On-board electrical system layout for a hybrid vehicle

Abstract

On-board electrical system arrangement (1) for a hybrid vehicle (200) with a first and a second on-board electrical system (2, 11) which are connected to each other via a coupling element (5) and each on-board electrical system (2, 11) comprises an energy converter (8; 18) and an energy storage device (4; 14), wherein an energy flow between the first and second on-board electrical systems (2, 11) is controlled by means of a control of the coupling element (5) and / or depending on an operating state, one of the energy converters (8; 18) and / or one of the energy storage devices (4; 14) can be controlled, a first and second electric machine (6, 7) are provided, which can be coupled to an internal combustion engine (19) to provide propulsion, one of the electric machines can be operated either in generator or motor mode and the first electric machine (6) drives an exhaust gas turbocharger and / or a charge air compressor.

Description

[0001] The invention relates to an on-board power supply arrangement for a hybrid vehicle with a first and a second on-board power supply which are connected to each other via a coupling element and each on-board power supply comprises at least one energy converter and / or an energy storage device.

[0002] Unlike earlier vehicles, which used combustion engines with simple electrical systems (such as starters and ignition), modern vehicle electrical systems (or electrical system topologies) are subject to higher and more complex requirements. Fundamentally, a vehicle electrical system still serves to supply the associated electrical consumers with electrical energy conveniently, efficiently, and with high availability, in order to ensure vehicle functions both during operation and when the vehicle is not in operation.

[0003] The vehicle electrical system includes all electrical power generators, storage devices, distribution systems, converters, cables, and consumers. Control and / or regulating devices (for example, an ECU) are also part of the vehicle electrical system.

[0004] In hybrid drives, the conventional twelve-volt electrical system architecture reaches its limits, as the vehicle drive is partially, temporarily or completely powered by electric motors or supported by them, which require a large amount of electrical power.

[0005] For example, DE 10 2013 013 541 B3 discloses a vehicle electrical system arrangement in which a high-voltage and a low-voltage electrical system are provided. Furthermore, an electric drive motor is provided for propelling the vehicle, as well as another electric motor suitable for starting the vehicle. To relieve the load on the low-voltage electrical system, these two electric motors are powered from a high-voltage electrical system. This concept requires a further electric motor, which operates as a generator, to charge a high-voltage battery during combustion engine operation.

[0006] Another concept is shown in DE 10 2005 024 411 A1. This document depicts an on-board electrical system arrangement in which a generator and an electric motor are coupled to an internal combustion engine via a belt drive. The electric motor, which can be connected to the engine via a common shaft, drives auxiliary components, either mechanically coupled via the internal combustion engine or electrically driven by a power supply from the generator or an energy storage device. The electric machines (motor and generator) provided here primarily serve for differentiated drive control and power supply of auxiliary components, as well as for differentiated charging and discharging of the electrical energy storage device. Furthermore, the motor can function as a starter and (auxiliary generator).

[0007] German patent DE 10 2006 013 502 A1 discloses a hybrid drive system comprising an internal combustion engine and an electric motor. The hybrid drive system also includes an air conditioning unit with an additional electric motor, which is also used to start the internal combustion engine. Different voltage levels are available, coupled via voltage converters.

[0008] The object of the present invention is to provide an on-board electrical system arrangement for a hybrid vehicle that at least partially overcomes the aforementioned disadvantages.

[0009] This problem is solved by the on-board network arrangement according to claim 1, the drive system according to claim 8 and a hybrid vehicle according to claim 9.

[0010] Further advantageous embodiments of the invention will become apparent from the dependent claims and the following description of preferred embodiments of the present invention.

[0011] An on-board electrical system arrangement according to the invention for a hybrid vehicle comprises a first and a second on-board electrical system, each connected to the other via a coupling element. Each on-board electrical system comprises at least one energy converter and one energy storage device, wherein an energy flow between the first and second on-board electrical systems can be controlled by means of a control of the coupling element and / or depending on an operating state of one of the energy converters and / or one of the energy storage devices, and wherein a first and second electric machine are provided, which can be coupled to an internal combustion engine to provide propulsion, wherein one of the machines can be operated either in generator or motor mode.

[0012] On-board power supply arrangements with a first and a second on-board power supply allow high power peaks to be provided in one on-board power supply without endangering the stability of the other on-board power supply.

[0013] Energy converters within the meaning of the present invention are all electrical energy generators or consumers (resistive and inductive loads). For example, so-called DC / DC converters or galvanically isolated DC-DC converters serve as coupling elements that control or regulate the energy flow between a first and a second vehicle electrical system. Depending on the operating state of the energy converters and also depending on the state of charge of the energy storage devices, the energy flow between the two vehicle electrical systems can thus be controlled.

[0014] The coupling of a first and second electric motor to an internal combustion engine, which acts on the drivetrain, allows for more targeted and differentiated control of the drivetrain's power output. Simultaneously, because one of the electric motors can be operated in either generator or motor mode, engine power from the internal combustion engine can be converted into electrical power and fed into the vehicle's electrical system, while the other electric motor simultaneously increases the drive power of the internal combustion engine. Conversely, it is also possible to increase the drivetrain's power output by using both electric motors in motor mode.

[0015] This allows for several different operating states, namely 1. Drive power is provided exclusively via the internal combustion engine (also known as internal combustion engine or ICE); 2. Drive power is provided by the internal combustion engine and one of the electric machines; 3. Drive power is provided by the combustion engine and by the motor operation of both electric machines; 4. Drive power is provided exclusively by the combustion engine, and part of the drive power is converted into electrical energy in generator mode by one of the electric machines and fed into the vehicle electrical system; 5. Drive energy is provided by the combustion engine and the electric motor operation of one of the electric machines, and part of the drive energy is converted into electrical energy by the generator operation of the other electric machine and fed into the on-board electrical system.

[0016] This makes it possible to use one combustion engine component and two electric machine components to implement both a differentiated drive power distribution and a differentiated power supply in the vehicle electrical system to supply the energy converters / energy consumers and to control the charging and discharging of the energy storage devices.

[0017] In one embodiment, the first electrical system is a lower-voltage system, in particular a 12-volt system, and the second electrical system is a higher-voltage system, in particular a 24-volt, 36-volt, or 48-volt system. This division into a first electrical system with a lower voltage, in particular a 12-volt system, and a second electrical system with a higher voltage, exceeding that of the first, is advantageous for supplying high-power electrical consumers / converters, especially for powering high-performance electric motors, and increases the overall stability of the power supply.

[0018] A design in which the first and second electric machines can each only be supplied from the second vehicle electrical system, in particular from the higher voltage electrical system, offers the advantage of realizing the primary energy supply via the higher voltage level, so that, for example, a sufficient power reserve can always be ensured in the lower voltage electrical system (e.g. the 12-volt electrical system) and the supply stability there remains stable regardless of consumption and power peaks occurring in the higher voltage electrical system.

[0019] In a design where the first electric machine is configured as a starter generator, in particular as a belt-driven starter generator (BSG), the advantage is that a suitably appropriate electric machine can be used both for starting the combustion engine (in short-term operation) and otherwise as a generator to supply electrical consumers / converters and / or the energy storage devices with electrical energy.

[0020] The belt-driven starter generator (BSG) design, in particular, allows for a very compact integration into the combustion engine's drive chain. A BSG quickly revs the combustion engine to high crankshaft speeds (up to starting speed), enabling a very fast, quiet, and fuel-efficient start, and is suitable for convenient start / stop systems. Additionally, the BSG's output can be used to temporarily power the vehicle (e.g., for acceleration) by drawing stored electricity to assist the combustion engine.

[0021] In generator mode, it is possible to use a portion of the engine's power to generate electricity and, if necessary, to recuperate braking energy and feed it back into the energy storage system. At the same time, a conventional starter (e.g., a pinion starter) can usually be omitted.

[0022] Since the second electric machine drives an exhaust gas turbocharger and / or a charge air compressor, the drive power of the combustion engine is further differentiated and effectively increased.

[0023] There is one concept in which the second electric machine is coupled to the exhaust gas turbocharger via a common drive shaft (euATL) and drives it additionally as needed, and the other concept in which an additional electrically driven compressor (eBooster) is provided as a pre-stage to the exhaust gas turbocharger, which briefly takes over the air supply of the combustion engine.

[0024] The advantage of the "eBooster" concept is that only the turbine wheel of the eBooster needs to be driven. At the same time, compared to the euATL concept, equivalent performance can be achieved at a lower engine speed. This effectively provides a two-stage controlled turbocharging system with a wider compressor map, allowing the torque of the combustion engine to be increased across the entire engine speed range.

[0025] In a design where the coupling element is configured as a controllable DC-DC converter, in particular as a potential-isolating DC-DC converter, it is possible to operate the two on-board networks largely independently of each other and at the same time to realize the desired energy flow between both networks in a differentiated manner.

[0026] A control system can be provided to regulate the energy flow between the first and second electrical systems. This can be achieved either by controlling the coupling element itself, or additionally and / or alternatively by controlling the power or consumption of the first and / or second electric machine, other energy converters / consumers, or other electric machines, or by controlling the charging and discharging of energy storage devices.

[0027] The vehicle electrical system can be configured to prioritize energy flow based on one or more criteria. These include, in particular, the driving state or operating state of a drive unit (comprising the combustion engine itself and one of the electrical components), the individual driving behavior of the driver or the vehicle, the stress on vehicle components, and comfort criteria such as restarting the combustion engine when transitioning from idling (with the combustion engine off) to driving. This also benefits the comfort aspect of air conditioning (heating) and reduces fuel consumption through optimal control of the components.

[0028] A drive system for a hybrid vehicle with an internal combustion engine, which is effectively connected to a first and second electric machine, which has a vehicle electrical system arrangement of the type described above, enables, in addition to a convenient start-stop function of the drive, a "mild hybrid operation", in particular with an increase in performance during start-up by a significant increase in torque at low speeds as well as a short-term or continuous increase in performance in the higher speed range (boost function).

[0029] A hybrid vehicle with a drive system according to the invention enables improved driving performance, increased comfort and reduced fuel consumption.

[0030] Exemplary embodiments of the invention will now be described by way of example and with reference to the accompanying drawing. This shows: Fig. 1 a schematic representation of an embodiment of a vehicle electrical system arrangement according to the invention, Fig. 2 a torque characteristic of a drive system according to the invention in comparison to other systems, Fig. 3 Full-load characteristic curves of a drive system according to the invention in comparison to other systems, and Fig. 4 the temporal profile of achievable motor speeds of a drive system according to the invention.

[0031] Fig. Figure 1 schematically shows an embodiment of a vehicle electrical system arrangement 1 according to the invention, which is part of a drive system 100 in a vehicle 200.

[0032] The electrical system arrangement 1 comprises a first, higher-voltage electrical system, which connects, via a wiring system 3 (solid lines), a first energy storage device 4 designed as a 48-volt battery, a coupling element 5 designed as a DC / DC converter (optionally with galvanic isolation), a first electric machine 6, a second electric machine 7, and a possible further energy converter 8. The energy converters 8 can be electrical loads (resistive or inductive loads) such as actuators, lighting elements, or heating elements, which are supplied from the higher-voltage electrical system 2.

[0033] The control and regulation of the vehicle electrical system components is carried out by a control unit, in particular an ECU 9. In this context, the term "control unit" is not limited to a device that performs only pure control functions, but also includes those control units that can also perform regulation functions. The ECU 9 is connected via signal lines to components of the vehicle electrical system 2 and the drive system 100.

[0034] The coupling element 5 connects the higher voltage electrical system 2 to a lower voltage electrical system 11, which connects a second energy storage device 14 to at least one further converter 18 via a line system 13 (dashed line).

[0035] The energy converters 8 and 18 are also controlled via the ECU 9 and can alternatively or optionally each include their own control elements, which are connected to the ECU 9 via the signal lines.

[0036] The energy flow between the higher voltage on-board network 2 and the lower voltage on-board network 11, which in the present embodiment are designed as a 48 volt on-board network and a 12 volt on-board network, takes place via the DC / DC converter, which can also be controlled via the ECU 9.

[0037] The drive system 100 comprises an internal combustion engine (ICE) 19, which is mechanically coupled via a belt drive to the second electric machine 7, which is designed as a belt starter generator (BSG), which in turn is part of the on-board network arrangement 1 or the 48 volt on-board network 2 (higher voltage on-board network).

[0038] The combustion engine 19 is coupled to the first electric machine 6 via the fresh air supply; in the present embodiment, the electric machine is designed as a so-called eBooster. This eBooster compresses the fresh air supplied to the combustion engine by means of an electrically driven compressor as a precursor to an exhaust gas turbocharger.

[0039] In an alternative (not shown) embodiment, the first electric machine 6 can also directly engage a drive shaft of the exhaust gas turbocharger, which is then designed as a so-called euATL (electrically assisted exhaust gas turbocharger).

[0040] The electric machines 6 and 7 are optionally connected to the 48 volt electrical system 2 via pulse inverters (not shown), which convert the direct current into three-phase current suitable for driving the electric machine, optionally with variably adjustable current magnitude and rotating field frequency.

[0041] The first and second energy storage devices 4, 14 and the DC / DC converter 5 are used to keep the on-board networks 2 and 11 operational by means of energy balancing, which may be controlled by the ECU 9.

[0042] When the drive system 100 is in operation, the drive-effective components combustion engine (VKM) 19, first electric machine (eBooster) 6 and second electric machine (RSG) 7 can be operated in different constellations. • The drive is provided solely by the internal combustion engine 19; the regenerative generator 7 may even be disengaged from the drivetrain by means of a clutch, and the eBooster 6 is not used. In this operating state, the full drive power of the internal combustion engine 19 is available. • In another operating state, the RSG 7 operates in generator mode, producing electricity that is fed into the higher voltage electrical system 2. There, it is used either to charge the energy storage unit or to power other consumers. The eBooster 6 is inactive, and the drive power is provided by the VKM 19. • In another operating state, particularly during start-up and / or acceleration, both the eBooster 6 and the RSG 7 work together with the VKM 19 to provide drive power. This significantly increases the effective drive torque, especially at low engine speeds. • In another operating mode, it is also possible to operate the eBooster 6 effectively as a drive and at the same time run the RSG 7 in generator mode in order to feed electrical energy into the on-board network 2 of higher voltage via the RSG 7 when engine power is increased.

[0043] The distribution of energy within the vehicle electrical system 1, and in particular between the vehicle electrical systems 2 and 11, is achieved via the DC / DC converter 5, which acts as a coupling element and is controllable via the ECU 9. The ECU is connected via signal lines to the components shown – first energy storage device 4, coupling element 5, eBooster 6, belt-driven starter-generator 7, energy converter 8, second energy storage device 14, and energy converter 18 – for the control and regulation of the drive system 100 and the vehicle electrical system 1. This allows the ECU to receive signals regarding different operating states, process these signals, and output control and / or regulation signals to modify the operating states as desired. Parameters such as the state of charge of the energy storage devices 4 and 14, the network load of the 48-volt vehicle electrical system 2 and the 12-volt vehicle electrical system 11, as well as the actual and target operating states of the internal combustion engine, are taken into account.

[0044] Fig. Figure 2 shows qualitative torque characteristics of different drive systems in comparison to a drive system 100 according to the invention. The torque M is plotted as a function of the rotational speed n.

[0045] M1 shows a torque characteristic curve for a 147 kW internal combustion engine with an exhaust gas turbocharger. M2 shows a 110 kW internal combustion engine with an exhaust gas turbocharger. M0 shows a characteristic curve for a 135 kW internal combustion engine according to the invention in two drive states in the starting range: • Characteristic curve M01 shows the torque curve over the speed without the eBooster 6 and RSG 7 being effectively coupled for drive. • Characteristic curve M02 shows the torque curve with drive-effectively coupled eBooster 6 and RSG 7. • The grey shaded area of ​​the map between the two characteristic curves M01 and M02 shows the power potential P of the eBooster 6 and the RSG 7.

[0046] Curve RS1 shows the torque curve of the belt-driven starter-generator 7 during engine operation. Below a certain speed (e.g., 1000 rpm), a relatively high torque is available, which can be used in particular for comfortable starting of the internal combustion engine 19.

[0047] The curve M02 shows that the internal combustion engine 19 achieves its maximum torque at significantly lower speeds when using the additional drive torque of the eBooster 6 and the RSG 7 than would be possible without the use of these units.

[0048] The RS2 range above the limit speed shows a range in which the RSG 7 can be used with comparatively low torque - for example, for the comfortable (unnoticeable) restart of the combustion engine 19 which was switched off in freewheeling mode while the vehicle is rolling.

[0049] Fig. Figure 3 shows a speed-crankshaft-torque map for different operating conditions of the [engine / engine]. Fig. Figure 1 shows the drive system according to the invention. The torque M is plotted as a function of the rotational speed n.

[0050] The dashed characteristic curve K1 shows the speed-dependent torque of the VKM 19 without operation of either the eBooster 6 or RSG 7 units.

[0051] The long-dashed characteristic curve K2 shows the torque curve of the drive system 100 with the RSG 7 operating in parallel to the VKM 19. A significant torque gain is evident in the low speed range.

[0052] The short-dashed characteristic curve K3 shows the torque curve of the drive system 100 with the eBooster 6 coupled in parallel to the VKM 19, which also provides a significant torque gain in the low speed range, but also additionally raises the torque characteristic curve in a higher speed range.

[0053] Finally, the solid characteristic curve K4 shows the torque curve when operating the VKM 19 together with the eBooster 6 and the RSG 7. Here, the available torque is more than doubled in the low speed range, while in the higher speed range an increase of between 15 and 5% is achievable.

[0054] The lower part of the graph shows the torque characteristic RS of the belt-driven starter generator 7.

[0055] Fig. Figure 4 shows the course of the engine speed n over time t when starting an internal combustion engine with different starter devices in comparison to a system according to the invention.

[0056] The dashed line shows the starting process of a turbodiesel combustion engine using a conventional pinion starter powered by a 12-volt system. Injection is enabled after a time t. R1after, and a speed at which a minimum driving torque is available (here 1000 rpm) is reached after a time t M1 reached.

[0057] When using a belt-driven starter-generator in a 12-volt system, the injection is enabled after a time t. R2 reached and a speed at which a driving torque is available (e.g. 1200 rpm) after a time t M2 . Therefore, there is a time saving of Δt1 when restarting an engine using a belt-driven starter-generator compared to a pinion starter.

[0058] Finally, the dotted curve shows the speed profile over time when using a 48-volt belt-driven starter-generator 7 in a drive system 100 according to the invention, which enables injection after a time t R3 enables, and an engine speed at which a driving torque is available (here about 1150 rpm) after a time of t M3 realized.

[0059] The diagram shows that restarting with an RSG 7 in a 48-volt electrical system allows for a significantly more comfortable (faster) restart in a start-stop application than with a pinion starter or a belt-driven starter-generator in a 12-volt electrical system. The time saving Δt2 is approximately twice that of Δt1. This considerably increases driving comfort. Using the RSG 7 in the higher voltage electrical system (here 48 volts) simultaneously ensures that the 12-volt electrical system remains unaffected by the starting process and avoids the well-known voltage drop that occurs when starting vehicles with a 12-volt pinion generator or a 12-volt belt-driven starter-generator. Reference symbol list 1 On-board electrical system arrangement 2. Higher voltage electrical system (48 volts) 3. Pipeline system 4. First energy storage device (high-voltage battery) 5 Coupling element (DC / DC converter) 6 first electric machine (eBooster or euAGL) 7 second electric machine (belt-driven starter-generator, RSG) 8 energy converters 9 ECU (engine control unit) 10 Signal line 11 Lower voltage electrical system (12 volts) 13. Piping system 14 Second energy storage (12 volt battery) 18 energy converters 19 Internal combustion engine (internal combustion engine, ICE) 20 Belt drive 100 drive system 200 vehicles M1 characteristic curve 147 kW motor M2 characteristic curve 110 kW motor M0 characteristic curve 135 kW motor M01 characteristic curve without electric auxiliary drive M02 characteristic curve with electric auxiliary drive P Performance potential RS characteristic curve 48 Volt belt starter generator K1 full load characteristic curve 135 kW motor K2 characteristic curve 135 kW motor with drive-effective belt starter-generator K3 characteristic curve 135 kW motor with drive-effective eBooster K4 characteristic curve 135 kW motor with drive-effective eBooster and belt-driven starter-generator t R1 Injection approval for 12V pinion starter t R2 Injection release 12V belt starter generator t R3 Injection approval 48V belt starter-generator t M1 Driving torque timing 12V pinion starter t M2 Driving torque timing 12 V belt starter generator t M3 Driving torque timing 48 V belt starter generator Δt1 Starting time saving 12 V pinion starter to 12 V belt starter generator Δt2 Starting time saving 12 V pinion starter to 48 V belt starter generator

Claims

On-board electrical system arrangement (1) for a hybrid vehicle (200) with a first and a second on-board electrical system (2, 11) which are connected to each other via a coupling element (5) and each on-board electrical system (2, 11) comprises an energy converter (8; 18) and an energy storage device (4; 14), wherein an energy flow between the first and second on-board electrical systems (2, 11) can be controlled by means of a control of the coupling element (5) and / or depending on an operating state of one of the energy converters (8; 18) and / or one of the energy storage devices (4; 14), a first and second electric machine (6, 7) are provided which can be coupled to an internal combustion engine (19) for propulsion, one of the electric machines can be operated either in generator or motor mode and the first electric machine (6) drives an exhaust gas turbocharger and / or a charge air compressor. On-board electrical system arrangement (1) according to claim 1, wherein the first on-board electrical system is a lower voltage on-board electrical system (11), in particular a 12 volt on-board electrical system, the second on-board electrical system is a higher voltage on-board electrical system (2), in particular a 24 volt, a 36 volt or a 48 volt on-board electrical system, and the first on-board electrical system (11) has a lower voltage level than the second on-board electrical system (2). On-board electrical system arrangement (1) according to claim 1 or 2, in which the first and second electric machine (6, 7) can each only be supplied with electrical energy via the second on-board electrical system (2). On-board electrical system arrangement (1) according to claim 1, 2 or 3, wherein the second electrical machine is designed as a starter generator, in particular as a belt starter generator (7). On-board electrical system arrangement (1) according to one of the preceding claims, in which the coupling element (5) is designed as a controllable DC-DC converter, in particular as a potential-isolating DC-DC converter. On-board electrical system arrangement (1) according to one of the preceding claims, in which a control (9) is provided by means of which an energy flow between the first and second on-board electrical system (2; 11) can be controlled, in particular by means of a control of one of the following elements: coupling element (5), first and / or second electrical machine (6; 7), energy converter (8; 18), other electrical machine, energy storage device (4; 14). On-board electrical system arrangement (1) according to claim 6, wherein the control unit (9) is configured to prioritize the energy flow based on one of the following criteria: driving condition, driving behavior, stress on vehicle components, comfort. Drive system (100) for a hybrid vehicle (200) with an internal combustion engine (19) which is effectively connected to a first and second electric machine (6, 7) which are connected to each other via an on-board network arrangement according to one of claims 1 to 7. Hybrid vehicle (200) with a drive system (100) according to claim 8 .

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