Motor vehicle with internal combustion engine and method for operating a motor vehicle with internal combustion engine

Abstract

Motor vehicle with an internal combustion engine (2) intended for vehicle propulsion, at least one electric machine (13) that can be operated as a generator and is mechanically rotatably coupled to a drive train (2) of the vehicle (12) for generating electrical energy, at least one energy storage device (14, 15) which is connected to the at least one electric machine (13) for storing the electrical energy generated by it, at least one friction brake for decelerating the vehicle (12) and at least one control unit (7) for controlling the at least one electric machine (13) and the at least one energy storage device (14, 15) as well as the at least one friction brake, wherein the control unit (7) is configured toa vehicle deceleration torque dependent on a braking request specified by a user of the vehicle (12) via a brake actuation element (8) up to a maximum deceleration torque achievable by the generator load of the at least one electric machine (13) to be provided solely by means of the at least one electric machine (13) and the resulting electrical energy to be stored in the at least one energy storage device (14, 15) and, in the event of a braking request exceeding this maximum achievable deceleration torque, the additional vehicle deceleration torque also to be provided by means of the at least one friction brake, wherein the electric machine (13) is an alternator or a starter generator, characterized in that the at least one energy storage device (14, 15) is a flexible heat storage container with an inner body and an outer body, between which insulation is arranged,and is equipped with an electric heating device (6), wherein the heating device (6) can be operated by means of the electrical energy generated by the electric machine (13), and the heat storage container stores the waste heat of the internal combustion engine (2) released to a coolant cooling the internal combustion engine (2), and the temperature of a heat storage medium contained in at least one energy storage device (14, 15) can be increased by means of the electric heating device (6) beyond a value achievable by means of the waste heat and can be maintained at such an increased value, wherein both a 12-volt electrical system and a parallel 48-volt electrical system are used, wherein the 12-volt electrical system has a first energy storage device (14) as a 12-volt battery and the 48-volt electrical system has a second energy storage device (15) as a 48-volt battery, and wherein the electric machine (13) is connected to both the first and the second energy storage devices (14, 15). is,so that both the 12-volt electrical system and the 48-volt electrical system are powered by the electric machine (13).

Description

[0001] The present invention relates to a motor vehicle with an internal combustion engine according to the preamble of claim 1 and to a method for operating a motor vehicle with an internal combustion engine according to the preamble of claim 5.

[0002] Conventional motor vehicles, such as passenger cars or trucks with an internal combustion engine dedicated to propulsion and a manual or automatic transmission as well as a 12-volt electrical system, i.e., not full hybrid and not electric vehicles, are generally not able to recover the kinetic energy of the vehicle when decelerating (also referred to here as recuperation); rather, it is converted into heat by the vehicle's conventional friction brakes and is lost.

[0003] Strategies have already been developed for full hybrid and electric vehicles to at least partially recuperate this kinetic energy during braking. Even for non-full hybrid and non-electric vehicles, developments have been undertaken that aim to recuperate at least a small portion of the vehicle's kinetic energy during coasting or braking using the vehicle's alternator, by utilizing the alternator to generate electrical energy in parallel with a conventional braking process using friction brakes.

[0004] The invention most closely related to DE 10 2010 061 439 A1 relates to a braking system for a motor vehicle comprising at least one braking system for friction braking of the vehicle's brakeable wheels and an electric machine for regenerative braking of the vehicle. A braking effect is generated by means of the braking system and / or the electric motor via a brake pedal, depending on its actuation. A restoring force corresponding to the state of the braking system, acting on the brake pedal, is generated by means of a pedal simulator. It is provided that in a first actuation range of the brake pedal, starting from the initial position of the brake pedal, a predetermined and constant braking effect is generated by regenerative braking.

[0005] In DE 10 2014 208 201 A1, a device for supplying at least one consumer is proposed, comprising at least one basic electrical system with at least one energy storage device, with at least one first path connected to the basic electrical system, with at least one second path connected to a functional module, with a functional module that can connect the second path to the basic electrical system and / or to another energy storage device, wherein at least one preferably simply existing, safety-related consumer can be connected to the first path and / or to the second path, wherein at least one preferably redundant safety-related consumer is connected to the first path, and wherein at least one further preferably redundant safety-related consumer can be connected to the second path.

[0006] For example, US Patent 5,125,469 A discloses a motor vehicle with an internal combustion engine and a system for storing vehicle deceleration energy and using the stored deceleration energy for vehicle propulsion assistance. For this purpose, the system comprises a generator mechanically coupled to a vehicle powertrain for converting the deceleration energy into electrical energy, an electrically connected means to the generator for storing the electrical energy generated by the generator, and a motor mechanically connected to the powertrain and electrically connected to the storage means for converting the stored electrical energy into mechanical energy for propulsion assistance of the vehicle.The generator is switched on and the auxiliary motor is switched off when the vehicle decelerates, the generator is switched off and the auxiliary motor is switched on when the vehicle accelerates, and the generator and the auxiliary motor are switched off when the vehicle is neither decelerating nor accelerating.

[0007] US Patent 8,392,030 B2 further discloses a system comprising at least one electric generator connected to a movable component of the system such that a change in the generator's effective impedance controls the generator's kinematic characteristics, which in turn influence the movement of the movable component. The system further comprises at least one electrical load, which includes one or more electrical components of the system, such as a vehicle battery, vehicle lighting, heating devices, and similar electrical energy-consuming devices. According to one embodiment, the electric generator can be a vehicle alternator, wherein the change in the alternator's kinematic characteristics can reduce the rotational speed of a motor vehicle's internal combustion engine to assist in deceleration.The electrical energy generated by the generator can be stored in an energy storage device.

[0008] US Patent 2014 / 0305260A1 further describes a kinetic energy recovery and electric propulsion system for a motor vehicle with an internal combustion engine, comprising an electric machine that can be operated either as a motor or as a generator, wherein the generator operation is activated when the vehicle is braking or coasting, and the motor operation is activated to assist the internal combustion engine when the vehicle is accelerating.

[0009] Furthermore, WO 2008 / 000 982 A2 discloses a method for recovering electrical energy in a vehicle with regenerative braking, in which electrical energy generated by an electric machine, which may be an alternator, is stored during regenerative braking both in a supercapacitor as a secondary storage medium and in a conventional vehicle battery.

[0010] US Patent 7,336,002 B2 discloses a vehicle electrical system that uses a lead-acid battery as the primary energy storage device and a lithium-ion battery as a secondary storage device, the latter offering a higher charge acceptance than the lead-acid battery. The secondary storage device stores electrical energy generated during vehicle deceleration by a generator, which may be an alternator coupled to the vehicle's internal combustion engine via a belt drive. The primary and secondary storage devices are connected via a DC-DC converter.

[0011] Furthermore, US 2013 / 0141231A1 describes an independent actuating device for activating a purely regenerative braking process without activating conventional friction brakes for an electric or hybrid vehicle, as well as a rear light separate from a conventional brake light to indicate the purely regenerative deceleration of the vehicle.

[0012] US patent 2014 / 0012476A1 discloses a motor vehicle powered by an electric motor, which is braked both regeneratively by means of the electric motor and by means of conventional friction brakes, wherein the proportion of the friction brakes to the total braking torque is adjusted based on the difference between a desired braking requirement and the regenerative braking torque that can be generated by the electric motor.

[0013] From US patent 2012 / 0022732A1, a micro-hybrid vehicle with an alternator and an electrochemical battery is also known, wherein the battery is charged during a braking process by electrical energy generated by the alternator.

[0014] Furthermore, DE 41 02 929 A1 discloses a motor vehicle with a device for brake energy recovery by switching on auxiliary units during braking and in overrun mode of the vehicle with storage of the energy thereby recovered in associated storage devices, such as the storage of hot coolant in an additional storage device.

[0015] Furthermore, DE 41 40 650 A1 describes a device for producing hydrogen in vehicles using the waste heat of an internal combustion engine by reducing water with a catalyst. The fuel produced in this way is then fed back into the same engine of the same vehicle.

[0016] Furthermore, DE 10 2014 213 674 A1 discloses a vehicle with at least one drive motor cooled by means of a coolant, a heat storage unit for storing the waste heat from the drive motor transferred to the coolant, and an electric heater for the coolant, in which an internal combustion engine or an electric machine intended for driving the vehicle supplies the waste heat, and the electric machine also supplies recuperation energy for operating the electric heater. The temperature of a heat storage medium contained in the heat storage unit is increased beyond a value achievable by means of the waste heat and / or maintained at such an increased value in order to store additional energy in the vehicle.

[0017] Furthermore, DE 10 2012 204 988 A1 describes a heat storage device for a vehicle engine coolant, comprising a flexible storage container with an inner and an outer body, with insulation arranged between the two bodies. The flexible design of the heat storage device allows for optimal adaptation to the available space in the vehicle by selecting the appropriate shape.

[0018] Against this background, the present invention is based on the objective of providing a motor vehicle with an internal combustion engine and a method for its operation, which enable improved, more efficient use of the vehicle's kinetic energy during a braking process and can be implemented cost-effectively.

[0019] This problem is solved by a motor vehicle having the features of claim 1 and by a method having the features of claim 5.

[0020] A motor vehicle is shown comprising an internal combustion engine intended for vehicle propulsion, at least one electric machine operable as a generator and mechanically rotatably coupled to a drive train of the vehicle for generating electrical energy, at least one energy storage device connected to the electric machine for storing the electrical energy generated by the electric machine, at least one friction brake for decelerating the vehicle, and at least one control unit for controlling the electric machine, the energy storage device, and the friction brake, wherein the control unit is configured toThe invention aims to provide a vehicle deceleration torque, dependent on a braking request specified by a vehicle user via a brake actuation element, up to a maximum deceleration torque achievable by the generator load of the at least one electric machine, solely by means of the at least one electric machine, and to store the resulting electrical energy in the at least one energy storage device. Furthermore, in the event of a braking request exceeding this maximum achievable deceleration torque, the additional vehicle deceleration torque is also provided by means of the at least one friction brake, wherein the electric machine is an alternator or a starter generator. According to the invention, the at least one energy storage device is designed as a flexible heat storage container with an inner body and an outer body, between which insulation is arranged, and with an electric heating element.wherein the heating device can be operated by means of the electrical energy generated by the electric machine, and the heat storage container stores the waste heat of the internal combustion engine transferred to a coolant cooling the internal combustion engine, and the temperature of a heat storage medium contained in at least one energy storage device can be increased by means of the electric heating device beyond a value achievable by means of the waste heat and can be maintained at such an increased value, wherein both a 12-volt electrical system and a parallel 48-volt electrical system are used, wherein the 12-volt electrical system has a first energy storage device as a 12-volt battery and the 48-volt electrical system has a second energy storage device as a 48-volt battery, and wherein the electric machine is connected to both the first and the second energy storage devices, so that both the 12-volt electrical system and the 48-volt electrical system are powered by the electric machine.

[0021] Further particularly advantageous embodiments of the invention are disclosed in the dependent claims.

[0022] It should be noted that the features listed individually in the following description can be combined in any technically sensible way and demonstrate further embodiments of the invention. The description further characterizes and specifies the invention, particularly in conjunction with the figures.

[0023] A motor vehicle has an internal combustion engine intended for propulsion, for example a gasoline, diesel, natural gas or LPG engine, at least one electric machine that can be operated as a generator and is mechanically rotaryally coupled to a drive train of the vehicle for generating electrical energy, at least one energy storage device that is connected to the at least one electric machine for storing the electrical energy generated by it, at least one friction brake for decelerating the vehicle and at least one control unit for controlling the at least one electric machine and the at least one energy storage device as well as the at least one friction brake.

[0024] The term "powertrain" of a motor vehicle is understood here to mean all components that generate the power for propulsion within the vehicle and transmit it to the road. In the powertrain used in the motor vehicle according to the invention, which employs an internal combustion engine, for example, a gasoline, diesel, natural gas, or LPG engine, these components include, in particular, the internal combustion engine itself with the flywheel, the crankshaft, the clutch with the vehicle transmission, and, in the case of multi-track vehicles, the differential, the drive shafts or axles, and the wheels. In a multi-track, rear-wheel-drive or all-wheel-drive vehicle, additional components include the drive shafts or cardan shafts, the viscous coupling, any reduction gear, the universal joint or flex disc, the center support bearing, and, if applicable, the center differential(s).

[0025] As mentioned above, the control unit is designed to provide a vehicle deceleration torque, depending on a braking request made by a user of the vehicle via a brake actuation element, up to a maximum deceleration torque achievable by the generator load of the at least one electric machine, solely by means of the at least one electric machine, and to store the resulting electrical energy in the at least one energy storage device, and, in the event of a braking request exceeding this maximum achievable deceleration torque, to provide the additional vehicle deceleration torque also by means of the at least one friction brake.

[0026] In other words, the vehicle according to the invention is decelerated by means of a serial recuperation strategy, in which the vehicle deceleration torque of the braking demand specified via the brake actuation element is initially provided solely by the electric machine (hereinafter also referred to as regenerative braking) up to the maximum deceleration torque achievable by the generator load of the at least one electric machine operating in generator mode, and only at higher vehicle decelerations are the friction brakes of the vehicle additionally used. Since the performance of the at least one electric machine is fully utilized in this process, the regenerative braking achieves a maximum effect, in which all of the vehicle's kinetic energy present before the vehicle deceleration, or a maximum proportion thereof, is converted into electrical energy.

[0027] The control unit can be, in particular, an electronic control unit. Several control units can also be provided to implement the function described above, whereby these control units are then interconnected, for example, in the case of electronic control units, by means of a suitable communication medium, such as a communication bus, in a data-transmitting manner.

[0028] The brake actuation element can be, for example, a brake pedal that can be operated with the user's foot or a brake lever that can be operated with the user's hand.

[0029] The rotary coupling of the electric machine to a part of the drive train that rotates during vehicle movement can be achieved, for example, via a friction connection, such as friction wheels or a belt drive with V-belts, or via a positive connection, such as gears or a belt drive with toothed belts.

[0030] The electric machine is either an alternator or a starter-generator. The alternator's primary function is to supply electrical energy to the vehicle's electrical consumers. The starter-generator, on the other hand, combines the functions of a starter motor for the internal combustion engine and an alternator in a single electric machine. It can therefore both accelerate (start) the vehicle's internal combustion engine and, in generator mode, produce electrical energy like an alternator. Since the electric machine used to generate the electrical energy recuperated during vehicle deceleration is the alternator or starter-generator already present in the vehicle with an internal combustion engine, no additional electric machine needs to be installed in the vehicle for energy recuperation.This simplifies the construction and reduces the weight and cost of the vehicle.

[0031] In an advantageous embodiment of the invention, the electric machine delivers a maximum electrical output of at least 5 kW in generator mode. Since the electric machine is designed as an alternator or starter-generator, a larger amount of electrical energy can be recuperated during braking than is possible with a conventional alternator or starter-generator in generator mode, which are currently designed for a maximum electrical output of approximately 3 kW. In other words, the electric machine according to this embodiment delivers at least 2000 watts more than a conventional alternator or starter-generator in generator mode.

[0032] A further advantageous embodiment of the invention provides that the electric machine, in generator mode, delivers a nominal output voltage of at least 12 V. This allows the electric machine, in particular the alternator or the starter generator, to be directly coupled to a conventional 12-volt electrical system of the motor vehicle, into which the electric machine can feed the electrical energy it generates.

[0033] In such a case, the energy storage device can be designed as an electric battery with a nominal voltage of at least 12 V, which forms part of the 12-volt electrical system of the motor vehicle.

[0034] In a particularly simple and cost-effective design, such a 12-volt battery can be a conventional lead-acid battery, which is charged by the electrical energy recuperated by the electric machine during vehicle deceleration.

[0035] To further increase the amount of electrical energy that can be stored in the energy storage device, such a 12-volt battery can, for example, also be designed as a lithium-ion battery, which generally has a significantly greater charge acceptance and a higher capacity than a conventional lead-acid battery.

[0036] A particularly advantageous embodiment of the invention, which is cost-effective and reduces weight, provides, for example, an electric machine with a nominal output voltage of 12 V, in particular an alternator or a starter generator, in combination with a 12-volt lithium-ion battery as an energy storage device, forming a 12-volt electrical system for the motor vehicle. Since the electric machine is designed as an alternator or starter generator, it should advantageously deliver a maximum output power that is at least 2000 watts higher than the maximum output power of a conventional alternator or a starter generator operated in generator mode, i.e., for example, at least 5 kW.Since motor vehicles with internal combustion engines are usually already equipped with a 12-volt electrical system to supply the vehicle's electrical consumers, this design advantageously requires only a 12-volt lithium-ion battery with sufficiently high charge acceptance and capacity, as well as an electric machine that can be operated as a generator, designed as an alternator or starter generator, for recuperating the electrical energy generated during vehicle deceleration. Thus, such a vehicle has a comparatively simple and cost-effective design, while allowing for the recuperation of a maximum amount of vehicle kinetic energy.

[0037] A further advantageous embodiment of the invention provides that the electric machine, in generator mode, delivers a nominal output voltage of at least 48 V. This allows the electric machine, in particular an alternator or a starter generator, to be directly coupled to a 48-volt electrical system of the vehicle, into which the electric machine can feed the electrical energy it generates. In this case, such a 48-volt electrical system preferably forms a parallel power supply network to a conventional 12-volt electrical system of the vehicle. This embodiment, with electrical recuperation at a higher voltage level than 12 volts, enables even more efficient use of the electrical energy generated during vehicle deceleration.

[0038] In such a case, the energy storage device can be an electric battery with a nominal voltage of at least 48 V, which then forms part of the vehicle's 48-volt electrical system. Particularly preferably, such a 48-volt battery can be a lithium-ion battery in which the electrical energy recuperated by the electric motor during vehicle deceleration is primarily stored. Of course, in this case, a 12-volt battery present in a parallel 12-volt electrical system of the vehicle can also be charged by the recuperated electrical energy by converting the 48-volt nominal output voltage of the electric motor to the 12-volt level of the 12-volt electrical system using a suitable converter, for example, a DC-DC converter.

[0039] Of course, other nominal output voltages besides the previously described 12-volt nominal output voltage or 48-volt nominal output voltage for the electric machine and for the battery designed as an electrical energy storage device are also conceivable, for example 24 volts or 110 volts.

[0040] A particularly advantageous embodiment of the invention provides, for example, an electric machine with a nominal output voltage of 48 V, in particular an alternator or a starter generator, in combination with a 48-volt lithium-ion battery as an energy storage device, forming a 48-volt electrical system of the motor vehicle. In parallel to the 48-volt electrical system of the motor vehicle, the vehicle also has a conventional 12-volt electrical system with a 12-volt battery, for example a lithium-ion battery or a conventional lead-acid battery.Both the 12-volt and 48-volt electrical systems of the vehicle are powered by the electric motor, which is designed as an alternator or starter generator. In this case, the electric motor is connected to the 12-volt electrical system via a suitable electrical converter, in particular a DC / DC converter, to convert the 48-volt nominal output voltage of the electric motor to the 12-volt voltage level of the 12-volt electrical system. With such a setup, a greater amount of electrical energy can be recuperated from the vehicle's kinetic energy during deceleration compared to a vehicle with only a single 12-volt electrical system, and stored in the energy storage device(s).

[0041] To further optimize the use of recuperated electrical energy and avoid unnecessary ohmic losses, a further advantageous embodiment of the invention provides that the at least one energy storage device is arranged as close as possible to the electric motor in the vehicle. This allows, in particular, the ohmic losses resulting from the resistance of the wiring required for electrical coupling between the electric motor and the energy storage device to be largely reduced.

[0042] As mentioned above, the energy storage device is designed as a heat storage device with an electric heating element, wherein the heating element can be operated by means of the electrical energy generated by the electric machine and the heat storage device stores the waste heat of the internal combustion engine which is transferred to a coolant which cools the internal combustion engine and the temperature of a heat storage medium contained in the heat storage device can be increased by means of the electric heating element beyond a value achievable by means of the waste heat and can be maintained at such an increased value.This allows the electrical energy generated by the electric machine to be at least partially converted into heat energy and stored during the recuperation of the vehicle's kinetic energy during vehicle deceleration, for example when the state of charge of one or more other electrical energy storage devices is sufficiently high and / or when there is no high electrical demand from the vehicle's electrical consumers.

[0043] The energy storage system, designed as a thermal storage unit, allows the heat contained in the storage medium to be retained for at least 24 hours, depending on the ambient temperature. This results in fuel savings and correspondingly lower emissions. The heat stored in the thermal storage unit during and / or at the end of a journey is used to bring the combustion engine and, if applicable, the drivetrain back up to their operating temperature as quickly as possible upon restarting. This significantly reduces friction losses in the combustion engine and drivetrain and allows for the creation of an optimal fuel-air mixture in terms of fuel consumption and emissions. The stored heat can also be used to quickly warm other vehicle components, such as an energy storage system designed as an electric battery, and / or the vehicle interior.

[0044] As mentioned above, the energy storage unit, designed as a heat storage system, also features a flexible storage container with an inner and an outer body, with insulation positioned between the two bodies. The flexible design of the heat storage unit allows for optimal adaptation to the specific space constraints within the vehicle by selecting the appropriate shape.

[0045] The energy storage device described above, designed as a thermal storage unit, can of course also be combined with at least one electrical energy storage device, for example, with an electrical energy storage device designed as a 12-volt battery and / or with an electrical energy storage device designed as a 48-volt battery. Other voltage values ​​for the electrical energy storage devices are naturally also possible, as already mentioned.

[0046] Also shown is a method for operating a motor vehicle with an internal combustion engine intended for vehicle propulsion, at least one electric machine operable as a generator and mechanically rotatably coupled to a drive train of the vehicle for generating electrical energy, at least one energy storage device connected to the at least one electric machine for storing the electrical energy generated by it, and at least one friction brake for decelerating the vehicle.wherein the vehicle, depending on a braking request specified by a user of the vehicle via a brake actuation element, is decelerated solely by means of the at least one electric machine up to a maximum deceleration torque achievable by the generator load of the at least one electric machine, and the resulting electrical energy is stored in the at least one energy storage device, and wherein, in the event of a braking request exceeding this maximum achievable deceleration torque, the vehicle is additionally decelerated by means of the at least one friction brake of the vehicle, wherein the electrical energy generated during the vehicle deceleration and stored in the at least one energy storage device is produced by an alternator or a starter generator. According to the invention, the at least one energy storage device is a flexible heat storage container with an inner body and an outer body,an insulation is arranged between them, and is equipped with an electric heating device, wherein the heating device can be operated by means of the electrical energy generated by the electric machine, and the heat storage container stores the waste heat of the internal combustion engine transferred to a coolant cooling the internal combustion engine, and the temperature of a heat storage medium contained in at least one energy storage device can be increased by means of the electric heating device beyond a value achievable by means of the waste heat and can be maintained at such an increased value, wherein both a 12-volt electrical system and a parallel 48-volt electrical system are used, wherein the 12-volt electrical system has a first energy storage device as a 12-volt battery and the 48-volt electrical system has a second energy storage device as a 48-volt battery.and wherein the electric machine provides a nominal output voltage of 48V and is connected to both the first and the second energy storage devices, with both the 12-volt electrical system and the 48-volt electrical system being supplied by the electric machine.

[0047] Regarding the effects and advantages of such a method, reference is made at this point to the preceding description of the motor vehicle according to the invention, since these also apply analogously to the method according to the invention.

[0048] The method described above can preferably be carried out by at least one control unit, and particularly preferably by at least one electronic control unit of the motor vehicle.

[0049] A particularly simple and therefore cost-effective embodiment of the invention provides that the motor vehicle is powered solely by the internal combustion engine. The electric machine, in particular an alternator or a starter-generator, thus serves only to recuperate the vehicle's kinetic energy during deceleration and not to propel the vehicle.

[0050] Further features and advantages of the invention will become apparent from the following description of exemplary embodiments of the invention, which are not to be understood as limiting and are explained in more detail below with reference to the drawing. This drawing schematically shows: Fig. Figure 1 shows a top view of a first embodiment of a motor vehicle, and Fig. Figure 2 shows a top view of a second embodiment of a motor vehicle, and Fig. 3 a top view of an embodiment of a motor vehicle according to the invention.

[0051] In the different figures, parts of equivalent function are always marked with the same reference symbols, so that they are generally only described once. This is shown in the Fig. 1 and Fig. The embodiment described in section 2 is not covered by the scope of protection of claim 1.

[0052] Fig. Figure 1 shows a top view of a first embodiment of a motor vehicle 1. As can be seen, the motor vehicle 1 has an internal combustion engine 2, for example a gasoline, diesel, natural gas or LPG engine, intended for propulsion, which is located in Fig. Engine 1 is shown with four cylinders. Of course, the internal combustion engine 2 can also have more or fewer cylinders.

[0053] Furthermore, the in Fig. The motor vehicle 1 depicted has an electrical machine 3, which can be operated as a generator and is mechanically rotaryally coupled to a drive train of the vehicle 1 for the generation of electrical energy. In the case of the Fig. In the embodiment of the motor vehicle 1 shown in Figure 1, the electric machine 3 is an alternator or a starter generator, which in this example is directly rotaryally coupled to the internal combustion engine 2, for example to its crankshaft (not shown) or its flywheel (not shown). The rotary coupling between the electric machine 3 and a part rotating during the operation of the internal combustion engine 2 can be achieved via a frictional connection, for example by means of friction wheels or a belt drive with a V-belt, or via a positive connection, for example by means of gears or a belt drive with a toothed belt.In the illustrated embodiment of the motor vehicle 1, the electric machine 3 delivers a nominal output voltage of 12 volts and a maximum electrical output power of at least 5 kW, which corresponds to approximately 2000 watts more output power than is available from today's conventional alternators or starter generators.

[0054] How Fig. As can be seen further in Figure 1, the motor vehicle 1 also comprises a first energy storage device 4 and a second energy storage device 5, both of which are connected to the electric machine 3 for storing the electrical energy generated by the electric machine 3 in generator mode. In the illustrated embodiment of the motor vehicle 1, the energy storage device 4 is an electric 12-volt battery, which in this case is designed as a conventional lead-acid battery. The energy storage device 4 is connected via corresponding, in Fig. 1 Indicated connecting cable to the electrical machine 3 electrically connected.

[0055] The embodiment of the in Fig. The motor vehicle 1 shown in Figure 1 has a single 12-volt electrical system for supplying the electrical consumers.

[0056] In the illustrated embodiment of the motor vehicle 1, the second energy storage device 5 is designed as a heat storage device with an electric heater 6. The heater 6 can be operated by means of the electrical energy generated by the electric motor 3 and is accordingly electrically connected to the electric motor 3 via appropriate electrical connecting cables. The heat storage device 5 is designed to store the waste heat from the internal combustion engine 2 that is transferred to a coolant which cools the internal combustion engine 2.Furthermore, the temperature of a heat storage medium contained in the heat storage unit 5 can be increased by means of the electric heating device 6 beyond a value achievable by means of the waste heat of the internal combustion engine 2 and kept at such an increased value in order to convert at least some of the electrical energy generated by the electric machine 3 during vehicle deceleration into heat energy and to store it in the heat storage unit 5.

[0057] The in Fig. The motor vehicle 1 shown further comprises, in a manner known per se, a friction brake (not shown) for each wheel (also not shown) for decelerating the vehicle 1.

[0058] In Fig. Figure 1 also shows an electronic control unit 7, which controls the electric machine 3, the two energy storage devices 4 and 5, and the friction brakes. A brake actuation element 8, in this case a brake pedal, is also connected to the control unit 7. In this way, the control unit 7 can detect a braking request made by a user of the vehicle 1 via the brake actuation element 8, for example by transmitting the current position of the brake pedal 8 to the user.

[0059] The control unit 7 is now configured to provide a vehicle deceleration torque, dependent on the braking demand specified by the user of the vehicle 1 via the brake actuation element 8, up to a maximum deceleration torque achievable solely by the electric machine 3 through its generator load. The resulting electrical energy is stored in both energy storage devices 4 and 5. If the braking demand exceeds this maximum achievable deceleration torque, the additional vehicle deceleration torque is also provided by means of the friction brakes. In this way, the entire kinetic energy of the vehicle 1 before deceleration, or at least a maximum proportion thereof, can be recuperated by the electric machine 3 operating in generator mode and stored in the energy storage devices 4 and 5.

[0060] Fig. Figure 2 shows a top view of a second embodiment of a motor vehicle 10. The motor vehicle 10 has features similar to the motor vehicle 1. Fig. 1. A 12-volt electrical system is installed, which is supplied by the electric machine 3 with a nominal output voltage of 12 volts in generator mode. The in Fig. However, the embodiment of the motor vehicle 10 shown in 2 includes an energy storage device 11 which, in comparison to the 12-volt lead-acid battery 4, consists of Fig. 1 exhibits a significantly higher charge acceptance and a considerably larger capacity. In the illustrated embodiment, the energy storage device 11 is designed as a 12-volt lithium-ion battery.

[0061] Fig. Figure 3 shows a top view of an embodiment of a motor vehicle 12 according to the invention. In this embodiment, the motor vehicle 12 has an electric machine 13, which can be operated as a generator and is mechanically rotaryally coupled to the drive train of the vehicle 12, here the internal combustion engine 2, for generating electrical energy. As in the embodiments described above, the electric machine 13 is preferably designed as an alternator or starter generator. In contrast to the embodiments described above, Fig. 1 and Fig. However, in the embodiments described in 2, the electric machine 13 delivers a nominal output voltage of 48 volts.

[0062] How Fig. As can be seen from Figure 3, the motor vehicle 12 has both a 12-volt electrical system and a parallel 48-volt electrical system. The 12-volt electrical system of the motor vehicle 12 further comprises a first energy storage device 14, which is designed as a 12-volt battery, for example, a lead-acid battery. The 48-volt electrical system of the motor vehicle 12, on the other hand, comprises a second energy storage device 15, which is designed as a 48-volt battery, for example, a lithium-ion battery. As shown in Figure 3, the 12-volt electrical system comprises a 12-volt electrical system and a 48-volt electrical system. Fig.As can be seen in Figure 3, the electric machine 13 is electrically connected to both the first energy storage device 14 and the second energy storage device 15. However, since the electric machine 13 provides a nominal output voltage of 48 volts, a DC-DC converter 16 is inserted in the connection between the electric machine 13 and the 12-volt battery 14. This converter reduces the nominal output voltage of the electric machine 13 from 48 volts to the nominal voltage of the 12-volt electrical system (12 volts). The second energy storage device 15 (48-volt battery), on the other hand, can be powered directly by the electric machine 13.

[0063] If one of the motor vehicles 1, 10, or 12 described in the preceding embodiments is to be braked, i.e., decelerated, by a user of the motor vehicle 1, 10, or 12 at the brake actuation element 8, the control unit 7 will first check whether the specified braking requirement can be met solely by the regenerative load of the electric machine 3 or 13 operating in generator mode during the deceleration process. In this case, the control unit 7 controls the electric machine 3 or 13 such that it decelerates the vehicle 1, 10, or 12 solely by its regenerative load. The electrical energy generated by the electric machine 3 or 13 is stored in the energy storage devices 4 and 5 or 11 or 14 and 15, with the respective storage share being distributed among the different energy storage devices 4 and 5 or 11 or 15.Depending on factors such as the current charge level of each energy storage device (4 and 5, 11, 14, and 15) and its capacity, control units 7 also adjust accordingly. The friction brakes are not used in this case.

[0064] If the specified braking requirement exceeds the maximum deceleration torque achievable by the generator load of the electric machine 3 or 13, the control unit 7 also activates the friction brakes of the vehicle 1, 10 or 12 in such a way that, in addition to the generator load of the electric machine 3 or 13, they are used to decelerate the vehicle 1, 10 or 12, so that the specified braking requirement is met by the sum of the deceleration torques of the electric machine 3 or 13 operating in generator mode and the friction brakes.

[0065] The motor vehicle according to the invention described above, as well as the method according to the invention for its operation, are not limited to the embodiments disclosed herein, but also include further embodiments with the same effect.

[0066] For example, it is not necessary to directly couple the electric machine to the internal combustion engine via a rotary coupling, as shown in the preceding embodiments; instead, it can also be rotary coupled to other rotating parts of the drivetrain during vehicle motion. For instance, the electric machine can be particularly advantageously directly rotary coupled to a vehicle transmission. This further increases the efficiency of the recuperated electrical energy during vehicle deceleration, as the internal combustion engine is decoupled from the transmission during deceleration, thus eliminating the need to expend work to overcome the engine's drag torque.

[0067] Furthermore, other combinations of two, three, or even more energy storage devices are conceivable for storing the electrical energy generated by the electric motor during vehicle deceleration, beyond those shown in the preceding embodiments. For example, a conventional 12-volt battery, such as a lead-acid or lithium-ion battery, can be used as a first energy storage device, part of the vehicle's 12-volt electrical system, combined with a thermal storage device as described herein as a second energy storage device, and a 48-volt battery, such as a lithium-ion battery, as a third energy storage device, part of a 48-volt electrical system connected in parallel to the 12-volt system. Likewise, other battery technologies besides lead-acid or lithium-ion batteries are possible for use as energy storage devices.

[0068] It is also conceivable to use one or more electrical capacitors or supercapacitors as energy storage devices. Reference symbol list: 1 motor vehicle 2 Internal combustion engine 3 Electric Machine 4 First energy storage device, 12-volt lead-acid battery 5 Second energy storage, heat storage 6 Electric heater 7 Control unit 8 Brake actuation element 10 motor vehicle 11 Energy storage devices, 12-volt lithium-ion battery 12 Motor vehicle 13 Electric Machine 14 First energy storage device, 12-volt lead-acid battery 15 Second energy storage, 48-volt lithium-ion battery 16 DC / DC converters

Claims

[1] Motor vehicle with an internal combustion engine (2) intended for propulsion of the vehicle, at least one electric machine (13) which can be operated as a generator and is mechanically rotatably coupled to a drive train (2) of the vehicle (12) for generating electrical energy, at least one energy storage device (14, 15) which is connected to the at least one electric machine (13) for storing the electrical energy generated by it, at least one friction brake for decelerating the vehicle (12) and at least one control unit (7) for controlling the at least one electric machine (13) and the at least one energy storage device (14, 15) as well as the at least one friction brake, wherein the control unit (7) is configured toa vehicle deceleration torque dependent on a braking request specified by a user of the vehicle (12) via a brake actuation element (8) up to a maximum deceleration torque achievable by the generator load of the at least one electric machine (13) solely by means of the at least one electric machine (13) and the resulting electrical energy to be stored in the at least one energy storage device (14, 15) and, in the event of a braking request exceeding this maximum achievable deceleration torque, the additional vehicle deceleration torque also to be provided by means of the at least one friction brake, wherein the electric machine (13) is an alternator or a starter generator, . characterized by, that the at least one energy storage device (14, 15) is designed as a flexible heat storage container with an inner body and an outer body, between which insulation is arranged, and with an electric heating device (6), wherein the heating device (6) can be operated by means of the electrical energy generated by the electric machine (13) and the heat storage container stores the waste heat of the internal combustion engine (2) which is transferred to a coolant cooling the internal combustion engine (2) and the temperature of a heat storage medium contained in at least one energy storage device (14, 15) can be increased by means of the electric heating device (6) beyond a value achievable by means of the waste heat and can be maintained at such an increased value, wherein both a 12-volt electrical system and a parallel 48-volt electrical system are used,wherein the 12-volt electrical system has a first energy storage device (14) as a 12-volt battery and the 48-volt electrical system has a second energy storage device (15) as a 48-volt battery, and wherein the electric machine (13) is connected to both the first and the second energy storage devices (14, 15) such that both the 12-volt electrical system and the 48-volt electrical system are powered by the electric machine (13). [2] Motor vehicle according to claim 1, characterized by , that the electric machine (13) delivers a maximum electrical output power of at least 5 kW in generator mode. [3] Motor vehicle according to any of the preceding claims, characterized by , that a direct current converter (16) is inserted into the connection between the electric machine (13) and the first energy storage device (14). [4] Motor vehicle according to any of the preceding claims, characterized by, that the electric machine (13) in generator operation delivers a nominal output voltage of at least 48 V. [5] Method for operating a motor vehicle (12) comprising an internal combustion engine (2) intended for propulsion of the vehicle, at least one electric machine (13) which can be operated as a generator and is mechanically rotatably coupled to a drive train (2) of the vehicle (12) for generating electrical energy, at least one energy storage device (14, 15) which is connected to the at least one electric machine (13) for storing the electrical energy generated by it, and at least one friction brake for decelerating the vehicle (12),wherein the vehicle (12) is decelerated, depending on a braking request specified by a user of the vehicle (12) via a brake actuation element (8), up to a maximum deceleration torque achievable by the generator load of the at least one electric machine (13), solely by means of the at least one electric machine (13), and the resulting electrical energy is stored in the at least one energy storage device (14, 15), and in the event of a braking request exceeding this maximum achievable deceleration torque, the vehicle (12) is additionally decelerated by means of the at least one friction brake of the vehicle (12), wherein the electrical energy generated during the vehicle deceleration and stored in the at least one energy storage device (14, 15) is generated by an alternator (13) or a starter generator (13). characterized by , that the at least one energy storage device (14, 15) is designed as a flexible heat storage container with an inner body and an outer body, between which insulation is arranged, and with an electric heating device (6), wherein the heating device (6) can be operated by means of the electrical energy generated by the electric machine (13) and the heat storage container stores the waste heat of the internal combustion engine (2) released to a coolant cooling the internal combustion engine (2) and the temperature of a heat storage medium contained in at least one energy storage device (14, 15) can be increased by means of the electric heating device (6) beyond a value achievable by means of the waste heat and can be maintained at such an increased value, wherein Both a 12-volt electrical system and a parallel 48-volt electrical system are used, wherein the 12-volt electrical system has a first energy storage device (14) as a 12-volt battery and the 48-volt electrical system has a second energy storage device (15) as a 48-volt battery, and wherein the electric machine (13) provides a nominal output voltage of 48V and is connected to both the first and the second energy storage devices (14, 15), and wherein both the 12-volt electrical system and the 48-volt electrical system are powered by the electric machine (13).

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