Automatic Gearbox Pressure Retention for Start-Stop Activation
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Solution Overview
Problem
Automatic transmissions with torque converters face long activation times after engine start in start-stop operations due to pressure loss in the hydraulic system, making frequent start-stop operations impractical.
Innovation Solution
Actuating or filling non-actuated shifting elements with pressure oil before engine shutdown to maintain pressure and reduce leakage, allowing quicker reactivation when the engine is restarted, eliminating the need for additional pumps or hydraulic impulse storage systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the combustion engine is switched off for start-stop operation, then fuel consumption and emissions are reduced, but the hydraulic system loses pressure and activation time increases
Solution Approach 1:
The patent applies preliminary action by actuating shifting elements and filling them with pressure oil before the engine is switched off. This pre-preparation ensures that when the engine restarts, the hydraulic system already has the necessary pressure in critical components, eliminating the need for pressure build-up time after restart and enabling immediate torque transmission.
Solution Approach 2:
The patent converts the harmful effect of pressure loss during engine shutdown into a benefit by using the pressure oil already present in the shifting elements to quickly repressurize the hydraulic system after restart. The oil that would normally be lost or depleted is instead retained in the shifting elements, serving as a ready reservoir for rapid system reactivation.
2Loss of time
If additional pumps or hydraulic impulse storage systems are used to maintain pressure, then activation time is reduced, but costs and energy consumption increase
Solution Approach 1:
The patent applies self-service by enabling the hydraulic system to maintain its own pressure using the oil already contained within the shifting elements. When the engine restarts, the system automatically repressurizes itself through the pre-filled shifting elements without requiring external pumps or additional hydraulic impulse storage systems, thereby avoiding increased complexity and energy consumption.
Solution Approach 2:
The patent makes the shifting elements serve multiple functions: they not only engage and disengage gears during normal operation but also serve as pressure storage reservoirs during engine shutdown and rapid repressurization sources after restart. This multi-functionality eliminates the need for separate pressure maintenance systems.
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 method significantly reduces the activation time of the automatic transmission after engine start, enabling more efficient start-stop operations without increasing costs or energy consumption.
Implementation Method 1
a hydraulic pump coupled to a transmission input shaft and driven by the combustion engine is provided and which provides the necessary oil pressure
Implementation Method 2
a so-termed hydraulic impulse storage (HIS) system can be connected to the oil circuit of the transmission, by means of which the pressure build-up after an engine start is made substantially faster
Data Source
AI summary
A method for operating an automatic transmission (1) of a motor vehicle in which a hydraulic pump, associated with a hydraulic system, for supplying pressure in the hydraulic system is driven by a drive engine and in which hydraulic shifting elements (B1, B2, B3, C1, C2) are actuated to engage gear steps. According to the method, before the drive engine is turned off for a short duration of time, at least one non-actuated shifting element (B1, B2, B3, C1, C2) of the automatic transmission (1) is actuated or filled with pressure oil.