Clamping Force Generator for CVT Pre-Load
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Solution Overview
Problem
Existing mechanical power transmission systems face challenges in generating adequate clamping force to prevent slip and inefficiencies, particularly at low torque inputs, due to difficulties in providing initial pre-load and managing slip between transmission components.
Innovation Solution
The implementation of clamping force generation mechanisms using torsion springs, compression coil springs, and magnetic elements to pre-load load cam rollers, which are positioned to roll up ramps and generate a consistent clamping force, ensuring traction and minimizing drag forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If rollers are placed between load cams and reacting surfaces to generate clamping force, then clamping force is produced through the rolling mechanism, but adequate pre-load (initial clamping force) is difficult to provide
Solution Approach 1:
The patent applies preliminary action by pre-loading the rollers onto the ramps using springs before the transmission begins operation. The springs are positioned to continuously exert force on the rollers, ensuring they maintain contact with the ramps and generate the necessary initial clamping force without requiring external adjustment mechanisms.
Solution Approach 2:
The spring-loaded mechanism serves itself by automatically generating and maintaining the required pre-load through the elastic deformation of the springs. As the transmission components move, the springs continuously adjust to maintain optimal roller contact force, eliminating the need for external control systems.
2Power
If rollers are used to generate clamping force through rolling up ramps, then torque transmission is facilitated, but slip and inefficiencies occur particularly at low torque inputs
Solution Approach 1:
The springs are pre-loaded to ensure rollers maintain constant contact with the ramps even before torque is applied. This preliminary positioning prevents slip at low torque inputs by ensuring the rollers are already engaged with the ramps and can immediately transmit torque without losing contact.
Solution Approach 2:
The patent changes the physical state of the roller-ramp interface by maintaining constant normal force through spring loading. This parameter change ensures that the friction force remains sufficient to prevent slip across the entire torque range, particularly at low torque inputs where slip would otherwise occur.
3Force
If opposing surfaces are constrained to react the pushing of rollers, then clamping force arises in the assembly, but drag forces increase
Solution Approach 1:
The patent employs curved or conical ramp surfaces instead of flat opposing surfaces. This curvature allows the rollers to roll more efficiently up the ramps while generating clamping force, reducing the sliding friction component that creates drag. The tapered geometry directs forces more effectively along the rolling path.
Solution Approach 2:
The invention replaces the traditional mechanical constraint system with a spring-based elastic system. Instead of rigidly constraining opposing surfaces to react roller pushing forces, the springs provide flexible, energy-storing constraints that reduce impact forces and drag while maintaining the necessary clamping force.
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 solution ensures a consistent and sufficient clamping force is maintained across varying torque inputs, reducing slip and inefficiencies, and effectively manages contact forces between power rollers and traction rings in continuously variable transmissions.
Implementation Method 1
The implementation of clamping force generation mechanisms using torsion springs, compression coil springs
Implementation Method 2
The implementation of clamping force generation mechanisms using torsion springs, compression coil springs
Implementation Method 3
The implementation of clamping force generation mechanisms using torsion springs, compression coil springs, and magnetic elements
Implementation Method 4
as the relative motion between the opposing surfaces drives the rollers up the ramps, the rollers act to push apart the opposing surfaces
Implementation Method 5
the rollers act to push apart the opposing surfaces. Since the opposing surfaces are typically substantially constrained to react the pushing of the rollers, a clamping force arises in the assembly
Data Source
AI summary
Mechanisms and methods for clamping force generation are disclosed. In one embodiment, a clamping force generator includes a spring coupled to a traction ring and to a load cam roller cage. The traction ring can be provided with a recess to receive the spring. In some embodiments, a relatively short spring is provided. In other embodiments, a spring couples to a wire and the spring-wire combination couples to the traction ring and the load cam roller cage. In some embodiments, the load cam roller cage is provided with tabs adapted to engage the wire and/or the spring. In yet other embodiments, the traction ring is configured to receive a dowel pin for coupling to the spring. One or more of the tabs can include a tab notch that cooperates with a stop pin coupled to the traction ring to provide adjustment of the travel of the load cam roller cage.