DE102022119846A1 - Method for operating a drive and braking system of a vehicle - Google Patents

Abstract

The invention relates to a method for operating a drive and braking system (1, 4) of a vehicle (10), wherein the drive system (1) comprises at least one electric motor (2, 3), comprising the step: regulating a braking deceleration depending on wheel slip by simultaneously generating a first braking torque by means of the braking system (4) of the vehicle (10) and a motor torque by means of the electric motor (2, 3).

Description

The invention relates to a method for operating a drive and braking system of a vehicle, and a vehicle.

Drive and braking systems for vehicles are known from the prior art, in which the wheel slip is regulated in the driving dynamic limit range by regulating the wheel brakes. For an optimal distribution of the braking forces to the wheels of the vehicle, valves are usually provided in the brake system, which are switched in a specially adapted manner. This requires a high degree of complexity for the braking system, so that the switching of the valves can be acoustically perceived by the occupants of the vehicle.

It is therefore an object of the present invention to provide a method for operating a drive and braking system of a vehicle that allows for low complexity of the braking system and reduced noise emissions.

This problem is solved by the features of the independent claim. The dependent claims contain advantageous developments of the invention.

The object is thus solved by a method for operating a drive and braking system of a vehicle, wherein the drive system comprises at least one electric motor, and wherein the method comprises the steps: regulating a braking deceleration of the vehicle, in particular while the vehicle is traveling, by simultaneously generating it a first braking torque by means of the braking system and a motor torque by means of the electric motor, and regulating the braking deceleration, preferably exclusively, by controlled adjustment of the motor torque generated by the electric motor. Preferably, at least partial regulation of the braking deceleration can additionally be carried out by controlled adjustment of the first braking torque generated by the braking system.

A braking system is considered in particular to be a system that includes a vehicle brake for braking the wheels of the vehicle. Such a vehicle brake is also referred to as a friction brake, for example. Such a vehicle brake is preferably designed to be hydraulically actuated.

A second braking torque is preferably generated as the engine torque.

In other words, in the method, the vehicle is decelerated in a controlled manner by operating the brake system and the electric motor in combination in such a way that both the brake system and the electric motor generate torque at the same time. The entire braking torque by which the vehicle is decelerated is regulated by adjusting the engine torque generated by the electric motor in a controlled manner. This means that the entire braking torque is flexibly adapted to the current driving situation by the electric motor. In particular, a torque distribution between the axles of the vehicle can be freely adjusted by the electric motor in a particularly simple and efficient manner. In particular, it can be avoided that rapid or strong changes in braking torque have to be carried out with the hydraulic brake system, whereby acoustic abnormalities during operation of the hydraulic brake system can be avoided in a particularly simple manner.

The method thus allows flexible coordination of the braking torques while the vehicle is traveling in a particularly simple and efficient manner. In particular, through the controlled generation of the engine torque by means of the electric motor, an effective overall braking torque can be adjusted in a simple and flexible manner. For example, switching valves in the brake system to regulate the braking deceleration can be dispensed with, which means that a particularly simple mode of operation with low acoustic emissions can be provided.

In particular, the entire braking deceleration of the vehicle is preferably regulated depending on the wheel slip, for example of exactly one wheel or alternatively several wheels of the vehicle. In particular, in the method, a driver's request for deceleration generated based on a brake actuation by a driver of the vehicle is adapted in a controlled manner depending on the wheel slip. Alternatively or additionally preferably, the controlled adjustment of the deceleration can already take place when the vehicle is coasting, in particular during recuperation operation of the drive system. This makes it possible to achieve a particularly effective prevention of the occurrence of acoustic abnormalities in the tragic braking system, particularly in driving dynamic situations.

The braking deceleration is preferably regulated individually for each axle of the vehicle. This means that an individual braking torque is generated independently on each axle of the vehicle. In particular, this is done by a controlled adjustment of the engine torque, which is generated by the at least one electric motor. With it The braking deceleration can be adapted particularly flexibly, for example to different road conditions, which in particular enables effective deceleration of the vehicle. In addition, the individual control of the electric motors can resolve a conflict of objectives between the highest possible energy recovery and optimum driving dynamics. The braking deceleration is particularly preferably regulated individually for each wheel of the vehicle. This means that the braking deceleration can be adjusted particularly flexibly and precisely.

Particularly preferably, in order to generate the first braking torque, an identical brake pressure is generated for each axle of the vehicle by means of the braking system. The brake pressure is considered in particular to be a hydraulic brake pressure of the, preferably hydraulic, brake system. In particular, the brake system is set up to be able to independently generate a separate brake pressure for each axle. This enables a particularly simple construction and operation of the braking system, whereby the controlled generation of the motor torque by means of the electric motor can provide a precise, needs-based adjustment of the braking power required on the axles.

The braking deceleration is preferably controlled depending on which wheel of the vehicle has the greatest wheel slip. In other words, the braking deceleration is controlled depending on the wheel that has the lowest coefficient of friction with the vehicle's surface. Such a control can, for example, be implemented as a “select-low” control. This enables a particularly high level of driving comfort with sufficient braking power.

The engine torque is preferably generated by operating the electric motor in motor operation. In particular, the engine torque can be viewed as the drive torque for propelling the vehicle. The first braking torque is preferably greater than the engine torque, so that overall the vehicle is decelerated. This allows the free distribution of torque between the vehicle axles to be maintained over a large effective range.

More preferably, the engine torque is generated by operating the electric motor in a generator mode. This means that the electric motor is operated as a generator, whereby the engine torque is generated in a controllable manner. In particular, the engine torque in this case corresponds to a second braking torque. In particular, this generates an electrical current that can advantageously be used in the vehicle. This enables particularly efficient operation of the vehicle.

An electrical feedback current generated by the generator operation of the electric motor is preferably stored in an electrical energy storage device, for example a vehicle battery, which is set up to provide electrical energy for driving the vehicle by means of the electric motor. This type of operation is also known as “recuperation”. This makes it possible to ensure particularly efficient operation of the vehicle, in which the greatest possible potential energy can be recovered during braking processes.

An adjustment of a torque ratio of axle braking torques of respective axles of the vehicle is preferably carried out exclusively by adjusting the engine torque generated by the drive motor. This means that during a braking process, the proportion of the total braking torque generated by the first braking torque of the braking system is always the same in relation to the two axes. Changes in the torque ratio between the two axes are caused exclusively by the torque components of the engine torque generated by the electric motor. This allows the braking forces to be flexibly adjusted, with a very simple structure and operation of the braking system being possible, in particular without the need to switch valves in the braking system.

Further preferably, the method is carried out during anti-lock braking operation, in particular during operation of an anti-lock braking system of the vehicle, and/or during normal operation, that is to say in particular while carrying out normal braking, of the vehicle.

The invention further relates to a vehicle, preferably an electric motor vehicle, in particular a passenger car, comprising a drive system that has at least one electric motor and a braking system. The vehicle also includes a control unit that is set up to carry out the method described. In particular, the electric motor is designed as a drive motor of the vehicle. For example, the vehicle can include exactly one electric motor that is set up to drive a front axle or a rear axle of the vehicle. Alternatively, the vehicle can preferably have a separate electric motor on both the front axle and the rear axle to drive the include the corresponding axis. Further alternatively, the vehicle can preferably include two electric motors per axle, in particular in order to be able to drive or brake each wheel of the vehicle separately by means of a respective electric motor.

• 1 eine vereinfachte schematische Ansicht eines Fahrzeugs, bei dem ein Verfahren gemäß einem bevorzugten Ausführungsbeispiel der Erfindung durchgeführt wird, und
• 2 eine vereinfachte schematische Ansicht eines beispielhaften Diagramms mit Betriebsparametern eines Antriebssystems des Fahrzeugs bei der Durchführung des erfindungsgemäßen Verfahrens.

Further details, features and advantages of the invention result from the following description and the figures. Show it:

• 1 a simplified schematic view of a vehicle in which a method according to a preferred embodiment of the invention is carried out, and
• 2 a simplified schematic view of an exemplary diagram with operating parameters of a drive system of the vehicle when carrying out the method according to the invention.

1 shows a simplified schematic view of a vehicle 10 in which a method according to a preferred embodiment of the invention is carried out. The vehicle 10 is a fully electric passenger car.

The vehicle 10 includes a drive system 1 with a first electric motor 2, which is arranged on the front axle 20 and is set up to drive the wheels 50 on the front axle 20. In addition, the drive system 1 includes a second electric motor 3, which is arranged on the rear axle 30 and is set up to drive the wheels 50 on the rear axle 30.

The two electric motors 2, 3 are supplied with electrical energy by means of an electrical energy storage device 60.

The drive system 1 also includes a brake system 4, which has a hydraulically actuated friction brake on each of the wheels 50. By means of the braking system 4, a first braking torque for braking the vehicle 10 can be generated while driving.

In addition, the vehicle 10 includes a control unit 5, which is set up to operate the electric motors 2, 3 and the brake system 4 in a controlled manner. The method according to the preferred exemplary embodiment of the invention is carried out by means of the control unit 5.

In the method, the entire braking deceleration of the vehicle 10 is regulated depending on a determined wheel slip on the wheels 50. Preferably, the wheel slip on each wheel 50 can be detected separately by means of a corresponding sensor, which can be part of an anti-lock braking system of the vehicle 10, for example .

In detail, the braking deceleration per axle 20, 30 is regulated depending on the wheel 50 of the corresponding axle 20, 30 on which the greatest wheel slip, that is to say the currently lowest coefficient of friction with a surface of the vehicle 10, is present. This control can, for example, be implemented as a “select low” control.

In the method, the braking deceleration is controlled by simultaneously generating the first braking torque by means of the braking system 4 by additionally generating a second braking torque through regenerative operation of the two electric motors 2, 3. A total braking torque, which causes the braking deceleration of the vehicle 10, is thus formed from a sum of the first braking torque and the second braking torque.

In the process, the braking deceleration for each axis 20, 30 is regulated individually. This is done by adjusting the torque ratios of the axle braking torques on the two axles 20, 30 relative to one another exclusively by adjusting the second braking torque generated by the electric motors 2, 3. This means that the respective proportion of the first braking torque in the torque ratio of the axle braking torques on the two axles 20, 30 remains constant at all times. This is achieved by always generating an identical brake pressure for both axles 20, 30 by means of the brake system 4.

For further explanation, see below 2 Reference is made, which shows a simplified schematic view of an exemplary diagram 70 in which operating parameters of the drive system 1 of the vehicle 10 are shown when performing the method.

Three sub-diagrams are shown in the diagram 70, each of which represents pressures or moments on the front axle 20 and on the rear axle 30 in a simplified, schematic manner. There is a value of zero on the common X-axis 71a.

A brake pressure diagram 70a is shown on the left, which shows respective brake pressures 71. A front axle pressure 75a and a rear axle pressure 76b always have identical values when carrying out the method, as described above. This allows particularly advantageous operation of the braking system 4 of the vehicle 10 be made possible. In addition to a particularly simple mode of operation, this makes it possible to dispense with switching valves in the brake system 4 due to the same pressures. This makes it possible, for example, to avoid undesirable acoustic emissions, which enables a particularly high level of comfort for the occupants of the vehicle 10.

In 2 A braking torque diagram 70b is shown in the middle, which represents braking torques 72 on the two axes 20, 30 in a simplified, schematic manner. In detail, there is a negative braking torque 72 on both axes 20, 30. A front axle braking torque 75c has a larger amount than a rear axle braking torque 76d, in particular due to a predetermined cp distribution of the vehicle 10. Front axle braking torque 75c and rear axle braking torque 76d each correspond to a braking torque 72 on the respective axle 20, 30, which results from the braking torque generated hydraulically by means of the braking system 4.

In 2 On the right, an engine torque diagram 70c is shown, which shows engine torques 73 on the two axes 20, 30 in a simplified, schematic manner. The entire scope of a front axle motor torque 75e and a rear axle motor torque 76f, which can be generated by means of the respective electric motor 2 or 3, is shown in detail. This means that each electric motor 2, 3 can be used to generate both a positive engine torque, which is suitable for propelling the vehicle 10, and a negative engine torque, which causes the vehicle 10 to decelerate. By appropriately regulating the front axle motor torque 75e and rear axle motor torque 75f, the braking torque required in each case according to the wheel slip is regulated in the method while maintaining the identical brake pressures on the front axle 20 and rear axle 30.

List of reference symbols:

1

Drive system

2

first electric motor

3

second electric motor

4

Braking system

5

Control unit

10

vehicle

20

Front axle

30

rear axle

50

Wheels

70

diagram

70a

Brake pressure diagram

70b

Braking torque diagram

70c

Engine torque diagram

71

Brake pressure

71 a

X axis

72

Braking torque

73

Engine torque

75a

Front axle pressure

76b

Rear axle pressure

75c

Front axle braking torque

75e

Front axle motor torque

76d

Rear axle braking torque

76f

Rear axle motor torque

Claims (11)

Method for operating a drive and braking system (1, 4) of a vehicle (10), the drive system (1) comprising at least one electric motor (2, 3), comprising the steps: - Generating a braking deceleration by simultaneously generating a first braking torque by means of the braking system (4) of the vehicle (10) and a motor torque by means of the electric motor (2, 3), and - Regulating the braking deceleration by controlled adjustment of the motor torque generated by the electric motor (2, 3). Procedure according to Claim 1 , whereby the braking deceleration is controlled depending on wheel slip. Method according to one of the preceding claims, wherein the braking deceleration is controlled individually for each axle (20, 30) of the vehicle (10). Method according to one of the preceding claims, wherein in order to generate the first braking torque for each axle (20, 30), an identical brake pressure is generated by means of the brake system (4). Method according to one of the preceding claims, wherein the braking deceleration is controlled, in particular per axle (20, 30), depending on the wheel (50) of the vehicle (10) with the greatest wheel slip. Method according to one of the preceding claims, wherein generating the engine torque by operating the electric motor (2, 3) in motor operation Procedure according to one of the Claims 1 until 5 , wherein the engine torque is generated by operating the electric motor (2, 3) in a generator mode. Procedure according to Claim 7 , wherein an electrical feedback current generated by the generator operation of the electric motor (2, 3) is stored in an electrical energy storage (60) of the vehicle (10). Method according to one of the preceding claims, wherein an adjustment of a torque ratio of axle braking torques of the axles (20, 30) of the vehicle (10) takes place exclusively by adjusting the engine torque generated by the electric motor (2, 3). Method according to one of the preceding claims, wherein the method is carried out during anti-lock braking operation and/or during normal operation of the vehicle (10). Vehicle (10), comprising a drive system (1) with at least one electric motor (2, 3), a braking system (4), and a control unit (5), which is set up to carry out a method according to one of the preceding claims.

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