DE102021206414A1 - Recuperation of electrical energy in a second battery of a vehicle - Google Patents

Abstract

The invention relates to a vehicle (1) with an electric machine (3), control unit (5), high-voltage battery (7) and low-voltage battery (9), the storable energy of the high-voltage battery (7) being higher than the storable energy of the low-voltage battery (9 ) and the high-voltage battery (7) is used to provide electrical energy to the electrical machine (3), the control unit (5) being designed to first supply the electrical energy generated in generator mode of the electrical machine (3) to the high-voltage battery (7) to monitor a state of charge of the high-voltage battery (7) and, when a predefined state of charge of the high-voltage battery (7) is reached, to supply at least some of the electrical energy generated by the electric machine (3) to the low-voltage battery (9) instead of the high-voltage battery (7).

Description

The invention relates to a vehicle with an electric machine with a generator mode and a drive mode, and with a high-voltage battery and a low-voltage battery.

Fully electric or hybrid vehicles have the advantage over vehicles powered exclusively by an internal combustion engine that recuperation can be carried out in certain vehicle states and phases of a journey, i.e. kinetic energy can be withdrawn from the vehicle and converted into electrical energy for charging a battery of the vehicle can be. Such phases occur, for example, when driving downhill, in which the increase in speed due to the downhill force is to be reduced, or in general road traffic when the vehicle is decelerated in order to relieve mechanical brakes.

Since each battery can of course not only be charged with a limited capacity but also only has a finite energy storage capacity, it can happen during longer braking processes such as long downhill rides that an electric machine (electric motor) of the vehicle is in generator mode for the above-mentioned Recuperation electrical energy can be provided, but the vehicle's battery already has too high a charge level, so that the battery can only be charged insufficiently or not at all.

In hybrid vehicles in particular, not only a high-voltage battery with a very large amount of storable energy for driving an electric motor of the vehicle is often installed, but also a low-voltage battery with a typical nominal voltage value of 12 volts in order to be able to supply subsystems of the vehicle and in particular an internal combustion engine . Such a vehicle electrical system of 12 volts can be used, for example, to control spark plugs in a gasoline engine. The voltage of the high-voltage battery is typically well above these 12 volts, often in the three-digit voltage range. It is known in the prior art to have several, but different, batteries in a vehicle and to coordinate the charging of these according to specific concepts.

the WO 2010/081611 A1 relates to an on-board power supply for a vehicle, with an electrical machine designed at least for generator operation, and a voltage converter connected at least indirectly to the electrical machine on the input side, and a first energy store, in particular an accumulator, connected to the voltage converter on the output side, the electrical machine being designed for recuperation operation and the voltage converter is designed to detect or limit a state of charge of the first energy store and to regulate the state of charge of the first energy store in such a way that the first energy store has a reserve capacity during generator operation, in particular when the vehicle is being driven, and depending on an input side received, a recuperation operation of the vehicle representing recuperation signal to load the reserve capacity of the first energy store.

For this describes the WO 2010/081611 A1 further that the second energy store is connected to the electrical machine and is designed to store electrical charge generated by the electrical machine in generator operation and/or recuperation operation. According to this embodiment, the voltage converter is designed to detect the state of charge of the second energy store and to charge the reserve capacity of the first energy store depending on the state of charge of the second energy store, in particular a voltage. As a result, in particular the reserve capacity of the first energy storage device can be charged when the second energy storage device, in particular the double-layer capacitor, is fully charged.

In addition, in the WO 2010/081611 A1 described that, for example, the second energy store, in particular the double-layer capacitor, can be charged with a voltage which is greater than the voltage of the first energy store. The vehicle electrical system can also advantageously have two sub-systems with different vehicle voltages.

The object of the invention is to improve the electric recuperation of a fully electric vehicle or hybrid vehicle (with electric drive and internal combustion engine) in such a way that more kinetic or potential energy can be stored while the vehicle is driving, especially in scenarios such as long downhill drives of the vehicle.

The invention results from the features of the independent claims. Advantageous developments and refinements are the subject matter of the dependent claims.

A first aspect of the invention relates to a vehicle with an electric machine, with a control unit, with a high-voltage battery and a low-voltage battery, wherein the elec ric machine can be operated either in a generator mode or in a drive mode, the storable energy of the high-voltage battery being higher than the storable energy of the low-voltage battery and the high-voltage battery for providing electrical energy to the electric machine in its drive mode, the control unit being designed for this purpose is to first supply the electrical energy generated in the generator mode of the electrical machine to the high-voltage battery, to monitor a state of charge of the high-voltage battery and, when a predefined state of charge of the high-voltage battery is reached, to supply at least some of the electrical energy generated by the electrical machine to the low-voltage battery instead of the high-voltage battery.

The electric machine of the vehicle is in particular an electric motor or a unit made up of a large number of electric motors, each of which has a generator mode and a drive mode. In the generator mode, mechanical energy from the wheels of the vehicle is converted into electrical energy and delivered by the electric machine in order in particular to be able to charge the high-voltage battery. In propulsion mode, on the other hand, the vehicle's electric machine acts as an electric motor or a set of electric motors to use electric energy, in particular from the high-voltage battery, in contrast to generator mode, in order to use this propulsion energy to apply torque to the vehicle's driven wheels.

The high-voltage battery serves as the main, essential energy store for providing electrical energy for the vehicle's electrical machine. The high-voltage battery is therefore typically designed with a correspondingly significantly higher volume than the low-voltage battery and, in contrast to the latter, typically occupies a significant proportion of the volume of the vehicle. The low-voltage battery, on the other hand, serves to supply subsystems of the vehicle in the vehicle electrical system, for example a multimedia unit, the operation of windshield wipers, in the case of a hybrid vehicle the supply of electrical energy to electrical spark plugs, and the like. Since these subsystems typically consume significantly less power and overall less energy than the vehicle's drive, the low-voltage battery will have a significantly smaller volume and a significantly smaller mass than the high-voltage battery in accordance with the above.

Against this background, the control unit is designed according to the invention to primarily supply the high-voltage battery with the electrical energy of the electrical machine in its generator mode. Such a generator mode occurs when energy is recuperated, ie kinetic or potential energy of the vehicle is converted into electrical energy by the generator mode of the electrical machine and can be used to charge the high-voltage battery or the low-voltage battery.

The control unit uses appropriate sensors to monitor the state of charge of the high-voltage battery. The state of charge of the high-voltage battery describes in particular the proportion of the energy already stored in relation to the maximum possible energy that can be stored by the high-voltage battery, which is electrochemically held in the high-voltage battery until it is called up.

If the high-voltage battery is charged until a predefined state of charge is reached (preferably through a current energy storage of 80%, particularly preferably 85%, further particularly preferably 90%, further particularly preferably 95%, further particularly preferably a value between 95% and 100 % of the maximum possible energy storage in the high-voltage battery), the control unit reduces the supply of electrical energy to the high-voltage battery and instead diverts at least part of this electrical energy to the low-voltage battery to charge the low-voltage battery.

It is therefore an advantageous effect of the invention that kinetic or potential energy of the vehicle is stored in reusable energy in the vehicle even when the high-voltage battery for the vehicle's electric machine has reached a very high state of charge. As a result, the overall energy consumption of the vehicle can be reduced and the vehicle can therefore be operated more cost-effectively and in a more environmentally friendly manner.

According to an advantageous embodiment, the vehicle is a hybrid vehicle having, in addition to the electric machine, an internal combustion engine for driving the vehicle, the low-voltage battery serving to provide electrical energy for subsystems of the internal combustion engine and the rest of the vehicle that are independent of the vehicle's drive. The subsystems of the internal combustion engine and the rest of the vehicle are described above, among other things, and can include, for example, spark plugs, windshield wipers, multimedia units, screens, electric windows or similar.

According to a further advantageous embodiment, the predefined state of charge of the high-voltage battery is a predetermined proportion of the energy already stored in the high-voltage battery in relation to the physically largest possible energy that can be stored in the high-voltage battery. The proportion of the energy already stored in the high-voltage battery in relation to the physically largest possible energy that can be stored in the high-voltage battery, which is used as a predefined state of charge, is preferably 70%, more preferably 75%, particularly preferably 80%, particularly preferably 85%, particularly preferably 90 %, particularly preferably 95%, or particularly particularly preferably >95%.

According to a further advantageous embodiment, the vehicle also has a DC-to-voltage converter, the electrical machine being designed to output electric current with the electrical voltage of the high-voltage battery, the DC-to-voltage converter being designed to convert the voltage of the electrical machine to the voltage of the low-voltage battery, so that electrical energy from the electric machine is routed either directly to the high-voltage battery or at a reduced voltage to the low-voltage battery. The DC voltage converter is also called a DC/DC converter, where 'DC' stands for direct current. The purpose of the DC-to-voltage converter is therefore to reduce the voltage of the electric current from the electric machine to the voltage of the low-voltage battery, in particular to 12 volts.

According to a further advantageous embodiment, the vehicle also has a DC-to-voltage converter, the electric machine being designed to output electric current with the electric voltage of the high-voltage battery, the DC-to-voltage converter being designed to convert the voltage at an output of the high-voltage battery step down the voltage of the low voltage battery such that electrical energy of the electric machine is routed to the high voltage battery and optionally is routed from the high voltage battery to the low voltage battery at a reduced voltage. The optional component in the above is determined by the control unit, which according to the invention exercises control over whether the electrical energy generated by the electric machine is fed only to the high-voltage battery or only to the low-voltage battery or divided between both.

According to a further advantageous embodiment, the electrical voltage of the low-voltage battery is 12 volts and the voltage of the high-voltage battery is at least 24 volts, in particular at least 48 volts, particularly preferably at least 92 volts.

According to a further advantageous embodiment, the control unit is designed to conduct the electrical energy generated by the electrical machine to the low-voltage battery using a fade function in an area around the predefined state of charge of the high-voltage battery as the state of charge of the high-voltage battery increases.

According to a further advantageous embodiment, the cross-fade function is linear, so that when the high-voltage battery has a maximum permissible state of charge, the electrical energy of the electrical machine is completely supplied to the low-voltage battery.

According to a further advantageous embodiment, the control unit is designed to supply all of the electrical energy generated by the electrical machine to the low-voltage battery when the predefined state of charge of the high-voltage battery is reached.

According to a further advantageous embodiment, the control unit is designed to determine the predefined state of charge of the high-voltage battery as a function of a current temperature state of the high-voltage battery or as a function of a current temperature of the vehicle's surroundings.

Further advantages, features and details result from the following description, in which at least one exemplary embodiment is described in detail-if necessary with reference to the drawing. Identical, similar and/or functionally identical parts are provided with the same reference symbols.

• 1: Ein Fahrzeug gemäß einem Ausführungsbeispiel der Erfindung.
• 2: Eine Überblendungsfunktion gemäß einem Ausführungsbeispiel der Erfindung.

Show it:

• 1 : A vehicle according to an embodiment of the invention.
• 2 : A fade function according to an embodiment of the invention.

The representations in the figures are schematic and not to scale.

1 1 shows a vehicle 1 with a respective electric machine 3 on the driven rear wheels of the vehicle 1. The vehicle 1 is a hybrid vehicle, with an internal combustion engine for driving the vehicle 1 being installed in addition to the electric motors on the rear wheels of the electric machine 3. The vehicle 1 therefore has a high-voltage battery 7 and a low-voltage battery 9, the high-voltage battery 7 primarily serving to provide electrical energy to the electric machine 3 in order to drive the electric motors of the electric machine 3 when they are in drive mode. Naturally, therefore, the low-voltage battery 9 with its nominal voltage range of twelve volts is designed to be significantly smaller than the high-voltage battery 7 , which makes up a significant part of the total mass of the vehicle 1 . The low-voltage battery 9, on the other hand, serves primarily to provide electrical energy for subsystems of the internal combustion engine and the rest of the vehicle 1 that are independent of the drive of the vehicle 1, such as windshield wipers, spark plugs, turn signals, electric windows and the like. A control unit 5 coordinates the switching of the electric machine 3 between the generator mode and the drive mode. In the generator mode of the electrical machine 3 , the electrical energy generated in the electrical machine 3 is first supplied to the high-voltage battery 7 by a corresponding activation of the control unit 15 . The control unit 5 monitors the state of charge of the high-voltage battery 7 continuously and leads to a in the 2 more precisely explained pattern when reaching a predefined state of charge of the high-voltage battery 7 increasingly electrical energy no longer the high-voltage battery 7, but the low-voltage battery 9. For this purpose, the voltage of the electrical machine 3 is reduced from three hundred and ninety-three volts, which corresponds to the voltage of the high-voltage battery 7 , to the twelve volts of the low-voltage battery 9 by a DC/DC converter 11 .

2 FIG. 1 shows a rule according to which the control unit 5 reduces the charging of the high-voltage battery 7 when the high-voltage battery 7 has a predefined state of charge and instead increasingly charges the low-voltage battery 9 . The state of charge of the high-voltage battery 7 is shown as L(7) on the horizontal axis. The vertical axis represents a measure of an energy flow by means of electric power, with the upper half-plane F(7) being assigned to the high-voltage battery 7 and the lower half-plane F(9) being assigned to the low-voltage battery 9 . The predefined state of charge of the high-voltage battery 7 is a predetermined proportion of the energy already stored in the high-voltage battery 7 in relation to the physically largest possible energy that can be stored in the high-voltage battery 7 . The control unit 5 conducts the electrical energy generated by the electrical machine 3 by a cross-fading function in a range around the predefined state of charge of the high-voltage battery 7 of L(7) = 85% as the state of charge of the high-voltage battery 7 increases to the low-voltage battery 9. The cross-fading function is linear in this case and begins with a state of charge L(7) of the high-voltage battery 7 of 80%, up to which all electrical energy of the electrical machine 13 is still completely fed to the high-voltage battery 7, denoted by F(7). The fade ends when the high-voltage battery 7 has a charge level L(7) of 90%, at which point electrical energy is no longer supplied to the high-voltage battery 7, but only to the low-voltage battery 9, symbolized by a single dashed curve in half-plane F(9).

Although the invention has been illustrated and explained in more detail by means of preferred exemplary embodiments, the invention is not restricted by the disclosed examples and other variations can be derived therefrom by a person skilled in the art without departing from the protective scope of the invention. It is therefore clear that a large number of possible variations exist. It is also understood that the exemplary embodiments given are really only examples and should not be construed as limiting in any way the scope, applications or configuration of the invention. Rather, the preceding description and the description of the figures enable the person skilled in the art to concretely implement the exemplary embodiments, whereby the person skilled in the art, knowing the disclosed inventive concept, can make a variety of changes, for example with regard to the function or the arrangement of individual elements mentioned in an exemplary embodiment. without departing from the scope of protection defined by the claims and their legal equivalents, such as further explanations in the description.

Reference List

1

vehicle

3

electric machine

5

control unit

7

high voltage battery

9

low voltage battery

11

DC voltage converter

QUOTES INCLUDED IN DESCRIPTION

This list of the documents cited 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

• WO 2010081611 A1 [0005, 0006, 0007]

Claims (10)

Vehicle (1) with an electrical machine (3), with a control unit (5), with a high-voltage battery (7) and with a low-voltage battery (9), the electrical machine (3) being operated either in a generator mode or in a drive mode where the energy that can be stored in the high-voltage battery (7) is higher than the energy that can be stored in the low-voltage battery (9) and the high-voltage battery (7) serves to provide electrical energy to the electric machine (3) in its drive mode, the control unit (5 ) is designed to first supply the electrical energy generated in the generator mode of the electrical machine (3) to the high-voltage battery (7), to monitor a state of charge of the high-voltage battery (7) and, when a predefined state of charge of the high-voltage battery (7) is reached, from the electrical machine (3) electrical energy generated at least partially by the low-voltage battery (9) instead of feeding it to the high-voltage battery (7). Vehicle (1) after claim 1 , wherein the vehicle (1) is a hybrid vehicle (1), having in addition to the electric machine (3) an internal combustion engine for driving the vehicle (1), wherein the low-voltage battery (9) for providing electrical energy for driving the vehicle (1) independent subsystems of the internal combustion engine and the rest of the vehicle (1) is used. Vehicle (1) according to one of the preceding claims, wherein the predefined state of charge of the high-voltage battery (7) is a predetermined proportion of the energy already stored in the high-voltage battery (7) in relation to the physically largest possible energy that can be stored in the high-voltage battery (7). Vehicle (1) according to one of Claims 1 until 3 , Having a DC-to-voltage converter (11), wherein the electric machine (3) is designed to output electric current with the electric voltage of the high-voltage battery (7), wherein the DC-to-voltage converter (11) is designed to convert the voltage of the electric Reduce machine (3) to the voltage of the low-voltage battery (9), so that electrical energy from the electric machine (3) is passed either directly to the high-voltage battery (7) or with reduced voltage to the low-voltage battery (9). Vehicle (1) according to one of Claims 1 until 3 , Having a DC-to-voltage converter (11), wherein the electric machine (3) is designed to output electric current with the electric voltage of the high-voltage battery (7), wherein the DC-to-voltage converter (11) is designed to convert the voltage at a Reduce the output of the high-voltage battery (7) to the voltage of the low-voltage battery (9), so that electrical energy from the electric machine (3) is routed to the high-voltage battery (7) and optionally from the high-voltage battery (7) to the low-voltage battery (9) with reduced voltage . Vehicle (1) according to one of the preceding claims, wherein the electrical voltage of the low-voltage battery (9) is 12 volts and the voltage of the high-voltage battery (7) is at least 24 volts, in particular at least 48 volts, particularly preferably at least 92 volts. Vehicle (1) according to one of Claims 1 until 6 , wherein the control unit (5) is designed to increasingly transfer the electrical energy generated by the electrical machine (3) to the low-voltage battery (9 ) to direct. Vehicle (1) after claim 7 , wherein the cross-fade function is linear, so that the electrical energy of the electrical machine (3) is completely supplied to the low-voltage battery (9) when the high-voltage battery (7) has a maximum permissible state of charge. Vehicle (1) according to one of Claims 1 until 6 , wherein the control unit (5) is designed to completely feed the electrical energy generated by the electrical machine (3) to the low-voltage battery (9) when the predefined state of charge of the high-voltage battery (7) is reached. Vehicle (1) according to one of the preceding claims, wherein the control unit (5) is designed to determine the predefined state of charge of the high-voltage battery (7) depending on a current temperature state of the high-voltage battery (7) or depending on a current temperature of the environment of the vehicle (1 ) to determine.

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