Intrinsically safe discharge element for an intermediate circuit of a high-voltage electrical system

Abstract

The invention relates to a discharge element (1) for an intermediate circuit of a high-voltage electrical system of a motor vehicle for discharging at least one intermediate circuit component of the intermediate circuit, comprising: - a current-carrying resistance element (2) which is designed to provide a discharge current path parallel to the at least one intermediate circuit component in the event of discharge, and which has a first melting temperature for disconnecting the discharge current path in the event of faulty loading of the intermediate circuit in the event of discharge, - a housing (3) in which the current-carrying resistance element (2) is arranged, wherein the housing (3) with the current-carrying resistance element (2) has electrically connected contact areas (6) for contacting the discharge element (1) with the at least one intermediate circuit component and a second melting temperature that is higher than the first melting temperature, - an arc quenching agent (7) which is arranged in the housing (3) and is designed to quench a fault arc that occurs when the resistive element (2) melts to separate the discharge current path.

Description

[0001] The invention relates to a discharge element for an intermediate circuit of a high-voltage electrical system of a motor vehicle for discharging at least one intermediate circuit component of the intermediate circuit. The invention further relates to an intermediate circuit, a high-voltage electrical system, and a motor vehicle.

[0002] The focus here is on high-voltage electrical systems for motor vehicles, particularly electrified vehicles. Such systems typically comprise several high-voltage components, such as a high-voltage energy storage device and high-voltage consumers, which are electrically connected via an intermediate circuit. In the event of an accident or crash, the high-voltage electrical system must be brought into an intrinsically safe state as quickly as possible, ideally within milliseconds, in which it is de-energized and completely discharged. This is usually achieved by first switching off the high-voltage components. For example, a signal can be sent to all high-voltage components, causing them to switch to an energy-neutral state.This energy-neutral state is characterized, for example, by the fact that the high-voltage energy storage device no longer feeds any current into the high-voltage electrical system, and the high-voltage consumers no longer draw any current from the high-voltage electrical system. Subsequently, the remaining energy, which is stored in the capacitors and inductors of the DC link, is discharged by a discharge device within a defined time, thus discharging the DC link. For this purpose, a discharge resistor of the discharge device is connected in parallel to the DC link components, providing a discharge current path to convert the remaining energy into heat.

[0003] In a crash, it can happen that the shutdown of at least one high-voltage component, such as the high-voltage energy storage system, fails, causing the component to continuously feed energy into the high-voltage electrical system and thus into the discharge device. This faulty load on the high-voltage electrical system can cause the discharge resistor to burn out, burst, or arc. To prevent this, the discharge resistor can be dimensioned to withstand the faulty continuous load. Alternatively, the discharge resistor can be protected with an additional protective element, such as a fuse, which interrupts the current flow before the discharge resistor reaches a dangerous state. Both solutions are disadvantageous due to space, weight, and cost considerations.

[0004] The object of the present invention is to provide a discharge device for an intermediate circuit of a high-voltage on-board network which can complete the discharge process in a timely manner under the required conditions and yet does not cause any dangerous consequential errors in the event of a fault.

[0005] This problem is solved according to the invention by a discharge element, an intermediate circuit, a high-voltage electrical system, and a motor vehicle with the features according to the respective independent claims. Advantageous embodiments of the invention are the subject of the dependent claims, the description, and the figure.

[0006] A discharge element according to the invention for a DC link of a high-voltage electrical system of a motor vehicle serves to discharge at least one DC link component of the DC link. The discharge element comprises a current-carrying resistance element, which is designed to provide a discharge current path parallel to the DC link during discharge and which has a first melting temperature for disconnecting the discharge current path in the event of an incorrect load on the DC link during discharge. Furthermore, the discharge element comprises a housing in which the current-carrying resistance element is arranged, the housing having electrically connected contact areas for contacting the discharge element with the DC link component and a second melting temperature that is higher than the first.Furthermore, the discharge element includes an arc quenching agent which is arranged in the housing and is designed to extinguish any arcing that occurs when the resistance element melts to separate the discharge current path.

[0007] The invention also includes an intermediate circuit for a high-voltage electrical system of a motor vehicle, comprising at least one intermediate circuit component and at least one discharge element according to the invention connected in parallel to the at least one intermediate circuit component. A high-voltage electrical system according to the invention for a motor vehicle comprises at least two high-voltage components and an intermediate circuit according to the invention, which is connected between the at least two high-voltage components. Furthermore, the invention relates to a motor vehicle, in particular an electrified one, with a high-voltage electrical system according to the invention. The high-voltage components of the high-voltage electrical system are, in particular, a high-voltage energy storage device, which serves as a traction battery for the motor vehicle, and at least one high-voltage consumer, for example, an electric drive unit of the motor vehicle.

[0008] The intermediate circuit, which is connected between the high-voltage energy storage device and at least one high-voltage consumer, includes at least one intermediate circuit component, for example, at least one intermediate circuit capacitor. To discharge this intermediate circuit component in the event of a vehicle accident, at least one discharge element is provided. This discharge element is intrinsically safe, ensuring that it can dissipate the energy stored in the intermediate circuit components within a predetermined time and that it does not cause any consequential damage in the event of an incorrect load on the high-voltage electrical system during the discharge process.

[0009] For this purpose, the discharge element comprises a resistance element designed as a supportless, specifically spiral, wire resistor. The resistance element is thus designed as a spirally wound wire, whereby the wire is not wound around a support, such as a ceramic body, and is therefore supportless or self-supporting. The wire resistor has the first melting temperature. The wire resistor is dimensioned or designed such that, under normal discharge conditions, the temperature of the discharge element remains below the first melting temperature and only exceeds the first melting temperature under faulty load conditions in the high-voltage electrical system during discharge. Under normal discharge conditions, the discharge element provides the parallel discharge current path and converts the energy stored in at least one intermediate circuit component into heat until complete discharge.In the event of a faulty discharge, the wire resistor melts and interrupts the discharge current path. This prevents the discharge element from overheating. The discharge element is therefore multifunctional, acting as both a discharge resistor and a fuse.

[0010] The housing in which the resistive element is located has a higher melting point than the resistive element itself. This allows the housing to withstand the temperatures that occur before the resistive element melts due to overload. In particular, the housing also has a compressive strength that is higher than the bursting pressure of the resistive element. Thus, the housing can withstand, for example, the pressure generated when the resistive element bursts. For instance, the housing can consist of a ceramic tube and metal caps, with the metal caps positioned at axially opposite ends of the ceramic tube and forming the contact areas.

[0011] Furthermore, the housing is filled with an extinguishing agent, such as quartz sand. This extinguishing agent can extinguish an arc fault that may occur when the resistive element melts, thus preventing arc-induced overheating of the housing and the resulting destruction of the discharge element, which could lead to further malfunctions.

[0012] The embodiments and advantages presented with reference to the discharge element according to the invention apply accordingly to the intermediate circuit according to the invention, to the high-voltage on-board network according to the invention, and to the motor vehicle according to the invention.

[0013] Further features of the invention will become apparent from the claims, the figure, and the figure description. The features and combinations of features mentioned above in the description, as well as the features and combinations of features mentioned below in the figure description and / or shown in the figure alone, are usable not only in the combinations specified, but also in other combinations or individually.

[0014] The invention will now be explained in more detail with reference to a preferred embodiment and the drawing.

[0015] It shows the only figure Fig.Figure 1 shows a schematic representation of a discharge element 1 for an intermediate circuit of a high-voltage electrical system in a motor vehicle. The discharge element 1 serves to dissipate energy in the event of a vehicle crash and fulfills the functions and properties of a discharge resistor and a fuse. The discharge element 1 has a current-carrying resistance element 2, for example, a wire resistor, which is arranged in a housing 3 of the discharge element 1. The housing 3 is made, for example, of a material that can withstand very high temperatures, or at least the temperatures that occur before the discharge element 1 disconnects itself due to overload.The discharge element 1 is therefore dimensioned so that it can safely and quickly dissipate the specified amount of energy, but in the event of a continuous faulty load on the high-voltage on-board network, it disconnects by melting the resistance element 2 before the temperature exceeds the melting temperature of the housing 3.

[0016] Furthermore, the housing 3, due to its material and / or design, can compensate for or selectively dissipate the pressure generated when the resistive element 2 bursts, thus preventing the contents of the housing 3 from being ejected. The housing 3 can, for example, be a ceramic tube 4 with metal caps 5 at its ends. The metal caps 5 form contact areas 6 for the discharge element 1, via which the discharge element 1 can be connected in parallel to at least one intermediate circuit component. Additionally, an arc-quenching medium 7, for example, sand, is integrated into the housing 3. The arc-quenching medium 7 can reliably extinguish any potential arc that may occur when the resistive element 2 melts, i.e., when the discharge element 1 separates.

Claims

[1] Discharge element (1) for an intermediate circuit of a high-voltage on-board network of a motor vehicle for discharging at least one intermediate circuit component of the intermediate circuit, comprising: - a current-carrying resistance element (2) which is designed to provide a discharge current path parallel to the at least one intermediate circuit component in the event of a discharge, and which has a first melting temperature for separating the discharge current path in the event of a faulty load on the intermediate circuit in the event of a discharge, - a housing (3) in which the current-carrying resistance element (2) is arranged, wherein the housing (3) has contacting regions (6) electrically connected to the current-carrying resistance element (2) for contacting the discharge element (1) with the at least one intermediate circuit component and a second melting temperature which is higher than the first melting temperature, - an arc extinguishing means (7) which is arranged in the housing (3) and is designed to extinguish an arc fault which occurs when the resistance element (2) melts to separate the discharge current path. [2] Discharge element (1) according to claim 1, characterized by that the housing (3) has a compressive strength which is higher than a bursting pressure of the resistance element (2). [3] Discharge element (1) according to claim 1 or 2, characterized by that the resistance element (2) is a carrierless wire resistor. [4] Discharge element (1) according to claim 3, characterized by that the wire resistor is spiral-shaped. [5] Discharge element (1) according to one of the preceding claims, characterized by that the housing (3) has a ceramic tube (4) and metal caps (5), wherein the metal caps (5) are arranged at axially opposite ends of the ceramic tube (4) and form the contacting regions (6). [6] Discharge element (1) according to one of the preceding claims, characterized by that the arc extinguishing agent (7) is quartz sand. [7] Intermediate circuit for a high-voltage on-board network of a motor vehicle, comprising at least one intermediate circuit component and at least one discharge element (1) connected in parallel to the at least one intermediate circuit component according to one of the preceding claims. [8] High-voltage electrical system for a motor vehicle comprising at least two high-voltage components and an intermediate circuit according to claim 7, which is connected between the at least two high-voltage components. [9] Motor vehicle with a high-voltage electrical system according to claim 8.

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