Method and device for controlling a free-rocking mode of a vehicle

Abstract

Method for controlling a rocking mode of a vehicle with a powertrain comprising an automatic or automated transmission and at least one internal combustion engine or electric motor drive unit that can be connected to the transmission for drive purposes, where the free-rocking mode provides a periodically fluctuating drive torque M(t) at at least one drive wheel, wherein an automatic check regarding the existence of a free swing situation (1) is carried out with the help of a free swing detection system, and wherein, upon detection of a rocking situation (1), the rocking mode is automatically activated or at least the existence of the rocking situation (1) is indicated to a driver of the vehicle, characterized by the fact that The rocking mode is started, stopped, or blocked preventively by the driver repeatedly and immediately applying the brake pedal briefly. The rocking mode is influenced by pressing an accelerator pedal, such that a drive torque request is specified via an accelerator pedal deflection.

Description

[0001] The invention relates to a method for controlling a rocking mode of a vehicle according to the preamble of patent claim 1 and a device for controlling a rocking mode of a vehicle according to the preamble of patent claim 7.

[0002] A vehicle that has become stuck in a pothole due to insufficient ground friction and spinning wheels can often be freed by rocking the vehicle free. In a vehicle with a manual transmission, the driver has the option of gradually freeing the vehicle from the pothole by rhythmically engaging the clutch and / or repeatedly shifting between forward and reverse gears. Automatic rocking modes are already known for vehicles with automatic or automated transmissions. These generate a periodically increasing and decreasing drive torque in a desired direction of travel or in both forward and reverse directions.The drive torque can be generated by an internal combustion engine in combination with automatically controlled forward and reverse gears of the transmission, or by an electric motor in combination with a gear and alternating current supply. An electric motor-controlled rocking mode is fundamentally more effective than a combustion engine-controlled rocking mode due to its greater dynamics.

[0003] DE 10 2010 043 250 A1 discloses a method for rocking a vehicle with an automatic or automated transmission. A rocking function is initiated when a rocking situation is automatically detected in the vehicle or is specified by the driver by operating a control element, and is automatically terminated when the vehicle reaches a distance-dependent or time-dependent limit point. To rock the vehicle, starting from the position of a stationary wheel in a hollow from which the vehicle is to be moved, a drive torque is first built up. This drive torque acts in a desired direction of travel selected by the engaged gear until the vehicle, moving in the desired direction of travel, reaches a front reversal point of the hollow. The reversal point is detected when the speed at a non-driven wheel drops to zero or the direction of movement of the vehicle is reversed.The drive torque is then reduced until the vehicle, now moving opposite to the desired direction of travel, reaches a rear reversal point, and then built up again. This is repeated cyclically, with the reversal points being continuously adjusted and successively moving out of the trough until the vehicle reaches a front or rear limit point that marks the end of the trough. The limit points are defined by a permissible distance from the starting position in the respective direction of travel or by a permissible period of time during which the drive torque is applied and are continuously adjusted.

[0004] During rocking, in addition to the alternating build-up and release of drive torque, the transmission can be shifted to neutral when the drive torque is released, allowing the vehicle to roll back passively in neutral, or a shift between forward and reverse gears can be made so that active drive torque is applied in both rocking directions. If an electric motor is available, switching between the drive torque acting in the desired direction of travel and the drive torque acting in the opposite direction to the desired direction of travel is not necessary, as the direction of torque can be changed via the electric drive. Rocking is essentially performed fully automatically.However, the driver can be given the opportunity to actively influence the rocking function by actuating the accelerator pedal, by activating or deactivating the function depending on a minimum actuation, i.e. a minimum deflection angle of the accelerator pedal, and / or by determining a maximum drive torque that is effective in each case depending on the accelerator pedal actuation.

[0005] DE 10 2008 036 048 A1 describes a method in which, during a start-up process and depending on predetermined operating parameters, an automatic check is performed to determine whether a rocking-free mode should be activated or not. The drive torque and any wheel slip are evaluated, taking into account the road gradient and any active traction control systems. Their temporal profiles are correlated with the accelerator pedal position and the vehicle speed, which can be measured at a non-driven wheel. Subsequently, a request signal is generated to start the rocking-free mode manually, or the rocking-free mode is activated automatically. The rocking-free mode itself operates automatically, with a periodically fluctuating drive torque acting in the forward and reverse directions.The required varying and reversing drive torque generation can be achieved in a hybrid or electric vehicle by controlling an electric drive motor with the starting gear engaged in the transmission. In a vehicle with only an internal combustion engine, a quick automatic change between a forward gear and a reverse gear can be achieved.

[0006] DE 10 2009 036 058 A1 discloses a rocking of a vehicle depending on an accelerator pedal operation.

[0007] DE 10 2008 036 047 A1 also concerns the rocking of a vehicle. A control device performs the rocking depending on detected environmental obstacles.

[0008] Against this background, the object of the invention is to further improve the known methods and devices for controlling a rocking mode of a vehicle, in particular with regard to comfort and safety.

[0009] The solution to this problem results from the features of the independent claims, while advantageous embodiments and further developments of the invention can be found in the subclaims.

[0010] The invention is based on the finding that in an automatic rocking mode of a vehicle with automatic detection of a rocking situation, although a large number of vehicle-related and / or environment-related parameters can be taken into account, ultimately the driver's wish should be taken more into account in order to prevent undesired actions of the automatically starting and running rocking mode or at least to better control them in accordance with a driver's wish, and thus to prevent or mitigate comfort-impairing or unexpected, possibly even safety-relevant situations.

[0011] Accordingly, the invention is based on a method for controlling a rocking-free mode of a vehicle with a drive train which has an automatic or automated transmission and at least one internal combustion engine or electric motor drive unit which can be connected to the transmission, wherein the rocking-free mode provides a periodically fluctuating drive torque M(t) on at least one drive wheel, in which an automatic check is carried out with regard to the presence of a rocking-free situation, and in which, upon detection of a rocking-free situation, the rocking-free mode is automatically activated or at least the presence of the rocking-free situation is displayed to a driver of the vehicle.

[0012] To achieve the stated objective of the method, the invention provides that the rocking mode is started or ended, or preventively blocked, by the driver repeatedly and briefly pressing a brake pedal in immediate succession. Furthermore, the invention provides that the rocking mode is influenced by pressing an accelerator pedal, with a desired drive torque being specified via an accelerator pedal deflection. Accordingly, the driver can increase or decrease the drive torque during rocking by means of an accelerator pedal deflection.

[0013] The invention also relates to a device for controlling a rocking-free mode of a vehicle with a drive train which has an automatic or automated transmission and at least one internal combustion engine or electric motor drive unit which can be connected to the transmission, wherein the rocking-free mode provides a periodically fluctuating drive torque M(t) on at least one drive wheel, by means of which an automatic check for the presence of a rocking-free situation can be carried out, and by means of which, upon detection of a rocking-free situation, the rocking-free mode can be automatically activated or at least the presence of the rocking-free situation can be displayed to a driver.To achieve the stated object with regard to the device, the invention provides that the device starts or ends or preventively blocks the rocking mode depending on a repeated, immediately successive, brief actuation of a brake pedal by the driver, and that the device influences the rocking mode depending on an actuation of an accelerator pedal in such a way that it specifies a drive torque request depending on an accelerator pedal deflection.

[0014] A rocking-free mode is an automatic process carried out by a drive train control system to free a vehicle from a rocking-free situation, for example when it is stuck in a depression on a slippery surface, whereby the vehicle performs one or more forward and backward movements.

[0015] The invention can in principle be used in all motor vehicles with automated or automatically controllable drive trains, both in the passenger car sector and in the commercial vehicle sector.

[0016] An automatic rocking-free detection function can record and evaluate various parameters. This can include, for example, the vehicle's route and speed, the angle of the accelerator pedal deflection and its temporal progression, the spinning of one or more of the driven wheels, or the vehicle coming to a stop after briefly rolling backward after the accelerator pedal is released.

[0017] Thanks to the invention, the driver retains control of the rocking mode at all times, despite the essentially automatic operation of the rocking mode. This ensures that the automatic rocking mode is only used when it is sensible and appropriate.

[0018] The following exemplary embodiments show various ways of incorporating a driver's request in this regard in a vehicle with a rocking-free mode. These design variants can be implemented individually or in appropriate combinations as functions in a vehicle's engine and / or transmission control system. The transmission can be designed, for example, as a planetary automatic transmission, a countershaft transmission with a controllable starting clutch, or a dual-clutch transmission with two controllable sub-transmission input clutches.

[0019] According to a first embodiment of the invention, it can be provided that the release or start of the rocking mode takes place by repeatedly, immediately successive, short-term actuation of a brake pedal when the vehicle is stationary.

[0020] Accordingly, if a potential rocking-free situation is automatically detected, it is at the driver's discretion whether to actually activate the rocking-free mode. This can be done, for example, by tapping the brake pedal three times, thus deliberately and clearly signaling a control device to initiate the rocking-free mode stored there as a control program. This eliminates the need for a separate switch operated by the driver, thereby reducing costs. However, the additional provision of such a separate switch is also possible in principle.

[0021] According to a second embodiment of the invention, the rocking mode can be terminated by repeatedly briefly pressing the brake pedal in immediate succession. Accordingly, if a rocking situation is automatically detected, the rocking mode can be automatically initiated, but the driver can deactivate the rocking mode spontaneously.

[0022] According to a further embodiment, it can be provided that a preventive blocking of the rocking mode occurs by repeatedly and briefly pressing the brake pedal in immediate succession. This allows the driver to proactively deactivate the rocking mode if they fear the risk of false activation when driving on a section of road ahead or negotiating an obstacle. Such a situation can arise, for example, when attempting to climb a high curb. Automatic activation of the rocking mode is not advisable in such a situation.

[0023] Furthermore, it can be provided that in the event of a spontaneous temporary actuation of the accelerator pedal, a reduction in a drive torque in a desired direction of travel provided by the rocking-free mode, or an interruption in the power flow of the drive train of the vehicle provided by the rocking-free mode, and / or a build-up of a drive torque opposite to the desired direction of travel provided by the rocking-free mode is blocked or revised.

[0024] This gives the driver the option of intuitively changing the periodically fluctuating drive torque if he finds the automatic rocking function rather annoying and wants to avoid it.

[0025] In a further embodiment of the invention, it can be provided that in the case of an essentially one-sided, angular obstacle, such as a curb, which is to be deliberately crossed slowly, the rocking mode is deactivated or at least influenced in the sense of a signaled driver request.

[0026] By incorporating the measured deflection angle of the accelerator pedal and its temporal change into the detection and / or execution of a rocking-free situation or the rocking-free mode, it can be ensured that when driving over a curb, it is not mistakenly recognized as a pothole, or at least that the driver can react accordingly. In particular, the driver can block a reduction in drive torque in the desired direction of travel or even a build-up of drive torque opposite to the desired direction of travel, or at least counteract this immediately after it occurs.

[0027] To further clarify the invention, a drawing of an embodiment is attached to the description. Fig. 1 a flowchart for the sequence of a method according to the invention for controlling a rocking mode of a vehicle, Fig. 2a a schematically simplified free swing situation, and Fig. 2b a diagram of a free-swing mode sequence.

[0028] A method for controlling a rocking mode of a vehicle, for example a bus, is explained below using a first and second driving situation.

[0029] Accordingly, in a first exemplary sequence, it is assumed that a vehicle with a hybrid drive and an automated transmission, for example a public transport bus or a touring coach, approaches a high curb that is bordered by a gutter on the roadway side. With the help of a control unit and associated sensors, the vehicle has the ability to automatically detect a rocking-free situation and to trigger and control an automatic rocking-free mode to rock the vehicle out of such a situation. The vehicle is to drive over the curb and is initially stopped a short distance from this curb. The vehicle then sets off at low speed, comes into contact with the curb, and then comes to a brief standstill or almost a standstill directly at the curb due to insufficient drive torque.

[0030] According to Fig. 1, the method according to the invention starts in a first function block F1. The activated rocking-free detection F2 in function block F4 incorrectly detects the stop at the curb as a hollow in which the vehicle is stuck, i.e., as a rocking-free situation from which the vehicle must be freed. This is indicated to the driver. It would not be logical for the driver to generate a periodically fluctuating drive torque at this point, since they want to drive the vehicle slowly over the edge in one go. As a result of their plausibility check F3, they then block the rocking-free mode by briefly tapping the brake pedal several times, which is communicated to the control unit via sensors. The driver then manually drives their vehicle up onto the curb by pressing the accelerator pedal accordingly.If rocking-free operation has already begun, it is influenced or terminated as desired when the driver spontaneously presses the accelerator pedal, and this is communicated to the control unit. The process ends in function block F8.

[0031] In a second example, assume that the vehicle, in a different situation, enters a pothole and stops with spinning wheels due to a snowy surface. The rocking detection function F2 detects the rocking situation. The driver wants to rock the vehicle out of the pothole using the rocking mode F5.

[0032] The free-swing mode F5 is shown in an example sequence in Fig. 2, whereby the drive of the vehicle in this situation is preferably carried out by means of a controllable electric motor. Fig. 2a schematically shows a rocking situation in a hollow 1 from which the vehicle is to free itself in a desired direction of travel 2. In Fig. Figure 2b shows two sinusoidal time courses 3, 4 of the vehicle speed v(t) and the vehicle position x(t) as well as a periodically fluctuating drive torque M(t).

[0033] The vehicle is initially in position A at the deepest point of the hollow 1. The driver wishes to rock the vehicle free, wants to move off and presses the accelerator pedal. With a starting gear engaged, the electric motor builds up drive torque in the desired direction of travel 2. The vehicle moves towards position B towards the edge of the hollow ahead and comes to a standstill in position B due to spinning wheels and / or insufficient drive torque. The direction of rotation of the drive torque is now reversed at the electric motor so that the vehicle moves in the opposite direction of travel 2, with the potential energy above position A being converted into additional kinetic energy. The vehicle then comes to a standstill again in the opposite position C of the hollow 1 because the kinetic energy is not yet sufficient to drive out of the hollow 1.The direction of rotation of the drive torque is therefore reversed again at the electric motor, so that the vehicle now moves in its original direction of travel 2. The electric motor is controlled in phase with the vehicle's movement. This process is repeated again, causing the vehicle to rock back and forth, with the reversal positions B and C shifting toward the edge of the pit until the vehicle's kinetic energy is so great that its speed remains greater than zero and the vehicle overcomes the edge of the pit at position D.

[0034] In the flowchart according to Fig.1, the rocking mode is terminated via a query in function block F6, provided the vehicle has successfully overcome the depression 1. If this fails after repeated rocking, the procedure can be aborted by a termination condition according to function block F7, or a new attempt can be initiated. Or the driver can initiate other appropriate measures. List of reference symbols 1 hollow, free swing situation 2 Desired direction of travel 3 Speed ​​curve in free rocking mode 4 Position history in free swing mode A First free swing position B Second free-swing position C Third free-swing position D Fourth free-swing position F1 - F8 function blocks M drive torque v Vehicle speed x Vehicle position t time

Claims

[1] Method for controlling a rocking mode of a vehicle with a drive train which has an automatic or automated transmission and at least one internal combustion engine or electric motor drive unit which can be connected to the transmission, wherein the rocking mode provides a periodically fluctuating drive torque M(t) to at least one drive wheel, wherein an automatic check for the presence of a free-swinging situation (1) is carried out with the aid of a free-swinging detection system, and wherein upon detection of a rocking-free situation (1), the rocking-free mode is automatically activated or at least the presence of the rocking-free situation (1) is displayed to a driver of the vehicle, characterized by , that the rocking mode is started or stopped by the driver repeatedly pressing the brake pedal in quick succession or is preventively blocked, the rocking mode is influenced by actuating an accelerator pedal in such a way that a drive torque request is specified via an accelerator pedal deflection. [2] Method according to claim 1, characterized by that the rocking mode is started by repeatedly and briefly pressing the brake pedal in immediate succession when the vehicle is stationary. [3] Method according to one of claims 1 to 2, characterized by that in the event of a spontaneous temporary actuation of the accelerator pedal, a reduction in drive torque in a desired direction of travel (2) provided for by the rocking mode is blocked or revised. [4] Method according to one of claims 1 to 3, characterized bythat in the event of a spontaneous temporary actuation of the accelerator pedal, an interruption in the power flow of the vehicle's drive train provided for by the rocking mode is blocked or revised. [5] Method according to one of claims 1 to 4, characterized by that in the event of a spontaneous temporary actuation of the accelerator pedal, a build-up of drive torque provided for by the rocking mode is blocked or revised against the desired direction of travel (2). [6] Method according to one of claims 1 to 5, characterized by that in the case of an essentially one-sided, angular obstacle, such as a curb, which is to be crossed deliberately slowly, the rocking mode is deactivated or at least influenced in the sense of a signalled driver request. [7] Device for controlling a rocking mode of a vehicle with a drive train which has an automatic or automated transmission and at least one internal combustion engine or electric motor drive unit which can be connected to the transmission, wherein the rocking mode provides a periodically fluctuating drive torque M(t) on at least one drive wheel, by means of which an automatic check for the presence of a rocking situation (1) can be carried out, and by means of which, upon detection of a rocking situation (1), the rocking mode can be automatically activated or at least the presence of the rocking situation (1) can be displayed to a driver, characterized bythat the device starts or ends the rocking mode depending on a repeated, immediate successive short actuation of a brake pedal by the driver or prevents it from being blocked, and that the device influences the rocking mode depending on an actuation of an accelerator pedal in such a way that it specifies a drive torque request depending on an accelerator pedal deflection.

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