Electrical transmission or interconnection systems – Vehicle mounted systems – Automobile
Reexamination Certificate
2000-05-11
2002-08-13
Fleming, Fritz (Department: 2836)
Electrical transmission or interconnection systems
Vehicle mounted systems
Automobile
C307S010100, C307S121000
Reexamination Certificate
active
06433442
ABSTRACT:
The invention concerns a method and apparatus for operating a safety device for motor vehicles.
BACKGROUND
A known safety circuit of this type in the form of an isolating switching device for motor vehicles is presented in DE 33 27 532 A1. It responds primarily to electrical instructions from an emergency instruction transmitter, that is to say it can be switched under remote control and permits the battery to be isolated from the vehicle's electrical system; however, it permits this not only in emergency cases but also when the vehicle is parked. Such a stationary vehicle turn-off circuit is, owing to an prevention circuit, permitted only when the engine is stationary or if no other current loads are connected into the circuit in the motor vehicle. However, it is a problem here that, in order to maintain its operational readiness, the control circuit remains connected to the battery even when disconnection from the vehicle's electrical system has taken place, and said control circuit continues to consume current, that is to say cannot be used for a relatively long stationary period of the vehicle or relatively long period of overseas transportation. The disconnection of the battery from the vehicle's electrical system is ultimately carried out by means of self-latching relays which possibly experience contact problems or tend towards contact sticking at the very high currents which occur here.
In modern motor vehicles, the number of electrical control units is increasing at an ever faster rate in accordance with the number of loads dependent on a vehicle's electrical system, with the result that, in order to increase the operational reliability, the control units are usually networked by means of a vehicle-internal bus system and receive digital switching signals from a central control device in a type of ring circuit, said switching signals being decrypted in the control units using microprocessors and being converted into appropriate instructions to the directly adjacent receivers.
Such databus systems in a motor vehicle are usually based on the so-called CAN standard (Controller Area Network). Therefore, as a rule, the control units and the microprocessors arranged in them change into a quiescent or sleeping mode after a delay time, dependent on the type of control unit, after the vehicle has been deactivated. In this state, the quiescent current consumption of the control unit is relatively low, but in total it can still amount to a current of several hundred mA which permanently loads a vehicle battery, in particular if a primed monitoring system is added to this.
If such a vehicle is then stationary over a relatively long time without the battery being able to be loaded by the generator when the engine is running, for example during a relatively long period of absence of the keeper of the vehicle, when the vehicle is taken out of service for the winter or during a relatively long period of transportation overseas by ship, such severe discharge may occur, in conjunction with the self-discharge of the battery which always occurs and which cannot be avoided, that under certain circumstances even the vehicle battery is irreparably damaged, or at any rate it is no longer possible for the vehicle to be started.
Such exhaustive discharge of batteries also gives rise to lasting damage because during normal operation the electrical voltage which is generated by the electrical charge at the electrodes protects said electrodes against the aggressiveness of the sulphuric acid. If this voltage collapses owing to an exhaustive discharge, the protection of the electrodes also fails and disintegration phenomena occur, which even after a short time damage the electrodes irreparably to such an extent that the drastic damage to the storage capacity destroys the storage function of the battery.
A vehicle with a highly discharged battery is frequently reactivated, that is to say started up, by starting using external means by connecting a second battery, usually originating from another vehicle, in parallel with the discharged vehicle battery. However, in such a case it is not unusual, especially at night, for the poles to be mixed up, as a result of which not only the vehicle battery which is in any case greatly weakened but also the electrical devices and control units in the vehicle, that is to say the entire electrical system of the vehicle including the generator and generator diodes as well as the electronics can suffer lasting damage.
If the vehicle's own, in this respect first, battery is very exhaustively discharged, an attempt at starting by external means can also fail because the voltage of the vehicle's electrical system can drop, as a result of the high current which the starter and furthermore also the exhaustively discharged first battery require during the starting time, below a limiting value of, for example, 5 volts, and the control units which are important for starting can thus no longer be supplied with sufficient voltage.
In addition, when vehicle accidents occur, it is occasionally found that electrical leads, but also equipment, are damaged especially in the case of an accident which is primarily in the engine compartment (area at risk during a crash), which can lead to a spark flashover or an arc if there is a short circuit. As a result, if fuel escapes at the same time, for example due to damaged lines, fires may occur.
Therefore, in motor vehicle electrical systems, problems are posed by the (automatic) protection of the installed vehicle battery against exhaustive discharge, such as may occur, for example, during transportation overseas, when the vehicle is stationary for a relatively long time, and when there is excessive loading and thus corresponding discharging, by the protection of the vehicle's electrical system and its components against polarity reversal, by the disconnection of at least electrical vehicle components which are at risk during a crash and of leads during a possible accident, and finally by the need to restore the basic setting in the event of disconnection occurring between the vehicle's electrical system and the battery, i.e. to return the vehicle to a normal state.
It is currently known to ensure protection of the battery against exhaustive discharge during transportation overseas by disconnecting the battery manually from the vehicle's electrical system using an isolating switch after the vehicle has been loaded onto the ship. During unloading, that is to say so that the vehicle can be driven off the ship, the isolating switch is closed again and ultimately removed by the appropriate dealer before the vehicle is ultimately put into service.
The aforementioned problem of incorrect polarity in the case of an external starter device is particularly serious because the damage can be overcome only by replacing, at a correspondingly high cost, the inadequately protected electrical and electronic components which have been irreparably damaged by the incorrect polarity.
The following specifications relate to known battery isolating switches and to the possibility of disconnecting a battery from its loads under certain circumstances if there is a risk of exhaustive discharge:
DE 34 02 372 A1, DE 42 11 578 C1, DE 33 03 185 A1, DE-B 1 086 322.
Thus, in DE 34 02 732 A1, two conductive electrodes which lie coaxially one opposite the other are disconnected by means of an insulator element which is located between them but which in normal circumstances is bridged by an electrically conductive switching bridge. The switching bridge can be opened by axially displacing a sheath.
DE 42 11 578 C1 presents a battery isolating device for motor vehicles having a battery isolating switch which can be actuated manually from the battery space and under remote control from the driver's seat with a main safety switch. Before the battery isolating switch is possibly opened, all the loads which are connected to the ignition lock must firstly be switched off and an engine turning-off procedure must be initiated.
A fu
Mäckel Rainer
Schulz Thomas
Crowell & Moring LLP
Daimler-Chrysler AG
Fleming Fritz
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