Hydraulic Control System for Engine Start-Stop Transmission
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Solution Overview
Problem
Conventional hydraulic control systems for transmissions in engine start-stop applications are complex and inefficient, particularly in reducing component count and improving controllability during engine restart.
Innovation Solution
A hydraulic control system comprising a pressurized fluid source, clutch pressure regulating valve, clutch pump valve, fluid flow check valves, pressure valve, and pressure control solenoid, which allows for efficient clutch actuation and lubrication, with a biasing mechanism and dual modes of operation to maintain hydraulic fluid pressure even when the engine is off.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a separate auxiliary electric pump or accumulators are used to provide pressurized hydraulic fluid when the IC engine is turned off, then the transmission can operate during engine stop, but the system complexity increases
Solution Approach 1:
The patent combines the auxiliary pump function with the existing main pump by using the same pump in two different modes: engine-driven mode during normal operation and electric motor-driven mode during engine stop. This eliminates the need for a completely separate auxiliary pump system, reducing overall system complexity while maintaining the capability to provide pressurized hydraulic fluid during engine stop.
Solution Approach 2:
The main pump is designed to serve multiple functions: it operates as an engine-driven pump during normal operation and as an electric motor-driven pump during engine stop. The pump housing and internal mechanism remain the same, but the drive source changes, allowing a single component to fulfill multiple roles in different operating conditions.
2Reliability
If conventional hydraulic control systems use multiple separate components for clutch actuation, then reliable clutch engagement is achieved, but the number of components and system complexity increases
Solution Approach 1:
The patent merges the clutch actuation function with the torque transmitting mechanism actuation by using a single hydraulic circuit that can serve both purposes. The same pressurized hydraulic fluid from the pump is used to actuate both the clutch and the torque transmitting mechanisms, eliminating the need for separate hydraulic systems for each function.
Solution Approach 2:
The hydraulic control system is designed to perform multiple functions through a unified circuit: it provides pressure for clutch actuation, torque transmitting mechanism engagement, and maintains lubrication pressure during both engine operation and engine stop conditions, reducing the need for multiple dedicated systems.
3Loss of energy
If the engine is turned off to improve fuel efficiency, then fuel consumption decreases, but hydraulic fluid pressure is lost and transmission control becomes difficult
Solution Approach 1:
The patent replaces the engine-driven mechanical pump with an electric motor-driven pump for the stop condition. The electric motor can be independently controlled to maintain hydraulic fluid pressure even when the engine is off, ensuring transmission control reliability during fuel-saving stop periods.
Solution Approach 2:
The system changes the operating parameters of the pump by switching from engine-driven rotation to electric motor-driven rotation at controlled speeds. The electric motor can maintain optimal pump speed for pressure generation independently of engine status, ensuring consistent hydraulic pressure during stop conditions.
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
The system reduces complexity and improves efficiency and controllability by maintaining hydraulic fluid pressure for clutch actuation and lubrication, ensuring smooth engine restart and preventing unintended power flow.
Implementation Method 1
The pressure control solenoid is arranged to actuate the valve spool of the clutch pressure regulating valve
Implementation Method 2
The first fluid flow check valve is in communication with both the first output port of the clutch pump valve and the second input port of the clutch pump valve thus preventing backpressure from the second input port to the first output port
Implementation Method 3
A biasing member is disposed between the second end of the valve spool and the second end of the valve bore
Implementation Method 4
The pressurized hydraulic fluid delivered to the torque transmitting devices is used to engage or disengage the devices in order to obtain different gear ratios
Data Source
AI summary
A hydraulic control system for a clutch of a transmission having a plurality of torque transmitting mechanisms and includes a source of pressurized hydraulic fluid, a clutch pressure regulating valve, a clutch pump valve, a first and a second fluid flow check valve, a pressure valve, a first torque transmitting mechanism actuation device, and a pressure control solenoid.