Differential Gear Axial Downsizing via Nested Yoke and Clutch
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Solution Overview
Problem
Current differential gear designs face challenges in achieving further downsizing, particularly in the axial direction, due to constraints from in-vehicle device layouts such as engines and accessories.
Innovation Solution
A differential gear design featuring a cylindrical electromagnetic coil, a yoke serving as a magnetic path, and a clutch member with an outer diameter smaller than the yoke's inner diameter, allowing for axial downsizing by utilizing a pressing mechanism that restricts differential action between the differential case and the side gears through magnetic force application.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the moving member is placed inside the electromagnet to achieve downsizing, then the axial dimension is reduced, but the radial space requirement increases
Solution Approach 1:
The patent transitions from a conventional axial arrangement where the moving member is placed inside the electromagnet to a radial arrangement where the clutch member is positioned within the yoke's inner diameter. This dimensional reconfiguration allows the magnetic circuit components to be arranged radially rather than axially, achieving axial downsizing while containing the radial footprint within the yoke structure.
Solution Approach 2:
The clutch member is nested within the yoke's inner diameter space, and the electromagnetic coil is positioned such that its magnetic flux passes through the yoke and clutch member. This nesting arrangement allows multiple functional components to occupy overlapping spatial zones, effectively reducing the overall axial dimension while maintaining all necessary functional clearances.
2Length of moving object
If the clutch member outer diameter is made smaller than the yoke inner diameter, then axial compactness is achieved, but the torque transmission capacity may be reduced
Solution Approach 1:
The clutch member is designed with locally optimized features including splines on its outer peripheral surface that engage with corresponding splines in the differential case. This localized engagement structure concentrates the torque transmission capability at specific contact points rather than requiring uniform distribution across the entire clutch member diameter, enabling reduced overall diameter while maintaining adequate torque capacity.
Solution Approach 2:
The clutch member is constructed as a composite structure integrating magnetic material properties for interaction with the electromagnetic field and mechanical engagement features for torque transmission. This composite design allows the same component to fulfill both magnetic actuation and mechanical power transmission functions, optimizing the balance between compactness and torque capacity.
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 configuration achieves significant axial downsizing while maintaining effective torque transmission and differential action, enhancing the gear's compactness without compromising performance.
Implementation Method 1
an electromagnetic coil having a cylindrical shape and configured to move the clutch member in the direction of the rotation axis by a magnetic force generated by current application
Implementation Method 2
a yoke having an annular shape and serving as a magnetic path of a magnetic flux of the electromagnetic coil
Data Source
AI summary
A differential gear includes: a first output gear; a second output gear; a differential case; a clutch member configured to move in a direction of a rotation axis between a connecting position where the differential case is connected to the first output gear in a relatively non-rotatable manner and a non-connecting position where the differential case and the first side gear are allowed to rotate relative to each other; an electromagnetic coil having a cylindrical shape and configured to move the clutch member in the direction of the rotation axis; and a yoke having an annular shape and serving as a magnetic path of a magnetic flux of the electromagnetic coil. The clutch member has an outermost diameter smaller than an inside diameter of the yoke.