Electric Oil Pump Control for HEV Transaxle Lubrication
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Solution Overview
Problem
Hybrid electric vehicles face challenges in maintaining transaxle lubrication and cooling when the engine is off, as the engine-driven transaxle pump is not operational, necessitating an auxiliary electric oil pump to ensure continuous lubrication and cooling of power transmission components.
Innovation Solution
A system and method for controlling the operation of an electric oil pump in hybrid electric vehicles, which includes a logic device to command the pump's speed based on various operating modes, temperature levels, and power loss conditions, ensuring adequate lubrication and cooling of the transaxle components even when the engine is off.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an engine-driven transaxle pump is used for cooling and lubrication, then the cooling and lubrication needs are met when the engine is running, but the transaxle components lack adequate cooling and lubrication when the engine is off
Solution Approach 1:
The system segments the cooling and lubrication function into two independent sources: an engine-driven pump for when the engine is running, and an electric auxiliary pump for when the engine is off. This allows each pump to operate independently based on engine state, ensuring continuous protection of transaxle components regardless of engine operation status.
2Reliability
If an auxiliary electric pump is added to provide cooling and lubrication when the engine is off, then continuous protection is achieved, but the system complexity increases
Solution Approach 1:
The electric auxiliary pump is designed to serve multiple functions: it provides cooling and lubrication when the engine is off, and can supplement or replace the engine-driven pump under certain operating conditions. This multi-functionality justifies the added complexity by providing versatile protection across all vehicle operating modes.
Solution Approach 2:
A control system acts as an intermediary between the engine state and the pump operations. The controller monitors engine running status and automatically activates or deactivates the electric auxiliary pump accordingly, managing the complexity through automated control logic rather than manual intervention.
3Reliability
If the electric oil pump operates at high speed continuously, then adequate lubrication and cooling are ensured, but energy consumption increases and NVH levels rise
Solution Approach 1:
The electric auxiliary pump operates dynamically with variable speed control rather than continuous high-speed operation. The pump speed is adjusted based on real-time monitoring of transaxle operating conditions, providing high flow rates only when necessary for adequate lubrication and cooling, while reducing speed during normal operation to minimize energy consumption and NVH.
Solution Approach 2:
The system changes the operational parameters of the electric pump based on vehicle operating conditions. By monitoring factors such as vehicle speed, acceleration, and transaxle temperature, the control system adjusts pump speed and flow rate parameters to match actual demand, avoiding unnecessary high-energy operation while ensuring adequate protection when needed.
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 effectively maintains transaxle lubrication and cooling by adjusting the electric oil pump's speed according to the vehicle's operating conditions, optimizing energy consumption and reducing noise, vibration, and harshness (NVH) levels, thereby extending the vehicle's operational efficiency and component lifespan.
Implementation Method 1
an auxiliary electric pump may be implemented for purposes such as meeting the cooling and lubrication needs of the HEV when the engine is off
Data Source
AI summary
A system and method is provided for controlling operation of an electric oil pump in a hybrid electric vehicle (HEV). The HEV includes an engine and a transaxle including an electric motor coupled to a traction battery. A commanded speed for the electric oil pump is determined and whether the engine in the HEV is in an off state is determined. When the engine is in the off state, the electric oil pump is controlled to operate at the commanded speed.