CVT Primary Shaft Axial Load Management
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Solution Overview
Problem
Existing belt type continuously variable transmissions experience abrasion between the engine crank portion and the transmission case due to axial movement of the primary shaft, which increases wear and potentially leads to abnormal noise and degraded lubrication performance.
Innovation Solution
Incorporating a clearance between the crank web and the case, and using a thrust washer or thrust bearing to prevent direct contact, along with restricting the primary shaft's movement to minimize contact, thereby preventing abrasion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the primary shaft is directly supported by the transmission case, then the structure is compact and simple, but axial movement of the shaft causes abrasion between the crank portion and the case
Solution Approach 1:
A bearing is introduced as an intermediary component between the primary shaft and the transmission case. The bearing supports the shaft while preventing direct contact between the crank portion and the case, thereby eliminating abrasion while maintaining structural compactness.
Solution Approach 2:
The support function is segmented into two distinct components: the bearing that supports the shaft and prevents axial movement, and the transmission case that provides structural housing. This segmentation allows each component to perform its specific function optimally without causing abrasion.
2Adaptability or versatility
If the moving flange is shifted to regulate groove width, then transmission gear ratio is controlled steplessly, but belt tension causes axial force on flanges forcing them apart and moving the shaft closer to the case
Solution Approach 1:
The bearing acts as a mediator that absorbs the axial forces generated during gear ratio regulation. When the moving flange shifts under belt tension, the bearing prevents these forces from transmitting to the transmission case, thereby allowing smooth gear ratio control without causing abrasion.
Solution Approach 2:
The bearing provides beforehand cushioning by being pre-installed between the shaft and the case. This cushioning effect is always present, preventing axial movement before it can cause abrasion, regardless of the gear ratio regulation state.
3Reliability
If clearance is provided between crank web and case, then abrasion is prevented, but the distance between components increases
Solution Approach 1:
Instead of relying on clearance to prevent abrasion, a bearing is introduced as an active intermediary that maintains optimal component spacing. The bearing ensures consistent distance between the crank web and case while providing positive mechanical support, rather than relying on passive clearance.
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
Prevents abrasion between the crank web and the case, reducing noise and maintaining lubrication performance by ensuring a consistent distance between the components under varying belt tension.
Implementation Method 1
using a thrust washer or thrust bearing to prevent direct contact
Data Source
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AI summary
A belt type continuously variable transmission 1001, 1002, 1003, 1004, 1005 comprises a primary shaft 11 including a crank portion 30 provided with a crank web 42, and a first extension 32 extending on a first side of the crank portion 30. A primary sheave 12 is mounted on the first extension 32 and includes a stationary flange 51 fixedly mounted on the first extension 32 and a moving flange 52 moveably mounted relative to the first extension 32, wherein a primary sheave groove is defined between the stationary flange 51 and the moving flange 52. A belt 17 is received within the primary sheave groove. A case 14 which covers the primary sheave 12 includes a portion which is proximate to a portion of the crank web 42 with a clearance defined therebetween. When in use, an axial load A, B applied on the primary sheave 12 from tension acting on the belt 17 causes relative movement between the proximate portions of the case 14 and crank web 42. In some disclosed embodiments the clearance between the proximate portions of the case 14 and crank web 42 when no tension acts on the belt 17 is greater than the maximum relative movement of the proximate portions of the case 14 and crank web 42 when tension acts on the belt 17.