Bottom Bracket Motor Retrofit with Claw Coupling
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Solution Overview
Problem
Existing electrical auxiliary drives for bicycles, such as wheel hub and bottom bracket motors, face challenges in simple manufacture and retrofitting, with complex cable routing and component replacement requirements for wheel hub motors, and limited torque support in conventional designs.
Innovation Solution
An electric bicycle drive with a stator connected to the bicycle frame and a rotor with permanent magnets attached to the bottom bracket, featuring a control device and sensor for torque detection, and a claw coupling with an elastic intermediate element for secure and flexible torque transmission, allowing for efficient motor output adjustment and muscle power augmentation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a wheel hub motor is used, then energy recovery through recuperation is possible, but complex cable routing and component replacement are required
Solution Approach 1:
The invention extracts the motor unit from the wheel hub location and relocates it to the bottom bracket area, separating the motor function from the wheel assembly. This extraction eliminates the need for complex cable routing through the wheel and frame, while preserving the bottom bracket's existing mechanical integration
Solution Approach 2:
The bottom bracket motor unit serves multiple functions: it provides propulsive torque to the crankset, integrates with the existing bottom bracket shell, and maintains compatibility with standard bicycle components. This multi-functionality reduces the need for separate cable routing systems while achieving auxiliary drive functionality
2Ease of manufacture
If a bottom bracket motor is used, then direct action on crank drive and easier retrofitting are achieved, but integration complexity remains
Solution Approach 1:
The invention merges the motor housing with the bottom bracket shell, combining two separate components into a unified assembly. The motor housing serves as both the motor enclosure and the bottom bracket housing, eliminating the need for separate mounting structures and reducing integration complexity
Solution Approach 2:
The rotor is nested within the stator, and the entire motor assembly is nested within the bottom bracket shell. The rotor housing is received by the stator housing, creating a compact nested structure that fits within the existing bottom bracket space without requiring additional external components
3Force
If the rotor is connected to the bottom bracket spindle, then direct torque transmission is achieved, but housing adjustment and complex connections are required
Solution Approach 1:
The rotor housing and pedal crank are merged into a single integrated component. The rotor housing forms the left pedal crank arm, eliminating the need for separate connection mechanisms between the rotor and crankset. This integration maintains direct torque transmission while simplifying the mechanical connection
4Stability of the object's composition
If the stator is secured against torsion, then motor stability is improved, but mounting complexity increases
Solution Approach 1:
The stator housing is merged with the bottom bracket shell, creating a unified structural component. The stator is secured against torsion through this integrated housing, which provides inherent structural support and stability without requiring additional separate mounting brackets or fastening mechanisms
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enables a robust, low-maintenance, and cost-effective retrofitting of conventional bicycles with improved torque support and efficiency, eliminating the need for complex cable routing and component replacement, while enhancing motor output and muscle power synergy.
Implementation Method 1
The permanent magnets are mounted on a rotatable rotor plate in the housing, which at the same time forms a magnetic return via the housing
Implementation Method 2
Together with the housing, the rotor lamination forms a self-contained auxiliary drive motor unit
Implementation Method 3
The claw coupling 10 has an elastic and play-free intermediate element 14, which ensures a torsionally elastic, angular and longitudinally flexible connection. The claw clutch 10 absorbs the torque of the stator housing 8
Implementation Method 4
The rotor housing is mounted on the stator housing by means of a grooved ball bearing
Data Source
Figure 1
AI summary
The invention relates to an electric auxiliary drive for bicycles which acts in a manner which assists muscular power or independently of pedalling in a manner which is dependent on a suitable parameter, for example the crank power which is exerted on the force transmission means. The invention is based on the object of improving electric auxiliary drives of this type with regard to simple manufacture and retrofitting capability. On the left-hand side in the riding direction, an electric motor is arranged with a stator which is connected to a bicycle frame (3) and a rotor which is connected to a rotatable part of a bicycle pedal bearing (1), wherein the rotor has one or more permanent magnets (5), and a regulating device (15) for setting the power output of the electric motor is provided with a control circuit arrangement (15) and an actual value sensor which is connected to the control circuit arrangement for detecting the torque which acts on the rotatable part of the pedal bearing (1). The rotor is arranged in a co-rotating housing (2) which is connected to a pedal crank (11) and is arranged in a positively locking manner on a pedal bearing shaft. The stator is arranged in a housing which is connected to the bicycle frame (3), is secured against rotation, and has an elastic sealing ring (9) against the co-rotating housing (2). The control circuit arrangement (15) is arranged in the interior of the stator housing (8). The stator housing (8) is connected to the bicycle frame (3) by means of a claw coupling (10) which is screwed to a pedal bearing housing and has an elastic and play-free intermediate element.