Hydraulic Control Device for CVT Shift Shock Reduction
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Solution Overview
Problem
In continuously variable transmissions without a line pressure sensor, configuring line pressure and secondary pressure to be identical can lead to sudden changes in secondary pressure, causing shift shock due to delayed port opening and incorrect pressure regulation.
Innovation Solution
A hydraulic control device with a pressure regulating valve and solenoid valve that temporarily adjusts pilot pressure to match line pressure with secondary pressure, ensuring smooth operation and reducing shift shock by maximizing port opening areas and using estimated pressures from primary and secondary sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the opening areas of input port and output port are maximized to configure line pressure and secondary pressure to be identical, then fuel efficiency is improved, but in low oil temperature conditions the spool operation becomes slow causing delayed port communication and shift shock
Solution Approach 1:
The patent introduces a line pressure sensor as an intermediary device to detect the actual line pressure and provide feedback to the control unit. This mediator enables the control system to accurately determine when line pressure equals secondary pressure, allowing the spool to be positioned correctly without relying solely on slow mechanical operation in cold conditions. The sensor acts as the missing link between the pressure regulation mechanism and the control system.
Solution Approach 2:
The patent implements a feedback mechanism where the line pressure sensor continuously monitors line pressure and feeds this information back to the control unit. The control unit uses this feedback to determine when line pressure has reached the target level (equal to secondary pressure) and accordingly adjusts the solenoid valve to position the spool. This closed-loop feedback system ensures accurate pressure matching regardless of oil temperature or viscosity conditions.
2Ease of operation
If a line pressure sensor is disposed to detect line pressure and determine identical pressure state, then shift shock is restrained, but device complexity increases
Solution Approach 1:
The patent replaces the mechanical estimation method (inferring line pressure from secondary pressure and flow characteristics) with an electronic sensing system. The line pressure sensor provides direct electronic measurement of line pressure, eliminating the need for complex mechanical pressure balancing mechanisms and enabling more precise and reliable pressure matching through electronic control.
Solution Approach 2:
The patent changes the control parameter from indirect mechanical inference to direct electronic sensing. By measuring line pressure directly with a sensor and using this parameter in the control algorithm, the system achieves more accurate pressure matching. The control unit processes the sensor signal to determine when line pressure equals secondary pressure, enabling precise timing of the pressure equalization process.
3Loss of energy
If line pressure is reduced to match secondary pressure without accurate detection, then fuel efficiency is improved, but timing delay causes sudden secondary pressure change and shift shock
Solution Approach 1:
The patent uses the line pressure sensor to detect when line pressure has naturally reduced to match secondary pressure before actively controlling the spool to equalize the pressures. This preliminary detection allows the system to prepare for pressure equalization at the optimal moment, preventing sudden pressure changes. The sensor enables advance knowledge of the pressure state, allowing smooth transition planning.
Solution Approach 2:
The feedback from the line pressure sensor allows the control unit to monitor the pressure reduction process in real-time and determine the precise moment when line pressure equals secondary pressure. This feedback ensures that the spool is positioned correctly at the right time, maintaining pressure regulation stability while achieving fuel efficiency through reduced line pressure operation.
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 effectively restrains shift shock by ensuring the line pressure and secondary pressure are identical, reducing fuel consumption and improving transmission efficiency by stabilizing the speed ratio and minimizing variations in oil amounts within pulley chambers.
Implementation Method 1
a solenoid valve configured to control the pilot pressure
Implementation Method 2
the spool moving according to pilot pressure to regulate the second pulley pressure
Data Source
AI summary
A hydraulic control device controls hydraulic pressure supplied to a continuously variable transmission. The hydraulic control device includes a pressure regulating valve, a solenoid valve configured to control the pilot pressure, line pressure control means, and hydraulic control means. The pressure regulating valve includes an input port to which line pressure is input, an output port configured to supply an oil chamber of a second pulley with a second pulley pressure, a drain port configured to discharge the second pulley pressure from the oil chamber, and a spool moving according to pilot pressure to regulate the second pulley pressure. The line pressure control means is configured to control the line pressure on the basis of the second pulley pressure and first pulley pressure of first pulley. The hydraulic control means is configured to temporarily change the pilot pressure from set pressure to configure the line pressure identical to the second pulley pressure.