Method for operating a drive unit for a trailer

Abstract

The present invention relates to a method for operating a drive unit (7) for a trailer (1). The drive unit (7) comprises a differential (9) for mechanically connecting two wheels (6) of the trailer (1) and a drive motor (8) for driving the wheels (6) of the trailer (1). It also comprises an electric parking brake (11) for braking one wheel (6) of the trailer (1). The method includes detecting (IV) a slip condition of the wheel (6) of the trailer (1) and applying (V) the parking brake (11) to reduce the slip condition of the wheel (6) of the trailer (1).

Description

Technical field

[0001] The present invention relates to a method for operating a drive unit for a trailer. Furthermore, the present invention relates to a control unit configured to carry out such a method, to a drive unit with such a control unit, and to a trailer with such a drive unit. State of the art

[0002] A trailer with its own electric drive and brake system is known from EP 3 656 619 A1. The electric drive and brake system has a detection device for recording physical movement parameters of the trailer and a control unit for controlling the electric drive and brake unit based on signals from the detection device. Description of the invention

[0003] The present invention relates to a method for operating a drive unit for a trailer. The trailer may be a caravan, a horse trailer, a cargo trailer, or any other type of trailer. The trailer may have one or more axles, each with two wheels. The trailer may have a coupling section for mechanically coupling it to a towing vehicle. The coupling section may be designed as a ball socket for mechanical coupling to a ball head provided on the towing vehicle. Alternatively, the coupling section may have an eyelet for coupling to the towing vehicle by means of a bolt in the form of a bolt coupling. Alternatively or additionally, the coupling section of the trailer may be configured to form a jaw coupling, a fifth wheel coupling, or any other type of coupling with a counterpart on the towing vehicle.The trailer has its own drive system for propelling itself. Energy for this drive system can be supplied by the trailer itself or alternatively or additionally by the towing vehicle. For example, the trailer may have a battery pack mounted on the trailer to power the drive system. The trailer can be designed to be towed by a towing vehicle, such as a passenger car, a construction machine, or alternatively or additionally, a commercial vehicle.

[0004] The trailer's drive system can also be designed to allow the trailer to move autonomously, independent of a towing vehicle. For example, a remote control can be provided to operate the drive system. In one embodiment, the remote control can manage both the longitudinal and lateral dynamics of the trailer. If the trailer is, for example, a caravan, such a design allows the drive system to maneuver the caravan, for instance, to align it, even when uncoupled from the vehicle.

[0005] The trailer's drive system includes a differential, such as a transverse differential, for mechanically connecting two of the trailer's wheels. This differential can be a planetary gear system or, alternatively or additionally, a bevel gear system. The differential acts as a compensating mechanism to compensate for speed differences between the trailer's wheels connected via the differential. Furthermore, the drive system includes a drive motor for powering the trailer's wheels. The drive motor can have a single drive unit to power both wheels or multiple drive units, for example, one for each wheel. Torque transmitted to one wheel via the drive motor can also be transferred to the other wheel of the trailer via the differential.The drive motor and the differential can be provided as separate components and located remotely. In an alternative embodiment, the drive motor and the differential are combined into a single assembly, which may, for example, share a common housing. The drive motor and the differential can be arranged coaxially or parallel to each other. In one embodiment, the trailer has an electric drive axle in which the drive motor, the differential, and the trailer wheels can be arranged coaxially.

[0006] Furthermore, the drive unit includes an electric parking brake for braking one of the trailer's wheels. In one embodiment, an electric parking brake is provided for each of the trailer's wheels. The electric parking brake can include an electric motor that drives a spindle drive for the translational adjustment of a brake bolt. The electric motor can be controlled by an electrical signal from a control unit to engage or disengage the electric parking brake. In one embodiment, different braking forces can be set via the electric parking brake to achieve varying degrees of braking force on the wheel. In addition to the electric parking brake, each of the trailer's wheels can also have a service brake, which can be actuated, for example, mechanically and alternatively or additionally hydraulically.In one embodiment, pneumatic actuation of the service brake is also provided.

[0007] The service brake can be activated by the towing vehicle. Alternatively or additionally, the service brake can be activated by the trailer itself. For example, the service brake is activated based on a relative quantity between the towing vehicle and the trailer, which can be detected by an overrun device. This relative quantity could be, for example, a force acting between the towing vehicle and the trailer. Furthermore, the relative quantity could be a relative velocity between the trailer and the towing vehicle. If, for example, the trailer pushes down on the towing vehicle when traveling downhill, the relative quantity can be identified as a compressive force exerted by the trailer on the towing vehicle. During acceleration, on the other hand, the towing vehicle can exert a tractive force on the trailer, which can then be identified as a relative quantity between the towing vehicle and the trailer.Based on such a relative quantity detected by the trailer itself, the trailer's service brake can be controlled. The parking brake can be designed to secure the trailer against rolling away when stationary. Alternatively or additionally, the parking brake can be designed to apply a braking torque to one of the wheels even while the trailer is in motion. In one embodiment, however, the braking torque applied by the parking brake may not be sufficient to decelerate the trailer. Instead, applying the service brake may be necessary to decelerate the trailer.

[0008] The method involves detecting wheel slippage on the trailer wheel, which can be braked via the electric parking brake. Wheel slippage refers to a condition in which the wheel spins freely. In wheel slippage, there can be a discrepancy between the trailer's speed and the wheel's peripheral speed at the point of contact with the ground. Such wheel slippage can be detected by a sensor, for example, a speed sensor, a torque sensor, or an optical, inductive, capacitive, and / or other sensor. Furthermore, the method includes applying the parking brake to reduce wheel slippage. For example, the parking brake is applied to slow the wheel experiencing wheel slippage, such as spinning freely, using the electric parking brake.The degree of application of the electric parking brake, for example, the strength of the application, can depend on the degree of wheel slippage of the trailer. Thus, with greater wheel slippage, the parking brake can be applied to a greater extent.

[0009] Due to the braking of the trailer wheel by the electric parking brake, a larger proportion of the drive motor's torque is diverted through the differential to the other trailer wheel. As a result, a method for operating a trailer drive system can be provided that prevents wheel spin and thus, for example, lateral fishtailing of the trailer. Consequently, the method of the present invention can be used to provide a trailer with anti-slip control and thus traction control.

[0010] In one embodiment, the method comprises determining the actual rotational speed of the trailer wheel and comparing this actual speed with a target rotational speed. The actual rotational speed can be determined, for example, using a speed sensor on the trailer wheel. By comparing the actual rotational speed with the target rotational speed, it is possible to easily and reliably determine whether the trailer wheel is slipping. For example, in this embodiment, slippage can be determined if the actual rotational speed exceeds the target rotational speed, for instance, by a certain amount. In one embodiment, the method can also include determining the target rotational speed of the trailer wheel.The drive motor of the drive unit can be controlled in such a way that the wheels of the trailer rotate at the specified target speed.

[0011] In one embodiment, the target rotational speed of the trailer wheel is determined based on the state of the trailer's overrun device, which detects a relative force between the trailer and the towing vehicle. The overrun device can be configured as described above. For example, if the overrun device detects that the trailer is pushing against the towing vehicle, the drive motor can be operated as a generator to brake the trailer. Alternatively or additionally, the trailer's service brake can be applied to brake the trailer. Conversely, if the overrun device detects that the towing vehicle is exerting a tractive force on the trailer, the drive motor can be operated as a motor to accelerate the trailer and thus reduce the tractive force.Depending on the relative size between the towing vehicle and the trailer, a different target rotational speed can be specified for the trailer's wheels. This embodiment can take into account whether the trailer is, for example, cornering. In such a case, different target rotational speeds can be determined for the various wheels to simulate cornering. The target rotational speeds of the wheels during such cornering can be calculated using suitable functions. Based on the respective target rotational speed of the wheel, a slip condition can then be easily and reliably detected by comparing it with the actual rotational speed. In an alternative embodiment, a slip condition can be detected based on a comparison of the actual rotational speeds of the two wheels.Alternatively or additionally, a slip condition can also be detected based on a speed gradient of one or, alternatively or additionally, both wheels.

[0012] In one embodiment, the method includes detecting when the two wheels are rotating at the same speed and activating a differential lock in the drive unit's differential. The differential described above can thus have a differential lock to ensure that the wheels, which are mechanically connected via the differential, rotate at the same speed. The differential lock prevents the two wheels from rotating at different speeds. If the method described above has prevented slippage of one of the trailer's wheels, then, in the present embodiment, the differential lock can subsequently be engaged when both wheels are rotating at the same speed. Activating the differential lock can involve engaging or disengaging it. In one embodiment, the differential lock is engaged.Engaging the differential lock improves the trailer's stability on poor road surfaces. For example, it can improve traction when starting off. Furthermore, it can improve straight-line driving, such as when the trailer is to be moved independently without a towing vehicle, using its own drive system, as described above.

[0013] In one embodiment, the method includes, upon detection of wheel slip, activating the drive motor to reduce torque. Reducing the drive motor's torque helps to eliminate the wheel slip at the trailer as quickly as possible. This torque reduction can occur simultaneously with the application of the parking brake. Alternatively or additionally, the drive motor's torque can be reduced only if applying the parking brake does not achieve the desired reduction in wheel slip.

[0014] The present invention further relates to a control unit that is configured, i.e., specifically prepared, for example, programmed, to execute the method according to one of the embodiments described above. The control unit can comprise one or more control units, which may be combined into an assembly or may be provided separately from one another, either spatially and / or functionally. The control unit can have one or more interfaces, each configured as an input and / or output interface, to communicate with the respective components of the drive unit for executing the method described above. In one embodiment, the trailer has a brake control unit for executing the method described above and a separate drive control unit for controlling the drive motor, the differential, and / or the service brakes.The brake control unit and the drive control unit can each have an interface to enable bidirectional communication. In an alternative embodiment, the brake control unit and the drive control unit are combined in a single control unit.

[0015] The control unit can have an interface for communication with an overrun device for detecting a relative value between a trailer and the towing vehicle. The overrun device can be designed according to the above specifications. Via the interface, the control unit can therefore detect the relative value between the trailer and the towing vehicle described above and, for example, control one or more components of the drive system based on this.

[0016] Furthermore, the present invention relates to a drive unit for a trailer with a differential for mechanically connecting two wheels of the trailer. The drive unit also includes a drive motor for driving the wheels of the trailer and an electric parking brake for braking one wheel of the trailer. In addition, the drive unit comprises a control unit according to one of the embodiments described above. In one embodiment, the drive unit also includes a differential lock for locking the differential. The present invention further relates to a trailer with a drive unit according to one of the embodiments described above. Regarding the configurations and advantages of the individual features, reference is made to the above descriptions in connection with the method for operating the drive unit for a trailer. Brief description of the characters Fig. Figure 1 shows a trailer according to one embodiment. Fig. Figure 2 shows a flowchart of a procedure for operating a drive unit of the trailer. Fig. 1. Detailed description of embodiments

[0017] Fig. Figure 1 shows a trailer 1 according to one embodiment. The trailer 1 has a frame 2 with a drawbar 3. Furthermore, the trailer 1 includes a coupling section 4 for coupling the trailer 1 to a towing vehicle (not shown). In the present embodiment, the coupling section 4 is designed as a ball socket, which can be coupled to a ball hitch of the towing vehicle. Alternative coupling sections are also provided in other embodiments. In the present embodiment, the trailer 1 is designed as a caravan. The trailer 1 of the present embodiment has one axle 5 with two wheels 6, although alternative embodiments may also provide multiple axles.

[0018] Furthermore, the trailer 1 includes a drive unit 7, which in the present embodiment is designed as an electric drive unit 7. In the present embodiment, the axle 5 is designed as an electric drive axle and is therefore part of the drive unit 7. The drive unit 7 has an electric drive motor 8 and a differential 9. The wheels 6 are mechanically connected to each other via the differential 9. The differential 9 is designed as a differential gear to compensate for differences in rotational speed between the wheels 6. The electric drive motor 8 can be operated with energy from a battery arrangement (not shown) which is located on the trailer 1 itself. In the present embodiment, the electric motor 8 is electrically connected to this battery arrangement via an inverter (not shown).The electric drive motor 8 is designed to transmit torque to the wheels 6 via the differential 9 to propel the trailer 1. Simultaneously, in the present embodiment, the electric motor 8 is also designed to function as a generator and thus recuperate electrical energy, for example when the trailer 1 is braking, via the inverter into the battery arrangement.

[0019] The trailer 1 includes a service brake 10 at each of its wheels 6, which in the present embodiment is mechanically actuated. In an alternative embodiment, the respective service brake 10 is hydraulically actuated. Furthermore, the drive unit 7 includes an electric parking brake 11 at each of its wheels 6, which is electrically actuated. The electric parking brakes 11 each have an electric motor that rotates a spindle to engage a brake piston with a brake disc. In the present embodiment, the electric parking brakes 11 of the trailer 1 are actuated via a brake control unit 12 of the drive unit 7. The trailer 1 also has a drive control unit 13 for actuating the drive motor 8, the differential 9, and the service brakes 10.In the present embodiment, the brake control unit 12 is provided separately from the drive control unit 13. However, both have an interface 14 through which they are electronically connected to each other for bidirectional communication.

[0020] Furthermore, the trailer 1 includes an overrun device 15, which is provided between the coupling section 4 and the drawbar 3. The overrun device 15 can detect a relative quantity between the trailer 1 and a towing vehicle. In the present embodiment, the overrun device 15 can detect a force acting between the towing vehicle and the trailer 1, for example, via a force sensor provided in the overrun device 15. The drive control unit 13 has an interface 16 that is electronically connected to the overrun device 15. Based on the relative quantity between the trailer 1 and the towing vehicle detected by the overrun device 15 via the interface 16, the drive control unit 13 controls the drive motor 8, the differential 9, and the service brakes 10.The drive control unit 13 has a drive interface 20 for controlling the drive motor 8, the differential 9, and the service brakes 10. If the drive control unit 13 detects via the overrun device 15 that the trailer 1 is exerting a force on the towing vehicle, the drive motor 8 can be operated in generator mode via the drive control unit 13 to brake the trailer 1. In such a case, the drive control unit 13 can also actuate the service brakes 10 of the wheels 6 to brake the trailer 1. Conversely, if the drive control unit 13 detects via the overrun device 15 that the towing vehicle is exerting a tractive force on the trailer 1, the drive control unit 13 can control the drive motor 8 to accelerate the trailer 1 to the speed of the towing vehicle.

[0021] Furthermore, the trailer 1 includes a speed sensor 17 at each of its wheels 6 for detecting the rotational speed of the respective wheel 6. The speed sensors 17 are electronically connected to the brake control unit 12 via a speed interface 18. The parking brakes 11 of the wheels 6 are also electronically connected to the brake control unit 12 via a brake interface 19. The brake control unit 12 is configured to perform the following, with reference to Fig. 2. To carry out the described procedures for operating the drive unit 7.

[0022] In a first step I, the brake control unit 12 determines a target rotational speed for each of the wheels 6. For this purpose, the drive control unit 13 supplies the brake control unit 12 with the force currently acting between the towing vehicle and the trailer 1 via the overrun device 15 via interfaces 14. This force is read by the drive control unit 13 via interface 16 and, in the present embodiment, transmitted to the brake control unit 12 via interfaces 14. Based on this and, if applicable, other parameters, for example, an intended and, alternatively or additionally, already occurring curve of the trailer 1, the brake control unit 12 determines a target rotational speed for each of the wheels 6. In an alternative embodiment, the target rotational speeds of the wheels 6 are determined by the drive control unit 13 and supplied to the brake control unit 12 via interfaces 14.

[0023] In a subsequent step II, the brake control unit 12 determines the current actual rotational speeds of the wheels 6. For this purpose, the respective rotational speed of the wheels 6 is read via the respective speed sensor 17 and supplied to the brake control unit 12 via the speed interface 18. In a subsequent step III, the brake control unit 12 now compares the actual rotational speeds determined in step II with the target rotational speeds of the wheels 6 determined in step I.

[0024] If one of the actual rotational speeds determined in step II exceeds the corresponding target rotational speed of the respective wheel 6 determined in step I by a certain amount, a slip condition of the wheel 6 of the trailer 1 is detected in a subsequent step IV. In such a case, the brake control unit 12, via the brake interface 19, activates the parking brake 11 of the wheel 6 with the slip condition detected in step IV in a subsequent step V such that the wheel 6 is braked down to the target rotational speed. Such braking of the wheel 6 with a slip condition by the corresponding parking brake 11 results in a larger portion of the torque of the drive motor 8 being diverted to the other wheel 6 due to the differential 9.

[0025] In subsequent step VI, the brake control unit 12 sends a signal to the drive control unit 13 via interfaces 14 to reduce the torque of the drive motor 8. The drive control unit 13 receives the corresponding signal from the brake control unit 12 via interfaces 14 and outputs it to the drive motor 8 via drive interface 20 to reduce its torque. The process then returns to step I and repeats steps I, II, and III.

[0026] If the comparison in step III shows that the actual rotational speeds of the wheels 6 correspond to the target rotational speeds and also to each other, the brake control unit 12 detects an equality of rotational speeds between the two wheels 6 in a subsequent step VII. In this case, the brake control unit 12 issues a control command to actuate the differential lock to the drive control unit 13 via the interfaces 14 in a step VIII. The drive control unit 13 receives this command and controls the differential 9 accordingly via the drive interface 20. The process then returns to step I. Reference sign 1 trailer 2 frames 3 Drawbar 4 Coupling section 5-axis 6 wheels 7 Drive unit 8 Drive motor 9 Differential 10 Service brake 11 electric parking brake 12 Brake control unit 13 Drive control unit 14 Interface 15 overrun device 16 Interface 17 Speed ​​sensor 18 Speed ​​interface 19 Brake interface 20 Drive interface I Determine target speed II. Recording actual rotational speed III. Compare actual speed with target speed IV. Detecting Slip State V Controlling the electric parking brake VI Controlling the drive motor to reduce torque VII. Detecting speed equality VIII Controlling the differential lock QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] EP 3 656 619 A1

[0002]

Claims

[1] Method for operating a drive device (7) for a trailer (1), wherein the drive device (7) comprises a differential (9) for mechanically connecting two wheels (6) of the trailer (1), a drive motor (8) for driving the wheels (6) of the trailer (1) and an electric parking brake (11) for braking a wheel (6) of the trailer (1), comprising a detection (IV) of a slip condition of the wheel (6) of the trailer (1) and an actuation (V) of the electric parking brake (11) to reduce the slip condition of the wheel (6) of the trailer (1). [2] Method according to claim 1, characterized by , that the procedure includes determining (II) an actual rotational speed of the wheel (6) of the trailer (1) and comparing (III) the determined actual rotational speed with a target rotational speed of the wheel (6) of the trailer (1). [3] Method according to claim 2, characterized by, that the method comprises determining (I) the target rotational speed of the wheel (6) of the trailer (1) based on a state of an overrun device (15) to detect a relative quantity between the trailer (1) and a towing vehicle of the trailer (1). [4] Method according to any one of the preceding claims, characterized by , that the method includes detecting (VII) an equality of rotational speeds between the two wheels (6) and controlling (VIII) a differential lock of the differential (9) of the drive unit (7). [5] Method according to any one of the preceding claims, characterized by , that the method, in the event of a detected slip condition, includes controlling (VI) the drive motor (8) to reduce a torque of the drive motor (8). [6] Control device (12) configured to perform the method according to any of the preceding claims. [7] Control device (12) according to claim 6, characterized by, that the control device (12) has an interface (14) for communication with an overrun device (15) for detecting a relative quantity between a trailer (1) and a towing vehicle of the trailer (1). [8] Drive device (7) for a trailer (1) comprising a differential (9) for mechanically connecting two wheels (6) of the trailer (1), a drive motor (8) for driving the wheels (6) of the trailer (1), an electric parking brake (11) for braking one wheel (6) of the trailer (1) and a control device (12) according to claim 6 or 7. [9] Drive device (7) according to claim 8, characterized by , that the differential (9) has a differential lock for locking the differential (9). [10] Trailer (1) with a drive unit (7) according to claim 8 or 9.

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