WO2007033983A1

WO2007033983A1 - Method and device for determining the battery state of a battery in a circuit with a starter for an internal combustion engine

Info

Publication number: WO2007033983A1
Application number: PCT/EP2006/066606
Authority: WO
Inventors: Hans-Michael Graf; Alexander Hahn; Carola Kühn
Original assignee: Siemens Aktiengesellschaft
Priority date: 2005-09-22
Filing date: 2006-09-21
Publication date: 2007-03-29

Abstract

In a method for determining the battery state (36) of a battery (6) in a circuit (8) with a starter (14) for an internal combustion engine (12), a measuring device (16) advantageously determines a single value (UC, min) for a measured variable (UC), which has been correlated with the minimum voltage (UB, min) of the battery (6) when the internal combustion engine (12) is started, the value (UC, min) is stored in an analogue memory (20) comprising passive components (26, 28, 30), an evaluation unit (18) reads the value (UC, min) from the analogue store (20) and determines the battery state (36) from this. A device for determining the battery state (36) of a battery (6) in a circuit (8) with a starter (14) for an internal combustion engine (12) contains a measuring device (16) for determining a value (UC, min) for a measured variable (UC), which has been correlated with the minimum voltage (UB, min) of the battery (6) when the internal combustion engine (12) is started, an analogue memory (20) comprising passive components (26, 28, 30) for storing the value (UC, min) and an evaluation unit (18) for reading the value (UC, min) from the analogue memory (20) and for determining the battery state (36) from this.

Description

Method and device for determining the battery condition of a battery in a circuit with a starter for an internal combustion engine

The invention relates to a method for determining the battery condition of a battery in a circuit with a starter for an internal combustion engine. In addition, the invention relates to a device for carrying out the method for determining the condition of batteries.

Such, also called starter batteries batteries are used for electrical starting of the engine by the starter upon actuation of a z. B. ignition key or starter button in the circuit, i. Closing the circuit. In order to successfully start the internal combustion engine, it is necessary here for the battery to be able to supply sufficient operating voltage and starting current, ie to provide a sufficient minimum power for the duration of the starting process, ie. until the internal combustion engine runs automatically.

Since such a starting process usually high currents flow, the battery voltage of each starter battery drops during the starting process. Particularly problematic in modern vehicles is the minimum voltage delivered by the battery during the starting process. This sinks namely in a conventional 12 V vehicle electrical system below a limit of z. B. 6 V, this can sometimes lead to a failure of the engine electronics and thus to cancel the startup process.

An exemplary voltage curve during a starting process, as is known in particular from DE 101 07 583 A1, is evident from FIG. 1 of the specific description part. There, the battery voltage U _{B is} plotted in volts over time t in milliseconds. The voltage curve 42 is shown from a time before pressing the start button in the starter circuit. The board voltage therefore initially corresponds to the open circuit voltage of the battery and is typically ^¬, between 12V and 13V. At time t = 0 ms, the circuit between starter and battery is closed. The voltage drops within 20ms to a value of about 8V as the minimum value. For the on-board electronics of this clamping voltage is ^¬ burglar critical and the starting process is continued. After 20 ms, the starter starts to rotate, and with it the internal combustion engine, and because of the decreasing electric power required, the voltage U _{B increases} until a time t = 200 ms, wherein it rises to a voltage level higher than the minimum of z. B. 10 V to 11 V fluctuates. Rise at t = 200 ms of the internal combustion engine and be ^¬ ignites autonomously starts to run, which is why the voltage U _B of the battery begins to to the operating level of about 14 V ^¬.

In still intact batteries voltage ^¬, that takes place while the burglar but is not critical. With older or insufficiently charged batteries, the voltage then breaks too far, eg. B. to the above value of less than 6 V and the startup process is not successful, ie the combus ^¬ tion motor does not start.

In order to start the engine reliably at any time, it is therefore desirable batteries that z. B. due to aging or excessive discharge, a pending or intended starting operation of the engine can not ensure timely to recognize. Corresponding batteries can then timely z. B. charged or replaced. The current battery status is to be judged, therefore, to predict the future start capability of the battery ^¬ ness to meet.

For the latter purpose known battery ^monitoring systems are suitable. Such monitoring systems measure - if necessary ^¬ together with additional quantities such as the battery current or the battery temperature - which during a starting operation or the presence let the internal combustion engine to the battery voltage applied, or the voltage curve over time.

Conventional battery monitoring systems work for this purpose with a voltage sampling, ie a repeated measurement of the instantaneous voltage z. B. directly on the battery, in short intervals. The measuring frequency moves here z. B. in the range between 100 Hz and 10 kHz. The measured voltage ^¬ course is recorded during the start and z. B. stored in a digital memory. By z. B. a Mikropro ^¬ processor, the recorded voltage waveform is evaluated. Frequently, as mentioned above, additionally a current profile, ie the time profile of the starting current supplied by the battery, is recorded in the same way, ie by sampling at the aforementioned measuring frequency. The current profile is then evaluated together with the voltage curve to z. B. to determine the internal resistance of the battery or its time course during the starting process.

In DE 101 075 583 Al, the entire voltage curve U (t) scanned after switching on the high-current load, and stored, and are formed over the curve U (t) with further battery parameters state values by linking particular span ^¬ voltage values. By appropriate mathematical see procedures are in this case formed from the preceding high-current Bela ^¬ obligations comparative values and it defaults be ^¬ expects be, where value of the difference between the pre ^¬ and the measured voltage value to the Powerful ^¬ ness of the battery is closed. This is intended to create a battery monitoring system.

The measurement used in the latter battery monitoring system ^¬ technology and the related evaluation, and evaluation ^¬ logic, however, is relatively complex and therefore expensive. With additional current measurement, the currents to be measured are in the multi-digit ampere range and are therefore difficult to measure. The object of the invention is therefore to provide an improved procedural ^¬ ren for determining the battery condition of a battery in an electrical circuit with a starter for an Verbrennungsmo ^¬ tor specify and create an associated facility.

With regard to the method, the object is achieved by the Abfol ^¬ ge of the measures of the claim and in terms of the device through the entirety of the features of the patent ^¬ award 10. Further developments of the method and the associated device are specified in the respective dependent claims.

In the inventive method for determining the battery ^¬ a battery condition in a circuit with a systems for starting ser for an internal combustion engine determines a measuring device, preferably a single value of a correlated with the minimum voltage of the battery when starting the internal combustion engine measured variable, the value is in a vorzugswei ^¬ se An analogue memory stores passive logic components and preferably reads an evaluation unit from this value from the analog memory and determines therefrom the battery status.

The invention is based on the insight that the minimum voltage of the battery during the starting procedure the determining large ^¬ SSE represents success for the start of the engine. Since ^¬ it is sufficient to perform an indirect voltage measurement, yet to obtain statements about the battery condition in sufficient accuracy. Therefore, according to the invention, instead of the minimum voltage itself, a value ei ^¬ ner measured variable correlated to the minimum voltage is determined. In this case, the measured variable chosen is one that can be buffer-stored without any effort, which can be done in particular in an analog memory. According to the invention, therefore, the value of the measured variable correlated with the minimum voltage is stored in a simple and cost-effective manner in order to be read out by the evaluation unit after a predeterminable time be further processed to determine the battery condition.

Since in contrast to the above-discussed prior art not the complete time course U (t), but only a einzi ^¬ ger value is determined and stored as a measure, its evaluation is also much easier than the evaluation of a voltage or combined voltage and current waveform so far. The entire method is thereby simple and inexpensive to carry out, especially with regard to the simplified evaluation or evaluation.

The device according to the invention advantageously requires only the aforementioned analog memory, which is constructed from passive components according to current state of the art.

If the analog memory is also constructed of purely passive elements with a capacitor, it will be cheaper and easier to produce. In addition, it does not require its own power supply and thus becomes error-prone.

Due to the storage of the measured value also the measuring rate or measuring frequency can be low, z. For example, in the IHz range. Appropriate measurement technique is compared to the above-mentioned range from 100Hz to 1OkHz also interpreting ^¬ simpler and more cost-effective.

As already mentioned, can be used as a measure of an electrical voltage and its value is stored in a one in an amount of log space contained Ana ^¬ capacitor. If the battery voltage is passed directly to the analog memory, the voltage curves and which correlated in the analog memory ^¬ adjusting minimum voltages of the minimum voltage of the battery. In particular, if the Bat ^¬ teriespannung performed on a capacitor whose voltage is correlated with the minimum voltage when the ent ^¬ speaking charging and discharging time in analog memory be chosen so that the capacitor voltage of the battery ^¬ voltage follows rapidly in the decreasing direction.

The fact that in the invention as a measure of a voltage used value, both the storage and evaluation by simple standard measuring equipment for the measurement ^¬ or evaluation possible. So it can be cost-effective measuring components, as z. B. also used in low-cost multimeters are used.

The stored on the capacitor voltage is indeed customary ^¬ a bit above the actual minimum voltage of Batte ^¬ rie, however, is sufficiently correlated therewith to Aussa ^¬ gen allow the battery condition. Since no conversion will take place to be measured, the minimum voltage to another measurement variable, but also as a measure of a voltage is USAGE ^¬ det, the analog memory is particularly simple and kos ^{¬-effectively} feasible. The use of a capacitor as a storage element is also particularly inexpensive.

The value of the voltage in the capacitor can be stored via a diode. The use of a poled in ent ^¬ speaking biased diode ensures during cranking operation that the voltage on capacitor teriespannung with decreasing bat- this may be followed with virtually no time delay. The correlation of stored value and minimum clamping voltage ^¬ is known about the diode voltages. Increases the Batte ^¬ riespannung but again, the diode is prevented by its barrier property to the voltage increases again and therefore the value of the measured variable at the condenser, leading to the desired

Storing correlated with the minimum voltage measured variables ^¬ SSE in the form of the capacitor voltage leads. With regard to the above-mentioned charge and discharge time of the analog memory ^¬ thus the diode part, a particularly suitable construction.

Determining the value of the measured variable in the Messeinrich ^¬ tung may be associated with a filter. With the filter is the Signal quality of the measured variable increased. By an appropriate filter can be such. B. noise from the measured who ^¬ the, to obtain more accurate readings readings.

In this context, it is then also possible to use known characteristics of the circuit of starter and internal combustion engine or the engine control or the on-board electronics, and through the filter in a way a pre ^¬ processing of the measured variable in their recording or storage tion in the analog memory perform. This preprocessing does not need to be performed by the evaluation unit later. As an example may be mentioned that the engine electronics of the engine voltage dips with a duration of z. B. tolerates less than three milliseconds without the startup process is affected. A corresponding filter is advantageously designed so that voltage spikes in the battery voltage that are shorter than three milliseconds are filtered out or suppressed from the voltage curve. The measured value stored in the analog memory is then not correlated with the actual, but uncritical, but with the minimum voltage and duration of the battery permitted with respect to the engine electronics. A corresponding, in particular analog preprocessing of the signal of the measured variables ^¬ SSE through a filter is especially simple, robust and cost-effective to carry out.

The inventive method can be used to determine the Batte ^¬ riezustandes in a road or rail vehicle USAGE ^¬ be det. In the case of road vehicles or rail vehicles, it is particularly desirable to make statements about the battery condition in order to be able to start these or their internal combustion engines at any time or on demand.

The method according to the invention can be carried out by a specific battery monitoring system. This is by using the method according to the invention, as already explained in detail above, inexpensive, simple and inexpensive executable, robust and error-prone. Thus, it is z. B. suitable for serial production in the automotive industry without causing significant additional costs in an automobile.

In the invention, the device mentioned above for determining the battery condition of a battery in a circuit with a starter for an internal combustion engine, a measuring device for determining a value of a correlated with the minimum voltage of the battery when starting the combus ^¬ tion motor, measured from a passive construction Elements existing analog memory for storing the Wer ^¬ tes and an evaluation unit for reading the value from the analog memory and to determine the battery status.

The advantages of the device according to the invention and its developments according to the subclaims have already been discussed in detail in connection with the method according to the invention. In particular, the device is simple, but all the requirements for effective battery monitoring are met.

For a further description of the invention, the fi ^¬ gurenbeschreibung of embodiments using the undersigned ^¬ voltage reference. Show it:

1 shows a typical voltage profile of a Starterbatte ^¬ rie when starting a motor vehicle,

2 shows a starter circuit of a motor vehicle having been ^¬ schlossenem battery monitoring system, Figure 3 shows the analog memory of Fig. 2 in detail, Figure 4 shows the time profile of the battery voltage and the capacitor voltage of FIG. 3 in a simplified Dar position,

5 shows an analog memory with upstream ^{Eingangsfil ¬} ter, Figure 6 shows the input voltage of the analog memory of Figure 5, Figure 7 shows the input voltage of the analog memory of Figure 5 with upstream input filter and Figure 8 th original traces of the battery voltage with the un ^¬ terschiedlichen voltage signals as Simulationsda ^¬.

On the figure 1, which shows the voltage curve U (t) when starting, has already been discussed in detail in the introduction. In the prior art, this signal is scanned, stored and evaluated in conjunction with other parameters mathematically ^¬.

Fig. 2 shows a starter circuit 2 of a motor vehicle, not shown, and a connected to the starter circuit 2 battery monitor 4. The starter circuit 2 includes a starter ^¬ battery 6, which via connecting lines 8 to an ignition switch 10 and a einwir ^¬ kenden starter for an internal combustion engine 12 14 are connected in series.

The battery monitor 4 comprises a measuring unit 16 and an evaluation unit 18 communicating therewith, wherein the measuring unit 16 in turn comprises an analog memory 20 and a voltmeter 22.

The analog memory 20 is connected via measuring lines 24 with the ^{¬ at} the battery ^{terminals of} the starter battery 6, so that the battery voltage U _B is applied to the analog memory 20.

FIG. 3 shows the analog memory 20 from FIG. 1 together with the starter battery 6 and the voltmeter 22 in detail. In the analog memory 20, one of the measuring line 24 is connected to a terminal of a capacitor 30 via the parallel connection of a resistor 26 with a diode 28. The other measuring line 24 leads directly to the other terminal of the condenser ^¬ sators 30. The voltmeter 22 in turn is connected directly to the two terminals of the capacitor 30 so that it detects the voltage applied to the capacitor U ₀ .

The capacitor 30 is together with the resistor 26 and the diode 28 with respect to the resulting time constant so dimensioned or interconnected, that with reduction of the battery voltage U _B, the capacitor voltage U ₀ follows this almost without a time delay, ie together with this decreases. This is essentially achieved by discharging the capacitor 30 via the then conducting diode 28 to the battery 6. By contrast, when the battery voltage U _B rises, the capacitor 30 is charged only very slowly, so that the capacitor voltage U ₀ rises only very slowly, or remains almost constant for short periods of time, in the example about one second. This is because the diode 28 is off.

The correspondingly dimensioned system of starter circuit 2 and battery monitor 4 from FIG. 2 shows, in the case of a typical voltage curve of the battery voltage U _B according to FIG. 6 already discussed, during the starting process of the motor vehicle the voltage profiles from FIG. 3.

Fig. 4 shows a simplified representation compared to FIG. 1 as a voltage curve 32, the course of the battery voltage U _B and 34 as the voltage curve of the capacitor voltage U _c , respectively in volts over time t in milliseconds for the starting process of the internal combustion engine 12th

Is located at the beginning of the time shown in FIG. 4, the starter circuit 2 alone, it ie flow there is no Strö ^¬ me, the battery voltage U _B has an open circuit voltage of about 12 V. The capacitor 30 is charged, that is, the ^¬ sen voltage U _c essentially corresponds to the battery ^voltage U _B , so is also greater than 12V. At the time t = 0 ms, the ignition switch 10 is now actuated, ie the circuit between the starter battery 6 and starter 14 ge ^¬ closed. Due to the battery 6, which is tert geal ^¬ in the example, this is no longer able to provide sufficient power for the starter 14 are available while keeping their battery voltage U _B sufficient. This breaks down to a value below 6V. In this case, the capacitor 30 is instantaneously discharged via the diode 28 to the starter battery 6, so that its voltage U _{0 is} the battery voltage U _B follows and also drops to a value below 6V. The starting process is not successful, ie the Verbrennungsmo ^¬ tor 12 does not start because the battery voltage U _B breaks below the critical value of 6 V and the engine electronics, not shown, the internal combustion engine 12 fails.

After 200 ms, the starting process is interrupted due to the failure of the engine electronics, ie, the ignition switch 10 is opened electronically from this again. The battery voltage U _B recovers quickly and rises again to its idling value of just over 12V. The starting process is therefore approximately in the voltage curve 32 as a rectangular pulse Darge ^¬ provides.

Since the battery voltage U _{B has} risen abruptly at t = 200 ms, the diode blocks 28 in Fig. 2 due to the Kon ^¬ capacitor voltage Uc of about 6 V. As mentioned, however, the resistor 26 for charging the capacitor 30 so dimensio ^¬ that it will only be recharged very slowly; only after 5 s does the capacitor voltage U ₀ exceed the limit of 6 V.

The voltmeter 22 is advantageously operated at a measuring rate of 1 Hz, so that it read the current value of the capacitor voltage U ₀ at the capacitor 30 at t = 1 s and transmitted to the evaluation unit 18. The clamping ^¬ voltage value Uc is in this case due to the aforementioned coagulating ^¬ gen time constants of the voltage rise in the voltage curve 34 below 6 V. The evaluation unit 18 therefore determines the battery state 36 of the starter battery 6 in this case as "not to start suitable". The operator of The motor vehicle, not shown, therefore receives an unillustrated message from the evaluation unit 18, for example on a multifunction display, to replace the battery 6, since this has caused the unsuccessful starting process of the internal combustion engine 12. 5 shows a variant of the battery monitor 4, with a filter 38 connected upstream of the analog memory 20 in the measuring lines 24. This prepares the battery voltage U _B and generates an input voltage U _E therefrom, which is then forwarded via the measuring lines 24 to the analog memory 20, finally influencing the capacitor voltage U _c .

Fig. 6 shows, for the embodiment of FIG. 5 is a voltage waveform alternatives of the battery voltage U _B according to Fig. 1. In contrast to FIG. 1, the course of Kon ^¬ densatorspannung Uc voltage spikes 40. These are, for possesses. B. vehicle caused by interference with other electronic components in the power ^¬. However, the voltage peaks 40 are ineffective for the engine electronics of the internal combustion engine 12, since this is protected by a corresponding input filter. For the assessment of the ability to start by the starter 14 or the starter battery 6, the voltage peaks 40 of ^¬ half are not important. Although in Fig. 6 the voltage U Mindestspan- _B, is particularly low min by superimposing one of the spikes 40, whose value is for the Beur ^¬ the starting ability of division is not relevant.

The filter 38 in FIG. 5 is therefore advantageously designed as a low-pass filter in order to filter the voltage peaks 40 from the course of the battery voltage U _B.

The input voltage U _E in Fig. 7 is therefore smoothed ge ^¬ genüber the profile of the battery voltage U _B in Fig. 6, ie, the voltage peaks 40 are eliminated. The minimum of the output voltage U A ^¬ _e, min in Fig. 7, therefore, remains greater than the minimum value U _B, _min of FIG. 6. However, this value corresponds to the actual minimum on-board electronics effective voltage of the battery voltage U _B. The voltage U _E causes in the analog memory 20 a profile of the graph 34 of the capaci ^¬ tors voltage U _c , which is shown in dashed lines in Fig. 7. In the capacitor 30 is as a minimum voltage U ₀ , min of the Assessing the starting capability correct value U _E, _min vomit ^¬ chert.

In Figure 8 Figure 42 shows the signal curve is the measured battery voltage U _B and shows the signal waveform 44 by a Filter ^¬ tion of the curve 42 graphs obtained. The curve 44 is smoothed against ^¬ over curve 42, wherein in both cases a prinzi ^¬ piell same curve corresponding to Figure 1 is present. Compared to the original battery ^voltage , the minimum of the curve 33 is slightly shifted in time and is slightly higher, which is caused by the low-pass filter 38.

Curves 33 and 34 show the signal stored in the capacitor without and with filtering. It can be seen that in the graphs 33 and 34 of the slight voltage dip does not appear when you press the ignition. In both cases, however, there is also a steep voltage drop, the minima due to the diode and possibly filters in the memory are slightly above the minima of the curves 42 and 44. Starting from the minimum value U ₀ , min, there is a slow rise, which due to the component is caused by discharging the capacitor but can be reproduced in time.

For the measurement technique, the latter means that in both cases no fast online measurement is necessary, but only needs to be measured after a predefinable time interval, for example after 0.5 s or 1 s. However, a significant point in the graphs 33 and 34 is nalwert with the thus detected Sig ^¬ in both cases detected, which is correlated with the minimum battery voltage.

Claims

claims

1. A method for determining the battery condition of a Bat ^¬ terie in a circuit with a starter for an internal combustion engine (12) with the following method steps: a) there is a single value (Uc, mm) one with the minimum ^¬ voltage (U _B , min ) of the battery (6) at the start of the internal combustion engine (12) correlated measured variable (U ₀ ) ermit ^¬ telt, b) this single value (U ₀ , mm) of the measured variable (U _c ) is stored between ^¬ rule, c) is evaluated the value (Uc, mm) of the measured variable (U _c ) is read out and d) the battery state (36) is determined from the read-out value (U _c , min) of the measured variable (U _c ).

2. The method according to claim 1, characterized in that for determining the value (U _c , _m in) of the measured variable (U _c ) a measuring device (16) and for reading the value (U _c , min) uses an evaluation unit (18) becomes.

3. The method according to claim 1, characterized in that for buffering a passive components (26, 28, 30) existing analog memory (20) is used.

4. The method according to claim 1 and claim 3, characterized marked ^¬ records that used as a measured variable (U ₀ ), an electrical voltage and their value (U ₀ , _mm ) in one in the analog memory

(20) contained capacitor (30) is stored.

5. The method according to claim 4, characterized in that the storage of the value (Uc, mm) of the voltage (U _c ) in the capacitor (30) via a diode (28).

6. The method features according to any one of claims 42 or 5, characterized ge ^¬ that as the value (Uc, mm) of the measured quantity (U _{0) is} the Mi ^¬ nimalspannung is determined the battery (6).

7. The method according to any one of the preceding claims, characterized in that the value (U ₀ , min) of the measured variable (U _c ) in the measuring device (16) with a filter (38) for increasing the signal quality of the measured variable (U _c ) determined becomes.

8. The method according to any one of the preceding claims, characterized in that it for determining the battery condition

(36) is used in a road or rail vehicle.

9. The method according to any one of the preceding claims, characterized in that it is performed by a battery monitoring system (4).

10. Device for determining the battery state (36) of a battery (6) in a circuit (8) with a Anlas ^¬ ser (14) for an internal combustion engine (12), with a Messein ^¬ direction (16) for determining a value (U ₀ , min) of a measured variable (U _c ) correlated with the minimum voltage (U _B , _m i _n ) of the battery (6) when the internal combustion engine (12) is started, having one of passive components (26, 28, 30) Ana ^¬ log memory (20) for storing the value (U ₀ , mm) and with an evaluation unit (18) for reading the value (U ₀ , mm) from the analog memory (20) and for determining the battery ^{¬ state} (36) thereof ,

11. Device according to claim 10, with an analog memory (20) having a capacitor (30) for storing a

Value (Uc, mm) of the measured variable (U _c ) contains detected electrical ^voltage .

12. Device according to claim 11, with a capacitor (30) for storing the voltage in the capacitor (30) to ^¬ ordered diode (28).

13. Device according to one of claims 10 to 12, with a measuring device (16) containing a filter (38) for increasing the signal quality of the measured variable (U _c ).

14. Device according to one of claims 10 to 13, which is included in a road or rail vehicle.

15. Device according to one of claims 10 to 14, which is included in a battery monitoring system (4).