TOW BAR WITH AN EVALUATION DEVICE

Description

[0001] The invention relates to a trailer coupling for a towing vehicle, according to the preamble of claim 1, and to a method according to the preamble of claim 13.

[0002] Such a trailer coupling and method are known from US 2010 / 0332049 A1.

[0003] DE 10 2010 009 986 A1 discloses a trailer coupling for a towing vehicle in which the spherical coupling body is movably mounted on a coupling arm, with a force sensor measuring the vertical load acting on the coupling element, namely the coupling ball. Furthermore, it is proposed to also measure a tensile load acting on the coupling ball using another force sensor. With this trailer coupling, the vertical load and a tensile load that occurs when the vehicle is towed can be measured. For safe driving, it is advantageous if the vertical load can be correctly measured and adjusted. Furthermore, the mass or total weight of the trailer must not be exceeded.

[0004] It is therefore the object of the present invention to provide devices and methods for determining a trailer mass value of the trailer.

[0005] To solve this problem, a trailer coupling according to the technical teaching of claim 1 and a method according to claim 13 are provided.

[0006] A basic idea of ​​the invention is that a force sensor, for example a force sensor dedicated to determining a deformation of the trailer coupling, in particular of the coupling support or the bracket, caused by tensile force, is able to determine the trailer mass based on the additional evaluation of the acceleration value. This is based on the consideration that a force can be determined as the product of mass and acceleration. Of course, it is expedient if the evaluation device is designed to take into account additional factors, for example to evaluate and consider friction values, inertial masses, and the like. However, the basic concept of the invention is based on deriving the mass of the trailer from the tensile force signal.

[0007] The acceleration value is an acceleration value in the direction of travel or x-direction, but not a yaw rate acceleration value oriented around the vertical axis, for example.

[0008] The evaluation device expediently has a signal input for an acceleration signal. For example, a connection terminal, a socket, or the like is provided for the acceleration sensor. In this embodiment, the acceleration sensor is a separate unit that can be connected to the evaluation device.

[0009] It is also possible that the evaluation device has an acceleration sensor on board.

[0010] Furthermore, it is advantageous if the evaluation device has a temperature sensor so that it can carry out temperature compensation.

[0011] This is based on the realization that the coupling arm or other location where the at least one force sensor is located, for example, is exposed to exhaust gases and is therefore heated. Temperature compensation or consideration of temperature influences when determining values ​​or data is therefore advantageous. It should be noted at this point that temperature compensation is naturally also useful for a pure vertical load measurement, thus representing an independent inventive concept in force measurement on a trailer coupling.

[0012] However, it is not absolutely necessary that a temperature sensor is provided. The at least one force sensor can also already serve to enable temperature compensation or to take a temperature into account: The temperature condensation can, for example, already occur at the beginning of a measurement, i.e. the force signal generated by a respective force sensor serves as the base value even without a support load or tensile load, comparable, for example, to the tare setting on a scale. In this way, the at least one force sensor is, so to speak, calibrated. With an unloaded trailer coupling, the force sensor, which is designed, for example, in the manner of a resistance measuring bridge, supplies, for example, a first force signal value at a first temperature and a second force signal value at a second temperature different from the first temperature.In a later evaluation of a load acting on the coupling beam, i.e. a determination of a size of the trailer, e.g. support load or mass of the trailer, the respective force signal value is used as a base value and is therefore suitable, for example, as a correction value.

[0013] Finally, it is also advantageous if the trailer coupling or its evaluation device also includes an inclination sensor for determining an inclination angle and / or an interface for receiving an inclination angle value, for example, from an inclination angle sensor on board the towing vehicle. The inclination angle corresponds to the diagonal inclination of the motor vehicle or combination consisting of motor vehicle and trailer, e.g., when the combination is facing downhill or uphill. The evaluation device or method according to the invention are expediently designed to determine the trailer mass value as a function of the inclination angle value and / or to eliminate the influence of the inclination angle.

[0014] The inclination sensor can also be formed by the acceleration sensor. For example, the acceleration sensor can detect acceleration in three mutually angular axes (X-axis, Y-axis, and Z-axis). When the vehicle is horizontal, the acceleration sensor only measures the force acting in the Z-direction, namely the force of gravity or g. When the vehicle is tilted, however, the acceleration sensor also measures a component of the force of gravity or gravitational acceleration g in the direction of the X-axis and / or the Y-axis, so that the tilt of the trailer or the acceleration sensor can be detected using a suitable algorithm, for example, one stored in the evaluation device.

[0015] At this point, it should be noted that the tilt angle compensation and / or the provision of an inclination sensor, in particular an acceleration sensor that performs the function of an inclination sensor, and / or an interface for an inclination angle signal is of course also expedient for a pure support load measurement, thus representing an independent inventive idea in the case of a force measurement on a trailer coupling.

[0016] The evaluation device expediently has a bus interface for a data bus of the towing vehicle. For example, the interface comprises a CAN interface, a LIN interface, or the like. For example, the acceleration value can be received via the bus interface. For example, the towing vehicle has one or more acceleration sensors. It is also possible for the towing vehicle's electrical system to transmit acceleration values ​​determined, for example, based on speed signals. The evaluation device is designed, for example, to transmit the trailer's mass value via the bus interface. It is understood that another data interface is also possible instead of a bus interface.

[0017] The evaluation device is also expediently designed to determine the vertical load acting on the trailer coupling due to the trailer. In this context, it is advantageous if the evaluation device takes into account the vertical load exerted by the trailer on the trailer coupling when determining the trailer mass value. One variant may provide for the vertical load to be determined externally and transmitted to the evaluation device via a corresponding data or signal input. However, it is preferred if the evaluation device itself is designed to determine the vertical load.

[0018] One advantageous consideration is that the evaluation device determines the trailer mass value when the towing vehicle is moving, rather than when the vehicle is stationary. For example, it is advantageous if the evaluation device determines the trailer mass value as a function of the driving speed of the towing vehicle. One variant provides that the evaluation device only begins to determine the trailer mass value when a lower speed limit is exceeded. It is expedient if the evaluation device only determines the trailer mass value until an upper speed limit is reached. This is based on the consideration that at low driving speeds the tractive force of the trailer coupling essentially acts, whereas at higher speeds, for example, air resistance influences would also have to be taken into account. It is of course conceivable to provide an algorithm for a trailer coupling according to the invention orin their evaluation device, which also takes into account air resistance influences and eliminates them if necessary.

[0019] It is also advantageous if the evaluation device only evaluates the force signal when a lower minimum acceleration value is exceeded to determine the trailer mass. Evaluating an acceleration value only when a lower minimum acceleration value is exceeded has the advantage, for example, that interference, such as vibrations, does not interfere with the evaluation or only slightly. Such interference, for example, does not need to be eliminated.

[0020] Furthermore, an upper limit can also be provided, i.e. the evaluation device only evaluates the force signal until a maximum acceleration value is reached.

[0021] A further variant of the invention advantageously provides that the evaluation device evaluates the force signal during a period of continuously increasing acceleration values ​​or continuously decreasing acceleration values ​​as a signal representing the tractive force and / or thrust acting on the trailer coupling. Thus, for example, if the acceleration curve increases (during acceleration) or decreases (during braking), the evaluation device evaluates the force signal as a tractive force signal and / or determines the trailer mass value from the force signal.

[0022] A variant of the invention provides that the evaluation device detects when the towing vehicle accelerates from a standstill. Preferably, the measurement of the support load or its determination is then stopped. Instead, the evaluation device begins evaluating the tractive force and acceleration values ​​and only stops this process when the acceleration ends or when the driving speed exceeds a certain limit, for example, 5 to 10 km / h.

[0023] A preferred embodiment provides that the force signal of the at least one force sensor represents both a support load acting on the trailer coupling and a towing load of the trailer acting on the trailer coupling. The evaluation device is expediently designed to evaluate the force signal to determine the support load and to determine the towing load depending on the driving condition of the towing vehicle.

[0024] Advantageously, the at least one force sensor comprises a deformation sensor which is sensitive to pressure and / or tension and which is arranged at a mounting location provided on the coupling support or the holder, at which mounting location an extension deformation and / or compression deformation due to a force acting on the trailer coupling and caused by the trailer can be measured, wherein the mounting location is selected such that at the mounting location a deformation which can be caused by a tensile load acting on the coupling element during towing of the trailer is present for actuating the at least one force sensor and a deformation which can be caused by a support load of the trailer acting on the trailer coupling is present for actuating the at least one force sensor.

[0025] The term "tractive load" should be understood to mean that both a tensile load (i.e., when pulling a trailer) and a compressive load (i.e., when pushing the trailer or hitting the towing vehicle during braking, for example) fall under the term "tractive load." Therefore, a horizontal load on the trailer coupling when the vehicle is traveling straight ahead can be considered a "tractive load."

[0026] Of course, not only a compressive load, referred to as a support load, occurs in the vertical direction, but also a vertically upward load, for example, when driving over a hill or uneven ground. The mounting location for at least one force sensor is preferably located in the area of ​​the greatest deformation of the dome beam or bracket caused by the tensile load.

[0027] The coupling support is designed, for example, as a coupling arm. The coupling arm can contain multiple curves, angles, and the like. The coupling element is, for example, a coupling ball, although other geometries, such as polygonal coupling elements that transmit rotational forces, are also possible. Preferably, the coupling element is fixedly mounted on the coupling support, in particular in one piece with it. However, a multi-part design is also possible.

[0028] The bracket can be a bracket to which the dome support is permanently mounted. Plug-in systems or other systems are also possible, in which the dome support can be releasably attached to the bracket, particularly by means of a plug-in connection. However, a movable mounting is also possible, in which the dome support is mounted on the bracket, for example, in a pivoting and / or sliding manner.

[0029] Furthermore, it is advantageous if the mounting location is in the area of ​​the greatest deformation of the dome support or the bracket that can be caused by the support load.

[0030] Of course, it is useful if a mounting location can be found where the extensional and compressional deformations are maximum under both the tensile load and the support load. However, there are also situations or geometries of the bracket and / or dome girder where such an optimal mounting location cannot be found at all. For example, the deformation under the support load may have its maximum at a different location than the deformation under the tensile load. It is then useful if a compromise, so to speak, is found so that the deformation caused by the tensile load and the deformation caused by the support load have a similar amount or the same amount at the mounting location found as a compromise.

[0031] Another factor or optimization criterion could be to ensure that the mounting location is, if possible, on the upper side of the dome support or bracket facing away from the roadway. This significantly reduces the risk of damage to the force sensor.

[0032] Furthermore, it is an optimization criterion that the installation location is as close as possible to an evaluation and / or display device. For example, a cable connection to an evaluation and / or display device can be selected as short as possible. For example, if two alternative installation locations are available, each of which has sufficient deformation to actuate the force sensor under vertical and tensile loads, but one installation location is closer to the evaluation and / or display device than the other, the closer installation location is expediently selected. The transmission losses for the signal transmission from the force sensor or deformation sensor to the evaluating and / or display unit are therefore short. The risk of interference from external signals or other interference is thereby significantly reduced.

[0033] For example, the deformation sensor may comprise a strain gauge and / or a pressure sensor.

[0034] Of course, it may be advantageous to have multiple force sensors, at least one of which is a deformation sensor capable of measuring both the tensile load and the support load. Having multiple force sensors, possibly even multiple multifunctional force sensors, each capable of measuring both the support load and the tensile load, increases measurement accuracy.

[0035] For example, the strain or deformation of the dome beam or bracket can be determined using a finite element calculation.

[0036] The force sensor or deformation sensor therefore delivers a force signal both when loaded with a tensile load and when the trailer coupling is loaded with a support load. In this embodiment, it is preferably provided that the trailer coupling comprises an evaluation device which is designed to evaluate the force signal as a function of an acceleration state and / or a speed state of the towing vehicle and thus also of the trailer coupling. When the vehicle is stationary, the support load essentially rests on the trailer coupling. The speed is therefore zero, for example. The acceleration or the acceleration value is also zero. The evaluation device then advantageously determines the support load based on the force signal. However, when the vehicle is moving, in particular when it accelerates or decelerates, a tensile load acts on the trailer coupling. The evaluation device then expediently determines the tensile load.

[0037] Preferably, an evaluation device is provided, for example, the aforementioned evaluation device, which is designed to determine a trailer mass value based on one or more force signals from the at least one force sensor and an acceleration value. Based on the values ​​for the support load and the towing load, as well as the acceleration value, the evaluation device according to this embodiment of the invention can thus determine a trailer mass.

[0038] The following procedure is preferred: In the vertical direction, ie in the Z direction, the support load Fz acts on the trailer coupling: F z = st ∗ g

[0039] In formula (1), g is the acceleration due to gravity and st is the supporting mass acting on the dome element.

[0040] A tensile load Fx acting on the trailer coupling in the x-direction or horizontally in the vehicle's longitudinal direction can be summarized using the following formula (2): F x = F r + F L + F R + F rot

[0041] The individual factors of the tensile load Fx are the inertial force FT, the air resistance force FL, a force FR caused by rolling friction and a force Frot, which summarizes the forces caused by the inertia of tires and other rotating masses.

[0042] At low speeds, the air resistance force FL can be neglected. It is therefore advantageous to determine the trailer mass according to the invention at relatively low speeds, where air resistance is still low. Of course, it is also conceivable that, for example, the influence of air resistance is determined by the evaluation device as a function of speed in order to eliminate the respective influence on the overall result of the towing load Fx.

[0043] However, if the air resistance force is eliminated, the above formula (2) can be simplified as follows: F x = F T + F R + F rot

[0044] The force FR acting on the trailer coupling caused by rolling friction is influenced by the mass m of the trailer, although part of this mass is supported by the trailer coupling, meaning that this support load or support mass has no influence on the rolling friction. The support mass st is therefore subtracted from the mass value m in the following formula (4): F R = m − st ∗ g ∗ μ

[0045] In formula (4), g is the acceleration due to gravity and µ is a rolling resistance coefficient. The rolling resistance coefficient can be considered a constant value, e.g., an average value, that is present for standard tires or average road surfaces.

[0046] The inertial force FT is essentially determined by the trailer mass m and the acceleration ax in the X direction: FT = m * ax

[0047] If formulas (4) and (5) are inserted into formula (3), the following results: F x − F rot = m ∗ a x + m − st ∗ g ∗ μ

[0048] If formula (1) is then taken into account, the following formula can be developed: F x − F rot + F z ∗ μ = m ∗ a x + g ∗ μ

[0049] By transforming the formula (7), the mass m of the trailer can be determined as follows: m = F x − F rot + F z ∗ μ a x + g ∗ μ

[0050] Taking into account that the rotational acceleration causes only small forces, i.e. the ratio of the force Frot to the total force Fx in the horizontal direction is as follows F rot F x ∗ 100 = 2 % bis 3 % In the above formula (8), the component of force Frot can be neglected. The mass of the trailer can therefore be determined from the two forces Fx and Fz as well as the acceleration value in the X direction or the vehicle's longitudinal direction ax.

[0051] An advantageous variant of the invention provides for both forces Fx and Fz to be determined using a single force sensor. The evaluation device is expediently designed such that it first determines the forces caused by the support load, i.e., the forces in the z-direction, namely the force Fz, while stationary, and then, upon subsequent acceleration of the trailer, the force Fx acting in the x-direction. In this context, it is advantageous for the evaluation device to evaluate an acceleration value and / or a speed value in order to switch between the individual force determinations, so to speak.

[0052] For example, it is advantageous that the force Fz acting in the vertical direction is first determined and the evaluation device uses the value determined in the above formula (8) as well as the value of the force Fx subsequently determined during the acceleration of the trailer to determine the mass of the trailer using, for example, formula (8).

[0053] A preferred embodiment provides for the acceleration sensor to be calibrated along the X-axis, so to speak. This means that during acceleration from a standstill, the acceleration value provided by the acceleration sensor or the electrical system of the towing vehicle is corrected by the portion of the acceleration value caused by the tilt of the motor vehicle or vehicle combination. The acceleration sensor is, so to speak, initialized.

[0054] A formula for correcting the acceleration value acting in the longitudinal direction of the vehicle, corrected for the effect of the inclination of the trailer, ie the acceleration value a x corrected acting in the X direction, corrected for the slope drag, is as follows: a x korigiert = a x + g ∗ sin θ where ax is the measured acceleration value in the X direction, g is the acceleration due to gravity, and θ is the inclination angle of the vehicle in the X direction. The inclination angle value is determined, for example, by the acceleration sensor, which can measure in multiple axes, or by a separate inclination angle sensor or the on-board electrical system of the towing vehicle.

[0055] The evaluation device is preferably designed to perform averaging. For example, the evaluation device calculates several intermediate averages of the acceleration value over consecutive time intervals and evaluates these averages.

[0056] For example, the evaluation device only evaluates an acceleration run if a first intermediate mean value represents an acceleration of, for example, more than 1 m / s. This then serves as an initial criterion.

[0057] Once the acceleration run has begun, a further mean value evaluation or evaluation of intermediate mean values ​​is advantageous: Insofar as an intermediate mean value represents a minimum acceleration value, for example of more than 1.5 m / s 2<, it is included in the evaluation.

[0058] For example, it is preferable if the evaluation refers to several intermediate mean values. This increases the accuracy. If several consecutive intermediate mean values, for example, three or four intermediate mean values, meet the minimum acceleration value criterion, the evaluation device performs an evaluation.

[0059] Preferably, the trailer mass m is evaluated or determined according to the following formula (10), where n is the number of intermediate mean values, Fx is the force acting on the trailer coupling in the X direction and ax is the acceleration in the X direction. m = 1 n ∑ i = 1 n F xt a xi

[0060] The method according to the invention is expediently applied in a range where the influences of rolling friction and wind resistance of the trailer are very low, e.g., when a minimum speed and / or minimum acceleration is exceeded, e.g., when the trailer is already rolling but is still below a predetermined maximum speed and / or maximum acceleration, at which the influences of wind resistance become greater. Thus, for example, the force values ​​Frot specified in the above formulas can be neglected. The averaging described above further increases the measurement accuracy.

[0061] Another criterion that should be considered is that an acceleration run (positive acceleration or accelerating towing vehicle, or negative acceleration / braking) has a minimum duration. For example, if an acceleration run lasts at least 0.5 to 5 seconds, preferably approximately 1 to 1.5 seconds, the acceleration is evaluated.

[0062] Of course, it is advantageous for detecting or determining the mass of the trailer if only a single force sensor is required that can measure both the towing load and the support load. It is also possible to have one or more separate force sensors, such as strain gauges, for determining and measuring both forces.

[0063] Furthermore, it represents an advantageous variant of the invention if the evaluation device is capable of averaging, i.e., it determines, for example, several vertical load values ​​and calculates an average from them in order to reduce or eliminate errors that can arise, for example, due to an unfavorable position of the coupling area in a road depression or above a road elevation. The trailer and trailer combination may be at an angle to each other in the vertical or X-direction, which influences the vertical load.

[0064] Furthermore, a plausibility check is useful, in which the evaluation device only takes into account those force values ​​and / or acceleration values ​​that are plausible when calculating the mass value of the trailer.

[0065] It is further advantageous if the evaluation device also determines several values ​​with regard to the mass value, for example at different acceleration values, on the basis of several successive acceleration processes and the like, in order to avoid errors in this way.

[0066] The trailer coupling has, for example, a display device for displaying the determined values ​​of the support load and / or towing load and / or trailer mass value.

[0067] The method according to the invention can be implemented, for example, using software, wherein a processor of the evaluation device is capable of executing the method steps according to the invention based on the software. Another aspect of the invention can provide that the evaluation device is a control unit of the towing vehicle, which is capable of executing the method according to the invention based on the aforementioned software.

[0068] Exemplary embodiments of the invention are explained below with reference to the drawings. They show: Figure 1 shows a trailer coupling according to the invention with a coupling support fixed to a bracket in a perspective view obliquely from above, Figure 2 shows a coupling support of the trailer coupling according to Figure 1 from above, Figure 3 the dome support according to Figure 2 from the vehicle side, Figure 4 a bottom of the dome support according to Figure 2 , 3 , Figure 5 a trailer coupling with a coupling carrier movably mounted on a bracket and an evaluation device, Figure 6 the coupling carrier of the trailer coupling according to Figure 5 from the front, Figure 7, a bottom side of the coupling support of the trailer coupling according to Figure 5, 6 , Figure 8 an acceleration curve of a towing vehicle, Figure 9 a block diagram of an evaluation device, Figure 10 a flow diagram of a method which is carried out by the evaluation device according to Figure 9is feasible, Figure 11 an acceleration curve of an acceleration value ax and an associated mean value evaluation of the evaluation device according to Figure 9 , and Figure 12a further acceleration curve of the acceleration value ax and an associated corrected curve.

[0069] The drawing shows trailer couplings 10 and 110, some of which have identical or similar components, which are accordingly provided with the same reference numerals or with reference numerals that are 100 times larger in the case of trailer coupling 110 than in the case of trailer coupling 10.

[0070] The trailer couplings 10, 110 have brackets 11, 111 which can be fastened to a towing vehicle 90, for example a passenger car.

[0071] For example, the bracket 11 comprises a base bracket 12 arranged on a cross member 91 of the towing vehicle 90, from which two holding legs 13 protrude. A coupling support 14 is arranged between the holding legs 13. The coupling support 14 is screwed to the holding legs 13 by means of screws 15 that penetrate holes 16 in the coupling support 14 on a vehicle-side holding section 20. Thus, the coupling support 14 is firmly attached to the bracket 11. A socket holder 17 protrudes laterally from the bracket 11, to which a trailer socket (not shown) can be attached.

[0072] The trailer coupling 110 includes a bracket 111 that can be attached to the towing vehicle 90, for example, to a cross member (not shown), and that movably supports the coupling support 114. For example, the coupling support 114 is pivotally and / or displaceably mounted on the bracket 111. A bearing head 118 of the bracket 111 engages in a bearing receptacle 119 on a holding section 20 of the coupling support 114 at the vehicle-side end region of the coupling support 114, thus providing a ball-and-socket type of support.

[0073] The coupling support 114 is adjustable, for example, between a use position shown in Figure 5, which is intended for towing a trailer 92, and a non-use position adjusted behind a bumper (not shown), for example, closer to the cross member. Additionally, a locking mechanism (not shown) is provided to lock the coupling support 114 at least in the use position.

[0074] The coupling supports 14, 114 each have a coupling ball 22 at their end regions 21 remote from the towing vehicle 90, which serves as a coupling element 23 for coupling the trailer 92 (shown schematically). The coupling balls 22 are provided on arm sections 24 that are upright in the use position of the trailer couplings 10, 110. The arm sections 24 transition with a curvature 25 into an arm section 26 that runs essentially horizontally when the coupling supports 14, 114 are in use.

[0075] In the dome support 14, the arm section 26 and the end region 21 are virtually integral, i.e., the end region 21 is provided at a free end of the arm section 26. However, the section of the dome support 14 that protrudes freely in front of the bracket 11 is referred to below as the arm section 26.

[0076] In the dome support 114, there is a further curvature 27 between the holding section 20 and the arm section 26.

[0077] The trailer couplings 10, 110 are designed to measure both a force acting on the coupling element 23 in a vertical direction or z-direction, hereinafter referred to as the vertical load Fz, and a load acting on the coupling element 23 in a horizontal direction or x-direction, hereinafter referred to as the tensile load Fx. A single force sensor 30 is sufficient for this purpose. The force sensor 30 can, for example, be a strain gauge 31 or another deformation sensor 35, e.g., a pressure sensor clamped between two actuating resistors on the coupling support 14. The force sensor 30 is optimally positioned at a mounting location 32 such that its force signal 33 represents both the tensile load Fx and the vertical load Fz.

[0078] In the Figure 2-4The dashed lines show strain curves or strain ranges that result from different force loading of the dome girder 14 with the tensile load Fx and the support load Fz. For example, when loaded with the support load Fz, the values ​​shown in the Figure 2 and 4 visible deformation areas 40 and 41 on an upper side 28 and a lower side 29 of the arm section 26. This expansion deformation occurs, for example, when a load of 100 kg is applied to the coupling element 23.

[0079] In Figure 3The coupling support 14 is shown under a tensile load Fx, for example, a force of 5 kN. In addition, it is expedient to allow the still acting support load Fz of, for example, 100 kg to act on the coupling element 23. This creates a deformation region 42, particularly on the inside of the curve 25. However, the deformation region 42 extends into the deformation region 40 ( Figure 2 ). Thus, there is essentially an intersection, namely an overlap region 43, where the deformation regions 40 and 42 overlap and where significant deformation occurs both when loaded with the tensile load Fx and the support load Fz. The force sensor 30 is therefore expediently arranged in the overlap region 43 so that it can be actuated by loading the coupling element 23 with the tensile load Fx and the support load Fz, and its force signal 33 represents both forces.

[0080] In principle, an overlapping area of ​​deformation zones is also present on the underside 29 of the coupling support 14, which occurs when the coupling element 23 is subjected to the tensile load and the support load. The arrangement of the force sensor 30 on the upper side 28, however, has the advantage that the force sensor 30 is better protected from environmental influences there and also allows the placement of a conveniently clearly visible evaluation device 50 closer to the force sensor 30. A cable connection 51 between the force sensor 30 and the evaluation device 50 is very short.

[0081] The trailer coupling 110 also requires a single force sensor 30. When the coupling support 114 is loaded with a tensile load Fx and also a support load Fz, for example, a deformation region 44 forms on the inside of the curve 27. When the coupling element 23 is loaded, deformation also occurs on the underside 29, which is located in a deformation region 45. However, as already mentioned, the arrangement of a force sensor on the underside of a coupling support, i.e. closer to a roadway, is rather unfavorable. Therefore, the force sensor 30 is arranged at the attachment location 132 in the curve 27. There, the force sensor 30 is also protected from environmental influences by the bumper of the towing vehicle 90 (not shown). An evaluation device 150 is located near the force sensor 30, for example directly next to the force sensor 30, so that a short line connection 51 is also provided here.

[0082] Now it would be possible for additional force sensors, for example pressure sensors or strain gauges, to be present on the trailer couplings 10, 110, so that separate measurement results dedicated to the tractive force and the support load would be available for the evaluation devices 50, 150.

[0083] For example, a further force sensor 34, in particular a strain gauge, could be provided on the underside 29 of the dome support 14 in the deformation region 41.

[0084] The evaluation devices 50, 150 can, for example, display the support load Fz and the towing load Fx, temporarily store them, transmit them to an on-board electrical system 93 of the towing vehicle 90, or the like. The evaluation devices 50, 150 can also determine a mass m of the trailer 92 from the force signal 33, for which the method explained above is preferred.

[0085] For example, the evaluation devices 50, 51 operate as follows, where Figure 9The block circuit diagram shown is exemplary for both evaluation devices 50 and 150.

[0086] The evaluation device 50 comprises, for example, a processor 52 and a memory 53 in which an evaluation module 54 is stored. Figure 10 shows a simplified program sequence of the evaluation module 54, whose commands can be executed by the processor 52 in order to determine the support load Fz and in particular the mass m of the trailer 92 based on the force signal 33.

[0087] In a step S1, the evaluation module 54 initializes the force sensor 30 and an acceleration sensor 55. The acceleration sensor 55 is on board the evaluation device 50.

[0088] The initialization in step S1 preferably provides that the evaluation device 50 or 150 or the evaluation module 54 also performs a temperature measurement, since the temperature in the rear area of ​​the towing vehicle 90 fluctuates considerably, for example due to exhaust gases. For this purpose, a temperature sensor 58 can be provided on board the evaluation device 50 or 150, for example.

[0089] However, a preferred embodiment provides that the evaluation device 50 or 150 first determines an initial value of the force sensor 36 when the trailer coupling 10 or 110 is still unloaded—a base value, so to speak, at a given temperature. Based on this base value, the force signal 33 then changes when the trailer coupling 10 or 110 is loaded, i.e., when the trailer is attached, exerting a force on the coupling support 14 or 114.

[0090] In a step S2, the evaluation module 54 detects that the towing vehicle 90 is stationary. The acceleration sensor 55 does not detect any acceleration a. For example, the evaluation module 54 observes over a longer period of time whether the acceleration of the towing vehicle 90 changes. If this is not the case, the force signal 33 essentially represents the support load Fz, so that the evaluation module 54 determines the support load Fz between a time t0 and a time t1.

[0091] The acceleration sensor 55 is preferably designed to determine not only the acceleration a acting in the X direction, which could actually be referred to as acceleration ax, but also the accelerations ay and az acting in the Y direction and in the Z direction. Based on the acceleration values ​​ax, ay, and az, the acceleration sensor 55 and / or the evaluation device 50, 150 are able to determine an angle of inclination θ at which the towing vehicle 90 is positioned in the X direction relative to a surface U, for example, downhill or uphill. When the towing vehicle 90 is on a horizontal, level surface, only one force acts on the coupling beam 14, 114 in the Z direction, namely the acceleration due to gravity g. The angle of inclination θ is expediently determined when the towing vehicle 90 is stationary.

[0092] However, an inclination sensor 59 can also be provided on board the evaluation device 50, 150.

[0093] In step S3, the evaluation module 54 detects an acceleration a of the towing vehicle 90, which begins at time t1. The evaluation module 54 then terminates the determination of the support load Fz.

[0094] However, the acceleration at time t1 is still relatively low. However, if the acceleration a reaches a value a1 at time t2, the evaluation module 54 detects a significant acceleration suitable for determining the mass m of the trailer 92. Advantageously using formulas (1) to (8), an algorithm for trailer mass detection then runs in a step S4, within which the evaluation device 50 determines the mass m of the trailer 92, expediently taking into account the previously determined support load Fz temporarily stored in the memory 53. The mass m is also expediently stored in the memory 53.

[0095] It is advantageous if the evaluation module 54 in step S3 takes into account the value for the angle of inclination, for example according to formula (9) and / or the initially determined temperature base value of the force signal (33).

[0096] In any case, step S4 ends at a time t3, namely when the acceleration of the towing vehicle 90 ends upon reaching an acceleration value a2 and / or the towing vehicle 90 exceeds a limit speed at which, for example, rolling resistance influences and / or air resistance influences increase so significantly that reliable mass detection is no longer readily possible.

[0097] Furthermore, the flow chart according to Figure 10 another state W, namely wait, into which the evaluation module 54 goes until the towing vehicle 90 has come to a standstill again.

[0098] The evaluation device 50 displays, for example, the support load and / or the mass m of the trailer 92 on a display 56. However, it is also possible for the evaluation device 50 to be connected to the on-board electrical system 93 of the towing vehicle 90 via a bus interface 57, for example to receive acceleration values ​​and / or to transmit values ​​determined by it for the support load and / or the mass of the trailer and / or the towing load to the on-board electrical system 93, so that, for example, an electronic stabilization program can regulate the driving stability of the towing vehicle 90 based on the values ​​thus obtained and / or the values ​​can be shown on a display, for example in the dashboard area of ​​the towing vehicle 90.

[0099] To improve measurement and / or calculation accuracy, additional force sensors can of course be provided on the brackets 11, 111 and / or the coupling supports 14, 114. Furthermore, force sensors intended primarily for dedicated support load detection or dedicated tensile force detection can also be advantageous, e.g., a force sensor 36 on the deformation region 42 that deforms when the coupling support 14 is subjected to tensile force. The deformation region 42 deforms only insignificantly when subjected to a support load, so that its force signal essentially represents the tensile load and can be evaluated accordingly by the evaluation devices 50, 150.

[0100] Based on Figure 11 a further, optimized evaluation logic of the evaluation device 50 or 150 is explained.

[0101] The evaluation device 50 or 150 calculates intermediate mean values ​​a0 to a10 of the acceleration value ax relevant in the X direction. Thus, not every small change in the acceleration value ax is considered, but rather an intermediate mean value calculated over a short period of time Δt, for example, 0.1 s or 0.2 s. On the other hand, the mean value is not calculated over a very long period of time, for example, between times t4 and t6. This is therefore a type of block formation or sampling method.

[0102] The evaluation device 50, 150 begins, for example, with the determination of the trailer mass m at a time t4 at which the intermediate mean value a0 of the acceleration value ax relevant in the X direction has exceeded a minimum acceleration value amin1.

[0103] For example, the intermediate mean value a0 is already above the minimum acceleration value amin1, but still below another minimum acceleration value amin2. At time t4, the evaluation or determination of the trailer mass value m has not yet begun, but the evaluation device 50, 150 is ready for it.

[0104] From time t5 onward, the intermediate mean values ​​a1 to a9 are above the upper minimum acceleration value amin2, but from time t6 onward, they are again below this threshold. For example, the intermediate mean value a10 is still above the lower minimum threshold amin1, but no longer above the upper minimum threshold amin2.

[0105] The evaluation device 50 or 150 selects several consecutive intermediate mean values ​​from the intermediate mean values ​​a1-a9, but only if at least 3 or 4 consecutive intermediate mean values ​​a1-a9 have exceeded the upper minimum threshold amin2. This is essentially another formulation for the fact that the duration of a journey of the towing vehicle 90 to be evaluated should have a minimum duration of, for example, tmin. Figure 11 tmin is shown as an example over, for example, four of the blocks or intermediate averages a1-a9. Of course, the minimum duration tmin can also be chosen differently, for example, shorter or longer, so that it extends completely between times t5 and t6.

[0106] In Figure 12A curve of the acceleration value ax is shown, which the acceleration sensor 55 detects in the X direction. However, the towing vehicle 90 is inclined, for example, uphill. At a time t7, the evaluation device 50 or 150 corrects the acceleration value ax and generates an acceleration value axk related to the towing vehicle 90, in which the influence of the inclination angle θ in the X direction is corrected. The acceleration sensor 55 is expediently designed to determine the gravitational acceleration g acting in the X, Y, and Z directions, and the evaluation device 50 determines the inclination angle θ therefrom.

[0107] In the subsequent evaluations, which have already been explained, the evaluation device 50, 150 expediently uses the corrected acceleration value axk as a basis (see, for example, formula (9)).

Claims

1. Trailer coupling for a towing vehicle (90) with a coupling support (14; 114) including a coupling arm, at the free end of which is arranged a coupling element (23), in particular a coupling ball (22), for attaching a trailer (92) and which is mounted movably or immovably on a mounting (11; 111) which may be fixed to the towing vehicle (90), and with at least one force sensor (30) for detecting a tensile force and / or thrust force which may be caused by a tensile load (Fx) acting on the coupling element (23) during towing of the trailer (92), and for the output of a force signal (33) representing the tensile force and / or thrust force, and wherein there is provided an evaluation unit (50; 150) which is designed to determine a trailer mass value of the trailer (92) with the aid of the force signal (33) and an acceleration value, characterised in that the evaluation unit (50; 150) is designed to carry out a compensation measurement with the coupling support (14; 114) as yet unloaded and, with the aid of a force signal (33) thereby generated and representing the tensile force and / or the thrust force and / or a support load acting on the coupling support (14; 114), to determine a base value which is used for temperature compensation in the subsequent determination of the trailer mass value of the trailer (92).

2. Trailer coupling according to claim 1, characterised in that the evaluation unit (50; 150) has a signal input for an acceleration signal and / or for a tilt angle value.

3. Trailer coupling according to claim 1 or 2, characterised in that the evaluation unit (50; 150) includes an acceleration sensor (55) and / or a temperature sensor and / or a tilt sensor.

4. Trailer coupling according to any of the preceding claims, characterised in that the evaluation unit (50; 150) is designed to evaluate acceleration values generated by the acceleration sensor (55) in coordinate axes at an angle to one another, in particular in an X-direction, a Y-direction and a Z-direction, to determine an angle of tilt of the coupling support or the towing vehicle (90).

5. Trailer coupling according to any of the preceding claims, characterised in that the evaluation unit (50; 150) has a data interface, in particular a bus interface (57), for a data bus of the towing vehicle (90), wherein expediently the acceleration value may be received via the data interface or the bus interface (57).

6. Trailer coupling according to any of the preceding claims, characterised in that the evaluation unit (50; 150) determines the trailer mass value on the basis of a driving speed of the towing vehicle (90), in particular only on exceeding a lower speed limit value and / or on reaching an upper speed limit value.

7. Trailer coupling according to any of the preceding claims, characterised in that the evaluation unit (50; 150) evaluates the force signal (33) in the presence of a minimum acceleration value and / or up to the reaching of a maximum acceleration value, to determine the trailer mass value or the support load (Fz).

8. Trailer coupling according to any of the preceding claims, characterised in that the evaluation unit (50; 150), during a period of time (t2-t3) of continuously rising acceleration values or continuously falling acceleration values or during a phase between changes in acceleration values, evaluates the force signal (33) as a signal representing the tensile force and / or thrust force acting on the trailer coupling (10, 110).

9. Trailer coupling according to any of the preceding claims, characterised in that the evaluation unit (50; 150) is designed to form an average of the acceleration values, in particular to form and evaluate intermediate averages (a1 - a9) of the acceleration values.

10. Trailer coupling according to any of the preceding claims, characterised in that the evaluation unit (50; 150) , in determining the trailer mass value of the trailer (92), evaluates a support load (Fz) which the trailer (92) exerts on the trailer coupling (10; 110).

11. Trailer coupling according to any of the preceding claims, characterised in that the force signal (33) of the force sensor or sensors (30) represents a support load (Fz) acting on the trailer coupling (10; 110) and a tensile load (Fx) acting on the trailer coupling (10; 110), wherein the evaluation unit (50; 150) is designed to evaluate the force signal (33) to determine the support load (Fz), and to determine the tensile load (Fx) on the basis of a driving status of the towing vehicle (90).

12. Trailer coupling according to any of the preceding claims, characterised in that the force sensor or sensors (30) includes or include a deformation sensor (35) sensitive to compression and / or tension and mounted at a point of attachment (32; 132) provided on the coupling support (14; 114) or the mounting (11; 111), at which a tensile strain deformation and / or compression deformation due to a force acting on the trailer coupling (10; 110) due to the trailer (92) may be measured, wherein the point of attachment (32; 132) is so chosen that, at the point of attachment (32; 132), there is a deformation which may be caused by a tensile load (Fx) acting on the coupling element (23) during towing of the trailer (92), for actuating the force sensor or sensors (30), and a deformation which may be caused by a support load (Fz) of the trailer (92) acting on the trailer coupling (10; 110), for actuating the force sensor or sensors (30).

13. Method of determining a trailer mass value of a trailer (92) with the aid of a trailer coupling (10; 110) for a towing vehicle (90), wherein the trailer coupling (10; 110) has a coupling support (14; 114) including a coupling arm, at the free end of which is arranged a coupling element (23), in particular a coupling ball (22), for attaching a trailer (92) and which is mounted movably or immovably on the mounting (11; 111) which is or may be fixed to the towing vehicle (90), and with at least one force sensor (30) for detecting a tensile force and / or thrust force which may be caused by a tensile load (Fx) acting on the coupling element (23) during towing of the trailer (92), and for the output of a force signal (33) representing the tensile force and / or thrust force, wherein the method has a determination of a trailer mass value of the trailer (92) with the aid of the force signal (33) and an acceleration value, characterised by carrying out a compensation measurement by the evaluation device (50, 150) with the coupling support (14; 114) as yet unloaded and, with the aid of a force signal (33) thereby generated and representing the tensile force and / or the thrust force and / or a support load acting on the coupling support (14; 114), determining a base value by the evaluation device (50, 150), the base value being used for temperature compensation in the subsequent determination of the trailer mass value of the trailer (92).

14. Evaluation module with program code which can be executed by a processor (52), so that the processor of the evaluation device (50; 150) of the device according to claim 1 carries out the steps of the method according to claim 13 when executing the program code.