EP4093621A1

EP4093621A1 - Device for coupling a trailer

Info

Publication number: EP4093621A1
Application number: EP20785970.3A
Authority: EP
Inventors: Christian Holz
Original assignee: ACPS Automotive GmbH
Current assignee: ACPS Automotive GmbH
Priority date: 2020-01-21
Filing date: 2020-10-01
Publication date: 2022-11-30
Also published as: US20220396106A1; CN115279602A; EP3854612A1

Abstract

The invention relates to a device, which can be mounted on the rear end of a motor vehicle body, for coupling a trailer or a load carrier unit, comprising a holding arm which, at a first end, is fixedly connected to the motor vehicle body during operation and which, at a second end, is designed to bear a coupling element, wherein the holding arm is equipped with a sensor arrangement with at least three deformation sensors, and wherein the at least three deformation sensors output sensor values from which at least one force component is ascertained by means of an evaluation unit.

Description

DEVICE FOR Hitching up a trailer

The invention relates to a rear-mountable device on a motor vehicle body for coupling a trailer or a load carrier unit, comprising a holding arm which is firmly connected at a first end to the motor vehicle body during operation and is designed to support a coupling element at a second end.

Such devices are known from the prior art.

The problem with these is to detect the forces acting on the holding arm as precisely and reliably as possible.

This object is achieved according to the invention in a device of the type described at the outset in that the holding arm is provided with a sensor arrangement that the holding arm is provided with at least three deformation sensors, which in particular act in different ways on the coupling element in three spatial directions running transversely to one another acting forces react, and that the three deformation sensors deliver sensor values from which at least one force component acting on the coupling element is determined by means of an evaluation unit.

The advantage of the solution according to the invention is to be seen in the fact that a suitable possibility is available to reliably determine the forces on the coupling element and thus also on the holding arm.

It is particularly favorable if the evaluation unit determines the values of its force components running in the spatial directions, so that the information about the alignment and the amounts of the force components is also available in a simple manner. It is particularly advantageous if the evaluation unit determines the value of its force component running in the direction of gravity.

This force component is particularly valuable for the question of how great the vertical load acting on the motor vehicle is, since the vertical load has a lasting effect on the driving characteristics and should not exceed a prescribed value.

In addition, it is advantageous if the evaluation unit determines the value of its force component running in the direction of travel of the motor vehicle.

The value of the force component acting in the direction of travel is also of significant importance for the driving characteristics of the motor vehicle and should therefore be known.

In addition, it is advantageous if the evaluation unit determines the value of its force component running transversely, in particular perpendicular to a vertical longitudinal center plane.

This value of the force component effective transversely to the longitudinal center plane is also important, in particular for driving stability, in particular for the driving stability of the motor vehicle that is necessary transversely to the driving direction.

A wide variety of solutions are conceivable with regard to the effect of the force acting on the coupling element and thus on the holding arm.

For example, it would be conceivable to use the sensor values supplied by the sensor arrangement directly without further correction for this purpose.

However, this leads to significant inaccuracies for a variety of reasons. For this reason, it is preferably provided that the evaluation unit checks, by means of a state detection stage, before determining the force components, whether there is a suitable state for determining the force components on the coupling element.

With this state detection stage, it can therefore be ruled out from the outset that a value is determined for the force components which, due to an unsuitable state of the device or the motor vehicle, can be faulty, in particular in the sense of highly faulty.

Thus, it is preferably provided that the state detection stage checks by detecting at least one of the parameters such as voltage supply, vehicle orientation in space, presence of the working position of the holding arm, whether there is a suitable state for determining the force components on the coupling element.

For example, an impermissible voltage supply has the consequence that the sensor values generated by the sensor arrangement are falsified, so that their evaluation would result in completely incorrect values of the force components.

In addition, the vehicle orientation in space, in particular the orientation such that the vehicle is oriented as standing on an essentially horizontal plane, is important, since otherwise excessive, unrepresentative forces act on the coupling element and the holding arm.

A substantially horizontal alignment of the plane means that the plane may be inclined by a maximum of ± 30 °, even better ± 20 ° and preferably ± 10 ° relative to an exactly horizontal plane in all directions of the plane in order to prevent that the sensor arrangement supplies non-usable sensor values for determining the values of the force components. Furthermore, it is also important that the holding arm is in the working position and not in a position that is inadmissible for an operating state, which would also again provide completely inaccurate values for the force components on the coupling element or the holding arm.

After checking a suitable state for determining the force components on the coupling element, it is preferably advantageous if the evaluation unit uses a zero load detection stage to record the force component values determined on the basis of the sensor values of the deformation sensors in the event of a Zero load takes place.

Such a detection of the values of the force components in the case of a zero load ensures that the values of the force components determined in the case of a load on the coupling element do not have any significant falsification.

Thus, it is preferably provided that after a movement of the holding arm into a working position on the part of the zero load acquisition stage, at least one of the values of the force components is acquired at zero load.

It can thus be ruled out that the zero load detection stage determines the values of the force components even outside the working position, which are therefore not representative for the case of zero load.

In addition, it is preferably provided that after a coupling element has been mounted on the holding arm by the zero load acquisition stage, at least one of the values of the force components is acquired at zero load. In addition, it is particularly advantageous if the values of the force components at zero load are only saved by the zero load detection stage when the values of the force components in the zero load detection stage sign predetermined values excluding an external force on the coupling element.

This check represents a plausibility check to ensure that the values of the force components are in a realistic range and are not falsified by other influences.

In addition, it is preferably provided that when an approach to an object, in particular a trailer or a load carrier, is detected by the zero load detection stage, at least one of the values of the force components is recorded at zero load.

This means that in this case, for example advantageously only in the course of approaching an object which can lead to a force on the coupling element and the holding arm, the values are recorded at zero load in order to obtain values of the force components that are falsified by other circumstances impede.

Finally, it is advantageous if, after recording at least one of the values of the force components at zero load, at least one of the values of the force components at zero load is recorded again after a predetermined period of time, in order to prevent that after too long a period of time after a determination of the values of the force components at zero load, a change in the values of the force components has occurred which would lead to incorrect results.

In addition, a further advantageous solution provides that the evaluation unit by means of a load detection stage to determine at least one of the load-related values of the force components that of the Subtracted the corresponding values of the force components delivered at zero load from the values of the force components delivered at a force on the coupling element.

This advantageously ensures that the values of the force components at zero load do not influence the load-related values of the force components that are caused solely by the object acting on the coupling element, for example the trailer or the load carrier.

When determining the force on the coupling element, tests are also carried out by the load detection stage in order to avoid falsification of the values of the force components.

One advantageous solution provides for a load detection stage to determine at least one of the values of the force components on the coupling element, provided that an on-board function of the motor vehicle is being carried out, so that without an on-board function being carried out, i.e. without an operating state of the motor vehicle, The force on the coupling element is determined, for example when the vehicle is in standby mode or in the switched-off state.

In addition, it is preferably provided that the load detection unit carries out a determination of at least one of the values of the force components on the coupling element, provided that a plug is plugged into a socket assigned to the holding arm.

The fact that a plug is plugged into a socket assigned to the holding arm is evaluated as a signal that a trailer or a load carrier unit is attacking the coupling element and therefore an object is only attacked when the force on the coupling element is determined he follows. Another advantageous solution provides that the load detection stage carries out a determination of at least one of the values of the force components on the coupling element after detecting an object engaging the coupling element.

Such a detection of an object attacking the coupling element can for example be done by a camera system or a sensor unit, for example ultrasonic sensors, with which a rear side of the vehicle is usually monitored, for example when reversing.

Furthermore, it is preferably provided that the load detection stage determines at least one of the values of the force components on the coupling element when the speed of the motor vehicle is less than 5 km per hour, in particular when the vehicle is stationary, in order to ensure that the determined force components on the coupling element are not falsified by dynamic influences but represent the static force acting on the coupling element.

In addition, it is provided in a preferred exemplary embodiment that the evaluation unit transmits at least one value of the load-related force components acting on the coupling element by means of a presentation stage.

This can be done in a wide variety of ways.

For example, one advantageous solution provides that the evaluation unit uses a presentation stage to transmit at least one value of the load-related force component acting in the vertical direction on the coupling element. Furthermore, an advantageous solution provides that the evaluation stage uses a presentation stage to transmit at least one value of the load-related force component acting on the coupling element in the direction of travel and in particular parallel to a vertical longitudinal center plane.

Another advantageous solution provides that the evaluation unit uses the presentation stage to transmit at least one value of the load-related force component acting transversely to a vertical longitudinal center plane of the holding arm and in particular in an approximately horizontal direction.

Such a transmission of the respective values of the force components can take place in the most varied of ways.

One advantageous solution provides for the presentation stage to display the at least one value of the respective force component by means of a presentation unit and, in particular, also to display the measurement accuracy associated with this value.

Another advantageous way of determining the value of the force components provides that the presentation stage qualitatively displays the at least one value of the respective force component by means of the presentation unit in order to give a user of the device according to the invention in a simple manner an impression of how strong the coupling element and the Hold arm loaded with force.

A further advantageous solution provides that the presentation stage uses the presentation unit to display the value of the load-related force component acting on the coupling element in the vertical direction in relation to a predetermined support load for the motor vehicle.

This solution has the particular advantage that the value of the support load, which is particularly important for the driving properties, can be recorded in a simple manner for the user of the vehicle in relation to the permitted support load. Another advantageous solution provides that the presentation stage uses the presentation unit to display the value of the force component acting in the direction of travel in relation to a maximum tensile force, so that the user of the motor vehicle can also easily see the influence of, for example, a trailer or a load carrier on the driving characteristics of the Vehicle to convey.

Another expedient solution provides that the presentation stage transmits at least one of the values of the force components acting on the coupling element to an electronic stabilization system of the motor vehicle.

Another expedient solution provides that the presentation stage transmits at least one of the values of the force components acting on the coupling element to a chassis control of the motor vehicle.

A particularly advantageous solution of the device according to the invention provides that the deformation sensors are arranged relative to the holding arm in such a way that they deliver different sensor values in each of the three transverse spatial directions when a force is applied with an identical amount.

In this case, it is provided in particular that four deformation sensors are arranged on the holding arm, as in the case of a force of the same amount effective in the different spatial directions running transversely to one another deliver different sensor values.

In the solution according to the invention, it is assumed that the values of the force components acting on the coupling element are linked to sensor values by means of transformation coefficients. In particular, it is assumed that the sensor values supplied by the deformation sensors are linked to the force components in the three spatial directions running transversely to one another by means of transformation coefficients of a transformation matrix.

It is advantageously provided that from the coupling element as the center of the space around the coupling element is divided into eight octants defined by the three spatial directions running transversely to each other, that an octant-based transformation matrix is specified in the evaluation circuit for each of the octants, that the evaluation circuit by means of one of the predetermined transformation matrices determines the values of the force components and assigns them to one of the octants and then, on the basis of the octant-based transformation matrix, determines the values for the force components again for the octant taking up the force vector.

With this solution, the possibility was created in a simple way to determine more precise values for the individual force components by means of the octant-based transformation matrices.

In addition, the above-mentioned object is achieved according to the invention by a method for detecting the force on a device that can be mounted on the rear of a motor vehicle body for coupling a trailer or a load carrier unit, comprising a holding arm which is firmly connected to the motor vehicle body at a first end during operation and is designed at a second end for carrying a coupling element, wherein the holding arm is provided with a sensor arrangement, wherein in this method according to the invention the holding arm is provided with at least three deformation sensors, which in particular in different ways in three transverse spatial directions on the coupling element acting forces react, and that the at least three deformation sensors supply sensor values from which at least one force component acting on the coupling element is determined. The advantage of the solution according to the invention is to be seen in the fact that it makes it possible in a simple manner to determine reliable values for the effective force.

It is particularly advantageous if at least one of the values of the force components running in these spatial directions are determined.

It is particularly favorable if at least the value of the force component running in the direction of gravity is determined.

It is also advantageous if at least the value of the force component running in the direction of travel of the motor vehicle is determined.

It is also advantageous if at least the value of the force component running transversely, in particular perpendicular to a vertical longitudinal center plane, is determined.

In order to avoid incorrect determination of the values of the force components on the coupling element, it is preferably provided that, before determining the values of the force components, a check is made as to whether there is a suitable state for determining the force components on the coupling element.

A wide variety of criteria can be used for this purpose.

A favorable solution provides that by detecting at least one of the parameters such as voltage supply, in particular the deformation sensors, vehicle orientation in space, i.e. a vehicle orientation such that it is essentially on a horizontal plane, and the presence of the working position of the holding arm is checked whether there is a suitable state for determining the force component on the coupling element. In order to avoid falsification of the values of the force components, at least one of the values of the force components is advantageously recorded in the case of a zero load before the force components are determined.

It is also advantageous if the values of the force components are recorded at zero load after a movement of the holding arm into a working position, so that it can be avoided that outside the working position the values of the force components are determined which would lead to incorrect results.

In addition, as an alternative or in addition to this, an advantageous solution provides that the values of the force components are recorded at zero load after the coupling element has been installed on the holding arm, provided that the coupling element is not firmly connected to the holding arm in order to also avoid incorrect measurements.

In addition, it is provided that the values of the force components are only saved at zero load if the values fall below specified values that exclude an external force on the coupling element, so that a plausibility check is possible in order to rule out incorrect detection of the zero load.

Another advantageous solution provides for the values of the force components to be recorded at zero load after an approach to an object, in particular a trailer or a load carrier, has been recognized.

Finally, it is preferably provided that, after the values of the force components at zero load have been recorded, the values at zero load are recorded again after a predetermined period of time in order to ensure that the values of the force components recorded once at zero load are not permanently retained and thus erroneous measurements can occur . In order to obtain the most accurate load-related values of the force components, it is preferably provided that, in order to determine at least one of the load-related values of the force components, the corresponding values of the force components supplied at zero load are subtracted from the values of the force components supplied when a force is applied to the coupling element.

The determination of the force on the coupling element can also be carried out in order to avoid incorrect determinations of the force on the coupling element, in particular if it is ensured that the condition of the motor vehicle and the device according to the invention allow the force on the coupling element to be determined as error-free as possible .

For example, it is provided that at least one of the values of the force components on the coupling element is determined if an on-board function of the motor vehicle is being carried out, i.e. the motor vehicle is in an operational state, but not in a standby state or, for example, in a switched off state.

Another advantageous solution provides that at least one of the values of the force components on the coupling element is determined if a plug has been inserted into a socket assigned to the holding arm.

The insertion of the plug into the socket associated with the holding arm can be interpreted as a signal that an object is attacking the holding arm, in particular its coupling element, and thus exerts a force on it.

Another expedient solution provides that at least one of the values of the force components on the coupling element is determined after the detection of an object engaging the coupling element, in particular a trailer or a load carrier. This detection of an object engaging the coupling element can for example take place by means of a camera system or a sensor arrangement, preferably an ultrasonic sensor arrangement, which are usually provided anyway to facilitate reversing with the motor vehicle.

Another useful solution provides that at least one of the values of the force components on the coupling element is determined when the speed of the motor vehicle is less than 5 km per hour, in particular when the motor vehicle is stationary, so that the occurrence of dynamic forces is ruled out can be and can be ensured that only static forces acting on the coupling element are detected.

After determining at least one of the values of the force components, this is transmitted in the most varied of ways.

It is preferably provided that at least one of the values of the force component acting in the vertical direction on the coupling element is transmitted.

It is also advantageous if at least one of the values of the force component acting on the coupling element in the direction of travel and in particular parallel to a vertical longitudinal center plane is transmitted.

Finally, a further expedient solution provides that at least one of the values of a force component acting transversely to a vertical longitudinal center plane of the holding arm, in particular in an approximately horizontal direction, is transmitted.

In addition, the values of the respective force components can be transmitted in the most varied of ways. One possibility provides that at least one of the values of the respective force component and in particular the measurement accuracy associated with this is displayed, that is to say is displayed on a presentation unit, for example a display.

This makes it easier for a user of the motor vehicle to very quickly recognize the quality of the determination of the value of the respective force component and to draw the conclusions required for moving the vehicle from this.

In order to enable a quick evaluation of the values of the force component, one solution in particular provides that at least one of the values of the respective force component is displayed qualitatively in order to enable a quick assessment of the forces acting on the device according to the invention without detailed study.

Another advantageous solution provides that the value of the force component acting on the coupling element in the vertical direction is displayed in relation to a predetermined support load for the respective motor vehicle.

Furthermore, an advantageous solution provides that the value of the force component acting in the direction of travel is displayed in relation to a maximum tensile force in order to also simplify the effect of the forces acting on the vehicle for a user of the vehicle.

Another advantageous solution provides that at least one of the values of the force components acting on the coupling element is transmitted to an electronic stabilization system of the motor vehicle, so that it is possible, in a simple manner, to carry out the electronic stabilization of the vehicle from the trailer or the load carrier acting forces must be taken into account. In addition, an advantageous solution provides that the value of the force components acting on the coupling element is transmitted to a chassis control of the motor vehicle.

In connection with the previous explanation of the individual execution variants of the method according to the invention, the manner in which the values of the force components acting on the coupling element are linked to the sensor values has not been discussed.

An advantageous solution provides that the values of the force components acting on the coupling element are linked to the sensor values by means of transformation coefficients.

Such a link represents a simple mathematical solution that takes the various relationships into account.

In particular, it is provided that the sensor values supplied by the deformation sensors are linked to the values of the force components in the three spatial directions running transversely to one another by means of the transformation coefficients of a transformation matrix.

With regard to the determination of the transformation coefficients of the transformation matrix, no further details have so far been given.

One advantageous solution provides that the transformation coefficients of the transformation matrix are determined as part of a calibration process. Such a calibration process provides, for example, that when a defined force component acts on the coupling element, the sensor values supplied by the deformation sensors are recorded, with different force components on the coupling element being used one after the other to generate different sensor values during the calibration process.

In particular, it is provided that during the calibration process the coupling element is acted upon with a defined force component in one of the three spatial directions running transversely to one another and the sensor values supplied by the deformation sensors are recorded.

In particular, the calibration can be carried out advantageously when each force component acting in one of the three spatial directions has the same amount during the calibration process, with the individual force components acting one after the other on the coupling element in order to obtain the respective sensor values for each of the individual force components.

A particularly simple mathematical model provides that the transformation coefficients are determined assuming a linear link between the values of the force components in the three spatial directions running transversely to one another and the sensor values supplied by the deformation sensors.

As an alternative or in addition to this, however, it is also conceivable to determine the transformation coefficients using other methods, for example using the least squares method.

A particularly simple procedure provides that the spatial directions running transversely to one another run perpendicular to one another. An improved procedure for determining the values of the force components provides that, starting from the coupling element as the center point, the space around the coupling element is divided into eight octants defined by the three spatial directions running transversely to one another Force components are acted on the coupling element which lie within the respective octant, that the sensor values are recorded and that octant-based transformation coefficients are determined for these force components in the respective octant.

However, in order to be able to use the octant-based transformation coefficients, it is preferably provided that one of the transformation matrices, which can be a non-octant-based transformation matrix or one of the octant-based transformation matrices, is used to determine the values of the force components on the coupling element, and which of the Octants are to be assigned to the force components and then a new determination of the values of the force components is carried out with the transformation matrix assigned to this octant.

As an alternative or in addition to the solutions described above, the object is also achieved in accordance with the invention in a device of the type described at the beginning in that, during operation, forces acting on the coupling element and transmitted from the holding arm to the motor vehicle body are detected by an evaluation unit with a sensor arrangement which has at least three deformation sensors and that in particular the at least three deformation sensors of the sensor arrangement are arranged on the same side of a neutral fiber of the holding arm which is not deformed in the event of a bending deformation of the holding arm.

The advantage of the solution according to the invention is that there is thus the possibility of detecting the deformations of the holding arm with the sensor arrangement in a simple manner. In particular, it is advantageous here if all the sensors of the sensor arrangement are arranged on the same side of the neutral fiber of the holding arm which is not deformed when the holding arm is deformed.

The object mentioned at the beginning is also achieved according to the invention in a device of the type described at the outset in that a force detection module is arranged on one side of the holding arm, which comprises a sensor arrangement, which forces acting on the coupling element during operation and transmitted from the holding arm to the motor vehicle body Forces captured.

Such a force detection module represents an advantageous, simple solution for detecting the forces acting on the holding arm.

In particular, it is provided that the sensor arrangement of the force detection module has at least three deformation sensors.

With regard to the arrangement of the motor vehicle module, no further details have so far been given.

Thus, one advantageous solution provides that the force detection module is not arranged in the operating state on any side of the holding arm facing a roadway, that is to say that the force detection module is only arranged on the sides of the holding arm that do not face the roadway, since this prevents that the force acquisition module is damaged by contact of the holding arm with objects arranged on a roadway or on a surface.

It is particularly advantageous if the force detection module is arranged in the operating state on a side of the holding arm facing away from a roadway. Such an arrangement of the force detection module has the advantage that it represents the least damaging side for the force detection module.

In order, on the one hand, to be able to advantageously arrange the deformation sensors and, on the other hand, to be able to advantageously transfer the deformations of the holding arm to the deformation sensors, a further solution to the above-mentioned object preferably provides that the coupling element acting on the coupling element during operation and transmitted from the holding arm to the motor vehicle body Forces are detected by an evaluation unit with a sensor arrangement which has at least three deformation sensors, that the deformation sensors are arranged on at least one deformation transmission element that is connected to the holding arm.

The deformations can be arranged on different deformation transmission elements.

In a further solution to the above-mentioned object, it is particularly favorable if forces acting on the coupling element during operation and transmitted from the holding arm to the motor vehicle body are detected by an evaluation unit with a sensor arrangement which has at least three deformation sensors, and if all deformation sensors of the sensor arrangement are arranged on a common deformation transmission element.

A particularly advantageous detection of the forces acting on the holding arm is particularly possible if each of the at least three deformation sensors detects deformations of different sizes when one and the same force acts on the coupling element, since differently oriented forces acting on the coupling element can act, let separate. With regard to the connection of the deformation transmission element to the holding arm, it is preferably provided that the deformation transmission element is relatively free of movement and thus rigidly connected to the holding arm at at least two fastening areas and that at least one of the deformation sensors is arranged between the fastening areas of the deformation element.

It is even more advantageous if the deformation transmission element is connected to the holding arm with at least three fastening areas and if at least one of the deformation sensors is arranged between two of the fastening areas.

With regard to the connection of the fastening areas of the deformation transmission element to the holding arm, no further details have been given so far.

In principle, it is conceivable to connect the fastening areas directly to the holding arm, for example by welding it to it.

A particularly advantageous solution, however, provides that the deformation transmission element is connected to the holding arm in the fastening areas by means of connecting elements.

Such a connection to the holding arm by means of the connecting elements can be implemented particularly favorably if the connecting elements are rigidly connected to the holding arm on the one hand and rigidly to the fastening areas of the deformation transmission element on the other hand.

A particularly advantageous solution provides that the connecting elements, in particular in one piece, are molded onto the holding arm. When such a connection is provided between the holding arm and the deformation transmission element, it is preferably provided that the connecting elements transmit deformations of the holding arm in deformation regions of the holding arm located between the connecting elements to the fastening regions of the deformation transmission element.

In particular, it is advantageous if there is a deformation area of the holding arm between two connecting elements.

A structurally particularly advantageous solution provides that the holding arm has at least two deformation areas, the deformations of which are transferred to fastening areas of the deformation transfer element via connecting elements arranged on both sides of the respective deformation area, between which a deformation-prone area of the deformation transfer element lies.

With regard to the arrangement of the two deformation areas in the holding arm, it is particularly advantageous if the at least two deformation areas are arranged one after the other in a direction of extent of the holding arm.

Furthermore, for detecting the deformations in the deformation-prone areas, at least one deformation sensor is arranged in one of the deformation-prone areas of the deformation transmission element.

In particular, at least one deformation sensor is arranged in each of the deformation-prone areas of the deformation transmission element. In addition, it is expediently provided that each deformation-prone area is connected to a deformation-resistant area of the deformation transmission element and that the fastening areas are each located in a deformation-resistant area so that they are encompassed by the respective deformation strip area.

A deformation-resistant area is to be understood in particular to mean that it has a significantly higher rigidity, that is to say at least a factor of two, even better at least a factor of five, than a deformation-prone area.

This solution has the advantage that the largest possible part of the deformations transmitted from the deformation areas of the holding arm to the deformation transmission element are not distributed over the entire deformation transmission element, but essentially affect the deformation-prone areas in order to achieve the greatest possible deformation in them Areas prone to deformation, in which in particular the deformation sensors are arranged, and to have as little or no deformation as possible in the deformation-resistant areas of the deformation transmission element.

It is particularly advantageous if the deformation-prone areas are each arranged between two deformation-resistant areas.

Furthermore, for an optimal displacement of all the deformations transferred to the deformation transmission element to the areas subject to deformation, it is favorable if the areas subject to deformation and areas subject to deformation are arranged one after the other in a deformation direction, i.e. when the area subject to deformation and the areas subject to deformation are arranged in the same direction , in which the essential deformation is transmitted to the deformation transmission element, are arranged successively. It is also advantageous if the areas subject to deformation are designed as deformation concentration areas.

A deformation concentration range is to be understood in particular as the fact that the predominant part, that is to say more than 50%, even better than 70%, of the deformations transferred to or acting on the deformation transmission element are formed in this area.

Such a design of the deformation-prone areas has the advantage that the deformations can essentially be concentrated in them and the largest possible deformations can thus be detected by the respective deformation sensors.

With regard to the formation of the material of the deformation transmission element, no details have been given so far.

It is preferably provided that the material of the deformation transmission element outside the deformation-prone areas is designed as a deformation-resistant or deformation-inert material, that is, for example, that outside the deformation-prone areas less than 30%, even better less than 20%, preferably less than 10%, of the deformations transmitted or acting on the deformation transmission element.

On the other hand, it is preferably provided that the material of the deformation transmission element is prone to deformation or suitable for deformation in the areas subject to deformation by a suitable shape, for example a cross-sectional constriction. In order not to be able to compensate for deformations of the deformation transmission element caused by the deformations of the holding arm, provision is preferably made for the deformation transmission element to have a deformation-free area next to the respective deformation-prone area on which at least one reference deformation sensor is arranged.

In a deformation-free area, due to its design and arrangement, essentially none, that is to say in particular less than 20%, even better less than 10% and preferably less than 5%, of the deformations transferred to or acting on the deformation transmission element occur.

With such a reference deformation sensor in a deformation-free area, there is the possibility of material deformations in the deformation transmission element caused by influences other than the deformations transmitted or acting on the deformation transmission element, which are caused, for example, by thermal influences, to be detected via the reference deformation sensors and then, since these are also from the Deformation sensor are detected, thereby correcting.

For this reason, it is preferably provided that the respective deformation-free area is formed from the same material as the deformation-prone area.

Furthermore, it is preferably provided that the respective deformation-free area is connected on one side to a deformation-resistant area of the deformation transmission element.

A particularly advantageous geometric design provides that the deformation-free area of the deformation transmission element is designed like a tongue. In addition, it is preferably provided that the deformation-free area of the deformation transmission element is made from the same material, in particular with the same material thickness, as the area subject to deformation.

In order to achieve an optimal coupling between the effects detected by the reference deformation sensors and the effects detected by the deformation sensors, it is preferably provided that the reference deformation sensors are thermally coupled to the deformation transmission element.

In particular, this makes it possible for the reference deformation sensors to be thermally coupled to the deformation sensors by means of the deformation transmission element.

In particular, in the event that a reference deformation sensor is assigned to each deformation sensor, optimal thermal coupling is achieved when, between the respective deformation sensor and the reference deformation sensor assigned to it, each deformation-prone area provided with a deformation sensor is thermally deformation-free with the deformation-free area that is assigned to it and carries the assigned reference deformation sensor Area is coupled.

Overall, it is advantageous if the deformation-free area carrying the respective reference deformation sensor has the same thermal behavior as the deformation-prone area carrying the corresponding deformation sensor. In order to have the same deformations as possible in the area of the reference deformation sensor as in the area of the deformation sensor, it is expediently provided that the respective deformation-free area carrying the reference deformation sensor has a geometric shape that is comparable, preferably identical, to the deformation-prone area carrying the deformation sensor, is.

In particular, it is also advantageous here if the deformation-free area of the deformation transmission element is made of the same material as the deformation-prone area of the deformation transmission element.

In order to monitor the functionality of the reference deformation sensors, it is preferably provided that at least one temperature sensor is assigned to the reference deformation sensors for function monitoring.

It is even better if each of the reference deformation sensors is assigned a temperature sensor for function monitoring.

With regard to the design of the deformation transmission element, no further details have so far been given.

An advantageous solution provides that the deformation transmission element is designed like a plate and each deformation-prone area carrying a deformation sensor is formed by a cross-sectional constriction of the deformation transmission element.

In particular, it is provided here if the cross-sectional constriction of the deformation transmission element is formed by a constriction of a surface extension of the deformation transmission element. The deformation sensors and the reference deformation sensors can be sensors of a wide variety of designs, which can detect expansion processes and / or compression processes in the areas subject to deformation.

One possibility provides that the deformation sensors and the reference deformation sensors are designed as strain sensors, in particular strain gauges.

Another possibility provides that the deformation sensors and the reference deformation sensors are designed as magnetostrictive sensors or as optical sensors that detect expansion and compression.

In particular, for optimal compensation of a strain sensor, it is advantageous if the reference strain sensor assigned to it is identical to the assigned strain sensor.

According to the invention, the above-mentioned object is also achieved in particular in that the holding arm has a first deformation area and a second deformation area between the first end and the second end, each of which undergoes deformations when a force acts in the longitudinal center plane of the holding arm in parallel to the direction of travel differ from the deformations in the case of a force acting in the longitudinal center plane and transversely to the direction of travel.

The advantage of the solution according to the invention can be seen in the fact that the first and second deformation areas act in the case of a force acting in the longitudinal center plane of the holding arm and parallel to the direction of travel and a force acting in the longitudinal center plane and transversely, in particular perpendicular, to the direction of travel , in particular the amount of the same force of equal magnitude, behave differently, that is, deform to different degrees, the possibility exists through these different deformations of the first To differentiate deformation area and the second deformation area between a force acting in the longitudinal center plane of the holding arm and parallel to the direction of travel and a force acting in the longitudinal center plane of the holding arm and transverse to the direction of travel when evaluating the signals of the deformation sensors.

It is even more favorable if the first and the second deformation area also differ in the case of a force acting transversely, in particular perpendicularly, to the longitudinal center plane, in particular the same amount as the forces acting in the longitudinal center plane and parallel to the direction of travel or transversely to this behave, that is, deform to different degrees.

The different behavior of the first and the second deformation area can be achieved by a different shape, in particular different cross-sections and / or a different course and / or a different length of the first and second deformation areas in the holding arm.

In particular, it is provided that the first and second deformation area are arranged one after the other in a direction of extent of the holding arm.

With regard to the processing of the signals from the deformation sensors and the reference deformation sensors, no further details have been given in connection with the previous explanation of the solution according to the invention.

One advantageous solution provides that each deformation sensor is connected to the assigned reference deformation sensor in a Wheatstone bridge. In this way, by using the signals from the deformation sensor and the reference deformation sensor directly, effects not caused by the deformation of one of the deformation regions of the holding arm, in particular thermal effects, can be compensated for.

Furthermore, an advantageous solution provides that the evaluation unit has a processor, which the values corresponding to the deformations in the deformation-afflicted areas with transformation values determined by calibration and stored in a memory in the corresponding values of three transverse, in particular perpendicular, spatial directions to each other forces acting on the coupling element.

Thus, from the values corresponding to the deformations, there is the possibility of determining the forces acting on the coupling element in three transverse, in particular perpendicular, spatial directions with respect to one another.

It is particularly favorable if two of the forces run parallel to, in particular in the longitudinal center plane of the holding arm, but transversely, in particular perpendicular, to one another and if the third force runs transversely, in particular perpendicular, to the longitudinal center plane of the holding arm.

An improvement in the conversion of the values corresponding to the deformations is possible if transformation values for combinations of forces acting in different octants on the coupling element are stored in the memory, since these different transformation values allow an optimized adaptation to the actual circumstances.

In particular, an evaluation unit according to the solution according to the invention is designed in such a way that the values of deformation sensors and, in particular, possibly also reference deformation sensors for determining the deformations, are recorded. In order to also have the possibility of performing a functional test of the reference deformation sensors, provision is made for the evaluation unit to include values from at least one temperature sensor for functional testing of the reference deformation sensors.

It is even better if the evaluation unit for the functional test of the reference deformation sensors detects values from a respective temperature sensor assigned to the respective reference deformation sensor.

The at least one temperature sensor or the temperature sensors can either be arranged on a circuit board carrying the evaluation unit or on the deformation transmission element.

In the preceding exemplary embodiments, it was not explained in more detail how the holding arm and the coupling element can be connected to one another.

An advantageous solution provides that the holding arm carries the coupling element at its second end.

In this case, it is particularly advantageous if the holding arm and the coupling element form a coherent part, so that a separation between the holding arm and the coupling element is not possible.

In particular, it is provided in such a case that the holding arm is designed as a ball neck and carries the coupling element comprising a coupling ball at the second end.

A further advantageous solution provides that the holding arm comprises a receiving body which is designed to detachably receive the coupling element. The coupling element is, for example, part of a carrier system for coupling it to the holding arm.

The coupling element is designed, for example, as a coupling element of a carrier system for goods, in particular luggage or bicycles.

In particular, the receptacle body is designed in such a way that it has an insertion receptacle which is accessible through an insertion opening.

In the case of a receiving body of the holding arm described above, it is preferably provided that the coupling element comprises a carrier arm.

In this case, the carrier arm is expediently provided with an insertion section which can be inserted into the insertion receptacle and can be fixed in it.

The carrier arm is then, for example, part of the carrier system.

Alternatively, in a further embodiment, the support arm is designed such that it carries a coupling ball.

In a further embodiment, the support arm is provided with other coupling devices, for example with a coupling mouth.

For precise fixation of the support arm, it is useful if the plug-in section is positively received in the plug-in receptacle transversely to an insertion direction and is fixed in the functional state in the plug-in direction by a form-fitting body.

The above description of solutions according to the invention thus includes, in particular, the various combinations of features defined by the following numbered execution forms: 1. A device for coupling a trailer or a load carrier unit which can be mounted on the rear of a motor vehicle body (12), comprising a holding arm (30) which is firmly connected to the motor vehicle body (12) at a first end (32) during operation and at a second end (34) is designed to carry a coupling element (40), the holding arm (30) being provided with a sensor arrangement (170), the holding arm (30) being provided with at least three deformation sensors (172, 174, 176, 178), which in particular react in different ways to three forces acting on the coupling element (40) in transverse spatial directions, and wherein the at least three deformation sensors (172, 174, 176, 178) supply sensor values (M) from which an evaluation unit (270 ) at least one force component acting on the coupling element (40) is determined.

2. Device according to embodiment 1, wherein the evaluation unit (270) determines at least one of the values (WF _X , WF _y , WF _Z ) of its force components running in the spatial directions (x, y, z).

3. Device according to one of the preceding embodiments, the evaluation unit (270) determining the value (WF _Z ) of its force component extending in the direction of gravity (Z).

4. Device according to one of the preceding embodiments, wherein the evaluation unit (270) determines the value (F _x ) of its force component extending in the direction of travel of the motor vehicle (10).

5. Device according to one of the preceding embodiments, wherein the evaluation unit (270) determines the value (F _y ) of its force component running transversely, in particular perpendicular, to a vertical longitudinal center plane (18). 6. Device according to one of the preceding embodiments, wherein the evaluation unit (270) checks before determining the force components by means of a state detection stage (282) whether a suitable state for determining the force components on the coupling element (40) is present.

7. Device according to embodiment 6, wherein the state detection stage (282) by detecting at least one of the parameters such as voltage supply, vehicle orientation in space, presence of the working position of the holding arm (30), checks whether a suitable state for determining the force on the coupling element (40) is available.

8. Device according to one of the preceding embodiments, wherein the evaluation unit (270) by means of a zero load detection stage (286) before determining the force components on the coupling element (40) a detection of the values (WF _x o, WF _y o, WF _Z0 ) Force components takes place in the case of no load.

_{9. Device according to one of the preceding embodiments, with at least one of the values (WF X} , WF _y , WF _Z ) of the force components being recorded at zero load after the holding arm (30) has moved into a working position on the part of the zero load detection stage (286) .

_{10. Device according to one of the preceding embodiments, with at least one of the values (WFx, WF y} , WF _Z ) force components being recorded at zero load after a coupling element (40) has been mounted on the holding arm (30) on the part of the zero load detection stage (286).

11. Device according to one of the preceding embodiments, the values (WF _X , WF _Z , WF _y ) of the force components being stored at zero load by the zero load detection stage (286) only if the values (WF _X , WF _y , WF _Z ) the force components fall below predetermined values that exclude an external force on the coupling element (40). 12. Device according to one of the preceding embodiments, wherein when an approach to an object, in particular a trailer or a load carrier, is recognized by the zero load detection stage (286), the at least one of the values (WF _X , WF _y , WF _Z ) is detected. takes place at zero load.

13. Device according to one of the preceding embodiments, wherein after a detection of at least one of the values (WF _X , WF _Z , WF _y ) of the force components at zero load, a renewed detection of at least one of the values (WF _X , WF _y , WF _Z ) Force components at zero load takes place after a specified period of time.

14. Device according to one of the preceding embodiments, the evaluation unit (270) using a load detection stage (288) to determine at least one of the load-related values (WFxi, WF _yi , WF _Zi ) of the force components the corresponding values (WFxo , WF _y0 , WF _Z0 ) of the force components are subtracted from the _{values (WF X} , WF _y , WF _Z ) of the force components supplied with a force on the coupling element (40).

15. Device according to one of the preceding embodiments, wherein the load detection stage (288) carries out a determination of at least one value of the force components on the coupling element (40) if an on-board function of the motor vehicle (10) is carried out.

16. Device according to one of the preceding embodiments, wherein the load detection stage (288 _{) carries out a determination of at least one of the values (WFx, WF y} , WF _Z ) of the force components on the coupling element (40) if a plug is inserted into one of the holding arm (30) assigned socket (31) is plugged in. 17. Device according to one of the preceding embodiments, the load detection stage (288) determining at least one of the values (WFx, WF _y , WF _Z ) of the force components on the coupling element (40) after detecting an object attacking the coupling element (40) , in particular a trailer or a load carrier.

18. Device according to one of the preceding embodiments, wherein the load detection stage (288) determines at least one of the values (WFx, WF _y , WF _Z ) of the force components on the coupling element (40) when the speed of the motor vehicle (10) is less than five kilometers per hour, especially when the motor vehicle (10) is stationary.

19. Device according to one of the preceding embodiments, the evaluation unit (270) _{transmitting at least one load-related value (F x} , F _y , F _z ) of the force components acting on the coupling element (40) by means of the presentation stage (292).

20. Device according to one of the preceding embodiments, the evaluation unit (270) _{transmitting at least one value (WF Z} ) of the load-related force component acting in the vertical direction (Z) on the coupling element (40) by means of a presentation stage (292).

21. Device according to one of the preceding embodiments, the evaluation unit (270) by means of a presentation stage (292) at least one value (WF _X ) of the load-related force component acting on the coupling element (40) in the direction of travel and in particular parallel to a vertical longitudinal center plane (18) transmitted.

22. Device according to one of the preceding embodiments, wherein the values of the force component acting on the coupling element (40) (WF _X ,

WFy, WF _Z ) from the sensor values are linked by means of transformation coefficients (tix, ..., t ...). 23. Device according to one of the preceding embodiments, wherein the evaluation unit (270) by means of the presentation stage (292) has at least one value (WF _y ) which is transverse to a vertical longitudinal center plane (18) of the holding arm (30), in particular in an approximately horizontal direction (Y) acting load-related force component (WF _y ) transmitted.

24. Device according to one of the preceding embodiments, the presentation stage (292) using a presentation unit (304) to display the at least one value (WF _X , WF _y , WF _Z ) of the respective force component and, in particular, also to display the measurement accuracy associated with this.

25. Device according to one of the preceding embodiments, the presentation stage (292) _{qualitatively displaying the at least one value (WF X} , WF _y , WF _Z ) of the respective force component by means of the presentation unit (304).

26. Device according to one of the preceding embodiments, wherein the presentation stage (292) by means of the presentation unit (304) the at least one value (WF _Z ) of the load-related force component acting on the coupling element (40) in the vertical direction in relation to a predetermined support load for the indicates the respective motor vehicle (10).

27. Device according to one of the preceding embodiments, the presentation stage (292) using the presentation unit (304) to display the at least one value (F _x ) of the force component acting in the direction of travel in relation to a maximum tensile force. 28. Device according to one of the preceding embodiments, the presentation stage (292) at least one of the values (WF _X , WF _y , WF _Z ) of the force components acting on the coupling element (40) being transmitted to an electronic stabilization system of the vehicle.

29. Device according to one of the preceding embodiments, wherein the presentation stage (292 _{) transmits at least one of the values (WF X} , WF _y , WF _Z ) of the force components acting on the coupling element (40) to a chassis controller (328) of the motor vehicle (10) .

30. Device according to one of the preceding embodiments, wherein the deformation sensors (172, 174, 176, 178) are arranged relative to the holding arm (30) in such a way that, when a force (F _x , F _y , F _z ) is applied, they are of identical magnitude deliver different sensor values in each of the three spatial directions (x, y, z).

31. Device according to one of the preceding embodiments, with four deformation sensors (172, 174, 176, 178) being arranged on the holding arm (30) which, in the event of a force ( F _x , F _y , F _z ) of the same amount provide different sensor values.

32. Device according to one of the preceding embodiments, wherein the sensor values supplied by the deformation sensors (172, 174, 176, 178) by means of transformation coefficients (ti, ... tu) of a transformation matrix (T) with the values (WF _X , WF _y , WF _Z ) of the force components (F _x , F _y , F _z ) in the three transverse spatial directions (x, y, z) are linked. 33. Device according to the preamble of embodiment 1 or according to one of the preceding embodiments, starting from the coupling element (40) as the center of the space around the coupling element (40) defined in the three spatial directions (x, y, z) running transversely to one another eight octants (I ... VIII) is divided, that for each of the octants (I ... VIII) an octant-based transformation matrix (T) is specified in the evaluation circuit (230) that the evaluation circuit (230) using one of the specified transformation matrices (T) the values (F _x , F _y , F _z ) of the force components are determined and assigned to one of the octants (I ... VIII) and then on the basis of the octant-based transformation matrix (T) the values ( WF _X , WF _y , WF _Z ) of the force components are determined again.

34. A method for detecting the force on a device for coupling a trailer or a load carrier unit, which can be mounted on the rear of a motor vehicle body (12), comprising a holding arm (30) which is fixedly connected to the motor vehicle body (12) at a first end (32) during operation ) and is designed at a second end (34) to carry a coupling element (40), the holding arm (30) being provided with a sensor arrangement (170), the holding arm (30) having at least three deformation sensors (172, 174) , 176, 178), which in particular react in different ways to three forces acting on the coupling element (40) in transverse spatial directions (x, y, z), and that the at least three deformation sensors (172, 174, 176 , 178) deliver sensor values (M) from which at least one force component (K) acting on the coupling element is determined.

35. The method according to embodiment 34, wherein at least one of the values (WF _X , WF _y , WF _Z ) of the force components running in these spatial directions (x, y, z) are determined for the force. 36. The method according to embodiment 34 or 35, wherein at least the value (WF _Z ) of the force component running in the direction of gravity (Z) is determined.

37. The method according to one of the embodiments 34 to 36, wherein at least the value (WF _X ) of the force component running in the direction of travel of the motor vehicle (10) is determined.

38. The method according to one of the preceding embodiments, wherein at least the value (WF _y ) of the force component running transversely, in particular perpendicular, to a vertical longitudinal center plane (18) is determined.

39. The method according to one of the embodiments 34 to 38, wherein prior to determining the values (WF _X , WF _y , WF _Z ) of the force component (K) it is checked whether a suitable state for determining the force components on the coupling element (40) is present .

40. The method according to embodiment 39, wherein by detecting at least one of the parameters such as voltage supply, vehicle orientation in space, the presence of the working position of the holding arm (30) it is checked whether a suitable state for determining the force components on the coupling element (40) is present.

41. The method according to one of the embodiments 34 to 40, wherein before the force components on the coupling element (40) are determined, at least one of the values (WF _X , WF _y , WF _Z ) of the force components is recorded in the case of no load.

42. The method according to one of the embodiments 34 to 41, the values (WF _X , WF _y , WF _Z ) of the force components being recorded at zero load after the holding arm (30) has moved into a working position. 43. The method according to one of the embodiments 34 to 42, the values (F _x , F _y , F _z ) of the force components being recorded at zero load after a coupling element (40) has been installed on the holding arm (30).

44. The method according to one of the preceding embodiments, the values (F _x , F _y , F _z ) of the force components being stored at zero load only when the values (F _x , F _y , F _z ) are given an external force the coupling element (40) fall below exclusive values.

45. The method according to one of the embodiments 34 to 44, wherein the values (F _x , F _y , F _z ) of the force components at zero load are detected after an approach to an object, in particular a trailer or a load carrier, is detected.

46. The method according to one of the embodiments 34 to 45, wherein, after the values (F _x , F _y , F _z ) of the force components at zero load have been recorded, the values (F _x , F _y , F _z ) of the force components at zero load are recorded again takes place after a specified period of time.

47. The method according to one of the embodiments 34 to 46, wherein to determine at least one of the load-related values (WFxi, WF _yi , WF _zi ) of the force components the corresponding values (WF _x o, WF _y o, WF _z o) the force components are subtracted from the _{values (WF X} , WF _y , WF _Z ) of the force components supplied when there is a force acting on the coupling element (40).

48. The method according to one of embodiments 34 to 47, wherein at least one of the values (WF _X , WF _y , WF _Z ) of the force components on the coupling element (40) is determined if an on-board function of the motor vehicle (10) is performed . 49. The method according to one of the preceding embodiments 34 to 48, wherein at least one of the values of the force components on the coupling element (40) is determined if a plug has been inserted into a socket (31) assigned to the holding arm (30) .

50. The method according to one of the embodiments 34 to 49, wherein at least one of the values of the force components on the coupling element (40) is determined after the detection of an object attacking the coupling element (40), in particular a trailer or a load carrier.

51. The method according to one of embodiments 34 to 50, wherein at least one of the values (WF _X , WF _y , WF _Z ) of the force component on the coupling element (40) is determined when the speed of the motor vehicle (10) is lower than five kilometers per hour, especially when the motor vehicle (10) is stationary.

52. The method according to one of the embodiments 34 to 51, wherein at least one value (WF _Z ) of the force component acting in the vertical direction (Z) on the coupling element (40) is transmitted.

53. The method according to one of the embodiments 34 to 52, wherein at least one value (WF _X ) of the force component acting on the coupling element (40) in the direction of travel and in particular parallel to a vertical longitudinal center plane (18) is transmitted.

54. The method according to one of the embodiments 34 to 53, wherein at least one value (WF _y ) of a force component acting transversely to a vertical longitudinal center plane (18) of the holding arm (30), in particular in an approximately horizontal direction, is transmitted. 55. The method according to one of the embodiments 34 to 54, wherein at least one of the values (WFxi, WF _yi , WF _Zi ) of the respective force component and in particular the measurement accuracy associated with this is displayed.

56. The method according to one of the embodiments 34 to 55, wherein at least one of the values (WFxi, WF _yi , WF _Zi ) of the respective force component is displayed qualitatively.

57. The method according to one of the embodiments 34 to 56, wherein the value (WF _Z ) of the force component acting on the coupling element (40) in the vertical direction is displayed in relation to a predetermined support load for the respective motor vehicle (10).

58. The method according to one of the embodiments 34 to 57, the value (WFx) of the force component acting in the direction of travel being displayed in relation to a maximum tensile force.

59. The method according to one of the embodiments 34 to 58, d wherein at least one of the values (WF _X , WF _y , WF _Z ) of the force components acting on the coupling element (40) are transmitted to an electronic stabilization system (326) of the motor vehicle (10).

60. The method according to one of the embodiments 34 to 59, wherein at least one of the values (WF _X , WF _y , WF _Z ) acting on the coupling element (40) force components of a chassis control (328) of the motor vehicle (10) is transmitted.

61. Method according to the preamble of embodiment 34 or according to one of embodiments 34 to 60, wherein the values (WF _X , WF _y , WF _Z ) of the force components acting on the coupling element (40) with the sensor values (M) by means of transformation coefficients (tix ... tn). 62. The method according to one of the embodiments 34 to 61, wherein the sensor values supplied by the deformation sensors (172, 174, 176, 178) are transverse to one another by means of the transformation coefficients (tix ... tn) of a transformation matrix (T) with the force components in the three running spatial directions (x, y, z) are linked.

63. The method according to embodiment 61 or 62, wherein the determination of the transformation coefficients (tix ... tn) of the transformation matrix (T) takes place within the scope of a calibration process.

64. The method according to embodiment 63, the sensor values supplied by the deformation sensors (172, 174, 176, 178) being recorded in the calibration process when a defined force component acts on the coupling element (40).

65. The method according to embodiment 63 or 64, wherein during the calibration process a defined force component is acted on the coupling element (40) in one of the three spatial directions (x, y, z) running transversely to one another and the deformation sensors (172, 174, 176, 178) delivered sensor values can be recorded.

66. The method according to one of the embodiments 64 to 65, wherein in the calibration process each force component acting in one of the three spatial directions (x, y, z) has the same amount.

67. The method according to one of the embodiments 34 to 66, wherein the determination of the values (WF _X , WF _y , WF _Z ) of the force components acting on the coupling element by means of the sensor values based on the calibration by a force component in one of the three spatial directions (x, y, z) determined transformation coefficients takes place. 68. The method according to one of the embodiments 34 to 67, wherein the determination of the transformation coefficient is based on the assumption of a linear link between the values (WF _X , WF _y , WF _Z ) of the force components in the three spatial directions (x, y, z) and the sensor values supplied by the deformation sensors (172, 174, 176, 178).

69. The method according to one of the embodiments 34 to 67, wherein the three spatial directions (x, y, z) running transversely to one another run perpendicular to one another.

70. The method according to one of the embodiments 34 to 67, wherein, starting from the coupling element (40) as the center point, the space around the coupling element (40) in eight octants (I ... VIII), that to determine the set of transformation coefficients in each of the octants (I ... VIII) the coupling element (40) is acted on with force components which are within the respective octant, that the sensor values are recorded and that for these force components are determined in the respective one of the octants (I to VIII) octant-based transformation coefficients.

71. The method according to one of the preceding embodiments, wherein _{one of the transformation matrices (T) is used to determine the values (WF X} , WF _y , WF _Z ) of the force components on the coupling element (40) and which of the octants (I. ... VIII) the values (F _x , F _y , F _z ) are to be assigned to force components and then a new determination of the values (WF _X , WF _y , WF _{Z) with the transformation matrix (T) assigned to this octant (I to VIII)} ) of the force components is carried out. 72. A device for coupling a trailer or a load carrier unit, which can be mounted on the rear of a motor vehicle body (12), comprising a holding arm (30) which is firmly connected to the motor vehicle body (12) at a first end (32) during operation and at a second end (34) is designed to carry a coupling element (40), in particular according to one of the preceding embodiments, with forces acting on the coupling element (40) during operation and transmitted from the holding arm (30) to the motor vehicle body (12) by an evaluation unit ( 230) are detected with a sensor arrangement (170) which has at least three deformation sensors (172, 174, 176), and that in particular the at least three deformation sensors (172, 174, 176, 178) of the sensor arrangement (170) on the same side of a in the event of a bending deformation of the holding arm (30), neutral fibers of the holding arm which are not variable in length are arranged.

73. Device according to the preamble of embodiment 72 or according to embodiment 72, wherein a force detection module (100) is arranged on one side of the holding arm (30, 30 ') which comprises a sensor arrangement (170) which, during operation, is attached to the coupling element (40 ) attacking forces transmitted by the holding arm (30) to the motor vehicle body (12) are detected.

74. Device according to embodiment 73, wherein the sensor arrangement has at least three deformation sensors (172, 174, 176).

75. Device according to embodiment 73 or 74, wherein the force detection module (100) in the operating state is not arranged on any side of the holding arm (30, 30 ') facing a roadway (44).

76. Device according to one of the embodiments 73 to 75, the force detection module (100) being arranged in the operating state on a side of the holding arm (30, 30 ') facing away from a roadway (44). 77. Device according to the preamble of embodiment 72 or according to one of the preceding embodiments, with forces acting on the coupling element (40) during operation and transmitted from the holding arm (30) to the motor vehicle body (12) by an evaluation unit (230) are detected with a sensor arrangement (170) which has at least three deformation sensors (172, 174, 176) that the deformation sensors (172, 174, 176, 178) are arranged on at least one deformation transmission element (102) that is connected to the holding arm (30).

78. Device according to the preamble of embodiment 72 or according to one of the preceding embodiments, in which, during operation, forces acting on the coupling element (40) and transmitted from the holding arm (30) to the motor vehicle body (12) are transmitted through an evaluation unit (230) with a Sensor arrangement (170) are detected, which has at least three deformation sensors (172, 174, 176) that all deformation sensors (172, 174, 176, 178) of the sensor arrangement (170) are arranged on a common deformation transmission element (102).

79. Device according to one of the preceding embodiments, wherein each of the at least three deformation sensors (172, 174, 176) detects different large deformations of the holding arm (30, 30 ') when one and the same force acts on the coupling element (40).

80. Device according to one of the preceding embodiments, wherein the deformation transmission element (102) is connected to the holding arm (30) without relative movement and thus rigidly at at least two fastening areas (104, 106, 108) and that at least one of the deformation sensors (172, 174, 176 , 178) are arranged between the fastening areas (104, 106, 108) of the deformation transmission element (102). 81. Device according to one of the preceding embodiments, wherein the deformation transmission element (102) with at least three fastening areas (104, 106, 108) is connected to the holding arm (30) and that in each case between two of the fastening areas (104, 106, 108) at least one of the deformation sensors (172, 174, 176, 178) is arranged.

82. Device according to one of the preceding embodiments, the deformation transmission element (102) being connected in the fastening areas (104, 106, 108) to the holding arm (30) by means of connecting elements (114, 116, 118).

83. Device according to embodiment 82, wherein the connecting elements (114, 116, 118) are rigidly connected on the one hand to the holding arm (30) and on the other hand rigidly to the fastening areas (104, 106, 108) of the deformation transmission element (102).

84. Device according to embodiment 83, wherein the connecting elements (114, 116, 118) are molded onto the holding arm (30).

85. Device according to one of the preceding embodiments, wherein the connecting elements (114, 116, 118) deformations of the holding arm (30) in deformation regions (82, 84) of the holding arm (30) lying between the connecting elements (114, 116, 118) the fastening areas (104, 106, 108) of the deformation transmission element (102) carry over.

86. Device according to one of the embodiments 82 to 85, a deformation area (82, 84) of the holding arm (30) lying between each two connecting elements (114, 116, 118). 87. Device according to one of the preceding embodiments, wherein the holding arm (30) has at least two deformation areas (82, 84), the deformations of which are applied to fastening areas (104) via connecting elements (114, 116, 118) arranged on both sides of the respective deformation area (82, 84) , 106, 108) of the deformation transmission element (102), between which a deformation-prone area (152, 154, 156) of the deformation transmission element (102) lies.

88. Device according to embodiment 87, wherein the at least two deformation regions (82, 84) are arranged one after the other in a direction of extent of the holding arm (30).

89. Device according to one of the preceding embodiments, wherein at least one deformation sensor (172, 174, 176, 178) is arranged in one of the deformation-prone areas (152, 154, 156, 158) of the deformation transmission element (102).

90. Device according to one of the embodiments 87 to 89, wherein each deformation-prone area (152, 154, 156, 158) is connected to a deformation-stiff area (144, 146, 148) of the deformation transmission element (102) and that the fastening areas (104, 106, 108) each lie in a deformation-resistant area (144, 146, 148).

91. Device according to embodiment 90, the deformation-prone areas (152, 154, 156, 158) each being arranged between two deformation-resistant areas (144, 146, 148).

92. Device according to embodiment 90 or 91, the deformation-stiff regions (144, 146, 148) and the deformation-prone regions (152, 154, 156, 158) being arranged one after the other in a deformation direction. 93. Device according to one of the embodiments 87 to 92, wherein the deformation-prone areas (152, 154, 156, 158) are designed as deformation concentration areas.

94. Device according to one of the preceding embodiments, the material of the deformation transmission element (102) outside the deformation-prone areas (152, 154, 156, 158) being designed as a deformation-resistant or deformation-inert material.

95. Device according to one of the preceding embodiments, wherein the material of the deformation transmission element (102) in the areas subject to deformation (152, 154, 156, 158) is prone to deformation by a shape, for example a cross-sectional constriction.

96. Device according to one of the preceding embodiments, wherein the deformation transmission element (102) has a deformation-free area (192, 194, 196, 198) next to the respective deformation-prone area (152, 154, 156, 158) on which at least one reference deformation sensor (182, 184, 186, 188) is arranged.

97. Device according to embodiment 96, the respective deformation-free area (192, 194, 196, 198) being made from the same material as the deformation-prone area (152, 154, 156, 158).

98. Device according to embodiment 96 or 97, the respective deformation-free area (192, 194, 196, 198) being connected on one side to a deformation-resistant area (144, 146, 148) of the deformation transmission element (102).

99. Device according to one of the embodiments 96 to 98, the deformation-free area (192, 194, 196, 198) of the deformation transmission element (102) being designed like a tongue. 100. Device according to one of the embodiments 96 to 99, wherein the deformation-free area (192, 194, 196, 198) of the deformation transmission element (102) is made from the same material, in particular with the same material thickness, as the deformation-prone area (152, 154 , 156, 158).

101. Device according to one of the embodiments 96 to 100, wherein the reference deformation sensors (182, 184, 186, 188) are thermally coupled to the deformation transmission element (102).

102. Device according to embodiment 101, wherein the reference deformation sensors (182, 184, 186, 188) are thermally coupled to the deformation sensors (172, 174, 176, 178) by means of the deformation transmission element (102).

103. Device according to embodiment 102, wherein for optimal thermal coupling between the respective deformation sensor (172, 174, 176, 178) and the reference deformation sensor (182, 184, 186, 188) assigned to it, each with a deformation sensor (172, 174, 176, 178) provided deformation-prone area (152, 154, 156, 158) is thermally coupled to the deformation-free area (192, 194, 196, 198) assigned to this and the assigned reference deformation sensor (182, 184, 186, 188).

104. Device according to one of the embodiments 96 to 103, wherein the deformation-free area (192, 194, 196, 198) carrying the respective reference deformation sensor (182, 184, 186, 188) has the same thermal behavior as that of the corresponding deformation sensor (172, 174, 176, 178) bearing deformation-prone areas (152, 154, 156, 158). 105. Device according to one of the embodiments 96 to 104, wherein the respective deformation-free area (192, 194, 196, 198) carrying the reference deformation sensor (182, 184, 186, 188) has a geometric shape which corresponds to the deformation sensor (172, 174, 176, 178) bearing deformation-prone area (152, 154, 156, 158) is comparable.

106. Device according to one of the embodiments 96 to 105, wherein the deformation-free area (192, 194, 196, 198) of the deformation transmission element (102) is made of the same material as the deformation-prone area (152, 154, 156, 158) of the deformation transmission element (102).

107. Device according to one of the embodiments 96 to 106, the reference deformation sensors (182, 184, 186, 188) being assigned at least one temperature sensor (252, 254, 256, 258) for function monitoring.

108. Device according to one of the preceding embodiments, wherein the deformation transmission element (102) is plate-like and each deformation-prone area (152, 154, 156, 158) carrying a deformation sensor (172, 174, 176, 178) by a cross-sectional constriction of the deformation transmission element ( 102) is formed.

109. Device according to embodiment 108, wherein the cross-sectional constriction of the deformation transmission element (102) is formed by a constriction of a surface extension of the deformation transmission element (102).

110. Device according to one of the preceding embodiments, wherein the deformation sensors and the reference deformation sensors are designed as strain sensors, in particular strain gauges. 111. Device according to one of the embodiments 72 to 109, wherein the deformation sensors and the reference deformation sensors are designed as magnetostrictive or optical sensors.

112. Device according to the preamble of embodiment 72 or according to one of the preceding embodiments, the holding arm (30) having a first deformation area (82) and a second deformation area (84) between the first end (32) and the second end (34) which, when a force (Fx) acts parallel to the direction of travel (24) in the longitudinal center plane (18) of the holding arm (30), each experience deformations that differ from the deformations in the case of a deformation in the longitudinal center plane (18) transverse to the direction of travel (24) Differentiate force (F _z ).

113. Device according to embodiment 112, wherein the first and the second deformation area (82, 84) in the case of a force (F _y ) acting transversely, in particular perpendicular to the longitudinal center plane (18), each experience deformations which differ from the deformations in a longitudinal center plane ( _{18) differentiate force F x} , F2) acting parallel and / or transversely to the direction of travel (24).

114. Device according to embodiment 112 or 113, wherein the first and the second deformation region (82, 84) are arranged one after the other in the extension direction of the holding arm (30).

115. Device according to one of the preceding embodiments, wherein each deformation sensor (172, 174, 176, 178) is connected to the assigned reference deformation sensor (182, 184, 186, 188) in a Wheatstone bridge (212, 214, 216, 218) . 116. Device according to one of the preceding embodiments, wherein the evaluation unit (230) has a processor (234) which the deformations in the deformation-prone areas (152, 154, 156,

158) corresponding values with transformation values determined and stored in a memory (236) by a calibration into the corresponding values (WFx, WFY, WFZ) of three forces (F _x ,

F _y , F2) converted to the coupling element (40).

117. Device according to one of the preceding embodiments, wherein two of the forces (Fx, Fz) run parallel to, in particular in, the longitudinal center plane (18) of the holding arm (30) but transversely, in particular perpendicular, to one another and that the third force (F _y ) runs transversely, in particular perpendicular, to the longitudinal center plane (18) of the holding arm (30).

118. Device according to embodiment 116 or 117, transformation values for combinations of forces acting in different octants on the coupling element (40) being stored in the memory (236).

119. Device according to one of the embodiments 116 to 118, the evaluation unit (230) detecting values from deformation sensors (172, 174, 176, 178) and in particular reference deformation sensors (182, 184, 186, 188) for determining the deformations.

120. Device according to embodiment 119, wherein the evaluation unit (230) detects values from at least one temperature sensor (252, 254, 256, 258) for functional testing of the reference deformation sensors (182, 184, 186, 188).

121. Device according to embodiment 120, wherein the evaluation unit (230) detects values from a respective temperature sensor assigned to the respective reference deformation sensor. 122. Device according to one of the preceding embodiments, wherein the holding arm (30) carries the coupling element (40) at its second end (34).

123. Device according to embodiment 122, wherein the holding arm (30) and the coupling element (40) form an integral part.

124. Device according to embodiment 122 or 123, wherein the holding arm (30) is designed as a ball neck and at the second end (34) carries the coupling element (40) comprising a coupling ball (43).

125. Device according to one of the embodiments 72 to 124, wherein the holding arm (30 ') comprises a receiving body (31') which is designed to detachably receive the coupling element (40 ').

126. Device according to embodiment 125, wherein the receiving body (31 ') has an insertion receptacle (33') which is accessible through an insertion opening (35 ').

127. Device according to embodiment 125 or 126, wherein the coupling element (40 ') comprises a support arm (42').

128. Device according to one of the embodiments 125 to 127, wherein the carrier arm (42 ') with an insertion section (45') can be inserted into the insertion receptacle (33 ') and can be fixed therein.

129. Device according to one of the embodiments 125 to 128, wherein the support arm (42 ') carries a coupling ball (43).

130. Device according to embodiment 128 or 129, wherein the insertion section (45 ') is received transversely in an insertion direction (E) in a form-fitting manner in the insertion receptacle (33') and is fixed in the functional state in the insertion direction by a form-fitting body (41). Further features and advantages of the solution according to the invention are the subject of the following description and the graphic representation of some exemplary embodiments.

In the drawing show:

Fig. 1 is a partially broken rear side view of a motor vehicle body according to a first embodiment of a device according to the invention for coupling a trailer;

FIG. 2 shows a rear view of the motor vehicle body looking in the direction of arrow X in FIG. 1; FIG.

3 shows an illustration of the first exemplary embodiment of the device for coupling a trailer or a load carrier unit in its working position corresponding to FIG. 2;

4 shows an illustration of the first exemplary embodiment of the device for coupling a trailer or a load carrier unit in a rest position R;

5 shows a side view of the holding arm of the first exemplary embodiment, showing the loading of the coupling element with a force Fx;

6 shows a plan view of the holding arm looking in the direction of arrow D in FIG. 5;

7 shows a side view of the holding arm when a force F _{z is applied} ;

8 shows a plan view of the holding arm corresponding to FIG. 6 when the force F _{z acts} ; 9 shows a side view of a holding arm when a force F _{y is applied} ;

FIG. 10 shows a plan view similar to FIG. 6 when the force F _{y acts} ;

11 shows a section along line 11-11 in FIG. 5;

Fig. 12 is an enlarged plan view of the holding arm with the

Deformation transmission element when the force F _{x acts} according to FIGS. 5 and 6;

13 shows a plan view corresponding to FIG. 12 with the action of the force F _z according to FIGS. 7 and 8;

14 shows a plan view similar to FIG. 12 with the action of a force F _y corresponding to FIGS. 9 and 10;

15 shows an enlarged plan view of the deformation transmission element according to a first exemplary embodiment with the deformation sensors and reference deformation sensors arranged thereon;

16 shows an illustration of a Wheatstone bridge for interconnecting a first deformation sensor and a first reference deformation sensor;

FIG. 17 shows a representation of the Wheatstone bridge corresponding to FIG. 16 for the interconnection of a second deformation sensor and a second reference deformation sensor; FIG.

18 shows a representation of a Wheatstone bridge corresponding to FIG. 16 for the interconnection of a third deformation sensor and a third reference deformation sensor; 19 shows a representation of a Wheatstone bridge corresponding to FIG. 16 for interconnecting a fourth deformation sensor and a fourth reference deformation sensor;

20 shows an illustration of an evaluation circuit for processing the voltages measured in the Wheatstone bridges according to FIGS. 16 to 19;

21 shows a representation of a coupling element 40 and the forces acting on the coupling element 40, determined by the evaluation circuit;

22 shows a representation of a side view of the first exemplary embodiment with the representation of a circuit board carrying the evaluation circuit;

23 shows an illustration of a unit comprising the circuit board carrying the evaluation circuit and the deformation transmission element with deformation sensors and reference deformation sensors in a side view;

24 shows a representation of a second exemplary embodiment of a device according to the invention with the unit arranged in reverse, comprising the deformation transmission element, the expansion sensors, the reference expansion sensors and the evaluation unit;

FIG. 25 shows a representation of a third exemplary embodiment of a device according to the invention, similar to FIG. 23, with a representation of the additional temperature sensors arranged on the circuit board; FIG. 26 shows a representation of a fourth exemplary embodiment of a device according to the invention with a representation of the deformation transmission element and additional temperature sensors arranged thereon;

27 shows an illustration of the evaluation unit according to the third or fourth exemplary embodiment, similar to FIG. 20;

28 shows a side view similar to FIG. 1 of a fifth exemplary embodiment of a device according to the invention;

29 shows a perspective illustration of the fifth exemplary embodiment of the device according to the invention in the working position;

FIG. 30 shows a view of the fifth exemplary embodiment looking in the direction of arrow X 'in FIG. 28 in the working position;

31 shows a section along line 31-31 in FIG. 30;

FIG. 32 shows a section along line 32-32 in FIG. 30; FIG.

33 shows a section similar to FIG. 31 of the exemplary embodiment in the rest position;

FIG. 34 shows a perspective illustration of the fifth exemplary embodiment in the rest position, looking in the direction of arrow V in FIG. 33; FIG.

35 shows a side view of the holding arm of the fifth exemplary embodiment, showing the loading of the coupling element with a force Fx;

36 shows a plan view of the holding arm looking in the direction of arrow D 'in FIG. 35; 37 shows a side view of the holding arm of the fifth exemplary embodiment when a force F _{z is applied} ;

38 shows a plan view of the holding arm corresponding to FIG. 36 when the force F _{z acts} ;

39 shows a side view of a holding arm of the fifth exemplary embodiment when a force F _{y is applied} ;

40 shows a plan view similar to FIG. 36 when the force F _{y acts} ;

41 shows an illustration of a first possibility of mathematically linking the values of the force components with the sensor values;

42 shows a schematic illustration of the procedure for calibrating a holding arm;

43 shows a representation of a second possibility of mathematically linking the values of the force components with the sensor values;

44 shows an illustration of a calibration on the basis of force components in octants with the coupling element as the center;

45 shows a schematic representation of an evaluation unit and its interaction with further components;

46 shows an exemplary illustration of a presentation of the load-dependent values of the force components in the form of a bar; 47 shows an illustration of a presentation of the load-dependent values of the force components together with the different measuring accuracies and

Fig. 48 is an illustration of a presentation of the value of the vertical force component in connection with a given support load.

A motor vehicle designated as a whole by 10 comprises a motor vehicle body 12 which is provided at a rear area 14, specifically near a vehicle floor 16, with a carrier unit 20, which has, for example, a cross member 22 which is connected to the rear area 14 near the vehicle floor 16 is.

The connection between the cross member 22 and the rear area 14 can take place, for example, via mounting flanges resting on the rear area 14 or, for example, by side beams 26 extending in a vehicle longitudinal direction 24, which abut against vehicle body sections 28 also extending in the vehicle longitudinal direction 24.

A holding arm designated as a whole by 30, in particular a ball neck, is connected to the carrier unit 20 in that a first end 32 of the holding arm 30 is held either directly or via a bearing unit 36 on the carrier unit 20, preferably on the cross member 22.

At a second end 34 opposite the first end 32, the holding arm 30 carries a coupling element 40 which is provided, for example, for attaching a trailer or for fixing a load carrier unit.

For example, such a coupling element 40 is designed as a coupling ball 43, which allows a common connection with a tow ball coupling of a trailer. However, the coupling ball 43 also allows a simple assembly of a load carrier unit, since frequently common load carrier units are also designed in such a way that they can be mounted on a coupling ball and, if necessary, additionally supported on the holding arm 30.

The coupling element 40 sits, for example, on a carrier 42 which is connected to the second end region 34 of the holding arm 30 and extends from a side of the carrier 42 facing away from a roadway 44 in the direction of a center axis 46 which runs approximately vertically with a horizontal roadway 44 and which in the Case of the coupling ball 43 through a ball center point 48 runs therethrough.

To improve the aesthetic effect, the cross member 22 is preferably arranged under a rear bumper unit 50 of the motor vehicle body 12, the bumper unit 50 covering, for example, the cross member 22 and the first end 32 of the retaining arm 30.

In the exemplary embodiment shown, the holding arm 30 carries the coupling element 40 designed as a coupling ball, the holding arm 30, as shown in particular in FIGS. 1 to 3, extending from the pivot bearing unit 36 with which the holding arm 30 is at its first end region 32 is connected, for example at the first end region 32 a pivot bearing body 52 of the pivot bearing unit 36 is formed.

The swivel bearing body 52 of the swivel bearing unit 36 is pivotably mounted on a swivel bearing receptacle 56 about a swivel axis 54 running at an angle to a vertical vehicle longitudinal center plane 18, which on the one hand guides the swivel bearing body 52 rotatably about the swivel axis 54 and on the other hand comprises a locking unit, not shown in the drawing, which is in The working position and the rest position enable the holding arm 30 to be fixed in a rotationally fixed manner with respect to pivoting movements about the pivot axis 54. The pivot bearing receptacle 56 is in turn firmly connected to the cross member 22 via a pivot bearing base 58.

As shown in Fig. 1 to 4, the holding arm 30 is in this embodiment example of a working position A, shown in Fig. 1 to 3, in which the coupling element formed as a coupling ball 40 is so that it is behind the bumper unit 50 on a one The side facing away from the track 44 is pivotable into a rest position R, shown in FIG. 4, in which the coupling element 40 is arranged facing the track 44.

The coupling element 40 can be moved under a lower edge 51 of the bumper unit 50 therethrough.

In particular, the holding arm 30 in the working position A extends essentially in the vertical vehicle longitudinal center plane 18, this intersecting the coupling element 40 in the middle if it is designed as a coupling ball, so that in the working position A a vertical ball center axis 48 lies in the longitudinal center plane 18 .

Starting from the first end region 32, the holding arm 30 extends in the illustrated embodiment with a first curved piece 62 to an intermediate piece 64, which extends to an annular body 66, on which a side opposite the intermediate piece 64 and the curved piece 62 extends adjoins second curved piece 68, which in turn carries the coupling element 40 designed as a coupling ball, the ball shoulder 42 being provided between the coupling element 40 designed as a coupling ball and the second curved piece 148.

The second curved piece 68 then forms the end region 34 of the holding arm 30 which then carries, for example, the ball attachment 42, to which the coupling element 40, designed as a coupling ball, is connected. As shown in particular in FIGS. 4 and 5, for simple assembly of a contact unit on the holding arm 30, the ring body 66 is arranged adjacent to the intermediate piece 64 and encloses a passage 72 in which a contact unit can be mounted.

The ring body 66 is preferably arranged in such a way that a transition into the second curved piece 68 takes place after the ring body 66.

A holding arm 30 designed in this way is formed approximately U-shaped by the first curved piece 62, the intermediate piece 64 and the second curved piece 68, and in the working position A, in which loads on the coupling element 40 occur and are to be detected, oriented so that the forces which act on the coupling element 40, in particular the ball center point 46, are transmitted to the pivot bearing body 52 of the pivot bearing unit 36 via the approximately U-shaped design of the holding arm 30, the pivot axis 54 being a center of the force absorption by the pivot bearing unit 36.

The forces acting on the coupling element 40 are, as shown in FIGS. 1 to 8, transmitted through the holding arm 30 to the bearing unit 36 and from there to the carrier unit 20, which then introduces the forces into the rear region 14 of the motor vehicle body 12, different areas of the holding arm 30 being used to detect the forces acting on the coupling element 40.

In the embodiment described above, a first deformation area 82 of the holding arm 30 is used as an example, which comprises a section of the intermediate piece 64 and the ring body 66, and a second deformation area of the holding arm 30 is used, which comprises a section of the ring body 66 and the second curved piece 68. Furthermore, it is assumed in this exemplary embodiment that the ring region 66 has a high level of stability with respect to bending forces running in the longitudinal center plane 18 and also transversely to this, and in particular reacts primarily to tensile loads.

_{For example, the force F x} shown in FIGS. 5 and 6, which is directed in the longitudinal center plane 18 and perpendicular to the center axis 46 and away from the pivot bearing body 52, leads to tensile forces ZX1 and ZX2 ( Fig. 6) occur and on the other hand also bending forces BX1 and BX2 (Fig. 5), which these tensile loads ZX1 and ZX2 are superimposed, these forces acting in the direction of the longitudinal center plane 18, in particular in the longitudinal center plane 18, of the holding arm 30.

Furthermore, in the deformation areas 82 and 84, as shown in FIGS. 7 and 8, when the coupling element 40 is loaded with a force F _z , which acts in the direction of the central axis 46, essentially bending forces BZ1 and BZ2 occur in the deformation areas 82 and 84 These forces act in the direction of the longitudinal center plane 18, in particular in the longitudinal center plane 18, of the holding arm 30, which thus have opposite effects on opposite sides in relation to a so-called length-invariable neutral fiber NF.

In addition, a force F _y acting on the coupling element 40, which is directed perpendicular to the longitudinal center plane 18 and perpendicular to the center axis 46, as shown in FIGS. 9 and 10, leads to bending forces BY1 acting opposite one another on both sides of the longitudinal center plane 18 but on different sides thereof and BY2.

To detect these tensile forces ZX1 and ZX2 as well as the bending forces BX1 and BX2, BZ1 and BZ2 and BY1 and BY2, a force detection module designated as a whole by 100 is arranged on the holding arm 30. This force detection module 100 comprises a deformation transmission element 102, which is rigidly connected to the holding arm 30 at three fastening areas 104, 106 and 108, the fastening area 104 lying on a side facing the first end 32 and rigidly with one seated, for example, on the center piece 64 , Extension 114 of the holding arm 30 is connected, the fastening area 106 is arranged approximately in the middle between the fastening areas 104 and 108 and is connected, for example, to a holding lug 116 sitting on the ring body 66, in particular in the middle thereof, and the fastening area 108 is connected to a bracket on the curved piece 68, for example, in a central region of the curved piece 68 between the ring body 66 and the end 34, the projection 118 of the holding arm 30 is connected.

The connection between the respective connecting elements 114, 116 and 118 of the holding arm 30 is rigid and free of play, preferably by a weld or adhesive that does not allow any elasticity of movement between the deformation transmission element 102 and the connecting elements 114, 116 and 118.

The connecting elements 114, 116 and 118 are preferably also rigidly connected to the holding arm, in particular molded onto it.

As shown in FIG. 11 using the example of the attachment 114, the connecting elements 114, 116 and 118 of the holding arm 30 are preferably designed so that they have a foot region 122 which extends from the holding arm 30 and forms a fixing pin 124, which penetrates an opening 126 which is arranged in the respective fastening area, in this case the fastening area 104 of the deformation transmission element 102.

The fixing pin 124 and the opening 126 are preferably adapted in shape in such a way that they can be rigidly connected to one another by a weld 128. In addition, the foot region 122 is preferably designed so that it has a shoulder 132 running around the fixing pin 124, on which the deformation transmission element 102 rests with a support surface 134 of the fastening region 104 surrounding the opening 126 and is thereby supported, for example, when the weld seam 128 is made .

The deformation transfer element 102 is also designed such that it has deformation-resistant areas 144, 146 and 148, which in particular also include the fastening areas 104, and that between the deformation-resistant areas 144, 146, 148 each deformation-prone areas 152, 154, 156, 158 are arranged are, for example, between the deformation-prone areas 144 and 146, the deformation-prone regions 152 and 154, which are preferably arranged at the same distance from the longitudinal center plane 18, but on opposite sides thereof, and between the deformation-prone regions 146 and 148, the deformation-prone regions 156 and 158, which are also arranged on opposite sides of the longitudinal center plane 18, but preferably at the same distance therefrom.

The areas 152 to 158 subject to deformation are preferably designed as deformation concentration areas, that is, in these deformation concentration areas 152, 154, 156, 158 a deformation acting on the deformation transmission element 102 has a much stronger effect than in the deformation-resistant areas 144, 146 and 148.

The formation of such a deformation concentration area can be implemented in the simplest case in that the material in the deformation concentration areas 152 to 158 has a lower rigidity than in the deformation-resistant areas 144, 146 and 148. Such a variation in rigidity can be achieved, for example, by changing the material in the area of the deformation concentration areas 152, 154, 156, 158 or also by changing the effective material cross-section.

In the illustrated embodiments according to FIGS. 6, 8 and 10, the deformation concentration areas 152, 154, 156 and 158 are designed as narrow webs of a plate 162 forming the deformation transmission element 102, while the deformation-resistant areas 144, 146 and 148 are formed by broadly expanding areas of the Plate 162 are formed.

Such a design of the deformation transmission element 102 has the consequence, in summary, that a deformation of the deformation area 82 of the holding arm 30 leads to a relative movement of the connecting elements 114 and 116 rigidly connected to the holding arm 30, which onto the fastening areas 104 and 106 and from them to the deformation stiff areas 144 and 146 of the deformation transmission element 102 are transferred, the deformation-stiff areas 144 and 146 of the deformation transfer element 102 experiencing essentially no deformation and thus the entire deformations formed in the deformation area 82 are transferred to the deformation-prone areas 152 and 154, which are thereby that they are also designed as deformation concentration areas, the entire deformation occurring between the connecting elements 114 and 116 in the deformation area 82 experienced concentrated.

This means that the deformation concentration areas 152 and 154 experience both deformations due to the bending forces BX1 effective in the longitudinal center plane 18 and deformations due to the tensile forces ZX1 and the deformations occurring due to the forces BZ1 and BZ2, whereby as a result, that these deformations are all based on forces acting essentially in the longitudinal center plane 18, both deformation concentration areas 152 and 154 experience the same deformation.

This is different with the bending forces BY1 shown in FIGS. 9 and 10, which act on different sides of the longitudinal center plane 18 in different directions, so that, for example, starting from the bending forces BY1 shown in FIGS. 9 and 10, the deformation concentration area 152 experiences a deformation which is based on a compressive load, while the deformation concentration area 154 undergoes a deformation based on a tensile load.

In an analogous manner, deformations of the deformation area 84 of the holding arm are transferred by the connecting elements 116 and 118 to the fastening areas 106 and 108, which are part of the deformation-resistant areas 146 and 148 and which thus transfer the deformations of the deformation area 84 to the deformation-prone areas 156 and 158 which are also designed as deformation concentration areas and thus experience the entire deformation of the deformation area 84.

This also means that the forces BX2, ZX2 and BZ2, all of which are essentially effective in the longitudinal center plane 18, have the same effect on the deformation concentration areas 156 and 158, while the forces BY2 lead to opposite deformations in the deformation areas 156 and 158 so that, for example, the deformation in the deformation concentration area 156 is based on a pressure load, while the deformation in the deformation concentration area 158 is based on a tensile load.

Because the deformation areas 82 and 84 of the holding arm _{experience a different deformation when the coupling element 40 is loaded by the force F x} than when the coupling element 40 is loaded by the force F _z , the different deformations of the Deformation areas 82 and 84 the possibility of recognizing on the basis of the different deformations occurring in the deformation concentration areas 152 and 154 or 156 and 158 whether a force F _x or a force F _{z is} acting on the coupling element 40, as will be explained in detail below.

As an example, it can be assumed that, as shown in FIG. 12, the deformations D152 in the deformation concentration area 152, the deformation D154 in the deformation concentration area 154, the deformation D156 in the deformation concentration area 156 and the deformation D158 in the deformation concentration area 158 in the Are essentially the same size if the deformation areas 82 and 84 behave essentially in the same way with the bending forces BX1 and BX2 that occur, combined with the tensile forces ZX1 and ZX2 that occur.

Furthermore, the behavior of the deformations in the deformation areas 82 and 84 can change when the force F _{z occurs} , so that, as shown by way of example in FIG. 13, the deformations D152 and D154 in the deformation concentration areas 152 and 154 can be significantly smaller than that Deformations D156 and D158 in the deformation concentration areas 156 and 158.

The situation is again different when the force F _{y acts} , as shown in FIG. 14.

In this case, compression occurs in the deformation concentration areas 152 and 156 as deformations D152 and D156, while expansion occurs as deformations D154 and D158 in the deformation concentration areas 154 and 158, respectively. The deformations D152 and D156 based on compression can be the same or different, and in the same way the deformations D154 and D158 based on expansions can also be the same or different.

To detect the expansions or compressions that _{occur in the deformation concentration areas 152, 154, 156 and 158 as a result of forces F x} and / or F2 and / or F _y , as shown in FIG. 15, the deformation concentration areas 152, 154, 156 and 158 each have a deformation sensor 172, 174, 176 and 178 arranged, with which there is the possibility of detecting the expansion and compression in the respective deformation concentration areas 152, 154, 156 and 158.

Since in the deformation concentration areas 152, 154, 156 and 158 not only expansions and compressions occur, which are caused by the deformation areas 82 and 84 of the holding arm 30, but also expansions and compressions can occur which are caused by a temperature expansion of the material in the deformation concentration areas 152 , 154, 156 and 158 occur, the deformation sensors 172, 174, 176 and 178 are assigned reference deformation sensors 182, 184, 186 and 188, which are arranged on stress-free reference areas 192, 194, 196 and 198 of the deformation transmission element 102, these stress-free reference areas 192, 194, 196 and 198 are preferably formed as tongues 202, 204, 206 and 208 arranged as close as possible to the deformation concentration areas 152, 154, 156, 158, which, starting from, for example, the deformation-free areas 144 and 148, are essentially parallel to the deformation concentration areas 152, 154, 156 and nd 158, however, extend without contact to these and also to the deformation-free area 146, the stress-free reference areas 192, 194, 196 and 198 preferably having essentially the same material cross-section in the area in which they carry the reference deformation sensors 182, 184, 186 and 188 have the same material cross-sectional shape as the deformation concentration areas 152, 154, 156 and 158 and also the reference deformation sensors 182, 184, 186, 188 with the deformation sensors 172, 174, 176 and 178 are preferably identical.

For the electronic detection of the expansion and compression in the deformation concentration areas 152, 154, 156 and 158, the deformation sensors 172, 174, 176 and 178 arranged in these are each arranged in Wheatstone bridges 212, 214, 216 and 218, the respective Wheatstone bridges 212, 214, 216 and 218 lie between supply connections V + and V-, as shown in FIGS. 16 to 19.

Furthermore, the deformation sensors 172, 174, 176 and 178 in the Wheatstone bridges 212, 214, 216, 218 are connected in series between the supply connections V + and V- with the reference deformation sensors 182, 184, 186 and 188 assigned to them, respectively. and this series connection of the deformation sensors 172, 174, 176 and 178 with the reference deformation sensors 182, 184, 186 and 188, resistors 222 and 224 are connected in parallel to form the Wheatstone bridges 212, 214, 216, 218, the resistors 222 and 224 also being fixed Have values.

Thus, in the respective Wheatstone bridges 212, 214, 216 and 218 at the center taps between the deformation sensors 172, 174, 176 and 178 and the reference deformation sensors 182, 184, 186 and 188 and the center taps between the resistors 222 and 224 in each case a voltage U are tapped, which essentially corresponds to the deformations, i.e. the expansions and compressions, which occur in the deformation concentration areas 152, 154, 156 and 158, with the provision of the reference deformation sensors 182, 184, 186, 188 temperature effects and in particular temperature expansions in the deformation concentration areas 152, 154, 156 and 158 are largely compensated, which is possible in particular if the reference deformation sensors 182, 184, 186 and 188 are identical sensors to the deformation sensors 172, 174, 176 and 178.

The voltages UD152, UD154, UD156 and UD158 corresponding to the deformations in the Wheatstone bridges 212, 214, 216, 218 are tapped off in an A / D converter 232 of one comprising them Evaluation circuit 230 is supplied, which also has a processor 234 coupled to the A / D converter 232, which is based on the digital values of the voltages UD152, UD154, UD156 and UD158 and by comparing them with those determined in the course of a calibration process and stored in a memory 236 Transformation values for the values of the voltages UD152, UD154, UD156 and UD158, for example outputs values WF _X , WF _Z and WF _{y assigned} to the forces F _x , F _z and F _y at corresponding outputs.

In the simplest case, a transformation matrix T valid for all spatial directions is stored in the memory 236, with which the digital values of the voltages UD152, UD154, UD156 and UD158 are converted into values WF _X and WF _Z and WF _y for the forces acting on the coupling element 40 let convert.

An improvement in the quality of the values WF _X , WF _Z and WF _y _{can be achieved if the calibration is carried out for value pairs WFx, WF Z} and WF _y located in each of the octants I to VIII arranged around the attachment element 40 according to FIG. so that there is also the possibility of nonlinear correlation between the forces F _z acting on the coupling element 40,

F _z , F _y and the digital values of the voltages UD152, UD154, UD156 and UD158 in the calibration and thus transformation of these values of the voltages UD152, UD154, UD156 and UD158 into the values WF _X , WF _Z and WFy for the coupling element 40 acting forces are to be included. This significantly improves the accuracy of the determined values WF _X , WF _Z and WF _y.

With regard to the arrangement of the evaluation circuit 230 including, in particular, the A / D converter 232, the processor 234 and the memory 236, the most varied of possibilities are conceivable.

For example, it would be conceivable to arrange the evaluation circuit 230 directly on the deformation transmission element 102.

However, it is particularly favorable if the evaluation circuit 230 is arranged on a circuit board 240 which is coupled to the deformation transmission element 102, but is arranged separately from it.

On this circuit board 240, not only the evaluation circuit 230, but also the resistors 222 and 224 of the respective Wheatstone bridges 212, 214, 216 and 218 can be arranged.

A particularly advantageous embodiment provides that the deformation sensors 172, 174, 176 and 178 and the reference deformation sensors 182, 184, 186 and 188 are arranged on one side of the deformation transmission element 102, namely on a side that faces the circuit board 240, while the evaluation circuit 230, in particular with the A / D converter 232, the processor 234 and the memory 236, are arranged on the circuit board 240 on a side which also faces the deformation transmission element 102.

The deformation transmission element 102 and the circuit board 240 are preferably also enclosed or cast in a covering material 242, so that the deformation transmission element 102, the circuit board 240 and the covering material 242 form a common unit 244 (FIG. 23). This unit 244 can either be mounted on the connecting elements 114, 116 and 118 in such a way that the circuit board 240 lies on a side of the deformation transmission element 102 facing away from the holding arm 30, as shown for example in FIG. 22.

In a second exemplary embodiment, however, there is also the possibility of arranging the unit 244 in such a way that the circuit board 240 lies on a side of the deformation transmission element facing the holding arm 30, as shown for example in FIG. 24.

In a third exemplary embodiment, a separate temperature sensor 252, 254, 256 and 258 is assigned to each of the reference deformation sensors 182, 184, 186, 188 to safeguard the functions of the reference deformation sensors 182, 184, 186 and 188, for example.

The separate temperature sensors 252, 254, 256, 258 can either be arranged on the circuit board 240, as shown in FIG. 25, or, as shown in a fourth exemplary embodiment in FIG. 26, on the deformation transmission element 102.

Such an additional temperature sensor 252, 254, 256, 258 opens up the possibility of performing an additional temperature measurement in order to check whether the reference deformation sensors 182, 184, 186 and 188 are fully functional or whether these reference deformation sensors 182, 184, 184, 186, 188 incorrect measurements with regard to the voltages UD152, UD154, UD156 and UD158 could be present. The voltages UD252, UD254, UD256 and UD258 measured, for example, at these temperature sensors 252, 254, 256 and 258 are used both in the case of the arrangement on the circuit board 240 (FIG. 25) and in the case of the arrangement on the deformation transmission element 102 (FIG. 26 ) also fed directly to the A / D converter 232 or the processor 234, as shown in FIG. 27, and checked by the processor 234 before the evaluation of the digital values corresponding to the voltages UD152, UD154, UD156 and UD158.

In a fifth embodiment, a holding arm designated as a whole by 30 'is connected to the carrier unit 20 in that the first end 32' of the holding arm 30 'is held either directly or via a bearing unit 36' on the carrier unit 20, preferably on the cross member 22 is.

The holding arm 30 'comprises a receiving body 31 and is arranged at the first end 32' and the second end 34 'and is designed to receive a coupling element 40', which is provided, for example, for attaching a trailer or for fixing a load carrier unit.

For example, such a coupling element 40 'is designed as a coupling ball 43' held on a support arm 42 ', which allows a common connection with a ball coupling of a trailer, the support arm 42' with an insertion section 45 in an insertion receptacle 33 'of the receptacle body 31' an insertion opening 35, which is rearwardly seen in the direction of travel in the working position A, can be inserted into the receiving body 31 and can be fixed therein.

The coupling element 40 'is connected, for example, by means of the support arm 42' to the holding arm 30 'in such a way that the coupling ball 43, starting from a side of the support arm 42' facing away from a roadway 44, moves in the direction of a center axis 46 that runs approximately vertically when the roadway 44 is horizontal , which in the case of the coupling ball 43 'extends through a center point 48 of the ball. In particular, the plug-in receptacle 33 ′ is designed in such a way that it receives the plug-in section 45 transversely to an insertion direction E in a form-fitting and detachable manner, and provides a safeguard against movement in the insertion direction ER by means of a form-fitting element 41.

In particular, the insertion section 45 of the support arm 42 'is releasably fixed in the receiving body 31 by a fixing bolt 41 running transversely to the vehicle longitudinal center plane 18 and penetrating both the receiving body 31 and the support arm 42'.

A coupling element 40 'designed in this way also allows simple assembly of a load carrier unit, since frequently common load carrier units are also designed so that they can be mounted on the coupling ball 43 and, if necessary, additionally supported on the holding arm 30.

As an alternative to this, however, only a carrier arm 42 held on the load carrier unit with an insertion section 45 suitable for insertion into the insertion receptacle 33 'can also be used as the coupling element 40'.

To improve the aesthetic effect, the cross member 22 is preferably arranged under a rear bumper unit 50 of the motor vehicle body 12, the bumper unit 50 covering, for example, the cross member 22 and part of the first end 32 'of the holding arm 30'.

The holding arm 30 ', in particular in the illustrated fifth embodiment, carries the coupling element 40' comprising the coupling ball 43 through the plug-in section 45 inserted into the plug-in receptacle 33 ', with the holding arm 30', as shown in particular in FIGS. 28 to 32, extending from the pivot bearing unit 36 ', with which the holding arm 30 'is connected at its first end region 32', wherein, for example, a pivot bearing body 52 'of the pivot bearing unit 36' is formed on the first end region 32 '.

In the fifth exemplary embodiment, the pivot bearing body 52 'of the pivot bearing unit 36' is pivotably mounted on a pivot bearing receptacle 56 'about a pivot axis 54' running particularly transversely to the vertical vehicle longitudinal center plane 18, which on the one hand guides the pivot bearing body 52 'rotatably about the pivot axis 54' and on the other hand comprises a lock which, in the working position A and the rest position R, enables the holding arm 30 'to be fixed in a rotationally fixed manner with respect to pivoting movements about the pivot axis 54'.

With regard to the design of the pivot bearing unit 36 'and the respective locking of the pivot bearing body 52' relative to the pivot bearing receptacle 56 ', reference is made in full to DE 10 2016 107 302 A1.

In particular, a stop element 59 'shown in FIG. 31 is provided for locking the pivot bearing body 52' in the working position A, which engages through an opening in the holding arm 30 'and is located on an end of the plug-in receptacle facing away from the plug-in opening 35' 33 'inserted plug-in section 45 of the support arm 42' and thereby a pivoting movement of the holding arm 30 'with the receiving body 31' about the pivot axis 54 'while simultaneously interacting with a stop unit 60' (Fig. 32), comprising the pivot bearing body 52 'and the pivot bearing receptacle 56 'arranged stop elements, blocked.

In addition, the pivot bearing body 52 'is locked in the rest position R by a latching device 61, shown in FIG. 33.

The pivot bearing receptacle 56 'is in turn firmly connected to the cross member 22 via a pivot bearing base 58'. As shown in FIGS. 28 to 34, the holding arm 30 ′ in this fifth exemplary embodiment is from a working position A, shown in FIGS. 28 to 32, in which the coupling element 40 ′ having the coupling ball 43 is in such a way that it is behind the bumper unit 50 stands on a side facing away from a roadway 44, can be pivoted into a rest position R, shown in FIGS. 33 and 34, in which, with the coupling element 40 'dismantled, an insertion opening 35 of the plug-in receptacle 33 is arranged facing the roadway 44.

In particular, the holding arm 30 'extends in the working position A essentially in the vertical longitudinal center plane 18 of the vehicle, which, if it is designed as a coupling ball 43 provided with the support arm 42, intersects the coupling element 40' in the middle, so that in the working position A a vertical center axis 48 of the sphere lies in the longitudinal center plane 18.

Starting from the first end region 32 ', the receiving body 31' of the holding arm 30 'extends in the illustrated embodiment with an extension piece 62' to an intermediate piece 64 ', which extends to an intermediate body 66, on which one of the intermediate piece 64 and the end piece 62 opposite side is connected to an end piece 68, over which the coupling element 40 'extends with the support arm 42 arranged between the coupling ball 43 and the end piece 68.

The end piece 68 here forms the end region 34 'of the holding arm 30', the holding arm 30 'with the plug-in receptacle 33' absorbing the forces transmitted to it by the plug-in section 45 of the support arm 42 '.

A holding arm 30 'designed in this way and absorbing the forces transmitted by the insertion section 45 is, as shown in FIGS. 35 to 40, approximately straight through the extension piece 62', the intermediate piece 64 'of the intermediate body 66 and the end piece 68, and is in the working position A, in which loads of the coupling element 40 'occur and recorded are to be aligned so that the forces acting on the coupling element 40 ', in particular the ball center point 46, are transmitted via the holding arm 30' to the pivot bearing body 52 'of the pivot bearing unit 36', the pivot axis 54 'being a center of the Force absorption by the pivot bearing unit 36 'represents.

The forces acting on the coupling element 40 are, as shown in FIGS. 28 to 32, transmitted through the holding arm 30 'to the bearing unit 36' and from there to the carrier unit 20, which then introduces these forces into the rear region 14 of the motor vehicle body 12, different areas of the holding arm 30 'are used to detect the forces acting on the coupling element 40.

In the exemplary embodiment described above, a first deformation area 82 of the holding arm 30 is used as an example, which is formed, for example, by a transition area from the intermediate piece 64 into the intermediate body 66 ', and a second deformation area of the holding arm 30' is used, which is formed by a transition area of the intermediate body 66 'is formed in the end piece 68'.

Furthermore, it is assumed in this exemplary embodiment that the intermediate body 66 ′ has a high level of stability with respect to bending forces running in the longitudinal center plane 18 and also transversely to this, and in particular reacts primarily to tensile loads.

The first and second deformation areas 82, 84 are formed, for example, by a specifically designed area, for example by material weakening, wherein in the simplest case the material weakening can result from an introduced cross-sectional variation. For example, the force Fx shown in FIGS. 35 and 36, which is directed in the longitudinal center plane 18 and perpendicular to the center axis 46 and away from the pivot bearing body 52, leads to tensile forces ZX1 and ZX2 (FIG . 36) and on the other hand, at least in the case of the coupling ball 43 'protruding from the support arm 42' in the operating position on a side facing away from the roadway 44, also bending forces BX1 and BX2 (Fig. 35), which are superimposed on these tensile loads ZX1 and ZX2 , these forces acting in the direction of the longitudinal center plane 18, in particular in the longitudinal center plane 18, of the holding arm 30 '.

Furthermore, in the deformation areas 82 and 84, as shown in FIGS. 37 and 38, when the coupling element 40 is loaded with a force F _z , which acts in the direction of the central axis 46, essentially bending forces BZ1 and BZ2 occur in the deformation areas 82 and 84 These forces act in the direction of the longitudinal center plane 18, in particular in the longitudinal center plane 18, of the holding arm 30, which thus have opposite effects on opposite sides in relation to a so-called length-invariable neutral fiber NF.

In addition, a force F _y acting on the coupling element 40, which is directed perpendicular to the longitudinal center plane 18 and perpendicular to the center axis 46, as shown in FIGS. 39 and 40, leads to bending forces BY1 acting opposite one another on both sides of the longitudinal center plane 18 but on different sides thereof and BY2.

In particular, the deformation regions 82 and 84 are designed in such a way that they react to the tensile forces Z and the bending forces B with deformations of different sizes.

To detect these tensile forces ZX1 and ZX2 and the bending forces BX1 and BX2, BZ1 and BZ2 and BY1 and BY2, a force detection module designated as a whole as 100 is arranged on the holding arm 30 '. This force detection module 100 comprises a deformation transmission element 102 which is rigidly connected to the holding arm 30 'at three fastening areas 104, 106 and 108, the fastening area 104 being on a side facing the first end 32 and rigidly to one, for example on the intermediate piece 64 seated, extension 114 of the holding arm 30 ', the fastening area 106 is arranged approximately in the middle between the fastening areas 104 and 108 and is connected, for example, to a holding lug 116 sitting on the intermediate body 66, in particular in the middle thereof, and the fastening area 108 is connected to one on the end piece 68 , for example in a central region of the end piece 68 between the intermediate body 66 and the end 34, extension 118 of the holding arm 30 is connected.

The connection between the respective connecting elements 114, 116 and 118 of the holding arm 30 'is rigid and free of play, preferably by a weld or an adhesive that does not allow any elasticity of movement between the deformation transmission element 102 and the connecting elements 114, 116 and 118.

The connecting elements 114, 116 and 118 are preferably also rigidly connected to the holding arm 30 ', in particular molded onto it.

The force detection module 100, the deformation transmission element 102, the connecting elements 114, 116, 118, the deformation sensors 172, 174, 176, 178, the reference deformation sensors 182, 184, 186, 188, the Wheatstone bridges 212, 214, 216, 218, the evaluation circuit 230 and the circuit board 240 with the wrapping material 242 and the temperature sensors 252, 254, 256, 258 are in the fifth embodiment, for example, formed in the same way as described in the first to fourth embodiments and also work in the same way. In all of the exemplary embodiments described above, a calibration or calibration is carried out to determine a relationship between a measured value vector M representing the measured voltages UD152, UD154, UD156 and UD158 for the sensor values and one of the values WF _X , WF _{y generated by the evaluation circuit 230 or 230 '} and WF _Z for the vector K representing the force components can be determined by a transformation matrix T as shown in FIG.

Since the force vector K has the three force components with the values WF _X , WF _y and WF _Z , only three sensor values from the sensor values UD152, UD154, DU156 and UD158, for example the sensor values UD152, UD154 and UD156, are used to form the measured value vector M. used.

Such a measured value vector M is then to be multiplied by the transformation matrix T in order to obtain the individual values WF _X , WF _Z and WF _{y of} the force components of the force vector K, as shown in FIG. 41.

The transformation matrix T in this case has nine transformation coefficients t _lx , t2x, t3x, t _ly , t2 _Y , t3 _Y , t _lZ , t2 _Z , t3z.

In order to determine these transformation coefficients tix to t _3z , as shown in FIG. 42, the holding arm 40, for example with the swivel bearing body 52 fixed in place, is acted on the coupling element 40 by means of a force-loaded arm KA with different forces in different spatial directions.

For example, the arm KA acts with a force F _x in the X direction and / or with a force F _z in the Z direction and / or with a force F _y in the Y direction or with one or more combinations of these forces. As already mentioned, in the simplest case a transformation matrix T valid for all spatial directions x, y, z is stored in the memory 236, with which the values of the voltages UD152, UD154, UD156 and UD158 are converted into values WF _X and WF _Z and WF _y for the force components acting on the coupling element 40 can be converted.

In such a calibration (Fig. 42) three calibration processes are carried out one after the other, and for example in the first calibration process only the force component F _x and in the third calibration process only the force component F _y or only the force component F _z acted on the coupling element 40 and the sensor values UD152, UD154 and UD156 are then measured with each calibration process.

Since the other force components F _y and F _z or F _x and F _z or F _x and F _{y are} zero in each of the three calibration processes mentioned, an equation system with nine equations for determining the total of nine unknown transformation coefficients results after all three calibration processes tix to t _3z .

There is also the possibility, with all four sensor values UD152, DU 154 to work UD156 and UD158, as shown in FIG. 43, in this case a total of four calibration procedures tix to determine the twelve transform coefficients make to t4 _Z to total to obtain twelve equations for the twelve unknown transform coefficients tix to t4 _Z.

During the calibration or calibration, the force F _z preferably acts in the direction of gravity when the holding arm 30 is aligned as in the case of a motor vehicle 10 standing on an essentially horizontal plane. The force F _{x also} acts in an orientation of the holding arm 30, as in a motor vehicle 10 standing on an essentially horizontal surface, in an essentially horizontal direction, in particular in a vertical vehicle longitudinal center plane 18 and thus also in the vertical longitudinal center plane 18 of the holding arm 30.

Furthermore, the force F _y acts transversely, in particular perpendicular to the vertical longitudinal center plane 18 and perpendicular to the force F _x and the force F _z .

The assumed physical relationship between the exerted forces F _x , F _y , F _z and the resulting deformations represents the simplest possible assumption.

An improvement in the quality of the results for the values WF _X , WF _Z and WF _y can be achieved if the calibration for value pairs WF in each of the octants I to VIII arranged in the space around the coupling element 40 according to FIGS. 21 and 44 _X , WF _Z and WF _y takes place, so that there is also the possibility of nonlinear spatial correlations between the forces F _z , F _z , F _y acting on the coupling element 40 and the digital values of the voltages UD152, UD154, UD156 and UD158 in the Calibration and thus transformation of these values of the voltages UD152, UD154, UD156 and UD158 into the values WF _X , WF _Z and WF _y for the forces acting on the coupling element 40.

This significantly improves the accuracy of the determined values WF _X , WF _Z and WF _y.

For calibration in relation to octants I to VIII, shown in FIG. 44, during the calibration or calibration to determine an octant-specific transformation matrix T, the forces F _x , F _y and F _{z are} each selected so that they lie within the respective octant , and in particular all act in the direction of the same point on the coupling element 40. _{For example, only forces with force components Fxl, Fzl and F y} I within the same are used to determine the transformation matrix TI for the octant I.

_{As a result, values WF X} , WF _Z and WF _{y of} the force components determined for the space within the respective octants I to VIII can be determined even more precisely.

Since when an unknown force on the coupling element 40 is determined, its orientation and thus also its assignment to one of the octants is unknown, the components WF _X , WF _y and WF _Z thereof are determined either with the transformation matrix T or determined for all spatial directions With one of the transformation matrices TI to TVIII and subsequently, the evaluation circuit 230 or 230 'uses the values WF _X , WF _y and WF _{Z to} check which of the octants, for example octant III, the force is to be assigned to, and this is followed by a renewed determination of the values WF _X , WF _y , WF _Z by means of the transformation matrix determined for this octant, for example the transformation matrix TIII.

In order to determine load-related forces on the coupling element 40 from the sensor values UD152, UD154, UD156 and UD158, an evaluation unit 270 is provided, as shown in FIG.

The sequence control 280 first checks in a state detection stage 282 whether a voltage supply to the evaluation circuit 230 is sufficient. The state detection stage 282 uses a voltage sensor 302 to check the battery voltage of the vehicle, in particular the voltage applied to the deformation sensors 182, 184, 186, 188 and possibly the temperature sensors 252, 254, 256, 258 and the evaluation circuit 230.

In particular, the state detection stage 282 also checks whether the motor vehicle 10 is in a state that is permissible for detecting the forces on the holding arm, that is to say whether the vehicle is essentially aligned in a horizontal plane, an essentially horizontal plane then being given, if the deviation from an exactly horizontal plane is a maximum of ± 20 ° in each plane direction.

For this purpose, the state detection stage 282 checks one or more inclination sensors 304 (Fig. 3 and Fig. 45) the alignment of the fiction, contemporary device of the vehicle relative to the horizontal, whereby the inclination sensor 304 can be provided, for example, in the sequence control 280 or in the motor vehicle 10 or on the Carrier unit 20 can be provided and is queried by the state detection stage 282.

Furthermore, the position of the holding arm 30 is checked in the state detection stage 282 to determine whether it is in the working position or outside the same.

For this purpose, the state detection stage 282 checks the working position and / or other positions of the holding arm 30 with a set of sensors 306 (FIGS. 3 and 45), at least one checking of the working position being carried out and, if this is not the case, this checking is assessed as negative will. If, on the one hand, a sufficient voltage supply and, on the other hand, a sufficient alignment of the motor vehicle 10 and, moreover, the existence of the working position of the holding arm 30 are determined in the state detection stage 282, then in an activation stage 284 that is used, the evaluation circuit 230 is activated so that this is due to the sensor values determine the values WF _X , WF _Z and WF _y in the current state of the motor vehicle 10.

After the state detection stage 282 has recognized a permissible state for detecting the forces on the holding arm 30, in particular on the coupling element 40 of the same, and the activation stage 284 has activated the evaluation circuit 230, a zero load detection stage 286 is used.

In the zero load detection stage 286, it is first checked whether a detection of the no load - that is, no load - on the holding arm 30, in particular the load when there is no external force acting on the coupling element 40 of the holding arm 30, can be detected.

The zero load detection stage 286 activates, for example, a zero load values memory 312i, which takes over the values of the evaluation circuit 230 output _{at the outputs WF X} , WF _Z , WF _y _{at the time of activation and uses them as values WF x} o, WF _z o and WF _y o, the are determined without external force, i.e. at zero load, stores.

These values stored in the no-load value memory 312i are then compared with reference values stored in a no-load reference memory 3122 for a state of the holding arm 30, in particular the coupling element 40, at no load in order to carry out a plausibility check to determine whether there is a load on the holding arm 30, in particular the Coupling element 40, can be excluded by an external force. These values stored in the no-load reference memory 3122 are recorded, for example, by previous or factory determinations of the values WFxo, WFzo, WF _y o at no-load.

In addition, the zero load detection stage 286 checks how long the time span has passed between the last movement of the holding arm 30 into the working position and the current point in time.

If, for example, it is found that the movement of the holding arm 30 and the coupling element 40 into the working position only took place a few seconds ago, it can be assumed that no external force is yet effective on the coupling element 40 and thus the zero load can be determined.

Another possibility is that the zero load detection stage 286 activates a camera system 314 on the motor vehicle 10 (FIGS. 1 and 44), which is integrated, for example, into the reversing camera system of the motor vehicle 10 and is able to detect whether the coupling element 40 is present and thus an object, in particular a ball coupling or a load carrier, effectively attacks or does not act on the holding arm 30.

Another possibility is that the zero load detection stage 286 activates a sensor system 316 (FIGS. 2 and 44), for example comprising a set of ultrasonic sensors, which are integrated in particular in the rear bumper unit 50 and are also able to recognize whether an object is acting on the holding arm 30 and the coupling element 40 or not.

Another possibility for checking whether no object is acting on the coupling element 40 and thus the holding arm 30 provides that the no-load detection stage 286 a socket 31 assigned to the device for supplying a trailer or a load carrier unit is active, i.e. a supply plug in this socket is plugged in (Fig. 2 and Fig. 45). If this is detected by a sensor 318 assigned to the socket 31, it can also be assumed that an object is acting on the coupling element 40 and / or the holding arm 30, so that no zero load detection is possible.

Based on this, the no-load memory 312 is then activated in order to store the values WF _X , WF _Z and WF _y supplied by the evaluation circuit 230 or 230 'as values WF _x o, WF _z o and WF _y o at no load, which correspond to a state of the holding arm 30 and the coupling element 40 correspond to without external force.

However, if the zero load detection stage 286 does not determine a state in which the detection of a no load state is possible, for example the values WFxo, WF _z o and WF _y o stored in the no load memory 3122 when the no load was recorded are not replaced by the values just in The values stored in the no-load value memory 312i are replaced, but are used further and the values stored in the no-load memory 312i are deleted.

After passing through the zero load detection stage 286, a load detection stage 288 is activated.

The load detection stage 288 only serves to detect the force components acting on the coupling element 40 and the holding arm 30 as a result of the load.

The load detection stage is preferably only active when an on-board function of the motor vehicle 10 is activated, that is to say, for example, the operation of all electrical components is activated. This is done, for example, by querying a suitable vehicle electrical system voltage. Furthermore, the load detection stage 288 checks with access to the sensor 318 whether a socket 31 assigned to the device according to the invention is activated, the activation of which indicates the presence of an external force acting on the coupling element 40, be it by a trailer or a load carrier unit (Fig. 45).

Furthermore, the load detection stage 288 checks by means of a sensor 322 or by querying a vehicle controller whether the vehicle is being moved at a speed of less than 5 km / h or not, so that a motor vehicle 10 that is basically stationary for the load detection can be assumed (FIG. 45). .

In addition, the load detection stage 288 checks, for example, likewise with the camera system 314, whether an external object, for example a trailer or a load carrier unit, has been attacked on the coupling element 40 and / or the load detection stage 288 uses the camera system 314 and / or the sensor system 316 to check whether the holding arm 30 and the coupling element 40 attack an external object, for example a trailer or a load carrier unit.

If necessary, the load detection stage 288 also uses the sensor 306 to check whether the holding arm 30 with the coupling element 40 is in the working position in which a trailer can be attached or a load carrier unit can be mounted.

If the load detection stage 288 detects that an external object is acting on the coupling element 40 and the holding arm 30, the load detection stage 288 causes on the one hand the values WF _X , WF _Z and WF _{y to be} taken over by the evaluation circuit 230 or 230 'and on the other hand the values WF _x o, WF _z o and WF _y o are taken over from the no-load memory 3122 and these values WFxo, WF _z o and WF _y o in a subtraction unit 320 are subtracted from the values WF _X , WF _Z and WF _y (FIG. 45), so that values WFxi, WF _Zi and WF _yi are then present which represent the load-dependent values for the external force components F acting on the holding element 30 and the coupling element 40 _x , F _z , F _y represent.

A presentation unit 304, for example a display, is controlled by a subsequent presentation stage 292 of the sequence control 280, which shows the individual load-related values WFxi, WF _Zi and WF _{yi of} the force components as easily as possible for a user.

The presentation stage 292 can for example represent the load-related values WF _X I, WF _Z I, WF _yi on the presentation unit 324 numerically or in the form of graphic bar charts (FIG. 46), with a length of the bar representing the value.

It is particularly advantageous if the presentation stage 292 shows the values WFxi, WF _Zi and WF _{yi of} the force components in relation to the measurement accuracy that can be achieved when determining the same by means of the transformation matrix T and thus also makes the measurement uncertainty visible to a user, as for example in Fig 47, whereby the individual bars are highlighted with different colors for different measurement accuracy.

Another possibility is that the presentation stage 292 shows the component WF _Zi , which represents the support load in comparison to the support load permissible for this motor vehicle 10, for example graphically as shown in FIG. 48, so that a vehicle user can immediately see whether the maximum permissible vertical load of this motor vehicle 10 has been reached or not. In addition, there is also the option of using the presentation stage 292 _{to transmit the load-related values WF xe} , WF _ze and WF _{ye of} the force components to a stabilization system 326 and / or a chassis control 328 of the motor vehicle (10) (FIGS. 1 and 44). to improve the driving characteristics when towing a trailer.

Claims

PATE NTAN S CHALLENGES

1. At the rear of a motor vehicle body (12) mountable device for coupling a trailer or a load carrier unit, comprising a holding arm (30) which is fixedly connected to the motor vehicle body (12) at a first end (32) during operation and to a second The end (34) is designed to carry a coupling element (40), because the holding arm (30) is provided with a sensor arrangement (170), that the holding arm (30) has at least three deformation sensors ( 172, 174, 176, 178), which in particular react in different ways to three forces acting on the coupling element (40) in transverse spatial directions, and that the at least three deformation sensors (172, 174, 176, 178) sensor values (M), from which at least one force component acting on the coupling element (40) is determined by means of an evaluation unit (270).

2. Device according to claim 1, characterized in that the evaluation unit (270) determines at least one of the values (WF _X , WF _y , WF _Z ) of their force components extending in the spatial directions (x, y, z).

3. Device according to one of the preceding claims, characterized in that the evaluation unit (270) determines the value (WF _Z ) of its force component extending in the direction of gravity (Z).

4. Device according to one of the preceding claims, characterized in that the evaluation unit (270) determines the value (F _x ) of its force component extending in the direction of travel of the motor vehicle (10).

5. Device according to one of the preceding claims, characterized in that the evaluation unit (270) determines the value (F _y ) of its force component extending transversely, in particular perpendicularly, to a vertical longitudinal center plane (18).

6. Device according to one of the preceding claims, characterized in that the evaluation unit (270) checks before determining the force components by means of a state detection stage (282) whether a suitable state for determining the force components on the coupling element (40) is present.

7. The device according to claim 6, characterized in that the state detection stage (282) by detecting at least one of the parameters such as voltage supply, vehicle orientation in space, presence of the working position of the holding arm (30), checks whether a suitable state for determining the force the coupling element (40) is present.

8. Device according to one of the preceding claims, characterized in that the evaluation unit (270) by means of a zero load detection stage (286) before determining the force components on the coupling element (40) a detection of the values (WFxo, WF _y o, WFzo) of the force components takes place in the case of no load.

9. Device according to one of the preceding claims, characterized in that after a movement of the holding arm (30) into a working position on the part of the zero load detection stage (286) a detection of at least one of the values (WF _X , WF _y , WF _Z ) of the force components takes place at zero load.

10. Device according to one of the preceding claims, characterized in that after assembly of a coupling element (40) on the holding arm (30) on the part of the zero load detection stage (286) a detection of at least one of the values (WF _X , WF _y , WF _Z ) force components Zero load takes place.

11. Device according to one of the preceding claims, characterized in that the values (WF _X , WF _Z , WF _y ) of the force components at zero load are only saved by the zero load detection stage (286) if the values (WF _X , WF _y , WF _Z ) of the force components fall below specified values that exclude an external force on the coupling element (40).

12. Device according to one of the preceding claims, characterized in that when an approach to an object, in particular a trailer or a load carrier, is recognized by the zero load detection stage (286), the at least one of the values (WF _X , WF _y , WF _Z ) takes place at zero load.

13. Device according to one of the preceding claims, characterized in that, after recording at least one of the values (WF _X , WF _Z , WF _y ) of the force components at zero load, at least one of the values (WF _X , WF _y , WF _Z ) Force components at zero load takes place after a specified period.

14. Device according to one of the preceding claims, characterized in that the evaluation unit (270) by means of a load detection stage (288) to determine at least one of the load-related values (WFxi, WF _yi , WF _Zi ) of the force components supplied by the zero load The corresponding values (WF _X0 , WF _y0 , WF _Z0 ) of the force components are subtracted from the _{values (WF X} , WF _y , WF _Z ) of the force components supplied with a force on the coupling element (40).

15. Device according to one of the preceding claims, characterized in that the load detection stage (288) carries out a determination of at least one value of the force components on the coupling element (40), provided that an on-board function of the motor vehicle (10) is carried out.

16. Device according to one of the preceding claims, characterized in that the load detection stage (288 _{) carries out a determination of at least one of the values (WF X} , WF _y , WF _Z ) of the force components on the coupling element (40) if a plug is in a the socket (31) assigned to the holding arm (30) is plugged in.

17. Device according to one of the preceding claims, characterized in that the load detection stage (288) determines at least one of the values (WF _X , WF _y , WF _Z ) of the force components on the coupling element (40) after detecting one on the coupling element (40) attacking object, in particular a trailer or a load carrier.

18. Device according to one of the preceding claims, characterized in that the load detection stage (288) determines at least one of the values (WF _X , WF _y , WF _Z ) of the force components on the coupling element (40) when the speed of the motor vehicle (10) is less than five kilometers per hour, in particular when the motor vehicle (10) is stationary.

19. Device according to one of the preceding claims, characterized in that the evaluation unit (270) by means of the presentation stage (292) _{transmits at least one load-related value (F x} , F _y , F _z ) of the force components acting on the coupling element (40).

20. Device according to one of the preceding claims, characterized in that the evaluation unit (270) _{transmits at least one value (WF Z} ) of the load-related force component acting in the vertical direction (Z) on the coupling element (40) by means of a presentation stage (292).

21. Device according to one of the preceding claims, characterized in that the evaluation unit (270) by means of a presentation stage (292) has at least one value (WF _X ) applied to the coupling element (40) in the direction of travel and in particular parallel to a vertical longitudinal center plane (18) acting load-related force component transmitted.

22. Device according to one of the preceding claims, characterized in that the values of the force components (WF _X , WF _y , WF _Z ) acting on the coupling element (40) are derived from the sensor values by means of transformation coefficients (tix, ..., t ... ) are linked.

23. Device according to one of the preceding claims, characterized in that the evaluation unit (270) by means of the presentation stage (292) has at least one value (WF _y ) transverse to a vertical longitudinal center plane (18) of the holding arm (30), in particular in an approximately horizontal direction (Y) acting load-related force component (WF _y ) transmitted.

24. Device according to one of the preceding claims, characterized in that the presentation stage (292) uses a presentation unit (304) to display the at least one value (WF _X , WF _y , WF _Z ) of the respective force component and in particular also the measurement accuracy associated with this indicates.

25. Device according to one of the preceding claims, characterized in that the presentation stage (292) _{qualitatively displays the at least one value (WF X} , WF _y , WF _Z ) of the respective force component by means of the presentation unit (304).

26. Device according to one of the preceding claims, characterized in that the presentation stage (292) by means of the presentation unit (304) the at least one value (WF _Z ) of the load-related force component acting on the coupling element (40) in the vertical direction in relation to a predetermined one Indicates vertical load for the respective motor vehicle (10).

27. Device according to one of the preceding claims, characterized in that the presentation stage (292) _{displays the at least one value (F x} ) of the force component acting in the direction of travel in relation to a maximum tensile force by means of the presentation unit (304).

28. Device according to one of the preceding claims, characterized in that the presentation stage (292) at least one of the values (WF _X , WF _y , WF _Z ) of the force components acting on the coupling element (40) are transmitted to an electronic stabilization system of the vehicle.

29. Device according to one of the preceding claims, characterized in that the presentation stage (292) has at least one of the values (WF _X , WF _y , WF _Z ) of the force components of a chassis control (328) of the motor vehicle (10 ) transmitted.

30. Device according to one of the preceding claims, characterized in that the deformation sensors (172, 174, 176, 178) are arranged relative to the holding arm (30) in such a way that when a force (F _x , F _y , F _z ) deliver different sensor values with an identical amount in each of the three spatial directions (x, y, z).

31. Device according to one of the preceding claims, characterized in that four deformation sensors (172, 174, 176, 178) are arranged on the holding arm (30), which in a direction in the different transverse spatial directions (x, y, z ) effective force (F _x , F _y , F _z ) of the same amount provide different sensor values.

32. Device according to one of the preceding claims, characterized in that the sensor values supplied by the deformation sensors (172, 174, 176, 178) by means of transformation coefficients (ti, ... tu) of a transformation matrix (T) with the values (WF _X , WF _y , WF _Z ) of the force components (F _x , F _y , F _z ) in the three transverse spatial directions (x, y, z) are linked.

33. Device according to the preamble of claim 1 or one of the preceding claims, characterized in that, starting from the coupling element (40) as the center point, the space around the coupling element (40) in the three spatial directions (x, y , z) defined eight octants (I ... VIII) is divided so that for each of the octants (I ... VIII) an octant-based transformation matrix (T) is specified in the evaluation circuit (230) that the evaluation circuit (230) by means of one of the predetermined transformation matrices (T) determines the values (F _x , F _y , F _z ) of the force components and assigns them to one of the octants (I ... VIII) and then on the basis of the octant-based transformation matrix (T) for the one that absorbs the force vector Octants the values (WF _X , WF _y , WF _Z ) of the force components are determined again.

34. A method for detecting the force on a device for coupling a trailer or a load carrier unit, which can be mounted on the rear of a motor vehicle body (12), comprising a holding arm (30) which is fixedly connected to the motor vehicle body (32) at a first end (32) during operation. 12) and is designed at a second end (34) to carry a coupling element (40), the holding arm (30) being provided with a sensor arrangement (170), characterized in that the holding arm (30) has at least three deformation sensors ( 172, 174, 176, 178), which in particular react in different ways to three forces acting on the coupling element (40) in transverse spatial directions (x, y, z), and that the at least three deformation sensors (172, 174 , 176, 178) deliver sensor values (M) from which at least one force component (K) acting on the coupling element is determined.

35. The method according to claim 34, characterized in that at least one of the values (WF _X , WF _y , WF _Z ) of the force components running in these spatial directions (x, y, z) are determined for the force.

36. The method according to claim 34 or 35, characterized in that at least the value (WF _Z ) of the force component extending in the direction of gravity (Z) is determined.

37. The method according to any one of claims 34 to 36, characterized in that at least the value (WF _X ) of the force component running in the direction of travel of the motor vehicle (10) is determined.

38. Method according to one of the preceding claims, characterized in that at least the value (WF _y ) of the force component running transversely, in particular perpendicularly, to a vertical longitudinal center plane (18) is determined.

39. The method according to any one of claims 34 to 38, characterized in that before determining the values (WF _X , WF _y , WF _Z ) of the force component (K), it is checked whether a suitable state for determining the force components on the coupling element (40) is available.

40. The method according to claim 39, characterized in that by detecting at least one of the parameters such as voltage supply, vehicle orientation in space, the presence of the working position of the holding arm (30), it is checked whether a suitable state for determining the force components on the coupling element ( 40) is available.

41. The method according to any one of claims 34 to 40, characterized in that before the force components on the coupling element (40) are determined, at least one of the values (WFx, WF _y , WF _Z ) of the force components is recorded in the case of no load .

42. The method according to any one of claims 34 to 41, characterized in that the values (WF _X , WF _y , WF _Z ) of the force components are recorded at zero load after the holding arm (30) has moved into a working position.

43. The method according to any one of claims 34 to 42, characterized in that the values (F _x , F _y , F _z ) of the force components are recorded at zero load after a coupling element (40) has been installed on the holding arm (30).

44. The method according to any one of the preceding claims, characterized in that the values (F _x , F _y , F _z ) of the force components are only stored at zero load if the values (F _x , F _y , F _z ) are predefined external force on the coupling element (40) fall below negative values.

45. The method according to any one of claims 34 to 44, characterized in that a detection of the values (F _x , F _y , F _z ) of the force components at zero load after a detection of an approach to an object, in particular a trailer or a burden bearer, takes place.

46. The method according to any one of claims 34 to 45, characterized in that after the values (F _x , F _y , F _z ) of the force components have been recorded at zero load, the values (F _x , F _y , F _z ) of the force components at zero load takes place after a specified period of time.

47. The method according to any one of claims 34 to 46, characterized in that, in order to determine at least one of the load-related values (WFxi, WF _yi , WF _zi ) of the force components, the corresponding values (WF _x o, WF _y o, WF _z _{o) of the force components are subtracted from the values (WF X} , WF _y , WF _Z ) of the force components supplied when a force is applied to the coupling element (40).

48. The method according to any one of claims 34 to 47, characterized in that at least one of the values (WF _X , WF _y , WF _Z ) of the force components on the coupling element (40) is determined if an on-board function of the motor vehicle (10 ) is performed.

49. The method according to any one of the preceding claims 34 to 48, characterized in that at least one of the values of the force components on the coupling element (40) is determined if a plug is inserted into a socket (31) assigned to the holding arm (30) ) has taken place.

50. The method according to any one of claims 34 to 49, characterized in that a determination of at least one of the values of the force components on the coupling element (40) after detection of an object attacking the coupling element (40), in particular a trailer or a load carrier, he follows.

51. The method according to any one of claims 34 to 50, characterized in that at least one of the values (WF _X , WF _y , WF _Z ) of the force component on the coupling element (40) is determined when the speed of the motor vehicle ( 10) is less than five kilometers per hour, especially when the motor vehicle (10) is stationary.

52. The method according to any one of claims 34 to 51, characterized in that at least one value (WF _Z ) of the force component acting in the vertical direction (Z) on the coupling element (40) is transmitted.

53. The method according to any one of claims 34 to 52, characterized in that at least one value (WF _X ) of the force component acting on the coupling element (40) in the direction of travel and in particular parallel to a vertical longitudinal center plane (18) is transmitted.

54. The method according to any one of claims 34 to 53, characterized in that at least one value (WF _y ) of a force component acting transversely to a vertical longitudinal center plane (18) of the holding arm (30), in particular in an approximately horizontal direction, is transmitted.

55. The method according to any one of claims 34 to 54, characterized in that at least one of the values (WFxi, WF _yi , WF _Zi ) of the respective force component and in particular the measurement accuracy associated with this is displayed.

56. The method according to any one of claims 34 to 55, characterized in that at least one of the values (WFxi, WF _yi , WF _Zi ) of the respective force component is displayed qualitatively.

57. The method according to any one of claims 34 to 56, characterized in that the value (WF _Z ) of the force component acting on the coupling element (40) in the vertical direction is displayed in relation to a predetermined support load for the respective motor vehicle (10).

58. The method according to any one of claims 34 to 57, characterized in that the value (WF _X ) of the force component acting in the direction of travel is displayed in relation to a maximum tensile force.

59. The method according to any one of claims 34 to 58, characterized in that at least one of the values (WF _X , WF _y , WF _Z ) of the force components acting on the coupling element (40) is an electronic stabilization system (326) of the motor vehicle (10) be transmitted.

60. The method according to any one of claims 34 to 59, characterized in that at least one of the values (WF _X , WF _y , WF _Z ) force components acting on the coupling element (40) are transmitted to a chassis controller (328) of the motor vehicle (10) will.

61. The method according to the preamble of claim 34 or one of claims 34 to 60, characterized in that the values (WFx, WF _y , WF _Z ) of the force acting on the coupling element (40) components with the sensor values (M) by means of Transformation coefficients (tix ... tn) are linked.

62. The method according to any one of claims 34 to 61, characterized in that the sensor values supplied by the deformation sensors (172, 174, 176, 178) by means of the transformation coefficients (tix ... tn) of a transformation matrix (T) with the force components in the three transverse spatial directions (x, y, z) are linked.

63. The method according to claim 61 or 62, characterized in that the transformation coefficients (tix ... tn) of the transformation matrix (T) are determined as part of a calibration process.

64. The method according to claim 63, characterized in that the sensor values supplied by the deformation sensors (172, 174, 176, 178) are recorded in the calibration process when a defined force component acts on the coupling element (40).

65. The method according to claim 63 or 64, characterized in that, during the calibration process, the coupling element (40) is acted upon with a defined force component in one of the three transverse spatial directions (x, y, z) and that of the Deformation sensors (172, 174, 176, 178) delivered sensor values are detected.

66. The method according to any one of claims 64 to 65, characterized in that in the calibration process each force component acting in one of the three spatial directions (x, y, z) has the same amount.

67. The method according to any one of claims 34 to 66, characterized in that the determination of the values (WF _X , WF _y , WF _Z ) of the force components acting on the coupling element by means of the sensor values based on the calibration by a force component determined in one of the three spatial directions (x, y, z)

Transformation coefficient takes place.

68. The method according to any one of claims 34 to 67, characterized in that the determination of the transformation coefficient is based on the assumption of a linear link between the values (WF _X , WF _y , WF _Z ) of the force components in the three spatial directions (x , y, z) and the sensor values supplied by the deformation sensors (172, 174, 176, 178).

69. The method according to any one of claims 34 to 67, characterized in that the three spatial directions (x, y, z) running transversely to one another run perpendicular to one another.

70. The method according to any one of claims 34 to 67, characterized in that, starting from the coupling element (40) as the center point, the space around the coupling element (40) is defined in the three spatial directions (x, y, z) running transversely to one another eight octants (I ... VIII) is divided so that in order to determine the set of transformation coefficients in each of the octants (I ... VIII) the coupling element (40) is acted on with force components which are within the respective octant that the sensor values are recorded and that for these force components in the respective one of the octants (I to VIII) octant-based transformation coefficients are determined.

71. The method according to any one of the preceding claims, characterized in that _{one of the transformation matrices (T) is used to determine the values (WF X} , WF _y , WF _Z ) of the force components on the coupling element (40) and which of the Octants (I ... VIII) the values (F _x , F _y , F _z ) are to be assigned to force components and then a new determination of the values (WF _X , WF _{y) with the transformation matrix (T) assigned to this octant (I to VIII)} , WF _Z ) of the force components is carried out.

72. A device which can be mounted on the rear of a motor vehicle body (12) for coupling a trailer or a load carrier unit, comprising a holding arm (30) which is firmly connected to the motor vehicle body (12) at a first end (32) during operation and to a second End (34) is designed to carry a coupling element (40), in particular according to one of the preceding claims, characterized in that forces acting on the coupling element (40) and transmitted from the holding arm (30) to the motor vehicle body (12) during operation an evaluation unit (230) can be detected with a sensor arrangement (170) which has at least three deformation sensors (172, 174, 176) and that in particular the at least three deformation sensors (172, 174, 176, 178) of the sensor arrangement (170) the same side of a neutral fiber of the holding arm which is not variable in length when the holding arm (30) is deformed.

73. Device according to the preamble of claim 72 or claim 72, characterized in that a force detection module (100) is arranged on one side of the holding arm (30, 30 ') which comprises a sensor arrangement (170) which, during operation, is connected to forces acting on the coupling element (40) and transmitted by the holding arm (30) to the motor vehicle body (12).

74. The device according to claim 73, characterized in that the sensor arrangement has at least three deformation sensors (172, 174, 176).

75. The device according to claim 73 or 74, characterized in that the force detection module (100) in the operating state is not arranged on any side of the holding arm (30, 30 ') facing a roadway (44).

76. Device according to one of claims 73 to 75, characterized in that the force detection module (100) is arranged in the operating state on a side of the holding arm (30, 30 ') facing away from a roadway (44).

77. Device according to the preamble of claim 72 or one of the preceding claims, characterized in that forces acting on the coupling element (40) during operation and transmitted from the holding arm (30) to the motor vehicle body (12) are carried out by an evaluation unit (230 ) are detected with a sensor arrangement (170) which has at least three deformation sensors (172, 174, 176) that the deformation sensors (172, 174, 176, 178) are arranged on at least one deformation transmission element (102) which is connected to the holding arm ( 30) is connected.

78. Device according to the preamble of claim 72 or one of the preceding claims, characterized in that forces acting on the coupling element (40) during operation and transmitted from the holding arm (30) to the motor vehicle body (12) are carried out by an evaluation unit (230 ) are detected with a sensor arrangement (170) which has at least three deformation sensors (172, 174, 176) so that all deformation sensors (172, 174, 176, 178) of the sensor arrangement (170) are arranged on a common deformation transmission element (102) .

79. Device according to one of the preceding claims, characterized in that each of the at least three deformation sensors (172, 174, 176) detects different large deformations of the holding arm (30, 30 ') when one and the same force acts on the coupling element (40).

80. Device according to one of the preceding claims, characterized in that the deformation transmission element (102) is connected to the holding arm (30) without relative movement and thus rigidly at at least two fastening areas (104, 106, 108) and that at least one of the deformation sensors (172, 174, 176, 178) are arranged between the fastening areas (104, 106, 108) of the deformation transmission element (102).

81. Device according to one of the preceding claims, characterized in that the deformation transmission element (102) is connected to the holding arm (30) with at least three fastening areas (104, 106, 108) and that in each case between two of the fastening areas (104, 106, 108 ) at least one of the deformation sensors (172, 174, 176, 178) is arranged.

82. Device according to one of the preceding claims, characterized in that the deformation transmission element (102) is connected to the holding arm (30) in the fastening areas (104, 106, 108) by means of connecting elements (114, 116, 118).

83. The device according to claim 82, characterized in that the connecting elements (114, 116, 118) are rigidly connected on the one hand to the holding arm (30) and on the other hand rigidly to the fastening areas (104, 106, 108) of the deformation transmission element (102).

84. The device according to claim 83, characterized in that the connecting elements (114, 116, 118) are molded onto the holding arm (30).

85. Device according to one of the preceding claims, characterized in that the connecting elements (114, 116, 118) deformations of the holding arm (30) in deformation regions (82, 84) of the holding arm lying between the connecting elements (114, 116, 118) (30) transferred to the fastening areas (104, 106, 108) of the deformation transmission element (102).

86. Device according to one of claims 82 to 85, characterized in that a deformation area (82, 84) of the holding arm (30) lies between two connecting elements (114, 116, 118).

87. Device according to one of the preceding claims, characterized in that the holding arm (30) has at least two deformation areas (82, 84), the deformations of which occur via connecting elements (114, 116, 118) arranged on both sides of the respective deformation area (82, 84) Fastening areas (104, 106, 108) of the deformation transmission element (102) is transmitted, between which a deformation-prone area (152, 154, 156) of the deformation transmission element (102) lies.

88. Device according to claim 87, characterized in that the at least two deformation areas (82, 84) are arranged one after the other in a direction of extension of the holding arm (30).

89. Device according to one of the preceding claims, characterized in that at least one deformation sensor (172, 174, 176, 178) is arranged in one of the deformation-prone areas (152, 154, 156, 158) of the deformation transmission element (102).

90. Device according to one of claims 87 to 89, characterized in that each deformation-prone area (152, 154, 156, 158) is connected to a deformation-resistant area (144, 146, 148) of the deformation transmission element (102) and that the fastening areas (104, 106, 108) each lie in a deformation-stiff area (144, 146, 148).

91. The device according to claim 90, characterized in that the deformation-prone areas (152, 154, 156, 158) are each arranged between two deformation-resistant areas (144, 146, 148).

92. Device according to claim 90 or 91, characterized in that the deformation-resistant areas (144, 146, 148) and the deformation-prone areas (152, 154, 156, 158) are arranged one after the other in a deformation direction.

93. Device according to one of claims 87 to 92, characterized in that the deformation-prone areas (152, 154, 156, 158) are designed as deformation concentration areas.

94. Device according to one of the preceding claims, characterized in that the material of the deformation transmission element (102) outside the deformation-prone areas (152, 154, 156, 158) is designed as a deformation-resistant or deformation-inert material.

95. Device according to one of the preceding claims, characterized in that the material of the deformation transmission element (102) is prone to deformation in the deformation-prone areas (152, 154, 156, 158) by a shape, for example a cross-sectional constriction.

96. Device according to one of the preceding claims, characterized in that the deformation transmission element (102) has a deformation-free area (192, 194, 196, 198) in addition to the respective deformation-prone area (152, 154, 156, 158) on which at least one Reference deformation sensor (182, 184, 186, 188) is arranged.

97. Apparatus according to claim 96, characterized in that the respective deformation-free area (192, 194, 196, 198) is formed from the same material as the deformation-prone area (152, 154, 156, 158).

98. Device according to claim 96 or 97, characterized in that the respective deformation-free area (192, 194, 196, 198) is connected on one side to a deformation-resistant area (144, 146, 148) of the deformation transmission element (102).

99. Device according to one of claims 96 to 98, characterized in that the deformation-free area (192, 194, 196, 198) of the deformation transmission element (102) is designed like a tongue.

100. Device according to one of claims 96 to 99, characterized in that the deformation-free area (192, 194, 196, 198) of the deformation transmission element (102) is made from the same material, in particular with the same material thickness, as the deformation-prone area ( 152, 154, 156, 158).

101. Device according to one of claims 96 to 100, characterized in that the reference deformation sensors (182, 184, 186, 188) are thermally coupled to the deformation transmission element (102).

102. The device according to claim 101, characterized in that the reference deformation sensors (182, 184, 186, 188) are thermally coupled to the deformation sensors (172, 174, 176, 178) by means of the deformation transmission element (102).

103. The device according to claim 102, characterized in that for optimal thermal coupling between the respective deformation sensor (172, 174, 176, 178) and the reference deformation sensor (182, 184, 186, 188) assigned to it, each with a deformation sensor (172, 174 , 176, 178) provided deformation-prone area (152, 154, 156, 158) thermally coupled to the deformation-free area (192, 194, 196, 198) assigned to this and the assigned reference deformation sensor (182, 184, 186, 188) is.

104. Device according to one of claims 96 to 103, characterized in that the deformation-free area (192, 194, 196, 198) carrying the respective reference deformation sensor (182, 184, 186, 188) has the same thermal behavior as that of the corresponding deformation sensor ( 172, 174, 176, 178) bearing deformation-prone areas (152, 154, 156, 158).

105. Device according to one of claims 96 to 104, characterized in that the respective deformation-free area (192, 194, 196, 198) carrying the reference deformation sensor (182, 184, 186, 188) has a geometric shape that corresponds to the Deformation sensor (172, 174, 176, 178) bearing deformation-prone area (152, 154, 156, 158) is comparable.

106. Device according to one of claims 96 to 105, characterized in that the deformation-free area (192, 194, 196, 198) of the deformation transmission element (102) is made of the same material as the deformation-prone area (152, 154, 156, 158 ) of the deformation transmission element (102).

107. Device according to one of claims 96 to 106, characterized in that the reference deformation sensors (182, 184, 186,

188) at least one temperature sensor (252, 254, 256, 258) is assigned for function monitoring.

108. Device according to one of the preceding claims, characterized in that the deformation transmission element (102) is plate-like and each deformation-prone area (152, 154, 156, 158) carrying a deformation sensor (172, 174, 176, 178) by a cross-sectional constriction of the Deformation transmission element (102) is formed.

109. Apparatus according to claim 108, characterized in that the cross-sectional constriction of the deformation transmission element (102) is formed by a constriction of a surface extension of the deformation transmission element (102).

110. Device according to one of the preceding claims, characterized in that the deformation sensors and the reference deformation sensors are designed as strain sensors, in particular strain gauges.

111. Device according to one of claims 72 to 109, characterized in that the deformation sensors and the reference deformation sensors are designed as magnetostrictive or optical sensors.

112. Device according to the preamble of claim 72 or one of the preceding claims, characterized in that the holding arm (30) has a first deformation area (82) and a second deformation area ( 84) which, when a force (Fx) acts parallel to the direction of travel (24) in the longitudinal center plane (18) of the holding arm (30), experience deformations that differ from the deformations in a direction transverse to the travel in the longitudinal center plane (18) different direction (24) acting force (F _z ).

113. The device according to claim 112, characterized in that the first and the second deformation area (82, 84 _{) each experience deformations in the case of a force (F y} ) acting transversely, in particular perpendicular to the longitudinal center plane (18), which are different from the deformations in an in the longitudinal center plane (18) parallel and / or transverse to the direction of travel (24) acting force F _x , F2) differentiate.

114. Device according to claim 112 or 113, characterized in that the first and the second deformation area (82, 84) are arranged one after the other in the direction of extent of the holding arm (30).

115. Device according to one of the preceding claims, characterized in that each deformation sensor (172, 174, 176, 178) with the assigned reference deformation sensor (182, 184, 186, 188) in a Wheatstone bridge (212, 214, 216, 218 ) is interconnected.

116. Device according to one of the preceding claims, characterized in that the evaluation unit (230) has a processor (234), which the values corresponding to the deformations in the deformation-prone areas (152, 154, 156, 158) with a calibration in a memory (236) determined and stored transformation values converted into the corresponding values (WFx, WFY, WFZ) of three transverse, in particular perpendicular, spatial directions acting forces (F _x , F _y , F2) on the coupling element (40).

117. Device according to one of the preceding claims, characterized in that two of the forces (Fx, Fz) run parallel to, in particular in, the longitudinal center plane (18) of the holding arm (30) but transversely, in particular perpendicular, to one another and that the third force ( F _y ) runs transversely, in particular perpendicular, to the longitudinal center plane (18) of the holding arm (30).

118. Device according to claim 116 or 117, characterized in that transformation values for combinations of forces acting in different octants on the coupling element (40) are stored in the memory (236).

119. Device according to one of claims 116 to 118, characterized in that the evaluation unit (230) values from deformation sensors (172, 174, 176, 178) and in particular reference deformation sensors (182, 184, 186, 188) for determining the Deformations recorded.

120. Device according to claim 119, characterized in that the evaluation unit (230) detects values from at least one temperature sensor (252, 254, 256, 258) for functional testing of the reference deformation sensors (182, 184, 186, 188).

121. Device according to claim 120, characterized in that the evaluation unit (230) detects values from a respective temperature sensor assigned to the respective reference deformation sensor.

122. Device according to one of the preceding claims, characterized in that the holding arm (30) carries the coupling element (40) at its second end (34).

123. Apparatus according to claim 122, characterized in that the holding arm (30) and the coupling element (40) form a coherent part.

124. Apparatus according to claim 122 or 123, characterized in that the holding arm (30) is designed as a ball neck and at the second end (34) carries the coupling element (40) comprising a coupling ball (43).

125. Device according to one of claims 72 to 124, characterized in that the holding arm (30 ') comprises a receiving body (31') which is designed to detachably receive the coupling element (40 ').

126. Device according to claim 125, characterized in that the receiving body (31 ') has an insertion receptacle (33') which is accessible through an insertion opening (35 ').

127. Device according to claim 125 or 126, characterized in that the coupling element (40 ') comprises a support arm (42').

128. Device according to one of claims 125 to 127, characterized in that the carrier arm (42 ') with an insertion section (45') can be inserted into the insertion receptacle (33 ') and can be fixed therein.

129. Device according to one of claims 125 to 128, characterized in that the carrier arm (42 ') carries a coupling ball (43).

130. Device according to claim 128 or 129, characterized in that the plug-in section (45 ') is received in the plug-in receptacle (33') in a form-fitting manner transversely in an insertion direction (E) and is fixed in the functional state in the plug-in direction by a form-fitting body (41).