Worm Shaft Dog Drive Assembly for Lighter Steering Gearboxes
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Solution Overview
Problem
The manufacture of wormshafts for gearbox assemblies in electric power steering systems is wasteful and expensive due to the large radius of the ring-shaped carrier used in prior art designs, leading to material inefficiency and increased weight.
Innovation Solution
A gearbox assembly design featuring an elongate shaft with a separate dog drive mechanism secured by a bearing assembly, where the dog drive mechanism includes radially offset teeth and a biasing mechanism to prevent axial movement, allowing for efficient torque transfer without the need for a large, heavy ring-shaped carrier.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a ring-shaped carrier with large radius is used to mount dog teeth on the worm shaft, then the dog teeth can effectively engage with the motor drive mechanism, but the shaft becomes heavier and more expensive to manufacture due to material waste
Solution Approach 1:
The invention divides the worm shaft into two separate components: a slender elongate shaft and a dog drive mechanism. The dog drive mechanism is secured to the end of the shaft by a bearing assembly, allowing the shaft itself to remain lightweight while the engagement function is provided by the separate dog drive mechanism. This segmentation resolves the contradiction by eliminating the need for a heavy ring-shaped carrier on the shaft.
Solution Approach 2:
The invention extracts the dog teeth and their mounting structure from the shaft body, creating a separate dog drive mechanism that is secured to the shaft end. This extraction allows the shaft to be optimized for minimal weight (slender elongate form) while the dog drive mechanism provides the necessary engagement capability without adding excessive weight to the rotating shaft assembly.
2Reliability
If a ring-shaped carrier with large radius is used to mount dog teeth on the worm shaft, then the dog teeth can effectively engage with the motor drive mechanism, but the manufacturing process becomes more wasteful and expensive
Solution Approach 1:
By segmenting the worm shaft into a slender shaft and a separate dog drive mechanism, the invention eliminates the need to manufacture a heavy ring-shaped carrier from solid material. The slender shaft uses minimal material, and the dog drive mechanism is a separate component that can be manufactured more efficiently, significantly reducing material waste and manufacturing cost.
Solution Approach 2:
The extraction of the dog teeth mounting function from the shaft body allows the shaft to be manufactured as a simple slender elongate component with minimal material usage. The dog drive mechanism is produced separately and secured to the shaft end, avoiding the material waste inherent in creating a large-radius ring-shaped carrier from solid material.
3Ease of manufacture
If a separate dog drive mechanism is secured to the elongate shaft by a bearing assembly, then material waste is reduced and production costs decrease, but the device complexity increases
Solution Approach 1:
While segmentation into separate components (shaft and dog drive mechanism) improves manufacturing efficiency by allowing each part to be optimized and produced independently, it does increase assembly complexity. The bearing assembly serves as the connecting element that secures the dog drive mechanism to the shaft end, managing the complexity through standardized bearing components rather than custom complex joints.
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
This design reduces material waste and production costs while maintaining efficient torque transfer, making the gearbox assembly lighter and more cost-effective.
Implementation Method 1
a separate dog drive mechanism secured to one end of the elongate shaft by a bearing assembly such that in use torque is transferred between the elongate shaft and the dog drive mechanism
Data Source
AI summary
A gearbox assembly includes a housing, a first shaft assembly having a worm gear and supported relative to the housing by a first bearing assembly, and a second shaft assembly including a wheel gear which is also supported relative to the housing by a second bearing assembly, the wheel gear engaging with the worm of the worm gear to permit the transfer of torque between the two shaft assemblies, wherein the first shaft assembly includes an elongate shaft carrying the worm gear, and a separate dog drive mechanism secured to one end of the elongate shaft by the first bearing such that in use torque is transferred between the elongate shaft and the dog drive mechanism.