Bicycle frame for an electric bicycle and motor carrier

Abstract

The invention relates to a bicycle frame (100) for an electric bicycle made of a thermoplastic material reinforced with tension-resistant fibres, which is designed as an injection-moulded bicycle frame (100), comprising multiple frame tubes (111, 112, 113) which are at least partially formed as continuous hollow profiles which are closed at least over a partial length and are largely smooth-walled on the inside, said hollow profiles being designed with a defined wall thickness and a defined profile cross-section, wherein at least some of the frame tubes (111, 112, 113) are connected to one another free from connecting means and with the same material, wherein the bicycle frame comprises at least one main frame (110) having at least one seat tube (111) and a down tube (113) and comprises a motor bearing housing (114) which integrally connects said seat tube and down tube, characterised in that the bicycle frame (100) further comprises a motor carrier (200) which is designed to receive and hold an electric motor or a transmission of an electric motor and which is permanently inserted into the motor bearing housing (114).

Description

[0001] PE-TK 04 December 2025

[0002] Applicant: igus SE & Co. KG, 51147 Cologne

[0003] Bicycle frame for an electric bicycle and motor carrier

[0004] The invention relates to a bicycle frame for an electric bicycle made of a thermoplastic material reinforced with tensile fibers, which is designed as an injection-molded bicycle frame. The invention relates in particular to a bicycle frame for an electric bicycle with a mid-drive motor.

[0005] Electric bicycles typically feature a drive housing or a bracket-shaped mount for the electric motor, located in the area of ​​the bicycle frame where the seat tube, down tube, and rear triangle are connected (and which, in non-motorized bicycles, serves as the bottom bracket shell). This "motor bracket" usually includes a recess adapted to the contour of the electric motor, to which the motor is bolted. This recess absorbs the reaction forces generated by the electric motor as well as those transmitted to the bicycle frame via the pedals.

[0006] From EP 3 294 616 Bl, a bicycle frame is known which has a mounting device fixed to the underside of the bicycle frame, a drive housing detachably connected to the mounting device for enclosing a gearbox and / or at least one electrical drive component, as well as a first and second mechanical interface. The two mechanical interfaces are designed differently, with a first mechanical interface on the mounting device and a second mechanical interface on the drive housing. The known bicycle frame includes at least one mechanical adapter for adapting the different mechanical interfaces in order to be able to attach different drive housings to one and the same bicycle frame.The bicycle frame known from EP 3 294 616 Bl is designed as a classic diamond frame, the construction principle of which was adopted from the construction of classic unpowered bicycle frames.

[0007] Modern e-bikes often feature lightweight frames, both as closed frames with a top tube and as step-through frames without a top tube. Fiber-reinforced plastics are increasingly used in frame construction. When designing such frames, a particularly favorable stiffness-to-weight ratio is crucial. It must be taken into account that, especially with sporty e-bikes, high torques are introduced into the frame, particularly in the area of ​​the motor mounting housing. As a result of weight optimization, carbon frames have become established, especially for sporty bicycles. These consist of woven or laid fibers made of high-tensile carbon fibers and a matrix material made of thermosetting plastic, usually epoxy resin.

[0008] It is also known in the art to manufacture bicycle parts, and in particular bicycle frames, from fiber-reinforced thermoplastic. Thermoplastics are easier to recycle than thermosets and can be molded, for example, by injection molding. However, the production of injection-molded frame components has the disadvantage that they must be geometrically designed to ensure demoldability from the injection mold. Furthermore, when designing injection-molded components, it is important that the wall thicknesses of certain areas of the components are designed so that sink marks are avoided as much as possible during the curing of the thermoplastic by cooling. Such sink marks occur particularly in areas of material accumulation and changes in thickness within the component.Such sink marks are caused by different cooling rates of the material in different areas. Sink marks lead, in particular, to externally visible surface defects of the article.

[0009] The bicycle frame, which is the subject of the present invention, is a bicycle frame injection-molded from thermoplastic plastic, the frame tubes of which are at least partially designed as hollow profiles made of thermoplastic plastic.

[0010] If the bicycle frame is designed to accommodate an electric drive component, be it a gearbox of an electric motor or an electric motor itself, the wall thickness of the material, particularly in the area where the electric motor and / or gearbox are mounted, must be dimensioned according to the expected reaction forces. This is especially true if, as provided for in the invention, no metal inserts are used.

[0011] The material is intended for use in this application. It should also be taken into account that thermoplastic materials tend to creep or flow under continuous mechanical stress, which necessitates appropriate material dimensioning in the area where an electrical drive component is mounted. For the reasons mentioned above, thick spots or material accumulations in the movement areas of a component made of injection-molded thermoplastic materials should be avoided as far as possible when designing a component.

[0012] The invention is therefore based on the objective of providing a bicycle frame of the type mentioned at the outset, which is designed, in particular, geometrically with a view to being manufactured predominantly in one piece by injection molding and which is designed, especially in the area of ​​mounting electrical drive components, to absorb correspondingly high reaction forces. In particular, the disadvantages described above in connection with thick spots in the material are to be avoided.

[0013] The problem is solved by providing a bicycle frame with the features of claim 1.

[0014] The problem is further solved by providing a motor mount designed for use with a bicycle frame according to the invention. Advantageous embodiments of the invention are set forth in the dependent claims.

[0015] According to a first aspect of the invention, a bicycle frame for an electric bicycle is provided, made of a thermoplastic material reinforced with tensile fibers, comprising several frame tubes, which are at least partially designed as continuous hollow profiles, wherein at least some of the frame tubes are connected to one another freely and with a single material connection, wherein the bicycle frame comprises at least one main frame with at least one seat tube and one down tube and a motor mounting housing that connects these in one piece. The bicycle frame according to the invention is characterized, among other things, by the fact that it further comprises a motor mount, which is designed to receive and hold at least one part of an electric drive component, in particular an electric motor or a gearbox of an electric motor, and which is permanently connected to the motor mounting housing, in particular inserted into the motor mounting housing.

[0016] The thermoplastic material of the bicycle frame according to the invention is preferably filled with short fibers made of a tensile-strength material. For the purposes of this application, short fibers are defined as fibers with a length greater than 0 mm and less than 50 mm, whereas long fibers are defined as tensile-strength fibers that can have a length greater than 50 mm up to an infinite length. The tensile-strength fibers can include carbon fibers, aramid fibers, glass fibers, or basalt fibers.

[0017] The bicycle frame according to the invention can be reinforced at least in certain areas with tensile-resistant long fibers, which are preferably oriented in the thermoplastic matrix material according to an expected static and / or dynamic load on the bicycle frame during its intended use.

[0018] In particular, the fact that the motor mount is inserted into the motor bearing housing as a separate component and is permanently attached to it creates a targeted reinforcement of the motor bearing housing, which makes the bicycle frame capable of absorbing the forces introduced into it by the electric motor or by drive components of the electric motor.

[0019] Preferably, the bicycle frame according to the invention is designed as an injection-molded bicycle frame, wherein at least some of the frame tubes are preferably designed as hollow profiles with a defined wall thickness and a defined profile cross-section that are closed at least over a partial length and have largely smooth walls on the inside.

[0020] The motor mount can be designed so that it extends at least partially into the hollow profile of the down tube, fits into it, and is at least partially enclosed by it. This interface between the motor mount and the down tube of the bicycle frame is particularly advantageous and practical with regard to a compartment provided in the down tube of the bicycle frame for housing a battery or accumulator to supply power to the electric motor.

[0021] The bicycle frame according to the invention is advantageously designed such that at least the motor bearing housing is formed using at least one movable slide of an injection mold and forms a communicating and, in particular, continuous profile chamber with the seat tube and the down tube. This ensures that the motor bearing housing has a uniform and defined wall thickness. The motor bearing housing can have a relatively thin wall. The motor mount is advantageously designed to fit into the motor bearing housing in such a way that thin-walled areas of the motor bearing housing are reinforced so that the reaction forces induced by the electric motor and the pedaling motion during the intended use of the bicycle are reliably absorbed.

[0022] A suitable method for manufacturing a bicycle frame of the type described above with the features described above comprises injection molding the bicycle frame as a one-piece molded part or one-piece article in a multi-part injection mold, wherein at least some of the frame tubes, preferably at least all frame tubes of the main frame, are formed as continuous hollow profile sections closed at least over a partial length, using a plurality of movable mold parts of the injection mold, in particular using a plurality of movable mold slides, each of which is movable from a demolding position to a functional position within an article cavity of the injection mold and from the functional position to the demolding position.

[0023] In the context of the invention, a functional position of a mold slide or other movable tool part refers to the position in which the thermoplastic material is injected into the closed part cavity. After the injection-molded part has been formed, the movable tool parts are moved to a position outside the part cavity to ensure the part can be demolded. This position is generally, and in the context of the invention, referred to as the demolding position. In the context of the present invention, a part cavity is defined as the cavity within the injection mold that forms the part, i.e., that is designed as a negative of the part. Consequently, gates, distributors, or the like are not part of the part cavity.A main frame of a bicycle according to the present invention is that part of the bicycle frame which comprises at least a seat tube, a bottom bracket shell or a motor bearing housing, a down tube, and a head tube. The main frame may further comprise a top tube which is connected to the head tube and the seat tube. According to one embodiment, the main frame of the bicycle frame according to the invention may include a top tube, whereas in another embodiment, the main frame may be designed without a top tube. A rear triangle is also an integral component of the bicycle frame according to the invention. A rear triangle within the meaning of the present invention refers to the seat stays and the chain stays of the bicycle frame. The term "chain stays" includes the corresponding structurally load-bearing elements of the bicycle frame, even in a bicycle which, for example, includes a belt drive.Generally, a fork is also considered a component of a bicycle frame; however, it is not the subject of the present application and is not manufactured in the same tool as the other components of the bicycle frame.

[0024] In principle, the engine mount can be made of metal or other materials. Preferably, the engine mount is made of a plastic, in particular a thermoplastic plastic.

[0025] As already explained above, the bicycle frame according to the invention is particularly characterized by the fact that it is designed without metal inserts, especially in the area of ​​the motor bearing housing. This ensures the recyclability of the bicycle frame.

[0026] The engine mount can be made up of multiple parts. It can be composed of several joined, preferably injection-molded, components. Particularly preferably, the engine mount is designed as a single, injection-molded component.

[0027] In one embodiment of the bicycle frame according to the invention, the motor mount may include at least one first and one second motor bearing, each designed to receive fastening elements for the electric motor, and the first motor bearing may have an outer contour that is complementary to the profile cross-section of the down tube, preferably to the inner cross-section of the down tube. In the simplest case, the motor bearings may be provided as through-holes for fastening elements, for example, in the form of threaded bolts for fixing the gearbox or the electric motor. In the area of ​​through-holes in the motor mount, the motor mount may, for example, be reinforced with tensile-resistant long fibers that may be oriented in the material of the motor mount to conform to the load.The motor mount itself may include metal inserts overmolded with thermoplastic material, such as nuts, threaded sleeves or the like.

[0028] One variant of the bicycle frame according to the invention is characterized in that the motor mount is welded or bonded to the motor bearing housing. Alternatively, the motor mount can be pressed or positively locked to the bicycle frame, preferably in such a way that it cannot be disassembled without damage.

[0029] The engine mount can, for example, be thermally welded to the engine mounting housing using an ultrasonic welding process, a mirror welding process, or a similar method, i.e., without the use of welding filler materials. It is advantageous if the engine mount is made of a thermoplastic material that is compatible with the thermoplastic material of the main frame in terms of weldability.

[0030] Alternatively, the engine mount may be glued to the engine mount housing, i.e., it may have been bonded to the engine mount housing using an adhesive.

[0031] Preferably, the motor mount is made of a thermoplastic material reinforced with tensile-strength fibers.

[0032] The thermoplastic material of the frame tubes and / or the engine mount can be selected from a group of thermoplastic materials including PA (polyamide), PP (polypropylene), PPA (polyphthalamide), PS (polystyrene), PE (polyethylene), ABS (acrylonitrile butadiene styrene), PC (polycarbonate), POM (polyoxymethylene), PEK (polyetherketone ketone), PEEK (polyetheretherketone), PA6 (polyamide 6), PA6.1 (polyamide 6.1), PA 12 (polyamide 12), HPPA (high-performance recycled polyamide), PARA (polyarylamide), PBT (polybutylene terephthalate), and PK (polyketones).

[0033] The bicycle frame according to the invention is particularly preferably made of a polyamide, and more preferably of a polyamide 6 (PA6) or a blend of PA66+PA6I / 6T as matrix material.

[0034] The tensile-strength fibers can be selected from a group of fibers comprising carbon fibers, glass fibers, aramid fibers, Kevlar fibers, and basalt fibers. A further aspect of the invention relates to a motor mount made of a thermoplastic material for use with a bicycle frame as described above, wherein the motor mount is characterized in that it is designed as a one-piece injection-molded component made of a fiber-reinforced plastic compatible with the bicycle frame in terms of weldability, wherein the motor mount comprises at least two motor bearings designed to receive fastening means for an electric motor, and wherein the motor mount has a contour conforming to the bicycle frame and an electric motor, which fits at least into the motor bearing housing.

[0035] The invention is explained below with reference to and based on an embodiment illustrated in the accompanying drawings.

[0036] They show:

[0037] Figure 1 shows a side view of the bicycle frame according to the invention,

[0038] Figure 2 shows a perspective view of the bicycle frame according to the invention with the motor carrier inserted into it.

[0039] Figure 3 is a perspective view of the bicycle frame shown in Figure 2 without the inserted motor mount.

[0040] Figure 4 shows a longitudinal section through the bicycle frame according to the invention,

[0041] Figure 5 is a top view of the bicycle frame shown in Figure 4, Figure 6 is a side view of the motor mount and

[0042] Figure 7 shows a perspective view of the engine mount.

[0043] The bicycle frame 100 according to the invention is designed as a bicycle frame for an electric bicycle in the form of a central tube frame or step-through frame. The frame shape is not critical for the invention. Those skilled in the art will recognize that the bicycle frame 100 according to the invention can, for example, also be designed as a classic diamond frame.

[0044] The bicycle frame 100 comprises a main frame 110 and a rear triangle 120, which are formed in one piece from a thermoplastic material.

[0045] The main frame 110 comprises a seat tube 111, a head tube 112, and a down tube 113. The seat tube 111 and the down tube 113 are connected to each other in one piece via a motor bearing housing 114 of the drive components of an electric motor (not shown).

[0046] The downtube 113 is designed to accommodate a battery or accumulator with a battery compartment 115. Battery and accumulator are used synonymously in connection with the present invention.

[0047] The battery compartment 115 includes an opening on the top side of the bicycle frame 100 which is returned to a user during normal use and which is closed by a cover or housing of the battery or accumulator.

[0048] The motor mount housing 114 is a single piece, or integrally connected to a lower part of the seat tube 111, the down tube 113, and the chainstays 121 of the rear triangle 120. The rear triangle 120 of the bicycle frame 100 also includes seat stays 122, which are designed as solid profiles injection-molded from thermoplastic and which may have integrated cable guides in the form of grooves on their underside facing away from the user of the bicycle frame 100.

[0049] The seat tube 111, the down tube 113, and the head tube 112 are each designed as continuous hollow profiles, with the down tube 113 comprising a fully enclosed profile cross-section with a first profile chamber 116 and a second profile chamber 117 extending parallel to it. The second profile chamber 117 forms the battery compartment 115.

[0050] The bicycle frame 100 according to the invention is manufactured almost entirely in one piece from an injection-molded thermoplastic material in a single injection mold using movable mold slides. The frame tubes of the main frame 110 are designed as continuous hollow profile sections, closed at least over a partial length, with a defined wall thickness and, due to the manufacturing process using movable mold slides, have smooth interior walls.

[0051] The bicycle frame 100 according to the invention further comprises a separately manufactured motor carrier 200, which is designed to receive and hold an electric motor or a gearbox of an electric motor and which is inseparably inserted into the motor bearing housing 114.

[0052] The motor mount 200 is shown in Figures 6 and 7. It is also manufactured as a one-piece, injection-molded component made of thermoplastic material. As can be seen particularly in Figure 1, the motor mount 200 is designed so that its contour fits into the motor bearing housing 114, such that the bicycle frame 100 has a smooth, closed, and essentially seamless outer contour in this area.

[0053] In the state inserted into the motor mount housing 114, as shown, for example, in Figure 2, the motor support 200 is intrinsically connected to the motor mount housing, i.e., welded or bonded to it on the inside. The motor support 200 has a substantially U-shaped contour with a first upper motor mount 201 and a second lower motor mount 202, which include mounting holes 203 for receiving fasteners in the form of threaded bolts or the like. The contour of the motor support 200 is designed such that it encloses an electric motor on its upper side, with the electric motor or a gear component of the electric motor being suspended in the motor mounts 201 and 202 via the fasteners.

[0054] The motor mount 200 is designed in the area of ​​the first upper motor bearing 201 such that it forms an upper extension 204 which is adapted to the inner cross-section of the down tube 113 and which fits into the inner cross-section of the down tube 113. The terms "top" and "bottom", as used in connection with this description, always refer to the intended installation position of the component in question and the intended use of the bicycle frame.

[0055] The extension 204 forms the lower end of the profile cross-section of the down tube 113 and is provided with feedthroughs for the power supply of the electric motor. The necessary supply cables are connected via a battery base with appropriately designed electrical contacts in the second profile chamber 117 of the down tube 113. The motor mount 200 is adapted in the area of ​​the second lower motor bearing 202 to the area of ​​the motor bearing housing 114 connected to the rear triangle 120 of the bicycle frame 100, such that it fits snugly into this part of the motor bearing housing 114, particularly advantageously in such a way that the second lower motor bearing 202 is inserted between the chainstays 121 of the rear triangle 120 in such a way that reaction forces introduced in this area by the electric motor and a pedal crank movement can also be absorbed by the rear triangle 120.

[0056] PE-TK 04 December 2025

[0057] Applicant: igus SE & Co. KG

[0058] 51147 Cologne

[0059] Reference symbol list

[0060] 100 bicycle frames

[0061] 110 main frames

[0062] 111 seat tube

[0063] 112 Head tube

[0064] 113 Down tube

[0065] 114 Engine mount housing

[0066] 115 Battery compartment

[0067] 116 first profile chamber of the down tube

[0068] 117 second profile chamber of the down tube

[0069] 120 rear triangle

[0070] 121 chainstays

[0071] 122 seat stays

[0072] 200 engine mounts

[0073] 201 upper engine mount

[0074] 202 lower engine mount

[0075] 203 Fastening bushings

[0076] 204 continuation

Claims

PE-TK December 4, 2025 Applicant: igus SE & Co. KG, 51147 Cologne Claims 1. Bicycle frame (100) for an electric bicycle made of a thermoplastic material reinforced with tensile fibers, comprising several frame tubes (111, 112, 113) which are at least partially designed as continuous hollow profiles closed at least over a partial length, wherein at least some of the frame tubes (111, 112, 113) are connected to one another without fasteners and with a single material, wherein the bicycle frame comprises at least one main frame (110) with at least one seat tube (111) and one down tube (113) and a motor bearing housing (114) which connects these in one piece, characterized in that the bicycle frame (100) further comprises a motor carrier (200) which is used for The mounting and support of an electric motor or a gearbox of an electric motor is designed and is inseparably inserted into the motor bearing housing (114).

2. Bicycle frame according to claim 1, characterized in that it is designed as an injection-molded bicycle frame (100) and that preferably at least some of the hollow profiles are designed as hollow profiles with largely smooth inner walls, a defined wall thickness and a defined profile cross-section.

3. Bicycle frame according to one of claims 1 or 2, characterized in that at least the motor bearing housing (114) is formed using at least one movable forming slide of an injection molding tool and forms a continuous profile chamber with the seat tube (111) and the down tube (113).

4. Bicycle frame according to one of claims 1 to 3, characterized in that the motor carrier (200) is made of a plastic, in particular a thermoplastic plastic.

5. Bicycle frame according to one of claims 1 to 4, characterized in that the motor carrier (200) is designed in multiple parts.

6. Bicycle frame according to one of claims 1 to 5, characterized in that the motor carrier (200) is formed in one piece, preferably as a one-piece injection-molded component.

7. Bicycle frame according to one of claims 1 to 6, characterized in that the motor carrier (200) comprises at least one first and one second motor bearing (201, 202), each designed to accommodate fastening means of the electric motor, and that the first motor bearing (201) has an outer contour designed to be complementary to the profile cross-section of the down tube (113), preferably to the inner cross-section of the down tube (113).

8. Bicycle frame according to one of claims 1 to 7, characterized in that the motor carriers (202) are welded or glued into the motor bearing housing (114) or 19 is locked in place or pressed into it in such a way that it cannot be removed from the motor bearing housing without damage.

9. Bicycle frame according to one of claims 1 to 8, characterized in that the motor carrier (200) is made of a thermoplastic material which is compatible with the thermoplastic material of the main frame (110) in the sense of weldability.

10. Bicycle frame according to one of claims 1 to 9, characterized in that the motor carrier (200) is made of a thermoplastic material reinforced with tensile fibers.

11. Bicycle frame according to one of claims 1 to 10, characterized in that the thermoplastic material of the frame tubes (111, 112, 113) and / or the motor mount is selected from a group of thermoplastic materials comprising PA (polyamide), PP (polypropylene), PPA (polyphthalamide), PS (polystyrene), PE (polyethylene), ABS (acrylonitrile butadiene styrene), PC (polycarbonate), POM (polyoxymethylene), PEK (polyetherketone ketone), PEEK (polyetheretherketone), PA6 (polyamide 6), PA6.1 (polyamide 6.1), PA 12 (polyamide 12), HPPA (high-performance recycled polyamide), PARA (polyarylamide), PBT (polybutylene terephthalate), and PK (polyketones).

12. Bicycle frame according to one of claims 1 to 11, characterized in that the tensile-strength fibers are selected from a group of fibers comprising carbon fibers, glass fibers, aramid fibers, Kevlar fibers and basalt fibers.

13. Motor carrier made of a thermoplastic material for use with a bicycle frame (100) according to at least one of claims 1 to 12, characterized in that the motor carrier (200) is designed as a preferably one-piece injection-molded component made of a fiber-reinforced plastic compatible with the bicycle frame (100) in the sense of weldability, that the motor carrier (200) comprises at least two motor bearings (202, 202) designed to receive fastening means for an electric motor, and that the motor carrier (200) has a contour conformable to the bicycle frame (100) and an electric motor.

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