CVT Belt Slippage Control via Secondary Pressure Calculation
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Solution Overview
Problem
In continuously variable transmissions without a primary pulley pressure sensor, belt slippage during rapid deceleration cannot be suppressed due to the inability to detect a reduction in primary pulley pressure.
Innovation Solution
A system comprising an input side primary pulley with varying groove width, an output side secondary pulley with varying groove width, a belt looped around both pulleys, sensors for detecting primary pulley rotation speed and secondary pulley pressure, and a controller that determines a rapid deceleration state and calculates a lower limit secondary pulley pressure to prevent slippage by adjusting oil pressures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a primary pulley pressure sensor is installed to detect pressure reduction and suppress belt slippage, then belt slippage suppression capability is improved, but device complexity and cost increase
Solution Approach 1:
The patent uses secondary pulley pressure as an intermediary parameter to infer the state of primary pulley pressure. Instead of directly measuring primary pulley pressure with a sensor, the system measures secondary pulley pressure and uses this as a proxy to determine when belt slippage is about to occur, thereby avoiding the need for a primary pulley pressure sensor while maintaining slippage suppression capability
Solution Approach 2:
The patent replaces the mechanical sensing approach (primary pulley pressure sensor) with a calculation-based approach. The ECU calculates the lower limit secondary pulley pressure based on primary pulley rotation speed and compares it with actual secondary pulley pressure to detect slippage conditions, substituting direct mechanical measurement with computational inference
2Measurement precision
If a primary pulley pressure sensor is installed to detect pressure reduction, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent creates a virtual copy of the primary pulley pressure measurement function using secondary pulley pressure data. By calculating the lower limit secondary pulley pressure from primary pulley rotation speed and comparing it with actual secondary pulley pressure, the system replicates the detection capability of a primary pulley pressure sensor without physically installing one
Solution Approach 2:
The secondary pulley pressure sensor serves multiple functions: it monitors secondary pulley pressure for normal operation and simultaneously acts as an indirect indicator for primary pulley pressure conditions during rapid deceleration. This multi-functional use eliminates the need for a dedicated primary pulley pressure sensor
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
Enables belt slippage determination and suppression without a primary pulley pressure sensor by calculating the lower limit secondary pulley pressure based on primary pulley rotation speed and adjusting oil pressures, effectively preventing slippage during rapid vehicle deceleration.
Implementation Method 1
to ensure that slippage does not occur in a belt looped around a primary pulley and secondary pulley
Data Source
AI summary
When a vehicle decelerates rapidly, a lower limit secondary pulley pressure (Plmt) is calculated on the basis of a primary pulley rotation speed (Npri) detected by a primary pulley rotation sensor. When a deceleration speed (Gdata) is greater than a predetermined deceleration speed (G1) and a secondary pulley pressure (Psec) detected by a secondary pulley pressure sensor is lower than the lower limit secondary pulley pressure (Plmt), it is determined that slippage is about to occur in a V-belt 4 on a primary pulley side in particular, and therefore speed ratio fixing control is performed.