DE102014107851A1 - Process for the production of pedelec frames made of plastic and pedelec frame produced accordingly - Google Patents

Abstract

The invention relates to a method for producing a Pedelec frame (1) made of plastic, which is produced by joining two corresponding plastic half-shells (2, 3), wherein the Pedelec frame (1) recordings (12, 13, 14) for a handlebar (4), a bottom bracket (5) and preferably for a driver's saddle (6), and wherein the two plastic half-shells (2, 3) peripherally, preferably circumferentially, by means of laser radiation cohesively with each other to Pedelec frame (1) be welded and in this case form at least one inner cavity (7), which preferably serves to receive at least one Pedelec component. The invention also relates to a correspondingly produced pedelec frame.

Description

The present invention relates to a method for the production of a Pedelec frame, are joined together in the two plastic half-shells and materially connected to each other. Pedelecs differ from a normal bicycle with an additional electric motor, a battery element for motor drive and usually by a control electronics for the engine. In practice pedelec frames are often made manually.

Usually, bicycle frames are made of steel tubes that are brazed or welded together. In addition to steel, other materials such as aluminum, titanium and fiber-reinforced plastics have been increasingly used for some time to reduce the weight of the frame. These are then welded or glued to obtain the desired frame geometry. The joining process is very time consuming and labor intensive.

In Pedelecs is the peculiarity that these - as mentioned above - must be additionally equipped with an electric motor and at least one battery element. The electric motor can be switched on to assist the pedal drive by the driver. Furthermore, pedelecs often include control electronics that measure the applied force or speed, and when the engine reaches certain levels it operates or shuts down the engine. The additional elements of a pedelec have the consequence that the frame tubes must be made with a comparatively large diameter in order to accommodate the supply elements therein. Partly, these elements are also attached to the outside of the frame, which is aesthetically not very appealing.

There have already been some approaches to making bicycle frames from two half-shells. Such a framework is for example in the DE 10 2011 053 100 A1 disclosed. The half-shells are joined together in one step and bonded together by gluing or welding. The disadvantage here, however, that the adhesive bond or the weld after the joining process is difficult to control and can not be corrected. Furthermore, the joining process is very time-consuming, even in this construction, since it requires very precise work and must then cure the adhesive bond. To connect two half shells, it is from the US 5,913,529 known to provide a groove-shaped intermediate element between the joining edges. So the frame halves can be assembled accurately. However, here too, the joining process must be carried out very carefully, since the adhesive is applied with the joining and thus a correction is later no longer possible even with this method.

It is also known to partially weld traditional bicycle frames made of metal by means of a laser beam. This shows, for example, the DE 1 98 248 33 A1 , Due to new developments in the field of electric bicycles, the needs and requirements for a bicycle have changed. Metal is only very conditionally suitable for pedelec frames. Due to the additional supply elements, it is more advantageous to choose a lightweight frame construction to minimize the overall weight of the frame.

The present invention has for its object to provide a method for producing a Pedelec frame made of plastic, which is feasible and easy to control with little expenditure of time, so that a high production level can be achieved in a cost effective manner.

• – wobei dieser durch Zusammenfügen zweier entsprechender Kunststoff-Halbschalen hergestellt wird,
• – wobei der Pedelec-Rahmen Aufnahmen für einen Lenker, für ein Tretlager und vorzugsweise für einen Fahrersattel aufweist, und
• – wobei die beiden Kunststoff-Halbschalen randseitig, vorzugsweise umlaufend, mittels Laserstrahlung stoffschlüssig miteinander zum Pedelec-Rahmen verschweißt werden und hierbei mindestens einen inneren Hohlraum bilden, der vorzugsweise zur Aufnahme mindestens einer Pedelec-Komponente dient.

The object is achieved by a method for producing a pedelec frame made of plastic,

• - Wherein this is made by joining two corresponding plastic half-shells,
• - The pedelec frame has receptacles for a handlebar, for a bottom bracket and preferably for a driver's saddle, and
• - Wherein the two plastic half-shells edge, preferably circumferentially, by means of laser radiation materially welded together to Pedelec frame and in this case form at least one inner cavity, which preferably serves to receive at least one Pedelec component.

The pedelec component received from the cavity may e.g. an energy storage, preferably a battery and / or an electric motor of the pedelec. Conveniently, in each case a defined positioning is created by the joining of the plastic half shells for the energy storage and / or the electric motor and / or the bottom bracket in the inner cavity. In addition to the shots for handlebars, bottom bracket and possibly the driver's saddle, the pedelec frame can have an integrated rear shroud for mounting the rear wheel in the shells. Alternatively, it is also possible that a separate rear triangle is attached to the storage of the rear wheel on the pedelec frame. This rear triangle can be provided with a suspension.

The half shells are preferably substantially mirror-inverted. By joining together creates an inner cavity between the half-shells, in which at least the essential components of a pedelec can be accommodated. The inner sides of the half shells advantageously contain positioning elements for the energy store, preferably a battery, and / or for the electric motor and / or for the bottom bracket. These positioning elements are expediently integrally formed on one of the two or in one piece on both half-shells. In the receptacles of the Pedelec frame corresponding receptacles for the handlebar, the bottom bracket or the driver's saddle may be provided to each create a seamless, stable recording device. The method according to the invention has the advantage that, due to the automatable laser welding, it enables cost-effective production of high-quality pedelec frames at high quantities. Furthermore, it is less time consuming than known adhesive methods, since no curing of the adhesive is required.

The laser welding method according to the invention can therefore also be automated very well, because only two components in the form of the two half-shells must be connected to one another. This feature is of particular importance in the manufacture of pedelec frames to keep manufacturing costs low. The automation also eliminates a turning process that must be performed when welding tubular parts.

The half shells are preferably made of a fiber-reinforced thermoplastic, which may in particular contain a partially aromatic polyamide. This material group is particularly suitable for the frame construction because of its high rigidity, low water absorption and high thermal resistance. Surprisingly, this group of materials is also very well suited for laser welding. The partially aromatic polyamide may contain aliphatic dicarbonyl repeating units and diamino aromatic repeating units, or alternatively aromatic dicarbonyl repeating units and aliphatic diamino repeating units. In the context of the invention is also a mixture of the aforementioned substances. In particular, the partially aromatic polyamide may contain meta-xylylenediamine repeating units and 1,6-hexanedionyl repeating units. In the context of the invention, it is the case that the thermoplastic material also contains an aliphatic polyamide in addition to the partly aromatic polyamide. The proportion by weight of the partially aromatic polyamide based on the total plastic composition without fiber reinforcement is at least 50%, preferably at least 70%.

The thermoplastic used is selected so that it is suitable for the production of injection molded parts. Injection molding is also the preferred method step for producing the two half-shells. It allows an extremely high variety of forms and is particularly suitable for the above-described positioning elements for positioning of electric motor and energy storage on a corresponding shape design of the injection molding tools in the simplest way to form the half-shell / n. The proportion by weight of the fibers in the fiber-reinforced thermoplastic material is expediently 15 to 70%, preferably 40 to 60%. Surprisingly, this highly filled and therefore highly resilient plastic is very well suited for laser welding. Alternatively, for somewhat lower requirements, the weight fraction may be 20 to 40%. With a weight fraction of the fibers below 15%, the marterial would have a too low strength. On the other hand, if the weight was more than 70%, the material would have a reduced formability. In addition, plastics with such a large fiber volume are too rigid and brittle for use in a pedelec frame.

To increase the strength of the plastic, it expediently contains glass and / or carbon and / or aramid fibers, preferably only glass fibers. These are more cost-effective compared to carbon and aramid fibers and still have a very good reinforcing effect at the same time very high thermal and chemical stability. Conveniently, the average length of the fibers in the final fabricated component, the pedelec frame, is less than 15 mm (e.g., using a long fiber compound), preferably less than 10 mm, more preferably less than 5 mm. In particular, short fibers having an average length of less than 3 mm, e.g. less than 2 mm or less than 1 mm, which can be easily processed in the plastic matrix finely distributed by injection molding. In addition, short fibers are much cheaper than long fibers.

Conveniently, the joining edge of a half-shell has a groove and the joining edge of the other half-shell on a engaging in the groove spring. Tongue and groove are preferably dimensioned so that even when they are joined before the laser welding process, a clamping connection is formed. For this purpose, either the spring has a slight oversize or the groove has a slight undersize. As a result, the two half-shells are first prefixed against each other before the welding process. This allows a check of the correct assembly of the half-shells before the irreversible welding process. If necessary, the tongue and groove connection can be solved again before the welding process. In particular, it is possible in this way, the correct positioning of the electric motor and energy storage in the of the two Half shell formed cavity to check before the welding process is performed.

According to one embodiment of the invention, a laser transmission welding process is used. In this case, one of the joining partners, which is laser-transparent, radiates and absorbs the energy from the second laser-absorbing joining partner on its surface. At this surface of the plastic melts, so that in this way the two joining partners can be firmly bonded together. For this purpose, it is necessary that one of the half-shells has a high degree of transmittance in the region of the laser wavelength, while the other half-shell has a high degree of absorption at this wavelength. The laser absorption can be achieved, for example, by adding laser pigments, preferably carbon black, to the plastic of the half shell. Conveniently, the half-shell whose joining edge forms the groove, laser-transparent and the half-shell whose joining edge forms a spring, laser absorbing. The laser employed may be a diode laser with a wavelength of 500 to 1100 nm, e.g. a solid-state diode laser with a wavelength of 1064 nm or a diode laser with a wavelength of 980 nm.

In a further preferred embodiment, a diode laser with a wavelength of 1300 nm to 2200 nm, preferably from 1400 nm to 2000 nm is used. In the range of these wavelengths, the macromolecules of the plastic can be excited directly by the laser radiation and this reaches the necessary welding temperature. Pigmentation of the plastic is therefore no longer necessary at these wavelengths. Preferably, the laser has a diode emitter with thulium and / or erbium. The fusion zone is determined in this welding process by focusing the laser beam to the desired area.

Regardless of the laser method used, at least one of the two half-shells can be produced from a plastic which is transparent to the human eye, so that optical control of the weld is possible after the welding process. Preferably, this is the groove-forming half-shell.

In order to make the pedelec frame aesthetically pleasing, an opaque finish of the pedelec frame together joined half shells is usually performed. This also eliminates the possibly different optics of the two half-shells, which can result, in particular in the case of the laser transmission method, from the above-described different pigmentation of the two half-shells.

The invention also relates to a pedelec frame produced by one of the above methods.

Brief description of the drawings

In the following, only exemplary embodiments of the invention will be explained in more detail with reference to a drawing. They show schematically:

1 a pedelec frame produced according to the invention in a three-dimensional representation;

2 the cross section AA in 1 during the joining process;

3 a further embodiment of the invention in one of 2 corresponding representation;

4 an enlarged section of the 2 in three-dimensional representation and

5 an enlarged section of the 3 in three-dimensional representation.

1 shows a pedelec frame according to the invention 1 , wherein this by the assembly of two corresponding plastic half shells 2 . 3 will be produced. The pedelec frame 1 has a recording 12 for a handlebar 4 , a recording 13 for a bottom bracket 5 and a recording 14 for a driver's saddle 6 on. handlebars 4 , Bottom bracket 5 and driver's saddle 6 are in the 1 merely hinted. On the pedelec frame is a dotted rear triangle 60 attached, which serves to receive the (not shown) rear of the pedelec and can be provided with a suspension not shown. When joining the two plastic half shells 2 . 3 at the edge forming a pedelec frame 1 circumferential weld 20 (Sat. 2 to 5 ) by means of laser radiation cohesively with each other to pedelec frame 1 welded. As a result, the plastic half shells together form an inner cavity 7 who has a battery 30 , an electric motor 40 and also the bottom bracket 5 of the pedelec. By assembling the plastic half shells 2 . 3 will also be battery 30 , Electric motor 40 and the bottom bracket 5 in the inner cavity 7 each positioned at a defined location. The plastic half shells produced by means of an injection molding process 2 . 3 have this integrally molded positioning elements 50 on, the electric motor 40 , Battery 30 and bottom bracket 5 each in the desired position.

The half-shells 2 . 3 are each made of a fiber-reinforced thermoplastic produced, wherein a partially aromatic polyamide was used as the plastic material. The fiber reinforcement consists of finely divided in the plastic matrix of this polyamide pure glass fibers with an average fiber length of about 3 mm in the finished component. The weight fraction of the fibers in the fiber-reinforced thermoplastic material in the exemplary embodiment is 50%. After the welding process, the half-shells welded together to the pedelec frame become 2 . 3 opaque lacquered.

The 2 to 5 it can be seen that the joining edge of a half-shell 3 in the form of a groove 9 is designed while the joining edge of the other half-shell 2 is designed so that he has a spring 10 forms. When assembling the half shells 2 . 3 become the front ends 70 the two joining countries brought into contact with each other (s. 4 . 5 ).

In the 2 shown cross-sectional view shows the section AA in 1 through the plastic half shells 2 . 3 , which peripherally and circumferentially by means of laser radiation 8th were cohesively welded together. The plastic of the half shell 3 which forms a groove 9 , is for the used laser 8th transparent. The other half shell 2 is, on the other hand, made of a material suitable for the laser used 8th is absorbent. To achieve the laser absorption, the plastic of this half-shell was 2 Carbon black (indicated by hatching) added. For connecting the two half shells 2 . 3 according to 2 the laser transmission welding method is used, wherein for generating the laser radiation, a diode laser 8th , eg with a wavelength of 1064 nm, is used. The laser beam radiates through the laser-transparent half-shell 3 and the energy of the laser is from the second laser-absorbing half-shell 2 absorbed on the surface. There, the plastic melts, so that there to form the weld 20 a cohesive connection of the two half-shells 2 . 3 arises. The half shell 3 also consists of a transparent to the human eye plastic material, so that the weld 20 can be optically controlled.

3 shows an alternative welding process. For connecting the two half shells 2 . 3 here is a diode laser 11 used with a wavelength of 1400 nm to 2000 nm. The macromolecules of the plastic can be excited directly at this wavelength by the laser beam is focused accordingly. The desired melting zone 20 arises by a corresponding focusing of the laser beam on the joint seam between the two half-shells 2 . 3 , Again, the half shell 3 made of a transparent to the human eye plastic material.

4 and 5 each show an enlarged section of the joint connection of the two half-shells 2 . 3 , The geometry of the tongue and groove connection is such that already by the insertion of the spring 10 in the groove 9 a clamping connection is formed, which the two half-shells 2 . 3 prefixed against each other before the laser welding. This has the spring 10 opposite the groove 9 a slight excess.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102011053100 A1 [0004]
• US 5913529 [0004]
• DE 19824833 A1 [0005]

Claims (16)

Method for producing a pedelec frame ( 1 ) made of plastic, - this by joining two corresponding plastic shells ( 2 . 3 ), the pedelec frame ( 1 ) Recordings ( 12 . 13 . 14 ) for a handlebar ( 4 ), a bottom bracket ( 5 ) and preferably for a driver's seat ( 6 ), and - wherein the two plastic half-shells ( 2 . 3 ) on the edge side, preferably encircling, by means of laser radiation with a material fit to each other to the pedelec frame ( 1 ) and in this case at least one inner cavity ( 7 ), which is preferably for receiving at least one pedelec component ( 30 . 40 ) serves. Method according to one of the preceding claims, wherein the half shells ( 2 . 3 ) are made of a fiber-reinforced thermoplastic.  The method of claim 2, wherein the weight fraction of the fibers in the fiber-reinforced thermoplastic material is 15 to 70%, preferably 40 to 60%.  The method of claim 2 or 3, wherein the thermoplastic material contains a partially aromatic polyamide.  Method according to one of claims 2 to 4, wherein for fiber reinforcement glass and / or carbon and / or aramid fibers are used. Method according to one of claims 2 to 5, wherein the average length of the fibers in the finished manufactured pedelec frame ( 1 ) is less than 15 mm, preferably less than 10 mm, in particular less than 5 mm. Method according to one of the preceding claims, wherein the geometry of the half shells ( 2 . 3 ) at their joining edges is such that the joining edge of a half-shell ( 3 ) a groove ( 9 ) and the joining edge of the other half shell ( 2 ) one when joining in the groove ( 9 ) engaging spring ( 10 ) having. Method according to one of the preceding claims, wherein the geometry of the tongue and groove connection is dimensioned so that already by the insertion of the spring ( 10 ) into the groove ( 9 ) creates a clamping connection, which the two half-shells ( 2 . 3 ) prefixed against each other for the laser welding. Method according to one of the preceding claims, wherein the one half-shell ( 2 ) made of a laser-absorbent plastic and the other half-shell ( 3 ) is made of a laser-transparent plastic. Method according to claim 9, wherein the half-shell ( 3 ) whose joining edge is the groove ( 9 ), from the laser-transparent plastic and the half-shell ( 2 ) whose joining edge is the spring ( 10 ), is made of the laser-absorbent plastic. A method according to claim 9 or 10, wherein the plastic of the laser-absorbing half-shell ( 2 ) Laser pigments, preferably carbon black, is added.  Method according to one of the preceding claims, wherein for generating the laser radiation, a diode laser having a wavelength of 500 nm to 1100 nm, in particular a solid-state diode laser having a wavelength of 980 nm, is used. Method according to one of claims 1 to 11, wherein for generating the laser radiation, a diode laser having a wavelength of 1300 nm to 2200 nm, preferably from 1400 nm to 2000 nm, used and in this case the laser radiation to the joint seam between the two half shells ( 2 . 3 ) is focused. Method according to one of the preceding claims, wherein at least one of the two half-shells ( 3 ) is made of a transparent plastic to the human eye, so that after welding a visual inspection of the weld is possible. Method according to one of the preceding claims, wherein the pedelec frame ( 1 ) welded together half-shells ( 2 . 3 ) are painted opaque. Pedelec frame ( 1 ) prepared by a method according to any one of the preceding claims.

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