Overvoltage protection unit of a vehicle electrical system and vehicle, in particular commercial vehicle with an electrical system

Abstract

Overvoltage protection unit of a vehicle electrical system with at least one vehicle battery, wherein the overvoltage protection unit comprises an electrical series connection of at least one overvoltage protection element (2, 3, 4; 16) and at least one thermal fuse (8, 9; 17) in a thermally coupled arrangement of the at least one overvoltage protection element (2, 3, 4; 16) and the at least one thermal fuse (8, 9; 17), and wherein the overvoltage protection unit (1) is arranged between a ground terminal (I) of the vehicle electrical system and a battery terminal (II or III) and / or between two battery terminals II and III, characterized in that the overvoltage protection unit (1) comprises an electrical delta connection of three overvoltage protection elements (2, 3, 4) with three intermediate connection points (5, 6, 7) and with two thermal fuses (8, 9), such thatthat a first connection point (5) is directly or indirectly connected to a ground connection (I) of the vehicle electrical system, that a first thermal fuse (8) is connected to a second connection point (6), which is further connected directly or indirectly to a first battery terminal connection (II), in particular to terminal 30 of the vehicle electrical system corresponding to battery +, and that a second thermal fuse (9) is connected to the third connection point (7), which is further connected directly or indirectly to a second battery terminal connection (III), in particular to terminal 31 of the vehicle electrical system corresponding to battery -.

Description

The invention relates to an overvoltage protection unit of a vehicle on-board power supply system having at least one vehicle battery according to the preamble of claim 1 and to a vehicle, in particular a commercial vehicle, having a vehicle on-board power supply system according to the preamble of claim 7.In vehicle on-board electrical systems, overvoltage phenomena can occur on account of various causes, in particular in the case of electrical loads in vehicle on-board electrical systems without sufficient protection against such overvoltage phenomena, vehicle field damage can occur with vehicle failures and high subsequent costs. Measures for protecting against voltage phenomena are known and can be attached to individual electrical / electronic components or construction modules of the vehicle electrical system.In general, overvoltage protection elements of different designs are known, which are arranged in a parallel connection on a component to be protected and which, after exceeding a voltage threshold in an overvoltage phenomenon, transition from a high-impedance state to a low-impedance state and thereby pass the current of an overvoltage pulse past the component to be protected. As a result, no voltage above the voltage threshold that destroys or damage the component to be protected should be able to build up.A suppressor diode (TVS diode) is such a known overvoltage protection element and is available on the market with a suitable voltage threshold or breakdown voltage in a region lying a little above a vehicle electrical system voltage.Further, a varistor is such a known overvoltage protection element. Such a varistor is a voltage-dependent resistor which, when a threshold voltage of less than approximately 39 volts is present, represents a virtually nonconductive blocking element and becomes a low-impedance conductor above the threshold voltage. Varistores are usually produced on the basis of zinc oxide together with other metal oxides, a corresponding powder being pressed and sintered in tablet form. On two sides, such a blank is then contacted with terminals and in particular cast into epoxy resin.Although such suppressor diodes and / or varistors can in principle also be used at a central point as overvoltage protection elements in a vehicle on-board electrical system, in conjunction with their protective function, they can lead to further problems and considerable damage:In the case of extreme overvoltage phenomena, such as can occur, for example, as a result of lightning strike in a vehicle on-board power supply system, very high overvoltage is generated with correspondingly high current intensities, which would then flow through a varistor and / or a suppressor diode. As a result, a suppressor diode or a varistor could be damaged by overheating. If the suppressor diode or the varistor would thereby become high-ohmic, for example as a result of a conductor interruption, the overvoltage protection would fail, but without further damage being able to originate from the protective element itself.It would be different and more critical if the heat damage would lead to the suppressor diode or the varistor having a low impedance. Then, in extreme overvoltage phenomena, the overvoltage protection element could become a hazardous heating element with great heat generation, whereby in extreme cases a fire acting outwards could be generated, in particular due to a housing. Thus, for extreme overvoltage phenomena, a suppressor diode or varistor could become a hazardous element as an overvoltage protection element itself.DE 10 2005 006 100 A1 discloses a safety circuit and a method for protecting an electronic circuit arrangement from damage in the event of polarity reversal of a connected energy supply unit. DE 100 59 800 A1 discloses polarity reversal protection. An overvoltage protection means is known from DE 91 14 784 U1. DE 39 08 236 A1 discloses an overvoltage protection device, in particular an overvoltage protection device. AT 373 739 B discloses a protective circuit for protecting an electrical arrangement. U.S. Pat. No. 4,586,104 A discloses passive overvoltage protection devices, in particular for protecting computer devices connected to data lines. EP 2 648 310 A1 discloses a monolithic device for protection against reverse batteries. EP 0 173 016 A2 discloses electrical installation systems with surge arresters. FR 2 528 253 A1 discloses an over-voltage protection circuit for electronic components. DE 10 2005 025 573 A1 discloses a multiplexing system for boats or residential vehicles. DE 92 11 808 U1 discloses an arrangement with overvoltage protection means.It is therefore the object of the invention to propose an overvoltage protection unit of a vehicle on-board power supply system in which overvoltage protection elements used, in particular suppressor diodes and / or varistors, do not form any hazardous element even in the event of extreme overvoltage phenomena. A further object of the invention is to propose a vehicle, in particular a commercial vehicle having a vehicle on-board power supply system, having a corresponding overvoltage protection unit.The object is achieved with respect to the overvoltage protection unit having the features of claim 1 and with respect to the vehicle having the features of claim 7. Further advantageous embodiments are the subject matter of the dependent claims.According to Claim 1, an overvoltage protection unit according to the invention of a vehicle on-board power supply system having at least one vehicle battery is characterized by an electrical series connection of at least one overvoltage protection element and at least one thermal fuse in a thermally coupled arrangement of the at least one overvoltage protection element and the at least one thermal fuse. In addition, such an overvoltage protection unit should be arranged directly or indirectly between a ground connection of the on-board power supply system and a battery pole connection and / or between battery pole connections, i.e. at a central location. Preferably, a varistor and / or a suppressor diode are used as overvoltage protection elements. Fuses or PTC resistors are preferably used as PTC thermistors as thermal conductors.The thermal coupling of an overvoltage protection element to a series-connected thermal fuse ensures that, given a corresponding design and dimensioning, the current through the overvoltage protection element is reduced even in the case of extreme saving phenomena such that no critical overheating with a risk of fire occurs therein. If a fuse is used as the thermal fuse, it melts through due to the thermal coupling with the hot overvoltage protection element and / or due to the high current intensity, so that the current path via the overvoltage protection element is interrupted and no further overheating can occur. If a PTC resistor is used as a PTC thermistor as a thermal fuse, the latter becomes very high-ohmic because of the thermal coupling to the overvoltage protection element and the temperature rise associated therewith, so that the then high-ohmic resistor likewise practically interrupts the current path through the overvoltage protection element and prevents further overheating.The overvoltage protection unit can advantageously have a housing as a protection module with outwardly guided connections, preferably with plug connections.In a specific arrangement of the overvoltage protection unit, the at least one overvoltage protection element, in particular a plurality of overvoltage protection elements, and the at least one thermal fuse, in particular a plurality of thermal fuses, can be assigned to one another for thermal coupling in a narrow arrangement, for example in a narrow planar arrangement (for example according to FIG. 2 to be appreciated below), for example on a printed circuit board, or alternatively (for example according to FIG. 3 to be appreciated below) in a narrow spatial arrangement or can be assigned to one another. The terminology "narrow" comprises any such assignment, in particular planar or spatial assignment, of the components to be thermally coupled to one another, in which these components are coupled to one another indirectly or directly by, for example, heat conduction and / or heat radiation or can be coupled to one another by, for example, heat conduction and / or heat radiation. In this case, it is preferably provided that the thermal coupling is preferably effected by the direct proximity and / or mutual contact and / or by means of elements and / or materials which are situated therebetween and / or are in contact with the components in a heat-conducting manner, for example, heat-conducting elements and / or materials, in particular by heat conduction and / or heat radiation. It is essential here that critical overheating with risk potential of the overvoltage protection elements is prevented by a thermal reaction of the series-connected thermal fuses.According to the invention, the overvoltage protection unit has an electrical delta circuit composed of three overvoltage protection elements with three connection points located therebetween and with two thermal fuses. In this case, a first connection point is connected directly or indirectly to a ground connection of the on-board power supply system. A first thermal fuse is connected to a second connection point, which is further connected directly or indirectly to a first battery terminal connection, in particular the terminal 30, that is to say to the positive terminal of the battery. A second thermal fuse is connected to the third connection point, which is further connected directly or indirectly to a second battery terminal connection, in particular to terminal 31, that is to say to the negative terminal of the battery.With this circuit, overvoltage protection is achieved centrally for the entire on-board power supply system, wherein protection against overvoltage in the event of overvoltage phenomena between a ground terminal and one of the battery pole terminals and in the event of overvoltage phenomena between the two battery pole terminals is provided centrally with only one module.Furthermore, in the region of the second connection point and / or the third connection point, a measurement line for a diagnostic tap can be connected, which measurement line is expediently led out of the housing to a plug connection, in particular in the case of an arrangement in a housing. With a corresponding diagnosis, the function of the overvoltage protection unit, for example the function of a protection device, can be checked.Furthermore, a vehicle, in particular a commercial vehicle, is claimed, which has an overvoltage protection unit described above in conjunction with its vehicle on-board power supply system. In this case, such an overvoltage protection unit can advantageously be accommodated in a housing corresponding to a standardized plug-in relay housing for motor vehicles, so that it can thus be inserted into a free plug-in location in the fuse box of the vehicle and in particular can also be retrofitted.The invention is explained further by way of example below with reference to a schematic drawing.The following are shown: FIG. 1 shows the electrical circuit of a preferred exemplary embodiment of an overvoltage protection unit according to the invention, FIG. 2 shows a specific exemplary planar arrangement of the elements of the circuit according to FIG. 1 on a printed circuit board, FIG. 3 shows an alternative spatial arrangement to FIG. 2, FIG. 4 shows a standardized plug-in relay housing for motor vehicles, FIG. 5 shows the bottom of the plug relay housing with standardized plug connection, FIG. 6 shows a schematic circuit diagram of the components contained in the plug relay housing, and FIG. 7 shows a stator characteristic curve of a varistor.FIG. 1 shows the circuit of a preferred exemplary embodiment of an overvoltage protection unit 1 with an electrical star connection comprising three overvoltage protection elements 2, 3, 4 with three connection points 5, 6, 7 located therebetween and with two thermal fuses 8, 9. Suppressor diodes with the corresponding switching symbols are used here as overvoltage protection elements 2, 3, 4 and thermal fuses with the corresponding switching symbols are used as thermal fuses 8, 9.A first connection point 5 is connected to a ground connection I of the on-board power supply system. A first thermal fuse 8 is connected to a second connection point 6 downstream of the overvoltage protection element 2, the further connection of said first thermal fuse being connected at the connection point II to the standardized connection terminal 30 corresponding to the positive pole (B+) of the battery directly or indirectly.At the third connection point 7 of the star connection between the overvoltage protection elements 3 and 4, the second thermal fuse 9 is connected, which is further connected directly or indirectly at the connection point III to the standardized connection terminal 31 corresponding to the negative pole (B-) of the battery.In FIG. 1, the thermal coupling which is absolutely necessary according to the invention is not yet shown graphically for reasons of better clarity. This is only indicated in FIG. 2 by the dashed arrow structure 11.FIG. 2 shows the schematically illustrated circuit according to FIG. 1 in a concrete, narrow or planar arrangement on a printed circuit board 10. The overvoltage protection elements 2, 3, 4 as suppressor diodes are arranged in series next to one another and between the overvoltage protection elements 2 and 3 and between the overvoltage protection elements 3 and 4 are arranged close to one another or close to one another or directly adjacent to the respective thermal fuses 8 and 9. Furthermore, the ground connection I and the connection points II and III are visible.In comparison with FIG. 1, optionally possible diagnostic lines 12 and 13 are additionally drawn in here, which are each connected to the connection point 6 or connection point 7 and which are led to external connections IV and V for a diagnostic tap for checking the function of the components.Whereas in FIG. 2 the thermal coupling of the overvoltage protection elements 2, 3, 4 to the thermal fuses 8, 9 is realized by a planar close packing arranged in a plane, FIG. 3 shows an alternative thermal coupling with a spatially dense arrangement of the elements used. The circuit of FIG. 1 or FIG. 2 has the following function:In the event of an overvoltage phenomenon between the terminals I and II or the terminals I and III or the terminals II and III, the overvoltage protection element applied to the latter in each case becomes conductive as a suppressor diode. For example, in the event of an overvoltage phenomenon between the terminals I and II, the suppressor diode 2 becomes conductive and the current is conducted away via the current path from the suppressor diode 2 and the thermal fuse as a fuse 8. In this case, the suppressor diode 2 heats up. Before critical overheating with a risk potential, the thermal fuse 8 is also heated by the thermal coupling and the current to such an extent that the thermal wire melts and the current path is interrupted.FIG. 4 shows a perspective view of a standardized plug-in relay housing, as can be inserted into the fuse box of a vehicle. FIG. 5 shows the plug relay housing from below with its housing base 15 and the standardized plug connections with the numbers 30, 85, 86, 87. Such a standardized plug relay housing 14 is well suited for receiving and as a component of the overvoltage protection unit 1. In FIG. 6, the first branch of the star circuit according to FIG. 1 corresponding to the suppressor diode 2 and the thermal fuse 8 is therefore shown here, but with a variator 16 and a PTC resistor 17. For accommodation in the plug relay housing 14, the corresponding connections I and II are assigned here to plug connections 19 and 20 on the housing base 15 of the plug relay housing 14.In Fig. 7, the standard characteristic of the variator 16 used in Fig. 6 is shown. It can be seen from this that the variator 16 blocks the current path in a high impedance manner when a voltage up to about 20 volts is present and then becomes lower impedance with an increasing voltage until it completely switches through at about 39 volts. It is thus suitable as an overvoltage protection element for the only slightly underlying, regular voltage in a vehicle on-board electrical system.List of reference characters1 Overvoltage protection unit 2 Overvoltage protection element (suppressor diode) 3 Overvoltage protection element 4 Overvoltage protection element 5 First connection point 6 Second connection point 7 Third connection point 8 First thermal fuse 9 Second thermal fuse 10 Circuit board 11 Dashed arrow structure 12 Diagnostic line 13 Diagnostic line 14 Plug relay housing 15 Housing base 16 Variator 17 PCT resistor 18 Arrow 19 Plug connection 20 Plug connection I Ground connection II Connection point terminal 30, Battery+III Connection point terminal 31, Battery-IV Connection V Connection

Claims

Overvoltage protection unit of a vehicle on-board power supply system having at least one vehicle battery, wherein the overvoltage protection unit has an electrical series connection of at least one overvoltage protection element (2, 3, 4; 16) and at least one thermal fuse (8, 9; 17) in a thermally coupled arrangement of the at least one overvoltage protection element (2, 3, 4; 16) and the at least one thermal fuse (8, 9; 17), and wherein the overvoltage protection unit (1) is arranged between a ground connection (I) of the on-board power supply system and a battery pole connection (II or III) and / or between two battery pole connections II and III, characterized in that the overvoltage protection unit (1) comprises an electrical delta connection of three overvoltage protection elements (2, 3, 4) with three connection points (5, 6, 4) lying therebetween, 7) and having two thermal fuses (8, 9) such that a first connection point (5) is connected directly or indirectly to a ground connection (I) of the on-board power supply system, that a first thermal fuse (8) is connected to a second connection point (6), which first thermal fuse is further connected directly or indirectly to a first battery terminal connection (II), in particular to the terminal 30 of the on-board power supply system corresponding to battery +, and that a second thermal fuse (9) is connected to the third connection point (7), which second thermal fuse is further connected directly or indirectly to a second battery terminal connection (III), in particular to the terminal 31 of the on-board power supply system corresponding to battery -.Overvoltage protection unit according to claim 1, characterised in that the at least one overvoltage protection element is a varistor (16) or a suppressor diode (2, 3, 4) and that the at least one thermal fuse is a fuse (8, 9) or a PTC resistor (17) as a PTC thermistor.Overvoltage protection unit according to claim 1 or claim 2, characterised in that the overvoltage protection unit (1) comprises a housing (14) with outwardly guided connections (19, 20), preferably with plug connections (19, 20), in which the at least one overvoltage protection element (16) and the at least one thermal fuse (17) with thermal coupling are contained.Overvoltage protection unit according to one of the preceding claims, characterized in that the at least one overvoltage protection element (2, 3, 4), preferably a plurality of overvoltage protection elements (2, 3, 4), and the at least one thermal fuse (8, 9), preferably a plurality of thermal fuses (8, 9), are assigned and / or attached to one another in a narrow arrangement for thermal coupling, preferably in a narrow planar arrangement, preferably on a printed circuit board, or in a narrow spatial arrangement.Overvoltage protection unit according to claim 4, characterised in that the thermal coupling of the components to be thermally coupled to one another is effected by thermal conduction and / or thermal radiation by the immediate vicinity and / or mutual contact and / or by means of elements and / or materials lying between them and / or in contact with the components.Overvoltage protection unit according to one of the preceding claims, characterized in that a measurement line is connected as a diagnostic line (12, 13) for a diagnostic tap in the region of the second connection point (6) and / or the third connection point (7).Vehicle, having a vehicle on-board power supply system, having a vehicle battery and having an overvoltage protection unit (1) according to one of the preceding claims.Vehicle according to claim 7, characterised in that the overvoltage protection unit (1) has a housing corresponding to a standardised plug-in relay housing (14) for motor vehicles and can thus be inserted, in particular retrofitted, in a free plug-in location in the fuse box of the vehicle.

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