Method and system for decelerating a vehicle and holding it at a standstill

Abstract

The invention relates to a method for decelerating a vehicle (1) and holding it at a standstill, the vehicle having a drivetrain (4) which has a transmission (9), wherein the method comprises the following steps: a) receiving and processing a deceleration signal by means of a transmission controller (15); b) activating and carrying out a transmission function for decelerating the vehicle, wherein the transmission controller (15) controls the drivetrain (4) on the basis of the deceleration signal until the vehicle (1) comes to a standstill; c) holding the vehicle (1) at a standstill; and d) returning the drivetrain (4) to normal operation as soon as the transmission function for decelerating the vehicle is deactivated again. The invention also relates to a system for decelerating the vehicle (1) and holding it at a standstill, to a drivetrain (4), and to a vehicle (1).

Description

[0001] ZF Friedrichshafen AG File 305575 Friedrichshafen 2024-11-26

[0002] Method and system for decelerating and bringing a vehicle to a standstill

[0003] The invention relates to a method and a system for decelerating and bringing a vehicle to a standstill. The invention further relates to a vehicle equipped with such a system. The vehicle is, in particular, a construction and / or agricultural machine. The method can therefore be advantageously used in the drive trains of construction or agricultural machines.

[0004] Methods for decelerating a vehicle by intervening in the transmission are generally known from the prior art. For example, JP 2012229722 A2 describes a method for optimizing braking performance by changing the gear ratio in a CVT transmission early on, in order to achieve better collision avoidance by utilizing engine braking. In this process, the gear ratio is changed before automatic braking or a warning signal to maximize engine braking and improve driver comfort.

[0005] Furthermore, EP2060455 B1 describes a vehicle control system designed to avoid collisions by either downshifting the transmission or maintaining the current gear to facilitate evasive maneuvers and preventing collisions through the braking effect of the transmission.

[0006] Although the aforementioned approaches support the braking process before a collision through transmission control, the ability to reliably hold the vehicle stationary and prevent unintentional acceleration remains insufficiently addressed. Particularly for mobile machinery, a suitable function is lacking that enables flexible deceleration combined with safe standstill and a controlled transition to normal operation through targeted transmission control.

[0007] The present invention is based on the objective of providing a method that, when obstacles are detected, allows the vehicle to avoid them by selectively intervening in the ZF Friedrichshafen AG file 305575 Friedrichshafen 2024-11-26

[0008] The system is capable of decelerating and holding the drivetrain at a standstill, and enables a targeted, and in particular smooth, transition back to normal operation. This problem is solved by a method and a system for decelerating and holding a vehicle at a standstill, comprising the features of claim 1 and 9, respectively. Further advantageous embodiments are described in the dependent claims.

[0009] According to a method according to the invention for decelerating and holding a vehicle at a standstill with a drivetrain comprising a transmission, a deceleration signal is received and processed by a transmission control unit, whereupon a transmission function for vehicle deceleration is activated and executed. The transmission control unit controls the drivetrain based on the deceleration signal until the vehicle comes to a standstill. After stopping, i.e., after reaching a standstill, the vehicle is held at a standstill. The drivetrain returns to normal operation as soon as the transmission function for vehicle deceleration is deactivated.

[0010] The deceleration signal is transmitted, for example, via a CAN interface or another interface, particularly a digital one, to a transmission control unit, which receives and processes it. The transmission control unit then activates the transmission function, which is executed as a deceleration request or deceleration operation. The transmission control unit can be part of an engine control unit or a vehicle control unit, particularly a vehicle management computer. The transmission control unit is connected to the powertrain via an information interface, such as a vehicle network. The powertrain sends the transmission control unit current information, such as internal transmission speeds, which the control unit then processes. Furthermore, the transmission control unit sends control signals to the powertrain, for example, in the form of target currents for actuating transmission valves.When the transmission function is activated, the drivetrain is controlled based on the deceleration signal so that the vehicle is braked or decelerated until it comes to a standstill. Once stationary, the vehicle is held in this position in a possible further step. As soon as the deceleration signal is deactivated, the drivetrain is controlled and regulated by the transmission control unit (ZF Friedrichshafen AG, File 305575, Friedrichshafen, 2024-11-26) to return the vehicle to normal operation.

[0011] In normal operation, the driver can, for example, exercise full control over the desired target speed of the vehicle via the accelerator pedal, whereby the driver's request is specified via an accelerator pedal and implemented accordingly by the transmission control and / or an engine control.

[0012] The transmission function is deactivated if no deceleration signal is present or if the value of the deceleration signal is no longer within a range that triggers or activates the transmission function. The deceleration signal is deactivated in particular if, for example, an obstacle or object located in front of and / or behind the vehicle in the direction of travel is no longer present or is no longer detected by an environmental monitoring system or similar device.

[0013] Normal operation can be resumed not only after the vehicle has come to a standstill. Rather, the powertrain can also be switched back to normal operation during deceleration, i.e., during a reduction in vehicle speed and at a speed other than that of a standstill, as soon as the transmission function is deactivated. Therefore, normal operation can be initiated both while the vehicle is moving and while stationary.

[0014] In this sense, the transmission control unit controls the drivetrain based on the deceleration signal as long as the deceleration function is active. The drivetrain returns to normal operation as soon as the transmission function for vehicle deceleration is deactivated. Deactivation can also be performed manually by the driver, for example, by manually acknowledging the function. An acknowledgment could be performed, for example, by manually shifting from a forward driving position to neutral or vice versa. An acknowledgment could also be performed by manually shifting from a reverse driving position to neutral or vice versa. Alternatively, an acknowledgment could be performed by activating a separate switch.

[0015] Preferably, the deceleration signal is generated based on an object detected by an environmental monitoring system. This improves the vehicle's responsiveness to detected obstacles, particularly those located in front of the vehicle in the direction of travel, and enables situation-appropriate deceleration. The deceleration signal can also be generated in other ways. The transmission control unit can retrieve or receive the deceleration signal from the environmental monitoring system that generates it. Alternatively, the transmission control unit can receive or retrieve sensor data from the environmental monitoring system and, based on this data, generate the deceleration signal and initiate or activate the corresponding transmission function. The generation of the deceleration signal is not limited to a specific component or a single system.The signal can be generated from various sources within or outside the system, triggered, and then provided to the transmission control unit for further processing. The delay signal can be generated by both internal and external devices and fed into the system via suitable interfaces. External sources can include, for example, manual input devices, external operating components, or higher-level control units that centrally monitor and control multiple systems or units.

[0016] The delay signal can be integrated into the system via various transmission methods, such as wired or wireless interfaces, a remote connection, or a cloud-based infrastructure. This flexibility allows the delay signal to be obtained from local or networked control units and transmitted to different systems to trigger and execute the desired functionality, such as delay operation.

[0017] Preferably, during the transition back to normal operation, vehicle acceleration is limited by restricting the acceleration of the transmission output speed. In other words, the transition from deceleration mode to normal operation (ZF Friedrichshafen AG File 305575, Friedrichshafen, November 26, 2024) is designed to prevent unexpectedly strong vehicle acceleration. This allows for a smooth return of the powertrain to normal operation. After acknowledging the deceleration mode as described above, limiting the acceleration for the transition back to normal operation is not necessary.

[0018] The deceleration operation is preferably effected or supported by controlling the speed and / or torque of a drive motor, by changing the gear ratio, by changing gear stages, by activating a reversing function of the transmission when a predefined speed threshold is reached and / or by deactivating an optional speed control device.

[0019] The speed control device can, for example, be configured as cruise control. An active cruise control can be automatically deactivated during deceleration or when the transmission function is active to decelerate the vehicle, in order to prevent unintended acceleration of the vehicle when there is no longer a deceleration signal or when deceleration is no longer triggered.

[0020] During deceleration, the drivetrain is preferably controlled such that a gear ratio is set in the transmission that opposes the vehicle's current direction of travel. When the vehicle is traveling forward, a reverse gear ratio can be selected or activated, so that a torque opposite to the forward direction acts at the transmission output. This reduces the transmission output speed and thus the vehicle's wheel speed when traveling forward, thereby assisting vehicle deceleration. Conversely, when the vehicle is traveling in reverse, a forward gear ratio can be selected or activated, so that a torque opposite to the reverse direction acts at the transmission output. This reduces the transmission output speed and thus the vehicle's wheel speed when traveling in reverse, thereby assisting vehicle deceleration.This is to be understood as the activation of a reversing function during deceleration operation and results in effective and low-wear deceleration of the vehicle. ZF Friedrichshafen AG File 305575 Friedrichshafen 2024-11-26.

[0021] If the reversing function of the transmission was previously activated upon reaching a predefined speed threshold, the reversing function can be deactivated again when the vehicle comes close to a standstill, i.e., a speed close to 0 km / h, or comes to a standstill, i.e., a speed of 0 km / h.

[0022] To keep the vehicle stationary, the rotational movement of an output element of the transmission is blocked. This output element can be an output shaft of the transmission. This prevents the vehicle from rolling away unintentionally. As a result, the vehicle remains stationary and any movement forward is prevented, even if the driver presses the accelerator pedal.

[0023] In one embodiment, the rotational movement of the transmission's output element is blocked by actuating at least one switching element. This allows one or more rotating components, particularly shafts, within the transmission to be locked against a housing or other fixed component. This measure ensures reliable immobilization of the vehicle. The at least one activated switching element prevents rotation of a transmission output shaft. In this case, it is preferred that a connection between the transmission and a drive motor is simultaneously opened to prevent the drive motor, for example an internal combustion engine, from stalling.

[0024] The invention includes the technical teaching that the speed of the drive motor is regulated below a limit speed, in particular an idle speed, when the vehicle comes to a standstill, thus supporting energy savings while stationary. Furthermore, noise reduction and / or a reduction in the load on the transmission can be achieved. In particular, the transmission heats up less.

[0025] A system according to the invention for decelerating and holding a vehicle at a standstill, as described in a second aspect of the invention, comprises a transmission control unit configured to receive and process a deceleration signal, activate and execute a transmission function for vehicle deceleration, control the drivetrain based on the deceleration signal until the vehicle comes to a standstill, and hold the vehicle at a standstill until the transmission function is deactivated. The drivetrain can be returned to normal operation as soon as the transmission function for vehicle deceleration is deactivated, in particular when no deceleration signal is present or when the value of the deceleration signal falls below a predefined threshold for triggering the aforementioned transmission function.

[0026] Preferably, the system comprises an environmental monitoring system that includes an imaging sensor, a radar sensor, and / or a LiDAR sensor. An environmental monitoring system is a sensor-based unit that continuously monitors the vehicle's surroundings and detects potential obstacles, such as objects, vehicles, or people. It typically uses sensors such as cameras, radar sensors, and / or LiDAR sensors to detect the position, movement, and distance of objects in the vehicle's environment. For example, 3D cameras, particularly stereoscopic sensors or cameras, are advantageously suited as imaging sensors. A 3D camera captures three-dimensional or spatial information of a detection area or object. In addition to two-dimensional image data such as brightness and color, 3D cameras can also capture depth information, i.e., the distance between the sensor and objects in the environment.Stereoscopic sensors capture three-dimensional information, especially depth information, using two or more cameras.

[0027] When an object or obstacle is detected, the environmental monitoring system generates a deceleration signal, which is forwarded to the transmission control unit for evaluation and / or processing. The transmission control unit can then initiate targeted vehicle deceleration by activating the transmission's deceleration function to first reduce the vehicle's speed and, if necessary, avoid a collision. The sensors of the environmental monitoring system provide precise detection of the surroundings and enable deceleration control based on external objects or obstacles. (ZF Friedrichshafen AG File 305575 Friedrichshafen 2024-11-26)

[0028] Obstacles. Alternatively, the environmental monitoring system can process the sensor data and make it available to the transmission control unit, which generates a delay signal based on the sensor data to trigger the aforementioned transmission function.

[0029] Preferably, the powertrain includes a powershift transmission or a CVT, which allows for stepless adjustment of the gear ratio. A powershift transmission is a transmission that allows shifting between different gears under load without interrupting power transmission to the drivetrain. This is achieved through clutches and shift elements that permit gear changes under load, thus providing a high degree of continuity of traction. The powershift transmission can generate strong deceleration torque through targeted shifts, such as a reversing function, by reversing the direction of travel solely through the transmission, generating a force that opposes the driving resistance. A speed threshold may sometimes be incorporated for this purpose.A CVT (Continuously Variable Transmission) is a continuously variable transmission that allows for stepless adjustment of the gear ratio. The CVT enables driving with constant traction through stepless adjustment of the gear ratio. It utilizes a system with variable pulleys and belts or hydrostatic power distribution, which allows for smooth acceleration and braking without gear changes. A CVT can also incorporate a multi-speed gearbox, enabling different driving ranges, with stepless gear ratio changes implemented as described above within each range.

[0030] Preferably, the transmission comprises a primary section directly operatively connected to the drive motor, with primary switching elements for shifting gears; a secondary section directly operatively connected to the transmission output, with secondary switching elements for shifting gears; and a switching element arranged in the power flow between the primary and secondary sections for selectively connecting or disconnecting the secondary section from the primary section. The switching element is designed to establish a power flow between the primary section and the ZF Friedrichshafen AG File 305575 Friedrichshafen 2024-11-26

[0031] The secondary part of the transmission is interrupted. Therefore, the switching element can selectively decouple or couple the primary part from the secondary part. The primary part forms the transmission input and is directly operatively connected to the drive motor without any intermediate switching element, i.e., neither a brake nor a disconnect clutch or the like. The secondary part forms the transmission output and is directly operatively connected to the output of the transmission, in particular a differential or a drive wheel of a vehicle axle, without any intermediate switching element, i.e., neither a brake nor a clutch or the like.

[0032] The primary component can be a power-shift transmission or a synchronizer. Similarly, the secondary component can be a power-shift transmission or a synchronizer. A power-shift transmission allows shifting between gears under load, meaning without interrupting the torque flow within the drivetrain. Gear changes are achieved through special clutch and shift elements that maintain the torque flow even during the shifting process. This allows vehicles to continuously transmit power to the wheels, enabling high tractive force during gear changes in construction machinery and commercial vehicles.

[0033] The synchronizer serves to equalize the rotational speeds of an input component, particularly an input shaft, and an output component, particularly an output shaft, before the actual gear change. This is achieved, for example, by means of synchronizer rings that generate friction and synchronize the components before the gear change takes place.

[0034] By arranging the switching element not as a disconnect clutch in the power flow between the drive motor and the transmission, but rather within the transmission itself, specifically between the primary and secondary sections, the primary section, and in particular its components and the primary switching elements, can be designed more compactly, as they have to bear or transmit less load. The loads are then primarily borne by the switching element. ZF Friedrichshafen AG File 305575 Friedrichshafen 2024-11-26

[0035] Such a gearbox structure allows for flexible control of the power flow in the drivetrain and ensures optimized deceleration of the vehicle when the gearbox function is actively engaged for vehicle deceleration.

[0036] According to a third aspect of the invention, the invention relates to a vehicle comprising a system according to the second aspect. The vehicle may have one or more transmissions that can interact. It is conceivable that the drivetrain includes a differential or is connected to a differential on an axle of the vehicle, which can divide or distribute the drive power of the drivetrain to the drive wheels of the respective axle of the vehicle. The vehicle is preferably an agricultural machine or a construction machine. Accordingly, the system according to the invention can be used particularly advantageously in an agricultural machine or a construction machine.

[0037] The above definitions and explanations regarding technical effects, advantages and advantageous embodiments of the inventive method for decelerating and holding a vehicle in a standstill according to the first aspect of the invention also apply mutatis mutandis to the inventive system according to the second aspect of the invention and to the inventive vehicle according to the third aspect of the invention, and vice versa.

[0038] An embodiment of the invention will be explained in more detail below with reference to the figures. Here, [the figure] shows

[0039] Fig. 1 shows a highly schematic top view of a motor vehicle according to the invention, comprising a system according to a preferred embodiment.

[0040] Fig. 2 shows a block diagram of a method according to the invention for decelerating and holding the vehicle at a standstill according to Fig. 1, and

[0041] Fig. 3 is a diagram illustrating the deceleration operation of the vehicle according to Fig. 1. ZF Friedrichshafen AG File 305575 Friedrichshafen 2024-11-26

[0042] Fig. 1 shows a highly schematic top view of a vehicle 1 according to the invention. The vehicle 1 is a construction or agricultural machine and, in this example, comprises a first axle 2 designed as a rear axle and a second axle 3 designed as a steerable front axle, wherein the first axle 2 comprises a drive train 4 which is operatively connected, for example, to a differential 5. The differential 5 distributes a drive power, i.e., a rotational speed and a torque, to two wheels 6, 7 of the first axle 2. The vehicle 1 can also have several steerable axles. It is also conceivable that all axles of the vehicle 1 are steerable.

[0043] The powertrain 4 comprises a drive motor 8 and a transmission 9 connected to it. The powertrain 4 is controlled by a transmission control unit 15, which enables deceleration and holding functions for the vehicle 1. The powertrain 4, together with an environmental monitoring system 11, is integrated into a system 10 for decelerating and holding the vehicle 1 at a standstill. The environmental monitoring system 11 has one or more sensors (e.g., imaging sensors, radar, or LiDAR) to detect potential obstacles in the vicinity of the vehicle 1. The environmental monitoring system 11 is configured to generate a deceleration signal based on an object 16 detected by its sensors and transmit this signal to the transmission control unit 15. Alternatively, the transmission control unit 15 can receive or retrieve sensor data from the environmental monitoring system 11 and independently generate a corresponding deceleration signal.

[0044] Depending on the requirements, the transmission 9 can be a powershift transmission or a CVT. In this case, the transmission 9 has a primary part 12 directly connected to the drive motor 8 and a secondary part 13 directly connected to the output, here the differential 5. "Directly connected" in this context means that no further switching elements, in particular clutches, are arranged between the respective part of the transmission and the drive motor 8 or the differential 5. A switching element 14 is located between the primary part 12 and the secondary part 13. This element controls the connection between the two parts and enables the disengagement or coupling for efficient deceleration and holding functions.

[0045] The primary part 12 has primary switching elements (not shown here), and the secondary part 13 has secondary switching elements, wherein the primary and / or secondary switching elements can each be friction-based and / or positive-locking clutches for shifting gears. One or more of the primary or secondary switching elements can be designed as brakes. It is merely intended to illustrate that the transmission 9 is divided into two parts, whereby the two parts 12 and 13 can be connected or disconnected via the switching element 14. In this case, the switching element 14 is, for example, designed as a multi-plate clutch to generate a friction-based connection between an output part of the primary part 12 and an input part of the secondary part 13.

[0046] Fig. 2 shows a block diagram of the inventive method for decelerating and holding the vehicle 1 at a standstill, which can be carried out with the above-mentioned system 10.

[0047] In the initial state of system 10, vehicle 1 is in a ready-to-use or drive-ready state, and the driver has full control over the vehicle's behavior. Vehicle 1 is either stationary or already in motion. Furthermore, an object 16 is located outside vehicle 1 and has been detected as such by the environmental monitoring system 11.

[0048] As a system response to object 16, the environmental monitoring system 11 generates and sends a delay signal to the transmission control unit 15 in one step 100. In other words, a delay signal is generated via downstream logic or logic integrated into the environmental monitoring system 11 when an obstacle or object 16 is detected. The object 16 can be stationary or immobile. The object 16 can also be moving. The signal trigger is forwarded to the transmission control unit 15 via a signal interface, for example, via a CAN interface (ZF Friedrichshafen AG File 305575 Friedrichshafen 2024-11-26). Thus, the transmission control unit 15 receives and processes the delay signal. The generation of the delay signal is explicitly not limited to the environmental monitoring system 11.The delay signal can also be generated or triggered by other units or devices and then provided to the transmission control 15 for further processing.

[0049] In a second step, 200, the transmission control unit 15 activates a transmission function for vehicle deceleration. The activation of this transmission function causes the transmission control unit 15 to control the drivetrain 4 in order to decelerate the vehicle 1 to a standstill in a deceleration mode, or in a third step, 300. The transmission control unit 15 controls the drivetrain 4, in particular the transmission 9, in such a way that the vehicle 1 is decelerated as effectively as possible and held at a standstill by the intervention in the drivetrain 4, a process also known as "slow-down braking".To decelerate the vehicle 1, the speed and / or torque of the drive motor 8 are regulated, a gear ratio is changed, a gear is shifted, a reversing function of the transmission 4 is activated when a predefined speed threshold is reached, and / or an optional speed control device, such as cruise control, is deactivated. Intervening in the operation of the drive motor 8 ensures that gear changes can be performed while simultaneously maintaining the highest possible engine speed. Deactivating the cruise control prevents unexpected acceleration of the vehicle 1, particularly if, during deceleration, no deceleration signal is suddenly generated or received by the transmission control unit 15.

[0050] In particular, in the third step 300, the drive train 4 is controlled such that a gear ratio is set in the transmission 9 that acts opposite to the current direction of travel of the vehicle 1. In other words, to achieve the deceleration of the vehicle 1 as a result of object detection and triggering of the aforementioned transmission function, a gear ratio required or acting for reverse travel is set or engaged when the vehicle 1 is currently traveling forward, and a gear ratio corresponding to reverse travel is engaged when the vehicle 1 is currently traveling backward. (ZF Friedrichshafen AG File 305575 Friedrichshafen 2024-11-26)

[0051] The required or effective gear ratio for forward travel is set or engaged. This is to be understood as a reversing function. This applies at least when the vehicle 1 is in motion when the aforementioned transmission function is activated.

[0052] The reversing function in transmission 9 can be triggered by the transmission control unit 15, even if the driver does not actively request reversing. This is also possible if the driver or vehicle 1 has deliberately deactivated the reversing function of transmission 9. In this case, a deactivated reversing function can be overridden and activated by the transmission control unit 15 to perform or assist deceleration. The reversing function decelerates vehicle 1 to near or complete standstill. Once standstill is reached, the system switches to the next function, meaning the active reversing function is terminated. The reversing function can thus be used specifically for decelerating vehicle 1, even if the driver has not generated or entered an input command required for a reverse driving function into system 10.

[0053] After the vehicle 1 has decelerated to a standstill, it is held at a standstill for a fourth step (400). Upon reaching a standstill, the speed of the drive motor 8 can be regulated below a limit speed, in particular to an idle speed.

[0054] In the alternative case that vehicle 1 is already at a standstill when the transmission function for deceleration of vehicle 1 is activated or triggered, vehicle 1 is held at a standstill until no further deceleration signal is generated, for example when object 16 is no longer in the vicinity of vehicle 1 as defined by the environmental monitoring system 11.

[0055] Holding the vehicle 1 stationary is achieved, for example, by blocking the rotational movement of an output element, in particular an output shaft of the transmission 9. Blocking the rotational movement of the output element can be accomplished by actuating several switching elements – not shown here – of the ZF Friedrichshafen AG file 305575 Friedrichshafen 2024-11-26

[0056] Transmission 9 is engaged. Transmission locking is achieved by activating switching elements that were not previously active in the load flow. The transmission can also be locked by a switching element that provides a rotationally fixed connection to the transmission housing. At least one switching element thus prevents an output shaft of transmission 9 from rotating. This prevents the vehicle 1 from moving. If transmission 9 is a powershift transmission or includes one, transmission 9 can be locked to keep the vehicle 1 stationary. In this case, active clutches in transmission 9 are engaged to prevent rotation at the output shaft, while simultaneously opening the connection to the drive motor 8 to prevent the drive motor 8 from stalling. This would not be necessary with an electric drive motor.If the transmission 9 is a CVT transmission, holding the vehicle 1 at a standstill can be achieved, for example, via a hydrostatic power split.

[0057] When the transmission function is switched back to inactive or deactivated, a fifth step (500) involves transferring the drivetrain 4 back to normal operation. The drivetrain 4 is controlled in such a way that the vehicle 1 starts moving again and accelerates to its normal driving speed. When the transmission function is inactive or switched to inactive, the vehicle 1 can be driven as usual.

[0058] From a standstill, vehicle 1 can transition back to normal operation by, for example, releasing any lock-up in a power-shiftable transmission section of the gearbox 9, allowing vehicle 1 to start moving normally, such as by the driver pressing the accelerator pedal. Acceleration of vehicle 1 from standstill back to normal operation can be limited by restricting the acceleration of a gearbox output speed. This is advantageous when the driver continuously presses the accelerator pedal. Unexpectedly strong accelerations are thus avoided during the transition back to normal operation.

[0059] The transition to normal operation can alternatively also take place during travel, particularly from deceleration mode. ZF Friedrichshafen AG File 305575 Friedrichshafen 2024-11-26

[0060] Normal operation is configured by the transmission control unit 15 in such a way that the driver is not surprised by an unexpectedly strong acceleration of the vehicle 1. Acceleration of the vehicle 1 during the transition from deceleration mode, i.e., when the transmission function for decelerating the vehicle 1 is active, back to normal operation can also be limited here by restricting the acceleration of the transmission output speed. The drivetrain 4 is controlled accordingly by the transmission control unit 15.

[0061] Fig. 3 illustrates in a diagram the previously described deceleration operation of vehicle 1 from a normal driving mode, i.e., while vehicle 1 is in motion. The time axis (plotted over the abscissa 19 of the diagram in Fig. 3) shows the steps of the deceleration process, beginning with the generation of the deceleration signal by the environmental monitoring system 11 and the processing of the deceleration signal by the transmission control unit 15 at a first time point T1. If, for example, the driver is pressing the accelerator pedal or the cruise control is engaged or activated, the system 10 or the transmission control unit 15 deactivates all automated acceleration functions, such as the cruise control or hand throttle, at time point T1 as soon as a deceleration signal is received.

[0062] The transmission control unit 15 controls the drive train 4 from time T1 such that the speed of the vehicle 1 (plotted over the ordinate 20 of the diagram according to Fig. 3) decreases continuously, for example by stepwise downshifting in the transmission 9 and / or by activating a reversing function (the transmission ratio is reversed in the opposite direction of travel) and / or by adjusting the speed and / or torque, until the vehicle 1 comes to a standstill. The deceleration and standstill control is advantageously implemented by the transmission 9 using an existing reversing strategy during deceleration, which is automatically terminated when the vehicle comes to a standstill.

[0063] Above a certain configurable speed threshold, the transmission control unit 15 briefly opens the shift element 14, which functions as the main clutch of the transmission 9. Subsequently, the primary part 12, which in this example is referred to as ZF Friedrichshafen AG File 305575 Friedrichshafen 2024-11-26

[0064] The power-shift assembly functions, or rather, the primary switching elements of the primary part 12 are actuated in such a way that a reversal of rotation occurs at the output of the primary part 12 facing the switching element 14, so that, depending on the direction of travel of the vehicle 1, the operating mode is reversed from forward to reverse, or vice versa. During this phase, the switching element 14 can already be moved to a stop position to save time. Afterwards, the switching element 14 is closed again, thereby initiating the deceleration operation of the vehicle 1 and braking the vehicle 1. The vehicle 1 is thus braked by the switching element 14, since a gear is effectively engaged that acts against the direction of travel. This results in a high braking effect due to the reversal of the torque flow, as the vehicle 1 is, for example, moving forward, but a reverse gear is engaged, and the switching element 14 is closed in a controlled manner.The transmission control unit 15 controls the drive train 4 in such a way that the drive motor 8, which can be an internal combustion engine, does not stall. The reversing function ensures that the internal combustion engine is not stalled.

[0065] Once the vehicle 1 has come to a standstill, it can be held, for example, by locking the primary part 12 of the transmission 9 against a stationary component (not shown here), such as a housing. See the horizontal section 17 in the speed profile 18 between the first time T1 and the second time T2. Simultaneously, the drive motor 8 is decoupled by at least one primary switching element of the primary part 12 to prevent the drive motor 8 from stalling. The output of the transmission 9 is supported by the locked primary part 12, which allows the vehicle 1 to remain stationary even on steep terrain.

[0066] Vehicle 1 is held stationary as long as the transmission function remains active, regardless of whether the driver operates the accelerator pedal or generates other input commands to change the vehicle's operation. This ensures that vehicle 1 cannot start moving. The transmission function is deactivated as soon as no further deceleration signal is generated. According to Fig. 3, this occurs at the second time point T2, whereupon the transmission control unit 15 [ZF Friedrichshafen AG File 305575 Friedrichshafen 2024-11-26]

[0067] The system controls drivetrain 4 in such a way that it returns to normal operation. Vehicle 1 starts moving and accelerating from the second point in time, T2.

[0068] As soon as the deceleration signal is inactive or deactivated, the transmission control unit 15 returns the drivetrain 4 to normal operation. If the driver is still pressing the accelerator pedal or the cruise control is reactivated, the transmission control unit 15 ensures smooth and controlled acceleration to prevent unexpected acceleration surges when starting off. The transition to normal operation can also occur while driving with active deceleration if the deceleration signal becomes inactive mid-deceleration. In such a case, the transmission control unit 15 regulates the transition back to normal operation, again without allowing abrupt acceleration spikes.

[0069] To increase performance, the aforementioned functional components of the process can be executed in an overlapping manner. Furthermore, an engine brake and / or a continuous brake (so-called retarder) can be activated to further increase the deceleration of vehicle 1 while driving.

[0070] ZF Friedrichshafen AG File 305575 Friedrichshafen 2024-11-26

[0071] Reference sign

[0072] 1 vehicle

[0073] 2-axis

[0074] 3-axis

[0075] 4 Powertrain

[0076] 5 Differential

[0077] 6 wheels

[0078] 7 wheel

[0079] 8 Drive motor

[0080] 9 gearboxes

[0081] 10 System

[0082] 11 Environmental monitoring system

[0083] 12 Primary part

[0084] 13 Secondary part

[0085] 14 Switching element

[0086] 15 Gearbox control

[0087] 16 objects

[0088] 17 Horizontal part of the velocity profile

[0089] 18 Speed ​​profile

[0090] 19 Abscissa

[0091] 20 ordinates

[0092] 100 steps

[0093] 200 steps

[0094] 300 steps

[0095] 400 steps

[0096] 500 steps

[0097] T 1 Time

[0098] T2 time

Claims

ZF Friedrichshafen AG File 305575 Friedrichshafen 2024-11-26 Patent claims 1. A method for decelerating and holding a vehicle (1) at a standstill, having a powertrain (4) comprising a transmission (9), the method comprising the following steps: a) receiving and processing a deceleration signal by a transmission control unit (15); b) activating and executing a transmission function for vehicle deceleration, wherein the transmission control unit (15) drives the powertrain (4) based on the deceleration signal until the vehicle (1) comes to a standstill; c) holding the vehicle (1) at a standstill; and d) returning the powertrain (4) to normal operation once the transmission function for vehicle deceleration is deactivated.

2. Method according to claim 1, wherein the delay signal is generated based on an object (16) detected by an environmental monitoring system (11).

3. Method according to claim 1 or claim 2, wherein the acceleration of the vehicle (1) during the transition back to normal operation is limited by limiting the acceleration of a transmission output speed.

4. Method according to any of the preceding claims, wherein step b) is carried out by decelerating the vehicle (1) - a speed and / or torque of a drive motor (8) is controlled; - a gear ratio is changed; - a gear change; - when a predefined speed threshold is reached, a reversing function of the gearbox (9) is activated and / or - an optional cruise control device is deactivated.

5. Method according to claim 4, wherein the drive train (4) is controlled in step b) such that a gear ratio is set in the transmission (9) which acts opposite to the current direction of travel of the vehicle (1 ). ZF Friedrichshafen AG File 305575 Friedrichshafen 2024-11-26 6. Method according to claim 4 or claim 5, wherein the reversing function for decelerating the vehicle (1) is deactivated when the vehicle (1) comes close to a standstill or comes to a standstill.

7. Method according to any one of claims 4 to 6, wherein a rotational movement of an output element of the transmission is blocked to keep the vehicle (1) stationary.

8. Method according to one of the preceding claims, wherein when the vehicle (1) comes to a standstill, the speed of the drive motor (8) is regulated below a limit speed, in particular an idle speed.

9. System (10) for decelerating and holding a vehicle (1) at a standstill, with a drive train (4) comprising a transmission (9), the system (10) comprising a transmission control unit (15) configured to - to receive and process a delay signal, - to activate and execute a transmission function for vehicle deceleration, wherein the transmission control (15) controls the drive train (4) on the basis of the deceleration signal until the vehicle (1) comes to a standstill and to keep the vehicle (1) at a standstill until the transmission function is deactivated, and wherein the drive train (4) can be returned to normal operation as soon as the transmission function for vehicle deceleration is deactivated.

10. System (10) according to claim 9, further comprising an environmental monitoring system (11) comprising an imaging sensor, a radar sensor and / or a LIDAR sensor.

11. System (10) according to claim 9 or claim 10, wherein the transmission (9) comprises a primary part (12) directly operatively connected to the drive motor (8) with primary switching elements for shifting gear stages, a secondary part (13) directly operatively connected to the output of the transmission (9) with secondary switching elements for shifting gear stages, and a power flow between the ZF Friedrichshafen AG File 305575 Friedrichshafen 2024-11-26 Switching element (14) arranged between the primary part (12) and the secondary part (13) for selective connection or separation of the secondary part (13) from the primary part (12).

12. Vehicle (1) comprising a system (10) according to any one of claims 9 to 11.

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