Patent Application
20150219140
The invention relates to a method for producing an assembly unit comprising an assembly part through which a bore passes and a sleeve which has a sleeve shaft through which a through-opening passes and a terminal flange that overhangs the sleeve shaft radially toward the outside. The sleeve shaft is arranged in the bore, i.e. it is plugged into the latter. The flange bears with its flange underside against the outer side, facing said flange, of the assembly part. In order to fix the assembly part, or the assembly unit, to another component, for example a structural element of a motor vehicle, a fastener having a head and a shank, generally a bolt, is plugged through the through-opening by way of the shank, wherein the latter has a fixing portion in the form for example of a thread, said fixing portion being fixable in a counterbore in the component. Furthermore, the invention relates to a fastener unit, consisting of the fastener and a sleeve, for carrying out said production method.
In assembly units of the present type, the joint present between the sleeve and the assembly part, to be more precise between the circumferential surface of the sleeve shaft and the wall of the bore, and between the flange and the outer side of the assembly part is frequently filled with an insulating compound. The purpose of this measure is for example to prevent the penetration of electrolytes that promote corrosion and to prevent direct contact between the sleeve and assembly part. In particular, assembly parts made of CFRP, that is to say carbon-fiber reinforced plastics, have a high potential for corrosion with respect to baser metals or metal alloys such as steel or aluminum.
It would, then, be conceivable, in order to produce assembly parts of the type in question, to use sleeves in which the flange underside and the circumferential surface of the sleeve shaft are coated with an insulating compound. However, when such a sleeve is plugged into the bore in an assembly part, there would be the risk of the coating of the sleeve shaft being partially scraped off by the often sharp-edged transition between the bore rim and the wall of the bore. Also, it would scarcely be possible to prevent the coating from being damaged during storage, transport and handling of the sleeves.
Proceeding therefrom, it is the object of the invention to propose a method for producing an assembly unit, said method providing a remedy with respect to the outlined problem. Furthermore, a further object of the invention is to specify a fastener unit consisting of fastener and sleeve, with which the method can be carried out in a simple manner.
The object is achieved according to claim 1 with regard to the method and according to claim 13 with regard to the fastener unit. In the method according to the invention, provision is made of a sleeve blank, the flange of which has a preassembly form. This differs from the form of the sleeve of the assembly unit in that the flange outer periphery, assigned to the flange underside, extends in a plane that extends at right angles to the longitudinal center axis of the sleeve shaft, wherein, however, the flange underside does not extend in this plane but is configured in a concave manner. If, thus, the flange of the sleeve blank bears against the outer side of the assembly part, a receiving space is formed between the latter and the flange, a store of flowable insulating compound being arranged in said receiving space. The store can either be applied to the bore rim before the sleeve blank is plugged into the bore, or is preferably applied to the flange underside of the flange of the sleeve blank, for instance by means of a cohesive connection. The size of the receiving space can be varied by a corresponding concavity of the flange underside such that at least a quantity of insulating compound sufficient for completely filling the joint is available. When the insulating compound store is applied to the sleeve blank, the concave cavity of the flange underside provides a degree of protection for the insulating compound store from damage, for example during transport.
If a sleeve blank of the described configuration is plugged into the bore in the assembly part in an introduction direction, the outer rim of the flange bears against the outer side of the assembly part. If a force is now applied to the sleeve blank in the introduction direction, the flange is pressed against the outer side of the assembly part with plastic deformation and at least partial elimination of the concavity of the flange underside, and in the process the insulating compound is displaced into the joint between the sleeve and assembly part. In this case, the flange outer rim, pressed against the outer side of the assembly part as a result of the application of force in the introduction direction, ensures that, on account of the relatively great flow resistance present in the region of the outer rim, the insulating compound is displaced reliably into the joint, in particular the joint portion present between the sleeve shaft and the assembly part. On account of the sealing of the flange-side joint, the displacement of the insulating compound into the joint between the sleeve shaft and bore wall is successful even when the joint is relatively narrow. This is the case for instance when the bore wall and the circumferential surface of the sleeve shaft are cylindrical and have a small difference in diameter.
The invention is now explained in more detail with reference to the appended drawings which, unless specified otherwise, are sectional illustrations.
In the drawings:
The aim of the method according to the invention is the production of an assembly unit 1 which comprises an assembly part 3 through which a bore 2 passes and at least one sleeve 4 (see for example
In order to produce an assembly unit 1 of the described type, it would be conceivable to provide the surfaces of the sleeve 4 of the assembly part 3 that are in contact with one another with an insulating compound 16 before said parts are joined, although this would be associated with a very large amount of effort and the abovementioned problems. According to the invention, use is made of a sleeve blank 4′ which differs from the subsequent sleeve 4 of the assembly unit 1 in that its flange 7′ is in a preassembly form. In this form, the outer rim 17, assigned to the flange underside 19′, of the flange 7′ extends in a plane 8 extending at right angles to the longitudinal center axis 9 of the sleeve blank 4′, wherein, however, the flange underside 19′ adjoining the outer rim 17 radially toward the inside is hollowed out in a concave manner and carries an insulating compound store 16′. The latter covers the flange underside 19′ at least in part and optionally also in the upper region, or region close to the flange, of the sleeve shaft 6. The sleeve blank 4′ is inserted by way of its sleeve shaft 6 into the bore 2 in the assembly part 3 in an introduction direction 20. In this case, the flange 7′ bears only with its outer rim 17 on the outer side 10 of the assembly part 3. The size, or the radial dimension, of the joint portion 15a present between the wall of the bore 2 and the sleeve shaft 6 results from the difference between the diameter 23 of the cylindrical bore 2 and the slightly smaller outside diameter 24 of the likewise cylindrical sleeve shaft 6.
Proceeding from the situation shown in
During said application of force, the outer rim 17 of the flange 7′ is pressed against the outer side 10 of the assembly part 3. This prevents insulating compound 16 from being able to be displaced radially toward the outside out of the receiving space 26, or the joint portion 15b formed therefrom, before the joint 15 has been completely filled with insulating compound 16. In the exemplary embodiments illustrated, the insulating compound store 16′ extends over the entire flange underside 19′ of the flange 7′ of the sleeve blank 4′, and so the joint portion 15b formed from the receiving space 26 is already filled with insulating compound 16. Furthermore, complete coating of the flange underside 19′ of the sleeve blank 4′ affords the advantage that the outer rim 17 does not bear directly on the outer side 10 of the assembly part, and so the risk of damage to the assembly part 3 or direct contact between the flange 7 and assembly part 3 does not occur or is at least reduced when the flange 7′ is plastically deformed.
In the depicted examples, the receiving space 26 is ensured with the aid of a conical flange 7′. In this case, the flange underside 19′ forms with the longitudinal center axis 9 of the sleeve blank 4′ an angle α that opens toward the flange-remote end 27 of the sleeve shaft 6.
The length 53 of the sleeve shaft 6 of the sleeve blank 4′ or of the sleeve 4 corresponds substantially to the thickness 34 of the assembly part 3 in the region of the bore rim 44, or to the length 54 of the bore 2. If the assembly part 3, or the assembly unit 1, is intended to be fixed to a component 35 with the aid of a fastener 37 preferably in the form of a bolt 36, the sleeve 4 bears with its flange-remote end side 38 against the component 35 or against an assembly surface 39 present thereon (see
The fastener 37 has a shank 45 which carries a fixing portion 46 at its one end, said fixing portion 46 being in the form of a thread in the case of a bolt (see
The insulating compound 16 introduced into the joint 15 can, in addition to its insulating property, also serve to fix the sleeve 4 in the bore 2. In this case, the insulating compound 16 is an adhesive. Preferably, use is made of a microencapsulated adhesive which contains two differently filled microcapsules, namely those which contain a crosslinkable polymer and those which contain a curing agent that brings about the crosslinking of the polymer. During the deformation of the flange 7′ of the sleeve blank 4′ and while the sleeve shaft 6 is pushed into the bore 2 of the assembly part 3, the microcapsules are destroyed as a result of compressive and shear forces, and so said components are released and the insulating compound cures. It is thus possible to prefabricate assembly units 1 in the bores 2 of which sleeves 4 have already been fixed at least with such a firmness that the assembly units 1 can be transported and handled without the sleeves 4 being lost.
Rather than with an adhesive as insulating compound 16 or in addition thereto, the sleeve 4 can be fixed to the assembly part 3 by use being made of a sleeve blank 4′ of which the sleeve shaft 6 has a length 53 greater than the thickness 34 in the region of the bore rim 44, or than the length 54 of the bore 2 (
If an assembly unit 1 that is already equipped both with a sleeve 4 and with a fastener 37 is intended to be produced, the use of a fastener unit 60 which consists of a sleeve blank 4′ of the above-described type and a fastener 37 is advantageous, wherein the fastener 37 engages through the sleeve blank 4′, or the through-opening 5 therein, with its shank 45. The fastener 37 is captively connected to the sleeve blank 4′ in that a rear-engagement element 58 is integrally formed on the flange-side end of the sleeve blank 4′, said rear-engagement element 58 extending radially toward the inside and radially overlapping a retaining element 59 that protrudes radially toward the outside from the shank 45 on its side facing the head 49.
The fastener unit 60 is plugged into the bore 2 in the assembly part 3 and subsequently the plastic deformation of the flange 7′ of the sleeve blank 4′ is carried out by application of force in the introduction direction 20. In this case, as is the case in the examples according to
In another method variant, the assembly unit 1 is formed only during the fixing of an assembly part 3 to a component 35. In this case, the force F to be applied to the sleeve blank 4′ in the introduction direction is generated with the aid of the fastener 37 in that the latter is fixed with its fixing portion 46 in the counterbore 48 in the component 35. On account of the pretensioning force of the fastener 37 that builds up in the process, the head 49 of said fastener 37 is pressed in the introduction direction 20 against the sleeve blank 4′ and the flange 7′ thereof is pressed against the outer side 10 of the assembly part 3 with plastic deformation.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102014000924.6 | Jan 2014 | DE | national |
