Hydraulic Control Arrangement for Automatic Transmission Parking Lock
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Solution Overview
Problem
Existing hydraulic control arrangements for automatic transmissions face challenges in quickly and securely engaging the parking lock, especially when system pressure is low, such as when the internal combustion engine is shut down, leading to prolonged activation times and potential vehicle instability.
Innovation Solution
The introduction of a discharge slide valve with low flow resistance allows for direct and rapid fluid discharge from the parking lock pressure chamber to the tank, facilitating quick engagement of the parking lock, even under low system pressure conditions, by providing an alternative path for fluid removal that bypasses the higher resistance parking lock slide valve.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If operating fluid is discharged via the parking lock slide valve, then the parking lock can be controlled securely and exactly, but the discharge time is prolonged due to high flow resistance
Solution Approach 1:
The patent divides the fluid discharge function into two separate pathways: one through the parking lock slide valve for controlled discharge, and another through the discharge slide valve for rapid discharge. This segmentation allows each valve to be optimized for its specific function, resolving the contradiction between controlled discharge and rapid discharge.
Solution Approach 2:
The discharge slide valve acts as an intermediary component that provides an alternative discharge path when rapid fluid removal is needed. It mediates between the pressure chamber and tank, enabling quick discharge without compromising the control function of the parking lock slide valve.
2Measurement precision
If the parking lock slide valve is designed with small cross-section for secure control, then control precision is improved, but fluid discharge speed decreases
Solution Approach 1:
The patent segments the fluid control function into two separate valves: the parking lock slide valve with small cross-section for precise control, and the discharge slide valve with large cross-section for rapid discharge. This allows each component to be optimized for its specific purpose without compromise.
Solution Approach 2:
Different parts of the hydraulic system are given different qualities: the parking lock slide valve has a small cross-section for precision control, while the discharge slide valve has a large cross-section for rapid flow. This local differentiation resolves the contradiction between control precision and discharge speed.
3Loss of energy
If system pressure is low (engine shut down), then energy consumption is reduced, but parking lock engagement becomes slow or fails
Solution Approach 1:
The patent changes the hydraulic parameter (flow resistance) by providing an alternative discharge path through the discharge slide valve. When system pressure is low, this alternative path allows sufficient flow rate to engage the parking lock reliably, regardless of the low driving pressure from the shutdown engine.
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 enables rapid and secure engagement of the parking lock, ensuring the vehicle can be quickly secured against rolling away, even when system pressure is low, by reducing fluid discharge time and maintaining control precision.
Implementation Method 1
the operating fluid can flow via the discharge slide valve directly into the tank without having to flow through the parking lock slide valve
Implementation Method 2
By supplying operating fluid via the locking slide valve to a first locking pressure chamber, the locking piston can be displaced in a first activation direction. When the locking piston is displaced in a second activation direction contrary to the first activation direction, operating fluid is removed from the first locking pressure chamber.
Data Source
AI summary
In a hydraulic control arrangement for an automatic transmission of a motor vehicle having a parking lock activation system wherein operating fluid is supplied via a parking lock slide valve to a first parking lock pressure chamber for moving a parking lock-up piston in one direction into a locking position or moving the parking lock piston in an opposite direction, whereby operating fluid is released from the first parking lock pressure chamber via a discharge slide valve by way of which the first parking brake pressure chamber is connected to a tank for releasing the parking lock-up.