CVT Drive Belt Cooling Flow Control for Rocking Edge Wear
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Solution Overview
Problem
Existing continuously variable transmissions experience increased wear of rocking edges in the drive belt at low cooling agent flow rates, leading to reduced efficiency due to increased slipping and clearance, particularly during low torque and high-speed vehicle operations or low ambient temperatures.
Innovation Solution
Implementing a minimum belt cooling flow of 1 to 1.5 liters per minute and adjusting the flow based on a target minimum temperature (120-140°C) to maintain optimal lubrication and prevent excessive wear, with options for direct or gradual flow changes and bypassing the oil cooler to quickly reach the target temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the belt cooling flow is regulated to be very low during low torque and high speed operations to improve transmission efficiency, then energy consumption is reduced, but wear of the rocking edges increases due to insufficient lubrication
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the cooling flow rate based on operating conditions (torque, speed, temperature). The system transitions from a fixed low flow rate to a variable flow rate that adapts to changing conditions, ensuring sufficient lubrication during high-wear conditions while maintaining energy efficiency during normal operation.
Solution Approach 2:
The patent implements dynamics by making the cooling flow rate adjustable and responsive to real-time operating parameters. The system uses sensors to monitor torque, speed, and temperature, then dynamically modifies the cooling flow to match actual wear risks, transforming a static system into an adaptive one that balances energy consumption and component protection.
2Reliability
If the belt cooling flow is increased to reduce wear and improve lubrication, then reliability is improved, but energy consumption increases due to higher pump power requirements
Solution Approach 1:
The patent uses parameter changes to optimize the balance between wear protection and energy consumption. By continuously monitoring operating conditions and adjusting the cooling flow rate accordingly, the system maintains minimum necessary flow for lubrication while avoiding excessive flow that would waste energy, achieving optimal protection efficiency.
Solution Approach 2:
The patent implements feedback control by using sensors to monitor operating parameters (torque, speed, temperature) and using this information to adjust the cooling flow rate. The system continuously compares actual conditions with desired conditions and modifies pump output accordingly, ensuring wear protection is provided only when and where needed, thereby minimizing energy consumption.
3Temperature
If the cooling agent temperature is reduced to improve cooling effectiveness, then temperature control is enhanced, but friction heat losses increase due to higher viscosity
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the cooling agent temperature based on real-time operating conditions. Rather than maintaining a constantly low temperature, the system raises the cooling agent temperature when operating conditions allow (reducing viscosity and friction losses) while still achieving effective cooling when needed, optimizing the balance between cooling effectiveness and energy efficiency.
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 approach minimizes wear on the drive belt, maintains optimal friction conditions, and enhances transmission efficiency by ensuring a consistent minimum cooling flow, even at low torque and high-speed conditions, while preventing chemical degradation and overheating.
Implementation Method 1
a cooling system, which system is arranged to supply a cooling agent, such as a synthetic oil, to at least the drive belt and to recirculate the cooling agent via a heat exchange device
Implementation Method 2
to recirculate the cooling agent via a heat exchange device, such as an oil cooler
Implementation Method 3
The clamping force allows a rotational movement of a driving pulley to be transferred to the drive belt by friction
Data Source
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AI summary
The invention relates to a method for operating a continuously variable transmission comprising two pulleys (1, 2), each defining an effectively V-shaped circumference groove of variable width, a drive belt (3), wrapped around the pulleys (1, 2), and a cooling system, which cooling system is provided with control means (40) for supplying a controlled amount of a cooling agent to the drive belt (3). According to the invention the control means (40) are arranged to supply at least a minimum amount of the cooling agent to the drive belt (3) during operation of the transmission.