DE102019203985A1 - Method for controlling a drive train, controller, drive train and motor vehicle - Google Patents

Abstract

The present invention relates to a method for controlling a drive train (2), the drive train (2) having a first electric machine (3) and a second electric machine (6), the method comprising: operating (21) the first electric machine (3) in a regenerative manner ), and supplying (26) the electrical energy generated by the first electrical machine (3) to the second electrical machine (6), a resulting loss of efficiency being used to brake the drive train (2).

Description

The invention relates to a method for controlling a drive train, a controller, a drive train and a motor vehicle.

In general, electrically or hybrid-powered (motor) vehicles are known in which, for example, more than one traction motor or drive motor is provided, e.g. B. a front and a rear axle drive.

If the battery charging power is limited, it may happen that the battery cannot be braked electrically due to the applied battery charging limits, since the electrical energy generated can no longer be fed to the battery. This can lead to an increased load on the hydraulic brake, especially on long downhill drives. In addition, it can be difficult in such cases to represent a reproducible overrun behavior or a reproducible vehicle deceleration.

In such cases, it is known in principle to convert the electrical energy into heat, for example by increasing an electrical auxiliary load. This can e.g. B. by connecting or increasing the (electrical) load of a high-voltage air conditioning compressor, by operating a PTC heater, by increasing a voltage in the 12V electrical system of the motor vehicle, etc. It is also known to increase the efficiency of an electric machine via settings of the power electronics , e.g. B. by changing the IGBT control to worsen and thus convert excess electrical energy into heat. However, these solutions have the disadvantages that the electrical braking energy that can be converted into heat is relatively low, that it is more difficult to scale, since, for example, the PTC typically only has fixed power levels and that it cannot be regulated as dynamically as the motor vehicle bus system, for example, only fixed Has maturities. For example, the LIN bus has fixed LIN transit times, which can prevent dynamic regulation.

Furthermore is from the German Offenlegungsschrift DE 10 2010 045 030 A1 a method for controlling a drive system of a hybrid vehicle is known, in which a braking function for braking the motor vehicle is provided by a generator operating function of an electric traction machine. If a high-voltage battery is in a charge limitation state, the electrical energy generated by the electrical traction machine is fed to a motor-generator which entrains an internal combustion engine. The disadvantage of this solution is that dragging a cold internal combustion engine for a long time can lead to unnecessary wear. In addition, this solution is not applicable to pure electric vehicles.

From the German Offenlegungsschrift 10 2013 111 951 A1 A method for operating a hybrid motor vehicle is known in which, in the event of a cold start and the simultaneous presence of a state of charge of a traction battery above a charging threshold, an internal combustion engine is prevented from taking over thrust to brake the motor vehicle. A purely electrical operating state can thus be conveyed to a user of the hybrid motor vehicle. The disadvantage of this method is that the braking effect is reduced by suppressing the transfer of thrust and its use in purely electric vehicles is not possible.

The object of the present invention is to provide a method for controlling a braking process in a drive train, a controller, a drive train and a motor vehicle which at least partially overcome the above-mentioned disadvantages.

This object is achieved by the method according to the invention according to claim 1, the control according to claim 7, the drive train according to claim 8 and the motor vehicle according to claim 10.

• Generatorisches Betreiben der ersten Elektromaschine, und
• Zuführen der von der ersten Elektromaschine erzeugten elektrischen Energie zur zweiten Elektromaschine, wobei eine dabei entstehende Wirkungsgradverlustleistung zum Bremsen des Antriebsstrangs verwendet wird.

According to a first aspect, the present invention provides a method for controlling a drive train, the drive train having a first electric machine and a second electric machine, the method comprising:

• Generator operation of the first electric machine, and
• Supplying the electrical energy generated by the first electrical machine to the second electrical machine, with a resulting loss of efficiency being used to brake the drive train.

According to a second aspect, the present invention provides a controller for a drive train, the drive train having a first electric machine and a second electric machine, the controller being set up to carry out the method according to the first aspect.

According to a third aspect, the present invention provides a drive train for a motor vehicle that comprises a first electric machine, a second electric machine and a controller that is configured to carry out the method according to the first aspect.

According to a fourth aspect, the present invention provides a motor vehicle with a drive train according to the third aspect.

Further advantageous embodiments of the invention emerge from the subclaims and the following description of preferred exemplary embodiments of the present invention.

As stated, some exemplary embodiments relate to a method for controlling a drive train, in particular for controlling a braking process and / or overrun recuperation, the drive train having a first electric machine and a second electric machine, the method comprising operating the first electric machine as a generator, and supplying the from The electrical energy generated by the first electric machine to the second electric machine, with a resulting loss of efficiency being used to brake the drive train.

Thus, in some exemplary embodiments, it is possible to display a negative electrical torque, for example a wheel torque, and thus a deceleration of a drive train (e.g. a vehicle) with limited battery charging power, for example to relieve a mechanical brake system and to e.g. B. to represent a reproducible driving behavior such as a reproducible vehicle deceleration.

In some exemplary embodiments, an additional braking deceleration power is generated (e.g. vehicle deceleration by braking or displaying a drag torque) by converting the mechanical power of the first electric machine (which is in generator mode) on a first axle (e.g. a front axle / primary axle ) in electrical power and use of this generated electrical power in the second electric machine (which is in motor operation) on a second axle (e.g. a rear axle / secondary axle (or vice versa)) in order to generate mechanical power again without this to change the total wheel torque acting on the drive train (e.g. the vehicle).

That is, through the conversion of the power and the existing efficiencies of the two electric machines, a power loss arises that can be used as (additional) drive or vehicle deceleration by using the torque of the second electric machine and, for example, not or only reduced a mechanical one Brake is used. This can relieve a (hydraulic) brake. The resulting electrical braking torque can be varied continuously via the amount of electrical power converted.

As a result, some exemplary embodiments use the efficiency losses of two electric machines working "against each other" to convert electrically generated recuperation energy into heat (e.g. in the two electric machines, in the power electronics, in the entire drive train (e.g. tires, gear ratios or gearboxes, drive shafts, which have corresponding friction losses deliver, etc.)).

The drive train can be designed for a motor vehicle, such as an electric vehicle, but also a hybrid vehicle which, for example, has an internal combustion engine in addition to the first and second electric machines, for example a gasoline engine, diesel engine or gas engine, etc.

In some exemplary embodiments, however, the method is also used in other drive trains. For example, some exemplary embodiments relate to industrial robots with a plurality of electrically operated axes that are used to move parts of the industrial robot, such as arms and the like, and in which some axes are operated as motors and others as generators in certain situations. Feeding electrical energy back from the robot into a power grid can be difficult due to the influence of the grid frequency. It is currently known to convert excess recuperation energy in industrial robots into heat via an ohmic resistor or to store it temporarily in an electrical capacitor. These components can consequently be dispensed with in some exemplary embodiments or they can be designed to be smaller. In contrast to the hybrid and electric vehicles described above, the axes of a robot typically cannot “work against one another”, as described herein. In some exemplary embodiments, however, it is provided that a necessary motor movement is carried out simultaneously on one or more axes during recuperation or that an “unnecessary” motor movement is also carried out on one or more axes that are not used at this point in time, whereby when the desired one is reached Target position these axes must have taken the intended position again.

The first or the second electric machine can be an asynchronous machine or a permanently excited synchronous machine or the like.

Without restricting the present invention in this regard, the first electric machine can be used to drive a first axle, e.g. B. a front drive, provided or designed as a motor starter generator and can, for example. Via a transmission and / or a clutch, a Drive the front axle or a front wheel. Accordingly, in some exemplary embodiments, the first electric machine can also be designed as a wheel hub motor or the like and can, for example, drive a front wheel directly.

Without restricting the present invention in this regard, the second electric machine can be used to drive a second axle, e.g. B. a rear drive can be provided and can, for example. Drive a rear axle or a rear wheel via a gearbox and / or a clutch. Accordingly, in some exemplary embodiments, the second electric machine can also be designed as a wheel hub motor or the like and can drive a rear wheel directly.

Even if the following description refers to a front axle and a rear axle, the present invention is not limited to drive trains or vehicles with two axles, but some exemplary embodiments also relate to drive trains or vehicles with more than two axles. The person skilled in the art will appreciate that the principle can be scaled as required via the number of electrical machines and / or via the number of axes.

In addition, the first electric machine can of course also be provided on a second axle (e.g. rear drive) and the second electric machine on a first axle (e.g. front drive).

In some exemplary embodiments, the first electric machine has a power which is less than the power of the second electric machine, without the present invention being restricted in this regard, and in other exemplary embodiments it is exactly the opposite or the powers are (almost) identical.

The same applies to the efficiencies of the first and second electric machines, which can be identical or different.

Furthermore, the first electric machine can also be operated in traction mode and designed for this, and conversely, the second electric machine can also be designed for generator operation.

As mentioned, the method comprises operating the first electric machine as a generator and supplying the electrical energy generated by the first electric machine to the second electric machine, with a resulting loss of efficiency being used to brake the drive train, as has already been explained above.

In some exemplary embodiments, the method is carried out as a function of a battery status. For example, the method can be carried out when a predefined state of a battery is recognized, which would otherwise be charged by the generator operation of the first electric machine. For example, the battery may be too hot, i. the battery temperature can be above a temperature threshold, beyond which the battery should not be charged, the battery state of charge can be too high so that further charging of the battery would lead to overcharging, etc. This has the advantage that the method is only carried out then when the battery is not in a state in which it can be charged, so that the electrical energy can otherwise be used for recuperation and for charging the battery.

In some exemplary embodiments, the first electric machine is operated as a generator by mechanical thrust and the second electric machine is then towed, since the energy supplied to it is not sufficient due to efficiency losses to provide the same torque that acts on the first electric machine. As stated above, in the case of a vehicle, for example, when driving downhill, thrust can be applied to the first electric machine so that it is operated mechanically and generates electrical energy due to the generator operating mode. Since the first electric machine has a predetermined efficiency that is less than 100%, and the second electric machine also has a predetermined efficiency that is less than 100%, and the second electric machine is only fed with the electrical energy generated by the first electric machine is, the torque generated by the second electric machine is smaller than that which acts on the first electric machine, so that the second electric machine is dragged and therefore a braking effect is achieved. This effect is intensified by further losses in efficiency, whereby the losses in efficiency can arise, for example, from mechanical friction, can arise in the power electronics, etc. Thus, advantageously, for example, the actuation of a brake can be omitted, so that the brake system is protected. Furthermore, any other measures known in the art, e.g. B. influencing the efficiency of the first or the second electric machine, the operation of electrical consumers, etc., can be added to any desired braking power.

In some exemplary embodiments, the method is carried out as a function of a predetermined route for a motor vehicle. For example, it can be recognized that the predetermined route, either by a User input, is calculated by a navigation device, is predetermined by a most likely route or the like, contains sections with corresponding positive and negative gradients. For example, a battery can be deliberately discharged when driving uphill so that the electrical energy generated by recuperation when driving downhill can be used to charge the battery.

In some exemplary embodiments, the method further comprises determining a braking power to be provided. The braking power can be determined, for example when driving downhill, in such a way that a current speed of the vehicle is maintained, a target speed of the vehicle is reached and then maintained, etc. In this way, the driving properties of a motor vehicle can advantageously be improved.

In some exemplary embodiments, the method further includes setting a gear ratio for the second electric machine as a function of the determined braking power to be provided. Since the gear ratio has an influence on the efficiency loss, for example the gear itself and / or parts of the drive train or the second electric machine itself can have a speed-dependent efficiency, the braking power can be appropriately adapted to current operating conditions.

Some embodiments relate to a control for a drive train, e.g. B. a motor vehicle, as described herein, wherein the controller is set up to carry out the method, as stated.

The control is to be understood functionally here and it can include, for example, control elements of an engine control, a hybrid coordinator, a battery management system, a vehicle control device and the like. In some exemplary embodiments, the controller includes one or more (micro) processors, logic circuits and the like, a volatile and / or non-volatile memory in which, for example, data required for the method are stored, an interface for communication with other elements of the vehicle, e.g. B. the first and second electric machine, automatic transmission, etc.

Some exemplary embodiments relate to a drive train for a motor vehicle, as described herein, the drive train having the first and the second electric machine and the controller described herein, which is set up to carry out the method described herein.

In some exemplary embodiments, the drive train further comprises a first axle (e.g. front axle) and a second axle (e.g. rear axle), the first electric machine being arranged on the first axis and the second electric machine being arranged on the second axis, as it was already described above.

In some exemplary embodiments, the first electric machine and the second electric machine are arranged together on the first or the second axis (or a further axis, if present). The first and the second electric machine can be directly mechanically connected to one another, so that, for example, transverse dynamic effects can be avoided. For this purpose, in some exemplary embodiments, the first and second electric machines are arranged one behind the other and not, for example, close to the wheels (e.g. not one on the left and the other on the right of the axle).

Some exemplary embodiments also relate to a motor vehicle, as described herein, with the drive train described herein.

• 1 schematisch ein Ausführungsbeispiel eines Kraftfahrzeugs mit einem Antriebsstrang veranschaulicht;
• 2 schematisch ein Ausführungsbeispiel einer Steuerung veranschaulicht; und
• 3 schematisch ein Ablaufdiagramm eines Ausführungsbeispiels eines Verfahrens zum Steuern eines Bremsvorgangs darstellt.

Embodiments of the invention will now be described by way of example and with reference to the accompanying drawing, in which:

• 1 schematically illustrates an embodiment of a motor vehicle with a drive train;
• 2 schematically illustrates an embodiment of a controller; and
• 3 schematically represents a flowchart of an exemplary embodiment of a method for controlling a braking process.

An embodiment of an electric motor vehicle 1 with a drive train 2 is in 1 illustrated schematically.

The drive train 2 has a first electric machine 3 , which is designed as a front (axles) drive. The first prime mover 3 drives through a first gearbox 4th a front axle 5 of the drive train 2 on.

The drive train 2 also has a second electric machine 6th which is designed as a rear (axles) drive. The second electric machine 6th drives through a second gearbox 7th a rear axle 8th of the drive train 2 on. The second gear 7th is designed here as an automatic transmission.

An electrical energy storage device designed as a lithium-ion high-voltage battery 9 is via a high-voltage electrical system 10 with the first electric machine 3 and the second electric machine 6th connected. The electrical energy storage 9 has e.g. 96 lithium-ion cells and an integrated battery management system. There is also a first electrical power converter 11 between the first electric machine 3 and the electrical energy storage 9 coupled and a second electrical power converter 12th is between the second electric machine 6th and the electrical energy storage 9 coupled. At the second electrical power converter 12th For example, a charging socket with a charger can be connected to the electrical energy store 9 to load externally.

2 schematically illustrates a controller 15th that are used to control the motor vehicle 1 is designed and is set up to carry out the methods described herein.

The control 15th is with the individual components of the vehicle to be controlled 1 connected, namely with the first electric machine 3 , the second electric machine 6th , the energy storage 9 , the electrical power converters 11 and 12th , the automatic transmission 7th , a navigation device 13 and other components that are omitted here for simplicity.

The following is a procedure 20th for controlling a braking process of a motor vehicle 1 with drive train 2 and control 15th using an in 3 described flowcharts, the method 20th without restricting the present invention to this, based on the motor vehicle 1 with drive train from 1 and using the control 15th from 2 is explained.

In the present exemplary embodiment, it is assumed, without loss of generality and merely by way of example and for the sake of simplicity, that the first 3 and second 6 electric machines operate at the same speed.

It is also assumed, purely by way of example, that the first electric machine 3 showing the front axle 5 drives, provides a regenerative torque of 100 Nm or through appropriate thrust, z. B. due to a downhill drive, a torque of 100 Nm acts on them.

The first electric machine also becomes corresponding at 21 3 operated as a generator.

It is also assumed, purely by way of example, that the first electric machine 3 has an efficiency of 95% and the second electric machine 6th has an efficiency of 90%, whereby due to further efficiency losses, z. B Frictional losses in the drive train 2 , in the power electronics for the electric machines, etc., results in an overall efficiency of 0.855, so that the second electric machine 6th due to the efficiency losses with the electrical energy, which is from the first electric machine 3 can produce a torque of +85.5 Nm. This results in a difference of 14.5 Nm between the moment that is generated due to thrust, for example due to the motor vehicle driving downhill 1 , acts on the first electric machine 3, namely 100 Nm, and the moment that the second electric machine 6th due to the from the first electric machine 3 can cause generated electrical energy, namely 85.5 Nm.

In other words, there is a negative (drag) torque of -14.5 Nm for the second electric machine 6th , which in the present embodiment is multiplied by the corresponding translation as the wheel braking torque on the rear axle 8th can be used. In the present exemplary embodiment, this translation is also due to a position of the automatic transmission 7th adjustable.

In the present exemplary embodiment, it is assumed, by way of example and without restricting the generality, that the setting range of the two electric machines 3 , 6th is +/- 250 Nm, so that with the assumed overall efficiency of 85.5%, an electric wheel braking torque between 0 and -36.25 Nm (multiplied by the corresponding gear ratio) can be set without the high-voltage battery 9 to charge (total electrical charge current of the high-voltage battery 9 = 0 A).

At 22nd the status of the high-voltage battery is now determined 9 is whether it can be loaded or not. If it can be charged, for example, charging is carried out by recuperation.

In the present example it is assumed that the high-voltage battery 9 cannot be charged because, for example, the high-voltage battery 9 is fully charged.

At 23 are navigation data from the navigation device 13 received and processed in order to determine a given route, which can be given by the user, through a most likely route (prediction), etc. For example, more electrical energy can be consumed even when driving uphill, even in the event of a train, and thus the high-voltage battery 9 Discharged in advance, so that a corresponding lead in the high-voltage battery 9 this can be loaded accordingly during a subsequent downhill drive.

At 24 a braking power to be provided is determined, for example on the basis of a or given speed when driving downhill.

At 25th is used for the switchable automatic transmission 7th the engaged gear is determined and, if necessary, a gear ratio of the automatic transmission based on the braking power to be provided 7th set to influence the overall efficiency.

At 26th the electrical energy generated by the first electrical machine is then correspondingly to the second electrical machine 6th supplied, with a resulting loss of efficiency being used to brake the drive train, as stated above and which in the present case corresponds to the negative torque of -14.5 Nm (multiplied by the corresponding translation including the gear ratio set at 25).

The order of the procedural steps 21st to 26th is purely exemplary and the order can be changed as required. Also, as stated, the steps are 22nd to 25th each optional and they can be implemented as desired in the exemplary embodiments or they can be omitted.

List of reference symbols

1

Motor vehicle

2

Powertrain

3

First electric machine

4th

First transmission

5

Front axle

6th

Second electric machine

7th

Second transmission / automatic transmission

8th

Rear axle

9

Energy storage

10

High-voltage electrical system

11

first electrical power converter

12

second electrical power converter

13

navigation device

15th

control

20th

Procedure

21st

Generic operation of the first electric machine

22nd

Determining the battery condition

23

Determining the route

24

Determine the braking power to be provided

25th

Setting the gear ratio

26th

Supplying electrical energy to the second electrical machine

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• DE 102010045030 A1 [0005]
• DE 102013111951 A1 [0006]

Claims (10)

A method for controlling a drive train (2), the drive train (2) having a first electric machine (3) and a second electric machine (6), the method comprising: Generic operation (21) of the first electric machine (3), and Feeding (26) the electrical energy generated by the first electrical machine (3) to the second electrical machine (6), a resulting loss of efficiency being used to brake the drive train (2). Procedure according to Claim 1 , wherein the method is carried out as a function of a battery condition. Procedure according to Claim 1 or 2 , the first electric machine being operated as a generator by mechanical thrust. Method according to one of the preceding claims, wherein the method is carried out as a function of a predetermined route for a motor vehicle. Method according to one of the preceding claims, wherein the method further comprises determining a braking power to be provided. Procedure according to Claim 5 , wherein the method further comprises setting a gear ratio for the second electric machine (6) as a function of the determined braking power to be provided. Control (15) for a drive train, the drive train (1) having a first electric machine (3) and a second electric machine (6), the control (15) being set up to carry out the method according to one of the preceding claims. Drive train for a motor vehicle, which comprises a first electric machine (3), a second electric machine (6) and a controller (15) which is set up to implement the method according to one of the Claims 1 to 6th execute. Drive train after Claim 8 , wherein the first electric machine (3) is arranged on a first axis (5) and the second electric machine (6) is arranged on a second axis (8) or wherein the first electric machine and the second electric machine together on the first or the second axis are arranged. Motor vehicle (1) with a drive train (2) according to Claim 8 or 9 .

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