Parking Lock Valve Pressure Boosting for Emergency Engagement
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Solution Overview
Problem
The existing electrohydraulic transmission control systems face challenges in maintaining the parking lock in the disengaged state during low system pressures, leading to inadequate hydraulic actuation and delayed engagement of the parking lock device, especially during emergency operations and shutdowns.
Innovation Solution
The electrohydraulic transmission control system incorporates an adjustable pressure source and electrohydraulic pressure adjusters to set and maintain an actuation pressure higher than normal levels during emergency operations, ensuring the parking lock valve can be held in a defined operating state, even when the system pressure is low, thereby preventing undesired engagement and ensuring quick engagement of the parking lock device upon shutdown.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the system pressure is reduced to improve transmission efficiency during normal operation, then the power consumption is reduced, but the parking lock valve cannot be held in the disengaged operating state
Solution Approach 1:
The patent changes the pressure parameter by introducing a pressure boosting mechanism that selectively increases the system pressure only in the region of the parking lock valve when needed for holding, while maintaining low system pressure elsewhere for energy efficiency. This allows the parking lock valve to be held in the disengaged state (requiring high pressure) without consuming excessive power throughout the entire hydraulic system.
2Reliability
If the self-holding pressure of the parking lock valve is increased to ensure reliable holding during low system pressure, then the parking lock can be held in the disengaged state, but the minimum system pressure level must be increased
Solution Approach 1:
The patent applies local quality by creating a localized high-pressure zone specifically at the parking lock valve using a pressure boosting mechanism, while the rest of the hydraulic system operates at low pressure. This differential pressure approach allows reliable parking lock holding without requiring the entire system to maintain high minimum pressure levels.
3Productivity
If the parking lock valve is held in the disengaged state during emergency operation with low system pressure, then the transmission can operate with high spontaneity, but the engagement response time is delayed when shutdown occurs
Solution Approach 1:
The patent prepares the system for rapid engagement by pre-charging the hydraulic fluid volume accumulator to maximum pressure during emergency operation while the parking lock is held disengaged. When shutdown occurs and engagement is required, the already pressurized accumulator can immediately supply the high pressure needed for quick parking lock engagement, eliminating the delay that would otherwise occur while waiting for pressure buildup.
4Productivity
If the hydraulic fluid volume accumulator is used to compensate for undersupplied operating states, then the transmission can operate with high spontaneity, but the accumulator is fully charged during emergency operation, preventing quick engagement upon shutdown
Solution Approach 1:
The patent dynamically manages the hydraulic fluid volume accumulator by controlling its charging state based on operational requirements. During emergency operation, the system dynamically charges the accumulator to maximum pressure to maintain high spontaneity. When engagement is required, the system dynamically switches to discharge mode, allowing the pre-charged accumulator to immediately supply pressure for rapid parking lock engagement.
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 optimizes the efficiency and spontaneity of the transmission system by maintaining the parking lock in the disengaged state with low actuation pressure during normal operation and ensuring rapid engagement of the parking lock during emergency operations, even when system pressures are low.
Implementation Method 1
a hydraulic fluid volume can be temporarily stored counter to a spring force of a spring device in the region of the hydraulic fluid volume accumulator, which hydraulic fluid volume can, in accordance with demand, be introduced into the line system of the hydraulic system downstream of a check valve device
Implementation Method 2
the parking lock valve is held in the operating state which corresponds to the disengaged operating state of the parking lock, by the pressure in the primary system pressure circuit in the region of a control surface of the valve slide of the parking lock valve, which control surface corresponds to a differential surface between two facing face surfaces of two valve slide sections configured with different diameters, counter to the spring force
Data Source
AI summary
An electrohydraulic transmission control system (1) includes a parking lock valve (2). The electrohydraulic transmission control system (1) is configured such that, during normal operation of the electrohydraulic transmission control system (1) in which at least one electrohydraulic pressure adjuster (EDSSYS) is actuatable with current, the parking lock valve (2) can be held in a defined operating state in which an actuation pressure (p_sys) acts on a parking lock cylinder (3) above a normal pressure level. The electrohydraulic transmission control system (1) is configured such that, during emergency operation of the electrohydraulic transmission control system (1) in which the at least one electrohydraulic pressure adjuster (EDSSYS) is not fed with current and the actuation pressure (p_sys) is at least temporarily set to an emergency pressure level higher than the normal pressure level by the at least one pressure source (7), a pressure level of the actuation pressure (p_sys) that holds the parking lock valve (2) in the defined operating state corresponds at least approximately to the emergency pressure level.