Electric Fluid Pump Speed Control for Hybrid Clutch Shifts
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Solution Overview
Problem
Battery-electric vehicles lack a reliable mechanism for fluid circulation in electric-only mode, as they do not have an engine-driven main fluid pump, which can lead to inconsistent clutch fill events and potential slippage during shifts.
Innovation Solution
An electrically-actuated fluid pump powered by a vehicle's battery, controlled by a controller that calculates and adjusts its speed based on predicted and actual flow values to ensure consistent fluid delivery to the clutch set during shift events, using a calibrated geometric model of the oncoming clutch.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an engine-driven main fluid pump is used, then reliable fluid circulation is achieved during engine-on modes, but the pump becomes unavailable when the vehicle operates in EV mode
Solution Approach 1:
The patent replaces the engine-driven mechanical pump with an electrically-actuated fluid pump that operates independently of the engine. This substitution allows the pump to function in both engine-on and EV modes, resolving the contradiction between reliability during engine operation and adaptability to EV mode where no engine is running.
2Ease of operation
If a constant speed electric pump is used, then simple control is achieved, but inconsistent clutch fill events and potential slippage occur during shifts
Solution Approach 1:
The patent implements dynamic speed control of the electric pump based on real-time operating conditions. The controller adjusts pump speed according to fluid temperature, viscosity, and clutch fill requirements, ensuring consistent clutch engagement while maintaining manageable control complexity through automated feedback mechanisms.
3Speed
If pump speed is increased to rapidly fill the clutch, then shift response time is improved, but fluid pressure control becomes more challenging
Solution Approach 1:
The patent employs a closed-loop control system that continuously monitors fluid pressure and pump operation. The controller adjusts pump speed in real-time based on feedback from pressure sensors and clutch fill status, enabling rapid clutch engagement while maintaining precise pressure control to prevent slippage and ensure smooth shifts.
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 ensures predictable and smooth clutch fill behavior, minimizing clutch slip and maintaining consistent line pressure, even in the absence of an engine-driven main pump, thereby enhancing the driving experience and extending the vehicle's electric range.
Implementation Method 1
The fluid pump delivers some of the fluid from the tank to the clutch set
Implementation Method 2
The controller calculates each of an actual flow value for holding torque across the clutch set and a predicted flow value for rapidly filling a designated oncoming clutch
Data Source
AI summary
A vehicle includes a clutch set, a tank with fluid, an auxiliary battery, an electric fuel pump, and a controller. The electric fluid pump delivers some of the fluid from the tank to a designated oncoming clutch of the clutch set. The controller calculates a predicted flow value for the oncoming clutch during the shift event, and selectively controls the speed of the pump using the predicted flow value during the shift event. The controller controls the pump using an actual flow value when the vehicle is not executing a shift event, i.e., when holding torque. The speed of the electric fluid pump is increased to a first calculated speed determined using the predicted flow value when the shift event is initiated and before filling of the oncoming clutch commences, and is reduced to a second calculated speed determined using the actual flow value when the shift event is complete.