Method for operating a vehicle brake system

Abstract

The invention relates to a method for operating a vehicle brake system, wherein the vehicle comprises at least one electric machine which can be used for vehicle regenerative braking and a drive unit which can be used for vehicle inertial travel braking in an inertial travel operation, the method comprising the following steps: detecting a deceleration start of the vehicle; detecting a regeneratively possible driving condition; starting an inertial travel operation of the drive unit, wherein a current actual drive torque (M ist ) of the drive unit is reduced to a target inertial travel regenerative torque (M Schub ) by inertial travel braking; activating regenerative braking (M Reku ) to achieve a target total regenerative torque (M Soll ), wherein regenerative braking is only activated if a difference (ΔM) between the actual inertial travel regenerative torque (M ist ) and the target inertial travel regenerative torque (M Schub ) is below a predetermined limit value.

Description

Technical Field

[0001] This invention relates to a method for operating a vehicle braking system. Background Technology

[0002] For reference to existing technology, see, for example, DE 10 2017 006 692 A1.

[0003] Regeneration is particularly known in electric and hybrid vehicles, i.e., vehicles with an electric drive unit (electric motor). During regeneration, the kinetic energy of the drive wheels is converted into electrical energy by the electric drive unit, especially the electric motor. Here, the electric drive unit operates as a generator. Therefore, the energy typically lost as frictional heat during braking can be fed into an energy storage device, such as a battery or capacitor, and subsequently utilized. Simultaneously, the generator-like operation of the electric motor achieves the braking effect on the vehicle, a process known as regenerative braking. This is also referred to as regenerative braking or regenerative braking.

[0004] To achieve regenerative braking, a regenerative torque is adjusted on the electric drive unit. This regenerative torque is a braking torque that decelerates the vehicle.

[0005] Here, especially in electric vehicles, it is known that the regeneration is used in such a way that when a braking desire is detected, for example, a braking desire achieved by the vehicle occupant operating the brake pedal, the regenerative torque (typically based on the brake pedal travel traversed by the vehicle occupant operating the brake pedal) is adjusted, and thereby the vehicle is braked in a targeted manner with the desired braking power.

[0006] Furthermore, it is known that the regeneration can also be used to decelerate the vehicle during inertial travel or towing operations of the drive unit. Here, typically when the vehicle occupant ends or reduces their operation of the accelerator pedal—for example, when the vehicle occupant reduces their accelerator pedal operation or completely leaves the accelerator pedal—the so-called inertial travel regeneration torque (also known as towing regeneration torque) on the drive unit is adjusted. The vehicle is thus braked. Typically, the inertial travel braking torque reaches its maximum value (the so-called target inertial travel regeneration torque) when the vehicle occupant ends their operation of the accelerator pedal.

[0007] To initiate the most effective braking process possible, it is known from the prior art that the regenerative torque is adjusted or applied immediately after a deceleration desire is detected. DE 10 2017006 692A1, for example, discloses a method in which the regenerative process is particularly aimed at avoiding delayed activation by rapidly adjusting the regenerative torque. Here, the regenerative braking is performed simultaneously with the inertial regeneration (by reducing or ending the operation of the accelerator pedal).

[0008] This rapid adjustment or superposition of regenerative torque immediately following the detection of a deceleration intention can cause unstable braking behavior under certain conditions, which the driver or occupants may find uncomfortable. This unstable braking behavior stems from a "lag" in the drivetrain, which requires a certain amount of time to achieve inertial torque at the start of inertial travel. For the driver, this time lag is perceived as unstable. Consequently, the vehicle's braking action is slightly out of sync with the brake pedal operation and therefore differs from the driver's expected effect. Furthermore, this braking behavior can lead to potential overbraking, as the driver perceives the vehicle as insufficiently responsive until inertial torque is achieved or until adjustment of inertial torque begins, thus initiating stronger braking maneuvers (also known as two-phase braking). Summary of the Invention

[0009] Therefore, the object of the present invention is to provide a method for operating a vehicle braking system so as to make the deceleration behavior of the vehicle using regenerative braking more predictable and thus improve the driving behavior of the vehicle.

[0010] The solution to this task is derived through a method having the features described below, and through a braking system described below, an electric vehicle described below, and a hybrid vehicle described below. In the method for operating a vehicle braking system according to the invention, the vehicle includes at least one motor capable of regenerative braking and a drive unit capable of inertial braking during inertial driving operation. The method comprises the following steps: detecting a deceleration start of the vehicle; detecting a regenerative driving condition; initiating inertial driving operation of the drive unit, wherein the current actual driving torque of the drive unit is reduced to a target inertial regenerative torque through inertial braking; activating regenerative braking to achieve a target total regenerative torque; characterized in that the regenerative braking is activated only when the difference between the actual inertial regenerative torque and the target inertial regenerative torque falls below a predetermined limit.

[0011] To address the aforementioned task, a method for operating a vehicle braking system is proposed, wherein the vehicle includes at least one motor that can be used for regenerative braking of the vehicle.

[0012] The vehicle is preferably a motor vehicle, especially a motor vehicle with double ruts. However, the invention is also possible with vehicles with single ruts, such as motorcycles.

[0013] Furthermore, the motor is preferably an electric motor used to drive at least one axle or wheel of the vehicle.

[0014] In the context of this invention, regenerative braking is understood as the braking initiation achieved by applying the regenerative torque of the motor, as described above. Here, the magnitude of the applied regenerative torque, and therefore the magnitude of the vehicle's deceleration due to regenerative braking, preferably depends on the travel of the brake pedal operated by the driver.

[0015] Furthermore, the regulations stipulate that the vehicle includes a drive unit that can be used for inertial braking during inertial driving operations.

[0016] The drive unit is preferably the electric motor already mentioned. Alternatively or additionally, the drive unit may also be an internal combustion engine. In any case, a drive unit capable of operating in inertial travel and performing inertial braking (also known as towing regeneration or inertial regeneration) in such inertial travel operation must be involved. Here, the drive unit must be able to achieve a predetermined target towing regeneration or a predetermined target inertial braking torque.

[0017] To achieve inertial regeneration, a so-called inertial regeneration torque (also known as drag regeneration torque) is adjusted on the drive unit. The vehicle is thus braked. Typically, the inertial braking torque reaches its maximum value after a defined time period following the end of accelerator pedal operation; this is the target inertial regeneration, or target drag regeneration. When this maximum value is reached depends largely on the corresponding application in the drive unit. For example, in a pure electric vehicle, this time period is usually slightly shorter than in a vehicle with a hybrid drive system, determined by the internal combustion engine.

[0018] Here, in particular, when the vehicle driver releases the accelerator pedal or completely ends acceleration, the drive unit's inertial driving operation begins. Therefore, if, for example, the vehicle driver operates the accelerator pedal less or ceases operation of the accelerator pedal, the drive unit is placed into inertial driving operation, and inertial braking, or so-called drag regeneration, begins; the vehicle thus decelerates. However, drag torque, or inertial driving torque, is only achieved in the drive unit after a defined duration; that is, inertial driving regeneration, or drag regeneration, is delayed by several milliseconds to several seconds.

[0019] Accordingly, the first step of the method specifies, for example, detecting the deceleration start of the vehicle by a control unit or a designated sensor.

[0020] Such deceleration initiation can be, for example, the driver's operation of the brake pedal. Alternatively or simultaneously, such deceleration initiation can be automatic or independent vehicle braking, for example, when the vehicle is in autonomous driving mode or braking mode (e.g., when automatic distance adjustment is activated).

[0021] Simultaneously, regenerative driving conditions are detected. This detection is also performed using appropriate sensors or through preset settings stored in the control unit.

[0022] In the context of this invention, a regenerative driving condition refers to a driving state in which the above-mentioned regenerative braking or regenerative braking is performed, that is, in the driving state, the motor is loaded with regenerative torque and thereby the vehicle is decelerated.

[0023] This regenerative operating condition is given, for example, during load changes. A rapid load change occurs if the motor, especially the electric motor as the drive unit, is under positive torque (i.e., driving torque) and the driver then leaves the accelerator pedal, and the driver subsequently wants to actively brake the vehicle by operating the brake pedal.

[0024] Other examples of regenerative driving conditions include the driver actively initiating braking by manipulating the brake pedal, engaging ACC or cruise control by manipulating the brake pedal, or so-called dual-pedal driving. In the case of dual-pedal driving, the accelerator pedal is operated simultaneously in addition to the brake pedal. Another regenerative driving condition is ending engine-off coasting, i.e., braking the vehicle while it is coasting with the internal combustion engine off by manipulating the brake pedal.

[0025] The specification then stipulates that the drive unit, preferably the motor itself, is placed in inertial driving operation. That is, the inertial driving regeneration torque, or drag regeneration torque, is adjusted on the drive unit to decelerate the vehicle. To achieve the target drag regeneration or target inertial driving regeneration, that is, to achieve the maximum drag regeneration torque, the drive unit requires a certain amount of time. To initiate inertial driving operation, the drive unit also requires a short duration; that is, there is a time delay between the driver leaving or removing the accelerator pedal, or between the drag regeneration initiation command from the control unit and the actual implementation of drag regeneration.

[0026] Then, the current actual driving torque is adjusted downward to the maximum or the desired target drag regeneration torque within a certain period of time.

[0027] Following the inertial travel operation of the drive unit, the regenerative braking is activated or initiated; that is, the regenerative torque is adjusted on the motor, preferably the motor serving as the drive unit, and the vehicle undergoes further deceleration. Here, a target total regeneration, i.e., a target total regenerative torque, is to be achieved through regenerative braking and inertial travel braking. This target total regenerative torque is the desired final braking torque. The target total regenerative torque is achieved by superimposing the inertial travel regenerative torque and the braking regenerative torque.

[0028] According to the present invention, regenerative braking is only performed by adjusting the regenerative torque on the motor once the difference between the actual driving torque, or the current actual inertial travel regenerative torque, and the target inertial travel regenerative torque falls below a predetermined limit. During the vehicle's inertial travel, the actual driving torque corresponds to the actual inertial travel regenerative torque. This difference is referred to as the so-called activation deviation in the context of the present invention. Here, activating regenerative braking, i.e., adjusting the regenerative torque according to the present invention, depends on the absolute difference between the actual driving torque and the target inertial travel regenerative torque. That is, regenerative braking is activated only when a definite activation deviation exists between the actual driving torque of the drive unit and the target inertial travel regenerative torque, or the target drag regenerative torque. Therefore, the difference between the actual driving torque and the target drag regenerative torque, as described by the activation deviation, must be below a predetermined threshold in order to require, activate, or initiate regenerative braking.

[0029] In an alternative embodiment of the invention, the regenerative torque is adjusted on the motor to activate regenerative braking only when the drive unit falls below a predetermined minimum actual drive torque or reaches a predetermined actual inertial travel regenerative torque during inertial travel. In this case, activating regenerative braking, i.e., adjusting the regenerative torque, is related to the relative value of the actual drive torque with respect to the target inertial travel regenerative torque according to the invention.

[0030] Regenerative braking is activated from the determined minimum actual driving torque, which can be 0-100% of the target inertial regenerative torque, particularly preferably 60-80% of the target inertial regenerative torque or the target drag regenerative torque. The range of 0-100% is conceivable in principle, where the relative value depends particularly on the absolute level of the target drag regenerative torque. This can be achieved not only within a vehicle (through different driving modes) but also between different vehicles (electric vehicles, hybrid vehicles, mild hybrid vehicles, etc.).

[0031] When the electric motor is used as a drive unit and as a motor, for example, when the electric motor first requires regenerative braking or regenerative torque, if the electric motor itself has already achieved most of its target inertial travel torque (preferably 60-80% of the inertial travel regenerative torque).

[0032] A particular advantage of this method is that the vehicle's driving (acceleration) and braking behaviors can be better estimated for the vehicle occupants, thereby preventing accidental braking (e.g., over-braking or two-phase braking). With the method according to the invention, the vehicle's deceleration becomes more harmonious, and thus more comfortable for the driver.

[0033] In addition to the method according to the invention, this application also claims a braking system for performing the method according to the invention, and also claims an electric vehicle and a hybrid vehicle including such a braking system.

[0034] The braking system according to the invention is a balancing braking system (also known as an integrated braking system). Unlike conventional braking systems, this balancing braking system is capable of balancing or oscillating between friction braking and regenerative braking. Particularly preferred is a pedal-decoupled braking system (also known as so-called "drive-by-wire" braking), in which the balance of braking torque between regenerative and friction braking is not apparent in the brake pedal.

[0035] The braking system according to the invention includes at least one motor, the motor being configured to enable the motor to perform regenerative braking of the vehicle.

[0036] As mentioned above, this motor is in particular an electric motor, which is used as a drive unit for vehicles.

[0037] In addition, the braking system includes at least one drive unit configured such that the drive unit can perform inertial braking of the vehicle during the inertial driving operation of the drive unit.

[0038] The drive unit can be the motor already mentioned, especially the electric motor that serves as the drive unit of the vehicle. Alternatively, as already mentioned above, it is also conceivable that the drive unit is an additional drive unit, such as an internal combustion engine, which decelerates or brakes the vehicle during inertial travel by means of inertial travel regenerative torque.

[0039] The vehicle is equipped with at least one control unit and / or at least one sensor unit (e.g., a known and existing brake regulation system in vehicles, such as DSC), which is configured to detect vehicle deceleration and regenerative driving conditions.

[0040] Furthermore, the braking system according to the invention includes at least one (additional or already mentioned) control unit configured to initiate regenerative braking of the vehicle or to adjust the regenerative torque on the motor, particularly the electric motor. The control unit is configured such that it activates regenerative braking only from the point where a predetermined actual driving torque is reached, or from the point where a predetermined difference between the current actual driving torque of the drive unit and the target inertial regenerative torque of the drive unit is reached or lowered.

[0041] In the claimed first embodiment, the braking system is arranged in an electric vehicle. Here, the electric vehicle according to the invention includes the braking system for performing the method according to the invention.

[0042] Here, the electrical mechanism serves as the vehicle's electric drive unit (also called an electric motor) and is responsible for providing energy to the vehicle's drive system. Here, the electric drive unit achieves not only inertial braking but also regenerative braking. Therefore, to achieve a predetermined target total regenerative torque, or predetermined total regeneration, the electric drive unit is first placed in inertial driving operation. Starting from the predetermined difference between the actual driving torque and the target inertial regeneration, regenerative braking is initiated or activated by adjusting the regenerative torque on the electric drive unit. Through the target inertial regeneration and the subsequently superimposed regenerative braking, the desired target total regeneration or target total regenerative torque is achieved, and the vehicle is braked accordingly.

[0043] The motor is thus configured such that it can operate not only during inertial travel (where inertial braking is performed) but also during regenerative operation (where regenerative braking of the vehicle is performed). Here, regenerative operation and inertial travel can be performed simultaneously or side-by-side.

[0044] Furthermore, protection is also claimed for a hybrid vehicle comprising a braking system according to the invention for implementing the method according to the invention.

[0045] Here, the hybrid vehicle includes at least one electric motor, particularly an electric drive unit, and another drive unit. Preferably, the vehicle can be driven not only by the electric drive unit but also by the other drive unit. Alternatively, the hybrid vehicle can be driven by only one of the two, particularly only by the electric motor. In the last mentioned case, the additional drive unit can be used to charge the electric motor's energy storage device, such as a capacitor or battery.

[0046] However, what is needed is that the motor or additional drive unit is configured such that the vehicle can be placed in both regenerative and inertial driving operations in order to achieve the stated goal of total regeneration.

[0047] These and other features are known not only from the claims and description but also from the drawings, wherein each feature is implemented individually or in combination in one embodiment of the invention and may constitute advantageous and insurable embodiments to which protection is claimed herein. Attached Figure Description

[0048] The present invention will be further described below with reference to embodiments.

[0049] The only Figure 1 The current braking torque (M) is shown here in Nm. istThe curve of the change of the current braking torque, which is applied to the vehicle according to time t during the method according to the invention. Detailed Implementation

[0050] To perform the method, the braking system of this embodiment includes an electric motor for driving the vehicle, which can achieve inertial braking of the vehicle by means of inertial torque during inertial driving operation, and can achieve regenerative braking of the vehicle during regenerative operation.

[0051] Under initial operating conditions, the driving torque M of the motor is ist It is within the positive range (not shown in the chart).

[0052] In the first step of this method, the vehicle's deceleration initiation, or deceleration intention, is detected, for example, by operating the vehicle's brake pedal or by reducing or ending operation of the accelerator pedal. This deceleration intention, or this deceleration initiation, occurs at time point t. brems The next step involves detecting regenerative braking conditions, that is, determining, through appropriate sensing mechanisms or calculations within the vehicle, that regenerative braking should be performed.

[0053] After detecting the driver's intention to decelerate or slow down, the inertial driving operation of the electric motor is initiated by: applying the actual driving torque M... ist Regenerative torque M for inertial driving to the target Schub However, in many driving conditions, the time point t when deceleration initiation or deceleration intention has been detected... brems The actual starting inertial driving operation, that is, the actual starting negative drive torque M through the inertial driving operation of the electric motor. ist The time point t Schub1 There is a time delay Δt between them.

[0054] If directly at time point t brems Adjusting regenerative braking, or regenerative torque M, after detecting deceleration expectation or deceleration initiation. Reku , such as this Figure 1 The dashed line in the middle (M) Reku As shown in the diagram, unstable braking behavior occurs because regenerative braking has begun, while inertial regeneration has not yet started due to a time delay ΔT. This braking behavior feels unstable and uncomfortable to the vehicle driver or occupants.

[0055] To avoid the aforementioned drawbacks, it is stipulated that only from the actual driving torque, or the actual inertial driving regenerative torque M, can the regenerative torque be achieved. ist Regenerative torque M of target inertial driving Schub The predetermined difference ΔM between them is used to adjust the regenerative torque M used to activate regenerative braking. RekuThis difference is also known as the activation bias ΔM.

[0056] Therefore, at time point t when activation bias is reached... Reku The regeneration torque M Reku It is superimposed or adjusted on the motor. The regenerative torque M is adjusted accordingly. Reku Activate regenerative braking.

[0057] Total regenerative torque, or total braking torque M Soll Then, by adjusting the target inertial driving regeneration torque M Schub and the adjusted regenerative torque M Reku To achieve this.

[0058] Therefore, stable braking behavior that feels comfortable to vehicle occupants was achieved.

Claims

1. A method for operating a vehicle braking system, wherein, The vehicle includes at least one motor capable of regenerative braking and a drive unit capable of inertial braking during inertial driving. The method comprises the following steps: Detect vehicle deceleration and start-up; Detect regenerative driving conditions; Initiate the inertial driving operation of the drive unit, wherein the current actual driving torque M of the drive unit is... ist The regenerative torque M is reduced to the target inertial braking torque. Schub ; Activate regenerative braking M Reku To achieve the target total regenerative torque M Soll ; Its characteristic is that only from the regenerative torque M during actual inertial driving ist Regenerative torque M of target inertial driving Schub The regenerative braking is activated only when the difference (ΔM) between them is lower than a predetermined limit.

2. A method for operating a vehicle braking system, wherein, The vehicle includes at least one motor capable of regenerative braking and a drive unit capable of inertial braking during inertial driving. The method comprises the following steps: Detect vehicle deceleration and start-up; Detect regenerative driving conditions; Initiate the inertial driving operation of the drive unit, wherein the current actual driving torque M of the drive unit is... ist The regenerative torque M is reduced to the target inertial braking torque. Schub ; Activate regenerative braking M Reku To achieve the target total regenerative torque M Soll ; Its characteristic is that only from the actual driving torque M ist Achieving the target inertial driving regenerative torque M Schub The regenerative braking is activated only when the predetermined relative value is reached.

3. The method according to claim 2, wherein, Once the actual driving torque M ist Achieving the target inertial driving regenerative torque M Schub When the regenerative braking is activated at 60-80% capacity.

4. The method according to any one of claims 1 to 3, wherein, Inertial braking is achieved through an internal combustion engine and / or an electric motor.

5. The method according to any one of claims 1 to 3, wherein, The vehicle is driven by an internal combustion engine and an electric motor.

6. The method according to any one of claims 1 to 3, wherein, The vehicle is driven by an electric motor, and the inertial braking is also performed by an electric motor.

7. The method according to any one of claims 1 to 3, wherein, As a regenerative driving condition, it detects load changes and / or ACC interruption and / or dual-foot driver and / or engine shutdown-coasting.

8. A braking system for a vehicle, said braking system being configured to perform the method according to any one of claims 1 to 7, said braking system comprising: At least one motor, the electrical mechanism being configured such that the motor can perform regenerative braking of the vehicle; At least one drive unit, the drive unit being configured such that the drive unit can perform inertial braking of the vehicle during inertial driving operation of the drive unit. At least one control unit and / or at least one sensor unit, the at least one control unit and / or at least one sensor unit being configured to detect deceleration start and regenerative driving conditions of the vehicle; And at least one control unit configured to initiate regenerative braking of the vehicle.

9. An electric vehicle, comprising the braking system of claim 8, wherein the electric vehicle includes a motor for driving the vehicle, wherein, The electrical mechanism is configured to enable inertial braking of the vehicle during inertial driving and regenerative braking of the vehicle during regenerative driving.

10. A hybrid vehicle, comprising the braking system of claim 8, wherein the hybrid vehicle includes at least one electric motor for driving the vehicle and an internal combustion engine for driving the vehicle, wherein, Regenerative braking can be performed by the motor during regenerative operation, and inertial braking can be performed by the internal combustion engine and / or by the motor during inertial driving operation.

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