CVT Belt Capacity Control for Fuel Economy
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional control devices for continuously variable transmission mechanisms with stepwise variable transmission mechanisms increase belt capacity unnecessarily, leading to deteriorated fuel economy when the stepwise variable transmission mechanism is not in its lowest gear ratio during coast traveling.
Innovation Solution
A control device that adjusts the belt capacity increase amount based on the transmission gear ratio of the stepwise variable transmission mechanism, setting a smaller increase for higher gear ratios, thereby suppressing belt capacity and improving fuel economy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the belt capacity is increased by a fixed value when the accelerator opening degree becomes zero, then the belt slippage is prevented during coast traveling, but the fuel economy is deteriorated when the stepwise variable transmission mechanism is not in the lowest gear ratio
Solution Approach 1:
The invention changes the fixed belt capacity increase to a dynamic increase amount that varies according to the gear stage of the stepwise variable transmission mechanism. The control device determines the increase amount based on the current gear stage, making the belt capacity adjustment adaptive to the operating conditions rather than static and uniform across all gear stages.
Solution Approach 2:
The invention changes the parameter of belt capacity increase amount based on the gear stage parameter. When the transmission mechanism is in higher gear stages during coast traveling, a smaller increase amount is applied compared to lower gear stages, optimizing the balance between preventing belt slippage and maintaining fuel economy.
2Reliability
If the belt capacity is increased to a fixed value during coast traveling, then the belt slippage is prevented, but the belt capacity becomes unnecessary when the transmission gear ratio is not the lowest, leading to increased energy consumption
Solution Approach 1:
The invention applies partial action by adjusting the belt capacity increase amount according to the necessary level for each gear stage. Instead of applying a uniform excessive increase across all gear stages, the control device applies only the necessary increase amount appropriate for the current gear stage, avoiding unnecessary energy consumption while ensuring sufficient belt capacity.
3Device complexity
If a fixed increase amount of belt capacity is applied regardless of gear stage, then the control system is simple, but the fuel economy deteriorates due to unnecessary belt capacity increase in higher gear stages
Solution Approach 1:
The control system transitions from a static fixed increase amount to a dynamic gear-stage-dependent increase amount. The control device determines the appropriate increase amount based on the current gear stage of the stepwise variable transmission mechanism, adding minimal complexity to the control logic while achieving significant fuel economy improvements.
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 control device effectively reduces belt capacity during coast traveling when the stepwise variable transmission mechanism is not in its lowest gear ratio, enhancing fuel efficiency by preventing unnecessary belt capacity increases.
Implementation Method 1
a belt capacity of a primary pulley and a belt capacity of a secondary pulley are controlled by supplied hydraulic pressures being controlled
Data Source
AI summary
A control device for a continuously variable transmission mechanism of a vehicle includes: a stepwise variable transmission mechanism which is disposed in series with the continuously variable transmission mechanism, and which has at least two or more forward gear stages; and a controller configured to increase the belt capacities to be greater than the belt capacity set when an accelerator opening degree is zero, at least in a time period from a timing when the accelerator opening degree becomes zero, to a timing when a braking force is generated by a depression of a brake pedal, the controller being configured to set an increase amount with respect to the belt capacity set when the accelerator opening degree is zero, to a smaller value as a transmission gear ratio of the stepwise variable transmission mechanism is higher.