METHOD FOR MANUFACTURING PLASTIC PEDELEC FRAMES, AND ACCORDINGLY MANUFACTURED PEDELEC FRAME

Abstract

The invention relates to a method for manufacturing a plastic pedelec frame (1) by, preferably integrally, joining two matching plastic half-shells (2, 3), said pedelec frame being provided with receptacles (12, 13, 14) for a handlebar (4), a bottom bracket (5) and preferably a seat (6). The two plastic half shells (2, 3) are made from a fiber-reinforced thermoplastic material containing a partially aromatic polyamide, using an injection molding process. The invention also relates to a pedelec frame (1) manufactured by said method.

Claims

1.-15. (canceled)

16. A method for producing a pedelec frame made of plastic, comprising: bringing two corresponding plastic half-shells into engagement with one another; wherein the pedelec frame includes recesses for a handlebar, a bottom bracket and a cyclist's saddle; and wherein the two plastic half-shells are produced by an injection molding process from a fiber-reinforced thermoplastic synthetic material that contains a partially aromatic polyamide.

17. The method according to claim 16, wherein the partially aromatic polyamide is selected from the group consisting of aliphatic dicarbonyl repeat units, aromatic diamino repeat units, aromatic dicarbonyl repeat units, aliphatic diamino repeat units and combinations thereof.

18. The method according to claim 16, wherein the partially aromatic polyamide comprises meta-xylylenediamine repeat units and 1,6-hexanedionyl repeat units.

19. The method according to claim 16, wherein the fiber-reinforced thermoplastic synthetic material further comprises an aliphatic polyamide.

20. The method according to claim 16, wherein a weight fraction of the partially aromatic polyamide is in the range of at least 50% to at least 70% based on a total mass of the thermoplastic synthetic material without the fiber reinforcement.

21. The method according to claim 16, wherein the fiber reinforcement is selected from the group consisting of glass fibers, carbon fibers, aramide fibers and combinations thereof.

22. The method according to claim 16, wherein a weight fraction of the fibers in the fiber-reinforced thermoplastic synthetic material is in the range of 15-70%.

23. The method according to claim 16, wherein an average length of the fibers in the pedelec frame is less than 15 mm.

24. The method according to claim 16, wherein one of the plastic half-shells, at a joining edge thereof, includes a groove formed thereon, while a joining edge of the other plastic half shell includes a spring that engages the groove during engagement of the plastic half-shells.

25. The method according to claim 24, wherein the spring and groove connection is such that a clamping connection is produced by the joining of the spring in the groove, which pre-fixes the plastic half-shells to one another.

26. The method according to claim 16, wherein the two plastic half-shells are bonded to one another through welding at corresponding joining edges thereof, and to the pedelec frame by means of laser radiation, thereby forming an inner cavity operable to accommodate an energy storage device and an electric motor therein.

27. The method according to claim 26, wherein one of the plastic half-shells is made of a laser-absorbing plastic material, while the other plastic half-shell is made of a laser-transparent plastic material.

28. The method according to claim 27, wherein a joining edge of one of the plastic half-shells includes a groove formed of the laser-transparent plastic, while a joining edge of the other plastic half-shell includes a spring formed of the laser-absorbing plastic.

29. The method according to claim 6, wherein recesses are milled into the plastic half-shells prior to their engagement with one another, wherein the recesses are configured to hold pedelec components, an electric motor, a battery element or a bottom bracket.

30. A pedelec frame produced by a method according to claim 16.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In the following, only exemplary embodiments of the invention are explained in more detail with reference to the drawings. These are as follows:

[0025] FIG. 1 shows a pedelec frame produced according to the invention in a three-dimensional representation;

[0026] FIG. 2 shows the cross-section A-A in FIG. 1 during the joining process;

[0027] FIG. 3 shows a further embodiment of the invention in a representation corresponding to FIG. 2;

[0028] FIG. 4 shows an enlarged detail of FIG. 2 in a three-dimensional representation, and

[0029] FIG. 5 shows an enlarged detail of FIG. 3 in a three-dimensional representation.

[0030] FIG. 1 shows a pedelec frame 1 according to the invention, which is produced by the assembly of two corresponding plastic half-shells 2, 3. The pedelec frame 1 has a receptacle 12 for handlebars 4, a receptacle 13 for a bottom bracket 5 and a receptacle 14 for a cyclist's saddle 6. The handlebars 4, bottom brackets 5 and cyclist saddles 6 are merely indicated in FIG. 1. A rear-mounted, optionally suspension-mounted, rear axle 60, which is shown in dashed lines, is fastened on the pedelec frame, and serves to support the rear wheel (not shown) of the pedelec. The two half-shells 2, 3 consist of a fiber-reinforced thermoplastic, which contains a partially aromatic polyamide. By joining the two half-shells 2, 3, an inner cavity 7 is formed, which accommodates a battery 30, an electric motor 40, and the bottom bracket 5 of the pedelec. Upon joining the plastic half-shells 2, 3, the battery 30, the electric motor 40 and the bottom bracket 5 are also positioned at defined locations in the inner cavity 7. The plastic half-shells 2, 3 produced by means of an injection-molding process comprise positioning elements 50 integrally formed, to hold the electric motor 40, the battery 30 and the bottom bracket 5 in the desired position.

[0031] The partially aromatic polyamide of the half-shells consists, in the exemplary embodiment, of meta-xylyenediamine 6, which is formed from meta-xylyenediamine and adipic acid. The structural formula of this material is:

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[0032] In addition, ribs and/or connecting elements and/or functional elements are injection-molded onto the half-shells 2, 3 during the injection molding process. These are used, for example, as mountings for other pedelec components such as forks, bottom brackets, saddles or handlebars. The weight fraction of the partially aromatic polyamide, based on the total plastic mass without fiber reinforcement, is 90% in the exemplary embodiment.

[0033] The fiber reinforcement of the thermoplastic consists comprises pure glass fibers finely distributed in the plastic matrix of this polyamide. The average fiber length is less than 1 mm. The weight fraction of the fibers in the fiber-reinforced thermoplastic is 50% in the exemplary embodiment. After joining, the two half-shells 2, 3 are connected together by material bonding and subsequently painted in opaque form.

[0034] The cross-sectional representation in FIG. 2 shows the section A-A through the plastic half-shells 2, 3 in FIG. 1. The plastic of the half-shell 3, which forms a groove 9, is provided for the joining process of the two half-shells 2, 3 through a laser 8 and is transparent to this laser 8. The other half-shell 2, on the other hand, is made of a material that absorbs the laser 8 used. To achieve the laser absorption, carbon black (indicated by hatching) is added to the plastic of this half shell 2. In a preferred embodiment, the laser beam welding method is used for connecting the two half-shells, wherein a diode laser 8 having, for example, a wavelength of 1064 nm is used to generate the laser beam. The laser beam passes through one laser-transparent half-shell 3 and the energy of the laser is absorbed by the second laser-absorbing half-shell 2 on its surface. The plastic melts there, so that a material bonding of the two half-shells 2, 3 forms the weld 20. The half-shell 3 also consists of a plastic material that is transparent to the human eye so that the weld 20 may be optically controlled.

[0035] FIG. 3 shows an alternative welding process. In this case, a diode laser 11 with a wavelength of 1400 nm to 2000 nm is used. By focusing the laser beam onto the desired melting zone 20, the macromolecules of the plastic may be directly excited without the need for absorbers. Again, the half-shell 3 is made of a plastic material transparent to the human eye. Within the scope of the invention, however, it is also generally possible to bond the two half-shells together by means of an adhesive.

[0036] FIGS. 4 and 5 respectively show an enlarged section of the joining connection of the two half-shells 2, 3. The geometry of the spring-and-groove connection is such that a clamping connection is already produced by the insertion of the spring 10 into the groove 9 of the half shells 2, 3 before the laser welding. For this purpose, the spring 10 is slight oversized with respect to the groove 9.