generate an electrical voltage in a receiving unit (not shown) of a motor vehicle for charging an electrical accumulator or a traction battery. The primary coil can be supplied with an electrical current via a connecting line 13. The current can be switched by a switching device 14. The switching device 14 can be designed in a manner known from the prior art.However, it can be provided that the switching device 14 only switches on or allows the current in the connecting line 13 to flow if a control unit 15 of the charging device 10 outputs an enabling signal or release signal 16 to the switching device 14.

[0033] The control device 15 can monitor whether an object is located on or above the ground unit 11 that should be absent during charging operation, because it would then be located in the intermediate range in which the power for charging operation is transmitted through the air. If such an object is detected, the enable signal 16 is interrupted or not generated. The switching device 14 thus prevents current from flowing through the connecting line 13. The control unit 15 can generate the enable signal 16 depending on the respective sensor signals from several distance sensors 19 and a weight sensor arrangement 20. Each distance sensor 19 signals a distance 17 using its sensor signal, and the weight sensor arrangement signals a weight value 18 using its sensor signal.

[0034] Fig. Figure 2 illustrates how the distance sensors 19 can be arranged along an edge 21 of the floor unit 11. They thus form a ring or a grid. The respective detection area 22 (see Fig. 1) Each of the distance sensors 19 can be installed in an area above the ground unit 11 in an environment. If an object moves over the edge 21 onto the ground unit 11, it passes through one or more detection zones 22. Such an object could, for example, be an animal walking onto the ground unit. If a motor vehicle is parked above the ground unit 11, the vehicle's underbody is located in the respective detection zone 22 of each of the distance sensors 19.

[0035] Fig. 3 illustrates the weight sensor arrangement 20 in a sectional view through the base unit 11. Fig. 3 illustrates an embodiment as a capacitive weight sensor assembly or capacitive weight sensor.

[0036] Fig. 4 shows an embodiment of the loading device 10 with a base unit 11, in which the weight sensor arrangement 20 can be formed on the basis of several pressure sensors or force sensors. Fig. 5 illustrates a top view of the ground unit 11 with the distance sensors 19 arranged on the edge 21. Fig. 6 illustrates in a view from below the floor unit 11 with the weight sensor arrangement 11 consisting of the plurality of pressure sensors or force sensors.

[0037] Using the ground unit, the charging device can transmit power from the ground unit 11 to a motor vehicle in a contactless and / or wireless manner. The transmitted power can be more than 3 kW, in particular more than 10 kW, so that damage to living tissue (e.g., small animals or body parts) in the area between the ground unit 11 and the motor vehicle should be prevented.

[0038] To achieve this, the charging device 10 is Fig. 1 and Fig. 4, a combination of the weight sensor arrangement 20 and the distance monitoring by means of the distance sensors 19 is provided. The weight sensor arrangement 20 can be according to Fig. 3 may comprise a capacitive measuring unit or a capacitive weight sensor with which the entire floor unit 11 can be monitored to determine the weight force acting from above on the floor unit 11. This has already been described above in connection with the detection of occupants on a vehicle seat in the prior art.

[0039] An advantageous constructive solution is obtained by placing the weight sensor arrangement 20 in such a way that it acts as an intermediate layer, as in Fig. 1, is inserted into the base unit 11 so that one plate is located above and one plate below the weight sensor arrangement 20.

[0040] A structural measure with at least one spacer can be provided to prevent overloading of the weight sensor assembly 20, for example, if a motor vehicle accidentally drives over the floor unit 11. The at least one spacer can be designed as described.

[0041] According to Fig. 4, the weight sensor arrangement 20 for weight monitoring may comprise weight sensors (pressure sensors or force sensors) which may be arranged such that the entire floor unit 11 may be monitored for the weight force acting from above.

[0042] With an advantageous design solution, even fewer than those in Fig. 4 and Fig. 6 can be used by mounting the floor unit 11 with respect to the floor 12, for example on a hinge or in a rail system, so that the entire floor unit is moved regardless of a contact point at which the weight force acts on the floor unit 11, i.e. the weight force is redirected to the weight sensors.

[0043] Even in the embodiment according to Fig. 4, an overload of the weight sensor arrangement 20 can be avoided by means of at least one spacer.

[0044] To prevent non-detection of organic tissue (e.g., a hand or a foot), additional monitoring of the distance between the floor unit 11 and the vehicle underbody or the vehicle floor can be incorporated or provided. At the very least, this prevents a lack of detection in the weight monitoring by means of the weight sensor arrangement 20 from causing a risk to the organic tissue. For this purpose, a ring or "grid" of distance sensors 19 is provided along the edge 21 of the floor unit 11. The distance sensors 19 thus form a ring around the floor unit 21 (arrangement outside at the edge 21, not shown) or along the edge 21 (arrangement inside at the edge 21, shown).

[0045] Each of the distance sensors 19 can be formed on the basis of an ultrasonic sensor, which advantageously signals a local reduction in distance and can thus signal an intrusion into the gap or intermediate area between the ground unit 11 and the motor vehicle. An ultrasonic sensor can be used for distance measurement, which can have a range of 1 cm to 250 cm. The receiving area or detection area 22 can, for example, be conical and have an opening angle in the range of 20° to 45° (measured with respect to the cone axis or vertical axis). While this does not allow for precise location of the object, this is also not necessary for controlling the switching device 14. Only detection is important.Thus, an ultrasonic sensor has the advantage that the area above the ground unit 11 is scanned, and even narrow objects that are narrower than 5 cm, especially narrower than 4 cm, from the perspective of a distance sensor 19 can be detected. For example, a hand can also be recognized or detected. In this case, the number of distance sensors can be reduced, meaning their spacing can remain greater, compared to distance sensors with a narrower detection range.

[0046] A distance sensor 19 can also be implemented based on a radar sensor. A radar sensor can operate according to the Doppler principle and can be used to detect a moving object regardless of its temperature. The advantage of a radar sensor is that it is suitable for so-called invisible installation (e.g., in the ground unit 11), since a radar sensor can transmit light through material. The radar sensor can therefore be concealed by a cover of the charging device 10. For use in the charging device 10, a so-called short-range radar can be used to map the relatively short distances for radar sensors, i.e., distance measurements of less than 250 cm, in particular less than 50 cm. In contrast to long-range radar, a short-range radar also has a relatively wide beam angle. Thus, as with the described ultrasonic sensor, the penetration of an object at the edge 21 can be reliably detected.

[0047] A distance sensor 19 can also be based on a light barrier sensor with a light source and a photosensor. The preferred design of the light barrier sensor for the light grid of the distance sensors 19 is the reflex light sensor type. In this case, the switching process depends on the distance of the object, and no interruption of the light beam between a light source and an oppositely arranged reflector is necessary. This is because the object itself represents the reflector.

[0048] Fig. Figure 7 illustrates a method that can be performed by the control unit 15. The method can be implemented, for example, based on a program code for a microcontroller of the control unit 15.

[0049] After a start step S0, a step S1 can be used to check whether an object flag is set. Setting and deleting the object flag is described below in connection with Fig. 8 explained.

[0050] If the object flag is set (positive results are displayed in Fig. 7 and Fig. 8 generally represented by a "+" sign, negative results with a "-" sign), the charging operation can be interrupted or blocked in a step S3, i.e. by not generating the release signal 16 or by interrupting the release signal 16. If, on the other hand, the object marker is recognized as being deleted in step S1, a check can be made in a step S4 to determine which distance 17 the distance sensors 19 are respectively signaling. If it is recognized in a step S5 that the distance 17 of all distance sensors 19 is smaller than a first distance threshold value, the process can continue in a step S6. Otherwise, the charging operation is blocked in step S3. The distance threshold value can be in a range from 20 cm to 70 cm, in particular in a range from 30 cm to 60 cm, for example 50 cm.

[0051] In step S6, a check can be made to determine whether a weight change has occurred in the weight sensor arrangement 20 during or since the detection of the distance violation in step S5. If the weight value 18 is greater than a predetermined weight threshold (detected in step S7), the charging operation is blocked in step S3. If a weight value 18 less than the weight threshold was detected in step S7, the monitoring of the vehicle position can be initiated in a step S8 so that the motor vehicle is brought into a defined charging position relative to the ground unit 11. If it is detected in a step S9 that the motor vehicle cannot reach the charging position, the charging operation is blocked or aborted in step S3.If the charging position has been detected as reached in step S9, the resulting distance between each distance sensor 19 on the one hand and the vehicle underbody on the other hand can be recorded in a step S10 and stored as a reference distance. In a step S11, the distance signaled by the distance sensors 19 during charging can then be monitored. If the reference distance is undershot, charging is interrupted in step S3. Otherwise, if only distances equal to or greater than the respective reference distance result, charging can be continued or enabled in step S12, i.e., the enable signal 16 can be generated or maintained.

[0052] The steps S0 to S6 represent a preparation 23 for the actual charging operation, while the steps S7 to S12 represent the actual monitoring 24 of the charging operation.

[0053] In summary, the procedure of Fig. 7, therefore, that in the event that no object is located on the ground unit 11, the distance sensors 19 monitor whether the distance between all distance sensors 19 falls below a distance threshold. If this is the case, it can be assumed that the motor vehicle is crossing. As a result, the weight monitoring is activated and monitored for an increase in weight. If no increase above the weight threshold is detected, the monitoring can be checked for the loading position of the motor vehicle. Once the loading position is reached, the charging process can be started.

[0054] Fig. Figure 8 illustrates how the object marker can be managed.

[0055] After a start step S13, the object marker can be reset or deleted in a step S14, for example, set to the value 0. In a step S15, the distance value signaled by the distance sensors 19 can be detected. As long as all distance sensors signal a distance greater than a second distance threshold, steps S15 and S16 can be repeated. If at least one of the distance sensors 19 signals a distance less than the second distance threshold, the weight value or weight force signaled by the weight sensor arrangement 20 can be checked in a step S17.

[0056] If it is detected in step S18 that a weight gain greater than a predetermined gain threshold exists, the distances signaled by the distance sensors 19 can be monitored again in step S19, and in step S20, the object flag can be set as set, for example, to the value 1. The second distance threshold can be 50 cm, for example. The gain threshold can be greater than 200 g, for example.

[0057] In a step S21, it can be checked whether all distances signaled by the distance sensors 19 are greater than the second distance threshold. If this is the case, the system can return to step S19. Otherwise, in a step S22, it can be checked which weight change the weight sensor arrangement 20 is signaling. If it is detected in a step S23 that a weight change to a weight value less than a distance threshold occurs, then in a step S24 it can be monitored again which distance the distance sensors 19 are signaling. The weight reduction can occur, for example, when an animal moves away from the ground unit 11. In this case, it is located for some time within the detection ranges 22 of the distance sensors 19.As long as it is detected in a step S25 that not all distance sensors 19 again signal a distance greater than the second distance threshold value, steps S24 and S25 are preferably repeated.

[0058] If, however, it is detected in step S25 that all distance sensors signal a distance greater than the distance threshold value, the object has obviously left the ground unit 11 and the object marker can be reset or deleted again.

[0059] Thus, the procedure according to Fig. 8 an object monitor that monitors whether an object is located on the ground unit 11 of the loading device 10. This is done by monitoring the distance sensors 19 for a distance 17 less than the second distance threshold, for example, 50 cm. If an object is located or detected by one of the distance sensors 19, the weight sensing of the weight sensor arrangement 20 is activated and a check for an increase in weight is carried out. If the weight increases above a certain amount, defined by the increase threshold, it can be assumed that an object is on the ground unit 11. The object flag then indicates this event. If a reduction in the distance is detected again, the check for leaving the object can be carried out. Leaving is detected if the weight decreases again and the distance is again detected to be greater than the second distance threshold.The object marker is reset or deleted again.

[0060] The object marker influences, as in Fig. 7 illustrates that if an object is detected, the charging process is also stopped, which is then not started.

[0061] Overall, the example shows how the invention can provide a method for monitoring an air gap of an inductive charging unit using a weight measurement and a distance measurement. List of reference symbols 10 Charging device 11 Ground unit 12 Floor 13 Connection cable 14 Switching device 15 Control unit 16 Release signal 17 Distance 18 Weight value 19 distance sensors 20 Weight sensor arrangement 21 edge 22 Detection range 23 Preparation 24-hour surveillance S0-S26 procedural steps

Claims

[1] Inductive charging device (10) for an electrically driven motor vehicle, comprising - a base unit (11) for arranging in a base (12) and for generating an alternating magnetic field for inductive charging, wherein: - distance sensors (19) are arranged along an edge (21) of the floor unit (11) for detecting a distance to at least one object arranged above the floor, and - a weight sensor arrangement (20) is provided for detecting a weight force acting on the floor unit (11) and - a control unit (15) for object monitoring is designed to enable the charging operation depending on a respective distance (17) signalled by the distance sensors (19) and depending on a weight signal (18) of the weight sensor arrangement (20), wherein the control unit (15) is configured to define (S10) the distances then signaled by the distance sensors (19) as respective reference distances when the charging position (S11) of a receiving unit of the motor vehicle is assumed and to generate an enable signal (16) for enabling the charging operation as long as each of the distance sensors (19) signals a distance (17) that corresponds to the respective reference distance, wherein the control unit (15) is arranged so that if such an object is detected, the release signal (16) is interrupted or not generated. [2] Charging device (10) according to claim 1, wherein the distance sensors (19) each comprise an ultrasonic sensor and / or a radar sensor and / or a combination of a light source and a photosensor. [3] Loading device (10) according to one of the preceding claims, wherein the weight sensor arrangement (20) comprises at least one capacitive sensor arrangement and / or at least one pressure sensor and / or at least one force sensor. [4] Loading device (10) according to one of the preceding claims, wherein the floor unit (11) has a hinge and / or a rail system, each of which is designed to support the floor unit (11) movably with respect to a floor area of ​​the floor (12) adjacent to the floor unit (11). [5] Loading device (10) according to one of the preceding claims, wherein at least one spacer is provided which is adapted to absorb a predetermined proportion of the weight force instead of the weight sensor arrangement (20) in the event that the weight force acting on the floor unit (11) is greater than a predetermined maximum value. [6] Loading device (10) according to claim 5, wherein the at least one spacer comprises at least one stop bolt and / or at least one spring and / or at least one support element. [7] Method for operating an inductive charging device (10) according to one of the preceding claims, in order to enable inductive charging operation for a motor vehicle, wherein a control unit (15) for object monitoring of the charging device (10), starting from a free state (S1) in which a base unit (11) of the charging device (10) is free of any object, detects that distance sensors (19) of the charging device (10) arranged along an edge (21) of a base unit (11) of the charging device (10) signal a distance smaller than a predetermined distance threshold value (S5), and in this case it is verified that a weight sensor arrangement (20) of the charging device (10) signals a weight value (18) smaller than a predetermined weight threshold value (S7), and in this case a predetermined positioning routine is triggered (S9) in order to position a receiving unit of the motor vehicle in a predetermined,to position the loading position defined with respect to the ground unit (11), and when the loading position is assumed (S11), the distances then respectively signaled by the distance sensors (19) are defined as respective reference distances (S10) and an enable signal (16) is generated to enable the loading operation as long as each of the distance sensors (19) signals a distance (17) corresponding to the respective reference distance, wherein if an object is detected, the enable signal (16) is interrupted or not generated. [8] Method according to claim 7, wherein in any other case the charging operation is blocked (S3). [9] Method according to claim 7 or 8, wherein the free state is detected by detecting, on the basis of a deleted object marker (S14), that at least one of the distance sensors (19) signals a distance (17) smaller than a predetermined second distance threshold value (S16), and by means of the weight sensor arrangement (20) during and / or after this, a weight value (18) greater than a predetermined increase threshold value is detected (S18) and in this case the object marker is set (S20), wherein the free state is only signaled if the object marker is deleted. [10] Method according to one of claims 7 to 9, wherein, when the object flag is set, it is detected that at least one of the distance sensors (19) signals a distance (17) smaller than the distance threshold value (S21), and by means of the weight sensor arrangement (20) during and / or after this, a weight value (18) smaller than a predetermined decrease threshold value is detected (S23) and the object flag is deleted (S26) if the distance sensors (19) subsequently only signal distances greater than the second distance threshold value (S25).

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