WO2007009675A1

WO2007009675A1 - Device for the overload protection of a supply line for an electric load in a motor vehicle

Info

Publication number: WO2007009675A1
Application number: PCT/EP2006/006919
Authority: WO
Inventors: Thorsten Kuhnen; Thomas Weingärtner; Bettina Köth
Original assignee: Brose Fahrzeugteile Gmbh & Co. Kommanditgesellschaft, Coburg
Priority date: 2005-07-16
Filing date: 2006-07-14
Publication date: 2007-01-25
Also published as: DE202005011235U1

Abstract

In order to provide overload protection for a supply line (12A, 14, 30), in particular for a window lifting motor (16), in a motor vehicle, a monitoring device (20A) is provided in a control device (10) for actuating the window lifting motor (16) and is embodied in such a way that the supply line (12A, 14, 30) is monitored for overloading by reference to operational data (B) from the supply line (12A, 14, 30). If an overload is detected, the supply line (12A, 14, 30) is disconnected. The monitoring device (20A) permits the supply line (12A, 14, 30) to be adapted to the actual power drain of the window lifting motor (16) without recourse to the rest of the structure of the on board power system.

Description

description

Device for overload protection of a supply line for an electrical

Load in a motor vehicle

The invention relates to a device for overload protection of a supply line for an electrical load, in particular for a window regulator motor, in a motor vehicle.

The electric window motor is usually connected to a hierarchically structured vehicle electrical system. This has several distribution levels for the distribution of the energy provided by the motor vehicle battery. To protect the vehicle electrical system against overload due to an overload current suitable fuses, usually fuses, are provided. In the motor vehicle, a plurality of fuse boxes are usually arranged for this purpose, in each of which a plurality of fuse elements are arranged. According to the hierarchical structure of the electrical system, a partial area or a lower area of the vehicle electrical system is protected by a single fuse element. The supply lines or supply cables of several end consumers are therefore protected against overload via a common fuse element, which is usually designed as a fuse.

The invention has for its object to ensure reliable protection of a supply line of a load in a motor vehicle against overload.

The object is achieved by a device according to claim 1. Thereafter, a monitoring device is provided for overload protection of the supply line, in particular for a window motor, which monitors based on the current operating data of the supply line on this overload and, if necessary, causes a disconnection of the supply line. By disconnecting the supply line, this becomes current-free, in particular over its entire length. In this case, the monitoring device is designed in particular for a reversible disconnection or switching of the supply line so that current can be conducted again after the fault responsible for the overload has been removed via the supply line. Under overload is understood here in particular a thermal overload, ie the exceeding of a temperature limit. Under supply line in this case are arranged in particular after a fuse element components

₅ understood a vehicle electrical system, via which the load is supplied with power. The main component here is a supply cable. Other components are in particular contact elements such as contact plugs and switching elements such as relays. For thermal overload monitoring of a supply line forming a supply line, at least one of these components, preferably at least the supply cable, is monitored for a component-specific thermal overload. Under operating data of the supply line operating data of that component are understood, which is monitored for thermal overload. This is especially the current flowing over or through the component. In the following, the overload monitoring is carried out, in particular in connection with the supply cable further i5. The explanations apply equally to other components of the supply line.

An essential consideration is the identification of actual actual operating data - either direct or indirect - of the supply cable. o As a result, the respective supply cable is individually monitored and a decentralized, on the individual supply cable related overload protection is realized. Thus, on the last hierarchical level within a vehicle electrical system structure - and thus very sensitively - the decision is made as to whether an overload exists.

5 In the usual automotive wiring system, in which several supply cables are secured by a common fuse element, it is not possible for safety reasons to adapt an individual of the jointly secured supply cable to the actual power consumption of the end user, since the supply cable, in particular its cross-section through the backup value of the o fuse element is determined. The use of a common fuse element with a smaller fuse value is eliminated due to the common supply of multiple end users. The supply cable-specific monitoring therefore has the particular advantage that the cable cross-section of the supply cable can be adapted without loss of security to the actual power consumption of the end user. In particular, this measure makes it possible to use new line technologies, such as, for example, foil cables or flat cables, which have space-saving and weight-saving conductor structures with small conductor cross-sections.

The monitoring device is, for example, an electronic circuit or an electronic module, which is designed in such a way that, in the event of an overcurrent, the current flow through the supply line is prevented. For this purpose, generally the supply line from the power supply or from the control electronics of a door control module or at a separation point of the door module to the rest of the vehicle electrical system, e.g. a plug, in particular separated by a switch.

According to an expedient development, a monitoring program is provided as monitoring device. The monitoring program reads in the operating data, decides whether there is an overload and, if necessary, initiates the disconnection of the supply line. As a result of this measure, reliable and reliable overload protection of the supply line is achieved purely by software or software, without requiring expensive hardware components and installation space.

By using a software-implemented line protection, the line protection is also very easy and easily adaptable to the current, line or load-specific operating parameters. Thus, further developments, for example, lead to the fact that smaller power window motors are used, easily considered and incorporated into the monitoring program by a suitable parameter setting, without a change to the wiring system is necessary or repercussions to other on-board power supplies are to be feared. The software overload protection therefore makes it easy to make adjustments even with existing wiring systems. - A -

According to an expedient development, the direct determination of the operating data of the supply cable is provided with the aid of at least one sensor element. Such a sensor element is for example a shunt resistor or a so-called SenseFET for direct current measurement. As a sensor element further example, a temperature sensor for direct measurement of the temperature of the supply cable as a measure of the current flow and as a criterion for an overload is provided. Operating parameters of the supply cable are therefore, for example, the current, the level of the applied voltage or their current temperature.

In a preferred embodiment, the monitoring device is designed such that operating data of a load connected via the supply line are detected and from this it is deduced whether there is an overload. In this embodiment, therefore, in particular an indirect detection of the operating data of the supply line on the operating data of the load is provided. Since the operating data of the load is often available anyway, no additional hardware components are required and provided for the additional implementation of the thermal overload protection for the supply line. The load is in particular an electric motor. The operating data of the motor are, for example, its current consumption, the applied voltage, its speed, etc.

Preferably, a sensor system for determining the operating data is further provided, from which then the temperature of the supply line is derived as a criterion for an overload.

In a preferred embodiment, in this case the sensor is designed such that an engine speed of the component and the supply voltage are detected and the monitoring program determined based on the current engine speed, the supply voltage and a stored motor characteristic, if an overload exists. Such a configuration is particularly suitable for those systems in which a so-called excess force limit is provided. In such systems, namely, a Hall sensor for speed measurement is usually already integrated, so that over the preferably software technically realized line protection only needs to be resorted to an existing sensors and only already available operating data are evaluated.

According to a preferred alternative, the sensor system is designed such that the supply voltage and the supply current of the load are detected. Such a configuration is particularly suitable for controlled drives or in systems with so-called Ripplestromauswertung. Because with regulated drives usually a power electronics in the form of a semiconductor circuit breaker is used instead of a relay, which has a current measuring output, at which the current current value can be tapped in each case. Again, no excessive additional effort is required for the software technical line protection and it is used on existing components.

Preferably, therefore, the load current is derived by means of a Ripplestromauswertung and / or with the aid of a Hall sensor. Under Ripplestrom is generally understood to be caused by the control electronics ripple of the drive current of the electric motor. From the ripple, the current level of the drive current can be derived.

According to an expedient development, a thermal overload protection for the load is provided in addition to the line protection, which is also implemented program or software technology. For this purpose, a further monitoring program is provided, which also monitors this based on operating data of the load on thermal overload. As a result of the software implemented thermal protection eliminates the need for a hardware thermal protection element, such as a bimetal, which usually leads to additional costs and claimed installation space. In principle, there is the possibility of combining the preferably software-implemented line protection integrated in the control unit with a hardware thermal protection element that is integrated directly in the window regulator motor.

Conveniently, the monitoring program and the further monitoring program form a combined program both for overload protection of the supply line and for thermal protection of the load. The program is here especially modular. This embodiment is based on the consideration that both monitoring programs build on similar algorithms and resort to similar or the same operating data of the window regulator motor. Overall, this allows a simplified programming.

Preferably, a thermal model of the supply line is used for monitoring the supply line for overload. In this thermal model, relevant line parameters are taken into account, such as line cross section, specific resistance, thermal conductivity, a coefficient for the heat dissipation to the environment, etc. On the basis of this thermal model, criteria are given and deposited, with which the decision is made whether there is an overload or not.

For the decision as to whether an overload exists, according to a preferred further development, at least one, preferably a plurality of characteristic curves stored in a memory are used. Such a characteristic is, for example, the motor characteristic. The characteristics are in each case specifically adapted to the currently realized component combination. The component combination here includes the type or type of supply line and the type of motor used. From the characteristic curve, the values of further operating parameters which are relevant for the decision as to whether there is an overload are taken without much computational effort and with knowledge of a specific operating value of an operating parameter. In addition to the load-specific operating parameters, further operating parameters of the supply line are taken into account. In general, variable operating parameters in which the value of the parameter changes during operation can be distinguished from fixed operating parameters in which the value of the parameter is independent of the current operating situation. Variable operating parameters are, for example, the engine speed, the supply current, the supply voltage. Fixed operating parameters are, for example, the material of the supply line or its cross-section.

Conveniently, the characteristic in this case the relationship between one of the operating parameters of the load or the supply line and a temperature of the supply line again. Temperature is therefore considered a decisive criterion in order to determine the overload and it only needs to be read from the characteristic curve whether an overload is already present at a certain value of an operating parameter.

Instead of or in addition to this, it is preferably provided that one or more threshold values are stored for one or more operating parameters, upon exceeding which overload is detected. This simplified method does not require online computing. The threshold values merely need to be calculated once beforehand on the basis of the thermal model or, alternatively, have also been determined empirically.

To determine whether an overload exists, a program routine (algorithm) is additionally or alternatively used in an expedient development, with the help of the operating data of the load and / or the supply line, the current load, in particular the current temperature of the supply cable is calculated. The program routine therefore takes into account the underlying thermal model and reads in as parameters the actual operating parameters measured via the sensor system or the sensor elements. Based on the current measured values for the operating parameters (operating data), the respective thermal load is then calculated.

To monitor for overload, therefore, a calculation model is used which reflects the real conditions of the supply line as accurately as possible, so that a current temperature of a component of the supply line is computationally calculated using a software routine, which comes as close as possible to the actual real temperature.

Conveniently, a component-specific parameter set is used in this case and, taking into account the current operating data, the current heat output, ie the heat supplied per unit time, is determined. From this, the actual temperature is finally derived as a criterion for the presence of a thermal overload. Preferably, in parallel with the determination of the supplied heat energy due to the current flowing through the supply line, the current thermal power loss is determined and created a heat balance, then derived from the temperature change of the component and can be closed to an absolute actual temperature. The thermal calculation model is based on the assumption that the heat output supplied corresponds to the electrical power loss due to the line resistance. At the same time, the calculation model assumes that the energy supplied does not lead to a 100% increase in temperature, but rather that there are also heat losses parallel to the heat input. For example, due to the fact that the electrical energy is not 100% converted into heat energy, or that there are radiation effects. Overall, a thermal or energy balance and from this a temperature change is determined with the help of the thermal calculation model. This temperature change is added (or subtracted) to a previously known or postulated temperature value of the component, so that the current temperature of the component results.

In the preparation of the heat balance, a heat capacity and preferably also a thermal resistance of the component is expediently taken into account. By this measure, the real behavior of the component is imaged as accurately as possible, since due to capacitive effects, a continuous supply of energy leads to a gradual increase in temperature.

For the calculation of the current temperature, the current ambient temperature or, alternatively, a maximally assumed postulated ambient temperature is taken into account in an expedient embodiment. This ambient temperature is used for the initial calculation of the temperature value using the routine as the output value for the current temperature of the component to which the temperature change is then calculated. At the same time, the ambient temperature is preferably included in the calculation of the temperature change, since the temperature increase or decrease is also influenced by the actual prevailing ambient temperature. With the aid of the program routine, the current temperature of the component is preferably determined continuously. For this, the program is called iteratively and cyclically. The cycle time between two program calls is in the millisecond range and in particular in the range of 1 millisecond. This continuous monitoring with the extremely short cycle times achieves a very fast response of the monitoring device in the event of an overload. Overall, this calculation algorithm is used to detect an overload case within a few milliseconds. Considering that between the detection of an overload case and switching off the power supply with the help of, for example, a relay or other switching element switching times are still required results in a total reaction time from the occurrence of the overload event to shutdown of less than 10 milliseconds. Thus, with this algorithm, a very fast and speedy and reliable shutdown is achieved.

In the case of overload monitoring, the temperature determined in the preceding routine run is preferably used in each subsequent routine pass as the starting temperature value for the component, to which the temperature change calculated in the next routine run is then added or subtracted.

As a criterion for detecting a thermal overload, a maximum temperature value is expediently set. As soon as this is exceeded, overload is detected. This maximum temperature value preferably forms an adjustable parameter value. As a result, it is possible to adjust the sensitivity of the overload device.

After detecting an overload, the program routine is preferably continued to run continuously and the temperature of the component is still monitored. In this case, it is now considered that no more electrical energy is supplied. Since the calculation algorithm simulates the real behavior, the cooling phase of the component is also determined in this way. As soon as the determined temperature falls below a minimum value, the power supply via the supply line is resumed. Thus, an automatic reset is provided, so that only temporarily occurring disturbing effects automatically feed is resumed. In the event that an overload is detected immediately after the power is reconnected, it is possible to permanently disconnect the power supply from the power supply and restore the power after a manual reset after a problem has been resolved allow.

For the calculation model, the current that is currently flowing via the supply line is preferably measured directly and used. Conveniently, this also directly checks whether the measured current has exceeded a short-circuit current threshold value. In this case, the flow of current through the supply line is suppressed. Conveniently, in this case, the check is made on the current threshold each before the start of the actual program run. With this measure of setting a short-circuit current threshold, short-circuit currents are detected very quickly and safely. Overall, therefore, the thermal model is constructed in two stages, which is checked in a first stage, if there is possibly a short-circuit current, in which case a shutdown has occurred. In the second stage, it is checked whether, for example due to a permanently high current, a temperature value is gradually reached, which could possibly lead to a line damage. This two-step approach therefore achieves particularly effective line protection.

The calculation model preferably includes a thermal model for different components of the supply string. These components are, for example, the supply cable, a switching element such as a relay or contacting elements such as plug-in contacts or other contacts. For each of these components, a special calculation model, that is, for example, a thermal conduction model, a thermal relay model or a thermal contacting model, is provided optionally or in combination.

These various individual models are expediently combined to form an overall model. This means that within this overall model, each of these calculation models is executed in parallel as part of a sequence routine. In addition, the threshold value is considered for the detection of a short-circuit current. The paral- Ie monitoring of each of the relevant components has the advantage that the entire supply line is effectively monitored for overload because current flow is inhibited whenever one of the components experiences thermal overload. For different components, different heating effects can occur in different situations, so that different components can be thermally overloaded depending on the situation.

For each of these individual calculation models of the different components, a special parameter set is provided which takes into account the specific circumstances of the different components. These different conditions are in particular the electrical resistance, which is preferably deposited depending on temperature, different heat capacities of the components, different thermal resistance or different radiation behavior, etc. About these parameter sets, the calculation algorithm can also be easily adapted if modifications are made to the individual components, if Thus, for example, another conductivity type or another type of connection is used, for example, has a different electrical resistance. It therefore only needs to be communicated to the device which of the components is in use by recording a corresponding parameter set.

This parameter set can also contain aging parameter values that take account of aging effects. It is also preferably provided that occurring overload events are taken into account for future overload monitoring. Thus, the history is used for the future overload monitoring. It is assumed here that certain overload cases can lead to permanent damage to the component to be monitored, for example the line, so that, for example, the maximum value due to this lasting damage which is recognized as being overloaded, is reduced for the future.

It is expediently also provided that the monitoring device, in particular the monitoring program, is also designed to check the supply line. In this case, checking means that conclusions are drawn from the measured operating data about the current line status and from this in the sense of a forward-looking diagnosis statements about the current state of the supply line are derived. For example, it is determined from a comparison of the current fed into the supply line and the current actually consumed by the load, whether any leakage currents exist. In general, it is determined by comparing the operating data of the supply line with those of the load, whether the supply line is defective. The check or diagnosis is done for this purpose, for example, directly from the monitoring device. As an alternative to this, it is also possible to store the measured operating data correlated to one another in a memory and to read out and evaluate them, for example during a normal inspection of the motor vehicle.

Preferably, a temperature sensor for detecting the ambient temperature is further provided and the ambient temperature is used to determine the temperature of the supply line, ie for the decision whether an overload exists. Alternatively, a fixed temperature value for the ambient temperature is preferably predetermined, which in particular corresponds to the maximum expected ambient temperature and is used for the decision on overload.

Expediently, furthermore, the number of switching operations of the component per unit of time, ie the switching frequency, is determined and taken into account in the decision as to whether an overload exists.

According to an expedient refinement, the supply cable is designed as a flat cable, for example a raster cable, an FFC cable (flexible hat cable) or as an FPC cable (flexible printed circuit).

Preferably, the supply cable is designed as an FPC line with integrated electronics. That is, in the line, for example, an electronic evaluation circuit and / or an electronic circuit breaker or an electronic fuse element for separating the supply line from the power supply is integrated directly. Alternatively, the supply line is connected via a plug to the power supply or a door control unit, wherein an integrated fuse element is provided in the plug, in particular a circuit breaker for disconnecting the supply line.

Preferably, in this case in the sense of a possible decentralized backup of the supply line, the fuse element is arranged outside a fuse box decentralized.

In particular, with regard to the desired use of new line technologies, such as foil lines or the like, is provided in an advantageous embodiment that the actual line cross-section of the supply line is smaller than a line cross-section, as would be required for the security value of a central security element. The basic structure of the electrical system therefore remains untouched and at the same time a supply cable is used with a reduced cable cross-section, which is adapted to the actual expected power consumption of the engine.

An embodiment of the invention will be explained in more detail below with reference to the drawing. These show in schematic and simplified representations

1 to 3 alternative embodiments of a partial section of a motor vehicle electrical system in block diagram representations,

4 shows a thermal equivalent circuit diagram for a thermal conduction model, and FIG. 5 shows the sequence of a program routine for monitoring a component of a supply strand for thermal overload.

The sectional electrical system shown in FIG. 1 comprises a central fuse box 2, in which a plurality of common fuse elements 4 are provided to protect against electrical system lines 6,6A against overload. In the exemplary embodiment, only a common fuse element 4 is indicated, which protects the line 6A of the electrical system against overload. The fuse box 2 itself is in turn connected by a supply line 8 with a higher hierarchical level of the electrical system, for example, with a Vorsicherungsdose which is directly downstream of the motor vehicle battery.

Via the line 6A, a control unit 10 is connected to the vehicle electrical system, from which depart several supply cables 12.12A. The supply cables 12.12A are therefore protected together by the common fuse element 4 against overload.

The control unit 10 is connected to a power window motor 16 via the supply cable 12A and via a switch 14 integrated in the control unit 10. The control unit 10 is usually integrated within a door module of a motor vehicle door and serves to control and supply the integrated components in the door module, such as for controlling the window regulator motor or for connecting control elements, for example for the remote controlled opening of the hood, the trunk, other window motors, etc In this case, the control device 10 is usually connected to the line 6A via a cutting or disconnecting point (not shown here). This interface is usually realized as a plug. As an alternative to the switch 14 implemented in the control unit 10, this is arranged downstream of the control unit. The switch 14 is used to disconnect the supply cable 12A and thus forms a fuse element designed as a circuit breaker.

The control unit 10 has a combined program 18, in which a first monitoring program 2OA and a second monitoring program 2OB are combined with one another. In the control unit 10, a memory 22 is also provided in addition to other components not shown here in detail. The control unit 10 receives operating data B 'of the window lift motor 16 via a first data line 24A. The operating data B' are the current actual values of operating parameters, such as engine speed, supply voltage, supply current, etc. As shown by the dashed arrow, operating data can also be used B of the supply cable 12A and the monitoring program 2OA be provided. For detecting the operating data B 'of the load 16, one or more sensor elements 25 which are suitably designed and form sensor systems are provided. In the exemplary embodiment, only one sensor element 25 is shown as part of the window lift motor 16. The sensor element 25 is, for example, the current output of a semiconductor power switch that is used instead of a relay. Alternatively, the sensor element 25 is a measuring or switching resistor. Also, the sensor element 25 may be a Hall sensor for speed measurement. In this case, reference is preferably made to sensor elements 25 which are already used for other functions, so that there is no additional outlay for the implementation of the sensor system.

Via a second data line 24B, the control unit 10 is connected to a temperature sensor 26. This serves to measure the ambient temperature and transmits corresponding temperature data X to the control unit 10.

In the embodiment according to FIG. 2, in contrast to that according to FIG. 1, no sensor system for detecting the operating data B 'of the load 16 is provided. Rather, in this exemplary embodiment, the operating data B of the supply cable 12A are directly detected with the aid of a further sensor element 28 and made available to the monitoring program 20A. In the exemplary embodiment, the further sensor element 28 is a shunt resistor for the direct current measurement of the current fed into the supply cable 12A.

Finally, in the case of the embodiment according to FIG. 3, the direct measurement of the current flowing via the supply cable 12A is likewise provided. The further sensor element 28 is in this case designed as a so-called SenseFet, which also simultaneously represents the switch 14, via which the supply cable 12A is disconnected if necessary. Sensor element 28 and fuse element 14 are therefore realized by a single component.

In the embodiment of FIG. 3, furthermore, the supply cable 12A is formed as an FPC line, and the senseFet 28 is implemented on this FPC line as an integrated component. The FPC line is connected directly to the control unit 10 as well to the window motor 16, for example via suitable connectors connected.

In the case of the embodiment variants according to FIGS. 2 and 3, the operating data B 'of the load 16 can additionally be used additionally as in the exemplary embodiment according to FIG.

Since several supply cables 12 are simultaneously secured via the securing element 4, the supply cable 12A can not be replaced by a supply line designed for smaller currents for safety-related reasons without supplementary measures. The fuse element 4 is designed to protect the supply cable 12.12A, for example, as a 3A fuse, so has a fuse rating of 3 amps. All cables 6A, 12, 12A which are subordinate hierarchically in the vehicle electrical system and which are protected by fuse element 4 must at least be designed for a current of 3 amperes, even if the actual power consumption of the respective load is significantly lower. Even if such a supply cable 12A with a smaller conductor cross-section for the power supply of the window regulator motor 16 would be sufficient. The use of smaller or more advanced power window motors 16 therefore conventionally does not allow adjustment of the power supply cable 12A.

In order to provide an effective overload protection for the supply cable 12A, a software-implemented overload protection is implemented. For this purpose, the expected temperature of the supply cable 12A is derived with the aid of the monitoring program 2OA on the basis of the obtained operating data B.B 'and taking into account the temperature data X and used as a criterion for the decision whether an overload exists or not. For this decision, the monitoring program 2OA accesses here not shown curves, which are stored in the memory 22.

Thus, for example, in a first alternative from the measured engine speed, the measured supply voltage and the motor characteristic on the expected temperature load of the supply cable 12A inferred. In a second Alternatively, for example, the supply voltage and the supply current are detected and from this the expected temperature of the supply cable 12A is determined.

The memory 22 stores the parameter sets and characteristics that are valid for the current configuration. The current configuration includes the type of supply cable 12A and the type of window regulator motor 16 used. In assessing whether an overload exists, the temperature data X for the outside temperature and the number of switching states in a predetermined time interval, ie the switching frequency, are used , This is preferably determined by the control unit 10 itself by evaluating the chronological sequence of the switching pulses caused by it to the window regulator motor 16.

If the monitoring program 2OA detects an overload of the supply cable 12A, then the switch 14 is opened and the window regulator motor 16 is disconnected from the rest of the vehicle electrical system. Subsequently, the switch 14 can be closed again and the window regulator motor 16 can resume its normal operation.

This software technical cable or line protection realizes an effective reversible protection mechanism. Due to the reversibility, unlike a fuse, no manual intervention is required after triggering of the protective mechanism. Due to the software technical realization of the line protection is also very inexpensive and there are no hardware components required. Furthermore, it is provided that the actual cable cross-section of the supply cable 12A is reduced in comparison to a cable cross-section necessary for the securing value of the securing element 4 and adapted to the actual power consumption of the window-lift motor 16. The supply cable 12A is preferably a new line technology, in particular a foil line.

In addition to the line protection, a software-implemented thermal protection for the window regulator motor 16 is formed via the second monitoring program 2OB. Thus, the entire hierarchical level following the controller 10 via a single program module, namely the combined program 18, both against an overcurrent and protected against thermal overload. For thermal overload protection, the second monitoring program 2OB also accesses operating data B 'of the window lift motor 16 and evaluates these. In case of a thermal overload, the switch 14 is also opened.

FIG. 4 shows a thermal equivalent circuit diagram which is used as a basis for the thermal calculation model for checking the supply cable 12A for thermal overload. The thermal equivalent circuit diagram is based on a simple electrical circuit. The thermal quantities can be considered equivalent to the electrical quantities. Namely, the electric voltage U is identified with a temperature difference ΔT between the temperature of the line 12A and the ambient temperature, the electric capacity C having a heat capacity C _0n , the electric resistance R having a heat resistance Ri _h . In this thermal model, therefore, essentially the input finds the heat capacity Cj _{h of} the respective component 12 A to be monitored and a thermal resistance R _{01 of} the respective component 12 A to be monitored. Thermal resistance R ₀₁ is here understood to mean the resistance which precludes a heat flow I during the propagation in component 12A. In analogy to Ohm's law, the thermal resistance R _t h is defined instead of the ohmic resistance R and a heat output P _th instead of the current and a temperature drop Δθ instead of a voltage drop. And it applies:

P _th = Δθ / R ₀₁ .

In addition to the heat conduction P _th defined thereby, the equation for the heat capacity C ₀₁ can be established

Temperature difference ΔT is the difference between the line temperature and the environment. Based on these fundamental considerations, an energy balance is established as follows:

twärmezu ⁼ twärmeab ^" * ^" t _a ufheizenι wherein Ewärmezu to the supplied energy, Ewarm _e a _b corresponds to the heat energy emitted and E _a u _fhe iz _e n of the resulting in a temperature change heating energy. The supplied heat energy Ewarmezu corresponds to the electrical loss energy due to the ohmic line resistance (P _v = I ² • R (T) • t). Taking these assumptions into account, a simple model can be set up by means of which the temperature change Δθ can be calculated.

In this case, the current I flowing through the cable 12A, which is preferably detected directly or also determined indirectly, is required as input data. Furthermore, the elek- fresh line resistance R _e ι is required, which is stored as a parameter value. Preferably, the electrical line resistance R _e ι temperature-dependent deposited. The thermal resistance R _th and the heat capacity Cm are calculated using empirical models. In this case, it is assumed that in the stationary state at a constant heat output P _th , ie when no heating or cooling effect occurs, the heat output P 1 can be equated with the electrical power loss P _v and the resulting temperature difference Δθ minus the final temperature of the line minus the ambient temperature is. After that can be after the formula

R _th = Δθ / P _v calculate the thermal resistance R ^. In a similar manner, the heat capacity C _t h can also be determined and stored as a parameter using empirical measurements on the respective component to be monitored.

Overload monitoring is continuous, cyclically starting the overload monitoring program. The cycle time is preferably about 1 millisecond. The cycle or program routine is shown in FIG. After the start of the program routine, the actual current value I is first determined, preferably measured directly. Alternatively, it can be derived, for example, from characteristics of the load 16. In a first decision step, it is then checked whether the measured, in particular average current value I 'exceeds a threshold value S. The threshold value S stands for a short-circuit current value. The average current value I 'is the current value I averaged over a certain measuring time. If the average current value I 'exceeds the threshold value S, this immediately leads to disconnection of the supply cable 12A from the power supply. That is, the switch 14 is made to be opened.

If the average current value I 'does not exceed the threshold value S, the current temperature T of the supply cable 12A is calculated in the next step with the aid of the thermal calculation model. If this exceeds a predeterminable maximum temperature value MAX, then again the supply cable 12A is disconnected from the power supply. Exceeding the temperature maximum value MAX is therefore used as a criterion for an overload. If T <MAX, the next step is to check whether T <is a temperature minimum value MIN. This is significant when the switch 14 has been opened, thus allowing the supply cable 12A to cool. If T <MIN, the switch 14 is closed again and the load 16 is supplied with power again. Then the routine starts again.

In the next routine, the previously calculated temperature value T is considered as the initial temperature value. When the routine is first started, either a measured temperature value, for example the ambient temperature, is used, or a postulated temperature value is assumed. Due to the iterative procedure and the assumption of the previously determined temperature value T, gradual temperature increases are detected. By this measure, therefore, a thermal overload is detected even if the measured current is well below the threshold value S, but is so large that the supply cable 12A continuously heats up and reaches a temperature value T, from which damage to the cable 12A at least is to be feared.

The procedure explained in connection with FIGS. 4 and 5 in connection with the supply cable 12A can equally be transferred to other components of a supply line (supply line). In particular, such further components are a relay 14 formed as a switch 14 or connecting elements 30, such as connectors or plugs, via which the supply cable 12A is connected to the load 16 and to the controller 10 (see, for example, Fig. 1). The supply line to be monitored is therefore formed by the supply cable 12A, the connecting elements 30 and switch 14th A separate thermal calculation model is preferably provided for each of these components, and a parameter set is stored in the control unit 10 for each of these components. The individual models are preferably combined to form an overall model, which operates in such a way that the individual models are run parallel to one another in each case, the current measured current value I arriving at all three models and being compared once with the stored threshold value S in the context of the overall model.

LIST OF REFERENCE NUMBERS

2 fuse box

4 fuse element

6 line

8 supply line

10 control unit

12, 12A supply cable

14 switches

16 window motor

18 program

2OA first monitoring program

2OB second monitoring program

22 memory

24A.B data line

25 sensor element

26 temperature sensor

28 additional sensor element

30 connecting element

B ₁ B 'Operating data

T temperature data

Δθ temperature difference of the line due to a heat supply

ΔT temperature difference line - environment t time

Rth thermal resistance

Cth heat capacity

Pth heat output

Pv electrical power loss

I measured current r averaged current value

S threshold

T calculated temperature value MAX temperature maximum value

MIN temperature minimum value

Claims

claims

1. Device for overload protection of a supply line (12A, 14,30) for an electrical load in a motor vehicle, in particular a Fensterhebermo- s tor (16), wherein for controlling the electrical load (16), a control device (10) with a monitoring device ( 20A) is provided and the monitoring device (20A) is designed such that on the basis of operating data (B) of the supply line (12A.14.30) it is monitored for overload and disconnecting the supply line (12A, 14.30) o is initiated.

2. Apparatus according to claim 1, wherein the monitoring device is a monitoring program (20A) is provided.

5. The apparatus of claim 1 or 2, wherein a sensor element (28) for direct determination of the operating data (B) of the supply line (12A, 14,30) is provided.

4. Device according to one of the preceding claims, wherein the supply line (12A, 14,30) a load (16) is connected and the monitoring device (20A) is designed such that on the basis of operating data (B ') of the load (16) the supply line (12A, 14,30) is monitored for overload.

5. Apparatus according to claim 4, wherein a sensor (22) for determining the operating data (B ') of the load (16) is provided.

6. Apparatus according to claim 5, wherein the sensor (25) is designed such that a motor speed of the load (16) and the supply voltage are detected and wherein furthermore a motor characteristic is deposited and the monitoring program (20A) is designed such that the motor speed, the supply voltage and the motor characteristic is determined whether an overload exists.

7. Apparatus according to claim 5 or 6, wherein the sensor (25) is designed such that the supply voltage and the supply current of the load (16) are detected.

8. Device according to one of claims 4 to 7, wherein the monitoring device is designed such that the load current with the aid of a Ripplestrom- evaluation or a Hall sensor is derived.

9. Device according to one of claims 2 to 8, in which a load (16) is connected via the supply line (12A, 14, 30), for which a thermal overload protection is provided and for this purpose a further monitoring program (20B) is implemented is designed such that on the basis of the operating data (B, B '), the load (16) is monitored for thermal overload.

10. Device according to claim 9, wherein the monitoring program (20A) and the further monitoring program (20B) comprise a combined program (18) both for overload protection of the supply line (12A, 14, 30) and for thermal overload protection of the electrical load (16). form.

11. Device according to one of the preceding claims, wherein for the monitoring of the supply line (12A.14.30) on overload, a thermal model of at least one component of the supply line (12A, 14,30) is based.

12. Device according to one of the preceding claims, wherein a memory (22) is provided, in which at least one characteristic is deposited and the monitoring device (20A) is designed such that, taking into account the current operating data (B, B ') and under to draw a conclusion on the existence of an overload with the help of the characteristic curve.

13. The apparatus of claim 12, wherein the characteristic curve the relationship between an operating parameter and a temperature of the supply line (12A,

14.30).

s 14. Device according to one of the preceding claims, in which a threshold value is stored for an operating parameter, is detected when exceeded for overload.

15. Device according to one of the preceding claims, in which a pro- gram routine is provided, with the aid of which based on a thermal calculation model from the operating data (B ₁ B '), the current load of at least one component (12 A, 14,30) Supply line is calculated.

16. The apparatus of claim 15, wherein the thermal calculation model, taking into account a component-specific parameter set of the component (12A.14.30) a current heat output (P _th ) determined based on the current flowing through the component current.

17. The apparatus of claim 15 or 16, wherein the current thermal power loss determined, created a heat balance and a temperature change (ΔP) of the component (12A ₁ 14.30) is calculated.

18. The apparatus of claim 17, wherein a heat capacity (C ₀₁ ) of the component (12A, 14.30) is taken into account for setting up the heat balance.

19. Device according to one of claims 15 to 18, wherein the program routine iteratively for continuous determination of the current temperature (T) is performed.

20. Device according to claim 19, wherein the temperature (T) determined in the preceding routine run is determined as the starting temperature in the next routine run. Temperature value for the temperature (T) of the component (12A, 14,30) is used.

21. Device according to one of claims 15 to 20, which is set up so that s is detected on a thermal overload and the flow of current through the supply line is suppressed if the determined temperature (T) exceeds a maximum value (MAX).

22. The apparatus of claim 21, which is arranged such that the current flow o is restored if the determined current temperature (T) falls below a minimum value (MAX).

23. Device according to one of claims 15 to 22, which is arranged to check whether a current flowing through the component (12A, 14.30) current has exceeded a threshold value (S) and when the threshold value (S) is exceeded

Current flow is prevented via the supply line.

24. The device according to claim 23, which is set up in such a way that, before the determination of the current temperature (T), it is checked whether the threshold value (S) is exceeded.

25. Device according to one of claims 15 to 24, wherein the calculation model is optionally a thermal conduction model, a thermal relay model or a thermal contacting model.

26. Device according to one of claims 15 to 25, wherein a plurality of electrical components (12A, 14,30) of a common supply line are monitored and for this purpose a plurality of thermal models are used, wherein when the temperature maximum value (MAX) is exceeded within a model of the supply line flowing current is prevented.

27. Device according to one of the preceding claims, wherein the monitoring device (20A) is also designed to check the supply line (12A, 14,30).

s 28. Device according to one of the preceding claims, wherein a temperature sensor (26) is provided for detecting the ambient temperature or a fixed temperature value for the ambient temperature is predetermined.

29. Device according to one of the preceding claims, wherein the monitoring device (20A) is designed such that, taking into account the

Number of switching operations of the load (16) per unit time is determined whether an overload exists.

30. Device according to one of the preceding claims, wherein the supply line as a supply cable has a flat cable.

31. Device according to one of the preceding claims, wherein the supply line as a supply cable (12A) has an FPC line with an integrated electronics.

32. Device according to one of the preceding claims, wherein the supply line (12A, 14,30) comprises a plug with an integrated fuse element.

33. Device according to one of the preceding claims, wherein at the beginning of the supply line (12A, 14,30) a securing element (14) for separating the supply line (12A, 14,30) is provided.

34. Device according to one of the preceding claims, wherein a securing element (14) for separating the supply line (12A, 14,30) outside a

Fuse box (2) is arranged decentrally.

35. Device according to one of the preceding claims, wherein a central fuse box (2) with a common fuse element (4) for hedging, inter alia, a supply cable (12 A) of the supply line (12 A, 14,30) against a by a security value of the common S fuse element (4) defined overload current is provided, wherein the actual cable cross-section of the supply cable (12A) for the expected current consumption of the load (16) is designed and the actual cable cross-section is smaller than a required for the backup value line cross-section. O

36. A method for monitoring a supply line for an electrical load overload, especially in a motor vehicle, in which evaluated by means of a monitoring device (20A) operating data (B) of the supply line in terms of overload and causes detection of overload on a separation of 5 supply line becomes.