WO2012130234A1

WO2012130234A1 - Electrically conductive screw connection and special bushing for a screw connection of said type

Info

Publication number: WO2012130234A1
Application number: PCT/DE2012/200017
Authority: WO
Inventors: Thorsten Schraer; Wolfgang Giraud
Original assignee: Ruia Global Fasteners Ag
Priority date: 2011-04-01
Filing date: 2012-03-26
Publication date: 2012-10-04
Also published as: DE202011004721U1; BR112013023854A2; CA2832037A1; CN103635700A; AU2012237597A1; JP2014514510A; MX2013011358A; EP2694824A1; KR20140012690A

Abstract

An electrically conductive screw connection between two parts (10, 12) which are screwed to one another by means of a screw (16) with a screw head (18) and with a shank (22) with an external thread (24) and by means of a nut (28), wherein the screw (16) runs through a bore (14) in one part (10), wherein the electrical contact between the other part (12) and the screw (16) is produced by teeth (27) on the workpiece-side surface of the screw head (18) and/or of the nut (28) or of a washer (30) arranged between the nut (28) and the other part (12), whereas the contact between the screw (16) and one part (10) is produced by a bushing (34; 34') which is formed so as to be radially elastic and which is arranged coaxially with respect to the shank (22) of the screw (16) in a portion (15) of the bore (14) with an enlarged inner diameter.

Description

Electrically conductive screw connection and special socket for such a screw connection

Technisches GebietTechnical area

The present invention relates to an electrically conductive screw connection between two parts screwed together by a screw having a screw head and a shaft, wherein the screw extends through a bore in a part. The present invention also relates to a special socket for such screw connections.

Stand der TechnikState of the art

After modern motor vehicles are more and more equipped with highly sensitive electronics, there is a need, all electrically conductive parts, that is, essentially all metal parts of a motor vehicle low impedance electrically connected to ground.

For this purpose, additional, large ground cables or other devices have previously been provided. This always meant that additional parts had to be installed, which meant additional costs and additional weight, and these parts often did not fulfill their function satisfactorily because often the contact was too bad, or by corrosion and electrochemical effects with time waned , For example, the automotive industry today requires a mass contact with two cables of ten millimeters in diameter for a steering gear made of aluminum.

A direct contact between the individual components of a vehicle today is no longer automatically given because the parts are coated for corrosion protection usually already before final assembly and / or painted, and because aluminum parts form an insulating passivation layer of aluminum oxide by itself.

Furthermore, from the German Utility Model 20 2010 007 769 U1 the applicant already known an electrically conductive screw for this purpose, in which the low-resistance electrical contact between a part and the screw by teeth on the workpiece side surface of the screw head and / or the mother or between the nut and the one part disposed washer is made, while the contact between the screw and the other part is made by protrusions on the shank of the screw whose outer diameter is slightly larger than the inner diameter of the bore, in which the screw is inserted is set, these elevations are arranged between the external thread and the screw head.

Although this solution has proven itself in principle, it has been found that when replacing such a screw in case of service due to the manufacturing tolerances contact problems can arise. Object of the present invention is therefore to provide such an electrically conductive screw available, even after multiple disassembly and assembly and also after replacement of the originally processed screw by a new, an equally good, extremely low-impedance contact between the screwed Is able to produce components. Object of the present invention is also to provide such a low-resistance ground connection, which is structurally easier to implement available.

Darstellung der ErfindungPresentation of the invention

According to the invention this object is achieved by an electrically conductive screw connection, in which a low-resistance electrical contact between one of the parts and the screw is made by teeth on the workpiece side surface of the screw head or between the screw head and the one part arranged washer, while the contact between the screw and the other part is made by a sleeve which is formed radially elastic and coaxial with the shaft of the screw in a portion of the bore with an enlarged inner diameter is arranged.

Likewise, the present object can be solved by a special socket into which a screw can be inserted, and which can be inserted into a correspondingly enlarged hole or in a correspondingly widened portion of a screw hole, and which is formed from a corrugated sheet metal strip , whose shafts are arranged parallel to the axis of rotation of the bushing.

It is particularly preferred if three wave crests and three Wellentä-ler are arranged over a circulation of the jack. This is the simplest possible embodiment for the bush, which allows symmetrical and centered guidance of the screw in the bushing.

Further, it is preferred that the metal strip from which the socket is formed, is endlessly closed. This increases the stability of the bushing under radial stress. But it is also possible a bush, which is wound and the ends of which loose abut each other or in which the ends are connected by dovetail or simple guide.

According to the invention, the wave crests of the socket can be provided with punched-out contact claws or with impressed warts or with a cross or transverse knurl in order to further reduce the contact resistance.

For the same purpose, the surfaces of the socket may be formed at least partially wavy or roughened.

In principle, the bush according to the invention can be used in an enlargement of the diameter of the bore at each end of the workpiece,

However, it is particularly preferred that the section of the bore with the enlarged inner diameter is arranged on the side of the one part facing the screw head, since ejection of the bush from the workpiece during insertion of the screw is then prevented.

If it is desired to introduce the bush only after the parts have been put together, it is preferable to provide the other part with a bore for the passage of the screw, the inner diameter of which is greater than the outer diameter of the bushing. In this case, a solution can then be selected in which the electrical contact between the two parts is made exclusively by the bushing by the socket is inserted in the extended bores of both parts, so that a corresponding special screw head or a corresponding special nut or special washer can be completely dispensed with. Due to its elasticity, the bush also compensates for slight dislocations between the two workpieces.

In the above solution, it is also possible to bring the bushing directly under the screw head rotatable but captive on the shaft of the screw. In this way, eliminates a special operation for mounting the socket and it must not be handled as a separate part and the socket. In contrast, of course, then a specially made screw is required.

In this solution, it is preferred if the shaft of the screw is provided for mounting the bushing above the external thread with a radially umlau-fenden web whose outer diameter is smaller than the enveloping circle of the socket.

To improve the mounting properties of such a screw, it is further preferred if the peripheral web is bevelled on the external thread of the screw, so that the web merges with decreasing height in the external thread. Thus, the screw centered in the enlarged hole sections by itself.

Kurze Beschreibung der ZeichnungenBrief description of the drawings

The present invention will be explained in more detail below with reference to the embodiment shown in the accompanying drawings. Show it:

1 shows a screw connection according to the invention with a special screw according to the invention in a sectional view along the axis of rotation of the screw.

2 shows a special screw according to the invention from the front;

3 shows a three-dimensional representation of a special socket according to the invention;

4 shows a sectional view through the special bushing according to the invention placed on a screw shaft;

FIG. 5 shows the special bush according to the invention of FIG. 1 from the side; FIG. and

Fig. 6 shows another embodiment of a special socket according to the invention.

Bester Weg zur Ausführung der ErfindungBest way to carry out the invention

Figure 1 shows a screw according to the invention, cut along the axis of rotation of the screw.

In the embodiment shown here, a part of a steering gear housing made of aluminum is enclosed as an inner part 10 of an axle carrier made of steel as the outer part 12, both parts are by means of a bore 14 in the inner part 10 and two holes 11, 13 in the outer part 12th extending screw 16 and a nut 28 connected with washer 30 by screwing. The screw head-side hole 11 and a screw-benkopfseitiger part 15 of the bore 14 in this case have an enlarged diameter.

In the present case, the screw according to the invention is designed so that it simultaneously produces a low-resistance electrical contract between the components 10 and 12, even if they are painted, coated or coated with a passivation layer of aluminum oxide.

As usual, the screw 16 has a screw head 18 with a hexalobular external force attack 20 and a shaft 22. As usual, the shaft 22 of the screw 16 is provided with an external thread 24. According to the invention, however, this external thread 24 does not extend to the screw head 18. Rather, under the screw head 18, a circumferential ridge 32 is arranged, which serves to hold a bush 34 according to the invention under the head 18 of the screw 16. The detailed structure of the bushing 34 is explained in more detail below with regard to FIGS. 3 to 5.

The outer diameter of the web 32 is smaller than the enveloping circle of the bush 34 and the smallest diameter of the widened portion 15 of the bore 14 and the screw head side hole eleventh

The diameter of the outer enveloping circle of the bushing 34 may be selected to be slightly larger than the inner diameter of the widened portion 15 of the bore 14, so that the bushing is slightly compressed radially during insertion and thereby a better electrical contact is made.

The hole 11 in the part 12 can either have a much larger inner diameter than the outer diameter of the enveloping circle of the bushing 34, then the insertion of the provided with the bush 34 screw 16 is facilitated, but it is also possible a solution in which the hole 11 has such a diameter as the widened part 15 of the bore 14. In this case, both the contact with the part 10 and with the part 12 can be produced by the bush 34. In such a case, if necessary, further contacting aids between the screw head 18 and the part 12 and between the nut 28 and / or the washer 30 and the part 12 can be dispensed with. In particular, in cases where the part 12 is substantially thicker than shown here, such a solution is recommended. Moreover, in other applications and a much thicker part 12, the bushing 34 may be used to make contact with the part 12, while the screw 16 may also be screwed into the part 10, for example, so that no separate nut 28 is required, and the electrical contact between the screw 16 and the part 10 can be ensured via the screwing of this screw in the part, for example by means of so-called thread-forming or thread-cutting screws.

Further, in the illustrated combination of components 10 and 12 to be joined, it is also possible to use a commercially available screw 16 when inserting the sleeve 34 into the enlarged portion 15 of the bore 14 of the part 10 prior to assembly. Then, the screw 16 must only be pushed through the socket and the remaining hole 14 in the part 10 after the part 12 is positioned accordingly. In this case, an extension of the hole 11 in the part 12 can be dispensed with.

In such a mounting, in which the bushing is inserted into the part 10 in advance, it is also not absolutely necessary to provide the widened portion 15 of the bore 14 on the screw head side of the part 10. In such a case, the widened portion 15 could also be provided on the nut side of the screw.

If the outer part 12 is provided with a coating or coating, for example with a cataphoretic coating (cataphoretic dip painting - KTL), according to the invention now still a low-resistance contact between this outer part 12 and the screw 18 must be prepared. According to the invention this can be done by mounted on the workpiece side surface of the screw head 18 teeth 27, which are shown in Figure 2.

In the present case, the screw by means of a lock nut 28 and a washer 30 is screwed. In the embodiment shown here, the washer 30 is still provided with punched holes 36 which have a resulting from the punching process in the direction of the workpiece 12 projecting edge, and thereby also on this page a good, low-resistance contact between the washer and the outer part 12th produce.

Alternatively, one could dispense with the washer 30 and the nut 28 can also provide with corresponding teeth, and in this way can establish an electrical contact between the nut 28 and the outer part 12 despite a coating or coating of this part 12.

Thus, according to the invention, it is both possible to use the teeth 27 under the screw head 18 for the electrical connection between the screw 16 and the outer part 12, alternatively or additionally, a washer 30 provided with corresponding teeth or elevations may be provided or it may be omit this shim 30 and provide the nut 28 with corresponding teeth and screw directly onto the outer part 12.

In most cases, however, it is sufficient according to the invention to produce the electrical connection between the screw and the outer part 12 via the teeth 27 on the underside of the screw head 18.

If the areas of the part 12, which are penetrated by the screw 16 are thicker in other applications than shown here, the contact can also be made exclusively through the sleeve 34 by the bushing 34 through the corresponding widened hole 11 and the spread -terten portion of the bush 15 of the bore 14 extends and even the contact with both workpieces 10, 12 mediates.

FIG. 2 shows a special screw 16 according to the invention, as used for the screw connection according to FIG. 1, from the front, that is to say seen from the shank of the screw.

In this case, in deviation from the usual rules of technical drawing for a better understanding of the different diameter ratios of the web 32 and the external thread 24 of the screw shaft 22 "as transparent" shown, so you clearly recognizes position and course of the sleeve 34 with respect to the other parts. About a circle on the left side of the outer edge of the web 32 is shown. On the right half of the base circle diameter of the shaft 22 and the outer diameter of the Außenge-wind 24 is shown, wherein the normal diameter of the shaft 22 through-pulled and the outer diameter of the thread 24 is shown in dashed lines.

Well visible here are the mounted on the workpiece side surface of the screw-benkopfes 18 radially extending ribs 27, which serve to improve the contact between the screw head 18 and the surface of the workpiece 12. The ribs 27 do not run through to the outer edge of the screw head 18, but go there in a circumferential ring 38, which serves to prevent the ingress of moisture and thus corrosion phenomena on the ribs 27.

The shape of the bush 34 according to the invention is explained in more detail in FIG.

As can be clearly seen in Figure 3, the bushing 34 consists of an endless self-contained sheet metal strip, which is corrugated so that it has three wave peaks 40 and three wave troughs 42 over a circuit. The result is thus seen in the direction of passage of the screw, the shape of a strongly rounded at the tips equilateral triangle with in its central region slightly inwardly arched side edges. To improve the contact, the surface of the sleeve 34 may be formed with a cross or cross knurl or roughened, as shown here by the hatching. The roughening need not be limited to the inside, the outside can be roughened.

Figure 4 shows again the interaction of screw shaft 22 and bushing 34 in the direction of coaxial with the screw shaft 22, the wave crests 40 and wave troughs 42 are clearly visible. Of the

corresponding outer envelope of the sleeve 34 is indicated by a dotted circular line.

FIG. 5 shows the bushing 34 from the side. Here it is clearly visible that the bushing 34 is provided with small, punched-out claws 44 in the region of the wave crests 40. These serve to improve the electrical contact with the inner surface of the enlarged portion 15 of the bore 14. Alternatively, it may be provided embossed warts or a cross or transverse knurls or a roughening of the surface.

FIG. 6 shows a further bushing 34 'according to the invention which, unlike the bushing 34 of FIG. 3, does not consist of an endless metal strip, but is wound from a metal strip. In this way, the production is easier and cheaper.

The ends of the sheet metal strip which forms the bushing 34 'may be either loosely abutting one another or, as shown, they may be connected by a dovetail joint 46 or a simple guide. The embodiment by dovetail or simple guide has the advantage of greater stability.

Incidentally, this bushing 34 'also has three wave crests 40 and three wave troughs alternately arranged thereon, and is provided with punched out contact claws 44 in the region of the wave crests 40.

The present invention allows electrically conductive parts, preferably metal parts of a motor vehicle, to be electrically connected to ground during the assembly of the connecting elements in a low-resistance manner in order to meet the EMC requirements. According to the invention, this object is achieved in that the sleeve 34 has three flat strip contact with the screw 16 and the socket 34 offset by 60 ° to three other planar contact points to the material has, in which the socket is inserted. In contrast to the special screw according to German Utility Model 20 2010 007 769 U1, the bush 34 according to the invention is able to compensate for tolerances of the hole into which it is used by virtue of its special corrugated shape. At the same time, the curvature pointing in the direction of the screw causes the screw 16 to always be clamped, even if the bushing 34 is compressed radially from the outside. In other forms, the sleeve would stand out from the screw by the radial compression, according to the invention while the pressure on the screw is even increased.

The bush 34 itself can either be inserted into the element to be connected prior to assembly, and a normal screw (possibly with the special head 18 with the ribs 27) is used in the assembly. Alternatively, the bushing 34, as shown here, may be prefixed to a special screw 16. For the insertion of screw 16 and bushing 34, the hole 11 in the workpiece 12, on which the head rest is located, must also be so large that the bushing 34 can be performed. Ideally, the bushing 34 has a chamfer to avoid jamming. In this case, the web 32 is preferably provided on the special screw 16 with a chamfer with the head 18 of the screw 16 towards increasing the diameter to avoid tilting of the sleeve 34 quite certainly. The web 32 must have a smaller diameter than the enveloping circle of the bush 34 and the smallest diameter of the holes 11 and 15.

The bushing 34 itself can be made to make contact in a variety of ways. The contact can be made by small punched out claws 44 as shown in FIG 5, alternatively can be applied thereto warts, similar to a wood rasp, or a wavy or roughened surface or a cross or cross knurls serve. Since the use of the sleeve 34 according to the invention only the extension 15 of the bore 14 in the one Werks piece 10 and possibly (depending on the type of assembly) an enlarged hole 11 must be provided in the other workpiece 12, this solution also offers as Retrofit solution or short-term solution shortly before the start of series production.

The special design of the sleeve 34 according to the invention always guarantees a tight fit of the screw 16, even if the bushing 34 is inserted in holes 15 of different sizes. Radial displacement by the use in smaller holes does not lead to the falling out of the screw 16, but to an increased tight fit. The bush 34 according to the invention can preferably be used as a retrofit solution. Other solutions, such as according to German Utility Model 20 2010 007 769 must always be considered early in the design, since the parts must be adjusted accordingly. The bushing 34 according to the invention, in contrast, can easily be retrofitted here, for example, introduced into a steering gear by merely enlarging the through-hole there so that the bushing 34 fits in. Then at most a suitable special screw with appropriate head geometry or a corresponding nut or shim would have to be used to make electrical contact with the other part 12. All other parts can remain unchanged.

The advantage of the present invention is that the ground connection between different motor vehicle parts can be ensured without additional earth cables, even if the corresponding parts are already coated with a coating, a coating or a passivation layer before the screw connection. In addition, the present invention has the advantage over the conventional ground cable that high frequency interference is also very well dissipated. This is not necessarily the case with ground cables due to their unavoidable inductance.

In contrast, according to the invention, a corresponding contact between the screw 16 and the outer part 12 is produced by the teeth 27 under the screw head 18, which intersect through the lacquer layer on the outer part 12. Alternatively or additionally, this can be done by appropriate teeth or other protruding burrs on a washer, the washer can be placed both under the screw head and under a nut. In addition, the nut may also be provided with appropriate teeth if no washers are used.

The screw head, the washer or the nut can still be provided with an outer circumferential ring to the screw, but in particular the contact points with the destroyed paint on the outer part 12 from the ingress of water and thus protect against corrosion. ren.

In addition, a perforation or other protrusions may also be provided on the workpiece side surface of the nut when connected to the bolt and nut. When using a connection with nut and washer, the washer may be provided with corresponding teeth or other protruding elements to make good contact between the screw and the outer part 12 at the other end of the screw.

Claims

Electrically conductive screw connection between two parts (10, 12) screwed together by a screw (16) with a screw head (18) and a shaft (22) with an external thread (24) and a nut (28), the screw ( 16) through a bore (14) in which one part (10) extends, ie, the electrical contact between the other part (12) and the screw (16) by teeth (27) on the workpiece side surface of the screw head (FIG. 18) and / or the nut (28) or between the nut (28) and the other part (12) arranged washer (30) is made, while the contact between the screw (16) and the one part (10) by a Bushing (34, 34 ') is produced, which is formed radially elastic and coaxial with the shaft (22) of the screw (16) in a portion (15) of the bore (14) is arranged with an enlarged inner diameter.
Is of a corrugated sheet metal strip formed whose Wel-len (40, 42) are arranged parallel to the rotation axis of the bore (14); electrically conductive screw connection of claim 1, d a d u r c hg e k e n n z e i c h n e t, d a s s the sleeve (34 '34).
Electrically conductive screw connection according to claim 2, characterized in that three wave crests (40) and three wave troughs (42) are arranged over one revolution of the bushing (34, 34 ').
An electrically conductive screw connection according to claim 2 or 3, characterized in that the sheet metal strip from which the bushing (34) is formed is endlessly closed.
Electrically conductive screw connection according to claim 2 or 3, d a d u r c hg e k e n n z e i c h n e t, d a s s of the sheet metal strip from which the sleeve (34 ') is formed, is wound and the ends loosely abut each other.
An electrically conductive screw connection according to claim 2 or 3, characterized in that the sheet metal strip from which the bush (34 ') is formed is wound and the ends are connected by dovetail or simple guide.
Electrically conductive screw connection k according to claim 2, 3, 4, 5 or 6, d a d u r c hg e e n n z e i c h n e t, d a s s the socket (34; 34 ') in the region of the wave crests (40) with out-punched contact claws (44) or with slightly embossed warts or with a Cross or cross knurl is provided.
Electrically conductive screw connection according to claim 2, 3, 4, 5 or 6, d a d u r c hg e k e n n z e i c h n e t, d a s s the upper surface of the sleeve (34; 34 ') is formed at least partially wavy or on-roughened.
Electrically conductive screw connection according to one of claims 1 to 8, d a d u r c h e c e n e c e s, the section (15) of the bore (14) with the enlarged inner diameter on the side facing the screw head (18) of the one part (10) is.
An electrically conductive screw connection according to claim 9, wherein the other part (12) has a hole (11) for the passage of the screw (16), the inner diameter of which is greater than the outer diameter of the bushing (34, 34 ').
Is directly below the screw head rotatably but captively on the shank (22) of the screw (16) mounted, electrically conductive screw connection of claim 9, d a d u r c hg e k e n n z e i c h n e t, d a s s the sleeve (34 '34).
Electrically conductive screw connection according to claim 11, characterized in that the shaft (22) of the screw (16) for attachment of the bushing (34, 34 ') above the external thread (24) is provided with a radially encircling web (32) Outer diameter is smaller than the enveloping circle of the bush (34, 34 ').
Electrically conductive screw connection according to claim 12, characterized in that the circumferential web (32) is bevelled on the external thread (24) of the screw (16), so that the web (32) with decreasing height into the external thread (24 ) passes over.
Special socket for the low-resistance connection of a screw (16) to a workpiece (10) into which the screw (16) is inserted , ie, the bush (34, 34 ') is formed from a corrugated sheet-metal strip whose shafts (40,42) are arranged parallel to the axis of rotation of the bushing (34; 34 ').
Special socket according to claim 14, characterized in that three wave crests (40) and three wave troughs (42) are arranged over one revolution of the bushing (34, 34 ').
A special socket according to claim 14 or 15, characterized in that the sheet metal strip from which the socket (34) is formed is endlessly closed.
Special socket according to claim 14 or 15, d a d u r c hg e k e n n z e i c h n e t, d a s s of the sheet metal strip from which the sleeve (34 ') is formed, is wound and the ends loosely abut each other.
Special socket according to claim 14 or 15, d a d u r c hg e k e n n z e i c h n e t, d a s s of the sheet metal strip from which the sleeve (34 ') is formed, is wound and the ends are connected by means of dovetail or a simple guide.
Special socket according to claim 14, 15, 16, 17 or 18, d a d u r c hg e k e n n z e i c h n e t, d a s s the socket (34; 34 ') in the region of the wave crests (40) with punched Kon clock claw (44) or with slightly embossed warts or with a cross or transverse spiral is provided.
A special socket according to claim 14, 15, 16, 17 or 18, characterized in that the outer surface of the bushing (34, 34 ') is formed at least partially wavy or roughened.