WO2021254706A1

WO2021254706A1 - Method for operating a braking device for electrically driven motor vehicles

Info

Publication number: WO2021254706A1
Application number: PCT/EP2021/062972
Authority: WO
Inventors: Thomas Schlender
Original assignee: Robert Bosch Gmbh
Priority date: 2020-06-16
Filing date: 2021-05-17
Publication date: 2021-12-23

Abstract

The present invention relates to a method for operating a recuperative braking device for electrically driven motor vehicles, said method comprising the steps of: starting a braking operation using a friction brake of the electrically driven motor vehicle; querying a charging state of an electric traction energy storage device; querying a temperature of the electric traction energy storage device; determining a receiving capability of the electric traction energy storage device for electric energy; recuperative braking with a braking power of the electric drive and charging the electric traction energy storage device and/or connecting electric consumers of a passenger compartment conditioning of the electrically driven motor vehicle. The present invention further relates to a device for carrying out the method, wherein the braking device comprises a friction brake and a recuperatively working braking system.

Description

Method for operating a braking device for electrically powered motor vehicles

The present invention relates to a method for operating a braking device for electrically driven motor vehicles, comprising the steps of: beginning braking with a friction brake of the electrically driven motor vehicle; Querying a state of charge of an electrical traction energy store; Querying a temperature of the electrical traction energy store; Determining a capacity of the electrical traction energy store for electrical energy; Recuperative braking with a braking power of the electric drive and charging of the electric traction energy storage and / or connection of electric consumers of a passenger compartment conditioning of the electrically driven motor vehicle. The present invention also relates to a device for carrying out the method, the braking device comprising a friction brake and a regenerative braking system.

State of the art

The electrification of the drive of motor vehicles, which are designed as battery-powered vehicles or as so-called hybrid vehicles, enables the use of the electric drive as a wear-free brake with the advantage of extending the electric range of electrically powered vehicles with the help of the regenerative braking generated and in the Traction battery stored electrical energy. The use of the electric drive as a wear-free brake enables long pass descents without the risk of overheating for the friction brakes. In the case of conventionally driven motor vehicles, the mechanical drag torque of the internal combustion engine must also be used in this case. In the case of manually shifted transmissions in conventionally powered motor vehicles, this can be done by engaging a low gear. Modern Automatic transmissions do this downshifting independently when driving downhill.

In electrically powered motor vehicles, the electric drive provides a wear-free brake. Depending on the design of the respective drive, this can offer a greater deceleration power than the drag torque of an internal combustion engine. The electrical energy recovered in the process is stored in the traction battery of the electrically powered motor vehicle. In any case, it is important that the electrical traction energy store has a capacity to absorb it.

DE 102008061 583 A1 describes an electric drive system for an electrically driven motor vehicle with a first energy storage system and a second energy storage system. The described second energy storage system can be switched on at times to increase the power consumption of the drive motor. The two energy storage systems can be designed differently. Due to the different design of the two energy storage systems, both the issue of the range of electrically driven motor vehicles and the peak performance of electrically driven motor vehicles can be taken into account. Due to the different design of the two energy storage systems, aspects of weight reduction, cooling and size of the energy storage systems can be taken into account.

If only one energy storage system is used or several identically designed energy storage systems are used, the number or size of energy storage systems must be based on the maximum power consumption (peak power) of the electric drive motor, although the aspect of maximum range cannot be taken into account separately. Many identically designed energy stores (energy cells, batteries) would therefore be required, which leads to increased weight and increased costs.

A correspondingly large dimensioning of the first energy storage system (for example a main battery) can now be avoided with the second energy storage system, which provides additional power to the drive motor at peak load. This second energy storage system is also referred to below for short as a boost battery. This boost battery can do something special be designed for high power output and at the same time be equipped with a low energy storage volume. This enables the drive system to be manufactured inexpensively.

In cases of high power consumption by the drive motor or high regenerative power (e.g. during regenerative braking), the peak load is taken from both the main battery and the boost battery or fed back into both the main battery and the boost battery. During normal travel of the electrically driven motor vehicle, however, the drive motor is preferably supplied exclusively by the main battery. The main battery can thus be designed for maximum range of the electrically powered motor vehicle and thus cost-effectively, while the peak power is supplied from the boost battery, which is designed accordingly for the delivery of peak power.

The disadvantage of this prior art proposal is that even the design with two energy storage systems does not allow regenerative braking when the two energy storage systems are fully charged and the electrically driven motor vehicle is to be braked. Disadvantageously, only the friction brake can be used in this case, which leads to disadvantageous heating of the friction brake due to the lack of recuperative braking effect of the electric drive during long braking, for example on downhill slopes or when driving down passes. The friction brake must therefore always be designed in such a way that the required braking power of the electrically driven motor vehicle can be applied over the long term by the friction brake alone.

EP 2 144794 B1 describes a method for operating a vehicle brake system and a vehicle brake system. In particular, a method for electrically driven motor vehicles with at least one front axle and at least one rear axle is described, with at least two vehicle wheels being assigned to each axle. At least one, preferably hydraulically actuated, wheel brake generating a braking torque is provided on the at least one front axle and / or on the at least one rear axle, the vehicle wheels assigned to an axle being at least partially driven by an electric motor, which can be operated as a generator during a recuperation of braking energy and thereby exerts a braking recuperation torque on the respective axle.

The recuperation torque of the axle braked by the electric drive is controlled as a function of a slip threshold.

A disadvantage of this prior art proposal is that the state of charge of the electrical traction energy store is not taken into account. With a fully charged electrical traction energy store, regenerative braking cannot be carried out if the electrically driven motor vehicle is to be braked. In this state-of-the-art proposal, only the use of the friction brake is disadvantageously possible in this case, which leads to disadvantageous heating of the friction brake due to the lack of recuperative braking effect of the electric drive during long braking processes such as downhill or downhill passes. The friction brake must therefore always be designed in such a way that the required braking power of the electrically driven motor vehicle can be applied over the long term by the friction brake alone.

There is therefore a need for a method for braking an electrically driven motor vehicle which enables regenerative braking in any case and in the long term, and a suitable device for this purpose.

The object of the invention is therefore to provide a method for regenerative braking of an electrically driven motor vehicle which enables regenerative braking over the long term even in the case of a fully charged traction battery.

According to the invention, this object is achieved by the subject matter of the independent claim. Advantageous further developments of the invention result from the features of the dependent claims.

Disclosure of the invention The method according to the invention for operating a braking device for electric motor vehicles according to claim 1 has the advantage that a friction brake is used in a first step to brake an electrically driven motor vehicle. In a second step that follows, the state of charge of the electrical traction energy storage device is queried. Furthermore, the temperature of the electrical traction energy store is determined in a further step and the capacity of the electrical traction energy store to absorb electrical energy in a further step. In the next step, the braking power of the electric drive is used for regenerative braking and the electric traction energy storage is charged. Furthermore, depending on the capacity of the electrical traction energy store for electrical energy, electrical consumers of the passenger compartment conditioning are switched on. Carrying out these steps advantageously means that, even in the case of an already fully charged electric traction energy store, the braking power of the electric drive can be used by switching on electric loads and thus the friction brake of the electrically driven motor vehicle is advantageously relieved. The electrical loads are advantageously electrical consumers of the passenger compartment conditioning. By using the braking power of the electric drive quickly for regenerative braking, the braking power of the friction brake can be reduced and / or reduced entirely.

The methods and devices mentioned in the dependent claims allow advantageous developments of the method given in the independent claim.

The method for operating a braking device for electrically driven motor vehicles also advantageously receives information about the expected route from a navigation system of the electrically driven motor vehicle to a charging controller of the electrical traction energy store. In this way, when driving downhill, the charging of the electrical traction energy store can advantageously be terminated before the fully charged state is reached, and the electrical energy store can thus absorb the electrical energy recovered by the regenerative braking. Furthermore, it is advantageous that, when driving downhill, the electrical traction energy storage device can be at least partially emptied before the start of the journey by activating the electrical consumers of the passenger compartment conditioning so that the electrical energy storage device can absorb the electrical energy recovered by the regenerative braking when driving downhill.

A service brake system, which comprises a friction brake and a regenerative braking system, is advantageously used to carry out the method. It is of great advantage that, through the operation according to the invention of the combination of the regenerative braking system with the friction brake, the friction brake can be designed together with the regenerative braking system. The simpler design and / or smaller dimensions of the friction brake result in advantages in terms of cost, space and weight savings.

Furthermore, the connection of the friction brake with the passenger conditioning via air ducts and switching flaps offers the great advantage that the cooling air generated by an electrically operated air conditioning system can be directed directly to the friction brake and this friction brake can be additionally cooled as a result. Due to the cooling of the friction brake, it can be designed more simply and / or dimensioned to be smaller, which results in advantages for the friction brake in terms of cost, installation space and weight savings.

Further features and advantages of the present invention will become apparent to the person skilled in the art from the following description of exemplary embodiments, which, however, are not to be interpreted as limiting the invention, with reference to the accompanying drawings.

Brief description of the drawings

It shows:

1 shows an exemplary method for operating a braking device for electric motor vehicles; 2 shows an exemplary device of a battery-powered motor vehicle for cooling the friction brake with the aid of means for passenger compartment conditioning.

All figures are merely schematic representations of the method according to the invention and the device according to the invention and its components according to exemplary embodiments of the invention. In particular, distances and size relationships are not shown true to scale in the figures. Corresponding elements are provided with the same reference numbers in the various figures.

FIG. 1 shows, by way of example, the sequence of the method 1 for operating a braking device 16 for electrically driven motor vehicles 2.

In a first step A, braking begins with the friction brake 3 of the electrically driven motor vehicle 2. Depending on the design of the electrically driven motor vehicle 2, this braking process can be triggered by the driver by actuating a brake actuation device. In a different design of the electrically powered motor vehicle, the braking process of the electrically powered motor vehicle 2 can be triggered by the driver in that the driver reduces the torque request to such an extent that a negative torque is requested.

In electrically driven motor vehicles 2 which are driven by a driver, the brake pedal forms the brake actuation device. In the case of electrically powered motorcycles, for example, a handbrake lever on the handlebar or a brake pedal that can be actuated by a foot forms the actuation device. Furthermore, in the case of electrically driven motor vehicles 2 which are driven by a driver, the drive torque is requested by the driver by actuating the accelerator pedal. In the case of electrically powered motorcycles, for example, a so-called throttle grip on the handlebars or a throttle lever on the handlebars form the device for requesting drive torque. In the case of electrically driven motor vehicles 2 which have devices for automated driving and for influencing the longitudinal dynamics, a braking process is triggered by the devices for automated driving.

At the beginning of the braking process, only the existing friction brake 3 is used in step A if the state of charge 5 of the electrical traction energy store 4 is not known.

In a further step B, the state of charge 5 of the electrical traction energy store 4 is queried. The state of charge 5 of the electric traction energy store 4 forms the first important information for the operation of the regenerative brake of the electric drive.

In a further step C, the temperature 6 of the electrical traction energy store 4 is queried. The temperature 6 of the electrical traction energy store 4 forms further important information for the operation of the regenerative brake of the electrical drive.

In the following step D, the capacity of the electrical traction energy store 4 to absorb electrical energy is determined with the aid of the information about the state of charge 5 and the temperature 6 of the electrical traction energy store 4 determined in steps B and C.

In step E, a recuperative braking process with the braking power 17 of the electric drive 10 and the charging of the electric traction energy store 4 and / or the connection of electrical consumers 7, 8, 9 of passenger compartment conditioning of the electrically powered motor vehicle 2 is initiated. The electrical traction energy store 4 is usually charged with the electrical energy obtained in the regenerative braking process. If this is not possible, for example due to a fully charged electrical traction energy store 4 and / or a too low temperature 6 of the electrical traction energy store 4, electrical loads 7, 8, 9 of the passenger compartment conditioning are switched on as electrical loads. Depending on the outside temperatures, this can be an electrically operated air conditioning compressor 7 or an electrically operated one Heating 8 or an electrically operated seat heating 9 and / or another type of surface heating. These electrical loads represent the largest energy consumers in the vehicle network in addition to the electrical drive of the motor vehicle. There is also the possibility of heating the electrical traction energy store 4 with the aid of an electrical heater 11 and thus lowering the high internal resistance of the electrical traction energy store at low temperatures so that the electrical energy obtained in the regenerative braking process can be used to charge the electrical traction energy store 4.

There is also the possibility of providing information from a navigation system 12 to the charging controller 13 of the electrical traction energy store 4. This can, for example, be information about the intended route. Thus, the charging controller 13 can end the charging process as soon as the electrical traction energy store 4 is partially charged to be determined in order to use the electrical energy gained in the recuperative braking process during an upcoming downhill drive to charge the electrical traction energy store 4.

There is also the possibility, based on the information provided by the navigation system 12, to automatically switch on the electrical consumers 7, 8, 9 of the passenger compartment conditioning 18 before the planned departure in order to discharge the electrical traction energy store 4 in a targeted manner and to absorb the recuperative effects during an upcoming downhill journey Prepare the electrical energy obtained during braking.

Figure 2 shows an exemplary device of a battery-powered motor vehicle 2 for cooling the friction brake 3 with the help of means of the passenger compartment conditioning 18 3 connected to means for air ducting 14 and switching flaps 15 in such a way that additional cooling of the friction brake 3 is achieved. Since not only fresh air is used to cool the brake unit of the friction brake 3, but already Prepared, cooler air from the passenger compartment conditioning system 18, particularly effective cooling of the friction brake 3 can be achieved. This additional cooling of the friction brake 3 can be taken into account when designing the brake unit of the friction brake 3 and leads to a reduction in installation space, unsprung masses and costs.

Another exemplary design is the consideration of a charging buffer in the electrical traction energy store 4. In this case, the state of charge of the electrical traction energy store 4 is limited, even when fully charged, that in any case the absorption of the energy during a downhill drive is recuperative

Braking operation obtained electrical energy in the electrical traction energy storage 4 is possible. This charging buffer and the associated possibility of charging the electrical energy gained during the recuperative braking process during downhill travel into the electrical traction energy store 4 can also be used in the design of the

Brake unit of the friction brake 3 are taken into account and also leads to a reduction in installation space, unsprung masses and costs.

Claims

Expectations

1. A method (1) for operating a braking device (16) for electrically powered motor vehicles (2) with the steps

A. Beginning of braking with a friction brake (3) of the electrically driven motor vehicle (2);

B. Querying a state of charge (5) of an electrical traction energy store (4);

C. Querying a temperature (6) of the electrical traction energy store (4);

D. determining a capacity of the electrical traction energy store (4) for electrical energy;

E. Recuperative braking with the braking power of the electric drive (10) and charging of the electric traction energy store (4) and / or switching on of electrical consumers (7, 8, 9) of a passenger compartment conditioning of the electrically powered motor vehicle (2).

2. The method (1) for operating a braking device (16) for electrically driven motor vehicles (2) according to claim 2, characterized in that a navigation system (12) of the electrically driven motor vehicle (2) of a charging controller (13) of the electrical traction energy store (4 ) for electrical energy provides information about the expected route.

3. The method (1) for operating a braking device (16) for electrically powered motor vehicles (2) according to claim 1, characterized in that the navigation system (12) puts the electrical loads (7, 8, 9) of the passenger compartment conditioning into operation before starting the journey .

4. Braking device (16) for performing the method (1) according to one of claims 1 to 3, characterized in that the service brake system comprises a friction brake (3) and a regenerative braking system.

5. Braking device (16) for carrying out the method (1) according to

Claim 4, characterized in that the friction brakes (3) are connected to the passenger compartment conditioning (18) via air ducts (14) and switching flaps (15).