Braking system for trailer and trailer having such braking system

Abstract

The invention relates to a brake system (7) for a trailer (3), comprising a brake circuit (17, 18); an actuating device (14), by means of which the brake pressure in the brake circuit (17, 18) can be adjusted; an inlet valve (23), which is arranged in the brake circuit (17, 18) between the actuating device (14) and the wheel brake element (16); a control unit (24), by means of which the inlet valve (23) can be adjusted to a blocking position, in which the flow of a brake medium (21) to the wheel brake element (16) is blocked; a brake pressure sensor (25), by means of which a brake pressure sensor signal can be provided to the control unit (24); and a wheel speed sensor system (30), by means of which a wheel speed signal can be provided to the control unit (24). According to the invention, the control unit (24) is designed to detect the reversing of the trailer (3) based on brake pressure sensor signals and wheel speed signals and to adjust the inlet valve (23) to a blocking position for the duration of the reversing based on the reversing. The invention also relates to a trailer (3) having a brake system (7).

Description

[0001] The invention according to claim 1 relates to a brake system for a trailer, and the invention according to claim 8 relates to a trailer equipped with such a brake system.

[0002] Modern trailer vehicles ("trailers"), in particular for passenger cars, are equipped with a mechanical inertia brake system. In towing operation, a passenger car ("tractor") tows the trailer, which is coupled to the tractor via a coupling and a drawbar. In coasting operation, in particular due to braking of the tractor, the trailer strikes the tractor, i.e., during braking or in braking operation, the driving speed of the tractor at least temporarily drops below the driving speed of the trailer.

[0003] In the event of a trailer colliding with the tractor, the sliding element of the trailer's service brake system, which is held in the traction position by the spring element, can be released from the traction position while the spring element is tensioned, i.e. can be adjusted into the braking position until it is adjusted into the full braking position. During this adjustment or due to the adjustment of the sliding element, the brake friction pads of the trailer's service brake system are applied to the brake drum and / or brake disc, in particular via the Bowden cable. The more the tractor brakes or is braked, the more the spring element is tensioned or compressed or the sliding element is adjusted further in the direction of the full braking position, and the more the wheels of the trailer are braked.

[0004] When a vehicle combination (train group, or "Gespann") consisting of a passenger car and a trailer coupled thereto needs to accelerate backwards, in particular from a stationary state, the tractor vehicle then hits the trailer in the opposite direction of the forward travel direction and thus hits the sliding element, which is thus also adjusted from the towing position to the braking position. As a result, the wheels of the trailer are braked in an undesirable manner, which at least prevents the desired reversing. In general, in order to enable the train group to reverse, there are so-called automatic reversing systems in the operating brake system of the trailer. By means of these automatic reversing systems, the brake drums or brake discs are set to be torque-free or released by moving the brake pads away from the brake drums or brake discs when the adjustment distance over which the sliding element has disengaged or has disengaged the towing position during the reversing process exceeds a certain limit distance. The disadvantage here is that the tractor vehicle presses against the braked trailer in the opposite direction of the forward travel direction until the limit distance is exceeded. In this case, the brake pads are suddenly released from the brake discs or brake drums, so that the trailer and / or the tractor vehicle are subjected to vibrations due to this sudden release. This may have an adverse effect on the components of the trainset and / or the cargo being transported.

[0005] Such conventional automatic reversing systems are implemented purely mechanically. When designing an automatic reversing system, special efforts must be made to ensure that the automatic reversing system is not triggered or activated unintentionally even in the event of particularly high and / or sudden deceleration during driving, in particular when driving forward, since the trailer would then disadvantageously no longer brake the vehicle group together.

[0006] Furthermore, the trailer can be designed to be hydraulically brakeable. For this purpose, a master brake cylinder and a brake fluid reservoir are arranged in or on the drawbar. In this case, the service brake system of the trailer cannot be actuated or operated by a Bowden cable, but can be actuated or operated hydraulically. Alternatively or additionally, the service brake system of the trailer can be designed to be pneumatically operated. Furthermore, it is conceivable to equip the vehicle group, in particular the trailer, with an automatic anti-lock braking system (ABV) or an anti-lock braking system (ABS) in order to avoid, ideally prevent, the wheels of the trailer from locking.

[0007] However, the same problem arises when the trailer has a hydraulically and / or pneumatically operable inertia brake, namely that an automatic reversing system is required in order to enable the reversing of the trailer or the vehicle group. For this purpose, it is usually necessary to move an operating element, such as a lever, from the normal position to the locked position (manually, i.e. by hand). As a result, the inertia brake device, such as a sliding element, is mechanically locked, so that in this locked state no hydraulic pressure is generated and the brake friction pad is locked in a position away from the brake drum or brake disc. However, if the operating element is forgotten or has been forgotten to be put back into its normal position after reversing, the trailer permanently no longer brakes the vehicle group together, which significantly prolongs the braking distance of the vehicle group in a disadvantageous manner, and the traffic safety of the vehicle group is therefore particularly low. Therefore, the known system is designed to automatically put the operating element or lever back into the normal position when a traction force occurs between the tractor and the trailer, for example at the coupling head of the coupling device.

[0008] Patent document DE 10 2018 110 011 A1 discloses an anti-skid system for a vehicle trailer, which has at least one actuating unit and a hydraulic brake device for actuating at least one wheel brake, wherein the actuating unit is connected to an electronic stability control system, and wherein the actuating unit can be effectively connected to the brake device or is effectively connected to the brake device in order to transmit a braking force. For reversing the trailer, the master brake cylinder and the actuating unit can be mechanically separated from each other, so that no braking force is transmitted to the master brake cylinder.

[0009] Patent document EP 1 375 279 A1 discloses a device for reducing the snaking motion of a coasting trailer, which device has a hydraulic brake force transmission device, wherein, in the event of snaking motion, the right and left sides of the trailer are braked differently to counteract the snaking motion. The device can have an anti-lock braking system (ABS), by which the brake pressure at the wheel brakes can be reduced in the event of intentional reversing.

[0010] Patent document DE 10 2007 024 108 A1 discloses a hydraulic trailer brake system with an electronic control or regulating unit, wherein at least two wheel brakes are connected to a master brake cylinder via a separating valve and the wheel brakes are provided with inlet valves which are closed when reversing. Reversing is detected when the reversing light is on.

[0011] In these conventional systems, the reversing of the respective trailer is based solely on purely electrical or electronic reference variables, based on which the respective inlet valves of the respective wheel brakes are closed for reversing. However, this is particularly error-prone and unsafe, especially when the electrical or electronic reference variables are provided due to a fault in the trailer.

[0012] The object of the present invention is to provide a braking system with particularly high traffic safety for a trailer that can be braked hydraulically or pneumatically, and a trailer with particularly high traffic safety.

[0013] This object is achieved by a brake system having the features specified in claim 1 and a trailer having the features specified in claim 8. The features, advantages and advantageous embodiments of the brake system according to the invention are to be regarded as the features, advantages and advantageous embodiments of the trailer according to the invention and vice versa.

[0014] The brake system for a trailer according to the invention comprises at least one brake circuit through which a brake medium can flow (or through which a brake medium can flow), the brake circuit having at least one wheel brake element. This means that the wheel brake element is integrated into the brake circuit in such a way that a brake medium can flow through the wheel brake element. The brake medium can be a brake fluid (e.g. brake fluid) or a gas (e.g. air).

[0015] The brake system furthermore has an actuating device, by means of which a brake pressure in the brake circuit can be adjusted, which corresponds to a braking position of the wheel brake element. The actuating device is arranged in particular on or in the drawbar of the trailer, or at least forms part of the drawbar. This is the case in particular when the actuating device comprises a sliding element of an inertia brake system of the trailer. Furthermore, an inlet valve is arranged in the brake circuit between the actuating device and the wheel brake element. Accordingly, the inlet valve is integrated into the brake circuit in such a way that a brake medium can flow through the inlet valve, at least when the inlet valve is in the flow-through position.

[0016] In addition, a control unit is provided, by means of which the inlet valve can be adjusted to a blocking position, in which the inlet valve blocks the flow of the brake medium to the wheel brake element. This means that the inlet valve can be adjusted between a flow-through position and a blocking position. Preferably, the inlet valve is designed as an inlet valve that can be electrically actuated or operated, is open when there is no current, and is connected to the control unit. In this respect, the control unit is designed to control the inlet valve so as to adjust it between a blocking position and a flow-through position. In the flow-through position, the inlet valve allows the flow of the brake medium to the wheel brake element, while in the blocking position, the inlet valve blocks or prevents the flow of the brake medium to the wheel brake element. In other words, in the blocking position of the inlet valve, the wheel brake element is fluid-tight relative to the rest of the brake circuit.

[0017] The brake system also has a brake pressure sensor, by means of which a sensor signal characterizing the brake pressure can be provided to the control unit. This means that the brake pressure sensor integrated into the brake circuit at or in the measuring position is designed to detect at least the brake pressure prevailing in the brake circuit at the measuring position and to provide a sensor signal corresponding to the brake pressure, for example in the form of an electrical signal, to the control unit.

[0018] Furthermore, the brake system comprises a wheel speed sensor system, via which wheel speed signals can be provided to the control unit.

[0019] In order to design the brake system to have a particularly high level of traffic safety, the invention provides that the control unit is designed to detect the reversing of the trailer based on the sensor signal characterizing the brake pressure and the wheel speed signal and, based on the detected reversing, to adjust the inlet valve to the blocking position for the duration of the reversing. This means conversely that the control unit is designed not to adjust the inlet valve to the blocking position if or as long as there is no reversing of the trailer, i.e., for example, there is forward travel.

[0020] The control unit is also designed to temporarily adjust the inlet valve to the blocking position according to the wheel speed signal. In particular, it is thus possible to distinguish between a stationary state and forward travel of the trailer, wherein it is particularly provided that the control unit temporarily adjusts the inlet valve to the blocking position only when a brake pressure characterizing reverse travel is generated in the brake circuit immediately after the trailer is stationary. In other words, if the trailer is traveling forward when the brake pressure characterizing reverse travel is reached, the inlet valve is not adjusted to the blocking position. For this purpose, it is particularly provided that the control unit and the wheel speed sensor system are connected to each other in order to transmit the wheel speed signal. As an alternative to this, it can be provided that the control unit includes the wheel speed sensor system, or that the wheel speed sensor system is at least partially formed by the control unit.

[0021] In this way, the brake system is designed to have a particularly high traffic safety, because the user of the trailer can save the manual auxiliary action of adjusting the manual operating element for reversing. Therefore, the risk that the user forgets to readjust the manual operating element to the flow-through position is also particularly low. Therefore, the brake system remains not accidentally adjusted to the following state, in which the wheel brake element is blocked in an undesirable manner and cannot brake. In addition, the pressure in the brake circuit is decisive as a reference quantity for adjusting the inlet valve, so that the purely electric reference signal that is prone to error for identifying or detecting reversing can be saved. For example, it is known that the reversing lights of traditional trailers are turned on or off by the switch on the transmission of the tractor. Therefore, although reversing can be identified in a simple way according to whether the switch is closed or the reversing lights are turned on, it is particularly prone to error. Because when the switch and / or the reversing lights are damaged or defective or the wiring is defective, this leads to no identification of reversing at all or leads to the trailer being mistakenly identified as reversing despite the trailer moving forward. In the latter case, the trailer will travel when the brake device is mistakenly disabled. By using the brake pressure as a reference quantity for adjusting the inlet valve as proposed by the present invention, this risk is eliminated. Accordingly, the brake system is designed to have not only a particularly high traffic safety, but also a particularly reliable one.

[0022] In particular, it is provided that the control unit is also designed to detect forward travel of the trailer based on a sensor signal characterizing the brake pressure and to keep the inlet valve permanently in the throughflow position based on the detected forward travel. In this way, it is ensured that after the end of the reverse movement, in particular at the start of the forward movement, the inlet valve is permanently arranged in the throughflow position again, so that the trailer can be braked in a defined manner by the wheel brake elements. Only in the special case of ABS control to prevent wheel locking can the inlet valve be briefly adjusted to the blocking position.

[0023] In another embodiment of the brake system, it is provided that, due to reaching / exceeding the limit brake pressure in the brake circuit, the sensor signal has a reverse signal that characterizes the reversing of the trailer, especially the start of reversing, and the inlet valve can be temporarily adjusted to the blocking position by the control unit based on the reverse signal. Here, the limit brake pressure is a predetermined value of the brake pressure, which is measured or can be measured by the brake pressure sensor in the brake circuit. The limit brake pressure is determined or specified in this way so that in normal driving operation, especially when the trailer is traveling forward, this limit brake pressure does not appear in the brake circuit. Therefore, this possibility is excluded, that is, in the driving operation of the trailer, for example, when the trailer is towed by a tractor and suddenly braked, the limit brake pressure is unintentionally generated in the brake circuit, thereby possibly unintentionally or undesirably adjusting the inlet valve to the blocking position. Therefore, the brake pressure sensor is designed to provide a sensor signal with a reverse signal when the limit brake pressure is reached or has been reached and / or exceeded in the brake circuit. Accordingly, the brake system is designed with increased traffic safety, since an erroneous adjustment of the inlet valve into the blocking position and thus deactivation of the wheel brake elements is effectively avoided during forward travel of the trailer.

[0024] In another advantageous embodiment of a brake system equipped with a wheel speed sensor system, the wheel speed signal has a rotation direction signal, wherein the inlet valve can be temporarily adjusted to the blocking position by the control unit according to the rotation direction signal. For this purpose, it is provided that the wheel speed sensor system has a rotation direction recognition function. In this way, it is possible to distinguish between forward travel and reverse travel of the trailer particularly efficiently. This is advantageous within the scope of a brake system designed to have a higher traffic safety, because based on the rotation direction signal, when the rotation direction signal indicates forward travel of the trailer, the control unit prevents the inlet valve from being adjusted to the blocking position. Accordingly, the control unit can also be designed to allow or carry out the adjustment of the inlet valve into the blocking position only when a rotation direction signal is provided to the control unit, which indicates reverse travel of the trailer or at least the start of reverse travel.

[0025] It is also advantageous about the wheel speed sensor system that the wheel speed signal has a speed signal, and the inlet valve can be temporarily adjusted to the blocking position by the control unit according to the speed signal. Accordingly, it is stipulated that the wheel speed sensor system has a speed recognition function. Therefore, the traffic safety of the braking system is further improved, because for example, when the instantaneous driving speed of the trailer reaches and / or exceeds the limit speed, especially when reversing, the control unit, for example, prevents the inlet valve from being adjusted to the blocking position according to the speed signal. In addition, the control unit can be designed to adjust (return) the inlet valve from the blocking position to the flow-through position when the maximum speed is reached and / or exceeded. Because it is extremely rare that the trailer reverses faster than, for example, 20 km / h. Therefore, for safety reasons or in order to further improve the traffic safety of the braking system, it is stipulated that, especially after exceeding or reaching a limit speed of, for example, 20 km / h, the inlet valve is adjusted to the flow-through position, or until the next stationary state of the trailer.

[0026] The trailer can include an automatic wheel slip control system or an automatic anti-lock braking system (ABV) or an anti-lock braking system (ABS). This is particularly advantageous when the trailer is coupled to a tractor, thereby forming a vehicle group consisting of trailer and tractor. Because in this case, the automatic wheel slip control system is used in the vehicle group to stabilize the vehicle group, especially during braking operation of the vehicle group. In this way, the traffic safety of the vehicle group is particularly high, because a side slip of the trailer relative to the tractor is avoided particularly effectively. In addition, the wheel slip control system can ensure particularly safe straight-line driving of the vehicle group, for example by preventing a swaying of the trailer relative to the tractor by selective braking intervention of the wheel slip control system.

[0027] In this context, the braking system can be manufactured particularly simply or at low cost if the braking system is at least partially composed of components of the wheel slip control system. Furthermore, a trailer equipped with the braking system can be manufactured particularly efficiently in terms of quality, since at least the components assigned to the braking system and the wheel slip control system each have a dual function, i.e. firstly contribute to the function of the wheel slip control system and secondly contribute to the function of the braking system. Therefore, in a preferred embodiment of the braking system, it is provided that the braking system is at least partially part of an automatic wheel slip control system. Thus, for example, the control unit, the inlet valve, the wheel speed sensor system and / or the line system of the brake circuit can be part of the automatic wheel slip control system.

[0028] Accordingly, the trailer can be equipped with a wheel slip control system for stabilizing the vehicle group, wherein the wheel slip control system has a control unit, which constitutes the control unit of the braking system. In addition, the wheel slip control system can have an inlet valve, which constitutes the inlet valve of the braking system. In addition, the wheel slip control system can have a wheel speed sensor system, which constitutes the wheel speed sensor system of the braking system. The wheel slip control system can in particular have a line system, through which a brake medium can flow, wherein the line system of the braking system is formed by the line system of the wheel slip control system.

[0029] The wheel slip control system is in particular a wheel slip control system known from the prior art, which has been expanded with the aforementioned properties or features. For example, it can be provided that the control unit of the wheel slip control system is modified only on the software side, so that the aforementioned features and / or advantages are achieved by the modified wheel slip control system. The idea of ​​a particularly low-cost or simple to manufacture brake system is thus taken into account to a particular extent. It is also conceivable that already manufactured trailers with such a wheel slip control system have an increased traffic safety by a simple software update, in that they have the advantageous features or functions described herein after the software update.

[0030] With regard to the wheel slip control system, it can also be provided that the brake system has a separation valve, by means of which the brake circuit of the wheel slip control system and the actuating device can be fluidically sealed or separated from one another. This advantageously enables the wheel slip control system to generate a brake pressure in the brake circuit of the wheel slip control system independently of whether the tractor vehicle is braking the vehicle set, thereby enabling drive slip control (ASR) or electronic stability control (ESC) for the trailer.

[0031] Finally, in another embodiment of the brake system, an electrical or electronic component is provided, the operating mode of which corresponds to reversing, wherein the control unit is designed to temporarily adjust the inlet valve to its blocking position according to the operating mode of the component. In this case, it can be provided that the component and the control unit are designed separately from each other and are connected to each other wirelessly and / or wired in such a way that the operating mode of the component can be provided to the control unit. As an alternative to this, it can be provided that the control unit has the component. This is the case in particular when the trailer is designed as a control device having the functions of a control unit for providing, controlling and / or regulating the brake system and other functions of the trailer.

[0032] The component can be, for example, an electrical and / or electronic load, which switches or can switch from a first operating mode, for example, a deactivated mode, to a second operating mode, for example, an activated mode, which is different from the first operating mode, only when reversing is present or begins. Furthermore, when reversing is no longer (anymore) present or ends, the component or load switches or can switch from the second operating mode or the activated mode to the first operating mode or the deactivated mode. In other words, when reversing begins, the load can, for example, switch from the first operating mode to the second operating mode, and when reversing ends, the load can, for example, (re)switch from the second operating mode to the first operating mode.

[0033] This achieves a particularly advantageous reference variable redundancy, based on which the control unit of the brake system switches the inlet valve between the flow-through position and the blocking position. Not only does this rely on the brake pressure in the brake circuit, but it also uses the operating mode of the electrical or electronic component. In this context, the control unit can be designed to evaluate the operating mode of the electrical or electronic component and a sensor signal characterizing the brake pressure, in particular a reverse signal, before adjusting the inlet valve, in order to particularly reliably prevent errors when adjusting the inlet valve.

[0034] The invention also relates to a trailer with a brake system, in particular the above-mentioned brake system. This means that the trailer equipped with the brake system has the features, advantages and advantageous designs of the brake system.

[0035] Since the trailer is equipped with the brake system, the trailer is designed with a particularly high level of traffic safety.

[0036] In another embodiment of the trailer, it can be provided that the trailer has an electric drive unit, by which the trailer can be driven or moved. The electric drive unit has at least one motor and an electric energy storage device, wherein the motor and the electric energy storage device are electrically connected to each other or can be electrically connected. In the motor operation of the motor, the electric energy storage device provides the motor with electric energy, which is converted into mechanical energy by the motor to drive or move the trailer. Alternatively or additionally, it can be provided that the motor operates in a generator mode, in which the motor, for example due to the coasting operation of the vehicle group or trailer, converts mechanical energy into electric energy and provides the electric energy to the electric energy storage device for charging or recharging.

[0037] The electric drive unit makes it possible to maneuver and / or shun the trailer alone, i.e. without a tractor, because the trailer user does not need to couple the tractor to the trailer, especially for smaller shunting maneuvers; thanks to the electric drive unit, he can shun the trailer, for example change the parking position of the trailer, without using any muscle power, i.e. in a particularly ergonomic manner.

[0038] Furthermore, the electric drive unit enables a particularly fuel-efficient and / or energy-efficient or low-emission operation of the vehicle combination having the trailer and the tractor coupled thereto.

[0039] In a particularly preferred embodiment of the trailer, the trailer is equipped with a braking system having a wheel speed sensor system. It is provided that the wheel speed sensor system is at least partially formed by the electric drive unit. Because for the electric motor of the drive unit, especially when the electric motor is designed as a wheel hub motor, the wheel speed corresponds to the instantaneous power consumption of the electric motor or the wheel hub motor. Therefore, the instantaneous wheel speed (Raddrehzahl, or wheel revolutions), the instantaneous direction of rotation and / or the instantaneous wheel rotation speed (Raddrehgeschwindigkeit) can be detected particularly easily by the control unit of the electric drive unit and can be provided to the control unit of the braking system in order to operate the braking system. In other words, the wheel speed sensor system can be part of the electric drive unit. In this case, the wheel speed recognition is carried out according to the commutation of one or more electric motors of the trailer.

[0040] The invention also includes combinations of features of the described embodiments.

[0041] Embodiments of the present invention are described below. To this end, in the accompanying drawings:

[0042] Figure 1 A schematic top view of a vehicle group with a tractor and a trailer is shown;

[0043] Figure 2 shows a schematic diagram of the brake system and

[0044] Figure 3 A schematic diagram of a brake system with a separating valve is shown.

[0045] The embodiment described below is a preferred embodiment of the present invention. In this embodiment, the components described in the embodiment are each individual, mutually independently viewable features of the present invention, which also form an expansion design of the present invention independently of each other and can therefore also be considered as a component of the present invention individually or in a combination different from the combination shown. In addition, the described embodiment can also be supplemented by other features of the present invention that have been described.

[0046] In the figures, functionally identical elements are in each case provided with the same reference symbols.

[0047] Figure 1 A vehicle group 1 is shown in a schematic top view, which has a tractor 2 and a trailer vehicle 3. In the present example, the tractor 2 is designed as a motor vehicle, in particular a passenger car. The trailer vehicle 3 can be referred to as a "trailer" for short.

[0048] The trailer 3 has a drawbar 4, at the tip of which a first coupling element 5 is arranged or mounted. The motor vehicle or tractor 2 has a trailer coupling, which includes a second coupling element 6 corresponding to the coupling element 5 of the trailer 3. If the tractor 2 and the trailer 3 are now connected or coupled to each other to form a vehicle combination 1, the coupling elements 5, 6 engage in each other, so that a mechanical connection is formed between the tractor 2 and the trailer 3. If the vehicle combination 1 is stretched, for example when the vehicle combination 1 is traveling straight, the vehicle longitudinal axis x of the tractor 2 and the vehicle longitudinal axis u of the trailer 3 coincide with each other.

[0049] The trailer 3 has a brake system 7 which is Figure 1 In the example, the trailer 3 is designed to be electrically driven or movable. This means that the trailer 3 in the example has an electric drive unit 8, which includes at least one electric motor 9. In addition, the electric drive unit 8 includes an electric energy storage device (not shown), via which electric energy can be supplied to the electric motor 9 in order to drive or move the trailer 3. Figure 1 , the electric motor 9 or electric motor is connected to the wheel 11 of the trailer 3 via the shaft 10, wherein the wheel 11 and the shaft 10 are fixed to each other in a rotationally fixed manner relative to each other. Alternatively or additionally, it can be provided that the electric drive unit 8 has more than one electric motor 9. In addition, the electric motor 9 can be connected to the wheel 11 of the trailer 3 via the shaft 10. Figure 1 The positions shown are also only exemplary. Thus, for example, it can be provided that the electric drive unit 8 has an electric motor 9, in particular for each wheel 11 of the trailer 3. In this case, the corresponding electric motor 9 can be designed, for example, as a wheel hub motor.

[0050] Regardless of whether the trailer 3 is designed with an electric drive unit 8, the trailer is equipped with an inertia brake device 12. For the vehicle group 1, this means that the trailer 3 is always braked by the inertia brake device 12 when the driving speed of the trailer 3 is higher than the driving speed of the tractor 2. In this case, the pipe system 15 (see Figure 2 ) applies a brake pressure to the brake medium 21 in the wheel brake 16, which acts on at least one wheel brake element 16. Due to the brake medium 21 to which the brake pressure is applied, the wheel brake element 16, which is designed as a brake friction pad, is applied to a brake disc or brake drum which is rotationally connected to the corresponding wheel 11, so that friction is formed between the wheel brake element 16 and the brake disc or brake drum, and thus the trailer 3 is braked.

[0051] The actuating element 13 is in particular part of the drawbar 4 and is held in the towing position by an at least substantially relaxed spring element. When the driving speed of the tractor 2 and the driving speed of the trailer 3 are the same, the spring element is relaxed or the actuating element 13 is in the towing position. This means that when the driving speed of the trailer 3 is greater than the driving speed of the tractor 2, the spring element is tensioned or the actuating element 13 is adjusted from the towing position to the braking position. In this case, as described above, a braking pressure is applied to the braking medium 21. Therefore, the braking pressure applied to the braking medium 21 when the trailer 3 hits the tractor 2 corresponds to the adjustment travel of the actuating element 13 in the direction of the braking position or into the braking position. In other words, the greater the adjustment travel of the actuating element 13 or the stronger the impact of the trailer 3 on the tractor 2, the higher the braking pressure.

[0052] However, this braking is also triggered when the tractor 2 hits the trailer 3 opposite to the forward driving direction (x or u), for example when the vehicle group 1 needs to reverse. In order to cope with this problem, the brake system 7 also has other elements, which will be explained in detail below.

[0053] to this end, Figure 2 1 shows a schematic diagram of a brake system 7. It can be seen that the brake system 7 has at least one brake circuit 17, in this case a first brake circuit 17, and optionally at least one further brake circuit 18. The brake system 7 or the trailer 3 can have a number of brake circuits which is equal to the number of axles and / or axle groups of the trailer 3. Alternatively, all wheels on one side of the trailer can be supplied with brake pressure by the same part of the brake circuit.

[0054] Braking medium 21 can flow through brake circuits 17, 18 and can be filled at least predominantly with brake medium 21. Figure 1 As described, the brake pressure in brake circuits 17 , 18 can be adjusted via actuating element 13 , for example by pressing additional brake medium 21 into line system 15 of brake circuits 17 , 18 via a piston of a master brake cylinder 22 when trailer 3 strikes tractor 2 .

[0055] Braking system 7 also has one wheel brake element 16 or a plurality of wheel brake elements 16 per inlet valve 23 , wherein the respective inlet valve 23 is integrated in brake circuit 17 , 18 between actuating device 14 or master brake cylinder 22 and the respective wheel brake element or elements 16 .

[0056] In the following, for simplicity of presentation, it is assumed that

[0057] - only one wheel brake element 16 is assigned to each inlet valve 23,

[0058] the trailer 3 has only one axle and therefore the brake system 7 has only one brake circuit 17, and

[0059] The inlet valve 23 is a valve which opens when there is no current, so that in the non-energized state it is always connected to the flow-through position due to the spring load and in the energized state it is connected to the blocking position.

[0060] In the present example, the brake circuits of brake system 7 are designed identically in terms of fluid technology, so that in the following, only brake circuit 17 will be described representatively of the brake circuits of brake system 7 .

[0061] Therefore, when the brake medium 21 flows from the master brake cylinder 22 in the direction of the wheel brake elements 16 due to the impact of the trailer 3 on the tractor 2, the brake medium 21 flows through the inlet valve 23 if it is arranged in the corresponding flow position, that is, it is not energized. In other words, when the inlet valve 23 is in the flow position, the corresponding inlet valve 23 allows the brake medium 21 to flow to the corresponding wheel brake element 16. The corresponding inlet valve 23 can be adjusted from the flow position to a blocking position, in which the corresponding inlet valve 23 blocks the flow of the brake medium 21 to the corresponding wheel brake element 16. If the corresponding inlet valve 23 is connected to the blocking position, the corresponding wheel brake element 16 is decoupled from the brake pressure prevailing in the brake circuit 17. In other words, after the inlet valve 23 is switched to the blocking position, the brake pressure of the brake medium in the wheel brake element 16 is frozen or kept constantly at the current brake pressure. That is, if inlet valve 23 is switched to the blocking position before the pressure buildup by master brake cylinder 22 begins, brake element 16 is pressure-free and no braking effect occurs.

[0062] The brake system 7 further comprises a control unit 24 which is connected to the respective inlet valves 23. Since the control unit 24 is in particular an electronic control unit, it is provided that the inlet valves 23 can be controlled electrically and / or electronically. In this case, the control unit 24 is designed to adjust the inlet valves 23 individually and / or in groups between a flow-through position and a blocking position.

[0063] Furthermore, a brake pressure sensor 25 is provided in the brake system 7, which detects the brake pressure in the line system 15 at or in a measuring point in the brake circuit 17 and provides a sensor signal corresponding thereto. Since the control unit 24 and the brake pressure sensor 25 are connected to one another, it is provided that the brake pressure sensor 25 provides a sensor signal that characterizes the brake pressure to the control unit 24. The measuring point or the brake pressure sensor 25 is designed, in particular, between the actuating device 14 or the master brake cylinder 22 and the inlet valve 23.

[0064] exist Figure 23 also shows a wheel speed sensor system 30, which in this example has four wheel speed sensors 31. This means that the wheel speed sensor system 30 has a number of wheel speed sensors 31 that is equal to the number of wheels 11 with which the trailer 3 is equipped. Wheel speed signals can be provided to the control unit 24 via the wheel speed sensor system 30 or via the wheel speed sensors 31, wherein the control unit 24 is designed to permanently adjust the corresponding inlet valve 23 to the blocking position as a function of the corresponding wheel speed signal.

[0065] When the tractor 2 starts to drive backwards from a stationary state and hits the stationary trailer 3, for example in order to push the trailer 3 backwards, the brake pressure in the brake circuit 17, in particular in the line system 15, increases, so that the control unit 24 recognizes from the combination of the wheel speed signal and the sensor signal representing the brake pressure that the vehicle combination 1 or the trailer 3 starts to reverse. Since the brake pressure in the brake circuit 17 increases due to the reverse movement or the start of reverse movement, the brake pressure sensor 25 of the control unit 24 provides a corresponding sensor signal, wherein the sensor signal represents the reverse movement or the start of reverse movement of the trailer 3 or the vehicle combination 1. In this case, it is provided that the control unit 24 adjusts the inlet valve 23 to the blocking position during the duration of the reverse movement according to the reverse movement or according to the sensor signal representing the reverse movement, by the control unit 24 correspondingly controlling the inlet valve 23. In this way, the wheel brake elements 16 are deactivated for the reverse movement or during the reverse movement, so that at least no further brake pressure is exerted on the wheel brake elements 16.

[0066] For example, the wheel speed sensor system 30 or the wheel speed sensor 31 can distinguish whether the trailer 3 is currently being moved or towed or driven in another way or whether the trailer 3 is at a standstill. It is therefore advantageous if the control unit 24 is designed so that the inlet valve 23 is only allowed to be switched to the blocking position during the duration of the reverse movement if the trailer 3 has been detected or determined to be at a standstill before, in particular just before, by the wheel speed sensor system 30. It is thus possible to prevent the wheel brake elements 16 from being erroneously or unintentionally deactivated and thus causing a reduction in the traffic safety of the brake system 7 or the trailer 3 equipped with the brake system.

[0067] In order to be able to release the brake pressure that has already been generated between the inlet valve 23 and the wheel brake element 16 before the inlet valve 23 is adjusted to the blocking position, the brake system 7 has an outlet valve 26 for each wheel brake element 16, which is adjusted to its throughflow position, in particular when the inlet valve 23 is adjusted to the blocking position or has been adjusted to the blocking position during the period of reversing. In this way, the brake pressure or the brake medium to which the brake pressure is applied can be discharged from the wheel brake element 16, in particular to or introduced into the hydraulic accumulator 27. In order to guide the brake medium 21 released from the wheel brake element 16 and, if necessary, flowing into the hydraulic accumulator 27 back to the actuating device 14, in particular to the master brake cylinder 22, the brake circuit 17 has a pumping device 28, for example a pumping device that can be driven by a pump motor 29. In this case, the suction side of the pumping device 28 is fluidically connected to the hydraulic accumulator 27, which can be designed as a low-pressure accumulator, for example, and can be fluidically connected to the wheel brake element 16 depending on the position of the outlet valve 26. The discharge side of pumping device 28 is fluidically connected to master brake cylinder 22 or to actuating device 14 , so that brake medium can be pumped from wheel brake elements 16 and / or hydraulic accumulator 27 toward master brake cylinder 22 and ultimately into master brake cylinder 22 via pumping device 28 .

[0068] In order to adjust the inlet valve 23 and / or the outlet valve 26 between its respective flow-through position and its respective blocking position, it is further provided that the control unit 24 carries out such adjustment of the valves 23, 26 when a reversing signal is provided to the control unit 24 by the brake pressure sensor 25, which generates the reversing signal when a predetermined limit brake pressure is reached and / or exceeded in the brake circuit 17. The control unit 24 is designed to maintain the respective position of the valves 23, 26 during the duration of the reversing. In order to design the brake system 7 to be particularly safe, it is particularly advantageous if a voltage should be supplied to the inlet valve 23 in order to adjust the inlet valve 23 to the blocking position. It is also advantageous if a voltage should be supplied to the outlet valve 26 in order to adjust the outlet valve 26 to the flow-through position. In other words (and as described above), the respective inlet valve 23 is open when there is no current and the respective outlet valve 26 is closed when there is no current.

[0069] The respective wheel speed sensor 31 can be designed to detect or determine the direction of rotation of the respective wheel 11, so that the wheel speed sensor system 30 is designed to provide the control unit 24 with the respective direction of rotation of the wheel 11 of the trailer 3 respectively associated with the respective wheel speed sensor 31. This enables a particularly efficient direction of travel detection of the instantaneous travel of the trailer 3, wherein the control unit 24 is advantageously designed to switch the inlet valve 23 to the blocking position only when the trailer 3 is not traveling forward. This effectively prevents the respective wheel brake element 16 from being deactivated during forward travel of the trailer 3, for example by the trailer 3 being towed by the tractor 2.

[0070] The control unit 24 is also designed to carry out or prevent the switching of the inlet valve 23 depending on the instantaneous speed of the trailer 3. For this purpose, it is provided that the corresponding instantaneous speed of the respectively assigned wheels 11 of the trailer 3 is detected by the wheel speed sensor 31 and the corresponding speed signal is provided to the control unit 24. In this example, the value of the maximum speed is stored in the control unit 24 until the maximum speed allows the inlet valve 23 to be switched to the blocking position or maintained in the blocking position by the control unit 24. Starting from the state in which the inlet valve 23 is maintained in the blocking position by the control unit 24, when the maximum speed is reached and / or exceeded, the inlet valve 23 is connected to the flow-through position by the control unit 24. In other words, when the maximum speed is reached and / or exceeded, the wheel brake element 16 is (re)activated. In another state of the brake system 7, the inlet valve 23 is maintained in the flow-through position by the control unit 24, and starting from this state, when the maximum speed is reached and / or exceeded, the control unit 24 prevents the inlet valve 23 from being adjusted to the blocking position.

[0071] As described above, the trailer 3 in this example has an electric drive unit 8, wherein it is provided with respect to the brake system 7 with the wheel speed sensor system 30 that the wheel speed sensor system is at least partially formed by the electric drive unit 8. For this purpose, it is provided that the control unit 24 and the electric drive unit 8 are connected to each other for data transmission, so that corresponding data or signals can be provided to the control unit 24 by the electric drive unit 8. Therefore, the electric drive unit 8 can provide the control unit 24 with a signal corresponding to the instantaneous acceleration and / or the instantaneous driving speed of the trailer 3 based on the instantaneous energy consumption or power consumption of the electric motor 9, which signal can in turn be used to decide whether it is necessary to switch the inlet valve 23 between the blocking position and the flow-through position. In addition, the wheel speed recognition can be carried out by the electric drive unit 8 and / or by the control unit 24, depending on the reversal of one electric motor 9 or multiple electric motors 9 of the trailer 3.

[0072] In the present example, the trailer 3 is equipped with an automatic wheel slip control system 32, by which the brake system 7 is at least partially formed. Thus, for example, it can be provided that the wheel slip control system 32 has a control unit 24 of the brake system 7 and / or that the control unit 24 is formed by the wheel slip control system 32. This means that the control unit 24 has a dual function, i.e., on the one hand, it provides the functions of the wheel slip control system 32 and on the other hand, it provides the functions of the brake system 7 described here. Furthermore, it can be advantageous if the inlet valve 23, the outlet valve 26 and / or the wheel speed sensor system 30 of the brake system 7 are at least partially formed by the valve device of the wheel slip control system 32. In this way, it can be particularly easy to realize that the wheel slip control system 32 and the brake system 7 are constructed together, for example in one structural unit.

[0073] Figure 3 A schematic diagram shows a brake system 7 equipped with a separating valve 33. In the present example, the brake circuit 17 and the actuating device 14 can be fluidically sealed from one another or separated from one another by the separating valve 33. For this purpose, the separating valve 33 can be switched between a flow-through position and a blocking position, wherein the separating valve 33 fluidically separates the brake circuit 17 and the actuating device 14 from one another when the separating valve 33 is switched to the blocking position. If the brake circuit 17 and the actuating device 14, in particular the master brake cylinder 22, are thus fluidically separated from one another, the pressure in the brake circuit 17 and the brake pressure in the actuating device 14 or the master brake cylinder 22 are thus decoupled from one another. It is thus possible to generate or regulate a brake pressure by the wheel slip control system 32, for example by the pumping device 28, independently of the actuating device 14, which brake pressure acts on the wheel brake elements 16, so that the trailer 3 can be braked, in particular wheel-specifically. In this way, the wheel slip control system 32 provides the trailer vehicle 3 with functions that are consistent with the ESP (Electronic Stability Program) and functions that are consistent with the drive slip control system (ASR). Thus, when the tractor vehicle 2 and the trailer vehicle 3 are coupled to form a vehicle group 1, a particularly effective vehicle group stabilization system is particularly advantageously provided by the wheel slip control system 32. This is independent of the instantaneous braking state of the tractor vehicle 2.

[0074] In general, the present invention shows how to improve traffic safety by means of a braking system 7 of a trailer 3. This is achieved in particular by means of a wheel slip control system 32, which is installed, for example, in the hydraulic brake system of a passenger car. In particular, when the trailer 3 is designed to be electrically driven or electrically drivable and a particularly long cruising range is to be achieved, the high-voltage battery or traction battery is expected to be designed in terms of its capacity to be approximately equivalent to that of an electrically driven or electrically drivable passenger car, i.e. between 50 kWh and 100 kWh. Together with the electric drive unit 8 in the trailer 3, the manufacturing costs of the trailer 3 are therefore expected to be particularly high. This results in a particularly high purchase price for the end consumer, who therefore expects the trailer 3 to have a correspondingly high-quality configuration, for example not just a crude rope brake device. Instead, the trailer 3 should have a brake device with ABS, a vehicle group stabilization system and measures for reducing the braking path.

[0075] Since the wheel slip control system 32, which is designed, for example, as an anti-lock braking system, has an inlet valve 23 and an outlet valve 26 for each wheel brake element 16, the reversing of the trailer 3 can be presented, for example, in such a way that, at the beginning of the reversing, a brake pressure is generated in the brake circuit 17 and the wheel brake element 16 by the master brake cylinder 22. Thereafter, the corresponding inlet valve 23 can be closed by the wheel slip control system 32, so that no further pressure can be built up in the wheel brake element 16. Furthermore, the corresponding outlet valve 26 can be opened by the wheel slip control system 32 in order to discharge the brake medium 21 exerting a brake pressure in the wheel brake element 16 into the hydraulic accumulator 27 or the low-pressure accumulator. The wheel brake element 16 thus becomes pressure-free.

[0076] By means of pumping device 28 , which may be a return pump of wheel slip control system 32 , brake medium 21 can be fed back to master brake cylinder 22 , in particular after the reverse maneuver has been completed.

[0077] Optionally, a separate, further brake pressure sensor can be provided between the master brake cylinder 22 and the inlet valve 23 relative to the brake pressure sensor 25 , by means of which it can be determined whether and to what extent or with what force the tractor 2 is pressed against the coupling head or the trailer coupling.

[0078] Reference numerals list

[0079] 1 car group

[0080] 2 Tractor

[0081] 3 trailer

[0082] 4 Traction bar

[0083] 5Connection elements

[0084] 6Connection elements

[0085] 7. Braking system

[0086] 8 drive units

[0087] 9 Motor

[0088] 10 axis

[0089] 11 wheels

[0090] 12Inertia brake equipment

[0091] 13. Control elements

[0092] 14 Control device

[0093] 15 Pipeline system

[0094] 16 wheel brake elements

[0095] 17 Brake circuit

[0096] 18 brake circuit

[0097] 19 Axles

[0098] 20 axles

[0099] 21 Braking medium

[0100] 22 Master brake cylinder

[0101] 23 Inlet valve

[0102] 24Control Unit

[0103] 25Brake pressure sensor

[0104] 26 outlet valve

[0105] 27 Hydraulic accumulator

[0106] 28 Pumping device

[0107] 29 Pump motor

[0108] 30 Wheel speed sensor system

[0109] 31 Wheel speed sensor

[0110] 32 Wheel slip control system

[0111] 33 Separation valve

[0112] uLongitudinal axis of vehicle

[0113] x Longitudinal axis of vehicle

Claims

1. A braking system (7) for a trailer (3), comprising: a brake circuit (17, 18) which has at least one wheel brake element (16) and through which a brake medium (21) can flow, an actuating device (14, 22), by means of which a brake pressure in a brake circuit (17, 18) corresponding to a braking position of a wheel brake element (16) can be adjusted, an inlet valve (23) which is arranged in the brake circuit (17, 18) between the actuating device (14, 22) and the wheel brake element (16), a control unit (24), by means of which the inlet valve (23) can be adjusted into a blocking position, in which the inlet valve (23) blocks the flow of brake medium (21) to the wheel brake element (16), a brake pressure sensor (25), by means of which a sensor signal representative of the brake pressure can be provided to the control unit (24), and a wheel speed sensor system (30), by means of which a wheel speed signal can be provided to the control unit (24), It is characterized in that The control unit (24) is designed to: - detecting the reversing of the trailer (3) based on the sensor signal representing the brake pressure and the wheel speed signal; and - depending on the detected reverse movement, the inlet valve (23) is adjusted into the blocking position for the duration of the reverse movement.

2. The brake system (7) according to claim 1, It is characterized in that Due to reaching or exceeding a limit brake pressure in the brake circuits (17, 18), the sensor signal has a reversing signal indicative of reversing of the trailer (3), and the inlet valve (23) can be adjusted by a control unit (24) into a blocking position for the duration of the reversing.

3. Braking system (7) according to any one of the preceding claims, It is characterized in that The wheel speed signal has a rotational direction signal and the inlet valve (23) can be adjusted by a control unit (24) into its blocking position during the duration of the reversing operation as a function of the rotational direction signal.

4. The brake system (7) according to claim 1, It is characterized in that The wheel speed signal has a speed signal, and the inlet valve (23) can be adjusted by a control unit (24) into its blocking position during the duration of the reversing operation as a function of the speed signal.

5. The brake system (7) according to claim 1, It is characterized in that The brake system (7) is at least partially part of a wheel slip control system (32).

6. The brake system (7) according to claim 5, It is characterized in that A separating valve (33) is provided, by means of which the brake circuits (17, 18) and the actuating device (14, 22) can be fluidically sealed from one another.

7. A trailer (3) having a braking system (7) according to any one of claims 1 to 6.

8. The trailer (3) according to claim 7, It is characterized in that At least one electric drive unit (8) is provided, by which the trailer (3) can be driven.

9. The trailer (3) according to claim 8, It is characterized in that The wheel speed sensor system (30) is formed at least partially by the at least one electric drive unit (8).

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