Method for coupling a trailer to a towing vehicle, coupling control device and vehicle

Abstract

The invention relates to a method for coupling a trailer (1b) to a towing vehicle (1a), wherein the towing vehicle (1a) has a height adjustment system (10), wherein the height of the chassis (2) relative to at least one rear axle (11) of the towing vehicle (1a) can be changed by actuation of the height adjustment system (10), the method having at least the following steps: - reading a reference height curve, wherein the reference height curve assigns a reference height gradient to different actual height values (HIst) of the height of the chassis (2) relative to the at least one rear axle (11); - changing the height of the chassis (2) relative to the at least one rear axle (11) and continuously ascertaining an actual height value (HIst) and an actual height gradient during the change in the height of the chassis (2) relative to the at least one rear axle (11), wherein the actual height value (HIst) is assigned the currently ascertained actual height gradient; - checking a coupling criterion by comparing the currently ascertained actual height gradient with a reference height gradient from the read reference height curve; - maintaining the height of the chassis (2) relative to the at least one rear axle (11) if the coupling criterion is met, wherein the coupling criterion is met when the currently ascertained actual height gradient deviates from the reference height gradient.

Description

Technical Field

[0001] The present invention relates to a method for coupling a trailer to a tractor, a coupling control device for performing the method, and a vehicle consisting of a tractor and a trailer. Background Technology

[0002] Methods are known in the prior art in which a tractor unit drives toward a target object, such as a trailer, to dock with it. This is typically laborious, as the driver manually adjusts the height of the coupling plate on the tractor unit and then brings the tractor unit close to the trailer, in which the kingpin of the trailer can be accommodated and secured. The coupling plate is then brought close to the kingpin under manual supervision to secure the kingpin in the coupling plate.

[0003] To facilitate this coupling process, methods described in DE 10 2006 057 610 A1, DE 10 2014 110498 A1, DE 10 2019 104 352 A1, WO2007102777A1, EP 1 740 400 B1, and EP 1 874 616 B1 are known. To achieve a coupling process that is as fast and smooth as possible, avoiding damage at the kingpin and / or coupling plate, DE 10 2016 011 323 A1 further specifies that the contact between the coupling plate of the tractor and the saddle plate of the semi-trailer is determined by adjusting the speed or the actual height gradient, wherein the actual height gradient describes the change in height between at least one rear axle of the tractor and the vehicle structure on which the coupling plate is tightly fitted. If a change exists, it can be inferred that the coupling plate is under load due to the saddle plate because the adjustment speed has been reduced. The disadvantage in this situation is that changes in adjusting speed or actual height gradient are not necessarily caused by contact between the saddle plate and the connecting plate. Summary of the Invention

[0004] Therefore, the object of the present invention is to describe a method for coupling a trailer to a tractor, which can be performed quickly and simply and achieves a reliable coupling process. A further object is to provide a coupling control device and a vehicle.

[0005] This task is solved by the method according to the invention for coupling a trailer to a tractor, the coupling control device according to the invention, and the vehicle according to the invention.

[0006] Therefore, according to the present invention, a method for coupling a trailer to a tractor is provided, wherein the tractor has a chassis and a coupling plate disposed on the chassis, and the trailer has a saddle plate equipped with a kingpin, wherein the kingpin can be pivotally secured to the coupling plate by a locking mechanism in the coupled state. The tractor also has a height adjustment system, wherein the height of the chassis relative to at least one rear axle of the tractor can be changed by manual or automatic drive control of the height adjustment system. Here, the method includes at least the following steps: - Read the reference height curve, which assigns a reference height gradient to different actual height values ​​of the chassis relative to at least one rear axle; - Change the height of the chassis relative to at least one rear axle so that the tractor's connecting plate is close to the trailer's saddle plate. - During the change of the chassis height relative to at least one rear axle, the actual height value and the actual height gradient are continuously obtained, wherein the actual height value is assigned to the currently known actual height gradient; - The coupling criterion is checked by comparing the currently known actual height gradient with the reference height gradient, wherein a reference height gradient with the same actual height value as the currently known actual height gradient is considered in the read reference height curve. - Maintain the height of the chassis relative to at least one rear axle while satisfying the coupling criterion, wherein the coupling criterion is satisfied when the currently known actual height gradient deviates from the reference height gradient.

[0007] Preferably, the tractor can then be brought close to the trailer so that the kingpin is received in the receiving opening of the coupling plate. The kingpin can then be secured by a locking mechanism to completely terminate the coupling process.

[0008] Therefore, it can be advantageously achieved, according to the method of the invention, that the contact between the connecting plate and the saddle plate is inferred only when the actual height gradient deviates from the reference height gradient. Thus, the measurement of this event is no longer the change in the actual height gradient itself, as described in the prior art, but rather the deviation from the reference. This is particularly advantageous in situations where, with no changing load acting on the connecting plate, the chassis moves upward at a changed adjustment speed and thus a changed actual height gradient as the connecting plate approaches the saddle plate due to the internal adjustments of the height adjustment system. The checking of the coupling criteria thus becomes more reliable, and the coupling process can be performed more reliably and without misinterpretation.

[0009] Preferably, for this purpose, it is further specified that: a reference height curve is determined in advance without loading the connecting plate of the tractor vehicle, wherein, for this purpose, the height of the chassis relative to at least one rear axle is changed once or more between a first height value, such as a minimum height and a second height value, such as a maximum height, and the actual height value and the actual height gradient are continuously obtained during the change of the height of the chassis relative to at least one rear axle, wherein the actual height value is assigned to the currently obtained actual height gradient as a reference height gradient and stored in the reference height curve.

[0010] This allows for a simple acquisition of the reference height profile, especially just before the coupling process begins, enabling the use of the current reference that reflects the current internal behavior of the height regulation system.

[0011] Preferably, it is further specified that the actual height gradient and / or reference height gradient are achieved by determining the actual height value with a time offset, wherein the time offset is between 100 ms and 300 ms. This allows for simple knowledge of the corresponding gradient, wherein the time offset is selected to enable a response to contact between the saddle plate and the connecting plate.

[0012] Preferably, the height is also specified that the height is set by determining a target height value via a height adjustment system. Therefore, in this method, for example by a coupling control device according to the invention, the change in height can be indicated in a simple manner at the corresponding steps of the method. This can preferably be achieved via a data bus in the vehicle, especially a CAN bus, thereby reducing costs, since the height adjustment system is connected to such a data bus.

[0013] Preferably, it is further specified that: after the tractor is brought close to the trailer, preferably manually or automatically, so that the trailer's saddle plate at least partially overlaps with the tractor's coupling plate, the height of the chassis relative to at least one rear axle is changed to bring the tractor's coupling plate closer to the trailer's saddle plate. This ensures that, during height changes, the saddle plate can act on the coupling plate, allowing the determination of the deviation between the actual height gradient and a reference height gradient.

[0014] Preferably, it is specified that before the connecting plate and the saddle plate overlap, the height of the chassis relative to at least one rear axle of the tractor is adjusted such that the connecting plate and the saddle plate do not touch when they overlap. This ensures that the two plates only touch each other when they are brought closer together by the height adjustment system. This avoids damage to the plates and the kingpin.

[0015] Additionally, this can be specified by stipulating that the connecting plate and the saddle plate overlap so that the kingpin does not overlap with the connecting plate, wherein a safe distance is maintained between the connecting plate and the kingpin. This prevents the kingpin from not pressing against the connecting plate when the saddle plate is not precisely aligned with the connecting plate during chassis raising. It also prevents deviations from the reference height gradient when the kingpin accidentally impacts the connecting plate. The kingpin only enters the receiving opening of the connecting plate by subsequently bringing the tractor close to the trailer, wherein their alignment can be checked beforehand.

[0016] Preferably, it is further specified that when the currently known actual height gradient is below a gradient threshold, the coupling criterion is met, wherein the gradient threshold (dHS) is determined from the reference height gradient (dHR) based on a tolerance factor (T), preferably according to dHS = T x dHR. This ensures that contact between the connecting plate and the saddle plate is not inferred in the case of any deviation, as these deviations may also be due to measurement techniques. Preferably, it is specified here that the tolerance factor is between 0.7 and 0.85, preferably 0.8. When the deviation is between at least 15% and at least 30%, preferably at least 20%, it can be concluded with high reliability that contact has occurred.

[0017] Preferably, it is further specified that, in order to meet the coupling criterion, an additional check is performed to determine whether the actual axle load value for at least one rear axle deviates upward from the reference axle load known before the chassis height relative to at least one rear axle was changed, given a deviation between the currently known actual height gradient and the reference height gradient. Therefore, it is advantageous to infer, through the evaluation of the axle load, whether the trailer additionally acts on the chassis or the rear axle. This allows for a reliability check. In particular, it can be specified that the coupling criterion is met when the axle load difference between the reference axle load and the actual axle load value, given a deviation between the currently known actual height gradient and the reference height gradient, indicates that the axle load of at least one rear axle has changed by more than 1 t. This is a reliable criterion for whether the trailer acts on the rear axle via the coupling plate.

[0018] Preferably, it is specified here that the actual axle load value and / or reference axle load are obtained through the height adjustment system. Therefore, advantageously, no other sensors are needed for this reliability check.

[0019] Preferably, the method is also specified to be executed entirely or partially autonomously. Therefore, the coupling process can also be executed without personnel, or at least partially, depending on the application, which reduces costs.

[0020] According to the present invention, a coupling control device for performing the method according to the present invention is also provided, wherein the coupling control device is designed to drive a height adjustment system in a tractor unit such that the height of the chassis of the tractor unit relative to at least one rear axle of the tractor unit is changed. The coupling control device is also designed to perform at least the following steps: - Read the reference height curve, which assigns a reference height gradient to different actual height values ​​of the chassis relative to at least one rear axle; - Drive the height adjustment system to change the height of the chassis relative to at least one rear axle so that the tractor's connecting plate is close to the trailer's saddle plate. - During the change of the chassis height relative to at least one rear axle, the actual height value and the actual height gradient are continuously obtained, wherein the actual height value is assigned to the currently known actual height gradient; - The coupling criterion is checked by comparing the currently known actual height gradient with the reference height gradient, wherein a reference height gradient with the same actual height value as the currently known actual height gradient is considered in the read reference height curve. - Drive the height adjustment system to maintain the chassis height relative to at least one rear axle while meeting the coupling criterion, wherein the coupling criterion is met when the currently known actual height gradient deviates from the reference height gradient.

[0021] Preferably, the coupling control device is also designed to receive the actual height value from the height sensor of the height adjustment system. Therefore, no other sensors are needed, as these sensors are already present in the height adjustment system and are controlled, for example, via the vehicle's data bus, particularly the CAN bus.

[0022] According to the present invention, a two-part vehicle consisting of a tractor and a trailer connectable to the tractor is also provided. The tractor has a chassis and a coupling plate disposed on the chassis, and the trailer has a saddle plate equipped with a kingpin, wherein the kingpin can be pivotally fixed to the coupling plate in a coupled state by a locking mechanism. The tractor also has a coupling control device according to the invention and a height adjustment system for changing the height of the tractor's chassis relative to at least one rear axle of the tractor. Here, the coupling control device can be integrated into the height adjustment system or communicate with the height adjustment system as an external control device, particularly via a data bus in the vehicle, especially a CAN bus, thereby facilitating the retrofitting of the coupling control device and / or the expansion of the height adjustment system. Attached Figure Description

[0023] The invention will now be described in more detail with reference to embodiments. Wherein: Figure 1 shows a two-part vehicle consisting of a tractor and a trailer; Figure 1a shows a detailed view of the connecting plate of the tractor according to Figure 1; Figure 2 A flowchart of the method according to the present invention is shown; Figures 3, 5, and 7 illustrate the two-part vehicle according to Figure 1 during the coupling process according to the invention; and Figure 4 , 6 A diagram is shown for performing the method according to the invention. Detailed Implementation

[0024] Figure 1 schematically illustrates a two-part vehicle 1, particularly a commercial vehicle, consisting of a tractor unit 1a and a parked trailer 1b. The tractor unit 1a has a chassis 2 or frame, a cab 3, and a coupling mechanism located on the chassis or frame, the coupling mechanism having a hook plate 5 for connecting the trailer 1b to the tractor unit 1a. On the trailer 1b, a kingpin 6 is fastened below a saddle plate 7, wherein the kingpin 6 can be received in a receiving opening 8 (see Figure 1a) in the hook plate 5 of the tractor unit 1a and locked or secured therein by a locking mechanism 4, so that the trailer 1b is pivotally coupled to the tractor unit 1a.

[0025] The tractor unit 1a also has a height adjustment system 10, such as ECAS ("Electronically Controlled Air Suspension"), through which the chassis 2 can be actively raised or lowered relative to one or more rear axles 11 of the tractor unit 1a. Since the coupling mechanism is fixedly connected to the chassis 2 by a connecting plate 5, the height of the connecting plate 5 relative to one or more rear axles 11 and thus relative to the ground U is also adjusted by the height adjustment system 10.

[0026] The height adjustment system 10 is controlled by a height adjustment control device 12. This device can actively raise or lower the chassis 2 relative to one or more rear axles 11 when a height adjustment signal SN is present, for example, by actively intake or exhausting air through the bellows (not shown) of the height adjustment system 10. The height adjustment signal SN may, for example, include a target height value HSoll, through which the desired height H between the chassis 2 and one or more rear axles 11 can be pre-set to the height adjustment control device 12.

[0027] The height adjustment system 10 also includes a height sensor 13, which is designed to measure the current height H between the chassis 2 and one or more rear axles 11. The height adjustment system 10 can output a corresponding actual height value HIst via a height signal SH, which represents the currently measured height H. Based on this actual height value HIst, the height between the connecting plate 5 and one or more rear axles 11 or the ground U can also be derived from simple geometric considerations.

[0028] A coupling control device 14 is also provided in the tractor 1a, through which the coupling process AV can be controlled. Here, the coupling control device 14 is designed to read the height signal SH with the actual height value HIst and output the height adjustment signal SN with the corresponding target height value HSoll to the height adjustment control device 12, so as to actively request the tractor 1a to lower or raise.

[0029] Therefore, the coupling control device 14 can be integrated into the height adjustment control device 12 or set as an external unit, for example, for retrofitting or expanding the existing height adjustment system 10. As an external unit, the coupling control device 14 can communicate with the height adjustment control device 12, for example, via a data bus 15, such as a CAN bus 15a, to exchange signals SN and SH.

[0030] For the coupling process AV, according to Figure 2 For example, it is specified that the following steps are performed via the coupling control device 14: First, it should be ensured that the height H between the chassis 2 and one or more rear axles 11 is adjusted so that the tractor 1a can approach the trailer 1b. To this end, in the first step ST1, the coupling control device 14 pre-sets a first height value H1, such as a minimum height HMin, as a target height value HSoll to the height adjustment control device 12 via a height adjustment signal SN. This first height value H1 is determined so that the tractor 1a can approach the trailer 1b after the first height value H1 is set without the coupling plate 5 and the saddle plate 7 touching. Preferably, the kingpin 6 should also be higher than the coupling plate 5 to avoid collision during approach. This state is shown in Figure 1.

[0031] In the subsequent second step ST2, the tractor 1a (manually or autonomously) is driven close to the parked trailer 1b, such that the connecting plate 5 and the saddle plate 7 at least partially overlap. Simultaneously, it is ensured that the kingpin 6 does not overlap with the connecting plate 7, for example by maintaining a longitudinal safety distance S of approximately 0.7 m, as shown in Figure 3. In the third step ST3, a pre-provided reference height curve HVR is read or loaded, which exemplarily... Figure 4As shown in the figure. In principle, the reading of the reference height curve HVR can also be performed before or in parallel with steps ST1 and ST2.

[0032] Here, the reference height curve HVR assigns a reference height gradient dHR to the height H between chassis 2 and one or more rear axles 11. The reference height gradient dHR describes how quickly or at what rate the height H changes when chassis 2 is raised or lowered when it is not under the additional load of trailer 1b (unladen condition). The reference height curve HVR is obtained by varying the height H between a first height value H1, such as the minimum height HMin, and a second height value H2, such as the maximum height HMax. Simultaneously, the reference height gradient dHR is continuously determined based on the actual height value HIst currently measured via height sensor 13. The reference height gradient dHR can be calculated, for example, from two actual height values ​​HIst, measured with a time offset dt between 100ms and 300ms, from which the adjustment speed (height gradient) is directly derived. Then, the reference height gradient dHR thus obtained is assigned to the currently existing height H, derived from the currently measured actual height value HIst. The reference height curve HVR is determined through this continuous acquisition.

[0033] The reference height curve HVR can also be derived from multiple implementations by repeatedly adjusting the height H in a ramp-like manner (in both directions) between a first height value H1 and a second height value H2, and recording the corresponding reference height gradient dHR. Figure 4 As shown in the figure. Next, based on multiple implementations, for example, the average value of the corresponding associated reference height gradient dHR can be calculated for each height H in order to filter out measurement errors.

[0034] The reference height curve HVR is known in advance, i.e., before the first step ST1, for example, immediately after the first height value H1 is set and the tractor 1a approaches the trailer 1b, so that the most current reference height curve HVR can be used. However, the reference height curve HVR can also be known all at once, for example at the end of the production line, or at any uniform interval. The reference height curve is then stored on the coupling control device 14 so that various values ​​of the reference height gradient dHR can be used for the coupling process AV.

[0035] Subsequently, in the fourth step ST4, a request to raise the chassis 2 is made by pre-setting a second height value H2, such as the maximum height HMax, as the target height value HSoll to the height adjustment control device 12 via the height adjustment signal SN. As a result, the connecting plate 5 moves closer to the overlapping saddle plate 7, such as... Figure 5 As shown in the image.

[0036] In step ST5, the current actual altitude gradient dHI is continuously calculated by evaluating the altitude signal SH or the actual altitude value HIst contained therein. This is achieved by measuring two actual altitude values ​​HIst with a time offset dt between 100ms and 300ms, and calculating the current actual altitude gradient dHI for the current ascent rate or the current altitude H. In this respect, the current actual altitude value HIst can be assigned the current actual altitude gradient dHI.

[0037] In the subsequent sixth step ST6, the coupling standard AK is checked, which indicates whether the saddle plate 7 is in contact with the connecting plate 5. This is achieved by comparing the actual altitude gradient dHI assigned to the current actual altitude value HIst with the reference altitude gradient dHR assigned to the same actual altitude value HIst. Here, for the current actual altitude value HIst, the reference altitude gradient dHR is derived from the reference altitude curve HVR read in the third step ST3.

[0038] By comparing in step ST6, it can be determined whether the same height gradient (see dHI) is obtained during the adjustment of the second height value H2 as in the unloaded state (see dHR). This directly indicates whether the saddle plate 7 acts on the connecting plate 5 at the current actual height value HIst. That is, the height change, or the known actual height gradient dHI, directly indicates how quickly the connecting plate 5 is raised, since it is fixedly connected to the chassis 2. Therefore, the contact between the connecting plate 5 and the saddle plate 7 directly affects the movement of the chassis 2 and thereby affects the actual height gradient dHI. If the saddle plate 7 is not abutting against the connecting plate 5, it can be expected that the actual height gradient dHI corresponds to the reference height gradient dHR, because no additional load acts on the chassis 2 and the chassis can move upward without obstruction. However, if the actual height gradient dHI assigned to the determined actual height value HIst deviates from the reference height gradient dHR also assigned to that actual height value HIst, then an additional load acts on the chassis 2, primarily through the weight of the trailer 1b via the connecting plate 5.

[0039] exist Figure 6This is illustrated exemplarily for two different trailers 1b, where the reference height curve HVR is plotted as a dashed line. Therefore, the curve of the actual height gradient dHI deviates from the reference height gradient dHR of the reference height curve HVR from the actual height value H3 or H4, where the third actual height value H3 and the fourth actual height value H4 are respectively assigned to the other trailer 1b. Thus, these two actual height values ​​H3 and H4 are different because the corresponding trailers 1b stop at different heights, meaning that the saddle plate 7 will eventually collide with the connecting plate 5, causing the measured height curve to bend relative to the reference height curve HVR.

[0040] Therefore, for the corresponding trailer 1b, if the comparison performed yields dHI(HIst) == dHR(HIst), then the coupling criterion AK is satisfied. This can also be done by considering the tolerance factor T to compensate for undesirable deviations caused by errors. Thus, the coupling criterion AK can be satisfied, for example, when the actual height gradient dHI deviates from the reference height gradient dHR by more than 20%. That is, if the actual height gradient dHIst known for the actual height value HIst drops below the gradient threshold dHS = T x dHR = 0.8 x dHR, then the coupling criterion AK is satisfied, because it can be assumed that trailer 1b, in particular saddle 7, acts on tractor 1a, in particular connecting plate 5.

[0041] Since the behavior under no-load conditions is considered for comparison in order to check the coupling standard AK, the change in adjustment speed or actual height gradient dHIst when the chassis 2 is raised is not attributed to the action of trailer 1b but to the normal behavior or characteristics of the height adjustment system 10 itself, which would occur even under no-load conditions. Therefore, contact between the connecting plate 5 and the saddle plate 7 can be reliably ruled out.

[0042] Additionally, to meet the coupling criterion AK, it can be checked how the axle load L acting on one or more rear axles 11 changes when the load is below the gradient threshold dHS. This axle load L can be known and output by the height adjustment system 10 itself, for example, by evaluating the aerodynamic pressure present in the air bellows when the ECAS is used as the height adjustment system 10. For this purpose, at a certain point in time before the tractor 1a approaches the trailer 1b, in step ST4, the actual axle load value LI present at that time is stored as a reference axle load LR based on the axle load signal SL output by the height adjustment system 10. After confirming in the sixth step ST6 that the load is below the gradient threshold dHS, the actual axle load value LI is compared with the reference axle load LR.

[0043] The axle load difference dL = LI - LR can be used to infer the extent to which the load or burden (axle load L) of one or more rear axles 11 changes. If the axle load difference dL indicates that the axle load L changes by more than 1t during the coupling process AV, then it is plausible that the load is below the gradient threshold dHS due to the saddle plate 7 abutting against the connecting plate 5. Therefore, the coupling criterion AK can be considered to be satisfied with high reliability.

[0044] If the coupling standard AK is met, the height adjustment signal SN can be output in step ST7: using the current actual height value HIst as the target height value HSoll, and then the height adjustment system 10 stops raising the chassis 2. If the coupling standard AK is not met, steps ST5 and ST6 continue, i.e., the chassis 2 continues to be raised.

[0045] If coupling standard AK is met and further raising of chassis 2 is stopped, then in the subsequent eighth step ST8, the tractor 1a can continue to approach trailer 1b (see...). Figure 7 In this process, the tractor 1a can be lowered via the height adjustment signal SN to facilitate the placement of the kingpin 6 in the receiving opening 8. Then, in the final ninth step ST9, the locking mechanism 4 can be manipulated to secure the kingpin 6 in the receiving opening 8. Furthermore, the support 16 on which the trailer 1b is initially placed can be pivoted upwards. This completes the coupling process AK.

[0046] List of reference numerals (part of the instruction manual)

[0047] 1 vehicle

[0048] 1a Tractor

[0049] 1b Trailer

[0050] 2. Chassis

[0051] 3. Driver's cab

[0052] 4. Locking mechanism

[0053] 5 Connecting plate

[0054] 6. Main Sales

[0055] 7. Saddle

[0056] 8. Accommodation opening

[0057] 10. Height Adjustment System

[0058] 11. Rear axle of tractor 1a

[0059] 12 Height Adjustment Control Device

[0060] 13. Height sensor

[0061] 14 Coupled control device

[0062] 15 Data Bus

[0063] 15a CAN bus

[0064] 16 Support components on trailer 1b

[0065] AK Coupling Standard

[0066] AV coupling process

[0067] dHI (Actual Height Gradient)

[0068] dHR reference height gradient

[0069] dHS gradient threshold

[0070] dL axle load difference

[0071] dt time offset

[0072] Height between chassis 2 and rear axle 11

[0073] H1 First height value

[0074] H2 Second Height Value

[0075] H3 Third Height Value

[0076] H4 fourth height value

[0077] HIst actual height value

[0078] HMax maximum height

[0079] HMin minimum height

[0080] HSoll target height value

[0081] HVR Reference Height Curve

[0082] L-axle load

[0083] LI Actual axle load value

[0084] LR Reference Axle Load

[0085] SH Altitude Signal

[0086] SL axle load signal

[0087] SN height adjustment signal

[0088] T tolerance factor

[0089] U Ground

[0090] ST1-ST9 Method Steps

Claims

1. A method for coupling a trailer (1b) to a tractor (1a), wherein, The tractor (1a) has a chassis (2) and a connecting plate (5) arranged on the chassis, and the trailer (1b) has a saddle plate (7) equipped with a kingpin (6), wherein the kingpin (6) can be pivotally fixed to the connecting plate (5) in a coupled state by means of a locking mechanism (4). The tractor (1a) also has a height adjustment system (10), wherein the height (H) of the chassis (2) relative to at least one rear axle (11) of the tractor (1a) can be changed by controlling the drive of the height adjustment system (10). The method comprises at least the following steps: - Read the reference height curve (HVR), where the reference height curve (HVR) assigns a reference height gradient (dHR) to different actual height values ​​(HIst) of the chassis (2) relative to at least one rear axle (11). - Change the height (H) of the chassis (2) relative to at least one rear axle (11) so that the connecting plate (5) of the tractor (1a) is close to the saddle plate (7) of the trailer (1b). - During the change of the height (H) of the chassis (2) relative to at least one rear axle (11), the actual height value (HIst) and the actual height gradient (dHI) are continuously obtained, wherein the actual height value (HIst) is assigned to the currently obtained actual height gradient (dHI). - Check the coupling criterion (AK) by comparing the currently known actual altitude gradient (dHI) with the reference altitude gradient (dHR), where the reference altitude gradient (dHR) with the same actual altitude value (HIst) as the currently known actual altitude gradient (dHI) is considered in the read reference altitude curve (HVR). - Maintain the height (H) of the chassis (2) relative to at least one rear axle (11) while satisfying the coupling criterion (AK), wherein the coupling criterion (AK) is satisfied when the currently known actual height gradient (dHI) deviates from the reference height gradient (dHR).

2. The method according to claim 1, characterized in that, The reference height curve (HVR) is known in advance without loading the connecting plate (5) of the tractor (1a), wherein the height (H) of the chassis (2) relative to the at least one rear axle (11) is changed once or more between a first height value (H1) and a second height value (H2), and the actual height value (HIst) and the actual height gradient (dHI) are continuously known during the change of the height (H) of the chassis (2) relative to the at least one rear axle (11). Specifically, the actual height value (HIst) is assigned the currently known actual height gradient (dHI) as a reference height gradient (dHR) and stored in the reference height curve (HVR).

3. The method according to any one of the preceding claims, characterized in that, The actual altitude gradient (dHI) and / or the reference altitude gradient (dHR) are achieved by determining the actual altitude value (HIst) with a time offset, wherein the time offset (dt) is between 100ms and 300ms.

4. The method according to claim 1 or 2, characterized in that, The height (H) is set by determining the target height value (HSoll) via the height adjustment system (10).

5. The method according to claim 1 or 2, characterized in that, After the saddle plate (7) of the trailer (1b) is at least partially overlapped with the connecting plate (5) of the tractor (1a), the height (H) of the chassis (2) relative to the at least one rear axle (11) is changed so that the connecting plate (5) of the tractor (1a) is close to the saddle plate (7) of the trailer (1b).

6. The method according to claim 5, characterized in that, Before the connecting plate (5) overlaps with the saddle plate (7), the height (H) of the chassis (2) relative to at least one rear axle (11) of the tractor (1a) is adjusted so that the connecting plate (5) and the saddle plate (7) do not touch (H1) when they overlap.

7. The method according to claim 5, characterized in that, The connecting plate (5) and the saddle plate (7) are overlapped so that the main pin (6) does not overlap with the connecting plate (5), wherein a safe distance (S) is maintained between the connecting plate (5) and the main pin (6).

8. The method according to claim 1 or 2, characterized in that, When the currently known actual height gradient (dHI) deviates from the reference height gradient (dHR), the connecting plate (5) touches the saddle plate (7).

9. The method according to claim 1 or 2, characterized in that, The coupling criterion (AK) is satisfied when the currently known actual height gradient (dHI) is lower than the gradient threshold (dHS).

10. The method according to claim 9, characterized in that, The gradient threshold (dHS) is determined from the reference height gradient (dHR) based on the tolerance factor (T).

11. The method according to claim 10, characterized in that, The tolerance factor (T) is between 0.7 and 0.

85.

12. The method according to claim 1 or 2, characterized in that, To satisfy the coupling criterion (AK), an additional check is performed to indicate whether the actual axle load value (LI) of the axle load (L) of the at least one rear axle (11) deviates upward from the reference axle load (LR) known before the change of the height (H) of the chassis (2) relative to the at least one rear axle (11) when there is a deviation between the currently known actual height gradient (dHI) and the reference height gradient (dHR).

13. The method according to claim 12, characterized in that, The coupling criterion (AK) is satisfied when the axle load difference (dL) between the reference axle load (LR) and the actual axle load value (LI) indicates that the axle load (L) of at least one rear axle (11) has changed by more than 1 ton, given that there is a deviation between the currently known actual height gradient (dHI) and the reference height gradient (dHR).

14. The method according to claim 12, characterized in that, The actual axle load value (LI) and / or the reference axle load (LR) are obtained via the height adjustment system (10).

15. The method according to claim 1 or 2, characterized in that, The method is executed completely or partially autonomously.

16. The method according to claim 5, characterized in that, The saddle plate (7) of the trailer (1b) is at least partially overlapped with the connecting plate (5) of the tractor (1a) by bringing the tractor (1a) close to the trailer (1b) manually or automatically.

17. The method according to claim 10, characterized in that, The gradient threshold (dHS) is determined as follows: the gradient threshold (dHS) is equal to the tolerance factor (T) multiplied by the reference height gradient (dHR).

18. The method according to claim 11, characterized in that, The tolerance factor (T) is 0.

8.

19. The method according to claim 2, characterized in that, The first height value (H1) is the minimum height (HMin).

20. The method according to claim 2, characterized in that, The second height value (H2) is the maximum height (HMax).

21. A coupling control device (14) for performing the method according to any one of the preceding claims, wherein, The coupling control device (14) is designed to drive the height adjustment system (10) in the tractor (1a) such that the height (H) of the chassis (2) of the tractor (1a) relative to at least one rear axle (11) of the tractor (1a) is changed, and at least the following steps are performed: - Read the reference height curve (HVR), where the reference height curve (HVR) assigns a reference height gradient (dHR) to different actual height values ​​(HIst) of the chassis (2) relative to at least one rear axle (11). - Drive control height adjustment system (10) for changing the height (H) of the chassis (2) relative to at least one rear axle (11) so that the connecting plate (5) of the tractor (1a) is close to the saddle plate (7) of the trailer (1b). - During the change of the height (H) of the chassis (2) relative to at least one rear axle (11), the actual height value (HIst) and the actual height gradient (dHI) are continuously obtained, wherein the actual height value (HIst) is assigned to the currently obtained actual height gradient (dHI). - Check the coupling criterion (AK) by comparing the currently known actual altitude gradient (dHI) with the reference altitude gradient (dHR), where the reference altitude gradient (dHR) with the same actual altitude value (HIst) as the currently known actual altitude gradient (dHI) is considered in the read reference altitude curve (HVR). - Drive the height adjustment system (10) to maintain the height (H) of the chassis (2) relative to at least one rear axle (11) while satisfying the coupling criterion (AK), wherein the coupling criterion (AK) is satisfied when the currently known actual height gradient (dHI) deviates from the reference height gradient (dHR).

22. The coupling control device (14) according to claim 21, characterized in that, The coupling control device (14) is designed to receive the actual height value (HIst) from the height sensor (13) of the height adjustment system (10).

23. A vehicle (1) consisting of a tractor (1a) and a trailer (1b) that can be attached to the tractor (1a), wherein, The tractor (1a) has a chassis (2) and a connecting plate (5) arranged on the chassis, and the trailer (1b) has a saddle plate (7) equipped with a kingpin (6), wherein the kingpin (6) can be pivotally fixed to the connecting plate (5) by a locking mechanism (4) in a coupled state, wherein the tractor (1a) also has a coupling control device (14) according to claim 21 or 22 and a height adjustment system (10) for changing the height (H) of the chassis (2) of the tractor (1a) relative to at least one rear axle (11) of the tractor (1a).

24. The vehicle (1) according to claim 23, characterized in that, The coupling control device (14) is connected to the height adjustment control device (12) of the height adjustment system (10) by means of conducting signals, or the coupling control device (14) is integrated into the height adjustment control device (12) of the height adjustment system (10).

25. The vehicle (1) according to claim 24, characterized in that, The coupling control device (14) is connected to the height adjustment control device (12) of the height adjustment system (10) via a data bus (15) by means of conducting signals.

26. The vehicle (1) according to claim 25, characterized in that, The data bus (15) is a CAN data bus (15a).

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