DE102004023502A1 - Energy storage method for hybrid motor vehicle lowering voltage level of the energy storage if allowable temperature to be expected with voltage level is exceeded - Google Patents

Abstract

The method involves determining, With the motor vehicle being turned off, the voltage of the capacitor (4) and temperature level of the capacitor . From the temperature level a temperature gradient of the capacitor is measured. The voltage level of the energy storage is lowered, if the allowable temperature to be expected with the given voltage level is exceeded and/or a maximum permissible temperature is reached and/or a temperature delta is exceeded.

Description

The The invention relates to a method and an apparatus for operating an energy store in a motor vehicle.

In Motor vehicles become electrical energy stores in the form of batteries or capacitors whose maximum allowable voltage depends on the temperature dependent is. In particular, electrolyte or double-layer capacitors are extremely sensitive too high voltage levels at a given temperature, so that whose life is reduced or it destroys the Component can come. Therefore, their temperature during the To monitor operations and the temperature by action like fans etc. limit.

One the preferred field of application of the capacitors is, for example the use in hybrid vehicles. A possible construction of a hybrid vehicle includes, for example, an internal combustion engine, an electric machine, a capacitor and a battery via a switch and / or DC / DC converters are connected in parallel. About another DC / DC converter is then the capacitor with the actual electrical system of the motor vehicle connected. In this case, the capacitor can be designed for higher voltages as the parallel switchable battery. It should be noted that if necessary, this concrete structure is itself new and inventive is.

The Charging the energy storage can either by regenerative Operation of the electric machine or, particularly efficiently, can be achieved by recuperation. Without active limitation of the charging voltage (for a given charging power) in generator operation, in particular in a parallel circuit of fast capacitor and slower battery the charge end voltage the battery due to the opposite the capacitor higher internal resistance exceeded relatively quickly and both energy stores need, about an overvoltage to avoid the battery, are electrically separated from each other. The additional generated energy is then absorbed in the capacitor, which continues rises in its tension level.

Of the Invention is the technical problem underlying a method and a device for operating an energy store in a motor vehicle to create, by means of which a high energy storage done can, without the energy storage in critical operating conditions too operate.

The solution the technical problem arises from the objects with the features of the claims 1 and 6. Further advantageous embodiments of the invention result from the dependent claims.

For this when the motor vehicle is turned off, the voltage of the energy store and at least one temperature value of the energy storage is detected or determined, wherein from the at least one temperature value, a temperature profile estimated the energy storage and the voltage level of the energy store is lowered, if exceeded the permissible Temperature at the given voltage level is to be expected and / or a maximum permissible Temperature reached and / or a freely applicable temperature delta is exceeded. This can be during of the operation the full storage capacity be exploited, whereas, if necessary, by Voltage reduction when the vehicle is parked a critical work area is avoided. It is understood that the vehicle is parked, that both internal combustion engine and electric machine are turned off. The lie based on the following considerations.

It must be in dependence the respective energy storage temperature a compromise in terms of life and storable energy can be found. Especially with a Installation of the energy storage in the engine compartment or in areas with elevated temperatures in the vehicle must be taken into account that after the parking of the vehicle, the ambient temperature due to the lack of air cooling very strong in the direction higher Temperature level can develop.

in this connection must be the maximum allowed Voltage level in the capacitor storage, depending on the design, to a corresponding voltage delta below the maximum permissible voltage for the occur during operation temperature of the energy storage. Becomes the tension is not reduced, this can lead to a reduction of the Lifespan or destruction lead the energy storage. However, the maximum storable energy is thereby clear reduced.

According to the invention, it is therefore proposed, in a combination of an energy store (in particular a storage capacitor) with an internal combustion engine as a function of the current energy storage temperature or a calculated temperature to reduce the energy content when the vehicle is parked or in the reheating phase accordingly. This can be utilized up to its maximum storage capacity during operation of the vehicle, the energy storage. If the vehicle is subsequently switched off, the current span is first of all in a freely applicable time in the control unit tion as well as the temperature rise in the energy storage evaluated and, when a corresponding temperature gradient or absolute temperature value or voltage value, the energy content of the storage capacitor is reduced by the control unit. In addition, it should be noted that the temperature monitoring can of course also be done while driving.

In a further preferred embodiment is time and / or event-controlled after parking the motor vehicle the temperature and voltage situation queried, if exceeding the permissible Temperature at the given voltage level is expected. For a time control For example, a time grid may be provided, with the event control offers a temperature measurement. This can also be passive Temperature increases in the system without direct operation by a consumption engine or electrical machine, for example, by increased Sunlight.

To the There are basically two options for reducing the voltage level. This can be achieved either by an extended overrun time of the control unit and thus done by the own electrical system supply of the control unit or, if this measure is not sufficient for the reduction, by a corresponding energy flow in a further energy storage, preferably a battery.

There the voltage level of a storage capacitor generally above which is a battery, the corresponding energy flow can also through a DC / DC converter between storage capacitor and battery be achieved. Here, the battery is at optimal charging voltage charged from the storage capacitor until the state of charge in the storage capacitor below the for the current temperature permissible Tension has dropped. For the case of a fully charged in vehicle operation battery can be optionally an increased charging voltage give the battery, in this case, the necessary energy remove from the storage capacitor. This procedure is special advantageous because the energy is not consumed by the needs of the controller is stored, but energetically more meaningful in the battery becomes and thus for the next Vehicle operation available again stands. Furthermore, this is a much faster reduction the state of charge possible, because the vehicle electrical system requirements of the control unit compared to the power consumption of a Battery rather neglect is.

In a further preferred embodiment is the energy store as a capacitor, preferably as a double-layer capacitor, educated.

By the inventive method is achieved that, especially in the parking phase or Nachheizphase of the vehicle, the state of charge in the energy storage in dependence the current temperature not above the maximum allowable voltage lies. As a result, in conventional vehicle operation of the energy storage in its maximum storage capacity be exploited. In case of a temperature overrun, the energy either consumed by the own needs of the control unit or energetically more advantageous in a further energy storage, preferably a Battery, charged and stands for a subsequent driving cycle again available.

The Invention will be described below with reference to a preferred embodiment explained in more detail. The single figure shows a schematic block diagram of an electrical Energy system in a hybrid motor vehicle.

The electrical energy system 1 includes an internal combustion engine 2 , an electric machine 3 , a capacitor 4 and a first battery 5 , Between the capacitor 4 and the battery 5 are a switch 6 and a DC / DC converter 7 connected. Furthermore, between the electric machine 3 and the capacitor 4 another DC / DC converter 8th arranged, which is connected to the actual electrical system. The electrical system includes electrical consumers 9 , optionally a second battery 10 and a controller 11 receiving signals from a temperature sensor 12 receives.

The internal combustion engine is designed, for example, as a direct-injection, lean-running gasoline engine and with the electric machine 3 fixed or connected via a releasable coupling. The electric machine 3 is designed for example as a crankshaft starter generator and can be operated both motor and generator. Motorically, the electric machine 3 the internal combustion engine 2 start as well as motor assist (boost operation). Generatorically, the electric machine 3 by the internal combustion engine 2 or be driven by recuperation by a not shown gear. The rated voltage of the capacitor 4 , which is preferably designed as a double-layer capacitor, is typically above the rated voltage of the battery 5 , The rated voltage of the second battery 10 typically corresponds to the conventional vehicle electrical system voltage of, for example 12 V. About the switch 6 can the capacitor 4 and the battery 5 be connected directly to each other as long as the voltage on the capacitor 4 below the charging voltage of the battery 5 lies. For capacitor voltages above the end-of-charge voltage becomes the switch 6 open, passing through the DC / DC converter 7 another charge flow from the condenser to the battery 5 is possible.

Now, if the motor vehicle is turned off, it may happen despite the trailing fan that the temperature at the condenser 4 increases, especially if this near the engine 2 and / or the electric machine 3 is arranged. For this purpose, the temperature sensor now detects during the shutdown phase 12 the temperature of the condenser 4 and transmits them to the control unit 11 , Alternative to the additional temperature sensor 12 on the capacitor 4 the determination of the energy storage temperature can be determined from already known sensor variables such as ambient temperature, engine temperature, evaluation of the last color profile before engine stop (eg highway driving) by means of a computer model. Furthermore, by a not shown voltmeter, the voltage across the capacitor 4 measured and also to the control unit 11 transfer. The control unit extrapolates on the basis of empirical data, calculation models and / or gradient formations 11 the temperature rise of the capacitor 4 , Represents the controller 11 determines that the expected temperature for the detected voltage is too high, the voltage is actively reduced. The control unit controls this 11 the DC / DC converter 7 and or 9 on, that in each case a voltage-reducing energy flow to the battery 5 and / or battery 10 takes place.

Claims (10)

Method for operating an energy storage device in a motor vehicle by means of at least one device for determining or detecting the temperature of the energy storage device, wherein the permissible voltage of the energy storage device depends on the temperature, characterized in that when the motor vehicle is switched off, the voltage of the energy storage device and at least one temperature value of the energy storage device is determined or detected, wherein from the at least one temperature value, a temperature profile of the energy storage is estimated, the voltage level of the energy storage is lowered, if exceeding the allowable temperature at the given voltage level is expected and / or reaches a maximum allowable temperature and / or a freely applicable temperature delta is exceeded. A method according to claim 1, characterized in that a Temperature gradient is determined, taking from the size of the gradient the maximum temperature is determined after switching off. Method according to one of claims 1 or 2, characterized that time and / or Event-controlled in the parked state, the temperature and voltage situation the energy storage is detected or detected, the voltage level is lowered if exceeding the permissible temperature is to be expected at the given voltage level and / or a maximum permissible temperature reached and / or exceeded a freely applicable temperature delta becomes. Method according to one of the preceding claims, characterized characterized in that the reduction of the voltage level by an electrical supply of closed circuit consumers and / or by an energy flow in another energy storage takes place. Method according to one of the preceding claims, characterized in that the energy store as a capacitor ( 4 ) is trained. Device for operating an energy store in a motor vehicle, comprising at least one device for detecting or determining the Temperature of the energy store, with the allowable voltage of the energy store depending on the temperature is, characterized in that when the motor vehicle the voltage of the energy store and at least one temperature value the energy storage can be detected or determined, wherein from the at least one temperature value, a temperature profile of the energy store can be estimated, wherein the voltage level of the energy storage is lowered, if a crossing the permissible Temperature at the given voltage level is expected and / or a maximum allowable Temperature reached and / or exceeded a freely applicable temperature delta becomes. Apparatus according to claim 6, characterized in that a Temperature gradient can be determined, taking the size of the gradient the maximum temperature after shutdown can be determined. Device according to claim 6 or 7, characterized that a control unit can be woken up after switching off time- and / or event-controlled and the temperature and Voltage of the energy storage can be detected or determined, wherein the voltage level is lowered, if exceeded the permissible Temperature at the given voltage level is to be expected and / or a maximum permissible Temperature reached and / or a freely applicable temperature delta is exceeded. Device according to one of claims 6 to 8, characterized that the degradation of the voltage level by an electrical supply from closed circuit consumers and / or through an energy flow into one further energy storage takes place. Device according to one of claims 6 to 9, characterized in that the energy store as a capacitor ( 4 ) is trained.