WO2021219292A1

WO2021219292A1 - Method and controller for operating a drive train of an electrically driven motor vehicle

Info

Publication number: WO2021219292A1
Application number: PCT/EP2021/057181
Authority: WO
Inventors: Bastian Gebhard
Original assignee: Audi Ag
Priority date: 2020-04-29
Filing date: 2021-03-22
Publication date: 2021-11-04
Also published as: DE102020111605A1

Abstract

The invention relates to a method for operating a drive train (100) of an electrically driven motor vehicle (10) having a first axle (110) driven by at least one first electric machine (112) and having a second axle (120) driven by at least one second electric machine (122), wherein the second axle (120) can be activated and deactivated and has a disconnect clutch (125) by means of which the flux of force between the wheels (126, 127) and the second electric machine (122) can be interrupted. The method according to the invention comprises a plurality of steps for deactivating the second axle (120) and/or a plurality of steps for activating the second axle (120) while the motor vehicle (10) is being driven. The invention also relates to a controller (130) for a corresponding drive train (100), which controller is suitable for carrying out the method according to the invention.

Description

Method and control device for operating a drive train of an electrically powered motor vehicle

DESCRIPTION:

According to the preamble of claim 1, the invention relates to a method for operating a drive train of an electrically powered motor vehicle (electric car) with a first axle driven by at least one first electric machine and with a second axle driven by at least one second electric machine, wherein the second axle can be switched on and off and furthermore has a separating clutch with which the power flow between the wheels (the second axle) and the second electric machine or the axle drive (the second axle) can be interrupted. The invention also relates to a control device for such a drive train.

DE 102017215477 B4 already describes a method for operating a drive train of a motor vehicle with a four-wheel drive that can be switched on and off. The drive train (10) has a drive motor (22) designed as an internal combustion engine or as an electrical machine, a first axle (36) that can be driven by the drive motor (22) and one that can also be driven by this drive motor (22) via a first clutch (12) second axis (44), the second axis (44) being decoupled from the drive motor (22) with the aid of the first coupling (12) when the four-wheel drive is switched off. The second axle (44) has a second clutch (52) which is opened when the four-wheel drive is switched off, so that the cardan shaft (54) leading from the first clutch (12) to the second axle (44) is shut down and neither from the Wheels (46, 48) of the uncoupled axle (44) is still driven by the drive motor (22). This enables a particularly efficient two-wheel drive to be achieved.

Based on this prior art, the invention in a drive train of the type mentioned at the outset with at least one first electrical machine for driving the first axis and with at least one second electrical machine for driving the second axis is a jolt-free and, in particular, largely noise-free The second axis can be switched on and off during ferry operations.

This is achieved with the method according to the invention of claim 1 and with the method according to the invention of claim 3. Coordination of at least one method according to the invention is formed. Additional features result analogously for all subjects of the invention from the dependent claims, the following description of the invention and the figures.

The invention provides that to switch off the second axis, i. H. When changing from two-axle mode or four-wheel drive to single-axle mode or two-wheel drive, the following steps are carried out in this order during ferry operation: second axis, wherein the drive torque of the first electrical machine increases successively and at the same time the drive torque of the second electrical machine in the same measure, d. H. the increase in drive power on the first axle is successively reduced until (finally) the first axle takes over the entire drive or propulsion power (of the vehicle);

- After the first axis has taken over the entire propulsive power, carry out a zero torque control on the second axis, with the help of of the second electrical machine, the power loss generated by the dragging of the second axle is compensated for;

- Opening the separating clutch, in particular with the aid of an actuator. It is preferably provided that the second electrical machine turns off or turns off after the disconnecting clutch is opened, in particular to a standstill, with electrical energy preferably being recuperated (from the mechanical energy) and, in particular, being fed to a vehicle battery. The invention also provides that for connecting or reconnecting the second axis, i. H. When changing from single-axle mode or two-wheel drive to two-axle mode or four-wheel drive, the following steps must be carried out in this order during ferry operation:

- Starting or starting the second electric machine, in particular from standstill, and increasing its speed to a driving situation-dependent, in particular speed-dependent, target speed, the second electric machine taking into account a gear ratio (on the second axis) to the speed of the ( rotating) wheels (of the second axis) is synchronized; - Closing the separating clutch, in particular with the aid of an actuator, as soon as the speeds (of the second electric machine and the wheels of the second axis) are synchronized, with an equal speed between the coupling elements being achieved on the separating clutch. When the speed of the second electrical machine is increased, the set speed can be monitored and, if necessary, adapted to a changed driving situation or updated accordingly. The speed of the second electrical machine and / or the target speed can also be monitored and, if necessary, adjusted when closing or closing the separating clutch.

After opening the separating clutch or possibly already during the opening of the separating clutch and / or after closing the separating clutch or possibly already during the closing of the Separating clutch, a safety check can be carried out to ensure that the separating clutch is properly opened or closed. This can be done, for example, with the help of position sensors that are installed on the separating coupling. Alternatively, the check can take place with the aid of a test torque generated by the second electrical machine and the plausibility check of the rotational speeds that are then measured or recorded.

The second axle or the final drive can be switched off and / or switched on automatically depending on the driving situation, in particular with the help of a central control unit or a main control unit (ECU), which continuously checks during the ferry operation whether the vehicle is better in single-axle mode or two-wheel drive or should be moved in two-axis mode or four-wheel drive. The following can be used as a basis for decision-making: wheel speeds, speeds of the electrical machines, accelerator pedal position, brake pedal position, weather conditions (e.g. temperature and humidity), GPS data (for forecasting the further course of the road) and the like, including their gradients. Switching off and / or on can also be done at the driver's request or triggered manually by the driver. A disconnection and / or connection according to the invention is preferably controlled or coordinated in both cases by a main control unit (ECU) of the drive train.

The invention is explained in more detail below with reference to the figures. The features shown in the figures and / or explained below can also be general features of the invention independently of certain combinations of features and further develop the invention accordingly.

Fig. 1 shows a schematic representation of a drive train of a motor vehicle.

FIG. 2 illustrates in a schematic diagram the switching off of the second axle on the drive train of FIG. 1. FIG. 3 illustrates in a schematic diagram the connection of the second axle to the drive train of FIG. 1.

1 shows a drive train, designated as a whole by 100, for a motor vehicle 10 which is designed, for example, as a passenger vehicle and which has a purely electric drive (electric car). The drive train 100 comprises a first axle 110 and a second axle 120, which are designed as a front and flinter axle in accordance with the direction of travel F. The first axle 110 is driven by a first electric machine (first electric machine) 112, which is connected to the wheels (front wheels) 116 and 117 via a gear stage 113 and a differential gear 114, the electric machine 112, the gear stage 113 and the differential gear 114 form an axle drive for the first axle or front axle 110.

The second axle 120 is driven by a second electric machine (second electric machine) 122, which is connected to the wheels (flint wheels) 126 and 127 via a gear stage 123 and a differential gear 124, the electric machine 122, the gear stage 123 and the differential gear 124 form an axle drive for the second axle or Flinter axle 120, which is essentially independent of the axle drive of the first axle 110. The second axle 120 also has a separating clutch 125 with an actuator (separating clutch actuator) 125a, with which the power flow between the wheels 126, 127 and the second electrical machine 122 or the axle drive can be interrupted. The coupling elements of the separating coupling 125 are, for example, designed as coupling claws with face or face gears. The second axle 120 can be switched on and off during the ferry operation of the motor vehicle 10, whereby the drive train 100 can optionally be operated in two-axle mode or four-wheel drive or in single-axle mode or two-wheel drive. The disconnection and connection of the second axis or flinter axis according to the invention is described below with reference to FIGS. 2 and 3 120, the explanations apply mutatis mutandis to a drive train in which the front axle is formed as a second axle that can be switched on and off. Switching on and off is quick and takes place in the millisecond range, i.e. takes place in a fraction of a second.

The disconnection and connection of the second axis 120 is controlled by a main control unit (ECU) 130, which in this case functions as a kind of coordinator. The main control device 130 is designed accordingly and, in particular, is equipped with suitable software. The main control unit 130 communicates (for example via a CAN bus) with the power electronics 111 of the first electrical machine 112, with the power electronics 121 of the second electrical machine 122 and with the separating clutch 125 or with its actuator 125a. The main control device 130 is furthermore connected to various sensors with which, for example, rotational speeds and positions can be measured or detected, and possibly also to other control devices.

As illustrated in FIG. 2, during a ferry operation with drive or propulsive power on both axles 110, 120 (for example 40% on the front axle 110 and 60% on the rear axle 120) at time t _0, the second axis 120 initiated, this being done automatically or at the request of the driver. After a short latency period (to to ti), a redistribution or shifting of the drive or drive power begins at time ti by increasing the drive power on the first axle 110 and reducing the drive power on the second axle 120 by increasing the drive torque M _{T of} the first electrical machine 112 is gradually increased and at the same time the drive torque M _{2 of} the second electrical machine 122 is successively reduced or reduced to the same extent, so that the entire drive or propulsive power M _tot remains essentially unchanged (provided that the motor vehicle is not accelerating or decelerating at the same time 10 takes place, which can be taken into account accordingly). In other words: during the redistribution or relocation phase (ti to t ₂ _{), the drive torque M 2} is reduced on the second axle 120 to be switched off to the same extent as the drive torque M _{T is built up} on the first axle 110, which is still driving. At time t2, the first axle 110 has taken over the entire drive or propulsion power. A zero torque control is now carried out on the second axis 120 (t ₂ to t ₃ ), the power loss generated by dragging the second axis 120 being compensated for with the aid of the second electrical machine 122, so that no torque is applied to the separating clutch 125 more can be transmitted and this can therefore be opened without jerks and largely without force. At time t ₃ , the separating clutch 125 is then opened by the actuator 125a (t ₃ to t4), whereby any flow of force or torque between the rotating wheels 126, 127 and the second electrical machine 122 or the rotating wheels is interrupted 126, 127 are decoupled from the final drive and only the differential gear 124 rotates without significant resistance. This realizes a particularly efficient two-wheel drive.

After the separating clutch 125 is opened, the second electric machine 122 can turn _{off from time t 4} _{, its speed n 2} reducing to a standstill (time ts) (provided that the second axis 120 is not switched on again during this time). The speed n _{2 of} the second electrical machine 122 is preferably reduced or reduced only after a safety check (see above) in order to ensure that the separating clutch 125 is open. During this turning or stopping phase (U to t ₅ ), electrical energy can be recuperated by the second electrical machine 122. By switching the second electrical machine 122 to the recuperation mode, a braking effect that shortens the turning-out or stopping time can also be generated.

As illustrated in FIG. 3, _{the switching on of the second axle 120 is initiated at time T 0} , this being done automatically or at the driver's request. After a short latency period (T ₀ to Ti), the second electrical machine 122 is _{started or started from standstill (n 2} = 0) at time Ti and its speed n _{2 is} increased, in particular adjusted, to a driving situation-dependent target speed n _{so n,} where the speed n _{2 of} the second electrical machine 122 taking into account the translation Zung ratio (in the gear stage 123 and / or in the differential gear 124) to the speed of the wheels 126, 127 is synchronized (Ti to T ₂ ). The target speed n _so n thus results from the current speed of the wheels 126, 127, corrected by the ratio of the axle ratio. Meanwhile, the setpoint speed n _SOii can be checked and, if necessary, adapted to a changed driving situation or updated accordingly.

At time T ₂ , the separating clutch 125 is closed by the actuator 125a (T ₂ to T ₃ ) as soon as the speeds are synchronized (ie n ₂ = n _S0 n) and thus a synchronous speed or speed equality at the separating clutch 125 (possibly below Taking into account a tolerance of, for example, 30 rpm) between the coupling elements is achieved. During the closing of the separating clutch 125, the speeds n ₂ and n _{SOii can be} monitored and, if necessary, adjusted. After the closing, a safety check (see above) is preferably carried out in order to ensure that the separating clutch 125 is closed. Since after (ie from T ₃ or after the safety check) the second electrical machine 122 can be used to drive the motor vehicle 10 or also for recuperation or to brake the motor vehicle 10.

Claims

PATENT CLAIMS:

1. A method for operating a drive train (100) of an electrically driven motor vehicle (10) with a first axle (110) driven by at least one first electrical machine (112) and with a second axle (110) driven by at least one second electrical machine (122) Axle (120), wherein the second axis (120) can be switched on and off and has a separating clutch (125) with which the power flow between the wheels (126, 127) and the second electrical machine (122) can be interrupted, characterized that the following steps are carried out to switch off the second axle (120) during ferry operation:

- Increase the drive power on the first axis (110) and reduce the drive power on the second axis (120), the drive torque (Mi) of the first electrical machine (112) increasing and at the same time the drive torque (M ₂ ) of the second electrical machine's rule (122) is successively reduced to the same extent until the first axis (110) takes over the entire drive power; - Execution of a zero torque control on the second axis (120), with the aid of the second electrical machine (122) the power loss generated by the dragging of the second axis (120) is compensated;

- Open the disconnect coupling (125).

2. The method according to claim 1, characterized in that the second electrical machine (122) after opening the separating clutch (125) turns to a standstill (n ₂ = 0), whereby electrical energy is recuperated.

3. The method, in particular according to claim 1 or 2, for operating a drive train (100) of an electrically driven motor vehicle (10) with a first, of at least one first electrical machine (112) driven axle (110) and with a second axle (120) driven by at least one second electrical machine (122), the second axle (120) being able to be switched on and off and having a separating clutch (125) with which the power flow between the wheels (126, 127) and the second electrical machine (122) can be interrupted, characterized in that the following steps are carried out to connect the second axle (120) during ferry operation: electric machine (122) and increasing its

Speed (n ₂ ) to a target speed (n _so n) dependent on the driving situation, the second electric machine (122) being synchronized to the speed of the wheels (126, 127) taking into account a gear ratio; - Close the clutch (125) as soon as the speeds are synchro nized (n ₂ = n _so n).

4. The method according to claim 3, characterized in that when increasing the speed (n ₂ ) of the second electrical machine

(122) the target speed (n _S0 n) is monitored and, if necessary, adapted to a changed driving situation.

5. The method according to claim 3 or 4, characterized in that when the clutch (125) closes, the speed of the second electrical machine (n ₂ ) and the target speed (n _S0 n) are monitored and adapted if necessary. 6. The method according to any one of the preceding claims, characterized in that after opening the separating clutch (125) and / or after closing the separating clutch (125) a safety check is carried out.

7. The method according to any one of the preceding claims 1 to 6, characterized in that depending on the driving situation, the switching off and / or switching on of the second axle (120) takes place automatically.

8. The method according to any one of the preceding claims 1 to 6, characterized in that the switching off and / or switching on of the second axle (120) is triggered manually by the driver.

9. Control device (130) for the drive train (10) of an electrically driven motor vehicle (10) according to the preamble of claim 1, wherein this control device (130) is designed to control at least one procedural Ren according to one of the preceding claims.