Epicyclic Step-Down Gear With Eccentric Axial Force Path
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Solution Overview
Problem
Conventional epicyclic reduction gears in electric parking brake actuators are prone to buckling due to mechanical forces applied during braking, leading to potential structural failures and increased mass and cost.
Innovation Solution
Incorporating a drive shaft with an internal sun gear and an external sun gear featuring an internal thread, along with axial force transmission pieces between a bearing ring and a cylinder, to redirect and recover axial forces, thereby reducing the diameter of the drive shaft and alleviating buckling risks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If the drive shaft diameter is reduced to decrease mass and cost, then weight and manufacturing cost are improved, but the shaft becomes more susceptible to buckling under mechanical forces during braking
Solution Approach 1:
The patent introduces axial force transmission pieces as intermediary elements between the bearing ring and the planet carrier/cylinder. These intermediaries redirect the axial forces away from the drive shaft, allowing the shaft to have reduced diameter without compromising buckling resistance. The force transmission pieces act as mediators that carry the compressive loads that would otherwise burden the drive shaft.
Solution Approach 2:
The invention extracts the axial force transmission function from the drive shaft by introducing separate axial force transmission pieces. This separation allows the drive shaft to be optimized for its primary rotational function with a smaller diameter, while the axial forces are handled by the dedicated transmission pieces positioned radially outward from the shaft.
2Device complexity
If axial forces are not recovered and transmitted away from the drive shaft, then the structure is simpler, but the drive shaft diameter must be increased to prevent buckling, increasing mass and cost
Solution Approach 1:
The axial force transmission pieces serve as intermediaries that simplify the overall structure by clearly separating force transmission paths. Rather than requiring a massively oversized drive shaft to handle all forces, the intermediaries create dedicated load paths that are more efficient and result in lower overall mass despite the additional components.
3Reliability
If axial force transmission pieces are introduced to redirect forces, then buckling resistance is improved, but device complexity increases
Solution Approach 1:
The axial force transmission pieces are designed to be integrated with existing components such as the planet carrier or cylinder. By merging the force transmission function with existing structural elements, the patent minimizes the increase in device complexity while achieving the desired buckling resistance improvement.
4Weight of moving object
If the drive shaft diameter is reduced, then mass and cost are decreased, but the strength and load-bearing capacity of the shaft are reduced
Solution Approach 1:
The invention extracts the axial load-bearing function from the drive shaft, allowing the shaft to be optimized for torsional and bending loads only. This functional separation enables a smaller diameter shaft that maintains adequate strength for its primary functions while axial forces are carried by the separate transmission pieces.
Solution Approach 2:
The axial force transmission pieces act as intermediaries that protect the drive shaft from excessive compressive loads. By intercepting and redirecting axial forces before they reach the shaft, these intermediaries preserve the shaft's load-bearing capacity within acceptable limits while allowing for mass reduction.
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 effectively reduces the mass and cost of the epicyclic reduction gear by minimizing the diameter of adjacent drive shaft parts, while preventing buckling and enhancing force transmission efficiency.
Implementation Method 1
this cylinder comprising an external thread cooperating with the internal thread of the external sun gear so that rotation of this cylinder about the longitudinal axis translationally drives the external sun gear along this longitudinal axis
Implementation Method 2
at least one axial force transmission piece interposed between this bearing ring and the cylinder so as to transmit axial forces exerted on one of the bearing ring and the cylinder to the other of this bearing ring and this cylinder
Implementation Method 3
a gear comprising one or more planet carriers and one or more planet gears carried by this or these planet carrier(s)
Data Source
AI summary
An epicyclic step-down gear for an electric parking brake, this step-down gear comprising a drive shaft, at least one step-down stage and a cylinder which forms a screw/nut system with an outer planet gear of this step-down gear. This step-down gear comprises at least one axial force transmission component which is positioned between a bearing ring of the drive shaft and the cylinder so as to transmit axial forces applied via either the bearing ring or the cylinder to either this bearing ring or this cylinder. Such an axial force transmission component prevents the drive shaft from buckling by defining an axial force transmission path which is radially eccentric.