Electric Power Steering Motor-Gearbox Assembly for Compact Packaging
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Solution Overview
Problem
The existing electric power assisted steering systems face challenges in achieving a compact design due to limited space for housing the motor, drive circuit, control circuit, and gearbox, necessitating improved connections to reduce overall package size and enhance spatial flexibility.
Innovation Solution
A combined motor and gearbox assembly featuring a baseplate that secures the motor housing to the gearbox housing using tubular rivets and bolts, allowing for a more compact assembly by reducing the space required for fastening, with the baseplate supporting the motor drive circuit and facilitating a sequential assembly process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If traditional separate fastening methods are used to connect motor housing to gearbox housing, then assembly is simpler, but the overall package size increases and spatial flexibility is reduced
Solution Approach 1:
The patent combines the motor housing fastening to the gearbox housing with the baseplate structure. The baseplate serves dual purposes: supporting the electrical components (ECU and drive circuit) and providing the fastening interface to the gearbox housing. This merging of functions reduces the number of separate fastening components and reduces overall package size by eliminating redundant structural elements.
Solution Approach 2:
The baseplate is designed as a multi-functional component that simultaneously supports electrical components, provides structural connection between motor and gearbox housings, and serves as a mounting platform for the drive circuit. This multi-functionality reduces the overall number of components needed and minimizes package volume.
2Adaptability or versatility
If compact assembly is achieved by reducing fastening space, then packaging efficiency improves, but assembly and testing flexibility may be reduced
Solution Approach 1:
The patent segments the assembly process into distinct phases: first attaching electrical components to the baseplate, then fastening the baseplate to the gearbox housing. The baseplate itself is segmented with separate attachment points for electrical components and for mechanical fastening to the gearbox, allowing independent assembly of different subsystems before final integration.
Solution Approach 2:
The electrical components (ECU and drive circuit) are pre-assembled and tested on the baseplate before the baseplate is permanently fastened to the gearbox housing. This preliminary assembly allows for easier testing and potential rework without requiring disassembly of the entire steering system, maintaining manufacturing flexibility despite the compact final assembly.
Data Source
AI summary
A combined motor and gearbox assembly for an electric power steering system comprising an electric motor, a gearbox which includes a gearset that is connected on an input part to a rotor of the motor and in use is connected on an output part at least indirectly to a steering column shaft to transfer torque from the motor rotor to the steering column shaft, a motor drive circuit, a gearbox housing which in use accommodates the gearset of the gearbox, the electric motor including a motor housing, and a baseplate which connects an end face of the gearbox housing to an end face of the gearbox housing and which supports the drive circuit. At least one bolt having a stem passes through a central hole in a tubular rivet that secures the motor housing to the baseplate, the bolt securing the baseplate to the gearbox housing.