Method for situational adaptation of the charging strategy of a vehicle's energy storage systems

Abstract

Method for situational adaptation of a charging strategy of energy storage devices (11) of a vehicle (100) with start-stop automatic functionality, comprising at least one energy storage device (11) with high power absorption capacity, wherein - in a first step (S1), a detection is carried out during a current driving situation of the vehicle (100) based on predetermined criteria as to whether a current stop-and-go situation exists, and - in a second step (S2), if a current stop-and-go situation has been detected, an increased charging of the energy storage device (11) takes place during engine operation between two automatically initiated engine-off phases, wherein predetermined criteria include that within a predetermined period - a specified number of automatically initiated engine stops has been recorded, and / or - a cumulative duration of automatically initiated engine stops was recorded, and / or - a cumulative discharge quantity from the energy storage device (11) was detected during detected automatically initiated engine stops, and wherein the increased charging between two automatically initiated engine off phases increases the charge state of the energy storage device such that an availability of automatically initiated engine stops is increased.

Description

[0001] The invention relates to a method for situational adaptation of the charging strategy of energy storage devices of a vehicle according to the preamble of patent claim 1.

[0002] The on-board electrical system and its power supply have become a key component of vehicle development. Micro-hybrid vehicles have been in series production for some time and have the advantage of being equipped with an automatic start-stop system, i.e., an electronic system that shuts off the engine when the vehicle has been braked to a standstill and the driver holds down the brake pedal (in vehicles with automatic transmission), and restarts the engine when the driver releases the brake. They also feature a recuperation function, i.e., brake energy recovery, to charge the starter battery. This technology can save fuel. Micro-hybrid vehicles cannot use their energy storage devices for electric propulsion.

[0003] The charging or discharging of the starter battery or, in general, of energy storage devices in the vehicle, depends almost exclusively on the current (actual) parameters of the on-board energy system, e.g. the charge state of the energy storage device(s), consumer current, generator utilization or even the temperature.

[0004] Systems often referred to as traffic jam assistants are already in series production, especially in (full) hybrid vehicles. These systems predictively adjust the battery charge level during the journey, for example, to enable purely electric driving when reaching a traffic jam or the resulting stop-and-go traffic, which has been detected in advance by corresponding systems. However, this requires predictive systems, i.e., systems that receive external data to implement this operating strategy.

[0005] However, with the operating strategy described above, it may also happen that, in the case of frequent automatically initiated engine stops, the charge level of the energy storage device is detected as too low to switch off the engine, so that the engine is not switched off automatically. Before this situation occurs, the poorer charge level of the energy storage device may result in inefficient operation of the automatic start-stop system, i.e., a less comfortable engine start-up, which may, for example, result in jerking. This means that the availability of the automatic start-stop system in known systems decreases in situations with frequent automatically initiated engine stops. The availability does depend on the vehicle's equipment, i.e.how many consumers still need to be served in an automatically initiated engine-off situation, but even with a small number of consumers or consumers that only require little energy, the charge level of the battery and thus the availability decreases.

[0006] One way to increase availability is to switch off certain consumers during the automatically initiated engine shutdown. However, this is undesirable for comfort reasons, among other things. To further improve this problem, newer systems feature a dual storage system (DSS) to ensure greater availability of the vehicle's power supply even during start-stop functionality. However, these systems are not, or only partially, adapted to the current driving situation; they continue to operate with predictive logic.

[0007] DE 10 2013 013 954 A1 discloses a method for situationally adapting the charging strategy of energy storage devices in a vehicle with automatic start-stop functionality. Detection of a current stop-and-go situation is performed during the vehicle's current driving situation based on predefined criteria. If a current stop-and-go situation is detected, the energy storage device is charged at a higher rate while the engine is running between two automatically initiated engine-off phases. A similar method is also known from DE 10 2015 225 424 A1 and US 2016 / 0 311 423 A1. Further prior art is JP 2007-125 913 A.

[0008] For this reason, it is an object of this invention to provide a method and a device that solves the aforementioned problems. In particular, the charging strategy of the energy storage device(s) present in the vehicle is to be adapted to the situation. This object is achieved according to the invention by the features of the independent patent claims. Advantageous embodiments are the subject of the dependent claims.

[0009] According to the invention, a method is proposed for situational adaptation of the charging strategy of energy storage devices of a vehicle with automatic start-stop functionality, comprising at least one energy storage device with high power absorption capacity, wherein in a first step, a detection takes place during the current driving situation of the vehicle based on predetermined criteria as to whether a current stop-and-go situation exists, and in a second step, if a current stop-and-go situation has been detected, an increased charging of the energy storage device takes place while the engine is running between two automatically initiated engine-off phases.

[0010] Predefined criteria include that a specified number of automatically initiated engine stops has been detected within a predetermined period of time, and / or that a cumulative duration of automatically initiated engine stops has been detected, and / or that a cumulative discharge amount from the first and / or the second energy storage device has been detected during detected automatically initiated engine stops. Preferably, the predetermined period of time is within a range of 1 minute to 8 minutes, preferably 5 minutes. Preferably, the cumulative discharge amount is within a range of 1 ampere hour (Ah) to 5 ampere hours (Ah), preferably 2 ampere hours (Ah).

[0011] In addition, the increased charging between two automatically initiated engine-off phases takes place in such a way that the charging quantity and thus the charge level of the energy storage device is increased to such an extent that the availability of automatically initiated engine stops is increased. This means that the charge level of the energy storage device is increased at least to a predetermined value. The predetermined value can be several ampere hours. On the one hand, the increased charging quickly reaches a charge level that enables automatically initiated engine stops. On the other hand, a higher charge level increases the availability of the automatic start-stop system, i.e. more and / or longer stops are possible. This can be achieved by increasing the charging between two (possible) automatically initiated engine stops compared to previous strategies, i.e. using a higher current for charging than would be the case without a detected stop-and-go situation.However, this can also be achieved by charging to a higher state of charge. This means that increased charging after an automatically initiated engine-off phase allows the engine to be switched off during the next standstill phase. Increased charging can occur either depending on the detected state of charge of the energy storage device or during each automatically initiated engine stop.

[0012] Furthermore, it is provided that in the second step the current charge state of the at least one energy storage device is additionally detected, and the increased charging of the energy storage device during engine operation between two automatically initiated engine off phases takes place depending on the detected charge state.

[0013] Furthermore, it is envisaged that the energy storage device be one or more lithium-ion batteries, one or more double-layer capacitors, or one or more flywheel storage devices. Furthermore, it is envisaged that the vehicle is a micro-hybrid vehicle. Furthermore, it is envisaged that, in the second step, the increased charging of the energy storage device takes place during engine operation between two automatically initiated engine-off phases by the combustion engine.

[0014] Furthermore, a control device is provided, comprising at least one control unit, wherein the control device is arranged in a vehicle and is configured to detect a current stop-and-go situation and to carry out the method according to one of the preceding claims or to send signals for carrying out the method to an implementation device.

[0015] Furthermore, it is provided that the control unit is further configured to detect the current charge state of at least one energy storage device arranged in the vehicle with a high charge absorption capacity.

[0016] Furthermore, a computer program product is provided which is suitable for processing the described method.

[0017] Further features and advantages of the invention will become apparent from the following description of exemplary embodiments of the invention, with reference to the figures of the drawing, which illustrate details of the invention, and from the claims. The individual features can be implemented individually or in combination in a variant of the invention.

[0018] Preferred embodiments of the invention are explained in more detail below with reference to the accompanying drawings. Fig. 1 shows a schematic representation of essential components according to an embodiment of the present invention. Fig. 2 shows a flowchart of the method according to an embodiment of the present invention.

[0019] In the following descriptions of the figures, the same elements or functions are provided with the same reference symbols.

[0020] Fig. 1 shows a schematic representation of essential components according to one embodiment of the present invention. The current electrical system of a vehicle 100 essentially consists of a generator, one or more energy storage devices 1, 11, one of which is usually a lead-acid battery and the other a battery with high power consumption capacity such as a lithium-ion battery, as well as various energy consumers 2, 3, 4. The energy consumers 2, 3, 4 have evolved from their beginnings, when only the starting, ignition, and lighting systems were operated. Today, a multitude of energy consumers 2, 3, 4 are installed in vehicle 100, which largely represent control, comfort, and safety functions. This multitude of energy consumers 2, 3, 4 increases the power demand placed on the energy supply or energy storage device 1, 11.The lead-acid battery 1 is now referred to as the on-board power supply battery, as it must increasingly meet the power demands of systems that the alternator can no longer operate. For example, in vehicles with a start-stop system (also known as MSA), the battery must assume sole responsibility for supplying the on-board power supply. The use and condition of the battery are determined by the manufacturer, for example.

[0021] Energy management system 10, which can be provided, for example, as a control device, e.g. as an engine control unit with an integrated start-stop coordinator and a sensor for monitoring the charge state of the energy storage device(s) 1, 11, determines and monitors.

[0022] Energy consumers 2, 3, 4 can be divided into groups, e.g. basic consumers 2 which are required for the operation of the vehicle, e.g. the engine control unit, comfort consumers 3, e.g. the navigation system, the air conditioning, driver assistance systems etc., and driving dynamics consumers 4, e.g. the anti-lock braking system, the electronic stability program etc.

[0023] To reduce fuel consumption in vehicles 100, including micro-hybrid vehicles, two functions are essential: recuperation and automatic engine start / stop. During recuperation, the generator output is increased during deceleration phases, and the excess energy is stored in the energy storage unit 1, 11. This allows the energy to be released during phases of increased energy demand, and the generator can operate at lower power. During automatically initiated engine stops, the (combustion) engine is switched off during standstill phases of the vehicle 100. The energy consumers 2, 3, 4 must be supplied via the energy storage unit 1, 11. As soon as it is detected that the journey should be continued, the engine is switched on again, and the consumed energy is fully or partially recovered (depending on the driving style) through recuperation.

[0024] The energy management system 10 monitors the state of the energy storage device 1, 11 and intervenes when the battery charge level reaches one or more predefined critical values. Intervention can include measures such as deactivating or downgrading consumers, e.g., heating / air conditioning consumers, as well as deactivating the automatic start-stop function.

[0025] In order to achieve greater availability, systems with several similar batteries or systems with larger lead-acid batteries have been proposed and are also in series production. As energy storage devices 1, 11 in DSS systems, which are used, for example, in micro-hybrid vehicles, more deep-cycle batteries are installed in addition to the conventional lead-acid battery 1, e.g. a lithium-ion battery 11. Compared to the lead-acid battery 1, this has a significantly higher resistance and a significantly higher charge absorption capacity, so that it meets the requirements, especially with regard to availability under high battery load. This in itself already guarantees higher availability. However, since the performance of lithium-ion batteries is very temperature-dependent, it is necessary to further improve the existing concepts and provide a corresponding charging concept.

[0026] In Fig.2 describes the illustrated flowchart of the method according to an embodiment of the present invention. In a first step S1, a detection is made during the current driving situation of the vehicle 100 based on predetermined criteria as to whether a stop-and-go situation currently exists. Such criteria include, for example, that a specified number of automatically initiated engine stops has been detected within a predetermined period of time, and / or that a cumulative duration of automatically initiated engine stops has been detected, and / or that a cumulative discharge amount from the first and / or second energy storage device 1, 11 has been detected during detected automatically initiated engine stops. The cumulative discharge amount is advantageously within a range of 1 ampere hour (Ah) to 5 ampere hours (Ah), and is preferably 2 ampere hours (Ah). The specified criteria are not exhaustive.Rather, additional criteria can be specified, for example, based on different traffic situations, countries, etc., to detect a stop-and-go situation. Predictive systems can also be included. However, this requires that the vehicle is equipped with such a system and that the corresponding data, especially with regard to GPS coordinates, real-time traffic information, or other, even predictive, processes, is sufficiently accurate, even without knowledge of the location.

[0027] By recording and evaluating predefined criteria, a stop-and-go situation can be detected directly, i.e. without predictive systems, when the situation occurs or when the above-mentioned criteria occur or are met within a certain period of time, e.g., within a period of 1 to 8, preferably 5 minutes. By detecting the stop-and-go situation, it can be assumed that an above-average number of stops relevant for the automatic start-stop system will occur in the near future. For this reason, in the second step S2, i.e., when a current stop-and-go situation has been detected, an increased charging of the energy storage device is initiated while the engine is running between two automatically initiated engine off phases. The triggering can be carried out by the energy management system 10. This ensures that the energy storage device, in a DSS system, the battery with a high charge absorption capacity, such asA lithium-ion battery 11 reaches a higher state of charge within a short period of time, i.e., between two automatically initiated engine-off phases. Although this is achieved through fuel consumption when charging is carried out by the generator driven by the combustion engine, it increases comfort, especially the availability of the automatic start-stop system, and saves energy and reduces emissions compared to not switching off the engine.

[0028] Increased charging here means that the charge level of the energy storage device, preferably the lithium-ion battery 11, is increased to such an extent that the availability of automatically initiated engine stops is increased. For example, if the charge level of a 10Ah storage device is increased by 10%, 1Ah more charge is available for automatically initiated engine stops. Assuming a 20A vehicle electrical system current, this is 3 minutes. The current charge level of the energy storage device(s) arranged in the vehicle can be recorded in the vehicle using a corresponding device, e.g., in the energy management system or the control unit as described above.

[0029] Furthermore, it can be specified that enhanced charging only occurs under certain conditions, e.g., depending on the detected state of charge. For example, it can be specified that enhanced charging only occurs when the detected state of charge is low or has fallen below a specified charging threshold. It can also be specified that enhanced charging occurs every time the engine is automatically shut down.

[0030] Not only a lithium-ion battery can be used as an energy storage device, but any energy storage device that meets the requirements for a given cycle stability and charge absorption capacity.

[0031] The method is preferably implemented by a control device, which may be an engine control unit, and may be embodied as a computer program product. The device for implementing the method may be the control device itself or another control device that receives the corresponding signals. It is therefore clear that the method can be implemented regardless of the number of control devices in the vehicle.

Claims

[1] Method for situational adaptation of a charging strategy of energy storage devices (11) of a vehicle (100) with start-stop automatic functionality, comprising at least one energy storage device (11) with high power absorption capacity, wherein - in a first step (S1), a detection is carried out during a current driving situation of the vehicle (100) based on predetermined criteria as to whether a current stop-and-go situation exists, and - in a second step (S2), if a current stop-and-go situation has been detected, an increased charging of the energy storage device (11) takes place during engine operation between two automatically initiated engine-off phases, wherein predetermined criteria include that within a predetermined period - a specified number of automatically initiated engine stops has been recorded, and / or - a cumulative duration of automatically initiated engine stops was recorded, and / or - a cumulative discharge quantity from the energy storage device (11) was detected during detected automatically initiated engine stops, and wherein the increased charging between two automatically initiated engine off phases increases the charge state of the energy storage device such that an availability of automatically initiated engine stops is increased. [2] The method according to claim 1, wherein the predetermined period of time is within a range of 1 minute to 8 minutes, and / or wherein the cumulative discharge amount is within a range of 1 ampere hour (Ah) to 5 ampere hours (Ah). [3] The method of claim 2, wherein the predetermined period of time is 5 minutes, and / or wherein the cumulative discharge amount is 2 ampere hours (Ah). [4] Method according to one of the preceding claims, wherein in the second step (S2) a current state of charge of the at least one energy storage device (11) is additionally detected, and the increased charging of the energy storage device (11) during engine running between two automatically initiated engine off phases takes place depending on the detected state of charge. [5] Method according to one of the preceding claims, wherein the energy storage device is one or more lithium-ion batteries, one or more double-layer capacitors, one or more flywheel storage devices, and / or wherein the vehicle is a micro-hybrid vehicle. [6] Method according to one of the preceding claims, wherein in the second step (S2) the increased charging of the energy storage device takes place during engine running between two automatically initiated engine-off phases by an internal combustion engine. [7] Control device comprising at least one control unit, wherein the control device is arranged in a vehicle (100) and is designed to - to record a current stop-and-go situation, and - to carry out the method according to one of the preceding claims or to send signals to an implementation device for carrying out the method. [8] Control device according to claim 7, wherein the control unit is further configured to detect the current state of charge of at least one energy storage device (11) with a high charge absorption capacity arranged in the vehicle (100). [9] Computer program product suitable for processing the method according to one of claims 1 to 6.

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