Device with an electrical contact connection between two electrical conductors by means of a bolt and bolts

Abstract

The device, designed in particular as a fuse box (2), has an electrical contact connection (4) between two electrical conductors (5) by means of a bolt, which is designed in particular as a screw (6). The bolt has a circumferential groove (38) in the area of ​​its head (26) with a groove depth (T) extending in the axial direction (A), whereby a shaft (24) is extended beyond the head bearing surface (28), thus increasing the clamping length (L) of the bolt. This measure achieves a permanently reliable screw contact connection with high clamping force, and washers for adjusting the clamping length (L) are not required.

Description

[0001] The invention relates to a device with an electrical contact connection between two electrical conductors by means of a bolt, which has a head and a shaft extending axially thereto, wherein the two electrical conductors are clamped between a bearing surface of the head and an opposing abutment surface. The invention further relates to a bolt, particularly for such a device.

[0002] The device in question is, for example, a fuse box in a motor vehicle, where electrical conductors are connected to a busbar, particularly with a fuse element, via screw connections. With such contact connections, a sufficient clamping length of the bolt is required to ensure adequate clamping force. Due to the typically flat contact areas of the conductors, the distance between the head bearing and the opposing abutment surface, determined by their thickness, is often insufficient for a sufficient clamping length. Washers are therefore frequently used to increase the clamping length. However, this increases assembly effort, requires an additional component, and complicates automated assembly.

[0003] Especially in the automotive sector, the problem is that the screw connection can loosen due to vibrations and / or temperature fluctuations occurring during driving, if it lacks sufficient elasticity and therefore an insufficient clamping length.

[0004] From the subsequently published DE 10 2024 100 428 A1, a contacting stud for connection to a conductor track is described, which has axially projecting teeth on its underside for anti-rotation protection, which engage positively with the conductor track during assembly. Additionally, a stop groove is formed on the shaft of the contacting stud, axially spaced from the underside of the head, into which the conductor track engages to form a positive connection acting in the axial direction.

[0005] German patent DE 10 2018 004 217 A1 describes a cable lug connection using a screw and a sleeve. The screw has a relief cut with a reduced diameter between its head and an axially spaced threaded section, into which a retaining element of the sleeve engages to prevent the sleeve from being lost axially.

[0006] DE 20 2018 102 346 U1 relates to a cable lug with a flat contact section having a through hole and a screw attached to it in a captive manner. This screw has a head with an adjoining shank, which subsequently has a transition section with a reduced diameter that fits into the through hole, so that the screw is held securely on both sides.

[0007] Based on this, the invention aims to provide a device with such an electrical contact connection between two electrical conductors by means of a bolt, in which a secure and permanent connection with sufficient clamping force is achieved. Furthermore, the invention aims to provide a suitable bolt, particularly for such a device.

[0008] The problem is solved according to the invention by a device with an electrical contact connection between two electrical conductors by means of a bolt which has a head and a shaft extending axially thereto. At least one of the conductors is clamped between a bearing surface of the head and an opposing abutment surface. The bolt is connected to the abutment in a suitable manner for this purpose. The bolt has a circumferential groove in the region of its head with a groove depth extending in the axial direction, whereby the shaft is extended beyond the bearing surface of the head. This measure achieves the particular advantage of increasing the clamping length of the bolt.

[0009] The clamping length is generally defined as the distance between the two spaced-apart longitudinal positions of the shank where the respective (clamping) force is applied. In conventional bolts, this is the head bearing surface, as this is where the shank transitions into the head. The groove described here shifts the (axial) position where the force is applied to the shank axially, effectively relocating it into the interior of the head. This results in increased elasticity and a longer clamping length for the bolt.

[0010] According to the invention, the groove is a free groove, meaning that no other component is located in the groove. It therefore forms a free annular space which runs around the (extended) shaft inside the head.

[0011] According to the invention, the problem is further solved by a bolt for fastening two components to one another. These components are, in particular but not necessarily, the conductors described above. The bolt can also be used for other component connections between the two components. As previously described, the bolt has a head with a bearing surface and a shank extending axially from the head. In the assembled state, the head rests on one of the components with its bearing surface. The bolt has a circumferential groove in the area of ​​its head, with a groove depth extending in the axial direction.

[0012] The advantages and preferred designs mentioned previously and subsequently in connection with the device are equally transferable to the bolt itself.

[0013] The bolt is specifically a screw, and the abutment is a threaded component, such as a nut. Alternatively, the threaded component can be any component, such as a wall of a support structure or a housing, into which a thread has been cut. In one embodiment, the component with the thread is formed directly by the second conductor. A threaded hole is therefore cut into the second conductor, into which the screw is inserted.

[0014] Preferably, however, the threaded component is an additional component to the two conductors.

[0015] Depending on the design of the contact connection between the two conductors – or more generally, a component connection between the two components – in one variant, the two components / conductors are clamped directly between the head support surface and the abutment surface of the abutment, without any further components. In a second variant, one component / conductor forms the abutment, and the other component / conductor is clamped directly between the head support surface and the abutment, without any further components.

[0016] As an alternative to using a screw, a rivet, such as a blind rivet, can be used as a bolt. Instead of a threaded component, a locking head is used as a counter-bearing in this case.

[0017] In a preferred embodiment, the groove depth is in the range between 1 mm and 4 mm, for example at 1.5 mm or at approximately 1.5 mm (1.5 mm ± 0.3 mm). The clamping length is generally extended by this groove depth compared to a bolt without a corresponding groove.

[0018] The screw is preferably a metric screw according to the standard designation M4, M6 or M8, and particularly according to M6. The bolt generally has a corresponding diameter in the range of 4 mm to 8 mm, and particularly 6 mm.

[0019] The groove preferably has a groove width in the radial direction, i.e. perpendicular to the axial direction and a central axis of the bolt, in the range of 0.2 mm to 0.5 mm and preferably of, for example, 0.3 mm.

[0020] The groove depth increases the clamping length – compared to a design without a groove – by at least a quarter in a preferred embodiment, more preferably by at least a third, and particularly by at least half. Depending on the design, it is also possible that the clamping length is (at least) doubled. Overall, the groove results in a significant increase in the clamping length. Accordingly, the distance between the head bearing surface and the abutment surface is within a suitable range. For example, this distance is 1 mm to 4 mm, and particularly 1.5 mm to 3 mm.

[0021] The clamping length is composed at least and preferably exclusively of the thickness of the two components formed by the conductors, plus the groove depth. In a variant where one component directly forms the abutment, the clamping length is composed solely of the thickness of the other component, plus the groove depth.

[0022] The at least one conductor preferably has a flat, solid connector with a through-hole through which the bolt passes. Preferably, both conductors have such a connector, each with a through-hole, through which the bolt passes. The solid, flat connector is, for example, designed as a terminal, such as a cable lug. The terminal is connected, for example, at its end to a cable, in particular a single-core sheathed cable. Alternatively, the terminal is a terminal of an electrical fuse, which is, for example, designed as an overcurrent protection device. Alternatively, the solid connector is a section of a busbar, which is in particular designed as a distribution busbar and has several such connectors.

[0023] Preferably, one conductor is configured as a busbar with a section designed as a connection piece, and the other conductor has a connection terminal. Alternatively, two connection terminals are connected to each other via a screw connection.

[0024] When a flat, solid connector is mentioned, this means that the connector is formed by a solid metallic strip with a thickness (material thickness) extending in the axial direction of the bolt that is many times less than the width and / or length of the connector. In particular, the thickness is at least 5, 10, or 20 times less than the width.

[0025] The thickness of the connecting pieces is typically between 0.5 mm and 2.5 mm. Preferably, the two connecting pieces have different or, alternatively, the same thickness. The total clamping length is comprised of the thicknesses of the two connecting pieces plus the groove depth.

[0026] In a preferred embodiment, the two conductors, and in particular the aforementioned connecting pieces, are in direct contact with one another, specifically such that one conductor, and especially one connecting piece, is in direct contact with the head bearing surface, and the other conductor, and especially the other connecting piece, is in direct contact with the abutment surface. The additional arrangement of a washer is preferably omitted. The contact connection is therefore formed without any additional separate intermediate elements. This results in simplified assembly and also simplified parts inventory.

[0027] In a preferred embodiment, the device is designed as a fuse box in which at least one electrical fuse element is mounted. The device therefore generally comprises a housing with an internal volume in which the fuse element is mounted. The housing, with the at least one fuse element arranged therein, is referred to as a fuse box. The fuse element is, in particular, an overcurrent fuse element such as a cartridge fuse. Preferably, the fuse box is an automotive fuse box, which is therefore installed in a motor vehicle.

[0028] The fuse in question is, for example, a fuse for overcurrent protection, designed as a 30A fuse or higher (50A, 80A, 100A or higher). Specifically, it protects a DC line. The voltage level is typically in the range of one or more tens of volts (for example, a conventional 12V or 42V electrical system) or even more than 100V in a high-voltage electrical system, as used particularly in electric vehicles (voltage levels up to, for example, 1000V).

[0029] In a preferred embodiment, the locking element has the connecting piece at least on one side at its end, as previously described.

[0030] The safety element preferably has two such connecting pieces designed as connection terminals.

[0031] In a preferred embodiment, the second connection piece of the contact connection is formed by a busbar or by a further connection terminal, in particular a cable lug, of a connected line.

[0032] In a preferred embodiment, the head of the bolt is cast into a base area of ​​the fuse box, specifically a base area designed as a dome-like projection. The housing of the fuse box, and thus the base area, is made of an insulating material and is particularly well-designed as a plastic injection-molded part. The bolt is thereby positively and / or frictionally connected to the base area and thus to the housing of the fuse box. For contact, the two conductors, specifically the two connecting pieces with their through-holes, are placed onto the upwardly projecting shaft and then tightened against each other with the nut.

[0033] In a preferred embodiment, the head is stepped and has an outer head region to which an annular rib, oriented towards the shaft, extends axially. This annular rib is set back radially from the outer head region. The annular rib forms the head bearing surface. It projects axially beyond the base region. In a preferred embodiment, the outer head region is also covered by the potting compound, thus achieving a reliable, positive-locking connection. The annular rib extends radially (inwards) to the groove.

[0034] In a preferred embodiment, the abutment surface is generally designed as an annular surface extending perpendicular to the axial direction and thus in a horizontal plane. In a preferred embodiment, it is designed as a flat surface or alternatively has anti-rotation elements, for example in the form of axially projecting lugs or ribs. In the contact connection, these elements penetrate the respective conductor, specifically the connecting piece.

[0035] An embodiment of the invention is explained in more detail below with reference to the figures. These show: Fig. 1. A perspective, partial view of a fuse box, Fig. 2 a simplified cross-sectional view of a fuse box, Fig. 3 a perspective view of a screw as well as Fig. 4 a partially cut side view of the screw according to Fig. 3 as well as Fig. 5 an enlarged representation of the circle in Fig. 4 marked sections.

[0036] In Fig. Figure 1 shows a device designed as a fuse box 2 with several contact connections 4 between each pair of conductors 5. Each contact connection 4 is designed as a screw connection, in which the two conductors 5 are clamped against each other by means of a bolt designed as a screw 6.

[0037] In Fig. In Figure 1, the fuse box 2 is only partially shown. It has a housing 8, which is only partially depicted in the figure. Fig. Figure 1 shows only a base part 10, which is usually combined with a lid part 12 (see below). Fig. 2) forms a closed housing when assembled.

[0038] A busbar 14, designed as a distribution busbar, is arranged in the fuse box 2 and is in particular designed as a flat sheet metal part. This is usually connected to a power supply line.

[0039] The busbar 14 has several outgoing current paths, each protected by a fuse element 16. Each fuse element 16 has a first terminal 18A designed as a solid, flat sheet metal part, which forms one conductor 5 of the respective contact connection 4. The fuse element 16 is, for example, designed as a fuse and has a corresponding fuse element, which is usually enclosed in an insulated housing.

[0040] A conductor 20 is connected to each current path and is inserted into the interior of the housing from the outside. The conductor 20 is, in particular, a single-core sheathed cable. A connection terminal is attached to the end of the conductor 20, which forms a second terminal 18B as part of the further conductor 5. This terminal, like the first terminal 18A, is designed as a flat, solid sheet metal part. Both terminals 18A and 18B each have a through-hole 22, which is, in particular, completely closed (see Figure 1). Fig. 2), through which the respective screw 6 is passed with a shaft 24.

[0041] At the in Fig. In the fuse box 2 shown, the fuse element 16 has a first terminal 18A on both sides, wherein the previously described line 20 is connected to one terminal 18A via the second terminal 18B, forming a first contact connection 4, and wherein the busbar 14 is connected to the other terminal 18A via a further contact connection 4. A section of the busbar 14 forms a second terminal 18B.

[0042] In the version of the Fig. 1 has only one contact connection 4 to each of the outgoing lines 20. The fuse elements 16 are directly connected to the busbar 14.

[0043] The screw 6, as it is also used in particular in the Fig. 3 and Fig. Figure 4 shows a head 26 to which the previously mentioned shaft 24 is attached in an axial direction A. This shaft is provided with an external thread, at least in some sections.

[0044] An underside of the head 26 oriented towards the shaft 24 forms a head support surface 28, which is designed in particular as a completely circumferential ring surface.

[0045] In the exemplary embodiment, the head bearing surface 28 is formed by an annular web 30, which transitions into an outer head region 32 by forming a step. The annular web 30 is therefore set back radially relative to this outer head region 32.

[0046] In the exemplary embodiment, the following are optional, as shown in particular: Fig. 3 or also Fig. As can be seen in section 4, 28 anti-rotation elements are arranged on the head support surface, which are designed, for example, as protruding cams.

[0047] How specifically based on Fig. As can be seen in Figure 2, the head 26 is embedded in a dome-shaped protruding base area 34 of the base part 10. The head 26 is therefore encased in material from the base area 34. This material covers the outer head area 32, so that in the axial direction A (only) the ring web 30 protrudes. This encasement provides axial pull-out protection. Simultaneously, it also provides anti-rotation protection. For this purpose, the outer head area 32 has a non-circular geometry, as can be seen, for example, in particular from the Fig. 3 is clearly visible.

[0048] How to proceed based on Fig. As can be seen in Figure 2, the two connecting pieces 18A and 18B are clamped between the head support surface 28 and an opposing abutment surface 36 to form the respective contact connection 4. This abutment surface 36 is formed by the underside of a nut 37, which forms an abutment and is screwed onto the screw 6.

[0049] The connectors 18A and 18B each have a thickness D, which in the exemplary embodiment is preferably between 0.5 mm and 2.5 mm. Preferably, the first connector 18A has a smaller thickness D than the second connectors 18B. Specifically, the second connector 18B, which is designed as a cable lug and connected to the conductor 20, has a larger thickness D. This is, for example, in the range between 1.5 mm and 2 mm, whereas the thickness D of the first connector 18A is in the range of, for example, 0.7 mm to 1 mm.

[0050] Of particular importance in the screw 6 is a ring-shaped (ring) groove 38 circumferentially around the shaft 24, which thus extends into the head bearing surface 28 against the axial direction A and reaches to a groove base 40 (compare in particular Fig. 5) The groove 38 has an axial groove depth T in the axial direction A, which in the exemplary embodiment is, for example, 1.5 mm. In the radial direction, the groove 38 also has a groove width B, which in the exemplary embodiment is preferably 0.2 mm. The groove depth T extends from the groove base 40 to the head bearing surface 28.

[0051] The groove 38 increases the clamping length L at the respective contact connection 4. The clamping length L specifies the length of a shaft section between two longitudinal sections in which the clamping force is applied to the shaft 24. In conventional face connections, this is defined by the distance between the head bearing surface 28 and the abutment surface 36. The groove 38 provides the particular advantage of increasing this clamping length L by the groove depth T.

[0052] This increases the overall elasticity required to apply the desired clamping force due to the increased clamping length L. A particular advantage of this is that other measures to increase the clamping length, such as washers, can be dispensed with and preferably are omitted. The groove thus achieves the required minimum clamping length for a locking screw connection without an additional insert (washer). For the fuse boxes 2 and the corresponding contact connections 4 described here, a minimum clamping length of, for example, 4 mm is often required. At the same time, the two connecting pieces 18A, 18B have a total thickness of, for example, 2.5 mm ± 0.5 mm. The groove 38 therefore extends the clamping length in a suitable manner, for example, by at least 1 mm and preferably by 1.5 mm, so that the minimum clamping length is achieved.This also ensures that preload losses and loosening of the screw connection are avoided during operation.

[0053] The groove 38 is formed, for example, during the manufacture of the screw 6 (generally a bolt), specifically during the formation of the head 26, particularly by a (cold) forming process, such as upsetting, as is common in the production of such headed bolts. For the forming process, a suitable die with a punch is provided, wherein the die, for example, forms the counter-form for the head 26, and the punch is moved against the die to form the bearing surface 36 and, in particular, the annular web 30. The punch has, in particular, a punch ring which forms the groove 38. Alternatively, the groove 38 is formed by a machining operation, for example, by a turning and / or milling process. Reference symbol list 2 fuse boxes 4 Contact connection 5 ladders 6 screws 8 cases 10 Base section 12 Lid part 14 busbar 16 safety element 18A first connector 18B second connector 20 Management 22 Through hole 24 creates 26 heads 28 Head support area 30 Ring Bridge 32 outer head area 34 Floor area 36 abutment area 37 Mother 38 Nut 40 Groove L clamping length A Axial direction Thickness T Groove depth B Groove width

Claims

Device with an electrical contact connection (4) between two electrical conductors (5) by means of a bolt which has a head (26) and a shaft (24) extending thereto in the axial direction (A), wherein at least one of the electrical conductors (5) is clamped between a head bearing surface (28) of the head (26) and an opposing abutment surface (36) of an abutment, characterized in that the bolt has a circumferential groove (38) in the region of its head (26) with a groove depth (T) extending in the axial direction (A), whereby the shaft (24) is extended beyond the head bearing surface (28), so that a clamping length (L) of the bolt is extended and a free annular space is formed by the circumferential groove (38) which runs around the shaft (24) inside the head (26). Device according to claim 1, characterized in that the bolt is a screw (6) and the abutment is a threaded component and in particular a nut (37). Device according to one of the preceding claims, characterized in that the groove depth (T) is in the range of 1 mm to 3 mm. Device according to one of the preceding claims, characterized in that the groove (38) has a groove width (B) in a radial direction in the range of 0.2 mm to 0.5 mm. Device according to one of the preceding claims, characterized in that the clamping length (L) is extended by at least a quarter and in particular by at least a third or at least half through the groove (38). Device according to one of the preceding claims, characterized in that the at least one conductor (5) has a flat, solid connecting piece (18A, 18B) with a through hole (22) through which the bolt is passed. Device according to one of the preceding claims, characterized in that the two conductors (5) are directly adjacent to each other and no washer is placed between the head support surface (28) and the abutment surface (36). Device according to one of the preceding claims, characterized in that it is designed as a fuse box (2) in which at least one electrical fuse element (16) is installed. Device according to the preceding claim, characterized in that the locking element (16) has the connecting piece (18A). Device according to one of the two preceding claims, characterized in that the head (26) of the bolt is cast in a base area (34) of the safety box (2), in particular in a base area (34) designed as a dome-like elevation. Device according to one of the preceding claims, characterized in that the head (26) is stepped with an outer head region (32) to which an annular web (30) is attached in the axial direction (A), which is radially offset from the outer head region (32) and which forms the abutment surface (36). Bolt for fastening two components to one another, in particular for a device according to one of the preceding claims, wherein the bolt has a head (26) with a head bearing surface (28) and a shaft (24) extending axially (A) to the head (26), characterized in that the bolt has a circumferential groove (38) in the region of its head (26) with a groove depth (T) extending axially (A), whereby the shaft (24) is extended beyond the head bearing surface (28), so that a clamping length (L) of the bolt is extended and a free annular space is formed by the circumferential groove (38), which runs around the shaft (24) inside the head (26).

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