Method and control device for operating an all-wheel drive vehicle associated with a road

Abstract

This invention relates to a method and control apparatus for operating an all-wheel-drive vehicle associated with a road, the vehicle having an electronic control unit, an electric primary motor associated with a primary axle, and an electric secondary motor associated with a secondary axle. The control unit includes a dynamic function module that, upon identifying a defined dynamic driving mode of the driver, determines a predetermined variation curve of the total torque through the activated primary motor and the deactivated secondary motor within a preset time window during single-axle operation, based on the driver's desired gradient. Even if the predetermined variation curve of the total torque is lower than the maximum possible torque of the primary motor, it is adjusted according to the same predetermined axle allocation coefficient by reducing the rated torque of the primary motor and by activating and increasing the rated torque of the secondary motor. A predetermined delay time is pre-determined when the secondary motor is required to be activated from its deactivated magnetic field.

Description

Technical Field

[0001] The present invention relates to a method and control apparatus for operating an all-wheel drive vehicle associated with a road, the all-wheel drive vehicle having at least one electronic control unit, a first electric drive motor associated with a primary axle (e.g., the rear axle), and a second electric drive motor associated with a secondary axle (e.g., the front axle). Background Technology

[0002] For example, a road-related hybrid vehicle is known from DE102014200427A1, which has two different drive units on corresponding axles. The different drive units, in particular an internal combustion engine and an electric drive motor, have different dynamic characteristics; that is, the rated torque on each axle cannot be adjusted as quickly. In particular, the torque increase by means of the electric drive motor is significantly faster than the same torque increase by means of the internal combustion engine. The electronic control devices known from DE102014200427A1 are specifically designed to address the problems of these different drive units.

[0003] In so-called road-connected all-wheel-drive vehicles, the primary and secondary motors are coupled in a driving relationship via the wheels, not via a clutch. Such road-connected all-wheel-drive vehicles are also known as "axle-split" vehicles. These all-wheel-drive vehicles typically operate with only the primary motor in a first operating mode (preferably an efficiency-optimized drive mode) and can also operate as an all-wheel-drive vehicle with two drive motors in a second operating mode (preferably a power-optimized drive mode), in which the secondary motor can be automatically engaged and disengaged.

[0004] Hereinafter, "electric drive motor" will be abbreviated as "electric motor" and "driving torque" will be abbreviated as "torque". Summary of the Invention

[0005] The objective of this invention is to improve the type of all-wheel drive vehicle described at the beginning in terms of driving power, efficiency, and comfort.

[0006] According to the present invention, the task is accomplished by a control device for operating a road-connected all-wheel-drive vehicle according to the present invention, an electronic control unit according to the present invention, and a computer program product according to the present invention.

[0007] This application relates to different strategies for automatically switching an electrically powered secondary motor on and off in the presence of a primary motor that is also electrically powered. In the prior art, driving stability is generally emphasized by distributing driving torque to the axle used to improve traction.

[0008] This invention relates to a control device for operating an all-wheel-drive vehicle associated with a road, the all-wheel-drive vehicle having at least one electronic control unit, a first electric drive motor (primary motor) assigned to a primary axle, and a second electric drive motor (secondary motor) assigned to a secondary axle. The control unit includes a dynamic function module that, during a (single-axle) operating mode where the primary motor is activated and the secondary motor is deactivated, when a defined dynamic driving mode of the driver is identified by means of a driver expectation gradient, determines a preset variation curve of the total torque for a predetermined time window based on a new driver expectation. Even if the preset variation curve of the total torque is lower than the maximum possible torque of the primary motor, the preset variation curve of the total torque is adjusted according to a preset axle allocation coefficient by reducing the rated torque of the primary motor and by activating and increasing the rated torque of the secondary motor, and at the end of the time window, the secondary motor is deactivated again, and the primary motor again provides the total rated torque further desired by the driver expectation.

[0009] The control unit is also configured such that when the activation of the secondary motor is requested from the closed magnetic field of the secondary motor, the required magnetization time is predetermined as a preset delay time. The primary motor individually provides the required total rated torque for the duration of this delay time. The rated torques of the two electric drive motors are then synchronously adjusted according to a preset all-wheel drive distribution coefficient.

[0010] The activation of the secondary motor's magnetic field, and thus the delay time, begins when the driver anticipates recognizing the inertial coasting-traction transition (Schub-Zugwechsel). Alternatively or additionally, the activation of the secondary motor's magnetic field, and thus the delay time, may begin upon the recognition of an increase in the load on the primary motor.

[0011] The driver's defined dynamic driving mode is identified by using the driver expectation gradient, preferably when the current driver expectation gradient exceeds a preset threshold.

[0012] Preferably, the preset variation curve of the total rated torque is determined based on the driver's expected gradient and the difference between the rated torque preset by the driver's expected torque and the currently available torque of the primary motor.

[0013] This invention is based on the following considerations:

[0014] The basic concept is an all-wheel drive strategy for an electrified vehicle in an unstable process with two electric drive motors, namely a first electric (drive) motor on the primary shaft and a second electric (drive) motor for the secondary shaft.

[0015] For efficiency reasons, it may be meaningful to operate in single-axle operation (rear-wheel drive or front-wheel drive) for as long as possible in electrified all-wheel drive vehicles. The axle driven in preferred single-axle operation is called the primary axle.

[0016] In dynamic (“unstable”) driving modes, it is meaningful for power reasons to engage the second axle (secondary axle) earlier in order to produce a sporty power response (also known as a “response” or “punch”) of the vehicle. Dynamic driving modes are particularly identified by the steep gradient of accelerator pedal operation (also known as “tip-in”).

[0017] Each drive shaft (the primary shaft with a primary motor and the secondary shaft with a secondary motor) is coupled only in at least one electric drive controller via corresponding software. There is no coupling via a longitudinal clutch in the transfer case as is present in conventional all-wheel drive vehicles.

[0018] Because each of the two drive shafts can be driven by at least one electric motor, they can be de-energized by disconnecting the magnetic field (in the case of a separately excited motor) when they cannot be decoupled from the drive via a clutch. In this invention, such a clutch should preferably be omitted for cost reasons.

[0019] Delayed coupling of the secondary shaft or delayed magnetic field excitation of the secondary motor and the resulting (too) late all-wheel engagement result in uncomfortable jolts during hard acceleration, delays in adjusting rated torque, reduced traction, and / or excessively high torque gradients on the drive shaft.

[0020] The control device according to the invention includes an electronic control unit that calculates and presets a defined all-wheel distribution in the form of an axle distribution coefficient based on the recognition of sudden acceleration. Sudden acceleration is preferably recognized via an existing driver expectation gradient exceeding a threshold and preferably via the difference (Delta) between the driver expectation and the currently available torque of the primary drive unit; that is, sudden acceleration is recognized when the acceleration of the accelerator pedal (or other driver-expected operating element) is greater than a preset first threshold and preferably when the difference between the actual torque of the primary motor and the rated torque of the primary motor preset by the new driver expectation is greater than a preset second threshold. This allows for earlier all-wheel engagement or secondary motor engagement.

[0021] After recognizing sudden acceleration, according to the invention, a defined time window is initiated within which a predetermined total rated torque variation curve (height and gradient) based on the new driver's expectation is determined, and adjustments are made by means of a predetermined axle distribution coefficient using two motors on two axles. Here, the rated torque of the primary motor is reduced and the rated torque of the secondary motor is increased.

[0022] The magnetic field of the secondary motor is preferably turned off during inertial coasting. If a transition from coasting to traction is detected within the range of sudden acceleration, the magnetic field must be (re-energized) from the turned-off magnetic field before the torque can be increased. This creates a delay time before the rated torque of the secondary motor can be increased.

[0023] In the first alternative, the rated torque of the secondary motor can be temporarily compensated by a corresponding increase in the rated torque of the primary motor, provided that the rated torque of the primary motor is still lower than the maximum possible torque of the primary motor.

[0024] However, in the advantageous second alternative, the increase in the total rated torque is generally delayed by the time required for the excitation magnetic field (on the order of 30 ms). The inventors have recognized that this delay is imperceptible to the driver (i.e., not "distinguishable"). Therefore, the rated torque of both shafts can be increased simultaneously, thereby further improving comfort.

[0025] The following method flow can be provided in advance through the present invention, for example:

[0026] 1. Calculate the maximum adjustable torque for each axis based on operating parameters, such as temperature or slippage.

[0027] 2. Check whether the total rated torque expected by the driver is less than the maximum adjustable torque of the primary shaft.

[0028] 3. Calculate the gradient of the driver's expected rise and the difference between the torque corresponding to the driver's expected rise before the rise and the torque corresponding to the driver's expected rise after the rise (also known as the "difference" or "bias").

[0029] 4. Taking into account the maximum adjustable torque of the two shafts, calculate the all-wheel drive distribution coefficient based on the results in 3.

[0030] 5. Calculate the dynamic function, which can adjust the total rated torque change curve of the motors of the two axes through the dynamic function for a preset time window (based on the predetermined bias and gradient of the driver's expected increase).

[0031] 6. Detect inertial gliding-traction conversion and vice versa, detect traction-inertial gliding conversion.

[0032] 7. Calculate the all-wheel drive distribution coefficient based on preset conditions, such as the load status of the primary motor.

[0033] 8. Check if the threshold is exceeded in order to pre-activate the coupling or excitation of the secondary motor and achieve the preset all-wheel drive distribution coefficient.

[0034] With this invention, it is no longer only the adjustment of the total torque that is given the highest priority, but also the optimized distribution of torque on each axis is taken into account in relation to efficiency, power and comfort. Attached Figure Description

[0035] The details of the invention are illustrated in more detail below with the aid of the accompanying drawings. In the drawings:

[0036] Figure 1 A schematic diagram of a road-connected electric all-wheel drive vehicle according to the present invention is shown, the electric all-wheel drive vehicle having components important for the dynamic functions according to the present invention;

[0037] Figure 2 A graph illustrating the basic concept of the control device according to the present invention;

[0038] Figure 3 The graph shows the problems caused by the magnetic field that de-excites the secondary motor, for example, in inertial gliding;

[0039] Figure 4 Show Figure 3 A graph of the first solution to the problem shown; and

[0040] Figure 5 This demonstrates an application area. Figure 3 The graph shows the second solution to the problem illustrated. Detailed Implementation

[0041] exist Figure 1 The diagram illustrates a so-called road-connected all-wheel-drive vehicle, which has a first electric motor 1 as a primary motor and a second electric motor 2 as a secondary motor. The first electric motor acts as a drive motor, for example, on the rear axle, and the second electric motor acts as a drive motor on the front axle. The primary motor 1 may have its own electromechanically connected sub-control unit 4, and the secondary motor 2 may have its own electromechanically connected sub-control unit 5. The two sub-control units 4 and 5 are connected to a central electronic control unit 3.

[0042] The method for controlling an electric all-wheel-drive vehicle is implemented via a central electronic control unit 3, which has corresponding programmable functional modules and connections to required sensors, actuators, and / or sub-control units 4 and 5. According to the invention, the control unit 3 includes, for example, dynamic functional modules 6 in the form of software programs (computer program products), for controlling... Figures 2 to 5 The description further explores the design scheme and working principle of the dynamic functional module.

[0043] Figure 2 representative of Figures 2 to 5 The following graph is shown, plotting time t on the x-axis and torque M on the y-axis. The driver's desired accelerator pedal position FP is represented by a dashed line. Continuous lines represent the variation of the total rated torque M_soll_ges as interpreted by the driver's desired FP via the accelerator pedal. The dashed line represents the rated torque M_soll_1 of the primary motor 1, and the dotted line represents the rated torque M_soll_2 of the secondary motor 2. The maximum adjustable torque via the primary motor 1 is represented by M_max_1.

[0044] according to Figure 2 The graph initially shows coasting operation with an all-wheel drive distribution coefficient F = 100:0 and negative torque M_soll_1. Torque M_soll_2 is zero because secondary motor 2 is initially off.

[0045] At time t0, the dynamic driver expectation (tip-in situation) is identified by the steep gradient of the accelerator pedal position FP. The dynamic function 6 according to the invention begins with a preset time window Δt. According to the invention, within the time window Δt, the change curve (height and gradient) of the total rated torque M_soll_ges based on the new driver expectation FP is determined and provided by means of a preset axle allocation coefficient F (here, 50:50) through two motors 1 and 2 on the two axles. Here, the rated torque M_soll_1 of the primary motor 1 is reduced and the rated torque M_soll_2 of the secondary motor 2 is increased. At the end of the time window Δt, the secondary motor 2 is comfortably shut off again, and the primary motor 1 again provides the total rated torque further expected by the driver expectation FP.

[0046] Figure 3 This discussion addresses the issue of decoupling secondary motor 2 by disconnecting AM via a magnetic field during inertial coasting. If, within the scope of detecting sudden acceleration, a transition from inertial coasting to traction is detected at time t1, then before the torque M_soll_2 of secondary motor 2 can be increased, the magnetic field must first (re-excite) the closed magnetic field. Therefore, as in... Figure 4 As shown, there is a delay time Δt_v before the rated torque M_soll_2 of the secondary motor 2 is increased.

[0047] exist Figure 4 In the advantageous improvement of the invention shown, the increase in the total constant torque M_soll_ges is generally delayed by the delay time Δt_v required for the excitation magnetic field. Thereafter, the rated torques M_soll_1 and M_soll_2 of the two motors 1 and 2 are increased synchronously.

[0048] Another application of delaying the total constant torque M_soll_ges by the overall delay time Δt_v required for the excitation magnetic field is performed when the primary motor 1 should be supported by the secondary motor 2 under increased load conditions (e.g., in the case of overheating or slippage). This embodiment concludes in Figure 5 As shown in the image.

Claims

1. Control device for operating an all-wheel drive vehicle associated with a roadway, the control device having at least one electronic control unit (3), the all-wheel drive vehicle having an electric primary motor (1) assigned to a primary axle and having an electric secondary motor (2) assigned to a secondary axle, wherein The control unit (3) includes a dynamic function module (6) that, during the operation mode in which the primary motor (1) is activated and the secondary motor (2) is deactivated, when the driver's limited dynamic driving mode is identified by means of the driver expectation gradient, the total torque (M_soll_ges) is determined for a preset time window (Δt) by a new driver expectation preset change curve, even if the preset change curve of the total torque is lower than the maximum possible torque of the primary motor (1), the preset change curve of the total torque is also adjusted according to a preset shaft distribution coefficient (F) by reducing the rated torque (M_soll_1) of the primary motor (1) and by activating and increasing the rated torque (M_soll_2) of the secondary motor (2), and at the end of the time window (Δt), the secondary motor (2) is turned off again, and the primary motor (1) again provides the total rated torque further expected by the driver expectation (FP); The control unit (3) is further configured such that when the secondary motor (2) is required to be activated from the closed magnetic field of the secondary motor (2), the required magnetization time is predetermined as a preset delay time (Δt_v), the primary motor (1) provides the required total rated torque separately for the duration of the preset delay time (Δt_v), and then the rated torque (M_soll_1) of the primary motor (1) and the rated torque (M_soll_2) of the secondary motor (2) are synchronously adjusted according to a preset all-wheel drive distribution coefficient (F). The magnetic field of the secondary motor (2) is switched on, and the resulting delay time (Δt_v) begins when the driver expects (FP) to identify the inertial coasting-traction transition, or when the load on the primary motor (1) is detected to be increased.

2. The control device according to claim 1, characterized by When the current driver expectation gradient exceeds a preset threshold, the driver's limited dynamic driving mode is identified by using the driver expectation gradient.

3. The control device according to claim 1 or 2, characterized by The preset variation curve of the total rated torque (M_soll_ges) is determined based on the driver expectation gradient and the difference between the rated torque preset by the driver expectation (FP) and the currently available torque of the primary motor (1).

4. An electronic control unit (3), the electronic control unit being used in a control device according to any one of claims 1 to 3, the electronic control unit having a dynamic functional module (6) in the form of a computer program product.

5. A computer program product for use in the electronic control unit (3) of the control device according to any one of claims 1 to 3.

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