This patent application is a national phase filing under section 371 of PCT/EP2019/059545, filed Apr. 12, 2019, which claims the priority of German patent application 102018109403.5, filed Apr. 19, 2018, each of which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

A switching device is specified.

BACKGROUND

The switching device is embodied, in particular, as a remotely operated, electromagnetically acting switch which can be operated by electrically conductive current. The switching device can be activated via an electrical control circuit and can switch an electrical load circuit. In particular, the switching device can be embodied as a relay or as a contactor, in particular as a power contactor. The switching device may particularly preferably be embodied as a gas-filled power contactor.

One possible application for switching devices of this kind, in particular power contactors, is opening and isolating electrical battery circuits, for example in motor vehicles such as electrically or partially electrically driven motor vehicles. These may be, for example, purely battery-operated vehicles (BEV: “battery electric vehicle”), hybrid electric vehicles which can be charged via a power outlet or charging station (PHEV: “plug-in hybrid electric vehicle”) and hybrid electric vehicles (HEV). In general here, both the positive and the negative contact of the battery are isolated using a power contactor. This disconnection is performed in normal operation for example when the vehicle is at a standstill and also in the event of a disturbance such as an accident or the like. The main task of the power contactor here is to switch the vehicle to a deenergized state and to interrupt the flow of current.

The service life of switches of this kind generally ends when the switch no longer has a sufficient insulation resistance in the open state. A switch is usually considered to have failed when a resistance of 50 MΩ is undershot in the open state. At system voltages of, for example, 900 V, powers in the milliwatt range can therefore already occur across the insulation resistor.

A frequent cause of the reduction in the insulation resistance may be erosion of contact materials in the interior of the switch since the materials of the contacts can be removed by switching arcs during the switching processes. These materials are then deposited on the inner walls and form conductive coatings which can lead to bridging of the switching contacts.

SUMMARY

Embodiments provide a switching device, particularly preferably a switching device in which described disadvantages can be prevented or at least reduced.

According to one embodiment, a switching device has at least two stationary contacts and at least one movable contact. The at least two stationary contacts and the at least one movable contact are intended and embodied to switch on and switch off an electrical load circuit which can be connected to the switching device and, in particular, to the at least two stationary contacts. The movable contact can move in the switching device in a corresponding manner between a non-switched-through state and a switched-through state of the switching device in such a way that the movable contact is at a distance from the at least two stationary contacts and is therefore DC-isolated in the non-switched-through state of the switching device and is in mechanical contact with the at least two stationary contacts and is therefore electrically conductively connected to said contacts in the switched-through state. The at least two stationary contacts are therefore arranged in the switching device in a manner isolated from one another and can be electrically conductively connected to one another or electrically isolated from one another by the movable contact depending on the state of the movable contact. The stationary contacts and/or the movable contact can, for example, contain or consist of copper, a copper alloy, one or more high melting metals such as, for example, tungsten, nickel and/or chromium, or a mixture of said materials, for example of copper with at least one further metal, for example tungsten, nickel and/or chromium.

According to a further embodiment, the switching device has a switching chamber in which the movable contact and the at least two stationary contacts are arranged. The movable contact can be arranged, in particular, entirely in the switching chamber. The fact that a stationary contact is arranged in the switching chamber can mean, in particular, that at least one contact region of the stationary contact, which is in mechanical contact with the movable contact in the switched-through state, is arranged within the switching chamber. For connection of a supply line of an electrical circuit which is to be switched by the switching device, electrical contact can be made with a stationary contact, which is arranged in the switching chamber, from the outside, that is to say from outside the switching chamber. To this end, a stationary contact which is arranged in the switching chamber can project out of the switching chamber by way of one portion and have a connection facility for a supply line outside the switching chamber.

According to a further embodiment, the switching device has a housing in which the movable contact and the at least two stationary contacts are arranged. The movable contact can be arranged, in particular, entirely in the housing. The fact that a stationary contact is arranged in the housing can mean, in particular, that at least one contact region of the stationary contact, which is in mechanical contact with the movable contact in the switched-through state, is arranged within the housing. For connection of a supply line of an electrical circuit which is to be switched by the switching device, electrical contact can be made with a stationary contact, which is arranged in the housing, from the outside, that is to say from outside the housing. To this end, a stationary contact which is arranged in the housing can project out of the housing by way of one portion and have a connection facility for a supply line outside the housing.

According to a further embodiment, the contacts are arranged in a gas atmosphere in the housing. This can mean, in particular, that the movable contact is arranged entirely in the gas atmosphere in the housing, and that furthermore at least portions of the stationary contacts, for example the contact regions of the stationary contacts, are arranged in the gas atmosphere in the housing. The switching device can accordingly particularly preferably be a gas-filled switching device such as a gas-filled contactor. The gas atmosphere can promote, in particular, quenching of arcs which can be produced during the switching processes. The gas of the gas atmosphere can preferably have an H2content of at least 50%. In addition to hydrogen, the gas can include an inert gas, particularly preferably N2and/or one or more noble gases.

According to a further embodiment, the switching chamber is located within the housing. Furthermore, in particular, the gas, that is to say at least a portion of the gas atmosphere, can be located in the switching chamber.

According to a further embodiment, the movable contact can be moved by means of a magnet armature. To this end, the magnet armature can have, in particular, a shaft which, at one end, is connected to the movable contact in such a way that the movable contact can be moved by means of the shaft, that is to say is likewise moved by the shaft in the event of movement of said shaft. The shaft can, in particular, project into the switching chamber through an opening in the switching chamber. In particular, the switching chamber can have a switching chamber base which has an opening through which the shaft projects. The magnet armature can be moved by a magnetic circuit in order to affect the above-described switching processes. To this end, the magnetic circuit can have a yoke which has an opening through which the shaft of the magnet armature projects.

The shaft can preferably include or consist of stainless steel. The yoke can preferably include or consist of pure iron or a low-doped iron alloy. The switching chamber, that is to say in particular the switching chamber wall and/or the switching chamber base, can preferably at least partially include or consist of a metal oxide ceramic such as, for example, Al2O3or a plastic. Suitable plastics are, in particular, those with a sufficient temperature resistance. For example, the switching chamber can include, as plastic, polyether ether ketone (PEEK), a polyethylene (PE) and/or glass-filled polybutylene terephthalate (PBT). Furthermore, the switching chamber can also at least partially include a polyoxymethylene (POM), in particular with the structure (CH2O)n. A plastic of this kind can be distinguished by a comparatively low carbon content and a very low tendency to form graphite. Owing to the identical contents of carbon and oxygen, in particular in the case of (CH2O)n, predominantly gaseous CO and H2can be produced in the case of heat- and, in particular, arc-induced decomposition. The additional hydrogen can boost arc quenching.

According to a further embodiment, the switching chamber has an inner side which faces the movable contact. In particular, the switching chamber wall has a corresponding inner side which faces the movable contact. The switching chamber base likewise has a corresponding inner side which faces the movable contact. The inner side of the switching chamber wall and the inner side of the switching chamber base can together form at least a portion and preferably the entire inner side of the switching chamber.

In the region of the openings through which the stationary contacts project into the switching chamber, the inner side of the switching chamber wall adjoins the stationary contacts. If electrically conductive deposits form on the inner side, for example owing to removal of contact material, an electrically conductive connection can form between the stationary contacts in principle. In order to prevent this, the switching chamber has, on the inner side of the switching chamber that faces the movable contact, a continuous surface region, which is occluded from the stationary contacts, between the openings in the switching chamber wall. This means, in particular, that there is no point of the occluded surface region that can be connected to any point on the surfaces of the stationary contacts via a direct connection through the interior of the switching chamber. Material which can be removed from the contacts during an arc can therefore not directly reach the occluded surface region and therefore cannot deposit on said surface region. The fact that the occluded surface region is continuous can mean, in particular, that any possible path between the stationary contacts via the inner side of the switching chamber wall that would form a leakage current path given a corresponding coating with conductive material is interrupted by the surface region, so that no continuous leakage current path can form between the stationary contacts on the inner side in spite of material being deposited on the inner side of the switching chamber wall.

In particular, the occluded surface region can be formed at least by a portion of a trench which, as seen from the stationary contacts, forms an undercut. Therefore, the occluding effect is achieved by the undercut. The occluded surface region can include or be formed by at least a portion of a base surface of the trench or else the entire base surface. Furthermore, the trench can have trench walls which can form at least a portion of the occluded surface region.

The trench can have, for example, a polygonal cross section. For example, the cross section can be rectangular. Furthermore, the trench can also have a wave-like cross section. A trench with a wave-like cross section can be associated with easier production on account of the lack of edges.

According to a further embodiment, the trench has a width B and a depth T. In particular, B<T, and particularly preferably 2·B<T. In other words, the trench is preferably deeper than wide, and particularly preferably more than twice as deep as wide. For example, B can be greater than or equal to 0.5 mm and less than or equal to 2 mm. Furthermore, T can be greater than or equal to 1 mm and less than or equal to 4 mm.

The surface region can be embodied in a recessed manner in relation to the surrounding region of the inner side of the switching chamber wall, that is to say as a region of a channel-like, recessed trench. Furthermore, the surface region can also be arranged between at least two dam-like raised portions which extend above the inner side of the switching chamber.

The surface region can particularly preferably be arranged symmetrically in relation to the stationary contacts. This can mean, in particular, that the surface region is arranged centrally and therefore at an equal distance between the stationary contacts.

According to a further embodiment, the switching chamber base has a continuous occluded surface region which can have one or more of the above-described features for the surface region of the switching chamber wall. In particular, the occluded surface region of the switching chamber wall and the occluded surface region of the switching chamber base can form a coherent occluded surface region, so that no continuous leakage current path can form between the stationary contacts on the inner side of the switching chamber.

The problem of a conductive coating being formed can be solved by the continuous occluded surface region since the surface region is formed by an undercut, on which vapor cannot deposit, in the switching chamber. Said undercut is particularly preferably arranged in an encircling manner in the chamber and separates the two stationary contacts in an effective manner even in the event of vapor being deposited on the inner side of the switching chamber.

