Method for operating a drive unit of a trailer, drive unit and computer program product

Abstract

Method for operating a drive unit (2) of a trailer (1), wherein the drive unit (2) comprises a drive motor (3) which is connected via a differential gear (4) to a right wheel (5) and a left wheel (6) of an axle (7) of the trailer (1), characterized in that in successive steps the right wheel (5) and the left wheel (6) are alternately driven in opposite directions of travel, while the non-driven wheel (6, 5) is braked.

Description

The present invention relates to a method for operating a drive unit of a trailer, wherein the drive unit comprises a drive motor for driving a right wheel and a left wheel of an axle and a differential gear, and wherein drive power can be transmitted from the drive motor via the differential gear to the two wheels. Furthermore, a corresponding drive unit for a trailer and a computer program product are proposed, wherein the computer program product comprises commands that effect the operation of the drive unit according to the aforementioned method. From DE 39 20 934 A1, a trailer with a tandem axle is known in which the two wheels of one axle each have a drive shaft that can be connected to a trailer-specific drive unit via a switchable clutch. The two drive shafts are driven, for example, by an electric motor via a differential gear. Such a trailer can be designed as a caravan or motorhome. It can be maneuvered relatively easily using its own drive system, even without a towing vehicle. This is advantageous for moving and parking such a caravan at a campsite without a towing vehicle. A drive unit for a trailer with only one drive motor, which drives two wheels of one axle via a differential gear, can be manufactured and operated more cost-effectively than trailer drives with individual wheel drives, which require at least two drive motors.However, the use of a differential gearbox limits maneuvering possibilities in confined spaces compared to trailer drives where each wheel is driven individually, i.e. by its own drive motor. Furthermore, EP 1 790 555 A1 discloses an arrangement and a method for maneuvering a trailer with two wheels on each side, with which the trailer can, among other things, be turned by 180 degrees. For this purpose, a drive unit for driving one wheel on each side of the trailer is alternately driven in a forward / reverse rotation and then in a reverse / forward rotation, whereby the power curves of the two drive units behave in opposite directions. The object of the present invention is to provide a method for operating a drive device of a trailer. In particular, the method should enable the trailer to be turned and swiveled in confined spaces. Furthermore, a corresponding drive device for a trailer and a computer program for carrying out such a method are to be provided. This problem is solved by a method for operating a drive unit of a trailer having the features of claim 1, by a drive unit for a trailer according to claim 7, and by a computer program product according to claim 10. Advantageous embodiments are specified in the respective dependent claims. A method for operating a trailer drive system is proposed, wherein a drive motor is connected via a differential gear to a right and a left wheel of one axle of the trailer. The drive power from the drive motor can be transmitted to the two wheels via the differential gear. Such a drive system is simpler in design and less expensive to manufacture compared to trailer drive systems with a separate drive motor for each wheel. The proposed method provides that, in successive steps, the right wheel and the left wheel are alternately driven in opposite directions, while the non-driven wheel is braked. Thus, the right and left wheels are not driven simultaneously, but sequentially.In this process, one wheel is driven forward in one step while the other wheel is braked. Then, in the next step, the other wheel is driven in reverse while the first wheel remains braked. Braked means that the respective wheel is stationary during this time, i.e., it does not rotate. It is irrelevant whether the left or right wheel is driven in the first step. These steps can be repeated multiple times, thus rotating the trailer step by step around a vertical axis. This step-by-step rotation of the trailer means that relatively little space is required around it, which is particularly advantageous in confined spaces, such as at a campsite. The proposed drive system is therefore especially suitable as a drive system for caravans. Preferably, the right and left wheels are driven in several steps by an equal drive angle. Equal drive angles can be achieved in a control unit of the drive system, for example, by driving the drive motor at the same speed for the same duration in each step. By using a high number of individual steps, the respective drive angle at the wheels can be kept small, allowing the trailer to rotate at least approximately on the spot around its vertical axis in small increments. In contrast, with large steps and a large drive angle each time, the trailer would swing further in one direction and require more space. For example, if the trailer were to rotate 180 degrees in a single step by continuously driving only one wheel and braking the other, the trailer would twist around the contact point of the braked wheel and be shifted laterally by almost the entire width of the trailer. The turning circle would be correspondingly large.Using the method according to the invention, it is possible to turn the trailer with a turning circle no larger than that of a turning maneuver where the rotation is carried out continuously by driving both wheels simultaneously in opposite directions. However, the latter is only possible with individually driven wheels, which requires more manufacturing effort compared to the differential drive. Even with the proposed method, the trailer is rotated slightly around the contact point of the braked wheel in each step. Due to the limited rotation angles in each step and the opposite direction of rotation of the other wheel in the subsequent step, the axle center of the trailer moves only slightly in both the longitudinal and lateral directions during the rotation, returning to its original position after a 180-degree turn. The lateral direction refers to the direction in which the trailer's axle runs. The longitudinal direction is therefore the direction in which the trailer is traveling. If the process is carried out with equal rotation angles, the trailer moves a short distance longitudinally during a 180-degree turn. Such an offset can be avoided if the right and left wheels are driven in several steps by slightly different drive angles. This allows for a 180-degree turn of the trailer, minimizing any offset of the axle center during the turn. The space required during the turn is therefore extremely small. The axle center of the trailer remains in the same position after the turn as before. Thus, this preferred method makes any trailer position achievable that would also be possible with a more complex individual wheel drive. Preferably, the drive angle is selected at each step such that the trailer rotates by an angle between 5 and 30 degrees at each step. The term drive angle refers to the angle by which the wheel rotates. The term rotation angle refers to the angle by which the trailer rotates around its vertical axis. To turn the trailer, as many steps as necessary can be taken until the trailer has rotated, for example, 180 degrees around its vertical axis. For example, nine steps are taken, with one wheel being driven at each step until the trailer has rotated by 20 degrees, i.e., until a rotation angle of 20 degrees is reached. After nine such steps, the trailer has rotated 180 degrees, i.e., turned around. Of course, the trailer can also be turned by more or less than 180 degrees, for example, by 90 degrees, using the proposed method.With appropriately small drive rotation angles at each step, the trailer can be rotated into almost any intermediate position. Besides simply rotating the trailer around its vertical axis, the method can also be used for cornering, particularly when the detached trailer is driven by its own drive system. For straight-line driving, no wheel is braked, and as soon as a curve is required, the trailer is rotated in the curve according to the inventive method. Between the alternating steps in which the brake of one wheel is engaged, further steps can be inserted in which neither the brake nor the wheel is engaged. In this way, for example, a caravan detached from a towing vehicle can be easily driven to a pitch on a campsite using its own drive system with differential drive. After the trailer has reached the desired target position, both brakes can be locked in a further step, thus preventing the trailer from unintentionally rolling away or twisting from the achieved target position. The present invention further comprises a drive unit for a trailer. The drive unit includes a drive motor which is connected via a differential gear to a right and a left wheel of an axle of the trailer. The drive unit is designed such that the drive power can be transmitted from the drive motor to the two wheels via the differential gear. The differential gear can, in particular, be designed as a bevel gear differential, as is frequently used as an axle differential. The drive unit further comprises a control unit which is connected or connectable to an input device, to the drive motor, and to a controllable brake for each of the right and left wheels.The connections between the control unit and the drive motor, brakes, and input device can be wired or wireless, with the control unit providing suitable interfaces for each. This means that the connections do not have to be permanent but can, for example, be established temporarily as wireless links to operate the drive system, particularly for maneuvering the trailer. The control unit can transmit the necessary control signals for powering the drive motor and actuating the brakes of the respective wheels via these connections. The control unit is fundamentally designed to control the trailer's drive system. The input device allows an operator to start and stop the proposed procedure. The input device can be attached to the trailer or be a mobile input device. A mobile device that performs other functions, such as a smartphone or tablet computer, can also serve as the input device. Such a mobile input device can be connected to the trailer's control unit to control the proposed procedure. The control unit preferably has a suitable interface for connecting to various mobile input devices and / or their operating systems. The control device can also be configured to control the brakes for the left and right wheels of the trailer independently of each other, so that the brakes can be alternately applied and released one after the other as part of the proposed procedure. The control device can include at least one software program or computer program product that controls the drive unit in such a way that, in successive steps, the right wheel and the left wheel are alternately driven in opposite directions, while the non-driven wheel is braked. The control device must therefore be configured to control the brakes for the left and right wheels of the trailer independently of each other. In particular, the control device can include a computer program product that automatically controls the proposed procedure and function of alternately driving and braking the left and right wheels. An operator can thus select a desired direction of rotation and start the rotation, after which the procedure runs automatically.The operator either selects a specific rotation angle by which the trailer is to be turned, for example, a 180-degree turn, or the operator starts the process and stops it once the desired position is reached. In particular, the control device may include a computer program that rotates the trailer 180 degrees, thus turning it around its vertical axis. In addition to the functions described, the control unit can perform further functions and include additional computer programs. For example, the control unit can also be used to control the drive system during driving, whereby the drive system can propel and brake the trailer in conjunction with the drive system of a towing vehicle coupled to the trailer. For this purpose, the control unit can have a suitable interface for connection to a control unit of the towing vehicle. The control unit can be configured, for example, as an ECU or domain ECU. The control unit can comprise multiple hardware and software components, enabling it to control any of the procedures described above. The control unit can also be configured to control other processes using the drive unit. For example, the same control unit can also support driving operations in which a vehicle and trailer combination is propelled by the drive unit. For such processes, it may also be necessary for the control unit to be able to control the simultaneous braking of both wheels. Finally, the invention comprises a computer program product that includes commands to operate a drive device according to the described method. The invention and its advantages will be explained in more detail below with reference to the embodiment shown in the accompanying figures. Figure 1 shows a schematic representation of a trailer with a drive device according to the invention in a bottom view; Figure 2 shows a schematic representation of a method according to the invention after a first step; Figure 3 shows a schematic representation of a method example according to the invention after a second step; Figure 4 shows a schematic representation of a method example according to the invention after a third step; Figure 5 shows a schematic representation of a method example according to the invention after a seventh step; and Figure 6 shows a schematic representation of a turning method according to the invention after the last step. Fig. 1 shows a trailer 1 with a drive unit 2. The drive unit 2 comprises a drive motor 3, which is connected to a right and a left wheel 5, 6 via a differential gear 4. The wheels 5 and 6 are rotatably mounted on an axle 7 of the trailer 1 on their respective sides. The drive connection is effected via the shafts 16, 17, and 18, through which the drive motor 3 is connected to the wheels 5 and 6 via the differential gear 4. The shafts 16, 17, and / or 18 can also be designed as cardan shafts. During operation, the drive power of the drive motor 3 can thus be distributed between the two wheels 5 and 6 by means of the differential gear 4. If one of the two wheels 5, 6 is braked, the other wheel 6, 5 can still be driven. Each of the two wheels 5 and 6 is equipped with a controllable brake 8.9 is assigned, with which the respective wheel 5, 6 can be locked in place. The trailer 1 comprises a supporting frame 12 to which the drive unit 2 and a drawbar 13 with a trailer coupling 14 are attached. The drawbar 13 is oriented in the direction of travel, i.e., longitudinally. The longitudinal direction is also indicated by the longitudinal axis 15. The drive unit 2 further comprises a control unit 10, which is connected to an input unit 11, to the drive motor 3, and to the two brakes 8 and 9 by means of signal-transmitting connections 19. The signal-transmitting connections 19 are shown as dashed lines in Fig. 1 and are labelled only once for clarity. The control device 10 comprises a computer program product which controls the drive device 2 in such a way that in successive steps the right wheel 5 and the left wheel 6 are alternately driven in opposite directions of travel, while the non-driven wheel 6, 5 is braked. Figures 2, 3, 4, 5 to 6 show an example of the method according to the invention in various steps. In this example, the rotation angle α of the trailer 1 is 20 degrees in each step. In Figures 2, 3, 4, 5 to 6, the respective positions of the right wheel 5 are designated by Rx, the left wheel 6 by Lx, and an axle center point M between the two wheels 5, 6 by Mx, where x is the index for the respective step being performed. Figure 2 shows the situation after the first step, in which the left wheel 6 was driven forward until a rotation angle α of 20 degrees was reached. In the starting position, the right wheel 5 was in position R0 and the left wheel 6 was in position L0. The axle center point M between the two wheels 5 and 6 was in position M0. By driving the left wheel 6, it moved to position L1 in the first step, while the right wheel 5 was braked and stationary. The position of the right wheel 5 is therefore the same before and after the first step, and is thus designated as R0 = R1. Figure 3 shows the situation after the second step, in which the right wheel 5 was driven in a reverse direction until a rotation angle α of 20 degrees was reached. In the second step, the trailer 1 was thus rotated by a rotation angle α of 20 degrees around the instantaneous position of the braked left wheel L1. Figure 4 shows the situation after the third step, in which the left wheel 6 was again driven forward until a rotation angle α of 20 degrees was reached. In the same manner, the trailer 1 is now rotated step by step by alternately driving the right and left wheels 5, 6, while the other wheel remains stationary with the brake applied. In this embodiment, the rotation angle α remains the same at each step. The situation after the fourth, fifth, and sixth steps is not shown separately. Figure 5 shows the situation after the seventh step. In the seventh step, the left wheel 6 was again driven forward until a rotation angle α of 20 degrees was reached. It is already apparent that one more step with the right and left wheels 5 and 6 is needed before the trailer 1 can complete a 180-degree turn. Finally, Fig. 6 shows the situation after the ninth step. Now the right wheel 5 is at the starting position L0 of the left wheel 6, and the left wheel 6 is at the starting position L0 of the right wheel R0. The trailer 1 is therefore in the same position as at the start of the process. The trailer has simply been turned around by 180 degrees. Figure 6 shows that the axle center M moves along a circular track during the process, with the circle having a very small radius compared to the track width. The track width is the distance between the right wheel 5 and the left wheel 6. It is important for the operator of the trailer 1 that the turning circle of the trailer 1 when turning according to the proposed method is no larger than the turning circle 22 of a turning maneuver in which the rotation is carried out continuously by driving both wheels simultaneously in opposite directions. To illustrate this relationship, a turning circle 22 for a trailer with individual wheel drive is shown in Figure 6. Reference sign 1 Trailer 2 Drive unit 3 Drive motor 4 Differential gear 5 Right wheel 6 Left wheel 7 Axle 8 Brake 9 Brake 10 Control unit 11 Input unit 12 Frame 13 Drawbar 14 Trailer coupling 15 Longitudinal axle 16 Shaft 17 Shaft 18 Shaft 19 Connections 20 Right wheel track 21 Left wheel track 22 Turning circle L0...Lx Left wheel wheel positions M Axle center M0...Mx Axle center positions R0...Rx Right wheel wheel positions α Angle of rotation

Claims

Method for operating a drive unit (2) of a trailer (1), wherein the drive unit (2) comprises a drive motor (3) which is connected via a differential gear (4) to a right wheel (5) and a left wheel (6) of an axle (7) of the trailer (1), characterized in that in successive steps the right wheel (5) and the left wheel (6) are alternately driven in opposite directions of travel, while the non-driven wheel (6, 5) is braked. Method according to claim 1, characterized in that the right and left wheels (5, 6) are driven in several steps by an equal drive rotation angle. Method according to claim 1, characterized in that the right and left wheels (5, 6) are driven in several steps by different drive rotation angles, so that an offset of an axle center point is minimized. Method according to one of the preceding claims, characterized in that the drive rotation angle in each step is selected such that the trailer (1) rotates by an angle of rotation between 5 degrees and 30 degrees in each step. Method according to one of the preceding claims, characterized in that so many steps are carried out until the trailer (1) has been turned about a vertical axis. Method according to one of the aforementioned claims, characterized in that the method is used for a curve movement of the trailer (1). Drive device (2) for a trailer (1), wherein the drive device (2) comprises a drive motor (3) which is connected via a differential gear (4) to a right and a left wheel (5, 6) of an axle (7) of the trailer (1) in a driving manner, characterized in that the drive device (2) comprises a control device (10) which is connected or connectable to an input device (11), to the drive motor (3) and to a controllable brake (8, 9) for each of the right and left wheels (5, 6). Drive device (2) according to claim 7, characterized in that the control device (10) comprises at least one computer program product which controls the drive device (2) such that in successive steps the right wheel (5) and the left wheel (6) are alternately driven in opposite directions of travel, while the non-driven wheel (6, 5) is braked. Drive device (2) according to claim 8, characterized in that the control device (10) comprises a computer program product which causes a rotation of the trailer (1) by 180 degrees. Computer program product comprising commands that cause a drive device (2) to be operated according to a method according to any one of claims 1 to 6.

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