Helical Differential Gear Layout for Compact Limited-Slip Torque
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Solution Overview
Problem
Existing vehicle differential devices face challenges in size reduction while maintaining differential limiting force and minimizing processing man-hours, as reducing size can lead to decreased frictional sliding diameters and increased load on pinion gears.
Innovation Solution
The proposed vehicle differential device incorporates first and second inner and outer helical gears, a housing, and pinion gear sets with specific tooth configurations and a friction member to distribute drive force efficiently, allowing for size reduction without compromising differential limiting force or increasing processing time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the size of the differential device is reduced, then the device dimensions are decreased, but the frictional sliding diameter between the side gears and washers is reduced, making it difficult to generate sufficient differential limiting force
Solution Approach 1:
The patent changes the geometric parameters of the side gears by introducing non-circular tooth profiles with variable radius of curvature. This allows the frictional sliding diameter to be optimized independently from the overall device size, enabling sufficient differential limiting force to be generated even in a compact differential device configuration
2Volume of moving object
If the size of the differential device is reduced, then the device dimensions are decreased, but the load on pinion gears increases, limiting the possibility of size reduction
Solution Approach 1:
The patent modifies the pinion gear parameters by introducing variable tooth profiles and optimized meshing angles. This redistributes the contact stress and reduces peak loads on pinion gears, enabling the use of smaller pinion gears without compromising strength, thus facilitating overall device size reduction
Solution Approach 2:
The patent transitions from conventional two-dimensional gear profiles to three-dimensional non-circular tooth surfaces with variable curvature. This dimensional enhancement allows for more efficient load distribution across the tooth contact area, reducing stress concentrations and enabling compact pinion gear design
3Ease of manufacture
If a gear support portion is formed in the housing to support the small diameter gear portion of the pinion gear, then the pinion gear can be supported, but the processing man-hours for the differential case increase
Solution Approach 1:
The patent merges the pinion gear support function into the existing housing structure by utilizing the outer peripheral surface of the side gears as support surfaces. This eliminates the need for separate gear support portions in the housing, reducing processing complexity and man-hours while maintaining proper pinion gear support
Solution Approach 2:
The side gears themselves serve as support structures for the pinion gears through their outer peripheral surfaces. This self-service approach eliminates the need for additional dedicated support features in the housing, simplifying manufacturing while ensuring proper pinion gear positioning and support
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 enables a compact differential device with enhanced differential limiting force and reduced processing complexity, maintaining performance on rough roads while allowing for smaller dimensions and reduced load on pinion gears.
Implementation Method 1
The right and left side gears and each of the pinion gears have helical teeth (twisted teeth). With the helical teeth of the right and left side gears and the helical teeth of each of the pinion gears meshing with each other, an axial thrust force is generated
Implementation Method 2
A frictional resistance force generated by the thrust force limits a differential rotation between the right and left side gears to suppress slipping of wheels of a vehicle, serving as a differential limiting force
Data Source
AI summary
A vehicle differential device includes a plurality of pinion gear sets. Each of the pinion gear sets includes a first pinion gear configured to mesh with a first outer helical gear and a plurality of second pinion gears configured to mesh with a second outer helical gear. The first pinion gear integrally includes an axially one end side gear portion configured to mesh with the first outer helical gear and an axially other end side gear portion configured to mesh with the second pinion gears. The second pinion gears are configured to mesh with the second outer helical gear at positions separated from each other in a circumferential direction of the second outer helical gear, and the axially other end side gear portion of the first pinion gear is configured to mesh with the second pinion gears at positions radially outward of the second outer helical gear.