Flow Accumulator for Hybrid Transmission Clutch Synchronization
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Solution Overview
Problem
During a flying engine start in hybrid vehicles, there is a need to minimize the time it takes to transfer torque from the internal combustion engine to the axles, as existing methods are inefficient in synchronizing the engagement of transmission clutches to achieve this.
Innovation Solution
A method and system utilizing a flow accumulator to control the transmission fluid flow between clutches, determining a gear ratio and timing to ensure simultaneous pressure threshold achievement by the first and second clutches, thereby optimizing torque transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If transmission fluid is supplied to multiple clutches simultaneously during a flying engine start, then the torque transfer process becomes simpler to control, but the time required to fill the clutches increases because the available fluid volume is divided among multiple clutches
Solution Approach 1:
The system pre-charges a flow accumulator with transmission fluid before the clutch engagement sequence begins. When the engine starts and torque transfer is needed, the pre-charged accumulator can immediately supply fluid to the first clutch without waiting for the pump to build pressure or for fluid to travel through lines, significantly reducing the fill time while maintaining simple control logic.
Solution Approach 2:
The clutch engagement process is divided into sequential phases: first clutch engagement followed by second clutch engagement. The flow accumulator is strategically positioned to supply fluid to the first clutch during its fill phase, ensuring rapid engagement. After the first clutch is filled, the same accumulator supplies fluid to the second clutch. This segmentation allows the limited accumulator volume to be used efficiently without requiring simultaneous supply to multiple clutches.
2Loss of time
If a flow accumulator is used to supply transmission fluid to clutches during a flying engine start, then the torque transfer time is reduced, but the system complexity increases due to additional components and control logic
Solution Approach 1:
The flow accumulator acts as an intermediary energy storage device between the transmission fluid pump and the clutches. It decouples the pump's continuous operation from the transient high-demand moments during clutch engagement. The accumulator absorbs excess fluid and pressure during normal operation, then releases it rapidly when clutches need to engage, reducing torque transfer time without requiring complex real-time control of fluid delivery.
Solution Approach 2:
The flow accumulator is pre-charged with transmission fluid and pressurized before the clutch engagement sequence begins. This preliminary action ensures that when the engine starts and torque transfer is needed, the accumulator can immediately supply fluid to the first clutch without waiting for the pump to build pressure or for fluid to travel through lines, significantly reducing the fill time while maintaining simple control logic.
3Ease of operation
If the first clutch is filled before the second clutch during a flying engine start, then the control sequence becomes simpler, but the overall torque transfer time increases due to sequential rather than simultaneous engagement
Solution Approach 1:
The system pre-charges a flow accumulator with transmission fluid before the clutch engagement sequence begins. When the engine starts and torque transfer is needed, the pre-charged accumulator can immediately supply fluid to the first clutch without waiting for the pump to build pressure or for fluid to travel through lines, significantly reducing the fill time while maintaining simple control logic.
Solution Approach 2:
The clutch engagement process is divided into sequential phases: first clutch engagement followed by second clutch engagement. The flow accumulator is strategically positioned to supply fluid to the first clutch during its fill phase, ensuring rapid engagement. After the first clutch is filled, the same accumulator supplies fluid to the second clutch. This segmentation allows the limited accumulator volume to be used efficiently without requiring simultaneous supply to multiple clutches.
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 approach significantly reduces the time required to transfer torque from the engine to the axles during a flying engine start, enhancing the efficiency and responsiveness of the vehicle's propulsion system.
Implementation Method 1
The accumulator may be a piston/spring type or a gas filled type accumulator having a spring or compressible gas, respectively, that provides a compressive force on the hydraulic fluid
Implementation Method 2
maintains the non-compressible hydraulic fluid under pressure by an external source
Data Source
AI summary
A system and method can control a transmission during a flying engine start. The method includes receiving a request for an internal combustion engine to be started while a vehicle is solely driven by an electric motor-generator. Further, the method determining a time lapse between a moment when a first clutch starts to be filled and a moment when a second clutch starts to be filled such that the first clutch and the second clutch reach first and second clutch pressure thresholds, respectively, at substantially the same time. The method includes transferring transmission fluid to the first clutch and transferring transmission fluid to the second clutch after the determined time lapse has passed since the first clutch started to be filled.