CVT Low Standby Control Using Secondary Pulley Pressure Feedback
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Solution Overview
Problem
In belt continuously variable transmission mechanisms, determining the completion of low standby control is challenging due to the inability to detect input/output rotation speeds when the system is stopped, leading to potential start lag from prolonged output limits on the driving source.
Innovation Solution
The control device releases the output limit of the driving source based on the actual pressure of the secondary pulley hydraulic pressure, rather than rotation speed sensors, to determine the completion of low standby control and improve starting ability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the output limit of the driving source is maintained until a set time elapses from the start of low standby control, then the downshift completion is ensured, but the start lag occurs and starting ability deteriorates
Solution Approach 1:
The control unit monitors the actual secondary pulley pressure in real-time during low standby control and uses this feedback to determine when the downshift is actually completed. This allows the output limit to be released immediately upon completion rather than waiting for a predetermined time period, eliminating start lag while ensuring reliable downshift completion.
Solution Approach 2:
The invention changes the detection parameter from rotation speed (which is unavailable during stopping) to secondary pulley pressure (which can be measured during stopping). By monitoring pressure changes, the system can accurately determine downshift completion without relying on rotation speed, enabling timely release of the output limit and improving starting ability.
2Measurement precision
If rotation speed sensors are used to calculate speed ratio, then speed ratio can be determined during operation, but speed ratio cannot be detected when the vehicle is stopped
Solution Approach 1:
The invention introduces secondary pulley pressure as an intermediary parameter to indirectly determine speed ratio and downshift completion during stopping. Since pressure changes correlate with belt position and speed ratio, this intermediary measurement enables detection capability during stopping without requiring direct rotation speed measurement.
Solution Approach 2:
The invention replaces the mechanical rotation speed sensing system with a hydraulic pressure sensing system. By substituting the measurement mechanism from mechanical (rotation speed sensors) to hydraulic (pressure sensors), the system gains the ability to detect downshift completion during stopping when mechanical rotation is absent.
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 allows for more accurate detection of the completion of low standby control, reducing start lag and enhancing the starting ability of the vehicle by directly monitoring the steep increase in secondary pulley pressure when the speed ratio reaches the maximum.
Implementation Method 1
a consumption flow rate of a secondary pulley disappears and a secondary pulley pressure rises steeply
Data Source
AI summary
A control device for a vehicle having: an engine; and a variator arranged downstream of the engine in a power transmission path connecting the engine and drive wheels, wherein the control device for the vehicle has a controller that executes a low standby control which downshifts the variator by moving a belt of the variator in a vertical direction (radial direction) during stopping of the vehicle. After starting the low standby control, the controller releases an output limit of the engine based on an actual secondary pressure of the variator.