DE102012004134A1 - Onboard network for motor car, has control unit which periodically switches voltage source between maximum and minimum sources, so that energy store is charged with maximum voltage and discharged with minimum voltage - Google Patents

Abstract

The onboard network (1) has an energy store (2), a regular or controllable voltage source and detection unit for detecting or estimating the energy storage temperature and/or the internal resistance (Ri) of the energy store. A control unit (10) is provided to periodically switch voltage source between maximum and minimum sources, below a limit value for energy storage tank temperature or above threshold value for internal resistance of energy store. The energy store is charged with the maximum voltage and discharged with minimum voltage. An independent claim is included for method for selectively heating energy store in electrical system.

Description

The invention relates to a vehicle electrical system and a method for the targeted heating of an energy storage in a vehicle electrical system.

• – großer Temperaturbereich (z. B. –40°C bis 125°C)
• – wenig Bauraum
• – kostenoptimal
• – Beherrschung hoher Stromgradienten und Spitzenstromanforderungen
• – lange Standzeiten (z. B. ≥ 50 Tage)
• – hohe Verfügbarkeitsanforderungen (in der Regel Redundanz notwendig)
• – zuverlässige Messung des SOH des Energiespeichers

Today's vehicle electrical systems for the power supply of electronics in motor vehicles or other mobile systems must meet the following challenges, some of which are difficult to reconcile:

• - wide temperature range (eg -40 ° C to 125 ° C)
• - little space
• - cost-optimal
• - Control of high current gradients and peak current requirements
• - long service life (eg ≥ 50 days)
• - high availability requirements (usually redundancy necessary)
• - reliable measurement of the SOH of the energy storage

Generally, at least one generator (or DC / DC converter) and an energy store (eg lead acid battery) are used to provide energy. To charge the energy storage and to compensate for fluctuations in energy requirements, the generator is equipped with a (smart) controller that adjusts the generator power suitable. The same applies if a DC / DC converter is installed.

For cost reasons, the maximum power of the generator is usually determined to be a value (just) above the maximum average current, with short-term higher power requirements must be covered by the energy storage. Also for cost reasons, the control dynamics of the generator is usually limited, so that high current gradients, caused for example by an electromechanical steering; must also be covered by the energy storage. The generous design of the energy storage is in turn limited by the space and cost points, so here always a compromise must be found.

Specifically, the requirements for occurring current gradients and peak currents require the lowest possible internal resistance of the energy storage. Too high an internal resistance would lead to voltage drops and thus loss of comfort (eg radio failure) or even the failure of safety-relevant systems (eg ABS). In combination with the temperature requirements, especially the lower temperature limit is the critical design criterion, since energy stores tend to have higher internal resistance at lower temperatures. This can be countered only with a sufficiently generous design of the energy storage or high demands on the internal resistance. This complicates the use of innovative technologies such. As UltraCaps (double-layer capacitors) by the internal resistance requirement at low temperatures require an unnecessarily large sizing and thus an unnecessarily high price. Another disadvantage of the current state of the art is the complex measurement of the SOH of the energy store. This is usually estimated by pure observation of the vehicle electrical system voltage or its course. This method is relatively inaccurate.

From the DE 10 2010 032 088 A1 a method for heating a battery system with at least two batteries or battery sections is known, wherein the heating of the battery system by the alternating charging and discharging of the battery system is carried out with an alternating current, wherein the application of the alternating current for the one battery or the one battery section out of phase for application with alternating current of the other battery or the other battery section, so that the battery system is provided during the heating an at least approximately constant voltage.

From the US 4,362,942 a battery heater is known, which uses the internal resistance of the battery as a heating element, for which purpose a programmable load is provided, which forms a closed circuit with the battery.

The invention is based on the technical problem of providing a vehicle electrical system as well as in methods for the targeted heating of an energy store in a vehicle electrical system, which are easy to implement.

The solution of the technical problem results from the objects with the features of claims 1 and 9. Further advantageous embodiments of the invention will become apparent from the dependent claims.

For this purpose, the on-board network, in particular a motor vehicle electrical system, at least one energy storage a controllable or controllable voltage source and means for detecting or estimating the energy storage temperature and / or the internal resistance of the energy storage, below a threshold value for the energy storage temperature or above a limit for the internal resistance of the energy storage the controllable or controllable voltage source is periodically switched between a maximum and a minimum voltage, wherein at the maximum voltage of the energy storage is charged and discharged at the minimum voltage. As a result, there is a permanent flow of current in different directions on Energy storage instead, the loss of heat generated at the internal resistance of the energy storage and this specifically heated. This heating leads to a reduction of the internal resistance. Through targeted heating, the requirements for the internal resistance of the energy storage can be reduced at low temperatures. The energy store (s) may be conventional lead-acid batteries, double-layer capacitors, Li-ion battery cells or similar types of battery cells. In this case, a plurality of energy stores can be connected in series and / or in parallel. The maximum voltage and the minimum voltage are chosen such that the maximum charging voltage of the energy storage is not exceeded. Another criterion for determining the voltage limits is that the connected on-board network consumers work reliably within the voltage limits. Therefore, the concrete values for the maximum voltage and the minimum voltage are dependent on the technology used for the energy storage devices and the installed on-board network consumers. For example, the minimum voltage is 12 V and the maximum voltage is 15 V. The energy storage temperature can for example be measured directly by means of a suitable sensor or, for example, estimated from the outside temperature. Alternatively or cumulatively, the internal resistance itself can be used as a control or controlled variable. This too can be measured or estimated.

In one embodiment, the controllable or controllable voltage source is designed as a generator or DC / DC converter. In particular, in motor vehicles with an internal combustion engine, the regulated or controllable voltage source is usually designed as a generator, wherein in electric vehicles or hybrid vehicles DC / DC converters are used, which transform the voltage from the traction side down to the electrical system side. The electrical system is therefore suitable for all types of motor vehicles.

In a further embodiment, a means for detecting the vehicle electrical system voltage is provided, wherein the internal resistance of the energy store can be determined from a jump in the vehicle electrical system voltage and / or the capacity of the energy store can be determined from a slope of the discharge curve of the vehicle electrical system voltage. Preferably, therefore, by means of a jump function between the minimum and maximum voltage switched back and forth, so that the voltage at the output of the controllable or controllable voltage source has a rectangular function. Other voltage forms are possible, but then require a certain amount of extra effort in determining the internal resistance.

It is exploited that when switching to the minimum voltage abruptly the energy storage must take over the power for the electrical system. Therefore breaks the voltage of the electrical system to the voltage drop at the internal resistance. By capturing or a sufficiently accurate estimation of the on-board electrical system current, the internal resistance of the energy store can thus be determined very simply. Now has the energy storage to provide the power for the electrical system, so the energy storage discharges. If the current removed is constant, the voltage at the energy store drops linearly. This linear drop in the voltage of the energy store can also be observed in the vehicle electrical system voltage, which was referred to as Entladekurve. Due to the linear relationship Q = C * U on the ideal capacitor, the capacity of the energy store can be determined very simply from the slope of the linear drop in the vehicle electrical system voltage. Thus, the SOH (state of health) of the energy storage can be determined very easily. In the practical implementation, it should be noted that the discharge curve is not an exact straight line, so that a compensation straight line must be determined at different measuring points.

In a further embodiment, vehicle functionalities can be limited by means of a control device as long as the energy storage temperature is below the limit value for the energy storage temperature and / or the internal resistance is above the limit value for the internal resistance. Thus, it is prevented that, for example due to high current gradients, a collapse of the vehicle electrical system voltage occurs or in the event of a failure (eg of the generator), the safe stopping of the vehicle could no longer be ensured, for example, the maximum permissible maximum speed of the motor vehicle can be limited. The withdrawal of the restrictions may be continuous, stepped or incremental as the energy storage temperatures increase or the internal resistance decreases.

In a further embodiment, means for detecting the outside temperature are provided, wherein at outside temperatures below a threshold value temporarily switched back and forth between the maximum and the minimum voltage. This is to ensure that the energy storage temperature does not fall below the limit again. In other words, this represents a holding phase Instead of the outside temperature, the internal resistance can also be measured directly for a short time and, if necessary, reheated.

In a further embodiment, the frequency of the switching cycle is between 1-50 Hz, more preferably between 10-20 Hz. In this case, the visibility is prevented by the human eye, for example, brightness fluctuations of illumination sources due to the On the other hand, the frequencies are low enough to produce no noise, for example in the radio.

In a further embodiment, the duty cycle between maximum and minimum voltage is selected such that the state of charge of the energy store does not change over a cycle. Ideally, the two duty cycles are the same size.

For many energy storage is then called by so-called "Micro Cycling", resulting in a very low aging with respect to charging and discharging cycles, so that the life of the energy storage is not significantly reduced.

In a further embodiment, the control of the maximum and minimum voltage is integrated into an existing control device or a gateway control device. For example, the controller may be integrated in a regulator of the voltage source or in a battery data module controller. The controller can be designed both in software and in hardware.

The invention will be explained in more detail below with reference to preferred embodiments. The figures show:

1 a vehicle electrical system in a first embodiment,

2 a vehicle electrical system in a second embodiment,

3 a vehicle electrical system in a third embodiment,

4 an exemplary course of the voltages in a warm-up cycle and

5 a course of the energy storage temperature over time.

The electrical system 1 for motor vehicles includes an energy storage 2 with internal resistance R _i , a starter 3 , a controllable voltage source in the form of a generator 4 , a regulator 5 for the generator 4 , Driving consumers 6 , Permanent consumers 7 , an outdoor temperature sensor 8th , an ignition 9 and a controller 10 for targeted heating of the energy storage 2 , The control 10 is in the controller 5 integrated, preferably in the form of software. In this case, there is a continuous positive line KL30, a switched positive KL15, a ground connection KL31 and an ignition starter line KL50. Will the ignition lock 9 closed, KL15 is connected to KL30 and the starter 3 Spurt on to throw an unillustrated internal combustion engine. The running internal combustion engine then drives the generator 4 on, then as a voltage source for the electrical system 1 is working. In doing so, the controller provides 5 the voltage and utilization of the generator 4 one. Before the generator 4 is driven by the internal combustion engine, takes over the energy storage 2 the power supply of the electrical system 1 , Via a direct connection or a bus connection 11 (eg LIN or CAN) is the outside temperature sensor 8th with the regulator 5 or the controller 10 connected. If the outside temperature is below a limit value for the energy storage temperature, it is estimated that the energy storage temperature is also below the limit value. In response, the controller then starts 10 a warm-up cycle for the energy storage 2 , later on the basis of 4 is explained in more detail.

In the 2 an alternative embodiment for a hybrid vehicle is shown, wherein the same elements with the same reference numerals as in 1 are provided. The controllable or controllable voltage source is a DC / DC converter 12 formed, which is connected via an input side, not shown, with a traction network of the hybrid vehicle. Furthermore, the energy storage 2 a battery data module controller 13 in which, the control is assigned 10 is integrated. Furthermore, the wiring system includes 1 a gateway controller 14 , The gateway controller 14 connects the DC / DC converter 12 , the battery data module controller 13 and the outside temperature sensor 8th for example, all connected to different data bus systems. For example, the outside temperature sensor 8th with a LOW-speed CAN bus 15 (CAN convenience), the battery data module controller 13 with a LIN bus 16 and the DC / DC converter 12 with a high-speed CAN bus 17 (CAN drive) connected.

In 3 is a third embodiment of a vehicle electrical system 1 shown, which is substantially the embodiment according to 2 corresponds to the comments on 2 can be referenced. The only difference is that the controller 10 in the gateway control unit 14 is integrated.

Based on 4 Now, the inventive method for targeted heating of the energy storage 2 be explained in more detail. In the illustration, the voltage U _G at the output of the generator 4 or DC / DC converter 12 and the vehicle electrical system voltage U _B over the time t shown. Now detects the control over the outside temperature that the energy storage temperature below a threshold T _gr (see 5 ), periodically the voltage U _G between a maximum voltage U _MAX and a minimum voltage U _{MN is switched} back and forth. In this case, T represents the period duration of a cycle, where f = 1 / T applies. The period duration or duty cycle T _MAX the maximum voltage U _MAX equal to the period or duty cycle T _{MIN of} the minimum voltage U _MIN , where T = T _MAX + T _MIN applies. For U _G = U _MAX the vehicle electrical system voltage U _{B is} almost equal to the voltage U _G. The energy storage 2 Loading. If U _G is then switched to the minimum voltage U _MIN , then the voltage is at the energy store 2 greater than U _G. As a result, now the energy storage 2 the electrical system 1 supply, in particular provide the power required for this purpose. Due to the flow of current from the energy storage 2 There is a voltage drop at the internal resistance R _{i of} the energy storage 2 , This voltage drop has a jump .DELTA.U the vehicle electrical system voltage U _B result. The almost constant current flow from the energy storage 2 then leads to a nearly linear drop in the voltage at the energy storage 2 and thus also the vehicle electrical system voltage U _B. It can from the size of .DELTA.U to the internal resistance R _{i of} the energy storage 2 be closed (the larger ΔU, the greater R _i ). From the slope m can the capacity C of the energy storage 2 are determined, wherein the smaller the amount of the slope m, the greater the capacity. While U _G = U _MIN becomes the energy storage 2 Thus, the charging current during U _G = U _{MAX is} equal to the discharge current during U _G = U _MIN .

Due to the permanent charging and discharging the energy storage temperature T _{E increases} continuously (see also 5 ), so that the internal resistance R _{i is} smaller and thus also ΔU. The energy storage _temperature can thus be indirectly determined via the internal resistance R _i . Then, if the energy storage temperature T _{E is} greater than / equal to a threshold T _gr , the process can be aborted.

In 5 is the energy storage temperature T _E over the time t shown, wherein at the time T _{gr of} the threshold T _{gr is} reached. The time from the start of the motor vehicle to t _gr is the heating phase A. In particular, at low outside temperatures is preferably after t _gr temporarily switching between U _MAX and U _MIN to keep the energy storage temperature T _E above or on the threshold T _gr . This can be referred to as holding phase W. In the heating phase certain functionalities of the motor vehicle, such as the maximum speed, can be limited. It should be noted that in the evaluation of ΔU for determining the internal resistance R _{i could be} completely dispensed with temperature sensors and can be controlled directly to a limit value for the internal resistance R _i .

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102010032088 A1 [0006]
• US 4362942 [0007]

Claims (10)

Electrical system ( 1 ), comprising at least one energy store ( 2 ), a controllable or controllable voltage source and means for detecting or estimating the energy storage temperature (T _E ) and / or the internal resistance (R _i ) of the energy store ( 2 ), wherein below a limit value (T _gr ) for the energy storage temperature (T _E ) or above a limit value for the internal resistance (R _i ) of the energy store ( 2 ) by means of a controller ( 10 ) the controllable or controllable voltage source is periodically switched between a maximum and a minimum source (U _MAX , U _MIN ), wherein at the maximum voltage (U _MAX ) of the energy storage ( 2 ) and discharged at the minimum voltage (U _MIN ). Vehicle electrical system according to claim 1, characterized in that the controllable or controllable voltage source as a generator ( 4 ) or DC / DC converters ( 12 ) is trained. Vehicle electrical system according to claim 1 or 2, characterized in that a means for detecting the vehicle electrical system voltage (U _B ) is provided, wherein from a jump (.DELTA.U) of the vehicle electrical system voltage (U _B ) of the internal resistance (R _i ) of the energy store ( 2 ) is determinable and / or from a slope (m) of the discharge curve of the vehicle electrical system voltage (U _B ), the capacity of the energy store ( 2 ) is determinable. Vehicle electrical system according to one of the preceding claims, characterized in that by means of a control vehicle functionalities are limited as long as the energy storage temperature (T _E ) below the threshold value (T _gr ) for the energy storage temperature (T _E ) and / or the internal resistance above the limit value for the internal resistance (R _i ) is located. Vehicle electrical system according to one of the preceding claims, characterized in that means are provided for detecting the outside temperature, wherein at outside temperatures below a threshold temporarily between the maximum and the minimum voltage (U _MAX , U _MIN ) is switched back and forth. Vehicle electrical system according to one of the preceding claims, characterized in that the frequency of the switching cycle is between 1-50 Hz. Vehicle electrical system according to one of the preceding claims, characterized in that the duty cycle between maximum and minimum voltage (U _MAX , U _MIN ) is selected such that the state of charge of the energy store ( 2 ) does not change over one cycle (T). Vehicle electrical system according to one of the preceding claims, characterized in that the controller ( 10 ) of the maximum and minimum voltage (U _MAX , U _MIN ) in an existing control unit ( 5 . 13 ) or a gateway controller ( 14 ) is integrated. Method for the targeted heating of an energy store ( 2 ) in a vehicle electrical system ( 1 ) according to claim 1, characterized in that below a limit value for the energy storage temperature (T _E ) or above a limit value for the internal resistance (R _i ) of the energy store ( 2 ) the controllable or controllable voltage source is periodically switched between a maximum and a minimum voltage (U _MAX , U _MIN ), wherein at the maximum voltage (U _MAX ) the energy storage is charged and discharged at the minimum voltage (U _MIN ). A method according to claim 9, characterized in that a means for detecting the vehicle electrical system voltage (U _B ) is provided, wherein from a jump (ΔU) of the vehicle electrical system voltage (U _B ) of the internal resistance (R _i ) of the energy store ( 2 ) is determined and / or from a slope of the Entladekurve the vehicle electrical system voltage (U _B ), the capacity of the energy storage ( 2 ) is determined.

Images