Method for maintaining a motor vehicle in a two-track

Abstract

The invention relates to a method for holding a motor vehicle in a two-wheel drive, the motor vehicle comprising at least one drive motor and each of the four wheels of the motor vehicle being able to be held by means of one service brake, - holding the motor vehicle in a stationary state of the motor vehicle by applying the motor torque of the drive motor to at least two wheels of the motor vehicle in an initial situation, - reducing the motor torque holding the at least two wheels of the motor vehicle on one wheel in dependence on the situation and / or in dependence on the gradient, - activating the service brake on the one wheel after the reduction of the motor torque on the one wheel, - reducing the motor torque on another wheel of the vehicle after the activation of the service brake on the one wheel, - and then activating the service brake on the other wheel of the vehicle after the reduction of the motor torque on the other wheel of the vehicle.

Description

Technical Field

[0001] This invention relates to a method for maintaining double wheel tracks in a motor vehicle, particularly on an inclined surface. Exemplary references to prior art are made to DE 10 2017 113 016 A1, DE 10 2012 223 867 A1, and DE 10 2012 223866 A1. Background Technology

[0002] In particular, known holding functions of motor vehicles with internal combustion engine drives (such as the so-called "Autohold function", "Hill-Assist", or so-called B-hold function) hold the vehicle with the help of service brakes, especially on inclined surfaces.

[0003] In motor vehicles with electric drive systems, the drive motor applies torque to the transmission system. To prevent the vehicle from rolling back after braking, especially when stopped on an inclined surface, the service brakes must conventionally be operated according to the inclination. Such braking and holding designs are known, for example, from DE 10 2017 113 016 A1.

[0004] In current designs for electric vehicles, a strong, prominent thrust is provided for deceleration upon releasing the accelerator pedal until a stop is reached. This involves adjusting the correspondingly high regenerative torque of the drive motor, allowing the driver to not only accelerate by manipulating the accelerator pedal but also achieve the desired deceleration upon releasing it. This results in what is known as "one-pedal-feeling," the feeling of controlling the vehicle solely with the accelerator pedal. This "one-pedal-feeling" significantly reduces the use of the brake pedal.

[0005] In this design, the electric vehicle differs from typical autonomous vehicles in that it does not exhibit creep, meaning that the vehicle does not move in the forward direction when engaged with a speed level assigned to the forward direction (typically referred to as D-Drive); the corresponding situation applies to the backward direction. Creep is difficult to reconcile with a "one-pedal feel" because it requires, for example, frequent operation of the brake pedal to prevent creep.

[0006] As also known from DE 10 2012 223 867 A1 and DE 10 2012 223 866 A1, vehicles with electric drive systems utilize motor torque to further hold a vehicle already stationary, especially on inclined surfaces. Depending on the gradient of the roadway and the length of time the vehicle remains stationary, the effective power of the drive motor decreases sooner or later. Then (e.g., after a defined time), the holding torque driven by the electric motor decreases, and an alternative holding system (especially a service brake) takes over and holds the vehicle stationary.

[0007] However, a disadvantage of the prior art is that the transition from holding driven by the drive motor to holding via the service brake, especially due to the reduction in motor torque of the drive motor during service brake take-off or activation, generates undesirable and uncomfortable noise and vibration for the occupants. This is because, in order to reliably keep the vehicle stationary, a simultaneous transition from holding via the drive end to holding via the service brake is necessary. In particular, vehicle occupants experience this vibration through creaking noise. Summary of the Invention

[0008] Therefore, the objective of this invention is to improve the method for keeping a vehicle with two wheels stuck in a stationary state in terms of occupant comfort.

[0009] The solution to this task was derived from a method for using a motor vehicle to maintain double wheel tracks.

[0010] In the sense of this application, the concept of "motor vehicle with drive motor" preferably includes not only electric vehicles with optional internal combustion engine range extenders that can be charged by an external power supply, but also hybrid vehicles with an internal combustion engine and one (or more) drive motors.

[0011] In an exemplary first embodiment, the motor vehicle includes two drive motors, one for driving wheels on the front axle and the other for driving wheels on the rear axle.

[0012] In another exemplary embodiment, the motor vehicle includes four wheel-specific drive motors, which are known in particular as so-called hub motors. In such a case with wheel-specific drive motors, each wheel can be driven individually by the drive motor configured for each wheel.

[0013] As mentioned at the beginning, the dual-track vehicle includes at least one (preferably at least two) drive motors. If the vehicle includes, for example, only one single drive motor, it is preferably configured to drive only the wheels of one axle, i.e., the wheels of the front axle or the wheels of the rear axle.

[0014] The dual-track motor vehicle also includes at least four wheels, each of which can be held in place or prevented from rotating by a service brake. The service brake may be, for example, an electrically, electro-hydraulic, electromechanical, or hydraulically operable braking device. Particularly preferred herein is the design described at the beginning of an electric vehicle with a "one-pedal feel."

[0015] In the initial position of the motor vehicle (hereinafter referred to as "vehicle"), the vehicle is stationary, wherein the vehicle is held in place by applying the motor torque of the at least one drive motor.

[0016] In the case of having only one single drive motor, it is preferable to set up one axle wheel to be held by the motor torque of that single drive motor, while the other axle wheel can be held by a conventional service brake.

[0017] Another feasible method is to keep the vehicle stationary by applying service brakes and simultaneously applying motor torque through the drive motor.

[0018] In the implementation described at the beginning, which has two drive motors (e.g., one for driving the front axle wheels and one for driving the rear axle wheels), it is preferable to arrange the vehicle in the initial position by the motor torque of the drive motors (and, if necessary, additionally by the corresponding service brakes) to keep all the wheels of the vehicle from rolling or rotating.

[0019] Similarly, in the implementation described at the beginning with a drive motor specific to (four) wheels, it is preferable to set up, in the initial position, all four wheels are kept in place by the motor torque of the respective drive motor, or in other words, to ensure that all four wheels are not rolled or rotated.

[0020] Particularly preferably, the motor vehicle is initially positioned on a sloping surface or a driving lane, i.e., on a ramp.

[0021] In the next step, the motor torque used to keep the vehicle in its initial position is reduced, particularly in relation to the situation and / or the slope and / or the time, on only one or at most two wheels of the vehicle.

[0022] In the case where a single drive motor generates the torque used to hold the two wheels of the vehicle, it is preferable to configure the system to reduce the torque on those two wheels. However, it is also preferable to configure the system to hold the other two wheels by means of a service brake.

[0023] In particular, in the case of two or more drive motors, it is preferred to first reduce the motor torque of the drive motor on only one unique wheel, while such reduction does not occur on the other wheels where the motor torque of the drive motor is maintained.

[0024] This ensures that during the period when the motor torque is reduced on only one wheel (or at most two wheels), the vehicle continues to be maintained by the motor torque preferably applied to the other wheels and prevents the vehicle from moving undesirably.

[0025] The torque reduction of the drive motor on the one wheel (or the most two wheels) is preferably carried out completely, that is, until no motor torque is applied to that wheel, that is, substantially reduced to 0 Nm.

[0026] During the duration of torque reduction of the drive motor on a corresponding wheel / multiple wheels, it is preferably configured such that no service braking torque is applied to that wheel / those wheels that is not subject to the service brake of the corresponding wheel. In other words, it is configured such that the service brake of the corresponding wheel is inactive or disengaged during the torque reduction of the drive motor.

[0027] After the (preferably complete) reduction of the motor torque on one or at most two wheels of the motor vehicle, the service brake takes over the holding of the corresponding wheel.

[0028] That is, for example, if the motor torque is completely reduced on the only wheel, the service brake on that wheel remains disengaged until the motor torque is completely reduced, i.e., it is not activated. The vehicle rolls off by the torsional braking of the other wheels, especially by applying the motor torque of the drive motor. In this example, the service brake on that wheel is then activated after the motor torque has completely reduced, so that the wheel that was held also helps to hold the vehicle.

[0029] By not activating the service brake during the (preferably complete) reduction of motor torque, but only after the torque reduction, the aforementioned undesirable squeaking noise is avoided. The vehicle is prevented from rolling away by maintaining the other wheels to compensate for the time gap (during which it is no longer guaranteed that the corresponding wheel where the reduction occurs will not roll until the service brakes then actually engage).

[0030] As already mentioned, it is preferable to reduce the motor torque of the drive motor on the respective wheels in relation to the situation and / or time and / or gradient. Such reduction may, for example, depend on the foreseeable duration of the vehicle's stationary position (e.g., due to known traffic light switching durations or foreseeable traffic jam durations or similar conditions). Alternatively or additionally, the reduction of the motor torque on the respective wheels may also depend on the corresponding gradient of the lane in which the vehicle is positioned. If the vehicle is, for example, on a flat lane (which can be determined by different sensors or data), the reduction of the motor torque may occur very late or not at all, because the drive motor, from an energy perspective, is capable of holding the vehicle in its initial position and in that position for a long period of time by applying motor torque to the respective wheels. If, contrary to this, it is determined that the vehicle is held on a lane with a steep gradient, in which the drive motor can only hold the vehicle for a defined period of time with the motor torque for energy reasons, then the aforementioned reduction of the motor torque on the respective wheels may be set to occur after a shorter period of time.

[0031] Alternatively or additionally, the motor torque can be reduced in a time-related manner. That is, if, for example, a predetermined dwell time of the vehicle in the initial position (the vehicle's holding position by the motor torque of the drive motor) is recorded, the motor torque on the corresponding wheels can be reduced.

[0032] Alternatively or additionally, the reduction may be performed based on the detected effective power of the drive motor.

[0033] Now, after a change or transition has been made in one of the vehicle's first wheels (or at most two wheels) from a hold determined by the drive unit through the motor torque of the drive motor to a hold determined by the brake through the service brake, the setup is now repeated in the other wheels, which are held by the motor torque of the drive motor.

[0034] That is, the configuration (preferably in relation to the situation and / or time and / or slope) is such that after activating the service brake on one wheel (or at most two wheels), the motor torque of the drive motor on the other wheel of the vehicle is reduced. This reduction is also preferably performed completely, i.e., until the applied torque is substantially 0 Nm. Then, after the reduction of torque on the other wheel, the service brake is activated on that other wheel.

[0035] These two steps (reduction of motor torque at the corresponding wheel and subsequent activation of the service brake) are preferably performed in relation to the situation, time, or slope, and thus sequentially at each wheel, which is held in the initial position of the vehicle by the motor torque of the drive motor.

[0036] During the process of these two steps on the corresponding wheels, the corresponding other wheels are responsible for keeping the vehicle in place either by the already activated service brake or by the remaining motor torque of the drive motor.

[0037] In other words, during the period when the motor torque of the drive motor on one wheel decreases, the service brake preferably does not operate on the vehicle's wheel. This advantageously avoids the squeaking noise mentioned above during the transition from holding by the drive motor to holding by the service brake. This ensures comfortable and noise-reduced holding characteristics for the vehicle.

[0038] In a preferred embodiment of the invention, the claimed method is implemented in relation to the situation or the slope. That is, while the vehicle is in the initial position (holding position), if a certain slope of the lane is reached, the method is implemented. Alternatively or additionally, the method may be implemented when, in addition to the slope, it is detected that the effective power of the drive motor is no longer sufficient to hold the vehicle in the holding position for a defined duration, or when it is detected that the foreseeable or reached holding duration is no longer energy-efficient enough to hold the vehicle by the motor torque of the drive motor.

[0039] In addition to the method described above, a motor vehicle is proposed that enables the implementation of the method. As already mentioned, the motor vehicle includes at least one drive motor and at least four wheels. Here, each of the four wheels can be held in place by a service brake for holding the wheels, or by a torsion stop.

[0040] These and other features are derived not only from the specification but also from the accompanying drawings, wherein each feature is implemented individually or in combination in embodiments of the invention and constitutes an advantageous and insurable implementation, the embodiments of which are claimed herein. Attached Figure Description

[0041] Figure 1 An example illustrating the torque change process (holding or braking torque change process) of a motor vehicle with four wheels over time. Detailed Implementation

[0042] The invention will then be further explained with reference to embodiments. All the features described in detail herein are essential to the invention.

[0043] The diagram shown schematically illustrates an embodiment of the torque change process (holding or braking torque change process) over time for a motor vehicle with four wheels (Rad_1; Rad_2; Rad_3, Rad_4). Each wheel (Rad_1; Rad_2; Rad_3, Rad_4) has a service brake capable of applying the braking torque, or service braking torque M. Brems (Dashed lines) are applied to the corresponding wheels. The motor torque M of the drive motor can also be applied individually to each wheel. Antrieb (Solid line). In particular, each wheel is equipped with a separate drive motor, for example, in the form of a hub motor.

[0044] In the initial position, the vehicle is in a holding position, especially on a slope. The vehicle continues to operate until time t1 by applying the motor torque M of the drive motor. Antrieb The motor torque is applied to all four wheels of the vehicle, Rad_1, Rad_2, Rad_3, and Rad_4. Additionally, but not limitingly, in this specific case, the vehicle is maintained by applying a service brake to all four wheels, Rad_1, Rad_2, Rad_3, and Rad_4. However, it is also conceivable to maintain the vehicle solely by applying the motor torque M. Antrieb The torque applied to each wheel keeps the vehicle stationary. Through a vehicle design featuring the "one-pedal feel" described at the beginning, the vehicle maintains this state by applying a motor torque M to each wheel via a corresponding wheel-specific drive motor. Antrieb Remain stationary.

[0045] For example, the vehicle may be at a red traffic light or on a sloping road.

[0046] The braking process until the vehicle comes to a standstill is preferably also achieved via a corresponding drive motor (refer to the "one-pedal feel" design mentioned above). As already mentioned, the vehicle can be kept in place by the drive motor while the driving braking torque M is applied. Brems Apply to the wheels to activate the service brakes.

[0047] If, at time t1, it is detected, for example, via sensors, navigation data, online data, vehicle data, or the like, that the effective power of the drive motor is low or its energy is unsuitable due to an excessively high gradient of the driving lane or an excessively long duration of foreseeable or past dwell time while the vehicle is in a holding position, then the service brake is set to apply the corresponding braking torque M. BremsApply to the corresponding wheels to ensure and take over the vehicle's holding position.

[0048] Unlike existing technologies, the service brake does not simultaneously and comprehensively engage with the motor torque M still applied to each wheel. Antrieb They are not activated together, but rather sequentially formed on each wheel when the motor torque on the corresponding wheel has been completely reduced.

[0049] If the service brake was activated while the vehicle was stationary, it will be completely disengaged on the first wheel Rad_1 before time t1, thus eliminating the service braking torque M. Brems At time t1, it is applied to the first wheel Rad_1.

[0050] At time t1, the motor torque M of the first wheel Rad_1 of the vehicle... Antrieb Reduced to 0 Nm. At time t2, when the motor torque M of the drive motor of the first wheel... Antrieb Only when the braking torque M generated by the service brake is completely reduced... Brems Activate the service brake on the first wheel. The motor torque M on the first wheel... Antrieb The moment when the braking force begins to decrease and the driving braking torque M Brems The insufficient braking force generated on the first wheel between the complete formation of the braking force can be mitigated by the braking torque M still applied to the other three wheels Rad_2, Rad_3, and Rad_4. Brems Or rather, M Antrieb Compensation, or rather, redundancy. This results in a holding torque M on the other three wheels, Rad_2, Rad_3, and Rad_4. Brems Or rather, M Antrieb High enough to keep the vehicle in the holding position. This is due to the motor torque M on the first wheel Rad_1. Antrieb The complete reduction of noise, while the service brake of the first wheel Rad_1 is disengaged or not activated during this period, can advantageously avoid the generation of uncomfortable noise.

[0051] In the next step, at time t3, when the braking torque M of the first wheel Rad_1... Brems When the first wheel has been fully formed and completely taken over the holding of the second wheel Rad_2, the motor torque M of the drive motor of the second wheel Rad_2 is... Antrieb Reduce until 0 Nm. Here, it is also necessary to ensure that the motor torque M on the second wheel Rad_2 is [missing information]. Antrieb At time t3, the service brake on the second wheel is no longer activated (i.e., disengaged). The motor torque M of the drive motor for the second wheel Rad_2... AntriebAfter complete reduction, at time t4, the service braking torque M through the service brake is... Brems The formation of the brake activates the service brake on the second wheel Rad_2. The service brake on the second wheel Rad_2 then takes over the holding of the second wheel.

[0052] Subsequently, as in Figure 1 As can be seen, the same method and steps are applied to the other two wheels, Rad_3 and Rad_4. The driving braking torque M on the second wheel, Rad_2... Brems After the system is fully formed and the service brake of the third wheel Rad_3 is deactivated, at time t5, the motor torque M of the third wheel Rad_3 is... Antrieb Reduced until 0 Nm. Then the motor torque M on the third wheel Rad_3 is... Antrieb Complete reduction begins at time t6, when the service brake of the third wheel Rad_3 is activated.

[0053] After the service brake on the third wheel Rad_3 is fully activated, and while ensuring that the service brake on the fourth wheel Rad_4 is not activated (i.e., disengaged), the applied motor torque M on the fourth wheel Rad_4... Antrieb Reduce until 0 Nm (time t7). This torque M at the fourth wheel Rad_4. Antrieb After the complete reduction (from the start of reduction until time t7), the service brake of the fourth wheel Rad_4 is activated (time t8).

[0054] Motor torque M is applied to the corresponding wheels. Antrieb The corresponding reduction and driving braking torque M Brems During the subsequent formation of the holding torque M acting on the other wheels Brems Or rather, M Antrieb Ensure the vehicle does not roll away while stationary.

[0055] By the motor torque M on the corresponding wheel Antrieb During the reduction period, the running brakes on the corresponding wheels are not activated (i.e., disconnected), and the aforementioned squeaking noise is not produced.

Claims

1. A method for a motor vehicle maintaining double wheel ruts, wherein, The motor vehicle includes at least one drive motor and each of the four wheels of the motor vehicle can be held in place by a service brake. - In the initial case, by measuring the motor torque (M) of the drive motor Antrieb Applying force to at least two wheels (Rad_1, Rad_2, Rad_3, Rad_4) of the vehicle to keep the vehicle stationary. - Reduce the motor torque (M) of the motor holding the at least two wheels (Rad_1, Rad_2, Rad_3, Rad_4) of the motor vehicle on one wheel (Rad_1, Rad_2, Rad_3, Rad_4) or two wheels. Antrieb ), - Motor torque (M) on one or both wheels Antrieb After the reduction, activate the service brake on that one wheel or on both wheels. - After activating the service brake on one or both wheels, reduce the motor torque (M) on the other wheel of the vehicle. Antrieb ), - Then the motor torque (M) on the other wheel of the vehicle Antrieb After the reduction, activate the service brake on the other wheel.

2. The method according to claim 1, wherein, The motor vehicle includes two drive motors, and initially, each wheel of the motor vehicle is driven by a motor torque (M) from one of the drive motors. Antrieb To maintain.

3. The method according to claim 1, wherein, The vehicle includes four drive motors, and initially, the four wheels of the vehicle (Rad_1, Rad_2, Rad_3, Rad_4) are driven by the motor torque (M) of each of the four drive motors. Antrieb To maintain.

4. The method according to any one of claims 1 to 3, wherein, The method according to any one of claims 1 to 3 is performed sequentially on all the motor-held wheels of the motor vehicle, depending on the situation and / or the slope and / or the time.

5. The method according to any one of claims 1 to 3, wherein, Depending on the situation and / or the slope and / or the time, reduce the motor torque (M) at the corresponding wheels. Antrieb ).

6. The method according to claim 5, wherein, Beginning with the foreseeable and / or achieved duration of the vehicle's residence in the held position and / or from the detection of the drive motor's maximum effective power, the motor torque (M) on the corresponding wheels is reduced. Antrieb ).

7. The method according to any one of claims 1 to 3, wherein, Starting from the detected extreme gradient of the vehicle's driving lane, the motor torque (M) is reduced at the corresponding wheels. Antrieb ).

8. The method according to any one of claims 1 to 3, wherein, The method is implemented starting from the point where the vehicle lane reaches its maximum gradient.

9. The method according to any one of claims 1 to 3, wherein, Motor torque (M) on the corresponding wheels Antrieb During the reduction period, the service brake on the corresponding wheel is not activated.

10. A motor vehicle for carrying out the method according to any one of claims 1 to 9, said motor vehicle comprising at least one drive motor, wherein, Each of the four wheels of the motor vehicle includes a service brake for holding the corresponding wheel.

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