current discharge element

Abstract

Current diverting element, comprising a carrier (2) with a bore (6) and a contact element (7) resting on a shaft (17) which, in the assembled position, passes through the bore (6) and projects into the bore (6), wherein the carrier (2) has at least one opening (11) for receiving a connecting element (18) for connection to a third object, and wherein at least one diverting wire (13) is provided which, on the one hand, is in contact with the contact element (7) and, on the other hand, is guided into the region of the opening (11) for contact with the connecting element (18).

Description

In rotating mechanical systems, it is sometimes possible for electrical currents to be generated which have to be dissipated in order to avoid any damage, i.e. for a possibly current-carrying component to be grounded. An example of this is high-voltage drives for motor vehicles, so-called E-axles comprising an electric motor drive with an associated transmission, in which the electric motor drive is operated with voltages of several 100 V. For grounding, it is known to use sliding contacts or brush contacts, the respective contact being connected to a rotating shaft and otherwise grounded. It is also known to carry out the grounding via a bearing via which a shaft is rotatably mounted by integrating into the bearing a contact element which is seated in a sliding manner on the shaft and via which the current is conducted away. However, such a bearing with such an integrated shunt function is complicated in its design and must be designed specifically for the application.The invention is based on the problem of specifying an improved current-diversion element.To solve the problem, the invention proposes a current-diversion element comprising a carrier with a bore and a contact element which bears against a shaft passing through the bore in the mounting position and projects into the bore, wherein the carrier has at least one aperture for receiving a connecting element for connection to a third object, and wherein at least one diversion wire is provided which is contacted on the one hand with the contact element and is guided on the other hand into the region of the aperture for contact with the connecting element.The current-diversion element according to the invention is a separate component which, on the one hand, accommodates the shaft therein and, on the other hand, is connected directly to a housing component. The current-diversion element comprises an essentially plate-shaped carrier with a bore and a contact element projecting into the bore, i.e. the actual shunt element, which is in contact with a shaft passing through the bore, i.e. abuts in a sliding manner against the latter. The carrier, in turn, and ultimately therefore the current-diverting element itself, is directly connected to a third object such as a housing component, for which purpose at least one aperture for receiving a connecting element such as, for example, a connecting screw for connecting the current-diverting element to the third object, that is to say, for example, the transmission housing component, is provided on the carrier. The connection screw therefore fixes the current-diverting element in the mounting position. In order to be able to conduct current, an electrically conductive connection must be provided between the shaft and the housing component via which the grounding takes place. Part of this connection is the contact element which is in electrical contact with the shaft. At least one lead wire is contacted with this contact element, which lead wire serves for the electrical connection to the connection element set in the mounting position, i.e. for example to the screw, which in turn is in electrical contact with the third object such as the housing component. For this purpose, the lead wire is guided into the region of the opening for contact with the connecting element. If the connecting element is thus set, i.e. for example the connecting screw is screwed in, a contact is automatically produced between the connecting screw and the drain wire. Thus, an electrical path is provided between the shaft and the third object, which is formed via the contact element, the lead wire and the connecting element. The wire can either be bonded to the carrier, or alternatively it can also be mechanically fixed.The configuration of the ground connection via the drain wire makes it possible to produce the carrier from plastic, i.e. a material which is not conductive or is only of extremely poor conductivity. This is because the electrical contact to ground is realized via the electrically conductive drain wire, for example a copper wire, i.e. the carrier itself is not incorporated into the drain path. The production of the carrier from plastic enables a very simple and cost-effective production, and the carrier can also be produced in virtually any desired shape. Alternatively, the support can of course also be made of metal, preferably of a stamped and optionally formed metal sheet. This is naturally itself conductive, but depending on the material, the conductivity can be lower than that of a conductor wire, for example a copper wire. This means that the electrical resistance of the metal carrier is higher than that of the drain wire, so that improved grounding and thus better current dissipation are possible via the drain wire. In such a case, the connecting element, i.e. for example the connecting screw, is then also to be selected from a corresponding, low-resistance material similar to the drain wire or to be provided with a corresponding low-resistance coating.According to an advantageous development of the invention, the drain wire can be laid in the manner of a loop in the region of the opening in such a way that a head of the connecting element is in contact with the drain wire in the mounting position. The drain wire is thus guided in the form of a loop or loop, so to speak, around the aperture, it runs relatively close to the aperture edge. If the connecting element, for example the connecting screw, is screwed in, then when the end position is reached, the head automatically runs axially onto the lead wire, which is firmly clamped between the head and the carrier and in the process is necessarily electrically contacted with the connecting element. Thus, an automatic grounding connection results during assembly.According to the invention, it can furthermore be provided that the carrier has at least two apertures, wherein either only one aperture is assigned a lead wire, or wherein both apertures are each assigned a lead wire or a common lead wire. Accordingly, the carrier is fastened at two different positions by means of two connecting elements or connecting screws, by means of which an even better fastening, connected with a rotation prevention, is realized. For grounding, it is sufficient if only one lead wire is provided, which runs from the contact element into the area of an opening. For reasons of redundancy, a second drain wire can also be provided, which runs from the contact element to the other opening, so that grounding is also possible via this path. A third alternative finally provides a common drain wire which runs from one opening over the contact element to the other opening. Thus, different contact-connection variants are possible.With regard to the specific laying of the conductor or conductors, different configurations are conceivable. According to a first variant, the or each lead wire can have two ends, with which it is contacted with the contact element. The drain wire is thus an elongate wire which is contacted at both ends on the contact element and runs to the connecting element and back from the latter again. The individual conductor wire is thus laid over its length as a whole quasi as a loop. Alternatively, according to a second variant, it is conceivable for a common drain wire to be designed as a closed ring, which is guided from one opening to the other and in sections along and in contact with the contact element. According to this variant, only one closed, i.e. endless, discharge wire is provided, which runs from one opening to the other and is preferably there, of course, guided in a loop-like manner around the opening. One or both longitudinal sections, which run between the perforations, are guided along the contact element and are in contact therewith.According to a further development of the invention, one or more stiffening ribs formed by groove-like depressions can be provided on the carrier. By means of these one or more stiffening ribs, the torsional stiffness of the quasi-plate-shaped carrier can be increased, and it therefore becomes more torsionally stiff. Such a stiffening rib can be formed directly during the production of the carrier, i.e. for example, in the case of a carrier manufactured from metal, it can also be formed during punching and forming. In the case of a carrier made of plastic, such a stiffening rib can already be defined directly via the injection mold. According to the invention, the lead wire can be guided at least in sections in one or more depressions. The groove-like depressions consequently serve as guides for the drain wire, wherein, if a plurality of drain wires are provided, both can naturally be guided in sections in corresponding depressions.In this case, one or more feed-through apertures, through which the drain wire runs from one side of the carrier to the other, can be provided on the carrier. If the contact is made between the lead wire and the contact element or the connecting element on one carrier side, and if the groove-like depressions are located on the other carrier side, with the result that the stiffening ribs protrude to the side with the lead wire contacts, then the or each lead wire can be guided from the contact side to the opposite side via passage apertures and introduced there into the groove-like depressions, and can be guided again to the contact side via a further passage apertures.The contact element itself is preferably annular and fixed to the carrier by means of an annular retaining disc. Such a contact element is also referred to as a round plate and is designed in its cross section such that it rests with its inner circumference in a sliding manner on the shaft and centers itself on it, wherein the contact surface is designed such that an optimum compromise is provided between a sufficient contact and no excessively high sliding stress. A holding disk serves for fixing in a simple manner, wherein the annular contact element, i.e. the round plate, is clamped or clamped between the holding disk and the carrier.In this case, the carrier can have an annular, recessed receptacle for the contact element, wherein the contact element is radially overlapped by the retaining disc. By means of this recessed, i.e. axially extended, receptacle, which is likewise formed, for example, by partial deep-drawing during sheet metal forming or else directly during plastic injection molding, an additional axial offset can be created between the plane of the annular contact element and the mounting plane on the housing side.The holding disk is preferably fastened to the carrier via a plurality of holding elements formed on the carrier and each passing through an aperture of the holding disk. These holding elements are expediently again embodied in one piece with the carrier. The holding elements can be designed, for example, as axially projecting pins which pass through the apertures and are caulked or snap-fitted to the free end passing through. A direct locking without separate forming is also conceivable.The invention is explained below on the basis of exemplary embodiments with reference to the drawings. The drawings are schematic representations and show: FIG. 1 shows a schematic illustration of a current-diverting element according to the invention of a first embodiment in a perspective view, FIG. 2 shows a schematic illustration of the current-diverting element from FIG. 1 in the mounting position, FIG. 3 shows a schematic illustration of a current-diverting element according to the invention of a second embodiment in a sectional view, and FIG. 4 shows an enlarged illustration of the connecting region of the retaining disc to the carrier.FIG. 1 shows a current-diversion element 1 according to the invention, consisting of a carrier 2, which in the example shown is made of plastic and is produced by means of a mold in an injection molding process. It therefore consists of a material which is not electrically conductive or is very poorly electrically conductive. The carrier 2 has the central, central carrier section 3 and two lateral protruding sections 4. The support 2 can be stiffened by stiffening ribs 5, which are raised on the other side by way of groove-like depressions introduced on one side, so that it becomes more torsionally stiff. The central carrier section 3 has a bore 6, into which an annular contact element 7 fastened to the carrier 3 projects with its inner periphery 8, which serves as a sliding contact with a shaft passing through the bore 6. The annular contact element 7, likewise made of metal, is held or tensioned between the holding disk 9 and the carrier 3 via an annular holding disk 9, which is fixed to the carrier 3 via suitable connecting means 10. The holding disk 9 is preferably likewise made of metal.The two protruding sections 4 each have an aperture 11 which is likewise cylindrical in the example shown. Each aperture 11 is adjoined by a spacer element 12 in the form of a separate spacer sleeve. Each spacer element 12 can likewise be made of plastic, but also of ceramic or metal. The carrier 3 is supported via the two spacer elements 12 in the mounting position on a third object, for example a housing component. This is because, in the assembly position, connecting screws pass through the apertures 11 which are screwed into corresponding threaded bores on the housing component, by means of which the current-diversion element 1 is fixed. The spacer elements 12 are thus separate elements in this example. Any currents present on the shaft, not shown in detail, are diverted directly into the housing component via the current diverting element 1, since the shaft is electrically contacted via the contact element 6, that is to say the round plate. In order to continue the current from the contact element 7, a metal drain wire 13, for example made of copper, is provided in the example shown, which is designed as a closed loop. It clearly extends from one aperture 11 to the other aperture 11, wherein it circulates around the respective aperture to form a loop 14. Via feed-through apertures 15, which are preferably already introduced into the carrier during its production, the lead wire 13, coming from the border of the aperture 11, can first be guided onto the opposite side, where it runs into a groove-like depression, via which the reinforcing ribs 5 protruding on the opposite side, i.e. the actual contact side, are formed. There, a defined wire guide thus takes place. The lead-out wire is again guided via further feed-through apertures 15 onto the contact side shown in FIG. 1 and runs under the holding disk 9, wherein it is fixed in a clamping manner via the holding disk 9 between the holding disk 9 and the contact element 7. The course below the holding disk 9 is shown in dashed lines. It extends as far as the opposite section 4, where it runs out again below the holding disk 9 and runs again via passage apertures 15 onto the opposite side into groove-like depressions provided there, from which side it runs again onto the contact side shown in FIG. 1 and wraps around the opposite aperture 11. The lead wire can be fixed on the side shown in FIG. 1, for example, by means of an adhesive, on the opposite side by means of the receptacle in the groove-like depressions or likewise by means of an adhesive.FIG. 2 shows the current-diverting element 1 according to the invention from FIG. 1 in the mounting position on a third object 16, for example a housing component. The current-diversion element 1 is supported on the third object 16 via the two spacer elements 12, i.e. the spacer sleeves, or is spaced apart therefrom in a defined manner, such that the contact element is positioned in a defined axial position with respect to a shaft 17 passing through the bore 6, for example a gear shaft. For fastening the current-diverting element 1, two connecting elements 18 in the form of connecting screws 19 are provided, which are screwed into corresponding threaded bores on the third object. Each connecting element 19 has a head 20 which rests firmly on the loop 14 of the drain wire 13, either directly or via an interposed metal washer, i.e. the loop 14 is braced between the head 20 and the support 2. This results in the electrical contacting of the lead wire 13 to the connecting elements 19 and via these to the third object 16, via which the grounding takes place.In the exemplary embodiment shown, the carrier 2 is made of plastic, for which reason the basic conductivity or electrical connection between the contact element 7 and the third object 16 is effected via the connecting elements 19 and the lead wire 13. Nevertheless, the carrier 2 can also be manufactured from metal or sheet metal. This can also serve for the purpose of discharging, since it is electrically conductive, but the conductivity of such a metal sheet is sometimes poorer compared with that of a discharging wire made of copper, for example. The current conductivity can be improved if, despite the metal carrier 2, a corresponding drain wire 13 is used which is of lower impedance than the metal carrier 2.FIG. 3 shows an alternative embodiment of a current-diversion element 1 according to the invention, wherein the same reference numerals are used for the same components. Here too, a carrier 2 is provided, with the central carrier section 3 and the two lateral sections 4, as is an annular contact element 7 with the inner circumference 8 forming the sliding contact and the retaining disk 9, which brings about the clamping fixing of the contact element 7 on the carrier 2. Likewise, the two apertures 12 are provided on the two sections 4. Instead of the separate spacer elements 12 in the form of the spacer sleeves, however, spacer projections 21 formed integrally on the carrier, which are hollow cylindrical here, are provided in the form of sleeves 22 formed integrally on the carrier. Here, the spacer projections 21 are therefore formed integrally with the carrier 2. In this example, the carrier 2 is likewise made of plastic, i.e. it is a plastic component which has been produced in a corresponding mold by injection processing. This means that no direct electrical contact can be established between the metal contact element 7 and the transmission housing component via the carrier 2.In order to still electrically connect the contact element 6 to the housing component and to conduct away currents, in the example shown a conductor wire 13 is again provided, which is correspondingly laid on the plastic carrier 2 as a closed ring and is guided around the respective aperture 11 as a loop 14. It likewise runs in a quasi-hidden manner between the holding disk 9 and the contact element 7, so that there is contact between the contact element 7 and the lead wire 13. The course of the lead wire 13 below the holding disk 9 is also indicated here by dashed lines. The alternating course of the lead wire 13 between the two sides of the carrier 2 is also provided in this example.As described, such an integral spacer protrusion 21 is likewise provided on the other opening 11, which may likewise be embodied as a hollow cylindrical sleeve 22. If a plurality of integral spacer projections are provided, they can have the same geometry, but they can also differ in the geometry. For example, the spacer projections can have the same shape, that is to say for example both can be hollow-cylindrical, but they can also differ in their shape. Likewise, the spacer projections can also have the same length, but they can also be of different lengths. The specific specific geometry of the spacer projections is in particular dependent on the installation space situation or the installation conditions on the transmission housing component. In fact, no spacer projection can also be provided on the second aperture if the mounting conditions do not require such.During assembly, i.e. when the connecting elements or connecting screws are inserted into the apertures 11 and fixed, the head 20 also rests here on the respective loop 14, i.e. is in electrical contact therewith.This means that the electrical contact is also provided here from the contact element 7 via the lead wire 13 and the respective connecting element to the housing component.As an alternative to the embodiment of the carrier 2 from plastic, an embodiment from metal is also conceivable in this form of the carrier 2 with the integrally formed spacer projections 21. In this case, the spacer projections 21 would be formed directly during the punching and forming of the metal sheet in order to produce the carrier 2 in the form of apertures.FIG. 4 is an enlarged view showing the portion of connection of the retainer plate 9 to the bracket 2 provided in each of the above-described embodiments. A recessed receptacle 23 is formed on the carrier 3, into which receptacle the annular contact element 7 is inserted. Also shown is the holding disk 9, which is non-releasably fixed to the carrier 3 via the connecting means 10 and which, as can be seen, engages over the contact element 9 on the outer circumference and clamps it in a quasi positive-locking manner toward the carrier 3 or the recessed receptacle 23. On the carrier 3 axially projecting pins 24 are formed, which pass through respective apertures 25 in the holding disc 9 during assembly, after which the free end of the pins 24 is formed, i.e. for example caulked, so that a corresponding holding head 26 results, which engages over the holding disc 9 and fixes it in a captive manner.List of reference characters1 Current-diverting element 2 Carrier 3 Carrier section 4 Section 5 Stiffening rib 6 Bore 7 Contact element 8 Inner periphery 9 Retaining disc 10 Connecting means 11 Aperture 12 Spacer element 13 Diverter wire 14 Loop 15 Passage aperture 16 Third object 17 Shaft 18 Connecting element 19 Connecting screw 20 Head 21 Spacer projection 22 Sleeve 23 Receptacle 24 Pin 25 Aperture 26 Retaining head

Claims

Current-diversion element, comprising a carrier (2) with a bore (6) and a contact element (7) which bears against a shaft (17) passing through the bore (6) in the assembly position and projects into the bore (6), wherein the carrier (2) has at least one aperture (11) for receiving a connecting element (18) for connection to a third object, and wherein at least one diversion wire (13) is provided which is contacted on the one hand with the contact element (7) and is guided on the other hand into the region of the aperture (11) for contact with the connecting element (18).Current-diversion element according to Claim 1, characterized in that the diversion wire (13) is laid in the manner of a loop (14) in the region of the aperture (11), in such a way that a head (20) of the connecting element (18) is in contact with the diversion wire (13) in the mounting position.Current-diversion element according to Claim 1 or 2, characterized in that the carrier has at least two apertures (11), either only one aperture (11) being assigned a diversion wire (13), or both apertures (11) being assigned a diversion wire (13) or a common diversion wire (13) in each case.Current-diversion element according to Claim 2 or 3, characterized in that the or each diversion wire (13) has two ends with which it is contacted by the contract element (7), or in that a common diversion wire (13) is designed as a closed ring which is guided in sections along and in contact with the contact element (7) from one aperture (11) to the other.Current-diversion element according to one of the preceding claims, characterized in that one or more stiffening ribs (5) formed via groove-like depressions is provided on the carrier (2), the diversion wire (13) being guided at least in sections in one or more depressions.Current-diverting element according to Claim 5, characterized in that one or more passage apertures (15) through which the diverting wire (13) runs from one side of the carrier (2) to the other are provided on the carrier.Current-diverting element according to one of the preceding claims, characterized in that the contact element (7) is annular and is fixed to the carrier (2) by means of an annular retaining disc (9).Current-diversion element according to Claim 7, characterized in that the or each diversion wire (13) is fixed in a clamping manner between the contact element (7) and the retaining disc (9).Current-diverting element according to Claim 7 or 8, characterized in that an annular, recessed receptacle (23) for the contact element (7) is formed on the carrier (2), the contact element (7) being radially overlapped by the retaining disc (9).Current-diversion element according to one of Claims 7 to 9, characterized in that the retaining disc (9) is fastened to the carrier (2) via a plurality of retaining elements (24) which are formed on the carrier (2) and each pass through an aperture (25) in the retaining disc (9).

Images