Ball Spline Constant Velocity Joint for Lighter Driveshaft Packaging
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Solution Overview
Problem
Existing constant velocity joints with ball spline structures face challenges such as increased diameter, weight, and higher production costs, while premium tripod joints offer limited solutions for vehicles with high height and are prone to lateral shaking due to resonance.
Innovation Solution
A constant velocity joint design incorporating a ball spline coupling structure that reduces the interconnecting shaft's diameter and weight, allowing for axial displacement functionality through a ball spline coupling between the inner race and the interconnecting shaft, with a simplified manufacturing process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a ball spline structure is applied to the interconnecting shaft to enable axial displacement, then axial displacement capability is improved, but the diameter and weight of the shaft increase significantly
Solution Approach 1:
The invention divides the axial displacement function from the torque transmission function. The ball spline structure is applied only to the inboard joint where axial displacement is needed, while the outboard joint uses a conventional Rzeppa structure for torque transmission. This segmentation allows axial displacement capability without requiring the entire shaft to have the complex ball spline structure, thereby reducing overall weight.
Solution Approach 2:
The ball spline structure is nested within the constant velocity joint assembly rather than being implemented as a separate shaft component. The inner race of the ball spline is positioned within the joint housing, and the spline balls are contained within the joint structure. This nesting eliminates the need for a separate heavy-duty shaft with integrated ball spline, reducing the overall weight of the moving components.
2Adaptability or versatility
If a ball spline structure is applied to the interconnecting shaft to enable axial displacement, then axial displacement capability is improved, but the diameter of the shaft increases
Solution Approach 1:
The invention segments the ball spline structure to be localized at the inboard joint only, rather than running along the entire length of the interconnecting shaft. This localized approach reduces the diameter increase to only the joint region, minimizing the overall impact on shaft dimensions and allowing the majority of the shaft to maintain a smaller, more space-efficient diameter.
Solution Approach 2:
The invention utilizes the radial dimension within the joint housing to accommodate the ball spline components. The inner race, outer race, and spline balls are arranged in a compact radial configuration within the joint assembly, rather than requiring increased axial length of the shaft. This dimensional arrangement allows axial displacement functionality without significantly increasing the shaft's overall diameter.
3Object-generated harmful factors
If a premium tripod constant velocity joint is used to minimize generated axial force, then NVH performance is improved, but the structure becomes more complex and cost increases
Solution Approach 1:
The invention merges the axial displacement function with the constant velocity joint structure by integrating the ball spline mechanism within the joint assembly. This combination eliminates the need for separate premium tripod joint designs that attempt to minimize axial force through complex geometries. The integrated ball spline provides axial displacement while the Rzeppa-style ball tracks handle torque transmission, achieving NVH improvement through functional integration rather than structural complexity.
Solution Approach 2:
The invention introduces the ball spline structure as an intermediary mechanism between the driveshaft and the constant velocity joint. This intermediary component specifically addresses the generated axial force issue by providing controlled axial displacement, isolating the axial force effects from the main joint structure. This approach reduces NVH problems without requiring complex modifications to the entire joint design.
4Adaptability or versatility
If a ball spline structure is applied to the interconnecting shaft, then axial displacement capability is improved, but the manufacturing process becomes more complex and production costs increase
Solution Approach 1:
The invention segments the manufacturing complexity by producing the ball spline components (inner race, outer race, spline balls, and cage) as separate, standardized parts that can be manufactured using conventional precision machining processes. These modular components are then assembled into the constant velocity joint, allowing for specialized manufacturing of small batches without requiring complex integrated shaft production. This segmentation significantly reduces manufacturing process complexity compared to producing a custom ball spline-integrated shaft.
Solution Approach 2:
The ball spline components (races, balls, and cage) are designed as universal elements that can be manufactured using standard precision machining and assembly processes similar to conventional constant velocity joint components. The modular design allows these components to be produced in small batches using existing manufacturing capabilities, eliminating the need for specialized, high-cost manufacturing processes required for integrated ball spline shafts.
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 design achieves reduced diameter and weight, lowers production costs, enhances vehicle design flexibility, and improves NVH performance by minimizing generated axial force and friction, while maintaining angular articulation functionality.
Implementation Method 1
The inner race is coupled to the interconnecting shaft via a ball spline coupling structure to implement a length displacement function through relative axial displacement along an axial direction of the interconnecting shaft
Implementation Method 2
a plurality of torque transmitting balls respectively disposed in spaces formed by the pairs of the outer and inner ball tracks in a state of being respectively housed in the windows
Data Source
AI summary
A constant velocity joint includes: an outer race forming a plurality of outer ball tracks; an inner race forming a plurality of inner ball tracks; a ball cage interposed between the outer race and the inner race; and a plurality of torque transmitting balls. The inner race is coupled to the interconnecting shaft via a ball spline coupling structure to implement a length displacement function through relative axial displacement along an axial direction of the interconnecting shaft. The ball spline coupling structure includes: an outer spline groove; an inner spline groove; a sleeve member interposed between the inner race and the interconnecting shaft; and a plurality of spline balls. The outer race comprises an inner circumferential surface having a shape of a spherical surface with a first diameter, and a diagonal length of the inner race is smaller than the first diameter.