Operating procedures for hybrid vehicles

Abstract

Operating method for a hybrid vehicle with at least two drive motors, of which the first drive motor is an internal combustion engine and can be supplied with fuel from a first energy storage device and a second drive motor which can be supplied with energy from a second energy storage device, wherein for determining a control command by which the switching off of the first drive motor can be brought about - a filling level of the first energy storage device is determined, - a filling level of the second energy storage device is detected, - the filling level of the first energy storage device is compared with a desired state value, - and depending on this comparison, a control command for switching off the first drive engine is determined, - wherein a priority parameter is determined by which this shutdown can be prevented and wherein, if such a priority parameter is present, the shutdown of the first drive machine is prevented or delayed, and wherein this priority parameter is selected from a group comprising at least the following parameters: - Driving requirements with an accelerator pedal position greater than 60%, - vehicle control parameters, - Parameters from driver assistance systems.

Description

The present invention relates to a method according to the preamble of claim 1. such a method is known from DE 198 33 932 A1.Hybrid vehicles within the meaning of this invention are motor vehicles which are characterized by at least two drive systems. As a rule, one of these drive systems is based on an internal combustion engine and the other is based on another type of drive engine, frequently an electric drive engine. In such vehicles, the synchronization of the two drive systems is of great importance, whether in order to operate the vehicle as efficiently as possible, or in order to let the two systems interact with one another as unnoticed as possible by the vehicle occupants. For the two drive systems, two different energy storage devices are usually provided in the vehicle. In the development of hybrid vehicles, an at least adapted or modified control strategy, in particular of the drive engines and their energy supply, is frequently required in comparison with conventional motor vehicles operated by internal combustion engines.In conventional motor vehicles, i.e. in motor vehicles with only one drive system based on an internal combustion engine, a fill level of the fuel tank (energy storage device) is frequently characterized as a so-called reserve. When this fill level is reached, the vehicle driver receives a warning that only a limited remaining range is available. If the vehicle is moved further without refueling fuel in good time, the fuel tank is emptied until fuel can no longer be delivered to the internal combustion engine. After fuel can no longer be delivered, the vehicle remains stationary; in modern internal combustion engines, this "running empty" frequently results in subsequent damage in highly stressed components, such as the high-pressure fuel pump or in the fuel injectors.Methods are known from the prior art in which the internal combustion engine is shut down when a critical filling degree of the fuel tank is reached. DE 198 33 932 A1 discloses a device which shuts off the fuel line and thus shuts off the internal combustion engine when a specific fill level of the fuel tank is undershot.DE 10 2008 006 028 A1 discloses a method and a device for automatically switching an internal combustion engine on and off.The object of the invention is to provide an improved operating strategy for hybrid vehicles, in particular with a low fill level of an energy storage device. Preferably, such an operating strategy enables continued travel with the vehicle even if energy can no longer be drawn from one of at least two energy storage devices. This object is achieved by a method according to independent claim 1, preferred developments of this method are the subject matter of the dependent claims.In the sense of the invention, a drive machine is understood to mean a device which is designed to provide drive power for overcoming driving resistances of a motor vehicle. Hybrid vehicles are generally distinguished in that they have at least two drive engines; frequently, these drive engines are different in their type, such as in particular an internal combustion engine and an electromechanical energy converter. A first drive engine is designed as an internal combustion engine. This internal combustion engine is preferably designed as an internal combustion engine of reciprocating piston construction.In the sense of the invention, a second drive machine is understood to mean a drive machine which is arranged in addition to the first drive machine in the hybrid vehicle. The second drive machine is preferably designed as a hydraulic, preferably pneumatic or particularly preferably as an electric drive machine. Further preferably, the second drive machine can also be designed as an internal combustion engine which can be operated, in particular with a different type of fuel, with respect to the first drive machine.In the sense of the invention, an energy storage device is understood to mean a device for storing and providing energy for the drive machines. A first energy storage device is understood to mean a device for storing fuel for the first drive engine. The energy storage device for the first drive machine is preferably designed as a container or tank. The second energy storage device, i.e. the energy storage device for the second drive machine, is preferably designed as a container or tank, preferably as a pressure container, more preferably as a kinematic storage device, in particular a flywheel storage device, and particularly preferably as an electrochemical energy storage device, in particular an accumulator or a battery.In the sense of the invention, the determination of the filling degree of the first energy storage device is understood to mean that the filling degree of this energy storage device is determined indirectly or directly. The state value can preferably be interpreted as a fill level of the first energy storage device.Preferably, the filling degree of the first energy storage device is measured for ascertaining the filling degree of the energy storage device, in particular the filling level of the fuel in the fuel is measured or the mass of the energy storage device is ascertained. Preferably, the internal combustion engine, in particular the combustion in the combustion chambers, is monitored, so that it is possible to infer a low filling level of the energy storage device, in particular from so-called "combustion misfires".Further preferably, the pressure in a fuel supply system is measured in order to determine this filling degree. In this case, the fuel supply system has, in particular, at least one delivery device, in particular a pump for delivering fuel, and one or more lines, for the targeted transport of the fuel to the first drive engine, in particular to the internal combustion engine, toward or away from the latter. More preferably, the pressure is measured in a high pressure section of the fuel delivery system. A high-pressure section is to be understood in particular as a section of this system in which, according to plan, a pressure of preferably more than 10 bar, preferably more than 100 bar prevails during operation of the internal combustion engine.Further preferably, the filling degree is determined indirectly. Such an indirect determination of the filling degree is preferably based on a comparison of the conveyed setpoint volume of fuel with the conveyed actual volume. For this purpose, the current consumption and / or the voltage drop across a fuel delivery pump are preferably monitored; furthermore, the delivered quantity of fuel is preferably measured. Further preferably, these values, in particular for current and voltage, or their temporal profile, are compared with setpoint values. Preferably, the so-called delivery angle of a fuel pump can be determined from such a measurement. The delivery angle of the fuel pump further preferably changes, in particular in the case of critical or low filling degree, the delivery angle preferably increases in such a case.Further preferably, one and / or one or more further of the aforementioned parameters is used for determining the filling degree of the first energy storage device. The fill level and / or the pressure in the high-pressure system, in particular a so-called rail pressure, and / or the comparison value of the setpoint delivery volume and the actual delivery volume, in particular the delivery angle, is preferably used for determining the fill level in the first energy storage device.Such a state value for the filling degree of the first energy storage device can describe, after a comparison with a setpoint value, at least two states for the energy storage device, "sufficient fuel in the energy storage device" or "too little fuel in the energy storage device".Detecting the filling degree of the second energy storage device is understood to mean that its filling degree is measured indirectly or directly. Preferably, detecting the filling degree of the second energy storage device is understood to mean measuring an electrical voltage and / or an electrical current. It is further preferred to mean measuring the time profile of an electrical voltage and / or of a current.In the sense of the invention, a setpoint state value is to be understood as a predefinable state value for the degree of filling of the energy storage devices, in particular of the first energy storage device. Such a setpoint state value can preferably be determined by calculation or simulator means; furthermore, such a setpoint state value can preferably be determined experimentally by means of test runs or test bench runs.In the sense of the invention, a control command for the drive machine is understood to mean a control parameter which results in the first drive machine being shut down from operation.In a preferred embodiment, the state value for the filling degree of the first energy storage device is determined from a specific group of parameters. Preferably, a tank fill level, i.e. the instantaneous content of the first energy storage device, is measured. In particular, the tank fill level represents a precise parameter from which the fill level of the first energy storage device can be derived.Further preferably, current driving state parameters such as, in particular, the vehicle longitudinal and / or transverse inclination and the vehicle longitudinal and / or transverse acceleration and the vehicle speed and the ambient and fuel temperature are taken into account in the determination of the filling degree of the first energy storage device. In particular, the aforementioned parameters can lead to a locally different distribution of a liquid fuel in the first energy storage device. In particular, by taking into account the aforementioned parameters, a particularly reliable state value for the filling degree of this energy storage device can be determined.Further preferably, the remaining range determined in the vehicle control is used for determining the state value for the fill level of the first energy storage device. In particular, this measured and calculated remaining range is already freed from many potential sources of error and permits a particularly precise determination of such a state value.In a further preferred embodiment, at least two, preferably a plurality of, state values are used for the degree of filling of the first energy storage device in order to determine that a minimum degree of filling of the first energy storage device has been reached or undershot. In particular, a particularly secure method is provided by using a plurality of state values.Preferably, the filling degree of the second energy storage device is also used for the method according to the invention. Further preferably, the filling degree of the second energy storage device influences the determination of the control command for the first drive machine. Furthermore, it is preferable not to take into account the absolute filling degree of the second energy storage device in the aforementioned manner, but rather to take into account the amount of energy that can be drawn from it, in particular without the energy storage device being damaged in an unscheduled manner indirectly or directly. In electrochemical energy storage devices, a deep discharge up to a fill level of zero or in the vicinity of zero is often not possible, or results in damage to the energy storage device. In particular in the case of such energy storage devices, only the "amount of energy that can be drawn" is taken into account, up to which there is no risk of indirect or direct damage to the energy storage device.Fuel delivery parameters are preferably used to determine the state value for the filling degree of the first energy storage device. Such fuel delivery parameters can preferably be derived at the fuel delivery system with which the first drive machine is supplied from the first energy storage device. The pressures in this fuel delivery system are preferably a pressure difference before and after throttle points or preferably a pressure curve over a time range. More preferably, the flow rate is. Further preferably, the acoustics in such a fuel delivery system can also be monitored. In particular, air bubbles in the conveyed fuel lead on the one hand to a changed acoustic compared to the fuel conveyed without bubbles and on the other hand indicate a low filling degree in the energy storage device.Furthermore, temporal or chronological parameters are also preferably taken into account. Such parameters are preferably to be understood as meaning in particular the time elapsed since the start of the trip and / or the distance covered since the start of the trip.In a further preferred embodiment, a plurality of the aforementioned parameters are compared with predefinable setpoint values and the state value for the filling degree of the first energy storage device is derived therefrom. In particular, by using at least two or more parameters when ascertaining the state value for the fill level of the first energy storage device, a particularly reliable method for switching off the first drive machine while continuing operation simultaneously with the second drive machine can be provided.In particular, by selecting the parameters which are used in the determination of the state value for the filling degree or for the determination of the control command for the first drive machine from the above-mentioned group of parameters, a particularly reliable state value for the filling degree and thus a reliable shutdown criterion for the first drive machine can be determined.In a preferred embodiment, the filling degree of the first energy storage device is determined at least twice with a time interval or multiple times. It has been found that the first drive machine can be incorrectly shut down if the filling degree is determined only once. Such false shut-offs can be caused, in particular, by the sloshing back and forth of liquid fuel in the energy storage device. In order to reduce or avoid these false shutdowns, the filling degree of the energy storage device is determined multiple times with a time interval. Preferably, a corresponding control command is determined only if at least two or more state values for the filling degree or filling degrees of the first energy storage device derived therefrom suggest the shutdown of the first drive machine.Preferably, a plurality of these state values for the filling degree are determined within a predeterminable period of time. This time period is preferably longer than 0.1 sec, preferably longer than 5 sec and particularly preferably longer than 30 sec and further preferably this time period is shorter than 300 sec, preferably shorter than 150 sec and particularly preferably shorter than 60 sec. In particular, by ascertaining a plurality of state values, unnecessary shut-downs of the internal combustion engine can be reduced and an improved operating method is thus provided. It has been found that the aforementioned range represents, on the one hand, a sufficient time period to reduce the faulty shutdowns and, on the other hand, is short enough to avoid damage due to the "idling".In a preferred embodiment, so-called priority parameters are determined which prevent or delay a shutdown of the internal combustion engine. Such priority parameters are selected from a specific group of parameters which comprises at least the following parameters:- Travel requirements,taking into account at least one further vehicle control parameter, in particular prioritized switch-off prevention reasons.Preferably, these priority parameters can be understood as reasons for shutdown hindrance. Such shutdown hindrance reasons are intended to prevent, in particular, a safety-critical shutdown or a shutdown of the first drive machine leading to damage.Preferably, switch-off prevention reasons can also be predeterminable by the vehicle driver.Furthermore, the driving requirements are preferably taken into account in the determination of the priority parameter. Instantaneous driving requirements, such as preferably a position of the accelerator pedal or a gradient of the movement of the accelerator pedal, are preferably taken into account. Further preferably, future travel requirements are taken into account, preferably those which are accessible from a route calculation. In particular, the shutdown of the first drive engine may be prevented or delayed when the accelerator pedal position is close to its 100% position. Preferably, close to 100% is understood to mean a range of preferably greater than 60%, preferably greater than 80% and particularly preferably greater than 90%. Further preferably, a shutdown of the internal combustion engine can be prevented if a kick-down acceleration is recognizable from the gradient of the accelerator pedal actuation.Furthermore, information from driver assistance systems is also preferably taken into account in the determination of the driving requirements. Driving requests can preferably be predefined via driver assistance systems; a driving request is preferably generated via the programming of a cruise control system. Driving requirements resulting from distance warning and / or stop systems are preferably taken into account when determining prioritized shutdown prevention reasons. In pictorial terms, a high acceleration requirement and thus a prioritized switch-off prevention reason can result from the fact that a specific distance from a vehicle driving ahead is set / programmed in the cruise control system with distance sensors and this vehicle driving ahead is greatly accelerated. Such an acceleration request is thus obtained from the driver assistance system without the vehicle driver actuating the accelerator pedal, but this can also be taken into account according to the invention.Further preferably, shutdown prevention reasons are taken into account in the determination of the priority parameter. Such hindrance reasons can result from higher-order operating strategies for the first drive engine, preferably from the start-stop operating strategy, preferably from one or more operating temperatures of the first drive engine.Further preferably, the control command can be influenced only in a time-limited manner with a priority parameter. Preferably, the first drive machine is nevertheless shut down in the event of a permanent presence of the priority parameter. Preferably, a term "permanent" is understood to mean a time period which is preferably greater than 10 sec, preferably greater than 30 sec and particularly preferably greater than 300 sec and further preferably less than 500 sec, preferably less than 200 sec and particularly preferably less than 90 sec.In particular, the priority parameter prevents the first drive engine from being shut down during an overtaking process (accelerator pedal position close to 100%).In a preferred embodiment, the switch-off is preferably displayed to the vehicle driver haptically, preferably acoustically and particularly preferably optically. More preferably, the display is performed with a combination of at least two of the aforementioned display types.In a preferred embodiment, the fill level of the first energy storage device is stored in a nonvolatile data memory. In this context, a non-volatile data memory in the sense of the invention is understood to mean a data memory of this type which still keeps the stored information stored even when and after the vehicle has been shut down, preferably a hard disk memory, preferably a solid state drive. Studies have shown that during the starting process a certain period of time elapses until the actual filling degree of the first energy storage device is determined. This can result in particular in the case that the internal combustion engine (first drive engine) is started, although before the motor vehicle is shut down a control command for shutting down the same was determined on the basis of an excessively low filling degree of the first energy storage device. In the preferred embodiment, the filling degree that is too low or the command for stopping the internal combustion engine is now stored in the nonvolatile memory device, and this command is then made available, preferably prioritized, to the control system of the motor vehicle for a long period of time, and thus a starting of the internal combustion engine after "tank empty travel" and stopping is prevented.A "complete time" in the sense of the invention is understood to mean a time period that is greater than 1 millisecond (ms), preferably greater than 50 ms and preferably greater than 100 ms, and furthermore this time period is less than 2000 ms, preferably less than 1500 ms and particularly preferably less than 1000 ms, very particularly preferably the time period is at least approximately 500 ms.In particular, because the stored state of the energy storage device is reserved / prioritized only for a wide period of time, it is ensured that, on the one hand, after a "tank empty travel", the internal combustion engine is not started when the motor vehicle is restarted, although the filling degree of the first energy storage device is still too low for this purpose. However, since the actual filling degree of the first energy storage device is determined after a certain time and is made available again to the vehicle control system, it is covered that the first drive engine can be started in the event that the vehicle has been fuelled during standstill. In this case, the time period is in particular dimensioned such that this process runs unnoticed by the vehicle occupants and an improved method for controlling the motor vehicle is thus provided.The figure shows a flow chart for the preferred method of operation. FIG. 1 shows a flow chart for an operating method according to the invention.FIG. 1 shows a partially simplified flow chart for a method according to the invention for operating a hybrid vehicle. In such a method, the state value for the filling degree of the first energy store is first determined. It has been found that the stability of the method can be increased if a combination of a plurality of parameters is taken into account. The tank fill level, as well as the pressure in the high pressure system of the fuel delivery device, can be controlled. Only when the tank fill level falls below a predefinable minimum (setpoint value for state value) and the so-called "rail pressure" in the high-pressure system also falls below a predefinable threshold value (further setpoint value for state value) is there probably a low fill level for the energy storage device present. When comparing the / the setpoint value with the / the state values for the filling degree, it is determined whether the minimum filling degree for the first energy store is already reached.The filling degree of the second energy storage device is likewise measured and compared with a setpoint value. In the case of an electrochemical energy store, it is checked whether electrical energy for driving the motor vehicle can still be stored out of this accumulator. Whether this filling degree is taken into account is purely optional and the connecting line to the node is therefore shown as a dashed line.If there is a low filling level for the first energy store, graphically referred to as "tank empty" and there is still sufficient energy available in the second energy store for further driving the motor vehicle, a control command for shutting down the internal combustion engine and for driving the motor vehicle alone by means of the second drive machine, in particular the electric motor, can be output.In one embodiment of the method, it is possible to take account of shutdown hindrance reasons. Although this criterion is also optional, as explained above with respect to the second energy storage device, it has been shown that an improvement in the stability of the method can be achieved with this criterion and the line connecting to the node is therefore represented as a solid line. For example, a full load acceleration (kick-down) set briefly indicates that the internal combustion engine is not to be shut down. In such a case, the vehicle may be in an overtaking situation and stopping the internal combustion engine and the associated worsening of the acceleration potential would be safety-critical. Only if there is no switch-off prevention reason, or if such a switch-off prevention reason is preferably not present permanently, in a method according to the invention the internal combustion engine is shut down or the internal combustion engine is shut down at least with a time delay.

Claims

Operating method for a hybrid vehicle having at least two drive engines, of which the first drive engine is an internal combustion engine and can be supplied with fuel from a first energy storage device, and a second drive engine, which can be supplied with energy from a second energy storage device, wherein, for determining a control command, by means of which the shutdown of the first drive engine can be brought about, - a filling degree of the first energy storage device is determined, - a filling degree of the second energy storage device is detected, - the filling degree of the first energy storage device is compared with a setpoint state value, - and, as a function of this comparison, a control command for the shutdown of the first drive engine is determined, - wherein a priority parameter is determined, by means of which this shutdown can be prevented, and wherein, if such a priority parameter is present, the shutdown of the first drive engine is prevented or delayed, and wherein this priority parameter is selected from a group comprising at least the following parameters: driving requirements with an accelerator pedal position greater than 60%, vehicle control parameters, parameters from driver assistance systems.Operating method according to Claim 1, characterized in that these vehicle control parameters are those which can be derived from automated start-stop processes.Operating method according to either of Claims 1 and 2, characterized in that the filling level of the first energy storage device is determined on the basis of at least one parameter selected from a group, and in that this group comprises the following parameters: - tank filling level, - current driving state parameters, - temperature within the first energy storage device, ambient temperature, - displayed remaining range, - filling level of the second energy storage device, - availability of the energy stored in the second energy storage device, - fuel delivery parameter, flow speed or acoustics at least in a section of the fuel delivery system of the first energy storage device, - chronological parameters.Operating method according to one of the preceding claims, characterized in that at least one first and at least one second filling degree is determined and in that these individual filling degrees are compared with setpoint values for these filling degrees.Operating method according to one of the preceding claims, characterized in that the filling degree of at least the first energy storage device can be stored in a nonvolatile memory when the motor vehicle is shut down.Operating method according to Claim 5, characterized in that this stored filling degree is prioritized for a complete time when the motor vehicle is restarted, and in that this complete time is selected from a specific range, in that this range is greater than 1 ms, and furthermore this range is less than 2000 ms.

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